Sample records for hadley-type meridional circulation
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NASA Astrophysics Data System (ADS)
Feng, Juan; Li, Jianping; Zhu, Jianlei; Li, Yang; Li, Fei
2018-02-01
The response of the Hadley circulation (HC) to the sea surface temperature (SST) is determined by the meridional structure of SST and varies according to the changing nature of this meridional structure. The capability of the models from the phase 5 of the Coupled Model Intercomparison Project (CMIP5) is utilized to represent the contrast response of the HC to different meridional SST structures. To evaluate the responses, the variations of HC and SST were linearly decomposed into two components: the equatorially asymmetric (HEA for HC, and SEA for SST) and equatorially symmetric (HES for HC, and SES for SST) components. The result shows that the climatological features of HC and tropical SST (including the spatial structures and amplitude) are reasonably simulated in all the models. However, the response contrast of HC to different SST meridional structures shows uncertainties among models. This may be due to the fact that the long-term temporal variabilities of HEA, HES, and SEA are limited reproduced in the models, although the spatial structures of their long-term variabilities are relatively reasonably simulated. These results indicate that the performance of the CMIP5 models to simulate long-term temporal variability of different meridional SST structures and related HC variations plays a fundamental role in the successful reproduction of the response of HC to different meridional SST structures.
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The Dynamics of Hadley Circulation Variability and Change
NASA Astrophysics Data System (ADS)
Davis, Nicholas Alexander
The Hadley circulation exerts a dominant control on the surface climate of earth's tropical belt. Its converging surface winds fuel the tropical rains, while subsidence in the subtropics dries and stabilizes the atmosphere, creating deserts on land and stratocumulus decks over the oceans. Because of the strong meridional gradients in temperature and precipitation in the subtropics, any shift in the Hadley circulation edge could project as major changes in surface climate. While climate model simulations predict an expansion of the Hadley cells in response to greenhouse gas forcings, the mechanisms remain elusive. An analysis of the climatology, variability, and response of the Hadley circulation to radiative forcings in climate models and reanalyses illuminates the broader landscape in which Hadley cell expansion is realized. The expansion is a fundamental response of the atmosphere to increasing greenhouse gas concentrations as it scales with other key climate system changes, including polar amplification, increasing static stability, stratospheric cooling, and increasing global-mean surface temperatures. Multiple measures of the Hadley circulation edge latitudes co-vary with the latitudes of the eddy-driven jets on all timescales, and both exhibit a robust poleward shift in response to forcings. Further, across models there is a robust coupling between the eddy-driving on the Hadley cells and their width. On the other hand, the subtropical jet and tropopause break latitudes, two common observational proxies for the tropical belt edges, lack a strong statistical relationship with the Hadley cell edges and have no coherent response to forcings. This undermines theories for the Hadley cell width predicated on angular momentum conservation and calls for a new framework for understanding Hadley cell expansion. A numerical framework is developed within an idealized general circulation model to isolate the mean flow and eddy responses of the global atmosphere to
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The Hadley circulation: assessing NCEP/NCAR reanalysis and sparse in-situ estimates
NASA Astrophysics Data System (ADS)
Waliser, D. E.; Shi, Zhixiong; Lanzante, J. R.; Oort, A. H.
We present a comparison of the zonal mean meridional circulations derived from monthly in situ data (i.e. radiosondes and ship reports) and from the NCEP/NCAR reanalysis product. To facilitate the interpretation of the results, a third estimate of the mean meridional circulation is produced by subsampling the reanalysis at the locations where radiosonde and surface ship data are available for the in situ calculation. This third estimate, known as the subsampled estimate, is compared to the complete reanalysis estimate to assess biases in conventional, in situ estimates of the Hadley circulation associated with the sparseness of the data sources (i.e., radiosonde network). The subsampled estimate is also compared to the in situ estimate to assess the biases introduced into the reanalysis product by the numerical model, initialization process and/or indirect data sources such as satellite retrievals. The comparisons suggest that a number of qualitative differences between the in situ and reanalysis estimates are mainly associated with the sparse sampling and simplified interpolation schemes associated with in situ estimates. These differences include: (1) a southern Hadley cell that consistently extends up to 200 hPa in the reanalysis, whereas the bulk of the circulation for the in situ and subsampled estimates tends to be confined to the lower half of the troposphere, (2) more well-defined and consistent poleward limits of the Hadley cells in the reanalysis compared to the in-situ and subsampled estimates, and (3) considerably less variability in magnitude and latitudinal extent of the Ferrel cells and southern polar cell exhibited in the reanalysis estimate compared to the in situ and subsampled estimates. Quantitative comparison shows that the subsampled estimate, relative to the reanalysis estimate, produces a stronger northern Hadley cell ( 20%), a weaker southern Hadley cell ( 20-60%), and weaker Ferrel cells in both hemispheres. These differences stem from
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NASA Astrophysics Data System (ADS)
Voigt, A.
2013-11-01
I study the Hadley circulation of a completely ice-covered Snowball Earth through simulations with a comprehensive atmosphere general circulation model. Because the Snowball Earth atmosphere is an example of a dry atmosphere, these simulations allow me to test to what extent dry theories and idealized models capture the dynamics of realistic dry Hadley circulations. Perpetual off-equatorial as well as seasonally varying insolation is used, extending a previous study for perpetual on-equatorial (equinox) insolation. Vertical diffusion of momentum, representing the momentum transport of dry convection, is fundamental to the momentum budgets of both the winter and summer cells. In the zonal budget, it is the primary process balancing the Coriolis force. In the meridional budget, it mixes meridional momentum between the upper and the lower branch and thereby decelerates the circulation. Because of the latter, the circulation intensifies by a factor of three when vertical diffusion of momentum is suppressed. For seasonally varying insolation, the circulation undergoes rapid transitions from the weak summer into the strong winter regime. Consistent with previous studies in idealized models, these transitions result from a mean-flow feedback, because of which they are insensitive to the treatment of vertical diffusion of momentum. Overall, the results corroborate previous findings for perpetual on-equatorial insolation. They demonstrate that descriptions of realistic dry Hadley circulations, in particular their strength, need to incorporate the vertical momentum transport by dry convection, a process that is neglected in most dry theories and idealized models. An improved estimate of the strength of the Snowball Earth Hadley circulation will also help to better constrain the climate of a possible Neoproterozoic Snowball Earth and its deglaciation threshold.
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NASA Astrophysics Data System (ADS)
Voigt, A.
2013-08-01
I study the Hadley circulation of a completely ice-covered Snowball Earth through simulations with a comprehensive atmosphere general circulation model. Because the Snowball Earth atmosphere is an example of a dry atmosphere, these simulations allow me to test to what extent dry theories and idealized models capture the dynamics of dry Hadley circulations. Perpetual off-equatorial as well as seasonally-varying insolation is used, extending a previous study for perpetual on-equatorial (equinox) insolation. Vertical diffusion of momentum, representing the momentum transport of dry convection, is fundamental to the momentum budgets of both the winter and summer cells. In the zonal budget, it is the primary process balancing the Coriolis force. In the meridional budget, it mixes meridional momentum between the upper and the lower branch and thereby decelerates the circulation. Because of the latter, the circulation intensifies by a factor of three when vertical diffusion of momentum is suppressed. For seasonally-varying insolation, the circulation undergoes rapid transitions from the weak summer into the strong winter regime. Consistent with previous studies in idealized models, these transitions result from a mean-flow feedback, because of which they are insensitive to the treatment of vertical diffusion of momentum. Overall, the results corroborate previous findings for perpetual on-equatorial insolation. They demonstrate that an appropriate description of dry Hadley circulations, in particular their strength, needs to incorporate the vertical momentum transport by dry convection, a process that is neglected in most dry theories and idealized models. An improved estimate of the strength of the Snowball Earth Hadley circulation will also help to better constrain the climate of a possible Neoproterozoic Snowball Earth and its deglaciation threshold.
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NASA Astrophysics Data System (ADS)
Nguyen, H.; Hendon, H. H.; Lim, E.-P.; Boschat, G.; Maloney, E.; Timbal, B.
2018-01-01
In order to understand the regional impacts of variations in the extent of the Hadley circulation in the Southern Hemisphere, regional Hadley circulations are defined in three sectors centered on the main tropical heat sources over Africa, Asia-Pacific (Maritime Continent) and the Americas. These regional circulations are defined by computing a streamfunction from the divergent component of the meridional wind. A major finding from this study is that year-to-year variability in the extent of the hemispheric Hadley circulation in the Southern Hemisphere is primarily governed by variations of the extent of the Hadley circulation in the Asia-Pacific sector, especially during austral spring and summer when there is little co-variability with the African sector, and the American sector exhibits an out of phase behavior. An expanded Hadley circulation in the Southern Hemisphere (both hemispherically and in the Asia-Pacific sector) is associated with La Niña conditions and a poleward expansion of the tropical wet zone in the Asia-Pacific sector. While La Niña also promotes expansion in the American and African sectors during austral winter, these tropical conditions tend to promote contraction in the two sectors during austral summer as a result of compensating convergence over the Americas and Africa sectors: a process driven by variations in the Walker circulation and Rossby wave trains emanating from the tropical Indian Ocean.
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NASA Astrophysics Data System (ADS)
Hu, Shujuan; Cheng, Jianbo; Xu, Ming; Chou, Jifan
2018-04-01
The three-pattern decomposition of global atmospheric circulation (TPDGAC) partitions three-dimensional (3D) atmospheric circulation into horizontal, meridional and zonal components to study the 3D structures of global atmospheric circulation. This paper incorporates the three-pattern decomposition model (TPDM) into primitive equations of atmospheric dynamics and establishes a new set of dynamical equations of the horizontal, meridional and zonal circulations in which the operator properties are studied and energy conservation laws are preserved, as in the primitive equations. The physical significance of the newly established equations is demonstrated. Our findings reveal that the new equations are essentially the 3D vorticity equations of atmosphere and that the time evolution rules of the horizontal, meridional and zonal circulations can be described from the perspective of 3D vorticity evolution. The new set of dynamical equations includes decomposed expressions that can be used to explore the source terms of large-scale atmospheric circulation variations. A simplified model is presented to demonstrate the potential applications of the new equations for studying the dynamics of the Rossby, Hadley and Walker circulations. The model shows that the horizontal air temperature anomaly gradient (ATAG) induces changes in meridional and zonal circulations and promotes the baroclinic evolution of the horizontal circulation. The simplified model also indicates that the absolute vorticity of the horizontal circulation is not conserved, and its changes can be described by changes in the vertical vorticities of the meridional and zonal circulations. Moreover, the thermodynamic equation shows that the induced meridional and zonal circulations and advection transport by the horizontal circulation in turn cause a redistribution of the air temperature. The simplified model reveals the fundamental rules between the evolution of the air temperature and the horizontal, meridional
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Hadley cell dynamics of a cold and virtually dry Snowball Earth atmosphere
NASA Astrophysics Data System (ADS)
Voigt, Aiko; Held, Isaac; Marotzke, Jochem
2010-05-01
We use the full-physics atmospheric general circulation model ECHAM5 to investigate a cold and virtually dry Snowball Earth atmosphere that results from specifying sea ice as the surface boundary condition everywhere, corresponding to a frozen aquaplanet, while keeping total solar irradiance at its present-day value of 1365 Wm-2. The aim of this study is the investigation of the zonal-mean circulation of a Snowball Earth atmosphere, which, due to missing moisture, might constitute an ideal though yet unexplored testbed for theories of atmospheric dynamics. To ease comparison with theories, incoming solar insolation follows permanent equinox conditions with disabled diurnal cycle. The meridional circulation consists of a thermally direct cell extending from the equator to 45 N/S with ascent in the equatorial region, and a weak thermally indirect cell with descent between 45 and 65 N/S and ascent in the polar region. The former cell corresponds to the present-day Earth's Hadley cell, while the latter can be viewed as an eddy-driven Ferrell cell; the present-day Earth's direct polar cell is missing. The Hadley cell itself is subdivided into a vigorous cell confined to the troposphere and a weak deep cell reaching well into the stratosphere. The dynamics of the vigorous Snowball Earth Hadley cell differ substantially from the dynamics of the present-day Hadley cell. The zonal momentum balance shows that in the poleward branch of the vigorous Hadley cell, mean flow meridional advection of absolute vorticity is not only balanced by eddy momentum flux convergence but also by vertical diffusion. Inside the poleward branch, eddies are more important in the upper part and vertical diffusion is more important in the lower part. Vertical diffusion also contributes to the meridional momentum balance as it decelerates the vigorous Hadley cell by downgradient momentum mixing between its poleward and equatorward branch. Zonal winds, therefore, are not in thermal wind balance in
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Linking the South Atlantic Meridional Overturning Circulation and the Global Monsoons
NASA Astrophysics Data System (ADS)
Lopez, H.; Dong, S.; Goni, G. J.; Lee, S. K.
2016-02-01
This study tested the hypothesis whether low frequency decadal variability of the South Atlantic meridional heat transport (SAMHT) influences decadal variability of the global monsoons. A multi-century run from a state-of-the-art coupled general circulation model is used as basis for the analysis. Our findings indicate that multi-decadal variability of the South Atlantic Ocean plays a key role in modulating atmospheric circulation via interhemispheric changes in Atlantic Ocean heat content. Weaker SAMHT produces anomalous ocean heat divergence over the South Atlantic resulting in negative ocean heat content anomaly about 15 years later. This, in turn, forces a thermally direct anomalous interhemispheric Hadley circulation in the atmosphere, transporting heat from the northern hemisphere (NH) to the southern hemisphere (SH) and moisture from the SH to the NH, thereby intensify (weaken) summer (winter) monsoon in the NH and winter (summer) monsoon in the SH. Results also show that anomalous atmospheric eddies, both transient and stationary, transport heat northward in both hemispheres producing eddy heat flux convergence (divergence) in the NH (SH) around 15-30°, reinforcing the anomalous Hadley circulation. Overall, SAMHT decadal variability leads its atmospheric response by about 15 years, suggesting that the South Atlantic is a potential predictor of global climate variability.
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TRANSPORT BY MERIDIONAL CIRCULATIONS IN SOLAR-TYPE STARS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wood, T. S.; Brummell, N. H., E-mail: tsw25@soe.ucsc.edu
2012-08-20
Transport by meridional flows has significant consequences for stellar evolution, but is difficult to capture in global-scale numerical simulations because of the wide range of timescales involved. Stellar evolution models therefore usually adopt parameterizations for such transport based on idealized laminar or mean-field models. Unfortunately, recent attempts to model this transport in global simulations have produced results that are not consistent with any of these idealized models. In an effort to explain the discrepancies between global simulations and idealized models, here we use three-dimensional local Cartesian simulations of compressible convection to study the efficiency of transport by meridional flows belowmore » a convection zone in several parameter regimes of relevance to the Sun and solar-type stars. In these local simulations we are able to establish the correct ordering of dynamical timescales, although the separation of the timescales remains unrealistic. We find that, even though the generation of internal waves by convective overshoot produces a high degree of time dependence in the meridional flow field, the mean flow has the qualitative behavior predicted by laminar, 'balanced' models. In particular, we observe a progressive deepening, or 'burrowing', of the mean circulation if the local Eddington-Sweet timescale is shorter than the viscous diffusion timescale. Such burrowing is a robust prediction of laminar models in this parameter regime, but has never been observed in any previous numerical simulation. We argue that previous simulations therefore underestimate the transport by meridional flows.« less
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Trends and variability in the Hadley circulation over the Last Millennium from the proxy record
NASA Astrophysics Data System (ADS)
Horlick, K. A.; Noone, D.; Hakim, G. J.; Tardif, R.; Anderson, D. M.; Perkins, W. A.; Erb, M. P.; Steig, E. J.
2017-12-01
The Hadley circulation (HC) is the dominant atmospheric overturning circulation controlling variability in precipitation distribution in the tropics and subtropics, affecting agricultural production and water resource allocation, among other human civilizational dependencies. A lack of pre-instrumental data-model synthesis has been cited as the barrier to diagnostic analyses of the variability in width, position, and intensity of the HC and its response to anthropogenic forcing. We analyze the HC, and its rising limb associated with the Intertropical Convergence Zone (ITCZ), over the past 1000 years using the Last Millennium Reanalysis (LMR) (Hakim et al. 2016). The LMR systematically blends the dynamical constraints of climate models with a proxy network of coral, tree ring, and ice core records. It allows for a spatiotemporal analysis with robust uncertainty measures. A three dimensional analysis of LMR wind fields shows an centennial-scale circulatory trend over the last 200 years resembling that which might be expected from an ENSO and PDO-like structure. An observed aridification of both the central equatorial Pacific and the southwest United States, a strengthening of the east-west sea surface temperature and sea level pressure gradient in the equatorial Pacific, and a strengthening of the Walker overturning circulation suggest a more "La Niña-like" mean state. This is compared to our statistical description of the centennial-scale mean circulation and variability of the previous millennia. Similarly, precipitation and relative humidity trends suggest expansion and asymmetric meridional movement of the Hadley circulation as a result of asymmetric shifts in mean ITCZ position and intensity. These observations are then compared to free running model simulations, other instrumental reanalysis products, and late-Holocene aerosol, solar, and greenhouse forcings. This LMR reconstruction improves upon previous work by enabling a proxy-consistent, quantitative
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A Robust Response of the Hadley Circulation to Global Warming
NASA Technical Reports Server (NTRS)
Lau, William K M.; Kim, Kyu-Myong
2014-01-01
Tropical rainfall is expected to increase in a warmer climate. Yet, recent studies have inferred that the Hadley Circulation (HC), which is primarily driven by latent heating from tropical rainfall, is weakened under global warming. Here, we show evidence of a robust intensification of the HC from analyses of 33 CMIP5 model projections under a scenario of 1 per year CO2 emission increase. The intensification is manifested in a deep-tropics squeeze, characterized by a pronounced increase in the zonal mean ascending motion in the mid and upper troposphere, a deepening and narrowing of the convective zone and enhanced rainfall in the deep tropics. These changes occur in conjunction with a rise in the region of maximum outflow of the HC, with accelerated meridional mass outflow in the uppermost branch of the HC away from the equator, coupled to a weakened inflow in the return branches of the HC in the lower troposphere.
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NASA Astrophysics Data System (ADS)
Sun, Bo
2018-03-01
This study investigates the variations in the tropical ascending branches (TABs) of Hadley circulations (HCs) during past decades, using a variety of reanalysis datasets. The northern tropical ascending branch (NTAB) and the southern tropical ascending branch (STAB), which are defined as the ascending branches of the Northern Hemisphere HC and Southern Hemisphere HC, respectively, are identified and analyzed regarding their trends and variability. The reanalysis datasets consistently show a persistent increase in STAB during past decades, whereas they show less consistency in NTAB regarding its decadalto multidecadal variability, which generally features a decreasing trend. These asymmetric trends in STAB and NTAB are attributed to asymmetric trends in the tropical SSTs. The relationship between STAB/NTAB and tropical SSTs is further examined regarding their interannual and decadal- to multidecadal variability. On the interannual time scale, the STAB and NTAB are essentially modulated by the eastern-Pacific type of ENSO, with a strengthened (weakened) STAB (NTAB) under an El Niño condition. On the decadal- to multidecadal time scale, the variability of STAB and NTAB is closely related to the southern tropical SSTs and the meridional asymmetry of global tropical SSTs, respectively. The tropical eastern Pacific SSTs (southern tropical SSTs) dominate the tropical SST-NTAB/STAB relationship on the interannual (decadal- to multidecadal) scale, whereas the NTAB is a passive factor in this relationship. Moreover, a cross-hemispheric relationship between the NTAB/STAB and the HC upper-level meridional winds is revealed.
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The Aqua-planet Experiment (APE): Response to Changed Meridional SST Profile
NASA Technical Reports Server (NTRS)
Williamson, David L.; Blackburn, Michael; Nakajima, Kensuke; Ohfuchi, Wataru; Takahashi, Yoshiyuki O.; Hayashi, Yoshi-Yuki; Nakamura, Hisashi; Ishiwatari, Masaki; Mcgregor, John L.; Borth, Hartmut;
2013-01-01
This paper explores the sensitivity of Atmospheric General Circulation Model (AGCM) simulations to changes in the meridional distribution of sea surface temperature (SST). The simulations are for an aqua-planet, a water covered Earth with no land, orography or sea- ice and with specified zonally symmetric SST. Simulations from 14 AGCMs developed for Numerical Weather Prediction and climate applications are compared. Four experiments are performed to study the sensitivity to the meridional SST profile. These profiles range from one in which the SST gradient continues to the equator to one which is flat approaching the equator, all with the same maximum SST at the equator. The zonal mean circulation of all models shows strong sensitivity to latitudinal distribution of SST. The Hadley circulation weakens and shifts poleward as the SST profile flattens in the tropics. One question of interest is the formation of a double versus a single ITCZ. There is a large variation between models of the strength of the ITCZ and where in the SST experiment sequence they transition from a single to double ITCZ. The SST profiles are defined such that as the equatorial SST gradient flattens, the maximum gradient increases and moves poleward. This leads to a weakening of the mid-latitude jet accompanied by a poleward shift of the jet core. Also considered are tropical wave activity and tropical precipitation frequency distributions. The details of each vary greatly between models, both with a given SST and in the response to the change in SST. One additional experiment is included to examine the sensitivity to an off-equatorial SST maximum. The upward branch of the Hadley circulation follows the SST maximum off the equator. The models that form a single precipitation maximum when the maximum SST is on the equator shift the precipitation maximum off equator and keep it centered over the SST maximum. Those that form a double with minimum on the equatorial maximum SST shift the double
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NASA Astrophysics Data System (ADS)
Zhou, Botao; Wang, Zunya; Shi, Ying
2017-11-01
This article revealed that strengthening of winter Hadley circulation in the context of climate change may partially contribute to interdecadal increasing of snowfall intensity over northeastern China in recent decades. This hypothesis is well supported by the process-based linkage between Hadley circulation and atmospheric circulations over the Asian-Pacific region on the interdecadal time scale. The strengthening of winter Hadley circulation corresponds to a weakening of the Siberian high, an eastward shifting of the Aleutian low, a reduction of the East Asian trough, and anomalous southwesterly prevailing over northeastern China. These atmospheric situations weaken the East Asian winter monsoon and lead to an increase of air temperature over northeastern China. Increased local evaporation due to the increase of air temperature, concurrent with more water vapor transported from the Pacific Ocean, can significantly enhance atmospheric water vapor content in the target region. Meanwhile, the ascending of airflows is also strengthened over northeastern China. All of these provide favorable interdecadal backgrounds for the occurrence of intense snowfalls, and thus, snowfall intensity is intensified over northeastern China after the 1980s. Further analysis suggests that the circum-Pacific-like teleconnection pattern may play an important role in connecting Hadley circulation strengthening signal and atmospheric circulation anomalies favoring interdecadal intensification of snowfalls over northeastern China.
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Meridional circulation and CNO anomalies in red giant stars
NASA Technical Reports Server (NTRS)
Sweigart, A. V.; Mengel, J. G.
1979-01-01
The possibility is investigated that meridional circulation driven by internal rotation might lead to the mixing of CNO-processed material from the vicinity of the hydrogen shell into the envelope of a red giant star. This theory of meridional mixing is found to be generally consistent with available data and to be capable of explaining a number of observational results without invoking a radical departure from the standard physics of stellar interiors. It is suggested that meridional circulation must be a normal characteristic of a rotating star and that meridional mixing provides a reasonable framework for understanding many of the CNO anomalies exhibited by weak-G-band and CN-strong stars as well as the low C-12/C-13 ratios measured among field red giants.
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Temperature influence on Hadley cell dynamics
NASA Astrophysics Data System (ADS)
Molnos, S.
2016-12-01
Over the last decades, satellite observations indicate that the Hadley cells have widened and possibly also intensified [1,2]. This might lead to a shift of fertile habitats with implications for biodiversity and agriculture [3]. Causes for these observed changes are uncertain and the possible role of global warming is debated. To better understand the key dynamical forcings involved, we investigate Hadley cell dynamics with an idealized atmosphere model [4,5] and compare its results with reanalysis data. This statistical-dynamical atmosphere model (SDAM) is based on time-averaged equations, and therefore much faster than the more widely used Atmospheric general circulations models (AGCMs).With SDAMS it is possible to perform climate simulations up to multi-millennia timescales. Here, we employ it to study the dominant processes related to the observed strengthening and widening of the Hadley cell using a very large ensemble sensitivity experiment testing the following possible underlying drivers: meridional temperature gradient, temperature anomaly and global mean temperature GMT. Interestingly, whereas the width of the Hadley cell depends nonlinearly on the temperature gradient, while its Intensification is nearly independent on temperature gradient. In contrast, a larger GMT always leads to an intensified Hadley cell. References: [1] Mitas, C. M.: Has the Hadley cell been strengthening in recent decades?, Geophys. Res. Lett., 32(3), 2005. [2] Seidel, D., Fu, Q., Randel, W. and Reichler, T.: Widening of the tropical belt in a changing climate, Nat. Geosci., 1(1), 21-248, 2008. [3] Heffernan, O.: The Mystery of Expanding Tropics, Nature, 530, 20-22, 2016. [4] Coumou, D., Petoukhov, V. and Eliseev, A. V.: Three-dimensional parameterizations of the synoptic scale kinetic energy and momentum flux in the Earth's atmosphere, Nonlinear Process. Geophys., 18(6), 807-827, 2011. [5] Eliseev, A. V., Coumou, D., Chernokulsky, A. V., Petoukhov, V. and Petri, S.: Scheme for
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The Sun's Meridional Circulation - not so Deep
NASA Astrophysics Data System (ADS)
Hathaway, David H.
2011-05-01
The Sun's global meridional circulation is evident as a slow poleward flow at its surface. This flow is observed to carry magnetic elements poleward - producing the Sun's polar magnetic fields as a key part of the 11-year sunspot cycle. Flux Transport Dynamo models for the sunspot cycle are predicated on the belief that this surface flow is part of a circulation which sinks inward at the poles and returns to the equator in the bottom half of the convection zone - at depths between 100 and 200 Mm. Here I use the advection of the supergranule cells by the meridional flow to map the flow velocity in latitude and depth. My measurements show that the equatorward return flow begins at a depth of only 35 Mm - the base of the Sun's surface shear layer. This is the first clear (10 sigma) detection of the meridional return flow. While the shallow depth of the return flow indicates a false foundation for Flux Transport Dynamo models it helps to explain the different meridional flow rates seen for different features and provides a mechanism for selecting the characteristic size of supergranules.
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The Pattern and Dynamics of the Meridional Overturning Circulation in the Upper Ocean
2008-09-01
Atlantic . Figure 4a shows that the center of meridional overturning circulation occurs at a level of about one kilometer. Circulation is weak at...maintenance of the meridional overturning circulation in the Atlantic Ocean. 5. Global Simulation The most exciting experiment would be to fully model the...mechanisms responsible for the strength and maintenance of the meridional overturning circulation in the Atlantic Ocean are not
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The Effect of Changes in the Hadley Circulation on Oceanic Oxygen Minimum Zones
NASA Astrophysics Data System (ADS)
De La Cruz Tello, G.; Ummenhofer, C.; Karnauskas, K. B.
2014-12-01
Recent research argued that the Hadley circulation (HC) is composed of three regional cells located at the eastern edges of the ocean basins, rather than a single, globe-encircling cell as the classic textbook view suggests. The HC is expected to expand in concert with global warming, which means that the dry regions beneath the descending branches of the HC are projected to become even drier. Changes in the HC are thus likely to impact freshwater resources on land, as well as the underlying ocean in the subtropics. The eastern edges of ocean basins are characterized by oxygen minimum zones (OMZs), which are regions of very low oxygen concentrations. They affect marine life, as many animals cannot handle the stress caused by such conditions. OMZs have expanded and shoaled in the last 50 years, and they are expected to continue to do so as global climate changes. The purpose of this research is to find links between the projected changes in OMZs and the HC. The National Center for Atmospheric Research (NCAR) Community Earth System Model 1.0 (CESM), Representative Concentration Pathways 8.5 (RCP8.5) experiment with a resolution of 0.9 by 1.25 degrees, which formed part of the Coupled Model Intercomparison Project phase 5 (CMIP5), was used for this analysis. Meridional winds and oceanic oxygen concentrations were the primarily analyzed variables. Latitudinal ocean oxygen slices demonstrate the OMZs' location along the eastern edges of ocean basins. Meridional winds overlayed with oxygen concentration are consistent with the idea that surface meridional 'Hadleywise flow' (i.e., towards the equator at the surface and towards the poles aloft) and OMZs are linked through changes in upwelling. Area-averaged time series spanning the historical period through to the end of the 21st century with RCP8.5 confirm that future changes in OMZs and the HC may be connected. Further research could lead to improved understanding of the factors that drive changes in both, which could
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Hadley circulation strength and width in a wide range of simulated climates
NASA Astrophysics Data System (ADS)
D'Agostino, R.; Adam, O.; Lionello, P.; Schneider, T.
2016-12-01
Understanding how the Hadley circulation (HC) responds to global warming is crucial because it determines climatic features such as the seasonal migration of the ITCZ, the extent of subtropical arid regions and the strength of the monsoons. Here we analyse changes in the HC strength and width in the set of PMIP3 and CMIP5 simulations, spanning a wide range of climate conditions from Last Glacial Maximum to future RCP projections. The large climate change signal emerging from comparing paleoclimate simulations to future scenarios offers the possibility to analyse the corresponding HC change and to investigate its response to large variations of the factors controlling it. The results confirm that the HC generally expands and weakens as the global mean temperature increases, consistent with results from other studies. Furthermore, we find an asymmetric HC response between the northern and southern hemisphere in the rate at which the HC edges shift poleward with global warming. The mid-latitude static stability and meridional temperature gradients affect the HC edges to different degrees in the two hemispheres. In the southern hemisphere the increase in the mid-latitude static stability is associated with a poleward shift of the southern HC edge, while in the northern hemisphere, the reduction in the meridional temperature gradient plays the dominant role in the poleward shift of the northern HC edge. The two hemispheres also exhibit very different changes of HC strength. The HC weakening with global warming occurs primarily in the northern hemisphere, while there is no change, or even a slighter weakening in the southern hemisphere. The HC changes also have pronounced seasonal signatures. The maximum poleward shift of the northern HC edge occurs one month later (from August to September) in future global warming scenarios than when comparing pre-industrial simulations with the Last Glacial Maximum.
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Hadley circulation extent and strength in a wide range of simulated climates
NASA Astrophysics Data System (ADS)
D'Agostino, Roberta; Adam, Ori; Lionello, Piero; Schneider, Tapio
2017-04-01
Understanding the Hadley circulation (HC) dynamics is crucial because its changes affect the seasonal migration of the ITCZ, the extent of subtropical arid regions and the strength of the monsoons. Despite decades of study, the factors controlling its strength and extent have remained unclear. Here we analyse how HC strength and extent change over a wide range of climate conditions from the Last Glacial Maximum to future projections. The large climate change between paleoclimate simulations and future scenarios offers the chance to analyse robust HC changes and their link to large-scale factors. The HC shrinks and strengthens in the coldest simulation relative to the warmest. A progressive poleward shift of its edges is evident as the climate warms (at a rate of 0.35°lat./K in each hemisphere). The HC extent and strength both depend on the isentropic slope, which in turn is related to the meridional temperature gradient, subtropical static stability and tropopause height. In multiple robust regression analysis using these as predictors, we find that the tropical tropopause height does not add relevant information to the model beyond surface temperature. Therefore, primarily the static stability and secondarily the meridional temperature contrast together account for the bulk of the almost the total HC variance. However, the regressions leave some of the northern HC edge and southern HC strength variance unexplained. The effectiveness of this analysis is limited by the correlation among the predictors and their relationship with mean temperature. In fact, for all simulations, the tropical temperature explains well the variations of HC except its southern hemisphere intensity. Hence, it can be used as the sole predictor to diagnose the HC response to greenhouse-induced global warming. How to account for the evolution of the southern HC strength remains unclear, because of the large inter-model spread in this quantity.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhao Junwei; Bogart, R. S.; Kosovichev, A. G.
2013-09-10
Meridional flow in the solar interior plays an important role in redistributing angular momentum and transporting magnetic flux inside the Sun. Although it has long been recognized that the meridional flow is predominantly poleward at the Sun's surface and in its shallow interior, the location of the equatorward return flow and the meridional flow profile in the deeper interior remain unclear. Using the first 2 yr of continuous helioseismology observations from the Solar Dynamics Observatory/Helioseismic Magnetic Imager, we analyze travel times of acoustic waves that propagate through different depths of the solar interior carrying information about the solar interior dynamics.more » After removing a systematic center-to-limb effect in the helioseismic measurements and performing inversions for flow speed, we find that the poleward meridional flow of a speed of 15 m s{sup -1} extends in depth from the photosphere to about 0.91 R{sub Sun }. An equatorward flow of a speed of 10 m s{sup -1} is found between 0.82 and 0.91 R{sub Sun} in the middle of the convection zone. Our analysis also shows evidence of that the meridional flow turns poleward again below 0.82 R{sub Sun }, indicating an existence of a second meridional circulation cell below the shallower one. This double-cell meridional circulation profile with an equatorward flow shallower than previously thought suggests a rethinking of how magnetic field is generated and redistributed inside the Sun.« less
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NASA Technical Reports Server (NTRS)
Lau, William K. M.; Kim, K. M.
2015-01-01
In this paper, we investigate changes in the Hadley Circulation (HC) and their connections to increased global dryness under CO2 warming from CMIP-5 model projections. We find a strengthening of the ascending branch of the HC manifested in a deep-tropics squeeze (DTS), i.e., a deepening and narrowing of the convective zone, increased high clouds, and a rise of the level of maximum meridional mass outflow in the upper troposphere (200-100 hectopascals) of the deep tropics. The DTS induces atmospheric moisture divergence, reduces tropospheric relative humidity in the tropics and subtropics, in conjunction with a widening of the subsiding branches of the HC, resulting in increased frequency of dry events in preferred geographic locations worldwide. Among water cycle parameters examined, global dryness has the highest signal-to-noise ratio. Our results provide scientific bases for inferring that the observed tend of prolonged droughts in recent decades is likely attributable to greenhouse warming.
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Sensitivity of the Meridional Overturning Circulation to the Pattern of the Surface Density Flux
2010-09-01
Atlantic alone, the Atlantic Meridional Overturning Circulation (AMOC) transports over 1015 W of heat (Ganachaud and Wunsch 2000) poleward...Phys. Oceanogr., 17, 970–985. Bryden, H. L., H. Longworth, and S. Cunningham, 2005: Slowing of the Atlantic meridional overturning circulation at 25...Rahmstorf, 2007: On the driving processes of the Atlantic meridional overturning circulation . Rev. Geophys., 45, RG2001, doi:
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McManus, J F; Francois, R; Gherardi, J-M; Keigwin, L D; Brown-Leger, S
2004-04-22
The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning. Here we report measurements of 231Pa/230Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the 231Pa/230Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes.
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A theoretical model of the variation of the meridional circulation with the solar cycle
NASA Astrophysics Data System (ADS)
Hazra, Gopal; Choudhuri, Arnab Rai
2017-12-01
Observations of the meridional circulation of the Sun, which plays a key role in the operation of the solar dynamo, indicate that its speed varies with the solar cycle, becoming faster during the solar minima and slower during the solar maxima. To explain this variation of the meridional circulation with the solar cycle, we construct a theoretical model by coupling the equation of the meridional circulation (the ϕ component of the vorticity equation within the solar convection zone) with the equations of the flux transport dynamo model. We consider the back reaction due to the Lorentz force of the dynamo-generated magnetic fields and study the perturbations produced in the meridional circulation due to it. This enables us to model the variations of the meridional circulation without developing a full theory of the meridional circulation itself. We obtain results which reproduce the observational data of solar cycle variations of the meridional circulation reasonably well. We get the best results on assuming the turbulent viscosity acting on the velocity field to be comparable to the magnetic diffusivity (i.e. on assuming the magnetic Prandtl number to be close to unity). We have to assume an appropriate bottom boundary condition to ensure that the Lorentz force cannot drive a flow in the subadiabatic layers below the bottom of the tachocline. Our results are sensitive to this bottom boundary condition. We also suggest a hypothesis on how the observed inward flow towards the active regions may be produced.
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The momentum constraints on the shallow meridional circulation associated with the marine ITCZ
NASA Astrophysics Data System (ADS)
Dixit, Vishal; Srinivasan, J.
2017-12-01
Recent studies have shown that the shallow meridional circulation (SMC) coexists with the deep circulation in the marine ITCZ. The SMC has been assumed to be forced by strong meridional gradients of Sea Surface Temperature (SST) which affect the atmosphere under hydrostatic balance. In this paper, we present a new viewpoint that the shallow meridional circulation is a part of circulation that forms when the marine ITCZ is located away from the equator. To support this view, we have used reanalysis data over east Pacific ocean to show that the shallow meridional circulation is absent when the ITCZ is located near the equator while it is strong to the south of the ITCZ when the ITCZ is located away from the equator. To further support this view, we have conducted idealized aquaplanet experiments by shifting SST maximum polewards to simulate the observed contrast in the meridional circulation associated with near equatorial and off-equatorial ITCZ. The detailed momentum budget of the flow above the boundary layer shows that, to the south of an off-equatorial ITCZ, the dominant balance between the Coriolis force and the advection of relative vorticity by the mean flow leads to cancellation of the planetary rotational effects. As a result, the net rotational effects experienced by the diverging flow above the boundary layer are negligible and a shallow meridional flow along the pressure gradients is generated. This dominant balance does not occur in the aquaplanet GCM when the ITCZ forms near the equator.
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NASA Technical Reports Server (NTRS)
Li, Feng; Stolarski, Richard S.; Pawson, Steven; Newman, Paul A.; Waugh, Darryn
2010-01-01
Changes in the width of the upwelling branch of the Brewer-Dobson circulation and Hadley cell in the 21st Century are investigated using simulations from a coupled chemistry-climate model. In these model simulations the tropical upwelling region narrows in the troposphere and lower stratosphere. The narrowing of the Brewer-Dobson circulation is caused by an equatorward shift of Rossby wave critical latitudes and Eliassen-Palm flux convergence in the subtropical lower stratosphere. In the troposphere, the model projects an expansion of the Hadley cell's poleward boundary, but a narrowing of the Hadley rising branch. Model results suggest that the narrowing of the Hadley cell ascent is also eddy-driven.
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Lau, William K M; Kim, Kyu-Myong
2015-03-24
In this paper, we investigate changes in the Hadley Circulation (HC) and their connections to increased global dryness (suppressed rainfall and reduced tropospheric relative humidity) under CO2 warming from Coupled Model Intercomparison Project Phase 5 (CMIP5) model projections. We find a strengthening of the HC manifested in a "deep-tropics squeeze" (DTS), i.e., a deepening and narrowing of the convective zone, enhanced ascent, increased high clouds, suppressed low clouds, and a rise of the level of maximum meridional mass outflow in the upper troposphere (200-100 hPa) of the deep tropics. The DTS induces atmospheric moisture divergence and reduces tropospheric relative humidity in the tropics and subtropics, in conjunction with a widening of the subsiding branches of the HC, resulting in increased frequency of dry events in preferred geographic locations worldwide. Among various water-cycle parameters examined, global dryness is found to have the highest signal-to-noise ratio. Our results provide a physical basis for inferring that greenhouse warming is likely to contribute to the observed prolonged droughts worldwide in recent decades.
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NASA Astrophysics Data System (ADS)
Huang, Ruping; Chen, Shangfeng; Chen, Wen; Hu, Peng
2018-01-01
This study investigates interannual variability of boreal winter regional Hadley circulation over western Pacific (WPHC) and its climatic impacts. A WPHC intensity index (WPHCI) is defined as the vertical shear of the divergent meridional winds. It shows that WPHCI correlates well with the El Niño-Southern Oscillation (ENSO). To investigate roles of the ENSO-unrelated part of WPHCI (WPHCIres), variables that are linearly related to the Niño-3 index have been removed. It reveals that meridional sea surface temperature gradient over the western Pacific plays an essential role in modulating the WPHCIres. The climatic impacts of WPHCIres are further investigated. Below-normal (above-normal) precipitation appears over south China (North Australia) when WPHCIres is stronger. This is due to the marked convergence (divergence) anomalies at the upper troposphere, divergence (convergence) at the lower troposphere, and the accompanied downward (upward) motion over south China (North Australia), which suppresses (enhances) precipitation there. In addition, a pronounced increase in surface air temperature (SAT) appears over south and central China when WPHCIres is stronger. A temperature diagnostic analysis suggests that the increase in SAT tendency over central China is primarily due to the warm zonal temperature advection and subsidence-induced adiabatic heating. In addition, the increase in SAT tendency over south China is primarily contributed by the warm meridional temperature advection. Further analysis shows that the correlation of WPHCIres with the East Asian winter monsoon (EAWM) is weak. Thus, this study may provide additional sources besides EAWM and ENSO to improve understanding of the Asia-Australia climate variability.
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NASA Astrophysics Data System (ADS)
Belucz, B.; Dikpati, M.; Forgacs-Dajka, E.
2014-12-01
Babcock-Leighton type solar dynamo models with single cell meridional circulation are successful in reproducing many solarcycle features, and recently such a model was applied for solarcycle 24 amplitude prediction. It seems that cycle 24 amplitudeforecast may not be validated. One of the reasons is the assumption of a single cell meridional circulation. Recent observations andtheoretical models of meridional circulation do not indicate a single-celledflow pattern. So it is nessecary to examine the role of complexmulti-cellular circulation patterns in a Babcock-Leighton solar dynamo model in the advection and diffusion dominated regimes.By simulating a Babcock-Leighton solar dynamo model with multi-cellularflow, we show that the presence of a weak, second, high-latitudereverse cell speeds up the cycle and slighty enhances the poleward branch in the butterfly diagram, whereas the presence of a second cellin depth reverses the tilt of the butterfly wing and leads to ananti-solar type feature. If, instead, the butterfly diagram isconstructed from the middle of the convection zone in that case, a solar-like pattern can be retrieved. All the above cases behavequalitatively similar in advection and diffusion-dominated regimes.However, our dynamo with a meridional circulation containing fourcells in latitude behaves distinctly different in the two regimes, producing a solar-like butterfly diagram with fast cycles indiffusion-dominated regime, and a complex branches in the butterflydiagram in the advection-dominated regime. Another interestingfinding from our studies is that a four-celled flow pattern containing two in radius and two in latitude always producesquadrupolar parity as the relaxed solution.
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NASA Astrophysics Data System (ADS)
McCarthy, G. D.; Menary, M. B.; Mecking, J. V.; Moat, B. I.; Johns, W. E.; Andrews, M. B.; Rayner, D.; Smeed, D. A.
2017-03-01
The Atlantic Meridional Overturning Circulation (AMOC) is a key process in the global redistribution of heat. The AMOC is defined as the maximum of the overturning stream function, which typically occurs near 30°N in the North Atlantic. The RAPID mooring array has provided full-depth, basinwide, continuous estimates of this quantity since 2004. Motivated by both the need to deliver near real-time data and optimization of the array to reduce costs, we consider alternative configurations of the mooring array. Results suggest that the variability observed since 2004 could be reproduced by a single tall mooring on the western boundary and a mooring to 1500 m on the eastern boundary. We consider the potential future evolution of the AMOC in two generations of the Hadley Centre climate models and a suite of additional CMIP5 models. The modeling studies show that deep, basinwide measurements are essential to capture correctly the future decline of the AMOC. We conclude that, while a reduced array could be useful for estimates of the AMOC on subseasonal to decadal time scales as part of a near real-time data delivery system, extreme caution must be applied to avoid the potential misinterpretation or absence of a climate time scale AMOC decline that is a key motivation for the maintenance of these observations.
type="synopsis"> type</span>="main">Plain Language SummaryThe Atlantic Overturning <span class="hlt">Circulation</span> is a system of ocean currents that carries heat northwards in the Atlantic. This heat is crucial to maintaining the mild climate of northwest Europe. The Overturning <span class="hlt">Circulation</span> is predicted to slow in future in response to man-made climate change. The RAPID program is designed to measure the Overturning <span class="hlt">Circulation</span> using a number of fixed point observations spanning the Atlantic between the Canary Islands and the Bahamas. We look at whether we could reduce the number of these fixed point observations to continue to get accurate estimates of the overturning</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070013776&hterms=climate+change+evidence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dclimate%2Bchange%2Bevidence','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070013776&hterms=climate+change+evidence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dclimate%2Bchange%2Bevidence"><span>Evidence for Interannual to Decadal Variations in <span class="hlt">Hadley</span> and Walker <span class="hlt">Circulations</span> and Links to Water and Energy Fluxes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robertson, Franklin; Bosilovich, Michael; Miller, Timothy</p> <p>2007-01-01</p> <p>Mass and energy transports associated with the <span class="hlt">Hadley</span> and Walker <span class="hlt">circulations</span> are important components of the earth s climate system and are strongly linked to hydrologic processes. Interannual to decadal variation in these flows likely signify a combination of natural climate noise as well as a response to anthropgenic forcing. There remains considerable uncertainty in quantifying variations in these flows. Evidence in the surface pressure record supports a weakening of the Walker <span class="hlt">circulation</span> over the Pacific in recent decades. Conversely the NCEP / NCAR and ERA 40 reanalyses indicate that the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> has increased in strength over the last two decades, though these analyses depict significantly different mass <span class="hlt">circulation</span> changes. Interestingly, the NCEP - II / DOE reanalysis contains essentially no <span class="hlt">Hadley</span> <span class="hlt">circulation</span> changes. Most climate model integrations anticipate a weakening of both tropical <span class="hlt">circulations</span> associated with stronger static stability. Clearly there is much uncertainty not only with the mass transports, but also how they are linked to water and energy balance of the planet through variations in turbulent heat and radiative fluxes and horizontal exports / imports of energy. Here we examine heat and water budget variations from a number of reanalysis products and focus on the linear and nonlinear response of ENSO warm and cold events as opportunities to study budget variations over the past 15-20 years. Our analysis addresses such questions as To what extent do <span class="hlt">Hadley</span> and Walker Cell variations compensate each other on mass and energy transport? Do static stability adjustments appear to constrain fractional precipitation response vs. fractional water vapor response? We appeal to constraints offered by GPCP precipitation, SSWI ocean evaporation estimates, and ISCCP-FD radiative fluxes, and other satellite data sets to interpret and confirm reanalysis-based diagnostics. Using our findings we also attempt to place in context the recent</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JGRD..10918112R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JGRD..10918112R"><span>Detection of the secondary <span class="hlt">meridional</span> <span class="hlt">circulation</span> associated with the quasi-biennial oscillation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ribera, P.; PeñA-Ortiz, C.; Garcia-Herrera, R.; Gallego, D.; Gimeno, L.; HernáNdez, E.</p> <p>2004-09-01</p> <p>The quasi-biennial oscillation (QBO) signal in stratospheric zonal and <span class="hlt">meridional</span> wind, temperature, and geopotential height fields is analyzed based on the use of the National Centers for Environmental Prediction (NCEP) reanalysis (1958-2001). The multitaper method-singular value decomposition (MTM-SVD), a multivariate frequency domain analysis method, is used to detect significant and spatially coherent narrowband oscillations. The QBO is found as the most intense signal in the stratospheric zonal wind. Then, the MTM-SVD method is used to determine the patterns induced by the QBO at every stratospheric level and data field. The secondary <span class="hlt">meridional</span> <span class="hlt">circulation</span> associated with the QBO is identified in the obtained patterns. This <span class="hlt">circulation</span> can be characterized by negative (positive) temperature anomalies associated with adiabatic rising (sinking) motions over zones of easterly (westerly) wind shear and over the subtropics and midlatitudes, while <span class="hlt">meridional</span> convergence and divergence levels are found separated by a level of maximum zonal wind shear. These vertical and <span class="hlt">meridional</span> motions form quasi-symmetric <span class="hlt">circulation</span> cells over both hemispheres, though less intense in the Southern Hemisphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22364172-meridional-circulation-dynamics-from-magnetohydrodynamic-global-simulations-solar-convection','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22364172-meridional-circulation-dynamics-from-magnetohydrodynamic-global-simulations-solar-convection"><span><span class="hlt">MERIDIONAL</span> <span class="hlt">CIRCULATION</span> DYNAMICS FROM 3D MAGNETOHYDRODYNAMIC GLOBAL SIMULATIONS OF SOLAR CONVECTION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Passos, Dário; Charbonneau, Paul; Miesch, Mark, E-mail: dariopassos@ist.utl.pt</p> <p></p> <p>The form of solar <span class="hlt">meridional</span> <span class="hlt">circulation</span> is a very important ingredient for mean field flux transport dynamo models. However, a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work, we use results from three-dimensional global simulations of solar convection to infer the dynamical behavior of the established <span class="hlt">meridional</span> <span class="hlt">circulation</span>. We make a direct comparison between the <span class="hlt">meridional</span> <span class="hlt">circulation</span> that arises in these simulations and the latest observations. Based on our results, we argue that there should be an equatorward flow at the base of the convection zone atmore » mid-latitudes, below the current maximum depth helioseismic measures can probe (0.75 R{sub ⊙}). We also provide physical arguments to justify this behavior. The simulations indicate that the <span class="hlt">meridional</span> <span class="hlt">circulation</span> undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of observation which involve long averaging periods of helioseismic data. Also noteworthy is the fact that these topological changes indicate a rich interaction between magnetic fields and plasma flows, which challenges the ubiquitous kinematic approach used in the vast majority of mean field dynamo simulations.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...800L..18P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...800L..18P"><span><span class="hlt">Meridional</span> <span class="hlt">Circulation</span> Dynamics from 3D Magnetohydrodynamic Global Simulations of Solar Convection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Passos, Dário; Charbonneau, Paul; Miesch, Mark</p> <p>2015-02-01</p> <p>The form of solar <span class="hlt">meridional</span> <span class="hlt">circulation</span> is a very important ingredient for mean field flux transport dynamo models. However, a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work, we use results from three-dimensional global simulations of solar convection to infer the dynamical behavior of the established <span class="hlt">meridional</span> <span class="hlt">circulation</span>. We make a direct comparison between the <span class="hlt">meridional</span> <span class="hlt">circulation</span> that arises in these simulations and the latest observations. Based on our results, we argue that there should be an equatorward flow at the base of the convection zone at mid-latitudes, below the current maximum depth helioseismic measures can probe (0.75 {{R}⊙ }). We also provide physical arguments to justify this behavior. The simulations indicate that the <span class="hlt">meridional</span> <span class="hlt">circulation</span> undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of observation which involve long averaging periods of helioseismic data. Also noteworthy is the fact that these topological changes indicate a rich interaction between magnetic fields and plasma flows, which challenges the ubiquitous kinematic approach used in the vast majority of mean field dynamo simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA537743','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA537743"><span>Salinity Boundary Conditions and the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in Depth and Quasi-Isopycnic Coordinate Global Ocean Models</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2009-06-30</p> <p>Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in Depth and Quasi-Isopycnic Coordinate Global Ocean...2009 4. TITLE AND SUBTITLE Salinity Boundary Conditions and the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in Depth and Quasi-Isopycnic Coordinate... Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) in global simulations performed with the depth coordinate Parallel Ocean Program (POP) ocean</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3621426','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3621426"><span>Surface changes in the North Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during the last millennium</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wanamaker, Alan D.; Butler, Paul G.; Scourse, James D.; Heinemeier, Jan; Eiríksson, Jón; Knudsen, Karen Luise; Richardson, Christopher A.</p> <p>2012-01-01</p> <p>Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> variability, and the significance of decadal-to-centennial scale changes in Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean <span class="hlt">circulation</span> and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector. PMID:22692542</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22692542','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22692542"><span>Surface changes in the North Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during the last millennium.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wanamaker, Alan D; Butler, Paul G; Scourse, James D; Heinemeier, Jan; Eiríksson, Jón; Knudsen, Karen Luise; Richardson, Christopher A</p> <p>2012-06-12</p> <p>Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> variability, and the significance of decadal-to-centennial scale changes in Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean <span class="hlt">circulation</span> and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active"><span>2</span></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_2 --> <div id="page_3" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="41"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017P%26SS..135....1K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017P%26SS..135....1K"><span>Impact of variations of gravitational acceleration on the general <span class="hlt">circulation</span> of the planetary atmosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kilic, Cevahir; Raible, Christoph C.; Stocker, Thomas F.; Kirk, Edilbert</p> <p>2017-01-01</p> <p>Fundamental to the redistribution of energy in a planetary atmosphere is the general <span class="hlt">circulation</span> and its <span class="hlt">meridional</span> structure. We use a general <span class="hlt">circulation</span> model of the atmosphere in an aquaplanet configuration with prescribed sea surface temperature and investigate the influence of the gravitational acceleration g on the structure of the <span class="hlt">circulation</span>. For g =g0 = 9.81 ms-2 , three <span class="hlt">meridional</span> cells exist in each hemisphere. Up to about g /g0 = 1.4 all cells increase in strength. Further increasing this ratio results in a weakening of the thermally indirect cell, such that a two- and finally a one-cell structure of the <span class="hlt">meridional</span> <span class="hlt">circulation</span> develops in each hemisphere. This transition is explained by the primary driver of the thermally direct <span class="hlt">Hadley</span> cell: the diabatic heating at the equator which is proportional to g. The analysis of the energetics of the atmospheric <span class="hlt">circulation</span> based on the Lorenz energy cycle supports this finding. For Earth-like gravitational accelerations transient eddies are primarily responsible for the <span class="hlt">meridional</span> heat flux. For large gravitational accelerations, the direct zonal mean conversion of energy dominates the <span class="hlt">meridional</span> heat flux.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5619637','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5619637"><span>The strength of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> of the stratosphere</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Linz, Marianna; Plumb, R. Alan; Gerber, Edwin P.; Haenel, Florian J.; Stiller, Gabriele; Kinnison, Douglas E.; Ming, Alison; Neu, Jessica L.</p> <p>2017-01-01</p> <p>The distribution of gases such as ozone and water vapour in the stratosphere — which affect surface climate — is influenced by the <span class="hlt">meridional</span> overturning of mass in the stratosphere, the Brewer–Dobson <span class="hlt">circulation</span>. However, observation-based estimates of its global strength are difficult to obtain. Here we present two calculations of the mean strength of the <span class="hlt">meridional</span> overturning of the stratosphere. We analyze satellite data that document the global diabatic <span class="hlt">circulation</span> between 2007– 2011, and compare these to three re-analysis data sets and to simulations with a state-of-the-art chemistry-climate model. Using measurements of sulfur hexafluoride (SF6) and nitrous oxide, we calculate the global mean diabatic overturning mass flux throughout the stratosphere. In the lower stratosphere, these two estimates agree, and at a potential temperature level of 460 K (about 20 km or 60 hPa in tropics), the global <span class="hlt">circulation</span> strength is 6.3–7.6 × 109 kg/s. Higher in the atmosphere, only the SF6-based estimate is available, and it diverges from the re-analysis data and simulations. Interpretation of the SF6 data-based estimate is limited because of a mesospheric sink of SF6; however, the reanalyses also differ substantially from each other. We conclude that the uncertainty in the mean <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> strength at upper levels of the stratosphere amounts to at least 100 %. PMID:28966661</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17412948','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17412948"><span>Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during the Last Glacial Maximum.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lynch-Stieglitz, Jean; Adkins, Jess F; Curry, William B; Dokken, Trond; Hall, Ian R; Herguera, Juan Carlos; Hirschi, Joël J-M; Ivanova, Elena V; Kissel, Catherine; Marchal, Olivier; Marchitto, Thomas M; McCave, I Nicholas; McManus, Jerry F; Mulitza, Stefan; Ninnemann, Ulysses; Peeters, Frank; Yu, Ein-Fen; Zahn, Rainer</p> <p>2007-04-06</p> <p>The <span class="hlt">circulation</span> of the deep Atlantic Ocean during the height of the last ice age appears to have been quite different from today. We review observations implying that Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during the Last Glacial Maximum was neither extremely sluggish nor an enhanced version of present-day <span class="hlt">circulation</span>. The distribution of the decay products of uranium in sediments is consistent with a residence time for deep waters in the Atlantic only slightly greater than today. However, evidence from multiple water-mass tracers supports a different distribution of deep-water properties, including density, which is dynamically linked to <span class="hlt">circulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1429322','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1429322"><span>Active Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (PMOC) during the warm Pliocene</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Burls, Natalie J.; Fedorov, Alexey V.; Sigman, Daniel M.</p> <p></p> <p>An essential element of modern ocean <span class="hlt">circulation</span> and climate is the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning <span class="hlt">circulation</span> is absent in the Pacific, theworld’s largest ocean,where relatively fresh surface waters inhibitNorth Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400–ppmv (parts per million by volume) CO 2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanyingmore » pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redoxsensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced <span class="hlt">meridional</span> sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28924606','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28924606"><span>Active Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (PMOC) during the warm Pliocene.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Burls, Natalie J; Fedorov, Alexey V; Sigman, Daniel M; Jaccard, Samuel L; Tiedemann, Ralf; Haug, Gerald H</p> <p>2017-09-01</p> <p>An essential element of modern ocean <span class="hlt">circulation</span> and climate is the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning <span class="hlt">circulation</span> is absent in the Pacific, the world's largest ocean, where relatively fresh surface waters inhibit North Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400-ppmv (parts per million by volume) CO 2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanying pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redox-sensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced <span class="hlt">meridional</span> sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5597313','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5597313"><span>Active Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (PMOC) during the warm Pliocene</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Burls, Natalie J.; Fedorov, Alexey V.; Sigman, Daniel M.; Jaccard, Samuel L.; Tiedemann, Ralf; Haug, Gerald H.</p> <p>2017-01-01</p> <p>An essential element of modern ocean <span class="hlt">circulation</span> and climate is the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning <span class="hlt">circulation</span> is absent in the Pacific, the world’s largest ocean, where relatively fresh surface waters inhibit North Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400–ppmv (parts per million by volume) CO2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanying pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redox-sensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced <span class="hlt">meridional</span> sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming. PMID:28924606</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1429322-active-pacific-meridional-overturning-circulation-pmoc-during-warm-pliocene','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1429322-active-pacific-meridional-overturning-circulation-pmoc-during-warm-pliocene"><span>Active Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (PMOC) during the warm Pliocene</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Burls, Natalie J.; Fedorov, Alexey V.; Sigman, Daniel M.; ...</p> <p>2017-09-13</p> <p>An essential element of modern ocean <span class="hlt">circulation</span> and climate is the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning <span class="hlt">circulation</span> is absent in the Pacific, theworld’s largest ocean,where relatively fresh surface waters inhibitNorth Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400–ppmv (parts per million by volume) CO 2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanyingmore » pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redoxsensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced <span class="hlt">meridional</span> sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...806..169B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...806..169B"><span>A Babcock-Leighton Solar Dynamo Model with Multi-cellular <span class="hlt">Meridional</span> <span class="hlt">Circulation</span> in Advection- and Diffusion-dominated Regimes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belucz, Bernadett; Dikpati, Mausumi; Forgács-Dajka, Emese</p> <p>2015-06-01</p> <p>Babcock-Leighton <span class="hlt">type</span>-solar dynamo models with single-celled <span class="hlt">meridional</span> <span class="hlt">circulation</span> are successful in reproducing many solar cycle features. Recent observations and theoretical models of <span class="hlt">meridional</span> <span class="hlt">circulation</span> do not indicate a single-celled flow pattern. We examine the role of complex multi-cellular <span class="hlt">circulation</span> patterns in a Babcock-Leighton solar dynamo in advection- and diffusion-dominated regimes. We show from simulations that the presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in the butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of the butterfly wing to an antisolar <span class="hlt">type</span>. A butterfly diagram constructed from the middle of convection zone yields a solar-like pattern, but this may be difficult to realize in the Sun because of magnetic buoyancy effects. Each of the above cases behaves similarly in higher and lower magnetic diffusivity regimes. However, our dynamo with a <span class="hlt">meridional</span> <span class="hlt">circulation</span> containing four cells in latitude behaves distinctly differently in the two regimes, producing solar-like butterfly diagrams with fast cycles in the higher diffusivity regime, and complex branches in butterfly diagrams in the lower diffusivity regime. We also find that dynamo solutions for a four-celled pattern, two in radius and two in latitude, prefer to quickly relax to quadrupolar parity if the bottom flow speed is strong enough, of similar order of magnitude as the surface flow speed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22522276-babcockleighton-solar-dynamo-model-multi-cellular-meridional-circulation-advection-diffusion-dominated-regimes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22522276-babcockleighton-solar-dynamo-model-multi-cellular-meridional-circulation-advection-diffusion-dominated-regimes"><span>A BABCOCK–LEIGHTON SOLAR DYNAMO MODEL WITH MULTI-CELLULAR <span class="hlt">MERIDIONAL</span> <span class="hlt">CIRCULATION</span> IN ADVECTION- AND DIFFUSION-DOMINATED REGIMES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Belucz, Bernadett; Forgács-Dajka, Emese; Dikpati, Mausumi, E-mail: bbelucz@astro.elte.hu, E-mail: dikpati@ucar.edu</p> <p></p> <p>Babcock–Leighton <span class="hlt">type</span>-solar dynamo models with single-celled <span class="hlt">meridional</span> <span class="hlt">circulation</span> are successful in reproducing many solar cycle features. Recent observations and theoretical models of <span class="hlt">meridional</span> <span class="hlt">circulation</span> do not indicate a single-celled flow pattern. We examine the role of complex multi-cellular <span class="hlt">circulation</span> patterns in a Babcock–Leighton solar dynamo in advection- and diffusion-dominated regimes. We show from simulations that the presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in the butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of the butterfly wing to an antisolar <span class="hlt">type</span>. A butterflymore » diagram constructed from the middle of convection zone yields a solar-like pattern, but this may be difficult to realize in the Sun because of magnetic buoyancy effects. Each of the above cases behaves similarly in higher and lower magnetic diffusivity regimes. However, our dynamo with a <span class="hlt">meridional</span> <span class="hlt">circulation</span> containing four cells in latitude behaves distinctly differently in the two regimes, producing solar-like butterfly diagrams with fast cycles in the higher diffusivity regime, and complex branches in butterfly diagrams in the lower diffusivity regime. We also find that dynamo solutions for a four-celled pattern, two in radius and two in latitude, prefer to quickly relax to quadrupolar parity if the bottom flow speed is strong enough, of similar order of magnitude as the surface flow speed.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.2355H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.2355H"><span>Three-pattern decomposition of global atmospheric <span class="hlt">circulation</span>: part I—decomposition model and theorems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, Shujuan; Chou, Jifan; Cheng, Jianbo</p> <p>2018-04-01</p> <p>In order to study the interactions between the atmospheric <span class="hlt">circulations</span> at the middle-high and low latitudes from the global perspective, the authors proposed the mathematical definition of three-pattern <span class="hlt">circulations</span>, i.e., horizontal, <span class="hlt">meridional</span> and zonal <span class="hlt">circulations</span> with which the actual atmospheric <span class="hlt">circulation</span> is expanded. This novel decomposition method is proved to accurately describe the actual atmospheric <span class="hlt">circulation</span> dynamics. The authors used the NCEP/NCAR reanalysis data to calculate the climate characteristics of those three-pattern <span class="hlt">circulations</span>, and found that the decomposition model agreed with the observed results. Further dynamical analysis indicates that the decomposition model is more accurate to capture the major features of global three dimensional atmospheric motions, compared to the traditional definitions of Rossby wave, <span class="hlt">Hadley</span> <span class="hlt">circulation</span> and Walker <span class="hlt">circulation</span>. The decomposition model for the first time realized the decomposition of global atmospheric <span class="hlt">circulation</span> using three orthogonal <span class="hlt">circulations</span> within the horizontal, <span class="hlt">meridional</span> and zonal planes, offering new opportunities to study the large-scale interactions between the middle-high latitudes and low latitudes <span class="hlt">circulations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22086282-supergranules-probes-sun-meridional-circulation','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22086282-supergranules-probes-sun-meridional-circulation"><span>SUPERGRANULES AS PROBES OF THE SUN'S <span class="hlt">MERIDIONAL</span> <span class="hlt">CIRCULATION</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Hathaway, David H., E-mail: david.hathaway@nasa.gov</p> <p>2012-11-20</p> <p>Recent analysis revealed that supergranules (convection cells seen at the Sun's surface) are advected by the zonal flows at depths equal to the widths of the cells themselves. Here we probe the structure of the <span class="hlt">meridional</span> <span class="hlt">circulation</span> by cross-correlating maps of the Doppler velocity signal using a series of successively longer time lags between maps. We find that the poleward <span class="hlt">meridional</span> flow decreases in amplitude with time lag and reverses direction to become an equatorward return flow at time lags >24 hr. These cross-correlation results are dominated by larger and deeper cells at longer time lags. (The smaller cells havemore » shorter lifetimes and do not contribute to the correlated signal at longer time lags.) We determine the characteristic cell size associated with each time lag by comparing the equatorial zonal flows measured at different time lags with the zonal flows associated with different cell sizes from a Fourier analysis. This association gives a characteristic cell size of {approx}50 Mm at a 24 hr time lag. This indicates that the poleward <span class="hlt">meridional</span> flow returns equatorward at depths >50 Mm-just below the base of the surface shear layer. A substantial and highly significant equatorward flow (4.6 {+-} 0.4 m s{sup -1}) is found at a time lag of 28 hr corresponding to a depth of {approx}70 Mm. This represents one of the first positive detections of the Sun's <span class="hlt">meridional</span> return flow and illustrates the power of using supergranules to probe the Sun's internal dynamics.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22078382-measurements-sun-high-latitude-meridional-circulation','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22078382-measurements-sun-high-latitude-meridional-circulation"><span>MEASUREMENTS OF THE SUN'S HIGH-LATITUDE <span class="hlt">MERIDIONAL</span> <span class="hlt">CIRCULATION</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Rightmire-Upton, Lisa; Hathaway, David H.; Kosak, Katie, E-mail: lar0009@uah.edu, E-mail: david.hathaway@nasa.gov, E-mail: mkosak2011@my.fit.edu</p> <p>2012-12-10</p> <p>The <span class="hlt">meridional</span> <span class="hlt">circulation</span> at high latitudes is crucial to the buildup and reversal of the Sun's polar magnetic fields. Here, we characterize the axisymmetric flows by applying a magnetic feature cross-correlation procedure to high-resolution magnetograms obtained by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. We focus on Carrington rotations 2096-2107 (2010 April to 2011 March)-the overlap interval between HMI and the Michelson Doppler Imager (MDI). HMI magnetograms averaged over 720 s are first mapped into heliographic coordinates. Strips from these maps are then cross-correlated to determine the distances in latitude and longitude that the magneticmore » element pattern has moved, thus providing <span class="hlt">meridional</span> flow and differential rotation velocities for each rotation of the Sun. Flow velocities were averaged for the overlap interval and compared to results obtained from MDI data. This comparison indicates that these HMI images are rotated counterclockwise by 0.{sup 0}075 with respect to the Sun's rotation axis. The profiles indicate that HMI data can be used to reliably measure these axisymmetric flow velocities to at least within 5 Degree-Sign of the poles. Unlike the noisier MDI measurements, no evidence of a <span class="hlt">meridional</span> flow counter-cell is seen in either hemisphere with the HMI measurements: poleward flow continues all the way to the poles. Slight north-south asymmetries are observed in the <span class="hlt">meridional</span> flow. These asymmetries should contribute to the observed asymmetries in the polar fields and the timing of their reversals.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21474498-importance-meridional-circulation-flux-transport-dynamo-possibility-maunder-like-grand-minimum','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21474498-importance-meridional-circulation-flux-transport-dynamo-possibility-maunder-like-grand-minimum"><span>IMPORTANCE OF <span class="hlt">MERIDIONAL</span> <span class="hlt">CIRCULATION</span> IN FLUX TRANSPORT DYNAMO: THE POSSIBILITY OF A MAUNDER-LIKE GRAND MINIMUM</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Karak, Bidya Binay, E-mail: bidya_karak@physics.iisc.ernet.i</p> <p>2010-12-01</p> <p><span class="hlt">Meridional</span> <span class="hlt">circulation</span> is an important ingredient in flux transport dynamo models. We have studied its importance on the period, the amplitude of the solar cycle, and also in producing Maunder-like grand minima in these models. First, we model the periods of the last 23 sunspot cycles by varying the <span class="hlt">meridional</span> <span class="hlt">circulation</span> speed. If the dynamo is in a diffusion-dominated regime, then we find that most of the cycle amplitudes also get modeled up to some extent when we model the periods. Next, we propose that at the beginning of the Maunder minimum the amplitude of <span class="hlt">meridional</span> <span class="hlt">circulation</span> dropped to amore » low value and then after a few years it increased again. Several independent studies also favor this assumption. With this assumption, a diffusion-dominated dynamo is able to reproduce many important features of the Maunder minimum remarkably well. If the dynamo is in a diffusion-dominated regime, then a slower <span class="hlt">meridional</span> <span class="hlt">circulation</span> means that the poloidal field gets more time to diffuse during its transport through the convection zone, making the dynamo weaker. This consequence helps to model both the cycle amplitudes and the Maunder-like minima. We, however, fail to reproduce these results if the dynamo is in an advection-dominated regime.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16319889','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16319889"><span>Slowing of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> at 25 degrees N.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bryden, Harry L; Longworth, Hannah R; Cunningham, Stuart A</p> <p>2005-12-01</p> <p>The Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> carries warm upper waters into far-northern latitudes and returns cold deep waters southward across the Equator. Its heat transport makes a substantial contribution to the moderate climate of maritime and continental Europe, and any slowdown in the overturning <span class="hlt">circulation</span> would have profound implications for climate change. A transatlantic section along latitude 25 degrees N has been used as a baseline for estimating the overturning <span class="hlt">circulation</span> and associated heat transport. Here we analyse a new 25 degrees N transatlantic section and compare it with four previous sections taken over the past five decades. The comparison suggests that the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> has slowed by about 30 per cent between 1957 and 2004. Whereas the northward transport in the Gulf Stream across 25 degrees N has remained nearly constant, the slowing is evident both in a 50 per cent larger southward-moving mid-ocean recirculation of thermocline waters, and also in a 50 per cent decrease in the southward transport of lower North Atlantic Deep Water between 3,000 and 5,000 m in depth. In 2004, more of the northward Gulf Stream flow was recirculating back southward in the thermocline within the subtropical gyre, and less was returning southward at depth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5832W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5832W"><span>Bjerknes Compensation in <span class="hlt">Meridional</span> Heat Transport under Freshwater Forcing and the Role of Climate Feedback</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wen, Qin</p> <p>2017-04-01</p> <p>Using a coupled Earth climate model, freshwater experiments are performed to study the Bjerknes compensation (BJC) between <span class="hlt">meridional</span> atmosphere heat transport (AHT) and <span class="hlt">meridional</span> ocean heat transport (OHT). Freshwater hosing in the North Atlantic weakens the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) and thus reduces the northward OHT in the Atlantic significantly, leading to a cooling (warming) in surface layer in the Northern (Southern) Hemisphere. This results in an enhanced <span class="hlt">Hadley</span> Cell and northward AHT. Meanwhile, the OHT in the Indo-Pacific is increased in response to the <span class="hlt">Hadley</span> Cell change, partially offsetting the reduced OHT in the Atlantic. Two compensations occur here: compensation between the AHT and the Atlantic OHT, and that between the Indo-Pacific OHT and the Atlantic OHT. The AHT change compensates the OHT change very well in the extratropics, while the former overcompensates the latter in the tropics due to the Indo-Pacific change. The BJC can be understood from the viewpoint of large-scale <span class="hlt">circulation</span> change. However, the intrinsic mechanism of BJC is related to the climate feedback of Earth system. Our coupled model experiments confirm that the occurrence of BJC is an intrinsic requirement of local energy balance, and local climate feedback determines the extent of BJC, consistent with previous theoretical results. Even during the transient period of climate change in the model, the BJC is well established when the ocean heat storage is slowly varying and its change is weaker than the net heat flux changes at the ocean surface and the top of the atmosphere. The BJC can be deduced from the local climate feedback. Under the freshwater forcing, the overcompensation in the tropics (undercompensation in the extratropics) is mainly caused by the positive longwave feedback related to cloud (negative longwave feedback related to surface temperature change). Different dominant feedbacks determine different BJC scenarios in different regions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120016995&hterms=atlantic+meridional+overturning+circulation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120016995&hterms=atlantic+meridional+overturning+circulation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation"><span>Introduction to: Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>(AMOC)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, Sirpa; Carton, James A.</p> <p>2011-01-01</p> <p>A striking conclusion of the Intergovernmental Panel on Climate Change 2007 report is the crucial role that the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) may play in anthropogenic climate change. However, these IPCC coupled climate simulations show a broad range of uncertainty in the magnitude and timing of AMOC transport change ranging from none to nearly complete collapse within the 21st century. The potential consequences of large changes in the characteristics of AMOC have motivated the creation in the United States of an interagency program and implementation plan to develop monitoring and prediction capabilities for the AMOC This program parallels the development of substantial monitoring efforts by European, South American and African countries -- notably the UK Rapid and Rapid-Watch programs. The papers contained in this volume are derived from presentations at the First U.S. Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) Meeting held 4 - 6 May, 2009 to review the US implementation plan and its coordination with other monitoring activities. The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> consists of multiple components illustrated in an attached figure. Water enters the South Atlantic at upper and intermediate depths through both western and eastern routes (where eddy transport is especially important) and is transported northward across the equator, where it recirculates within the northern subtropical and subpolar gyres. The northern end is defined by the sinking regions of the Nordic Seas and the Labrador Sea where the waters that eventually form the upper and lower branches of North Atlantic Deep Water are conditioned. High surface salinities, the result of high net evaporation in the tropics and subtropics (including the Mediterranean Sea), and presence of regions of the Arctic Ocean that remain ice-free even in winter allow for the rapid cooling and thus densification of surface water. This dense surface water becomes the source of deep</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A11M..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A11M..02S"><span>Observational Evidence of the "Tightening of <span class="hlt">Hadley</span> Ascent"</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Su, H.; Wu, L.; Jiang, J. H.</p> <p>2017-12-01</p> <p>Recent studies show that the <span class="hlt">Hadley</span> <span class="hlt">Circulation</span> undergoes complicated structure changes under global warming (e.g., Su et al., 2014; Lau and Kim 2015; Byrne and Schneider 2016; Su et al., 2017)). Accompanied by the widening of the descent zone, a narrowing of the ascending branch of the <span class="hlt">Hadley</span> <span class="hlt">Circulation</span> is simulated in most climate models. The magnitude of the tightening of <span class="hlt">Hadley</span> ascent (THA) in the models is found to be highly correlated with the decrease of tropical high cloud fraction, which is a major contributor to the inter-model spread of the longwave radiative cooling rate and the global-mean precipitation change per degree of surface warming (Su et al. 2017). While the THA is a common feature in the models, its observational evidence is limited. We have examined a number of reanalyses and satellite datasets to identify the indicators of the THA in terms of large-scale winds, water vapor, cloud and precipitation changes in the past decades. The robustness of the THA in the observations and the differences between various datasets will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27814029','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27814029"><span>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> and Abrupt Climate Change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lynch-Stieglitz, Jean</p> <p>2017-01-03</p> <p>Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). This review examines the evidence from ocean sediments for ocean <span class="hlt">circulation</span> change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for <span class="hlt">circulation</span> changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4459181','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4459181"><span>Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> slowdown cooled the subtropical ocean</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cunningham, Stuart A; Roberts, Christopher D; Frajka-Williams, Eleanor; Johns, William E; Hobbs, Will; Palmer, Matthew D; Rayner, Darren; Smeed, David A; McCarthy, Gerard</p> <p>2013-01-01</p> <p>[1] Observations show that the upper 2 km of the subtropical North Atlantic Ocean cooled throughout 2010 and remained cold until at least December 2011. We show that these cold anomalies are partly driven by anomalous air-sea exchange during the cold winters of 2009/2010 and 2010/2011 and, more surprisingly, by extreme interannual variability in the ocean's northward heat transport at 26.5°N. This cooling driven by the ocean's <span class="hlt">meridional</span> heat transport affects deeper layers isolated from the atmosphere on annual timescales and water that is entrained into the winter mixed layer thus lowering winter sea surface temperatures. Here we connect, for the first time, variability in the northward heat transport carried by the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> to widespread sustained cooling of the subtropical North Atlantic, challenging the prevailing view that the ocean plays a passive role in the coupled ocean-atmosphere system on monthly-to-seasonal timescales. PMID:26074634</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26074634','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26074634"><span>Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> slowdown cooled the subtropical ocean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cunningham, Stuart A; Roberts, Christopher D; Frajka-Williams, Eleanor; Johns, William E; Hobbs, Will; Palmer, Matthew D; Rayner, Darren; Smeed, David A; McCarthy, Gerard</p> <p>2013-12-16</p> <p>[1] Observations show that the upper 2 km of the subtropical North Atlantic Ocean cooled throughout 2010 and remained cold until at least December 2011. We show that these cold anomalies are partly driven by anomalous air-sea exchange during the cold winters of 2009/2010 and 2010/2011 and, more surprisingly, by extreme interannual variability in the ocean's northward heat transport at 26.5°N. This cooling driven by the ocean's <span class="hlt">meridional</span> heat transport affects deeper layers isolated from the atmosphere on annual timescales and water that is entrained into the winter mixed layer thus lowering winter sea surface temperatures. Here we connect, for the first time, variability in the northward heat transport carried by the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> to widespread sustained cooling of the subtropical North Atlantic, challenging the prevailing view that the ocean plays a passive role in the coupled ocean-atmosphere system on monthly-to-seasonal timescales.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2288Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2288Y"><span>Reduced connection between the East Asian Summer Monsoon and Southern Hemisphere <span class="hlt">Circulation</span> on interannual timescales under intense global warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Tianlei; Guo, Pinwen; Cheng, Jun; Hu, Aixue; Lin, Pengfei; Yu, Yongqiang</p> <p>2018-03-01</p> <p>Previous studies show a close relationship between the East Asian Summer Monsoon (EASM) and Southern Hemisphere (SH) <span class="hlt">circulation</span> on interannual timescales. In this study, we investigate whether this close relationship will change under intensive greenhouse-gas effect by analyzing simulations under two different climate background states: preindustrial era and Representative Concentration Pathway (RCP) 8.5 stabilization from the Community Climate System Model Version 4 (CCSM4). Results show a significantly reduced relationship under stabilized RCP8.5 climate state, such a less correlated EASM with the sea level pressure in the southern Indian Ocean and the SH branch of local <span class="hlt">Hadley</span> Cell. Further analysis suggests that the collapse of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) due to this warming leads to a less vigorous northward <span class="hlt">meridional</span> heat transport, a decreased intertropical temperature contrast in boreal summer, which produces a weaker cross-equatorial <span class="hlt">Hadley</span> Cell in the monsoonal region and a reduced Interhemispheric Mass Exchange (IME). Since the monsoonal IME acts as a bridge connecting EASM and SH <span class="hlt">circulation</span>, the reduced IME weakens this connection. By performing freshwater hosing experiment using the Flexible Global Ocean—Atmosphere—Land System model, Grid-point Version 2 (FGOALS-g2), we show a weakened relationship between the EASM and SH <span class="hlt">circulation</span> as in CCSM4 when AMOC collapses. Our results suggest that a substantially weakened AMOC is the main driver leading to the EASM, which is less affected by SH <span class="hlt">circulation</span> in the future warmer climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...854...67P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...854...67P"><span>On the Origin of the Double-cell <span class="hlt">Meridional</span> <span class="hlt">Circulation</span> in the Solar Convection Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pipin, V. V.; Kosovichev, A. G.</p> <p>2018-02-01</p> <p>Recent advances in helioseismology, numerical simulations and mean-field theory of solar differential rotation have shown that the <span class="hlt">meridional</span> <span class="hlt">circulation</span> pattern may consist of two or more cells in each hemisphere of the convection zone. According to the mean-field theory the double-cell <span class="hlt">circulation</span> pattern can result from the sign inversion of a nondiffusive part of the radial angular momentum transport (the so-called Λ-effect) in the lower part of the solar convection zone. Here, we show that this phenomenon can result from the radial inhomogeneity of the Coriolis number, which depends on the convective turnover time. We demonstrate that if this effect is taken into account then the solar-like differential rotation and the double-cell <span class="hlt">meridional</span> <span class="hlt">circulation</span> are both reproduced by the mean-field model. The model is consistent with the distribution of turbulent velocity correlations determined from observations by tracing motions of sunspots and large-scale magnetic fields, indicating that these tracers are rooted just below the shear layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1410681W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1410681W"><span>The Deep <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in the Indian Ocean Inferred from the GECCO Synthesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, W.; Koehl, A.; Stammer, D.</p> <p>2012-04-01</p> <p>The <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> in the Indian Ocean and its temporal variability in the GECCO ocean synthesis are being investigated. An analysis of the integrated <span class="hlt">circulation</span> in different layers suggests that, on time average, 2.1 Sv enter the Indian Ocean in the bottom layer (>3200m) from the south and that 12.3 Sv leave the Indian Ocean in the upper and intermediate layers (<1500m), composed of the up-welled bottom layer inflow water, augmented by 9.6 Sv Indonesian Throughflow (ITF) water. The GECCO time-mean results differ significantly from those obtained by box inverse models, which, being based on individual hydrographic sections, are susceptible to aliasing. The GECCO solution has a large seasonal variation in its <span class="hlt">meridional</span> overturning caused by the seasonal reversal of monsoon-related wind stress forcing. Associated seasonal variations of the deep <span class="hlt">meridional</span> overturning range from -7 Sv in boreal winter to 3 Sv in summer. In addition, the upper and bottom transports across 34°S section show pronounced interannual variability with roughly biennial variations superimposed by strong anomalies during each La Niña phase as well as the ITF, which mainly affect the upper layer transports. On decadal and longer timescale, the <span class="hlt">meridional</span> overturning variability as well as long-term trends differ before and after 1980. Notably, our analysis shows a rather stable trend for the period 1960-1979 and significant changes in the upper and bottom layer for the period 1980-2001. By means of a multivariate EOF analysis, the importance of Ekman dynamics as driving forces of the deep <span class="hlt">meridional</span> overturning of the Indian Ocean on the interannual timescale is highlighted. The leading modes of the zonal and <span class="hlt">meridional</span> wind stress favour a basin-wide <span class="hlt">meridional</span> overturning mode via Ekman upwelling or downwelling mostly in the central and eastern Indian Ocean. Moreover, tropical zonal wind stress along the equator and alongshore wind stress off the Sumatra-Java coast</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998DSRI...45..573M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998DSRI...45..573M"><span>A sigma-coordinate primitive equation model for studying the <span class="hlt">circulation</span> in the South Atlantic Part II: <span class="hlt">Meridional</span> transports and seasonal variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marchesiello, P.; Barnier, B.; de Miranda, A. P.</p> <p>1998-04-01</p> <p>The mean and seasonal variability of the <span class="hlt">circulation</span> and <span class="hlt">meridional</span> heat transport in the South Atlantic are investigated using a set of numerical experiments. The primitive equation model uses a topography-following (sigma) coordinate. The model domain is limited to the South Atlantic basin. Artificial boundaries at Drake Passage, between Brazil and Angola, and between South Africa and Antarctica are treated as open boundaries. Finally, recent and self-consistent estimates of seasonal fluxes are used to define a model-dependent atmospheric forcing. Quasi-diagnostic simulations forced by constant climatological winds are first conducted to determine the sensitivity of model solutions to bottom topography smoothing, and to diagnose <span class="hlt">meridional</span> fluxes from a mass field that is relaxed to the annual climatology of Levitus (1982). Model results show good agreement with known climatological <span class="hlt">circulation</span> features in this basin, especially in the Confluence Region, where coarse resolution models usually give smooth structures. Sensitivity studies show that the more detailed features of the <span class="hlt">circulation</span> are influenced by the model bathymetry. The model simulates a <span class="hlt">meridional</span> <span class="hlt">circulation</span> whose upper branch (the return flow that balances the southward flow of North Atlantic Deep Water) is composed of Intermediate (IW) and Thermocline (TW) Waters. The transport of IW is found to be predominant, and the value of <span class="hlt">meridional</span> heat transport consequently falls within the low estimates. We notice that the <span class="hlt">meridional</span> heat balance is sensitive to the position of the Confluence. When this region occurs too far south, the amount of IW contributing to the return flow of the overturning cell is reduced. Prognostic simulations forced by seasonal winds and heat fluxes are studied to quantify the impact of wind forcing on the <span class="hlt">circulation</span> in the South Atlantic. Particular attention is focused on <span class="hlt">meridional</span> transports at 30°S. Analysis of the mean annual <span class="hlt">circulation</span> confirms that the upper</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GeoRL..37.3610N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GeoRL..37.3610N"><span>Tracing global biogeochemical cycles and <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> using chromophoric dissolved organic matter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nelson, Norman B.; Siegel, David A.; Carlson, Craig A.; Swan, Chantal M.</p> <p>2010-02-01</p> <p>Basin-scale distributions of light absorption by chromophoric dissolved organic matter (CDOM) are positively correlated (R2 > 0.8) with apparent oxygen utilization (AOU) within the top kilometer of the Pacific and Indian Oceans. However, a much weaker correspondence is found for the Atlantic (R2 < 0.05). Strong correlation between CDOM and AOU indicates that CDOM is created as a byproduct of the oxidation of organic matter from sinking particles. The observed <span class="hlt">meridional</span>-depth sections of CDOM result from a balance between biogeochemical processes (autochthonous production and solar bleaching) and the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>. Rapid mixing in the Atlantic dilutes CDOM in the interior and implies that the time scale for CDOM accumulation is greater than ˜50 years. CDOM emerges as a unique tracer for diagnosing changes in biogeochemistry and the overturning <span class="hlt">circulation</span>, similar to dissolved oxygen, with the additional feature that it can be quantified from satellite observation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26089521','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26089521"><span>OCEAN <span class="hlt">CIRCULATION</span>. Observing the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> yields a decade of inevitable surprises.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Srokosz, M A; Bryden, H L</p> <p>2015-06-19</p> <p>The importance of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) heat transport for climate is well acknowledged. Climate models predict that the AMOC will slow down under global warming, with substantial impacts, but measurements of ocean <span class="hlt">circulation</span> have been inadequate to evaluate these predictions. Observations over the past decade have changed that situation, providing a detailed picture of variations in the AMOC. These observations reveal a surprising degree of AMOC variability in terms of the intraannual range, the amplitude and phase of the seasonal cycle, the interannual changes in strength affecting the ocean heat content, and the decline of the AMOC over the decade, both of the latter two exceeding the variations seen in climate models. Copyright © 2015, American Association for the Advancement of Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080036107&hterms=atlantic+meridional+overturning+circulation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080036107&hterms=atlantic+meridional+overturning+circulation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation"><span>Mechanisms of Interannual Variations of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> of the North Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cabanes, Cecile; Lee, Tong; Fu, Lee-Lueng</p> <p>2008-01-01</p> <p>The authors investigate the nature of the interannual variability of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) of the North Atlantic Ocean using an Estimating the <span class="hlt">Circulation</span> and Climate of the Ocean (ECCO) assimilation product for the period of 1993-2003. The time series of the first empirical orthogonal function of the MOC is found to be correlated with the North Atlantic Oscillation (NAO) index, while the associated <span class="hlt">circulation</span> anomalies correspond to cells extending over the full ocean depth. Model sensitivity experiments suggest that the wind is responsible for most of this interannual variability, at least south of 40(deg)N. A dynamical decomposition of the <span class="hlt">meridional</span> streamfunction allows a further look into the mechanisms. In particular, the contributions associated with 1) the Ekman flow and its depth-independent compensation, 2) the vertical shear flow, and 3) the barotropic gyre flowing over zonally varying topography are examined. Ekman processes are found to dominate the shorter time scales (1.5-3 yr), while for longer time scales (3-10 yr) the MOC variations associated with vertical shear flow are of greater importance. The latter is primarily caused by heaving of the pycnocline in the western subtropics associated with the stronger wind forcing. Finally, how these changes in the MOC affect the <span class="hlt">meridional</span> heat transport (MHT) is examined. It is found that overall, Ekman processes explain a larger part of interannual variability (3-10 yr) for MHT (57%) than for the MOC (33%).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860003448','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860003448"><span>Large-scale <span class="hlt">circulation</span> departures related to wet episodes in northeast Brazil</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sikdar, D. N.; Elsner, J. B.</p> <p>1985-01-01</p> <p>Large scale <span class="hlt">circulation</span> features are presented as related to wet spells over northeast Brazil (Nordeste) during the rainy season (March and April) of 1979. The rainy season season is devided into dry and wet periods, the FGGE and geostationary satellite data was averaged and mean and departure fields of basic variables and cloudiness were studied. Analysis of seasonal mean <span class="hlt">circulation</span> features show: lowest sea level easterlies beneath upper level westerlies; weak <span class="hlt">meridional</span> winds; high relative humidity over the Amazon basin and relatively dry conditions over the South Atlantic Ocean. A fluctuation was found in the large scale <span class="hlt">circulation</span> features on time scales of a few weeks or so over Nordeste and the South Atlantic sector. Even the subtropical High SLP's have large departures during wet episodes, implying a short period oscillation in the Southern Hemisphere <span class="hlt">Hadley</span> <span class="hlt">circulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19897722','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19897722"><span>On the stability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hofmann, Matthias; Rahmstorf, Stefan</p> <p>2009-12-08</p> <p>One of the most important large-scale ocean current systems for Earth's climate is the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). Here we review its stability properties and present new model simulations to study the AMOC's hysteresis response to freshwater perturbations. We employ seven different versions of an Ocean General <span class="hlt">Circulation</span> Model by using a highly accurate tracer advection scheme, which minimizes the problem of numerical diffusion. We find that a characteristic freshwater hysteresis also exists in the predominantly wind-driven, low-diffusion limit of the AMOC. However, the shape of the hysteresis changes, indicating that a convective instability rather than the advective Stommel feedback plays a dominant role. We show that model errors in the mean climate can make the hysteresis disappear, and we investigate how model innovations over the past two decades, like new parameterizations and mixing schemes, affect the AMOC stability. Finally, we discuss evidence that current climate models systematically overestimate the stability of the AMOC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2791639','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2791639"><span>On the stability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hofmann, Matthias; Rahmstorf, Stefan</p> <p>2009-01-01</p> <p>One of the most important large-scale ocean current systems for Earth's climate is the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). Here we review its stability properties and present new model simulations to study the AMOC's hysteresis response to freshwater perturbations. We employ seven different versions of an Ocean General <span class="hlt">Circulation</span> Model by using a highly accurate tracer advection scheme, which minimizes the problem of numerical diffusion. We find that a characteristic freshwater hysteresis also exists in the predominantly wind-driven, low-diffusion limit of the AMOC. However, the shape of the hysteresis changes, indicating that a convective instability rather than the advective Stommel feedback plays a dominant role. We show that model errors in the mean climate can make the hysteresis disappear, and we investigate how model innovations over the past two decades, like new parameterizations and mixing schemes, affect the AMOC stability. Finally, we discuss evidence that current climate models systematically overestimate the stability of the AMOC. PMID:19897722</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870063383&hterms=nordeste&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dnordeste','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870063383&hterms=nordeste&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dnordeste"><span>Large-scale <span class="hlt">circulation</span> departures related to wet episodes in north-east Brazil</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sikdar, Dhirendra N.; Elsner, James B.</p> <p>1987-01-01</p> <p>Large scale <span class="hlt">circulation</span> features are presented as related to wet spells over northeast Brazil (Nordeste) during the rainy season (March and April) of 1979. The rainy season is divided into dry and wet periods; the FGGE and geostationary satellite data was averaged; and mean and departure fields of basic variables and cloudiness were studied. Analysis of seasonal mean <span class="hlt">circulation</span> features show: lowest sea level easterlies beneath upper level westerlies; weak <span class="hlt">meridional</span> winds; high relative humidity over the Amazon basin and relatively dry conditions over the South Atlantic Ocean. A fluctuation was found in the large scale <span class="hlt">circulation</span> features on time scales of a few weeks or so over Nordeste and the South Atlantic sector. Even the subtropical High SLPs have large departures during wet episodes, implying a short period oscillation in the Southern Hemisphere <span class="hlt">Hadley</span> <span class="hlt">circulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PApGe.tmp...18D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PApGe.tmp...18D"><span>The Influence of the Regional <span class="hlt">Hadley</span> and Walker <span class="hlt">Circulations</span> on Precipitation Patterns over Africa in El Niño, La Niña, and Neutral Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Oliveira, Cristiano Prestrelo; Aímola, Luis; Ambrizzi, Tércio; Freitas, Ana Carolina Vasques</p> <p>2018-02-01</p> <p>This study focuses on the differential impacts of the positive (El Niño), negative (La Niña), and neutral phases of the El Niño Southern Oscillation (ENSO) on precipitation over Africa during DJF and JJA, evaluated through changes in the regional <span class="hlt">Hadley</span> and Walker <span class="hlt">Circulations</span>. Identification of the <span class="hlt">Hadley</span> and Walker Cells was done using stream function mass transport calculations of ERA-Interim reanalysis data from 1979 to 2014. Analysis of the spatial pattern of precipitation anomalies shows that during DJF, El Niño (La Niña) negatively (positively) impacts precipitation over the African continent. During JJA, El Niño (La Niña) influences precipitation variability over the Sahel region, producing positive (negative) anomalies. Negative precipitation anomalies associated with El Niño (DJF) over southern Africa are linked to a strengthening in subsidence of the descending branch of the regional <span class="hlt">Hadley</span> Cell, and during JJA the negative precipitation anomalies over the Sahel are associated with a weakening of the ascending branch of the regional <span class="hlt">Hadley</span> Cell. During La Niña events in DJF, there is a tendency toward increased convection in southern Africa, associated with a stronger ascending branch and weaker descending branch of the regional <span class="hlt">Hadley</span> Cell. During La Niña events in JJA, positive precipitation anomalies over the Sahel are associated with an intensification of the ascending branch of the regional <span class="hlt">Hadley</span> Cell north of the equator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JOUC...17..219L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JOUC...17..219L"><span>Plausible Effect of Weather on Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> with a Coupled General <span class="hlt">Circulation</span> Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Zedong; Wan, Xiuquan</p> <p>2018-04-01</p> <p>The Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) is a vital component of the global ocean <span class="hlt">circulation</span> and the heat engine of the climate system. Through the use of a coupled general <span class="hlt">circulation</span> model, this study examines the role of synoptic systems on the AMOC and presents evidence that internally generated high-frequency, synoptic-scale weather variability in the atmosphere could play a significant role in maintaining the overall strength and variability of the AMOC, thereby affecting climate variability and change. Results of a novel coupling technique show that the strength and variability of the AMOC are greatly reduced once the synoptic weather variability is suppressed in the coupled model. The strength and variability of the AMOC are closely linked to deep convection events at high latitudes, which could be strongly affected by the weather variability. Our results imply that synoptic weather systems are important in driving the AMOC and its variability. Thus, interactions between atmospheric weather variability and AMOC may be an important feedback mechanism of the global climate system and need to be taken into consideration in future climate change studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012DyAtO..58...44W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012DyAtO..58...44W"><span>The deep <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> in the Indian Ocean inferred from the GECCO synthesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Weiqiang; Köhl, Armin; Stammer, Detlef</p> <p>2012-11-01</p> <p>The deep time-varying <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) in the Indian Ocean in the German “Estimating the <span class="hlt">Circulation</span> and Climate of the Ocean” consortium efforts (GECCO) ocean synthesis is being investigated. An analysis of the integrated <span class="hlt">circulation</span> suggests that, on time average, 2.1 Sv enter the Indian Ocean in the bottom layer (>3200 m) from the south and that 12.3 Sv leave the Indian Ocean in the upper and intermediate layers (<1500 m), composed of the up-welled bottom layer inflow water, augmented by 9.6 Sv Indonesian Throughflow (ITF) water. The GECCO time-mean results differ substantially from those obtained by inverse box models, which being based on individual hydrographic sections and due to the strong seasonal cycle are susceptible to aliasing. The GECCO solution shows a large seasonal variation in its deep MOC caused by the seasonal reversal of monsoon-related wind stress forcing. The associated seasonal variations of the deep MOC range from -7 Sv in boreal winter to 3 Sv in summer. In addition, the upper and bottom transports across the 34°S section show pronounced interannual variability with roughly biennial variations superimposed by strong anomalies during each La Niña phase as well as the ITF, which mainly affect the upper layer transports. On decadal and longer timescale, the <span class="hlt">meridional</span> overturning variability as well as long-term trends differs before and after 1980. GECCO shows a stable trend for the period 1960-1979 and substantial changes in the upper and bottom layer for the period 1980-2001. By means of an extended EOF analysis, the importance of Ekman dynamics as driving forces of the deep MOC of the Indian Ocean on the interannual timescale is highlighted. The leading modes of the zonal and <span class="hlt">meridional</span> wind stress favour a basin-wide <span class="hlt">meridional</span> overturning mode via Ekman upwelling or downwelling mostly in the central and eastern Indian Ocean. Moreover, tropical zonal wind stress along the equator and alongshore wind stress</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCC...7..604S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCC...7..604S"><span>Arctic sea-ice decline weakens the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sévellec, Florian; Fedorov, Alexey V.; Liu, Wei</p> <p>2017-08-01</p> <p>The ongoing decline of Arctic sea ice exposes the ocean to anomalous surface heat and freshwater fluxes, resulting in positive buoyancy anomalies that can affect ocean <span class="hlt">circulation</span>. In this study, we use an optimal flux perturbation framework and comprehensive climate model simulations to estimate the sensitivity of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) to such buoyancy forcing over the Arctic and globally, and more generally to sea-ice decline. It is found that on decadal timescales, flux anomalies over the subpolar North Atlantic have the largest impact on the AMOC, while on multi-decadal timescales (longer than 20 years), flux anomalies in the Arctic become more important. These positive buoyancy anomalies spread to the North Atlantic, weakening the AMOC and its poleward heat transport. Therefore, the Arctic sea-ice decline may explain the suggested slow-down of the AMOC and the `Warming Hole’ persisting in the subpolar North Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42..871D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42..871D"><span>Impact of Greenland orography on the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davini, P.; Hardenberg, J.; Filippi, L.; Provenzale, A.</p> <p>2015-02-01</p> <p>We show that the absence of the Greenland ice sheet would have important consequences on the North Atlantic Ocean <span class="hlt">circulation</span>, even without taking into account the effect of the freshwater input to the ocean from ice melting. These effects are investigated in a 600year long coupled ocean-atmosphere simulation with the high-resolution global climate model EC-Earth 3.0.1. Once a new equilibrium is established, a cooling of Eurasia and of the North Atlantic and a poleward shift of the subtropical jet are observed. These hemispheric changes are ascribed to a weakening of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) by about 12%. We attribute this slowdown to a reduction in salinity of the Arctic basin and to the related change of the mass and salt transport through the Fram Strait—a consequence of the new surface wind pattern over the lower orography. This idealized experiment illustrates the sensitivity of the AMOC to local surface winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6400D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6400D"><span>Impact of Greenland orography on the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davini, Paolo; von Hardenberg, Jost; Filippi, Luca; Provenzale, Antonello</p> <p>2015-04-01</p> <p>We show that the absence of the Greenland Ice Sheet would have important consequences on the North Atlantic Ocean <span class="hlt">circulation</span>, even without taking into account the effect of the freshwater input from ice melting. These effects are investigated in a 200-year long coupled ocean-atmosphere simulation with the high-resolution global climate model EC-Earth 3.0.1. Once a new equilibrium is established, cooling of Eurasia and of the North Atlantic and poleward shift of the subtropical jet are observed. These hemispheric changes are ascribed to a weakening of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) by about 20%. Such slowdown is associated to the freshening of the Arctic basin and to the related reduction in the freshwater export through the Fram Strait, as a result of the new wind pattern generated by the lower orography. This idealized experiment reveals the possibility of decreasing the AMOC by locally changing the surface winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GGG....18.2177A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GGG....18.2177A"><span>The onset of modern-like Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> at the Eocene-Oligocene transition: Evidence, causes, and possible implications for global cooling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abelson, Meir; Erez, Jonathan</p> <p>2017-06-01</p> <p>A compilation of benthic δ18O from the whole Atlantic and the Southern Ocean (Atlantic sector) shows two major jumps in the interbasinal gradient of δ18O (Δδ18O) during the Eocene and the Oligocene: one at ˜40 Ma and the second concomitant with the isotopic event of the Eocene-Oligocene transition (EOT), ˜33.7 Ma ago. From previously published <span class="hlt">circulation</span> models and proxies, we show that the first Δδ18O jump reflects the thermal isolation of Antarctica associated with the proto-Antarctic circumpolar current (ACC). The second marks the onset of interhemispheric northern-sourced <span class="hlt">circulation</span> cell, similar to the modern Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). The onset of AMOC-like <span class="hlt">circulation</span> slightly preceded (100-300 kyr) the EOT, as we show by the high-resolution profiles of δ18O and δ13C previously published from DSDP/ODP sites in the Southern Ocean and South Atlantic. These events coincide with the onset of antiestuarine <span class="hlt">circulation</span> between the Nordic seas and the North Atlantic which started around the EOT and may be connected to the deepening of the Greenland-Scotland Ridge. We suggest that while the shallow proto-ACC supplied the energy for deep ocean convection in the Southern Hemisphere, the onset of the interhemispheric northern <span class="hlt">circulation</span> cell was due to the significant EOT intensification of deepwater formation in the North Atlantic driven by the Nordic antiestuarine <span class="hlt">circulation</span>. This onset of the interhemispheric northern-sourced <span class="hlt">circulation</span> cell could have prompted the EOT global cooling.<abstract <span class="hlt">type</span>="synopsis"><title <span class="hlt">type</span>="main">Plain Language SummaryThe Eocene-Oligocene transition is the major abrupt climatic event during the Cenozoic, which marks the major step to the icehouse world. We show that this transition is a shift to a world with Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) and slightly preceded this transition. Thus, possibly was a major factor in this climatic shift.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.tmp..209M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.tmp..209M"><span>On the role of precipitation latent heating in modulating the strength and width of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mathew, Sneha Susan; Kumar, Karanam Kishore</p> <p>2018-05-01</p> <p>The latent heat released in the clouds over the tropics plays a vital role in driving the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> (HC). The present study discusses the influence of latent heating (LH) on the HC parameters viz., centre, strength and total width by using precipitation LH profiles derived from the space-borne observations of the Precipitation Radar (PR) onboard Tropical Rain Measuring Mission (TRMM) and <span class="hlt">meridional</span> stream function (MSF) derived from ECMWF-Interim reanalysis. The latitude of peak latent heating, width of the latent heating distribution and the total LH released within the ascending limb of the HC are estimated and their influence on the HC centre, strength and width is quantified, for the first time. The present results show that the latitude of peak LH significantly influences the position of the HC centre with correlation coefficient of 0.90. This high correlation between these two quantities seems to be due to their co-variability with the apparent motion of the Sun across the latitudes. The intensity of the HC in the NH as well as SH shows high correlation with the latitude of peak LH with coefficients - 0.85 and - 0.78, respectively. These results indicate that farther the latitude of peak LH from the equator in the summer hemisphere, stronger is the HC intensity in the winter hemisphere. The present analysis also reveals that the total LH released within the ascending limb of HC substantially influence the total width of the HC, with correlation coefficient 0.52, as compared to the other two LH parameters. This observation can be attributed to the fact that the HC is sensitive to the latent heat release in the mid-tropospheric levels in the tropics. An attempt is also made to investigate the degree of variability of these parameters after deseasonalization and results are discussed in the light of present understanding. The significance of the present study lies in providing the observational evidence for the influence of latent heating on the HC</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24940739','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24940739"><span>An electrical analogy relating the Atlantic multidecadal oscillation to the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kurtz, Bruce E</p> <p>2014-01-01</p> <p>The Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) is the northward flow of surface water to subpolar latitudes where deepwater is formed, balanced by southward abyssal flow and upwelling in the vicinity of the Southern Ocean. It is generally accepted that AMOC flow oscillates with a period of 60-80 years, creating a regular variation in North Atlantic sea surface temperature known as the Atlantic multidecadal oscillation (AMO). This article attempts to answer two questions: how is the AMOC driven and why does it oscillate? Using methods commonly employed by chemical engineers for analyzing processes involving flowing liquids, apparently not previously applied to trying to understand the AMOC, an equation is developed for AMOC flow as a function of the <span class="hlt">meridional</span> density gradient or the corresponding temperature gradient. The equation is based on the similarity between the AMOC and an industrial thermosyphon loop cooler, which <span class="hlt">circulates</span> a heat transfer liquid without using a mechanical pump. Extending this equation with an analogy between the flow of heat and electricity explains why the AMOC flow oscillates and what determines its period. Calculated values for AMOC flow and AMO oscillation period are in good agreement with measured values.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4062526','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4062526"><span>An Electrical Analogy Relating the Atlantic Multidecadal Oscillation to the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kurtz, Bruce E.</p> <p>2014-01-01</p> <p>The Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) is the northward flow of surface water to subpolar latitudes where deepwater is formed, balanced by southward abyssal flow and upwelling in the vicinity of the Southern Ocean. It is generally accepted that AMOC flow oscillates with a period of 60–80 years, creating a regular variation in North Atlantic sea surface temperature known as the Atlantic multidecadal oscillation (AMO). This article attempts to answer two questions: how is the AMOC driven and why does it oscillate? Using methods commonly employed by chemical engineers for analyzing processes involving flowing liquids, apparently not previously applied to trying to understand the AMOC, an equation is developed for AMOC flow as a function of the <span class="hlt">meridional</span> density gradient or the corresponding temperature gradient. The equation is based on the similarity between the AMOC and an industrial thermosyphon loop cooler, which <span class="hlt">circulates</span> a heat transfer liquid without using a mechanical pump. Extending this equation with an analogy between the flow of heat and electricity explains why the AMOC flow oscillates and what determines its period. Calculated values for AMOC flow and AMO oscillation period are in good agreement with measured values. PMID:24940739</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663298-dynamics-massive-atmospheres','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663298-dynamics-massive-atmospheres"><span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Chemke, Rei; Kaspi, Yohai, E-mail: rei.chemke@weizmann.ac.il</p> <p></p> <p>The many recently discovered terrestrial exoplanets are expected to hold a wide range of atmospheric masses. Here the dynamic-thermodynamic effects of atmospheric mass on atmospheric <span class="hlt">circulation</span> are studied using an idealized global <span class="hlt">circulation</span> model by systematically varying the atmospheric surface pressure. On an Earth analog planet, an increase in atmospheric mass weakens the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> and decreases its latitudinal extent. These changes are found to be related to the reduction of the convective fluxes and net radiative cooling (due to the higher atmospheric heat capacity), which, respectively, cool the upper troposphere at mid-low latitudes and warm the troposphere at highmore » latitudes. These together decrease the <span class="hlt">meridional</span> temperature gradient, tropopause height and static stability. The reduction of these parameters, which play a key role in affecting the flow properties of the tropical <span class="hlt">circulation</span>, weakens and contracts the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. The reduction of the <span class="hlt">meridional</span> temperature gradient also decreases the extraction of mean potential energy to the eddy fields and the mean kinetic energy, which weakens the extratropical <span class="hlt">circulation</span>. The decrease of the eddy kinetic energy decreases the Rhines wavelength, which is found to follow the <span class="hlt">meridional</span> jet scale. The contraction of the jet scale in the extratropics results in multiple jets and <span class="hlt">meridional</span> <span class="hlt">circulation</span> cells as the atmospheric mass increases.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29769741','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29769741"><span>Tropical <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> Observed by Subsurface Moorings in the Western Pacific.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Song, Lina; Li, Yuanlong; Wang, Jianing; Wang, Fan; Hu, Shijian; Liu, Chuanyu; Diao, Xinyuan; Guan, Cong</p> <p>2018-05-16</p> <p><span class="hlt">Meridional</span> ocean current in the northwestern Pacific was documented by seven subsurface moorings deployed at 142°E during August 2014-October 2015. A sandwich structure of the tropical <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (TMOC) was revealed between 0-6°N that consists of a surface northward flow (0-80 m), a thermocline southward flow (80-260 m; 22.6-26.5 σ θ ), and a subthermocline northward flow (260-500 m; 26.5-26.9 σ θ ). Based on mooring data, along with satellite and reanalysis data, prominent seasonal-to-interannual variations were observed in all three layers, and the equatorial zonal winds were found to be a dominant cause of the variations. The TMOC is generally stronger in boreal winter and weaker in summer. During 2014-2015, the TMOC was greatly weakened by westerly wind anomalies associated with the El Niño condition. Further analysis suggests that the TMOC can affect equatorial surface temperature in the western Pacific through anomalous upwelling/downwelling and likely plays a vital role in the El Niño-Southern Oscillation (ENSO).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPC43A..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPC43A..04B"><span>Temporal Variability of North Atlantic Carbon Fluxes and their Sensitivity to the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, P.; McDonagh, E.; Sanders, R.; King, B.; Watson, A. J.; Schuster, U.; Henson, S.</p> <p>2016-02-01</p> <p>The North Atlantic plays a critical role in the global carbon cycle both as a region of substantial air-sea carbon dioxide uptake and as a location for the transfer of CO2 to depth on climatically-important timescales. While the magnitude of surface fluxes is relatively well constrained, our understanding of the processes that drive variability in ocean-atmosphere exchange and subsequent subsurface carbon accumulation is not as well defined. Here we present observation-derived high-resolution estimates of short-term 10-day <span class="hlt">meridional</span> ocean carbon transport variability across the subtropical North Atlantic for 2004-2012. Substantial seasonal, sub-annual and interannual transport variability is observed that is highly sensitive to the strength of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>. While the recently identified multi-year decrease in AMOC strength similarly impacts carbon transports, its full effect is masked by the northwards transport of increasing surface CO2 levels. A 30% slowdown in the <span class="hlt">meridional</span> <span class="hlt">circulation</span> in 2009-2010 and the anomalous effects it had on the transport, storage and divergence of heat and freshwater in the subtropical and subpolar gyres and local wind regimes are investigated for their impact on local air-sea CO2 fluxes. Temperature and salt content anomalies identified in each gyre are found to drive (subtropics) or hinder (subpolar) additional carbon uptake from the atmosphere by affecting the physical solubility pump for CO2. Additionally their simultaneous effect on mixed layer depth and the vertical supply of nutrients to the surface is shown to magnify the CO2 flux observed by driving anomalous primary production rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JGR...10526117G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JGR...10526117G"><span><span class="hlt">Meridional</span> overturning and large-scale <span class="hlt">circulation</span> of the Indian Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ganachaud, Alexandre; Wunsch, Carl; Marotzke, Jochem; Toole, John</p> <p>2000-11-01</p> <p>The large scale Indian Ocean <span class="hlt">circulation</span> is estimated from a global hydrographic inverse geostrophic box model with a focus on the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC). The global model is based on selected recent World Ocean <span class="hlt">Circulation</span> Experiment (WOCE) sections which in the Indian Basin consist of zonal sections at 32°S, 20°S and 8°S, and a section between Bali and Australia from the Java-Australia Dynamic Experiment (JADE). The <span class="hlt">circulation</span> is required to conserve mass, salinity, heat, silica and "PO" (170PO4+O2). Near-conservation is imposed within layers bounded by neutral surfaces, while permitting advective and diffusive exchanges between the layers. Conceptually, the derived <span class="hlt">circulation</span> is an estimate of the average <span class="hlt">circulation</span> for the period 1987-1995. A deep inflow into the Indian Basin of 11±4 Sv is found, which is in the lower range of previous estimates, but consistent with conservation requirements and the global data set. The Indonesian Throughflow (ITF) is estimated at 15±5 Sv. The flow in the Mozambique Channel is of the same magnitude, implying a weak net flow between Madagascar and Australia. A net evaporation of -0.6±0.4 Sv is found between 32°S and 8°S, consistent with independent estimates. No net heat gain is found over the Indian Basin (0.1 ± 0.2PW north of 32°S) as a consequence of the large warm water influx from the ITF. Through the use of anomaly equations, the average dianeutral upwelling and diffusion between the sections are required and resolved, with values in the range 1-3×10-5 cm s-1 for the upwelling and 2-10 cm2 s-1 for the diffusivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22348562-role-asymmetric-meridional-circulation-producing-north-south-asymmetry-solar-cycle-dynamo-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22348562-role-asymmetric-meridional-circulation-producing-north-south-asymmetry-solar-cycle-dynamo-model"><span>Role of asymmetric <span class="hlt">meridional</span> <span class="hlt">circulation</span> in producing north-south asymmetry in a solar cycle dynamo model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Belucz, Bernadett; Dikpati, Mausumi</p> <p>2013-12-10</p> <p>Solar cycles in the north and south hemispheres differ in cycle length, amplitude, profile, polar fields, and coronal structure. To show what role differences in <span class="hlt">meridional</span> flow could play in producing these differences, we present the results of three sets of numerical simulations from a flux transport dynamo in which one property of <span class="hlt">meridional</span> <span class="hlt">circulation</span> has been changed in the south only. The changes are in amplitude and the presence of a second cell in latitude or in depth. An ascending phase speedup causes weakening of polar and toroidal fields; a speed decrease in a late descending phase does notmore » change amplitudes. A long-duration speed increase leads to lower toroidal field peaks but unchanged polar field peaks. A second high-latitude <span class="hlt">circulation</span> cell in an ascending phase weakens the next polar and toroidal field peaks, and the ascending phase is lengthened. A second cell in a late descending phase speeds up the cycle. A long-duration second cell leads to a poleward branch of the butterfly diagram and weaker polar fields. A second cell in depth reverses the tilt of the butterfly wing, decreasing polar fields when added during an ascending phase and increasing them during a late descending phase. A long-duration presence of a second cell in radius evolves the butterfly diagram far away from the observed one, with different dynamo periods in low and high latitudes. Thus, a second cell in depth is unlikely to persist more than a few years if the solar dynamo is advection-dominated. Our results show the importance of time variation and north-south asymmetry in <span class="hlt">meridional</span> <span class="hlt">circulation</span> in producing differing cycles in the north and south.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017A%26A...601A..46L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017A%26A...601A..46L"><span>Comparison of acoustic travel-time measurements of solar <span class="hlt">meridional</span> <span class="hlt">circulation</span> from SDO/HMI and SOHO/MDI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, Zhi-Chao; Birch, Aaron C.; Duvall, Thomas L., Jr.; Gizon, Laurent; Schou, Jesper</p> <p>2017-05-01</p> <p>Context. Time-distance helioseismology is one of the primary tools for studying the solar <span class="hlt">meridional</span> <span class="hlt">circulation</span>, especially in the lower convection zone. However, travel-time measurements of the subsurface <span class="hlt">meridional</span> flow suffer from a variety of systematic errors, such as a center-to-limb variation and an offset due to the position angle (P-angle) uncertainty of solar images. It has been suggested that the center-to-limb variation can be removed by subtracting east-west from south-north travel-time measurements. This ad hoc method for the removal of the center-to-limb effect has been adopted widely but not tested for travel distances corresponding to the lower convection zone. Aims: We explore the effects of two major sources of the systematic errors, the P-angle error arising from the instrumental misalignment and the center-to-limb variation, on the acoustic travel-time measurements in the south-north direction. Methods: We apply the time-distance technique to contemporaneous medium-degree Dopplergrams produced by SOHO/MDI and SDO/HMI to obtain the travel-time difference caused by <span class="hlt">meridional</span> <span class="hlt">circulation</span> throughout the solar convection zone. The P-angle offset in MDI images is measured by cross-correlating MDI and HMI images. The travel-time measurements in the south-north and east-west directions are averaged over the same observation period (May 2010 to Apr. 2011) for the two data sets and then compared to examine the consistency of MDI and HMI travel times after applying the above-mentioned corrections. Results: The offsets in the south-north travel-time difference from MDI data induced by the P-angle error gradually diminish with increasing travel distance. However, these offsets become noisy for travel distances corresponding to waves that reach the base of the convection zone. This suggests that a careful treatment of the P-angle problem is required when studying a deep <span class="hlt">meridional</span> flow. After correcting the P-angle and the removal of the center</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...46.3387Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...46.3387Y"><span>Wind effect on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> via sea ice and vertical diffusion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Haijun; Wang, Kun; Dai, Haijin; Wang, Yuxing; Li, Qing</p> <p>2016-06-01</p> <p>Effects of wind and fresh water on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) are investigated using a fully coupled climate model. The AMOC can change significantly when perturbed by either wind stress or freshwater flux in the North Atlantic. This study focuses on wind stress effect. Our model results show that the wind forcing is crucial in maintaining the AMOC. Reducing wind forcing over the ocean can cause immediately weakening of the vertical salinity diffusion and convection in the mid-high latitudes Atlantic, resulting in an enhancement of vertical salinity stratification that restrains the deep water formation there, triggering a slowdown of the thermohaline <span class="hlt">circulation</span>. As the thermohaline <span class="hlt">circulation</span> weakens, the sea ice expands southward and melts, providing the upper ocean with fresh water that weakens the thermohaline <span class="hlt">circulation</span> further. The wind perturbation experiments suggest a positive feedback between sea-ice and thermohaline <span class="hlt">circulation</span> strength, which can eventually result in a complete shutdown of the AMOC. This study also suggests that sea-ice variability may be also important to the natural AMOC variability on decadal and longer timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29433125','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29433125"><span><span class="hlt">Meridional</span> overturning <span class="hlt">circulation</span> conveys fast acidification to the deep Atlantic Ocean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Perez, Fiz F; Fontela, Marcos; García-Ibáñez, Maribel I; Mercier, Herlé; Velo, Anton; Lherminier, Pascale; Zunino, Patricia; de la Paz, Mercedes; Alonso-Pérez, Fernando; Guallart, Elisa F; Padin, Xose A</p> <p>2018-02-22</p> <p>Since the Industrial Revolution, the North Atlantic Ocean has been accumulating anthropogenic carbon dioxide (CO 2 ) and experiencing ocean acidification, that is, an increase in the concentration of hydrogen ions (a reduction in pH) and a reduction in the concentration of carbonate ions. The latter causes the 'aragonite saturation horizon'-below which waters are undersaturated with respect to a particular calcium carbonate, aragonite-to move to shallower depths (to shoal), exposing corals to corrosive waters. Here we use a database analysis to show that the present rate of supply of acidified waters to the deep Atlantic could cause the aragonite saturation horizon to shoal by 1,000-1,700 metres in the subpolar North Atlantic within the next three decades. We find that, during 1991-2016, a decrease in the concentration of carbonate ions in the Irminger Sea caused the aragonite saturation horizon to shoal by about 10-15 metres per year, and the volume of aragonite-saturated waters to reduce concomitantly. Our determination of the transport of the excess of carbonate over aragonite saturation ( xc [CO 3 2- ])-an indicator of the availability of aragonite to organisms-by the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> shows that the present-day transport of carbonate ions towards the deep ocean is about 44 per cent lower than it was in preindustrial times. We infer that a doubling of atmospheric anthropogenic CO 2 levels-which could occur within three decades according to a 'business-as-usual scenario' for climate change-could reduce the transport of xc [CO 3 2- ] by 64-79 per cent of that in preindustrial times, which could severely endanger cold-water coral habitats. The Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> would also export this acidified deep water southwards, spreading corrosive waters to the world ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Natur.554..515P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Natur.554..515P"><span><span class="hlt">Meridional</span> overturning <span class="hlt">circulation</span> conveys fast acidification to the deep Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perez, Fiz F.; Fontela, Marcos; García-Ibáñez, Maribel I.; Mercier, Herlé; Velo, Anton; Lherminier, Pascale; Zunino, Patricia; de La Paz, Mercedes; Alonso-Pérez, Fernando; Guallart, Elisa F.; Padin, Xose A.</p> <p>2018-02-01</p> <p>Since the Industrial Revolution, the North Atlantic Ocean has been accumulating anthropogenic carbon dioxide (CO2) and experiencing ocean acidification, that is, an increase in the concentration of hydrogen ions (a reduction in pH) and a reduction in the concentration of carbonate ions. The latter causes the ‘aragonite saturation horizon’—below which waters are undersaturated with respect to a particular calcium carbonate, aragonite—to move to shallower depths (to shoal), exposing corals to corrosive waters. Here we use a database analysis to show that the present rate of supply of acidified waters to the deep Atlantic could cause the aragonite saturation horizon to shoal by 1,000-1,700 metres in the subpolar North Atlantic within the next three decades. We find that, during 1991-2016, a decrease in the concentration of carbonate ions in the Irminger Sea caused the aragonite saturation horizon to shoal by about 10-15 metres per year, and the volume of aragonite-saturated waters to reduce concomitantly. Our determination of the transport of the excess of carbonate over aragonite saturation (xc[CO32-])—an indicator of the availability of aragonite to organisms—by the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> shows that the present-day transport of carbonate ions towards the deep ocean is about 44 per cent lower than it was in preindustrial times. We infer that a doubling of atmospheric anthropogenic CO2 levels—which could occur within three decades according to a ‘business-as-usual scenario’ for climate change—could reduce the transport of xc[CO32-] by 64-79 per cent of that in preindustrial times, which could severely endanger cold-water coral habitats. The Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> would also export this acidified deep water southwards, spreading corrosive waters to the world ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RvGeo..54....5B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RvGeo..54....5B"><span>Observations, inferences, and mechanisms of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>: A review</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buckley, Martha W.; Marshall, John</p> <p>2016-03-01</p> <p>This is a review about the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC), its mean structure, temporal variability, controlling mechanisms, and role in the coupled climate system. The AMOC plays a central role in climate through its heat and freshwater transports. Northward ocean heat transport achieved by the AMOC is responsible for the relative warmth of the Northern Hemisphere compared to the Southern Hemisphere and is thought to play a role in setting the mean position of the Intertropical Convergence Zone north of the equator. The AMOC is a key means by which heat anomalies are sequestered into the ocean's interior and thus modulates the trajectory of climate change. Fluctuations in the AMOC have been linked to low-frequency variability of Atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses. On intra-annual timescales, variability in AMOC is large and primarily reflects the response to local wind forcing; <span class="hlt">meridional</span> coherence of anomalies is limited to that of the wind field. On interannual to decadal timescales, AMOC changes are primarily geostrophic and related to buoyancy anomalies on the western boundary. A pacemaker region for decadal AMOC changes is located in a western "transition zone" along the boundary between the subtropical and subpolar gyres. Decadal AMOC anomalies are communicated <span class="hlt">meridionally</span> from this region. AMOC observations, as well as the expanded ocean observational network provided by the Argo array and satellite altimetry, are inspiring efforts to develop decadal predictability systems using coupled atmosphere-ocean models initialized by ocean data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27240625','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27240625"><span>Dissolved Organic Carbon in the North Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fontela, Marcos; García-Ibáñez, Maribel I; Hansell, Dennis A; Mercier, Herlé; Pérez, Fiz F</p> <p>2016-05-31</p> <p>The quantitative role of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr(-1)). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr(-1)) is considerable and represents almost a third of the atmospheric CO2 uptake in the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4886255','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4886255"><span>Dissolved Organic Carbon in the North Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fontela, Marcos; García-Ibáñez, Maribel I.; Hansell, Dennis A.; Mercier, Herlé; Pérez, Fiz F.</p> <p>2016-01-01</p> <p>The quantitative role of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr−1). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr−1) is considerable and represents almost a third of the atmospheric CO2 uptake in the region. PMID:27240625</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23118168','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23118168"><span>Comment on "Multiyear prediction of monthly mean Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> at 26.5°N".</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vecchi, Gabriel A; Msadek, Rym; Delworth, Thomas L; Dixon, Keith W; Guilyardi, Eric; Hawkins, Ed; Karspeck, Alicia R; Mignot, Juliette; Robson, Jon; Rosati, Anthony; Zhang, Rong</p> <p>2012-11-02</p> <p>Matei et al. (Reports, 6 January 2012, p. 76) claim to show skillful multiyear predictions of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC). However, these claims are not justified, primarily because the predictions of AMOC transport do not outperform simple reference forecasts based on climatological annual cycles. Accordingly, there is no justification for the "confident" prediction of a stable AMOC through 2014.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150019489','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150019489"><span>Mid-Pliocene Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> Not Unlike Modern</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhang, Z.-S.; Nisancioglu, K. H.; Chandler, M. A.; Haywood, A. M.; Otto-Bliesner, B. L.; Ramstein, G.; Stepanek, C.; Abe-Ouchi, A.; Chan, W. -L.; Sohl, L. E.</p> <p>2013-01-01</p> <p>In the Pliocene Model Intercomparison Project (PlioMIP), eight state-of-the-art coupled climate models have simulated the mid-Pliocene warm period (mPWP, 3.264 to 3.025 Ma). Here, we compare the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC), northward ocean heat transport and ocean stratification simulated with these models. None of the models participating in PlioMIP simulates a strong mid-Pliocene AMOC as suggested by earlier proxy studies. Rather, there is no consistent increase in AMOC maximum among the PlioMIP models. The only consistent change in AMOC is a shoaling of the overturning cell in the Atlantic, and a reduced influence of North Atlantic Deep Water (NADW) at depth in the basin. Furthermore, the simulated mid-Pliocene Atlantic northward heat transport is similar to the pre-industrial. These simulations demonstrate that the reconstructed high-latitude mid-Pliocene warming can not be explained as a direct response to an intensification of AMOC and concomitant increase in northward ocean heat transport by the Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5881L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5881L"><span>The impact of oceanic heat transport on the atmospheric <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lucarini, Valerio; Lunkeit, Frank</p> <p>2017-04-01</p> <p>A general <span class="hlt">circulation</span> model of intermediate complexity with an idealized Earth-like aquaplanet setup is used to study the impact of changes in the oceanic heat transport on the global atmospheric <span class="hlt">circulation</span>. Focus is on the atmospheric mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> and global thermodynamic properties. The atmosphere counterbalances to a large extent the imposed changes in the oceanic heat transport, but, nonetheless, significant modifications to the atmospheric general <span class="hlt">circulation</span> are found. Increasing the strength of the oceanic heat transport up to 2.5 PW leads to an increase in the global mean near-surface temperature and to a decrease in its equator-to-pole gradient. For stronger transports, the gradient is reduced further, but the global mean remains approximately constant. This is linked to a cooling and a reversal of the temperature gradient in the tropics. Additionally, a stronger oceanic heat transport leads to a decline in the intensity and a poleward shift of the maxima of both the <span class="hlt">Hadley</span> and Ferrel cells. Changes in zonal mean diabatic heating and friction impact the properties of the <span class="hlt">Hadley</span> cell, while the behavior of the Ferrel cell is mostly controlled by friction. The efficiency of the climate machine, the intensity of the Lorenz energy cycle and the material entropy production of the system decline with increased oceanic heat transport. This suggests that the climate system becomes less efficient and turns into a state of reduced entropy production as the enhanced oceanic transport performs a stronger large-scale mixing between geophysical fluids with different temperatures, thus reducing the available energy in the climate system and bringing it closer to a state of thermal equilibrium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP34B..05G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP34B..05G"><span><span class="hlt">Meridional</span> Transect of Atlantic Overturning <span class="hlt">Circulation</span> across the Mid-Pleistocene Transition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goldstein, S. L.; Pena, L. D.; Seguí, M. J.; Kim, J.; Yehudai, M.; Farmer, J. R.; Ford, H. L.; Haynes, L.; Hoenisch, B.; Raymo, M. E.; Ferretti, P.; Bickert, T.</p> <p>2016-12-01</p> <p>The Mid-Pleistocene Transition (MPT) marked a major transition in glacial-interglacial periodicity from dominantly 41 kyr to 100 kyr cycles between 1.3-0.7 Ma. From Nd isotope records in the South Atlantic, Pena and Goldstein (Science, 2014) concluded that the Atlantic overturning <span class="hlt">circulation</span> <span class="hlt">circulation</span> experienced major weakening between 950-850 ka (MIS 25-21), which generated the climatic conditions that intensified cold periods, prolonged their duration, and stabilized 100 kyr cycles. Such weakening would provide a mechanism for decreased atmospheric CO2 (Hönisch et al., Science, 2009) by allowing for additional atmospheric CO2 to be stored in the deep ocean. We present a summary of work in-progress to generate two dimensional representations of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>, from the north Atlantic to the Southern Ocean, at different time slices over the past 2Ma, including the MPT, based on Nd isotope ratios measured on Fe-Mn-oxide encrusted foraminifera and fish debris. Thus far we are analyzing samples from DSDP/ODP Sites 607, 1063 from the North Atlantic, 926 from the Equatorial Atlantic, 1264, 1267, 1088, 1090 in the South Atlantic, and 1094 from the Southern Ocean. Our data generated thus far support important changes in the overturning <span class="hlt">circulation</span> during the MPT, and greater glacial-interglacial variability in the 100 kyr world compared with the 40 kyr world. In addition, the data indicate a North Atlantic-sourced origin for the ocean <span class="hlt">circulation</span> disruption during the MPT. Comparison with ɛNd records in different ocean basins and with benthic foraminiferal δ13C and B/Ca ratios will also allow us to understand the links between deep ocean <span class="hlt">circulation</span> changes and the global carbon cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21582858-mean-field-solar-dynamo-models-strong-meridional-flow-bottom-convection-zone','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21582858-mean-field-solar-dynamo-models-strong-meridional-flow-bottom-convection-zone"><span>MEAN-FIELD SOLAR DYNAMO MODELS WITH A STRONG <span class="hlt">MERIDIONAL</span> FLOW AT THE BOTTOM OF THE CONVECTION ZONE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Pipin, V. V.; Kosovichev, A. G.</p> <p>2011-09-01</p> <p>This paper presents a study of kinematic axisymmetric mean-field dynamo models for the case of <span class="hlt">meridional</span> <span class="hlt">circulation</span> with a deep-seated stagnation point and a strong return flow at the bottom of the convection zone. This kind of <span class="hlt">circulation</span> follows from mean-field models of the angular momentum balance in the solar convection zone. The dynamo models include turbulent sources of the large-scale poloidal magnetic field production due to kinetic helicity and a combined effect due to the Coriolis force and large-scale electric current. In these models the toroidal magnetic field, which is responsible for sunspot production, is concentrated at the bottommore » of the convection zone and is transported to low-latitude regions by a <span class="hlt">meridional</span> flow. The <span class="hlt">meridional</span> component of the poloidal field is also concentrated at the bottom of the convection zone, while the radial component is concentrated in near-polar regions. We show that it is possible for this <span class="hlt">type</span> of <span class="hlt">meridional</span> <span class="hlt">circulation</span> to construct kinematic dynamo models that resemble in some aspects the sunspot magnetic activity cycle. However, in the near-equatorial regions the phase relation between the toroidal and poloidal components disagrees with observations. We also show that the period of the magnetic cycle may not always monotonically decrease with the increase of the <span class="hlt">meridional</span> flow speed. Thus, for further progress it is important to determine the structure of the <span class="hlt">meridional</span> <span class="hlt">circulation</span>, which is one of the critical properties, from helioseismology observations.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4103L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4103L"><span>A Possible Cause for Recent Decadal Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> Decline</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Latif, Mojib; Park, Taewook; Park, Wonsun</p> <p>2017-04-01</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is a major oceanic current system with widespread climate impacts. AMOC influences have been discussed among others with regard to Atlantic hurricane activity, regional sea level variability, and surface air temperature and precipitation changes on land areas adjacent to the North Atlantic Ocean. Most climate models project significant AMOC slowing during the 21st century, if atmospheric greenhouse gas concentrations continue to rise unabatedly. Recently, a marked decadal decline in AMOC strength has been observed, which was followed by strongly reduced oceanic poleward heat transport and record low sea surface temperature in parts of the North Atlantic. Here, we provide evidence from observations, re-analyses and climate models that the AMOC decline was due to the combined action of the North Atlantic Oscillation and East Atlantic Pattern, the two leading modes of North Atlantic atmospheric surface pressure variability, which prior to the decline both transitioned into their negative phases. This change in atmospheric <span class="hlt">circulation</span> diminished oceanic heat loss over the Labrador Sea and forced ocean <span class="hlt">circulation</span> changes lowering upper ocean salinity transport into that region. As a consequence, Labrador Sea deep convection weakened, which eventually slowed the AMOC. This study suggests a new mechanism for decadal AMOC variability, which is important to multiyear climate predictability and climate change detection in the North Atlantic sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....4999G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....4999G"><span>Atlantic freshwater balance in the hysteresis of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gregory, J. M.; Saenko, O. A.</p> <p>2003-04-01</p> <p>We have studied the hysteresis behaviour of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMO) in the UVic climate model, which comprises an ocean GCM coupled to an energy-moisture balance atmosphere model and a dynamic-thermodynamic sea ice model, all with a resolution of 3.6x1.8 degrees. As with some other models, we find that a slowly increasing freshwater flux applied to the north Atlantic causes the AMO to collapse rapidly when it passes a threshold, and that it returns equally quickly when the freshwater forcing falls below a negative freshwater flux threshold. During the collapse, the Atlantic becomes less saline because of the import of about 80 Sv yr of freshwater by the ocean across 30S; during the switch-on this freshwater is exported again. These abrupt import and export of freshwater at 30S of the Atlantic are associated with, respectively, the appearance and disappearance of a shallower reverse overturning <span class="hlt">circulation</span> south of the Equator. Qualitatively similar hysteresis behaviour, with the same salinity flip-flop, can be produced by an internal transfer of water within the Atlantic from low to high latitudes, with no net freshwater forcing input north of 30S.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPO43A..02J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPO43A..02J"><span>The relation between AMOC, gyre <span class="hlt">circulation</span>, and <span class="hlt">meridional</span> heat transports in the North Atlantic in model simulations of the last millennium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jungclaus, J. H.; Moreno-Chamarro, E.; Lohmann, K.; Zanchettin, D.</p> <p>2016-02-01</p> <p>While it is clear that the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is responsible for <span class="hlt">meridional</span> heat transfer from the South Atlantic and the tropics to the North Atlantic, the majority of the heat transport in the northern North Atlantic and the Nordic seas is carried by the gyre system. However, the detailed mechanisms determining the interaction between and the temporal modulation of the components of the northward heat transport system are not clear. Long-term climate records and model simulations can help to identify important processes and to provide background for the changes that are presently observed. Multi-centennial proxy records from the subpolar North Atlantic and the Nordic Seas indicate, for example, an out-of-phase behavior of sea surface temperature and gyre <span class="hlt">circulation</span> between the two regions with consequences for regional climate. Paleoceanographic evidence from Fram Strait shows a pronounced modulation of heat transfer to the Arctic by the Atlantic Water layer during the last 2000 years and reconstructions from the Subpolar North Atlantic suggest a role of ocean <span class="hlt">circulation</span> in the transition between the Medieval Climate Anomaly and the Little Ice Age. Here we explore a small ensemble of last millennium simulations, carried out with the Max Planck Institute Earth System Model, and analyze mechanisms connecting the AMOC and gyre <span class="hlt">circulation</span> and their relation to external forcing. Our results support the important role of the Subpolar Gyre strength and the related <span class="hlt">meridional</span> mass and temperature fluxes. We find that the modulation of the northward heat transport into the Nordic Seas and the Arctic has pronounced impact on sea-ice distribution, ocean-atmosphere interaction, and the surface climate in Scandinavia and Western Europe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814627J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814627J"><span>The relation between AMOC, gyre <span class="hlt">circulation</span>, and <span class="hlt">meridional</span> heat transports in the North Atlantic in model simulations of the last millennium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jungclaus, Johann; Moreno-Chamarro, Eduardo; Lohmann, Katja</p> <p>2016-04-01</p> <p>While it is clear that the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is responsible for <span class="hlt">meridional</span> heat transfer from the South Atlantic and the tropics to the North Atlantic, the majority of the heat transport in the northern North Atlantic and the Nordic seas is carried by the gyre system. However, the detailed mechanisms determining the interaction between and the temporal modulation of the components of the northward heat transport system are not clear. Long-term climate records and model simulations can help to identify important processes and to provide background for the changes that are presently observed. Multi-centennial proxy records from the subpolar North Atlantic and the Nordic Seas indicate, for example, an out-of-phase behavior of sea surface temperature and gyre <span class="hlt">circulation</span> between the two regions with consequences for regional climate. Paleoceanographic evidence from Fram Strait shows a pronounced modulation of heat transfer to the Arctic by the Atlantic Water layer during the last 2000 years and reconstructions from the Subpolar North Atlantic suggest a role of ocean <span class="hlt">circulation</span> in the transition between the Medieval Climate Anomaly and the Little Ice Age. Here we explore a small ensemble of last millennium simulations, carried out with the Max Planck Institute Earth System Model, and analyze mechanisms connecting the AMOC and gyre <span class="hlt">circulation</span> and their relation to external forcing. Our results support the important role of the Subpolar Gyre strength and the related <span class="hlt">meridional</span> mass and temperature fluxes. We find that the modulation of the northward heat transport into the Nordic Seas and the Arctic has pronounced impact on sea-ice distribution, ocean-atmosphere interaction, and the surface climate in Scandinavia and Western Europe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.4263Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.4263Z"><span>Basinwide response of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> to interannual wind forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Jian</p> <p>2017-12-01</p> <p>An eddy-resolving Ocean general <span class="hlt">circulation</span> model For the Earth Simulator (OFES) and a simple wind-driven two-layer model are used to investigate the role of momentum fluxes in driving the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) variability throughout the Atlantic basin from 1950 to 2010. Diagnostic analysis using the OFES results suggests that interior baroclinic Rossby waves and coastal topographic waves play essential roles in modulating the AMOC interannual variability. The proposed mechanisms are verified in the context of a simple two-layer model with realistic topography and only forced by surface wind. The topographic waves communicate high-latitude anomalies into lower latitudes and account for about 50% of the AMOC interannual variability in the subtropics. In addition, the large scale Rossby waves excited by wind forcing together with topographic waves set up coherent AMOC interannual variability patterns across the tropics and subtropics. The comparisons between the simple model and OFES results suggest that a large fraction of the AMOC interannual variability in the Atlantic basin can be explained by wind-driven dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22011787-theory-solar-meridional-circulation-high-latitudes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22011787-theory-solar-meridional-circulation-high-latitudes"><span>THEORY OF SOLAR <span class="hlt">MERIDIONAL</span> <span class="hlt">CIRCULATION</span> AT HIGH LATITUDES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Dikpati, Mausumi; Gilman, Peter A., E-mail: dikpati@ucar.edu, E-mail: gilman@ucar.edu</p> <p>2012-02-10</p> <p>We build a hydrodynamic model for computing and understanding the Sun's large-scale high-latitude flows, including Coriolis forces, turbulent diffusion of momentum, and gyroscopic pumping. Side boundaries of the spherical 'polar cap', our computational domain, are located at latitudes {>=} 60 Degree-Sign . Implementing observed low-latitude flows as side boundary conditions, we solve the flow equations for a Cartesian analog of the polar cap. The key parameter that determines whether there are nodes in the high-latitude <span class="hlt">meridional</span> flow is {epsilon} = 2{Omega}n{pi}H{sup 2}/{nu}, where {Omega} is the interior rotation rate, n is the radial wavenumber of the <span class="hlt">meridional</span> flow, H ismore » the depth of the convection zone, and {nu} is the turbulent viscosity. The smaller the {epsilon} (larger turbulent viscosity), the fewer the number of nodes in high latitudes. For all latitudes within the polar cap, we find three nodes for {nu} = 10{sup 12} cm{sup 2} s{sup -1}, two for 10{sup 13}, and one or none for 10{sup 15} or higher. For {nu} near 10{sup 14} our model exhibits 'node merging': as the <span class="hlt">meridional</span> flow speed is increased, two nodes cancel each other, leaving no nodes. On the other hand, for fixed flow speed at the boundary, as {nu} is increased the poleward-most node migrates to the pole and disappears, ultimately for high enough {nu} leaving no nodes. These results suggest that primary poleward surface <span class="hlt">meridional</span> flow can extend from 60 Degree-Sign to the pole either by node merging or by node migration and disappearance.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004ClDy...22..701B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004ClDy...22..701B"><span>Simulated variability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bentsen, M.; Drange, H.; Furevik, T.; Zhou, T.</p> <p></p> <p>To examine the multi-annual to decadal scale variability of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) we conducted a four-member ensemble with a daily reanalysis forced, medium-resolution global version of the isopycnic coordinate ocean model MICOM, and a 300-years integration with the fully coupled Bergen Climate Model (BCM). The simulations of the AMOC with both model systems yield a long-term mean value of 18 Sv and decadal variability with an amplitude of 1-3 Sv. The power spectrum of the inter-annual to decadal scale variability of the AMOC in BCM generally follows the theoretical red noise spectrum, with indications of increased power near the 20-years period. Comparison with observational proxy indices for the AMOC, e.g. the thickness of the Labrador Sea Water, the strength of the baroclinic gyre <span class="hlt">circulation</span> in the North Atlantic Ocean, and the surface temperature anomalies along the mean path of the Gulf Stream, shows similar trends and phasing of the variability, indicating that the simulated AMOC variability is robust and real. Mixing indices have been constructed for the Labrador, the Irminger and the Greenland-Iceland-Norwegian (GIN) seas. While convective mixing in the Labrador and the GIN seas are in opposite phase, and linked to the NAO as observations suggest, the convective mixing in the Irminger Sea is in phase with or leads the Labrador Sea. Newly formed deep water is seen as a slow, anomalous cold and fresh, plume flowing southward along the western continental slope of the Atlantic Ocean, with a return flow of warm and saline water on the surface. In addition, fast-travelling topographically trapped waves propagate southward along the continental slope towards equator, where they go east and continue along the eastern rim of the Atlantic. For both <span class="hlt">types</span> of experiments, the Northern Hemisphere sea level pressure and 2 m temperature anomaly patterns computed based on the difference between climate states with strong and weak AMOC</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeoRL..3920709W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeoRL..3920709W"><span>Stability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>: A model intercomparison</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weaver, Andrew J.; Sedláček, Jan; Eby, Michael; Alexander, Kaitlin; Crespin, Elisabeth; Fichefet, Thierry; Philippon-Berthier, Gwenaëlle; Joos, Fortunat; Kawamiya, Michio; Matsumoto, Katsumi; Steinacher, Marco; Tachiiri, Kaoru; Tokos, Kathy; Yoshimori, Masakazu; Zickfeld, Kirsten</p> <p>2012-10-01</p> <p>The evolution of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC) in 30 models of varying complexity is examined under four distinct Representative Concentration Pathways. The models include 25 Atmosphere-Ocean General <span class="hlt">Circulation</span> Models (AOGCMs) or Earth System Models (ESMs) that submitted simulations in support of the 5th phase of the Coupled Model Intercomparison Project (CMIP5) and 5 Earth System Models of Intermediate Complexity (EMICs). While none of the models incorporated the additional effects of ice sheet melting, they all projected very similar behaviour during the 21st century. Over this period the strength of MOC reduced by a best estimate of 22% (18%-25% 5%-95% confidence limits) for RCP2.6, 26% (23%-30%) for RCP4.5, 29% (23%-35%) for RCP6.0 and 40% (36%-44%) for RCP8.5. Two of the models eventually realized a slow shutdown of the MOC under RCP8.5, although no model exhibited an abrupt change of the MOC. Through analysis of the freshwater flux across 30°-32°S into the Atlantic, it was found that 40% of the CMIP5 models were in a bistable regime of the MOC for the duration of their RCP integrations. The results support previous assessments that it is very unlikely that the MOC will undergo an abrupt change to an off state as a consequence of global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPO43A..03B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPO43A..03B"><span><span class="hlt">Meridional</span> overturning <span class="hlt">circulations</span> driven by surface wind and buoyancy forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bell, M. J.</p> <p>2016-02-01</p> <p>A conceptual picture of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC) is developed using 2- and 3-layer models governed by the planetary geostrophic equations and simple global geometries. The picture has four main elements. First cold water driven to the surface in the South Atlantic north of Drake passage by Ekman upwelling is transformed into warmer water by heat input at the surface from the atmosphere. Second the model's boundary conditions constrain the depths of the isopycnal layers to be almost flat along the eastern boundaries of the ocean. This results in, third, warm water reaching high latitudes in the northern hemisphere where it is transformed into cold water by surface heat loss. Finally it is assumed that western boundary currents are able to close the <span class="hlt">circulations</span>. The results from a set of numerical experiments for the upwelling limb in the Southern Hemisphere are summarised in a simple conceptual schematic. Analytical solutions have been found for the down-welling limb assuming the wind stress in the Northern Hemisphere is negligible. Expressions for the depth of the isopycnal interface on the eastern boundary and the strength of the MOC obtained by combining these solutions in a 2-layer model are generally consistent with and complementary to those obtained by Gnandesikan (1999). The MOC in two basins one of which has a strong halocline is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920033894&hterms=kinematics+reverse&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dkinematics%2Breverse','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920033894&hterms=kinematics+reverse&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dkinematics%2Breverse"><span>A new solar cycle model including <span class="hlt">meridional</span> <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wang, Y.-M.; Sheeley, N. R., Jr.; Nash, A. G.</p> <p>1991-01-01</p> <p>A kinematic model is presented for the solar cycle which includes not only the transport of magnetic flux by supergranular diffusion and a poleward bulk flow at the sun's surface, but also the effects of turbulent diffusion and an equatorward 'return flow' beneath the surface. As in the earlier models of Babcock and Leighton, the rotational shearing of a subsurface poloidal field generates toroidal flux that erupts at the surface in the form of bipolar magnetic regions. However, such eruptions do not result in any net loss of toroidal flux from the sun (as assumed by Babcock and Leighton); instead, the large-scale toroidal field is destroyed both by 'unwinding' as the local poloidal field reverses its polarity, and by diffusion as the toroidal flux is transported equatorward by the subsurface flow and merged with its opposite hemisphere counterpart. The inclusion of <span class="hlt">meridional</span> <span class="hlt">circulation</span> allows stable oscillations of the magnetic field, accompanied by the equatorward progression of flux eruptions, to be achieved even in the absence of a radial gradient in the angular velocity. An illustrative case in which a subsurface flow speed of order 1 m/s and subsurface diffusion rate of order 10 sq km/s yield 22-yr oscillations in qualitative agreement with observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC44B..07F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC44B..07F"><span>Can Arctic Sea Ice Decline Weaken the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fedorov, A. V.; Sevellec, F.; Liu, W.</p> <p>2017-12-01</p> <p>The ongoing decline of Arctic sea ice exposes the ocean to anomalous surface heat and freshwater fluxes, resulting in positive buoyancy anomalies that can affect ocean <span class="hlt">circulation</span>. In this study (detailed in Sevellec, Fedorov, Liu 2017, Nature Climate Change) we apply an optimal flux perturbation framework and comprehensive climate model simulations (using CESM) to estimate the sensitivity of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) to such buoyancy forcing over the Arctic and globally, and more generally AMOC sensitivity to sea ice decline. We find that on decadal timescales flux anomalies over the subpolar North Atlantic have the largest impact on the AMOC; however, on multi-decadal timescales (longer than 20 years), anomalies in the Arctic become more important. These positive buoyancy anomalies from the Arctic spread to the North Atlantic, weakening the AMOC and its poleward heat transport after several decades. Therefore, the Arctic sea ice decline may explain the suggested slow-down of the AMOC and the "Warming Hole" persisting in the subpolar North Atlantic. Further, we discuss how the proposed connection, i.e. Arctic sea ice contraction would lead to an AMOC slow-down, varies across different earth system models. Overall, this study demonstrates that Arctic sea ice decline can play an active role in ocean and climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160007354&hterms=cell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcell','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160007354&hterms=cell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcell"><span>Midlatitude Cloud Shifts, Their Primary Link to the <span class="hlt">Hadley</span> Cell, and Their Diverse Radiative Effects</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tselioudis, George; Lipat, Bernard R.; Konsta, Dimitra; Grise, Kevin M.; Polvani, Lorenzo M.</p> <p>2016-01-01</p> <p>We investigate the interannual relationship among clouds, their radiative effects, and two key indices of the atmospheric <span class="hlt">circulation</span>: the latitudinal positions of the <span class="hlt">Hadley</span> cell edge and the midlatitude jet. From reanalysis data and satellite observations, we find a clear and consistent relationship between the width of the <span class="hlt">Hadley</span> cell and the high cloud field, statistically significant in nearly all regions and seasons. In contrast, shifts of the midlatitude jet correlate significantly with high cloud shifts only in the North Atlantic region during the winter season. While in that region and season poleward high cloud shifts are associated with shortwave radiative warming, over the Southern Oceans during all seasons they are associated with shortwave radiative cooling. Finally, a trend analysis reveals that poleward high cloud shifts observed over the 1983-2009 period are more likely related to <span class="hlt">Hadley</span> cell expansion, rather than poleward shifts of the midlatitude jets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AIPC..784..574G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AIPC..784..574G"><span>Exploring a deep <span class="hlt">meridional</span> flow hypothesis for a <span class="hlt">circulation</span> dominated solar dynamo model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guerrero, G. A.; Muñoz, J. D.; de Gouveia dal Pino, E. M.</p> <p>2005-09-01</p> <p><span class="hlt">Circulation</span>-dominated solar dynamo models, which employ a helioseismic rotation profile and a fixed <span class="hlt">meridional</span> flow, give a good approximation to the large scale solar magnetic phenomena, such as the 11-year cycle or the so called Hale's law of polarities. Nevertheless, the larger amplitude of the radial shear ∂Ω/∂r at the high latitudes makes the dynamo to produce a strong toroidal magnetic field at high latitudes, in contradiction with the observations of the sunspots (Sporer's Law). A possible solution was proposed by Nandy and Choudhuri in which a deep <span class="hlt">meridional</span> flow can conduct the magnetic field inside of a stable layer (the radiative core) and then allow that it erupts just at lower latitudes. Although they obtain good results, this hypothesis generates new problems like the mixture of elements in the radiative core (that alters the abundance of the elements) and the transfer of angular momentum. We have recently explored this hypothesis in a different approximation, using the magnetic buoyancy mechanism proposed by Dikpati and Charbonneau (1999) and found that a deep <span class="hlt">meridional</span> flow pushes the maximum of the toroidal magnetic field towards the solar equator, but, in contrast to Nandy and Choudhuri (2002 ), a second zone of maximum fields remains at the poles. In that work, we have also introduced a bipolytropic density profile in order to better reproduce the stratification in the radiative zone. We here review these results and also discuss a new possible scenario where the tachocline has an ellipsoidal shape, following early helioseismologic observations, and find that the modification of the geometry of the tachocline can lead to results which are in good agreement with observations and opens the possibility to explore in more detail, through the dynamo model, the place where the magnetic field could be really stored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950034013&hterms=rolando+garcia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D10%26Ntt%3Drolando%2Bgarcia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950034013&hterms=rolando+garcia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D10%26Ntt%3Drolando%2Bgarcia"><span>'Downward control' of the mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> and temperature distribution of the polar winter stratosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Garcia, Rolando R.; Boville, Byron A.</p> <p>1994-01-01</p> <p>According to the 'downward control' principle, the extratropical mean vertical velocity on a given pressure level is approximately proportional to the <span class="hlt">meridional</span> gradient of the vertically integrated zonal force per unit mass exerted by waves above that level. In this paper, a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the influence of gravity wave breaking in the mesosphere on the mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> and temperature distribution at lower levels in the polar winter stratosphere. The results of these calculations suggest that gravity wave drag in the mesosphere can affect the state of the polar winter stratosphere down to altitudes below 30 km. The effect is most important when planetary wave driving is relatively weak: that is, during southern winter and in early northern winter. In southern winter, downwelling weakens by a factor of 2 near the stratospause and by 20% at 30 km when gravity wave drag is not included in the calculations. As a consequence, temperatures decrease considerably throughout the polar winter stratosphere (over 20 K above 40 km and as much as 8 K at 30 km, where the effect is enhanced by the long radiative relaxation timescale). The polar winter states obtained when gravity wave drag is omitted in this simple model resemble the results of simulations with some general <span class="hlt">circulation</span> models and suggest that some of the shortcomings of the latter may be due to a deficit in mesospheric momentum deposition by small-scale gravity waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25517093','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25517093"><span>Strong and deep Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during the last glacial cycle.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Böhm, E; Lippold, J; Gutjahr, M; Frank, M; Blaser, P; Antz, B; Fohlmeister, J; Frank, N; Andersen, M B; Deininger, M</p> <p>2015-01-01</p> <p>Extreme, abrupt Northern Hemisphere climate oscillations during the last glacial cycle (140,000 years ago to present) were modulated by changes in ocean <span class="hlt">circulation</span> and atmospheric forcing. However, the variability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC), which has a role in controlling heat transport from low to high latitudes and in ocean CO2 storage, is still poorly constrained beyond the Last Glacial Maximum. Here we show that a deep and vigorous overturning <span class="hlt">circulation</span> mode has persisted for most of the last glacial cycle, dominating ocean <span class="hlt">circulation</span> in the Atlantic, whereas a shallower glacial mode with southern-sourced waters filling the deep western North Atlantic prevailed during glacial maxima. Our results are based on a reconstruction of both the strength and the direction of the AMOC during the last glacial cycle from a highly resolved marine sedimentary record in the deep western North Atlantic. Parallel measurements of two independent chemical water tracers (the isotope ratios of (231)Pa/(230)Th and (143)Nd/(144)Nd), which are not directly affected by changes in the global cycle, reveal consistent responses of the AMOC during the last two glacial terminations. Any significant deviations from this configuration, resulting in slowdowns of the AMOC, were restricted to centennial-scale excursions during catastrophic iceberg discharges of the Heinrich stadials. Severe and multicentennial weakening of North Atlantic Deep Water formation occurred only during Heinrich stadials close to glacial maxima with increased ice coverage, probably as a result of increased fresh-water input. In contrast, the AMOC was relatively insensitive to submillennial meltwater pulses during warmer climate states, and an active AMOC prevailed during Dansgaard-Oeschger interstadials (Greenland warm periods).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMNG31A1842L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMNG31A1842L"><span>The Sensitivity of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> to Dynamical Framework in an Ocean General <span class="hlt">Circulation</span> Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, X.; Yu, Y.</p> <p>2016-12-01</p> <p>The horizontal coordinate systems commonly used in most global ocean models are the sphere latitude-longitude grid and displaced poles such as tripolar grid. The effect of the horizontal coordinate system on Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is evaluated using an oceanic general <span class="hlt">circulation</span> model (OGCM). Two experiments are conducted with the model using latitude-longitude grid (Lat_1) and tripolar grid (Tri). Results show that Tri simulates a stronger NADW than Lat_1, as more saline water masses enter into the GIN Seas in Tri. Two reasons can be attributed to the stronger NADW. One is the removal of zonal filter in Tri, which leads to an increasing of zonal gradient of temperature and salinity, thus strengthens the north geostrophic flow. In turn, it decreases the positive subsurface temperature and salinity biases in the subtropical regions. The other may be associated with topography at the North Pole, because the realistic topography is applied in tripolar grid and the longitude-latitude grid employs an artificial island around the North Pole. In order to evaluate the effect of filter on AMOC, three enhanced filter experiments are carried out. Compared to Lat_1, enhanced filter can also increase the NADW, for more saline water is suppressed to go north and accumulated in the Labrador Sea, especially in the experiment with enhanced filter on salinity (Lat_2_S).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4812739','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4812739"><span>Reduced interdecadal variability of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> under global warming</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Dong, Lina; Liu, Peng; Li, Hongli</p> <p>2016-01-01</p> <p>Interdecadal variability of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC-IV) plays an important role in climate variation and has significant societal impacts. Past climate reconstruction indicates that AMOC-IV has likely undergone significant changes. Despite some previous studies, responses of AMOC-IV to global warming remain unclear, in particular regarding its amplitude and time scale. In this study, we analyze the responses of AMOC-IV under various scenarios of future global warming in multiple models and find that AMOC-IV becomes weaker and shorter with enhanced global warming. From the present climate condition to the strongest future warming scenario, on average, the major period of AMOC-IV is shortened from ∼50 y to ∼20 y, and the amplitude is reduced by ∼60%. These reductions in period and amplitude of AMOC-IV are suggested to be associated with increased oceanic stratification under global warming and, in turn, the speedup of oceanic baroclinic Rossby waves. PMID:26951654</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26951654','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26951654"><span>Reduced interdecadal variability of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> under global warming.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Dong, Lina; Liu, Peng; Li, Hongli</p> <p>2016-03-22</p> <p>Interdecadal variability of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC-IV) plays an important role in climate variation and has significant societal impacts. Past climate reconstruction indicates that AMOC-IV has likely undergone significant changes. Despite some previous studies, responses of AMOC-IV to global warming remain unclear, in particular regarding its amplitude and time scale. In this study, we analyze the responses of AMOC-IV under various scenarios of future global warming in multiple models and find that AMOC-IV becomes weaker and shorter with enhanced global warming. From the present climate condition to the strongest future warming scenario, on average, the major period of AMOC-IV is shortened from ∼50 y to ∼20 y, and the amplitude is reduced by ∼60%. These reductions in period and amplitude of AMOC-IV are suggested to be associated with increased oceanic stratification under global warming and, in turn, the speedup of oceanic baroclinic Rossby waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatCo...5E5752B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatCo...5E5752B"><span>Early warning signals of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> collapse in a fully coupled climate model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boulton, Chris A.; Allison, Lesley C.; Lenton, Timothy M.</p> <p>2014-12-01</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) exhibits two stable states in models of varying complexity. Shifts between alternative AMOC states are thought to have played a role in past abrupt climate changes, but the proximity of the climate system to a threshold for future AMOC collapse is unknown. Generic early warning signals of critical slowing down before AMOC collapse have been found in climate models of low and intermediate complexity. Here we show that early warning signals of AMOC collapse are present in a fully coupled atmosphere-ocean general <span class="hlt">circulation</span> model, subject to a freshwater hosing experiment. The statistical significance of signals of increasing lag-1 autocorrelation and variance vary with latitude. They give up to 250 years warning before AMOC collapse, after ~550 years of monitoring. Future work is needed to clarify suggested dynamical mechanisms driving critical slowing down as the AMOC collapse is approached.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4268699','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4268699"><span>Early warning signals of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> collapse in a fully coupled climate model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Boulton, Chris A.; Allison, Lesley C.; Lenton, Timothy M.</p> <p>2014-01-01</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) exhibits two stable states in models of varying complexity. Shifts between alternative AMOC states are thought to have played a role in past abrupt climate changes, but the proximity of the climate system to a threshold for future AMOC collapse is unknown. Generic early warning signals of critical slowing down before AMOC collapse have been found in climate models of low and intermediate complexity. Here we show that early warning signals of AMOC collapse are present in a fully coupled atmosphere-ocean general <span class="hlt">circulation</span> model, subject to a freshwater hosing experiment. The statistical significance of signals of increasing lag-1 autocorrelation and variance vary with latitude. They give up to 250 years warning before AMOC collapse, after ~550 years of monitoring. Future work is needed to clarify suggested dynamical mechanisms driving critical slowing down as the AMOC collapse is approached. PMID:25482065</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25482065','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25482065"><span>Early warning signals of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> collapse in a fully coupled climate model.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boulton, Chris A; Allison, Lesley C; Lenton, Timothy M</p> <p>2014-12-08</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) exhibits two stable states in models of varying complexity. Shifts between alternative AMOC states are thought to have played a role in past abrupt climate changes, but the proximity of the climate system to a threshold for future AMOC collapse is unknown. Generic early warning signals of critical slowing down before AMOC collapse have been found in climate models of low and intermediate complexity. Here we show that early warning signals of AMOC collapse are present in a fully coupled atmosphere-ocean general <span class="hlt">circulation</span> model, subject to a freshwater hosing experiment. The statistical significance of signals of increasing lag-1 autocorrelation and variance vary with latitude. They give up to 250 years warning before AMOC collapse, after ~550 years of monitoring. Future work is needed to clarify suggested dynamical mechanisms driving critical slowing down as the AMOC collapse is approached.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...44..163A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...44..163A"><span>An event-based approach to understanding decadal fluctuations in the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allison, Lesley; Hawkins, Ed; Woollings, Tim</p> <p>2015-01-01</p> <p>Many previous studies have shown that unforced climate model simulations exhibit decadal-scale fluctuations in the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC), and that this variability can have impacts on surface climate fields. However, the robustness of these surface fingerprints across different models is less clear. Furthermore, with the potential for coupled feedbacks that may amplify or damp the response, it is not known whether the associated climate signals are linearly related to the strength of the AMOC changes, or if the fluctuation events exhibit nonlinear behaviour with respect to their strength or polarity. To explore these questions, we introduce an objective and flexible method for identifying the largest natural AMOC fluctuation events in multicentennial/multimillennial simulations of a variety of coupled climate models. The characteristics of the events are explored, including their magnitude, <span class="hlt">meridional</span> coherence and spatial structure, as well as links with ocean heat transport and the horizontal <span class="hlt">circulation</span>. The surface fingerprints in ocean temperature and salinity are examined, and compared with the results of linear regression analysis. It is found that the regressions generally provide a good indication of the surface changes associated with the largest AMOC events. However, there are some exceptions, including a nonlinear change in the atmospheric pressure signal, particularly at high latitudes, in HadCM3. Some asymmetries are also found between the changes associated with positive and negative AMOC events in the same model. Composite analysis suggests that there are signals that are robust across the largest AMOC events in each model, which provides reassurance that the surface changes associated with one particular event will be similar to those expected from regression analysis. However, large differences are found between the AMOC fingerprints in different models, which may hinder the prediction and attribution of such events in</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22223804','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22223804"><span>Multiyear prediction of monthly mean Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> at 26.5°N.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Matei, Daniela; Baehr, Johanna; Jungclaus, Johann H; Haak, Helmuth; Müller, Wolfgang A; Marotzke, Jochem</p> <p>2012-01-06</p> <p>Attempts to predict changes in Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) have yielded little success to date. Here, we demonstrate predictability for monthly mean AMOC strength at 26.5°N for up to 4 years in advance. This AMOC predictive skill arises predominantly from the basin-wide upper-mid-ocean geostrophic transport, which in turn can be predicted because we have skill in predicting the upper-ocean zonal density difference. Ensemble forecasts initialized between January 2008 and January 2011 indicate a stable AMOC at 26.5°N until at least 2014, despite a brief wind-induced weakening in 2010. Because AMOC influences many aspects of climate, our results establish AMOC as an important potential carrier of climate predictability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26163010','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26163010"><span>Effects of Southern Hemisphere Wind Changes on the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in Ocean Models.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gent, Peter R</p> <p>2016-01-01</p> <p>Observations show that the Southern Hemisphere zonal wind stress maximum has increased significantly over the past 30 years. Eddy-resolving ocean models show that the resulting increase in the Southern Ocean mean flow <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) is partially compensated by an increase in the eddy MOC. This effect can be reproduced in the non-eddy-resolving ocean component of a climate model, providing the eddy parameterization coefficient is variable and not a constant. If the coefficient is a constant, then the Southern Ocean mean MOC change is balanced by an unrealistically large change in the Atlantic Ocean MOC. Southern Ocean eddy compensation means that Southern Hemisphere winds cannot be the dominant mechanism driving midlatitude North Atlantic MOC variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840038605&hterms=cell+basics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dcell%2Bbasics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840038605&hterms=cell+basics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dcell%2Bbasics"><span>Three-dimensional baroclinic instability of a <span class="hlt">Hadley</span> cell for small Richardson number</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Antar, B. N.; Fowlis, W. W.</p> <p>1983-01-01</p> <p>For the case of a baroclinic flow whose Richardson number, Ri, is of order unity, a three-dimensional linear stability analysis is conducted on the basis of a model for a thin, horizontal, rotating fluid layer which is subjected to horizontal and vertical temperature gradients. The <span class="hlt">Hadley</span> cell basic state and stability analysis are both based on the Navier-Stokes and energy equations, and perturbations possessing zonal, <span class="hlt">meridional</span>, and vertical structures are considered. An attempt is made to extend the previous theoretical work on three-dimensional baroclinic instability for small Ri to a more realistic model involving the Prandtl and Ekman numbers, as well as to finite growth rates and a wider range of the zonal wavenumber. In general, it is found that the symmetric modes of maximum growth are not purely symmetric, but have a weak zonal structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1107722','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1107722"><span>"What Controls the Structure and Stability of the Ocean <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>: Implications for Abrupt Climate Change?"</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Fedorov, Alexey</p> <p>2013-11-23</p> <p>The central goal of this research project is to understand the properties of the ocean <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) – a topic critical for understanding climate variability and stability on a variety of timescales (from decadal to centennial and longer). Specifically, we have explored various factors that control the MOC stability and decadal variability in the Atlantic and the ocean thermal structure in general, including the possibility abrupt climate change. We have also continued efforts on improving the performance of coupled ocean-atmosphere GCMs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC33C1252H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC33C1252H"><span>Terrestrial water cycle induced <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> variability over the Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hsu, C. W.; Velicogna, I.</p> <p>2016-12-01</p> <p>Terrestrial water cycle has a significant role in the long-term changes of Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). With the fresh water input over the ocean from the river runoff or ice melting at the higher latitude, AMOC transport has been predicted to slow down at the end of the century. We compare ocean bottom pressure measured from the GRACE satellite data with the conventional density derived transport observations from the RAPID MOC/MOCHA array to study the impact of the terrestrial water cycle on the seasonal and inter annual AMOC variability detected by the RAPID MOC/MOCHA array observations. We propose that the observed short-term variability is due to coupling of wind driven and terrestrial water cycle changes. We show that the proposed mechanism explains a significant portion of the transport variance and we present new possible mechanism that can explain the residual transport signal in AMOC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A23I0342C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A23I0342C"><span>Robust impact of coupled stratospheric ozone chemistry on the response of the Austral <span class="hlt">circulation</span> to increased greenhouse gases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chiodo, G.; Polvani, L. M.</p> <p>2016-12-01</p> <p>Due to computational constraints, interactive stratospheric chemistry is commonly neglected in most GCMs participating in inter-comparison projects. The impact of this simplification on the modeled response to external forcings remains largely unexplored. In this work, we examine the impact of the stratospheric chemistry coupling on the SH <span class="hlt">circulation</span> response to an abrupt quadrupling of CO2. We accomplish this with a version of the Whole Atmosphere Community Climate (WACCM) model, which allows coupling and de-coupling stratospheric chemistry, without altering any other physical parameterization. We find that the chemistry coupling in WACCM significantly reduces (by about 20%) the response of both eddy-driven mid-latitude jet and the <span class="hlt">Hadley</span> Cell strength, without altering the surface temperature response. This behavior is linked to the representation of stratospheric ozone, and its effects on the <span class="hlt">meridional</span> temperature gradient at the extratropical tropopause. Our results imply that neglecting stratospheric ozone chemistry results in a potential overestimation of the <span class="hlt">circulation</span> response to GHGs. Hence, stratospheric ozone chemistry produces a substantial negative feedback on the response of the atmospheric <span class="hlt">circulation</span> to increased greenhouse gases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17702940','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17702940"><span>Temporal variability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> at 26.5 degrees N.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cunningham, Stuart A; Kanzow, Torsten; Rayner, Darren; Baringer, Molly O; Johns, William E; Marotzke, Jochem; Longworth, Hannah R; Grant, Elizabeth M; Hirschi, Joël J-M; Beal, Lisa M; Meinen, Christopher S; Bryden, Harry L</p> <p>2007-08-17</p> <p>The vigor of Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) is thought to be vulnerable to global warming, but its short-term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain. We combine continuous measurements of the MOC (beginning in 2004) using the purposefully designed transatlantic Rapid Climate Change array of moored instruments deployed along 26.5 degrees N, with time series of Gulf Stream transport and surface-layer Ekman transport to quantify its intra-annual variability. The year-long average overturning is 18.7 +/- 5.6 sverdrups (Sv) (range: 4.0 to 34.9 Sv, where 1 Sv = a flow of ocean water of 10(6) cubic meters per second). Interannual changes in the overturning can be monitored with a resolution of 1.5 Sv.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS43D1310S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS43D1310S"><span>Stronger Ocean Meridinal Heat Transport with a Weaker Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sevellec, F.; Fedorov, A. V.</p> <p>2014-12-01</p> <p>It is typically assumed that oceanic heat transport is well and positively correlated with the Atlantic <span class="hlt">Meridional</span> Ocean <span class="hlt">Circulation</span> (AMOC). In numerical "water-hosing" experiments, for example, imposing an anomalous freshwater flux in the northern hemisphere leads to a slow-down of the AMOC and a corresponding reduction of the northward heat transport. Here, we study the sensitivity of the heat transport to surface freshwater fluxes using a generalized stability analysis and find that, while the direct relationship between the AMOC and heat transport holds on shorter time scales, it completely reverses on timescales longer than ~500 yr. That is, a reduction in the AMOC volume transport can actually lead to a stronger heat transport on those long timescales, which results from the gradual increase in ocean thermal stratification. We discuss the implications of these results for the problem of steady state (statistically equilibrium) in ocean and climate GCM as well as various paleoclimate problems such as millennial climate variability and the maintenance of equable climate states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28070560','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28070560"><span>Overlooked possibility of a collapsed Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in warming climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Wei; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang</p> <p>2017-01-01</p> <p>Changes in the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) are moderate in most climate model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturbations. By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO 2 concentration is abruptly doubled from the 1990 level. Compared to an uncorrected model, the AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic. Our results highlight the need to develop dynamical metrics to constrain models and the importance of reducing model biases in long-term climate projection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5217057','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5217057"><span>Overlooked possibility of a collapsed Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in warming climate</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liu, Wei; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang</p> <p>2017-01-01</p> <p>Changes in the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) are moderate in most climate model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturbations. By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO2 concentration is abruptly doubled from the 1990 level. Compared to an uncorrected model, the AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic. Our results highlight the need to develop dynamical metrics to constrain models and the importance of reducing model biases in long-term climate projection. PMID:28070560</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JMetR..31..490L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JMetR..31..490L"><span>Sensitivity of Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> to the dynamical framework in an ocean general <span class="hlt">circulation</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Xiaolan; Yu, Yongqiang; Liu, Hailong; Lin, Pengfei</p> <p>2017-06-01</p> <p>The horizontal coordinate systems commonly used in most global ocean models are the spherical latitude-longitude grid and displaced poles, such as a tripolar grid. The effect of the horizontal coordinate system on Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) is evaluated by using an OGCM (ocean general <span class="hlt">circulation</span> model). Two experiments are conducted with the model—one using a latitude-longitude grid (referred to as Lat_1) and the other using a tripolar grid (referred to as Tri). The results show that Tri simulates a stronger North Atlantic deep water (NADW) than Lat_1, as more saline water masses enter the Greenland-Iceland-Norwegian (GIN) seas in Tri. The stronger NADW can be attributed to two factors. One is the removal of the zonal filter in Tri, which leads to an increasing of the zonal gradient of temperature and salinity, thus strengthening the north geostrophic flow. In turn, it decreases the positive subsurface temperature and salinity biases in the subtropical regions. The other may be associated with topography at the North Pole, because realistic topography is applied in the tripolar grid while the latitude-longitude grid employs an artificial island around the North Pole. In order to evaluate the effect of the filter on AMOC, three enhanced filter experiments are carried out. Compared to Lat_1, an enhanced filter can also augment NADW formation, since more saline water is suppressed in the GIN seas, but accumulated in the Labrador Sea, especially in experiment Lat_2_S, which is the experiment with an enhanced filter on salinity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MAP...129..145N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MAP...129..145N"><span>The increase in September precipitation in the Mediterranean region as a result of changes in atmospheric <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nojarov, Peter</p> <p>2017-04-01</p> <p>The study analyzes changes in September precipitation in the Mediterranean region and their possible causes. The research period is 1950-2014. The main finding is that the reduction in aerosol pollution over Europe in the late twentieth century has led to an upward shift of air temperatures in the region, which in turn has reduced the <span class="hlt">meridional</span> temperature gradient, leading to weakening and shift to the north of the Azores High (the north end of <span class="hlt">Hadley</span> <span class="hlt">circulation</span>). This northward shift placed the Mediterranean region in an area with decreasing SLP, which results in an increase in the number or intensity of cyclones, increase in cloudiness and precipitation and a decrease in air temperatures. In the period 1995-2014 the region (especially its eastern part) lies within the boundaries of Inter Tropical Convergence Zone in September.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcSci..10...29S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcSci..10...29S"><span>Observed decline of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> 2004-2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smeed, D. A.; McCarthy, G. D.; Cunningham, S. A.; Frajka-Williams, E.; Rayner, D.; Johns, W. E.; Meinen, C. S.; Baringer, M. O.; Moat, B. I.; Duchez, A.; Bryden, H. L.</p> <p>2014-02-01</p> <p>The Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) has been observed continuously at 26° N since April 2004. The AMOC and its component parts are monitored by combining a transatlantic array of moored instruments with submarine-cable-based measurements of the Gulf Stream and satellite derived Ekman transport. The time series has recently been extended to October 2012 and the results show a downward trend since 2004. From April 2008 to March 2012, the AMOC was an average of 2.7 Sv (1 Sv = 106 m3 s-1) weaker than in the first four years of observation (95% confidence that the reduction is 0.3 Sv or more). Ekman transport reduced by about 0.2 Sv and the Gulf Stream by 0.5 Sv but most of the change (2.0 Sv) is due to the mid-ocean geostrophic flow. The change of the mid-ocean geostrophic flow represents a strengthening of the southward flow above the thermocline. The increased southward flow of warm waters is balanced by a decrease in the southward flow of lower North Atlantic deep water below 3000 m. The transport of lower North Atlantic deep water slowed by 7% per year (95% confidence that the rate of slowing is greater than 2.5% per year).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...853...58L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...853...58L"><span>Atmospheric <span class="hlt">Circulation</span>, Chemistry, and Infrared Spectra of Titan-like Exoplanets around Different Stellar <span class="hlt">Types</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lora, Juan M.; Kataria, Tiffany; Gao, Peter</p> <p>2018-01-01</p> <p>With the discovery of ever smaller and colder exoplanets, terrestrial worlds with hazy atmospheres must be increasingly considered. Our solar system’s Titan is a prototypical hazy planet, whose atmosphere may be representative of a large number of planets in our Galaxy. As a step toward characterizing such worlds, we present simulations of exoplanets that resemble Titan but orbit three different stellar hosts: G, K, and M dwarf stars. We use general <span class="hlt">circulation</span> and photochemistry models to explore the <span class="hlt">circulation</span> and chemistry of these Titan-like planets under varying stellar spectra, in all cases assuming a Titan-like insolation. Due to the strong absorption of visible light by atmospheric haze, the redder radiation accompanying later stellar <span class="hlt">types</span> produces more isothermal stratospheres, stronger <span class="hlt">meridional</span> temperature gradients at mbar pressures, and deeper and stronger zonal winds. In all cases, the planets’ atmospheres are strongly superrotating, but <span class="hlt">meridional</span> <span class="hlt">circulation</span> cells are weaker aloft under redder starlight. The photochemistry of hydrocarbon and nitrile species varies with stellar spectra, with variations in the FUV/NUV flux ratio playing an important role. Our results tentatively suggest that column haze production rates could be similar under all three hosts, implying that planets around many different stars could have similar characteristics to Titan’s atmosphere. Lastly, we present theoretical emission spectra. Overall, our study indicates that, despite important and subtle differences, the <span class="hlt">circulation</span> and chemistry of Titan-like exoplanets are relatively insensitive to differences in the host star. These findings may be further probed with future space-based facilities, like WFIRST, LUVOIR, HabEx, and OST.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.5419Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.5419Z"><span>On the evolution of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> Fingerprint and implications for decadal predictability in the North Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Jinting; Zhang, Rong</p> <p>2015-07-01</p> <p>It has been suggested previously that the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) anomaly associated with changes in the North Atlantic Deep Water formation propagates southward with an advection speed north of 34°N. In this study, using Geophysical Fluid Dynamics Laboratory Coupled Model version 2.1 (GFDL CM2.1), we show that this slow southward propagation of the AMOC anomaly is crucial for the evolution and the enhanced decadal predictability of the AMOC fingerprint—the leading mode of upper ocean heat content (UOHC) in the extratropical North Atlantic. A positive AMOC anomaly in northern high latitudes leads to a convergence/divergence of the Atlantic <span class="hlt">meridional</span> heat transport (MHT) anomaly in the subpolar/Gulf Stream region, thus warming in the subpolar gyre (SPG) and cooling in the Gulf Stream region after several years. Recent decadal prediction studies successfully predicted the observed warm shift in the SPG in the mid-1990s. Our results here provide the physical mechanism for the enhanced decadal prediction skills in the SPG UOHC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP53C..03G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP53C..03G"><span>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> over time: a Nd isotope perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goldstein, S. L.; Pena, L. D.; Yehudai, M.; Seguí, M. J.; Kim, J.; Knudson, K. P.; Basak, C.</p> <p>2017-12-01</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is a major means for distributing heat between the tropics and the high latitudes, and thus its temporal variability has major impacts on ice age cycles. We present a summary of work in-progress to generate north-south profiles of the AMOC from the North Atlantic to the Southern Ocean, at various time slices over the past 2 Ma, based on Nd isotopes in Fe-Mn oxide encrusted foraminifera and fish debris. Our sites show a consistent north-south gradient in the North Atlantic source water (NSW) signal strength throughout, providing strong evidence that the data represent the fluctuations of the AMOC. The North Atlantic data show strong evidence that the eNd of the NSW end-member remained similar to today through this time interval (Kim et al. this meeting). We have identified 5 modes of the AMOC <span class="hlt">circulation</span>. The most common ones are the (1) "interglacial norm" where the NSW signal remains strong into the South Atlantic similar to the present-day, and the (2) "glacial norm" where moderate southern source water (SSW) signals extend into the deep North Atlantic. Less common are the (3) "weak AMOC" mode, typical of Heinrich events, the Mid-Pleistocene Transition (MPT), and MIS 10,16, where even the deep North Atlantic shows a strong SSW signal, and its counterpart the (4) "ultra-strong AMOC", in MIS 9, 11, 19, 21 and 25, when the NSW signal is unusually strong south of the equator. Finally, during the (5) "pre-MPT" mode, in MIS 26 and 27, uniquely low Nd isotope ratios in the North Atlantic signals major input of Nd from the Canadian Shield directly preceding the MPT AMOC crisis (Pena and Goldstein, Science 2014), reflecting events there that likely triggered it. Overall we expect that the AMOC profiles will be useful as a means to directly relate climate to concurrent ocean <span class="hlt">circulation</span> through time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850012295','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850012295"><span>Three-dimensional baroclinic instability of a <span class="hlt">Hadley</span> cell for small Richardson number</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Antar, B. N.; Fowlis, W. W.</p> <p>1985-01-01</p> <p>A three-dimensional, linear stability analysis of a baroclinic flow for Richardson number, Ri, of order unity is presented. The model considered is a thin horizontal, rotating fluid layer which is subjected to horizontal and vertical temperature gradients. The basic state is a <span class="hlt">Hadley</span> cell which is a solution of the complete set of governing, nonlinear equations and contains both Ekman and thermal boundary layers adjacent to the rigid boundaries; it is given in a closed form. The stability analysis is also based on the complete set of equations; and perturbation possessing zonal, <span class="hlt">meridional</span>, and vertical structures were considered. Numerical methods were developed for the stability problem which results in a stiff, eighth-order, ordinary differential eigenvalue problem. The previous work on three-dimensional baroclinic instability for small Ri was extended to a more realistic model involving the Prandtl number, sigma, and the Ekman number, E, and to finite growth rates and a wider range of the zonal wavenumber.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19444214','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19444214"><span>Interior pathways of the North Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bower, Amy S; Lozier, M Susan; Gary, Stefan F; Böning, Claus W</p> <p>2009-05-14</p> <p>To understand how our global climate will change in response to natural and anthropogenic forcing, it is essential to determine how quickly and by what pathways climate change signals are transported throughout the global ocean, a vast reservoir for heat and carbon dioxide. Labrador Sea Water (LSW), formed by open ocean convection in the subpolar North Atlantic, is a particularly sensitive indicator of climate change on interannual to decadal timescales. Hydrographic observations made anywhere along the western boundary of the North Atlantic reveal a core of LSW at intermediate depths advected southward within the Deep Western Boundary Current (DWBC). These observations have led to the widely held view that the DWBC is the dominant pathway for the export of LSW from its formation site in the northern North Atlantic towards the Equator. Here we show that most of the recently ventilated LSW entering the subtropics follows interior, not DWBC, pathways. The interior pathways are revealed by trajectories of subsurface RAFOS floats released during the period 2003-2005 that recorded once-daily temperature, pressure and acoustically determined position for two years, and by model-simulated 'e-floats' released in the subpolar DWBC. The evidence points to a few specific locations around the Grand Banks where LSW is most often injected into the interior. These results have implications for deep ocean ventilation and suggest that the interior subtropical gyre should not be ignored when considering the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA497072','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA497072"><span>Influence of the Antarctic Circumpolar Current on the Atlantic Meriodional <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2009-03-01</p> <p>Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> . Rev. Geophys., 45, 2004RG000166. Marshall, J., and T. Radko (2003): Residual...ANTARCTIC CIRCUMPOLAR CURRENT ON THE ATLANTIC <span class="hlt">MERIDIONAL</span> <span class="hlt">CIRCULATION</span> by David J. Widener March 2009 Thesis Advisor: Timour Radko...distribution is unlimited 12b. DISTRIBUTION CODE 13. ABSTRACT (maximum 200 words) The physics of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70193565','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70193565"><span>Increased hurricane frequency near Florida during Younger Dryas Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> slowdown</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Toomey, Michael; Korty, Robert L.; Donnelly, Jeffrey P.; van Hengstum, Peter J.; Curry, William B.</p> <p>2017-01-01</p> <p>The risk posed by intensification of North Atlantic hurricane activity remains controversial, in part due to a lack of available storm proxy records that extend beyond the relatively stable climates of the late Holocene. Here we present a record of storm-triggered turbidite deposition offshore the Dry Tortugas, south Florida, USA, that spans abrupt transitions in North Atlantic sea-surface temperature and Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) during the Younger Dryas (12.9–11.7 ka). Despite potentially hostile conditions for cyclogenesis in the tropical North Atlantic at that time, our record and numerical experiments suggest that strong hurricanes may have regularly affected Florida. Less severe surface cooling at mid-latitudes (∼20°–40°N) than across much of the tropical North Atlantic (∼10°–20°N) in response to AMOC reduction may best explain strong hurricane activity during the Younger Dryas near the Dry Tortugas and possibly along the entire southeastern coast of the United States.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917050Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917050Z"><span>Mesoscale eddies control <span class="hlt">meridional</span> heat flux variability in the subpolar North Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Jian; Bower, Amy; Yang, Jiayan; Lin, Xiaopei; Zhou, Chun</p> <p>2017-04-01</p> <p>The <span class="hlt">meridional</span> heat flux in the subpolar North Atlantic is vital to the climate of the high-latitude North Atlantic. For the basinwide heat flux across a section between Greenland and Scotland, much of the variability occurs in the Iceland basin, where the North Atlantic Current (NAC) carries relatively warm and salty water northward. As a component of the Overturning in the Subpolar North Atlantic Program (OSNAP), WHOI and OUC are jointly operating gliders in the Iceland Basin to continuously monitor the <span class="hlt">circulation</span> and corresponding heat flux in this eddy-rich region. Based on one year of observations, two <span class="hlt">circulation</span> regimes in the Iceland basin have been identified: a mesoscale eddy like <span class="hlt">circulation</span> pattern and northward NAC <span class="hlt">circulation</span> pattern. When a mesoscale eddy is generated, the rotational currents associated with the eddy lead to both northward and southward flow in the Iceland basin. This is quite different from the broad northward flow associated with the NAC when there is no eddy. The transition between the two regimes coupled with the strong temperature front in the Iceland basin can modify the <span class="hlt">meridional</span> heat flux on the order of 0.3PW, which is the dominant source for the heat flux change the Iceland Basin. According to high-resolution numerical model results, the Iceland Basin has the largest contribution to the <span class="hlt">meridional</span> heat flux variability along the section between Greenland and Scotland. Therefore, mesoscale eddies in the Iceland Basin provide important dynamics to control the <span class="hlt">meridional</span> heat flux variability in the subpolar North Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70170271','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70170271"><span>Late Holocene sea level variability and Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Cronin, Thomas M.; Farmer, Jesse R.; Marzen, R. E.; Thomas, E.; Varekamp, J.C.</p> <p>2014-01-01</p> <p>Pre-twentieth century sea level (SL) variability remains poorly understood due to limits of tide gauge records, low temporal resolution of tidal marsh records, and regional anomalies caused by dynamic ocean processes, notably multidecadal changes in Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC). We examined SL and AMOC variability along the eastern United States over the last 2000 years, using a SL curve constructed from proxy sea surface temperature (SST) records from Chesapeake Bay, and twentieth century SL-sea surface temperature (SST) relations derived from tide gauges and instrumental SST. The SL curve shows multidecadal-scale variability (20–30 years) during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), as well as the twentieth century. During these SL oscillations, short-term rates ranged from 2 to 4 mm yr−1, roughly similar to those of the last few decades. These oscillations likely represent internal modes of climate variability related to AMOC variability and originating at high latitudes, although the exact mechanisms remain unclear. Results imply that dynamic ocean changes, in addition to thermosteric, glacio-eustatic, or glacio-isostatic processes are an inherent part of SL variability in coastal regions, even during millennial-scale climate oscillations such as the MCA and LIA and should be factored into efforts that use tide gauges and tidal marsh sediments to understand global sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810799B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810799B"><span>Further influence of the eastern boundary on the seasonal variability of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> at 26N</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baehr, Johanna; Schmidt, Christian</p> <p>2016-04-01</p> <p>The seasonal cycle of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) at 26.5 N has been shown to arise predominantly from sub-surface density variations at the Eastern boundary. Here, we suggest that these sub-surface density variations have their origin in the seasonal variability of the Canary Current system, in particular the Poleward Undercurrent (PUC). We use a high-resolution ocean model (STORM) for which we show that the seasonal variability resembles observations for both sub-surface density variability and <span class="hlt">meridional</span> transports. In particular, the STORM model simulation density variations at the eastern boundary show seasonal variations reaching down to well over 1000m, a pattern that most model simulations systematically underestimate. We find that positive wind stress curl anomalies in late summer and already within one degree off the eastern boundary result -through water column stretching- in strong transport anomlies in PUC in fall, coherent down to 1000m depth. Simultaneously with a westward propagation of these transport anomalies, we find in winter a weak PUC between 200 m and 500m, and southward transports between 600m and 1300m. This variability is in agreement with the observationally-based suggestion of a seasonal reversal of the <span class="hlt">meridional</span> transports at intermediate depths. Our findings extend earlier studies which suggested that the seasonal variability at of the <span class="hlt">meridional</span> transports across 26N is created by changes in the basin-wide thermocline through wind-driven upwelling at the eastern boundary analyzing wind stress curl anomalies 2 degrees off the eastern boundary. Our results suggest that the investigation of AMOC variability and particular its seasonal cycle modulations require the analysis of boundary wind stress curl and the upper ocean transports within 1 degree off the eastern boundary. These findings also implicate that without high-resolution coverage of the eastern boundary, coarser model simulation might not fully</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.8214G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.8214G"><span>Destabilization of glacial climate by the radiative impact of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> disruptions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galbraith, Eric D.; Merlis, Timothy M.; Palter, Jaime B.</p> <p>2016-08-01</p> <p>During each of the dramatic global warmings that ended the Pleistocene ice ages, the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) was disrupted. It is not clear whether this was a contributing cause or simply an effect of deglaciation. Here we show that in an ensemble of simulations with a global climate model, AMOC disruption causes a consistent and sustained positive radiative imbalance of 0.4 W m-2. The imbalance is accommodated by heat accumulation in the ocean interior, representing an overall planetary warming, subsequently released by deep convection in the North Atlantic when the AMOC resumes. The results suggest a means by which AMOC disruptions could have helped to tip the planet out of stable glaciated states. However, the fact that AMOC disruptions occurred during prior Heinrich Stadials without causing deglaciation shows that other factors, such as ice sheet dynamics, or controls on CO2, were also key for deglaciation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880053846&hterms=diffusion+concept&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddiffusion%2Bconcept','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880053846&hterms=diffusion+concept&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddiffusion%2Bconcept"><span>Venus' superrotation, mixing length theory and eddy diffusion - A parametric study</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mayr, H. G.; Harris, I.; Schatten, K. H.; Stevens-Rayburn, D. R.; Chan, K. L.</p> <p>1988-01-01</p> <p>The concept of the <span class="hlt">Hadley</span> mechanism is adopted to describe the axisymmetric <span class="hlt">circulation</span> of the Venus atmosphere. It is shown that, for the atmosphere of a slowly rotating planet such as Venus, a form of the nonliner 'closure' (self-consistent solution) of the fluid dynamics system which constrains the magnitude of the eddy diffusion coefficients can be postulated. A nonlinear one-layer spectral model of the zonally symmetric <span class="hlt">circulation</span> was then used to establish the relationship between the heat source, the <span class="hlt">meridional</span> <span class="hlt">circulation</span>, and the eddy diffusion coefficients, yielding large zonal velocities. Computer experiments indicated that proportional changes in the heat source and eddy diffusion coefficients do not significantly change the zonal velocities. It was also found that, for large eddy diffusion coefficients, the <span class="hlt">meridional</span> velocity is virtually constant; below a threshold in the diffusion rate, the <span class="hlt">meridional</span> velocity decreases; and, for large eddy diffusion and small heating rates, the zonal velocities decrease with decreasing planetary rotation rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.4150C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.4150C"><span>Observed decline of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">circulation</span> 2004 to 2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cunningham, Stuart; Smeed, David; Johns, William; Meinen, Chris; Rayner, Darren; Moat, Ben; Duchez, Aurelie; Bryden, Harry; Baringer Molly, O.; McCarthy, Gerard</p> <p>2014-05-01</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) has been observed continuously at 26° N since April 2004. The AMOC and its component parts are monitored by combining a transatlantic array of moored instruments with submarine-cable based measurements of the Gulf Stream and satellite derived Ekman transport. The time series has recently been extended to October 2012 and the results show a downward trend since 2004. From April~2008 to March 2012 the AMOC was an average of 2.7 Sv weaker than in the first four years of observation (95% confidence that the reduction is 0.3 Sv or more). Ekman transport reduced by about 0.2 Sv and the Gulf Stream by 0.5 Sv but most of the change (2.0 Sv) is due to the mid-ocean geostrophic flow. The change of the mid-ocean geostrophic flow represents a strengthening of the subtropical gyre above the thermocline. The increased southward flow of warm waters is balanced by a decrease in the southward flow of Lower North Atlantic Deep Water below 3000 m. The transport of Lower North Atlantic Deep Water slowed by 7% per year (95% confidence that the rate of slowing is greater than 2.5% per year).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018OcSci..14...53M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018OcSci..14...53M"><span>South Atlantic <span class="hlt">meridional</span> transports from NEMO-based simulations and reanalyses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mignac, Davi; Ferreira, David; Haines, Keith</p> <p>2018-02-01</p> <p>The <span class="hlt">meridional</span> heat transport (MHT) of the South Atlantic plays a key role in the global heat budget: it is the only equatorward basin-scale ocean heat transport and it sets the northward direction of the global cross-equatorial transport. Its strength and variability, however, are not well known. The South Atlantic transports are evaluated for four state-of-the-art global ocean reanalyses (ORAs) and two free-running models (FRMs) in the period 1997-2010. All products employ the Nucleus for European Modelling of the Oceans (NEMO) model, and the ORAs share very similar configurations. Very few previous works have looked at ocean <span class="hlt">circulation</span> patterns in reanalysis products, but here we show that the ORA basin interior transports are consistently improved by the assimilated in situ and satellite observations relative to the FRMs, especially in the Argo period. The ORAs also exhibit systematically higher <span class="hlt">meridional</span> transports than the FRMs, which is in closer agreement with observational estimates at 35 and 11° S. However, the data assimilation impact on the <span class="hlt">meridional</span> transports still greatly varies among the ORAs, leading to differences up to ˜ 8 Sv and 0.4 PW in the South Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> and the MHTs, respectively. We narrow this down to large inter-product discrepancies in the western boundary currents (WBCs) at both upper and deep levels explaining up to ˜ 85 % of the inter-product differences in MHT. We show that <span class="hlt">meridional</span> velocity differences, rather than temperature differences, in the WBCs drive ˜ 83 % of this MHT spread. These findings show that the present ocean observation network and data assimilation schemes can be used to consistently constrain the South Atlantic interior <span class="hlt">circulation</span> but not the overturning component, which is dominated by the narrow western boundary currents. This will likely limit the effectiveness of ORA products for climate or decadal prediction studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.7237P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.7237P"><span>The Canary Basin contribution to the seasonal cycle of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> at 26°N</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pérez-Hernández, M. D.; McCarthy, G. D.; Vélez-Belchí, P.; Smeed, D. A.; Fraile-Nuez, E.; Hernández-Guerra, A.</p> <p>2015-11-01</p> <p>This study examines the seasonal cycle of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) and its eastern boundary contributions. The cycle has a magnitude of 6 Sv, as measured by the RAPID/MOCHA/WBTS project array at 26°N, which is driven largely by the eastern boundary. The eastern boundary variations are explored in the context of the regional <span class="hlt">circulation</span> around the Canary Islands. There is a 3 month lag between maximum wind forcing and the largest eastern boundary transports, which is explained in terms of a model for Rossby wave generated at the eastern boundary. Two dynamic processes take place through the Lanzarote Passage (LP) in fall: the recirculation of the Canary Current and the northward flow of the Intermediate Poleward Undercurrent. In contrast, during the remaining seasons the transport through the LP is southward due to the Canary Upwelling Current. These processes are linked to the seasonal cycle of the AMOC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.455...73R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.455...73R"><span><span class="hlt">Meridional</span> <span class="hlt">circulation</span> across the Antarctic Circumpolar Current serves as a double 231Pa and 230Th trap</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rutgers van der Loeff, Michiel; Venchiarutti, Celia; Stimac, Ingrid; van Ooijen, Jan; Huhn, Oliver; Rohardt, Gerd; Strass, Volker</p> <p>2016-12-01</p> <p>Upwelling of Circumpolar Deep Water in the Weddell Gyre and low scavenging rates south of the Antarctic Circumpolar Current (ACC) cause an accumulation of particle reactive nuclides in the Weddell Gyre. A ventilation/reversible scavenging model that successfully described the accumulation of 230Th in this area was tested with other particle reactive nuclides and failed to adequately describe the depth-distributions of 231Pa and 210Pb. We present here a modified model that includes a nutrient-like accumulation south of the Antarctic Polar Front in an upper <span class="hlt">meridional</span> <span class="hlt">circulation</span> cell, as well as transport to a deep <span class="hlt">circulation</span> cell in the Weddell Gyre by scavenging and subsequent release at depth. The model also explains depletion of 231Pa and 230Th in Weddell Sea Bottom Water (WSBW) by ventilation of newly formed deep water on a timescale of 10 years, but this water mass is too dense to leave the Weddell Gyre. In order to quantify the processes responsible for the 231Pa- and 230Th-composition of newly formed Antarctic Bottom Water (AABW) we present a mass balance of 231Pa and 230Th in the Atlantic sector of the Southern Ocean based on new data from the GEOTRACES program. The ACC receives 6.0 ± 1.5 ×106 dpms-1 of 230Th from the Weddell Sea, similar in magnitude to the net input of 4.2 ± 3.0 ×106 dpms-1 from the north. For 231Pa, the relative contribution from the Weddell Sea is much smaller, only 0.3 ± 0.1 ×106, compared to 2.7 ± 1.4 ×106 dpms-1 from the north. Weddell Sea Deep Water (WSDW) leaving the Weddell Gyre northward to form AABW is exposed in the ACC to resuspended opal-rich sediments that act as efficient scavengers with a Th/Pa fractionation factor F ≤ 1. Hydrothermal inputs may provide additional removal with low F. Scavenging in the full <span class="hlt">meridional</span> <span class="hlt">circulation</span> across the opal-rich ACC thus acts as a double 231Pa and 230Th trap that preconditions newly formed AABW.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890062290&hterms=balance+general&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dbalance%2Bgeneral','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890062290&hterms=balance+general&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dbalance%2Bgeneral"><span>Minimal modeling of the extratropical general <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>O'Brien, Enda; Branscome, Lee E.</p> <p>1989-01-01</p> <p>The ability of low-order, two-layer models to reproduce basic features of the mid-latitude general <span class="hlt">circulation</span> is investigated. Changes in model behavior with increased spectral resolution are examined in detail. Qualitatively correct time-mean heat and momentum balances are achieved in a beta-plane channel model which includes the first and third <span class="hlt">meridional</span> modes. This minimal resolution also reproduces qualitatively realistic surface and upper-level winds and mean <span class="hlt">meridional</span> <span class="hlt">circulations</span>. Higher <span class="hlt">meridional</span> resolution does not result in substantial changes in the latitudinal structure of the <span class="hlt">circulation</span>. A qualitatively correct kinetic energy spectrum is produced when the resolution is high enough to include several linearly stable modes. A model with three zonal waves and the first three <span class="hlt">meridional</span> modes has a reasonable energy spectrum and energy conversion cycle, while also satisfying heat and momentum budget requirements. This truncation reproduces the basic mechanisms and zonal <span class="hlt">circulation</span> features that are obtained at higher resolution. The model performance improves gradually with higher resolution and is smoothly dependent on changes in external parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.2881S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.2881S"><span>Influence of glacial ice sheets on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> through surface wind change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sherriff-Tadano, Sam; Abe-Ouchi, Ayako; Yoshimori, Masakazu; Oka, Akira; Chan, Wing-Le</p> <p>2018-04-01</p> <p>Coupled modeling studies have recently shown that the existence of the glacial ice sheets intensifies the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). However, most models show a strong AMOC in their simulations of the Last Glacial Maximum (LGM), which is biased compared to reconstructions that indicate both a weaker and stronger AMOC during the LGM. Therefore, a detailed investigation of the mechanism behind this intensification of the AMOC is important for a better understanding of the glacial climate and the LGM AMOC. Here, various numerical simulations are conducted to focus on the effect of wind changes due to glacial ice sheets on the AMOC and the crucial region where the wind modifies the AMOC. First, from atmospheric general <span class="hlt">circulation</span> model experiments, the effect of glacial ice sheets on the surface wind is evaluated. Second, from ocean general <span class="hlt">circulation</span> model experiments, the influence of the wind stress change on the AMOC is evaluated by applying wind stress anomalies regionally or at different magnitudes as a boundary condition. These experiments demonstrate that glacial ice sheets intensify the AMOC through an increase in the wind stress at the North Atlantic mid-latitudes, which is induced by the North American ice sheet. This intensification of the AMOC is caused by the increased oceanic horizontal and vertical transport of salt, while the change in sea ice transport has an opposite, though minor, effect. Experiments further show that the Eurasian ice sheet intensifies the AMOC by directly affecting the deep-water formation in the Norwegian Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.2718Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.2718Z"><span>Response of North Atlantic Ocean Chlorophyll a to the Change of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Min; Zhang, Yuanling; Shu, Qi; Zhao, Chang; Wang, Gang; Wu, Zhaohua; Qiao, Fangli</p> <p>2017-04-01</p> <p>Changes in marine phytoplankton are a vital component in global carbon cycling. Despite this far-reaching importance, the variable trend in phytoplankton and its response to climate variability remain unclear. This work presents the spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean by using merged ocean color products for the period 1997-2016. We find a dipole pattern between the subpolar gyre and the Gulf Stream path,and chlorophyll a trend signal propagatedalong the opposite direction of the North Atlantic Current. Such a dipole pattern and opposite propagation of chlorophyll a signal are consistent with the recent distinctive signature of the slowdown of the Atlantic <span class="hlt">Meridional</span>Overturning <span class="hlt">Circulation</span> (AMOC). It is suggested that the spatiotemporal evolution of chlorophyll a during the two most recent decades is a part of the multidecadal variation and regulated byAMOC, which could be used as an indicator of AMOC variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27194601','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27194601"><span>Punctuated Shutdown of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> during Greenland Stadial 1.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hogg, Alan; Southon, John; Turney, Chris; Palmer, Jonathan; Bronk Ramsey, Christopher; Fenwick, Pavla; Boswijk, Gretel; Friedrich, Michael; Helle, Gerhard; Hughen, Konrad; Jones, Richard; Kromer, Bernd; Noronha, Alexandra; Reynard, Linda; Staff, Richard; Wacker, Lukas</p> <p>2016-05-19</p> <p>The Greenland Stadial 1 (GS-1; ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC), resulting in an antiphase temperature response between the hemispheres (the 'bipolar seesaw'). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon ((14)C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring (14)C records with marine (14)C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric (14)C offset was close to zero prior to GS-1, before reaching 'near-modern' values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4872135','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4872135"><span>Punctuated Shutdown of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> during Greenland Stadial 1</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hogg, Alan; Southon, John; Turney, Chris; Palmer, Jonathan; Bronk Ramsey, Christopher; Fenwick, Pavla; Boswijk, Gretel; Friedrich, Michael; Helle, Gerhard; Hughen, Konrad; Jones, Richard; Kromer, Bernd; Noronha, Alexandra; Reynard, Linda; Staff, Richard; Wacker, Lukas</p> <p>2016-01-01</p> <p>The Greenland Stadial 1 (GS-1; ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC), resulting in an antiphase temperature response between the hemispheres (the ‘bipolar seesaw’). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon (14C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring 14C records with marine 14C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric 14C offset was close to zero prior to GS-1, before reaching ‘near-modern’ values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes. PMID:27194601</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008ESPM...122.119Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008ESPM...122.119Z"><span><span class="hlt">Meridional</span> Flow Measurements: Comparisons Between Ring Diagram Analysis and Fourier-Hankel Analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaatri, A.; Roth, M.</p> <p>2008-09-01</p> <p>The <span class="hlt">meridional</span> <span class="hlt">circulation</span> is a weak flow with amplitude in the order of 10 m/s on the solar surface. As this flow could be responsible for the transport of magnetic flux during the solar cycle it has become a crucial ingredient in some dynamo models. However, only less is known about the overall structure of the <span class="hlt">meridional</span> <span class="hlt">circulation</span>. Helioseismology is able to provide information on the structure of this flow in the solar interior. One widely used helioseismic technique for measuring frequency shifts due to horizontal flows in the subsurface layers of the sun is the ring diagram analyis (Corbard et al. 2003). It is based on the analysis of frequency shifts in the solar oscillation power spectrum as a function of the orientation of the wave vector. This then allows drawing conclusions on the strength of <span class="hlt">meridional</span> flow, too. Ring diagram analysis is currently limited to the analysis of the wave field in only a small region on the solar surface. Consequently, information on the solar interior can only be inferred down to a depth of about 16 Mm. Another helioseismology method that promises to estimate the <span class="hlt">meridional</span> flow strength down to greater depths is the Fourier-Hankel analysis (Krieger et al. 2007). This technique is based on a decomposition of the wave field in poleward and equatorward propagating waves. A possible frequency shift between them is then due to the <span class="hlt">meridional</span> flow. We have been motivated for carrying out a comparative study between the two techniques to measure the <span class="hlt">meridional</span> flow. We investigate the degree of coherence between the two methods by analyzing the same data sets recorded by the SOHO-MDI and GONG instruments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1214170M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1214170M"><span>Links Between the Deep Western Boundary Current, Labrador Sea Water Formation and Export, and the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Myers, Paul G.; Kulan, Nilgun</p> <p>2010-05-01</p> <p>Based on an isopyncal analysis of historical data, 3-year overlapping triad fields of objectively analysed temperature and salinity are produced for the Labrador Sea, covering 1949-1999. These fields are then used to spectrally nudge an eddy-permitting ocean general <span class="hlt">circulation</span> model of the sub-polar gyre, otherwise forced by inter annually varying surface forcing based upon the Coordinated Ocean Reference Experiment (CORE). High frequency output from the reanalysis is used to examine Labrador Sea Water formation and its export. A number of different apprpoaches are used to estimate Labrador Sea Water formation, including an instanteous kinematic approach to calculate the annual rate of water mass subduction at a given density range. Historical transports are computed along sections at 53 and 56N for several different water masses for comparison with recent observations, showing a decline in the stength of the deep western boundary current with time. The variability of the strength of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) from the reanalysis is also examined in both depth and density space. Linkages between MOC variability and water mass formation variability is considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=apollo&pg=3&id=ED055923','ERIC'); return false;" href="https://eric.ed.gov/?q=apollo&pg=3&id=ED055923"><span>Apollo 15 at <span class="hlt">Hadley</span> Base.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>National Aeronautics and Space Administration, Washington, DC.</p> <p></p> <p>This publication highlights the mission of Apollo 15 and includes many detailed black and white and color photographs taken near the lunar Apennine Mountains and the mile-wide, meandering <span class="hlt">Hadley</span> Rille. Some of the photographs are full page (9 by 12 inch) reproductions. (Author/PR)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...44....1P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...44....1P"><span>Hydrographic biases in global coupled climate models and their relation to the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plancherel, Yves</p> <p>2015-01-01</p> <p>Comparison of the volumetric θ/S distribution of models participating in the Climate Model Intercomparison Project 3 (CMIP3) indicates that these models differ widely in their ability to represent the thermohaline properties of water masses. Relationships between features of the quasi-equilibrium hydrographic mean state of these models and aspects of their overturning <span class="hlt">circulations</span> are investigated. This is achieved quantitatively with the help of seven diagnostic hydrographic stations. These few stations were specifically selected to provide a minimalist schematic of the global water mass system. Relationships between hydrographic conditions in the North Atlantic measured with a subset of these stations suggest that hydrographic properties in the subpolar North Atlantic are set by the <span class="hlt">circulation</span> field of each model, pointing towards deficiencies in the models ability to resolve the Gulf Stream-North Atlantic Current system as a major limitation. Since diapycnal mixing and viscosity parameterizations differ across CMIP3 models and exert a strong control on the overturning, it is likely that these architectural differences ultimately explain the main across-model differences in overturning <span class="hlt">circulation</span>, temperature and salinity in the North Atlantic. The analysis of properties across the quasi-equilibrium states of the CMIP3 models agrees with previously reported relationships between <span class="hlt">meridional</span> steric height gradients or horizontal density contrasts at depth and the strength of the deep water cell. Robust relationships are also found in the Southern Ocean linking measures of vertical stratification with the strength of the abyssal <span class="hlt">circulations</span> across the CMIP3 models. Consistent correlations between aspects of the quasi-equilibrium hydrography in the Southern Ocean and the sensitivity of the abyssal cell to increasing radiative forcing by 2100 were found. Using these relations in conjunction with modern hydrographic observations to interpolate the fate of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120016994&hterms=atlantic+meridional+overturning+circulation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120016994&hterms=atlantic+meridional+overturning+circulation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation"><span>Warm and Saline Events Embedded in the <span class="hlt">Meridional</span> <span class="hlt">Circulation</span> of the Northern North Atlantic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.</p> <p>2011-01-01</p> <p>Ocean state estimates from 1958 to 2005 from the Simple Ocean Assimilation System (SODA) system are analyzed to understand <span class="hlt">circulation</span> between subtropical and subpolar Atlantic and their connection with atmospheric forcing. This analysis shows three periods (1960s, around 1980, and 2000s) with enhanced warm, saline waters reaching high latitudes, alternating with freshwater events originating at high latitudes. It complements surface drifter and altimetry data showing the subtropical -subpolar exchange leading to a significant temperature and salinity increase in the northeast Atlantic after 2001. The warm water limb of the Atlantic <span class="hlt">meridional</span> overturning cell represented by SODA expanded in density/salinity space during these warm events. Tracer simulations using SODA velocities also show decadal variation of the Gulf Stream waters reaching the subpolar gyre and Nordic seas. The negative phase of the North Atlantic Oscillation index, usually invoked in such variability, fails to predict the warming and salinization in the early 2000s, with salinities not seen since the 1960s. Wind stress curl variability provided a linkage to this subtropical/subpolar gyre exchange as illustrated using an idealized two ]layer <span class="hlt">circulation</span> model. The ocean response to the modulation of the climatological wind stress curl pattern was found to be such that the northward penetration of subtropical tracers is enhanced when amplitude of the wind stress curl is weaker than normal. In this case both the subtropical and subpolar gyres weaken and the subpolar density surfaces relax; hence, the polar front moves westward, opening an enhanced northward access of the subtropical waters in the eastern boundary current.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.5470L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.5470L"><span>Impact of the Indonesian Throughflow on the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Bars, Dewi; Dijkstra, Henk</p> <p>2014-05-01</p> <p>Understanding the mechanisms controlling the strength and variability of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is one of the main topics of climate science and in particular physical oceanography. Current simple representations of the global ocean overturning separates the surface return flow to the Atlantic basin into a cold water path through the Drake Passage and a warm water path through the Indonesian Throughflow and Agulhas leakage. The relative importance of these two paths has been investigated in non-eddying ocean models. In these models the Agulhas retroflection cannot be modelled properly, which leads to an important overestimation of the Agulhas leakage. Furthermore, it seems that the in these models the relation between the <span class="hlt">meridional</span> density gradient and the overturning strength is greatly simplified and changes significantly when eddies are resolved (Den Toom et al. 2013). As a result, the impact of the Pacific-Indian Oceans exchange through the Indonesian Throughflow on the AMOC is still unknown. To investigate this question we run a state-of-the-art ocean model, the Parallel Ocean Program (POP), globally, at eddy resolving resolution (0.1º). Using climatological forcing from the CORE dataset we perform two simulations of 110 years, a control experiment with realistic coastlines and one in which the Indonesian Passages are closed. Results show that, for a closed Indonesian Throughflow, the Indian Ocean cools down but its salinity increases. The Agulhas leakage reduces also by 3Sv (Le Bars et al. 2013) and the net effect on the south Atlantic is a cooling down and decrease salinity. The anomalies propagate slowly northward and a significant decrease of the AMOC is found at 26ºN after 50 years. This decrease AMOC also leads to reduced northward heat flux in the Atlantic. These processes are investigated with a detailed analysis of the heat and freshwater balances in the Atlantic-Arctic region and in the region south of 34ºS where</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC31F1164O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC31F1164O"><span>Reducing the Uncertainty in Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> Projections Using Bayesian Model Averaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olson, R.; An, S. I.</p> <p>2016-12-01</p> <p>Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) in the ocean might slow down in the future, which can lead to a host of climatic effects in North Atlantic and throughout the world. Despite improvements in climate models and availability of new observations, AMOC projections remain uncertain. Here we constrain CMIP5 multi-model ensemble output with observations of a recently developed AMOC index to provide improved Bayesian predictions of future AMOC. Specifically, we first calculate yearly AMOC index loosely based on Rahmstorf et al. (2015) for years 1880—2004 for both observations, and the CMIP5 models for which relevant output is available. We then assign a weight to each model based on a Bayesian Model Averaging method that accounts for differential model skill in terms of both mean state and variability. We include the temporal autocorrelation in climate model errors, and account for the uncertainty in the parameters of our statistical model. We use the weights to provide future weighted projections of AMOC, and compare them to un-weighted ones. Our projections use bootstrapping to account for uncertainty in internal AMOC variability. We also perform spectral and other statistical analyses to show that AMOC index variability, both in models and in observations, is consistent with red noise. Our results improve on and complement previous work by using a new ensemble of climate models, a different observational metric, and an improved Bayesian weighting method that accounts for differential model skill at reproducing internal variability. Reference: Rahmstorf, S., Box, J. E., Feulner, G., Mann, M. E., Robinson, A., Rutherford, S., & Schaffernicht, E. J. (2015). Exceptional twentieth-century slowdown in atlantic ocean overturning <span class="hlt">circulation</span>. Nature Climate Change, 5(5), 475-480. doi:10.1038/nclimate2554</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C11D..04L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C11D..04L"><span>The relationship between Arctic sea ice and the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> in a warming climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, W.; Fedorov, A. V.</p> <p>2017-12-01</p> <p>A recent study (Sevellec, Fedorov, Liu 2017, Nature Climate Change) has suggested that Arctic sea ice decline can lead to a slow-down of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). Here, we build on this previous work and explore the relationship between Arctic sea ice and the AMOC in climate models. We find that the current Arctic sea ice decline can contribute about 40% to the AMOC weakening over the next 60 years. This effect is related to the warming and freshening of the upper ocean in the Arctic, and the subsequent spread of generated buoyancy anomalies downstream where they affect the North Atlantic deep convection sites and hence the AMOC on multi-decadal timescales. The weakening of the AMOC and its poleward heat transport, in turn, sustains the "Warming Hole" - a region in the North Atlantic with anomalously weak (or even negative) warming trends. We discuss the key factors that control this robust AMOC response to changes in Arctic sea ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013QSRv...63....1B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013QSRv...63....1B"><span>Interglacial climates and the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>: is there an Arctic controversy?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bauch, Henning A.</p> <p>2013-03-01</p> <p>Arctic palaeorecords are important to understand the "natural range" of forcing and feedback mechanisms within the context of past and present climate change in this temperature-sensitive region. A wide array of methods and archives now provide a robust understanding of the Holocene climate evolution. By comparison rather little is still known about older interglacials, and in particular, on the effects of the northward propagation of heat transfer via the Atlantic <span class="hlt">meridional</span> ocean <span class="hlt">circulation</span> (AMOC) into the Arctic. Terrestrial records from this area often indicate a warmer and moister climate during past interglacials than in the Holocene implying a more vigorous AMOC activity. This is in conflict with marine data. Although recognized as very prominent interglacials in Antarctic ice cores, cross-latitudinal surface ocean temperature reconstructions show that little of the surface ocean warmth still identified in the Northeast Atlantic during older interglacial peaks (e.g., MIS5e, 9, 11) was further conveyed into the polar latitudes, and that each interglacial developed its own specific palaeoclimate features. Interactive processes between water mass overturning and the hydrological system of the Arctic, and how both developed together out of a glacial period with its particular ice sheet configuration and relative sea-level history, determined the efficiency of an evolving interglacial AMOC. Because of that glacial terminations developed some very specific water mass characteristics, which also affected the climate evolution of the ensuing interglacial periods. Moreover, the observed contrasts in the Arctic-directed <span class="hlt">meridional</span> ocean heat flux between past interglacials have implications for the palaeoclimatic evaluation of this polar region. Crucial environmental factors of the Arctic climate system, such as the highly dynamical interactions between deep water mass flow, surface ocean temperature/salinity, sea ice, and atmosphere, exert strong feedbacks on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4811303S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4811303S"><span>Progress Towards a Time-Dependent Theory of Solar <span class="hlt">Meridional</span> Flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shirley, James H.</p> <p>2017-08-01</p> <p>Large-scale <span class="hlt">meridional</span> motions of solar materials play an important role in flux transport dynamo models. <span class="hlt">Meridional</span> flows transport surface magnetic flux to polar regions of the Sun, where it may later be subducted and conveyed back towards the equatorial region by a deep return flow in the convection zone. The transported flux may thereafter lead to the generation of new toroidal fields, thereby completing the dynamo cycle. More than two decades of observations have revealed that <span class="hlt">meridional</span> flow speeds vary substantially with time. Further, a complex morphological variability of <span class="hlt">meridional</span> flow cells is now recognized, with multiple cell structures detected both in latitude and in depth. ‘Countercells’ with reversed flow directions have been detected at various times. Flow speeds are apparently influenced by the proximity of flows to active regions. This complexity represents a considerable challenge to dynamo modeling efforts. Flows morphology and speed changes may be arbitrarily prescribed in models, but physical realism of model outputs may be questionable, and elusive: The models are ‘trying to hit a moving target.’ Considerations such as these led Belucz et al. (2013; Ap. J. 806:169) to call for “time-dependent theories that can tell us theoretically how this <span class="hlt">circulation</span> may change its amplitude and form in each hemisphere.” Such a theory now exists for planetary atmospheres (Shirley, 2017; Plan. Sp. Sci. 141, 1-16). Proof of concept for the non-tidal orbit-spin coupling hypothesis of Shirley (2017) was obtained through numerical modeling of the atmospheric <span class="hlt">circulation</span> of Mars (Mischna & Shirley, 2017; Plan. Sp. Sci. 141, 45-72). Much-improved correspondence of numerical modeling outcomes with observations was demonstrated. In this presentation we will briefly review the physical hypothesis and some prior evidence of its possible role in solar dynamo excitation. We show a strong correlation between observed <span class="hlt">meridional</span> flow speeds of magnetic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-as15-87-11849.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-as15-87-11849.html"><span>View of Mount <span class="hlt">Hadley</span> as photographed by Apollo 15 during EVA</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1971-07-31</p> <p>AS15-87-11849 (31 July-2 Aug. 1971) --- An excellent view of Mount <span class="hlt">Hadley</span>, fully lighted, showing abundant linear features, as photographed during the Apollo 15 lunar surface extravehicular activity (EVA). This view is looking north from the Apollo Lunar Surface Experiments Package (ALSEP) site. Mount <span class="hlt">Hadley</span> rises about 4,500 meters (approximately 14,765 feet) above the plain. While astronauts David R. Scott, commander, and James B. Irwin, lunar module pilot, descended in the Apollo 15 Lunar Module (LM) "Falcon" to explore the <span class="hlt">Hadley</span>-Apennine area of the moon, astronaut Alfred M. Worden, command module pilot, remained with the Command and Service Modules (CSM) in lunar orbit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-S71-33432.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-S71-33432.html"><span>Artist's concept of <span class="hlt">Hadley</span>-Apennine landing site with alternate traverses</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1971-06-01</p> <p>S71-33432 (1 July 1971) --- These alternative traverses can be carried out on foot. They will be used if the Lunar Roving Vehicle (LRV) becomes inoperative. This artist's concept showing part of the <span class="hlt">Hadley</span> Rille and several of the Apennine Mountains was excerpted from "On the Moon with Apollo 15: A Guidebook to the <span class="hlt">Hadley</span>-Apennine Region," by Gene Simmons. Artwork by Jerry Elmore.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000DPS....32.5005R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000DPS....32.5005R"><span>Changes in the Martian <span class="hlt">Circulation</span> and Climate in Response to Orbital Parameter Variations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richardson, M. I.; Wilson, R. J.</p> <p>2000-10-01</p> <p> obliquity, the model does not develop a permanent CO2 ice cap at either pole (this likely reflects the fact that uniform and non-varying ice properties are gravely inadequate to realistically simulate Martian polar ices); Water ice deposits do not stabilize at the equator, even at high obliquity - instead they slosh backwards-and-forwards between the seasonal ice caps, as they do at present. We note that the southern summer <span class="hlt">Hadley</span> <span class="hlt">circulation</span> remains the dominant cell when integrated over the annual cycle, even when the timing of perihelion passage is varied by 180 degrees. We suggest that this reflects the greater importance of the global topographic dichotomy for the strength of the mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> over that of eccentricity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1344180-atlantic-meridional-heat-transports-computed-from-balancing-earth-energy-locally-amoc-ocean-meridional-heat-transport','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1344180-atlantic-meridional-heat-transports-computed-from-balancing-earth-energy-locally-amoc-ocean-meridional-heat-transport"><span>Atlantic <span class="hlt">meridional</span> heat transports computed from balancing Earth's energy locally: AMOC and Ocean <span class="hlt">Meridional</span> Heat Transport</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Trenberth, Kevin E.; Fasullo, John T.</p> <p></p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> plays a major role in moving heat and carbon around in the ocean. A new estimate of ocean heat transports for 2000 through 2013 throughout the Atlantic is derived. Top-of-atmosphere radiation is combined with atmospheric reanalyses to estimate surface heat fluxes and combined with vertically integrated ocean heat content to estimate ocean heat transport divergence as a residual. Atlantic peak northward ocean heat transports average 1.18 ± 0.13PW (1 sigma) at 15°N but vary considerably in latitude and time. Results agree well with observational estimates at 26.5°N from the RAPID array, but for 2004–2013 themore » <span class="hlt">meridional</span> heat transport is 1.00 ± 0.11PW versus 1.23 ± 0.11PW for RAPID. In addition, these results have no hint of a trend, unlike the RAPID results. Finally, strong westerlies north of a meridian drive ocean currents and an ocean heat loss into the atmosphere that is exacerbated by a decrease in ocean heat transport northward.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1344180-atlantic-meridional-heat-transports-computed-from-balancing-earth-energy-locally-amoc-ocean-meridional-heat-transport','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1344180-atlantic-meridional-heat-transports-computed-from-balancing-earth-energy-locally-amoc-ocean-meridional-heat-transport"><span>Atlantic <span class="hlt">meridional</span> heat transports computed from balancing Earth's energy locally: AMOC and Ocean <span class="hlt">Meridional</span> Heat Transport</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Trenberth, Kevin E.; Fasullo, John T.</p> <p>2017-02-18</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> plays a major role in moving heat and carbon around in the ocean. A new estimate of ocean heat transports for 2000 through 2013 throughout the Atlantic is derived. Top-of-atmosphere radiation is combined with atmospheric reanalyses to estimate surface heat fluxes and combined with vertically integrated ocean heat content to estimate ocean heat transport divergence as a residual. Atlantic peak northward ocean heat transports average 1.18 ± 0.13PW (1 sigma) at 15°N but vary considerably in latitude and time. Results agree well with observational estimates at 26.5°N from the RAPID array, but for 2004–2013 themore » <span class="hlt">meridional</span> heat transport is 1.00 ± 0.11PW versus 1.23 ± 0.11PW for RAPID. In addition, these results have no hint of a trend, unlike the RAPID results. Finally, strong westerlies north of a meridian drive ocean currents and an ocean heat loss into the atmosphere that is exacerbated by a decrease in ocean heat transport northward.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770011040','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770011040"><span>The morphology and origin of <span class="hlt">Hadley</span> Rille, the moon</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brewer, T.</p> <p>1976-01-01</p> <p><span class="hlt">Hadley</span> Rille is directly related to the emplacement of mare basalts in Palus Putredinis. Existing hypotheses of sinuous rille origin are in discord with the cooling behavior of deep lava flows and the strength of materials. It is proposed that <span class="hlt">Hadley</span> Rille is a channel which returned lava to the southern vent from which it initially extruded and that the channel persisted through many episodes of volcanism. This view is supported by available topographic information obtained by the lunar orbiter photography and the Apollo 15 mission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ERL....12c4009H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ERL....12c4009H"><span>Impact of the GeoMIP G1 sunshade geoengineering experiment on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hong, Yu; Moore, John C.; Jevrejeva, Svetlana; Ji, Duoying; Phipps, Steven J.; Lenton, Andrew; Tilmes, Simone; Watanabe, Shingo; Zhao, Liyun</p> <p>2017-03-01</p> <p>We analyze the multi-earth system model responses of ocean temperatures and the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) under an idealized solar radiation management scenario (G1) from the Geoengineering Model Intercomparison Project. All models simulate warming of the northern North Atlantic relative to no geoengineering, despite geoengineering substantially offsetting the increases in mean global ocean temperatures. Increases in the temperature of the North Atlantic Ocean at the surface (˜0.25 K) and at a depth of 500 m (˜0.10 K) are mainly due to a 10 Wm-2 reduction of total heat flux from ocean to atmosphere. Although the AMOC is slightly reduced under the solar dimming scenario, G1, relative to piControl, it is about 37% stronger than under abrupt4 × CO2 . The reduction of the AMOC under G1 is mainly a response to the heat flux change at the northern North Atlantic rather than to changes in the water flux and the wind stress. The AMOC transfers heat from tropics to high latitudes, helping to warm the high latitudes, and its strength is maintained under solar dimming rather than weakened by greenhouse gas forcing acting alone. Hence the relative reduction in high latitude ocean temperatures provided by solar radiation geoengineering, would tend to be counteracted by the correspondingly active AMOC <span class="hlt">circulation</span> which furthermore transports warm surface waters towards the Greenland ice sheet, warming Arctic sea ice and permafrost.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AAS...23113303S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AAS...23113303S"><span>Anelastic Models of Fully-Convective Stars: Differential Rotation, <span class="hlt">Meridional</span> <span class="hlt">Circulation</span> and Residual Entropy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sainsbury-Martinez, Felix; Browning, Matthew; Miesch, Mark; Featherstone, Nicholas A.</p> <p>2018-01-01</p> <p>Low-Mass stars are typically fully convective, and as such their dynamics may differ significantly from sun-like stars. Here we present a series of 3D anelastic HD and MHD simulations of fully convective stars, designed to investigate how the <span class="hlt">meridional</span> <span class="hlt">circulation</span>, the differential rotation, and residual entropy are affected by both varying stellar parameters, such as the luminosity or the rotation rate, and by the presence of a magnetic field. We also investigate, more specifically, a theoretical model in which isorotation contours and residual entropy (σ‧ = σ ‑ σ(r)) are intrinsically linked via the thermal wind equation (as proposed in the Solar context by Balbus in 2009). We have selected our simulation parameters in such as way as to span the transition between Solar-like differential rotation (fast equator + slow poles) and ‘anti-Solar’ differential rotation (slow equator + fast poles), as characterised by the convective Rossby number and △Ω. We illustrate the transition from single-celled to multi-celled MC profiles, and from positive to negative latitudinal entropy gradients. We show that an extrapolation involving both TWB and the σ‧/Ω link provides a reasonable estimate for the interior profile of our fully convective stars. Finally, we also present a selection of MHD simulations which exhibit an almost unsuppressed differential rotation profile, with energy balances remaining dominated by kinetic components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.3559A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.3559A"><span>How Robust Are the Surface Temperature Fingerprints of the Atlantic Overturning <span class="hlt">Meridional</span> <span class="hlt">Circulation</span> on Monthly Time Scales?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander-Turner, R.; Ortega, P.; Robson, J. I.</p> <p>2018-04-01</p> <p>It has been suggested that changes in the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) can drive sea surface temperature (SST) on monthly time scales (Duchez et al., 2016, https://doi.org/10.1002/2017GB005667). However, with only 11 years of continuous observations, the validity of this result over longer, or different, time periods is uncertain. In this study, we use a 120 yearlong control simulation from a high-resolution climate model to test the robustness of the AMOC fingerprints. The model reproduces the observed AMOC seasonal cycle and its variability, and the observed 5-month lagged AMOC-SST fingerprints derived from 11 years of data. However, the AMOC-SST fingerprints are very sensitive to the particular time period considered. In particular, both the Florida current and the upper mid-ocean transport produce highly inconsistent fingerprints when using time periods shorter than 30 years. Therefore, several decades of RAPID observations will be necessary to determine the real impact of the AMOC on SSTs at monthly time scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA488977','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA488977"><span>The Gulf Stream Pathway and the Impacts of the Eddy-Driven Abyssal <span class="hlt">Circulation</span> and the Deep Western Boundary Current</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2008-07-06</p> <p>bathymetry, wind forcing, and a <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC), the latter specified via ports in the northern and southern boundaries. The...small values below the sill depth in all of the simulations. e The upper ocean northward flow of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) is...plus the northward upper ocean flow (14 Sv) of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC). The mean Gulf Stream IR northwall pathway ±lrr from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940020409&hterms=planetary+motion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dplanetary%2Bmotion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940020409&hterms=planetary+motion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dplanetary%2Bmotion"><span>Regarding tracer transport in Mars' winter atmosphere in the presence of nearly stationary, forced planetary waves</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hollingsworth, Jeffrey L.; Haberle, R. M.; Houben, Howard C.</p> <p>1993-01-01</p> <p>Large-scale transport of volatiles and condensates on Mars, as well as atmospheric dust, is ultimately driven by the planet's global-scale atmospheric <span class="hlt">circulation</span>. This <span class="hlt">circulation</span> arises in part from the so-called mean <span class="hlt">meridional</span> (<span class="hlt">Hadley</span>) <span class="hlt">circulation</span> that is associated with rising/poleward motion in low latitudes and sinking/equatorward motion in middle and high latitudes. Intimately connected to the mean <span class="hlt">circulation</span> is an eddy-driven component due to large-scale wave activity in the planet's atmosphere. During winter this wave activity arises both from traveling weather systems (i.e., barotropic and baroclinic disturbances) and from 'forced' disturbances (e.g., the thermal tides and surface-forced planetary waves). Possible contributions to the effective (net) transport <span class="hlt">circulation</span> from forced planetary waves are investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018OcMod.122...57G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018OcMod.122...57G"><span>A commentary on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> stability in climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gent, Peter R.</p> <p>2018-02-01</p> <p>The stability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) in ocean models depends quite strongly on the model formulation, especially the vertical mixing, and whether it is coupled to an atmosphere model. A hysteresis loop in AMOC strength with respect to freshwater forcing has been found in several intermediate complexity climate models and in one fully coupled climate model that has very coarse resolution. Over 40% of modern climate models are in a bistable AMOC state according to the very frequently used simple stability criterion which is based solely on the sign of the AMOC freshwater transport across 33° S. In a recent freshwater hosing experiment in a climate model with an eddy-permitting ocean component, the change in the gyre freshwater transport across 33° S is larger than the AMOC freshwater transport change. This casts very strong doubt on the usefulness of this simple AMOC stability criterion. If a climate model uses large surface flux adjustments, then these adjustments can interfere with the atmosphere-ocean feedbacks, and strongly change the AMOC stability properties. AMOC can be shut off for many hundreds of years in modern fully coupled climate models if the hosing or carbon dioxide forcing is strong enough. However, in one climate model the AMOC recovers after between 1000 and 1400 years. Recent 1% increasing carbon dioxide runs and RCP8.5 future scenario runs have shown that the AMOC reduction is smaller using an eddy-resolving ocean component than in the comparable standard 1° ocean climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=atmospheric+AND+pressure&pg=4&id=EJ627270','ERIC'); return false;" href="https://eric.ed.gov/?q=atmospheric+AND+pressure&pg=4&id=EJ627270"><span>Understanding and Portraying the Global Atmospheric <span class="hlt">Circulation</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Harrington, John, Jr.; Oliver, John E.</p> <p>2000-01-01</p> <p>Examines teaching models of atmospheric <span class="hlt">circulation</span> and resultant surface pressure patterns, focusing on the three-cell model and the meaning of <span class="hlt">meridional</span> <span class="hlt">circulation</span> as related to middle and high latitudes. Addresses the failure of the three-cell model to explain seasonal variations in atmospheric <span class="hlt">circulation</span>. Suggests alternative models. (CMK)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890023496&hterms=ever+mozart&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfor%2Bever%2Bmozart','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890023496&hterms=ever+mozart&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfor%2Bever%2Bmozart"><span>The formation of <span class="hlt">Hadley</span> Rille and implications for the geology of the Apollo 15 region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Spudis, Paul D.; Swann, Gordon A.; Greeley, Ronald</p> <p>1988-01-01</p> <p>The results of studies of terrestrial lava tube systems and the regional and detailed site geology of the Apollo 15 area have been combined to develop a model for the formation of <span class="hlt">Hadley</span> Rille. The regional geology of the Apennine bench formation and its relation to Mozart and <span class="hlt">Hadley</span> Rilles is discussed. It is shown that the total thickness of mare basalt at the Apollo landing site is on the order of a few tens of meters, mostly less than 50 m. It is suggested that the role of thermal erosion in the development of sinuous rilles on the moon may be less important than previously assumed and that the assimilation of refractory highland rock <span class="hlt">types</span> into mare basaltic magma is a minor lunar process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17..169W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17..169W"><span>Effects of Wind and Freshwater on the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>: Role of Sea Ice and Vertical Diffusion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Kun; Yang, Haijun; Dai, Haijin; Wang, Yuxing; Li, Qing</p> <p>2015-04-01</p> <p>Effects of wind and fresh water on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) are investigated in a fully coupled climate model (CESM1.0). The AMOC can change significantly when perturbing either the wind stress or fresh water flux in the northern North Atlantic. This work pays special attention on the wind stress effect. Our model results show that the wind forcing is a crucial element in maintaining the AMOC. When the wind-stress is reduced, the vertical convection and diffusion are weakened immediately, triggering a salt deficit in the northern North Atlantic that prevents the deep water formation there. The salinity advection from the south, however, plays a contrary role to salt the upper ocean. As the AMOC weakens, the sea ice expends southward and melts, freshening the upper ocean that weakens the AMOC further. There is a positive feedback between the sea ice melting and AMOC strength, which eventually determines the AMOC strength in the reduced wind world.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...10Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...10Y"><span>A closer look at the relationships between <span class="hlt">meridional</span> mass <span class="hlt">circulation</span> pulses in the stratosphere and cold air outbreak patterns in northern hemispheric winter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Yueyue; Cai, Ming; Ren, Rongcai; Rao, Jian</p> <p>2018-01-01</p> <p>The relationship between continental-scale cold air outbreaks (CAOs) in the mid-latitudes and pulse signals in the stratospheric mass <span class="hlt">circulation</span> in Northern Hemisphere winter (December-February) is investigated using ERA-Interim data for the 32 winters from 1979 to 2011. Pulse signals in the stratospheric mass <span class="hlt">circulation</span> include "PULSE_TOT", "PULSE_W1", and "PULSE_W2" events, defined as a period of stronger <span class="hlt">meridional</span> mass transport into the polar stratosphere by total flow, wavenumber-1, and wavenumber-2, respectively. Each <span class="hlt">type</span> of PULSE event occurs on average 4-6 times per winter. A robust relationship is found between two dominant patterns of winter CAOs and PULSE_W1 and PULSE_W2 events. Cold temperature anomalies tend to occur over Eurasia with the other continent anomalously warm during the 2 weeks before the peak dates of PULSE_W1 events, while the opposite temperature anomaly pattern can be found after the peak dates; and during the 1-2 weeks centered on the peak dates of PULSE_W2 events, a higher probability of occurrence of CAOs is found over both continents. These relationships become more robust for PULSE_W1 and PULSE_W2 events of larger peak intensity. PULSE_TOT events are classified into five <span class="hlt">types</span>, which have a distinct coupling relationship with PULSE_W1 and PULSE_W2 events. The specific pattern of CAOs associated with each <span class="hlt">type</span> of PULSE_TOT event is found to be a combination of the CAO patterns associated with PULSE_W1 and PULSE_W2 events. The percentage of PULSE_TOT events belonging to the <span class="hlt">types</span> that are dominated by PULSE_W2 events increases with the peak intensity of PULSE_TOT events. Accordingly, the related CAO pattern is close to that associated with PULSE_W1 for PULSE_TOT events with small-to-medium intensity, but tends to resemble that associated with PULSE_W2 events as the peak intensity of PULSE_TOT events increases.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=S71-44667&hterms=serenity&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dserenity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=S71-44667&hterms=serenity&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dserenity"><span>View of <span class="hlt">Hadley</span>-Apennine area, looking north, photographed by Apollo 15</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1971-01-01</p> <p>An oblique view of the <span class="hlt">Hadley</span>-Apennine area, looking north, as photographed by the Fairchild metric camera in the SIM bay of the Apollo 15 Command/Service Module in lunar orbit. <span class="hlt">Hadley</span> Rille meanders through the lower center of the picture. The Apennine Mountains are at lower right. The Apollo 15 Lunar Module touchdown point is on the east side of the 'chicken beak' of <span class="hlt">Hadley</span> Rille. The Caucasus Mountains are at upper right. The dark mare area at the extreme upper right is a portion of the Sea of Serenity. The Marsh of Decay is at lower left. The large crater near the horizon is Aristillus, which is about 55 kilometers (34.18 statute miles) in diameter. The crater just to the south of Aristillus is Autolycus, which is about 40 kilometers (35 statute miles) in diameter. The crater Cassini is barely visible on the horizon at upper right.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5020648','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5020648"><span>Linkages between atmospheric blocking, sea ice export through Fram Strait and the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ionita, M.; Scholz, P.; Lohmann, G.; Dima, M.; Prange, M.</p> <p>2016-01-01</p> <p>As a key persistent component of the atmospheric dynamics, the North Atlantic blocking activity has been linked to extreme climatic phenomena in the European sector. It has also been linked to Atlantic multidecadal ocean variability, but its potential links to rapid oceanic changes have not been investigated. Using a global ocean-sea ice model forced with atmospheric reanalysis data, here it is shown that the 1962–1966 period of enhanced blocking activity over Greenland resulted in anomalous sea ice accumulation in the Arctic and ended with a sea ice flush from the Arctic into the North Atlantic Ocean through Fram Strait. This event induced a significant decrease of Labrador Sea water surface salinity and an abrupt weakening of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) during the 1970s. These results have implications for the prediction of rapid AMOC changes and indicate that an important part of the atmosphere-ocean dynamics at mid- and high latitudes requires a proper representation of the Fram Strait sea ice transport and of the synoptic scale variability such as atmospheric blocking, which is a challenge for current coupled climate models. PMID:27619955</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27619955','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27619955"><span>Linkages between atmospheric blocking, sea ice export through Fram Strait and the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ionita, M; Scholz, P; Lohmann, G; Dima, M; Prange, M</p> <p>2016-09-13</p> <p>As a key persistent component of the atmospheric dynamics, the North Atlantic blocking activity has been linked to extreme climatic phenomena in the European sector. It has also been linked to Atlantic multidecadal ocean variability, but its potential links to rapid oceanic changes have not been investigated. Using a global ocean-sea ice model forced with atmospheric reanalysis data, here it is shown that the 1962-1966 period of enhanced blocking activity over Greenland resulted in anomalous sea ice accumulation in the Arctic and ended with a sea ice flush from the Arctic into the North Atlantic Ocean through Fram Strait. This event induced a significant decrease of Labrador Sea water surface salinity and an abrupt weakening of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) during the 1970s. These results have implications for the prediction of rapid AMOC changes and indicate that an important part of the atmosphere-ocean dynamics at mid- and high latitudes requires a proper representation of the Fram Strait sea ice transport and of the synoptic scale variability such as atmospheric blocking, which is a challenge for current coupled climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ClDy...39.1021P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ClDy...39.1021P"><span>Decadal-timescale changes of the Atlantic overturning <span class="hlt">circulation</span> and climate in a coupled climate model with a hybrid-coordinate ocean component</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Persechino, A.; Marsh, R.; Sinha, B.; Megann, A. P.; Blaker, A. T.; New, A. L.</p> <p>2012-08-01</p> <p>A wide range of statistical tools is used to investigate the decadal variability of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) and associated key variables in a climate model (CHIME, Coupled <span class="hlt">Hadley</span>-Isopycnic Model Experiment), which features a novel ocean component. CHIME is as similar as possible to the 3rd <span class="hlt">Hadley</span> Centre Coupled Model (HadCM3) with the important exception that its ocean component is based on a hybrid vertical coordinate. Power spectral analysis reveals enhanced AMOC variability for periods in the range 15-30 years. Strong AMOC conditions are associated with: (1) a Sea Surface Temperature (SST) anomaly pattern reminiscent of the Atlantic Multi-decadal Oscillation (AMO) response, but associated with variations in a northern tropical-subtropical gradient; (2) a Surface Air Temperature anomaly pattern closely linked to SST; (3) a positive North Atlantic Oscillation (NAO)-like pattern; (4) a northward shift of the Intertropical Convergence Zone. The primary mode of AMOC variability is associated with decadal changes in the Labrador Sea and the Greenland Iceland Norwegian (GIN) Seas, in both cases linked to the tropical activity about 15 years earlier. These decadal changes are controlled by the low-frequency NAO that may be associated with a rapid atmospheric teleconnection from the tropics to the extratropics. Poleward advection of salinity anomalies in the mixed layer also leads to AMOC changes that are linked to processes in the Labrador Sea. A secondary mode of AMOC variability is associated with interannual changes in the Labrador and GIN Seas, through the impact of the NAO on local surface density.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-S71-33433.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-S71-33433.html"><span>Artist's concept of <span class="hlt">Hadley</span>-Apennine landing site with LRV traverses outlined</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1971-06-01</p> <p>S71-33433 (1 July 1971) --- An artist's concept of the <span class="hlt">Hadley</span>-Apennine landing site, depicting the traverses planned on the Apollo 15 lunar landing mission using the Lunar Roving Vehicle (LRV). The Roman numerals indicate the three periods of extravehicular activity (EVA). The Arabic numbers represent the station stops. This artist's concept was excerpted from "On the Moon with Apollo 15: A Guidebook to <span class="hlt">Hadley</span> Rille and the Apennine Mountains," by Gene Simmons. The station stops indicated here are keyed to information given in the publication. Artwork by Jerry Elmore.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950033279&hterms=homogenization&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dhomogenization','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950033279&hterms=homogenization&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dhomogenization"><span>A PV view of the zonal mean distribution of temperature and wind in the extratropical troposphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sun, De-Zheng; Lindzen, Richard S.</p> <p>1994-01-01</p> <p>The dependence of the temperature and wind distribution of the zonal mean flow in the extratropical troposphere on the gradient of pontential vorticity along isentropes is examined. The extratropics here refer to the region outside the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. Of particular interest is whether the distribution of temperature and wind corresponding to a constant potential vorticity (PV) along isentropes resembles the observed, and the implications of PV homogenization along isentropes for the role of the tropics. With the assumption that PV is homogenized along isentropes, it is found that the temperature distribution in the extratropical troposphere may be determined by a linear, first-order partial differential equation. When the observed surface temperature distribution and tropical lapse rate are used as the boundary conditions, the solution of the equation is close to the observed temperature distribution except in the upper troposphere adjacent to the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, where the troposphere with no PV gradient is considerably colder. Consequently, the jet is also stronger. It is also found that the <span class="hlt">meridional</span> distribution of the balanced zonal wind is very sensitive to the <span class="hlt">meridional</span> distribution of the tropopause temperature. The result may suggest that the requirement of the global momentum balance has no practical role in determining the extratropical temperature distribution. The authors further investigated the sensitivity of the extratropical troposphere with constant PV along isentropes to changes in conditions at the tropical boundary (the edge of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>). It is found that the temperature and wind distributions in the extratropical troposphere are sensitive to the vertical distribution of PV at the tropical boundary. With a surface distribution of temperature that decreases linearly with latitude, the jet maximum occurs at the tropical boundary and moves with it. The overall pattern of wind distribution is not sensitive to the change of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25520057','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25520057"><span>231Pa/230Th evidence for a weakened but persistent Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during Heinrich Stadial 1.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bradtmiller, Louisa I; McManus, Jerry F; Robinson, Laura F</p> <p>2014-12-18</p> <p>The strength of Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> is believed to affect the climate over glacial-interglacial and millennial timescales. The marine sedimentary (231)Pa/(230)Th ratio is a promising paleocirculation proxy, but local particle effects may bias individual reconstructions. Here we present new Atlantic sedimentary (231)Pa/(230)Th data from the Holocene, the last glacial maximum and Heinrich Stadial 1, a period of abrupt cooling ca. 17,500 years ago. We combine our results with published data from these intervals to create a spatially distributed sedimentary (231)Pa/(230)Th database. The data reveal a net (231)Pa deficit during each period, consistent with persistent (231)Pa export. In highly resolved cores, Heinrich (231)Pa/(230)Th ratios exceed glacial ratios at nearly all depths, indicating a significant reduction, although not cessation, of overturning during Heinrich Stadial 1. These results support the inference that weakened overturning was a driver of Heinrich cooling, while suggesting that abrupt climate oscillations do not necessarily require a complete shutdown of overturning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030011345&hterms=mit&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmit','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030011345&hterms=mit&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmit"><span>On the Pathways of the Return Flow of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in the Tropical Atlantic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jochum, Markus</p> <p>2002-01-01</p> <p>A numerical model of the tropical Atlantic ocean is used to investigate the upper layer pathways of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC) in the tropical Atlantic. The main focus of this thesis is on those parts of the tropical <span class="hlt">circulation</span> that are thought to be important for the MOC return flow, but whose dynamics have not been understood yet. It is shown how the particular structure of the tropical gyre and the MOO act to inhibit the flow of North Atlantic water into the equatorial thermocline. As a result, the upper layers of the tropical Atlantic are mainly fed by water from the South Atlantic. The processes that carry the South Atlantic water across the tropical Atlantic into the North Atlantic as part of the MOO are described here, and three processes that were hitherto not understood are explained as follows: The North Brazil Current rings are created as the result of the reflection of Rossby waves at the South American coast. These Rossby waves are generated by the barotropically unstable North Equatorial Countercurrent. The deep structure of the rings can be explained by merger of the wave's anticyclones with the deeper intermediate eddies that are generated as the intermediate western boundary current crosses the equator. The bands of strong zonal velocity in intermediate depths along the equator have hitherto been explained as intermediate currents. Here, an alternative interpretation of the observations is offered: The Eulerian mean flow along the equator is negligible and the observations are the signature of strong seasonal Rossby waves. The previous interpretation of the observations can then be explained as aliasing of the tropical wave field. The Tsuchyia Jets are driven by the Eliassen-Palm flux of the tropical instability waves. The equatorial current system with its strong shears is unstable and generates tropical instability waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-S71-44667.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-S71-44667.html"><span>View of <span class="hlt">Hadley</span>-Apennine area, looking north, photographed by Apollo 15</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1971-08-25</p> <p>S71-44667 (31 July-2 Aug. 1971) --- An oblique view of the <span class="hlt">Hadley</span>-Apennine area, looking north, as photographed by the Fairchild metric camera in the Scientific Instrumentation Module (SIM) bay of the Apollo 15 Command and Service Modules (CSM) in lunar orbit. <span class="hlt">Hadley</span> Rille meanders through the lower center of the picture. The Apennine Mountains are at lower right. The Apollo 15 Lunar Module (LM) touchdown point is on the east side of the "chicken beak" of <span class="hlt">Hadley</span> Rille. The Caucasus Mountains are at upper right. The dark mare area at the extreme upper right is a portion of the Sea of Serenity. The Marsh of Decay is at lower left. The large crater near the horizon is Aristillus, which is about 55 kilometers (34.18 statute miles) in diameter. The crater just to the south of Aristillus is Autolycus, which is about 40 kilometers (25 statute miles) in diameter. The crater Cassini is barely visible on the horizon at upper right. The three-inch mapping camera was one of eight lunar orbital science experiments mounted in the SIM bay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714427E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714427E"><span>Decadal slowdown in global air temperature rise triggered by variability in the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>England, Matthew H.</p> <p>2015-04-01</p> <p>Various explanations have been proposed for the recent slowdown in global surface air temperature (SAT) rise, either involving enhanced ocean heat uptake or reduced radiation reaching Earth's surface. Among the mechanisms postulated involving enhanced ocean heat uptake, past work has argued for both a Pacific and Atlantic origin, with additional contributions from the Southern Ocean. Here we examine the mechanisms driving 'hiatus' periods originating out of the Atlantic Ocean. We show that while Atlantic-driven hiatuses are entirely plausible and consistent with known climate feedbacks associated with variability in the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC), the present climate state is configured to enhance global-average SAT, not reduce it. We show that Atlantic hiatuses are instead characterised by anomalously cool fresh oceanic conditions in the North Atlantic, with the atmosphere advecting the cool temperature signature zonally. Compared to the 1980s and 1990s, however, the mean climate since 2001 has been characterised by a warm saline North Atlantic, suggesting the AMOC cannot be implicated as a direct driver of the current hiatus. We further discuss the impacts of a warm tropical Atlantic on the unprecedented trade wind acceleration in the Pacific Ocean, and propose that this is the main way that the Atlantic has contributed to the present "false pause" in global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870002240','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870002240"><span>The Martian climate and energy balance models with CO2/H2O atmospheres</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoffert, M. I.</p> <p>1986-01-01</p> <p>The analysis begins with a seasonal energy balance model (EBM) for Mars. This is used to compute surface temperature versus x = sin(latitude) and time over the seasonal cycle. The core model also computes the evolving boundaries of the CO2 icecaps, net sublimational/condensation rates, and the resulting seasonal pressure wave. Model results are compared with surface temperature and pressure history data at Viking lander sites, indicating fairly good agreement when <span class="hlt">meridional</span> heat transport is represented by a thermal diffusion coefficient D approx. 0.015 W/sq. m/K. Condensational wind distributions are also computed. An analytic model of Martian wind <span class="hlt">circulation</span> is then proposed, as an extension of the EMB, which incorporates vertical wind profiles containing an x-dependent function evaluated by substitution in the equation defining the diffusion coefficient. This leads to a parameterization of D(x) and of the <span class="hlt">meridional</span> <span class="hlt">circulation</span> which recovers the high surface winds predicted by dynamic Mars atmosphere models (approx. 10 m/sec). Peak diffusion coefficients, D approx. 0.6 w/sq m/K, are found over strong <span class="hlt">Hadley</span> zones - some 40 times larger than those of high-latitude baroclinic eddies. When the wind parameterization is used to find streamline patterns over Martian seasons, the resulting picture shows overturning hemispheric <span class="hlt">Hadley</span> cells crossing the equator during solstices, and attaining peak intensities during the south summer dust storm season, while condensational winds are most important near the polar caps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-as15-87-11748.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-as15-87-11748.html"><span>View of <span class="hlt">Hadley</span> Delta from top hatch of Apollo 15 Lunar Module after landing</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1971-07-31</p> <p>AS15-87-11748 (31 July 1971) --- A view of <span class="hlt">Hadley</span> Delta, looking southeasterly, as photographed from the top hatch of the Apollo 15 Lunar Module (LM) by astronaut David R. Scott, commander, during his stand-up extravehicular activity (EVA) just after the LM "Falcon" touched down at the <span class="hlt">Hadley</span>-Apennine landing site. The prominent feature on the horizon in the center of the picture was called Silver Spur by the Apollo 15 crew men. <span class="hlt">Hadley</span> Delta Mountain rises approximately 4,000 meters (about 13,124 feet) above the plain. While astronauts Scott and James B. Irwin, lunar module pilot, descended in the LM to explore the moon, astronaut Alfred M. Worden, command module pilot, remained with the Command and Service Module's (CSM) in lunar orbit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820048187&hterms=ants&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dants','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820048187&hterms=ants&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dants"><span>Compositional variation in the <span class="hlt">Hadley</span> Apennine region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Clark, P. E.; Hawke, B. R.</p> <p>1982-01-01</p> <p>Orbital geochemical data in the <span class="hlt">Hadley</span> Apennine region are related to typical rock compositions and used in determining the distribution of soils derived from the rock <span class="hlt">types</span> found in this region. Orbital XRF Mg/Si and Al/Si intensities are the orbital data that are used primarily. These data are corrected for spurious interorbit variation using a modification of a previously developed method. The corrected values are than converted to % MgO and % Al2O3, respectively, from theoretical considerations, and as such are compared with similar concentrations for typical lunar rocks and soils of the Apollo 15 landing site. The relationship of the XRF values to Fe, Ti, and Th concentrations, derived from gamma-ray observations, is also considered. It is established that the orbital geochemistry data for this region are consistent with the presence of a mixture of ANT suite and Fra Mauro basalt components frequently dominated by a KREEP basalt component toward the west and by a mafic pyroclastic component toward the east.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...45.1789D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...45.1789D"><span>Global radiative adjustment after a collapse of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drijfhout, Sybren S.</p> <p>2015-10-01</p> <p>The transient climate response to a collapse of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) is analysed from the difference between two ensembles of climate model simulations with ECHAM5/MPI-OM, one with hosing and the other without hosing. The primary effect of the collapse is to redistribute heat over the two hemispheres. However, Northern Hemisphere sea ice increase in response to the AMOC collapse induces a hemisphere-wide cooling, amplified by atmospheric feedbacks, in particular water vapour. The Southern Hemisphere warming is governed by slower processes. After 25 years the global cooling peaks. Thereafter, the response is characterised by a gradual readjustment of global mean temperature. During the AMOC collapse a downward radiation anomaly arises at the top of the atmosphere (TOA), heating the earth's surface. The net downward radiation anomaly at TOA arises from reduced longwave emission by the atmosphere, overcompensating the increased net upward anomalies in shortwave and longwave radiation at the surface. This radiation anomaly is associated with net ocean heat uptake: cooling of the overlying atmosphere results from reduced ocean heat release through the increase of sea-ice cover in the North Atlantic. The change in energy flow arises from the reduction in latent and sensible heat flux, which dominate the surface radiation budget. Similar experiments with a climate model of intermediate complexity reveal a stronger shortwave response that acts to reduce the net downward radiation anomaly at TOA. The net shortwave and longwave radiation anomalies at TOA always decrease during the first 100 years after the AMOC collapse, but in the intermediate complexity model this is associated with a sign change after 90 years when the net radiation anomaly at TOA becomes upward, accompanied by net ocean heat loss. After several hundred years the longwave and shortwave anomalies increase again, while the net residual at TOA remains small. This radiative</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11907570','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11907570"><span>A topographically forced asymmetry in the martian <span class="hlt">circulation</span> and climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Richardson, Mark I; Wilson, R John</p> <p>2002-03-21</p> <p>Large seasonal and hemispheric asymmetries in the martian climate system are generally ascribed to variations in solar heating associated with orbital eccentricity. As the orbital elements slowly change (over a period of >104 years), characteristics of the climate such as dustiness and the vigour of atmospheric <span class="hlt">circulation</span> are thought to vary, as should asymmetries in the climate (for example, the deposition of water ice at the northern versus the southern pole). Such orbitally driven climate change might be responsible for the observed layering in Mars' polar deposits by modulating deposition of dust and water ice. Most current theories assume that climate asymmetries completely reverse as the angular distance between equinox and perihelion changes by 180 degrees. Here we describe a major climate mechanism that will not precess in this way. We show that Mars' global north-south elevation difference forces a dominant southern summer <span class="hlt">Hadley</span> <span class="hlt">circulation</span> that is independent of perihelion timing. The <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, a tropical overturning cell responsible for trade winds, largely controls interhemispheric transport of water and the bulk dustiness of the atmosphere. The topography therefore imprints a strong handedness on climate, with water ice and the active formation of polar layered deposits more likely in the north.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A51L..06V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A51L..06V"><span>GCM simulations of cold dry Snowball Earth atmospheres</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Voigt, A.; Held, I.; Marotzke, J.</p> <p>2009-12-01</p> <p>We use the full-physics atmospheric general <span class="hlt">circulation</span> model ECHAM5 to investigate cold and virtually dry Snowball Earth atmospheres. These result from specifying sea ice as the surface boundary condition everywhere, corresponding to a frozen aquaplanet, while keeping total solar irradiance at its present-day value of 1365 Wm-2 and setting atmospheric carbon dioxide to 300 ppmv. Here, we present four simulations corresponding to the four possible combinations of enabled or disabled diurnal and seasonal cycles. The aim of this study is twofold. First, we focus on the zonal-mean <span class="hlt">circulation</span> of Snowball Earth atmospheres, which, due to missing moisture, might constitute an ideal though yet unexplored testbed for theories of atmospheric dynamics. Second, we investigate tropical surface temperatures with an emphasis on the impact of the diurnal and seasonal cycles. This will indicate whether the presence of the diurnal or seasonal cycle would facilitate or anticipate the escape from Snowball Earth conditions when total solar irradiance or atmospheric CO2 levels were increased. The dynamics of the tropical <span class="hlt">circulation</span> in Snowball Earth atmospheres differs substantially from that in the modern atmosphere. The analysis of the mean zonal momentum budget reveals that the mean flow <span class="hlt">meridional</span> advection of absolute vorticity is primarily balanced by vertical diffusion of zonal momentum. The contribution of eddies is found to be even smaller than the contribution of mean flow vertical advection of zonal momentum, the latter being usually neglected in theories for the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, at least in its upper tropospheric branch. Suppressing vertical diffusion of horizontal momentum above 850 hPa leads to a stronger <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. This behaviour cannot be understood from axisymmetric models of the atmosphere, nor idealized atmospheric general <span class="hlt">circulation</span> models, which both predict a weakening of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> when the vertical viscosity is decreased globally. We</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP51A1052K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP51A1052K"><span>Reconstruction of the North Atlantic end-member of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> over glacial-interglacial cycles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, J.; Seguí, M. J.; Knudson, K. P.; Yehudai, M.; Goldstein, S. L.; Pena, L. D.; Basak, C.; Ferretti, P.</p> <p>2017-12-01</p> <p>North Atlantic Deep Water (NADW) represents the major water mass that drives the Atlantic <span class="hlt">Meridional</span> Ocean <span class="hlt">Circulation</span> (AMOC), which undergoes substantial reorganization with changing climate. In order to understand its impact on ocean <span class="hlt">circulation</span> and climate through time, it is necessary to constrain its composition. We report Nd isotope ratios of Fe-Mn oxide encrusted foraminifera and fish debris from DSDP Site 607 (41.00N 32.96W, 3427m), in the present-day core of NADW, and ODP 1063 (33.68N 57.62W, 4585m), on the deep abyssal plain at the interface between NADW and Antarctic Bottom Water. We provide a new North Atlantic paleocirculation record covering 2 Ma. At Site 607 interglacial ɛNd-values are consistently similar to present-day NADW (ɛNd -13.5), with median ɛNd-values of -14.3 in the Early Pleistocene and -13.8 in the Late Pleistocene. Glacial ɛNd-values are higher by 1 ɛNd-unit in the Early Pleistocene, and 1.5-2 ɛNd-units in the Late Pleistocene. Site 1063 shows much greater variability, with ɛNd ranging from -10 to -26. We interpret the North Atlantic AMOC source as represented by the Site 607 interglacial ɛNd-values, which has remained nearly stable throughout the entire period. The higher glacial ɛNd-values reflect incursions of some southern-sourced waters to Site 607, which is supported by coeval shifts to lower benthic foraminiferal d13C. In contrast, the Site 1063 ɛNd-values do not appear to reflect the AMOC end-member, and likely reflects local effects from a bottom source. A period of greatly disrupted ocean <span class="hlt">circulation</span> marks 950-850 Ma, which may have been triggered by enhanced ice growth in the Northern Hemisphere that began around 1.2 Ma, as suggested by possible input events of Nd from the surrounding cratons into the North Atlantic observed in Site 607. Interglacial AMOC only recovers to the previously observed vigor over 200 ka following the disruption, whereas further intensified SSW incursion into the deep North Atlantic come to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ClDy...42.3323J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ClDy...42.3323J"><span>Response of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> to a reversal of greenhouse gas increases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jackson, L. C.; Schaller, N.; Smith, R. S.; Palmer, M. D.; Vellinga, M.</p> <p>2014-06-01</p> <p>The reversibility of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) is investigated in multi-model experiments using global climate models (GCMs) where CO2 concentrations are increased by 1 or 2 % per annum to 2× or 4× preindustrial conditions. After a period of stabilisation the CO2 is decreased back to preindustrial conditions. In most experiments when the CO2 decreases, the AMOC recovers before becoming anomalously strong. This "overshoot" is up to an extra 18.2Sv or 104 % of its preindustrial strength, and the period with an anomalously strong AMOC can last for several hundred years. The magnitude of this overshoot is shown to be related to the build up of salinity in the subtropical Atlantic during the previous period of high CO2 levels. The magnitude of this build up is partly related to anthropogenic changes in the hydrological cycle. The mechanisms linking the subtropical salinity increase to the subsequent overshoot are analysed, supporting the relationship found. This understanding is used to explain differences seen in some models and scenarios. In one experiment there is no overshoot because there is little salinity build up, partly as a result of model differences in the hydrological cycle response to increased CO2 levels and partly because of a less aggressive scenario. Another experiment has a delayed overshoot, possibly as a result of a very weak AMOC in that GCM when CO2 is high. This study identifies aspects of overshoot behaviour that are robust across a multi-model and multi-scenario ensemble, and those that differ between experiments. These results could inform an assessment of the real-world AMOC response to decreasing CO2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.4518V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.4518V"><span>On the seasonal variability of the Canary Current and the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vélez-Belchí, Pedro; Pérez-Hernández, M. Dolores; Casanova-Masjoan, María.; Cana, Luis; Hernández-Guerra, Alonso</p> <p>2017-06-01</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is continually monitored along 26°N by the RAPID-MOCHA array. Measurements from this array show a 6.7 Sv seasonal cycle for the AMOC, with a 5.9 Sv contribution from the upper mid-ocean. Recent studies argue that the dynamics of the eastern Atlantic is the main driver for this seasonal cycle; specifically, Rossby waves excited south of the Canary Islands. Using inverse modeling, hydrographic, mooring, and altimetry data, we describe the seasonal cycle of the ocean mass transport around the Canary Islands and at the eastern boundary, under the influence of the African slope, where eastern component of the RAPID-MOCHA array is situated. We find a seasonal cycle of -4.1 ± 0.5 Sv for the oceanic region of the Canary Current, and +3.7 ± 0.4 Sv at the eastern boundary. This seasonal cycle along the eastern boundary is in agreement with the seasonal cycle of the AMOC that requires the lowest contribution to the transport in the upper mid-ocean to occur in fall. However, we demonstrate that the linear Rossby wave model used previously to explain the seasonal cycle of the AMOC is not robust, since it is extremely sensitive to the choice of the zonal range of the wind stress curl and produces the same results with a Rossby wave speed of zero. We demonstrate that the seasonal cycle of the eastern boundary is due to the recirculation of the Canary Current and to the seasonal cycle of the poleward flow that characterizes the eastern boundaries of the oceans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A21Q..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A21Q..07S"><span>Does coupled ocean enhance ozone-hole-induced Southern Hemisphere <span class="hlt">circulation</span> changes?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Son, S. W.; Han, B. R.; Kim, S. Y.; Park, R.</p> <p>2017-12-01</p> <p>The ozone-hole-induced Southern Hemisphere (SH) <span class="hlt">circulation</span> changes, such as poleward shift of westerly jet and <span class="hlt">Hadley</span> cell widening, have been typically explored with either coupled general <span class="hlt">circulation</span> models (CGCMs) prescribing stratospheric ozone or chemistry-climate models (CCMs) prescribing surface boundary conditions. Only few studies have utilized ocean-coupled CCMs with a relatively coarse resolution. To better quantify the role of interactive chemistry and coupled ocean in the ozone-hole-induced SH <span class="hlt">circulation</span> changes, the present study examines a set of CGCM and CCM simulations archived for the Coupled Model Intercomparison Project phase 5 (CMIP5) and CCM initiative (CCMI). Although inter-model spread of Antarctic ozone depletion is substantially large especially in the austral spring, both CGCMs with relatively simple ozone chemistry and CCMs with fully interactive comprehensive chemistry reasonably well reproduce long-term trends of Antarctic ozone and the associated polar-stratospheric temperature changes. Most models reproduce a poleward shift of SH jet and <span class="hlt">Hadley</span>-cell widening in the austral summer in the late 20th century as identified in reanalysis datasets. These changes are quasi-linearly related with Antarctic ozone changes, confirming the critical role of Antarctic ozone depletion in the austral-summer zonal-mean <span class="hlt">circulation</span> changes. The CGCMs with simple but still interactive ozone show slightly stronger <span class="hlt">circulation</span> changes than those with prescribed ozone. However, the long-term <span class="hlt">circulation</span> changes in CCMs are largely insensitive to the coupled ocean. While a few models show the enhanced <span class="hlt">circulation</span> changes when ocean is coupled, others show essentially no changes or even weakened <span class="hlt">circulation</span> changes. This result suggests that the ozone-hole-related stratosphere-troposphere coupling in the late 20th century may be only weakly sensitive to the coupled ocean.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993PhDT.......110S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993PhDT.......110S"><span>The Thermal Structure, Dust Loading, and <span class="hlt">Meridional</span> Transport in the Martian Atmosphere during Late Southern Summer.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santee, Michelle</p> <p></p> <p>The thermal structure, dust loading, and <span class="hlt">meridional</span> transport in the Martian atmosphere are investigated using thermal emission spectra recorded by the Mariner 9 infrared interferometer spectrometer (IRIS). The analysis is restricted to a subset of the IRIS data consisting of approximately 2400 spectra spanning L_{S} = 343^circ-348^ circ, corresponding to late southern summer on Mars. Simultaneous retrieval of the vertical distribution of both atmospheric temperature and dust optical depth is accomplished through an iterative procedure which is performed on each spectrum. Although atmospheric temperatures decrease from equator to pole at lower altitudes, both dayside and nightside temperatures above about 0.1 mbar (~40 km) are warmer over the winter (north) polar region than over the equator or the summer (south) polar region. Zonal-mean zonal winds are derived from the atmospheric temperatures assuming gradient wind balance and zero surface zonal wind. Both hemispheres have intense mid-latitude westerly jets (with velocities of 80-90 m/s near 50 km); in the southern tropics the winds are strongly easterly (with velocities of 100 m/s near 50 km). A comprehensive radiative transfer model (Crisp, 1990) is used to compute solar heating and thermal cooling rates from the retrieved IRIS temperature and dust distributions. There are large net heating rates (up to 8 K/day) in the equatorial region and large net cooling rates (up to 20 K/day) in the polar regions. These net heating rates are used in a diagnostic stream function model which solves for the <span class="hlt">meridional</span> and vertical components of the diabatic <span class="hlt">circulation</span> simultaneously. The results show a vigorous two-cell <span class="hlt">circulation</span>, with rising motion over the equatorial region ( ~1.5 cm/s), poleward flow in both hemispheres (~2 m/s), sinking motion over both polar regions (1-2 cm/s), and return flow in the lowest atmospheric levels. The <span class="hlt">meridional</span> transport time scale is ~13 days. Water vapor desorbed from the low</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=AS15-87-11748&hterms=hatch&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dhatch','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=AS15-87-11748&hterms=hatch&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dhatch"><span>View of <span class="hlt">Hadley</span> Delta from top hatch of Apollo 15 Lunar Module after landing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1971-01-01</p> <p>A view of <span class="hlt">Hadley</span> Delta, looking southeasterly, as photographed from the top hatch of the Apollo 15 Lunar Module by Astronaut David R. Scott during his stand-up extravehicular activity just after the Lunar Module 'Falcon' touched down at the Hadly Apennine landing site. The prominent feature on the horizon in the center of the picture was called Silver Spur by the Apollo 15 crewmen. <span class="hlt">Hadley</span> Delta mountain rises approximately 4,000 meters (about 13,124 feet) above the plain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JThSc..20..312H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JThSc..20..312H"><span>Prototyping of ultra micro centrifugal compressor-influence of <span class="hlt">meridional</span> configuration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirano, Toshiyuki; Muto, Tadataka; Tsujita, Hoshio</p> <p>2011-08-01</p> <p>In order to investigate the design method for a micro centrifugal compressor, which is the most important component of an ultra micro gas turbine, two <span class="hlt">types</span> of centrifugal impeller with 2-dimensional blade were designed, manufactured and tested. These impellers have different shapes of hub on the <span class="hlt">meridional</span> plane with each other. Moreover, these <span class="hlt">types</span> of impeller were made for the 5 times and the 6 times size of the final target centrifugal impeller with the outer diameter of 4mm in order to assess the similitude for the impellers. The comparison among the performance characteristics of the impellers revealed the influence of the <span class="hlt">meridional</span> configuration on the performance and the similitude of the compressors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22167252-solar-wave-field-simulation-testing-prospects-helioseismic-measurements-deep-meridional-flows','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22167252-solar-wave-field-simulation-testing-prospects-helioseismic-measurements-deep-meridional-flows"><span>SOLAR WAVE-FIELD SIMULATION FOR TESTING PROSPECTS OF HELIOSEISMIC MEASUREMENTS OF DEEP <span class="hlt">MERIDIONAL</span> FLOWS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Hartlep, T.; Zhao, J.; Kosovichev, A. G.</p> <p>2013-01-10</p> <p>The <span class="hlt">meridional</span> flow in the Sun is an axisymmetric flow that is generally directed poleward at the surface, and is presumed to be of fundamental importance in the generation and transport of magnetic fields. Its true shape and strength, however, are debated. We present a numerical simulation of helioseismic wave propagation in the whole solar interior in the presence of a prescribed, stationary, single-cell, deep <span class="hlt">meridional</span> <span class="hlt">circulation</span> serving as synthetic data for helioseismic measurement techniques. A deep-focusing time-distance helioseismology technique is applied to the synthetic data, showing that it can in fact be used to measure the effects of themore » <span class="hlt">meridional</span> flow very deep in the solar convection zone. It is shown that the ray approximation that is commonly used for interpretation of helioseismology measurements remains a reasonable approximation even for very long distances between 12 Degree-Sign and 42 Degree-Sign corresponding to depths between 52 and 195 Mm. From the measurement noise, we extrapolate that time-resolved observations on the order of a full solar cycle may be needed to probe the flow all the way to the base of the convection zone.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920023117&hterms=regis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D40%26Ntt%3Dregis','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920023117&hterms=regis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D40%26Ntt%3Dregis"><span>Numerical simulation of the <span class="hlt">circulation</span> of the atmosphere of Titan</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hourdin, F.; Levan, P.; Talagrand, O.; Courtin, Regis; Gautier, Daniel; Mckay, Christopher P.</p> <p>1992-01-01</p> <p>A three dimensional General <span class="hlt">Circulation</span> Model (GCM) of Titan's atmosphere is described. Initial results obtained with an economical two dimensional (2D) axisymmetric version of the model presented a strong superrotation in the upper stratosphere. Because of this result, a more general numerical study of superrotation was started with a somewhat different version of the GCM. It appears that for a slowly rotating planet which strongly absorbs solar radiation, <span class="hlt">circulation</span> is dominated by global equator to pole <span class="hlt">Hadley</span> <span class="hlt">circulation</span> and strong superrotation. The theoretical study of this superrotation is discussed. It is also shown that 2D simulations systemically lead to instabilities which make 2D models poorly adapted to numerical simulation of Titan's (or Venus) atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.8829M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.8829M"><span>Weather <span class="hlt">types</span> in the South Shetlands (Antarctica) using a <span class="hlt">circulation</span> <span class="hlt">type</span> approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mora, Carla; João Rocha, Maria; Dutra, Emanuel; Trigo, Isabel; Vieira, Gonçalo; Fragoso, Marcelo; Ramos, Miguel</p> <p>2010-05-01</p> <p>Weather <span class="hlt">types</span> in the South Shetlands (Antarctica) were defined using an automated method based on the Lamb Weather <span class="hlt">Type</span> classification scheme (Jones et al. 1993). This is an objective classification originally developed for the British Isles (Jones et al., 1993) and also applied to southeast (Goodess and Palutikof 1998) and northwest Spain (Lorenzo et al, 2009), Portugal (Trigo and DaCamara 2000) and Greece (Maheras et al. 2004) with good results. Daily atmospheric <span class="hlt">circulation</span> in the South Shetlands region from 1989 to 2009 was classified using a 16-node grid of sea level pressure data from the ERA Interim. The classification is obtained through the comparison of the magnitudes of the directional and rotational components of the geostrophic flow. Basic <span class="hlt">circulation</span> <span class="hlt">types</span> were combined into 10 groups of weather <span class="hlt">types</span>: four directional <span class="hlt">types</span> (NW, N, S and SW), three anticyclonic <span class="hlt">types</span> (A, ASW and ANW), and three cyclonic <span class="hlt">types</span> (C, CSW and CNW). Westerly flow and cyclonic <span class="hlt">circulation</span> are the most frequent events throughout the year. The sea level pressure field for each weather <span class="hlt">type</span> is presented and the synoptic characteristics are described. The analysis is based on ERA-Interim fields, including mean sea level pressure, precipitation, cloud cover, humidity and air temperature. Snow thickess modelled using HTESSEL is also considered. Analysis of variance (anova) and multivariate analysis (principal component analysis) are applied to evaluate the characteristics of each weather <span class="hlt">type</span>. This <span class="hlt">circulation-type</span> approach showed good results in the past for the downscaling of precipitation in other regions, and we are interested in evaluating the possibilities that the classification offers for downscaling precipitation, but also for snow and air temperature. For this we will be using observational data at test sites in Livingston and Deception islands. We are also motivated by the possibility of using the <span class="hlt">circulation-type</span> approach as a predictor in statistical downscaling</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15800620','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15800620"><span>Decline of the marine ecosystem caused by a reduction in the Atlantic overturning <span class="hlt">circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schmittner, Andreas</p> <p>2005-03-31</p> <p>Reorganizations of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> were associated with large and abrupt climatic changes in the North Atlantic region during the last glacial period. Projections with climate models suggest that similar reorganizations may also occur in response to anthropogenic global warming. Here I use ensemble simulations with a coupled climate-ecosystem model of intermediate complexity to investigate the possible consequences of such disturbances to the marine ecosystem. In the simulations, a disruption of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> leads to a collapse of the North Atlantic plankton stocks to less than half of their initial biomass, owing to rapid shoaling of winter mixed layers and their associated separation from the deep ocean nutrient reservoir. Globally integrated export production declines by more than 20 per cent owing to reduced upwelling of nutrient-rich deep water and gradual depletion of upper ocean nutrient concentrations. These model results are consistent with the available high-resolution palaeorecord, and suggest that global ocean productivity is sensitive to changes in the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.5969Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.5969Z"><span>The influence of <span class="hlt">meridional</span> ice transport on Europa's ocean stratification and heat content</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, Peiyun; Manucharyan, Georgy E.; Thompson, Andrew F.; Goodman, Jason C.; Vance, Steven D.</p> <p>2017-06-01</p> <p>Jupiter's moon Europa likely hosts a saltwater ocean beneath its icy surface. Geothermal heating and rotating convection in the ocean may drive a global overturning <span class="hlt">circulation</span> that redistributes heat vertically and <span class="hlt">meridionally</span>, preferentially warming the ice shell at the equator. Here we assess the previously unconstrained influence of ocean-ice coupling on Europa's ocean stratification and heat transport. We demonstrate that a relatively fresh layer can form at the ice-ocean interface due to a <span class="hlt">meridional</span> ice transport forced by the differential ice shell heating between the equator and the poles. We provide analytical and numerical solutions for the layer's characteristics, highlighting their sensitivity to critical ocean parameters. For a weakly turbulent and highly saline ocean, a strong buoyancy gradient at the base of the freshwater layer can suppress vertical tracer exchange with the deeper ocean. As a result, the freshwater layer permits relatively warm deep ocean temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.U13B..31Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.U13B..31Z"><span>The influence of <span class="hlt">meridional</span> ice transport on Europa's ocean stratification and heat content</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, P.; Manucharyan, G.; Thompson, A. F.; Goodman, J. C.; Vance, S.</p> <p>2017-12-01</p> <p>Jupiter's moon Europa likely hosts a saltwater ocean beneath its icy surface. Geothermal heating and rotating convection in the ocean may drive a global overturning <span class="hlt">circulation</span> that redistributes heat vertically and <span class="hlt">meridionally</span>, preferentially warming the ice shell at the equator. Here we assess thepreviously unconstrained influence of ocean-ice coupling on Europa's ocean stratification and heat transport. We demonstrate that a relatively fresh layer can form at the ice-ocean interface due to a <span class="hlt">meridional</span> ice transport forced by the differential ice shell heating between the equator and the poles. We provide analytical and numerical solutions for the layer's characteristics, highlighting their sensitivity to critical ocean parameters. For a weakly turbulent and highly saline ocean, a strong buoyancy gradient at the base of the freshwater layer can suppress vertical tracer exchange with the deeper ocean. As a result, the freshwater layer permits relatively warm deep ocean temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A52E..05L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A52E..05L"><span>Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> Influence on North Atlantic Sector Surface Air Temperature and its Predictability in the Kiel Climate Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Latif, M.</p> <p>2017-12-01</p> <p>We investigate the influence of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) on the North Atlantic sector surface air temperature (SAT) in two multi-millennial control integrations of the Kiel Climate Model (KCM). One model version employs a freshwater flux correction over the North Atlantic, while the other does not. A clear influence of the AMOC on North Atlantic sector SAT only is simulated in the corrected model that depicts much reduced upper ocean salinity and temperature biases in comparison to the uncorrected model. Further, the model with much reduced biases depicts significantly enhanced multiyear SAT predictability in the North Atlantic sector relative to the uncorrected model. The enhanced SAT predictability in the corrected model is due to a stronger and more variable AMOC and its enhanced influence on North Atlantic sea surface temperature (SST). Results obtained from preindustrial control integrations of models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) support the findings obtained from the KCM: models with large North Atlantic biases tend to have a weak AMOC influence on SST and exhibit a smaller SAT predictability over the North Atlantic sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MAP...128..649P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MAP...128..649P"><span><span class="hlt">Circulation</span> weather <span class="hlt">types</span> and their influence on precipitation in Serbia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Putniković, Suzana; Tošić, Ivana; Đurđević, Vladimir</p> <p>2016-10-01</p> <p>An objective classification scheme of atmospheric <span class="hlt">circulation</span>, in which daily <span class="hlt">circulation</span> is determined by the strength, direction, and vorticity of geostrophic flow, has been applied to the atmosphere over Serbia for the time period 1961-2010. The results for the sea level and isobaric level of 500 hPa for winter and summer are presented. The 26 <span class="hlt">circulation</span> <span class="hlt">types</span> (eight pure direction, 16 hybrid, cyclonic, and anticyclonic <span class="hlt">types</span>) are determined and described. Each of the <span class="hlt">circulation</span> <span class="hlt">types</span> has a distinct underlying synoptic pattern that produces the expected <span class="hlt">type</span> and direction of flow over the study area. The relative frequencies of the <span class="hlt">circulation</span> <span class="hlt">types</span>, and the relationship between the precipitation and <span class="hlt">circulation</span> <span class="hlt">types</span> at three stations on a seasonal time scale are analyzed. The anticyclonic weather <span class="hlt">type</span> dominates in winter (18.93 %) and summer (18.70 %), followed by the northeasterly <span class="hlt">type</span> (16.65 %) in summer, and the cyclonic <span class="hlt">type</span> (12.83 %) in winter. The cyclonic <span class="hlt">types</span> (C and hybrid) have a higher than average probability of rain at all stations. Conversely, the anticyclonic <span class="hlt">types</span> are associated with a lower than average probability and intensity of rainfall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=AS15-84-11250&hterms=bedding&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dbedding','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=AS15-84-11250&hterms=bedding&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dbedding"><span>Telephoto lens view of Silver Spur in the <span class="hlt">Hadley</span> Delta region from Apollo 15</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1971-01-01</p> <p>A telephoto lens view of the prominent feature called Silver Spur in the <span class="hlt">Hadley</span> Delta region, photographed during the Apollo 15 lunar surface extravehicular activity at the <span class="hlt">Hadley</span>-Apennine landing site. The distance from the camera to the spur is about 10 miles. The field of view across the bottom is about one mile. Structural formations in the mountain are clearly visible. There are two major units. The upper unit is characterized by massive subunits, each one of which is approximately 200 feet deep. The lower major unit is characterized by thinner bedding and cross bedding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AcGeo.tmp...63A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AcGeo.tmp...63A"><span>The variability of the Atlantic <span class="hlt">meridional</span> <span class="hlt">circulation</span> since 1980, as hindcast by a data-driven nonlinear systems model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ayala-Solares, J. R.; Wei, Hua-Liang; Bigg, G. R.</p> <p>2018-06-01</p> <p>The Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC), an important component of the climate system, has only been directly measured since the RAPID array's installation across the Atlantic at 26°N in 2004. This has shown that the AMOC strength is highly variable on monthly timescales; however, after an abrupt, short-lived, halving of the strength of the AMOC early in 2010, its mean has remained 15% below its pre-2010 level. To attempt to understand the reasons for this variability, we use a control systems identification approach to model the AMOC, with the RAPID data of 2004-2017 providing a trial and test data set. After testing to find the environmental variables, and systems model, that allow us to best match the RAPID observations, we reconstruct AMOC variation back to 1980. Our reconstruction suggests that there is inter-decadal variability in the strength of the AMOC, with periods of both weaker flow than recently, and flow strengths similar to the late 2000s, since 1980. Recent signs of weakening may therefore not reflect the beginning of a sustained decline. It is also shown that there may be predictive power for AMOC variability of around 6 months, as ocean density contrasts between the source and sink regions for the North Atlantic Drift, with lags up to 6 months, are found to be important components of the systems model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/EJ765547.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/EJ765547.pdf"><span>Spanning the Pacific Ocean through Voice-Over Internet Protocol Chat with the <span class="hlt">Hadley</span> School for the Blind--China</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gilson, Christie L.; Rongqiang, Xia</p> <p>2007-01-01</p> <p>Founded in 1920, the <span class="hlt">Hadley</span> School for the Blind is known worldwide for its tuition-free distance-education courses for people who are visually impaired. <span class="hlt">Hadley</span>'s main school in the United States serves more than 9,000 students, and the overseas school in the People's Republic of China provides vital educational services to more than 1,000 Chinese…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870044380&hterms=Divergence+Theorem&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DDivergence%2BTheorem','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870044380&hterms=Divergence+Theorem&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DDivergence%2BTheorem"><span>Nongeostrophic theory of zonally averaged <span class="hlt">circulation</span>. I - Formulation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tung, Ka Kit</p> <p>1986-01-01</p> <p>A nongeostrophic theory of zonally averaged <span class="hlt">circulation</span> is formulated using the nonlinear primitive equations (mass conservation, thermodynamics, and zonal momentum) on a sphere. The relationship between the mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> and diabatic heating rate is studied. Differences between results of nongeostropic theory and the geostrophic formulation concerning the role of eddy forcing of the diabatic <span class="hlt">circulation</span> and the nonlinear nearly inviscid limit versus the geostrophic limit are discussed. Consideration is given to the Eliassen-Palm flux divergence, the Eliassen-Palm pseudodivergence, the nonacceleration theorem, and the nonlinear nongeostrophic Taylor relationship.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A23A0173W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A23A0173W"><span>Optimized <span class="hlt">circulation</span> and weather <span class="hlt">type</span> classifications relating large-scale atmospheric conditions to local PM10 concentrations in Bavaria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weitnauer, C.; Beck, C.; Jacobeit, J.</p> <p>2013-12-01</p> <p> classification approaches, a k-means cluster analysis and an objective version of the Grosswetter <span class="hlt">types</span>. They have been run with varying spatial and temporal settings as well as modified numbers of classes. As an evaluation metric for their performance several skill scores are used. Taking into account the outcome further attempts towards the optimization of <span class="hlt">circulation</span> <span class="hlt">type</span> classifications are made. These are varying meteorological input parameters (e.g. geopotential height, zonal and <span class="hlt">meridional</span> wind, specific humidity, temperature) on several pressure levels (1000, 850 and 500 hPa) and combinations of these variables. All classification variants are again evaluated. Based on these analyses it is further intended to develop robust downscaling models for estimating possible future - climate change induced - variations of local PM10 concentrations in Bavaria from scenario runs of global CMIP5 climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820052792&hterms=balance+general&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dbalance%2Bgeneral','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820052792&hterms=balance+general&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dbalance%2Bgeneral"><span>A January angular momentum balance in the OSU two-level atmospheric general <span class="hlt">circulation</span> model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, J.-W.; Grady, W.</p> <p>1982-01-01</p> <p>The present investigation is concerned with an analysis of the atmospheric angular momentum balance, based on the simulation data of the Oregon State University two-level atmospheric general <span class="hlt">circulation</span> model (AGCM). An attempt is also made to gain an understanding of the involved processes. Preliminary results on the angular momentum and mass balance in the AGCM are shown. The basic equations are examined, and questions of turbulent momentum transfer are investigated. The methods of analysis are discussed, taking into account time-averaged balance equations, time and longitude-averaged balance equations, mean <span class="hlt">meridional</span> <span class="hlt">circulation</span>, the mean <span class="hlt">meridional</span> balance of relative angular momentum, and standing and transient components of motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-as15-84-11250.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-as15-84-11250.html"><span>Telephoto lens view of Silver Spur in the <span class="hlt">Hadley</span> Delta region from Apollo 15</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1971-07-31</p> <p>AS15-84-11250 (31 July-2 Aug. 1971) --- A telephoto lens view of the prominent feature called Silver Spur in the <span class="hlt">Hadley</span> Delta region, photographed during the Apollo 15 lunar surface extravehicular activity (EVA) at the <span class="hlt">Hadley</span>-Apennine landing site. The distance from the camera to the spur is about 10 miles. The field of view across the bottom is about one mile. Structural formations in the mountain are clearly visible. There are two major units. The upper unit is characterized by massive subunits, each one of which is approximately 200 feet deep. The lower major unit is characterized by thinner bedding and cross bedding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A11G..01K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A11G..01K"><span>Sensitivity of South American tropical climate to Last Glacial Maximum boundary conditions: focus on teleconnections with tropics and extratropics (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khodri, M.; Kageyama, M.; Roche, D. M.</p> <p>2009-12-01</p> <p>Proxy data over tropical latitudes for the Last Glacial Maximum (LGM) has been interpreted as a southward shift of the Inter Tropical Convergence Zone (ITCZ) and so far linked to a mechanism analogous to the modern day “<span class="hlt">meridional</span>-mode” in the Atlantic Ocean. Here we have explored alternative mechanisms, related to the direct impact of the LGM global changes in the dry static stability on tropical moist deep convection. We have used a coupled ocean-atmosphere model capable of capturing the thermodynamical structure of the atmosphere and the tropical component of the <span class="hlt">Hadley</span> and Walker <span class="hlt">circulations</span>. In each experiment, we have applied either all the LGM forcings, or the individual contributions of greenhouse gases (GHG) concentrations, ice sheet topography and/or albedo to explore the hydrological response over tropical latitudes with a focus on South America. The dominant forcing for the LGM tropical temperature and precipitation changes is found to be due to the reduced GHG, through the direct effect of reduced radiative heating (Clausius-Clapeyron relationship). The LGM GHG is also responsible for increased extra-tropical static stability which strengthens the <span class="hlt">Hadley</span> Cell. Stronger subsidence over northern tropics then produces an amplification of the northern tropics drying initially due to the direct cooling effect. The land ice sheet is also able to promote the <span class="hlt">Hadley</span> cell feedback mostly via the topographic effect on the extra-tropical dry static stability and on the position of the subtropical jets. Our results therefore suggest that the communication between the extratropics and the tropics is tighter during LGM and does not necessarily rely on the “<span class="hlt">meridional</span>-mode” mechanism. The <span class="hlt">Hadley</span> cell response is constrained by the requirement that diabatic heating in the tropics balances cooling in subtropics. We show that such extratropics-tropics dependence is stronger at the LGM because of the stronger perturbation of northern extra tropical thermal and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4180M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4180M"><span><span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> Transport Variability at 34.5°S During 2009-2017: Baroclinic and Barotropic Flows and the Dueling Influence of the Boundaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meinen, Christopher S.; Speich, Sabrina; Piola, Alberto R.; Ansorge, Isabelle; Campos, Edmo; Kersalé, Marion; Terre, Thierry; Chidichimo, Maria Paz; Lamont, Tarron; Sato, Olga T.; Perez, Renellys C.; Valla, Daniel; van den Berg, Marcel; Le Hénaff, Matthieu; Dong, Shenfu; Garzoli, Silvia L.</p> <p>2018-05-01</p> <p>Six years of simultaneous moored observations near the western and eastern boundaries of the South Atlantic are combined with satellite winds to produce a daily time series of the basin-wide <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) volume transport at 34.5°S. The results demonstrate that barotropic and baroclinic signals at both boundaries cause significant transport variations, and as such must be concurrently observed. The data, spanning 20 months during 2009-2010 and 4 years during 2013-2017, reveal a highly energetic MOC record with a temporal standard deviation of 8.3 Sv, and strong variations at time scales ranging from a few days to years (peak-to-peak range = 54.6 Sv). Seasonal transport variations are found to have both semiannual (baroclinic) and annual (Ekman and barotropic) timescales. Interannual MOC variations result from both barotropic and baroclinic changes, with density profile changes at the eastern boundary having the largest impact on the year-to-year variations.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JMS....12...83F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JMS....12...83F"><span>Anti-cyclonic <span class="hlt">circulation</span> driven by the estuarine <span class="hlt">circulation</span> in a gulf <span class="hlt">type</span> ROFI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujiwara, T.; Sanford, L. P.; Nakatsuji, K.; Sugiyama, Y.</p> <p>1997-08-01</p> <p>Baroclinic residual <span class="hlt">circulation</span> processes are examined in gulf <span class="hlt">type</span> Regions Of Freshwater Influence (ROFIs), which have large rivers discharging into a rounded head wider than the Rossby internal deformation radius. Theoretical and observational investigations concentrate on Ise Bay, Japan, with supporting data from Osaka Bay and Tokyo Bay. Simplified analytical solutions are derived to describe the primary features of the <span class="hlt">circulation</span>. Three dimensional residual current data collected using moored current meters and shipboard acoustic doppler current profilers (ADCPs), satellite imagery and density structure data observed using STDs, are presented for comparison to the theoretical predictions. There are three key points to understanding the resulting <span class="hlt">circulation</span> in gulf <span class="hlt">type</span> ROFIs. First, there are likely to be three distinct water masses: the river plume, a brackish upper layer, and a higher salinity lower layer. Second, baroclinic processes in gulf <span class="hlt">type</span> ROFIs are influenced by the Earth's rotation at first order. Residual currents are quasi-geostrophic and potential vorticity is approximately conserved. Third, the combined effects of a classical longitudinal estuarine <span class="hlt">circulation</span> and the Earth's rotation are both necessary to produce the resulting <span class="hlt">circulation</span>. Anti-cyclonic vorticity is generated in the upper layer by the horizontal divergence associated with upward entrainment, which is part of the estuarine <span class="hlt">circulation</span>. The interaction between anti-cyclonic vorticity and horizontal divergence results in two regions of qualitatively different <span class="hlt">circulation</span>, with gyre-like <span class="hlt">circulation</span> near the bay head and uniformly seaward anti-cyclonicly sheared flow further towards the mouth. The stagnation point separating the two regions is closer to (further away from) the bay head for stronger (weaker) horizontal divergence, respectively. The vorticity and spin-up time of this <span class="hlt">circulation</span> are-(ƒ-ω 1)/2 and h/2w 0, respectively, where ƒ is the Coriolis parameter, ω 1 is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.6006B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.6006B"><span>Ockham's Razorblade Shaving Wind-Induced <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bergmann, Juan Carlos</p> <p>2010-05-01</p> <p>Terrestrial physical oceanography is fortunate because of the existence of the continents that divide the low-latitude oceans into basins. At first glance, the previous statement appears to be not obvious because an ocean-planet should be much simpler to describe. Simple-case explanation is the central aspect of Ockham's Razorblade: If a theory fails to describe the most-simple case properly, the theory is, at least, ‘not good'. Also Descartes' methodical rules take the most-simple case as starting point. The analysis of wind-induced <span class="hlt">circulation</span> on an ocean-planet will support the initial statement. Earth's south hemisphere is dominated by the oceans. The continents' influence on the zonal-average zonal-wind climate is relatively small. Therefore, South Hemisphere's zonal wind pattern is a relatively good proxy for that of an ocean planet. Application of this wind-stress pattern to an ocean planet yields reasonable <span class="hlt">meridional</span> mass-flow results from the polar-regions down to the high-pressure belts: Down-welling and up-welling of water-mass are approximately balanced. However, the entire tropical <span class="hlt">circulation</span> can in principle not be closed because there is only down-welling - even if the extreme down-welling in the equatorial belt (± 8°, with a singularity at the equator) is disregarded. The only input to the calculations is the observed terrestrial south-hemisphere zonal wind-stress pattern. <span class="hlt">Meridional</span> stress is irrelevant because it produces a closed zonal Ekman-transport around the ocean planet (sic!). Vertical mass-transport is calculated from the divergence of the wind-induced <span class="hlt">meridional</span> Ekman-mass-transport, which in its turn is a necessary consequence of angular-momentum conservation. No assumptions are made on how the return-flows at depth are forced because the wind-force equations cannot contribute hereto. This circumstance expresses a fundamental difference to atmospheric <span class="hlt">circulation</span>, where mechanical forcing is caused by the pressure-fields that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=S71-33433&hterms=Arabic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DArabic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=S71-33433&hterms=Arabic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DArabic"><span>Artist's concept of <span class="hlt">Hadley</span>-Apennine landing site with LRV traverses outlined</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1971-01-01</p> <p>An artist's concept of the <span class="hlt">Hadley</span>-Apennine landing site, depicting the traverses planned on the Apollo 15 lunar landing mission using the Lunar Roving Vehicle (LRV). The Roman numerals indicate the three periods of extravehicular activity (EVA). The Arabic numbers represent the station stops. Art work by Jerry Elmore.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ThCFD..31...89D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ThCFD..31...89D"><span>A zonally symmetric model for the monsoon-<span class="hlt">Hadley</span> <span class="hlt">circulation</span> with stochastic convective forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>De La Chevrotière, Michèle; Khouider, Boualem</p> <p>2017-02-01</p> <p>Idealized models of reduced complexity are important tools to understand key processes underlying a complex system. In climate science in particular, they are important for helping the community improve our ability to predict the effect of climate change on the earth system. Climate models are large computer codes based on the discretization of the fluid dynamics equations on grids of horizontal resolution in the order of 100 km, whereas unresolved processes are handled by subgrid models. For instance, simple models are routinely used to help understand the interactions between small-scale processes due to atmospheric moist convection and large-scale <span class="hlt">circulation</span> patterns. Here, a zonally symmetric model for the monsoon <span class="hlt">circulation</span> is presented and solved numerically. The model is based on the Galerkin projection of the primitive equations of atmospheric synoptic dynamics onto the first modes of vertical structure to represent free tropospheric <span class="hlt">circulation</span> and is coupled to a bulk atmospheric boundary layer (ABL) model. The model carries bulk equations for water vapor in both the free troposphere and the ABL, while the processes of convection and precipitation are represented through a stochastic model for clouds. The model equations are coupled through advective nonlinearities, and the resulting system is not conservative and not necessarily hyperbolic. This makes the design of a numerical method for the solution of this system particularly difficult. Here, we develop a numerical scheme based on the operator time-splitting strategy, which decomposes the system into three pieces: a conservative part and two purely advective parts, each of which is solved iteratively using an appropriate method. The conservative system is solved via a central scheme, which does not require hyperbolicity since it avoids the Riemann problem by design. One of the advective parts is a hyperbolic diagonal matrix, which is easily handled by classical methods for hyperbolic equations, while</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22522368-meridional-flow-solar-convection-zone-ii-helioseismic-inversions-gong-data','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22522368-meridional-flow-solar-convection-zone-ii-helioseismic-inversions-gong-data"><span><span class="hlt">MERIDIONAL</span> FLOW IN THE SOLAR CONVECTION ZONE. II. HELIOSEISMIC INVERSIONS OF GONG DATA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Jackiewicz, J.; Serebryanskiy, A.; Kholikov, S., E-mail: jasonj@nmsu.edu</p> <p>2015-06-01</p> <p><span class="hlt">Meridional</span> flow is thought to play a very important role in the dynamics of the solar convection zone; however, because of its relatively small amplitude, precisely measuring it poses a significant challenge. Here we present a complete time–distance helioseismic analysis of about 2 years of ground-based Global Oscillation Network Group (GONG) Doppler data to retrieve the <span class="hlt">meridional</span> <span class="hlt">circulation</span> profile for modest latitudes in an attempt to corroborate results from other studies. We use an empirical correction to the travel times due to an unknown center-to-limb systematic effect. The helioseismic inversion procedure is first tested and reasonably validated on artificial datamore » from a large-scale numerical simulation followed by a test to broadly recover the solar differential rotation found from global seismology. From GONG data, we measure poleward photospheric flows at all latitudes with properties that are comparable with earlier studies and a shallow equatorward flow about 65 Mm beneath the surface, in agreement with recent findings from Helioseismic and Magnetic Imager (HMI) data. No strong evidence of multiple <span class="hlt">circulation</span> cells in depth or latitude is found, yet the whole phase space has not yet been explored. Tests of mass flux conservation are then carried out on the inferred GONG and HMI flows and compared to a fiducial numerical baseline from models, and we find that the continuity equation is poorly satisfied. While the two disparate data sets do give similar results for about the outer 15% of the interior radius, the total inverted <span class="hlt">circulation</span> pattern appears to be unphysical in terms of mass conservation when interpreted over modest time scales. We can likely attribute this to both the influence of realization noise and subtle effects in the data and measurement procedure.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26PSL.484..253M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26PSL.484..253M"><span>Changes of deep Pacific overturning <span class="hlt">circulation</span> and carbonate chemistry during middle Miocene East Antarctic ice sheet expansion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Xiaolin; Tian, Jun; Ma, Wentao; Li, Ke; Yu, Jimin</p> <p>2018-02-01</p> <p>East Antarctic ice sheet expansion (EAIE) at ∼13.9 Ma in the middle Miocene represents a major climatic event during the long-term Cenozoic cooling, but ocean <span class="hlt">circulation</span> and carbon cycle changes during this event remain unclear. Here, we present new fish teeth isotope (εNd) and benthic foraminiferal B/Ca records from the South China Sea (SCS), newly integrated <span class="hlt">meridional</span> Pacific benthic foraminiferal δ18O and δ13C records and simulated results from a biogeochemical box model to explore the responses of deep Pacific Ocean <span class="hlt">circulation</span> and carbon cycle across EAIE. The εNd and <span class="hlt">meridional</span> benthic δ13C records reveal a more isolated Pacific Deep Water (PDW) and a sluggish Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during the post-EAIE with respect to the pre-EAIE owing to weakened southern-sourced deep water formation. The deep-water [CO23-] and calcium carbonate mass accumulation rate in the SCS display markedly similar increases followed by recoveries to the pre-EAIE level during EAIE, which were probably caused by a shelf-basin shift of CaCO3 deposition and strengthened weathering due to a sea level fall within EAIE. The model results show that the ∼1‰ positive δ13C excursion during EAIE could be attributed to increased weathering of high-δ13C shelf carbonates and a terrestrial carbon reservoir expansion. The drawdown of atmospheric CO2 over the middle Miocene were probably caused by combined effects of increased shelf carbonate weathering, expanded land biosphere carbon storage and a sluggish deep Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A33B0217T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A33B0217T"><span>Ocean <span class="hlt">Circulation</span>-Cloud Interactions Reduce the Pace of Transient Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trossman, D.; Palter, J. B.; Merlis, T. M.; Huang, Y.; Xia, Y.</p> <p>2016-12-01</p> <p>We argue that a substantial fraction of the uncertainty in the cloud radiative feedback during transient climate change may be due to uncertainty in the ocean <span class="hlt">circulation</span> perturbation. A suite of climate model simulations in which the ocean <span class="hlt">circulation</span>, the cloud radiative feedback, or a combination of both are held fixed while CO2 doubles, shows that changes in the ocean <span class="hlt">circulation</span> reduce the amount of transient global warming caused by the radiative cloud feedback. Specifically, a slowdown in the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) helps to maintain low cloud cover in the Northern Hemisphere extratropics. We propose that the AMOC decline increases the <span class="hlt">meridional</span> SST gradient, strengthening the storm track, its attendant clouds and the amount of shortwave radiation they reflect back to space. If the results of our model were to scale proportionately in the CMIP5 models, whose AMOC decline ranges from 15 to 60% under RCP8.5, then as much as 70% of the intermodel spread in the cloud radiative feedback and 35% of the spread in the transient climate response could possibly stem from the model representations of AMOC decline.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A22E..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A22E..02S"><span>On the nonlinear forced response of the North Atlantic atmosphere to <span class="hlt">meridional</span> shifts of the Gulf Stream path</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seo, H.; Kwon, Y. O.; Joyce, T. M.; Ummenhofer, C.</p> <p>2016-12-01</p> <p>This study examines the North Atlantic atmospheric <span class="hlt">circulation</span> response to the <span class="hlt">meridional</span> shift of Gulf Stream path using a large-ensemble, high-resolution, and hemispheric-scale WRF simulations. The model is forced with wintertime SST anomalies derived from a wide range of Gulf Stream shift scenarios. The key result of the model experiments, supported in part by an independent analysis of a reanalysis data set, is that the large-scale, quasi-steady North Atlantic <span class="hlt">circulation</span> response is unambiguously nonlinear about the sign and amplitude of chosen SST anomalies. This nonlinear response prevails over the weak linear response and resembles the negative North Atlantic Oscillation, the leading intrinsic mode of variability in the model and the observations. Further analysis of the associated dynamics reveals that the nonlinear responses are accompanied by the anomalous southward shift of the North Atlantic eddy-driven jet stream, which is reinforced nearly equally by the high-frequency transient eddy feedback and the low-frequency high-latitude wave breaking events. The result highlights the importance of the intrinsically nonlinear transient eddy dynamics and eddy-mean flow interactions in generating the nonlinear forced response to the <span class="hlt">meridional</span> shift in the Gulf Stream.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.3089L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.3089L"><span>The subpolar North Atlantic - Response to North Atlantic oscillation like forcing and Influence on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lohmann, Katja; Drange, Helge; Jungclaus, Johann</p> <p>2010-05-01</p> <p>The extent and strength of the North Atlantic subpolar gyre (SPG) changed rapidly in the mid-1990s, going from large and strong in 1995 to substantially weakened in the following years. The abrupt change in the intensity of the SPG is commonly linked to the reversal of the North Atlantic Oscillation (NAO) index, changing from strong positive to negative values, in the winter 1995/96. In this study we investigate the impact of the initial SPG state on its subsequent behavior by means of an ocean general <span class="hlt">circulation</span> model driven by NCEP-NCAR reanalysis fields. Our sensitivity integrations suggest that the weakening of the SPG cannot be explained by the change in the atmospheric forcing alone. Rather, for the time period around 1995, the SPG was about to weaken, irrespective of the actual atmospheric forcing, due to the ocean state governed by the persistently strong positive NAO during the preceding seven years (1989 to 1995). Our analysis indicates that it was this preconditioning of the ocean, in combination with the sudden drop in the NAO in 1995/96, that lead to the strong and rapid weakening of the SPG in the second half of the 1990s. In the second part, the sensitivity of the low-frequency variability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> to changes in the subpolar North Atlantic is investigated using a 2000 year long control integration as well as sensitivity experiments with the MPI-M Earth System Model. Two 1000 year long sensitivity experiments will be performed, in which the low-frequency variability in the overflow transports from the Nordic Seas and in the subpolar deep water formation rates is suppressed respectively. This is achieved by nudging temperature and salinity in the GIN Sea or in the subpolar North Atlantic (up to about 1500m depth) towards a monthly climatology obtained from the last 1000 years of the control integration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPSC...10...63T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPSC...10...63T"><span>Sun-stirred Kraken Mare: <span class="hlt">Circulation</span> in Titan's seas induced by solar heating and methane precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tokano, T.; Lorenz, R. D.</p> <p>2015-10-01</p> <p>Density-driven <span class="hlt">circulation</span> in Titan's seas forced by solar heating and methane evaporation/precipitation is simulated by an ocean <span class="hlt">circulation</span> model. If the sea is transparent to sunlight, solar heating can induce anti-clockwise gyres near the sea surface and clockwise gyres near the sea bottom. The gyres are in geostrophic balance between the radially symmetric pressure gradient force and Coriolis force. If instead the sea is turbid and most sunlight is absorbed near the sea surface, the sea gets stratified in warm seasons and the <span class="hlt">circulation</span> remains weak. Strong summer precipitation at high latitudes causes compositional stratification and increase of the nearsurface methane mole fraction towards the north pole. The resultant latitudinal density contrast drives a <span class="hlt">meridional</span> overturning with equatorward currents near the sea surface and poleward currents near the sea bottom. Weak precipitation induces gyres rather than <span class="hlt">meridional</span> overturning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060039137&hterms=Tracer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DTracer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060039137&hterms=Tracer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DTracer"><span>(abstract) Cometary Particles as a Tracer of Jupiter's Stratospheric <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>West, R. A.; Friedson, A. J.</p> <p>1993-01-01</p> <p>The impact of fragments of comet Shoemaker-Levy 9 on Jupiter's atmosphere in July 1994 may provide an unprecedented opportunity to study Jupiter's stratospheric <span class="hlt">circulation</span>. Recent calculations by Z. Sekanina predict that much of the comet material will be deposited in Jupiter's stratosphere. If so, and if the material is deposited in a confined region (10 000 km or less, horizontally) we can expect a situation analogous to an El Chichon or Pinatubo event for the terrestrial stratosphere. Initially the volatile material will be vaporized and will rapidly recondense. The large ice crystals and dust particles will rain out and be lost to the troposphere. The cloud of small particles which remain may have settling times of more than a year. These submicron to micron particles would probably be easily seen in methane filter images in the near-IR, and possibly in the ultraviolet. An observational program to monitor the dispersal of this cloud or clouds would reveal much about the nature of the <span class="hlt">circulation</span>. Some predictions about the <span class="hlt">meridional</span> evolution of the clouds can be made already, based on the <span class="hlt">meridional</span> <span class="hlt">circulation</span> model of West et al. unless the impact itself significantly disrupts the annual average <span class="hlt">circulation</span> well after the initial transients die away.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25753914','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25753914"><span><span class="hlt">Circulating</span> betatrophin is elevated in patients with <span class="hlt">type</span> 1 and <span class="hlt">type</span> 2 diabetes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yamada, Hodaka; Saito, Tomoyuki; Aoki, Atsushi; Asano, Tomoko; Yoshida, Masashi; Ikoma, Aki; Kusaka, Ikuyo; Toyoshima, Hideo; Kakei, Masafumi; Ishikawa, San-E</p> <p>2015-01-01</p> <p>There is evidence that betatrophin, a hormone derived from adipose tissue and liver, affects the proliferation of pancreatic beta cells in mice. The aim of this study was to examine <span class="hlt">circulating</span> betatrophin concentrations in Japanese healthy controls and patients with <span class="hlt">type</span> 1 and <span class="hlt">type</span> 2 diabetes. A total of 76 subjects (12 healthy controls, 34 <span class="hlt">type</span> 1 diabetes, 30 <span class="hlt">type</span> 2 diabetes) were enrolled in the study. <span class="hlt">Circulating</span> betatrophin was measured with an ELISA kit and clinical parameters related to betatrophin were analyzed statistically. <span class="hlt">Circulating</span> betatrophin (Log transformed) was significantly increased in patients with diabetes compared with healthy subjects (healthy controls, 2.29 ± 0.51; <span class="hlt">type</span> 1 diabetes, 2.94 ± 0.44; <span class="hlt">type</span> 2 diabetes, 3.17 ± 0.18; p<0.001, 4.1 to 5.4 times in pg/mL order). Age, HbA1c, fasting plasma glucose and Log triglyceride were strongly associated with Log betatrophin in all subjects (n=76) in correlation analysis. In <span class="hlt">type</span> 1 diabetes, there was a correlation between Log betatrophin and Log CPR. These results provide the first evidence that <span class="hlt">circulating</span> betatrophin is significantly elevated in Japanese patients with diabetes. The findings of this pilot study also suggest a possibility of association between the level of betatrophin and the levels of glucose and triglycerides.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018CliPa..14..789H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018CliPa..14..789H"><span>Climate sensitivity and <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> in the late Eocene using GFDL CM2.1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hutchinson, David K.; de Boer, Agatha M.; Coxall, Helen K.; Caballero, Rodrigo; Nilsson, Johan; Baatsen, Michiel</p> <p>2018-06-01</p> <p>The Eocene-Oligocene transition (EOT), which took place approximately 34 Ma ago, is an interval of great interest in Earth's climate history, due to the inception of the Antarctic ice sheet and major global cooling. Climate simulations of the transition are needed to help interpret proxy data, test mechanistic hypotheses for the transition and determine the climate sensitivity at the time. However, model studies of the EOT thus far typically employ control states designed for a different time period, or ocean resolution on the order of 3°. Here we developed a new higher resolution palaeoclimate model configuration based on the GFDL CM2.1 climate model adapted to a late Eocene (38 Ma) palaeogeography reconstruction. The ocean and atmosphere horizontal resolutions are 1° × 1.5° and 3° × 3.75° respectively. This represents a significant step forward in resolving the ocean geography, gateways and <span class="hlt">circulation</span> in a coupled climate model of this period. We run the model under three different levels of atmospheric CO2: 400, 800 and 1600 ppm. The model exhibits relatively high sensitivity to CO2 compared with other recent model studies, and thus can capture the expected Eocene high latitude warmth within observed estimates of atmospheric CO2. However, the model does not capture the low <span class="hlt">meridional</span> temperature gradient seen in proxies. Equatorial sea surface temperatures are too high in the model (30-37 °C) compared with observations (max 32 °C), although observations are lacking in the warmest regions of the western Pacific. The model exhibits bipolar sinking in the North Pacific and Southern Ocean, which persists under all levels of CO2. North Atlantic surface salinities are too fresh to permit sinking (25-30 psu), due to surface transport from the very fresh Arctic ( ˜ 20 psu), where surface salinities approximately agree with Eocene proxy estimates. North Atlantic salinity increases by 1-2 psu when CO2 is halved, and similarly freshens when CO2 is doubled, due</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920050746&hterms=layers+atmosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlayers%2Batmosphere','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920050746&hterms=layers+atmosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlayers%2Batmosphere"><span>Role of a cumulus parameterization scheme in simulating atmospheric <span class="hlt">circulation</span> and rainfall in the nine-layer Goddard Laboratory for Atmospheres General <span class="hlt">Circulation</span> Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sud, Y. C.; Chao, Winston C.; Walker, G. K.</p> <p>1992-01-01</p> <p>The influence of a cumulus convection scheme on the simulated atmospheric <span class="hlt">circulation</span> and hydrologic cycle is investigated by means of a coarse version of the GCM. Two sets of integrations, each containing an ensemble of three summer simulations, were produced. The ensemble sets of control and experiment simulations are compared and differentially analyzed to determine the influence of a cumulus convection scheme on the simulated <span class="hlt">circulation</span> and hydrologic cycle. The results show that cumulus parameterization has a very significant influence on the simulation <span class="hlt">circulation</span> and precipitation. The upper-level condensation heating over the ITCZ is much smaller for the experiment simulations as compared to the control simulations; correspondingly, the <span class="hlt">Hadley</span> and Walker cells for the control simulations are also weaker and are accompanied by a weaker Ferrel cell in the Southern Hemisphere. Overall, the difference fields show that experiment simulations (without cumulus convection) produce a cooler and less energetic atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21452855-characteristics-solar-meridional-flows-during-solar-cycle','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21452855-characteristics-solar-meridional-flows-during-solar-cycle"><span>CHARACTERISTICS OF SOLAR <span class="hlt">MERIDIONAL</span> FLOWS DURING SOLAR CYCLE 23</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Basu, Sarbani; Antia, H. M., E-mail: sarbani.basu@yale.ed, E-mail: antia@tifr.res.i</p> <p>2010-07-01</p> <p>We have analyzed available full-disk data from the Michelson Doppler Imager on board SOHO using the 'ring diagram' technique to determine the behavior of solar <span class="hlt">meridional</span> flows over solar cycle 23 in the outer 2% of the solar radius. We find that the dominant component of <span class="hlt">meridional</span> flows during solar maximum was much lower than that during the minima at the beginning of cycles 23 and 24. There were differences in the flow velocities even between the two minima. The <span class="hlt">meridional</span> flows show a migrating pattern with higher-velocity flows migrating toward the equator as activity increases. Additionally, we find thatmore » the migrating pattern of the <span class="hlt">meridional</span> flow matches those of sunspot butterfly diagram and the zonal flows in the shallow layers. A high-latitude band in <span class="hlt">meridional</span> flow appears around 2004, well before the current activity minimum. A Legendre polynomial decomposition of the <span class="hlt">meridional</span> flows shows that the latitudinal pattern of the flow was also different during the maximum as compared to that during the two minima. The different components of the flow have different time dependences, and the dependence is different at different depths.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870003613&hterms=Experimental+design&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DExperimental%2Bdesign','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870003613&hterms=Experimental+design&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DExperimental%2Bdesign"><span>Theoretical and experimental design studies for the Atmospheric General <span class="hlt">Circulation</span> Experiment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fowlis, W. W.; Hathaway, D. H.; Miller, T. L.; Roberts, G. O.; Kopecky, K. J.</p> <p>1985-01-01</p> <p>The major criterion for the Atmospheric General <span class="hlt">Circulation</span> Experiment (AGCE) design is that it be possible to realize strong baroclinic instability in the spherical configuration chosen. A configuration was selected in which a hemispherical shell of fluid is subjected to latitudinal temperature gradients on its spherical boundaries and the latitudinal boundaries are insulators. Work in the laboratory with a cylindrical version of this configuration revealed more instabilities than baroclinic instability. Since researchers fully expect these additional instabilities to appear in the spherical configuration also, they decided to continue the laboratory cylindrical annulus studies. Four flow regimes were identified: an axisymmetric <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, boundary layer convection, baroclinic waves and deep thermal convection. Regime diagrams were prepared.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820005161','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820005161"><span>On the global <span class="hlt">circulation</span> and the hurricane system of the Jovian atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mayr, H. G.; Meada, K.; Harris, I.</p> <p>1981-01-01</p> <p>An argument is made to support the proposal that Jupiter's red spot and the white and brown ovals are hurricanes or cyclones. Against the background of a convectively unstable troposphere, the general condition exists for the formation of hurricanes. The energy Jupiter emits must be transported upwards through the troposphere. If that transport is accelerated by the prevailing upward motions in the solar driven multicellular <span class="hlt">meridional</span> <span class="hlt">circulation</span>, eastward jets develop such as observed in the l region. But if that vertical transport is impeded by the prevailing downward motions in the <span class="hlt">meridional</span> <span class="hlt">circulation</span>, the atmosphere reacts and tends to maintain the process through the development of hurricanes. Dynamically induced by solar differential heating, an ordered latitudinal structure with alternating stability and instability is impressed on the troposphere to form alternating zonal strata where hurricanes are forbidden and permitted, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS41A1989L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS41A1989L"><span>Interhemispheric Changes in Atlantic Ocean Heat Content and Their Link to Global Monsoons</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lopez, H.; Lee, S. K.; Dong, S.; Goni, G. J.</p> <p>2015-12-01</p> <p>This study tested the hypothesis whether low frequency decadal variability of the South Atlantic <span class="hlt">meridional</span> heat transport (SAMHT) influences decadal variability of the global monsoons. A multi-century run from a state-of-the-art coupled general <span class="hlt">circulation</span> model is used as basis for the analysis. Our findings indicate that multi-decadal variability of the South Atlantic Ocean plays a key role in modulating atmospheric <span class="hlt">circulation</span> via interhemispheric changes in Atlantic Ocean heat content. Weaker SAMHT produces anomalous ocean heat divergence over the South Atlantic resulting in negative ocean heat content anomaly about 15 years later. This, in turn, forces a thermally direct anomalous interhemispheric <span class="hlt">Hadley</span> <span class="hlt">circulation</span> in the atmosphere, transporting heat from the northern hemisphere (NH) to the southern hemisphere (SH) and moisture from the SH to the NH, thereby intensify (weaken) summer (winter) monsoon in the NH and winter (summer) monsoon in the SH. Results also show that anomalous atmospheric eddies, both transient and stationary, transport heat northward in both hemispheres producing eddy heat flux convergence (divergence) in the NH (SH) around 15-30°, reinforcing the anomalous <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. The effect of eddies on the NH (SH) poleward of 30° is opposite with heat flux divergence (convergence), which must be balanced by sinking (rising) motion, consistent with a poleward (equatorward) displacement of the jet stream and mean storm track. The mechanism described here could easily be interpreted for the case of strong SAMHT, with the reverse influence on the interhemispheric atmospheric <span class="hlt">circulation</span> and monsoons. Overall, SAMHT decadal variability leads its atmospheric response by about 15 years, suggesting that the South Atlantic is a potential predictor of global climate variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912015W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912015W"><span>Spatio-temporal atmospheric <span class="hlt">circulation</span> variability around the Antarctic Peninsula based on hemispheric <span class="hlt">circulation</span> modes and weather <span class="hlt">types</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wachter, Paul; Beck, Christoph; Philipp, Andreas; Jacobeit, Jucundus; Höppner, Kathrin</p> <p>2017-04-01</p> <p>Large parts of the Polar Regions are affected by a warming trend associated with substantial changes in the cryosphere. In Antarctica this positive trend pattern is most dominant in the western part of the continent and on the Antarctic Peninsula (AP). An important driving mechanism of temperature variability and trends in this region is the atmospheric <span class="hlt">circulation</span>. Changes in atmospheric <span class="hlt">circulation</span> modes and frequencies of <span class="hlt">circulation</span> <span class="hlt">types</span> have major impacts on temperature characteristics at a certain station or region. We present results of a statistical downscaling study focused on AP temperature variability showing both results of large-scale atmospheric <span class="hlt">circulation</span> modes and regional weather <span class="hlt">type</span> classifications derived from monthly and daily gridded reanalysis data sets. In order to investigate spatial trends and variabilities of the Southern Annular Mode (SAM), we analyze spatio-temporally resolved SAM-pattern maps from 1979 to 2015. First results show dominant multi-annual to decadal pattern variabilities which can be directly linked to temperature variabilities at the Antarctic Peninsula. A sub-continental to regional view on the influence of atmospheric <span class="hlt">circulation</span> on AP temperature variability is given by the analysis of weather <span class="hlt">type</span> classifications (WTC). With this analysis we identify significant changes in the frequency of occurrence of highly temperature-relevant <span class="hlt">circulation</span> patterns. The investigated characteristics of weather <span class="hlt">type</span> frequencies can also be related to the identified changes of the SAM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013DPS....4520208H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013DPS....4520208H"><span>Venus winds from ultraviolet, visible and near infrared images from the VIRTIS instrument on Venus Express</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hueso, Ricardo; Garate-Lopez, I.; Peralta, J.; Bandos, T.; Sánchez-Lavega, A.</p> <p>2013-10-01</p> <p>After more than 6 years orbiting Venus the Venus Express mission has provided the largest database of observations of Venus atmosphere at different cloud layers with the combination of VMC and VIRTIS instruments. We present measurements of cloud motions in the South hemisphere of Venus analyzing images from the VIRTIS-M visible channel at different wavelengths sensitive to the upper cloud haze at 65-70 km height (dayside ultraviolet images) and the middle cloud deck (dayside visible and near infrared images around 1 μm) about 5-8 km deeper in the atmosphere. We combine VIRTIS images in nearby wavelengths to increase the contrast of atmospheric details and measurements were obtained with a semi-automatic cloud correlation algorithm. Both cloud layers are studied simultaneously to infer similarities and differences in these vertical levels in terms of cloud morphologies and winds. For both levels we present global mean zonal and <span class="hlt">meridional</span> winds, latitudinal distribution of winds with local time and the wind shear between both altitudes. The upper branch of the <span class="hlt">Hadley</span> cell <span class="hlt">circulation</span> is well resolved in UV images with an acceleration of the <span class="hlt">meridional</span> <span class="hlt">circulation</span> at mid-latitudes with increasing local time peaking at 14-16h. This organized <span class="hlt">meridional</span> <span class="hlt">circulation</span> is almost absent in NIR images. Long-term variability of zonal winds is also found in UV images with increasing winds over time during the VEX mission. This is in agreement with current analysis of VMC images (Kathuntsev et al. 2013). The possible long-term acceleration of zonal winds is also examined for NIR images. References Khatuntsev et al. Icarus 226, 140-158 (2013)</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-as15-88-11894.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-as15-88-11894.html"><span>View of Commemorative plaque left on moon at <span class="hlt">Hadley</span>-Apennine landing site</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>1971-08-01</p> <p>AS15-88-11894 (31 July-2 Aug. 1971) --- A close-up view of a commemorative plaque left on the moon at the <span class="hlt">Hadley</span>-Apennine landing site in memory of 14 NASA astronauts and USSR cosmonauts, now deceased. Their names are inscribed in alphabetical order on the plaque. The plaque was stuck in the lunar soil by astronauts David R. Scott, commander, and James B. Irwin, lunar module pilot, during their Apollo 15 lunar surface extravehicular activity (EVA). The names on the plaque are Charles A. Bassett II, Pavel I. Belyayev, Roger B. Chaffee, Georgi Dobrovolsky, Theodore C. Freeman, Yuri A. Gagarin, Edward G. Givens Jr., Virgil I. Grissom, Vladimir Komarov, Viktor Patsayev, Elliot M. See Jr., Vladislav Volkov, Edward H. White II, and Clifton C. Williams Jr. The tiny, man-like object represents the figure of a fallen astronaut/cosmonaut. While astronauts Scott and Irwin descended in the Lunar Module (LM) "Falcon" to explore the <span class="hlt">Hadley</span>-Apennine area of the moon, astronaut Alfred M. Worden, command module pilot, remained with the Command and Service Modules (CSM) in lunar orbit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22190490','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22190490"><span>Mid-latitude afforestation shifts general <span class="hlt">circulation</span> and tropical precipitation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Swann, Abigail L S; Fung, Inez Y; Chiang, John C H</p> <p>2012-01-17</p> <p>We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global <span class="hlt">circulation</span> patterns. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric <span class="hlt">circulation</span> redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the Sahel and Sahara regions in Africa. We find that the response of climate to afforestation in mid-latitudes is determined by the amount of soil moisture available to plants with the greatest warming found in water-limited regions. Mid-latitude afforestation is found to have a small impact on modeled global temperatures and on global CO(2), but regional heating from the increase in forest cover is capable of driving unintended changes in <span class="hlt">circulation</span> and precipitation. The ability of vegetation to affect remote <span class="hlt">circulation</span> has implications for strategies for climate mitigation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1179513-tropical-meteorology-climate-hadley-circulation','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1179513-tropical-meteorology-climate-hadley-circulation"><span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Lu, Jian; Vecchi, Gabriel A.</p> <p></p> <p>The <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, a prominent <span class="hlt">circulation</span> feature characterized by rising air near the Equator and sinking air in the subtropics, defines the position of dry subtropical areas and is a fundamental regulator of the earth’s energy and momentum budgets. The character of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, and its related precipitation regimes, exhibits variation and change in response to both climate variability and radiative forcing changes. The strength and position of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> change from year to year paced by El Niño and La Niña events. Over the last few decades of the twentieth century, the <span class="hlt">Hadley</span> cell has expanded polewardmore » in both hemispheres, with changes in atmospheric composition (including stratospheric ozone depletion and greenhouse gas increases) thought to have contributed to its expansion. This article introduces the basic phenomenology and driving mechanism of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> and discusses its variations under both natural and anthropogenic climate forcings.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980213327','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980213327"><span>Wind Streaks on Venus: Clues to Atmospheric <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greeley, Ronald; Schubert, Gerald; Limonadi, Daniel; Bender, Kelly C.; Newman, William I.; Thomas, Peggy E.; Weitz, Catherine M.; Wall, Stephen D.</p> <p>1994-01-01</p> <p>Magellan images reveal surface features on Venus attributed to wind processes. Sand dunes, wind-sculpted hills, and more than 5830 wind streaks have been identified. The streaks serve as local "wind vanes," representing wind direction at the time of streak formation and allowing the first global mapping of near-surface wind patterns on Venus. Wind streaks are oriented both toward the equator and toward the west. When streaks associated with local transient events, such as impact cratering, are deleted, the westward component is mostly lost but the equatorward component remains. This pattern is consistent with a <span class="hlt">Hadley</span> <span class="hlt">circulation</span> of the lower atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70020975','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70020975"><span>General-<span class="hlt">circulation</span>-model simulations of future snowpack in the western United States</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McCabe, G.J.; Wolock, D.M.</p> <p>1999-01-01</p> <p>April 1 snowpack accumulations measured at 311 snow courses in the western United States (U.S.) are grouped using a correlation-based cluster analysis. A conceptual snow accumulation and melt model and monthly temperature and precipitation for each cluster are used to estimate cluster-average April 1 snowpack. The conceptual snow model is subsequently used to estimate future snowpack by using changes in monthly temperature and precipitation simulated by the Canadian Centre for Climate Modeling and Analysis (CCC) and the <span class="hlt">Hadley</span> Centre for Climate Prediction and Research (<span class="hlt">HADLEY</span>) general <span class="hlt">circulation</span> models (GCMs). Results for the CCC model indicate that although winter precipitation is estimated to increase in the future, increases in temperatures will result in large decreases in April 1 snowpack for the entire western US. Results for the <span class="hlt">HADLEY</span> model also indicate large decreases in April 1 snowpack for most of the western US, but the decreases are not as severe as those estimated using the CCC simulations. Although snowpack conditions are estimated to decrease for most areas of the western US, both GCMs estimate a general increase in winter precipitation toward the latter half of the next century. Thus, water quantity may be increased in the western US; however, the timing of runoff will be altered because precipitation will more frequently occur as rain rather than as snow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016usc..confE..55K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016usc..confE..55K"><span>Subsurface Zonal and <span class="hlt">Meridional</span> Flows from SDO/HMI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Komm, Rudolf; Howe, Rachel; Hill, Frank</p> <p>2016-10-01</p> <p>We study the solar-cycle variation of the zonal and <span class="hlt">meridional</span> flows in the near-surface layers of the solar convection zone from the surface to a depth of about 16 Mm. The flows are determined from SDO/HMI Dopplergrams using the HMI ring-diagram pipeline. The zonal and <span class="hlt">meridional</span> flows vary with the solar cycle. Bands of faster-than-average zonal flows together with more-poleward-than-average <span class="hlt">meridional</span> flows move from mid-latitudes toward the equator during the solar cycle and are mainly located on the equatorward side of the mean latitude of solar magnetic activity. Similarly, bands of slower-than-average zonal flows together with less-poleward-than-average <span class="hlt">meridional</span> flows are located on the poleward side of the mean latitude of activity. Here, we will focus on the variation of these flows at high latitudes (poleward of 50 degree) that are now accessible using HMI data. We will present the latest results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Icar..270...67T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Icar..270...67T"><span>Sun-stirred Kraken Mare: <span class="hlt">Circulation</span> in Titan's seas induced by solar heating and methane precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tokano, Tetsuya; Lorenz, Ralph D.</p> <p>2016-05-01</p> <p>Density-driven <span class="hlt">circulation</span> in Titan's seas forced by solar heating and methane evaporation/precipitation is simulated by an ocean <span class="hlt">circulation</span> model. If the sea is transparent to sunlight, solar heating can induce anti-clockwise gyres near the sea surface and clockwise gyres near the sea bottom. The gyres are in geostrophic balance between the radially symmetric pressure gradient force and Coriolis force. If instead the sea is turbid and most sunlight is absorbed near the sea surface, the sea gets stratified in warm seasons and the <span class="hlt">circulation</span> remains weak. Precipitation causes compositional stratification of the sea to an extent that the sea surface temperature can be lower than the sea interior temperature without causing a convective overturning. Non-uniform precipitation can also generate a latitudinal gradient in the methane mole fraction and density, which drives a <span class="hlt">meridional</span> overturning with equatorward currents near the sea surface and poleward currents near the sea bottom. However, gyres are more ubiquitous than <span class="hlt">meridional</span> overturning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010BGeo....7.3549P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010BGeo....7.3549P"><span>Fueling export production: nutrient return pathways from the deep ocean and their dependence on the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palter, J. B.; Sarmiento, J. L.; Gnanadesikan, A.; Simeon, J.; Slater, R. D.</p> <p>2010-11-01</p> <p>In the Southern Ocean, mixing and upwelling in the presence of heat and freshwater surface fluxes transform subpycnocline water to lighter densities as part of the upward branch of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC). One hypothesized impact of this transformation is the restoration of nutrients to the global pycnocline, without which biological productivity at low latitudes would be significantly reduced. Here we use a novel set of modeling experiments to explore the causes and consequences of the Southern Ocean nutrient return pathway. Specifically, we quantify the contribution to global productivity of nutrients that rise from the ocean interior in the Southern Ocean, the northern high latitudes, and by mixing across the low latitude pycnocline. In addition, we evaluate how the strength of the Southern Ocean winds and the parameterizations of subgridscale processes change the dominant nutrient return pathways in the ocean. Our results suggest that nutrients upwelled from the deep ocean in the Antarctic Circumpolar Current and subducted in Subantartic Mode Water support between 33 and 75% of global export production between 30° S and 30° N. The high end of this range results from an ocean model in which the MOC is driven primarily by wind-induced Southern Ocean upwelling, a configuration favored due to its fidelity to tracer data, while the low end results from an MOC driven by high diapycnal diffusivity in the pycnocline. In all models, nutrients exported in the SAMW layer are utilized and converted rapidly (in less than 40 years) to remineralized nutrients, explaining previous modeling results that showed little influence of the drawdown of SAMW surface nutrients on atmospheric carbon concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010BGD.....7.4045P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010BGD.....7.4045P"><span>Fueling primary productivity: nutrient return pathways from the deep ocean and their dependence on the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palter, J. B.; Sarmiento, J. L.; Gnanadesikan, A.; Simeon, J.; Slater, D.</p> <p>2010-06-01</p> <p>In the Southern Ocean, mixing and upwelling in the presence of heat and freshwater surface fluxes transform subpycnocline water to lighter densities as part of the upward branch of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC). One hypothesized impact of this transformation is the restoration of nutrients to the global pycnocline, without which biological productivity at low latitudes would be catastrophically reduced. Here we use a novel set of modeling experiments to explore the causes and consequences of the Southern Ocean nutrient return pathway. Specifically, we quantify the contribution to global productivity of nutrients that rise from the ocean interior in the Southern Ocean, the northern high latitudes, and by mixing across the low latitude pycnocline. In addition, we evaluate how the strength of the Southern Ocean winds and the parameterizations of subgridscale processes change the dominant nutrient return pathways in the ocean. Our results suggest that nutrients upwelled from the deep ocean in the Antarctic Circumpolar Current and subducted in Subantartic Mode Water support between 33 and 75% of global primary productivity between 30° S and 30° N. The high end of this range results from an ocean model in which the MOC is driven primarily by wind-induced Southern Ocean upwelling, a configuration favored due to its fidelity to tracer data, while the low end results from an MOC driven by high diapycnal diffusivity in the pycnocline. In all models, the high preformed nutrients subducted in the SAMW layer are converted rapidly (in less than 40 years) to remineralized nutrients, explaining previous modeling results that showed little influence of the drawdown of SAMW surface nutrients on atmospheric carbon concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51O..07R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51O..07R"><span>Understanding the robustness of <span class="hlt">Hadley</span> cell response to wide variations in ocean heat transport</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rencurrel, M. C.; Rose, B. E. J.</p> <p>2017-12-01</p> <p>One important aspect of our climate system is the relationship between surface climate and the poleward energy transport in the atmosphere and ocean. Previous studies have shown that increases in poleward ocean heat transport (OHT) tend to warm the midlatitudes without strongly affecting tropical SSTs, resulting in a reduction in the equator-to-pole temperature gradient. This "tropical thermostat" effect depends crucially on a slowdown of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> (HC), with consequent changes in surface evaporation, atmospheric water vapor, and cloudiness. Here we extend previous studies by considering a wide range of spatial patterns of OHT, which we impose in a suite of slab-ocean aquaplanet GCM simulations. The forcing patterns are idealized but sample a variety of ocean <span class="hlt">circulation</span> features. We find that the tropical thermostat and HC slowdown effects are relatively robust across all forcing patterns. A 1 PW increase in the amplitude of the prescribed OHT spatial pattern results in a global mean warming and a roughly 5 x 1010 kg/s decrease in HC mass flux, regardless of the detailed spatial structure of the imposed OHT. While the rate of HC slowdown is relatively robust, the mechanisms driving it are less so. Smaller, equator-to-subtropical scale OHT patterns are associated with greater reduced Gross Moist Stability (GMS) than the larger-scale OHT patterns. As the imposed OHT is limited equatorward, the HC becomes less efficient at transporting energy out of the tropics, implying that GMS has a modulating effect on the dynamical response of the cell. These experiments offer some new insights on the interplay between atmospheric dynamics and the radiative and hydrological aspects of global climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51O..05A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51O..05A"><span>The Interplay of Internal and Forced Modes of <span class="hlt">Hadley</span> Cell Expansion: Lessons from the Global Warming Hiatus</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amaya, D. J.; Siler, N.; Xie, S. P.; Miller, A. J.</p> <p>2017-12-01</p> <p>The poleward branches of the <span class="hlt">Hadley</span> Cells show a robust shift poleward shift during the satellite era, leading to concerns over the possible encroachment of the globe's subtropical dry zones into currently temperate climates. The extent to which this trend is caused by anthropogenic forcing versus internal variability remains the subject of considerable debate. In this study, we us a joint EOF method to identify two distinct modes of <span class="hlt">Hadley</span> Cell variability: (i) an anthropogenically-forced mode, which we identify using a 20-member simulation of the historical climate, and (ii) an internal mode, which identify using a 1000-year pre-industrial control simulation with a global climate model. The forced mode is found to be closely related to the TOA radiative imbalance and exhibits a long-term trend since 1860, while the internal mode is found to be essentially indistinguishable from the El Niño Southern Oscillation (ENSO). Together these two modes explain an average of 70% of the interannual variability seen in model "edge indices" over the historical period. Since 1980, the superposition of forced and internal modes has resulted in a period of accelerated <span class="hlt">Hadley</span> Cell expansion and decelerated global warming (i.e., the "hiatus"). A comparison of the change in these modes since 1980 indicates that by 2013 the signal has emerged above the noise of internal variability in the Southern Hemisphere (SH), but not in the Northern Hemisphere (NH), with the latter also exhibiting strong zonal asymmetry, particularly in the North Atlantic. Our results highlight the important interplay of internal and forced modes of <span class="hlt">Hadley</span> Cell width change and improve our understanding of the interannual variability and long-term trend seen in observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AREPS..46..549M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AREPS..46..549M"><span>Responses of the Tropical Atmospheric <span class="hlt">Circulation</span> to Climate Change and Connection to the Hydrological Cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Jian; Chadwick, Robin; Seo, Kyong-Hwan; Dong, Changming; Huang, Gang; Foltz, Gregory R.; Jiang, Jonathan H.</p> <p>2018-05-01</p> <p>This review describes the climate change–induced responses of the tropical atmospheric <span class="hlt">circulation</span> and their impacts on the hydrological cycle. We depict the theoretically predicted changes and diagnose physical mechanisms for observational and model-projected trends in large-scale and regional climate. The tropical <span class="hlt">circulation</span> slows down with moisture and stratification changes, connecting to a poleward expansion of the <span class="hlt">Hadley</span> cells and a shift of the intertropical convergence zone. Redistributions of regional precipitation consist of thermodynamic and dynamical components, including a strong offset between moisture increase and <span class="hlt">circulation</span> weakening throughout the tropics. This allows other dynamical processes to dominate local <span class="hlt">circulation</span> changes, such as a surface warming pattern effect over oceans and multiple mechanisms over land. To improve reliability in climate projections, more fundamental understandings of pattern formation, <span class="hlt">circulation</span> change, and the balance of various processes redistributing land rainfall are suggested to be important.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1355939-cloud-circulation-feedbacks-near-global-aquaplanet-cloud-resolving-model','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1355939-cloud-circulation-feedbacks-near-global-aquaplanet-cloud-resolving-model"><span>Cloud and <span class="hlt">circulation</span> feedbacks in a near-global aquaplanet cloud-resolving model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Narenpitak, Pornampai; Bretherton, Christopher S.; Khairoutdinov, Marat F.</p> <p>2017-05-08</p> <p>A near-global aquaplanet cloud-resolving model (NGAqua) with fixed <span class="hlt">meridionally</span> varying sea-surface temperature (SST) is used to investigate cloud feedbacks due to three climate perturbations: a uniform 4 K SST increase, a quadrupled-CO2 concentration, and both combined. NGAqua has a horizontal resolution of 4 km with no cumulus parameterization. Its domain is a zonally periodic 20,480 km-long tropical channel, spanning 46°S–N. It produces plausible mean distributions of clouds, rainfall, and winds. After spin-up, 80 days are analyzed for the control and increased-SST simulations, and 40 days for those with quadrupled CO 2. The Intertropical Convergence Zone width and tropical cloud covermore » are not strongly affected by SST warming or CO 2 increase, except for the expected upward shift in high clouds with warming, but both perturbations weaken the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. Increased SST induces a statistically significant increase in subtropical low cloud fraction and in-cloud liquid water content but decreases midlatitude cloud, yielding slightly positive domain-mean shortwave cloud feedbacks. CO 2 quadrupling causes a slight shallowing and a statistically insignificant reduction of subtropical low cloud fraction. Warming-induced low cloud changes are strongly correlated with changes in estimated inversion strength, which increases modestly in the subtropics but decreases in the midlatitudes. Enhanced clear-sky boundary layer radiative cooling in the warmer climate accompanies the robust subtropical low cloud increase. The probability distribution of column relative humidity across the tropics and subtropics is compared between the control and increased-SST simulations. It shows no evidence of bimodality or increased convective aggregation in a warmer climate.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1355939-cloud-circulation-feedbacks-near-global-aquaplanet-cloud-resolving-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1355939-cloud-circulation-feedbacks-near-global-aquaplanet-cloud-resolving-model"><span>Cloud and <span class="hlt">circulation</span> feedbacks in a near-global aquaplanet cloud-resolving model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Narenpitak, Pornampai; Bretherton, Christopher S.; Khairoutdinov, Marat F.</p> <p></p> <p>A near-global aquaplanet cloud-resolving model (NGAqua) with fixed <span class="hlt">meridionally</span> varying sea-surface temperature (SST) is used to investigate cloud feedbacks due to three climate perturbations: a uniform 4 K SST increase, a quadrupled-CO2 concentration, and both combined. NGAqua has a horizontal resolution of 4 km with no cumulus parameterization. Its domain is a zonally periodic 20,480 km-long tropical channel, spanning 46°S–N. It produces plausible mean distributions of clouds, rainfall, and winds. After spin-up, 80 days are analyzed for the control and increased-SST simulations, and 40 days for those with quadrupled CO 2. The Intertropical Convergence Zone width and tropical cloud covermore » are not strongly affected by SST warming or CO 2 increase, except for the expected upward shift in high clouds with warming, but both perturbations weaken the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. Increased SST induces a statistically significant increase in subtropical low cloud fraction and in-cloud liquid water content but decreases midlatitude cloud, yielding slightly positive domain-mean shortwave cloud feedbacks. CO 2 quadrupling causes a slight shallowing and a statistically insignificant reduction of subtropical low cloud fraction. Warming-induced low cloud changes are strongly correlated with changes in estimated inversion strength, which increases modestly in the subtropics but decreases in the midlatitudes. Enhanced clear-sky boundary layer radiative cooling in the warmer climate accompanies the robust subtropical low cloud increase. The probability distribution of column relative humidity across the tropics and subtropics is compared between the control and increased-SST simulations. It shows no evidence of bimodality or increased convective aggregation in a warmer climate.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP23A1282C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP23A1282C"><span>The role of <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC) on Ancient Climates and Implications for Anthropogenic Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cumming, M.</p> <p>2017-12-01</p> <p>Our increasingly robust history of ancient climates indicates that high latitude glaciation is the ultimate product of an episodic cooling trend that began about 100-million years ago rather than a result of a yet-to-be identified modal change. Antarctic geography (continent surrounded by ocean) allowed ice to develop prior to significant glaciation in the Northern Hemisphere (ocean surrounded by land), but global ice volume generally increased as Earth cooled. The question of what caused the Ice Ages should be reframed as to "What caused the Cenozoic Cooling?" Records tell us that changes in temperature and CO2 levels rise and fall together, however it is not clear when CO2 acts as a driver versus when it is primarily an indicator of temperature change. The episodic nature of the cooling trend suggests other more dynamic phenomena are involved. It is proposed that oceanic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) plays a significant role in regulating Earth's surface temperature. Robust MOC has a cooling effect which results from its sequestration of cold waters (together with their increased heat-absorbing potential) below the surface. Unable to better absorb equatorial insolation for great lengths of time, oceanic deep waters are not able to fully compensate for the heat lost by warm-water transport to Polar Regions. A lag-time between cooling and subsequent warming yields lower operating temperatures commensurate with the strength of global MOC. The long-term decline in global temperatures is largely explained by the tectonic reshaping of ocean basins and the connections between them such that MOC has generally, but not uniformly, increased. Geophysically Influenced MOC (GIMOC) has caused a significant proportion of the lowering of global temperatures in the Cenozoic Era. Short-term disruptions in MOC (and subsequent impacts on global temperatures) were likely involved in Late Pleistocene glacial termination events and may already be compounding present</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000791','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000791"><span><span class="hlt">Meridional</span> Distribution of Aerosol Optical Thickness over the Tropical Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kishcha, P.; Silva, Arlindo M.; Starobinets, B.; Long, C. N.; Kalashnikova, O.; Alpert, P.</p> <p>2015-01-01</p> <p>Previous studies showed that, over the global ocean, there is hemispheric asymmetry in aerosols and no noticeable asymmetry in cloud fraction (CF). In the current study, we focus on the tropical Atlantic (30 Deg N 30 Deg S) which is characterized by significant amounts of Saharan dust dominating other aerosol species over the North Atlantic. We found that, by contrast to the global ocean, over a limited area such as the tropical Atlantic, strong <span class="hlt">meridional</span> asymmetry in dust aerosols was accompanied by <span class="hlt">meridional</span> CF asymmetry. During the 10-year study period (July 2002 June 2012), NASA Aerosol Reanalysis (aka MERRAero) showed that, when the <span class="hlt">meridional</span> asymmetry in dust aerosol optical thickness (AOT) was the most pronounced (particularly in July), dust AOT averaged separately over the tropical North Atlantic was one order of magnitude higher than dust AOT averaged over the tropical South Atlantic. In the presence of such strong <span class="hlt">meridional</span> asymmetry in dust AOT in July, CF averaged separately over the tropical North Atlantic exceeded CF averaged over the tropical South Atlantic by 20%. Our study showed significant cloud cover, up to 0.8 - 0.9, in July along the Saharan Air Layer which contributed to above-mentioned <span class="hlt">meridional</span> CF asymmetry. Both Multi-Angle Imaging SpectroRadiometer (MISR) measurements and MERRAero data were in agreement on seasonal variations in <span class="hlt">meridional</span> aerosol asymmetry. <span class="hlt">Meridional</span> asymmetry in total AOT over the Atlantic was the most pronounced between March and July, when dust presence over the North Atlantic was maximal. In September and October, there was no noticeable <span class="hlt">meridional</span> asymmetry in total AOT and <span class="hlt">meridional</span> CF distribution over the tropical Atlantic was almost symmetrical.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21283703','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21283703"><span>Changes in present and future <span class="hlt">circulation</span> <span class="hlt">types</span> frequency in northwest Iberian Peninsula.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lorenzo, María N; Ramos, Alexandre M; Taboada, Juan J; Gimeno, Luis</p> <p>2011-01-21</p> <p>The aim of the work described herein was to study projection scenarios in order to find changes in the synoptic variability of the northwest Iberian Peninsula in the 21st century. To this end, we investigated the changes in the frequency of the different <span class="hlt">circulation</span> <span class="hlt">types</span> computed for the study area using three different models used in the IPCC 4(th) assessment report. The <span class="hlt">circulation</span> <span class="hlt">types</span> were computed using the procedure known as Lamb <span class="hlt">circulation</span> <span class="hlt">types</span>. The control simulation for the late 20th century was evaluated objectively from the results obtained using data from the NCEP/NCAR reanalysis, as to evaluate the ability of the model to reproduce the present climate. We have compared not only seasonal mean sea level pressure fields but also the mean seasonal frequency of <span class="hlt">circulation</span> <span class="hlt">types</span>. The results for the end of the 21st century show a decrease in the frequency of cyclonic, W, and SW <span class="hlt">circulation</span> <span class="hlt">types</span> in the spring and summer months. This trend also appears in the autumn, with a concomitant increase in the anticyclonic <span class="hlt">types</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3025019','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3025019"><span>Changes in Present and Future <span class="hlt">Circulation</span> <span class="hlt">Types</span> Frequency in Northwest Iberian Peninsula</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lorenzo, María N.; Ramos, Alexandre M.; Taboada, Juan J.; Gimeno, Luis</p> <p>2011-01-01</p> <p>The aim of the work described herein was to study projection scenarios in order to find changes in the synoptic variability of the northwest Iberian Peninsula in the 21st century. To this end, we investigated the changes in the frequency of the different <span class="hlt">circulation</span> <span class="hlt">types</span> computed for the study area using three different models used in the IPCC 4th assessment report. The <span class="hlt">circulation</span> <span class="hlt">types</span> were computed using the procedure known as Lamb <span class="hlt">circulation</span> <span class="hlt">types</span>. The control simulation for the late 20th century was evaluated objectively from the results obtained using data from the NCEP/NCAR reanalysis, as to evaluate the ability of the model to reproduce the present climate. We have compared not only seasonal mean sea level pressure fields but also the mean seasonal frequency of <span class="hlt">circulation</span> <span class="hlt">types</span>. The results for the end of the 21st century show a decrease in the frequency of cyclonic, W, and SW <span class="hlt">circulation</span> <span class="hlt">types</span> in the spring and summer months. This trend also appears in the autumn, with a concomitant increase in the anticyclonic <span class="hlt">types</span>. PMID:21283703</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22365081-effects-meridional-flow-variations-solar-cycles','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22365081-effects-meridional-flow-variations-solar-cycles"><span>Effects of <span class="hlt">meridional</span> flow variations on solar cycles 23 and 24</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Upton, Lisa; Hathaway, David H., E-mail: lisa.a.upton@vanderbilt.edu, E-mail: lar0009@uah.edu, E-mail: david.hathaway@nasa.gov</p> <p>2014-09-10</p> <p>The faster <span class="hlt">meridional</span> flow that preceded the solar cycle 23/24 minimum is thought to have led to weaker polar field strengths, producing the extended solar minimum and the unusually weak cycle 24. To determine the impact of <span class="hlt">meridional</span> flow variations on the sunspot cycle, we have simulated the Sun's surface magnetic field evolution with our newly developed surface flux transport model. We investigate three different cases: a constant average <span class="hlt">meridional</span> flow, the observed time-varying <span class="hlt">meridional</span> flow, and a time-varying <span class="hlt">meridional</span> flow in which the observed variations from the average have been doubled. Comparison of these simulations shows that the variationsmore » in the <span class="hlt">meridional</span> flow over cycle 23 have a significant impact (∼20%) on the polar fields. However, the variations produced polar fields that were stronger than they would have been otherwise. We propose that the primary cause of the extended cycle 23/24 minimum and weak cycle 24 was the weakness of cycle 23 itself—with fewer sunspots, there was insufficient flux to build a big cycle. We also find that any polar counter-cells in the <span class="hlt">meridional</span> flow (equatorward flow at high latitudes) produce flux concentrations at mid-to-high latitudes that are not consistent with observations.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26820730','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26820730"><span>Molecular Characteristics of Influenza Virus <span class="hlt">Type</span> B Lineages <span class="hlt">Circulating</span> in Poland.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bednarska, K; Hallmann-Szelińska, E; Kondratiuk, K; Rabczenko, D; Brydak, L B</p> <p>2016-01-01</p> <p>From the time of the Hong Kong pandemic of 1968-1969, vaccines against influenza are trivalent, containing two subtypes of influenza <span class="hlt">type</span> A: A/H1N1/ and A/H3N2/, and influenza <span class="hlt">type</span> B. In 1980, <span class="hlt">circulation</span> of the new Yamagata and Victoria lineages of influenza B virus was noted. Since both lineages have continued to <span class="hlt">circulate</span>, the second lineage of influenza B was included into the trivalent vaccine as of the 2013/2014 epidemic season. In Poland, co-<span class="hlt">circulation</span> of influenza <span class="hlt">type</span> A and B has been registered over many seasons, although <span class="hlt">type</span> A has predominated. According to the ACIP recommendations, quadrivalent vaccines against influenza are administered in some continents due to <span class="hlt">circulation</span> of the B-Yamagata and B-Victoria lineages. Currently, only trivalent vaccines against influenza are available in Poland. The aim of the present research was to determine which of the two influenza <span class="hlt">type</span> B lineages, or possibly both, would be isolated in Poland. The study was conducted with the use of RT-PCR. Generally, in the 2014/2015 epidemic season in Poland, <span class="hlt">circulation</span> of <span class="hlt">type</span> B virus was confirmed in 34 % of influenza cases. A total of 89 specimens of influenza B were tested, including co-infections of influenza B with influenza A subtypes: A/H1N1/pdm09 and A/H3N2/. The findings were that only lineage B-Yamagata <span class="hlt">circulates</span> in the Polish population. Therefore, vaccines available on the Polish market do not require the introduction of a fourth component.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ThApC.121..713B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ThApC.121..713B"><span>Interannual drought index variations in Central Europe related to the large-scale atmospheric circulation—application and evaluation of statistical downscaling approaches based on <span class="hlt">circulation</span> <span class="hlt">type</span> classifications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beck, Christoph; Philipp, Andreas; Jacobeit, Jucundus</p> <p>2015-08-01</p> <p>This contribution investigates the relationship between the large-scale atmospheric <span class="hlt">circulation</span> and interannual variations of the standardized precipitation index (SPI) in Central Europe. To this end, <span class="hlt">circulation</span> <span class="hlt">types</span> (CT) have been derived from a variety of <span class="hlt">circulation</span> <span class="hlt">type</span> classifications (CTC) applied to daily sea level pressure (SLP) data and mean <span class="hlt">circulation</span> indices of vorticity ( V), zonality ( Z) and <span class="hlt">meridionality</span> ( M) have been calculated. Occurrence frequencies of CTs and <span class="hlt">circulation</span> indices have been utilized as predictors within multiple regression models (MRM) for the estimation of gridded 3-month SPI values over Central Europe, for the period 1950 to 2010. CTC-based MRMs used in the analyses comprise variants concerning the basic method for CT classification, the number of CTs, the size and location of the spatial domain used for CTCs and the exclusive use of CT frequencies or the combined use of CT frequencies and mean <span class="hlt">circulation</span> indices as predictors. Adequate MRM predictor combinations have been identified by applying stepwise multiple regression analyses within a resampling framework. The performance (robustness) of the resulting MRMs has been quantified based on a leave-one-out cross-validation procedure applying several skill scores. Furthermore, the relative importance of individual predictors has been estimated for each MRM. From these analyses, it can be stated that model skill is improved by (i) the consideration of vorticity characteristics within CTCs, (ii) a relatively small size of the spatial domain to which CTCs are applied and (iii) the inclusion of mean <span class="hlt">circulation</span> indices. However, model skill exhibits distinct variations between seasons and regions. Whereas promising skill can be stated for the western and northwestern parts of the Central European domain, only unsatisfactory skill is reached in the more continental regions and particularly during summer. Thus, it can be concluded that the presented approaches feature the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.A34B..01T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.A34B..01T"><span>Can Arctic sea-ice melt be explained by atmospheric <span class="hlt">meridional</span> transports? (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tjernstrom, M. K.; Graversen, R. G.</p> <p>2010-12-01</p> <p>The Arctic summer sea ice is melting away at an alarming rate, and it is now expected that an principally sea-ice free Arctic summer will occur much earlier than projected by the IPCC AR4 models. At the same time Arctic near-surface temperatures are rising at a rate much faster than the global average. The processes responsible for these changes are debated and many claim that local feedbacks, such as the surface albedo feedback, are the main culprits while other argue that remote effects, such as atmospheric <span class="hlt">circulation</span> changes on synoptic and hemispheric scales, are the most important. We will explore the effects of the <span class="hlt">meridional</span> transport by synoptic and larger scale atmospheric <span class="hlt">circulation</span> on recent changes, using reanalysis data. It will be illustarated how this transport can contribute significant amounts of sensible heat, but also of atmospheric moisture such that local cloud feedbacks as well as the direct greenhouse effect of the water vapor contributes significantly to the surface energy balance over the Arctic polar cap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP52A..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP52A..02B"><span>The role of clouds in early Pliocene warmth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burls, N.; Fedorov, A. V.</p> <p>2013-12-01</p> <p>The climate of the early Pliocene (4-5 million years ago) presents a challenging puzzle to climate scientists - although the Earth experienced atmospheric CO2 concentrations similar to the elevated levels seen today, many climate characteristics in both low to high latitudes were very different. In particular, a salient feature of the modern climate, the pronounced cold tongues on the eastern sides of the Pacific and Atlantic equatorial basins, were much weaker. At the same time the ocean <span class="hlt">meridional</span> (equator-to-pole) temperature gradient was also reduced. However, state-of-the-art coupled general <span class="hlt">circulation</span> models forced with elevated CO2 concentrations and reconstructed Pliocene boundary conditions fail to capture the full extent of warming in the equatorial cold tongues and high-latitude regions relative to present-day conditions, and hence the corresponding reduction in <span class="hlt">meridional</span> and zonal sea surface temperature gradients suggested by paleoclimatic evidence (as reviewed by Fedorov et al., 2013, Nature 496). A number of physical processes unresolved or underestimated by these models have been proposed as a contributing factor or a potential driving force resulting in these differences. Amongst the proposed hypotheses is the idea that different cloud properties might be the key to the Pliocene puzzle. In this study we demonstrate how a modified spatial distribution in cloud albedo could have been responsible for sustaining Pliocene climate. In particular, we show that a reduction in the <span class="hlt">meridional</span> gradient in cloud albedo can sustain reduced <span class="hlt">meridional</span> and zonal gradients in sea surface temperature, an expanded warm pool in the ocean, weaker <span class="hlt">Hadley</span> and Walker <span class="hlt">circulations</span> in the atmosphere, and amplified high-latitude warming. Having conducted a range of modified cloud albedo experiments, we arrive at our Pliocene simulation, which shows an excellent agreement with proxy sea surface temperature data from the major equatorial and coastal upwelling regions, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19980210073&hterms=cell+crisp&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcell%2Bcrisp','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19980210073&hterms=cell+crisp&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcell%2Bcrisp"><span>Diagnostic calculations of the <span class="hlt">circulation</span> in the Martian atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Santee, Michelle L.; Crisp, David</p> <p>1995-01-01</p> <p>The <span class="hlt">circulation</span> of the Martian atmosphere during late southern summer is derived from atmospheric temperature and dust distributions retrieved from a subset of the Mariner 9 infrared interferometer spectrometer (IRIS) thermal emission spectra (L(sub s) = 343-348 deg). Zonal-mean zonal winds are calculated by assuming gradient wind balance and zero surface zonal wind. Both hemispheres have intense midlatitude westerly jets with velocities of 80-90 m/s near 50 km; in the southern tropics the winds are easterly with velocities of 40 m/s near 50 km. The net effect of the zonal mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> and large-scale waves can be approximated by the diabatic <span class="hlt">circulation</span>, which is defined from the atmospheric thermal structure and net radiative heating rates. The radiative transfer model described by Crisp (1990) and Santee (1993) is used to compute solar heating and thermal cooling rates from diurnal averages of the retrieved IRIS temperature and dust distributions. At pressures below 4 mbar, there are large net radiative heating rates (up to 5 K/d) in the equatorial region and large net radiative cooling rates (up to 12 K/d) in the polar regions. These net radiative heating rates are used in a diagnostic stream function model which solves for the <span class="hlt">meridional</span> and vertical components of the diabatic <span class="hlt">circulation</span> simultaneously. We find a two-cell <span class="hlt">circulation</span>, with rising motion over the equator, poleward flow in both hemispheres, sinking motion over both polar regions, and return flow in the lowest atmospheric levels. The maximum poleward velocity is 3 m/s in the tropics at approx. 55 km altitude, and the maximum vertical velocity is 2.5 cm/s downward over the north pole at approx. 60 km altitude. If these large transport rates are sustained for an entire season, the Martian atmosphere above the 1-mbar level is overturned in about 38 days. This diabatic <span class="hlt">circulation</span> is qualitatively similar to the terrestrial diabatic <span class="hlt">circulation</span> at the comparable season, but is more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040081245&hterms=Asian&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DAsian','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040081245&hterms=Asian&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DAsian"><span><span class="hlt">Meridional</span> Propagation of the MJO/ISO and Asian Monsoon Variability</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, Man Li C.; Schubert, Siegfried; Suarez, Max; Pegion, Phil; Waliser, D.</p> <p>2003-01-01</p> <p>In this study we examine the links between tropical heating, the Madden Julian Oscillation (MJO)/Intraseasonal Oscillation (ISO), and the Asian monsoon. We are particularly interested in isolating the nature of the poleward propagation of the ISO/MJO in the monsoon region. We examine both observations and idealized "MJO heating" experiments employing the NASA Seasonal-Interannual Prediction Project (NSIPP) atmospheric general <span class="hlt">circulation</span> model (AGCM). In the idealized 10-member ensemble simulations, the model is forced by climatological SST and an idealized eastward propagating heating profile that is meant to mimic the canonical heating associated with the MJO in the Indian Ocean and western Pacific. In order to understand the impact of SST on the off equatorial convection (or Rossby-wave response), a second set of 10-member ensemble simulations is carried out with the climatological SSTs shifted in time by 6-months. The observational analysis highlights the strong link between the Indian summer monsoon and the tropical ISO/MJO activity and heating. This includes the well-known <span class="hlt">meridional</span> propagation that affects the summer monsoons of both hemispheres. The AGCM experiments with the idealized eastward propagating MJO-like heating reproduce the observed <span class="hlt">meridional</span> propagation including the observed seasonal differences. The impact of the SSTs are to enhance the magnitude of the propagation into the summer hemispheres. The results suggest that the winter/summer differences associated with the MJO/ISO are auxiliary features that depend on the MJO's environment (basic state and boundary conditions) and are not the result of fundamental differences in the MJO itself.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994ClDy...10..313H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994ClDy...10..313H"><span>A zonally averaged, three-basin ocean <span class="hlt">circulation</span> model for climate studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hovine, S.; Fichefet, T.</p> <p>1994-09-01</p> <p>A two-dimensional, three-basin ocean model suitable for long-term climate studies is developed. The model is based on the zonally averaged form of the primitive equations written in spherical coordinates. The east-west density difference which arises upon averaging the momentum equations is taken to be proportional to the <span class="hlt">meridional</span> density gradient. Lateral exchanges of heat and salt between the basins are explicitly resolved. Moreover, the model includes bottom topography and has representations of the Arctic Ocean and of the Weddell and Ross seas. Under realistic restoring boundary conditions, the model reproduces the global conveyor belt: deep water is formed in the Atlantic between 60 and 70°N at a rate of about 17 Sv (1 Sv=106 m3 s-1) and in the vicinity of the Antarctic continent, while the Indian and Pacific basins show broad upwelling. Superimposed on this thermohaline <span class="hlt">circulation</span> are vigorous wind-driven cells in the upper thermocline. The simulated temperature and salinity fields and the computed <span class="hlt">meridional</span> heat transport compare reasonably well with the observational estimates. When mixed boundary conditions (i.e., a restoring condition on sea-surface temperature and flux condition on sea-surface salinity) are applied, the model exhibits an irregular behavior before reaching a steady state characterized by self-sustained oscillations of 8.5-y period. The conveyor-belt <span class="hlt">circulation</span> always results at this stage. A series of perturbation experiments illustrates the ability of the model to reproduce different steady-state <span class="hlt">circulations</span> under mixed boundary conditions. Finally, the model sensitivity to various factors is examined. This sensitivity study reveals that the bottom topography and the presence of a submarine <span class="hlt">meridional</span> ridge in the zone of the Drake Passage play a crucial role in determining the properties of the model bottom-water masses. The importance of the seasonality of the surface forcing is also stressed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20180001315','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20180001315"><span>Large-Scale <span class="hlt">Circulation</span> and Climate Variability. Chapter 5</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Perlwitz, J.; Knutson, T.; Kossin, J. P.; LeGrande, A. N.</p> <p>2017-01-01</p> <p>The causes of regional climate trends cannot be understood without considering the impact of variations in large-scale atmospheric <span class="hlt">circulation</span> and an assessment of the role of internally generated climate variability. There are contributions to regional climate trends from changes in large-scale latitudinal <span class="hlt">circulation</span>, which is generally organized into three cells in each hemisphere-<span class="hlt">Hadley</span> cell, Ferrell cell and Polar cell-and which determines the location of subtropical dry zones and midlatitude jet streams. These <span class="hlt">circulation</span> cells are expected to shift poleward during warmer periods, which could result in poleward shifts in precipitation patterns, affecting natural ecosystems, agriculture, and water resources. In addition, regional climate can be strongly affected by non-local responses to recurring patterns (or modes) of variability of the atmospheric <span class="hlt">circulation</span> or the coupled atmosphere-ocean system. These modes of variability represent preferred spatial patterns and their temporal variation. They account for gross features in variance and for teleconnections which describe climate links between geographically separated regions. Modes of variability are often described as a product of a spatial climate pattern and an associated climate index time series that are identified based on statistical methods like Principal Component Analysis (PC analysis), which is also called Empirical Orthogonal Function Analysis (EOF analysis), and cluster analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018IJEaS.107..505S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018IJEaS.107..505S"><span>Interhemispheric teleconnections: Late Pliocene change in Mediterranean outflow water linked to changes in Indonesian Through-Flow and Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>, a review and update</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sarnthein, Michael; Grunert, Patrick; Khélifi, Nabil; Frank, Martin; Nürnberg, Dirk</p> <p>2018-03-01</p> <p>The ultimate, possibly geodynamic control and potential impact of changes in <span class="hlt">circulation</span> activity and salt discharge of Mediterranean outflow waters (MOW) on Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> have formed long-standing objectives in paleoceanography. Late Pliocene changes in the distal advection of MOW were reconstructed on orbital timescales for northeast Atlantic DSDP/ODP sites 548 and 982 off Brittany and on Rockall Plateau, supplemented by a proximal record from Site U1389 west off Gibraltar, and compared to Western Mediterranean surface and deep-water records of Alboran Sea Site 978. From 3.43 to 3.3 Ma, MOW temperatures and salinities form a prominent rise by 2-4 °C and 3 psu, induced by a preceding and coeval rise in sea surface and deep-water salinity and increased summer aridity in the Mediterranean Sea. We speculate that these changes triggered an increased MOW flow and were ultimately induced by a persistent 2.5 °C cooling of Indonesian Through-Flow waters. The temperature drop resulted from the northward drift of Australia that crossed a threshold value near 3.6-3.3 Ma and led to a large-scale cooling of the eastern subtropical Indian Ocean and in turn, to a reduction of African monsoon rains. Vice versa, we show that the distinct rise in Mediterranean salt export after 3.4 Ma induced a unique long-term rise in the formation of Upper North Atlantic Deep Water, that followed with a phase lag of 100 ky. In summary, we present evidence for an interhemispheric teleconnection of processes in the Indonesian Gateways, the Mediterranean and Labrador Seas, jointly affecting Pliocene climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26472908','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26472908"><span>The Atlantic Multidecadal Oscillation without a role for ocean <span class="hlt">circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Clement, Amy; Bellomo, Katinka; Murphy, Lisa N; Cane, Mark A; Mauritsen, Thorsten; Rädel, Gaby; Stevens, Bjorn</p> <p>2015-10-16</p> <p>The Atlantic Multidecadal Oscillation (AMO) is a major mode of climate variability with important societal impacts. Most previous explanations identify the driver of the AMO as the ocean <span class="hlt">circulation</span>, specifically the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC). Here we show that the main features of the observed AMO are reproduced in models where the ocean heat transport is prescribed and thus cannot be the driver. Allowing the ocean <span class="hlt">circulation</span> to interact with the atmosphere does not significantly alter the characteristics of the AMO in the current generation of climate models. These results suggest that the AMO is the response to stochastic forcing from the mid-latitude atmospheric <span class="hlt">circulation</span>, with thermal coupling playing a role in the tropics. In this view, the AMOC and other ocean <span class="hlt">circulation</span> changes would be largely a response to, not a cause of, the AMO. Copyright © 2015, American Association for the Advancement of Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MS%26E..308a2006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MS%26E..308a2006S"><span>Analysis of bullwhip effect on supply chain with Q model using <span class="hlt">Hadley</span>-Within approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siregar, I.; Nasution, A. A.; Matondang, N.; Persada, M. R.; Syahputri, K.</p> <p>2018-02-01</p> <p>This research held on a tapioca flour industry company that uses cassava as raw material to produce tapioca starch product. Problems that occur in this company is inaccurate planning, consequently there is a shortage of variation between the number of requests with the total supply is met, so it is necessary to do research with the formulation of the problem that is how to analyze the Bullwhip Effect on the supply chain using Q model through <span class="hlt">Hadley</span>-Within approach so as not to disturb the product distribution system at the company. Product distribution system at the company, obtained by the number of requests. The 2015 forecast result is lower than actual demand for distributors and manufactures in 2016 with average percentage difference for Supermarket A distributor, Supermarket B and manufacturing respectively 38.24%, 89.57% and 43.11%. The occurrence of information distortion to the demand of this product can identify the existence of bullwhip effect on the supply chain. The proposed improvement to overcome the bullwhip effect is by doing inventory control policy with Q model using <span class="hlt">Hadley</span>-Within approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PCE....35..507F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PCE....35..507F"><span>Inter-comparison of weather and <span class="hlt">circulation</span> <span class="hlt">type</span> classifications for hydrological drought development</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fleig, Anne K.; Tallaksen, Lena M.; Hisdal, Hege; Stahl, Kerstin; Hannah, David M.</p> <p></p> <p>Classifications of weather and <span class="hlt">circulation</span> patterns are often applied in research seeking to relate atmospheric state to surface environmental phenomena. However, numerous procedures have been applied to define the patterns, thus limiting comparability between studies. The COST733 Action “ Harmonisation and Applications of Weather <span class="hlt">Type</span> Classifications for European regions” tests 73 different weather <span class="hlt">type</span> classifications (WTC) and their associate weather <span class="hlt">types</span> (WTs) and compares the WTCs’ utility for various applications. The objective of this study is to evaluate the potential of these WTCs for analysis of regional hydrological drought development in north-western Europe. Hydrological drought is defined in terms of a Regional Drought Area Index (RDAI), which is based on deficits derived from daily river flow series. RDAI series (1964-2001) were calculated for four homogeneous regions in Great Britain and two in Denmark. For each region, WTs associated with hydrological drought development were identified based on antecedent and concurrent WT-frequencies for major drought events. The utility of the different WTCs for the study of hydrological drought development was evaluated, and the influence of WTC attributes, i.e. input variables, number of defined WTs and general classification concept, on WTC performance was assessed. The objective Grosswetterlagen (OGWL), the objective Second-Generation Lamb Weather <span class="hlt">Type</span> Classification (LWT2) with 18 WTs and two implementations of the objective Wetterlagenklassifikation (WLK; with 40 and 28 WTs) outperformed all other WTCs. In general, WTCs with more WTs (⩾27) were found to perform better than WTCs with less (⩽18) WTs. The influence of input variables was not consistent across the different classification procedures, and the performance of a WTC was determined primarily by the classification procedure itself. Overall, classification procedures following the relatively simple general classification concept of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122.5903M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122.5903M"><span>The role of the <span class="hlt">meridional</span> sea surface temperature gradient in controlling the Caribbean low-level jet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maldonado, Tito; Rutgersson, Anna; Caballero, Rodrigo; Pausata, Francesco S. R.; Alfaro, Eric; Amador, Jorge</p> <p>2017-06-01</p> <p>The Caribbean low-level jet (CLLJ) is an important modulator of regional climate, especially precipitation, in the Caribbean and Central America. Previous work has inferred, due to their semiannual cycle, an association between CLLJ strength and <span class="hlt">meridional</span> sea surface temperature (SST) gradients in the Caribbean Sea, suggesting that the SST gradients may control the intensity and vertical shear of the CLLJ. In addition, both the horizontal and vertical structure of the jet have been related to topographic effects via interaction with the mountains in Northern South America (NSA), including funneling effects and changes in the <span class="hlt">meridional</span> geopotential gradient. Here we test these hypotheses, using an atmospheric general <span class="hlt">circulation</span> model to perform a set of sensitivity experiments to examine the impact of both SST gradients and topography on the CLLJ. In one sensitivity experiment, we remove the <span class="hlt">meridional</span> SST gradient over the Caribbean Sea and in the other, we flatten the mountains over NSA. Our results show that the SST gradient and topography have little or no impact on the jet intensity, vertical, and horizontal wind shears, contrary to previous works. However, our findings do not discount a possible one-way coupling between the SST and the wind over the Caribbean Sea through friction force. We also examined an alternative approach based on barotropic instability to understand the CLLJ intensity, vertical, and horizontal wind shears. Our results show that the current hypothesis about the CLLJ must be reviewed in order to fully understand the atmospheric dynamics governing the Caribbean region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018QSRv..180..214M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018QSRv..180..214M"><span>Hemispherically asymmetric trade wind changes as signatures of past ITCZ shifts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McGee, David; Moreno-Chamarro, Eduardo; Green, Brian; Marshall, John; Galbraith, Eric; Bradtmiller, Louisa</p> <p>2018-01-01</p> <p>The atmospheric <span class="hlt">Hadley</span> cells, which meet at the Intertropical Convergence Zone (ITCZ), play critical roles in transporting heat, driving ocean <span class="hlt">circulation</span> and supplying precipitation to the most heavily populated regions of the globe. Paleo-reconstructions can provide concrete evidence of how these major features of the atmospheric <span class="hlt">circulation</span> can change in response to climate perturbations. While most such reconstructions have focused on ITCZ-related rainfall, here we show that trade wind proxies can document dynamical aspects of <span class="hlt">meridional</span> ITCZ shifts. Theoretical expectations based on angular momentum constraints and results from freshwater hosing simulations with two different climate models predict that ITCZ shifts due to anomalous cooling of one hemisphere would be accompanied by a strengthening of the <span class="hlt">Hadley</span> cell and trade winds in the colder hemisphere, with an opposite response in the warmer hemisphere. This expectation of hemispherically asymmetric trade wind changes is confirmed by proxy data of coastal upwelling and windblown dust from the Atlantic basin during Heinrich stadials, showing trade wind strengthening in the Northern Hemisphere and weakening in the Southern Hemisphere subtropics in concert with southward ITCZ shifts. Data from other basins show broadly similar patterns, though improved constraints on past trade wind changes are needed outside the Atlantic Basin. The asymmetric trade wind changes identified here suggest that ITCZ shifts are also marked by intensification of the ocean's wind-driven subtropical cells in the cooler hemisphere and a weakening in the warmer hemisphere, which induces cross-equatorial oceanic heat transport into the colder hemisphere. This response would be expected to prevent extreme <span class="hlt">meridional</span> ITCZ shifts in response to asymmetric heating or cooling. Understanding trade wind changes and their coupling to cross-equatorial ocean cells is key to better constraining ITCZ shifts and ocean and atmosphere dynamical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMPP13A1367M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMPP13A1367M"><span>Deglacial Neodymium Isotopic Ratios in the Florida Straits and the Response of Intermediate Waters to Reduced <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marcantonio, F.; Schmidt, M. W.; Franklin, A.; Lynch-Stieglitz, J. M.</p> <p>2009-12-01</p> <p>Neodymium behaves quasi-conservatively in seawater, and its isotopic signature can be used as a tracer for oceanic water masses. By analyzing Nd in the authigenic ferromanganese oxide component of marine sediments, past changes in water mass movements have been hypothesized. In the Atlantic Ocean, Nd isotope analysis has been used to trace the variable strength of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) during the last deglaciation (e.g., Pahnke et al., 2008). Here, we use Nd isotopes to investigate whether a decrease in the strength of the past MOC manifests itself as a reduction (Came et al., 2008) or an increase (Pahnke et al., 2008) in the northward incursion of Antarctic Intermediate Water (AAIW) into the North Atlantic. Sediments from two core sites currently bathed by AAIW within the Florida Straits (546 m and 751 m water depth) are well suited for profiling authigenic Nd isotope ratios. Because the Florida Current represents a major pathway of the Atlantic MOC surface return flow, the Florida Strait sites can shed light on how variations in AAIW are related to changes in Atlantic MOC strength. The sediments range in age from 0 to 25 kyr, and the high sedimentation rates (8 - 200 cm/kyr) ensure that millennial climate events during the deglaciation are captured. The range in ɛNd measured in the shallower core thus far is low (~ 1.5 epsilon units), but significant. There is a trend in the data which suggests more unradiogenic values during the Younger Dryas event when Atlantic MOC slowed down. Such a trend supports the idea based on benthic foraminiferal Cd/Ca data (Came et al., 2008) that, during the Younger Dryas, there was a reduction within the Florida Current of the flow of intermediate, southern-sourced waters. Came et al., 2008, Paleoceanography 23, PA1217. Pahnke et al., 2008, Nature Geoscience 1, 870-874.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CliPD..10.2519L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CliPD..10.2519L"><span>An abrupt slowdown of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> during 1915-1935 induced by solar forcing in a coupled GCM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, P.; Song, Y.; Yu, Y.; Liu, H.</p> <p>2014-06-01</p> <p>In this study, we explore an abrupt change of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) apparent in the historical run simulated by the second version of the Flexible Global Ocean-Atmosphere-Land System model - Spectral Version 2 (FGOALS-s2). The abrupt change is noted during the period from 1915 to 1935, in which the maximal AMOC value is weakened beyond 6 Sv (1 Sv = 106 m3 s-1). The abrupt signal first occurs at high latitudes (north of 46° N), then shifts gradually to middle latitudes (∼35° N) three to seven years later. The weakened AMOC can be explained in the following. The weak total solar irradiance (TIS) during early twentieth century decreases pole-to-equator temperature gradient in the upper stratosphere. The North polar vortex is weakened, which forces a negative North Atlantic Oscillation (NAO) phase during 1905-1914. The negative phase of NAO induces anomalous easterly winds in 50-70° N belts, which decrease the release of heat fluxes from ocean to atmosphere and induce surface warming over these regions. Through the surface ice-albedo feedback, the warming may lead to continuously melting sea ice in Baffin Bay and Davis Strait, which results in freshwater accumulation. This can lead to salinity and density reductions and then an abrupt slowdown of AMOC. Moreover, due to increased TIS after 1914, the enhanced Atlantic northward ocean heat transport from low to high latitudes induces an abrupt warming of sea surface temperature or upper ocean temperature in mid-high latitudes, which can also weaken the AMOC. The abrupt change of AMOC also appears in the PiControl run, which is associated with the lasting negative NAO phases due to natural variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP41C1320R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP41C1320R"><span>Bering Sea Nd isotope records of North Pacific Intermediate Water <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rabbat, C.; Knudson, K. P.; Goldstein, S. L.</p> <p>2017-12-01</p> <p>North Pacific Intermediate Water (NPIW) is the primary water mass associated with Pacific <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>. While the relationship between Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> and climate has been extensively studied, a lack of suitable sediment cores has limited past investigations of North Pacific climate and NPIW variability. Integrated Ocean Drilling Program Site U1342 (818 m water depth) on Bower's Ridge in the Bering Sea is located at a sensitive depth for detecting changes in NPIW, and it is the only available sub-arctic North Pacific site that offers long, continuous core recovery, relatively high sedimentation rates, excellent foraminifera preservation, and a well-constrained age model over multiple glacial-interglacial cycles. Previous work at Site U1342 from Knudson and Ravelo (2015), using non-quantitative <span class="hlt">circulation</span> proxies, provides evidence for enhanced NPIW formation during extreme glacials associated with the closure of the Bering Strait and suggest that NPIW was formed locally within the Bering Sea. Our work builds on the potential importance of these results and applies more robust and potentially quantitative <span class="hlt">circulation</span> proxies to constrain NPIW variability. Here, we present new records of NPIW <span class="hlt">circulation</span> from Site U1342 based on Nd isotope analyses on fish debris and Fe-Mn encrusted foraminifera, which serve as semi-quantitative "water mass tracers." Weak Bering Sea NPIW formation and ventilation are reflected by relatively lower eNd values indicative of open subarctic North Pacific waters, which are presently predominant, whereas enhanced Bering Sea NPIW formation and ventilation are be reflected by relatively higher eNd values due to the input of Nd from regional volcanic rocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PalOc..30..751C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PalOc..30..751C"><span>Impact of global SST gradients on the Mediterranean runoff changes across the Plio-Pleistocene transition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colleoni, Florence; Cherchi, Annalisa; Masina, Simona; Brierley, Christopher M.</p> <p>2015-06-01</p> <p>This work explores the impact of the development of global <span class="hlt">meridional</span> and zonal sea surface temperature (SST) gradients on the Mediterranean runoff variability during the Plio-Pleistocene transition, about 3 Ma. Results show that total annual mean Pliocene Mediterranean runoff is about 40% larger than during the preindustrial period due to more increased extratropical specific humidity. As a consequence of a weakened and extended <span class="hlt">Hadley</span> cell, the Pliocene northwest Africa hydrological network produces a discharge 30 times larger than today. Our results support the conclusion that during the Pliocene, the Mediterranean water deficit was reduced relative to today due to a larger river discharge. By means of a stand-alone atmospheric general <span class="hlt">circulation</span> model, we simulate the separate impact of extratropical and equatorial SST cooling on the Mediterranean runoff. While cooling the equatorial SST does not imply significant changes to the Pliocene Mediterranean hydrological budget, the extratropical SST cooling increases the water deficit due to a decrease in precipitation and runoff. Consequently, river discharge from this area reduces to preindustrial levels. The main teleconnections acting upon the Mediterranean area today, i.e., the North Atlantic Oscillation during winter and the "monsoon-desert" mechanism during summer already have a large influence on the climate of our Pliocene simulations. Finally, our results also suggest that in a climate state significantly warmer than today, changes of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> could potentially lead to increased water resources in northwest Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.6373R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.6373R"><span>Can energy fluxes be used to interpret glacial/interglacial precipitation changes in the tropics?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roberts, W. H. G.; Valdes, P. J.; Singarayer, J. S.</p> <p>2017-06-01</p> <p>Recent theoretical advances in the relationship between heat transport and the position of the Intertropical Convergence Zone (ITCZ) present an elegant framework through which to interpret past changes in tropical precipitation patterns. Using a very large ensemble of climate model simulations, we investigate whether it is possible to use this framework to interpret changes in the position of the ITCZ in response to glacial and interglacial boundary conditions. We find that the centroid of tropical precipitation, which represents the evolution of precipitation in the whole tropics, is best correlated with heat transport changes. We find that the response of the annual mean ITCZ to glacial and interglacial boundary conditions is quite different to the response of the climatological annual cycle of the ITCZ to the seasonal cycle of insolation. We show that the reason for this is that while the <span class="hlt">Hadley</span> <span class="hlt">Circulation</span> plays a dominant role in transporting heat over the seasonal cycle, in the annual mean response to forcing, the <span class="hlt">Hadley</span> <span class="hlt">Circulation</span> is not dominant. When we look regionally, rather than at the zonal mean, we find that local precipitation is poorly related either to the zonal mean ITCZ or to <span class="hlt">meridional</span> heat transport. We demonstrate that precipitation is spatially highly variable even when the zonal mean ITCZ is in the same location. This suggests only limited use for heat transport in explaining local precipitation records; thus, there is limited scope for using heat transport changes to explain individual paleoprecipitation records.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=AS15-88-11894&hterms=first+moon+landing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfirst%2Bmoon%2Blanding','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=AS15-88-11894&hterms=first+moon+landing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfirst%2Bmoon%2Blanding"><span>View of Commemorative plaque left on moon at <span class="hlt">Hadley</span>-Apennine landing site</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1971-01-01</p> <p>A close-up view of a commemorative plaque left on the Moon at the <span class="hlt">Hadley</span>-Apennine landing site in memory of 14 NASA astronauts and USSR cosmonauts, now deceased. Their names are inscribed in alphabetical order on the plaque. The plaque was stuck in the lunar soil by Astronauts David R. Scott and James B. Irwin during their Apollo 15 lunar surface extravehicular activity. The tin, man-like object represents the figure of a fallen astronaut/cosmonaut.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21460075-changes-solar-meridional-velocity-profile-during-cycle-explained-flows-toward-activity-belts','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21460075-changes-solar-meridional-velocity-profile-during-cycle-explained-flows-toward-activity-belts"><span>CHANGES OF THE SOLAR <span class="hlt">MERIDIONAL</span> VELOCITY PROFILE DURING CYCLE 23 EXPLAINED BY FLOWS TOWARD THE ACTIVITY BELTS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Cameron, R. H.; Schuessler, M., E-mail: cameron@mps.mpg.d</p> <p></p> <p>The solar <span class="hlt">meridional</span> flow is an important ingredient in Babcock-Leighton <span class="hlt">type</span> models of the solar dynamo. Global variations of this flow have been suggested to explain the variations in the amplitudes and lengths of the activity cycles. Recently, cycle-related variations in the amplitude of the P{sup 1}{sub 2} term in the Legendre decomposition of the observed <span class="hlt">meridional</span> flow have been reported. The result is often interpreted in terms of an overall variation in the flow amplitude during the activity cycle. Using a semi-empirical model based upon the observed distribution of magnetic flux on the solar surface, we show that themore » reported variations of the P{sup 1}{sub 2} term can be explained by the observed localized inflows into the active region belts. No variation of the overall <span class="hlt">meridional</span> flow amplitude is required.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GGG....17.2336D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GGG....17.2336D"><span>South Atlantic intermediate water advances into the North-east Atlantic with reduced Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during the last glacial period</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dubois-Dauphin, Quentin; Bonneau, Lucile; Colin, Christophe; Montero-Serrano, Jean-Carlos; Montagna, Paolo; Blamart, Dominique; Hebbeln, Dierk; Van Rooij, David; Pons-Branchu, Edwige; Hemsing, Freya; Wefing, Anne-Marie; Frank, Norbert</p> <p>2016-06-01</p> <p>The Nd isotopic composition (ɛNd) of seawater and cold-water coral (CWC) samples from the Gulf of Cádiz and the Alboran Sea, at a depth of 280-827 m were investigated in order to constrain middepth water mass dynamics within the Gulf of Cádiz over the past 40 ka. ɛNd of glacial and Holocene CWC from the Alboran Sea and the northern Gulf of Cádiz reveals relatively constant values (-8.6 to -9.0 and -9.5 to -10.4, respectively). Such values are similar to those of the surrounding present-day middepth waters from the Mediterranean Outflow Water (MOW; ɛNd ˜ -9.4) and Mediterranean Sea Water (MSW; ɛNd ˜ -9.9). In contrast, glacial ɛNd values for CWC collected at thermocline depth (550-827 m) in the southern Gulf of Cádiz display a higher average value (-8.9 ± 0.4) compared to the present-day value (-11.7 ± 0.3). This implies a higher relative contribution of water masses of Mediterranean (MSW) or South Atlantic origin (East Antarctic Intermediate Water, EAAIW). Our study has produced the first evidence of significant radiogenic ɛNd values (˜ -8) at 19, 23-24, and 27 ka, which are coeval with increasing iceberg discharges and a weakening of Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC). Since MOW ɛNd values remained stable during the last glacial period, it is suggested that these radiogenic ɛNd values most likely reflect an enhanced northward propagation of glacial EAAIW into the eastern Atlantic Basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050019491&hterms=charbonneau&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcharbonneau','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050019491&hterms=charbonneau&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcharbonneau"><span>Erratum: Evidence That a Deep <span class="hlt">Meridional</span> Flow Sets the Sunspot Cycle Period</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hathaway, David H.; Nandy, Dibyendu; Wilson, Robert M.; Reichmann, Edwin J.</p> <p>2004-01-01</p> <p>An error was made in entering the data. This changes the results concerning the length of the time lag between the variations in the <span class="hlt">meridional</span> flow speed and those in the cycle amplitude. The final paragraph on page 667 should read: Finally, we study the relationship between the drift velocities and the amplitudes of the hemisphere/cycles. We compare the drift velocity at the maximum of the cycle to the amplitude of that cycle for that hemisphere. There is a positive (0.5) and significant (95%) correlation between the two. However, an even stronger relationship is found between the drift velocity and the amplitude of the N + 2 cycle. The correlation is stronger (0.7) and more significant (99%), as shown. This relationship is suggestive of a "memory" in the solar cycle, again a property of dynamo models that use <span class="hlt">meridional</span> <span class="hlt">circulation</span>. Indeed, the two-cycle lag is precisely the relationship found by Charbonneau & Dikpati. This behavior is, however, more difficult to interpret, and we elaborate on this in the next section. In either case, these correlations only explain part of the variance in cycle amplitude (25% for the current cycle and 50% for the N + 2 cycle). Obviously, other mechanisms, such as variations in the gradient in the rotation rate, also contribute to the cycle amplitude variations. Our investigation of possible connections between drift rates and the amplitudes of the N + 1 and N + 3 cycles gives no significant correlations at these alternative time lags.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT.......153B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT.......153B"><span>Inferences of the deep solar <span class="hlt">meridional</span> flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Böning, Vincent G. A.</p> <p>2017-10-01</p> <p>Understanding the solar <span class="hlt">meridional</span> flow is important for uncovering the origin of the solar activity cycle. Yet, recent helioseismic estimates of this flow have come to conflicting conclusions in deeper layers of the solar interior, i.e., at depths below about 0.9 solar radii. The aim of this thesis is to contribute to a better understanding of the deep solar <span class="hlt">meridional</span> flow. Time-distance helioseismology is the major method for investigating this flow. In this method, travel times of waves propagating between pairs of locations on the solar surface are measured. Until now, the travel-time measurements have been modeled using the ray approximation, which assumes that waves travel along infinitely thin ray paths between these locations. In contrast, the scattering of the full wave field in the solar interior due to the flow is modeled in first order by the Born approximation. It is in general a more accurate model of the physics in the solar interior. In a first step, an existing model for calculating the sensitivity of travel-time measurements to solar interior flows using the Born approximation is extended from Cartesian to spherical geometry. The results are succesfully compared to the Cartesian ones and are tested for self-consistency. In a second step, the newly developed model is validated using an existing numerical simulation of linear wave propagation in the Sun. An inversion of artificial travel times for <span class="hlt">meridional</span> flow shows excellent agreement for noiseless data and reproduces many features in the input flow profile in the case of noisy data. Finally, the new method is used to infer the deep <span class="hlt">meridional</span> flow. I used Global Oscillation Network Group (GONG) data that were earlier analyzed using the ray approximation and I employed the same Substractive Optimized Local Averaging (SOLA) inversion technique as in the earlier study. Using an existing formula for the covariance of travel-time measurements, it is shown that the assumption of uncorrelated errors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920051644&hterms=models+linear&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmodels%2Blinear','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920051644&hterms=models+linear&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmodels%2Blinear"><span><span class="hlt">Meridionally</span> propagating interannual-to-interdecadal variability in a linear ocean-atmosphere model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mehta, Vikram M.</p> <p>1992-01-01</p> <p><span class="hlt">Meridional</span> oscillation modes in a global, primitive-equation coupled ocean-atmosphere model have been analyzed in order to determine whether they contain such <span class="hlt">meridionally</span> propagating modes as surface-pressure perturbations with years-to-decades oscillation periods. A two-layer global ocean model and a two-level global atmosphere model were then formulated. For realistic parameter values and basic states, <span class="hlt">meridional</span> modes oscillating at periods of several years to several decades are noted to be present in the coupled ocean-atmosphere model; the oscillation periods, travel times, and <span class="hlt">meridional</span> structures of surface pressure perturbations in one of the modes are found to be comparable to the corresponding characteristics of observed sea-level pressure perturbations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910004519','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910004519"><span>Tropical Pacific moisture variability: Its detection, synoptic structure and consequences in the general <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcguirk, James P.</p> <p>1990-01-01</p> <p>Satellite data analysis tools are developed and implemented for the diagnosis of atmospheric <span class="hlt">circulation</span> systems over the tropical Pacific Ocean. The tools include statistical multi-variate procedures, a multi-spectral radiative transfer model, and the global spectral forecast model at NMC. Data include in-situ observations; satellite observations from VAS (moisture, infrared and visible) NOAA polar orbiters (including Tiros Operational Satellite System (TOVS) multi-channel sounding data and OLR grids) and scanning multichannel microwave radiometer (SMMR); and European Centre for Medium Weather Forecasts (ECHMWF) analyses. A primary goal is a better understanding of the relation between synoptic structures of the area, particularly tropical plumes, and the general <span class="hlt">circulation</span>, especially the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. A second goal is the definition of the quantitative structure and behavior of all Pacific tropical synoptic systems. Finally, strategies are examined for extracting new and additional information from existing satellite observations. Although moisture structure is emphasized, thermal patterns are also analyzed. Both horizontal and vertical structures are studied and objective quantitative results are emphasized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA510021','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA510021"><span>Slope/Shelf <span class="hlt">Circulation</span> and Cross-Slope/Shelf Transport Out of a Bay Driven by Eddies from the Open Ocean</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2009-09-01</p> <p>channel. More recently, they examined the role of eddies in the overturning <span class="hlt">circulation</span> of the Southern Ocean using the hemispheric HIM with realistic... <span class="hlt">meridional</span> velocity with intervals of 0.1 · 10−3ms−1 159 PV equation to study the bay-scale <span class="hlt">circulations</span> : d dt ( f + ζ H0 − f0h0 H 20 ) = F, (4.30) where...2009-18 DOCTORAL DISSERTATION by Yu Zhang September 2009 Slope/shelf <span class="hlt">Circulation</span> and Cross-slope/shelf Transport Out of a Bay Driven by Eddies from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPO53E..04K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPO53E..04K"><span>Sources of <span class="hlt">Meridional</span> Heat and Freshwater Transport Anomalies in the Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kelly, K. A.; Thompson, L.; Drushka, K.</p> <p>2016-02-01</p> <p>Observations of thermosteric and halosteric sea level from hydrographic data, ocean mass from GRACE and altimetric sea surface height are used to infer <span class="hlt">meridional</span> heat transport (MHT) and freshwater convergence (FWC) anomalies for the Atlantic Ocean for 1993-2014. A Kalman filter extracts smooth estimates of heat transport convergence (HTC) and FWC from discrepancies between the sea level response to monthly surface heat and freshwater fluxes and observed heat and freshwater content in each of eight regions. Estimates of MHT anomalies are derived by summing the HTC from north to south and adding an integration constant derived from updated MHT estimates at 41N (Willis 2010). MHT estimates are relatively insensitive to the choice of heat flux products and are highly coherent spatially. Anomalies in MHT are comparable to those observed at the RAPID/MOCHA line at 26.5N and show a continued recovery from the minimum in 2010 throughout the Atlantic. MHT anomalies resemble estimates of Agulhas Leakage derived from altimeter (LeBars et al 2014) suggesting that the Indian Ocean is the source of the anomalous heat inflow. FWC estimates are also insensitive to choice of flux products. Interannual anomalies of FWC integrated from 67N to 35S resemble estimates of Atlantic river inflow (de Couet and Maurer, GRDC 2009), whereas the trend is consistent with estimates of freshwater input from Greenland. Increasing values of FWC after 2002 at a time when MHT was decreasing may indicate a feedback between the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> and FWC that would accelerate the AMOC slowdown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016usc..confE.111C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016usc..confE.111C"><span>An comprehensive time-distance measurement of deep <span class="hlt">meridional</span> flow and its temporal variation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Ruizhu; Zhao, Junwei</p> <p>2016-10-01</p> <p>We report our latest results on the Sun's deep solar <span class="hlt">meridional</span>-flow measurements by time-distance helioseismology technique using 6 years of SDO/HMI Doppler-velocity data. Determination of the <span class="hlt">meridional</span> flow by time-distance helioseismology depends on a precise measurement of the flow-induced travel-time shifts of acoustic waves traveling in the solar interior. To resolve the weak travel-time-shift signals due to deep <span class="hlt">meridional</span> flow, we need a high signal-to-noise ratio and a robust removal of the center-to-limb (CtoL) effect, which dominates the travel-time shifts. Here we perform an ultimately comprehensive measurement that tracks acoustic waves between any two points on solar surface. The travel-time shifts are composed of CtoL effect, which is a function of disk-centric distances, and contribution from the flow component parallel to wave traveling direction, which is a function of latitude and orientation. Assuming these two effects are independent, we can derive the CtoL effect and <span class="hlt">meridional</span>-flow contributions by solving a set of linear equations in a least-square sense. We show the solved CtoL effect and the inversion results for the solar <span class="hlt">meridional</span> flow, and analyze the annual variation of <span class="hlt">meridional</span> flow from May 2010 to Apr 2016.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160006514&hterms=climate+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dclimate%2Bchange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160006514&hterms=climate+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dclimate%2Bchange"><span>Large-Scale Ocean <span class="hlt">Circulation</span>-Cloud Interactions Reduce the Pace of Transient Climate Change</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Trossman, D. S.; Palter, J. B.; Merlis, T. M.; Huang, Y.; Xia, Y.</p> <p>2016-01-01</p> <p>Changes to the large scale oceanic <span class="hlt">circulation</span> are thought to slow the pace of transient climate change due, in part, to their influence on radiative feedbacks. Here we evaluate the interactions between CO2-forced perturbations to the large-scale ocean <span class="hlt">circulation</span> and the radiative cloud feedback in a climate model. Both the change of the ocean <span class="hlt">circulation</span> and the radiative cloud feedback strongly influence the magnitude and spatial pattern of surface and ocean warming. Changes in the ocean <span class="hlt">circulation</span> reduce the amount of transient global warming caused by the radiative cloud feedback by helping to maintain low cloud coverage in the face of global warming. The radiative cloud feedback is key in affecting atmospheric <span class="hlt">meridional</span> heat transport changes and is the dominant radiative feedback mechanism that responds to ocean <span class="hlt">circulation</span> change. Uncertainty in the simulated ocean <span class="hlt">circulation</span> changes due to CO2 forcing may contribute a large share of the spread in the radiative cloud feedback among climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998BAMS...79...39L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998BAMS...79...39L"><span>Clarifying the Dynamics of the General <span class="hlt">Circulation</span>: Phillips's 1956 Experiment.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lewis, John M.</p> <p>1998-01-01</p> <p>In the mid-1950s, amid heated debate over the physical mechanisms that controlled the known features of the atmosphere's general <span class="hlt">circulation</span>, Norman Phillips simulated hemispheric motion on the high-speed computer at the Institute for Advanced Study. A simple energetically consistent model was integrated for a simulated time of approximately 1 month. Analysis of the model results clarified the respective roles of the synoptic-scale eddies (cyclones-anticyclones) and mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> in the maintenance of the upper-level westerlies and the surface wind regimes. Furthermore, the modeled cyclones clearly linked surface frontogenesis with the upper-level Charney-Eady wave. In addition to discussing the model results in light of the controversy and ferment that surrounded general <span class="hlt">circulation</span> theory in the 1940s-1950s, an effort is made to follow Phillips's scientific path to the experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004TellA..56..371G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004TellA..56..371G"><span>Application of classical thermodynamic principles to the study of oceanic overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gade, Herman G.; Gustafsson, Karin E.</p> <p>2004-08-01</p> <p>Stationary deep-reaching overturning <span class="hlt">circulation</span> in the ocean is studied by means of classical thermodynamic methods employing closed cycles in pV-space (p, pressure; V, volume). From observed (or computed) density fields, the pV-method may be used to infer the power required for driving a <span class="hlt">circulation</span> with a given mass flux, or, if the available power is known, the resulting mass flux of the <span class="hlt">circulation</span> may be assessed. Here, the <span class="hlt">circulation</span> is assumed to be driven by diapycnal mixing caused by internal disturbances of meteorological and tidal origin and from transfer of geothermal heat through the ocean bottom. The analysis is developed on the basis that potential energy produced by any of these mechanisms is available for driving a <span class="hlt">circulation</span> of the water masses above its level of generation. The method also takes into account secondary generated potential energy resulting from turbulence developed by the ensuing <span class="hlt">circulation</span>.Models for different <span class="hlt">types</span> of <span class="hlt">circulation</span> are developed and applied to four <span class="hlt">types</span> of hemispheric <span class="hlt">circulation</span> with deep-water formation, convection and sinking in an idealized North Atlantic. Our calculations show that the energy input must exceed 15 J kg<img src="/entityImage/script/2212.gif" alt="-" border="0" style="font-weight: bold"></img>1 for a cycle to the bottom to exist. An energy supply of 2 TW would in that case support a constant vertical mass flux of 3.2 G kg s<img src="/entityImage/script/2212.gif" alt="-" border="0" style="font-weight: bold"></img>1 (3.1 Sv). Computed mass fluxes reaching the surface in the subtropics, corresponding to the same energy input, range between 2.3 5.2 G kg s<img src="/entityImage/script/2212.gif" alt="-" border="0" style="font-weight: bold"></img>1, depending on the <span class="hlt">type</span> of convection/sinking involved. Much higher flux values ensue with ascending water masses reaching the surface at higher geographical latitudes.The study reveals also that compressibility of sea water does not enhance the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1214696N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1214696N"><span>Open oceanic productivity changes at mid-latitudes during interglacials and its relation to the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nave, Silvia; Lebreiro, S.; Kissel, C.; Guihou, A.; Figueiredo, M. O.; Silva, T. P.; Michel, E.; Cortijo, E.; Labeyrie, L.; Voelker, A.</p> <p>2010-05-01</p> <p>-size variations and magnetic properties, suggests stronger/faster bottom currents during cold phases, in agreement with a stronger component of Antarctic sourced Bottom Water (AABW) at the Eastern Atlantic Margin. The probable enhancement of AABW during these periods may also account for a higher preservation of siliceous biogenic particles at the ocean floor sediment/water interface. Given that MD01-2446 is placed far from the continent, productivity records should mainly reflect local conditions. Still, we should not fully discard the preservation of punctual influence of coastal processes derived from upwelling filament plumes at the Estremadura Plateau. Lebreiro et al., 1997 [Paleoceanography, 12, 718-727] reported for a near location, the dominance of pre-upwelling and post-upwelling related foraminifera species during MIS 6 implying less intense or persistent upwelling during MIS 6 than MIS 4. On the contrary, opal and organic carbon data reveals a clear increase in productivity also during MIS 6, reinforcing the idea that productivity variations are likely related to open ocean conditions and therefore, nutrients availability associated to the Atlantic <span class="hlt">Meridional</span> Oceanic <span class="hlt">Circulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010TellA..62..737U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010TellA..62..737U"><span>Probabilistic hindcasts and projections of the coupled climate, carbon cycle and Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> system: a Bayesian fusion of century-scale observations with a simple model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Urban, Nathan M.; Keller, Klaus</p> <p>2010-10-01</p> <p>How has the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) varied over the past centuries and what is the risk of an anthropogenic AMOC collapse? We report probabilistic projections of the future climate which improve on previous AMOC projection studies by (i) greatly expanding the considered observational constraints and (ii) carefully sampling the tail areas of the parameter probability distribution function (pdf). We use a Bayesian inversion to constrain a simple model of the coupled climate, carbon cycle and AMOC systems using observations to derive multicentury hindcasts and projections. Our hindcasts show considerable skill in representing the observational constraints. We show that robust AMOC risk estimates can require carefully sampling the parameter pdfs. We find a low probability of experiencing an AMOC collapse within the 21st century for a business-as-usual emissions scenario. The probability of experiencing an AMOC collapse within two centuries is 1/10. The probability of crossing a forcing threshold and triggering a future AMOC collapse (by 2300) is approximately 1/30 in the 21st century and over 1/3 in the 22nd. Given the simplicity of the model structure and uncertainty in the forcing assumptions, our analysis should be considered a proof of concept and the quantitative conclusions subject to severe caveats.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22153095','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22153095"><span>Lenticular <span class="hlt">meridional</span> astigmatism secondary to iris mesectodermal leiomyoma.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chalam, K V; Cutler Peck, Carolee M; Grover, Sandeep; Radhakrishnan, Ravi</p> <p>2012-01-01</p> <p>A 61-year-old African American man presented with decreased vision of 2 months duration. Examination revealed a significant lenticular astigmatism and sectoral cataract as a result of an amelanotic iris lesion. Slitlamp optical coherence tomography (OCT) revealed angle crowding. An excisional biopsy was performed along with phacoemulsification in the right eye, with intraocular lens implantation for <span class="hlt">meridional</span> lenticular astigmatism. Histopathology and histoimmunochemistry confirmed a diagnosis of uveal mesectodermal leiomyoma. Lenticular astigmatism may be a subtle sign of an anterior segment tumor. Anterior segment slitlamp OCT is an effective tool in diagnosing as well as monitoring small interval changes in these <span class="hlt">types</span> of tumors. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP51A1058G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP51A1058G"><span>Coherent response of Antarctic Intermediate Water and Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> during the last deglaciation: reconciling contrasting neodymium isotope reconstructions in tropical Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gu, S.; Liu, Z.; Zhang, J.; Rempfer, J.; Joos, F.; Oppo, D.</p> <p>2017-12-01</p> <p>Antarctic Intermediate Water (AAIW) plays important roles in the global climate system and the global ocean nutrient and carbon cycles. However, it is unclear how AAIW responds to global climate changes. In particular, neodymium isotopic composition (ɛNd) reconstructions from different locations in tropical Atlantic, have led to a debate on the relationship between the northward penetration of AAIW into the tropical Atlantic and Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) variability during the last deglaciation. We resolve this controversy by studying the transient oceanic evolution during the last deglaciation using a neodymium-enabled ocean model. Our results suggest a coherent response of AAIW and AMOC: when AMOC weakens, the northward penetration and transport of AAIW decreases while its depth and thickness increase. Our study highlights that as part of the return flow of the North Atlantic Deep Water (NADW), the northward penetration of AAIW in Atlantic is determined predominately by AMOC intensity. Moreover, the inconsistency among different tropical Atlantic ɛNd reconstructions is reconciled by considering their corresponding core locations and depths, which were influenced by different water masses and ocean currents in the past. The very radiogenic water from the bottom of the Gulf of Mexico and Caribbean Sea, which was previously overlooked in interpretations of deglacial ɛNd variability, can be transported to shallow layers during active AMOC, and modulates ɛNd in the tropical Atlantic. Changes in the AAIW core depth must also be considered. Thus, interpretation of ɛNd reconstructions from the tropical Atlantic is more complicated than suggested in previous studies. </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000IAUJD..13E..24S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000IAUJD..13E..24S"><span>Automated Quantitative Spectral Classification of Stars in Areas of the main <span class="hlt">Meridional</span> Section of the Galaxy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shvelidze, T. D.; Malyuto, V. D.</p> <p></p> <p>Quantitative spectral classification of F, G and K stars with the 70-cm telescope of the Ambastumani Astrophysical Observatory in areas of the main <span class="hlt">meridional</span> section of the Galaxy, and for which proper motion data are available, has been performed. Fundamental parameters have been obtained for 333 stars in four areas. Space densities of stars of different spectral <span class="hlt">types</span>, the stellar luminosity function and the relationships between the kinematics and metallicity of stars have been studied. The results have confirmed and completed the conclusions made on the basis of some previous spectroscopic and photometric surveys. Many plates have been obtained for other important directions in the sky: the Kapteyn areas, the Galactic anticentre and the main <span class="hlt">meridional</span> section of the Galaxy. The data can be treated with the same quantitative method applied here. This method may also be applied to other available and future spectroscopic data of similar resolution, notably that obtained with large format CCD detectors on Schmidt-<span class="hlt">type</span> telescopes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.5933B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.5933B"><span>Interannual drought index variations in Central Europe related to large-scale atmospheric <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beck, Christoph; Philipp, Andreas; Jacobeit, Jucundus</p> <p>2014-05-01</p> <p>This contribution investigates the relationship between large-scale atmospheric <span class="hlt">circulation</span> and interannual variations of the standardized precipitation index (SPI) in central Europe. To this end occurrence frequencies of <span class="hlt">circulation</span> <span class="hlt">types</span> (CT) derived from a variety of <span class="hlt">circulation</span> <span class="hlt">type</span> classifications (CTC) applied to daily sea level pressure (SLP) data and mean <span class="hlt">circulation</span> indices of vorticity (V), zonality (Z) and <span class="hlt">meridionality</span> (M) have been utilized as predictors within multiple regression models (MRM) for the estimation of gridded 3-month SPI values over central Europe for the period 1950 to 2010. CTC based MRMs used in the analyses comprise variants concerning the basic method for CT classification, the number of CTs, the size and location of the spatial domain used for CTCs and the exclusive use of CT frequencies or the combined use of CT frequencies and mean <span class="hlt">circulation</span> indices as predictors. Adequate MRM predictor combinations have been identified by applying stepwise multiple regression analyses within a resampling framework. The performance (robustness) of the resulting MRMs has been quantified based on a leave-one out cross-validation procedure applying several skill scores. Furthermore the relative importance of individual predictors has been estimated for each MRM. From these analyses it can be stated that i.) the consideration of vorticity characteristics within CTCs, ii.) a relatively small size of the spatial domain to which CTCs are applied and iii.) the inclusion of mean <span class="hlt">circulation</span> indices appear to improve model skill. However model skill exhibits distinct variations between seasons and regions. Whereas promising skill can be stated for the western and northwestern parts of the central European domain only unsatisfactorily skill is reached in the more continental regions and particularly during summer. Thus it can be concluded that the here presented approaches feature the potential for the downscaling of central European drought index</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1221466-impact-cloud-radiative-heating-east-asian-summer-monsoon-circulation','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1221466-impact-cloud-radiative-heating-east-asian-summer-monsoon-circulation"><span>Impact of cloud radiative heating on East Asian summer monsoon <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Guo, Zhun; Zhou, Tianjun; Wang, Minghuai; ...</p> <p>2015-07-17</p> <p>The impacts of cloud radiative heating on East Asian Summer Monsoon (EASM) over the southeastern China (105°-125°E, 20°-35°N) are explained by using the Community Atmosphere Model version 5 (CAM5). Sensitivity experiments demonstrate that the radiative heating of clouds leads to a positive effect on the local EASM <span class="hlt">circulation</span> over southeastern China. Without the radiative heating of cloud, the EASM <span class="hlt">circulation</span> and precipitation would be much weaker than that in the normal condition. The longwave heating of clouds dominates the changes of EASM <span class="hlt">circulation</span>. The positive effect of clouds on EASM <span class="hlt">circulation</span> is explained by the thermodynamic energy equation, i.e. themore » different heating rate between cloud base and cloud top enhances the convective instability over southeastern China, which enhances updraft consequently. The strong updraft would further result in a southward <span class="hlt">meridional</span> wind above the center of the updraft through Sverdrup vorticity balance.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdAtS..35...52H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdAtS..35...52H"><span>Teleconnection between sea ice in the Barents Sea in June and the Silk Road, Pacific-Japan and East Asian rainfall patterns in August</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, Shengping; Gao, Yongqi; Furevik, Tore; Wang, Huijun; Li, Fei</p> <p>2018-01-01</p> <p>In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a <span class="hlt">meridional</span> overturning wave-like pattern extending to midlatitudes. Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning <span class="hlt">circulation</span> along the subtropical jet stream, exhibiting the east-west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the <span class="hlt">Hadley</span> cell, the Bonin high anomaly ultimately triggers a <span class="hlt">meridional</span> overturning, establishing the Pacific-Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly <span class="hlt">meridionally</span> oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53D2275H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53D2275H"><span>Teleconnection between Sea Ice in the Barents Sea in June and the Silk Road, Pacific-Japan and East Asian Rainfall Patterns in August</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, S.; Gao, Y.; Furevik, T.; Huijun, W.; Li, F.</p> <p>2017-12-01</p> <p>In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a <span class="hlt">meridional</span> overturning wave-like pattern extending to midlatitudes. Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning <span class="hlt">circulation</span> along the subtropical jet stream, exhibiting the east-west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the <span class="hlt">Hadley</span> cell, the Bonin high anomaly ultimately triggers a <span class="hlt">meridional</span> overturning, establishing the Pacific-Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly <span class="hlt">meridionally</span> oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211868E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211868E"><span>Classification of <span class="hlt">circulation</span> <span class="hlt">type</span> sequences applied to snow avalanches over the eastern Pyrenees (Andorra and Catalonia)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Esteban, Pere; Beck, Christoph; Philipp, Andreas</p> <p>2010-05-01</p> <p>Using data associated with accidents or damages caused by snow avalanches over the eastern Pyrenees (Andorra and Catalonia) several atmospheric <span class="hlt">circulation</span> <span class="hlt">type</span> catalogues have been obtained. For this purpose, different <span class="hlt">circulation</span> <span class="hlt">type</span> classification methods based on Principal Component Analysis (T-mode and S-mode using the extreme scores) and on optimization procedures (Improved K-means and SANDRA) were applied . Considering the characteristics of the phenomena studied, not only single day <span class="hlt">circulation</span> patterns were taken into account but also sequences of <span class="hlt">circulation</span> <span class="hlt">types</span> of varying length. Thus different classifications with different numbers of <span class="hlt">types</span> and for different sequence lengths were obtained using the different classification methods. Simple between <span class="hlt">type</span> variability, within <span class="hlt">type</span> variability, and outlier detection procedures have been applied for selecting the best result concerning snow avalanches <span class="hlt">type</span> classifications. Furthermore, days without occurrence of the hazards were also related to the avalanche centroids using pattern-correlations, facilitating the calculation of the anomalies between hazardous and no hazardous days, and also frequencies of occurrence of hazardous events for each <span class="hlt">circulation</span> <span class="hlt">type</span>. Finally, the catalogues statistically considered the best results are evaluated using the avalanche forecaster expert knowledge. Consistent explanation of snow avalanches occurrence by means of <span class="hlt">circulation</span> sequences is obtained, but always considering results from classifications with different sequence length. This work has been developed in the framework of the COST Action 733 (Harmonisation and Applications of Weather <span class="hlt">Type</span> Classifications for European regions).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMPP33B1699F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMPP33B1699F"><span>Laurentide Ice Sheet meltwater and the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> since the last glacial maximum: A view from the Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Flower, B. P.; Williams, C.; Brown, E. A.; Hastings, D. W.; Hendricks, J.; Goddard, E. A.</p> <p>2010-12-01</p> <p>The influence of ice sheet meltwater on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) since the last glacial maximum represents an important issue in abrupt climate change. Comparison of Greenland and Antarctic ice core records has revealed a complex interhemispheric linkage and led to different models of ocean <span class="hlt">circulation</span> including the “bipolar seesaw.” Meltwater input from the Laurentide Ice Sheet has been invoked as a cause of proximal sea-surface temperature (SST) and salinity change in the North Atlantic, and of regional to global climate change via its influence on the AMOC. We present published and new Mg/Ca, Ba/Ca, and δ18O data on the planktic foraminifer Globigerinoides ruber from northern Gulf of Mexico sediment cores that provide detailed records of SST, δ18O of seawater (δ18Osw), and inferred salinity for the 20-8 ka interval. Age control for Orca Basin core MD02-2550 is based on >40 AMS 14C dates on Globigerinoides ruber and documents continuous sedimentation at rates >35 cm/kyr. Early meltwater input is inferred from δ18Osw and Ba/Ca data prior to and during the Mystery Interval, consistent with a high sensitivity to solar insolation and greenhouse forcing. New bulk sediment δ18O data show major spikes reaching -5.5‰ ca. 14.6 and 12.6 ka. We speculate that these excursions represent fine carbonate sediment from Canadian Paleozoic marine carbonates, analogous to detrital carbonate in the North Atlantic which has a δ18O value of -5‰. Partial support for our hypothesis comes from SEM photomicrographs of bulk sediment from this section, which show no coccoliths or foraminifera in contrast to other intervals. The biogenic carbonate flux seems to have been greatly reduced by fine sediment input. Inferred peak meltwater flow appears to have been associated with the Bolling warming and meltwater pulse 1a. Finally, meltwater reduction at the start of the Younger Dryas supports models for a diversion to North Atlantic outlets and AMOC</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950030015&hterms=rolando+garcia&qs=N%3D0%26Ntk%3DAuthor-Name%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drolando%2Bgarcia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950030015&hterms=rolando+garcia&qs=N%3D0%26Ntk%3DAuthor-Name%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drolando%2Bgarcia"><span>Application of a planetary wave breaking parameterization to stratospheric <span class="hlt">circulation</span> statistics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Randel, William J.; Garcia, Rolando R.</p> <p>1994-01-01</p> <p>The planetary wave parameterization scheme developed recently by Garcia is applied to statospheric <span class="hlt">circulation</span> statistics derived from 12 years of National Meteorological Center operational stratospheric analyses. From the data a planetary wave breaking criterion (based on the ratio of the eddy to zonal mean <span class="hlt">meridional</span> potential vorticity (PV) gradients), a wave damping rate, and a <span class="hlt">meridional</span> diffusion coefficient are calculated. The equatorward flank of the polar night jet during winter is identified as a wave breaking region from the observed PV gradients; the region moves poleward with season, covering all high latitudes in spring. Derived damping rates maximize in the subtropical upper stratosphere (the 'surf zone'), with damping time scales of 3-4 days. Maximum diffusion coefficients follow the spatial patterns of the wave breaking criterion, with magnitudes comparable to prior published estimates. Overall, the observed results agree well with the parameterized calculations of Garcia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012cosp...39..458D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012cosp...39..458D"><span>The solar dynamo and prediction of sunspot cycles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dikpati, Mausumi</p> <p>2012-07-01</p> <p>Much progress has been made in understanding the solar dynamo since Parker first developed the concepts of dynamo waves and magnetic buoyancy around 1955, and the German school first formulated the solar dynamo using the mean-field formalism. The essential ingredients of these mean-field dynamos are turbulent magnetic diffusivity, a source of lifting of flux, or 'alpha-effect', and differential rotation. With the advent of helioseismic and other observations at the Sun's photosphere and interior, as well as theoretical understanding of solar interior dynamics, solar dynamo models have evolved both in the realm of mean-field and beyond mean-field models. After briefly discussing the status of these models, I will focus on a class of mean-field model, called flux-transport dynamos, which include <span class="hlt">meridional</span> <span class="hlt">circulation</span> as an essential additional ingredient. Flux-transport dynamos have been successful in simulating many global solar cycle features, and have reached the stage that they can be used for making solar cycle predictions. <span class="hlt">Meridional</span> <span class="hlt">circulation</span> works in these models like a conveyor-belt, carrying a memory of the magnetic fields from 5 to 20 years back in past. The lower is the magnetic diffusivity, the longer is the model's memory. In the terrestrial system, the great-ocean conveyor-belt in oceanic models and <span class="hlt">Hadley</span>, polar and Ferrel <span class="hlt">circulation</span> cells in the troposphere, carry signatures from the past climatological events and influence the determination of future events. Analogously, the memory provided by the Sun's <span class="hlt">meridional</span> <span class="hlt">circulation</span> creates the potential for flux-transport dynamos to predict future solar cycle properties. Various groups in the world have built flux-transport dynamo-based predictive tools, which nudge the Sun's surface magnetic data and integrated forward in time to forecast the amplitude of the currently ascending cycle 24. Due to different initial conditions and different choices of unknown model-ingredients, predictions can vary; so</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1454704-simulating-pliocene-warmth-permanent-el-nino-like-state-role-cloud-albedo','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1454704-simulating-pliocene-warmth-permanent-el-nino-like-state-role-cloud-albedo"><span>Simulating Pliocene warmth and a permanent El Niño-like state: The role of cloud albedo</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Burls, N. J.; Fedorov, A. V.</p> <p>2014-09-13</p> <p>We present that available evidence suggests that during the early Pliocene (4–5 Ma) the mean east-west sea surface temperature (SST) gradient in the equatorial Pacific Ocean was significantly smaller than today, possibly reaching only 1–2°C. The <span class="hlt">meridional</span> SST gradients were also substantially weaker, implying an expanded ocean warm pool in low latitudes. Subsequent global cooling led to the establishment of the stronger, modern temperature gradients. Given our understanding of the physical processes that maintain the present-day cold tongue in the east, warm pool in the west and hence sharp temperature contrasts, determining the key factors that maintained early Pliocene climatemore » still presents a challenge for climate theories and models. This study demonstrates how different cloud properties could provide a solution. We show that a reduction in the <span class="hlt">meridional</span> gradient in cloud albedo can sustain reduced <span class="hlt">meridional</span> and zonal SST gradients, an expanded warm pool and warmer thermal stratification in the ocean, and weaker <span class="hlt">Hadley</span> and Walker <span class="hlt">circulations</span> in the atmosphere. Having conducted a range of hypothetical modified cloud albedo experiments, we arrive at our Pliocene simulation, which shows good agreement with proxy SST data from major equatorial and coastal upwelling regions, the tropical warm pool, middle and high latitudes, and available subsurface temperature data. As suggested by the observations, the simulated Pliocene-like climate sustains a robust El Niño-Southern Oscillation despite the reduced mean east-west SST gradient. In conclusion, our results demonstrate that cloud albedo changes may be a critical element of Pliocene climate and that simulating the <span class="hlt">meridional</span> SST gradient correctly is central to replicating the geographical patterns of Pliocene warmth.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Icar..282....1N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Icar..282....1N"><span>The <span class="hlt">circulation</span> pattern and day-night heat transport in the atmosphere of a synchronously rotating aquaplanet: Dependence on planetary rotation rate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noda, S.; Ishiwatari, M.; Nakajima, K.; Takahashi, Y. O.; Takehiro, S.; Onishi, M.; Hashimoto, G. L.; Kuramoto, K.; Hayashi, Y.-Y.</p> <p>2017-01-01</p> <p>In order to investigate a possible variety of atmospheric states realized on a synchronously rotating aquaplanet, an experiment studying the impact of planetary rotation rate is performed using an atmospheric general <span class="hlt">circulation</span> model (GCM) with simplified hydrological and radiative processes. The entire planetary surface is covered with a swamp ocean. The value of planetary rotation rate is varied from zero to the Earth's, while other parameters such as planetary radius, mean molecular weight and total mass of atmospheric dry components, and solar constant are set to the present Earth's values. The integration results show that the atmosphere reaches statistically equilibrium states for all runs; none of the calculated cases exemplifies the runaway greenhouse state. The <span class="hlt">circulation</span> patterns obtained are classified into four <span class="hlt">types</span>: <span class="hlt">Type</span>-I characterized by the dominance of a day-night thermally direct <span class="hlt">circulation</span>, <span class="hlt">Type</span>-II characterized by a zonal wave number one resonant Rossby wave over a <span class="hlt">meridionally</span> broad westerly jet on the equator, <span class="hlt">Type</span>-III characterized by a long time scale north-south asymmetric variation, and <span class="hlt">Type</span>-IV characterized by a pair of mid-latitude westerly jets. With the increase of planetary rotation rate, the <span class="hlt">circulation</span> evolves from <span class="hlt">Type</span>-I to <span class="hlt">Type</span>-II and then to <span class="hlt">Type</span>-III gradually and smoothly, whereas the change from <span class="hlt">Type</span>-III to <span class="hlt">Type</span>-IV is abrupt and discontinuous. Over a finite range of planetary rotation rate, both <span class="hlt">Types</span>-III and -IV emerge as statistically steady states, constituting multiple equilibria. In spite of the substantial changes in <span class="hlt">circulation</span>, the net energy transport from the day side to the night side remains almost insensitive to planetary rotation rate, although the partition into dry static energy and latent heat energy transports changes. The reason for this notable insensitivity is that the outgoing longwave radiation over the broad area of the day side is constrained by the radiation limit of a moist atmosphere, so that the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP21B1792X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP21B1792X"><span>Abrupt changes in Antarctic Intermediate Water strength lead Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> changes during the last deglacial</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, R.; Marcantonio, F.; Schmidt, M. W.</p> <p>2011-12-01</p> <p>Reorganization of <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> that is a response to or a trigger of climate change in the North Atlantic has been a subject of intense interest. During the last deglaciation, cold periods such as the Younger Dryas (YD) and Heinrich 1 (H1) are thought to be coincident with significant reductions in North Atlantic Deep Water (NADW) formation. Yet, the role that Antarctic Intermediate Water (AAIW) played during these cold events is still poorly constrained. Benthic Cd/Ca data from sediment cores in the Florida Straits suggest a reduced contribution of AAIW in the North Atlantic western boundary current during the YD [1]. However, ɛNd evidence in sediment cores from Tobago basin suggests a greater influence of AAIW in the North Atlantic during YD and H1 [2]. In this study, we measure ɛNd values in the authigenic Fe-Mn oxyhydroxide fraction of sediment from three cores, KNR166-2-26JPC (24°19.62'N, 83°15.14'W; 546 m) and KNR166-2-31JPC (24°13.18'N, 83°17.75'W; 751 m) within the Florida Straits, and VM12-107 (11.33°N, 66.63°W; 1079 m) in the Southern Carribean Sea. All three cores lie within the path of AAIW and are, therefore, useful to gauge the waxing and waning of AAIW during the last deglaciation. Cores 26JPC and 31JPC are located within the Florida Current, which under modern conditions represents a mixture of recirculated North Atlantic subtropical gyre water and Southern origin waters. Our preliminary results from 26JPC and 31JPC show significantly less radiogenic ɛNd values during the YD and H1 than during the Holocene (~1 epsilon unit for 26JPC and ~0.6 epsilon units for 31JPC during both periods). We interpret the lower ɛNd during the YD and H1 as signifying a decreased input of Southern-sourced waters (i.e., AAIW) arriving at these sites, in agreement with the study of Came et al.[1], but not that of Pahnke et al. in the Tobago Basin [2]. We suggest that ɛNd values in the latter study, in which the core site location is at a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12857906','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12857906"><span><span class="hlt">Circulation</span> of endemic <span class="hlt">type</span> 2 vaccine-derived poliovirus in Egypt from 1983 to 1993.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yang, Chen-Fu; Naguib, Tary; Yang, Su-Ju; Nasr, Eman; Jorba, Jaume; Ahmed, Nahed; Campagnoli, Ray; van der Avoort, Harrie; Shimizu, Hiroyuki; Yoneyama, Tetsuo; Miyamura, Tatsuo; Pallansch, Mark; Kew, Olen</p> <p>2003-08-01</p> <p>From 1988 to 1993, 30 cases of poliomyelitis associated with poliovirus <span class="hlt">type</span> 2 were found in seven governorates of Egypt. Because many of the cases were geographically and temporally clustered and because the case isolates differed antigenically from the vaccine strain, it was initially assumed that the cases signaled the continued <span class="hlt">circulation</span> of wild <span class="hlt">type</span> 2 poliovirus. However, comparison of sequences encoding the major capsid protein, VP1 (903 nucleotides), revealed that the isolates were related (93 to 97% nucleotide sequence identity) to the Sabin <span class="hlt">type</span> 2 oral poliovirus vaccine (OPV) strain and unrelated (<82% nucleotide sequence identity) to the wild <span class="hlt">type</span> 2 polioviruses previously indigenous to Egypt (last known isolate: 1979) or to any contemporary wild <span class="hlt">type</span> 2 polioviruses found elsewhere. The rate and pattern of VP1 divergence among the <span class="hlt">circulating</span> vaccine-derived poliovirus (cVDPV) isolates suggested that all lineages were derived from a single OPV infection that occurred around 1983 and that progeny from the initiating infection <span class="hlt">circulated</span> for approximately a decade within Egypt along several independent chains of transmission. Complete genomic sequences of an early (1988) and a late (1993) cVDPV isolate revealed that their 5' untranslated region (5' UTR) and noncapsid- 3' UTR sequences were derived from other species C enteroviruses. <span class="hlt">Circulation</span> of <span class="hlt">type</span> 2 cVDPVs occurred at a time of low OPV coverage in the affected communities and ceased when OPV coverage rates increased. The potential for cVDPVs to <span class="hlt">circulate</span> in populations with low immunity to poliovirus has important implications for current and future strategies to eradicate polio worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18680651','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18680651"><span>Endemic <span class="hlt">circulation</span> of European bat lyssavirus <span class="hlt">type</span> 1 in serotine bats, Spain.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vázquez-Morón, Sonia; Juste, Javier; Ibáñez, Carlos; Ruiz-Villamor, Eduardo; Avellón, Ana; Vera, Manuel; Echevarría, Juan E</p> <p>2008-08-01</p> <p>To determine the presence of European bat lyssavirus <span class="hlt">type</span> 1 in southern Spain, we studied 19 colonies of serotine bats (Eptesicus isabellinus), its main reservoir, during 1998-2003. Viral genome and antibodies were detected in healthy bats, which suggests subclinical infection. The different temporal patterns of <span class="hlt">circulation</span> found in each colony indicate independent endemic <span class="hlt">circulation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP22B..08H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP22B..08H"><span>A 400-kyr record of millennial-scale carbonate preservation events in the Southern Ocean: Implications for Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> and atmospheric CO2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hodell, D. A.; Vautravers, M. J.; Barker, S.; Charles, C.; Crowhurst, S.</p> <p>2014-12-01</p> <p>Hodell et al. (2001) suggested that carbonate preservation in the deep Cape Basin represented a qualitative, high-resolution record of the temporal evolution of the carbonate saturation state of the deep sea. The carbonate signal reflects both transient events in the redistribution of alkalinity and DIC in the deep ocean and steady-state mass balance processes. Here we re-analyzed the carbonate records of Sites 1089/TN057-21 using an Avaatech XRF core scanner and measured elemental variations at 2.5-mm resolution for the past 400 kyrs. Log Ca/Ti is highly correlated to weight percent carbonate content and other dissolution proxies and resolves millennial-scale events in carbonate preservation. A high-pass filter removes the low-frequency (orbital) variability in carbonate preservation, which is attributed mainly to steady-state mass balance processes. The high-frequency (suborbital) component reflects transient responses to the redistribution of carbonate ion that is related mainly to changing deep-water <span class="hlt">circulation</span>. During the last glacial period, distinct millennial-scale increases in carbonate preservation in piston core TN057-21 occurred during times of enhanced Atlantic <span class="hlt">Meridional</span> Overtunring <span class="hlt">Circulation</span> (AMOC) (Barker et al., 2010; Barker and Diz, 2014), as supported by increases in benthic δ13C and less radiogenic ɛNd values. Carbonate preservation peaked particularly during long, warm interstadials in Greenland when a deep water mass with high carbonate ion concentration was formed in the North Atlantic. Export of NADW may have been greater than the Holocene during some of these events ("overshoots") and/or preformed carbonate ion concentrations in North Atlantic source areas may have been higher owing to lower atmospheric CO2 and less carbonate production in surface water. Each South Atlantic carbonate peak is associated with the start of Antarctic cooling and declining or leveling of atmospheric CO2, reflecting the signature of a thermal bipolar seesaw</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MAP...tmp...31P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MAP...tmp...31P"><span>Relationship between atmospheric <span class="hlt">circulation</span> weather <span class="hlt">types</span> and seasonal precipitation in Serbia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Putniković, Suzana; Tošić, Ivana</p> <p>2017-04-01</p> <p>An automated version of the Lamb weather <span class="hlt">type</span> classification scheme was used to classify daily <span class="hlt">circulation</span> <span class="hlt">types</span> over Serbia. The synoptic characteristics of 26 weather <span class="hlt">types</span> and their relative frequencies are discussed for spring and autumn, complementing research previously published by Putniković et al. (Meteorol Atmos Phys 128:649-662, 2016) for winter and summer. Trends of the <span class="hlt">circulation</span> <span class="hlt">types</span> are presented, as well as precipitation trends during the period 1961-2010. Precipitation was modeled by the stepwise regression at six stations, defining weather <span class="hlt">types</span> as independent variables. The anticyclonic (A) <span class="hlt">type</span> is the most frequent class occurring in autumn (23.87%), displaying a positive trend for spring and significant negative trend for autumn. The frequencies of anticyclonic and cyclonic (C) <span class="hlt">types</span> are almost the same for spring: 14.33 and 14.02%, respectively. The C <span class="hlt">type</span> shows a significant negative trend only in spring. The increasing trend of the frequency of the C <span class="hlt">types</span> and decreasing trend of the A <span class="hlt">types</span> are in agreement with the increasing trend of precipitation in Serbia during autumn. Results suggest that the C <span class="hlt">type</span> affects precipitation occurrence over most of the country, while the remaining 25 <span class="hlt">types</span> provide more negligible or regional contributions to precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880004460','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880004460"><span>Global atmospheric <span class="hlt">circulation</span> statistics: Four year averages</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, M. F.; Geller, M. A.; Nash, E. R.; Gelman, M. E.</p> <p>1987-01-01</p> <p>Four year averages of the monthly mean global structure of the general <span class="hlt">circulation</span> of the atmosphere are presented in the form of latitude-altitude, time-altitude, and time-latitude cross sections. The numerical values are given in tables. Basic parameters utilized include daily global maps of temperature and geopotential height for 18 pressure levels between 1000 and 0.4 mb for the period December 1, 1978 through November 30, 1982 supplied by NOAA/NMC. Geopotential heights and geostrophic winds are constructed using hydrostatic and geostrophic formulae. <span class="hlt">Meridional</span> and vertical velocities are calculated using thermodynamic and continuity equations. Fields presented in this report are zonally averaged temperature, zonal, <span class="hlt">meridional</span>, and vertical winds, and amplitude of the planetary waves in geopotential height with zonal wave numbers 1-3. The northward fluxes of sensible heat and eastward momentum by the standing and transient eddies along with their wavenumber decomposition and Eliassen-Palm flux propagation vectors and divergences by the standing and transient eddies along with their wavenumber decomposition are also given. Large interhemispheric differences and year-to-year variations are found to originate in the changes in the planetary wave activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.1636B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.1636B"><span>An analysis of the synoptic and climatological applicability of <span class="hlt">circulation</span> <span class="hlt">type</span> classifications for Ireland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Broderick, Ciaran; Fealy, Rowan</p> <p>2013-04-01</p> <p><span class="hlt">Circulation</span> <span class="hlt">type</span> classifications (CTCs) compiled as part of the COST733 Action, entitled 'Harmonisation and Application of Weather <span class="hlt">Type</span> Classifications for European Regions', are examined for their synoptic and climatological applicability to Ireland based on their ability to characterise surface temperature and precipitation. In all 16 different objective classification schemes, representative of four different methodological approaches to <span class="hlt">circulation</span> <span class="hlt">typing</span> (optimization algorithms, threshold based methods, eigenvector techniques and leader algorithms) are considered. Several statistical metrics which variously quantify the ability of CTCs to discretize daily data into well-defined homogeneous groups are used to evaluate and compare different approaches to synoptic <span class="hlt">typing</span>. The records from 14 meteorological stations located across the island of Ireland are used in the study. The results indicate that while it was not possible to identify a single optimum classification or approach to <span class="hlt">circulation</span> <span class="hlt">typing</span> - conditional on the location and surface variables considered - a number of general assertions regarding the performance of different schemes can be made. The findings for surface temperature indicate that that those classifications based on predefined thresholds (e.g. Litynski, GrossWetter<span class="hlt">Types</span> and original Lamb Weather <span class="hlt">Type</span>) perform well, as do the Kruizinga and Lund classification schemes. Similarly for precipitation predefined <span class="hlt">type</span> classifications return high skill scores, as do those classifications derived using some optimization procedure (e.g. SANDRA, Self Organizing Maps and K-Means clustering). For both temperature and precipitation the results generally indicate that the classifications perform best for the winter season - reflecting the closer coupling between large-scale <span class="hlt">circulation</span> and surface conditions during this period. In contrast to the findings for temperature, spatial patterns in the performance of classifications were more evident for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP41C2254M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP41C2254M"><span>Diatom Evidence for Climatic Changes Associated With the Slowdown of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> in the Last 50 Years in the Mexican Tropical Pacific.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Machain-Castillo, M. L.; Almaraz-Ruiz, L.; Esparza-Alvarez, M. A.; Ruiz-Fernandez, A. C.; Sanchez-Cabeza, J. A.; Hernandez-Becerril, D. U.</p> <p>2016-12-01</p> <p>Laminated sediments from the Gulf of Tehuantepec, Mexican Tropical Pacific, reveal climatic variability during the last 50 years. The Gulf of Tehuantepec is characterized by strong upwelling during the autumn-winter season due to intense northern winds. Upwelling supplies high nutrient concentrations and cold water to the ocean surface, resulting in high biological productivity, including diatom blooms. The rest of the year winds are relatively calm and currents predominantly flow to the Northeast. A box core collected in the area beneath the wind axes (750m water depth) showed sub-millimeter to millimeter scale laminated sediments. Laminae were separated and analyzed for diatoms. Chronology was obtained by 210Pb dating. Three diatom associations were recognized in the sediments studied: a cold water association dominated by Thalasionema nitzschioides, T. nitzchioides var. parva, Lioloma pacificum and Chaetoceros spores; an association dominated by Fragilariopsis doliolus, T. bacillare and Thalassiosira oestrupii, more characteristic of temperate waters, and an association of warm waters characterized by Neodelphineis pelagica, T. pseudonitzschioides, Actinocyclus ellipticus, Cyclotella litoralis and Thalassiosira decipiens. Abundance of diatoms is higher (up to 344 106 valves g-1) in the coldest association and lowest (83 106 valves g-1) in the warmer one. Although upwelling species are present throughout the core, we observed a decrease in diatom abundance and an increase in temperate and warm water taxa from the 1960's-1970's. This trend is coincident with the climatic changes produced by the slowdown of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> proposed for the past century and global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..303..131Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..303..131Y"><span>Dynamical relationship between wind speed magnitude and <span class="hlt">meridional</span> temperature contrast: Application to an interannual oscillation in Venusian middle atmosphere GCM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, Masaru; Takahashi, Masaaki</p> <p>2018-03-01</p> <p>We derive simple dynamical relationships between wind speed magnitude and <span class="hlt">meridional</span> temperature contrast. The relationship explains scatter plot distributions of time series of three variables (maximum zonal wind speed UMAX, <span class="hlt">meridional</span> wind speed VMAX, and equator-pole temperature contrast dTMAX), which are obtained from a Venus general <span class="hlt">circulation</span> model with equatorial Kelvin-wave forcing. Along with VMAX and dTMAX, UMAX likely increases with the phase velocity and amplitude of a forced wave. In the scatter diagram of UMAX versus dTMAX, points are plotted along a linear equation obtained from a thermal-wind relationship in the cloud layer. In the scatter diagram of VMAX versus UMAX, the apparent slope is somewhat steep in the high UMAX regime, compared with the low UMAX regime. The scatter plot distributions are qualitatively consistent with a quadratic equation obtained from a diagnostic equation of the stream function above the cloud top. The plotted points in the scatter diagrams form a linear cluster for weak wave forcing, whereas they form a small cluster for strong wave forcing. An interannual oscillation of the general <span class="hlt">circulation</span> forming the linear cluster in the scatter diagram is apparent in the experiment of weak 5.5-day wave forcing. Although a pair of equatorial Kelvin and high-latitude Rossby waves with a same period (Kelvin-Rossby wave) produces equatorward heat and momentum fluxes in the region below 60 km, the equatorial wave does not contribute to the long-period oscillation. The interannual fluctuation of the high-latitude jet core leading to the time variation of UMAX is produced by growth and decay of a polar mixed Rossby-gravity wave with a 14-day period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C43D0647G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C43D0647G"><span>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> Stability Influenced by the Melting of the Greenland Ice Sheet under Various Warming Scenarios</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gierz, P.; Lohmann, G.; Wei, W.; Barbi, D.</p> <p>2012-12-01</p> <p>In this study, we aim to model melting processes of the Greenland ice sheet over the next 1000 years using the Earth system model COSMOS with a dynamic ice sheet module. Of primary interest is the resulting impact on the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (GMOC/AMOC), which is expected to slow in response to a large freshwater (eg melt water) input. Six warming scenarios will be considered, one set corresponding to the IPCC's RPC Scenario 6, and another set corresponding to RPC Scenario 4.5, each time with 0.5, 1, and 2% increase of greenhouse gas concentration per year. It is expected that the freshwater input will slow down the AMOC overturning; each scenario producing a unique braking signal corresponding to how rapidly the Greenland ice sheet is forced to melt. It will be interesting to see if there is a CO2 threshold level at which the slowdown of the AMOC begins and the melting phenomena becomes unstable and positively reinforces itself or instead, as previous studies have demonstrated with a prescribed amount of melting, if the freshwater input always allows for an eventual recovery of the AMOC to a stable state regardless of the rapidity with which the salinity anomalies develop. The primary difference between this set of experiments and those in previous studies shall be the dynamic nature of the ice sheet model, as we will allow the Greenland ice sheet to melt solely based upon atmospheric conditions rather than prescribing a salinity change directly into the ocean model. It is expected that higher levels of greenhouse gases will result in more rapid melting, which in turn will have a stronger braking affect on the AMOC, possibly with longer recovery times to the starting equilibrium point. It will additionally be of interest to see if it is possible to create a shift in this equilibrium, suggesting that the rapidity with which density anomalies are introduced may create a new stable deep water formation rate. PRELIMINARY RESULTS - AMOC</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...47.2601K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...47.2601K"><span>The tropospheric biennial oscillation defined by a biennial mode of sea surface temperature and its impact on the atmospheric <span class="hlt">circulation</span> and precipitation in the tropical eastern Indo-western Pacific region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Jinju; Kim, Kwang-Yul</p> <p>2016-10-01</p> <p>Temporal and spatial patterns of anomalous atmospheric <span class="hlt">circulation</span> and precipitation over the Indo-Pacific region are analyzed in conjunction with the Tropospheric Biennial Oscillation as represented by the biennial mode of sea surface temperature anomalies (SSTA). The biennial components of key variables are identified independently of other variability via CSEOF analysis. Then, its impact on the Asian-Australian monsoon is examined. The biennial mode exhibits a seasonally distinctive atmospheric response over the tropical eastern Indo-western Pacific (EIWP) region (90°-150°E, 20°S-20°N). In boreal summer, local <span class="hlt">meridional</span> <span class="hlt">circulation</span> is a distinguishing characteristic over the tropical EIWP region, whereas a <span class="hlt">meridionally</span> expanded branch of intensified zonal <span class="hlt">circulation</span> develops in austral summer. Temporally varying evolution and distinct timing of SSTA phase transition in the Indian and Pacific Oceans is considered a main factor for this variation of <span class="hlt">circulation</span> in the tropical EIWP region. The impact of the biennial mode is not the same between the two seasons, with different impacts over ocean areas in Asian monsoon and Australian monsoon regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=165252','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=165252"><span><span class="hlt">Circulation</span> of Endemic <span class="hlt">Type</span> 2 Vaccine-Derived Poliovirus in Egypt from 1983 to 1993</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Yang, Chen-Fu; Naguib, Tary; Yang, Su-Ju; Nasr, Eman; Jorba, Jaume; Ahmed, Nahed; Campagnoli, Ray; van der Avoort, Harrie; Shimizu, Hiroyuki; Yoneyama, Tetsuo; Miyamura, Tatsuo; Pallansch, Mark; Kew, Olen</p> <p>2003-01-01</p> <p>From 1988 to 1993, 30 cases of poliomyelitis associated with poliovirus <span class="hlt">type</span> 2 were found in seven governorates of Egypt. Because many of the cases were geographically and temporally clustered and because the case isolates differed antigenically from the vaccine strain, it was initially assumed that the cases signaled the continued <span class="hlt">circulation</span> of wild <span class="hlt">type</span> 2 poliovirus. However, comparison of sequences encoding the major capsid protein, VP1 (903 nucleotides), revealed that the isolates were related (93 to 97% nucleotide sequence identity) to the Sabin <span class="hlt">type</span> 2 oral poliovirus vaccine (OPV) strain and unrelated (<82% nucleotide sequence identity) to the wild <span class="hlt">type</span> 2 polioviruses previously indigenous to Egypt (last known isolate: 1979) or to any contemporary wild <span class="hlt">type</span> 2 polioviruses found elsewhere. The rate and pattern of VP1 divergence among the <span class="hlt">circulating</span> vaccine-derived poliovirus (cVDPV) isolates suggested that all lineages were derived from a single OPV infection that occurred around 1983 and that progeny from the initiating infection <span class="hlt">circulated</span> for approximately a decade within Egypt along several independent chains of transmission. Complete genomic sequences of an early (1988) and a late (1993) cVDPV isolate revealed that their 5′ untranslated region (5′ UTR) and noncapsid- 3′ UTR sequences were derived from other species C enteroviruses. <span class="hlt">Circulation</span> of <span class="hlt">type</span> 2 cVDPVs occurred at a time of low OPV coverage in the affected communities and ceased when OPV coverage rates increased. The potential for cVDPVs to <span class="hlt">circulate</span> in populations with low immunity to poliovirus has important implications for current and future strategies to eradicate polio worldwide. PMID:12857906</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22365754-solar-meridional-flow-shallow-interior-during-rising-phase-cycle','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22365754-solar-meridional-flow-shallow-interior-during-rising-phase-cycle"><span>SOLAR <span class="hlt">MERIDIONAL</span> FLOW IN THE SHALLOW INTERIOR DURING THE RISING PHASE OF CYCLE 24</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Zhao, Junwei; Bogart, R. S.; Kosovichev, A. G.</p> <p>2014-07-01</p> <p>Solar subsurface zonal- and <span class="hlt">meridional</span>-flow profiles during the rising phase of solar cycle 24 are studied using the time-distance helioseismology technique. The faster zonal bands in the torsional-oscillation pattern show strong hemispheric asymmetries and temporal variations in both width and speed. The faster band in the northern hemisphere is located closer to the equator than the band in the southern hemisphere and migrates past the equator when the magnetic activity in the southern hemisphere is reaching maximum. The <span class="hlt">meridional</span>-flow speed decreases substantially with the increase of magnetic activity, and the flow profile shows two zonal structures in each hemisphere. Themore » residual <span class="hlt">meridional</span> flow, after subtracting a mean <span class="hlt">meridional</span>-flow profile, converges toward the activity belts and shows faster and slower bands like the torsional-oscillation pattern. More interestingly, the <span class="hlt">meridional</span>-flow speed above latitude 30° shows an anti-correlation with the poleward-transporting magnetic flux, slower when the following-polarity flux is transported and faster when the leading-polarity flux is transported. It is expected that this phenomenon slows the process of magnetic cancellation and polarity reversal in high-latitude areas.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.4564B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.4564B"><span>Role of dust direct radiative effect on the tropical rain belt over Middle East and North Africa: A high-resolution AGCM study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bangalath, Hamza Kunhu; Stenchikov, Georgiy</p> <p>2015-05-01</p> <p>To investigate the influence of direct radiative effect of dust on the tropical summer rain belt across the Middle East and North Africa (MENA), the present study utilizes the high-resolution capability of an Atmospheric General <span class="hlt">Circulation</span> Model, the High-Resolution Atmospheric Model. Ensembles of Atmospheric Model Intercomparison Project style simulations have been conducted with and without dust radiative impacts, to differentiate the influence of dust on the tropical rain belt. The analysis focuses on summer season. The results highlight the role of dust-induced responses in global- and regional-scale <span class="hlt">circulations</span> in determining the strength and the latitudinal extent of the tropical rain belt. A significant response in the strength and position of the local <span class="hlt">Hadley</span> <span class="hlt">circulation</span> is predicted in response to <span class="hlt">meridionally</span> asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional <span class="hlt">circulation</span> features such as African Easterly Jet and West African Monsoon <span class="hlt">circulation</span>. Consistent with these dynamic responses at various scales, the tropical rain belt across MENA strengthens and shifts northward. Importantly, the summer precipitation over the semiarid strip south of Sahara, including Sahel, increases up to 20%. As this region is characterized by the "Sahel drought," the predicted precipitation sensitivity to the dust loading over this region has a wide range of socioeconomic implications. Overall, the study demonstrates the extreme importance of incorporating dust radiative effects and the corresponding <span class="hlt">circulation</span> responses at various scales, in the simulations and future projections of this region's climate.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP14B..05M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP14B..05M"><span>Sensitivity of the Southern Ocean overturning <span class="hlt">circulation</span> to surface buoyancy forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morrison, A.; Hogg, A.; Ward, M.</p> <p>2011-12-01</p> <p>The southern limb of the ocean's <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> plays a key role in the Earth's response to climate change. The rise in atmospheric CO2 during glacial-interglacial transitions has been attributed to outgassing of enhanced upwelling water masses in the Southern Ocean. However a dynamical understanding of the physical mechanisms driving the change in overturning is lacking. Previous modelling studies of the Southern Ocean have focused on the effect of wind stress forcing on the overturning, while largely neglecting the response of the upper overturning cell to changes in surface buoyancy forcing. Using a series of eddy-permitting, idealised simulations of the Southern Ocean, we show that surface buoyancy forcing in the mid-latitudes is likely to play a significant role in setting the strength of the overturning <span class="hlt">circulation</span>. Air-sea fluxes of heat and precipitation over the Antarctic Circumpolar Current region act to convert dense upwelled water masses into lighter waters at the surface. Additional fluxes of heat or freshwater thereby facilitate the <span class="hlt">meridional</span> overturning up to a theoretical limit derived from Ekman transport. The sensitivity of the overturning to surface buoyancy forcing is strongly dependent on the relative locations of the wind stress profile, buoyancy forcing and upwelling region. The idealised model results provide support for the hypothesis that changes in upwelling during deglaciations may have been driven by changes in heat and freshwater fluxes, instead of, or in addition to, changes in wind stress. Morrison, A. K., A. M. Hogg, and M. L. Ward (2011), Sensitivity of the Southern Ocean overturning <span class="hlt">circulation</span> to surface buoyancy forcing, <it>Geophys. Res. Lett.</it>, 38, L14602, doi:10.1029/2011GL048031.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22167758-meridional-tilt-stellar-velocity-ellipsoid-during-bar-buckling-instability','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22167758-meridional-tilt-stellar-velocity-ellipsoid-during-bar-buckling-instability"><span><span class="hlt">MERIDIONAL</span> TILT OF THE STELLAR VELOCITY ELLIPSOID DURING BAR BUCKLING INSTABILITY</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Saha, Kanak; Pfenniger, Daniel; Taam, Ronald E., E-mail: saha@mpe.mpg.de</p> <p>2013-02-20</p> <p>The structure and evolution of the stellar velocity ellipsoid play an important role in shaping galaxies undergoing bar-driven secular evolution and the eventual formation of a boxy/peanut bulge such as is present in the Milky Way. Using collisionless N-body simulations, we show that during the formation of such a boxy/peanut bulge, the <span class="hlt">meridional</span> shear stress of stars, which can be measured by the <span class="hlt">meridional</span> tilt of the velocity ellipsoid, reaches a characteristic peak in its time evolution. It is shown that the onset of a bar buckling instability is closely connected to the maximum <span class="hlt">meridional</span> tilt of the stellar velocitymore » ellipsoid. Our findings bring a new insight to this complex gravitational instability of the bar which complements the buckling instability studies based on orbital models. We briefly discuss the observed diagnostics of the stellar velocity ellipsoid during such a phenomenon.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..138W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..138W"><span>How East Asian westerly jet's <span class="hlt">meridional</span> position affects the summer rainfall in Yangtze-Huaihe River Valley?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Shixin; Zuo, Hongchao; Zhao, Shuman; Zhang, Jiankai; Lu, Sha</p> <p>2017-03-01</p> <p>Existing studies show that the change in the <span class="hlt">meridional</span> position of East Asian westerly jet (EAWJ) is associated with rainfall anomalies in Yangtze-Huaihe River Valley (YHRV) in summer. However, the dynamic mechanism has not been resolved yet. The present study reveals underlying mechanisms for this impact for early summer and midsummer, separately. Mechanism1: associated with EAWJ's anomalously southward displacement, the 500-hPa westerly wind over YHRV is strengthened through midtropospheric horizontal <span class="hlt">circulation</span> anomalies; the westerly anomalies are related to the formation of warm advection anomalies over YHRV, which cause increased rainfall through adiabatic ascent motion and convective activities; the major difference in these processes between early summer and midsummer is the midtropospheric <span class="hlt">circulation</span> anomaly pattern. Mechanism 2: associated with EAWJ's anomalously southward displacement, the large day-to-day variability of midtropospheric temperature advection in midlatitudes is displaced southward by the jet's trapping transient eddies; this change enhances the day-to-day variability of temperature advection over YHRV, which in turn causes the increased rainfall in most part of YHRV through "lower-bound effect" (rainfall amount can not become negative); there is not much difference in these processes between early summer and midsummer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CliPD...8.2819H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CliPD...8.2819H"><span>Climate and vegetation changes around the Atlantic Ocean resulting from changes in the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during deglaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Handiani, D.; Paul, A.; Dupont, L.</p> <p>2012-07-01</p> <p>The Bølling-Allerød (BA, starting ~ 14.5 ka BP) is one of the most pronounced abrupt warming periods recorded in ice and pollen proxies. The leading explanation of the cause of this warming is a sudden increase in the rate of deepwater formation in the North Atlantic Ocean and the resulting effect on the heat transport by the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC). In this study, we used the University of Victoria (UVic) Earth System-Climate Model (ESCM) to run simulations, in which a freshwater perturbation initiated a BA-like warming period. We found that under present climate conditions, the AMOC intensified when freshwater was added to the Southern Ocean. However, under Heinrich event 1 (HE1, ~ 16 ka BP) climate conditions, the AMOC only intensified when freshwater was extracted from the North Atlantic Ocean, possibly corresponding to an increase in evaporation or a decrease in precipitation in this region. The intensified AMOC led to a warming in the North Atlantic Ocean and a cooling in the South Atlantic Ocean, resembling the bipolar seesaw pattern typical of the last glacial period. In addition to the physical response, we also studied the simulated vegetation response around the Atlantic Ocean region. Corresponding with the bipolar seesaw hypothesis, the rainbelt associated with the Intertropical Convergence Zone (ITCZ) shifted northward and affected the vegetation pattern in the tropics. The most sensitive vegetation area was found in tropical Africa, where grass cover increased and tree cover decreased under dry climate conditions. An equal but opposite response to the collapse and recovery of the AMOC implied that the change in vegetation cover was transient and robust to an abrupt climate change such as during the BA period, which is also supported by paleovegetation data. The results are in agreement with paleovegetation records from Western tropical Africa, which also show a reduction in forest cover during this time period. Further</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.3068P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.3068P"><span>Are flood occurrences in Europe linked to specific atmospheric <span class="hlt">circulation</span> <span class="hlt">types</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prudhomme, C.; Genevier, M.</p> <p>2009-04-01</p> <p>Flood damages are amongst the most costly climate-related hazard damages, with annual average flood damage in Europe in the last few decades of around €4bn per year (Barredo, 2007). With such economic and sometimes human losses, it is important to improve our estimations of flood risk for time scales from a few months (for increased preparedness) and to several decades (necessary to establish long-term flood management strategies). This paper investigates links between the occurrence of flood events and the atmospheric <span class="hlt">circulation</span> patterns that have prevailed in the days leading to the flood. With the recent advances in climate modelling, such links could be exploited to anticipate the extent of potential damages due to flood using seasonal atmospheric forecasts products or future climate projections. The research is undertaken at a pan-European scale and exploits latest research in automatic classification techniques developed within the EU research network COST733 Action. Daily flow data from over 450 sites were used, available from the Global Runoff Data Centre, the European Water Archive, the UK National River Flow Archive and the French Banque Hydro. The atmospheric <span class="hlt">circulation</span> <span class="hlt">types</span> were defined following the Objective GrossWetterLagen classification (OGWL) developed by (James, 2007) using the ERA-40 mslp re-analysis, similar to the Hess-Brezowsky subjective classification (Hess and Brezowsky, 1977). Flood events were here defined according to the peak-over-threshold method, selecting the highest independent peaks observed in streamflow time series. The association between flood and atmospheric <span class="hlt">circulation</span> <span class="hlt">types</span> is assessed using two indicators. The first indicator calculates the difference between the frequency of occurrence of a <span class="hlt">circulation</span> <span class="hlt">type</span> CTi during a flood event to that for any day, expressed in percent. The significance of the anomaly is assessed using the χ2 statistics. The second indicator measures the probability of finding at last k days of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720009074','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720009074"><span>Effect of two <span class="hlt">types</span> of helium <span class="hlt">circulators</span> on the performance of a subsonic nuclear powered airplane</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Strack, W. C.</p> <p>1971-01-01</p> <p>Two <span class="hlt">types</span> of helium <span class="hlt">circulators</span> are analytically compared on the bases of their influence on airplane payload and on propulsion system variables. One <span class="hlt">type</span> of <span class="hlt">circulator</span> is driven by the turbofan engines with power takeoff shafting while the other, a turbocirculator, is powered by a turbine placed in the helium loop between the nuclear reactor and the helium-to-air heat exchangers inside the engines. Typical results show that the turbocirculator yields more payload for <span class="hlt">circulator</span> efficiencies greater than 0.82. Optimum engine and heat exchanger temperatures and pressures are significantly lower in the turbocirculator case compared to the engine-driven <span class="hlt">circulator</span> scheme.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820002779','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820002779"><span>Equatorial superrotation in a thermally driven zonally symmetric <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mayr, H. G.; Harris, I.</p> <p>1981-01-01</p> <p>Near the equator where the Coriolis force vanishes, the momentum balance for the axially symmetric <span class="hlt">circulation</span> is established between horizontal and vertical diffusion, which, a priori, does not impose constraints on the direction or magnitude of the zonal winds. Solar radiation absorbed at low latitudes is a major force in driving large scale motions with air rising near the equator and falling at higher latitudes. In the upper leg of the <span class="hlt">meridional</span> cell, angular momentum is redistributed so that the atmosphere tends to subrotate (or corotate) at low latitudes and superrotate at high latitudes. In the lower leg, however, the process is reversed and produces a tendency for the equatorial region to superrotate. The outcome depends on the energy budget which is closely coupled to the momentum budget through the thermal wind equation; a pressure (temperature) maximum is required to sustain equatorial superrotation. Such a condition arises in regions which are convectively unstable and the temperature lapse rate is superadiabatic. It should arise in the tropospheres of Jupiter and Saturn; planetary energy from the interior is carried to higher altitudes where radiation to space becomes important. Upward equatorial motions in the direct and indirect <span class="hlt">circulations</span> (Ferrel-Thomson <span class="hlt">type</span>) imposed by insolation can then trap dynamic energy for equatorial heating which can sustain the superrotation of the equatorial region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.4492H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.4492H"><span><span class="hlt">Circulation</span> <span class="hlt">Type</span> Classifications and their nexus to Van Bebber's storm track Vb</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hofstätter, M.; Chimani, B.</p> <p>2012-04-01</p> <p><span class="hlt">Circulation</span> <span class="hlt">Type</span> Classifications (CTCs) are tools to identify repetitive and predominantly stationary patterns of the atmospheric <span class="hlt">circulation</span> over a certain area, with the purpose to enable the recognition of specific characteristics in surface climate variables. On the other hand storm tracks can be used to identify similar <span class="hlt">types</span> of synoptic events from a non-stationary, kinematic perspective. Such a storm track classification for Europe has been done in the late 19th century by Van Bebber (1882, 1891), from which the famous <span class="hlt">type</span> Vb and Vc/d remained up to the present day because of to their association with major flooding events like in August 2002 in Europe. In this work a systematic tracking procedure has been developed, to determine storm track <span class="hlt">types</span> and their characteristics especially for the Eastern Alpine Region in the period 1961-2002, using ERA40 and ERAinterim reanalysis. The focus thereby is on cyclone tracks of <span class="hlt">type</span> V as suggested by van Bebber and congeneric <span class="hlt">types</span>. This new catalogue is used as a reference to verify the hypothesis of a certain coherence of storm track Vb with certain <span class="hlt">circulation</span> <span class="hlt">types</span> (e.g. Fricke and Kaminski, 2002). Selected objective and subjective classification schemes from the COST733 action (http://cost733.met.no/, Phillip et al. 2010) are used therefore, as well as the manual classification from ZAMG (Lauscher 1972 and 1985), in which storm track Vb has been classified explicitly on a daily base since 1948. The latter scheme should prove itself as a valuable and unique data source in that issue. Results show that not less than 146 storm tracks are identified as Vb between 1961 and 2002, whereas only three events could be found from literature, pointing to big subjectivity and preconception in the issue of Vb storm tracks. The annual number of Vb storm tracks do not show any significant trend over the last 42 years, but large variations from year to year. <span class="hlt">Circulation</span> <span class="hlt">type</span> classification CAP27 (Cluster Analysis of Principal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002cosp...34E2661W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002cosp...34E2661W"><span>General <span class="hlt">Circulation</span> Model Simulations of the Annual Cycle of Martian Climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, R.; Richardson, M.; Rodin, A.</p> <p></p> <p>Observations of the martian atmosphere have revealed a strong annual modulation of global mean atmospheric temperature that has been attributed to the pronounced seasonal asymmetry in solar radiation and the highly variable distribution of aerosol. These observations indicate little interannual variability during the relatively cool aphelion season and considerable variability in the perihelion season that is associated with the episodic occurrence of regional and major dust storms. The atmospheric <span class="hlt">circulation</span> responds to the evolving spatial distribution of aerosol-induced heating and, in turn, plays a major role in determining the sources, sinks, and transport of radiatively active aerosol. We will present simulations employing the GFDL Mars General <span class="hlt">Circulation</span> Model (MGCM) that show that aspects of the seasonally evolving climate may be simulated in a self-consistent manner using simple dust source parameterizations that represent the effects of lifting associated with local dust storms, dust devil activity, and other processes. Aerosol transport is accomplished, in large part, by elements of the large-scale <span class="hlt">circulation</span> such as the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, baroclinic storms, tides, etc. A seasonal cycle of atmospheric opacity and temperature results from the variation in the strength and distribution of dust sources as well as from seasonal variations in the efficiency of atmospheric transport associated with changes in the <span class="hlt">circulation</span> between solstice and equinox, and between perihelion and aphelion. We examine the efficiency of atmospheric transport of dust lifted along the perimeter of the polar caps to gauge the influence of these storms on the global <span class="hlt">circulation</span>. We also consider the influence of water, as the formation of water ice clouds on dust nuclei may also affect the vertical distribution of dust and strongly influence the aerosol radiative properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012Icar..221..276T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012Icar..221..276T"><span>The impact of resolution on the dynamics of the martian global atmosphere: Varying resolution studies with the MarsWRF GCM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toigo, Anthony D.; Lee, Christopher; Newman, Claire E.; Richardson, Mark I.</p> <p>2012-09-01</p> <p>We investigate the sensitivity of the <span class="hlt">circulation</span> and thermal structure of the martian atmosphere to numerical model resolution in a general <span class="hlt">circulation</span> model (GCM) using the martian implementation (MarsWRF) of the planetWRF atmospheric model. We provide a description of the MarsWRF GCM and use it to study the global atmosphere at horizontal resolutions from 7.5° × 9° to 0.5° × 0.5°, encompassing the range from standard Mars GCMs to global mesoscale modeling. We find that while most of the gross-scale features of the <span class="hlt">circulation</span> (the rough location of jets, the qualitative thermal structure, and the major large-scale features of the surface level winds) are insensitive to horizontal resolution over this range, several major features of the <span class="hlt">circulation</span> are sensitive in detail. The northern winter polar <span class="hlt">circulation</span> shows the greatest sensitivity, showing a continuous transition from a smooth polar winter jet at low resolution, to a distinct vertically “split” jet as resolution increases. The separation of the lower and middle atmosphere polar jet occurs at roughly 10 Pa, with the split jet structure developing in concert with the intensification of <span class="hlt">meridional</span> jets at roughly 10 Pa and above 0.1 Pa. These <span class="hlt">meridional</span> jets appear to represent the separation of lower and middle atmosphere mean overturning <span class="hlt">circulations</span> (with the former being consistent with the usual concept of the “<span class="hlt">Hadley</span> cell”). Further, the transition in polar jet structure is more sensitive to changes in zonal than <span class="hlt">meridional</span> horizontal resolution, suggesting that representation of small-scale wave-mean flow interactions is more important than fine-scale representation of the <span class="hlt">meridional</span> thermal gradient across the polar front. Increasing the horizontal resolution improves the match between the modeled thermal structure and the Mars Climate Sounder retrievals for northern winter high latitudes. While increased horizontal resolution also improves the simulation of the northern high</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P34A..03Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P34A..03Z"><span>The Influence of Ice-Ocean Interactions on Europa's Overturning <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, P.; Manucharyan, G. E.; Thompson, A. F.; Goodman, J. C.; Vance, S.</p> <p>2016-12-01</p> <p>Jupiter's moon Europa appears to have a global liquid ocean, which is located beneath an ice shell that covers the moon's entire surface. Linking ocean dynamics and ice-ocean interactions is crucial to understanding observed surface features on Europa as well as other satellite measurements. Ocean properties and <span class="hlt">circulation</span> may also provide clues as to whether the moon has the potential to support extraterrestrial life through chemical transport governed by ice-ocean interactions. Previous studies have identified a <span class="hlt">Hadley</span> cell-like overturning <span class="hlt">circulation</span> extending from the equator to mid latitudes. However, these model simulations do not consider ice-ocean interactions. In this study, our goal is to investigate how the ocean <span class="hlt">circulation</span> may be affected by ice. We study two ice-related processes by building idealized models. One process is horizontal convection driven by an equator-to-pole buoyancy difference due to latitudinal ice transport at the ocean surface, which is found to be much weaker than the convective overturning <span class="hlt">circulation</span>. The second process we consider is the freshwater layer formed by ice melting at the equator. A strong buoyancy contrast between the freshwater layer and the underlying water suppresses convection and turbulent mixing, which may modify the surface heat flux from the ocean to the bottom of the ice. We find that the salinity of the ocean below the freshwater layer tends to be homogeneous both vertically and horizontally with the presence of an overturning <span class="hlt">circulation</span>. Critical values of <span class="hlt">circulation</span> strength constrain the freshwater layer depth, and this relationship is sensitive to the average salinity of the ocean. Further coupling of temperature and salinity of the ice and the ocean that includes mutual influences between the surface heat flux and the freshwater layer may provide additional insights into the ice-ocean feedback, and its influence on the latitudinal difference of heat transport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21452860-effect-activity-related-meridional-flow-modulation-strength-solar-polar-magnetic-field','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21452860-effect-activity-related-meridional-flow-modulation-strength-solar-polar-magnetic-field"><span>THE EFFECT OF ACTIVITY-RELATED <span class="hlt">MERIDIONAL</span> FLOW MODULATION ON THE STRENGTH OF THE SOLAR POLAR MAGNETIC FIELD</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Jiang, J.; Cameron, R. H.; Schmitt, D.</p> <p></p> <p>We studied the effect of the perturbation of the <span class="hlt">meridional</span> flow in the activity belts detected by local helioseismology on the development and strength of the surface magnetic field at the polar caps. We carried out simulations of synthetic solar cycles with a flux transport model, which follows the cyclic evolution of the surface field determined by flux emergence and advective transport by near-surface flows. In each hemisphere, an axisymmetric band of latitudinal flows converging toward the central latitude of the activity belt was superposed onto the background poleward <span class="hlt">meridional</span> flow. The overall effect of the flow perturbation is tomore » reduce the latitudinal separation of the magnetic polarities of a bipolar magnetic region and thus diminish its contribution to the polar field. As a result, the polar field maximum reached around cycle activity minimum is weakened by the presence of the <span class="hlt">meridional</span> flow perturbation. For a flow perturbation consistent with helioseismic observations, the polar field is reduced by about 18% compared to the case without inflows. If the amplitude of the flow perturbation depends on the cycle strength, its effect on the polar field provides a nonlinearity that could contribute to limiting the amplitude of a Babcock-Leighton <span class="hlt">type</span> dynamo.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130013860','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130013860"><span>Effects of the Observed <span class="hlt">Meridional</span> Flow Variations since 1996 on the Sun's Polar Fields</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hathaway, David; Upton, Lisa</p> <p>2013-01-01</p> <p>The cause of the low and extended minimum in solar activity between Sunspot Cycles 23 and 24 was the small size of Sunspot Cycle 24 itself - small cycles start late and leave behind low minima. Cycle 24 is small because the polar fields produced during Cycle 23 were substantially weaker than those produced during the previous cycles and those (weak) polar fields are the seeds for the activity of the following cycle. The polar fields are produced by the latitudinal transport of magnetic flux that emerged in low-latitude active regions. The polar fields thus depend upon the details of both the flux emergence and the flux transport. We have measured the flux transport flows (differential rotation, <span class="hlt">meridional</span> flow, and supergranules) since 1996 and find systematic and substantial variation in the <span class="hlt">meridional</span> flow alone. Here we present experiments using a Surface Flux Transport Model in which magnetic field data from SOHO/MDI and SDO/HMI are assimilated into the model only at latitudes between 45-degrees north and south of the equator (this assures that the details of the active region flux emergence are well represented). This flux is then transported in both longitude and latitude by the observed flows. In one experiment the <span class="hlt">meridional</span> flow is given by the time averaged (and north-south symmetric) <span class="hlt">meridional</span> flow profile. In the second experiment the time-varying and north-south asymmetric <span class="hlt">meridional</span> flow is used. Differences between the observed polar fields and those produced in these two experiments allow us to ascertain the effects of these <span class="hlt">meridional</span> flow variations on the Sun s polar fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21811241','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21811241"><span>Silver hake tracks changes in Northwest Atlantic <span class="hlt">circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nye, Janet A; Joyce, Terrence M; Kwon, Young-Oh; Link, Jason S</p> <p>2011-08-02</p> <p>Recent studies documenting shifts in spatial distribution of many organisms in response to a warming climate highlight the need to understand the mechanisms underlying species distribution at large spatial scales. Here we present one noteworthy example of remote oceanographic processes governing the spatial distribution of adult silver hake, Merluccius bilinearis, a commercially important fish in the Northeast US shelf region. Changes in spatial distribution of silver hake over the last 40 years are highly correlated with the position of the Gulf Stream. These changes in distribution are in direct response to local changes in bottom temperature on the continental shelf that are responding to the same large scale <span class="hlt">circulation</span> change affecting the Gulf Stream path, namely changes in the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). If the AMOC weakens, as is suggested by global climate models, silver hake distribution will remain in a poleward position, the extent to which could be forecast at both decadal and multidecadal scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA495384','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA495384"><span>Radiation and Dissipation of Internal Waves Generated by Geostrophic Motions Impinging on Small-Scale Topography</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2009-02-01</p> <p>the largest zonal current in the world, which links the Atlantic , Indian and Pacific Oceans. The associated <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC...formed in polar regions (Wunsch and Ferrari, 2004). Mixing is especially important in the Southern Ocean where the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> ...general <span class="hlt">circulation</span> of the ocean and an important driver of the lower cell of the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> . Wunsch (1998) estimated that the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.4171O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.4171O"><span>North Atlantic observations sharpen <span class="hlt">meridional</span> overturning projections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olson, R.; An, S.-I.; Fan, Y.; Evans, J. P.; Caesar, L.</p> <p>2018-06-01</p> <p>Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) projections are uncertain due to both model errors, as well as internal climate variability. An AMOC slowdown projected by many climate models is likely to have considerable effects on many aspects of global and North Atlantic climate. Previous studies to make probabilistic AMOC projections have broken new ground. However, they do not drift-correct or cross-validate the projections, and do not fully account for internal variability. Furthermore, they consider a limited subset of models, and ignore the skill of models at representing the temporal North Atlantic dynamics. We improve on previous work by applying Bayesian Model Averaging to weight 13 Coupled Model Intercomparison Project phase 5 models by their skill at modeling the AMOC strength, and its temporal dynamics, as approximated by the northern North-Atlantic temperature-based AMOC Index. We make drift-corrected projections accounting for structural model errors, and for the internal variability. Cross-validation experiments give approximately correct empirical coverage probabilities, which validates our method. Our results present more evidence that AMOC likely already started slowing down. While weighting considerably moderates and sharpens our projections, our results are at low end of previously published estimates. We project mean AMOC changes between periods 1960-1999 and 2060-2099 of -4.0 Sv and -6.8 Sv for RCP4.5 and RCP8.5 emissions scenarios respectively. The corresponding average 90% credible intervals for our weighted experiments are [-7.2, -1.2] and [-10.5, -3.7] Sv respectively for the two scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870008190','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870008190"><span>Cloud-top <span class="hlt">meridional</span> momentum transports on Saturn and Jupiter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stromovsky, L. A.; Revercomb, H. E.; Krauss, R. J.</p> <p>1986-01-01</p> <p>Cloud-tracked wind measurements reported by Sromovsky et al. were analyzed to determine <span class="hlt">meridional</span> momentum transports in Saturn's northern middle latitudes. Results are expressed in terms of eastward and northward velocity components (u and v), and eddy components u and v. At most latitudes between 13 and 44 deg N (planetocentric), the transport by the mean flow (<u><v>) is measurably southward, tending to support Saturn's large equatorial jet, and completely dominating the eddy transport. <span class="hlt">Meridional</span> velocities are near zero at the peak of the relatively weak westward jet; along the flanks of that jet, measurements indicate divergent flow out of the jet. In this region the dominant eddy transport (<u'v'>) is northward on the north side of the jet, but not resolvable on the south side. Eddy transports at most other latitudes are not significantly different from measurement error. The conversion of eddy kinetic energy to mean kinetic energy, indicated by the correlation between <u'v'> and d<y>/dy (where y is <span class="hlt">meridional</span> distance) is clearly smaller than various values reported for Jupiter, and not significantly different from zero. Both Jovian and Saturnian results may be biased by the tendency for cloud tracking to favor high contrast features, and thus may not be entirely representative of the cloud level motions as a whole.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171651','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171651"><span>Intra-seasonal Oscillations (ISO) of Zonal-Mean <span class="hlt">Meridional</span> Winds and Temperatures as Measured by UARS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huang, Frank T.; Mayr, Hans G.; Reber, Carl A.</p> <p>2004-01-01</p> <p>Based on an empirical analysis of measurements with the High Resolution Doppler Imager (HRDI) on the UARS spacecraft in the upper mesosphere (95 km), persistent and regular intra-seasonal oscillations (ISO) with periods of about 2 to 4 months have recently been reported in the zonal-mean <span class="hlt">meridional</span> winds. Similar oscillations have also been discussed independently in a modeling study, and they were attributed to wave-mean-flow interactions. The observed and modeled <span class="hlt">meridional</span> wind ISOs were largely confined to low latitudes. We report here an analysis of concurrent temperature measurements on UARS, which produces oscillations similar to those seen in the <span class="hlt">meridional</span> winds. Although the temperature oscillations are observed at lower altitudes (55 km), their phase variations with latitude are qualitatively consistent with the inferred properties seen in the <span class="hlt">meridional</span> winds and thus provide independent evidence for the existence of ISOs in the mesosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JThSc..22..111K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JThSc..22..111K"><span>Numerical analysis of flow in ultra micro centrifugal compressor -influence of <span class="hlt">meridional</span> configuration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kaneko, Masanao; Tsujita, Hoshio; Hirano, Toshiyuki</p> <p>2013-04-01</p> <p>A single stage ultra micro centrifugal compressor constituting ultra micro gas turbine is required to operate at high rotational speed in order to achieve the pressure ratio which establishes the gas turbine cycle. As a consequence, the aerodynamic losses can be increased by the interaction of a shock wave with the boundary layer on the blade surface. Moreover, the centrifugal force which exceeds the allowable stress of the impeller material can act on the root of blades. On the other hand, the restrictions of processing technology for the downsizing of impeller not only relatively enlarge the size of tip clearance but also make it difficult to shape the impeller with the three-dimensional blade. Therefore, it is important to establish the design technology for the impeller with the two-dimensional blade which possesses the sufficient aerodynamic performance and enough strength to bear the centrifugal force caused by the high rotational speed. In this study, the flow in two <span class="hlt">types</span> of impeller with the two-dimensional blade which have different <span class="hlt">meridional</span> configuration was analyzed numerically. The computed results clarified the influence of the <span class="hlt">meridional</span> configuration on the loss generations in the impeller passage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4353W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4353W"><span>Nonlinear <span class="hlt">Meridional</span> Moisture Advection and the ENSO-Southern China Rainfall Teleconnection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Qiang; Cai, Wenju; Zeng, Lili; Wang, Dongxiao</p> <p>2018-05-01</p> <p>In the boreal cooler months of 2015, southern China (SC) experienced the largest rainfall since 1950, exceeding 4 times the standard deviation of SC rainfall. Although an El Niño typically induces a positive SC rainfall anomaly during these months, the unprecedented rainfall increase cannot be explained by the strong El Niño of 2015/2016, and the dynamics is unclear. Here we show that a nonlinear <span class="hlt">meridional</span> moisture advection contributes substantially to the unprecedented rainfall increase. During cooler months of 2015, the <span class="hlt">meridional</span> flow anomaly over the South China Sea region, which acts on an El Niño-induced anomalous <span class="hlt">meridional</span> moisture gradient, is particularly large and is supported by an anomalous zonal sea surface temperature gradient over the northwestern Pacific, which recorded its largest value in 2015 since 1950. Our study highlights, for the first time, the importance of the nonlinear process associated with the combined impact of a regional sea surface temperature gradient and large-scale El Niño anomalies in forcing El Niño rainfall teleconnection.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4740379','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4740379"><span>The puzzling Venusian polar atmospheric structure reproduced by a general <span class="hlt">circulation</span> model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ando, Hiroki; Sugimoto, Norihiko; Takagi, Masahiro; Kashimura, Hiroki; Imamura, Takeshi; Matsuda, Yoshihisa</p> <p>2016-01-01</p> <p>Unlike the polar vortices observed in the Earth, Mars and Titan atmospheres, the observed Venus polar vortex is warmer than the midlatitudes at cloud-top levels (∼65 km). This warm polar vortex is zonally surrounded by a cold latitude band located at ∼60° latitude, which is a unique feature called ‘cold collar' in the Venus atmosphere. Although these structures have been observed in numerous previous observations, the formation mechanism is still unknown. Here we perform numerical simulations of the Venus atmospheric <span class="hlt">circulation</span> using a general <span class="hlt">circulation</span> model, and succeed in reproducing these puzzling features in close agreement with the observations. The cold collar and warm polar region are attributed to the residual mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> enhanced by the thermal tide. The present results strongly suggest that the thermal tide is crucial for the structure of the Venus upper polar atmosphere at and above cloud levels. PMID:26832195</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000053088','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000053088"><span>Variability in Sea Surface Height: A Qualitative Measure for the <span class="hlt">Meridional</span> Overturning in the North Atlantic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, Sirpa</p> <p>1999-01-01</p> <p>Sea surface height (SSH) from altimeter observations from 1992 on and from modeling results is investigated to determine the modes of variability and the linkages to the state of oceanic <span class="hlt">circulation</span> in the North Atlantic. First the altimeter and model simulated SSH are analyzed using the empirical orthogonal function (EOF) analysis. They are found to share a similar leading mode where the center of action is along the Gulf Stream and North Atlantic Current with opposite sign anomalies in the subpolar gyre and in the slope waters along the Eastern Seaboard. The time series of the leading EOF mode from the altimeter data shows that between winters of 1995 and 1996, SSH over the Gulf Stream decreased by about 12cm which change is reproduced by the model simulation. Based on the relationship from the model simulations between the time series of the SSH EOF1 and <span class="hlt">meridional</span> heat transport, it is suggested that associated with this SSH change in 1995-96, the overturning has slowed down from its heights in the early 90's. Furthermore, it is shown that decadal variability in the leading SSH mode originates from the thermal forcing component. This adds confidence to the qualitative relationship between the state of overturning/<span class="hlt">meridional</span> heat transport and SSH in the limited area described by the EOF1. SSH variability in the eastern side of the North Atlantic basin, outside the western boundary current region, is determined by local and remote (Rossby waves) wind stress curl forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018QSRv..191..238W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018QSRv..191..238W"><span>Relative influence of precession and obliquity in the early Holocene: Topographic modulation of subtropical seasonality during the Asian summer monsoon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Chi-Hua; Lee, Shih-Yu; Chiang, John C. H.</p> <p>2018-07-01</p> <p>On orbital timescales, higher summer insolation is thought to strengthen the continental monsoon while weakening the maritime monsoon in the Northern hemisphere. Through simulations using the Community Earth System Model, we evaluated the relative influence of perihelion precession and high obliquity in the early Holocene during the Asian summer monsoon. The major finding was that precession dominates the atmospheric heating change over the Tibetan Plateau-Himalayas and Maritime Continent, whereas obliquity is responsible for the heating change over the equatorial Indian Ocean. Thus, precession and obliquity can play contrasting roles in driving the monsoons on orbital timescales. In late spring-early summer, interior Asian continental heating drives the South and East Asian monsoons. The broad-scale monsoonal <span class="hlt">circulation</span> further expands zonally in July-August, corresponding to the development of summer monsoons in West Africa and the subtropical Western North Pacific (WNP) as well as a sizable increase in convection over the equatorial Indian Ocean. Tropical and oceanic heating becomes crucial in late summer. Over South Asia-Indian Ocean (50°E-110°E), the precession maximum intensifies the monsoonal <span class="hlt">Hadley</span> cell (heating with an inland/highland origin), which is opposite to the <span class="hlt">meridional</span> <span class="hlt">circulation</span> change induced by high obliquity (heating with a tropical origin). The existence of the Tibetan Plateau-Himalayas intensifies the precessional impact. During the late-summer phase of the monsoon season, the effect of obliquity on tropical heating can be substantial. In addition to competing with Asian continental heating, obliquity-enhanced heating over the equatorial Indian Ocean also has a Walker-<span class="hlt">type</span> <span class="hlt">circulation</span> impact, resulting in suppression of precession-enhanced heating over the Maritime Continent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.5884M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.5884M"><span>Model representation of salinity anomalies and the stability of the North Atlantic overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Megann, A.; New, A.; Blaker, A.</p> <p>2012-04-01</p> <p>Vellinga and Wu (2004) and others have identified feedback cycles governing the decadal variability of the North Atlantic overturning <span class="hlt">circulation</span>, in which modulation of tropical rainfall creates near-surface salinity anomalies that propagate northward to the winter convection regions, where they affect the wintertime convection through changes in surface density. Freshwater "hosing" experiments, in which 0.1 Sv of extra freshwater is added to the convection region, are described using two climate models: the UK Met Office's HadCM3; and CHIME, which is identical to HadCM3 except for the replacement of the z-coordinate ocean component of HadCM3 with the hybrid isopycnic model HYCOM. While HadCM3 shows an unambiguous weakening of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) by 5 Sv, the MOC in CHIME initially starts to decrease but returns to a value close to that in the control experiment after 40-50 years even though the hosing flux is still being applied. It will be shown that the recovery of the overturning in CHIME is mainly due to enhanced advective transport of salt from the subtropics by salinity anomalies. These are found to be substantially more coherent <span class="hlt">meridionally</span> in CHIME than in HadCM3, consistent with the known superior ability of the isopycnic model formulation to preserve watermass properties over long distances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004MNRAS.350..317G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004MNRAS.350..317G"><span>Kinematic solar dynamo models with a deep <span class="hlt">meridional</span> flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guerrero, G. A.; Muñoz, J. D.</p> <p>2004-05-01</p> <p>We develop two different solar dynamo models to verify the hypothesis that a deep <span class="hlt">meridional</span> flow can restrict the appearance of sunspots below 45°, proposed recently by Nandy & Choudhuri. In the first one, a single polytropic approximation for the density profile was taken, for both radiative and convective zones. In the second one, that of Pinzon & Calvo-Mozo, two polytropes were used to distinguish between both zones. The magnetic buoyancy mechanism proposed by Dikpati & Charbonneau was chosen in both models. We have in fact obtained that a deep <span class="hlt">meridional</span> flow pushes the maxima of toroidal magnetic field towards the solar equator, but, in contrast to Nandy & Choudhuri, a second zone of maximal fields remains at the poles. The second model, although closely resembling the solar standard model of Bahcall et al., gives solar cycles three times longer than observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140002703','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140002703"><span><span class="hlt">Meridional</span> Flow Variations in Cycles 23 and 24: Active Latitude Control of Sunspot Cycle Amplitudes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hathaway, David H.; Upton, Lisa</p> <p>2013-01-01</p> <p>We have measured the <span class="hlt">meridional</span> motions of magnetic elements observed in the photosphere over sunspot cycles 23 and 24 using magnetograms from SOHO/MDI and SDO/HMI. Our measurements confirm the finding of Komm, Howard, and Harvey (1993) that the poleward <span class="hlt">meridional</span> flow weakens at cycle maxima. Our high spatial and temporal resolution analyses show that this variation is in the form of a superimposed inflow toward the active latitudes. This inflow is weaker in cycle 24 when compared to the inflow in 23, the stronger cycle. This systematic modulation of the <span class="hlt">meridional</span> flow can modulate the amplitude of the following sunspot cycle through its influence on the Sun's polar fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP31C2283B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP31C2283B"><span>Large Scale Eocene Ocean <span class="hlt">Circulation</span> Transition Could Help Antarctic Glaciation.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baatsen, M.</p> <p>2016-12-01</p> <p>The global climate underwent major changes going from the Eocene into the Oligocene, including the formation of a continental-scale Antarctic ice sheet. In addition to a gradual drawdown of CO2 since the Early Eocene, the changing background geography of the earth may also have played a crucial role in setting the background oceanic <span class="hlt">circulation</span> pattern favorable to ice growth. On the other hand, the ocean <span class="hlt">circulation</span> may have changed only after the ice sheet started growing, with a similar climatic imprint. It is, therefore, still under debate what the primary forcing or trigger of this transition was. Using an ocean general <span class="hlt">circulation</span> model (POP) and two different geography reconstruc-tions for the middle-late Eocene, we find two distinctly different patterns of the oceanic <span class="hlt">circulation</span> to be possible under the same forcing. The first one features deep-water formation and warmer SSTs in the Southern Pacific while in the second, deep water forms in the North Pacific Ocean and Southern Ocean SSTs are colder. The presence of a double equilibrium shows that the ocean <span class="hlt">circulation</span> was highly susceptible to large scale transitions during the middle-late Eocene. Additionally, changes in benthic oxygen and Neodymium isotopes depict significant changes during the same period. We suggest that a transition in the global <span class="hlt">meridional</span> overturing <span class="hlt">circulation</span> can explain the observed changes and preconditions the global climate for the two-step transition into an Icehouse state at the Eocene-Oligocene boundary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA33B..07D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA33B..07D"><span>MENTAT: A New Magnetic <span class="hlt">Meridional</span> Neutral Wind Model for Earth's Thermosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dandenault, P. B.</p> <p>2017-12-01</p> <p>We present a new model of thermosphere winds in the F region obtained from variations in the altitude of the peak density of the ionosphere (hmF2). The new Magnetic <span class="hlt">mEridional</span> NeuTrAl Thermospheric (MENTAT) wind model produces magnetic-<span class="hlt">meridional</span> neutral winds as a function of year, day of year, solar local time, solar flux, geographic latitude, and geographic longitude. The winds compare well with Fabry-Pérot Interferometer (FPI) wind observations and are shown to provide accurate specifications in regions outside of the observational database such as the midnight collapse of hmF2 at Arecibo, Puerto Rico. The model winds are shown to exhibit the expected seasonal, diurnal, and hourly behavior based on geophysical conditions. The magnetic <span class="hlt">meridional</span> winds are similar to those from the well-known HWM14 model but there are important differences. For example, Townsville, Australia has a strong midnight collapse similar to that at Arecibo, but winds from HWM14 do not reproduce it. Also, the winds from hmF2 exhibit a moderate solar cycle dependence under certain conditions, whereas, HWM14 has no solar activity dependence. For more information, please visit http://www.mentatwinds.net/.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22661035-proposed-paradigm-solar-cycle-dynamics-mediated-via-turbulent-pumping-magnetic-flux-babcockleighton-type-solar-dynamos','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22661035-proposed-paradigm-solar-cycle-dynamics-mediated-via-turbulent-pumping-magnetic-flux-babcockleighton-type-solar-dynamos"><span>A PROPOSED PARADIGM FOR SOLAR CYCLE DYNAMICS MEDIATED VIA TURBULENT PUMPING OF MAGNETIC FLUX IN BABCOCK–LEIGHTON-<span class="hlt">TYPE</span> SOLAR DYNAMOS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Hazra, Soumitra; Nandy, Dibyendu</p> <p></p> <p>At present, the Babcock–Leighton flux transport solar dynamo models appear to be the most promising models for explaining diverse observational aspects of the sunspot cycle. The success of these flux transport dynamo models is largely dependent upon a single-cell <span class="hlt">meridional</span> <span class="hlt">circulation</span> with a deep equatorward component at the base of the Sun’s convection zone. However, recent observations suggest that the <span class="hlt">meridional</span> flow may in fact be very shallow (confined to the top 10% of the Sun) and more complex than previously thought. Taken together, these observations raise serious concerns on the validity of the flux transport paradigm. By accounting formore » the turbulent pumping of magnetic flux, as evidenced in magnetohydrodynamic simulations of solar convection, we demonstrate that flux transport dynamo models can generate solar-like magnetic cycles even if the <span class="hlt">meridional</span> flow is shallow. Solar-like periodic reversals are recovered even when <span class="hlt">meridional</span> <span class="hlt">circulation</span> is altogether absent. However, in this case, the solar surface magnetic field dynamics does not extend all the way to the polar regions. Very importantly, our results demonstrate that the Parker–Yoshimura sign rule for dynamo wave propagation can be circumvented in Babcock–Leighton dynamo models by the latitudinal component of turbulent pumping, which can generate equatorward propagating sunspot belts in the absence of a deep, equatorward <span class="hlt">meridional</span> flow. We also show that variations in turbulent pumping coefficients can modulate the solar cycle amplitude and periodicity. Our results suggest the viability of an alternate magnetic flux transport paradigm—mediated via turbulent pumping—for sustaining solar-stellar dynamo action.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720010338','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720010338"><span>FORTRAN program for calculating velocities in the <span class="hlt">meridional</span> plane of a turbomachine 1: Centrifugal compressor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vanco, M. R.</p> <p>1972-01-01</p> <p>The program will determine the velocities in the <span class="hlt">meridional</span> plane of a backward-swept impeller, a radial impeller, and a vaned diffuser. The velocity gradient equation with the assumption of a hub-to-shroud mean stream surface is solved along arbitrary quasi-orthogonals in the <span class="hlt">meridional</span> plane. These quasi-orthogonals are fixed straight lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611896H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611896H"><span>When did Mediterranean Outflow Water begin to <span class="hlt">circulate</span> into the North Atlantic?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hernández Molina, Francisco Javier; Stow, Dorrik A. V.; Zarikian, Carlos</p> <p>2014-05-01</p> <p>The southwestern Iberian margin records critical evidence of Mediterranean Outflow Water (MOW) following its exit through the Strait of Gibraltar. Data collected during Integrated Ocean Drilling Program (IODP) Expedition 339 provide new constraints on MOW <span class="hlt">circulation</span> patterns from Pliocene to present time, which indicate an alternative sequence of events in the establishment of global ocean <span class="hlt">circulation</span> patterns. Following the opening of the Strait of Gibraltar (5.46 Ma), a limited volume of weak MOW entered the Atlantic at about 4.5- 4.2 Ma. Two depositional hiatuses evident at 3.2-3.0 Ma and 2.4-2.1 Ma indicate that significant MOW <span class="hlt">circulation</span> into the North Atlantic did not occur until the Late Pliocene and early Pleistocene. These hiatuses accompany other changes in sedimentary processes. A younger event at 0.9-0.7 Ma suggests additional Pleistocene phase of MOW intensification. These events are coeval with global changes in deep-water sedimentation associated with shifts in global thermohaline <span class="hlt">circulation</span> (THC). The events evident from sediment cores and seismic records interpreted here suggest that MOW provided an important, additional component of warm, saline waters to northern latitudes, thus enhancing Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC). Similar changes have been globally described, suggesting a link between climatic shifts, THC and plate tectonic events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22364108-global-helioseismic-evidence-deeply-penetrating-solar-meridional-flow-consisting-multiple-flow-cells','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22364108-global-helioseismic-evidence-deeply-penetrating-solar-meridional-flow-consisting-multiple-flow-cells"><span>GLOBAL HELIOSEISMIC EVIDENCE FOR A DEEPLY PENETRATING SOLAR <span class="hlt">MERIDIONAL</span> FLOW CONSISTING OF MULTIPLE FLOW CELLS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Schad, A.; Roth, M.; Timmer, J., E-mail: ariane.schad@kis.uni-freiburg.de</p> <p>2013-12-01</p> <p>We use a novel global helioseismic analysis method to infer the <span class="hlt">meridional</span> flow in the deep Solar interior. The method is based on the perturbation of eigenfunctions of Solar p modes due to <span class="hlt">meridional</span> flow. We apply this method to time series obtained from Dopplergrams measured by the Michelson Doppler Imager aboard the Solar and Heliospheric Observatory covering the observation period 2004-2010. Our results show evidence that the <span class="hlt">meridional</span> flow reaches down to the base of the convection zone. The flow profile has a complex spatial structure consisting of multiple flow cells distributed in depth and latitude. Toward the Solarmore » surface, our results are in good agreement with flow measurements from local helioseismology.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1290364-meridional-dipole-premonsoon-bay-bengal-tropical-cyclone-activity-induced-enso-tropical-cyclones-monsoon-enso','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1290364-meridional-dipole-premonsoon-bay-bengal-tropical-cyclone-activity-induced-enso-tropical-cyclones-monsoon-enso"><span>A <span class="hlt">meridional</span> dipole in premonsoon Bay of Bengal tropical cyclone activity induced by ENSO: TROPICAL CYCLONES, MONSOON AND ENSO</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Balaguru, Karthik; Leung, L. Ruby; Lu, Jian</p> <p>2016-06-27</p> <p>Analysis of Bay of Bengal tropical cyclone (TC) track data for the month of May during 1980-2013 reveals a <span class="hlt">meridional</span> dipole in TC intensification: TC intensification rates increased in the northern Bay and decreased in the southern Bay. The dipole was driven by an increase in low-level vorticity and atmospheric humidity in the northern Bay, making the environment more favorable for TC intensification, and enhanced vertical wind shear in the southern Bay, tending to reduce TC development. These environmental changes were associated with a strengthening of the monsoon <span class="hlt">circulation</span> for the month of May, driven by a La Nin˜a-like shiftmore » in tropical Pacific SSTs andassociated tropical wave dynamics. Analysis of a suite of climate models fromthe CMIP5 archive for the 150-year historical period shows that most models correctly reproduce the link between ENSO and Bay of Bengal TC activity through the monsoon at interannual timescales. Under the RCP 8.5 scenario the same CMIP5 models produce an El Nin˜o like warming trend in the equatorial Pacific, tending to weaken the monsoon <span class="hlt">circulation</span>. These results suggest« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PCE....35..469P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PCE....35..469P"><span><span class="hlt">Circulation</span> <span class="hlt">types</span> related to lightning activity over Catalonia and the Principality of Andorra</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pineda, N.; Esteban, P.; Trapero, L.; Soler, X.; Beck, C.</p> <p></p> <p>In the present study, we use a Principal Component Analysis (PCA) to characterize the surface 6-h <span class="hlt">circulation</span> <span class="hlt">types</span> related to substantial lightning activity over the Catalonia area (north-eastern Iberia) and the Principality of Andorra (eastern Pyrenees) from January 2003 to December 2007. The gridded data used for classification of the <span class="hlt">circulation</span> <span class="hlt">types</span> is the NCEP Final Analyses of the Global Tropospheric Analyses at 1° resolution over the region 35°N-48°N by 5°W-8°E. Lightning information was collected by the SAFIR lightning detection system operated by the Meteorological Service of Catalonia (SMC), which covers the region studied. We determined nine <span class="hlt">circulation</span> <span class="hlt">types</span> on the basis of the S-mode orthogonal rotated Principal Component Analysis. The “extreme scores” principle was used previous to the assignation of all cases, to obtain the number of final <span class="hlt">types</span> and their centroids. The distinct differences identified in the resulting mean Sea Level Pressure (SLP) fields enabled us to group the <span class="hlt">types</span> into three main patterns, taking into account their scale/dynamical origin. The first group of <span class="hlt">types</span> shows the different distribution of the centres of action at synoptic scale associated with the occurrence of lightning. The second group is connected to mesoscale dynamics, mainly induced by the relief of the Pyrenees. The third group shows <span class="hlt">types</span> with low gradient SLP patterns in which the lightning activity is a consequence of thermal dynamics (coastal and mountain breezes). Apart from reinforcing the consistency of the groups obtained, analysis of the resulting classification improves our understanding of the geographical distribution and genesis factors of thunderstorm activity in the study area, and provides complementary information for supporting weather forecasting. Thus, the catalogue obtained will provide advances in different climatological and meteorological applications, such as nowcasting products or detection of climate change trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2255365S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2255365S"><span>Automated Quantitative Spectral Classification of Stars in Areas of the main <span class="hlt">Meridional</span> Section of the Galaxy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shvelidze, Teimuraz; Malyuto, Valeri</p> <p>2015-08-01</p> <p>Quantitative spectral classification of F, G and K stars with the 70-cm telescope of the Ambastumani Astrophysical Observatory in areas of the main <span class="hlt">meridional</span> section of the Galaxy, and for which proper motion data are available, has been performed. Fundamental parameters have been obtained for several hundred stars. Space densities of stars of different spectral <span class="hlt">types</span>, the stellar luminosity function and the relationships between the kinematics and metallicity of stars have been studied. The results have confirmed and completed the conclusions made on the basis of some previous spectroscopic and photometric surveys. Many plates have been obtained for other important directions in the sky: the Kapteyn areas, the Galactic anticentre, the main <span class="hlt">meridional</span> section of the Galaxy and etc. Very rich collection of photographic objective spectral plates (30,000 were accumulated during last 60 years) is available at Abastumani Observatory-wavelength range 3900-4900 A, about 2A resolution. Availability of new devices for automatic registration of spectra from photographic plates as well as some recently developed classification techniques may allow now to create a modern system of automatic spectral classification and with expension of classification techniques to additional <span class="hlt">types</span> (B-A, M spectral classes). The data can be treated with the same quantitative method applied here. This method may also be applied to other available and future spectroscopic data of similar resolution, notably that obtained with large format CCD detectors on Schmidt-<span class="hlt">type</span> telescopes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27365315','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27365315"><span>North Atlantic ocean <span class="hlt">circulation</span> and abrupt climate change during the last glaciation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D</p> <p>2016-07-29</p> <p>The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic <span class="hlt">meridional</span> heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean <span class="hlt">circulation</span> proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning <span class="hlt">circulation</span> during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. Copyright © 2016, American Association for the Advancement of Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49..869F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49..869F"><span>Enhancement of the southward return flow of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> by data assimilation and its influence in an assimilative ocean simulation forced by CORE-II atmospheric forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujii, Yosuke; Tsujino, Hiroyuki; Toyoda, Takahiro; Nakano, Hideyuki</p> <p>2017-08-01</p> <p>This paper examines the difference in the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) mean state between free and assimilative simulations of a common ocean model using a common interannual atmospheric forcing. In the assimilative simulation, the reproduction of cold cores in the Nordic Seas, which is absent in the free simulation, enhances the overflow to the North Atlantic and improves AMOC with enhanced transport of the deeper part of the southward return flow. This improvement also induces an enhanced supply of North Atlantic Deep Water (NADW) and causes better representation of the Atlantic deep layer despite the fact that correction by the data assimilation is applied only to temperature and salinity above a depth of 1750 m. It also affects Circumpolar Deep Water in the Southern Ocean. Although the earliest influence of the improvement propagated by coastal waves reaches the Southern Ocean in 10-15 years, substantial influence associated with the arrival of the renewed NADW propagates across the Atlantic Basin in several decades. Although the result demonstrates that data assimilation is able to improve the deep ocean state even if there is no data there, it also indicates that long-term integration is required to reproduce variability in the deep ocean originating from variations in the upper ocean. This study thus provides insights on the reliability of AMOC and the ocean state in the Atlantic deep layer reproduced by data assimilation systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950056374&hterms=balance+general&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbalance%2Bgeneral','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950056374&hterms=balance+general&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbalance%2Bgeneral"><span>Cloud-radiative effects on implied oceanic energy transport as simulated by atmospheric general <span class="hlt">circulation</span> models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gleckler, P. J.; Randall, D. A.; Boer, G.; Colman, R.; Dix, M.; Galin, V.; Helfand, M.; Kiehl, J.; Kitoh, A.; Lau, W.</p> <p>1995-01-01</p> <p>This paper summarizes the ocean surface net energy flux simulated by fifteen atmospheric general <span class="hlt">circulation</span> models constrained by realistically-varying sea surface temperatures and sea ice as part of the Atmospheric Model Intercomparison Project. In general, the simulated energy fluxes are within the very large observational uncertainties. However, the annual mean oceanic <span class="hlt">meridional</span> heat transport that would be required to balance the simulated surface fluxes is shown to be critically sensitive to the radiative effects of clouds, to the extent that even the sign of the Southern Hemisphere ocean heat transport can be affected by the errors in simulated cloud-radiation interactions. It is suggested that improved treatment of cloud radiative effects should help in the development of coupled atmosphere-ocean general <span class="hlt">circulation</span> models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA523188','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA523188"><span>The Seasonal and Interannual Variability of the West Greenland Current System in the Labrador Sea</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2010-06-01</p> <p>Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> ”, Nature, 459 [6] P. Brandt, F. Schott, A. Funk, and C. Sena Martins (2004). “Seasonal to inter- annual...variations in the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> and its relationship with the net northward heat transport in the South Atlantic ”, Geophys...water formation, plays an important role in the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> . While the interior of the Labrador Sea, where the deepest convection</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA556185','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA556185"><span>Dynamical Evaluation of Ocean Models Using the Gulf Stream as an Example</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-02-10</p> <p>Hellerman and Rosenstein (1983) wind stress climatology and the northward upper ocean flow (14 Sv) of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> ...30 35 55N 65N Fig. 21.14 Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) streamfunction from the same four simulations as Fig. 21.11. An AMOC...typically develops a northern or southern bias. A shallow bias in the southward abyssal flow of the Atlan- tic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM41A2222H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM41A2222H"><span>Storm-Time <span class="hlt">Meridional</span> Wind Perturbations in the Equatorial Thermosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haaser, R. A.; Davidson, R.; Heelis, R. A.; Earle, G. D.; Venkatraman, S.; Klenzing, J.</p> <p>2013-12-01</p> <p>We present observations from the Coupled Ion Neutral Dynamics Investigation (CINDI) of storm-time modifications to the neutral atmosphere at equatorial latitudes near the magnetic equator at 400 km altitude during the active period near solar maximum in 2011 and 2012. Perturbations in the neutral temperature on the dayside and the nightside are consistent with observed increases in the neutral density in accord with hydrostatic equilibrium. In the evening and midnight sectors these modifications are additionally accompanied by perturbations in the <span class="hlt">meridional</span> neutral wind, which are the focus of the work. The observations are made in the southern hemisphere near the magnetic equator, usually dominated by energy inputs from the southern polar regions that produce south to north (northward) wind perturbations to accompany perturbations in the neutral density and temperature. In one exceptional case when observations are made near midnight and the north magnetic pole rotates through the midnight sector, north to south (southward) <span class="hlt">meridional</span> wind perturbations are observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22522456-atmospheric-dynamics-terrestrial-exoplanets-over-wide-range-orbital-atmospheric-parameters','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22522456-atmospheric-dynamics-terrestrial-exoplanets-over-wide-range-orbital-atmospheric-parameters"><span>ATMOSPHERIC DYNAMICS OF TERRESTRIAL EXOPLANETS OVER A WIDE RANGE OF ORBITAL AND ATMOSPHERIC PARAMETERS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Kaspi, Yohai; Showman, Adam P., E-mail: yohai.kaspi@weizmann.ac.il</p> <p></p> <p>The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric <span class="hlt">circulation</span> regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone—including transitions to Snowball-like states and runaway-greenhouse feedbacks—depend on the equator-to-pole temperature differences, patterns of relativemore » humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general <span class="hlt">circulation</span> model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric <span class="hlt">circulation</span> and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, <span class="hlt">meridional</span> heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric <span class="hlt">circulation</span>. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, <span class="hlt">Hadley</span> and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric <span class="hlt">circulation</span> influences the global climate.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA503620','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA503620"><span>Impact of GODAE Products on Nested HYCOM Simulations of the West Florida Shelf</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2009-01-20</p> <p><span class="hlt">circulation</span> and the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> . For temperature, the non-assimilative outer model had a cold...associated with the basin-scale wind-driven gyres and with the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> is incor- rectly represented. In contrast...not contain realistic LC transport variability associated with the wind-driven gyre <span class="hlt">circulation</span> and the Atlantic Meridio- nal Overturning <span class="hlt">Circulation</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMOS51B1254H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMOS51B1254H"><span>Sensible and latent heat forced divergent <span class="hlt">circulations</span> in the West African Monsoon System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hagos, S.; Zhang, C.</p> <p>2008-12-01</p> <p>Field properties of divergent <span class="hlt">circulation</span> are utilized to identify the roles of various diabatic processes in forcing moisture transport in the dynamics of the West African Monsoon and its seasonal cycle. In this analysis, the divergence field is treated as a set of point sources and is partitioned into two sub-sets corresponding to latent heat release and surface sensible heat flux at each respective point. The divergent <span class="hlt">circulation</span> associated with each set is then calculated from the Poisson's equation using Gauss-Seidel iteration. Moisture transport by each set of divergent <span class="hlt">circulation</span> is subsequently estimated. The results show different roles of the divergent <span class="hlt">circulations</span> forced by surface sensible and latent heating in the monsoon dynamics. Surface sensible heating drives a shallow <span class="hlt">meridional</span> <span class="hlt">circulation</span>, which transports moisture deep into the continent at the polar side of the monsoon rain band and thereby promotes the seasonal northward migration of monsoon precipitation during the monsoon onset season. In contrast, the <span class="hlt">circulation</span> directly associated with latent heating is deep and the corresponding moisture convergence is within the region of precipitation. Latent heating also induces dry air advection from the north. Neither effect promotes the seasonal northward migration of precipitation. The relative contributions of the processes associated with latent and sensible heating to the net moisture convergence, and hence the seasonal evolution of monsoon precipitation, depend on the background moisture.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22357213-meridional-flow-solar-convection-zone-measurements-from-gong-data','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22357213-meridional-flow-solar-convection-zone-measurements-from-gong-data"><span><span class="hlt">Meridional</span> flow in the solar convection zone. I. Measurements from gong data</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Kholikov, S.; Serebryanskiy, A.; Jackiewicz, J., E-mail: kholikov@noao.edu</p> <p>2014-04-01</p> <p>Large-scale plasma flows in the Sun's convection zone likely play a major role in solar dynamics on decadal timescales. In particular, quantifying <span class="hlt">meridional</span> motions is a critical ingredient for understanding the solar cycle and the transport of magnetic flux. Because the signal of such features can be quite small in deep solar layers and be buried in systematics or noise, the true <span class="hlt">meridional</span> velocity profile has remained elusive. We perform time-distance helioseismology measurements on several years worth of Global Oscillation Network Group Doppler data. A spherical harmonic decomposition technique is applied to a subset of acoustic modes to measure travel-timemore » differences to try to obtain signatures of <span class="hlt">meridional</span> flows throughout the solar convection zone. Center-to-limb systematics are taken into account in an intuitive yet ad hoc manner. Travel-time differences near the surface that are consistent with a poleward flow in each hemisphere and are similar to previous work are measured. Additionally, measurements in deep layers near the base of the convection zone suggest a possible equatorward flow, as well as partial evidence of a sign change in the travel-time differences at mid-convection zone depths. This analysis on an independent data set using different measurement techniques strengthens recent conclusions that the convection zone may have multiple 'cells' of <span class="hlt">meridional</span> flow. The results may challenge the common understanding of one large conveyor belt operating in the solar convection zone. Further work with helioseismic inversions and a careful study of systematic effects are needed before firm conclusions of these large-scale flow structures can be made.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ThApC.105..143D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ThApC.105..143D"><span>The COST733 <span class="hlt">circulation</span> <span class="hlt">type</span> classification software: an example for surface ozone concentrations in Central Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Demuzere, Matthias; Kassomenos, P.; Philipp, A.</p> <p>2011-08-01</p> <p>In the framework of the COST733 Action "Harmonisation and Applications of Weather <span class="hlt">Types</span> Classifications for European Regions" a new <span class="hlt">circulation</span> <span class="hlt">type</span> classification software (hereafter, referred to as cost733class software) is developed. The cost733class software contains a variety of (European) classification methods and is flexible towards choice of domain of interest, input variables, time step, number of <span class="hlt">circulation</span> <span class="hlt">types</span>, sequencing and (weighted) target variables. This work introduces the capabilities of the cost733class software in which the resulting <span class="hlt">circulation</span> <span class="hlt">types</span> (CTs) from various <span class="hlt">circulation</span> <span class="hlt">type</span> classifications (CTCs) are applied on observed summer surface ozone concentrations in Central Europe. Firstly, the main characteristics of the CTCs in terms of <span class="hlt">circulation</span> pattern frequencies are addressed using the baseline COST733 catalogue (cat 2.0), at present the latest product of the new cost733class software. In a second step, the probabilistic Brier skill score is used to quantify the explanatory power of all classifications in terms of the maximum 8 hourly mean ozone concentrations exceeding the 120-μg/m3 threshold; this was based on ozone concentrations from 130 Central European measurement stations. Averaged evaluation results over all stations indicate generally higher performance of CTCs with a higher number of <span class="hlt">types</span>. Within the subset of methodologies with a similar number of <span class="hlt">types</span>, the results suggest that the use of CTCs based on optimisation algorithms are performing slightly better than those which are based on other algorithms (predefined thresholds, principal component analysis and leader algorithms). The results are further elaborated by exploring additional capabilities of the cost733class software. Sensitivity experiments are performed using different domain sizes, input variables, seasonally based classifications and multiple-day sequencing. As an illustration, CTCs which are also conditioned towards temperature with various weights</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21576610-unified-approach-helioseismic-inversion-problem-solar-meridional-flow-from-global-oscillations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21576610-unified-approach-helioseismic-inversion-problem-solar-meridional-flow-from-global-oscillations"><span>A UNIFIED APPROACH TO THE HELIOSEISMIC INVERSION PROBLEM OF THE SOLAR <span class="hlt">MERIDIONAL</span> FLOW FROM GLOBAL OSCILLATIONS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Schad, A.; Timmer, J.; Roth, M.</p> <p>2011-06-20</p> <p>Measurements from tracers and local helioseismology indicate the existence of a <span class="hlt">meridional</span> flow in the Sun with strength in the order of 15 m s{sup -1} near the solar surface. Different attempts were made to obtain information on the flow profile at depths up to 20 Mm below the solar surface. We propose a method using global helioseismic Doppler measurements with the prospect of inferring the <span class="hlt">meridional</span> flow profile at greater depths. Our approach is based on the perturbation of the p-mode eigenfunctions of a solar model due to the presence of a flow. The distortion of the oscillation eigenfunctionsmore » is manifested in the mixing of p-modes, which may be measured from global solar oscillation time series. As a new helioseismic measurement quantity, we propose amplitude ratios between oscillations in the Fourier domain. We relate this quantity to the <span class="hlt">meridional</span> flow and unify the concepts presented here for an inversion procedure to infer the <span class="hlt">meridional</span> flow from global solar oscillations.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...860...48L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...860...48L"><span>Solar-cycle Variations of <span class="hlt">Meridional</span> Flows in the Solar Convection Zone Using Helioseismic Methods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Chia-Hsien; Chou, Dean-Yi</p> <p>2018-06-01</p> <p>The solar <span class="hlt">meridional</span> flow is an axisymmetric flow in solar <span class="hlt">meridional</span> planes, extending through the convection zone. Here we study its solar-cycle variations in the convection zone using SOHO/MDI helioseismic data from 1996 to 2010, including two solar minima and one maximum. The travel-time difference between northward and southward acoustic waves is related to the <span class="hlt">meridional</span> flow along the wave path. Applying the ray approximation and the SOLA inversion method to the travel-time difference measured in a previous study, we obtain the <span class="hlt">meridional</span> flow distributions in 0.67 ≤ r ≤ 0.96R ⊙ at the minimum and maximum. At the minimum, the flow has a three-layer structure: poleward in the upper convection zone, equatorward in the middle convection zone, and poleward again in the lower convection zone. The flow speed is close to zero within the error bar near the base of the convection zone. The flow distribution changes significantly from the minimum to the maximum. The change above 0.9R ⊙ shows two phenomena: first, the poleward flow speed is reduced at the maximum; second, an additional convergent flow centered at the active latitudes is generated at the maximum. These two phenomena are consistent with the surface <span class="hlt">meridional</span> flow reported in previous studies. The change in flow extends all the way down to the base of the convection zone, and the pattern of the change below 0.9R ⊙ is more complicated. However, it is clear that the active latitudes play a role in the flow change: the changes in flow speed below and above the active latitudes have opposite signs. This suggests that magnetic fields could be responsible for the flow change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140002611','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140002611"><span><span class="hlt">Meridional</span> Flow Variations in Cycles 23 and 24: Active Latitude Control of Sunspot Cycle Amplitudes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hathaway, David H.; Upton, Lisa</p> <p>2013-01-01</p> <p>We have measured the <span class="hlt">meridional</span> motions of magnetic elements observed in the photosphere over sunspot cycles 23 and 24 using magnetograms from SOHO/MDI and SDO/HMI. Our measurements confirm the finding of Komm, Howard, and Harvey (1993) that the poleward <span class="hlt">meridional</span> flow weakens at cycle maxima. Our high spatial and temporal resolution analyses show that this variation is in the form of a superimposed inflow toward the active latitudes. This inflow is weaker in cycle 24 when compared to the inflow in 23, the stronger cycle. This systematic modulation of the <span class="hlt">meridional</span> flow should also modulate the amplitude of the following sunspot cycle through its influence on the Sun's polar fields. The observational evidence and the theoretical consequences (similar to those of Cameron and Schussler (2012)) will be described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...34E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...34E"><span>The role of Amundsen-Bellingshausen Sea anticyclonic <span class="hlt">circulation</span> in forcing marine air intrusions into West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Emanuelsson, B. Daniel; Bertler, Nancy A. N.; Neff, Peter D.; Renwick, James A.; Markle, Bradley R.; Baisden, W. Troy; Keller, Elizabeth D.</p> <p>2018-01-01</p> <p>Persistent positive 500-hPa geopotential height anomalies from the ECMWF ERA-Interim reanalysis are used to quantify Amundsen-Bellingshausen Sea (ABS) anticyclonic event occurrences associated with precipitation in West Antarctica (WA). We demonstrate that multi-day (minimum 3-day duration) anticyclones play a key role in the ABS by dynamically inducing <span class="hlt">meridional</span> transport, which is associated with heat and moisture advection into WA. This affects surface climate variability and trends, precipitation rates and thus WA ice sheet surface mass balance. We show that the snow accumulation record from the Roosevelt Island Climate Evolution (RICE) ice core reflects interannual variability of blocking and geopotential height conditions in the ABS/Ross Sea region. Furthermore, our analysis shows that larger precipitation events are related to enhanced anticyclonic <span class="hlt">circulation</span> and <span class="hlt">meridional</span> winds, which cause pronounced dipole patterns in air temperature anomalies and sea ice concentrations between the eastern Ross Sea and the Bellingshausen Sea/Weddell Sea, as well as between the eastern and western Ross Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..4410560S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..4410560S"><span>Multidecadal Weakening of Indian Summer Monsoon <span class="hlt">Circulation</span> Induces an Increasing Northern Indian Ocean Sea Level</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swapna, P.; Jyoti, J.; Krishnan, R.; Sandeep, N.; Griffies, S. M.</p> <p>2017-10-01</p> <p>North Indian Ocean sea level has shown significant increase during last three to four decades. Analyses of long-term climate data sets and ocean model sensitivity experiments identify a mechanism for multidecadal sea level variability relative to global mean. Our results indicate that North Indian Ocean sea level rise is accompanied by a weakening summer monsoon <span class="hlt">circulation</span>. Given that Indian Ocean <span class="hlt">meridional</span> heat transport is primarily regulated by the annual cycle of monsoon winds, weakening of summer monsoon <span class="hlt">circulation</span> has resulted in reduced upwelling off Arabia and Somalia and decreased southward heat transport, and corresponding increase of heat storage in the North Indian Ocean. These changes in turn lead to increased retention of heat and increased thermosteric sea level rise in the North Indian Ocean, especially in the Arabian Sea. These findings imply that rising North Indian Ocean sea level due to weakening of monsoon <span class="hlt">circulation</span> demands adaptive strategies to enable a resilient South Asian population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.tmp...83S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.tmp...83S"><span>Organized convection over southwest peninsular India during the pre-monsoon season</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sreelekha, P. N.; Babu, C. A.</p> <p>2018-03-01</p> <p>The paper addresses observational aspects of widespread rain associated with the organized convection that forms over the southwest peninsular India during the pre-monsoon season. The evolution of the cloud band over the equatorial region, its northward propagation, development of cross equatorial flow near the Somalia coast, and appearance of equatorial westerly wind resemble closely to that of the monsoon organized convection. Low-level convergence, cyclonic vorticity, and ascending motion are other major characteristics of the cloud bands associated with the pre-monsoon organized convection which exhibits similarity with that of monsoon. The ascending motion plays vital role on the formation of cloud band that produces widespread rainfall persisting for more than a week. The vertical shear of <span class="hlt">meridional</span> winds is found to co-exist with precipitation over the Arabian Sea off the southwest peninsular India. The velocity potential values derived from the winds at 850 and 200 hPa levels confirm the rising motion on the basis of low-level convergence and upper level divergence. Also, shifting of ascending limb of the local <span class="hlt">Hadley</span> <span class="hlt">circulation</span> to the north of the equator is observed during the days of the presence of organized convection over the southwest peninsular region. Noticeable shift in the Walker <span class="hlt">circulation</span> rising limb is also identified during the same time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/879599','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/879599"><span>One-Piece Battery Incorporating A <span class="hlt">Circulating</span> Fluid <span class="hlt">Type</span> Heat Exchanger</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Verhoog, Roelof</p> <p>2001-10-02</p> <p>A one-piece battery comprises a tank divided into cells each receiving an electrode assembly, closure means for the tank and a <span class="hlt">circulating</span> fluid <span class="hlt">type</span> heat exchanger facing the relatively larger faces of the electrode assembly. The fluid flows in a compartment defined by two flanges which incorporate a fluid inlet orifice communicating with a common inlet manifold and a fluid outlet orifice communicating with a common outlet manifold. The tank comprises at least two units and each unit comprises at least one cell delimited by walls. The wall facing a relatively larger face of the electrode assembly constitutes one of the flanges. Each unit further incorporates a portion of an inlet and outlet manifold. The units are fastened together so that the flanges when placed face-to-face form a sealed <span class="hlt">circulation</span> compartment and the portions of the same manifold are aligned with each other.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950046311&hterms=climate+change+rainfall&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dclimate%2Bchange%2Brainfall','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950046311&hterms=climate+change+rainfall&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dclimate%2Bchange%2Brainfall"><span>The influence of tropical heating displacements on the extratropical climate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hou, Arthur Y.</p> <p>1993-01-01</p> <p>The hypothesis is advanced that a latitudinal shift in the tropical convective heating pattern can significantly alter temperatures in the extratropics. Results of a simplified general <span class="hlt">circulation</span> model (GCM) show that the shift of a prescribed tropical heating toward the summer pole, on time scales longer than a few weeks, leads to a more intense cross-equatorial 'winter' <span class="hlt">Hadley</span> <span class="hlt">circulation</span>, enhanced upper-level tropical easterlies, and a slightly stronger subtropical winter jet, accompanied by warming at the winter middle and high latitudes as a result of increased dynamical heating. The indications are that there is a robust connection between the net dynamic heating in the extratropics and the implied changes in the subtropical wind shear resulting from adjustments in the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> associated with convective heating displacements in the tropics. The implications are that (1) the low-frequency temporal variability in the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> may play an important role in modulating wave transport in the winter extratropics, (2) the global climate may be sensitive to those processes that control deep cumulus convection in the tropics, and (3) systematic temperature biases in GCMs may be reduced by improving the tropical rainfall simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APJAS..53..243A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APJAS..53..243A"><span>Baseline predictability of daily east Asian summer monsoon <span class="hlt">circulation</span> indices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ai, Shucong; Chen, Quanliang; Li, Jianping; Ding, Ruiqiang; Zhong, Quanjia</p> <p>2017-05-01</p> <p>The nonlinear local Lyapunov exponent (NLLE) method is adopted to quantitatively determine the predictability limit of East Asian summer monsoon (EASM) intensity indices on a synoptic timescale. The predictability limit of EASM indices varies widely according to the definitions of indices. EASM indices defined by zonal shear have a limit of around 7 days, which is higher than the predictability limit of EASM indices defined by sea level pressure (SLP) difference and <span class="hlt">meridional</span> wind shear (about 5 days). The initial error of EASM indices defined by SLP difference and <span class="hlt">meridional</span> wind shear shows a faster growth than indices defined by zonal wind shear. Furthermore, the indices defined by zonal wind shear appear to fluctuate at lower frequencies, whereas the indices defined by SLP difference and <span class="hlt">meridional</span> wind shear generally fluctuate at higher frequencies. This result may explain why the daily variability of the EASM indices defined by zonal wind shear tends be more predictable than those defined by SLP difference and <span class="hlt">meridional</span> wind shear. Analysis of the temporal correlation coefficient (TCC) skill for EASM indices obtained from observations and from NCEP's Global Ensemble Forecasting System (GEFS) historical weather forecast dataset shows that GEFS has a higher forecast skill for the EASM indices defined by zonal wind shear than for indices defined by SLP difference and <span class="hlt">meridional</span> wind shear. The predictability limit estimated by the NLLE method is shorter than that in GEFS. In addition, the June-September average TCC skill for different daily EASM indices shows significant interannual variations from 1985 to 2015 in GEFS. However, the TCC for different <span class="hlt">types</span> of EASM indices does not show coherent interannual fluctuations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917314E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917314E"><span>Effect of gravity waves on the North Atlantic <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eden, Carsten</p> <p>2017-04-01</p> <p>The recently proposed IDEMIX (Internal wave Dissipation, Energy and MIXing) parameterisation for the effect of gravity waves offers the possibility to construct consistent ocean models with a closed energy cycle. This means that the energy available for interior mixing in the ocean is only controlled by external energy input from the atmosphere and the tidal system and by internal exchanges. A central difficulty is the unknown fate of meso-scale eddy energy. In different scenarios for that eddy dissipation, the parameterized internal wave field provides between 2 and 3 TW for interior mixing from the total external energy input of about 4 TW, such that a transfer between 0.3 and 0.4 TW into mean potential energy contributes to drive the large-scale <span class="hlt">circulation</span> in the model. The impact of the different mixing on the <span class="hlt">meridional</span> overturning in the North Atlantic is discussed and compared to hydrographic observations. Furthermore, the direct energy exchange of the wave field with the geostrophic flow is parameterized in extended IDEMIX versions and the sensitivity of the North Atlantic <span class="hlt">circulation</span> by this gravity wave drag is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004ApJ...602..543H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004ApJ...602..543H"><span>Erratum: ``Evidence that a Deep <span class="hlt">Meridional</span> Flow Sets the Sunspot Cycle Period'' (ApJ, 589, 665 [2003])</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hathaway, David H.; Nandy, Dibyendu; Wilson, Robert M.; Reichmann, Edwin J.</p> <p>2004-02-01</p> <p>An error was made in entering the data used in Figure 6. This changes the results concerning the length of the time lag between the variations in the <span class="hlt">meridional</span> flow speed and those in the cycle amplitude. The final paragraph on page 667 should read: ``Finally, we study the relationship between the drift velocities and the amplitudes of the hemisphere/cycles. In Figure 5 we compare the drift velocity at the maximum of the cycle to the amplitude of that cycle for that hemisphere. There is a positive (0.5) and significant (95%) correlation between the two. However, an even stronger relationship is found between the drift velocity and the amplitude of the N+2 cycle. The correlation is stronger (0.7) and more significant (99%), as shown in Figure 6. This relationship is suggestive of a ``memory'' in the solar cycle, again a property of dynamo models that use <span class="hlt">meridional</span> <span class="hlt">circulation</span>. Indeed, the two-cycle lag is precisely the relationship found by Charbonneau & Dikpati (ApJ, 589, 665 [2003]). This behavior is, however, more difficult to interpret, and we elaborate on this in the next section. In either case, these correlations only explain part of the variance in cycle amplitude (25% for the current cycle and 50% for the N+2 cycle). Obviously, other mechanisms, such as variations in the gradient in the rotation rate, also contribute to the cycle amplitude variations. Our investigation of possible connections between drift rates and the amplitudes of the N+1 and N+3 cycles gives no significant correlations at these alternative time lags.'' The revised Figure 6 and its caption are given below</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.2413S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.2413S"><span>Does Southern Ocean Surface Forcing Shape the Global Ocean Overturning <span class="hlt">Circulation</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Shantong; Eisenman, Ian; Stewart, Andrew L.</p> <p>2018-03-01</p> <p>Paleoclimate proxy data suggest that the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) was shallower at the Last Glacial Maximum (LGM) than its preindustrial (PI) depth. Previous studies have suggested that this shoaling necessarily accompanies Antarctic sea ice expansion at the LGM. Here the influence of Southern Ocean surface forcing on the AMOC depth is investigated using ocean-only simulations from a state-of-the-art climate model with surface forcing specified from the output of previous coupled PI and LGM simulations. In contrast to previous expectations, we find that applying LGM surface forcing in the Southern Ocean and PI surface forcing elsewhere causes the AMOC to shoal only about half as much as when LGM surface forcing is applied globally. We show that this occurs because diapycnal mixing renders the Southern Ocean overturning <span class="hlt">circulation</span> more diabatic than previously assumed, which diminishes the influence of Southern Ocean surface buoyancy forcing on the depth of the AMOC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2413C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2413C"><span><span class="hlt">Circulation</span> responses to regional aerosol climate forcing in summer over East Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Guoxing; Wang, Wei-Chyung; Chen, Jen-Ping</p> <p>2018-05-01</p> <p>For East Asia, <span class="hlt">circulation</span> responses to anthropogenic aerosol radiative forcing dominate aerosol-precipitation interactions. To gain insights, this study analyzed CESM simulated <span class="hlt">circulation</span> changes related to the `north drought and south flood' pattern caused by aerosol increases between two cases. One case was driven by the year-1850 global emission inventory, whereas the other used identical emissions for all regions except East Asia where anthropogenic emissions of aerosols and precursors of the year-2000 were imposed. Results show that the cooling caused by increased aerosols, which peaks at the middle latitudes, induces two intervened anomalous <span class="hlt">circulations</span> in the troposphere. Near the surface, the increased land pressure weakens the southerlies and reduces the moisture transport for the entire eastern China. Meanwhile, in the free troposphere, the anomalous <span class="hlt">circulation</span> exhibits remarkable <span class="hlt">meridional</span> variations. While convergence occurs over 25°-45°N which partially compensates the decrease of moisture transport from lower levels, divergence develops over regions to the north which enhances the moisture deficiency. In addition, the southward shift of the jet stream stimulates anomalous rising and sinking motions over the south and north of 32°N. The combination of these changes leads to precipitation increase in the Yangtze River Valley but decrease over North China.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeCoA.204..286B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeCoA.204..286B"><span>Barium isotopes reveal role of ocean <span class="hlt">circulation</span> on barium cycling in the Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bates, Stephanie L.; Hendry, Katharine R.; Pryer, Helena V.; Kinsley, Christopher W.; Pyle, Kimberley M.; Woodward, E. Malcolm S.; Horner, Tristan J.</p> <p>2017-05-01</p> <p>We diagnose the relative influences of local-scale biogeochemical cycling and regional-scale ocean <span class="hlt">circulation</span> on Atlantic barium cycling by analysing four new depth profiles of dissolved Ba concentrations and isotope compositions from the South and tropical North Atlantic. These new profiles exhibit systematic vertical, zonal and <span class="hlt">meridional</span> variations that reflect the influence of both local-scale barite cycling and large-scale ocean <span class="hlt">circulation</span>. Epipelagic decoupling of dissolved Ba and Si reported previously in the tropics is also found to be associated with significant Ba isotope heterogeneity. As such, we contend that this decoupling originates from the depth segregation of opal and barite formation but is exacerbated by weak vertical mixing. Zonal influence from isotopically-'heavy' water masses in the western North Atlantic evidence the advective inflow of Ba-depleted Upper Labrador Sea Water, which is not seen in the eastern basin or the South Atlantic. <span class="hlt">Meridional</span> variations in Atlantic Ba isotope systematics below 2000 m appear entirely controlled by conservative mixing. Using an inverse isotopic mixing model, we calculate the Ba isotope composition of the Ba-poor northern end-member as +0.45 ‰ and the Ba-rich southern end-member +0.26 ‰, relative to NIST SRM 3104a. The near-conservative behaviour of Ba below 2000 m indicates that Ba isotopes can serve as an independent tracer of the provenance of northern- versus southern-sourced water masses in the deep Atlantic Ocean. This finding may prove useful in palaeoceanographic studies, should appropriate sedimentary archives be identified, and offers new insights into the processes that cycle Ba in seawater.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA553616','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA553616"><span>Impact of Data Assimilation And Resolution On Modeling The Gulf Stream Pathway</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2011-11-18</p> <p>currents could be generated by either the Deep Western Boundary Current (DWBC) associated with the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC) or by...abyssal gyre centered directly beneath the surface gyre. Figure 7. <span class="hlt">Meridional</span> overturning <span class="hlt">circulation</span> stream function for four 1/12° global HYCOM... <span class="hlt">circulation</span> and have a weak overturning <span class="hlt">circulation</span> . The Gulf Stream path is poorly simulated without the steering by the abyssal <span class="hlt">circulation</span> . A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17051216','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17051216"><span>Eastern Pacific cooling and Atlantic overturning <span class="hlt">circulation</span> during the last deglaciation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kienast, Markus; Kienast, Stephanie S; Calvert, Stephen E; Eglinton, Timothy I; Mollenhauer, Gesine; François, Roger; Mix, Alan C</p> <p>2006-10-19</p> <p>Surface ocean conditions in the equatorial Pacific Ocean could hold the clue to whether millennial-scale global climate change during glacial times was initiated through tropical ocean-atmosphere feedbacks or by changes in the Atlantic thermohaline <span class="hlt">circulation</span>. North Atlantic cold periods during Heinrich events and millennial-scale cold events (stadials) have been linked with climatic changes in the tropical Atlantic Ocean and South America, as well as the Indian and East Asian monsoon systems, but not with tropical Pacific sea surface temperatures. Here we present a high-resolution record of sea surface temperatures in the eastern tropical Pacific derived from alkenone unsaturation measurements. Our data show a temperature drop of approximately 1 degrees C, synchronous (within dating uncertainties) with the shutdown of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during Heinrich event 1, and a smaller temperature drop of approximately 0.5 degrees C synchronous with the smaller reduction in the overturning <span class="hlt">circulation</span> during the Younger Dryas event. Both cold events coincide with maxima in surface ocean productivity as inferred from 230Th-normalized carbon burial fluxes, suggesting increased upwelling at the time. From the concurrence of equatorial Pacific cooling with the two North Atlantic cold periods during deglaciation, we conclude that these millennial-scale climate changes were probably driven by a reorganization of the oceans' thermohaline <span class="hlt">circulation</span>, although possibly amplified by tropical ocean-atmosphere interaction as suggested before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910031763&hterms=climate+facts&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dclimate%2Bfacts','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910031763&hterms=climate+facts&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dclimate%2Bfacts"><span>On the limitations of General <span class="hlt">Circulation</span> Climate Models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stone, Peter H.; Risbey, James S.</p> <p>1990-01-01</p> <p>General <span class="hlt">Circulation</span> Models (GCMs) by definition calculate large-scale dynamical and thermodynamical processes and their associated feedbacks from first principles. This aspect of GCMs is widely believed to give them an advantage in simulating global scale climate changes as compared to simpler models which do not calculate the large-scale processes from first principles. However, it is pointed out that the <span class="hlt">meridional</span> transports of heat simulated GCMs used in climate change experiments differ from observational analyses and from other GCMs by as much as a factor of two. It is also demonstrated that GCM simulations of the large scale transports of heat are sensitive to the (uncertain) subgrid scale parameterizations. This leads to the question whether current GCMs are in fact superior to simpler models for simulating temperature changes associated with global scale climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8963P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8963P"><span>Walker <span class="hlt">circulation</span> in a transient climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plesca, Elina; Grützun, Verena; Buehler, Stefan A.</p> <p>2016-04-01</p> <p>The tropical overturning <span class="hlt">circulations</span> modulate the heat exchange across the tropics and between the tropics and the poles. The anthropogenic influence on the climate system will affect these <span class="hlt">circulations</span>, impacting the dynamics of the Earth system. In this work we focus on the Walker <span class="hlt">circulation</span>. We investigate its temporal and spatial dynamical changes and their link to other climate features, such as surface and sea-surface temperature patterns, El-Niño Southern Oscillation (ENSO), and ocean heat-uptake, both at global and regional scale. In order to determine the impact of anthropogenic climate change on the tropical <span class="hlt">circulation</span>, we analyze the outputs of 28 general <span class="hlt">circulation</span> models (GCMs) from the CMIP5 project. We use the experiment with 1% year-1 increase in CO2 concentration from pre-industrial levels to quadrupling of the concentration. Consistent with previous studies (ex. Ma and Xie 2013), we find that for this experiment most GCMs associate a weakening Walker <span class="hlt">circulation</span> to a warming transient climate. Due to the role of the Walker Pacific cell in the <span class="hlt">meridional</span> heat and moisture transport across the tropical Pacific and also the connection to ENSO, we find that a weakened Walker <span class="hlt">circulation</span> correlates with more extreme El-Niño events, although without a change in their frequency. The spatial analysis of the Pacific Walker cell suggests an eastward displacement of the ascending branch, which is consistent with positive SST anomalies over the tropical Pacific and the link of the Pacific Walker cell to ENSO. Recent studies (ex. England et al. 2014) have linked a strengthened Walker <span class="hlt">circulation</span> to stronger ocean heat uptake, especially in the western Pacific. The inter-model comparison of the correlation between Walker <span class="hlt">circulation</span> intensity and ocean heat uptake does not convey a robust response for the investigated experiment. However, there is some evidence that a stronger weakening of the Walker <span class="hlt">circulation</span> is linked to a higher transient climate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150023450','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150023450"><span>The Coupled Mars Dust and Water Cycles: Understanding How Clouds Affect the Vertical Distribution and <span class="hlt">Meridional</span> Transport of Dust and Water.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kahre, M. A.</p> <p>2015-01-01</p> <p>The dust and water cycles are crucial to the current Martian climate, and they are coupled through cloud formation. Dust strongly impacts the thermal structure of the atmosphere and thus greatly affects atmospheric <span class="hlt">circulation</span>, while clouds provide radiative forcing and control the hemispheric exchange of water through the modification of the vertical distributions of water and dust. Recent improvements in the quality and sophistication of both observations and climate models allow for a more comprehensive understanding of how the interaction between the dust and water cycles (through cloud formation) affects the dust and water cycles individually. We focus here on the effects of clouds on the vertical distribution of dust and water, and how those vertical distributions control the net <span class="hlt">meridional</span> transport of water. For this study, we utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) combined with the NASA ARC Mars Global Climate Model (MGCM). We demonstrate that the magnitude and nature of the net <span class="hlt">meridional</span> transport of water between the northern and southern hemispheres during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. We further examine how clouds influence the atmospheric thermal structure and thus the vertical structure of the cloud belt. Our goal is to identify and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70020984','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70020984"><span>Estimates of runoff using water-balance and atmospheric general <span class="hlt">circulation</span> models</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wolock, D.M.; McCabe, G.J.</p> <p>1999-01-01</p> <p>The effects of potential climate change on mean annual runoff in the conterminous United States (U.S.) are examined using a simple water-balance model and output from two atmospheric general <span class="hlt">circulation</span> models (GCMs). The two GCMs are from the Canadian Centre for Climate Prediction and Analysis (CCC) and the <span class="hlt">Hadley</span> Centre for Climate Prediction and Research (HAD). In general, the CCC GCM climate results in decreases in runoff for the conterminous U.S., and the HAD GCM climate produces increases in runoff. These estimated changes in runoff primarily are the result of estimated changes in precipitation. The changes in mean annual runoff, however, mostly are smaller than the decade-to-decade variability in GCM-based mean annual runoff and errors in GCM-based runoff. The differences in simulated runoff between the two GCMs, together with decade-to-decade variability and errors in GCM-based runoff, cause the estimates of changes in runoff to be uncertain and unreliable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870053487&hterms=balance+general&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dbalance%2Bgeneral','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870053487&hterms=balance+general&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dbalance%2Bgeneral"><span>The role of earth radiation budget studies in climate and general <span class="hlt">circulation</span> research</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ramanathan, V.</p> <p>1987-01-01</p> <p>The use of earth radiation budget (ERB) data for climate and general <span class="hlt">circulation</span> research is studied. ERB measurements obtained in the 1960's and 1970's have provided data on planetary brightness, planetary global energy balances, the greenhouse effect, solar insolation, <span class="hlt">meridional</span> heat transport by oceans and atmospheres, regional forcing, climate feedback processes, and the computation of albedo values in low latitudes. The role of clouds in governing climate, in influencing the general <span class="hlt">circulation</span>, and in determining the sensitivity of climate to external perturbations needs to be researched; a procedure for analyzing the ERB data, which will address these problems, is described. The approach involves estimating the clear-sky fluxes from the high spatial resolution scanner measurement and defining a cloud radiative forcing; the global average of the sum of the solar and long-wave cloud forcing yields the net radiative effect of clouds on the climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1052920-fast-slow-responses-south-asian-monsoon-system-anthropogenic-aerosols','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1052920-fast-slow-responses-south-asian-monsoon-system-anthropogenic-aerosols"><span>Fast and Slow Responses of the South Asian Monsoon System to Anthropogenic Aerosols</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Ganguly, Dilip; Rasch, Philip J.; Wang, Hailong</p> <p>2012-09-25</p> <p>Using a global climate model with fully predictive aerosol life cycle, we investigate the fast and slow responses of the South Asian monsoon system to anthropogenic aerosol forcing. Our results show that the feedbacks associated with sea surface temperature (SST) change caused by aerosols play a more important role than the aerosol's direct impact on radiation, clouds and land surface (rapid adjustments) in shaping the total equilibrium climate response of the monsoon system to aerosol forcing. Inhomogeneous SST cooling caused by anthropogenic aerosols eventually reduces the <span class="hlt">meridional</span> tropospheric temperature gradient and the easterly shear of zonal winds over the region,more » slowing down the local <span class="hlt">Hadley</span> cell <span class="hlt">circulation</span>, decreasing the northward moisture transport, and causing a reduction in precipitation over South Asia. Although total responses in precipitation are closer to the slow responses in general, the fast component dominates over land areas north of 25°N. Our results also show an east-west asymmetry in the fast responses to anthropogenic aerosols causing increases in precipitation west of 80°E but decreases east of it.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17349887','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17349887"><span>Evidence for functional heterogeneity of <span class="hlt">circulating</span> B-<span class="hlt">type</span> natriuretic peptide.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liang, Faquan; O'Rear, Jessica; Schellenberger, Ute; Tai, Lungkuo; Lasecki, Michael; Schreiner, George F; Apple, Fred S; Maisel, Alan S; Pollitt, N Stephen; Protter, Andrew A</p> <p>2007-03-13</p> <p>These studies describe molecular forms of <span class="hlt">circulating</span> B-<span class="hlt">type</span> natriuretic peptide (BNP) as well as their biological activity. Increased <span class="hlt">circulating</span> levels of immunoreactive BNP correlate with the severity of heart failure and are considered a sensitive biomarker. However, little is known about the molecular forms of <span class="hlt">circulating</span> BNP and their biological activity. Western blot analysis was used to characterize immunoreactive BNP species in heart failure plasma. Recombinant proBNP was assessed for reactivity in commercially available BNP assays and cell activity by cyclic guanosine monophosphate production in vascular cells. Heart failure plasma contained both low- (LMW-BNP) and high-molecular-weight (HMW-BNP) forms. The LMW-BNP migrated similarly to a 32-amino acid BNP standard, whereas HMW-BNP, when deglycosylated, was similar to deglycosylated recombinant proBNP. Recombinant proBNP and BNP were equally recognized by the Triage BNP assay (Biosite, San Diego, California). Furthermore, recombinant proBNP and BNP were both recognized by the Advia Centaur BNP test (Bayer Diagnostics, Tarrytown, New York), but only recombinant proBNP was recognized by the Elecsys NTproBNP assay (Roche Diagnostics, Indianapolis, Indiana). Recombinant proBNP exerted significantly less biological activity than BNP on human endothelial and vascular smooth muscle cells. Comparison of effective concentration (50%) values indicates that proBNP is 6- to 8-fold less potent than BNP in these human cells. This study demonstrates that proBNP, constituting a substantial portion of immunoreactive BNP in heart failure plasma, possesses significantly lower biological activity than the processed 32-amino acid hormone. These results implicate a discordance in heart failure between the high <span class="hlt">circulating</span> levels of immunoreactive BNP and hormone activity, suggesting that some patients may be in a state of natriuretic peptide deficiency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.132..273W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.132..273W"><span>Variability of sea surface height and <span class="hlt">circulation</span> in the North Atlantic: Forcing mechanisms and linkages</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Zeliang; Lu, Youyu; Dupont, Frederic; W. Loder, John; Hannah, Charles; G. Wright, Daniel</p> <p>2015-03-01</p> <p>Simulations with a coarse-resolution global ocean model during 1958-2004 are analyzed to understand the inter-annual and decadal variability of the North Atlantic. Analyses of Empirical Orthogonal Functions (EOFs) suggest relationships among basin-scale variations of sea surface height (SSH) and depth-integrated <span class="hlt">circulation</span>, and the winter North Atlantic Oscillation (NAO) or the East Atlantic Pattern (EAP) indices. The linkages between the atmospheric indices and ocean variables are shown to be related to the different roles played by surface momentum and heat fluxes in driving ocean variability. In the subpolar region, variations of the gyre strength, SSH in the central Labrador Sea and the NAO index are highly correlated. Surface heat flux is important in driving variations of SSH and <span class="hlt">circulation</span> in the upper ocean and decadal variations of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC). Surface momentum flux drives a significant barotropic component of flow and makes a noticeable contribution to the AMOC. In the subtropical region, momentum flux plays a dominant role in driving variations of the gyre <span class="hlt">circulation</span> and AMOC; there is a strong correlation between gyre strength and SSH at Bermuda.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911799N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911799N"><span>Sensitivity of the ocean overturning <span class="hlt">circulation</span> to wind and mixing: theoretical scalings and global ocean models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nikurashin, Maxim; Gunn, Andrew</p> <p>2017-04-01</p> <p>The <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (MOC) is a planetary-scale oceanic flow which is of direct importance to the climate system: it transports heat <span class="hlt">meridionally</span> and regulates the exchange of CO2 with the atmosphere. The MOC is forced by wind and heat and freshwater fluxes at the surface and turbulent mixing in the ocean interior. A number of conceptual theories for the sensitivity of the MOC to changes in forcing have recently been developed and tested with idealized numerical models. However, the skill of the simple conceptual theories to describe the MOC simulated with higher complexity global models remains largely unknown. In this study, we present a systematic comparison of theoretical and modelled sensitivity of the MOC and associated deep ocean stratification to vertical mixing and southern hemisphere westerlies. The results show that theories that simplify the ocean into a single-basin, zonally-symmetric box are generally in a good agreement with a realistic, global ocean <span class="hlt">circulation</span> model. Some disagreement occurs in the abyssal ocean, where complex bottom topography is not taken into account by simple theories. Distinct regimes, where the MOC has a different sensitivity to wind or mixing, as predicted by simple theories, are also clearly shown by the global ocean model. The sensitivity of the Indo-Pacific, Atlantic, and global basins is analysed separately to validate the conceptual understanding of the upper and lower overturning cells in the theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CliPa..13..201M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CliPa..13..201M"><span>Changes in Holocene <span class="hlt">meridional</span> <span class="hlt">circulation</span> and poleward Atlantic flow: the Bay of Biscay as a nodal point</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mary, Yannick; Eynaud, Frédérique; Colin, Christophe; Rossignol, Linda; Brocheray, Sandra; Mojtahid, Meryem; Garcia, Jennifer; Peral, Marion; Howa, Hélène; Zaragosi, Sébastien; Cremer, Michel</p> <p>2017-03-01</p> <p>This paper documents the evolution over the last 10 kyr of one of the key parameters of climate: sea-surface temperatures (SSTs) in the North Atlantic. We focus on the southern Bay of Biscay, a highly sensitive oceanographic area regarding the dynamics of the North Atlantic subpolar and subtropical gyres (SPG and STG respectively). This site furthermore offers unique sedimentary environments characterized by exceptional accumulation rates, enabling the study of Holocene archives at (infra)centennial scales. Our results mainly derive from planktonic foraminiferal association analysis on two cores from the southern Landes Plateau. These associations are used as the basis of modern analogue technique transfer functions to track past hydrographical changes. SST reconstructions were thus obtained at an exceptional resolution and compared to a compilation of Holocene records from the northeastern North Atlantic. From this regional perspective are shown fundamental timing differences between the gyre dynamics, nuancing classical views of a simple <span class="hlt">meridional</span> overturning cell. Our study highlights that western Europe underwent significant oscillations of (annual) SST during the last 10 kyr. During well-known intervals of mild boreal climate, warm shifts of more than 3 °C per century are accurately concomitant with positive sea-surface temperature anomalies and rise of micropalaeontological indicators of gyre dynamics in the northern North Atlantic, pointing to periods of greater intensity of the North Atlantic Current (SPG cell especially). Conversely, the SST signal records short-term cold anomalies which could be related to weaker SPG dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...47.1497S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...47.1497S"><span>AMOC sensitivity to surface buoyancy fluxes: Stronger ocean <span class="hlt">meridional</span> heat transport with a weaker volume transport?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sévellec, Florian; Fedorov, Alexey V.</p> <p>2016-09-01</p> <p>Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). For example, in numerical "water-hosing" experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reverse on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. We discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1437164','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1437164"><span>AMOC sensitivity to surface buoyancy fluxes: Stronger ocean <span class="hlt">meridional</span> heat transport with a weaker volume transport?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Sevellec, Florian; Fedorov, Alexey V.</p> <p></p> <p>Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). For example, in numerical "water-hosing" experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reversemore » on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. Finally, we discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1437164-amoc-sensitivity-surface-buoyancy-fluxes-stronger-ocean-meridional-heat-transport-weaker-volume-transport','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1437164-amoc-sensitivity-surface-buoyancy-fluxes-stronger-ocean-meridional-heat-transport-weaker-volume-transport"><span>AMOC sensitivity to surface buoyancy fluxes: Stronger ocean <span class="hlt">meridional</span> heat transport with a weaker volume transport?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Sevellec, Florian; Fedorov, Alexey V.</p> <p>2016-01-04</p> <p>Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC). For example, in numerical "water-hosing" experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reversemore » on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. Finally, we discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24784218','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24784218"><span>North Atlantic forcing of tropical Indian Ocean climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mohtadi, Mahyar; Prange, Matthias; Oppo, Delia W; De Pol-Holz, Ricardo; Merkel, Ute; Zhang, Xiao; Steinke, Stephan; Lückge, Andreas</p> <p>2014-05-01</p> <p>The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic <span class="hlt">circulation</span> slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040016323','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040016323"><span>Sensitivity of Middle Atmospheric Temperature and <span class="hlt">Circulation</span> in the UIUC Mesosphere-Stratosphere-Troposphere GCM to the Treatment of Subgrid-Scale Gravity-Wave Breaking</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yang, Fanglin; Schlesinger, Michael E.; Andranova, Natasha; Zubov, Vladimir A.; Rozanov, Eugene V.; Callis, Lin B.</p> <p>2003-01-01</p> <p>The sensitivity of the middle atmospheric temperature and <span class="hlt">circulation</span> to the treatment of mean- flow forcing due to breaking gravity waves was investigated using the University of Illinois at Urbana-Champaign 40-layer Mesosphere-Stratosphere-Troposphere General <span class="hlt">Circulation</span> Model (MST-GCM). Three GCM experiments were performed. The gravity-wave forcing was represented first by Rayleigh friction, and then by the Alexander and Dunkerton (AD) parameterization with weak and strong breaking effects of gravity waves. In all experiments, the Palmer et al. parameterization was included to treat the breaking of topographic gravity waves in the troposphere and lower stratosphere. Overall, the experiment with the strong breaking effect simulates best the middle atmospheric temperature and <span class="hlt">circulation</span>. With Rayleigh friction and the weak breaking effect, a large warm bias of up to 60 C was found in the summer upper mesosphere and lower thermosphere. This warm bias was linked to the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. With the strong breaking effect, the GCM was able to simulate this reversal, and essentially eliminated the warm bias. This improvement was the result of a much stronger <span class="hlt">meridional</span> transport <span class="hlt">circulation</span> that possesses a strong vertical ascending branch in the summer upper mesosphere, and hence large adiabatic cooling. Budget analysis indicates that 'in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the <span class="hlt">meridional</span> transport <span class="hlt">circulation</span> and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are small. To obtain a transport <span class="hlt">circulation</span> in the mesosphere of the UIUC MST-GCM that is strong enough to produce the observed cold summer mesopause, gravity-wave forcing larger than 100 m/s/day in magnitude is required near the summer mesopause. In</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040015113&hterms=iso&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Diso','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040015113&hterms=iso&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Diso"><span><span class="hlt">Meridional</span> Propagation of the MJO/ISO and Prediction of Off-equatorial Monsoon Variability</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, Man Li C.; Schubert, S.; Suarez, M.; Pegion, P.; Waliser, D.</p> <p>2003-01-01</p> <p>This study was examine the links between tropical heating, the Madden Julian Oscillation (MJO)/Intraseasonal Oscillation (ISO), and the off-equatorial monsoon development. We examine both observations and idealized "MJO heating" experiments employing the NASA Seasonal-Interannual Prediction Project (NSIPP) atmospheric general <span class="hlt">circulation</span> model (AGCM). In the simulations, the model is forced by climatological SST and an idealized eastward propagating heating profile that is meant 'to mimic the canonical heating associated with the MJO in the Indian Ocean and western Pacific. The observational analysis highlights the strong link between the Indian summer monsoon and the tropical ISO/MJO activity and heating. Here we focus on the potential for skillful predictions of the monsoon on sub-seasonal time scales associated with the <span class="hlt">meridional</span> propagation of the ISO/MJO. In particular, we show that the variability of the Indian summer monsoon lags behind the variability of tropical ISO/MJO heating by about 15 days when the tropical heating is around 60E and 90E. This feature of the ISO/MJO is reproduced in the AGCM experiments with the idealized eastward propagating MJO-like heating, suggesting that models with realistic ISO/MJO variability should provide useful skill of monsoon breaks and surges on sub-seasonal time scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040081405&hterms=iso&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Diso','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040081405&hterms=iso&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Diso"><span><span class="hlt">Meridional</span> Propagation of the MJO/ISO and Prediction of Off-equatorial Monsoon Variability</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, Man Li C.; Schubert, S.; Suarez, M.; Pegion, P.; Bacmeister, J.; Waliser, D.</p> <p>2004-01-01</p> <p>In this study we examine the links between tropical heating, the Madden Julian Oscillation (MJO)/Intraseasonal Oscillation (ISO), and the off-equatorial monsoon development. We examine both observations and idealized "MJO heating" experiments employing the NASA Seasonal-Interannual Prediction Project (NSIPP) atmospheric general <span class="hlt">circulation</span> model (AGCM). In the simulations, the model is forced by climatological SST and an idealized eastward propagating heating profile that is meant to mimic the canonical heating associated with the MJO in the Indian Ocean and western Pacific. The observational analysis highlights the strong link between the Indian summer monsoon and the tropical ISO/MJO activity and heating. Here we focus on the potential for skillful predictions of the monsoon on subseasonal time scales associated with the <span class="hlt">meridional</span> propagation of the ISOMJO. In particular, we show that the variability of the Indian summer monsoon lags behind the variability of tropical ISOMJO heating by about 15 days when the tropical heating is around 60E and 90E. This feature of the ISOMJO is reproduced in the AGCM experiments with the idealized eastward propagating MJO-like heating, suggesting that models with realistic ISOM0 variability should provide useful skill of monsoon breaks and surges on subseasonal time scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRE..123..335T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRE..123..335T"><span>Three-Dimensional Structures of Thermal Tides Simulated by a Venus GCM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takagi, Masahiro; Sugimoto, Norihiko; Ando, Hiroki; Matsuda, Yoshihisa</p> <p>2018-02-01</p> <p>Thermal tides in the Venus atmosphere are investigated by using a GCM named as AFES-Venus. The three-dimensional structures of wind and temperature associated with the thermal tides obtained in our model are fully examined and compared with observations. The result shows that the wind and temperature distributions of the thermal tides depend complexly on latitude and altitude in the cloud layer, mainly because they consist of vertically propagating and trapped modes with zonal wave numbers of 1-4, each of which predominates in different latitudes and altitudes under the influence of mid- and high-latitude jets. A strong <span class="hlt">circulation</span> between the subsolar and antisolar (SS-AS) points, which is equivalent to a diurnal component of the thermal tides, is superposed on the superrotation. The vertical velocity of SS-AS <span class="hlt">circulation</span> is about 10 times larger than that of the zonal-mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> (ZMMC) in 60-70 km altitudes. It is suggested that the SS-AS <span class="hlt">circulation</span> could contribute to the material transport, and its upward motion might be related to the UV dark region observed in the subsolar and early afternoon regions in low latitudes. The terdiurnal and quaterdiurnal tides, which may be excited by the nonlinear interactions among the diurnal and semidiurnal tides in middle and high latitudes, are detected in the solar-fixed Y-shape structure formed in the vertical wind field in the upper cloud layer. The ZMMC is weak and has a complex structure in the cloud layer; the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> is confined to latitudes equatorward of 30°, and the Ferrel-like one appears in middle and high latitudes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040060044&hterms=Tracer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DTracer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040060044&hterms=Tracer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DTracer"><span>South Polar Ar Enhancement as a Tracer for Southern Winter Horizontal <span class="hlt">Meridional</span> Mixing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sprague, A. L.; Boynton, W. V.; Kim, K.; Reedy, R.; Kerry, K.; Janes, D.</p> <p>2004-01-01</p> <p>Measurements made by the Gamma Ray Spectrometer (GRS) on Mars Odyssey during 2002 and 2003 show an obvious increase in the gamma flux of 1294 keV gamma rays resulting from the decay of (41)Ar. (41)Ar is made by the capture of thermal neutrons by atmospheric (40)Ar. The increase measured above the southern polar region has permitted calculation of the increase in mixing ratio of Ar from L(sub s) 8 to 100 between latitudes 75 S and 90 S. The peak in Ar enhancement occurs about 200 Earth days after CO2 freeze-out has begun, indicating that up to this time equatorward <span class="hlt">meridional</span> mixing is rapid enough to move enhanced Ar from the polar regions northward. Although the CO2 frost depth continues to increase from L(sub s) 110 deg to 190 deg, the Ar enhancement steadily decreases to its baseline value reached at about L(sub s) 200 deg. Our data permit an estimate of the horizontal eddy mixing coefficient useful for constraining equatorward <span class="hlt">meridional</span> mixing during southern winter and a characteristic mixing time for the polar southern winter atmosphere. Also, using the drop in excess Ar measured by the GRS from L(sub s) 110 deg to 200 deg, we estimate an eddy coefficient appropriate for <span class="hlt">meridional</span> mixing of the entire Ar excess back to the baseline value. The horizontal eddy mixing coefficients are derived using Ar as a tracer much as the vertical eddy mixing coefficient for the Earth's troposphere is derived using CH4 as a minor constituent tracer. The estimation of <span class="hlt">meridional</span> mixing for high latitudes at Mars is important for constraining parameters used in atmospheric modeling and predicting seasonal and daily behavior. The calculations are order of magnitude estimates that should improve as the data set becomes more robust and improves our models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ARMS...10..503P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ARMS...10..503P"><span>A Synoptic View of the Ventilation and <span class="hlt">Circulation</span> of Antarctic Bottom Water from Chlorofluorocarbons and Natural Tracers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Purkey, Sarah G.; Smethie, William M.; Gebbie, Geoffrey; Gordon, Arnold L.; Sonnerup, Rolf E.; Warner, Mark J.; Bullister, John L.</p> <p>2018-01-01</p> <p>Antarctic Bottom Water (AABW) is the coldest, densest, most prolific water mass in the global ocean. AABW forms at several distinct regions along the Antarctic coast and feeds into the bottom limb of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>, filling most of the global deep ocean. AABW has warmed, freshened, and declined in volume around the globe in recent decades, which has implications for the global heat and sea level rise budgets. Over the past three decades, the use of tracers, especially time-varying tracers such as chlorofluorocarbons, has been essential to our understanding of the formation, <span class="hlt">circulation</span>, and variability of AABW. Here, we review three decades of temperature, salinity, and tracer data and analysis that have led to our current knowledge of AABW and how the southern component of deep-ocean ventilation is changing with time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28877009','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28877009"><span>A Synoptic View of the Ventilation and <span class="hlt">Circulation</span> of Antarctic Bottom Water from Chlorofluorocarbons and Natural Tracers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Purkey, Sarah G; Smethie, William M; Gebbie, Geoffrey; Gordon, Arnold L; Sonnerup, Rolf E; Warner, Mark J; Bullister, John L</p> <p>2018-01-03</p> <p>Antarctic Bottom Water (AABW) is the coldest, densest, most prolific water mass in the global ocean. AABW forms at several distinct regions along the Antarctic coast and feeds into the bottom limb of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>, filling most of the global deep ocean. AABW has warmed, freshened, and declined in volume around the globe in recent decades, which has implications for the global heat and sea level rise budgets. Over the past three decades, the use of tracers, especially time-varying tracers such as chlorofluorocarbons, has been essential to our understanding of the formation, <span class="hlt">circulation</span>, and variability of AABW. Here, we review three decades of temperature, salinity, and tracer data and analysis that have led to our current knowledge of AABW and how the southern component of deep-ocean ventilation is changing with time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23152663','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23152663"><span><span class="hlt">Meridional</span> lenticular astigmatism associated with bilateral concurrent uveal metastases in renal cell carcinoma.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Priluck, Joshua C; Grover, Sandeep; Chalam, Kv</p> <p>2012-01-01</p> <p>To demonstrate a case illustrating <span class="hlt">meridional</span> lenticular astigmatism as a result of renal cell carcinoma uveal metastases. Case report with images. Clinical findings and diagnostic testing of a patient with acquired <span class="hlt">meridional</span> lenticular astigmatism are described. The refraction revealed best-corrected visual acuity of 20/20-1 OD (-2.50 + 0.25 × 090) and 20/50 OS (-8.25 + 3.25 × 075). Bilateral concurrent renal cell carcinoma metastases to the choroid and ciliary body are demonstrated by utilizing ultrasonography, ultrawidefield fluorescein angiography, and unique spectral-domain optical coherence tomography. Metastatic disease should be included in the differential of acquired astigmatism. Spectral-domain optical coherence tomography, ultrawidefield fluorescein angiography, and ultrasonography have roles in delineating choroidal metastases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020090258','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020090258"><span>The Breath of Planet Earth: Atmospheric <span class="hlt">Circulation</span>. Assimilation of Surface Wind Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Atlas, Robert; Bloom, Stephen; Otterman, Joseph</p> <p>2000-01-01</p> <p>Differences in air pressure are a major cause of atmospheric <span class="hlt">circulation</span>. Because heat excites the movement of atoms, warm temperatures cause, air molecules to expand. Because those molecules now occupy a larger space, the pressure that their weight exerts is decreased. Air from surrounding high-pressure areas is pushed toward the low-pressure areas, creating <span class="hlt">circulation</span>. This process causes a major pattern of global atmosphere movement known as <span class="hlt">meridional</span> <span class="hlt">circulation</span>. In this form of convection, or vertical air movement, heated equatorial air rises and travels through the upper atmosphere toward higher latitudes. Air just above the equator heads toward the North Pole, and air just below the equator moves southward. This air movement fills the gap created where increased air pressure pushes down cold air. The ,cold air moves along the surface back toward the equator, replacing the air masses that rise there. Another influence on atmospheric. <span class="hlt">circulation</span> is the Coriolis force. Because of the Earth's rotation, large-scale wind currents move in the direction of this axial spin around low-pressure areas. Wind rotates counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. just as the Earth's rotation affects airflow, so too does its surface. In the phenomenon of orographic lifting, elevated topographic features such as mountain ranges lift air as it moves up their surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..782A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..782A"><span>The interplay of internal and forced modes of <span class="hlt">Hadley</span> Cell expansion: lessons from the global warming hiatus</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amaya, Dillon J.; Siler, Nicholas; Xie, Shang-Ping; Miller, Arthur J.</p> <p>2017-09-01</p> <p>The poleward branches of the <span class="hlt">Hadley</span> Cells and the edge of the tropics show a robust poleward shift during the satellite era, leading to concerns over the possible encroachment of the globe's subtropical dry zones into currently temperate climates. The extent to which this trend is caused by anthropogenic forcing versus internal variability remains the subject of considerable debate. In this study, we use a Joint EOF method to identify two distinct modes of tropical width variability: (1) an anthropogenically-forced mode, which we identify using a 20-member simulation of the historical climate, and (2) an internal mode, which we identify using a 1000-year pre-industrial control simulation. The forced mode is found to be closely related to the top of the atmosphere radiative imbalance and exhibits a long-term trend since 1860, while the internal mode is essentially indistinguishable from the El Niño Southern Oscillation. Together these two modes explain an average of 70% of the interannual variability seen in model "edge indices" over the historical period. Since 1980, the superposition of forced and internal modes has resulted in a period of accelerated <span class="hlt">Hadley</span> Cell expansion and decelerated global warming (i.e., the "hiatus"). A comparison of the change in these modes since 1980 indicates that by 2013 the signal has emerged above the noise of internal variability in the Southern Hemisphere, but not in the Northern Hemisphere, with the latter also exhibiting strong zonal asymmetry, particularly in the North Atlantic. Our results highlight the important interplay of internal and forced modes of tropical width change and improve our understanding of the interannual variability and long-term trend seen in observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.1353T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.1353T"><span>Venus atmosphere from Venus Express</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Titov, Dmitri; Taylor, Fredric W.; Svedhem, Håkan; Titov, D.; Svedhem, H.; Taylor, F. W.; Bertaux, J.-L.; Drossart, P.; Haeusler, B.; Korablev, O. I.; Markiewicz, W. J.; Paetzold, M.; Piccioni, G.; Vandaele, A.-C.</p> <p></p> <p>Since April 2006 Venus Express has been performing a global survey of the remarkably dense, cloudy, and dynamic atmosphere of our near neighbour. A consistent picture of the climate on Venus is emerging on the basis of the new data on the global temperature structure, the com-position and its variations, the cloud morphology at various levels, the atmospheric dynamics and general <span class="hlt">circulation</span>, and near-infrared emissions from trace species such as oxygen in the mesosphere. Vertical profiles of atmospheric temperature in the mesosphere and upper tropo-sphere show strong variability correlated with changes in the cloud top structure and many fine details indicating dynamical processes. Temperature sounding also shows that the main cloud deck at 50-60 km is convectively unstable over large portion of the planet, in agreement with the analysis of UV images. Imaging also reveals strong latitudinal variations and significant temporal changes in the global cloud top morphology, which will inevitably modulate the solar energy deposited in the atmosphere. The cloud top altitude varies from 72 km in the low and middle latitudes to 64 km in the polar region, marking vast polar depressions that form as a re-sult of the <span class="hlt">Hadley-type</span> <span class="hlt">meridional</span> <span class="hlt">circulation</span>. Stellar and solar occultation measurements have revealed an extended upper haze of submicron particles and provided information on its optical properties. Solar occultation observations and deep atmosphere spectroscopy have quantified the distribution of the major trace gases H2O, SO2, CO, COS above and below the clouds, and so provided important input and validation for models of chemical cycles and dynamical trans-port. Cloud motion monitoring has characterised the mean state of the atmospheric <span class="hlt">circulation</span> as well as its variability. Low and middle latitudes show an almost constant zonal wind speed of 100+/-20 m/s at the cloud tops and vertical wind shear of 2-3 m/s/km. Towards the pole, the wind speed drops quickly and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A51H0157X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A51H0157X"><span>Extreme Temperature Regimes during the Cool Season and their Associated Large-Scale <span class="hlt">Circulations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, Z.</p> <p>2015-12-01</p> <p>In the cool season (November-March), extreme temperature events (ETEs) always hit the continental United States (US) and provide significant societal impacts. According to the anomalous amplitudes of the surface air temperature (SAT), there are two typical <span class="hlt">types</span> of ETEs, e.g. cold waves (CWs) and warm waves (WWs). This study used cluster analysis to categorize both CWs and WWs into four distinct regimes respectively and investigated their associated large-scale <span class="hlt">circulations</span> on intra-seasonal time scale. Most of the CW regimes have large areal impact over the continental US. However, the distribution of cold SAT anomalies varies apparently in four regimes. In the sea level, the four CW regimes are characterized by anomalous high pressure over North America (near and to west of cold anomaly) with different extension and orientation. As a result, anomalous northerlies along east flank of anomalous high pressure convey cold air into the continental US. To the middle troposphere, the leading two groups feature large-scale and zonally-elongated <span class="hlt">circulation</span> anomaly pattern, while the other two regimes exhibit synoptic wavetrain pattern with <span class="hlt">meridionally</span> elongated features. As for the WW regimes, there are some patterns symmetry and anti-symmetry with respect to CW regimes. The WW regimes are characterized by anomalous low pressure and southerlies wind over North America. The first and fourth groups are affected by remote forcing emanating from North Pacific, while the others appear mainly locally forced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005GeoRL..3210604M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005GeoRL..3210604M"><span>Thermohaline <span class="hlt">circulation</span> at three key sections in the North Atlantic over 1985-2002</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marsh, Robert; de Cuevas, Beverly A.; Coward, Andrew C.; Bryden, Harry L.; Álvarez, Marta</p> <p>2005-05-01</p> <p>Efforts are presently underway to monitor the Thermohaline <span class="hlt">Circulation</span> (THC) in the North Atlantic. A measuring strategy has been designed to monitor both the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (MOC) in the subtropics and dense outflows at higher latitudes. To provide a historical context for these new observations, we diagnose an eddy-permitting ocean model simulation of the period 1985-2002. We present time series of the THC, MOC and heat transport, at key hydrographic sections in the subtropics, the northeast Atlantic and the Labrador Sea. The simulated THC compares well with observations. We find considerable variability in the THC on each section, most strikingly in the Labrador Sea during the early 1990's, consistent with observed changes. Overturning in the northeast Atlantic declines by ~20% over the 1990's, coincident with an increase in the subtropics. We speculate that MOC weakening may soon be detected in the subtropics, if the decline continues in mid-latitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA555622','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA555622"><span>Seasonal Variability of Salt Transport During the Indian Ocean Monsoons</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2011-08-27</p> <p>Wunsch, J. Marotzkc, and J. Toolc (2000). <span class="hlt">Meridional</span> overturning and large-scale <span class="hlt">circulation</span> of the Indian Ocean, J. Geophvs Res., W5(C\\ 1), 26,117...and II. Hasumi (2006), Effects of model resolution on salt transport through northern high-latitude passages and Atlantic <span class="hlt">meridional</span> overturning ...affects <span class="hlt">meridional</span> <span class="hlt">circulation</span> and aids the transport of salt [Sevellec et ai, 2008; Czaja, 2009]. Deep convection could be inhibited by the freshening</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS41B1952W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS41B1952W"><span>Mooring Measurements of the Abyssal <span class="hlt">Circulations</span> in the Western Pacific Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, J.; Wang, F.</p> <p>2016-12-01</p> <p>A scientific observing network in the western tropical Pacific has initially been established by the Institute of Oceanology, Chinese Academy of Sciences (IOCAS). Using fifteen moorings that gives unprecedented measurements in the intermediate and abyssal layers, we present multi-timescale variations of the deep ocean <span class="hlt">circulations</span> prior to and during 2015 El Niño event. The deep ocean velocities increase equatorward with high standard deviation and nearly zero mean. The deep ocean currents mainly flow in <span class="hlt">meridional</span> direction in the central Philippine Basin, and are dominated by a series of alternating westward and eastward zonal jets in the Caroline Basin. The currents in the deep channel connecting the East and West Mariana Basins mainly flow southeastward. Seasonal variation is only present in the deep jets in the Caroline Basin, associating with vertical propagating annual Rossby wave. The high-frequency flow bands are dominated by diurnal, and semi-diurnal tidal currents, and near-inertial currents. The rough topography has a strong influence on the abyssal <span class="hlt">circulations</span>, including the intensifications in velocity and internal tidal energy, and the formation of upwelling flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUSMSP32A..02H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUSMSP32A..02H"><span>Determining the Sun's Deep <span class="hlt">Meridional</span> Flow Speed Using Active Latitude Drift Rates Since 1874</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hathaway, D. H.; Wilson, R. M.</p> <p>2005-05-01</p> <p>Dynamo models that incorporate a deep <span class="hlt">meridional</span> return flow indicate that this flow regulates both the period and the amplitude of the sunspot cycle (Dikpati & Charbonneau 1999, ApJ, 518, 508 and Charbonneau & Dikpati 2000, ApJ, 543, 1027). We recently examined the equatorward drift of the active latitudes (as given by the centroid of the sunspot areas in each hemisphere) and found evidence supporting this view (Hathaway et al. 2003, ApJ, 589, 665 and Hathaway et al. 2004, ApJ, 602, 543). In those studies we fit the equatorward drift in each hemisphere for each sunspot cycle with a simple parabola - giving us a drift rate and its deceleration for each hemisphere/cycle. Here we analyze the same data (the Royal Greenwich Observatory/USAF/NOAA daily active region summaries) to determine the drift rates in each hemisphere on a yearly basis (rotation-by-rotation measurements smoothed to remove high frequencies) and fit them with a simple model for the <span class="hlt">meridional</span> flow that provides the <span class="hlt">meridional</span> flow speed as a function of latitude and time from 1874 to 2005. These flow speeds can be used to test dynamo models -- some of which have predictive capabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130001807','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130001807"><span>High Latitude <span class="hlt">Meridional</span> Flow on the Sun May Explain North-South Polar Field Asymmetry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kosak, Katie; Upton, Lisa; Hathaway, David</p> <p>2012-01-01</p> <p>We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north ]south symmetric, <span class="hlt">meridional</span> flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the <span class="hlt">meridional</span> flow at high latitudes indicate systematic north ]south differences. There was a strong flow in the North while the flow in the South was weaker. With these results, we have a possible solution to the polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun fs polar regions in general and the polar <span class="hlt">meridional</span> flow in particular</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27299822','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27299822"><span>[MicroRNAs: <span class="hlt">circulating</span> biomarkers in <span class="hlt">type</span> 2 Diabetes Mellitus and physical exercise].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gómez-Banoy, Nicolás; Mockus, Ismena</p> <p>2016-03-01</p> <p>MicroRNAs are small, non-coding molecules with a crucial function in the cell´s biologic regulation. <span class="hlt">Circulating</span> levels of miRNAs may be useful biomarkers in metabolic diseases such as <span class="hlt">type</span> 2 Diabetes Mellitus (DM2), which alters the <span class="hlt">circulating</span> concentrations of several <span class="hlt">types</span> of miRNA. Specific serum profiles of these molecules have been identified in high-risk patients before the development of DM2 and its chronic complications. Most importantly, these profiles can be modified with physical exercise, which is crucial in the treatment of metabolic diseases. Acute physical activity alone can induce changes in tissue specific miRNAs, and responses are different in aerobic or non-aerobic training. Muscle and cardiovascular miRNAs, which may play an important role in the adap tation to exercise, are predominantly altered. Even further, there is a correlation between serum levels of miRNAs and fitness, suggesting a role for chronic exercise in their regulation. Thus, miRNAs are molecules of growing importance in exercise physiology, and may be involved in the mechanisms behind the beneficial effects of physical activity for patients with metabolic diseases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15564462','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15564462"><span><span class="hlt">Circulation</span> of <span class="hlt">type</span> 1 vaccine-derived poliovirus in the Philippines in 2001.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shimizu, Hiroyuki; Thorley, Bruce; Paladin, Fem Julia; Brussen, Kerri Anne; Stambos, Vicki; Yuen, Lilly; Utama, Andi; Tano, Yoshio; Arita, Minetaro; Yoshida, Hiromu; Yoneyama, Tetsuo; Benegas, Agnes; Roesel, Sigrun; Pallansch, Mark; Kew, Olen; Miyamura, Tatsuo</p> <p>2004-12-01</p> <p>In 2001, highly evolved <span class="hlt">type</span> 1 <span class="hlt">circulating</span> vaccine-derived poliovirus (cVDPV) was isolated from three acute flaccid paralysis patients and one contact from three separate communities in the Philippines. Complete genomic sequencing of these four cVDPV isolates revealed that the capsid region was derived from the Sabin 1 vaccine strain but most of the noncapsid region was derived from an unidentified enterovirus unrelated to the oral poliovirus vaccine (OPV) strains. The sequences of the cVDPV isolates were closely related to each other, and the isolates had a common recombination site. Most of the genetic and biological properties of the cVDPV isolates were indistinguishable from those of wild polioviruses. However, the most recently identified cVDPV isolate from a healthy contact retained the temperature sensitivity and partial attenuation phenotypes. The sequence relationships among the isolates and Sabin 1 suggested that cVDPV originated from an OPV dose given in 1998 to 1999 and that cVDPV <span class="hlt">circulated</span> along a narrow chain of transmission. <span class="hlt">Type</span> 1 cVDPV was last detected in the Philippines in September 2001, and population immunity to polio was raised by extensive OPV campaigns in late 2001 and early 2002.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120003759&hterms=climatology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dclimatology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120003759&hterms=climatology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dclimatology"><span>Recent Trends of the Tropical Hydrological Cycle Inferred from Global Precipitation Climatology Project and International Satellite Cloud Climatology Project data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhou, Y. P.; Xu, Kuan-Man; Sud, Y. C.; Betts, A. K.</p> <p>2011-01-01</p> <p>Scores of modeling studies have shown that increasing greenhouse gases in the atmosphere impact the global hydrologic cycle; however, disagreements on regional scales are large, and thus the simulated trends of such impacts, even for regions as large as the tropics, remain uncertain. The present investigation attempts to examine such trends in the observations using satellite data products comprising Global Precipitation Climatology Project precipitation and International Satellite Cloud Climatology Project cloud and radiation. Specifically, evolving trends of the tropical hydrological cycle over the last 20-30 years were identified and analyzed. The results show (1) intensification of tropical precipitation in the rising regions of the Walker and <span class="hlt">Hadley</span> <span class="hlt">circulations</span> and weakening over the sinking regions of the associated overturning <span class="hlt">circulation</span>; (2) poleward shift of the subtropical dry zones (up to 2deg/decade in June-July-August (JJA) in the Northern Hemisphere and 0.3-0.7deg/decade in June-July-August and September-October-November in the Southern Hemisphere) consistent with an overall broadening of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>; and (3) significant poleward migration (0.9-1.7deg/decade) of cloud boundaries of <span class="hlt">Hadley</span> cell and plausible narrowing of the high cloudiness in the Intertropical Convergence Zone region in some seasons. These results support findings of some of the previous studies that showed strengthening of the tropical hydrological cycle and expansion of the <span class="hlt">Hadley</span> cell that are potentially related to the recent global warming trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3497461','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3497461"><span><span class="hlt">Meridional</span> lenticular astigmatism associated with bilateral concurrent uveal metastases in renal cell carcinoma</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Priluck, Joshua C; Grover, Sandeep; Chalam, KV</p> <p>2012-01-01</p> <p>Purpose To demonstrate a case illustrating <span class="hlt">meridional</span> lenticular astigmatism as a result of renal cell carcinoma uveal metastases. Methods Case report with images. Results Clinical findings and diagnostic testing of a patient with acquired <span class="hlt">meridional</span> lenticular astigmatism are described. The refraction revealed best-corrected visual acuity of 20/20–1 OD (−2.50 + 0.25 × 090) and 20/50 OS (−8.25 + 3.25 × 075). Bilateral concurrent renal cell carcinoma metastases to the choroid and ciliary body are demonstrated by utilizing ultrasonography, ultrawidefield fluorescein angiography, and unique spectral-domain optical coherence tomography. Conclusions Metastatic disease should be included in the differential of acquired astigmatism. Spectral-domain optical coherence tomography, ultrawidefield fluorescein angiography, and ultrasonography have roles in delineating choroidal metastases. PMID:23152663</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...47.3335R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...47.3335R"><span>Constraints on oceanic <span class="hlt">meridional</span> heat transport from combined measurements of oxygen and carbon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Resplandy, L.; Keeling, R. F.; Stephens, B. B.; Bent, J. D.; Jacobson, A.; Rödenbeck, C.; Khatiwala, S.</p> <p>2016-11-01</p> <p>Despite its importance to the climate system, the ocean <span class="hlt">meridional</span> heat transport is still poorly quantified. We identify a strong link between the northern hemisphere deficit in atmospheric potential oxygen (APO = O_2 + 1.1 × CO_2) and the asymmetry in <span class="hlt">meridional</span> heat transport between northern and southern hemispheres. The recent aircraft observations from the HIPPO campaign reveal a northern APO deficit in the tropospheric column of -10.4 ± 1.0 per meg, double the value at the surface and more representative of large-scale air-sea fluxes. The global northward ocean heat transport asymmetry necessary to explain the observed APO deficit is about 0.7-1.1 PW, which corresponds to the upper range of estimates from hydrographic sections and atmospheric reanalyses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUSMPP52A..06P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUSMPP52A..06P"><span>An Exploration of Mechanisms for Mediating the Influence of Extratropical Glaciation on the Tropical Climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pierrehumbert, R. T.; Frierson, D. M.</p> <p>2006-05-01</p> <p> the NHWARM and NHCOLD cases, despite the substantial reduction in atmospheric water vapor in the cold case. The extremely strong midlatitude cooling produces a modest southward shift in the January ITCZ, and none at all in the July ITCZ, indicating that basic <span class="hlt">Hadley</span> dynamics can make the ITCZ very resistant to moving; we find that the ITCZ position closely follows the tropical temperature maximum. The ITCZ shifts are discussed in terms of theoretical concepts applying to the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. Using an energy balance model (EBM) based on diffusion of moist static energy, Frierson and Held have shown that there is a compensation between changes in latent and sensible heat transport as climate warms, provided the <span class="hlt">meridional</span> distribution of absorbed solar radiation remains fixed. We have extended this analysis to the case in which the solar forcing gradient is allowed to change, as is the case in our simulations owing to the change in surface albedo between the two simulations. In this case, the EBM does not require strict compensation, and in fact correctly reproduces the fact that tropical heat export increases in the NHCOLD case. However, the EBM over-estimates the penetration of the cooling past the Equator, owing to inadequacies in the diffusive treatment of the <span class="hlt">Hadley</span> <span class="hlt">circulation</span>. The EBM also misprepresents the magnitude of midlatitude heat flux changes, owing to the bottom-trapped nature of extratropical cooling seen in the GCM experiments, which is not reflected in the assumptions about the vertical profile of temperature built into the EBM. The implications of incorporating this effect will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...710525Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...710525Y"><span>Recent increases in Arctic freshwater flux affects Labrador Sea convection and Atlantic overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Qian; Dixon, Timothy H.; Myers, Paul G.; Bonin, Jennifer; Chambers, Don; van den Broeke, M. R.</p> <p>2016-01-01</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is an important component of ocean thermohaline <span class="hlt">circulation</span>. Melting of Greenland's ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4736158','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4736158"><span>Recent increases in Arctic freshwater flux affects Labrador Sea convection and Atlantic overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Yang, Qian; Dixon, Timothy H.; Myers, Paul G.; Bonin, Jennifer; Chambers, Don; van den Broeke, M. R.; Ribergaard, Mads H.; Mortensen, John</p> <p>2016-01-01</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is an important component of ocean thermohaline <span class="hlt">circulation</span>. Melting of Greenland's ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening. PMID:26796579</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26796579','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26796579"><span>Recent increases in Arctic freshwater flux affects Labrador Sea convection and Atlantic overturning <span class="hlt">circulation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yang, Qian; Dixon, Timothy H; Myers, Paul G; Bonin, Jennifer; Chambers, Don; van den Broeke, M R</p> <p>2016-01-22</p> <p>The Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) is an important component of ocean thermohaline <span class="hlt">circulation</span>. Melting of Greenland's ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950051191&hterms=cell+crisp&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcell%2Bcrisp','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950051191&hterms=cell+crisp&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcell%2Bcrisp"><span>Diagnostic calculations of the <span class="hlt">circulation</span> in the Martian atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Santee, Michelle L.; Crisp, David</p> <p>1995-01-01</p> <p>The <span class="hlt">circulation</span> of the Martian atmosphere during late southern summer is derived from atmospheric temperature and dust distributions retrieved from a subset of the Mariner 9 infrared interferometer spectrometer (IRIS) thermal emission spectra (LS = 343-348 deg) (Santee and Crisp, 1933). Zonal-mean zonal winds are calculated by assuming gradient wind balance and zero surface zonal wind. Both hemispheres have intense midlatitude westerly jets with velocities of 80-90 m/s near 50 km; in the southern tropics the winds are easterly with velocities of 40 m/s near 50 km. The net effect of the zonal-mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> and large-scale waves can be approximated by the diabatic ciculation, which is defined from the atmospheric thermal structure and net radiative heating rates. The radiative transfer model described by Crisp (1990) and Santee (1993) is used to compute solar heating and thermal cooling rates from diurnal averages of the retrieved IRIS temperature and dust distributions. At pressures below 4 mbar, there are large net radiative heating rates (up to 5 K/d) in the equatorial region and large net radiative cooling rates (up to 12 K/d) in the polar regions. These net radiative heating rates are used in a diagnostic stream function model which solves for the meridonal and vertical components of the diabatic <span class="hlt">circulation</span> simultaneously. We find a two cell <span class="hlt">circulation</span>, with rising motion over the equator, poleward flow in both hemispheres, sinking motion over both polar regions, and return flow in the lowest atmospheric levels. The maximum poleward velocity is 3 m/s in the tropics at approximately 55 km altitude, and the maximum vertical velocity is 2.5 cm/s downward over the north pole at approximately 60 km altitude. If these large transport rates are sustained for an entire season, the Martian atmosphere above the 1-mbar level is overturned in about 38 days. This diabatic <span class="hlt">circulation</span> is qualitatively similar to the terrestial diabatic <span class="hlt">circulation</span> at the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995JGR...100.5465S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995JGR...100.5465S"><span>Diagnostic calculations of the <span class="hlt">circulation</span> in the Martian atmosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santee, Michelle L.; Crisp, David</p> <p>1995-03-01</p> <p>The <span class="hlt">circulation</span> of the Martian atmosphere during late southern summer is derived from atmospheric temperature and dust distributions retrieved from a subset of the Mariner 9 infrared interferometer spectrometer (IRIS) thermal emission spectra (LS = 343-348 deg) (Santee and Crisp, 1933). Zonal-mean zonal winds are calculated by assuming gradient wind balance and zero surface zonal wind. Both hemispheres have intense midlatitude westerly jets with velocities of 80-90 m/s near 50 km; in the southern tropics the winds are easterly with velocities of 40 m/s near 50 km. The net effect of the zonal-mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> and large-scale waves can be approximated by the diabatic ciculation, which is defined from the atmospheric thermal structure and net radiative heating rates. The radiative transfer model described by Crisp (1990) and Santee (1993) is used to compute solar heating and thermal cooling rates from diurnal averages of the retrieved IRIS temperature and dust distributions. At pressures below 4 mbar, there are large net radiative heating rates (up to 5 K/d) in the equatorial region and large net radiative cooling rates (up to 12 K/d) in the polar regions. These net radiative heating rates are used in a diagnostic stream function model which solves for the meridonal and vertical components of the diabatic <span class="hlt">circulation</span> simultaneously. We find a two cell <span class="hlt">circulation</span>, with rising motion over the equator, poleward flow in both hemispheres, sinking motion over both polar regions, and return flow in the lowest atmospheric levels. The maximum poleward velocity is 3 m/s in the tropics at approximately 55 km altitude, and the maximum vertical velocity is 2.5 cm/s downward over the north pole at approximately 60 km altitude. If these large transport rates are sustained for an entire season, the Martian atmosphere above the 1-mbar level is overturned in about 38 days. This diabatic <span class="hlt">circulation</span> is qualitatively similar to the terrestial diabatic <span class="hlt">circulation</span> at the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24990748','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24990748"><span>Abrupt pre-Bølling-Allerød warming and <span class="hlt">circulation</span> changes in the deep ocean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thiagarajan, Nivedita; Subhas, Adam V; Southon, John R; Eiler, John M; Adkins, Jess F</p> <p>2014-07-03</p> <p>Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean <span class="hlt">circulation</span>--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>. Our results are based on coupled radiocarbon and uranium-series dates, along with clumped isotope temperature estimates, from water column profiles of fossil deep-sea corals in a limited area of the western North Atlantic. We find that during Heinrich stadial 1 (the cool period immediately before the Bølling-Allerød interstadial), the deep ocean was about three degrees Celsius warmer than shallower waters above. This reversal of the ocean's usual thermal stratification pre-dates the Bølling-Allerød warming and must have been associated with increased salinity at depth to preserve the static stability of the water column. The depleted radiocarbon content of the warm and salty water mass implies a long-term disconnect from rapid surface exchanges, and, although uncertainties remain, is most consistent with a Southern Ocean source. The Heinrich stadial 1 ocean profile is distinct from the modern water column, that for the Last Glacial Maximum and that for the Younger Dryas, suggesting that the patterns we observe are a unique feature of the deglacial climate system. Our observations indicate that the deep ocean influenced dramatic Northern Hemisphere warming by storing heat at depth that preconditioned the system for a subsequent abrupt overturning event during the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2757910','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2757910"><span>New Genotype of Dengue <span class="hlt">Type</span> 3 Virus <span class="hlt">Circulating</span> in Brazil and Colombia Showed a Close Relationship to Old Asian Viruses</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Aquino, Victor Hugo; Amarilla, Alberto Anastacio; Alfonso, Helda Liz; Batista, Weber Cheli; Figueiredo, Luiz Tadeu Moraes</p> <p>2009-01-01</p> <p>Dengue <span class="hlt">type</span> 3 genotype V viruses have been recently detected in Brazil and Colombia. In this study, we described another Brazilian isolate belonging to this genotype. Phylogenetic analysis including dengue <span class="hlt">type</span> 3 viruses isolated worldwide showed that Brazilian and Colombian viruses were closely related to viruses isolated in Asia more than two decades ago. The characteristic evolutionary pattern of dengue <span class="hlt">type</span> 3 virus cannot explain the close similarity of new <span class="hlt">circulating</span> viruses with old viruses. Further studies are needed to confirm the origin of the new dengue <span class="hlt">type</span> III genotype <span class="hlt">circulating</span> in Brazil and Colombia. PMID:19823677</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.2537W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.2537W"><span>Effect of AMOC collapse on ENSO in a high resolution general <span class="hlt">circulation</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williamson, Mark S.; Collins, Mat; Drijfhout, Sybren S.; Kahana, Ron; Mecking, Jennifer V.; Lenton, Timothy M.</p> <p>2018-04-01</p> <p>We look at changes in the El Niño Southern Oscillation (ENSO) in a high-resolution eddy-permitting climate model experiment in which the Atlantic <span class="hlt">Meridional</span> <span class="hlt">Circulation</span> (AMOC) is switched off using freshwater hosing. The ENSO mode is shifted eastward and its period becomes longer and more regular when the AMOC is off. The eastward shift can be attributed to an anomalous eastern Ekman transport in the mean equatorial Pacific ocean state. Convergence of this transport deepens the thermocline in the eastern tropical Pacific and increases the temperature anomaly relaxation time, causing increased ENSO period. The anomalous Ekman transport is caused by a surface northerly wind anomaly in response to the <span class="hlt">meridional</span> sea surface temperature dipole that results from switching the AMOC off. In contrast to a previous study with an earlier version of the model, which showed an increase in ENSO amplitude in an AMOC off experiment, here the amplitude remains the same as in the AMOC on control state. We attribute this difference to variations in the response of decreased stochastic forcing in the different models, which competes with the reduced damping of temperature anomalies. In the new high-resolution model, these effects approximately cancel resulting in no change in amplitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APJAS..53..181L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APJAS..53..181L"><span>Competing influences of greenhouse warming and aerosols on Asian summer monsoon <span class="hlt">circulation</span> and rainfall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lau, William Ka-Ming; Kim, Kyu-Myong</p> <p>2017-05-01</p> <p>In this paper, we have compared and contrasted competing influences of greenhouse gases (GHG) warming and aerosol forcing on Asian summer monsoon <span class="hlt">circulation</span> and rainfall based on CMIP5 historical simulations. Under GHG-only forcing, the land warms much faster than the ocean, magnifying the pre-industrial climatological land-ocean thermal contrast and hemispheric asymmetry, i.e., warmer northern than southern hemisphere. A steady increasing warm-ocean-warmer-land (WOWL) trend has been in effect since the 1950's substantially increasing moisture transport from adjacent oceans, and enhancing rainfall over the Asian monsoon regions. However, under GHG warming, increased atmospheric stability due to strong reduction in mid-tropospheric and near surface relative humidity coupled to an expanding subsidence areas, associated with the Deep Tropical Squeeze (DTS, Lau and Kim, 2015b) strongly suppress monsoon convection and rainfall over subtropical and extratropical land, leading to a weakening of the Asian monsoon <span class="hlt">meridional</span> <span class="hlt">circulation</span>. Increased anthropogenic aerosol emission strongly masks WOWL, by over 60% over the northern hemisphere, negating to a large extent the rainfall increase due to GHG warming, and leading to a further weakening of the monsoon <span class="hlt">circulation</span>, through increasing atmospheric stability, most likely associated with aerosol solar dimming and semi-direct effects. Overall, we find that GHG exerts stronger positive rainfall sensitivity, but less negative <span class="hlt">circulation</span> sensitivity in SASM compared to EASM. In contrast, aerosols exert stronger negative impacts on rainfall, but less negative impacts on <span class="hlt">circulation</span> in EASM compared to SASM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.1277M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.1277M"><span>The influence of orography on modern ocean <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maffre, Pierre; Ladant, Jean-Baptiste; Donnadieu, Yannick; Sepulchre, Pierre; Goddéris, Yves</p> <p>2018-02-01</p> <p>The effects of orography on climate are investigated with a coupled ocean-atmosphere general <span class="hlt">circulation</span> model (IPSL-CM5). Results are compared with previous investigations in order to dig out robust consequences of the lack of orography on the global scale. Emphasis is made on the thermohaline <span class="hlt">circulation</span> whose sensitivity to orography has only been subject to a very limited number of studies using coupled models. The removal of the entire orography switches the <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> from the Atlantic to the Pacific, following freshwater transfers from the latter to the former that reverse the salinity gradient between these oceans. This is in part due to the increased freshwater export from the Pacific to the Atlantic through North America in the absence of the Rocky Mountains and the consecutive decreased evaporation in the North Atlantic once the Atlantic MOC weakens, which cools the northern high-latitudes. In addition and unlike previous model studies, we find that tropical freshwater transfers are a major driver of this switch. More precisely, the collapse of the Asian summer monsoon, associated with westward freshwater transfer across Africa, is critical to the freshening of the Atlantic and the increased salt content in the Pacific. Specifically, precipitations are increasing over the Congo catchment area and induce a strong increase in runoff discharging into the tropical Atlantic. In addition, the removal of the Andes shifts the area of strong precipitation toward the Amazonian catchment area and results in a larger runoff discharging into the Tropical Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130003206','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130003206"><span>High Latitude <span class="hlt">Meridional</span> Flow on the Sun May Explain North-South Polar Field Asymmetry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kosak, Katie; Upton, Lisa; Hathaway, David</p> <p>2012-01-01</p> <p>We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north-south symmetric, <span class="hlt">meridional</span> flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the <span class="hlt">meridional</span> flow at high latitudes indicate systematic north-south differences. In the fall of 2010 (when the North Pole was most visible), there was a strong flow in the North while in the spring of 2011 (when the South Pole was most visible) the flow there was weaker. With these results, we have a possible solution to this polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun s polar regions in general and the polar <span class="hlt">meridional</span> flow in particular.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA511958','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA511958"><span>Relating Agulhas Leakage to the Agulhas Current Retroflection Location</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2009-11-03</p> <p>branch return flow of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (Gordon, 1986; Weijer et al., 1999; Peeters et al., 2004; Biastoch et al., 2008a...demonstrated that the mesoscale dynamics reflected in the decadal variability of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (Biastoch et al...Lutjeharms, J. R. E.: Agulhas leakage dynamics affects decadal variability in Atlantic overturn - ing <span class="hlt">circulation</span> , Nature, 456, 489–492, 2008a. Biastoch, A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880062502&hterms=fashion+models&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dfashion%2Bmodels','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880062502&hterms=fashion+models&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dfashion%2Bmodels"><span>Rossby wave activity in a two-dimensional model - Closure for wave driving and <span class="hlt">meridional</span> eddy diffusivity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hitchman, Matthew H.; Brasseur, Guy</p> <p>1988-01-01</p> <p>A parameterization of the effects of Rossby waves in the middle atmosphere is proposed for use in two-dimensional models. By adding an equation for conservation of Rossby wave activity, closure is obtained for the <span class="hlt">meridional</span> eddy fluxes and body force due to Rossby waves. Rossby wave activity is produced in a climatological fashion at the tropopause, is advected by a group velocity which is determined solely by model zonal winds, and is absorbed where it converges. Absorption of Rossby wave activity causes both an easterly torque and an irreversible mixing of potential vorticity, represented by the <span class="hlt">meridional</span> eddy diffusivity, K(yy). The distribution of Rossby wave driving determines the distribution of K(yy), which is applied to all of the chemical constituents. This provides a self-consistent coupling of the wave activity with the winds, tracer distributions and the radiative field. Typical winter stratospheric values for K(yy) of 2 million sq m/sec are obtained. Poleward tracer advection is enhanced and <span class="hlt">meridional</span> tracer gradients are reduced where Rossby wave activity is absorbed in the model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913328T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913328T"><span><span class="hlt">Circulation</span> in the region of the Reykjanes Ridge in June-July 2015</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tillys, Petit; Herle, Mercier; Virginie, Thierry</p> <p>2017-04-01</p> <p>The Reykjanes Ridge is a major topographic feature of the North-Atlantic Ocean lying south of Iceland that strongly influences the pathways of the upper and lower limbs of the <span class="hlt">meridional</span> overturning cell. The <span class="hlt">circulation</span> in the vicinity of the Reykjanes Ridge is anticyclonic and characterized by a southwestward flow (the East Reykjanes Ridge Current, ERRC) along the eastern flank and a northeastward flow (the Irminger Current, IC) along the western flank. Even if it is admitted that the ERRC feeds the IC through a cross-ridge flow, details and magnitude of this <span class="hlt">circulation</span> remain unclear. In this study, the <span class="hlt">circulation</span> in the region of the Reykjanes Ridge was investigated based on ADCP and CTDO2 measurements carried out from the R/V Thalassa during the RREX cruise, which provided a snapshot of the water mass distribution and <span class="hlt">circulation</span> during summer 2015. One hydrographic section followed the top of the Reykjanes Ridge between Iceland and 50˚ N and three other sections were carried out perpendicularly to the ridge at 62˚ N, 58.5˚ N and 56˚ N. Geostrophic transports were estimated by combining ADCP and hydrographic data. Those observations were used to provide an estimate of the <span class="hlt">circulation</span> around the Ridge and to discuss the <span class="hlt">meridional</span> evolutions of the ERRC and IC transports along the Ridge and their connection to the cross-Ridge flows. The section along the top of the Reykjanes Ridge allowed us to describe the cross ridge exchanges. A westward flow crossed the Ridge between Iceland and 53˚ N. Its top to bottom integrated transport was estimated at 17.7 Sv. Two main passages were identified for the westward crossing. A first passage is located near 57˚ N (Bight Fracture Zone, BFZ) in agreement with previous studies. More surprisingly, a second passage is located near 59˚ N. The top-to-bottom transports of those two main flows were estimated at 6.5 and 8 Sv respectively. The IC and ERRC top-to-bottom integrated transports were maximum at 58.5˚ N and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42..411B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42..411B"><span>Atlantic Ocean <span class="hlt">circulation</span> changes preceded millennial tropical South America rainfall events during the last glacial</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burckel, Pierre; Waelbroeck, Claire; Gherardi, Jeanne Marie; Pichat, Sylvain; Arz, Helge; Lippold, Joerg; Dokken, Trond; Thil, François</p> <p>2015-01-01</p> <p>the last glacial period, Greenland's climate shifted between cold (stadial) and warm (interstadial) phases that were accompanied by ocean <span class="hlt">circulation</span> changes characterized by reduced Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) during stadials. Here we present new data from the western tropical Atlantic demonstrating that AMOC slowdowns preceded some of the large South American rainfall events that took place during stadials. Based on 231Pa/230Th and Ti/Ca measurements in the same sediment core, we determine that the AMOC started to slowdown 1420 ± 250 and 690 ± 180 (1σ) years before the onset of two large precipitation events associated with Heinrich stadials. Our results bring unprecedented evidence that AMOC changes could be at the origin of the large precipitation events observed in tropical South America during Heinrich stadials. In addition, we propose a mechanism explaining the differences in the extent and timing of AMOC slowdowns associated with shorter and longer stadials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6403A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6403A"><span>Instabilities in the relation between European Weather <span class="hlt">Types</span> and mid-latitude <span class="hlt">circulation</span> in the Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alvarez Castro, Maria del Carmen; Gallego, David; Trigo, Ricardo M.; García-Herrera, Ricardo; Ribera, Pedro</p> <p>2015-04-01</p> <p>Recently, a new instrumental index (Westerly Index or "WI") measuring the frequency of the westerlies over the English Channel has been developed for the period 1685-1750 (Wheeler et al. 2009) and further extended to the present (Barriopedro et al. 2014). This index holds a climatic signal similar to the North Atlantic Oscillation (NAO) in the temperature and precipitation over large areas of Europe. Nevertheless we are confident that the WI offers two major advantages: first the WI signatures are not restricted to the winter being significant during the entire year and second, the WI does not rely on proxy data and, as such, it is less prone to the uncertainties associated to the calibration process of the NAO reconstructions. During the last decades, regional mid-latitude <span class="hlt">circulation</span> has also been quantified objectively through the widespread use of so-called Weather <span class="hlt">Types</span> (WT). WT are used to identify and classify the different patterns of Sea Level Pressure configurations originating particular weather in a given area. In consequence, WT over most Western Europe should be closely related to atmospheric <span class="hlt">circulation</span> indexes such as the WI. Here we adopted a similar WT classification of the classical WTs developed empirically by Hubert Lamb for the UK and automated by Jones et al. (1993) but centered at the English Channel latitudinal band to be compatible with the window used to define the WI (Wheeler et al., 2009). In this work we compare the long-term (1850-2003) monthly values of WI with the corresponding monthly frequency of directional weather <span class="hlt">types</span> in the WI area. As expected, we found significant positive (negative) correlation values with WTs dominated by a westerly (easterly) component but interestingly, some quasi periodic intervals of lack of correlation have been found, suggesting an oscillating behaviour on the lack of stationarity between the large-scale north Atlantic <span class="hlt">circulation</span> and local weather <span class="hlt">types</span>. Wheeler, D.; García-Herrera, R.; Wilkinson</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA597661','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA597661"><span>Toward Better Intraseasonal and Seasonal Prediction: Verification and Evaluation of the NOGAPS Model Forecasts</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-09-30</p> <p><span class="hlt">Circulation</span> (HC) in terms of the <span class="hlt">meridional</span> streamfunction. The interannual variability of the Atlantic HC in boreal summer was examined using the EOF...large-scale <span class="hlt">circulations</span> in the NAVGEM model and the source of predictability for the seasonal variation of the Atlantic TCs. We have been working...EOF analysis of <span class="hlt">Meridional</span> <span class="hlt">Circulation</span> (JAS). (a) The leading mode (M1); (b) variance explained by the first 10 modes. 9</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA530415','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA530415"><span>Dynamical Evaluation of Ocean Models using the Gulf Stream as an Example</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2010-01-01</p> <p>transport for the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) as the 3 nonlinear solutions discussed in Section 2. The model boundary is...Hellerman and Rosenstein (1983) wind stress climatology and the northward upper ocean flow (14 Sv) of the Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> ... overturning <span class="hlt">circulation</span> (AMOC) streamfunction with a 5 Sv contour interval from (a) 1/12° Atlantic MICOM, (b) 1/12° Atlantic HYCOM, and (c) 1/12</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA533846','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA533846"><span>Effects of Small-Scale Bathymetric Roughness on the Global Internal Wave Field</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2008-09-30</p> <p>Navy. Much of the interest stems from the suggestion by Munk and Wunsch (1998) that the strength of the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> is controlled... <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> . Journal of Physical Oceanography 32, 3578-3595. St. Laurent, L.C., 1999. Diapycnal advection by double diffusion...waves generated by flows over the rough seafloor. On the time scales of internal waves, mesoscale eddies and the general <span class="hlt">circulation</span> can be regarded as</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5248985','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5248985"><span><span class="hlt">Circulating</span> MicroRNA-122 Is Associated With the Risk of New-Onset Metabolic Syndrome and <span class="hlt">Type</span> 2 Diabetes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Skroblin, Philipp; Moschen, Alexander R.; Yin, Xiaoke; Kaudewitz, Dorothee; Zampetaki, Anna; Barwari, Temo; Whitehead, Meredith; Ramírez, Cristina M.; Goedeke, Leigh; Rotllan, Noemi; Bonora, Enzo; Hughes, Alun D.; Santer, Peter; Fernández-Hernando, Carlos; Tilg, Herbert; Willeit, Johann; Kiechl, Stefan</p> <p>2017-01-01</p> <p>MicroRNA-122 (miR-122) is abundant in the liver and involved in lipid homeostasis, but its relevance to the long-term risk of developing metabolic disorders is unknown. We therefore measured <span class="hlt">circulating</span> miR-122 in the prospective population-based Bruneck Study (n = 810; survey year 1995). <span class="hlt">Circulating</span> miR-122 was associated with prevalent insulin resistance, obesity, metabolic syndrome, <span class="hlt">type</span> 2 diabetes, and an adverse lipid profile. Among 92 plasma proteins and 135 lipid subspecies quantified with mass spectrometry, it correlated inversely with zinc-α-2-glycoprotein and positively with afamin, complement factor H, VLDL-associated apolipoproteins, and lipid subspecies containing monounsaturated and saturated fatty acids. Proteomics analysis of livers from antagomiR-122–treated mice revealed novel regulators of hepatic lipid metabolism that are responsive to miR-122 inhibition. In the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT, n = 155), 12-month atorvastatin reduced <span class="hlt">circulating</span> miR-122. A similar response to atorvastatin was observed in mice and cultured murine hepatocytes. Over up to 15 years of follow-up in the Bruneck Study, multivariable adjusted risk ratios per one-SD higher log miR-122 were 1.60 (95% CI 1.30–1.96; P < 0.001) for metabolic syndrome and 1.37 (1.03–1.82; P = 0.021) for <span class="hlt">type</span> 2 diabetes. In conclusion, <span class="hlt">circulating</span> miR-122 is strongly associated with the risk of developing metabolic syndrome and <span class="hlt">type</span> 2 diabetes in the general population. PMID:27899485</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004Geo....32..393B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004Geo....32..393B"><span>Migration history of air-breathing fishes reveals Neogene atmospheric <span class="hlt">circulation</span> patterns</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Böhme, M.</p> <p>2004-05-01</p> <p>The migration history of an air-breathing fish group (Channidae; snakehead fishes) is used for reconstructing Neogene Eurasian precipitation and atmospheric <span class="hlt">circulation</span> patterns. The study shows that snakeheads are sensitive indicators of summer precipitation maxima in subtropical and temperate regions, and are present regularly if the wettest month exceeds 150 mm precipitation and 20 °C mean temperature. The analysis of 515 fossil freshwater fish deposits of the past 50 m.y. from Africa and Eurasia shows two continental-scale migration events from the snakeheads' center of origin in the south Himalayan region, events that can be related to changes in the Northern Hemisphere <span class="hlt">circulation</span> pattern. The first migration, ca. 17.5 Ma, into western and central Eurasia may have been caused by a northward shift of the Intertropical Convergence Zone that brought western Eurasia under the influence of trade winds that produced a zonal and <span class="hlt">meridional</span> precipitation gradient in Europe. During the second migration, between 8 and 4 Ma, into Africa and East Asia, snakeheads reached their present-day distribution. This migration could have been related to the intensification of the Asian monsoon that brought summer precipitation to their migratory pathways in East Africa Arabia and East Asia.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP43A1458K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP43A1458K"><span>Role of Atmospheric <span class="hlt">Circulation</span> and Westerly Jet Changes in the mid-Holocene East Asian Summer Monsoon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kong, W.; Chiang, J. C. H.</p> <p>2014-12-01</p> <p>The East Asian Summer Monsoon (EASM) varies on inter-decadal to interglacial-glacial timescales. The EASM is stronger in the mid-Holocene than today, and these changes can be readily explained by orbitally-driven insolation increase during the boreal summer. However, a detailed understanding of the altered seasonal evolution of the EASM during this time is still lacking. In particular, previous work has suggested a close link between seasonal migration of the EASM and that of the mid-latitude westerlies impinging on the Tibetan Plateau. In this study, we explore, this problem in PMIP3 climate model simulations of the mid-Holocene, focusing on the role of atmospheric <span class="hlt">circulation</span> and in particular how the westerly jet modulates the East Asia summer climate on paleoclimate timescales. Analysis of the model simulations suggests that, compared to the preindustrial simulations, the transition from Mei-Yu to deep summer rainfall occurs earlier in the mid-Holocene. This is accompanied by an earlier weakening and northward shift of westerly jet away from the Tibetan Plateau. The variation in the strength and the 3-D structure of the westerly jet in the mid-Holocene is summarized. We find that changes to the monsoonal rainfall, westerly jet and <span class="hlt">meridional</span> <span class="hlt">circulation</span> covary on paleoclimate timescales. <span class="hlt">Meridional</span> wind changes in particular are tied to an altered stationary wave pattern, resembling today's the so-called 'Silk Road' teleconnection pattern, riding along the westerly jet. Diagnostic analysis also reveals changes in moist static energy and eddy energy fluxes associated with the earlier seasonal transition of the EASM. Our analyses suggest that the westerly jet is critical to the altered dynamics of the East Asian summer monsoon during the mid-Holocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.3020R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.3020R"><span>The use of <span class="hlt">circulation</span> weather <span class="hlt">types</span> to predict upwelling activity along the Western Iberian Peninsula coast</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramos, Alexandre M.; Cordeiro Pires, Ana; Sousa, Pedro M.; Trigo, Ricardo M.</p> <p>2013-04-01</p> <p>Coastal upwelling is a phenomenon that occurs in most western oceanic coasts due to the presence of mid-latitude high-pressure systems that generate equatorward winds along the coast and consequent offshore displacement of surface waters that in turn cause deeper, colder, nutrient-rich waters to arise. In western Iberian Peninsula (IP) the high-pressure system associated to northerly winds occurs mainly during spring and summer. Upwelling systems are economically relevant, being the most productive regions of the world ocean and crucial for fisheries. In this work, we evaluate the intra- and inter-annual variability of the Upwelling Index (UI) off the western coast of the IP considering four locations at various latitudes: Rias Baixas, Aveiro, Figueira da Foz and Cabo da Roca. In addition, the relationship between the variability of the occurrence of several <span class="hlt">circulation</span> weather <span class="hlt">types</span> (Ramos et al., 2011) and the UI variability along this coast was assessed in detail, allowing to discriminate which <span class="hlt">types</span> are frequently associated with strong and weak upwelling activity. It is shown that upwelling activity is mostly driven by wind flow from the northern quadrant, for which the obtained correlation coefficients (for the N and NE <span class="hlt">types</span>) are higher than 0.5 for the four considered test locations. Taking into account these significant relationships, we then developed statistical multi-linear regression models to hindcast upwelling series (April to September) at the four referred locations, using monthly frequencies of <span class="hlt">circulation</span> weather <span class="hlt">types</span> as predictors. Modelled monthly series reproduce quite accurately observational data, with correlation coefficients above 0.7 for all locations, and relatively small absolute errors. Ramos AM, Ramos R, Sousa P, Trigo RM, Janeira M, Prior V (2011) Cloud to ground lightning activity over Portugal and its association with <span class="hlt">Circulation</span> Weather <span class="hlt">Types</span>. Atmospheric Research 101:84-101. doi: 10.1016/j.atmosres.2011.01</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3046819','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3046819"><span>Mendelian Randomization Studies Do Not Support a Role for Raised <span class="hlt">Circulating</span> Triglyceride Levels Influencing <span class="hlt">Type</span> 2 Diabetes, Glucose Levels, or Insulin Resistance</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>De Silva, N. Maneka G.; Freathy, Rachel M.; Palmer, Tom M.; Donnelly, Louise A.; Luan, Jian'an; Gaunt, Tom; Langenberg, Claudia; Weedon, Michael N.; Shields, Beverley; Knight, Beatrice A.; Ward, Kirsten J.; Sandhu, Manjinder S.; Harbord, Roger M.; McCarthy, Mark I.; Smith, George Davey; Ebrahim, Shah; Hattersley, Andrew T.; Wareham, Nicholas; Lawlor, Debbie A.; Morris, Andrew D.; Palmer, Colin N.A.; Frayling, Timothy M.</p> <p>2011-01-01</p> <p>OBJECTIVE The causal nature of associations between <span class="hlt">circulating</span> triglycerides, insulin resistance, and <span class="hlt">type</span> 2 diabetes is unclear. We aimed to use Mendelian randomization to test the hypothesis that raised <span class="hlt">circulating</span> triglyceride levels causally influence the risk of <span class="hlt">type</span> 2 diabetes and raise normal fasting glucose levels and hepatic insulin resistance. RESEARCH DESIGN AND METHODS We tested 10 common genetic variants robustly associated with <span class="hlt">circulating</span> triglyceride levels against the <span class="hlt">type</span> 2 diabetes status in 5,637 case and 6,860 control subjects and four continuous outcomes (reflecting glycemia and hepatic insulin resistance) in 8,271 nondiabetic individuals from four studies. RESULTS Individuals carrying greater numbers of triglyceride-raising alleles had increased <span class="hlt">circulating</span> triglyceride levels (SD 0.59 [95% CI 0.52–0.65] difference between the 20% of individuals with the most alleles and the 20% with the fewest alleles). There was no evidence that the carriers of greater numbers of triglyceride-raising alleles were at increased risk of <span class="hlt">type</span> 2 diabetes (per weighted allele odds ratio [OR] 0.99 [95% CI 0.97–1.01]; P = 0.26). In nondiabetic individuals, there was no evidence that carriers of greater numbers of triglyceride-raising alleles had increased fasting insulin levels (SD 0.00 per weighted allele [95% CI −0.01 to 0.02]; P = 0.72) or increased fasting glucose levels (0.00 [−0.01 to 0.01]; P = 0.88). Instrumental variable analyses confirmed that genetically raised <span class="hlt">circulating</span> triglyceride levels were not associated with increased diabetes risk, fasting glucose, or fasting insulin and, for diabetes, showed a trend toward a protective association (OR per 1-SD increase in log10 triglycerides: 0.61 [95% CI 0.45–0.83]; P = 0.002). CONCLUSIONS Genetically raised <span class="hlt">circulating</span> triglyceride levels do not increase the risk of <span class="hlt">type</span> 2 diabetes or raise fasting glucose or fasting insulin levels in nondiabetic individuals. One explanation for our results is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21282362','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21282362"><span>Mendelian randomization studies do not support a role for raised <span class="hlt">circulating</span> triglyceride levels influencing <span class="hlt">type</span> 2 diabetes, glucose levels, or insulin resistance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>De Silva, N Maneka G; Freathy, Rachel M; Palmer, Tom M; Donnelly, Louise A; Luan, Jian'an; Gaunt, Tom; Langenberg, Claudia; Weedon, Michael N; Shields, Beverley; Knight, Beatrice A; Ward, Kirsten J; Sandhu, Manjinder S; Harbord, Roger M; McCarthy, Mark I; Smith, George Davey; Ebrahim, Shah; Hattersley, Andrew T; Wareham, Nicholas; Lawlor, Debbie A; Morris, Andrew D; Palmer, Colin N A; Frayling, Timothy M</p> <p>2011-03-01</p> <p>The causal nature of associations between <span class="hlt">circulating</span> triglycerides, insulin resistance, and <span class="hlt">type</span> 2 diabetes is unclear. We aimed to use Mendelian randomization to test the hypothesis that raised <span class="hlt">circulating</span> triglyceride levels causally influence the risk of <span class="hlt">type</span> 2 diabetes and raise normal fasting glucose levels and hepatic insulin resistance. We tested 10 common genetic variants robustly associated with <span class="hlt">circulating</span> triglyceride levels against the <span class="hlt">type</span> 2 diabetes status in 5,637 case and 6,860 control subjects and four continuous outcomes (reflecting glycemia and hepatic insulin resistance) in 8,271 nondiabetic individuals from four studies. Individuals carrying greater numbers of triglyceride-raising alleles had increased <span class="hlt">circulating</span> triglyceride levels (SD 0.59 [95% CI 0.52-0.65] difference between the 20% of individuals with the most alleles and the 20% with the fewest alleles). There was no evidence that the carriers of greater numbers of triglyceride-raising alleles were at increased risk of <span class="hlt">type</span> 2 diabetes (per weighted allele odds ratio [OR] 0.99 [95% CI 0.97-1.01]; P = 0.26). In nondiabetic individuals, there was no evidence that carriers of greater numbers of triglyceride-raising alleles had increased fasting insulin levels (SD 0.00 per weighted allele [95% CI -0.01 to 0.02]; P = 0.72) or increased fasting glucose levels (0.00 [-0.01 to 0.01]; P = 0.88). Instrumental variable analyses confirmed that genetically raised <span class="hlt">circulating</span> triglyceride levels were not associated with increased diabetes risk, fasting glucose, or fasting insulin and, for diabetes, showed a trend toward a protective association (OR per 1-SD increase in log(10) triglycerides: 0.61 [95% CI 0.45-0.83]; P = 0.002). Genetically raised <span class="hlt">circulating</span> triglyceride levels do not increase the risk of <span class="hlt">type</span> 2 diabetes or raise fasting glucose or fasting insulin levels in nondiabetic individuals. One explanation for our results is that raised <span class="hlt">circulating</span> triglycerides are predominantly secondary to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A11E0066K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A11E0066K"><span>On the three dimensional structure of stratospheric material transport associated with various <span class="hlt">types</span> of waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinoshita, T.; Sato, K.</p> <p>2016-12-01</p> <p>The Transformed Eulerian-Mean (TEM) equations were derived by Andrews and McIntyre (1976, 1978) and have been widely used to examine wave-mean flow interaction in the <span class="hlt">meridional</span> cross section. According to previous studies, the Brewer-Dobson <span class="hlt">circulation</span> in the stratosphere is driven by planetary waves, baroclinic waves, and inertia-gravity waves, and that the <span class="hlt">meridional</span> <span class="hlt">circulation</span> from the summer hemisphere to the winter hemisphere in the mesosphere is mainly driven by gravity waves (e.g., Garcia and Boville 1994; Plumb and Semeniuk 2003; Watanabe et al. 2008; Okamoto et al. 2011). However, the TEM equations do not provide the three-dimensional view of the transport, so that the three dimensional TEM equations have been formulated (Hoskins et al. 1983, Trenberth 1986, Plumb 1985, 1986, Takaya and Nakamura 1997, 2001, Miyahara 2006, Kinoshita et al. 2010, Noda 2010, Kinoshita and Sato 2013a, b, and Noda 2014). On the other hand, the TEM equations cannot properly treat the lower boundary and unstable waves. The Mass-weighted Isentropic Mean (MIM) equations derived by Iwasaki (1989, 1990) are the equations that overcome those problems and the formulation of three-dimensional MIM equations have been studied. The present study applies the three-dimensional TEM and MIM equations to the ERA-Interim reanalysis data and examines the climatological character of three-dimensional structure of Stratospheric Brewer-Dobson <span class="hlt">circulation</span>. Next, we will discuss how to treat the flow associated with spatial structure of stationary waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRD..11316103P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRD..11316103P"><span>Forcing mechanism of the seasonally asymmetric quasi-biennial oscillation secondary <span class="hlt">circulation</span> in ERA-40 and MAECHAM5</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peña-Ortiz, C.; Ribera, P.; García-Herrera, R.; Giorgetta, M. A.; García, R. R.</p> <p>2008-08-01</p> <p>The seasonality of the quasi-biennial oscillation (QBO) and its secondary <span class="hlt">circulation</span> is analyzed in the European Reanalysis (ERA-40) and Middle Atmosphere European Centre Hamburg Model (MAECHAM5) general <span class="hlt">circulation</span> model data sets through the multitaper method-singular value decomposition (MTM-SVD). In agreement with previous studies, the results reveal a strong seasonal dependence of the QBO secondary <span class="hlt">circulation</span>. This is characterized by a two-cell structure symmetric about the equator during autumn and spring. However, anomalies strongly weaken in the summer hemisphere and strengthen in the winter hemisphere, leading to an asymmetric QBO secondary <span class="hlt">circulation</span> characterized by a single-cell structure displaced into the winter hemisphere during the solstices. In ERA-40, this asymmetry is more pronounced during the northern than during the southern winter. These results provide the first observation of the QBO secondary <span class="hlt">circulation</span> asymmetries in the ERA-40 reanalysis data set across the full stratosphere and the lower mesosphere, up to 0.1 hPa. The MTM-SVD reconstruction of the seasonal QBO signals in the residual <span class="hlt">circulation</span> and the QBO signals in Eliassen Palm (EP) flux divergences suggest a particular mechanism for the seasonal asymmetries of the QBO secondary <span class="hlt">circulation</span> and its extension across the midlatitudes. The analysis shows that the QBO modulates the EP flux in the winter hemispheric surf zone poleward of the QBO jets. The zonal wind forcing by EP flux divergence is transformed by the Coriolis effect into a <span class="hlt">meridional</span> wind signal. The seasonality in the stratospheric EP flux and the hemispheric differences in planetary wave forcing cause the observed seasonality in the QBO secondary <span class="hlt">circulation</span> and its hemispheric differences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123.1457B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123.1457B"><span>The Role of the New Zealand Plateau in the Tasman Sea <span class="hlt">Circulation</span> and Separation of the East Australian Current</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bull, Christopher Y. S.; Kiss, Andrew E.; van Sebille, Erik; Jourdain, Nicolas C.; England, Matthew H.</p> <p>2018-02-01</p> <p>The East Australian Current (EAC) plays a major role in regional climate, <span class="hlt">circulation</span>, and ecosystems, but predicting future changes is hampered by limited understanding of the factors controlling EAC separation. While there has been speculation that the presence of New Zealand may be important for the EAC separation, the prevailing view is that the time-mean partial separation is set by the ocean's response to gradients in the wind stress curl. This study focuses on the role of New Zealand, and the associated adjacent bathymetry, in the partial separation of the EAC and ocean <span class="hlt">circulation</span> in the Tasman Sea. Here utilizing an eddy-permitting ocean model (NEMO), we find that the complete removal of the New Zealand plateau leads to a smaller fraction of EAC transport heading east and more heading south, with the mean separation latitude shifting >100 km southward. To examine the underlying dynamics, we remove New Zealand with two linear models: the Sverdrup/Godfrey Island Rule and NEMO in linear mode. We find that linear processes and deep bathymetry play a major role in the mean Tasman Front position, whereas nonlinear processes are crucial for the extent of the EAC retroflection. Contrary to past work, we find that <span class="hlt">meridional</span> gradients in the basin-wide wind stress curl are not the sole factor determining the latitude of EAC separation. We suggest that the Tasman Front location is set by either the maximum <span class="hlt">meridional</span> gradient in the wind stress curl or the northern tip of New Zealand, whichever is furthest north.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...40M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...40M"><span>Interannual variability of the North Pacific winter storm track and its relationship with extratropical atmospheric <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Xiaojiao; Zhang, Yaocun</p> <p>2018-01-01</p> <p>Interannual variability of the North Pacific storm track and the three-dimensional atmosphere <span class="hlt">circulation</span> during winter are investigated using NCEP/NCAR reanalysis data during 1950-2015. Results show that year-to-year variations of the storm track exhibit two principal modes, i.e. the monopole intensity change and the <span class="hlt">meridional</span> shift of the storm track, respectively. The intensity change mode is linked to weakening of the Siberian high, northward shift of the western Pacific jet stream and Aleutian Low, and well corresponding to the Western Pacific teleconnection. The <span class="hlt">meridional</span> shift mode is related to intensification and south-eastward extension of western Pacific jet stream and Aleutian Low, and linked to the Pacific-North America teleconnection. The internal atmospheric dynamics responsible for the storm track variability is further investigated from the perspective of wave-flow energy conversion. For the intensity change mode, accompanied by the enhanced baroclinity over the entrance region of the storm track, more energy is converted from mean available potential energy to eddy available potential energy and then transferred to eddy kinetic energy, which is favorable for the overall enhancement of the storm track intensity. For the <span class="hlt">meridional</span> shift mode, more energy is transformed from mean available potential energy to eddy available potential energy and further transferred to eddy kinetic energy over the southern (northern) areas of the storm track, contributing to the southward (northward) shift of the storm track. Additionally, the increased (decreased) conversion from mean-flow kinetic energy to eddy kinetic energy over the north-eastern Pacific region is also in favor of the southward (northward) shift of the storm track.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080044712','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080044712"><span>Cloud Effects on <span class="hlt">Meridional</span> Atmospheric Energy Budget Estimated from Clouds and the Earth's Radiant Energy System (CERES) Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kato, Seiji; Rose, Fred G.; Rutan, David A.; Charlock, Thomas P.</p> <p>2008-01-01</p> <p>The zonal mean atmospheric cloud radiative effect, defined as the difference of the top-of-atmosphere (TOA) and surface cloud radiative effects, is estimated from three years of Clouds and the Earth's Radiant Energy System (CERES) data. The zonal mean shortwave effect is small, though it tends to be positive (warming). This indicates that clouds increase shortwave absorption in the atmosphere, especially in midlatitudes. The zonal mean atmospheric cloud radiative effect is, however, dominated by the longwave effect. The zonal mean longwave effect is positive in the tropics and decreases with latitude to negative values (cooling) in polar regions. The <span class="hlt">meridional</span> gradient of cloud effect between midlatitude and polar regions exists even when uncertainties in the cloud effect on the surface enthalpy flux and in the modeled irradiances are taken into account. This indicates that clouds increase the rate of generation of mean zonal available potential energy. Because the atmospheric cooling effect in polar regions is predominately caused by low level clouds, which tend to be stationary, we postulate that the <span class="hlt">meridional</span> and vertical gradients of cloud effect increase the rate of <span class="hlt">meridional</span> energy transport by dynamics in the atmosphere from midlatitude to polar region, especially in fall and winter. Clouds then warm the surface in polar regions except in the Arctic in summer. Clouds, therefore, contribute in increasing the rate of <span class="hlt">meridional</span> energy transport from midlatitude to polar regions through the atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28951327','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28951327"><span><span class="hlt">Circulating</span> B cells in <span class="hlt">type</span> 1 diabetics exhibit fewer maturation-associated phenotypes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hanley, Patrick; Sutter, Jennifer A; Goodman, Noah G; Du, Yangzhu; Sekiguchi, Debora R; Meng, Wenzhao; Rickels, Michael R; Naji, Ali; Luning Prak, Eline T</p> <p>2017-10-01</p> <p>Although autoantibodies have been used for decades as diagnostic and prognostic markers in <span class="hlt">type</span> 1 diabetes (T1D), further analysis of developmental abnormalities in B cells could reveal tolerance checkpoint defects that could improve individualized therapy. To evaluate B cell developmental progression in T1D, immunophenotyping was used to classify <span class="hlt">circulating</span> B cells into transitional, mature naïve, mature activated, and resting memory subsets. Then each subset was analyzed for the expression of additional maturation-associated markers. While the frequencies of B cell subsets did not differ significantly between patients and controls, some T1D subjects exhibited reduced proportions of B cells that expressed transmembrane activator and CAML interactor (TACI) and Fas receptor (FasR). Furthermore, some T1D subjects had B cell subsets with lower frequencies of class switching. These results suggest <span class="hlt">circulating</span> B cells exhibit variable maturation phenotypes in T1D. These phenotypic variations may correlate with differences in B cell selection in individual T1D patients. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48.1187G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48.1187G"><span>Projections of Southern Hemisphere atmospheric <span class="hlt">circulation</span> interannual variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grainger, Simon; Frederiksen, Carsten S.; Zheng, Xiaogu</p> <p>2017-02-01</p> <p>An analysis is made of the coherent patterns, or modes, of interannual variability of Southern Hemisphere 500 hPa geopotential height field under current and projected climate change scenarios. Using three separate multi-model ensembles (MMEs) of coupled model intercomparison project phase 5 (CMIP5) models, the interannual variability of the seasonal mean is separated into components related to (1) intraseasonal processes; (2) slowly-varying internal dynamics; and (3) the slowly-varying response to external changes in radiative forcing. In the CMIP5 RCP8.5 and RCP4.5 experiments, there is very little change in the twenty-first century in the intraseasonal component modes, related to the Southern annular mode (SAM) and mid-latitude wave processes. The leading three slowly-varying internal component modes are related to SAM, the El Niño-Southern oscillation (ENSO), and the South Pacific wave (SPW). Structural changes in the slow-internal SAM and ENSO modes do not exceed a qualitative estimate of the spatial sampling error, but there is a consistent increase in the ENSO-related variance. Changes in the SPW mode exceed the sampling error threshold, but cannot be further attributed. Changes in the dominant slowly-varying external mode are related to projected changes in radiative forcing. They reflect thermal expansion of the tropical troposphere and associated changes in the <span class="hlt">Hadley</span> Cell <span class="hlt">circulation</span>. Changes in the externally-forced associated variance in the RCP8.5 experiment are an order of magnitude greater than for the internal components, indicating that the SH seasonal mean <span class="hlt">circulation</span> will be even more dominated by a SAM-like annular structure. Across the three MMEs, there is convergence in the projected response in the slow-external component.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMPP11A1362H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMPP11A1362H"><span>Searching for Abrupt <span class="hlt">Circulation</span> Shifts in Marine Isotope Stage 2 and 3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Henry, L. E.; Lynch-Stieglitz, J.; Schmidt, M. W.</p> <p>2008-12-01</p> <p>During Marine Isotope Stage 3, DO events were recorded in the Greenland ice cores and North Atlantic Ocean sediment records. Some cold DO stadials have been associated with massive freshwater inputs, termed Heinrich Events. These Heinrich Events are frequently associated with "drop dead" <span class="hlt">circulation</span> periods in which the production of North Atlantic Deep Water is greatly diminished. DO events are thought to result from a restructuring of the overturning <span class="hlt">circulation</span>. We explore these proposed changes in Atlantic Ocean <span class="hlt">circulation</span> by examining changes in seawater density in the Florida Straits. The density is inferred from the δ18O of the benthic foraminifera C. pachyderma and P. ariminensis taken from core-sites on the Florida and Greater Bahamas Bank margins. The flow through the Florida Straits is in near- geostrophic balance. This means that the vertical shear in the current is reflected in a strong density gradient across the Straits. During the Younger Dryas and the Last Glacial Maximum the density gradient was reduced consistent with weaker flow through the Straits at these times. A weakening of the Florida Current would be expected if the large scale Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> weakened, as has been proposed based on other studies. The Younger Dyras event manifests itself as well-correlated decreases in δ18O from the cores on the Florida margin, while their counterparts taken from the Bahamas remain relatively stable when adjusted for global ice volume. Here, we will present data extending back 32kyr, focusing on those cores taken from the Florida Margin which can resolve millennial scale changes during Marine Isotope Stage 2 and Late Stage 3. We will examine the relationship between <span class="hlt">circulation</span> changes, as reflected in Florida Margin density, and the three most recent Heinrich events, as well as the most recent DO events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcSci..10..907B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcSci..10..907B"><span>On the glacial and interglacial thermohaline <span class="hlt">circulation</span> and the associated transports of heat and freshwater</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ballarotta, M.; Falahat, S.; Brodeau, L.; Döös, K.</p> <p>2014-11-01</p> <p>The thermohaline <span class="hlt">circulation</span> (THC) and the oceanic heat and freshwater transports are essential for understanding the global climate system. Streamfunctions are widely used in oceanography to represent the THC and estimate the transport of heat and freshwater. In the present study, the regional and global changes of the THC, the transports of heat and freshwater and the timescale of the <span class="hlt">circulation</span> between the Last Glacial Maximum (LGM, ≈ 21 kyr ago) and the present-day climate are explored using an Ocean General <span class="hlt">Circulation</span> Model and streamfunctions projected in various coordinate systems. We found that the LGM tropical <span class="hlt">circulation</span> is about 10% stronger than under modern conditions due to stronger wind stress. Consequently, the maximum tropical transport of heat is about 20% larger during the LGM. In the North Atlantic basin, the large sea-ice extent during the LGM constrains the Gulf Stream to propagate in a more zonal direction, reducing the transport of heat towards high latitudes by almost 50% and reorganising the freshwater transport. The strength of the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> depends strongly on the coordinate system. It varies between 9 and 16 Sv during the LGM, and between 12 to 19 Sv for the present day. Similar to paleo-proxy reconstructions, a large intrusion of saline Antarctic Bottom Water takes place into the Northern Hemisphere basins and squeezes most of the Conveyor Belt <span class="hlt">circulation</span> into a shallower part of the ocean. These different haline regimes between the glacial and interglacial period are illustrated by the streamfunctions in latitude-salinity coordinates and thermohaline coordinates. From these diagnostics, we found that the LGM Conveyor Belt <span class="hlt">circulation</span> is driven by an enhanced salinity contrast between the Atlantic and the Pacific basin. The LGM abyssal <span class="hlt">circulation</span> lifts and makes the Conveyor Belt cell deviate from the abyssal region, resulting in a ventilated upper layer above a deep stagnant layer, and an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23422667','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23422667"><span>Increased ventilation of Antarctic deep water during the warm mid-Pliocene.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Zhongshi; Nisancioglu, Kerim H; Ninnemann, Ulysses S</p> <p>2013-01-01</p> <p>The mid-Pliocene warm period is a recent warm geological period that shares similarities with predictions of future climate. It is generally held the mid-Pliocene Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> must have been stronger, to explain a weak Atlantic <span class="hlt">meridional</span> δ(13)C gradient and large northern high-latitude warming. However, climate models do not simulate such stronger Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>, when forced with mid-Pliocene boundary conditions. Proxy reconstructions allow for an alternative scenario that the weak δ(13)C gradient can be explained by increased ventilation and reduced stratification in the Southern Ocean. Here this alternative scenario is supported by simulations with the Norwegian Earth System Model (NorESM-L), which simulate an intensified and slightly poleward shifted wind field off Antarctica, giving enhanced ventilation and reduced stratification in the Southern Ocean. Our findings challenge the prevailing theory and show how increased Southern Ocean ventilation can reconcile existing model-data discrepancies about Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> while explaining fundamental ocean features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3586712','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3586712"><span>Increased ventilation of Antarctic deep water during the warm mid-Pliocene</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhang, Zhongshi; Nisancioglu, Kerim H.; Ninnemann, Ulysses S.</p> <p>2013-01-01</p> <p>The mid-Pliocene warm period is a recent warm geological period that shares similarities with predictions of future climate. It is generally held the mid-Pliocene Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> must have been stronger, to explain a weak Atlantic <span class="hlt">meridional</span> δ13C gradient and large northern high-latitude warming. However, climate models do not simulate such stronger Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>, when forced with mid-Pliocene boundary conditions. Proxy reconstructions allow for an alternative scenario that the weak δ13C gradient can be explained by increased ventilation and reduced stratification in the Southern Ocean. Here this alternative scenario is supported by simulations with the Norwegian Earth System Model (NorESM-L), which simulate an intensified and slightly poleward shifted wind field off Antarctica, giving enhanced ventilation and reduced stratification in the Southern Ocean. Our findings challenge the prevailing theory and show how increased Southern Ocean ventilation can reconcile existing model-data discrepancies about Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> while explaining fundamental ocean features. PMID:23422667</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatCC...5..475R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatCC...5..475R"><span>Exceptional twentieth-century slowdown in Atlantic Ocean overturning <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rahmstorf, Stefan; Box, Jason E.; Feulner, Georg; Mann, Michael E.; Robinson, Alexander; Rutherford, Scott; Schaffernicht, Erik J.</p> <p>2015-05-01</p> <p>Possible changes in Atlantic <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> (AMOC) provide a key source of uncertainty regarding future climate change. Maps of temperature trends over the twentieth century show a conspicuous region of cooling in the northern Atlantic. Here we present multiple lines of evidence suggesting that this cooling may be due to a reduction in the AMOC over the twentieth century and particularly after 1970. Since 1990 the AMOC seems to have partly recovered. This time evolution is consistently suggested by an AMOC index based on sea surface temperatures, by the hemispheric temperature difference, by coral-based proxies and by oceanic measurements. We discuss a possible contribution of the melting of the Greenland Ice Sheet to the slowdown. Using a multi-proxy temperature reconstruction for the AMOC index suggests that the AMOC weakness after 1975 is an unprecedented event in the past millennium (p > 0.99). Further melting of Greenland in the coming decades could contribute to further weakening of the AMOC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22270720-mean-field-solar-dynamo-double-cell-meridional-circulation-pattern','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22270720-mean-field-solar-dynamo-double-cell-meridional-circulation-pattern"><span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Pipin, V. V.; Kosovichev, A. G.</p> <p></p> <p>Recent helioseismology findings, as well as advances in direct numerical simulations of global dynamics of the Sun, have indicated that in each solar hemisphere <span class="hlt">meridional</span> <span class="hlt">circulation</span> may form more than one cell along the radius in the convection zone. In particular, recent helioseismology results revealed a double-cell structure of the <span class="hlt">meridional</span> <span class="hlt">circulation</span>. We investigate properties of a mean-field solar dynamo with such double-cell <span class="hlt">meridional</span> <span class="hlt">circulation</span>. The dynamo model also includes the realistic profile of solar differential rotation (including the tachocline and subsurface shear layer) and takes into account effects of turbulent pumping, anisotropic turbulent diffusivity, and conservation of magnetic helicity.more » Contrary to previous flux-transport dynamo models, we find that the dynamo model can robustly reproduce the basic properties of the solar magnetic cycles for a wide range of model parameters and <span class="hlt">circulation</span> speeds. The best agreement with observations is achieved when the surface <span class="hlt">meridional</span> <span class="hlt">circulation</span> speed is about 12 m s{sup –1}. For this <span class="hlt">circulation</span> speed, the simulated sunspot activity shows good synchronization with the polar magnetic fields. Such synchronization was indeed observed during previous sunspot Cycles 21 and 22. We compare theoretical and observed phase diagrams of the sunspot number and the polar field strength and discuss the peculiar properties of Cycle 23.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJBm...60..507R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJBm...60..507R"><span>Winter <span class="hlt">circulation</span> weather <span class="hlt">types</span> and hospital admissions for respiratory diseases in Galicia, Spain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Royé, D.; Taboada, J. J.; Martí, A.; Lorenzo, M. N.</p> <p>2016-04-01</p> <p>The link between various pathologies and atmospheric conditions has been a constant topic of study over recent decades in many places across the world; knowing more about it enables us to pre-empt the worsening of certain diseases, thereby optimizing medical resources. This study looked specifically at the connections in winter between respiratory diseases and <span class="hlt">types</span> of atmospheric weather conditions (<span class="hlt">Circulation</span> Weather <span class="hlt">Types</span>, CWT) in Galicia, a region in the north-western corner of the Iberian Peninsula. To do this, the study used hospital admission data associated with these pathologies as well as an automatic classification of weather <span class="hlt">types</span>. The main result obtained was that weather <span class="hlt">types</span> giving rise to an increase in admissions due to these diseases are those associated with cold, dry weather, such as those in the east and south-east, or anticyclonic <span class="hlt">types</span>. A second peak was associated with humid, hotter weather, generally linked to south-west weather <span class="hlt">types</span>. In the future, this result may help to forecast the increase in respiratory pathologies in the region some days in advance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26307637','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26307637"><span>Winter <span class="hlt">circulation</span> weather <span class="hlt">types</span> and hospital admissions for respiratory diseases in Galicia, Spain.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Royé, D; Taboada, J J; Martí, A; Lorenzo, M N</p> <p>2016-04-01</p> <p>The link between various pathologies and atmospheric conditions has been a constant topic of study over recent decades in many places across the world; knowing more about it enables us to pre-empt the worsening of certain diseases, thereby optimizing medical resources. This study looked specifically at the connections in winter between respiratory diseases and <span class="hlt">types</span> of atmospheric weather conditions (<span class="hlt">Circulation</span> Weather <span class="hlt">Types</span>, CWT) in Galicia, a region in the north-western corner of the Iberian Peninsula. To do this, the study used hospital admission data associated with these pathologies as well as an automatic classification of weather <span class="hlt">types</span>. The main result obtained was that weather <span class="hlt">types</span> giving rise to an increase in admissions due to these diseases are those associated with cold, dry weather, such as those in the east and south-east, or anticyclonic <span class="hlt">types</span>. A second peak was associated with humid, hotter weather, generally linked to south-west weather <span class="hlt">types</span>. In the future, this result may help to forecast the increase in respiratory pathologies in the region some days in advance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5462A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5462A"><span>Influence of SST anomalies in low latitudes on atmospheric heat transport to the Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alekseev, Genrikh; Kuzmina, Svetlana; Glok, Natalia</p> <p>2017-04-01</p> <p>The purpose of the study is to assess the influence of SST anomalies in the low latitudes of the Atlantic, Indian and Pacific oceans to climatic change of the winter atmospheric <span class="hlt">meridional</span> heat transport (MAHT) to the Arctic and to propose the mechanisms of this influence. Estimates of sensible and latent heat transport to the Arctic through the "Atlantic Gate" at 70 ° N in winter (December-February) 1980-2015 fulfilled on base ERA / Interim and monthly SST from HadISST were used. Multi-dimensional cross-correlation analysis was applied. The area and month in each ocean were found with maximal correlations between SST and winter MAHT. Mean SST in selected areas for each month of 1980-2015 were calculated and its correlations with MAHT were estimated. The correlation coefficients equal from 0.57 to 0.42, and after removing the noise increased up to 0.75 with MAHT lag from 27 to 30 months. The SST and MAHT series include together with positive trend the 5-7 years fluctuations. The mechanism of SST anomalies influence on winter MAHT to the Arctic includes the interaction of atmospheric (<span class="hlt">Hadley</span> and Ferrel <span class="hlt">circulations</span>, jet streams, NAO) and oceanic (Gulf Stream, the North Atlantic, the Norwegian currents) <span class="hlt">circulation</span> patterns. To justify the proposed scheme the evaluation of the links between SST anomalies, the NAO index, the Atlantic water inflow to the Barents Sea, are investigated. The study is supported with RFBR project 15-05-03512.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870044310&hterms=power+balance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dpower%2Bbalance','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870044310&hterms=power+balance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dpower%2Bbalance"><span>Seasonal <span class="hlt">meridional</span> energy balance and thermal structure of the atmosphere of Uranus - A radiative-convective-dynamical model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Friedson, James; Ingersoll, Andrew P.</p> <p>1987-01-01</p> <p>A model is presented for the thermodynamics of the seasonal <span class="hlt">meridional</span> energy balance and thermal structure of the Uranian atmosphere. The model considers radiation and small-scale convection, and dynamical heat fluxes due to large-scale baroclinic eddies. Phase oscillations with a period of 0.5 Uranian year are discerned in the total internal power and global enthalpy storage. The variations in the identity of the main transport agent with the magnitude of the internal heat source are discussed. It is shown that <span class="hlt">meridional</span> heat transport in the atmosphere is sufficient to lower seasonal horizontal temperature contrasts below those predicted with radiative-convection models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP13A1818R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP13A1818R"><span>A new multi-proxy reconstruction of Atlantic deep ocean <span class="hlt">circulation</span> during the warm mid-Pliocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riesselman, C. R.; Dowsett, H. J.; Scher, H. D.; Robinson, M. M.</p> <p>2011-12-01</p> <p>The mid-Pliocene (3.264 - 3.025 Ma) is the most recent interval in Earth's history with sustained global temperatures in the range of warming predicted for the 21st century, providing an appealing analog with which to examine the Earth system changes we might encounter in the coming century. Ongoing sea surface and deep ocean temperature reconstructions and coupled ocean-atmosphere general <span class="hlt">circulation</span> model simulations by the USGS PRISM (Pliocene Research Interpretation and Synoptic Mapping) Group identify a dramatic North Atlantic warm anomaly coupled with increased evaporation in the mid-Pliocene, possibly driving enhanced <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span> and North Atlantic Deep Water production. However deep ocean temperature is not a conclusive proxy for water mass, and most coupled model simulations predict transient decreases in North Atlantic Deep Water production in 21st century, presenting a contrasting picture of future warmer worlds. Here, we present early results from a new multi-proxy reconstruction of Atlantic deep ocean <span class="hlt">circulation</span> during the warm mid-Pliocene, using δ13C of benthic foraminifera as a proxy for water mass age and the neodymium isotopic imprint on fossil fish teeth as a proxy for water mass source region along a three-site depth transect from the Walvis Ridge (subtropical South Atlantic). The deep ocean <span class="hlt">circulation</span> reconstructions resulting from this project will add a new dimension to the PRISM effort and will be useful for both initialization and evaluation of future model simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.1429C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.1429C"><span>Indian Ocean and Indian summer monsoon: relationships without ENSO in ocean-atmosphere coupled simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crétat, Julien; Terray, Pascal; Masson, Sébastien; Sooraj, K. P.; Roxy, Mathew Koll</p> <p>2017-08-01</p> <p>The relationship between the Indian Ocean and the Indian summer monsoon (ISM) and their respective influence over the Indo-Western North Pacific (WNP) region are examined in the absence of El Niño Southern Oscillation (ENSO) in two partially decoupled global experiments. ENSO is removed by nudging the tropical Pacific simulated sea surface temperature (SST) toward SST climatology from either observations or a fully coupled control run. The control reasonably captures the observed relationships between ENSO, ISM and the Indian Ocean Dipole (IOD). Despite weaker amplitude, IODs do exist in the absence of ENSO and are triggered by a boreal spring ocean-atmosphere coupled mode over the South-East Indian Ocean similar to that found in the presence of ENSO. These pure IODs significantly affect the tropical Indian Ocean throughout boreal summer, inducing a significant modulation of both the local Walker and <span class="hlt">Hadley</span> cells. This <span class="hlt">meridional</span> <span class="hlt">circulation</span> is masked in the presence of ENSO. However, these pure IODs do not significantly influence the Indian subcontinent rainfall despite overestimated SST variability in the eastern equatorial Indian Ocean compared to observations. On the other hand, they promote a late summer cross-equatorial quadrupole rainfall pattern linking the tropical Indian Ocean with the WNP, inducing important zonal shifts of the Walker <span class="hlt">circulation</span> despite the absence of ENSO. Surprisingly, the interannual ISM rainfall variability is barely modified and the Indian Ocean does not force the monsoon <span class="hlt">circulation</span> when ENSO is removed. On the contrary, the monsoon <span class="hlt">circulation</span> significantly forces the Arabian Sea and Bay of Bengal SSTs, while its connection with the western tropical Indian Ocean is clearly driven by ENSO in our numerical framework. Convection and diabatic heating associated with above-normal ISM induce a strong response over the WNP, even in the absence of ENSO, favoring moisture convergence over India.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...51L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...51L"><span>Impact of Gulf Stream SST biases on the global atmospheric <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Robert W.; Woollings, Tim J.; Hoskins, Brian J.; Williams, Keith D.; O'Reilly, Christopher H.; Masato, Giacomo</p> <p>2018-02-01</p> <p>The UK Met Office Unified Model in the Global Coupled 2 (GC2) configuration has a warm bias of up to almost 7 K in the Gulf Stream SSTs in the winter season, which is associated with surface heat flux biases and potentially related to biases in the atmospheric <span class="hlt">circulation</span>. The role of this SST bias is examined with a focus on the tropospheric response by performing three sensitivity experiments. The SST biases are imposed on the atmosphere-only configuration of the model over a small and medium section of the Gulf Stream, and also the wider North Atlantic. Here we show that the dynamical response to this anomalous Gulf Stream heating (and associated shifting and changing SST gradients) is to enhance vertical motion in the transient eddies over the Gulf Stream, rather than balance the heating with a linear dynamical <span class="hlt">meridional</span> wind or <span class="hlt">meridional</span> eddy heat transport. Together with the imposed Gulf Stream heating bias, the response affects the troposphere not only locally but also in remote regions of the Northern Hemisphere via a planetary Rossby wave response. The sensitivity experiments partially reproduce some of the differences in the coupled configuration of the model relative to the atmosphere-only configuration and to the ERA-Interim reanalysis. These biases may have implications for the ability of the model to respond correctly to variability or changes in the Gulf Stream. Better global prediction therefore requires particular focus on reducing any large western boundary current SST biases in these regions of high ocean-atmosphere interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A13E0313S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A13E0313S"><span>Low-frequency climate anomalies, changes in synoptic scale <span class="hlt">circulation</span> patterns and statistics of extreme events over south-east Poland during the Last Millennium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slawinska, J. M.; Bartoszek, K.; Gabriel, C. J.</p> <p>2016-12-01</p> <p>Long-term predictions of changes in extreme event frequency are of utmost importance due to their high societal and economic impact. Yet, current projections are of limited skills as they rely on satellite records that are relatively short compared to the timescale of interest, and also due to the presence of a significant anthropogenic trend superimposed onto other low-frequency variabilities. Novel simulations of past climates provide unique opportunity to separate external perturbations from internal climate anomalies and to attribute the latter to systematic changes in different <span class="hlt">types</span> of synoptic scale <span class="hlt">circulation</span> and distributions of high-frequency events. Here we study such changes by employing the Last Millennium Ensemble of climate simulations carried out with the Community Earth System Model (CESM) at the U.S. National Center for Atmospheric Research, focusing in particular on decadal changes in frequency of extreme precipitation events over south-east Poland. We analyze low-frequency modulations of dominant patterns of synoptic scale <span class="hlt">circulations</span> over Europe and their dependence on the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span>, along with their coupling with the North Atlantic Oscillation. Moreover, we examine whether some decades of persistently anomalous statistics of extreme events can be attributed to externally forced (e.g., via volcanic eruptions) perturbations of the North Atlantic climate. In the end, we discuss the possible linkages and physical mechanisms connecting volcanic eruptions, low-frequency variabilities of North Atlantic climate and changes in statistics of high impact weather, and compare briefly our results with some historical and paleontological records.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8894K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8894K"><span>A Study of Subseasonal Predictability of the Atmospheric <span class="hlt">Circulation</span> Low-frequency Modes based on SL-AV forecasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kruglova, Ekaterina; Kulikova, Irina; Khan, Valentina; Tischenko, Vladimir</p> <p>2017-04-01</p> <p>The subseasonal predictability of low-frequency modes and the atmospheric <span class="hlt">circulation</span> regimes is investigated based on the using of outputs from global Semi-Lagrangian (SL-AV) model of the Hydrometcentre of Russia and Institute of Numerical Mathematics of Russian Academy of Science. Teleconnection indices (AO, WA, EA, NAO, EU, WP, PNA) are used as the quantitative characteristics of low-frequency variability to identify zonal and <span class="hlt">meridional</span> flow regimes with focus on control distribution of high impact weather patterns in the Northern Eurasia. The predictability of weekly and monthly averaged indices is estimated by the methods of diagnostic verification of forecast and reanalysis data covering the hindcast period, and also with the use of the recommended WMO quantitative criteria. Characteristics of the low frequency variability have been discussed. Particularly, it is revealed that the <span class="hlt">meridional</span> flow regimes are reproduced by SL-AV for summer season better comparing to winter period. It is shown that the model's deterministic forecast (ensemble mean) skill at week 1 (days 1-7) is noticeably better than that of climatic forecasts. The decrease of skill scores at week 2 (days 8-14) and week 3( days 15-21) is explained by deficiencies in the modeling system and inaccurate initial conditions. It was noticed the slightly improvement of the skill of model at week 4 (days 22-28), when the condition of atmosphere is more determined by the flow of energy from the outside. The reliability of forecasts of monthly (days 1-30) averaged indices is comparable to that at week 1 (days 1-7). Numerical experiments demonstrated that the forecast accuracy can be improved (thus the limit of practical predictability can be extended) through the using of probabilistic approach based on ensemble forecasts. It is shown that the quality of forecasts of the regimes of <span class="hlt">circulation</span> like blocking is higher, than that of zonal flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA534204','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA534204"><span>Climate Change Planning for Military Installations: Findings and Implications</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2010-10-01</p> <p><span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> ARFORGEN Army Force Generation BASH Bird Aircraft Strike Hazard BLM Bureau of Land Management BOR Bureau of Reclamation...Cover and Land Use Change LLNL Lawrence Livermore National Laboratory MOC <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> NASA National Aeronautics and Space...to discern effects of climate change. D.7.9 Bureau of Land Management BLM is responsible for managing much of the federal land affected by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5222508','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5222508"><span>Influenza Vaccine Effectiveness in the Netherlands from 2003/2004 through 2013/2014: The Importance of <span class="hlt">Circulating</span> Influenza Virus <span class="hlt">Types</span> and Subtypes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dijkstra, Frederika; van Doorn, Eva; Bijlsma, Maarten J.; Donker, Gé A.; de Lange, Marit M. A.; Cadenau, Laura M.; Hak, Eelko; Meijer, Adam</p> <p>2017-01-01</p> <p>Influenza vaccine effectiveness (IVE) varies over different influenza seasons and virus (sub)<span class="hlt">types</span>/lineages. To assess the association between IVE and <span class="hlt">circulating</span> influenza virus (sub)<span class="hlt">types</span>/lineages, we estimated the overall and (sub)<span class="hlt">type</span> specific IVE in the Netherlands. We conducted a test-negative case control study among subjects with influenza-like illness or acute respiratory tract infection consulting the Sentinel Practices over 11 influenza seasons (2003/2004 through 2013/2014) in the Netherlands. The adjusted IVE was estimated using generalized linear mixed modelling and multiple logistic regression. In seven seasons vaccine strains did not match the <span class="hlt">circulating</span> viruses. Overall adjusted IVE was 40% (95% CI 18 to 56%) and 20% (95% CI -5 to 38%) when vaccine (partially)matched and mismatched the <span class="hlt">circulating</span> viruses, respectively. When A(H3N2) was the predominant virus, IVE was 38% (95% CI 14 to 55%). IVE against infection with former seasonal A(H1N1) virus was 83% (95% CI 52 to 94%), and with B virus 67% (95% CI 55 to 76%). In conclusion IVE estimates were particularly low when vaccine mismatched the <span class="hlt">circulating</span> viruses and A(H3N2) was the predominant influenza virus subtype. Tremendous effort is required to improve vaccine production procedure and to explore the factors that influence the IVE against A(H3N2) virus. PMID:28068386</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013CSR....63S..13H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013CSR....63S..13H"><span>Disruption of a cyclonic eddy <span class="hlt">circulation</span> by wind stress in Prince William Sound, Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Halverson, Mark J.; Carter Ohlmann, J.; Johnson, Mark A.; Scott Pegau, W.</p> <p>2013-07-01</p> <p>Oceanographic observations made during the Sound Predictions 2009 field experiment in Prince William Sound, Alaska, have documented rapid changes in the upper water column (0-40m) <span class="hlt">circulation</span>. An assortment of drifting buoys, sampling four different depths, and HF radar surface current mapping, revealed three modes of <span class="hlt">circulation</span>: anticyclonic, open cyclonic, and closed cyclonic. Each mode was observed at least once within an 18-day window, and the transition between them took as little as a day. Time-resolved hydrographic measurements show that the mass field was variable, but generally arranged such that the surface geostrophic flow should be in a closed-core cyclonic eddy configuration. Observations show that the mass field was likely influenced by relatively low salinity water flowing into Prince William Sound from the shelf, and from local freshwater input. We quantitatively examine why a closed-core <span class="hlt">circulation</span> was not always observed by focusing on the transition between the closed and open cyclonic flow patterns. The western region of the central sound is a key area for this transition. Here, the high-frequency radar revealed that the closed <span class="hlt">circulation</span> was established when the net flow shifted direction from northward to southward. A detailed comparison of the <span class="hlt">meridional</span> geostrophic and wind-driven flows, using measured winds and hydrographic data from CTD profiles and two autonomous vehicles, shows that the geostrophic flow was mostly southward while the wind-driven flow was mostly northward. A net southward flow can be caused by a decrease in the northward wind-driven flow or an increase in the southward geostrophic flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APS..DFDQ32008S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APS..DFDQ32008S"><span>Turbulent convection in geostrophic <span class="hlt">circulation</span> with wind and buoyancy forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sohail, Taimoor; Gayen, Bishakhdatta; Hogg, Andy</p> <p>2017-11-01</p> <p>We conduct a direct numerical simulation of geostrophic <span class="hlt">circulation</span> forced by surface wind and buoyancy to model a circumpolar ocean. The imposed buoyancy forcing (represented by Rayleigh number) drives a zonal current and supports small-scale convection in the buoyancy destabilizing region. In addition, we observe eddy activity which transports heat southward, supporting a large amount of heat uptake. Increasing wind stress enhances the <span class="hlt">meridional</span> buoyancy gradient, triggering more eddy activity inside the boundary layer. Therefore, heat uptake increases with higher wind stress. The majority of dissipation is confined within the surface boundary layer, while mixing is dominant inside the convective plume and the buoyancy destabilizing region of the domain. The relative strength of the mixing and dissipation in the system can be expressed by mixing efficiency. This study finds that mixing is much greater than viscous dissipation, resulting in higher values of mixing efficiency than previously used. Supported by Australian Research Council Grant DP140103706.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70016437','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70016437"><span>Galileo infrared imaging spectroscopy measurements at venus</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Carlson, R.W.; Baines, K.H.; Encrenaz, Th.; Taylor, F.W.; Drossart, P.; Kamp, L.W.; Pollack, James B.; Lellouch, E.; Collard, A.D.; Calcutt, S.B.; Grinspoon, D.; Weissman, P.R.; Smythe, W.D.; Ocampo, A.C.; Danielson, G.E.; Fanale, F.P.; Johnson, T.V.; Kieffer, H.H.; Matson, D.L.; McCord, T.B.; Soderblom, L.A.</p> <p>1991-01-01</p> <p>During the 1990 Galileo Venus flyby, the Near Infrared Mapping Spectrometer investigated the night-side atmosphere of Venus in the spectral range 0.7 to 5.2 micrometers. Multispectral images at high spatial resolution indicate substantial cloud opacity variations in the lower cloud levels, centered at 50 kilometers altitude. Zonal and <span class="hlt">meridional</span> winds were derived for this level and are consistent with motion of the upper branch of a <span class="hlt">Hadley</span> cell. Northern and southern hemisphere clouds appear to be markedly different. Spectral profiles were used to derive lower atmosphere abundances of water vapor and other species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJC...75..194S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJC...75..194S"><span>Instability of <span class="hlt">meridional</span> axial system in f( R) gravity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharif, M.; Yousaf, Z.</p> <p>2015-05-01</p> <p>We analyze the dynamical instability of a non-static reflection axial stellar structure by taking into account the generalized Euler equation in metric f( R) gravity. Such an equation is obtained by contracting the Bianchi identities of the usual anisotropic and effective stress-energy tensors, which after using a radial perturbation technique gives a modified collapse equation. In the realm of the gravity model, we investigate instability constraints at Newtonian and post-Newtonian approximations. We find that the instability of a <span class="hlt">meridional</span> axial self-gravitating system depends upon the static profile of the structure coefficients, while f( R) extra curvature terms induce the stability of the evolving celestial body.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17195957','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17195957"><span><span class="hlt">Circulation</span> of a <span class="hlt">type</span> 1 recombinant vaccine-derived poliovirus strain in a limited area in Romania.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Combiescu, M; Guillot, S; Persu, A; Baicus, A; Pitigoi, D; Balanant, J; Oprisan, G; Crainic, R; Delpeyroux, F; Aubert-Combiescu, A</p> <p>2007-01-01</p> <p>After intensive immunisation campaigns with the oral polio vaccine (OPV) as part of the Global Polio Eradication Initiative, poliomyelitis due to wild viruses has disappeared from most parts of the world, including Europe. Here, we report the characterization of a serotype 1 vaccine-derived poliovirus (VDPV) isolated from one acute flaccid paralysis (AFP) case with tetraplegia and eight healthy contacts belonging to the same small socio-cultural group having a low vaccine coverage living in a small town in Romania. The genomes of the isolated strains appeared to be tripartite <span class="hlt">type</span> 1/<span class="hlt">type</span> 2/<span class="hlt">type</span> 1 vaccine intertypic recombinant genomes derived from a common ancestor strain. The presence of 1.2% nucleotide substitutions in the VP1 capsid protein coding region of most of the strains indicated a <span class="hlt">circulation</span> time of about 14 months. These VDPVs were thermoresistant and, in transgenic mice expressing the human poliovirus receptor, appeared to have lost the attenuated phenotype. These results suggest that small populations with low vaccine coverage living in globally well-vaccinated countries can be the origin of VDPV emergence and <span class="hlt">circulation</span>. These results reaffirm the importance of active surveillance for acute flaccid paralysis and poliovirus in both polio-free and polio-endemic countries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000038181&hterms=atlantic+meridional+overturning+circulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000038181&hterms=atlantic+meridional+overturning+circulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation"><span>Influence of Sea Ice on the Thermohaline <span class="hlt">Circulation</span> in the Arctic-North Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mauritzen, Cecilie; Haekkinen, Sirpa</p> <p>1997-01-01</p> <p>A fully prognostic coupled ocean-ice model is used to study the sensitivity of the overturning cell of the Arctic-North-Atlantic system to sea ice forcing. The strength of the thermohaline cell will be shown to depend on the amount of sea ice transported from the Arctic to the Greenland Sea and further to the subpolar gyre. The model produces a 2-3 Sv increase of the <span class="hlt">meridional</span> <span class="hlt">circulation</span> cell at 25N (at the simulation year 15) corresponding to a decrease of 800 cu km in the sea ice export from the Arctic. Previous modeling studies suggest that interannual and decadal variability in sea ice export of this magnitude is realistic, implying that sea ice induced variability in the overturning cell can reach 5-6 Sv from peak to peak.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15543567','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15543567"><span>Changing epidemiology of rotavirus G-<span class="hlt">types</span> <span class="hlt">circulating</span> in Hong Kong, China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lo, Janice Yee Chi; Szeto, Kai Cheung; Tsang, Dominic Ngai Chong; Leung, Kwok Hung; Lim, Wilina Wei Ling</p> <p>2005-01-01</p> <p>Group A rotaviruses are the most common cause of severe diarrhoeal disease in young children worldwide. The development of a vaccine is advocated by the World Health Organization. Obtaining local baseline information regarding rotavirus strain variation is important to ensure matching of <span class="hlt">circulating</span> and vaccine strains. The current study was undertaken to determine the epidemiology of rotavirus G-<span class="hlt">types</span> in Hong Kong in anticipation of a vaccination program. From 2001 to 2002 over a period of one year, diarrhoeal stool specimens known to be positive for rotavirus were subjected to G-<span class="hlt">typing</span> by reverse transcriptase-polymerase chain reaction using nested <span class="hlt">type</span>-specific primers. Rotavirus G-<span class="hlt">type</span> distribution was correlated with patient demographics. Among 747 rotavirus positive stool specimens, 723 strains could be G-<span class="hlt">typed</span> as G1 (302, 40.4%), G2 (128, 17.1%), G3 (231, 30.9%), G4 (24, 3.2%), and G9 (38, 5.1%). G1 strains were found predominantly in those 5 years old or younger (P < 0.0001), while G2 strains were more prevalent among those over 5 years of age (P < 0.001). When compared with similar studies in 1983 to 1984 and 1999 to 2000, there were significant changes in the prevalence of various G-<span class="hlt">types</span>, with consistent detection of G9 strains in the current study. It is concluded that rotavirus G-<span class="hlt">type</span> distribution in Hong Kong has varied with time. Continuous monitoring of the epidemiology of rotavirus is important, especially in anticipation of the introduction of a vaccine, in order to document its impact and to ensure its continued effectiveness. Copyright 2005 Wiley-Liss, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2290F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2290F"><span>Tropical cyclogenesis in warm climates simulated by a cloud-system resolving model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fedorov, Alexey V.; Muir, Les; Boos, William R.; Studholme, Joshua</p> <p>2018-03-01</p> <p>Here we investigate tropical cyclogenesis in warm climates, focusing on the effect of reduced equator-to-pole temperature gradient relevant to past equable climates and, potentially, to future climate change. Using a cloud-system resolving model that explicitly represents moist convection, we conduct idealized experiments on a zonally periodic equatorial β-plane stretching from nearly pole-to-pole and covering roughly one-fifth of Earth's circumference. To improve the representation of tropical cyclogenesis and mean climate at a horizontal resolution that would otherwise be too coarse for a cloud-system resolving model (15 km), we use the hypohydrostatic rescaling of the equations of motion, also called reduced acceleration in the vertical. The simulations simultaneously represent the <span class="hlt">Hadley</span> <span class="hlt">circulation</span> and the intertropical convergence zone, baroclinic waves in mid-latitudes, and a realistic distribution of tropical cyclones (TCs), all without use of a convective parameterization. Using this model, we study the dependence of TCs on the <span class="hlt">meridional</span> sea surface temperature gradient. When this gradient is significantly reduced, we find a substantial increase in the number of TCs, including a several-fold increase in the strongest storms of Saffir-Simpson categories 4 and 5. This increase occurs as the mid-latitudes become a new active region of TC formation and growth. When the climate warms we also see convergence between the physical properties and genesis locations of tropical and warm-core extra-tropical cyclones. While end-members of these <span class="hlt">types</span> of storms remain very distinct, a large distribution of cyclones forming in the subtropics and mid-latitudes share properties of the two.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.8200C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.8200C"><span>Interannual Variability in the Position and Strength of the East Asian Jet Stream and Its Relation to Large - scale <span class="hlt">Circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chan, Duo; Zhang, Yang; Wu, Qigang</p> <p>2013-04-01</p> <p>East Asian Jet Stream (EASJ) is charactered by obvious interannual variability in strength and position (latitude), with wide impacts on East Asian climate in all seasons. In this study, two indices are established to measure the interannual variability in intensity and position of EAJS. Possible causing factors, including both local signals and non-local large-scale <span class="hlt">circulation</span>, are examined using NCAP-NCAR reanalysis data to investigate their relations with jet variation. Our analysis shows that the relationship between the interannual variations of EASJ and these factors depends on seasons. In the summer, both the intensity and position of EASJ are closely related to the <span class="hlt">meridional</span> gradient of local surface temperature, but display no apparent relationship with the larg-scale <span class="hlt">circulation</span>. In cold seasons (autumn, winter and spring), both the local factor and the large-scale <span class="hlt">circulation</span>, i.e. the Pacific/North American teleconnection pattern (PNA), play important roles in the interannual variability of the jet intensity. The variability in the jet position, however, is more correlated to the Arctic Oscillation (AO), especially in winter. Diagnostic analysis indicates that transient eddy activity plays an important role in connecting the interannual variability of EASJ position with AO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPC21A..04S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPC21A..04S"><span>Predominant nonlinear atmospheric response to <span class="hlt">meridional</span> shift of the Gulf Stream path from the WRF atmospheric model simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seo, H.; Kwon, Y. O.; Joyce, T. M.</p> <p>2016-02-01</p> <p>A remarkably strong nonlinear behavior of the atmospheric <span class="hlt">circulation</span> response to North Atlantic SST anomalies (SSTA) is revealed from a set of large-ensemble, high-resolution, and hemispheric-scale Weather Research and Forecasting (WRF) model simulations. The model is forced with the SSTA associated with <span class="hlt">meridional</span> shift of the Gulf Stream (GS) path, constructed from a lag regression of the winter SST on a GS Index from observation. Analysis of the systematic set of experiments with SSTAs of varied amplitudes and switched signs representing various GS-shift scenarios provides unique insights into mechanism for emergence and evolution of transient and equilibrium response of atmospheric <span class="hlt">circulation</span> to extratropical SSTA. Results show that, independent of sign of the SSTA, the equilibrium response is characterized by an anomalous trough over the North Atlantic Ocean and the Western Europe concurrent with enhanced storm track, increased rainfall, and reduced blocking days. To the north of the anomalous low, an anomalous ridge emerges over the Greenland, Iceland, and Norwegian Seas accompanied by weakened storm track, reduced rainfall and increased blocking days. This nonlinear component of the total response dominates the weak and oppositely signed linear response that is directly forced by the SSTA, yielding an anomalous ridge (trough) downstream of the warm (cold) SSTA. The amplitude of the linear response is proportional to that of the SSTA, but this is masked by the overwhelmingly strong nonlinear behavior showing no clear correspondence to the SSTA amplitude. The nonlinear pattern emerges 3-4 weeks after the model initialization in November and reaches its first peak amplitude in December/January. It appears that altered baroclinic wave activity due to the GS SSTA in November lead to low-frequency height responses in December/January through transient eddy vorticity flux convergence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990116473&hterms=daniel+bender&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddaniel%2Bbender','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990116473&hterms=daniel+bender&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddaniel%2Bbender"><span>Wind-Related Features and Processes on Venus: Summary of Magellan Results</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greeley, Ronald; Bender, Kelly; Thomas, Peggy E.; Schubert, Gerald; Limonadi, Daniel; Weitz, Catherine M.</p> <p>1995-01-01</p> <p>A search of Magellan synthetic aperture radar images covering approximately 98% of the venusian surface shows that aeolian features occur at all longitudes and latitudes. A global data base for wind streaks, the most common <span class="hlt">type</span> of aeolian feature, was developed. For each of the 5970 streaks in the data base, information was compiled on location, streak <span class="hlt">type</span>, radar backscatter, dimensions, azimuth, orientation with respect to local slope, and <span class="hlt">type</span> of landform with which it is associated. In addition, streaks occurring in association with parabolic ejecta deposits were designated <span class="hlt">type</span> P streaks, which constitute about 31% of the data base. Wind streak azimuths were analyzed to assess wind patterns at the time of their formation. Both hemispheres show strong westward and equatorward trends in azimuths, consistent with <span class="hlt">Hadley</span> <span class="hlt">circulation</span> and inferred upper atmospheric westward zonal winds. When <span class="hlt">type</span> P streaks (those considered to result from transient impact events) were removed, the westward component was greatly reduced, suggesting that the upper zonal winds do not extend to the surface. The presence of equator-oriented streaks at high latitudes suggests that <span class="hlt">Hadley</span> <span class="hlt">circulation</span> extends to the poles. A field of possible yardangs found southwest of Mead Crater strikes NE-SW and occupies plains situated in a shallow topographic depression. Analysis of non-<span class="hlt">type</span> P streaks in the area suggests that equatorward winds are funneled through the depression and are responsible for the erosion of the terrain to form the yardangs. Dune deposits are limited on Venus. Two dune fields were identified (Aglonice and Fortuna-Meshkenet) which total in area about 18,300 sq km. Microdunes are proposed for some southern hemisphere areas which show distinctive radar reflectivities. Bragg scattering and/or subpixel reflections from the leeward faces of microdune bedforms could account for the unusual radar backscatter cross sections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990116097&hterms=daniel+bender&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddaniel%2Bbender','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990116097&hterms=daniel+bender&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddaniel%2Bbender"><span>Wind-Related Features and Processes on Venus Summary of Magellan Results</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greeley, Ronald; Bender, Kelly; Thomas, Peggy E.; Schubert, Gerald; Limonadi, Daniel; Weitz, Catherine M.</p> <p>1995-01-01</p> <p>A search of Magellan synthetic aperture radar images covering about 98% of the venusian surface shows that aeolian features occur at all longitudes and latitudes. A global data base for wind streaks, the most common <span class="hlt">type</span> of aeolian feature, was developed. For each of the 5970 streaks in the data base, information was compiled on location, streak <span class="hlt">type</span>, radar backscatter, dimensions, azimuth, orientation with respect to local slope, and <span class="hlt">type</span> of landform with which it is associated. In addition, streaks occurring in association with parabolic ejecta deposits were designated <span class="hlt">type</span> P streaks, which constitute about 31% of the data base. Wind streak azimuths were analyzed to assess wind patterns at the time of their formation. Both hemispheres show strong westward and equatorward trends in azimuths, consistent with <span class="hlt">Hadley</span> <span class="hlt">circulation</span> and inferred upper atmospheric westward zonal winds. When <span class="hlt">type</span> P streaks (those considered to result from transient impact events) were removed, the westward component was greatly reduced, suggesting that the upper zonal winds do not extend to the surface. The presence of equator-oriented streaks at high latitudes suggests that <span class="hlt">Hadley</span> <span class="hlt">circulation</span> extends to the poles. A field of possible yardangs found southwest of Mead Crater strikes NE-SW and occupies plains situated in a shallow topographic depression. Analysis of non-<span class="hlt">type</span> P streaks in the area suggests that equatorward winds are funneled through the depression and are responsible for the erosion of the terrain to form the yardangs. Dune deposits are limited on Venus. Two dune fields were identified (Aglonice and Fortuna-Meshkenet) which total in area about 18,300 square km. Microdunes are proposed for some southern hemisphere areas which show distinctive radar reflectivities. Bragg scattering and/or subpixel reflections from the leeward faces of microdune bedforms could account for the unusual radar backscatter cross sections.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AtmRe.118..180Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AtmRe.118..180Z"><span>An advanced method for classifying atmospheric <span class="hlt">circulation</span> <span class="hlt">types</span> based on prototypes connectivity graph</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zagouras, Athanassios; Argiriou, Athanassios A.; Flocas, Helena A.; Economou, George; Fotopoulos, Spiros</p> <p>2012-11-01</p> <p>Classification of weather maps at various isobaric levels as a methodological tool is used in several problems related to meteorology, climatology, atmospheric pollution and to other fields for many years. Initially the classification was performed manually. The criteria used by the person performing the classification are features of isobars or isopleths of geopotential height, depending on the <span class="hlt">type</span> of maps to be classified. Although manual classifications integrate the perceptual experience and other unquantifiable qualities of the meteorology specialists involved, these are typically subjective and time consuming. Furthermore, during the last years different approaches of automated methods for atmospheric <span class="hlt">circulation</span> classification have been proposed, which present automated and so-called objective classifications. In this paper a new method of atmospheric <span class="hlt">circulation</span> classification of isobaric maps is presented. The method is based on graph theory. It starts with an intelligent prototype selection using an over-partitioning mode of fuzzy c-means (FCM) algorithm, proceeds to a graph formulation for the entire dataset and produces the clusters based on the contemporary dominant sets clustering method. Graph theory is a novel mathematical approach, allowing a more efficient representation of spatially correlated data, compared to the classical Euclidian space representation approaches, used in conventional classification methods. The method has been applied to the classification of 850 hPa atmospheric <span class="hlt">circulation</span> over the Eastern Mediterranean. The evaluation of the automated methods is performed by statistical indexes; results indicate that the classification is adequately comparable with other state-of-the-art automated map classification methods, for a variable number of clusters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP41C2267S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP41C2267S"><span>North Pacific <span class="hlt">Meridional</span> Mode over the Common Era</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanchez, S. C.; Charles, C. D.; Amaya, D. J.; Miller, A. J.</p> <p>2016-12-01</p> <p>The Pacific <span class="hlt">Meridional</span> Mode (PMM) has been increasingly recognized as an influential mode of variability for channeling extratropical anomalies to the equatorial ocean-atmosphere system. The PMM has been identified as an important precursor for ENSO, a source of much decadal power in the tropical Pacific, and is potentially intensifying. It is still unknown why the Pacific <span class="hlt">Meridional</span> Mode might be intensifying; most arguments center around the changing mean state associated with anthropogenic global warming. There are a number of processes by which the background state could influence the PMM: altering the location of trade winds, the characteristics of stochastic forcing, the sensitivity of latent heat flux to surface wind anomalies, the wind response to SST anomalies, or changing the Intertropical Convergence Zone (ITCZ) structure. Recent work has found that the PMM is particularly sensitive to ITCZ shifts in intensity and location (using a simple linear coupled model, [Martinez-Villalobos and Vimont 2016]). Over the last millennium the ITCZ has experienced epochs of notable latitudinal shifts to balance the cross equatorial energy transport. Here we investigate how the strength of the PMM may have varied with these shifts in the ITCZ over the Common Era using the CESM-Last Millennium Ensemble (LME). We assess the strength of the PMM pathway by the degree of air-sea coupling and the amplitude of tropical decadal variability. We expect the ITCZ location and the degree of air-sea coupling (WES feedback) to play a critical role in determining the effectiveness and intensity of the PMM pathway. We verify our inferences in the LME with coral paleoproxy records from the central tropical Pacific. Chiefly we target records from the Line Islands (spanning 1°N to 6°N) to infer variations in the location of the ITCZ and the amplitude of decadal variability. This work enables us to discuss the idea of an intensifying PMM in a more historical context.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22047928-systematic-center-limb-variation-measured-helioseismic-travel-times-its-effect-inferences-solar-interior-meridional-flows','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22047928-systematic-center-limb-variation-measured-helioseismic-travel-times-its-effect-inferences-solar-interior-meridional-flows"><span>SYSTEMATIC CENTER-TO-LIMB VARIATION IN MEASURED HELIOSEISMIC TRAVEL TIMES AND ITS EFFECT ON INFERENCES OF SOLAR INTERIOR <span class="hlt">MERIDIONAL</span> FLOWS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Zhao Junwei; Nagashima, Kaori; Bogart, R. S.</p> <p></p> <p>We report on a systematic center-to-limb variation in measured helioseismic travel times, which must be taken into account for an accurate determination of solar interior <span class="hlt">meridional</span> flows. The systematic variation, found in time-distance helioseismology analysis using SDO/HMI and SDO/AIA observations, is different in both travel-time magnitude and variation trend for different observables. It is not clear what causes this systematic effect. Subtracting the longitude-dependent east-west travel times, obtained along the equatorial area, from the latitude-dependent north-south travel times, obtained along the central meridian area, gives remarkably similar results for different observables. We suggest this as an effective procedure for removingmore » the systematic center-to-limb variation. The subsurface <span class="hlt">meridional</span> flows obtained from inversion of the corrected travel times are approximately 10 m s{sup -1} slower than those obtained without removing the systematic effect. The detected center-to-limb variation may have important implications in the derivation of <span class="hlt">meridional</span> flows in the deep interior and needs to be better understood.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010271','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010271"><span>Systematic Center-To-Limb Variation in Measured Helioseismic Travel Times and Its Effect on Inferences of Solar Interior <span class="hlt">Meridional</span> Flows</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhao, Junwei; Nagashima, Kaori; Bogart, R. S.; Kosovichev, Alexander; Duvall, T. L., Jr.</p> <p>2012-01-01</p> <p>We report on a systematic center-to-limb variation in measured helioseismic travel times, which must be taken into account for an accurate determination of solar interior <span class="hlt">meridional</span> flows. The systematic variation, found in time-distance helioseismology analysis using SDO/HMI and SDO/AIA observations, is different in both travel-time magnitude and variation trend for different observables. It is not clear what causes this systematic effect. Subtracting the longitude-dependent east-west travel times, obtained along the equatorial area, from the latitude-dependent north-south travel times, obtained along the central meridian area, gives remarkably similar results for different observables. We suggest this as an effective procedure for removing the systematic center-to-limb variation. The subsurface <span class="hlt">meridional</span> flows obtained from inversion of the corrected travel times are approximately 10 m s-1 slower than those obtained without removing the systematic effect. The detected center-to-limb variation may have important implications in the derivation of <span class="hlt">meridional</span> flows in the deep interior and needs to be better understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860007321','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860007321"><span>Zonally averaged model of dynamics, chemistry and radiation for the atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tung, K. K.</p> <p>1985-01-01</p> <p>A nongeostrophic theory of zonally averaged <span class="hlt">circulation</span> is formulated using the nonlinear primitive equations on a sphere, taking advantage of the more direct relationship between the mean <span class="hlt">meridional</span> <span class="hlt">circulation</span> and diabatic heating rate which is available in isentropic coordinates. Possible differences between results of nongeostrophic theory and the commonly used geostrophic formulation are discussed concerning: (1) the role of eddy forcing of the diabatic <span class="hlt">circulation</span>, and (2) the nonlinear nearly inviscid limit vs the geostrophic limit. Problems associated with the traditional Rossby number scaling in quasi-geostrophic formulations are pointed out and an alternate, more general scaling based on the smallness of mean <span class="hlt">meridional</span> to zonal velocities for a rotating planet is suggested. Such a scaling recovers the geostrophic balanced wind relationship for the mean zonal flow but reveals that the mean <span class="hlt">meridional</span> velocity is in general ageostrophic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1344654-satellite-sounder-observations-contrasting-tropospheric-moisture-transport-regimes-saharan-air-layers-hadley-cells-atmospheric-rivers','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1344654-satellite-sounder-observations-contrasting-tropospheric-moisture-transport-regimes-saharan-air-layers-hadley-cells-atmospheric-rivers"><span>Satellite Sounder Observations of Contrasting Tropospheric Moisture Transport Regimes: Saharan Air Layers, <span class="hlt">Hadley</span> Cells, and Atmospheric Rivers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Nalli, Nicholas R.; Barnet, Christopher D.; Reale, Tony</p> <p></p> <p>This paper examines the performance of satellite sounder atmospheric vertical moisture proles (AVMP) under tropospheric conditions encompassing moisture contrasts driven by convection and advection transport mechanisms, specifically Atlantic Ocean Saharan air layers (SALs) and Pacific Ocean moisture conveyer belts (MCBs) commonly referred to as atmospheric rivers (ARs), both of these being mesoscale to synoptic meteorological phenomena within the vicinity of subtropical <span class="hlt">Hadley</span> subsidence zones. Operational AVMP environmental data records retrieved from the Suomi National Polar-orbiting Partnership (SNPP) NOAA-Unique Combined Atmospheric Processing System (NUCAPS) are collocated with dedicated radiosonde observations (RAOBs) obtained from ocean-based intensive field campaigns; these RAOBs provide uniquelymore » independent correlative truth data not assimilated into numerical weather prediction models for satellite sounder validation over open ocean. Using these marine-based data, we empirically assess the performance of the operational NUCAPS AVMP product for detecting and resolving these tropospheric moisture features over otherwise RAOB-sparse regions.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130003300','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130003300"><span>High Latitude <span class="hlt">Meridional</span> Flow on the Sun May Explain North-South Polar Field Asymmetry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kosak, Katie; Upton, Lisa; Hathaway, David</p> <p>2012-01-01</p> <p>We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north-south symmetric, <span class="hlt">meridional</span> flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the <span class="hlt">meridional</span> flow at high latitudes indicate systematic north-south differences. There was a strong flow in the North while the flow in the South was weaker. With these results, we have a possible solution to the polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun's polar regions in general and the polar meridonal flow in particular.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A43D3301S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A43D3301S"><span>Using a Very Large Ensemble to Examine the Role of the Ocean in Recent Warming Trends.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sparrow, S. N.; Millar, R.; Otto, A.; Yamazaki, K.; Allen, M. R.</p> <p>2014-12-01</p> <p>Results from a very large (~10,000 member) perturbed physics and perturbed initial condition ensemble are presented for the period 1980 to present. A set of model versions that can shadow recent surface and upper ocean observations are identified and the range of uncertainty in the Atlantic <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> (AMOC) assessed. This experiment uses the Met Office <span class="hlt">Hadley</span> Centre Coupled Model version 3 (HadCM3), a coupled model with fully dynamic atmosphere and ocean components as part of the climateprediction.net distributive computing project. Parameters are selected so that the model has good top of atmosphere radiative balance and simulations are run without flux adjustments that "nudge" the climate towards a realistic state, but have an adverse effect on important ocean processes. This ensemble provides scientific insights on the possible role of the AMOC, among other factors, in climate trends, or lack thereof, over the past 20 years. This ensemble is also used to explore how the occurrence of hiatus events of different durations varies for models with different transient climate response (TCR). We show that models with a higher TCR are less likely to produce a 15-year warming hiatus in global surface temperature than those with a lower TCR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012IJBm...56..591S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012IJBm...56..591S"><span>Correlations between the modelled potato crop yield and the general atmospheric <span class="hlt">circulation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sepp, Mait; Saue, Triin</p> <p>2012-07-01</p> <p>Biology-related indicators do not usually depend on just one meteorological element but on a combination of several weather indicators. One way to establish such integral indicators is to classify the general atmospheric <span class="hlt">circulation</span> into a small number of <span class="hlt">circulation</span> <span class="hlt">types</span>. The aim of present study is to analyse connections between general atmospheric <span class="hlt">circulation</span> and potato crop yield in Estonia. Meteorologically possible yield (MPY), calculated by the model POMOD, is used to characterise potato crop yield. Data of three meteorological stations and the biological parameters of two potato sorts were applied to the model, and 73 different classifications of atmospheric <span class="hlt">circulation</span> from catalogue 1.2 of COST 733, domain 05 are used to qualify <span class="hlt">circulation</span> conditions. Correlation analysis showed that there is at least one <span class="hlt">circulation</span> <span class="hlt">type</span> in each of the classifications with at least one statistically significant (99%) correlation with potato crop yield, whether in Kuressaare, Tallinn or Tartu. However, no classifications with <span class="hlt">circulation</span> <span class="hlt">types</span> correlating with MPY in all three stations at the same time were revealed. <span class="hlt">Circulation</span> <span class="hlt">types</span> inducing a decrease in the potato crop yield are more clearly represented. Clear differences occurred between the observed geographical locations as well as between the seasons: derived from the number of significant <span class="hlt">circulation</span> <span class="hlt">types</span>, summer and Kuressaare stand out. Of potato varieties, late 'Anti' is more influenced by <span class="hlt">circulation</span>. Analysis of MSLP maps of <span class="hlt">circulation</span> <span class="hlt">types</span> revealed that the seaside stations (Tallinn, Kuressaare) suffer from negative effects of anti-cyclonic conditions (drought), while Tartu suffers from the cyclonic activity (excessive water).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53N..04K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53N..04K"><span>Transient Atmospheric <span class="hlt">Circulation</span> Changes in a Grand ensemble of Idealized CO2 Increase Experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karpechko, A.; Manzini, E.; Kornblueh, L.</p> <p>2017-12-01</p> <p>The yearly evolution with increasing forcing of the large-scale atmospheric <span class="hlt">circulation</span> is examined in a 68-member ensemble of 1pctCO2 scenario experiments performed with the MPI-ESM model. Each member of the experiment ensemble is integrated for 155 years, from initial conditions taken from a 2000-yr long pre-industrial control climate experiment. The 1pctCO2 scenario experiments are conducted following the protocol of including as external forcing only a CO2 concentration increase at 1%/year, till quadrupling of CO2 concentrations. MPI-ESM is the Max-Planck-Institute Earth System Model (including coupling between the atmosphere, ocean and seaice). By averaging over the 68 members (ensemble mean), atmospheric variability is greatly reduced. Thus, it is possible to investigate the sensitivity to the climate state of the atmospheric response to CO2 doubling. Indicators of global change show the expected monotonic evolution with increasing CO2 and a weak dependence of the thermodynamical response to CO2 doubling on the climate state. The surface climate response of the atmospheric <span class="hlt">circulation</span>, diagnosed for instance by the pressure at sea level, and the eddy-driven jet response show instead a marked dependence to the climate state, for the Northern winter season. We find that as the CO2 concentration increases above doubling, Northern winter trends in some indicators of atmospheric <span class="hlt">circulation</span> changes decrease or even reverse, posing the question on what are the causes of this nonlinear behavior. The investigation of the role of stationary waves, the <span class="hlt">meridional</span> overturning <span class="hlt">circulation</span>, the decrease in Arctic sea ice and the stratospheric vortex points to the latter as a plausible cause of such nonlinear response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810059491&hterms=1091&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231091','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810059491&hterms=1091&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231091"><span>Evidence for wavelike anomalies with short <span class="hlt">meridional</span> and large zonal scales in the lower stratospheric temperature field</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stanford, J. L.; Short, D. A.</p> <p>1981-01-01</p> <p>Global microwave brightness temperature measurements are analyzed to investigate the range of <span class="hlt">meridional</span> wavelengths 2000-3000 km where spectral studies reveal larger than expected variance. The data, from the TIROS-N Microwave Sounding Unit, are sensitive to lower stratospheric temperatures (30-150 mb). The results reveal striking temperature anomalies with short <span class="hlt">meridional</span> wavelengths (2000-3000 km) and long zonal wavelengths (zonal wavenumbers 1-4). The anomalies, with amplitudes approximately 1-2 K, extend from the equatorial region to at least as high as 70 deg N and 70 deg S during January 1979. The features exhibit slow eastward movement or else are nearly stationary for several days. In the Northern Hemisphere, comparison with NMC data reveals that the strongest features tend to be associated with major jet streams.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4032512','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4032512"><span><span class="hlt">Meridional</span> displacement of the Antarctic Circumpolar Current</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Gille, Sarah T.</p> <p>2014-01-01</p> <p>Observed long-term warming trends in the Southern Ocean have been interpreted as a sign of increased poleward eddy heat transport or of a poleward displacement of the entire Antarctic Circumpolar Current (ACC) frontal system. The two-decade-long record from satellite altimetry is an important source of information for evaluating the mechanisms governing these trends. While several recent studies have used sea surface height contours to index ACC frontal displacements, here altimeter data are instead used to track the latitude of mean ACC transport. Altimetric height contours indicate a poleward trend, regardless of whether they are associated with ACC fronts. The zonally averaged transport latitude index shows no long-term trend, implying that ACC <span class="hlt">meridional</span> shifts determined from sea surface height might be associated with large-scale changes in sea surface height more than with localized shifts in frontal positions. The transport latitude index is weakly sensitive to the Southern Annular Mode, but is uncorrelated with El Niño/Southern Oscillation. PMID:24891396</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018NatAs...2...43A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018NatAs...2...43A"><span>Dynamics of the global <span class="hlt">meridional</span> ice flow of Europa's icy shell</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ashkenazy, Yosef; Sayag, Roiy; Tziperman, Eli</p> <p>2018-01-01</p> <p>Europa is one of the most probable places in the solar system to find extra-terrestrial life1,2, motivating the study of its deep ( 100 km) ocean3-6 and thick icy shell3,7-11. The chaotic terrain patterns on Europa's surface12-15 have been associated with vertical convective motions within the ice8,10. Horizontal gradients of ice thickness16,17 are expected due to the large equator-to-pole gradient of surface temperature and can drive a global horizontal ice flow, yet such a flow and its observable implications have not been studied. We present a global ice flow model for Europa composed of warm, soft ice flowing beneath a cold brittle rigid ice crust3. The model is coupled to an underlying (diffusive) ocean and includes the effect of tidal heating and convection within the ice. We show that Europa's ice can flow <span class="hlt">meridionally</span> due to pressure gradients associated with equator-to-pole ice thickness differences, which can be up to a few km and can be reduced both by ice flow and due to ocean heat transport. The ice thickness and <span class="hlt">meridional</span> flow direction depend on whether the ice convects or not; multiple (convecting and non-convecting) equilibria are found. Measurements of the ice thickness and surface temperature from future Europa missions18,19 can be used with our model to deduce whether Europa's icy shell convects and to constrain the effectiveness of ocean heat transport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009DPS....41.6302H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009DPS....41.6302H"><span>Long-term Behaviour Of Venus Winds At Cloud Level From Virtis/vex Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hueso, Ricardo; Peralta, J.; Sánchez-Lavega, A.; Pérez-Hoyos, S.; Piccioni, G.; Drossart, P.</p> <p>2009-09-01</p> <p>The Venus Express (VEX) mission has been in orbit to Venus for more than three years now. The VIRTIS instrument onboard VEX observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. Images in the ultraviolet range are used to study the upper cloud at 66 km while images in the infrared (1.74 μm) map the opacity of the lower cloud deck at 48 km. Here we present an analysis of the overall dynamics of Venus’ atmosphere at both levels using observations that cover a large fraction of the VIRTIS dataset. We will present our latest results concerning the zonal winds, the overall stability in the lower cloud deck motions and the variability in the upper cloud. <span class="hlt">Meridional</span> winds are also observed in the upper and lower cloud in the UV and IR images obtained with VIRTIS. While the upper clouds present a net <span class="hlt">meridional</span> motion consistent with the upper branch of a <span class="hlt">Hadley</span> cell the lower cloud present more irregular, variable and less intense motions in the <span class="hlt">meridional</span> direction. Acknowledgements This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07. RH acknowledges a "Ramón y Cajal” contract from MEC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611332V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611332V"><span>Towards the impact of eddies on the response of the global ocean <span class="hlt">circulation</span> to Southern Ocean gateway opening</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Viebahn, Jan; von der Heydt, Anna S.; Dijkstra, Henk A.</p> <p>2014-05-01</p> <p>During the past 65 Million (Ma) years, Earth's climate has undergone a major change from warm 'greenhouse' to colder 'icehouse' conditions with extensive ice sheets in the polar regions of both hemispheres. The Eocene-Oligocene (~34 Ma) and Oligocene-Miocene (~23 Ma) boundaries reflect major transitions in Cenozoic global climate change. Proposed mechanisms of these transitions include reorganization of ocean <span class="hlt">circulation</span> due to critical gateway opening/deepening, changes in atmospheric CO2-concentration, and feedback mechanisms related to land-ice formation. A long-standing hypothesis is that the formation of the Antarctic Circumpolar Current due to opening/deepening of Southern Ocean gateways led to glaciation of the Antarctic continent. However, while this hypothesis remains controversial, its assessment via coupled climate model simulations depends crucially on the spatial resolution in the ocean component. More precisely, only high-resolution modeling of the turbulent ocean <span class="hlt">circulation</span> is capable of adequately describing reorganizations in the ocean flow field and related changes in turbulent heat transport. In this study, for the first time results of a high-resolution (0.1° horizontally) realistic global ocean model simulation with a closed Drake Passage are presented. Changes in global ocean temperatures, heat transport, and ocean <span class="hlt">circulation</span> (e.g., <span class="hlt">Meridional</span> Overturning <span class="hlt">Circulation</span> and Antarctic Coastal Current) are established by comparison with an open Drake Passage high-resolution reference simulation. Finally, corresponding low-resolution simulations are also analyzed. The results highlight the essential impact of the ocean eddy field in palaeoclimatic change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.1033S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.1033S"><span>Some remarks on using <span class="hlt">circulation</span> classifications to evaluate <span class="hlt">circulation</span> model and atmospheric reanalysis data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stryhal, Jan; Huth, Radan</p> <p>2017-04-01</p> <p>Automated classifications of atmospheric <span class="hlt">circulation</span> patterns represent a tool widely used for studying the <span class="hlt">circulation</span> in both the real atmosphere, represented by atmospheric reanalyses, and in <span class="hlt">circulation</span> model outputs. It is well known that the results of studies utilizing one of these methods are influenced by several subjective choices, of which one of the most crucial is the selection of the method itself. Authors of the present study used eight methods from the COST733 classification software (Grosswettertypes, two variants of Jenkinson-Collison, Lund, T-mode PCA with oblique rotation of principal components, k-medoids, k-means with differing starting partitions, and SANDRA) to assess the winter 1961-2000 daily sea level pressure patterns in five reanalysis datasets (ERA-40, NCEP-1, JRA-55, 20CRv2, and ERA-20C), as well as in the historical runs and 21st century projections of an ensemble of CMIP5 GCMs. The classification methods were quite consistent in displaying the strongest biases in GCM simulations. However, the results also showed that multiple classifications are required to quantify the biases in certain <span class="hlt">types</span> of <span class="hlt">circulation</span> (e.g., zonal <span class="hlt">circulation</span> or blocking-like patterns). There was no sign that any method should have a tendency to over- or underestimate the biases in <span class="hlt">circulation</span> <span class="hlt">type</span> frequency. The bias found by a particular method for a particular domain clearly reflects the ability of the algorithm to detect groups of similar patterns within the data space, and whether these groups do or do not differ one dataset to another is to a large extend coincidental. There were, nevertheless, systematic differences between groups of methods that use some form of correlation to classify the patterns to <span class="hlt">circulation</span> <span class="hlt">types</span> (CTs) and those which use the Euclidean distance. The comparison of reanalyses, which was conducted over eight European domains, showed that there is even a weak negative correlation between the average differences of CT frequency found</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3068031','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3068031"><span>Outbreak of <span class="hlt">Type</span> 2 Vaccine-Derived Poliovirus in Nigeria: Emergence and Widespread <span class="hlt">Circulation</span> in an Underimmunized Population</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pate, Muhammad Ali; Wannemuehler, Kathleen; Jenks, Julie; Burns, Cara; Chenoweth, Paul; Abanida, Emmanuel Ade; Adu, Festus; Baba, Marycelin; Gasasira, Alex; Iber, Jane; Mkanda, Pascal; Williams, A. J.; Shaw, Jing; Pallansch, Mark; Kew, Olen</p> <p>2011-01-01</p> <p>Wild poliovirus has remained endemic in northern Nigeria because of low coverage achieved in the routine immunization program and in supplementary immunization activities (SIAs). An outbreak of infection involving 315 cases of <span class="hlt">type</span> 2 <span class="hlt">circulating</span> vaccine-derived poliovirus (cVDPV2; >1% divergent from Sabin 2) occurred during July 2005–June 2010, a period when 23 of 34 SIAs used monovalent or bivalent oral poliovirus vaccine (OPV) lacking Sabin 2. In addition, 21 “pre-VDPV2” (0.5%–1.0% divergent) cases occurred during this period. Both cVDPV and pre-VDPV cases were clinically indistinguishable from cases due to wild poliovirus. The monthly incidence of cases increased sharply in early 2009, as more children aged without trivalent OPV SIAs. Cumulative state incidence of pre-VDPV2/cVDPV2 was correlated with low childhood immunization against poliovirus <span class="hlt">type</span> 2 assessed by various means. Strengthened routine immunization programs in countries with suboptimal coverage and balanced use of OPV formulations in SIAs are necessary to minimize risks of VDPV emergence and <span class="hlt">circulation</span>. PMID:21402542</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28990933','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28990933"><span><span class="hlt">Circulating</span> osteocrin stimulates bone growth by limiting C-<span class="hlt">type</span> natriuretic peptide clearance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kanai, Yugo; Yasoda, Akihiro; Mori, Keita P; Watanabe-Takano, Haruko; Nagai-Okatani, Chiaki; Yamashita, Yui; Hirota, Keisho; Ueda, Yohei; Yamauchi, Ichiro; Kondo, Eri; Yamanaka, Shigeki; Sakane, Yoriko; Nakao, Kazumasa; Fujii, Toshihito; Yokoi, Hideki; Minamino, Naoto; Mukoyama, Masashi; Mochizuki, Naoki; Inagaki, Nobuya</p> <p>2017-11-01</p> <p>Although peptides are safe and useful as therapeutics, they are often easily degraded or metabolized. Dampening the clearance system for peptide ligands is a promising strategy for increasing the efficacy of peptide therapies. Natriuretic peptide receptor B (NPR-B) and its naturally occurring ligand, C-<span class="hlt">type</span> natriuretic peptide (CNP), are potent stimulators of endochondral bone growth, and activating the CNP/NPR-B system is expected to be a powerful strategy for treating impaired skeletal growth. CNP is cleared by natriuretic peptide clearance receptor (NPR-C); therefore, we investigated the effect of reducing the rate of CNP clearance on skeletal growth by limiting the interaction between CNP and NPR-C. Specifically, we generated transgenic mice with increased <span class="hlt">circulating</span> levels of osteocrin (OSTN) protein, a natural NPR-C ligand without natriuretic activity, and observed a dose-dependent skeletal overgrowth phenotype in these animals. Skeletal overgrowth in OSTN-transgenic mice was diminished in either CNP- or NPR-C-depleted backgrounds, confirming that CNP and NPR-C are indispensable for the bone growth-stimulating effect of OSTN. Interestingly, double-transgenic mice of CNP and OSTN had even higher levels of <span class="hlt">circulating</span> CNP and additional increases in bone length, as compared with mice with elevated CNP alone. Together, these results support OSTN administration as an adjuvant agent for CNP therapy and provide a potential therapeutic approach for diseases with impaired skeletal growth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SoPh..293...59R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SoPh..293...59R"><span><span class="hlt">Meridional</span> Motions and Reynolds Stress Determined by Using Kanzelhöhe Drawings and White Light Solar Images from 1964 to 2016</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruždjak, Domagoj; Sudar, Davor; Brajša, Roman; Skokić, Ivica; Poljančić Beljan, Ivana; Jurdana-Šepić, Rajka; Hanslmeier, Arnold; Veronig, Astrid; Pötzi, Werner</p> <p>2018-04-01</p> <p>Sunspot position data obtained from Kanzelhöhe Observatory for Solar and Environmental Research (KSO) sunspot drawings and white light images in the period 1964 to 2016 were used to calculate the rotational and <span class="hlt">meridional</span> velocities of the solar plasma. Velocities were calculated from daily shifts of sunspot groups and an iterative process of calculation of the differential rotation profiles was used to discard outliers. We found a differential rotation profile and <span class="hlt">meridional</span> motions in agreement with previous studies using sunspots as tracers and conclude that the quality of the KSO data is appropriate for analysis of solar velocity patterns. By analyzing the correlation and covariance of <span class="hlt">meridional</span> velocities and rotation rate residuals we found that the angular momentum is transported towards the solar equator. The magnitude and latitudinal dependence of the horizontal component of the Reynolds stress tensor calculated is sufficient to maintain the observed solar differential rotation profile. Therefore, our results confirm that the Reynolds stress is the dominant mechanism responsible for transport of angular momentum towards the solar equator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70026009','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70026009"><span>Potential effects of climate change on ground water in Lansing, Michigan</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Croley, T.E.; Luukkonen, C.L.</p> <p>2003-01-01</p> <p>Computer simulations involving general <span class="hlt">circulation</span> models, a hydrologic modeling system, and a ground water flow model indicate potential impacts of selected climate change projections on ground water levels in the Lansing, Michigan, area. General <span class="hlt">circulation</span> models developed by the Canadian Climate Centre and the <span class="hlt">Hadley</span> Centre generated meteorology estimates for 1961 through 1990 (as a reference condition) and for the 20 years centered on 2030 (as a changed climate condition). Using these meteorology estimates, the Great Lakes Environmental Research Laboratory's hydrologic modeling system produced corresponding period streamflow simulations. Ground water recharge was estimated from the streamflow simulations and from variables derived from the general <span class="hlt">circulation</span> models. The U.S. Geological Survey developed a numerical ground water flow model of the Saginaw and glacial aquifers in the Tri-County region surrounding Lansing, Michigan. Model simulations, using the ground water recharge estimates, indicate changes in ground water levels. Within the Lansing area, simulated ground water levels in the Saginaw aquifer declined under the Canadian predictions and increased under the <span class="hlt">Hadley</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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