The Variability of the Horizontal Circulation in the Troposphere and Stratosphere: A Comparison

NASA Technical Reports Server (NTRS)

Perlwitz, Judith; Graf, Hans-F.; Hansem, James E. (Technical Monitor)

2001-01-01

The variability of the horizontal circulation in the stratosphere and troposphere of the Northern Hemisphere (NH) is compared by using various approaches. Spatial degrees of freedom (dof) on different time scales were derived. Modes of variability were computed in geopotential height fields at the tropospheric and stratospheric pressure levels by applying multivariate statistical approaches. Features of the spatial and temporal variability of the winterly zonal wind were studied with the help of recurrence and persistence analyses. The geopotential height and zonally-averaged zonal wind at the 50-, 500- and 1000-hPa level are used to investigate the behavior of the horizontal circulation in the lower stratosphere, mid-troposphere and at the near surface level, respectively. It is illustrated that the features of the variability of the horizontal circulation are very similar in the mid-troposphere and at the near surface level. Due to the filtering of tropospheric disturbances by the stratospheric and upper tropospheric zonal mean flow, the variability of the stratospheric circulation exhibits less spatial complexity than the circulation at tropospheric pressure levels. There exist enormous differences in the number of degrees of freedom (or free variability modes) between both atmospheric layers. Results of the analyses clearly show that the concept of a zonally symmetric AO with a simple structure in the troposphere similar to the one in the stratosphere is not valid. It is concluded that the spatially filtered climate change signal can be detected earlier in the stratosphere than in the mid-troposphere or at the near surface level.

Mars Characterization for Future Missions

NASA Technical Reports Server (NTRS)

Bridger, Alison F. C.; Haberle, Robert M.

1999-01-01

Annual simulations of Mars' atmosphere made with the NASA Ames Mars General Circulation Model have been used to extract and generate products to provide statistical products that detail the variability of Mars' atmosphere on fairly short time scales. These products are needed for the creation of a new version of Mars-GRAM, due for completion in June, 1999. The updated Mars-Gram, in turn, will provide guidance for forthcoming aerobraking and aerocapture activities. We have created files containing zonally-averaged fields (temperatures, densities, pressures, and winds, all on z-surfaces), as well as zonally-averaged diurnal and semidiurnal tidal amplitudes and phases. All fields represent a time averaged state (over either 5 or 30 sols), and all fields are available at each of 12 seasons for a Mars year (the seasons being 30deg of Ls apart). Files for low and moderate dust loading cases are liable via anonymous ftp. Files for a high dust case will be in place shortly.

Jet and storm track variability and change: adiabatic QG zonal averages and beyond... (Invited)

NASA Astrophysics Data System (ADS)

Robinson, W. A.

2013-12-01

The zonally averaged structures of extratropical jets and stormtracks, their slow variations, and their responses to climate change are all tightly constrained on the one hand by thermal wind balance and the necessary application of eddy torques to produce zonally averaged meridional motion, and, on the other hand, by the necessity that eddies propagate upshear to extract energy from the mean flow. Combining these constraints with the well developed theory of linear Rossby-wave propagation on zonally symmetric basic states has led to a large and growing number of plausible mechanisms to explain observed and modeled jet/storm track variability and responses to climate change and idealized forcing. Hidden within zonal averages is the reality that most baroclinic eddy activity is destroyed at the same latitude at which is generated: from one end to another of the fixed stormtracks in the Northern Hemisphere and baroclinic wave packets in the Southern Hemisphere. Ignored within adiabatic QG theory is the reality that baroclinic eddies gain significant energy from latent heating that involves sub-syntopic scale structures and dynamics. Here we use results from high-resolution regional and global simulations of the Northern Hemisphere storm tracks to explore the importance of non-zonal and diabatic dynamics in influencing jet change and variability and their influences on the much-studied zonal means.

Do initial conditions matter? A comparison of model climatologies generated from different initial states

NASA Technical Reports Server (NTRS)

Spar, J.; Cohen, C.; Wu, P.

1981-01-01

A coarse mesh (8 by 10) 7 layer global climate model was used to compute 15 months of meteorological history in two perpetual January experiments on a water planet (without continents) with a zonally symmetric climatological January sea surface temperature field. In the first of the two water planet experiments the initial atmospheric state was a set of zonal mean values of specific humidity, temperature, and wind at each latitude. In the second experiment the model was initialized with globally uniform mean values of specific humidity and temperature on each sigma level surface, constant surface pressure (1010 mb), and zero wind everywhere. A comparison was made of the mean January climatic states generated by the two water planet experiments. The first two months of each 15 January run were discarded, and 13 month averages were computed from months 3 through 15.

Convectively driven decadal zonal accelerations in Earth's fluid core

NASA Astrophysics Data System (ADS)

More, Colin; Dumberry, Mathieu

2018-04-01

Azimuthal accelerations of cylindrical surfaces co-axial with the rotation axis have been inferred to exist in Earth's fluid core on the basis of magnetic field observations and changes in the length-of-day. These accelerations have a typical timescale of decades. However, the physical mechanism causing the accelerations is not well understood. Scaling arguments suggest that the leading order torque averaged over cylindrical surfaces should arise from the Lorentz force. Decadal fluctuations in the magnetic field inside the core, driven by convective flows, could then force decadal changes in the Lorentz torque and generate zonal accelerations. We test this hypothesis by constructing a quasi-geostrophic model of magnetoconvection, with thermally driven flows perturbing a steady, imposed background magnetic field. We show that when the Alfvén number in our model is similar to that in Earth's fluid core, temporal fluctuations in the torque balance are dominated by the Lorentz torque, with the latter generating mean zonal accelerations. Our model reproduces both fast, free Alfvén waves and slow, forced accelerations, with ratios of relative strength and relative timescale similar to those inferred for the Earth's core. The temporal changes in the magnetic field which drive the time-varying Lorentz torque are produced by the underlying convective flows, shearing and advecting the magnetic field on a timescale associated with convective eddies. Our results support the hypothesis that temporal changes in the magnetic field deep inside Earth's fluid core drive the observed decadal zonal accelerations of cylindrical surfaces through the Lorentz torque.

Dependence of wind speed and UV albedo at Venus top cloud layer on topography and local time revealed from VMC images

NASA Astrophysics Data System (ADS)

Patsaeva, Marina; Khatuntsev, Igor; Turin, Alexander; Zasova, Ludmila; Bertaux, Jean-loup

2017-04-01

A set of UV (365 nm) and IR (965 nm) images obtained by the Venus Monitoring Camera (VMC) was used to study the circulation of the mesosphere at two altitude levels. Displacement vectors were obtained by wind tracking in automated mode for observation period from 2006 to 2014 for UV images [1,2] and from 2006 to 2012 for IR images. The long observation period and good longitude-latitude coverage by single measurements allowed us to focus on the study of the slow-periodic component. The influence of the underlying surface topography on the change of speed of the average zonal wind at UV level at low latitudes, discovered by visual methods has been described in [3]. Analysis of the longitude-latitude distribution of the zonal and meridional components for 172000 (257 orbits) digital individual wind measurements at UV level and for 32,000 (150 orbits) digital individual wind measurements at IR level allows us to compare the influence of Venus topography on the change of the zonal and meridional components at both cloud levels. At the UV level (67±2 km) longitudinal profiles of the zonal speed for different latitude bins in low latitudes correlate with surface profiles. These correlations are most noticeable in the region of Aphrodite Terra. The correlation shift depends on the surface height. Albedo profiles correlate with surface profiles also at high latitudes. Zonal speed profiles at low latitude (5-15°S) depend not only on altitude, but also on local time. Minimum of the zonal speed is observed over Aphrodite Terra (90-100°E) at about 12 LT. A diurnal harmonic with an extremum over Aphrodite Terra was found. It can be considered as a superposition of a solar-synchronous tide and a stationary wave caused by interaction of the windstream with the surface. At the IR level (55±4 km) a correlation between surface topography and meridional speed was found in the region 10-30°S. The average meridional flow is equatorward at the IR level, but in the region Aphrodite Terra it is poleward. Acknowledgements: M.V. Patsaeva, I.V. Khatuntsev and J.-L. Bertaux were supported by the Ministry of Education and Science of Russian Federation grant 14.W03.31.0017. References: [1] Khatuntsev, I.V., M.V. Patsaeva, D.V. Titov, N.I. Ignatiev, A.V. Turin, S.S. Limaye, W.J. Markiewicz, M. Almeida, T. Roatsch and R. Moissl (2013), Cloud level winds from the Venus Express Monitoring Camera imaging., Icarus, 226, 140-158. [2] Patsaeva, M.V., I.V. Khatuntsev, D.V. Patsaev, D.V. Titov, N.I. Ignatiev, W.J. Markiewicz, A.V. Rodin (2015), The relationship between mesoscale circulation and cloud morphology at the upper cloud level of Venus from VMC/Venus Express, Planet. Space Sci. 113(08), 100-108, doi:10.1016/j.pss.2015.01.013. [3] Bertaux, J.-L., I. V. Khatuntsev, A. Hauchecorne, W. J. Markiewicz, E. Marcq, S. Lebonnois, M. Patsaeva, A. Turin, and A. Fedorova (2016), Influence of Venus topography on the zonal wind and UV albedo at cloud top level: The role of stationary gravity waves, J. Geophys. Res. Planets, 121, 1087-1101, doi:10.1002/2015JE004958.

The observed life cycle of a baroclinic instability

NASA Technical Reports Server (NTRS)

Randel, W. J.; Stanford, J. L.

1985-01-01

Medium-scale waves (zonal wavenumbers 4-7) frequently dominate Southern Hemisphere summer circulation patterns. Randel and Stanford have studied the dynamics of these features, demonstrating that the medium-scale waves result from baroclinic excitation and exhibit well-defined life cycles. This study details the evolution of the medium-scale waves during a particular life cycle. The specific case chosen exhibits a high degree of zonal symmetry, prompting study based upon zonally averaged diagnostics. An analysis of the medium-scale wave energetics reveals a well-defined life cycle of baroclinic growth, maturity, and barotropic decay. Eliassen-Palm flux diagrams detail the daily wave structure and its interaction with the zonally-averaged flow.

The Diagnosis and application of a convective vorticity vector associated with convective systems

NASA Astrophysics Data System (ADS)

Gao, S.; Zhou, Y.; Tao, W.

2005-05-01

Although dry/moist potential vorticity is a very useful and powerful physical quantity in the large scale dynamics, it is not a quite ideal dynamical tool for the study of convective systems or severe storms. A new convective vorticity vector (CVV) is introduced in this study to identify the development of convective systems or severe storms. The daily Aviation (AVN) Model Data is used to diagnose the distribution of the CVV associated with rain storms occurred in the period of Meiyu in 1998. The results have clearly demonstrated that the CVV is an effective vector for indicating the convective actions along the Meiyu front. The CVV also is used to diagnose a 2-D cloud-resolving simulation data associated with 2-D tropical convection. The cloud model is forced by the vertical velocity, zonal wind, horizontal advection, and sea surface temperature obtained from the Tropical cean-Global tmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) and is integrated for a selected 10-day period. The CVV has zonal and vertical components in the 2-D x-z frame. Analysis of zonally averaged and mass-integrated quantities shows that the correlation coefficient between the vertical component of the CVV and the sum of the cloud hydrometeor mixing ratios is 0.81, whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0.18. This indicates that the vertical component of the CVV is closely associated with tropical convection. The tendency equation for the vertical component of the CVV is derived and the zonally averaged and mass-integrated tendency budgets are analyzed. The tendency of the vertical component of the CVV is determined by the interaction between the vorticity and the zonal gradient of cloud heating. The results demonstrate that the vertical component of the CVV is a cloud-linked parameter and can be used to study tropical convection.

The Effects of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in an AOGCM

NASA Technical Reports Server (NTRS)

Li, Feng; Newman, Paul; Pawson, Steven; Waugh, Darryn

2014-01-01

Stratospheric ozone depletion has played a dominant role in driving Antarctic climate change in the last decades. In order to capture the stratospheric ozone forcing, many coupled atmosphere-ocean general circulation models (AOGCMs) prescribe the Antarctic ozone hole using monthly and zonally averaged ozone field. However, the prescribed ozone hole has a high ozone bias and lacks zonal asymmetry. The impacts of these biases on model simulations, particularly on Southern Ocean and the Antarctic sea ice, are not well understood. The purpose of this study is to determine the effects of using interactive stratospheric chemistry instead of prescribed ozone on Antarctic and Southern Ocean climate change in an AOGCM. We compare two sets of ensemble simulations for the 1960-2010 period using different versions of the Goddard Earth Observing System 5 - AOGCM: one with interactive stratospheric chemistry, and the other with prescribed monthly and zonally averaged ozone and 6 other stratospheric radiative species calculated from the interactive chemistry simulations. Consistent with previous studies using prescribed sea surface temperatures and sea ice concentrations, the interactive chemistry runs simulate a deeper Antarctic ozone hole and consistently larger changes in surface pressure and winds than the prescribed ozone runs. The use of a coupled atmosphere-ocean model in this study enables us to determine the impact of these surface changes on Southern Ocean circulation and Antarctic sea ice. The larger surface wind trends in the interactive chemistry case lead to larger Southern Ocean circulation trends with stronger changes in northerly and westerly surface flow near the Antarctica continent and stronger upwelling near 60S. Using interactive chemistry also simulates a larger decrease of sea ice concentrations. Our results highlight the importance of using interactive chemistry in order to correctly capture the influences of stratospheric ozone depletion on climate change over Antarctic and the Southern Ocean.

Residual-Mean Analysis of the Air-Sea Fluxes and Associated Oceanic Meridional Overturning

DTIC Science & Technology

2006-12-01

the adiabatic component of the MOC which is based entirely on the sea surface data . The coordinate system introduced in this study is somewhat...heat capacity of water. The technique utilizes the observational data based on meteorological re- analysis (density flux at the sea surface) and...Figure 8. Annual mean and temporal standard deviation of the zonally-averaged mixed- layer depth. The plotted data are based on Levitus 94 climatology

Insights Into the Biogeochemical Cycling of Iron, Nitrate, and Phosphate Across a 5,300 km South Pacific Zonal Section (153°E-150°W)

NASA Astrophysics Data System (ADS)

Ellwood, Michael J.; Bowie, Andrew R.; Baker, Alex; Gault-Ringold, Melanie; Hassler, Christel; Law, Cliff S.; Maher, William A.; Marriner, Andrew; Nodder, Scott; Sander, Sylvia; Stevens, Craig; Townsend, Ashley; van der Merwe, Pier; Woodward, E. Malcolm S.; Wuttig, Kathrin; Boyd, Philip W.

2018-02-01

Iron, phosphate, and nitrate are essential nutrients for phytoplankton growth, and hence, their supply into the surface ocean controls oceanic primary production. Here we present a GEOTRACES zonal section (GP13; 30-33°S, 153°E-150°W) extending eastward from Australia to the oligotrophic South Pacific Ocean gyre outlining the concentrations of these key nutrients. Surface dissolved iron concentrations are elevated at >0.4 nmol L-1 near continental Australia (west of 165°E) and decreased eastward to ≤0.2 nmol L-1 (170°W-150°W). The supply of dissolved iron into the upper ocean (<100 m) from the atmosphere and vertical diffusivity averaged 11 ± 10 nmol m-2 d-1. In the remote South Pacific Ocean (170°W-150°W), atmospherically sourced iron is a significant contributor to the surface dissolved iron pool with average supply contribution of 23 ± 17% (range 3% to 55%). Surface water nitrate concentrations averaged 5 ± 4 nmol L-1 between 170°W and 150°W, while surface water phosphate concentrations averaged 58 ± 30 nmol L-1. The supply of nitrogen into the upper ocean is primarily from deeper waters (24-1647 μmol m-2 d-1) with atmospheric deposition and nitrogen fixation contributing <1% to the overall flux along the eastern part of the transect. The deep water N:P ratio averaged 14.5 ± 0.5 but declined to <1 above the deep chlorophyll maximum (DCM) indicating a high N:P assimilation ratio by phytoplankton leading to almost quantitative removal of nitrate. The supply stoichiometry for iron and nitrogen relative to phosphate at and above the DCM declines eastward leading to two biogeographical provinces: one with diazotroph production and the other without diazotroph production.

Indian Ocean zonal mode activity in 20th century observations and simulations

NASA Astrophysics Data System (ADS)

Sendelbeck, Anja; Mölg, Thomas

2016-04-01

The Indian Ocean zonal mode (IOZM) is a coupled ocean-atmosphere system with anomalous cooling in the east, warming in the west and easterly wind anomalies, resulting in a complete reversal of the climatological zonal sea surface temperature (SST) gradient. The IOZM has a strong influence on East African climate by causing anomalously strong October - December (OND) precipitation. Using observational data and historical CMIP5 (Coupled Model Intercomparison Project phase 5) model output, the September - November (SON) dipole mode index (DMI), OND East African precipitation and SON zonal wind index (ZWI) are calculated. We pay particular attention to detrending SSTs for calculating the DMI, which seems to have been neglected in some published research. The ZWI is defined as the area-averaged zonal wind component at 850 hPa over the central Indian Ocean. Regression analysis is used to evaluate the models' capability to represent the IOZM and its impact on east African climate between 1948 and 2005. Simple correlations are calculated between SST, zonal wind and precipitation to show their interdependence. High correlation in models implies a good representation of the influence of IOZM on East African climate variability and our goal is to detect the models with the highest correlation coefficients. In future research, these model data might be used to investigate the impact of IOZM on the East African climate variability in the late 20's century with regard to anthropogenic causes and internal variability.

Observed variability in the upper layers at the Equator, 90°E in the Indian Ocean during 2001-2008, 1: zonal currents

NASA Astrophysics Data System (ADS)

Rao, R. R.; Horii, T.; Masumoto, Y.; Mizuno, K.

2017-08-01

The observed variability of zonal currents (ZC) at the Equator, 90°E shows a strong seasonal cycle in the near-surface 40-350 m water column with periodic east-west reversals most pronounced at semiannual frequency. Superposed on this, a strong intraseasonal variability of 30-90 day periodicity is also prominently seen in the near-surface layer (40-80 m) almost throughout the year with the only exception of February-March. An eastward flowing equatorial undercurrent (EUC) is present in the depth range of 80-160 m during March-April and October-November. The observed intraseasonal variability in the near-surface layer is primarily determined by the equatorial zonal westerly wind bursts (WWBs) through local frictional coupling between the zonal flow in the surface layer and surface zonal winds and shows large interannual variability. The eastward flowing EUC maintained by the ZPG set up by the east-west slope of the thermocline remotely controlled by the zonal wind (ZW) and zonally propagating wave fields also shows significant interannual variability. This observed variability on interannual time scales appears to be controlled by the corresponding variability in the alongshore winds off the Somalia coast during the preceding boreal winter, the ZW field along the equator, and the associated zonally propagating Kelvin and Rossby waves. The salinity induced vertical stratification observed in the near-surface layer through barrier layer thickness (BLT) effects also shows a significant influence on the ZC field on intraseasonal time scale. Interestingly, among all the 8 years (2001-2008), relatively weaker annual cycle is seen in both ZC in the 40-350 m water column and boreal spring sea surface temperature (SST) only during 2001 and 2008 along the equator caused through propagating wave dynamics.

Earth radiation budget measurements from satellites and their interpretation for climate modeling and studies

NASA Technical Reports Server (NTRS)

Vonderhaar, T. H.; Stephens, G. L.; Campbell, G. G.

1980-01-01

The annual and seasonal averaged Earth atmosphere radiation budgets derived from the most complete set of satellite observations available are presented. The budgets were derived from a composite of 48 monthly mean radiation budget maps. Annually and seasonally averaged radiation budgets are presented as global averages and zonal averages. The geographic distribution of the various radiation budget quantities is described. The annual cycle of the radiation budget was analyzed and the annual variability of net flux was shown to be largely dominated by the regular semi and annual cycles forced by external Earth-Sun geometry variations. Radiative transfer calculations were compared to the observed budget quantities and surface budgets were additionally computed with particular emphasis on discrepancies that exist between the present computations and previous surface budget estimates.

Titan's Atmospheric Dynamics and Meteorology

NASA Technical Reports Server (NTRS)

Flasar, F. M.; Baines, K. H.; Bird, M. K.; Tokano, T.; West, R. A.

2008-01-01

Titan, after Venus, is the second example of an atmosphere with a global cyclostrophic circulation in the solar system, but a circulation that has a strong seasonal modulation in the middle atmosphere. Direct measurement of Titan's winds, particularly observations tracking the Huygens probe at 10degS, indicate that the zonal winds are generally in the sense of the satellites rotation. They become cyclostrophic approx. 35 km above the surface and generally increase with altitude, with the exception of a sharp minimum centered near 75 km, where the wind velocity decreases to nearly zero. Zonal winds derived from the temperature field retrieved from Cassini measurements, using the thermal wind equation, indicate a strong winter circumpolar vortex, with maximum winds at mid northern latitudes of 190 ms-' near 300 km. Above this level, the vortex decays. Curiously, the zonal winds and temperatures are symmetric about a pole that is offset from the surface pole by approx.4 degrees. The cause of this is not well understood, but it may reflect the response of a cyclostrophic circulation to the offset between the equator, where the distance to the rotation axis is greatest, and the solar equator. The mean meridional circulation can be inferred from the temperature field and the meridional distribution of organic molecules and condensates and hazes. Both the warm temperatures in the north polar region near 400 km and the enhanced concentration of several organic molecules suggests subsidence there during winter and early spring. Stratospheric condensates are localized at high northern latitudes, with a sharp cut-off near 50degN. Titan's winter polar vortex appears to share many of the same characteristics of winter vortices on Earth-the ozone holes. Global mapping of temperatures, winds, and composition in he troposphere, by contrast, is incomplete. The few suitable discrete clouds that have bee found for tracking indicate smaller velocities than aloft, consistent with the Huygens measurements. At low latitudes the zonal winds near the surface appear not to be westward as on Earth, but eastward. Because the net zonal-mean time-averaged torq exerted by the surface on the atmosphere should vanish, this implies westward flow o part of the surface; the question is where. The latitude contrast in tropospheric temperatures, deduced from radio occultations at low, mid, and high latitudes, is small approx.5 K at the tropopause and approx.3 K at the surface.

Estimation of Venus wind velocities from high-resolution infrared spectra. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Smith, M. A. H.

1978-01-01

Zonal velocity profiles in the Venus atmosphere above the clouds were estimated from measured asymmetries of HCl and HF infrared absorption lines in high-resolution Fourier interferometer spectra of the planet. These asymmetries are caused by both pressure-induced shifts in the positions of the hydrogen-halide lines perturbed by CO2 and Doppler shifts due to atmospheric motions. Particularly in the case of the HCl 2-0 band, the effects of the two types of line shifts can be easily isolated, making it possible to estimate a profile of average Venus equatorial zonal velocity as a function of pressure in the region roughly 60 to 70 km above the surface of the planet. The mean profiles obtained show strong vertical shear in the Venus zonal winds near the cloud-top level, and both the magnitude and direction of winds at all levels in this region appear to vary greatly with longitude relative to the sub-solar point.

Nongeostrophic theory of zonally averaged circulation. I - Formulation

NASA Technical Reports Server (NTRS)

Tung, Ka Kit

1986-01-01

A nongeostrophic theory of zonally averaged circulation is formulated using the nonlinear primitive equations (mass conservation, thermodynamics, and zonal momentum) on a sphere. The relationship between the mean meridional circulation 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 circulation 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.

Zonally averaged model of dynamics, chemistry and radiation for the atmosphere

NASA Technical Reports Server (NTRS)

Tung, K. K.

1985-01-01

A nongeostrophic theory of zonally averaged circulation is formulated using the nonlinear primitive equations on a sphere, taking advantage of the more direct relationship between the mean meridional circulation 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 circulation, 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 meridional 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 meridional velocity is in general ageostrophic.

Dynamics of zonal flows in helical systems.

PubMed

Sugama, H; Watanabe, T-H

2005-03-25

A theory for describing collisionless long-time behavior of zonal flows in helical systems is presented and its validity is verified by gyrokinetic-Vlasov simulation. It is shown that, under the influence of particles trapped in helical ripples, the response of zonal flows to a given source becomes weaker for lower radial wave numbers and deeper helical ripples while a high-level zonal-flow response, which is not affected by helical-ripple-trapped particles, can be maintained for a longer time by reducing their bounce-averaged radial drift velocity. This implies a possibility that helical configurations optimized for reducing neoclassical ripple transport can simultaneously enhance zonal flows which lower anomalous transport.

Walker Circulation, El Niño and La Niña

NASA Astrophysics Data System (ADS)

Halpern, D.

2014-12-01

Ocean surface wind vector is likely the critical variable to predict onset, maintenance and dissipation of El Niño and La Niña. Analyses of SeaWinds and ASCAT 10-m height (called "surface") vector winds in the Atlantic, Indian and Pacific Oceans from 1°S-1°N during March 2000 - June 2011 revealed the longitudinal distribution of the surface zonal wind component associated with the Walker Circulation. In the Pacific Ocean east of 140°E and west of 85°W, the mean wind direction was westward towards the maritime continent with maximum mean zonal wind speed (- 6.5 m s-1) at 150°W; east of 85°W the mean direction was toward the convection zone over South America. Four El Niños and five La Niñas occurred from March 2000 - June 2011. In the Pacific from 150°E to 160°W, the average El Niño (La Niña) westward wind speed was 2 m s-1 (1 m s-1) smaller (larger) than normal. In the west Pacific, the variation in westward wind speeds in El Niño and La Niña conditions relative to normal conditions would be expected to substantially uplift the thermocline during El Niño compared to La Niña, which is consistent with conventional wisdom. In the east Pacific from 130°W - 100°W, average El Niño westward wind speeds were less than normal and La Niña conditions by 0.5 m s-1 and 1 m s-1, respectively. The "central" Pacific nature of the El Niños may have influenced the smaller difference between El Niño and La Niña westward wind speeds in the east Pacific compared to the west Pacific. Analyses of longitudinal distributions of thermocline depths will be discussed. Surface zonal wind speeds in the Atlantic and Indian Oceans showed no evidence of El Niño and La Niña; surface meridional winds showed an apparent response in the Indian and Pacific Oceans but not in the Atlantic Ocean. At 700-m height, the MISR zonal wind component in the Atlantic, Indian and Pacific Oceans had similar features as those at the surface, except in the east Pacific where the westward wind speeds were identical during El Niño, La Niña and normal conditions. In the east Pacific, the shear between 10- and 700-m heights increased (decreased) during La Niña (El Niño).

Chapter 13. Atmospheric Dynamics and Meteorology

NASA Technical Reports Server (NTRS)

Flasar, F. M.; Baines, K. H.; Bird, M. K.; Tokano, T.

2009-01-01

Titan, after Venus, is the second example in the solar system of an atmosphere with a global cyclostrophic circulation, but in this case a circulation that has a strong seasonal modulation in the middle atmosphere. Direct measurement of Titan's winds, particularly observations tracking the Huygens probe at 10 deg S, indicate that the zonal winds are mostly in the sense of the satellite's rotation. They generally increase with altitude and become cyclostrophic near 35 km above the surface. An exception to this is a sharp minimum centered near 75 km, where the wind velocity decreases to nearly zero. Zonal winds derived from temperatures retrieved from Cassini orbiter measurements, using the thermal wind equation, indicate a strong winter circumpolar vortex, with maximum winds of 190 m/s at mid northern latitudes near 300 km. Above this level, the vortex decays. Curiously, the stratospheric zonal winds and temperatures in both hemispheres are symmetric about a pole that is offset from the surface pole by about 4 deg. The cause of this is not well understood, but it may reflect the response of a cyclostrophic circulation to the onset between the equator, where the distance to the rotation axis is greatest, and the seasonally varying subsolar latitude. The mean meridional circulation can be inferred from the temperature field and the meridional distribution of organic molecules and condensates and hazes. Both the warm temperatures near 400 km and the enhanced concentration of several organic molecules suggest subsidence in the north polar region during winter and early spring. Stratospheric condensates are localized at high northern latitudes, with a sharp cut-off near 50 deg N. Titan's winter polar vortex appears to share many of the same characteristics of isolating high and low-latitude air masses as do the winter polar vortices on Earth that envelop the ozone holes. Global mapping of temperatures, winds, and composition in the troposphere, by contrast, is incomplete. The few suitable discrete clouds that have been found for tracking indicate smaller velocities than aloft, consistent: with the Huygens measurements, Along the descent trajectory, the Huygens measurements indicate eastward zonal winds down to 7 km, where they shift westward, and then eastward again below 1 km dawn to the surface. The low-latitude dune fields seen in Cassini RADAR images have been interpreted as longitudinal dunes occurring in a mean eastward zonal wind. This is not like Earth, where the low-latitude winds are westward above the surface. Because the net zonal-mean time-averaged torque exerted by the surface on the atmosphere should vanish, there must be westward flow over part of the surface; the question is where and when. The meridional contrast in tropospheric temperatures deduced from radio occultations at low, mid, and high latitudes. is small, approximately 5 K at the tropopause and approximately 3 K at the surface. This implies efficient heat transport, probably by axisymmetric meridional circulations. The effect of the methane "hydrological" cycle on the atmospheric circulation is not well constrained by existing measurements, Understanding the mature of the surface-atmosphere coupling will be critical to elucidating the atmospheric transports of momentum, heat, and volatiles.

Remotely-sensed, nocturnal, dew point correlates with malaria transmission in Southern Province, Zambia: a time-series study

PubMed Central

2014-01-01

Background Plasmodium falciparum transmission has decreased significantly in Zambia in the last decade. The malaria transmission is influenced by environmental variables. Incorporation of environmental variables in models of malaria transmission likely improves model fit and predicts probable trends in malaria disease. This work is based on the hypothesis that remotely-sensed environmental factors, including nocturnal dew point, are associated with malaria transmission and sustain foci of transmission during the low transmission season in the Southern Province of Zambia. Methods Thirty-eight rural health centres in Southern Province, Zambia were divided into three zones based on transmission patterns. Correlations between weekly malaria cases and remotely-sensed nocturnal dew point, nocturnal land surface temperature as well as vegetation indices and rainfall were evaluated in time-series analyses from 2012 week 19 to 2013 week 36. Zonal as well as clinic-based, multivariate, autoregressive, integrated, moving average (ARIMAX) models implementing environmental variables were developed to model transmission in 2011 week 19 to 2012 week 18 and forecast transmission in 2013 week 37 to week 41. Results During the dry, low transmission season significantly higher vegetation indices, nocturnal land surface temperature and nocturnal dew point were associated with the areas of higher transmission. Environmental variables improved ARIMAX models. Dew point and normalized differentiated vegetation index were significant predictors and improved all zonal transmission models. In the high-transmission zone, this was also seen for land surface temperature. Clinic models were improved by adding dew point and land surface temperature as well as normalized differentiated vegetation index. The mean average error of prediction for ARIMAX models ranged from 0.7 to 33.5%. Forecasts of malaria incidence were valid for three out of five rural health centres; however, with poor results at the zonal level. Conclusions In this study, the fit of ARIMAX models improves when environmental variables are included. There is a significant association of remotely-sensed nocturnal dew point with malaria transmission. Interestingly, dew point might be one of the factors sustaining malaria transmission in areas of general aridity during the dry season. PMID:24927747

Remotely-sensed, nocturnal, dew point correlates with malaria transmission in Southern Province, Zambia: a time-series study.

PubMed

Nygren, David; Stoyanov, Cristina; Lewold, Clemens; Månsson, Fredrik; Miller, John; Kamanga, Aniset; Shiff, Clive J

2014-06-13

Plasmodium falciparum transmission has decreased significantly in Zambia in the last decade. The malaria transmission is influenced by environmental variables. Incorporation of environmental variables in models of malaria transmission likely improves model fit and predicts probable trends in malaria disease. This work is based on the hypothesis that remotely-sensed environmental factors, including nocturnal dew point, are associated with malaria transmission and sustain foci of transmission during the low transmission season in the Southern Province of Zambia. Thirty-eight rural health centres in Southern Province, Zambia were divided into three zones based on transmission patterns. Correlations between weekly malaria cases and remotely-sensed nocturnal dew point, nocturnal land surface temperature as well as vegetation indices and rainfall were evaluated in time-series analyses from 2012 week 19 to 2013 week 36. Zonal as well as clinic-based, multivariate, autoregressive, integrated, moving average (ARIMAX) models implementing environmental variables were developed to model transmission in 2011 week 19 to 2012 week 18 and forecast transmission in 2013 week 37 to week 41. During the dry, low transmission season significantly higher vegetation indices, nocturnal land surface temperature and nocturnal dew point were associated with the areas of higher transmission. Environmental variables improved ARIMAX models. Dew point and normalized differentiated vegetation index were significant predictors and improved all zonal transmission models. In the high-transmission zone, this was also seen for land surface temperature. Clinic models were improved by adding dew point and land surface temperature as well as normalized differentiated vegetation index. The mean average error of prediction for ARIMAX models ranged from 0.7 to 33.5%. Forecasts of malaria incidence were valid for three out of five rural health centres; however, with poor results at the zonal level. In this study, the fit of ARIMAX models improves when environmental variables are included. There is a significant association of remotely-sensed nocturnal dew point with malaria transmission. Interestingly, dew point might be one of the factors sustaining malaria transmission in areas of general aridity during the dry season.

Projected Changes in Persistent Extreme Warm-Season Weather Events: The Role of Quasi-Resonant Amplification

NASA Astrophysics Data System (ADS)

Mann, M. E.; Rahmstorf, S.; Kornhuber, K.; Steinman, B. A.; Miller, S. K.; Coumou, D.

2017-12-01

Persistent episodes of extreme weather in the Northern Hemisphere summer are typically associated with high-amplitude quasi-stationary atmospheric Rossby waves with zonal wavenumbers. Such disturbances are favoured by the phenomenon of Quasi-Resonant Amplification (QRA). A fingerprint for the occurrence of QRA can be defined in terms of the zonally-averaged surface temperature field. Examining future state-of-the-art (CMIP5) climate model projections we find that such events are likely to increase by 50% over the next century under business-as-usual carbon emissions, but there is considerable variation among climate models, with some models predicting a near tripling of QRA events by the end of the century. These results are strongly dependent on assumptions regarding the prominence of changes in radiative forcing associated with anthropogenic aerosols over the next century.

Unsteady Airfoil Flow Solutions on Moving Zonal Grids

DTIC Science & Technology

1992-12-17

for the angle-of-attack of 15.5’, the comparisons diverge. This happens because of the different turbulence models used . At this angle- of attack, the...downstream in the wake . This vortex shedding phenomenon alters the chordwise pressure distribution on the upper surface of the airfoil resulting in higher...in- terest, turbulence modeling is used . Turbulence models are implemented with the time-averaged forms of the Navier-Stokes equations. Two widely

Zonal flow as pattern formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, Jeffrey B.; Krommes, John A.

2013-10-15

Zonal flows are well known to arise spontaneously out of turbulence. We show that for statistically averaged equations of the stochastically forced generalized Hasegawa-Mima model, steady-state zonal flows, and inhomogeneous turbulence fit into the framework of pattern formation. There are many implications. First, the wavelength of the zonal flows is not unique. Indeed, in an idealized, infinite system, any wavelength within a certain continuous band corresponds to a solution. Second, of these wavelengths, only those within a smaller subband are linearly stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets.

Northern Winter Climate Change: Assessment of Uncertainty in CMIP5 Projections Related to Stratosphere-Troposphere Coupling

NASA Technical Reports Server (NTRS)

Manzini, E.; Karpechko, A.Yu.; Anstey, J.; Shindell, Drew Todd; Baldwin, M.P.; Black, R.X.; Cagnazzo, C.; Calvo, N.; Charlton-Perez, A.; Christiansen, B.;

Self-generated zonal flows in the plasma turbulence driven by trapped-ion and trapped-electron instabilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drouot, T.; Gravier, E.; Reveille, T.

This paper presents a study of zonal flows generated by trapped-electron mode and trapped-ion mode micro turbulence as a function of two plasma parameters—banana width and electron temperature. For this purpose, a gyrokinetic code considering only trapped particles is used. First, an analytical equation giving the predicted level of zonal flows is derived from the quasi-neutrality equation of our model, as a function of the density fluctuation levels and the banana widths. Then, the influence of the banana width on the number of zonal flows occurring in the system is studied using the gyrokinetic code. Finally, the impact of themore » temperature ratio T{sub e}/T{sub i} on the reduction of zonal flows is shown and a close link is highlighted between reduction and different gyro-and-bounce-average ion and electron density fluctuation levels. This reduction is found to be due to the amplitudes of gyro-and-bounce-average density perturbations n{sub e} and n{sub i} gradually becoming closer, which is in agreement with the analytical results given by the quasi-neutrality equation.« less

Zonal flows and turbulence in fluids and plasmas

NASA Astrophysics Data System (ADS)

Parker, Jeffrey Bok-Cheung

In geophysical and plasma contexts, zonal flows are well known to arise out of turbulence. We elucidate the transition from statistically homogeneous turbulence without zonal flows to statistically inhomogeneous turbulence with steady zonal flows. Starting from the Hasegawa--Mima equation, we employ both the quasilinear approximation and a statistical average, which retains a great deal of the qualitative behavior of the full system. Within the resulting framework known as CE2, we extend recent understanding of the symmetry-breaking 'zonostrophic instability'. Zonostrophic instability can be understood in a very general way as the instability of some turbulent background spectrum to a zonally symmetric coherent mode. As a special case, the background spectrum can consist of only a single mode. We find that in this case the dispersion relation of zonostrophic instability from the CE2 formalism reduces exactly to that of the 4-mode truncation of generalized modulational instability. We then show that zonal flows constitute pattern formation amid a turbulent bath. Zonostrophic instability is an example of a Type I s instability of pattern-forming systems. The broken symmetry is statistical homogeneity. Near the bifurcation point, the slow dynamics of CE2 are governed by a well-known amplitude equation, the real Ginzburg-Landau equation. The important features of this amplitude equation, and therefore of the CE2 system, are multiple. First, the zonal flow wavelength is not unique. In an idealized, infinite system, there is a continuous band of zonal flow wavelengths that allow a nonlinear equilibrium. Second, of these wavelengths, only those within a smaller subband are stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets. These behaviors are shown numerically to hold in the CE2 system, and we calculate a stability diagram. The stability diagram is in agreement with direct numerical simulations of the quasilinear system. The use of statistically-averaged equations and the pattern formation methodology provide a path forward for further systematic investigations of zonal flows and their interactions with turbulence.

Three-dimensional elliptic grid generation for an F-16

NASA Technical Reports Server (NTRS)

Sorenson, Reese L.

1988-01-01

A case history depicting the effort to generate a computational grid for the simulation of transonic flow about an F-16 aircraft at realistic flight conditions is presented. The flow solver for which this grid is designed is a zonal one, using the Reynolds averaged Navier-Stokes equations near the surface of the aircraft, and the Euler equations in regions removed from the aircraft. A body conforming global grid, suitable for the Euler equation, is first generated using 3-D Poisson equations having inhomogeneous terms modeled after the 2-D GRAPE code. Regions of the global grid are then designated for zonal refinement as appropriate to accurately model the flow physics. Grid spacing suitable for solution of the Navier-Stokes equations is generated in the refinement zones by simple subdivision of the given coarse grid intervals. That grid generation project is described, with particular emphasis on the global coarse grid.

3D shape reconstruction of specular surfaces by using phase measuring deflectometry

NASA Astrophysics Data System (ADS)

Zhou, Tian; Chen, Kun; Wei, Haoyun; Li, Yan

2016-10-01

The existing estimation methods for recovering height information from surface gradient are mainly divided into Modal and Zonal techniques. Since specular surfaces used in the industry always have complex and large areas, considerations must be given to both the improvement of measurement accuracy and the acceleration of on-line processing speed, which beyond the capacity of existing estimations. Incorporating the Modal and Zonal approaches into a unifying scheme, we introduce an improved 3D shape reconstruction version of specular surfaces based on Phase Measuring Deflectometry in this paper. The Modal estimation is firstly implemented to derive the coarse height information of the measured surface as initial iteration values. Then the real shape can be recovered utilizing a modified Zonal wave-front reconstruction algorithm. By combining the advantages of Modal and Zonal estimations, the proposed method simultaneously achieves consistently high accuracy and dramatically rapid convergence. Moreover, the iterative process based on an advanced successive overrelaxation technique shows a consistent rejection of measurement errors, guaranteeing the stability and robustness in practical applications. Both simulation and experimentally measurement demonstrate the validity and efficiency of the proposed improved method. According to the experimental result, the computation time decreases approximately 74.92% in contrast to the Zonal estimation and the surface error is about 6.68 μm with reconstruction points of 391×529 pixels of an experimentally measured sphere mirror. In general, this method can be conducted with fast convergence speed and high accuracy, providing an efficient, stable and real-time approach for the shape reconstruction of specular surfaces in practical situations.

Zonal average earth radiation budget measurements from satellites for climate studies

NASA Technical Reports Server (NTRS)

Ellis, J. S.; Haar, T. H. V.

1976-01-01

Data from 29 months of satellite radiation budget measurements, taken intermittently over the period 1964 through 1971, are composited into mean month, season and annual zonally averaged meridional profiles. Individual months, which comprise the 29 month set, were selected as representing the best available total flux data for compositing into large scale statistics for climate studies. A discussion of spatial resolution of the measurements along with an error analysis, including both the uncertainty and standard error of the mean, are presented.

Mapping potential vorticity dynamics on saturn: Zonal mean circulation from Cassini and Voyager data

NASA Astrophysics Data System (ADS)

Read, P. L.; Conrath, B. J.; Fletcher, L. N.; Gierasch, P. J.; Simon-Miller, A. A.; Zuchowski, L. C.

2009-12-01

Maps of Ertel potential vorticity on isentropic surfaces (IPV) and quasi-geostrophic potential vorticity (QGPV) are well established in dynamical meteorology as powerful sources of insight into dynamical processes involving 'balanced' flow (i.e. geostrophic or similar). Here we derive maps of zonal mean IPV and QGPV in Saturn's upper troposphere and lower stratosphere by making use of a combination of velocity measurements, derived from the combined tracking of cloud features in images from the Voyager and Cassini missions, and thermal measurements from the Cassini Composite Infrared Spectrometer (CIRS) instrument. IPV and QGPV are mapped and compared for the entire globe between latitudes 89∘S-82∘N. As on Jupiter, profiles of zonally averaged PV show evidence for a step-like "stair-case" pattern suggestive of local PV homogenisation, separated by strong PV gradients in association with eastward jets. The northward gradient of PV (IPV or QGPV) is found to change sign in several places in each hemisphere, however, even when baroclinic contributions are taken into account. The stability criterion with respect to Arnol'd's second stability theorem may be violated near the peaks of westward jets. Visible, near-IR and thermal-IR Cassini observations have shown that these regions exhibit many prominent, large-scale eddies and waves, e.g. including 'storm alley'. This suggests the possibility that at least some of these features originate from instabilities of the background zonal flow.

SVD analysis of Aura TES spectral residuals

NASA Technical Reports Server (NTRS)

Beer, Reinhard; Kulawik, Susan S.; Rodgers, Clive D.; Bowman, Kevin W.

2005-01-01

Singular Value Decomposition (SVD) analysis is both a powerful diagnostic tool and an effective method of noise filtering. We present the results of an SVD analysis of an ensemble of spectral residuals acquired in September 2004 from a 16-orbit Aura Tropospheric Emission Spectrometer (TES) Global Survey and compare them to alternative methods such as zonal averages. In particular, the technique highlights issues such as the orbital variation of instrument response and incompletely modeled effects of surface emissivity and atmospheric composition.

Numerical experiments with a general circulation model concerning the stratospheric distribution of ozone

NASA Technical Reports Server (NTRS)

Kurzeja, R. J.; Haggard, K. V.; Grose, W. L.

1981-01-01

Three experiments have been performed using a three-dimensional, spectral quasi-geostrophic model in order to investigate the sensitivity of ozone transport to tropospheric orographic and thermal effects and to the zonal wind distribution. In the first experiment, the ozone distribution averaged over the last 30 days of a 60 day transport simulation was determined; in the second experiment, the transport simulation was repeated, but nonzonal orographic and thermal forcing was omitted; and in the final experiment, the simulation was conducted with the intensity and position of the stratospheric jets altered by addition of a Newtonian cooling term to the zonal-mean diabatic heating rate. Results of the three experiments are summarized by comparing the zonal-mean ozone distribution, the amplitude of eddy geopotential height, the zonal winds, and zonal-mean diabatic heating.

Statistical inhomogeneity of dates of sudden stratospheric warmings in the wintertime northern hemisphere

NASA Astrophysics Data System (ADS)

Savenkova, E. N.; Gavrilov, N. M.; Pogoreltsev, A. I.; Manuilova, R. O.

2017-05-01

Using the data of meteorological information reanalysis, a statistical analysis of dates of the main sudden stratospheric warmings observed in 1958-2014 has been performed and their inhomogeneous distribution in winter months with maximums in the beginning of January, from the end of January to the beginning of February, and in the end of February has been shown. To explain these regularities, a climatological analysis of variations in the amplitudes and vertical components of Eliassen-Palm fluxes created by large-scale planetary waves (PWs), as well as of zonal-mean winds and deviations of temperature from their winter-average values in high northern latitudes at heights of up to 50 km from the surface has been carried out using the 20-year (1995-2014) collection of daily meteorological information from the UK Met Office database. During the aforementioned intervals of observing more frequent sudden stratospheric warmings, climatological maximums of temperature perturbations, local minimums of eastward winds, and local maximums of the amplitude and Eliassen-Palm fluxes of PWs with a zonal wavenumber of 1 in the high-latitude northern stratosphere were found. Distinctions between atmospheric characteristics averaged over two last decades have been revealed.

Towards a more consistent picture of isopycnal mixing in climate models

NASA Astrophysics Data System (ADS)

Gnanadesikan, A.; Pradal, M. A. S.; Koszalka, I.; Abernathey, R. P.

2014-12-01

The stirring of tracers by mesoscale eddies along isopycnal surfaces is often represented in coarse-resolution models by the Redi diffusion parameter ARedi. Theoretical treatments of ARedi often assume it should scale as the eddy energy or the growth rate of mesoscale eddies,. producing a picture where it is high in boundary currents and low )of order a few hundred m2/s) in the gyre interiors. However, observational estimates suggest that ARedi should be very large (of order thousands of m2/s) in the gyre interior. We present results of recent simulations comparing a range of spatially constant values ARedi (with values of 400, 800, 1200 and 2400 m2/s) to a spatially resolved estimate based on altimetry and a zonally averaged version of the same estimate. In general, increasing the ARedi coefficient destratifies and warms the high latitudes. Relative to our control simulation, the spatially dependent coefficient is lower in the Southern Ocean, but high in the North Pacific, and so the temperature changes mirror this. We also examine the response of ocean hypoxia to these changes. In general, the zonally averaged version of the altimetry-based estimate of ARedi does not capture the full 2d representation.

First comparison of simultaneous IRIS, BUV, and ground-based measurements of total ozone

NASA Technical Reports Server (NTRS)

Prior, E. J.; Oza, B. J.

1978-01-01

In the present paper, the zonally-averaged global distribution of total ozone obtained simultaneously from different measurements are compared with respect to differences in the measured latitudinal and seasonal variations of total ozone. Emphasis is placed on systematic discrepancies that appear to be related to differences in the sensing methodologies or instruments. While the zonal averages of the IRIS and BUV satellite techniques agree quite well at low latitudes, the results are consistently higher for IRIS than for BUV above mid-latitudes in both the Northern and Southern Hemispheres. The BUV and ground-based ultraviolet averages agree better with each other than with infrared IRIS measurements.

Uncertainty in regional and zonal monthly mean downward surface irradiances from Edition 4.0 CERES Energy Balanced and Filled (EBAF) data product

NASA Astrophysics Data System (ADS)

Kato, S.; Rutan, D. A.; Rose, F. G.; Loeb, N. G.

2017-12-01

The surface of the Earth receives solar radiation (shortwave) and emission from the atmosphere (longwave). At a global and annual mean approximately 12% of solar radiation incident on the surface is reflected and the rest is absorbed by the surface. The surface emits radiation proportional to the forth power of the temperature. Although the uncertainty in global and annual mean surface irradiances is estimated in earlier studies (Zhang et al. 1995, 2004; L'Ecuyer et al. 2008; Stephens et al. 2012; Kato et al. 2012), only a few studies estimated the uncertainty in computed surface irradiances at smaller spatial and temporal scales (Zhang et al. 1995, 2004; Kato et al. 2012). We use surface observations at 46 buoys and 36 land sites and newly released the Edition 4.0 Clouds and the Earth's Radiant Energy System (CERES) Energy Balanced and Filled (EBAF)-surface data product to estimate the uncertainty in regional and zonal monthly mean downward shortwave and longwave surface irradiances. The root-mean-square difference of monthly mean computed and observed irradiances is used for the regional uncertainty. The uncertainty is separated into bias and spatially random components. The random component decreases when irradiances are averaged over a larger area, nearly inversely proportional to the number of surface observation sites. The presentation provides the uncertainty in the regional and zonal monthly mean downward surface irradiances over ocean and land. ReferencesKato, S. and N.G.Loeb, D. A.Rutan, F. G. Rose, S. Sun-Mack,W.F.Miller, and Y. Chen, 2012. Surv. Geophys., 33, 395-412, doi:10.1007/s10712-012-9179-x. L'Ecuyer, T. S., N. B. Wood, T. Haladay, G. L. Stephens, and P. W. Stackhouse Jr., 2008, J. Geophys. Res., 113, D00A15, doi:10.1029/2008JD009951. Stephens, G. L. and Coauthors, 2012, Nat. Geosci., 5, 691-696, doi:10.1038/ngeo1580. Zhang, Y., W. B. Rossow, A. A. Lacis, V. Oinas, and M. I. Mishchenko, 2004, J. Geophys. Res., 109, D19105, doi:10.1029/2003JD004457. Zhang, Y.-C., W. B. Rossow, and A. A. Lacis, 1995, J. Geophys. Res., 100, 1149-1165.

Impacts of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in the Goddard Earth Observing System Version 5 (GEOS-5)

NASA Technical Reports Server (NTRS)

Li, Feng; Vikhliaev, Yury V.; Newman, Paul A.; Pawson, Steven; Perlwitz, Judith; Waugh, Darryn W.; Douglass, Anne R.

2016-01-01

Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer's evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. In this study we investigate the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean. Two sets of 1960-2010 ensemble transient simulations are conducted with the coupled ocean version of the Goddard Earth Observing System Model, version 5: one with interactive stratospheric chemistry and the other with prescribed ozone derived from the same interactive simulations. The model's climatology is evaluated using observations and reanalysis. Comparison of the 1979-2010 climate trends between these two simulations reveals that interactive chemistry has important effects on climate change not only in the Antarctic stratosphere, troposphere, and surface, but also in the Southern Ocean and Antarctic sea ice. Interactive chemistry causes stronger Antarctic lower stratosphere cooling and circumpolar westerly acceleration during November-December-January. It enhances stratosphere-troposphere coupling and leads to significantly larger tropospheric and surface westerly changes. The significantly stronger surface wind stress trends cause larger increases of the Southern Ocean Meridional Overturning Circulation, leading to year-round stronger ocean warming near the surface and enhanced Antarctic sea ice decrease.

Detecting Global Hydrological Cycle Intensification in Sea Surface Salinity

NASA Astrophysics Data System (ADS)

Poague, J.; Stine, A.

2016-12-01

Global warming is expected to intensify the global hydrological cycle, but significant regional differences exist in the predicted response. The proposed zonal mean thermodynamic response is enhanced horizontal moisture transport associated with increased saturation vapor pressure, which in turn drives additional net precipitation in the tropics and at high latitudes and additional net evaporation in the subtropics. Sea surface salinity (SSS) anomalies are forced from above by changes in evaporation minus precipitation (E-P) and thus will respond to changes in the global hydrological cycle, opening the possibility of using historical SSS anomalies to diagnose the response of the hydrological cycle to warming. We estimate zonal mean SSS trends in the Atlantic and Pacific ocean basins from 1955-2015 to test whether historical changes in the global hydrological cycle are consistent with a primarily thermodynamic response. Motivated by this observation, we calculate the sensitivity of basin zonal-mean SSS anomalies to sea surface temperature (SST) forcing as a function of timescale to diagnose and estimate the signal-to-noise ratio of the purely thermodynamic signal as a function of timescale. High-frequency variability in SSS anomalies is likely to be influenced by variability in atmospheric circulation, complicating the attribution of the link between basin zonal-mean SSS anomalies and global SST anomalies. We therefore estimate the basin zonal mean SSS anomaly response to the major modes of large-scale dynamic variability. We find a strong correlation between detrended zonal-mean SSS anomalies and the Pacific-North American index (R=0.71,P<0.01) in the Pacific Ocean. We interpret the relationship between zonal mean SSS anomalies and temperature in terms of the relative contribution of thermodynamic and dynamic processes.

Zonal Flows and Turbulence in Fluids and Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, Jeffrey

2014-09-01

In geophysical and plasma contexts, zonal flows are well known to arise out of turbulence. We elucidate the transition from statistically homogeneous turbulence without zonal flows to statistically inhomogeneous turbulence with steady zonal flows. Starting from the Hasegawa--Mima equation, we employ both the quasilinear approximation and a statistical average, which retains a great deal of the qualitative behavior of the full system. Within the resulting framework known as CE2, we extend recent understanding of the symmetry-breaking `zonostrophic instability'. Zonostrophic instability can be understood in a very general way as the instability of some turbulent background spectrum to a zonally symmetricmore » coherent mode. As a special case, the background spectrum can consist of only a single mode. We find that in this case the dispersion relation of zonostrophic instability from the CE2 formalism reduces exactly to that of the 4-mode truncation of generalized modulational instability. We then show that zonal flows constitute pattern formation amid a turbulent bath. Zonostrophic instability is an example of a Type Is instability of pattern-forming systems. The broken symmetry is statistical homogeneity. Near the bifurcation point, the slow dynamics of CE2 are governed by a well-known amplitude equation, the real Ginzburg-Landau equation. The important features of this amplitude equation, and therefore of the CE2 system, are multiple. First, the zonal flow wavelength is not unique. In an idealized, infinite system, there is a continuous band of zonal flow wavelengths that allow a nonlinear equilibrium. Second, of these wavelengths, only those within a smaller subband are stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets. These behaviors are shown numerically to hold in the CE2 system, and we calculate a stability diagram. The stability diagram is in agreement with direct numerical simulations of the quasilinear system. The use of statistically-averaged equations and the pattern formation methodology provide a path forward for further systematic investigations of zonal flows and their interactions with turbulence.« less

Why do modelled and observed surface wind stress climatologies differ in the trade wind regions?

NASA Astrophysics Data System (ADS)

Simpson, I.; Bacmeister, J. T.; Sandu, I.; Rodwell, M. J.

2017-12-01

Global climate models (GCMs) exhibit stronger easterly zonal surface wind stress and near surface winds in the Northern Hemisphere (NH) trade winds than observationally constrained reanalyses or other observational products. A comparison, between models and reanalyses, of the processes that contribute to the zonal mean, vertically integrated balance of momentum, reveals that this wind stress discrepancy cannot be explained by either the resolved dynamics or parameterized tendencies that are common to each. Rather, a substantial residual exists in the momentum balance of the reanalyses, pointing toward a role for the analysis increments. Indeed, they are found to systematically weaken the NH near surface easterlies in winter, thereby reducing the surface wind stress. Similar effects are found in the Southern Hemisphere and further analysis of the spatial structure and seasonality of these increments, demonstrates that they act to weaken the near surface flow over much of the low latitude oceans in both summer and winter. This suggests an erroneous /missing process in GCMs that constitutes a missing drag on the low level zonal flow over oceans. Either this indicates a mis-representation of the drag between the surface and the atmosphere, or a missing internal atmospheric process that amounts to an additional drag on the low level zonal flow. If the former is true, then observation based surface stress products, which rely on similar drag formulations to GCMs, may be underestimating the strength of the easterly surface wind stress.

Sources and distribution of NO(x) in the upper troposphere at northern midlatitudes

NASA Technical Reports Server (NTRS)

Rohrer, Franz; Ehhalt, Dieter H.; Wahner, Andreas

1994-01-01

A simple quasi 2-D model is used to study the zonal distribution of NO(x). The model includes vertical transport in form of eddy diffusion and deep convection, zonal transport by a vertically uniform wind, and a simplified chemistry of NO, NO2 and HNO3. The NO(x) sources considered are surface emissions (mostly from the combustion of fossil fuel), lightning, aircraft emissions, and downward transport from the stratosphere. The model is applied to the latitude band of 40 deg N to 50 deg N during the month of June; the contributions to the zonal NO(x) distribution from the individual sources and transport processes are investigated. The model predicted NO(x) concentration in the upper troposphere is dominated by air lofted from the polluted planetary boundary layer over the large industrial areas of Eastern North America and Europe. Aircraft emissions are also important and contribute on average 30 percent. Stratospheric input is minor about 10 percent, less even than that by lightning. The model provides a clear indication of intercontinental transport of NO(x) and HNO3 in the upper troposphere. Comparison of the modelled NO profiles over the Western Atlantic with those measured during STRATOZ 3 in 1984 shows good agreement at all altitudes.

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;

A zonally averaged, three-basin ocean circulation model for climate studies

NASA Astrophysics Data System (ADS)

Hovine, S.; Fichefet, T.

1994-09-01

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 meridional 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 circulation are vigorous wind-driven cells in the upper thermocline. The simulated temperature and salinity fields and the computed meridional 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 circulation always results at this stage. A series of perturbation experiments illustrates the ability of the model to reproduce different steady-state circulations 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 meridional 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.

Madden-Julian Oscillation: Western Pacific and Indian Ocean

NASA Astrophysics Data System (ADS)

Fuchs, Z.; Raymond, D. J.

2016-12-01

The MJO has been and still remains a "holy grail" of today's atmospheric science research. Why does the MJO propagate eastward? What makes it unstable? What is the scaling for the MJO, i.e. why does it prefer long wavelengths or planetary wavenumbers 1-3? The MJO has the strongest signal in the Indian ocean and in the West Pacific, but the average vertical structure is very different in each of those basins. We look at the reanalysis/analysis FNL, ERAI vertical structure of temperature and moisture as well as the surface zonal winds for two ocean basins. We also look at data from DYNAMO and TOGA_COARE in great detail (saturation fraction, temperature, entropy, surface zonal winds, gross moist stability, etc). The findings from observations and field projects for the two ocean basins are then compared to a linear WISHE model on an equatorial beta plane. Though linear WISHE has long been discounted as a plausible model for the MJO, the version we have developed explains many of the observed features of this phenomenon, in particular, the preference for large zonal scale, the eastward propagation, the westward group velocity, and the thermodynamic structure. There is no need to postulate large-scale negative gross moist stability, as destabilization occurs via WISHE at long wavelengths only. This differs from early WISHE models because we take a moisture adjustment time scale of order one day in comparison to the much shorter time scales assumed in earlier models. Linear modeling cannot capture all of the features of the MJO, so we are in the process of adding nonlinearity.

Impact of Stratospheric Ozone Zonal Asymmetries on the Tropospheric Circulation

NASA Technical Reports Server (NTRS)

Tweedy, Olga; Waugh, Darryn; Li, Feng; Oman, Luke

2015-01-01

The depletion and recovery of Antarctic ozone plays a major role in changes of Southern Hemisphere (SH) tropospheric climate. Recent studies indicate that the lack of polar ozone asymmetries in chemistry climate models (CCM) leads to a weaker and warmer Antarctic vortex, and smaller trends in the tropospheric mid-latitude jet and the surface pressure. However, the tropospheric response to ozone asymmetries is not well understood. In this study we report on a series of integrations of the Goddard Earth Observing System Chemistry Climate Model (GEOS CCM) to further examine the effect of zonal asymmetries on the state of the stratosphere and troposphere. Integrations with the full, interactive stratospheric chemistry are compared against identical simulations using the same CCM except that (1) the monthly mean zonal mean stratospheric ozone from first simulation is prescribed and (2) ozone is relaxed to the monthly mean zonal mean ozone on a three day time scale. To analyze the tropospheric response to ozone asymmetries, we examine trends and quantify the differences in temperatures, zonal wind and surface pressure among the integrations.

Effect of cloud cover and surface type on earth's radiation budget derived from the first year of ERBE data

NASA Technical Reports Server (NTRS)

Gibson, G. G.; Denn, F. M.; Young, D. F.; Harrison, E. F.; Minnis, P.; Barkstrom, B. R.

1990-01-01

One year of ERBE data is analyzed for variations in outgoing LW and absorbed solar flux. Differences in land and ocean radiation budgets as well as differences between clear-sky and total scenes, including clouds, are studied. The variation of monthly average radiative parameters is examined for February 1985 through January 1986 for selected study regions and on zonal and global scales. ERBE results show significant seasonal variations in both outgoing LW and absorbed SW flux, and a pronounced difference between oceanic and continental surfaces. The main factors determining cloud radiative forcing in a given region are solar insolation, cloud amount, cloud type, and surface properties. The strongest effects of clouds are found in the midlatitude storm tracks over the oceans. Over much of the globe, LW warming is balanced by SW cooling. The annual-global average net cloud forcing shows that clouds have a net cooling effect on the earth for the year.

The Role of Monsoon-Like Zonally Asymmetric Heating in Interhemispheric Transport

NASA Technical Reports Server (NTRS)

Chen, Gang; Orbe, Clara; Waugh, Darryn

2017-01-01

While the importance of the seasonal migration of the zonally averaged Hadley circulation on interhemispheric transport of trace gases has been recognized, few studies have examined the role of the zonally asymmetric monsoonal circulation. This study investigates the role of monsoon-like zonally asymmetric heating on interhemispheric transport using a dry atmospheric model that is forced by idealized Newtonian relaxation to a prescribed radiative equilibrium temperature. When only the seasonal cycle of zonally symmetric heating is considered, the mean age of air in the Southern Hemisphere since last contact with the Northern Hemisphere midlatitude boundary layer, is much larger than the observations. The introduction of monsoon-like zonally asymmetric heating not only reduces the mean age of tropospheric air to more realistic values, but also produces an upper-tropospheric cross-equatorial transport pathway in boreal summer that resembles the transport pathway simulated in the NASA Global Modeling Initiative (GMI) Chemistry Transport Model driven with MERRA meteorological fields. These results highlight the monsoon-induced eddy circulation plays an important role in the interhemispheric transport of long-lived chemical constituents.

Global atmospheric circulation statistics: Four year averages

NASA Technical Reports Server (NTRS)

Wu, M. F.; Geller, M. A.; Nash, E. R.; Gelman, M. E.

1987-01-01

Four year averages of the monthly mean global structure of the general circulation 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. Meridional and vertical velocities are calculated using thermodynamic and continuity equations. Fields presented in this report are zonally averaged temperature, zonal, meridional, 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.

Atmospheric Response to Zonal Variations in Midlatitude SST: Transient and Stationary Eddies and Their Feedback(.

NASA Astrophysics Data System (ADS)

Inatsu, Masaru; Mukougawa, Hitoshi; Xie, Shang-Ping

2003-10-01

Midwinter storm track response to zonal variations in midlatitude sea surface temperatures (SSTs) has been investigated using an atmospheric general circulation model under aquaplanet and perpetual-January conditions. Zonal wavenumber-1 SST variations with a meridionally confined structure are placed at various latitudes. Having these SST variations centered at 30°N leads to a zonally localized storm track, while the storm track becomes nearly zonally uniform when the same SST forcing is moved farther north at 40° and 50°N. Large (small) baroclinic energy conversion north of the warm (cold) SST anomaly near the axis of the storm track (near 40°N) is responsible for the large (small) storm growth. The equatorward transfer of eddy kinetic energy by the ageostrophic motion and the mechanical damping are important to diminish the storm track activity in the zonal direction.Significant stationary eddies form in the upper troposphere, with a ridge (trough) northeast of the warm (cold) SST anomaly at 30°N. Heat and vorticity budget analyses indicate that zonally localized condensational heating in the storm track is the major cause for these stationary eddies, which in turn exert a positive feedback to maintain the localized storm track by strengthening the vertical shear near the surface. These results indicate an active role of synoptic eddies in inducing deep, tropospheric-scale response to midlatitude SST variations. Finally, the application of the model results to the real atmosphere is discussed.

Seasonal changes in the atmospheric heat balance simulated by the GISS general circulation model

NASA Technical Reports Server (NTRS)

Stone, P. H.; Chow, S.; Helfand, H. M.; Quirk, W. J.; Somerville, R. C. J.

1975-01-01

Tests of the ability of numerical general circulation models to simulate the atmosphere have focussed so far on simulations of the January climatology. These models generally present boundary conditions such as sea surface temperature, but this does not prevent testing their ability to simulate seasonal changes in atmospheric processes that accompany presented seasonal changes in boundary conditions. Experiments to simulate changes in the zonally averaged heat balance are discussed since many simplified models of climatic processes are based solely on this balance.

Heat balances of the surface mixed layer in the equatorial Atlantic and Indian Ocean during FGGE

NASA Technical Reports Server (NTRS)

Molinari, R. L.

1985-01-01

Surface meteorological and surface and subsurface oceanographic data collected during FGGE in the equatorial Atlantic and Indian Oceans are used to estimate the terms in a heat balance relation for the mixed layer. The first balance tested is between changes in mixed layer temperature (MLT) and surface energy fluxes. Away from regions of low variance in MLT time series and equatorial and coastal upwelling, surface fluxes can account for 75 percent of the variance in the observed time series. Differences between observed and estimated MLTs indicate that on the average, maximum errors in surface flux are of the order of 20 to 30 W/sq m. In the Atlantic, the addition of zonal advection does not significantly improve the estimates. However in regions of equatorial upwelling, the eastern Atlantic vertical mixing and meridional advection can play an important role in the evolution of MLTs.

Observations of the Mf ocean tide from Geosat altimetry

NASA Technical Reports Server (NTRS)

Cartwright, David E.; Ray, Richard D.

1990-01-01

Zonal averages of the 13.66-day Mf tide are derived from one year of Geosat altimetry records. The orbit errors are reduced by 1/revolution corrections taken over long (several day) arcs. The short-period tides are removed using a model previously derived from the same data. The Mf zonal averages indicate definite nonequilibrium character at nearly all latitudes. The imaginary admittances indicate a Q of at least 8; such a value is consistent with a simplified theory of coupled gravitational and vorticity modes and suggests a value for Proudman's 'friction period' about 123 days.

Calculation of surface temperature and surface fluxes in the GLAS GOM

NASA Technical Reports Server (NTRS)

Sud, Y. C.; Abeles, J. A.

1981-01-01

Because the GLAS model's surface fluxes of sensible and latent heat exhibit strong 2 delta t oscillations at the individual grid points as well as in the zonal hemispheric averages and because a basic weakness of the GLAS model lower evaporation over oceans and higher evaporation over land in a typical monthly simulation, the GLAS model PBL parameterization was changed to calculate the mixed layer temperature gradient by solution of a quadratic equation for a stable PBL and by a curve fit relation for an unstable PBL. The new fluxes without any 2 delta t oscillation. Also, the geographical distributions of the surface fluxes are improved. The parameterization presented is incorporated into the new GLAS climate model. Some results which compare the evaporation over land and ocean between old and new calculations are appended.

CO2 Annual and Semiannual Cycles from Satellite Retrievals and Models

NASA Astrophysics Data System (ADS)

Jiang, X.; Crisp, D.; Olsen, E. T.; Kulawik, S. S.; Miller, C. E.; Pagano, T. S.; Yung, Y. L.

2014-12-01

We have compared satellite CO2 retrievals from the Greenhouse gases Observing SATellite (GOSAT), Atmospheric Infrared Sounder (AIRS), and Tropospheric Emission Spectrometer (TES) with in-situ measurements from the Earth System Research Laboratory (NOAA-ESRL) Surface CO2 and Total Carbon Column Observing Network (TCCON), and utilized zonal means to characterize variability and distribution of CO2. In general, zonally averaged CO2 from the three satellite data sets are consistent with the surface and TCCON XCO2 data. Retrievals of CO2 from the three satellites show more (less) CO2 in the northern hemisphere than that in the southern hemisphere in the northern hemispheric winter (summer) season. The difference between the three satellite CO2 retrievals might be related to the different averaging kernels in the satellites CO2 retrievals. A multiple regression method was used to calculate the CO2 annual cycle and semiannual cycle amplitudes from different satellite CO2 retrievals. The CO2 annual cycle and semiannual cycle amplitudes are largest at the surface, as seen in the NOAA-ESRL CO2 data sets. The CO2 annual cycle and semiannual cycle amplitudes in the GOSAT XCO2, AIRS mid-tropospheric CO2, and TES mid-tropospheric CO2 are smaller compared with those from the surface CO2. Similar regression analysis was applied to the Model for OZone And Related chemical Tracers-2 (MOZART-2) and CarbonTracker model CO2. The convolved model CO2 annual cycle and semiannual cycle amplitudes are similar to those from the satellite CO2 retrievals, although the model tends to under-estimate the CO2 seasonal cycle amplitudes in the northern hemisphere mid-latitudes from the comparison with GOSAT and TES CO2 and underestimate the CO2 semi-annual cycle amplitudes in the high latitudes from the comparison with AIRS CO2. The difference between model and satellite CO2 can be used to identify possible deficiency in the model and improve the model in the future.

The Tropical Upper Troposphere and Lower Stratosphere in the GEOS-2 GCM

NASA Technical Reports Server (NTRS)

Pawson, S.; Takacs, L.; Molod, A.; Nebuda, S.; Chen, M.; Rood, R.; Read, W. L.; Fiorino, M.

1999-01-01

The structure of the tropical upper troposphere and lower stratosphere in the GEOS-2 General Circulation Model (GCM) is discussed. The emphasis of this study is on the reality of monthly-mean temperature and water vapor distributions in the model, compared to reasonable observational estimates. It is shown that although the zonal-mean temperature is in good agreement with observations, the GCM supports an excessive zonal asymmetry near the tropopause compared to the ECMWF Reanalyses. In reality there is a QBO-related variability in the zonally averaged lower stratospheric temperature which is not captured by the model. The observed upper tropospheric temperature and humidity fields show variations related to those in the sea surface temperature, which are not incorporated in the GCM; nevertheless, there is some interannual variability in the GCM, indicating a component arising from internal processes. The model is too moist in the middle troposphere (500 hPa) but too dry in the upper troposphere, suggesting that there is too little vertical transport or too much drying in the GCM. Transport into the stratosphere shows a pronounced annual cycle, with drier air entering the tropical stratosphere when the tropopause is coldest in northern winter; while the alternating dry and moist air masses can be traced ascending through the tropical lower stratosphere, the progression of the anomalies is too rapid.

Southern Ocean air-sea heat flux, SST spatial anomalies, and implications for multi-decadal upper ocean heat content trends.

NASA Astrophysics Data System (ADS)

Tamsitt, V. M.; Talley, L. D.; Mazloff, M. R.

2014-12-01

The Southern Ocean displays a zonal dipole (wavenumber one) pattern in sea surface temperature (SST), with a cool zonal anomaly in the Atlantic and Indian sectors and a warm zonal anomaly in the Pacific sector, associated with the large northward excursion of the Malvinas and southeastward flow of the Antarctic Circumpolar Current (ACC). To the north of the cool Indian sector is the warm, narrow Agulhas Return Current (ARC). Air-sea heat flux is largely the inverse of this SST pattern, with ocean heat gain in the Atlantic/Indian, cooling in the southeastward-flowing ARC, and cooling in the Pacific, based on adjusted fluxes from the Southern Ocean State Estimate (SOSE), a ⅙° eddy permitting model constrained to all available in situ data. This heat flux pattern is dominated by turbulent heat loss from the ocean (latent and sensible), proportional to perturbations in the difference between SST and surface air temperature, which are maintained by ocean advection. Locally in the Indian sector, intense heat loss along the ARC is contrasted by ocean heat gain of 0.11 PW south of the ARC. The IPCC AR5 50 year depth-averaged 0-700 m temperature trend shows surprising similarities in its spatial pattern, with upper ocean warming in the ARC contrasted by cooling to the south. Using diagnosed heat budget terms from the most recent (June 2014) 6-year run of the SOSE we find that surface cooling in the ARC is balanced by heating from south-eastward advection by the current whereas heat gain in the ACC is balanced by cooling due to northward Ekman transport driven by strong westerly winds. These results suggest that spatial patterns in multi-decadal upper ocean temperature trends depend on regional variations in upper ocean dynamics.

Measuring Zonal Transport Variability of the Antarctic Circumpolar Current Using GRACE Ocean Bottom Pressure

NASA Astrophysics Data System (ADS)

Makowski, J.; Chambers, D. P.; Bonin, J. A.

2012-12-01

Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). Using OBP data from the JPL ECCO model and the Gravity Recovery and Climate Experiment (GRACE), we examine the zonal transport variability of the ACC integrated between the major fronts between 2003-2010. The JPL ECCO data are used to determine average front positions for the time period studies, as well as where transport is mainly zonal. Statistical analysis will be conducted to determine the uncertainty of the GRACE observations using a simulated data set. We will also begin looking at low frequency changes and how coherent transport variability is from region to region of the ACC. Correlations with bottom pressure south of the ACC and the average basin transports will also be calculated to determine the probability of using bottom pressure south of the ACC as a means for describing the ACC dynamics and transport.

Cloud Effects on Meridional Atmospheric Energy Budget Estimated from Clouds and the Earth's Radiant Energy System (CERES) Data

NASA Technical Reports Server (NTRS)

Kato, Seiji; Rose, Fred G.; Rutan, David A.; Charlock, Thomas P.

2008-01-01

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 meridional 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 meridional and vertical gradients of cloud effect increase the rate of meridional 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 meridional energy transport from midlatitude to polar regions through the atmosphere.

Role of Atmospheric Transport on the Arctic Amplification: Adjusting Role

NASA Astrophysics Data System (ADS)

KUG, J.; Yim, B.; Jin, F.

2013-12-01

It is controversial whether the atmospheric transport plays a role in arctic amplification. Recently, Hwang et al. (2011) showed that the magnitude of the arctic amplification is negatively correlated with anomalous poleward atmospheric transport. That is, when the arctic amplification is strong (weak), the atmospheric transport plays a negative (positive) role in the arctic amplification. In this study, it is discussed what is a physical mechanism to determine the role of atmospheric transport and relation with the arctic amplification. Here, we suggest adjusting roles of atmospheric transport. The strength of local feedback over the Arctic determines zonal wind changes. The zonal wind changes are determined by two factors. The first one is polar cap cooling, and second is surface warming. They play opposite roles. So, there will be two different zonal wind responses in high-latitude to the greenhouse warming. Depending on the zonal wind response, the atmospheric transport can play a different role because the zonal wind changes can organize synoptic eddy feedbacks including heat flux, which largely contributes to poleward energy transport. We show here that when polar cap cooling is strong, and surface warming over Arctic is relatively weak, the Jet stream tends to be shifted poleward, so it leads to poleward atmospheric transport. On the other hand, when the surface warming is too strong, it lead to southward shift of Jet stream and equatorward atmospheric transport, which paly a negative role in the Arctic amplification.

On the relative role of meridional convergence and downwelling motion during the heat buildup leading to El Niño events

NASA Astrophysics Data System (ADS)

Ballester, Joan; Bordoni, Simona; Petrova, Desislava; Rodó, Xavier

2015-04-01

Despite steady progress in the understanding of El Niño-Southern Oscillation (ENSO) in the past decades, questions remain on the exact mechanisms leading to the onset of El Niño (EN) events. Several authors have highlighted how the subsurface heat buildup in the western tropical Pacific and the recharged phase in equatorial heat content are intrinsic elements of ENSO variability, leading to those changes in zonal wind stress, sea surface temperature and thermocline tilt that characterize the growing and mature phases of EN. Here we use an ensemble of ocean and atmosphere assimilation products to identify the mechanisms contributing to the heat buildup that precedes EN events by about 18-24 months on average. Anomalous equatorward subsurface mass convergence due to meridional Sverdrup transport is found to be an important mechanism of thermocline deepening near and to the east of the dateline. In the warm pool, instead, surface horizontal convergence and downwelling motion have a leading role in subsurface warming, since equatorward mass convergence is weaker and counterbalanced by subsurface zonal divergence. The picture emerging from our results highlights the complexity of the three dimensional dynamic and thermodynamic structure of the tropical Pacific during the heat buildup leading to EN events.

Post World War II trends in tropical Pacific surface trades

NASA Technical Reports Server (NTRS)

Harrison, D. E.

1989-01-01

Multidecadal time series of surface winds from central tropical Pacific islands are used to compute trends in the trade winds between the end of WWII and 1985. Over this period, averaged over the whole region, there is no statistically significant trend in speed or zonal or meridional wind (or pseudostress). However, there is some tendency, within a few degrees of the equator, toward weakening of the easterlies and increased meridional flow toward the equator. Anomalous conditions subsequent to the 1972-73 ENSO event make a considerable contribution to the long-term trends. The period 1974-80 has been noted previously to have been anomalous, and trends over that period are sharply greater than those over the longer records.

Longitudinal variability in Jupiter's zonal winds derived from multi-wavelength HST observations

NASA Astrophysics Data System (ADS)

Johnson, Perianne E.; Morales-Juberías, Raúl; Simon, Amy; Gaulme, Patrick; Wong, Michael H.; Cosentino, Richard G.

2018-06-01

Multi-wavelength Hubble Space Telescope (HST) images of Jupiter from the Outer Planets Atmospheres Legacy (OPAL) and Wide Field Coverage for Juno (WFCJ) programs in 2015, 2016, and 2017 are used to derive wind profiles as a function of latitude and longitude. Wind profiles are typically zonally averaged to reduce measurement uncertainties. However, doing this destroys any variations of the zonal-component of winds in the longitudinal direction. Here, we present the results derived from using a "sliding-window" correlation method. This method adds longitudinal specificity, and allows for the detection of spatial variations in the zonal winds. Spatial variations are identified in two jets: 1 at 17 ° N, the location of a prominent westward jet, and the other at 7 ° S, the location of the chevrons. Temporal and spatial variations at the 24°N jet and the 5-μm hot spots are also examined.

Zonal wavefront reconstruction in quadrilateral geometry for phase measuring deflectometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Lei; Xue, Junpeng; Gao, Bo

2017-06-14

There are wide applications for zonal reconstruction methods in slope-based metrology due to its good capability of reconstructing the local details on surface profile. It was noticed in the literature that large reconstruction errors occur when using zonal reconstruction methods designed for rectangular geometry to process slopes in a quadrilateral geometry, which is a more general geometry with phase measuring deflectometry. In this paper, we present a new idea for the zonal methods for quadrilateral geometry. Instead of employing the intermediate slopes to set up height-slope equations, we consider the height increment as a more general connector to establish themore » height-slope relations for least-squares regression. The classical zonal methods and interpolation-assisted zonal methods are compared with our proposal. Results of both simulation and experiment demonstrate the effectiveness of the proposed idea. In implementation, the modification on the classical zonal methods is addressed. Finally, the new methods preserve many good aspects of the classical ones, such as the ability to handle a large incomplete slope dataset in an arbitrary aperture, and the low computational complexity comparable with the classical zonal method. Of course, the accuracy of the new methods is much higher when integrating the slopes in quadrilateral geometry.« less

Deep Zonal Flow and Time Variation of Jupiter’s Magnetic Field

NASA Astrophysics Data System (ADS)

Cao, Hao; Stevenson, David J.

2017-10-01

All four giant planets in the Solar System feature zonal flows on the order of 100 m/s in the cloud deck, and large-scale intrinsic magnetic fields on the order of 1 Gauss near the surface. The vertical structure of the zonal flows remains obscure. The end-member scenarios are shallow flows confined in the radiative atmosphere and deep flows throughout the entire planet. The electrical conductivity increases rapidly yet smoothly as a function of depth inside Jupiter and Saturn. Deep zonal flows will advect the non-axisymmetric component of the magnetic field, at depth with even modest electrical conductivity, and create time variations in the magnetic field.The observed time variations of the geomagnetic field has been used to derive surface flows of the Earth’s outer core. The same principle applies to Jupiter, however, the connection between the time variation of the magnetic field (dB/dt) and deep zonal flow (Uphi) at Jupiter is not well understood due to strong radial variation of electrical conductivity. Here we perform a quantitative analysis of the connection between dB/dt and Uphi for Jupiter adopting realistic interior electrical conductivity profile, taking the likely presence of alkali metals into account. This provides a tool to translate expected measurement of the time variation of Jupiter’s magnetic field to deep zonal flows. We show that the current upper limit on the dipole drift rate of Jupiter (3 degrees per 20 years) is compatible with 10 m/s zonal flows with < 500 km vertical scale height below 0.972 Rj. We further demonstrate that fast drift of resolved magnetic features (e.g. magnetic spots) at Jupiter is a possibility.

FPI observations of nighttime mesospheric and thermospheric winds in China and their comparisons with HWM07

NASA Astrophysics Data System (ADS)

Yuan, Wei

2015-04-01

We analyzed the nighttime horizontal neutral winds in the middle atmosphere (˜87 and ˜98 km) and thermosphere (˜250 km) derived from a Fabry-Perot interferometer (FPI), which was installed at Xinglong station (40.2◦ N, 117.4◦ E) in central China. The wind data covered the period from April 2010 to July 2012. We studied the annual, semiannual and terannual variations of the midnight winds at ˜87 km, ˜98 km and ˜250 km for the first time and compared them with Horizontal Wind Model 2007 (HWM07). Our results show the following: (1) at ˜ 87 km, both the observed and model zonal winds have similar phases in the annual and semiannual variations. However, the HWM07 amplitudes are much larger. (2) At ˜98 km, the model shows strong eastward wind in the summer solstice, resulting in a large annual variation, while the observed strongest component is semiannual. The observation and model midnight meridional winds agree well. Both are equatorward throughout the year and have small amplitudes in the annual and semiannual variations. (3) There are large discrepancies between the observed and HWM07 winds at ˜250 km. This discrepancy is largely due to the strong semiannual zonal wind in the model and the phase difference in the annual variation of the meridional wind. The FPI annual variation coincides with the results from Arecibo, which has similar geomagnetic latitude as Xinglong station. In General, the consistency of FPI winds with model winds is better at ˜87 and ˜98 km than that at ˜250 km. We also studied the seasonally and monthly averaged nighttime winds. The most salient features include the following: (1) the seasonally averaged zonal winds at ˜87 and ˜98 km typically have small variations throughout the night. (2) The model zonal and meridional nighttime wind variations are typically much larger than those of observations at ˜87 km and ˜98 km. (3) At ˜250 km, model zonal wind compares well with the observation in the winter. For spring and autumn, the model wind is more eastward before ˜ 03:00 LT but more westward after. The observed nighttime zonal and meridional winds on average are close to zero in the summer and autumn, which indicates a lack of strong stable tides. The consistency of FPI zonal wind with model wind at ˜250 km is better than the meridional wind.

The effect of surface boundary conditions on the climate generated by a coarse-mesh general circulation model

NASA Technical Reports Server (NTRS)

Cohen, C.

1981-01-01

A hierarchy of experiments was run, starting with an all water planet with zonally symmetric sea surface temperatures, then adding, one at a time, flat continents, mountains, surface physics, and realistic sea surface temperatures. The model was run with the sun fixed at a perpetual January. Ensemble means and standard deviations were computed and the t-test was used to determine the statistical significance of the results. The addition of realistic surface physics does not affect the model climatology to as large as extent as does the addition of mountains. Departures from zonal symmetry of the SST field result in a better simulation of the real atmosphere.

Long-term Internal Variability of the Tropical Pacific Atmosphere-Ocean System

NASA Astrophysics Data System (ADS)

Hadi Bordbar, Mohammad; Martin, Thomas; Park, Wonsun; Latif, Mojib

2016-04-01

The tropical Pacific has featured some remarkable trends during the recent decades such as an unprecedented strengthening of the Trade Winds, a strong cooling of sea surface temperatures (SST) in the eastern and central part, thereby slowing global warming and strengthening the zonal SST gradient, and highly asymmetric sea level trends with an accelerated rise relative to the global average in the western and a drop in the eastern part. These trends have been linked to an anomalously strong Pacific Walker Circulation, the major zonal atmospheric overturning cell in the tropical Pacific sector, but the origin of the strengthening is controversial. Here we address the question as to whether the recent decadal trends in the tropical Pacific atmosphere-ocean system are within the range of internal variability, as simulated in long unforced integrations of global climate models. We show that the recent trends are still within the range of long-term internal decadal variability. Further, such variability strengthens in response to enhanced greenhouse gas concentrations, which may further hinder detection of anthropogenic climate signals in that region.

Relating Nimbus-7 37 GHz data to global land-surface evaporation, primary productivity and the atmospheric CO2 concentration

NASA Technical Reports Server (NTRS)

Choudhury, B. J.

1988-01-01

Global observations at 37 GHz by the Nimbus-7 SMMR are related to zonal variations of land surface evaporation and primary productivity, as well as to temporal variations of atmospheric CO2 concentration. The temporal variation of CO2 concentration and the zonal variations of evaporation and primary productivity are shown to be highly correlated with the satellite sensor data. The potential usefulness of the 37-GHz data for global biospheric and climate studies is noted.

Highly variable Pliocene sea surface conditions in the Norwegian Sea

NASA Astrophysics Data System (ADS)

Bachem, Paul E.; Risebrobakken, Bjørg; De Schepper, Stijn; McClymont, Erin L.

2017-09-01

The Pliocene was a time of global warmth with small sporadic glaciations, which transitioned towards the larger-scale Pleistocene glacial-interglacial variability. Here, we present high-resolution records of sea surface temperature (SST) and ice-rafted debris (IRD) in the Norwegian Sea from 5.32 to 3.14 Ma, providing evidence that the Pliocene surface conditions of the Norwegian Sea underwent a series of transitions in response to orbital forcing and gateway changes. Average SSTs are 2 °C above the regional Holocene mean, with notable variability on millennial to orbital timescales. Both gradual changes and threshold effects are proposed for the progression of regional climate towards the Late Pliocene intensification of Northern Hemisphere glaciation. Cooling from 4.5 to 4.3 Ma may be linked to the onset of poleward flow through the Bering Strait. This cooling was further intensified by a period of cool summers due to weak obliquity forcing. A 7 °C warming of the Norwegian Sea at 4.0 Ma suggests a major increase in northward heat transport from the North Atlantic, leading to an enhanced zonal SST gradient in the Nordic Seas, which may be linked to the expansion of sea ice in the Arctic and Nordic Seas. A warm Norwegian Sea and enhanced zonal temperature gradient between 4.0 and 3.6 Ma may have been a priming factor for increased glaciation around the Nordic Seas due to enhanced evaporation and precipitation at high northern latitudes.

SPCZ zonal events and downstream influence on surface ocean conditions in the Indonesian Throughflow region

NASA Astrophysics Data System (ADS)

Linsley, Braddock K.; Wu, Henry C.; Rixen, Tim; Charles, Christopher D.; Gordon, Arnold L.; Moore, Michael D.

2017-01-01

Seasonal surface freshening of the Makassar Strait, the main conduit of the Indonesian Throughflow (ITF), is a key factor controlling the ITF. Here we present a 262 year reconstruction of seasonal sea-surface-salinity variability from 1742 to 2004 Common Era by using coral δ18O records from the central Makassar Strait. Our record reveals persistent seasonal freshening and also years with significant truncations of seasonal freshening that correlate exactly with South Pacific Convergence Zone (SPCZ) zonal events >4000 km to the east. During these events, the SPCZ dramatically rotates 15° north to near the equator and stronger westward flowing South Pacific boundary currents force higher-salinity water through the Makassar Strait in February-May halting the normal seasonal freshening in the strait. By these teleconnections, our Makassar coral δ18O series provides the first record of the recurrence interval of these zonal SPCZ events and demonstrates that they have occurred on a semiregular basis since the mid-1700s.

Evolution of the eastward shift in the quasi-stationary minimum of the Antarctic total ozone column

NASA Astrophysics Data System (ADS)

Grytsai, Asen; Klekociuk, Andrew; Milinevsky, Gennadi; Evtushevsky, Oleksandr; Stone, Kane

2017-02-01

The quasi-stationary pattern of the Antarctic total ozone has changed during the last 4 decades, showing an eastward shift in the zonal ozone minimum. In this work, the association between the longitudinal shift of the zonal ozone minimum and changes in meteorological fields in austral spring (September-November) for 1979-2014 is analyzed using ERA-Interim and NCEP-NCAR reanalyses. Regressive, correlative and anomaly composite analyses are applied to reanalysis data. Patterns of the Southern Annular Mode and quasi-stationary zonal waves 1 and 3 in the meteorological fields show relationships with interannual variability in the longitude of the zonal ozone minimum. On decadal timescales, consistent longitudinal shifts of the zonal ozone minimum and zonal wave 3 pattern in the middle-troposphere temperature at the southern midlatitudes are shown. Attribution runs of the chemistry-climate version of the Australian Community Climate and Earth System Simulator (ACCESS-CCM) model suggest that long-term shifts of the zonal ozone minimum are separately contributed by changes in ozone-depleting substances and greenhouse gases. As is known, Antarctic ozone depletion in spring is strongly projected on the Southern Annular Mode in summer and impacts summertime surface climate across the Southern Hemisphere. The results of this study suggest that changes in zonal ozone asymmetry accompanying ozone depletion could be associated with regional climate changes in the Southern Hemisphere in spring.

Linear simulation of the stationary eddies in a GCM. II - The 'Mountain' model

NASA Technical Reports Server (NTRS)

Nigam, Sumant; Held, Isaac M.; Lyons, Steven W.

1988-01-01

Linear stationary wave theory is used to account for zonal asymmetries of the winter-averaged tropospheric circulation obtained in a GCM. The eddy zonal velocity field in the upper troposphere indicates that the orographic and thermal plus transient contributions are nearly equal in amplitude, while the eddy meridional velocity field (which is dominated by shorter zonal scales) shows the orographic contribution to be dominant. The two contributions are found to be roughly in phase over the east Asian coast, and they contribute roughly equal amounts to the low level Siberian high. Results indicate that the 300 mb extratropical response to tropical forcing reaches 50 gpm over Alaska, and that the responses to sensible heating and lower tropospheric transients are strongly anticorrelated.

Wind regime peculiarities in the lower thermosphere in the winter of 1983/84

NASA Technical Reports Server (NTRS)

Lysenko, I. A.; Makarov, N. A.; Portnyagin, Yu. I.; Petrov, B. I.; Greisiger, K. M.; Schminder, R.; Kurschner, D.

1987-01-01

Temporal variations of prevailing winds at 90 to 100 km obtained from measurements carried out in winter 1983 to 1984 at three sites in the USSR and two sites in East Germany are reported. These variations are compared with those of the thermal stratospheric regime. Measurements were carried out using the drifts D2 method (meteor wind radar) and the D1 method (ionospheric drifts). Temporal variations of zonal and meridional prevailing wind components for all the sites are given. Also presented are zonal wind data obtained using the partial reflection wind radar. Wind velocity values were obtained by averaging data recorded at between 105 and 91 km altitude. Wind velocity data averaged in such a way can be related to about the same height interval to which the data obtained by the meteor radar and ionospheric methods at other sites, i.e., the mean height of the meteor zone (about 95 km). The results presented show that there are significant fluctuations about the seasonal course of both zonal and meridional prevailing winds.

Gyrokinetic Simulations of Transport Scaling and Structure

NASA Astrophysics Data System (ADS)

Hahm, Taik Soo

2001-10-01

There is accumulating evidence from global gyrokinetic particle simulations with profile variations and experimental fluctuation measurements that microturbulence, with its time-averaged eddy size which scales with the ion gyroradius, can cause ion thermal transport which deviates from the gyro-Bohm scaling. The physics here can be best addressed by large scale (rho* = rho_i/a = 0.001) full torus gyrokinetic particle-in-cell turbulence simulations using our massively parallel, general geometry gyrokinetic toroidal code with field-aligned mesh. Simulation results from device-size scans for realistic parameters show that ``wave transport'' mechanism is not the dominant contribution for this Bohm-like transport and that transport is mostly diffusive driven by microscopic scale fluctuations in the presence of self-generated zonal flows. In this work, we analyze the turbulence and zonal flow statistics from simulations and compare to nonlinear theoretical predictions including the radial decorrelation of the transport events by zonal flows and the resulting probability distribution function (PDF). In particular, possible deviation of the characteristic radial size of transport processes from the time-averaged radial size of the density fluctuation eddys will be critically examined.

Climatology of mesopause region nocturnal temperature, zonal wind, and sodium density observed by sodium lidar over Hefei, China (32°N, 117°E)

NASA Astrophysics Data System (ADS)

Li, T.; Ban, C.; Fang, X.; Li, J.; Wu, Z.; Xiong, J.; Feng, W.; Plane, J. M. C.

2017-12-01

The University of Science and Technology of China narrowband sodium temperature/wind lidar, located in Hefei, China (32°N, 117°E), was installed in November 2011 and have made routine nighttime measurements since January 2012. We obtained 154 nights ( 1400 hours) of vertical profiles of temperature, sodium density, and zonal wind, and 83 nights ( 800 hours) of vertical flux of gravity wave (GW) zonal momentum in the mesopause region (80-105 km) during the period of 2012 to 2016. In temperature, it is likely that the diurnal tide dominates below 100 km in spring, while the semidiurnal tide dominates above 100 km throughout the year. A clear semiannual variation in temperature is revealed near 90 km, likely related to the tropical mesospheric semiannual oscillation (MSAO). The variability of sodium density is positively correlated with temperature, suggesting that in addition to dynamics, the chemistry may also play an important role in the formation of sodium atoms. The observed sodium peak density is 1000 cm-3 higher than that simulated by the model. In zonal wind, the diurnal tide dominates in both spring and fall, while semidiurnal tide dominates in winter. The observed semiannual variation in zonal wind near 90 km is out-of-phase with that in temperature, consistent with tropical MSAO. The GW zonal momentum flux is mostly westward in fall and winter, anti-correlated with eastward zonal wind. The annual mean flux averaged over 87-97 km is -0.3 m2/s2 (westward), anti-correlated with eastward zonal wind of 10 m/s. The comparisons of lidar results with those observed by satellite, nearby radar, and simulated by model show generally good agreements.

On the tertiary instability formalism of zonal flows in magnetized plasmas

NASA Astrophysics Data System (ADS)

Rath, F.; Peeters, A. G.; Buchholz, R.; Grosshauser, S. R.; Seiferling, F.; Weikl, A.

2018-05-01

This paper investigates the so-called tertiary instabilities driven by the zonal flow in gyro-kinetic tokamak core turbulence. The Kelvin Helmholtz instability is first considered within a 2D fluid model and a threshold in the zonal flow wave vector kZF>kZF,c for instability is found. This critical scale is related to the breaking of the rotational symmetry by flux-surfaces, which is incorporated into the modified adiabatic electron response. The stability of undamped Rosenbluth-Hinton zonal flows is then investigated in gyro-kinetic simulations. Absolute instability, in the sense that the threshold zonal flow amplitude tends towards zero, is found above a zonal flow wave vector kZF,cρi≈1.3 ( ρi is the ion thermal Larmor radius), which is comparable to the 2D fluid results. Large scale zonal flows with kZF

Zonal flow generation and its feedback on turbulence production in drift wave turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pushkarev, Andrey V.; Bos, Wouter J. T.; Nazarenko, Sergey V.

2013-04-15

Plasma turbulence described by the Hasegawa-Wakatani equations is simulated numerically for different models and values of the adiabaticity parameter C. It is found that for low values of C turbulence remains isotropic, zonal flows are not generated and there is no suppression of the meridional drift waves and particle transport. For high values of C, turbulence evolves towards highly anisotropic states with a dominant contribution of the zonal sector to the kinetic energy. This anisotropic flow leads to a decrease of turbulence production in the meridional sector and limits the particle transport across the mean isopycnal surfaces. This behavior allowsmore » to consider the Hasegawa-Wakatani equations a minimal PDE model, which contains the drift-wave/zonal-flow feedback loop mechanism.« less

Transonic Navier-Stokes wing solutions using a zonal approach. Part 2: High angle-of-attack simulation

NASA Technical Reports Server (NTRS)

Chaderjian, N. M.

1986-01-01

A computer code is under development whereby the thin-layer Reynolds-averaged Navier-Stokes equations are to be applied to realistic fighter-aircraft configurations. This transonic Navier-Stokes code (TNS) utilizes a zonal approach in order to treat complex geometries and satisfy in-core computer memory constraints. The zonal approach has been applied to isolated wing geometries in order to facilitate code development. Part 1 of this paper addresses the TNS finite-difference algorithm, zonal methodology, and code validation with experimental data. Part 2 of this paper addresses some numerical issues such as code robustness, efficiency, and accuracy at high angles of attack. Special free-stream-preserving metrics proved an effective way to treat H-mesh singularities over a large range of severe flow conditions, including strong leading-edge flow gradients, massive shock-induced separation, and stall. Furthermore, lift and drag coefficients have been computed for a wing up through CLmax. Numerical oil flow patterns and particle trajectories are presented both for subcritical and transonic flow. These flow simulations are rich with complex separated flow physics and demonstrate the efficiency and robustness of the zonal approach.

Some observed seasonal changes in extratropical general circulation: A study in terms of vorticity. [seasonal migrations of extra tropical frontal jet streams

NASA Technical Reports Server (NTRS)

Srivatsangam, S.; Reiter, E. R.

1973-01-01

Extratropical eddy distributions in four months typical of the four seasons are treated in terms of temporal mean and temporal r.m.s. values of the geostrophic relative vorticity. The geographical distributions of these parameters at the 300 mb level show that the arithmetic mean fields are highly biased representatives of the extratropical eddy distributions. The zonal arithmetic means of these parameters are also presented. These show that the zonal-and-time mean relative vorticity is but a small fraction of the zonal mean of the temporal r.m.s. relative vorticity, K. The reasons for considering the r.m.s. values as the temporal normal values of vorticity in the extratropics are given in considerable detail. The parameter K is shown to be of considerable importance in locating the extratropical frontal jet streams (EFJ) in time-and-zonal average distributions. The study leads to an understanding of the seasonal migrations of the EFJ which have not been explored until now.

An Earth longwave radiation climate model

NASA Technical Reports Server (NTRS)

Yang, S. K.

1984-01-01

An Earth outgoing longwave radiation (OLWR) climate model was constructed for radiation budget study. Required information is provided by on empirical 100mb water vapor mixing ratio equation of the mixing ratio interpolation scheme. Cloud top temperature is adjusted so that the calculation would agree with NOAA scanning radiometer measurements. Both clear sky and cloudy sky cases are calculated and discussed for global average, zonal average and world-wide distributed cases. The results agree well with the satellite observations. The clear sky case shows that the OLWR field is highly modulated by water vapor, especially in the tropics. The strongest longitudinal variation occurs in the tropics. This variation can be mostly explained by the strong water vapor gradient. Although in the zonal average case the tropics have a minimum in OLWR, the minimum is essentially contributed by a few very low flux regions, such as the Amazon, Indonesian and the Congo.

The 1984 ASEE-NASA summer faculty fellowship program (aeronautics and research)

NASA Technical Reports Server (NTRS)

Dah-Nien, F.; Hodge, J. R.; Emad, F. P.

1984-01-01

The 1984 NASA-ASEE Faculty Fellowship Program (SFFP) is reported. The report includes: (1) a list of participants; (2) abstracts of research projects; (3) seminar schedule; (4) evaluation questionnaire; and (5) agenda of visitation by faculty programs committee. Topics discussed include: effects of multiple scattering on laser beam propagation; information management; computer techniques; guidelines for writing user documentation; 30 graphics software; high energy electron and antiproton cosmic rays; high resolution Fourier transform infrared spectrum; average monthly annual zonal and global albedos; laser backscattering from ocean surface; image processing systems; geomorphological mapping; low redshift quasars; application of artificial intelligence to command management systems.

Simulation of an Ice Giant-style Dynamo

NASA Astrophysics Data System (ADS)

Soderlund, K. M.; Aurnou, J. M.

2010-12-01

The Ice Giants, Uranus and Neptune, are unique in the solar system. These planets are the only known bodies to have multipolar magnetic fields where the quadrupole and octopole components have strengths comparable to or greater than that of the dipole. Cloud layer observations show that the planets also have zonal (east-west) flows that are fundamentally different from the banded winds of Jupiter and Saturn. The surface winds are characterized by strong retrograde equatorial jets that are flanked on either side by prograde jets at high latitudes. Thermal emission measurements of Neptune show that the surface energy flux pattern peaks in the equatorial and polar regions with minima at mid-latitudes. (The measurements for Uranus cannot adequately resolve the emission pattern.) The winds and magnetic fields are thought to be the result of convection in the planetary interior, which will also affect the heat flux pattern. Typically, it is implicitly assumed that the zonal winds are generated in a shallow layer, separate from the dynamo generation region. However, if the magnetic fields are driven near the surface, a single region can simultaneously generate both the zonal flows and the magnetic fields. Here, we present a novel numerical model of an Ice Giant-style dynamo to investigate this possibility. An order unity convective Rossby number (ratio of buoyancy to Coriolis forces) has been chosen because retrograde equatorial jets tend to occur in spherical shells when the effects of rotation are relatively weak. Our modeling results qualitatively reproduce all of the structural features of the global dynamical observations. Thus, a self-consistent model can generate magnetic field, zonal flow, and thermal emission patterns that agree with those of Uranus and Neptune. This model, then, leads us to hypothesize that the Ice Giants' zonal flows and magnetic fields are generated via dynamically coupled deep convection processes.

Mesospheric circulation at the cloud top level of Venus according to Venus Monitoring Camera images

NASA Astrophysics Data System (ADS)

Khatuntsev, Igor; Patsaeva, Marina; Ignatiev, Nikolay; Titov, Dmitri; Markiewicz, Wojciech; Turin, Alexander

We present results of wind speed measurements at the cloud top level of Venus derived from manual cloud tracking in the UV (365 nm) and IR (965 nm) channels of the Venus Monitoring Camera Experiment (VMC) [1] on board the Venus Express mission. Cloud details have a maximal contrast in the UV range. More then 90 orbits have been processed. 30000 manual vectors were obtained. The period of the observations covers more than 4 venusian year. Zonal wind speed demonstrates the local solar time dependence. Possible diurnal and semidiurnal components are observed [2]. According to averaged latitude profile of winds at level of the upper clouds: -The zonal speed is slightly increasing by absolute values from 90 on the equator to 105 m/s at latitudes —47 degrees; -The period of zonal rotation has the maximum at the equator (5 earth days). It has the minimum (3 days) at altitudes —50 degrees. After minimum periods are slightly increasing toward the South pole; -The meridional speed has a value 0 on the equator, and then it is linear increasing up to 10 m/s (by absolute value) at 50 degrees latitude. "-" denotes movement from the equator to the pole. -From 50 to 80 degrees the meridional speed is again decreasing by absolute value up to 0. IR (965+10 nm) day side images can be used for wind tracking. The obtained speed of the zonal wind in the low and middle latitudes are systematically less than the wind speed derived from the UV images. The average zonal speed obtained from IR day side images in the low and average latitudes is about 65-70 m/s. The given fact can be interpreted as observation of deeper layers of mesosphere in the IR range in comparison with UV. References [1] Markiewicz W. J. et al. (2007) Planet. Space Set V55(12). P.1701-1711. [2] Moissl R., et al. (2008) J. Geophys. Res. 2008. doi:10.1029/2008JE003117. V.113.

CERES Monthly TOA and SRB Averages (SRBAVG) data in HDF-EOS Grid (CER_SRBAVG_Terra-FM2-MODIS_Edition2C)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly TOA/Surface Averages (SRBAVG) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SRBAVG is also produced for combinations of scanner instruments. The monthly average regional flux is estimated using diurnal models and the 1-degree regional fluxes at the hour of observation from the CERES SFC product. A second set of monthly average fluxes are estimated using concurrent diurnal information from geostationary satellites. These fluxes are given for both clear-sky and total-sky scenes and are spatially averaged from 1-degree regions to 1-degree zonal averages and a global average. For each region, the SRBAVG also contains hourly average fluxes for the month and an overall monthly average. The cloud properties from SFC are column averaged and are included on the SRBAVG. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-02-01; Stop_Date=2003-02-28] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 month; Temporal_Resolution_Range=Monthly - < Annual].

CERES Monthly TOA and SRB Averages (SRBAVG) data in HDF-EOS Grid (CER_SRBAVG_TRMM-PFM-VIRS_Edition2B)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly TOA/Surface Averages (SRBAVG) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SRBAVG is also produced for combinations of scanner instruments. The monthly average regional flux is estimated using diurnal models and the 1-degree regional fluxes at the hour of observation from the CERES SFC product. A second set of monthly average fluxes are estimated using concurrent diurnal information from geostationary satellites. These fluxes are given for both clear-sky and total-sky scenes and are spatially averaged from 1-degree regions to 1-degree zonal averages and a global average. For each region, the SRBAVG also contains hourly average fluxes for the month and an overall monthly average. The cloud properties from SFC are column averaged and are included on the SRBAVG. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-02-01; Stop_Date=2000-03-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 month; Temporal_Resolution_Range=Monthly - < Annual].

CERES Monthly TOA and SRB Averages (SRBAVG) data in HDF-EOS Grid (CER_SRBAVG_Terra-FM1-MODIS_Edition2C)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly TOA/Surface Averages (SRBAVG) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SRBAVG is also produced for combinations of scanner instruments. The monthly average regional flux is estimated using diurnal models and the 1-degree regional fluxes at the hour of observation from the CERES SFC product. A second set of monthly average fluxes are estimated using concurrent diurnal information from geostationary satellites. These fluxes are given for both clear-sky and total-sky scenes and are spatially averaged from 1-degree regions to 1-degree zonal averages and a global average. For each region, the SRBAVG also contains hourly average fluxes for the month and an overall monthly average. The cloud properties from SFC are column averaged and are included on the SRBAVG. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-02-01; Stop_Date=2003-02-28] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 month; Temporal_Resolution_Range=Monthly - < Annual].

CERES Monthly TOA and SRB Averages (SRBAVG) data in HDF-EOS Grid (CER_SRBAVG_Terra-FM1-MODIS_Edition2D)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly TOA/Surface Averages (SRBAVG) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SRBAVG is also produced for combinations of scanner instruments. The monthly average regional flux is estimated using diurnal models and the 1-degree regional fluxes at the hour of observation from the CERES SFC product. A second set of monthly average fluxes are estimated using concurrent diurnal information from geostationary satellites. These fluxes are given for both clear-sky and total-sky scenes and are spatially averaged from 1-degree regions to 1-degree zonal averages and a global average. For each region, the SRBAVG also contains hourly average fluxes for the month and an overall monthly average. The cloud properties from SFC are column averaged and are included on the SRBAVG. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-02-01; Stop_Date=2004-05-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 month; Temporal_Resolution_Range=Monthly - < Annual].

Elevated Tropospheric Ozone over the Atlantic

NASA Technical Reports Server (NTRS)

Chandra, S.; Ziemke, J. R.; Tie, X.

2003-01-01

Tropospheric column ozone (TCO) is derived from differential measurements of TOMS total column ozone and Microwave Limb Sounder stratospheric column ozone. It is shown that TCO during summer months over the Atlantic and Pacific Oceans in northern midlatitudes is about the same (50 to 60 Dobson Units) as over the continents of North America, Europe, and Asia, where surface emissions of nitrogen oxides from industrial sources, biomass and biofuel burning and biogenic emissions are significantly larger. This nearly uniform zonal variation in TCO is modulated by surface topography of the Rocky and Himalayan mountains, and Tibetan plateau where TCO is reduced by 20 to 30 Dobson Units. The zonal variation in TCO is well simulated by a global chemical transport model called MOZART-2 (Model of Ozone and Related Chemical Tracers, version 2). The model results are analyzed to delineate the relative importance of various processes contributing to observed zonal characteristics of TCO.

Monthly Maps of Sea Surface Height in the North Atlantic and Zonal Indices for the Gulf Stream Using TOPEX/Poseidon Altimeter Data

NASA Technical Reports Server (NTRS)

Singh, Sandipa; Kelly, Kathryn A.

1997-01-01

Monthly Maps of sea surface height are constructed for the North Atlantic Ocean using TOPEX/Poseidon altimeter data. Mean sea surface height is reconstructed using a weighted combination of historical, hydrographic data and a synthetic mean obtained by fitting a Gaussian model of the Gulf Stream jet to altimeter data. The resultant mean shows increased resolution over the hydrographic mean, and incorporates recirculation information that is absent in the synthetic mean. Monthly maps, obtained by adding the mean field to altimeter sea surface height residuals, are used to derive a set of zonal indices that describe the annual cycle of meandering as well as position and strength of the Gulf Stream.

Temperature Trends in the Tropical Upper Troposphere and Lower Stratosphere: Connections with Sea Surface Temperatures and Implications for Water Vapor and Ozone

NASA Technical Reports Server (NTRS)

Garfinkel, C. I.; Waugh, D. W.; Oman, L. D.; Wang, L.; Hurwitz, M. M.

2013-01-01

Satellite observations and chemistry-climate model experiments are used to understand the zonal structure of tropical lower stratospheric temperature, water vapor, and ozone trends. The warming in the tropical upper troposphere over the past 30 years is strongest near the Indo-Pacific warm pool, while the warming trend in the western and central Pacific is much weaker. In the lower stratosphere, these trends are reversed: the historical cooling trend is strongest over the Indo-Pacific warm pool and is weakest in the western and central Pacific. These zonal variations are stronger than the zonal-mean response in boreal winter. Targeted experiments with a chemistry-climate model are used to demonstrate that sea surface temperature (hereafter SST) trends are driving the zonal asymmetry in upper tropospheric and lower stratospheric tropical temperature trends. Warming SSTs in the Indian Ocean and in the warm pool region have led to enhanced moist heating in the upper troposphere, and in turn to a Gill-like response that extends into the lower stratosphere. The anomalous circulation has led to zonal structure in the ozone and water vapor trends near the tropopause, and subsequently to less water vapor entering the stratosphere. The radiative impact of these changes in trace gases is smaller than the direct impact of the moist heating. Projected future SSTs appear to drive a temperature and water vapor response whose zonal structure is similar to the historical response. In the lower stratosphere, the changes in water vapor and temperature due to projected future SSTs are of similar strength to, though slightly weaker than, that due directly to projected future CO2, ozone, and methane.

Diagnostic calculations of the circulation in the Martian atmosphere

NASA Technical Reports Server (NTRS)

Santee, Michelle L.; Crisp, David

1995-01-01

The circulation 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 meridional circulation 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 circulation simultaneously. We find a two cell circulation, 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 circulation is qualitatively similar to the terrestial diabatic circulation at the comparable season, but is more vigorous.

Diagnostic calculations of the circulation in the Martian atmosphere

NASA Astrophysics Data System (ADS)

Santee, Michelle L.; Crisp, David

1995-03-01

The circulation 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 meridional circulation 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 circulation simultaneously. We find a two cell circulation, 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 circulation is qualitatively similar to the terrestial diabatic circulation at the comparable season, but is more vigorous.

Diagnostic calculations of the circulation in the Martian atmosphere

NASA Technical Reports Server (NTRS)

Santee, Michelle L.; Crisp, David

1995-01-01

The circulation 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 meridional circulation and large-scale waves can be approximated by the diabatic circulation, 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 meridional and vertical components of the diabatic circulation simultaneously. We find a two-cell circulation, 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 circulation is qualitatively similar to the terrestrial diabatic circulation at the comparable season, but is more vigorous.

Reexamination of the relation between depth of the Antarctic ozone hole, and equatorial QBO and SST, 1962-1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Angell, J.K.

1993-08-06

This paper reports on an examination of previous data to see if a correlation can be found between the average depth of the Antarctic ozone hole, and the equatorial quasi-biennial oscillation (QBO) and/or sea surface temperature (SST). Data from the period 1962 to 1992 is examined. The only ozone data which spans this period is the Dobson total ozone data from the South Pole. The data considered is the average from mid October through November. The 50 mb zonal wind at Singapore is taken as a measure of the QBO. The average SST in the region 12S - 2N, 180Wmore » - 90W, the El Nino region, is taken for the SST value. The objective of this correlation is for predictive purposes. There is a weak correlation to the QBO, and a much weaker correlation to the SST from this data set.« less

Gyroaverage effects on nontwist Hamiltonians: Separatrix reconnection and chaos suppression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Del-Castillo-Negrete, Diego B; Martinell, J.

2012-01-01

A study of finite Larmor radius (FLR) effects on E x B test particle chaotic transport in non-monotonic zonal flows with drift waves in magnetized plasmas is presented. Due to the non-monotonicity of the zonal flow, the Hamiltonian does not satisfy the twist condition. The electrostatic potential is modeled as a linear superposition of a zonal flow and the regular neutral modes of the Hasegawa-Mima equation. FLR effects are incorporated by gyro-averaging the E x B Hamiltonian. It is shown that there is a critical value of the Larmor radius for which the zonal flow transitions from a profile withmore » one maximum to a profile with two maxima and a minimum. This bifurcation leads to the creation of additional shearless curves and resonances. The gyroaveraged nontwist Hamiltonian exhibits complex patterns of separatrix reconnection. A change in the Larmor radius can lead to heteroclinic-homoclinic bifurcations and dipole formation. For Larmor radii for which the zonal flow has bifurcated, double heteroclinic-heteroclinic, homoclinic-homoclinic and heteroclinic-homoclinic separatrix topologies are observed. It is also shown that chaotic transport is typically reduced as the Larmor radius increases. Poincare sections show that, for large enough Larmor radius, chaos can be practically suppressed. In particular, changes of the Larmor radius can restore the shearless curve.« less

Gyroaverage effects on nontwist Hamiltonians: separatrix reconnection and chaos suppression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Del-Castillo-Negrete, Diego B; Martinell, J.

2012-01-01

A study of nite Larmor radius (FLR) eects on E B test particle chaotic transport in non- monotonic zonal ows with drift waves in magnetized plasmas is presented. Due to the non- monotonicity of the zonal ow, the Hamiltonian does not satisfy the twist condition. The electro- static potential is modeled as a linear superposition of a zonal ow and regular neutral modes of the Hasegawa-Mima equation. FLR eects are incorporated by gyro-averaging the EB Hamiltonian. It is shown that there is a critical value the Larmor radius for which the zonal ow transitions from a prole with one maximummore » to a prole with two maxima and a minimum. This bifurcation leads to the creation of additional shearless curves and resonances. The gyroaveraged nontwist Hamiltonian exhibits complex patterns of separatrix reconnection. A change in the Larmor ra- dius can lead to heteroclinic-homoclinic bifurcations and dipole formation. For Larmor radii for which the zonal ow has bifurcated, double heteroclinic-heteroclinic, homoclinic-homoclinic and heteroclinic-homoclinic topologies are observed. It is also shown that chaotic transport is typically reduced as the Larmor radius increases. Poincare sections shows that, for large enough Larmor radius, chaos can be practically suppressed. In particular, small changes on the Larmor radius can restore the shearless curve.« less

Development of a two-dimensional zonally averaged statistical-dynamical model. III - The parameterization of the eddy fluxes of heat and moisture

NASA Technical Reports Server (NTRS)

Stone, Peter H.; Yao, Mao-Sung

1990-01-01

A number of perpetual January simulations are carried out with a two-dimensional zonally averaged model employing various parameterizations of the eddy fluxes of heat (potential temperature) and moisture. The parameterizations are evaluated by comparing these results with the eddy fluxes calculated in a parallel simulation using a three-dimensional general circulation model with zonally symmetric forcing. The three-dimensional model's performance in turn is evaluated by comparing its results using realistic (nonsymmetric) boundary conditions with observations. Branscome's parameterization of the meridional eddy flux of heat and Leovy's parameterization of the meridional eddy flux of moisture simulate the seasonal and latitudinal variations of these fluxes reasonably well, while somewhat underestimating their magnitudes. New parameterizations of the vertical eddy fluxes are developed that take into account the enhancement of the eddy mixing slope in a growing baroclinic wave due to condensation, and also the effect of eddy fluctuations in relative humidity. The new parameterizations, when tested in the two-dimensional model, simulate the seasonal, latitudinal, and vertical variations of the vertical eddy fluxes quite well, when compared with the three-dimensional model, and only underestimate the magnitude of the fluxes by 10 to 20 percent.

The Relationship Between the Zonal Mean ITCZ and Regional Precipitation during the mid-Holocene

NASA Astrophysics Data System (ADS)

Niezgoda, K.; Noone, D.; Konecky, B.

2017-12-01

Characteristics of the zonal mean Tropical Rain Belt (TRB, i.e. the ITCZ + the land-based monsoons) are often inferred from individual proxy records of precipitation or other hydroclimatic variables. However, these inferences can be misleading. Here, an isotope-enabled climate model simulation is used to evaluate metrics of the zonal mean ITCZ vs. regional hydrological characteristics during the mid-Holocene (MH, 6 kya). The MH provides a unique perspective on the relationship between the ITCZ and regional hydrology because of large, orbitally-driven shifts in tropical precipitation as well as a critical mass of proxy records. By using a climate model with simulated water isotopes, characteristics of atmospheric circulation and water transport processes can be inferred, and comparison with isotope proxies can be made more directly. We find that estimations of the zonal-mean ITCZ are insufficient for evaluating regional responses of hydrological cycles to forcing changes. For example, one approximation of a 1.5-degree northward shift in the zonal-mean ITCZ position during the MH corresponded well with northward shifts in maximum rainfall in tropical Africa, but did not match southward shifts in the tropical Pacific or longitudinal shifts in the Indian monsoon region. In many regions, the spatial distribution of water vapor isotopes suggests that changes in moisture source and atmospheric circulation were a greater influence on precipitation distribution, intensity, and isotope ratio than the average northward shift in ITCZ latitude. These findings reinforce the idea that using tropical hydrological proxy records to infer zonal-mean characteristics of the ITCZ may be misleading. Rather, tropical proxy records of precipitation, particularly those that record precipitation isotopes, serve as a guideline for regional hydrological changes while model simulations can put them in the context of zonal mean tropical convergence.

Seasonal air and water mass redistribution effects on LAGEOS and Starlette

NASA Technical Reports Server (NTRS)

Gutierrez, Roberto; Wilson, Clark R.

1987-01-01

Zonal geopotential coefficients have been computed from average seasonal variations in global air and water mass distribution. These coefficients are used to predict the seasonal variations of LAGEOS' and Starlette's orbital node, the node residual, and the seasonal variation in the 3rd degree zonal coefficient for Starlette. A comparison of these predictions with the observed values indicates that air pressure and, to a lesser extent, water storage may be responsible for a large portion of the currently unmodeled variation in the earth's gravity field.

Seasonal Correlations of SST, Water Vapor, and Convective Activity in Tropical Oceans: A New Hyperspectral Data Set for Climate Model Testing

NASA Technical Reports Server (NTRS)

Aumann, Hartmut H.; Gregorich, David T.; Broberg, Steven E.; Elliott, Denis A.

2007-01-01

The analysis of the response of the Earth Climate System to the seasonal changes of solar forcing in the tropical oceans using four years of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) data between 2002 and 2006 gives new insight into amplitude and phase relationships between surface and tropospheric temperatures, humidity, and convective activity. The intensity of the convective activity is measured by counting deep convective clouds. The peaks of convective activity, temperature in the mid-troposphere, and water vapor in the 0 - 30 N and 0 - 30 S tropical ocean zonal means occur about two months after solstice, all leading the peak of the sea surface temperature by several weeks. Phase is key to the evaluation of feedback. The evaluation of climate models in terms of zonal and annual means and annual mean deviations from zonal means can now be supplemented by evaluating the phase of key atmospheric and surface parameters relative to solstice. The ability of climate models to reproduce the statistical flavor of the observed amplitudes and relative phases for broad zonal means should lead to increased confidence in the realism of their water vapor and cloud feedback algorithms. AIRS and AMSU were launched into a 705 km altitude polar sun-synchronous orbit on the EOS Aqua spacecraft on May 4, 2002, and have been in routine data gathering mode since September 2002.

Seasonal Correlations of SST, Water Vapor, and Convective Activity in Tropical Oceans: A New Hyperspectral Data Set for Climate Model Testing

NASA Technical Reports Server (NTRS)

Aumann, Hartmut H.; Gregorich, David T.; Broberg, Steven E.; Elliott, Denis A.

2007-01-01

The analysis of the response of the Earth Climate System to the seasonal changes of solar forcing in the tropical oceans using four years of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) data between 2002 and 2006 gives new insight into amplitude and phase relationships between surface and tropospheric temperatures, humidity, and convective activity. The intensity of the convective activity is measured by counting deep convective clouds. The peaks of convective activity, temperature in the mid-troposphere, and water vapor in the 0-30 N and 0-30 S tropical ocean zonal means occur about two months after solstice, all leading the peak of the sea surface temperature by several weeks. Phase is key to the evaluation of feedback. The evaluation of climate models in terms of zonal and annual means and annual mean deviations from zonal means can now be supplemented by evaluating the phase of key atmospheric and surface parameters relative to solstice. The ability of climate models to reproduce the statistical flavor of the observed amplitudes and relative phases for broad zonal means should lead to increased confidence in the realism of their water vapor and cloud feedback algorithms. AIRS and AMSU were launched into a 705 km altitude polar sun-synchronous orbit on the EOS Aqua spacecraft on May 4, 2002, and have been in routine data gathering mode since September 2002.

Future Effects of Southern Hemisphere Stratospheric Zonal Asymmetries on Climate

NASA Astrophysics Data System (ADS)

Stone, K.; Solomon, S.; Kinnison, D. E.; Fyfe, J. C.

2017-12-01

Stratospheric zonal asymmetries in the Southern Hemisphere have been shown to have significant influences on both stratospheric and tropospheric dynamics and climate. Accurate representation of stratospheric ozone in particular is important for realistic simulation of the polar vortex strength and temperature trends. This is therefore also important for stratospheric ozone change's effect on the troposphere, both through modulation of the Southern Annular Mode (SAM), and more localized climate. Here, we characterization the impact of future changes in Southern Hemisphere zonal asymmetry on tropospheric climate, including changes to future tropospheric temperature, and precipitation. The separate impacts of increasing GHGs and ozone recovery on the zonal asymmetric influence on the surface are also investigated. For this purpose, we use a variety of models, including Chemistry Climate Model Initiative simulations from the Community Earth System Model, version 1, with the Whole Atmosphere Community Climate Model (CESM1(WACCM)) and the Australian Community Climate and Earth System Simulator-Chemistry Climate Model (ACCESS-CCM). These models have interactive chemistry and can therefore more accurately represent the zonally asymmetric nature of the stratosphere. The CESM1(WACCM) and ACCESS-CCM models are also compared to simulations from the Canadian Can2ESM model and CESM-Large Ensemble Project (LENS) that have prescribed ozone to further investigate the importance of simulating stratospheric zonal asymmetry.

A compound reconstructed prediction model for nonstationary climate processes

NASA Astrophysics Data System (ADS)

Wang, Geli; Yang, Peicai

2005-07-01

Based on the idea of climate hierarchy and the theory of state space reconstruction, a local approximation prediction model with the compound structure is built for predicting some nonstationary climate process. By means of this model and the data sets consisting of north Indian Ocean sea-surface temperature, Asian zonal circulation index and monthly mean precipitation anomaly from 37 observation stations in the Inner Mongolia area of China (IMC), a regional prediction experiment for the winter precipitation of IMC is also carried out. When using the same sign ratio R between the prediction field and the actual field to measure the prediction accuracy, an averaged R of 63% given by 10 predictions samples is reached.

Zonal pressure gradient, velocity and transport in the Atlantic Equatorial Undercurrent from focal cruises (July 1982-February 1984)

NASA Astrophysics Data System (ADS)

Hisard, Philippe; Hénin, Christian

The zonal pressure gradient (ZPG) along the Atlantic equator and the Equatorial Undercurrent (EUC) transport are discussed for four cruises representative of each season. A very clear sea surface slope reversal occurred in the eastern area during autumn as far west as 14°W. An early onset of the equatorial thermocline rising was evident during spring 1983. An eastward equatorial surface jet clearly distinct from the EUC was observed at 35°W and 29°W. The greatest ZPG but the lowest EUC transport were observed during summer 1983. A nearly total absence of the ZPG and a large surfacing of the EUC as far as 10°W characterized the 1984 winter.

Calculation of the flow field including boundary layer effects for supersonic mixed compression inlets at angles of attack

NASA Technical Reports Server (NTRS)

Vadyak, J.; Hoffman, J. D.

1982-01-01

The flow field in supersonic mixed compression aircraft inlets at angle of attack is calculated. A zonal modeling technique is employed to obtain the solution which divides the flow field into different computational regions. The computational regions consist of a supersonic core flow, boundary layer flows adjacent to both the forebody/centerbody and cowl contours, and flow in the shock wave boundary layer interaction regions. The zonal modeling analysis is described and some computational results are presented. The governing equations for the supersonic core flow form a hyperbolic system of partial differential equations. The equations for the characteristic surfaces and the compatibility equations applicable along these surfaces are derived. The characteristic surfaces are the stream surfaces, which are surfaces composed of streamlines, and the wave surfaces, which are surfaces tangent to a Mach conoid. The compatibility equations are expressed as directional derivatives along streamlines and bicharacteristics, which are the lines of tangency between a wave surface and a Mach conoid.

Feedback process responsible for the suppression of ENSO activity during the mid-Holocene

NASA Astrophysics Data System (ADS)

An, Soon-Il; Bong, Hayoung

2018-05-01

Using the output of 12 models from the Paleoclimate Modeling Intercomparison Project Phase 3, we investigate the feedback process responsible for changes in El Niño-Southern Oscillation activity during the mid-Holocene based on a linear stability index (Bjerknes stability index; BJ index) analysis. The multi-model ensemble mean (MME) variance of the Niño-3.4 index (sea surface temperature anomalies averaged over 5°S-5°N, 170°-120°W) simulated for 6000 years ago (6 kya) was 13% lower than that for the pre-industrial era (0 kya), while changes in the MME BJ index were negligible. This is due to a balance between enhanced damping by anomalous thermal advection by mean currents (MA) and enhanced positive thermocline feedback (TH). Seven of the models show that MME variance of the Niño-3.4 and BJ indexes for the 6 kya run is 21 and 70% lower, respectively, than the 0 kya run. However, two models show the opposite change. Interestingly, MA in both model groups increases, especially due to the mean meridional current associated with enhanced trade winds, indicating a robust mechanism. The opposite tendency between the two groups is mainly due to large TH in the second group 6 kya, as a result of enhanced air-sea coupling and strongly reduced ocean stratification due to subsurface warming, which led to increased sensitivity of the zonal thermocline contrast to surface zonal wind stress.

The climatology of low-latitude ionospheric densities and zonal drifts from IMAGE-FUV.

NASA Astrophysics Data System (ADS)

Immel, T. J.; Sagawa, E.; Frey, H. U.; Mende, S. B.; Patel, J.

2004-12-01

The IMAGE satellite was the first dedicated to magnetospheric imaging, but has also provided numerous images of the nightside ionosphere with its Far-Ultraviolet (FUV) spectrographic imager. Nightside emissions of O I at 135.6-nm originating away from the aurora are due to recombination of ionospheric O+, and vary in intensity with (O+)2. IMAGE-FUV, operating in a highly elliptical orbit with apogee at middle latitudes and >7 Re altitude, measures this emission globally with 100-km resolution. During each 14.5 hour orbit, IMAGE-FUV is able to monitor nightside ionospheric densities for up to 6-7 hours. Hundreds of low-latitude ionospheric bubbles, their development and drift speed, and a variety of other dynamical variations in brightness and morphology of the equatorial anomalies have been observed during this mission. Furthermore, the average global distribution of low-latitude ionospheric plasma densities can be determined in 3 days. Imaging data collected from February through June of 2002 are used to compile a dataset containing a variety of parameters (e.g., latitude and brightness of peak plasma density, zonal bubble drift speed) which can be drawn from for climatological studies. Recent results indicate that the average ground speed of low-latitude zonal plasma drifts vary with longitude by up to 50%, and that a periodic variation in ionospheric densities with longitude suggests the influence of a lower-thermospheric non-migrating tide with wave number = 4 on ionospheric densities. An excellent correlation between zonal drift speed and the magnetic storm index Dst is also found.

Secular variations in zonal harmonics of Earth's geopotential and their implications for mantle viscosity and Antarctic melting history due to the last deglaciation

NASA Astrophysics Data System (ADS)

Nakada, Masao; Okuno, Jun'ichi

2017-06-01

Secular variations in zonal harmonics of Earth's geopotential based on the satellite laser ranging observations, {\\dot{J}_n}, contain important information about the Earth's deformation due to the glacial isostatic adjustment (GIA) and recent melting of glaciers and the Greenland and Antarctic ice sheets. Here, we examine the GIA-induced {\\dot{J}_n}, \\dot{J}_n^{GIA} (2 ≤ n ≤ 6), derived from the available geopotential zonal secular rate and recent melting taken from the IPCC 2013 Report (AR5) to explore the possibility of additional information on the depth-dependent lower-mantle viscosity and GIA ice model inferred from the analyses of the \\dot{J}_2^{GIA} and relative sea level changes. The sensitivities of the \\dot{J}_n^{GIA} to lower-mantle viscosity and GIA ice model with a global averaged eustatic sea level (ESL) of ∼130 m indicate that the secular rates for n = 3 and 4 are mainly caused by the viscous response of the lower mantle to the melting of the Antarctic ice sheet regardless of GIA ice models adopted in this study. Also, the analyses of the \\dot{J}_n^{GIA} based on the available geopotential zonal secular rates indicate that permissible lower-mantle viscosity structure satisfying even zonal secular rates of n = 2, 4 and 6 is obtained for the GIA ice model with an Antarctic ESL component of ∼20 or ∼30 m, but there is no viscosity solution satisfying \\dot{J}_3^{GIA} and \\dot{J}_5^{GIA} values. Moreover, the inference model for the lower-mantle viscosity and GIA ice model from each odd zonal secular rate is distinctly different from that satisfying GIA-induced even zonal secular rate. The discrepancy between the inference models for the even and odd zonal secular rates may partly be attributed to uncertainties of the geopotential zonal secular rates for n > 2 and particularly those for odd zonal secular rates due to weakness in the orbital geometry. If this problem is overcome at least for the secular rates of n < 5, then the analyses of the \\dot{J}_n^{GIA} would make it possible to put more convincing constraints on the lower-mantle viscosity structure and GIA ice model, particularly for the controversial Antarctic melting history in GIA community.

Tracking the complete revolution of Surface Westerlies over Northern Hemisphere using radionuclides emitted from Fukushima.

PubMed

Hernández-Ceballos, M A; Hong, G H; Lozano, R L; Kim, Y I; Lee, H M; Kim, S H; Yeh, S-W; Bolívar, J P; Baskaran, M

2012-11-01

Massive amounts of anthropogenic radionuclides were released from the nuclear reactors located in Fukushima (northeastern Japan) between 12 and 16 March 2011 following the earthquake and tsunami. Ground level air radioactivity was monitored around the globe immediately after the Fukushima accident. This global effort provided a unique opportunity to trace the surface air mass movement at different sites in the Northern Hemisphere. Based on surface air radioactivity measurements around the globe and the air mass backward trajectory analysis of the Fukushima radioactive plume at various places in the Northern Hemisphere by employing the Hybrid Single-Particle Lagrangian Integrated Trajectory model, we show for the first time, that the uninterrupted complete revolution of the mid-latitude Surface Westerlies took place in less than 21 days, with an average zonal velocity of>60 km/h. The position and circulation time scale of Surface Westerlies are of wide interest to a large number of global researchers including meteorologists, atmospheric researchers and global climate modellers. Copyright © 2012 Elsevier B.V. All rights reserved.

Seasonal Changes in Titan's Surface Temperatures

NASA Technical Reports Server (NTRS)

Jennins, Donald E.; Cottini, V.; Nixon, C. A.; Flasar, F. M.; Kunde, V. G.; Samuelson, R. E.; Romani, P. N.; Hesman, B. E.; Carlson, R. C.; Gorius, N. J. P.;

The effects of surface evaporation parameterizations on climate sensitivity to solar constant variations

NASA Technical Reports Server (NTRS)

Chou, S.-H.; Curran, R. J.; Ohring, G.

1981-01-01

The effects of two different evaporation parameterizations on the sensitivity of simulated climate to solar constant variations are investigated by using a zonally averaged climate model. One parameterization is a nonlinear formulation in which the evaporation is nonlinearly proportional to the sensible heat flux, with the Bowen ratio determined by the predicted vertical temperature and humidity gradients near the earth's surface (model A). The other is the formulation of Saltzman (1968) with the evaporation linearly proportional to the sensible heat flux (model B). The computed climates of models A and B are in good agreement except for the energy partition between sensible and latent heat at the earth's surface. The difference in evaporation parameterizations causes a difference in the response of temperature lapse rate to solar constant variations and a difference in the sensitivity of longwave radiation to surface temperature which leads to a smaller sensitivity of surface temperature to solar constant variations in model A than in model B. The results of model A are qualitatively in agreement with those of the general circulation model calculations of Wetherald and Manabe (1975).

Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern Indian Ocean

NASA Astrophysics Data System (ADS)

Makowski, Jessica K.; Chambers, Don P.; Bonin, Jennifer A.

2015-06-01

Previous studies have suggested that ocean bottom pressure (OBP) from the Gravity Recovery and Climate Experiment (GRACE) can be used to measure the depth-averaged, or barotropic, transport variability of the Antarctic Circumpolar Current (ACC). Here, we use GRACE OBP observations to calculate transport variability in a region of the southern Indian Ocean encompassing the major fronts of the ACC. We use a statistical analysis of a simulated GRACE-like data set to determine the uncertainty of the estimated transport for the 2003.0-2013.0 time period. We find that when the transport is averaged over 60° of longitude, the uncertainty (one standard error) is close to 1 Sv (1 Sv = 106 m3 s-1) for low-pass filtered transport, which is significantly smaller than the signal and lower than previous studies have found. The interannual variability is correlated with the Southern Annual mode (SAM) (0.61), but more highly correlated with circumpolar zonally averaged winds between 45°S and 65°S (0.88). GRACE transport reflects significant changes in transport between 2007 and 2009 that is observed in the zonal wind variations but not in the SAM index. We also find a statistically significant trend in transport (-1.0 ± 0.4 Sv yr-1, 90% confidence) that is correlated with a local deceleration in zonal winds related to an asymmetry in the SAM on multidecadal periods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, G.; Abarbanel, H.; Carruthers, P.

The questions of the sources of atmospheric carbon dioxide are addressed; distribution of the present carbon dioxide among the atmospheric, oceanic, and biospheric reservoirs is considered; and the impact on climate as reflected by the average ground temperature at each latitude of significant increases in atmospheric carbon dioxide is assessed. A new model for the mixing of carbon dioxide in the oceans is proposed. The proposed model explicitly takes into account the flow of colder and/or saltier water to great depths. We have constructed two models for the case of radiative equilibrium treating the atmosphere as gray and dividing themore » infrared emission region into nine bands. The gray atmosphere model predicts an increase of average surface temperature of 2.8/sup 0/K for a doubling of CO/sub 2/, a result about a degree less than the nine band model. An analytic model of the atmosphere was constructed (JASON Climate Model). Calculation with this zonally averaged model shows an increase of average surface temperature of 2.4/sup 0/ for a doubling of CO/sub 2/. The equatorial temperature increases by 0.7/sup 0/K while the poles warm up by 10 to 12/sup 0/K. The JASON climate model suffers from a number of fundamental weaknesses. The role of clouds in determining the albedo is not adequately taken into account nor are the asymmetries between the northern and southern hemisphere. (JGB)« less

A Earth Outgoing Longwave Radiation Climate Model

NASA Astrophysics Data System (ADS)

Yang, Shi-Keng

An Earth outgoing longwave radiation (OLWR) climate model has been constructed for radiation budget study. The model consists of the upward radiative transfer parameterization of Thompson and Warren (1982), the cloud cover model of Sherr et al. (1968) and a monthly average climatology defined by the data from Crutcher and Meserve (1971) and Taljaard et al. (1969). Additional required information is provided by the empirical 100mb water vapor mixing ratio equation of Harries (1976), and the mixing ratio interpolation scheme of Briegleb and Ramanathan (1982). Cloud top temperature is adjusted so that the calculation would agree with NOAA scanning radiometer measurements. Both clear sky and cloudy sky cases are calculated and discussed for global average, zonal average and world-wide distributed cases. The results agree well with the satellite observations. The clear sky case shows that the OLWR field is highly modulated by water vapor, especially in the tropics. The strongest longitudinal variation occurs in the tropics. This variation can be mostly explained by the strong water vapor gradient. Although in the zonal average case the tropics have a minimum in OLWR, the minimum is essentially contributed by a few very low flux regions, such as the Amazon, Indonesia and the Congo. There are regions in the tropics such that their OLWR is as large as that of the subtropics. In the high latitudes, where cold air contains less water vapor, OLWR is basically modulated by the surface temperature. Thus, the topographical heat capacity becomes a dominant factor in determining the distribution. Clouds enhance water vapor modulation of OLWR. Tropical clouds have the coldest cloud top temperatures. This again increases the longitudinal variation in the region. However, in the polar region, where temperature inversion is prominent, cloud top temperature is warmer than the surface. Hence, cloud has the effect of increasing OLWR. The implication of this cloud mechanism is that the latitudinal gradient of net radiation is thus further increased, and the forcing of the general atmospheric circulation is substantially different due to the increased additional available energy. The analysis of the results also suggests that to improve the performance of the Budyko-Sellers type energy balance climate model in the tropical region, the parameterization of the longwave cooling should include a water vapor absorbing term.

Comparison of Profile Total Ozone from SBUV (v8.6) with GOME-Type and Ground-Based Total Ozone for a 16-Year Period (1996 to 2011)

NASA Technical Reports Server (NTRS)

Chiou, E. W.; Bhartia, P. K.; McPeters, R. D.; Loyola, D. G.; Coldewey-Egbers, M.; Fioletov, V. E.; Van Roozendael, M.; Spurr, R.; Lerot, C.; Frith, S. M.

2014-01-01

This paper describes the comparison of the variability of total column ozone inferred from the three independent multi-year data records, namely, (i) Solar Backscatter Ultraviolet Instrument (SBUV) v8.6 profile total ozone, (ii) GTO (GOME-type total ozone), and (iii) ground-based total ozone data records covering the 16-year overlap period (March 1996 through June 2011). Analyses are conducted based on area-weighted zonal means for 0-30degS, 0-30degN, 50-30degS, and 30-60degN. It has been found that, on average, the differences in monthly zonal mean total ozone vary between -0.3 and 0.8% and are well within 1 %. For GTO minus SBUV, the standard deviations and ranges (maximum minus minimum) of the differences regarding monthly zonal mean total ozone vary between 0.6-0.7% and 2.8-3.8% respectively, depending on the latitude band. The corresponding standard deviations and ranges regarding the differences in monthly zonal mean anomalies show values between 0.4-0.6% and 2.2-3.5 %. The standard deviations and ranges of the differences ground-based minus SBUV regarding both monthly zonal means and anomalies are larger by a factor of 1.4-2.9 in comparison to GTO minus SBUV. The ground-based zonal means demonstrate larger scattering of monthly data compared to satellite-based records. The differences in the scattering are significantly reduced if seasonal zonal averages are analyzed. The trends of the differences GTO minus SBUV and ground-based minus SBUV are found to vary between -0.04 and 0.1%/yr (-0.1 and 0.3DU/yr). These negligibly small trends have provided strong evidence that there are no significant time-dependent differences among these multiyear total ozone data records. Analyses of the annual deviations from pre-1980 level indicate that, for the 15-year period of 1996 to 2010, all three data records show a gradual increase at 30-60degN from -5% in 1996 to -2% in 2010. In contrast, at 50-30degS and 30degS- 30degN there has been a leveling off in the 15 years after 1996. The deviations inferred from GTO and SBUV show agreement within 1 %, but a slight increase has been found in the differences during the period 1996-2010.

Theoretical and experimental zonal drift velocities of the ionospheric plasma bubbles over the Brazilian region

NASA Astrophysics Data System (ADS)

Arruda, Daniela C. S.; Sobral, J. H. A.; Abdu, M. A.; Castilho, Vivian M.; Takahashi, H.; Medeiros, A. F.; Buriti, R. A.

2006-01-01

This work presents equatorial ionospheric plasma bubble zonal drift velocity observations and their comparison with model calculations. The bubble zonal velocities were measured using airglow OI630 nm all-sky digital images and the model calculations were performed taking into account flux-tube integrated Pedersen conductivity and conductivity weighted neutral zonal winds. The digital images were obtained from an all-sky imaging system operated over the low-latitude station Cachoeira Paulista (Geogr. 22.5S, 45W, dip angle 31.5S) during the period from October 1998 to August 2000. Out of the 138 nights of imager observation, 29 nights with the presence of plasma bubbles are used in this study. These 29 nights correspond to geomagnetically rather quiet days (∑K P < 24+) and were grouped according to season. During the early night hours, the calculated zonal drift velocities were found to be larger than the experimental values. The best matching between the calculated and observed zonal velocities were seen to be for a few hours around midnight. The model calculation showed two humps around 20 LT and 24 LT that were not present in the data. Average decelerations obtained from linear regression between 20 LT and 24 LT were found to be: (a) Spring 1998, -8.61 ms -1 h -1; (b) Summer 1999, -0.59 ms -1 h -1; (c) Spring 1999, -11.72 ms -1 h -1; and (d) Summer 2000, -8.59 ms -1 h -1. Notice that Summer and Winter here correspond to southern hemisphere Summer and Winter, not northern hemisphere.

Determination of some dominant parameters of the global dynamic sea surface topography from GEOS-3 altimetry

NASA Technical Reports Server (NTRS)

Mather, R. S.; Lerch, F. J.; Rizos, C.; Masters, E. G.; Hirsch, B.

1978-01-01

The 1977 altimetry data bank is analyzed for the geometrical shape of the sea surface expressed as surface spherical harmonics after referral to the higher reference model defined by GEM 9. The resulting determination is expressed as quasi-stationary dynamic SST. Solutions are obtained from different sets of long arcs in the GEOS-3 altimeter data bank as well as from sub-sets related to the September 1975 and March 1976 equinoxes assembled with a view to minimizing seasonal effects. The results are compared with equivalent parameters obtained from the hydrostatic analysis of sporadic temperature, pressure and salinity measurements of the oceans and the known major steady state current systems with comparable wavelengths. The most clearly defined parameter (the zonal harmonic of degree 2) is obtained with an uncertainty of + or - 6 cm. The preferred numerical value is smaller than the oceanographic value due to the effect of the correction for the permanent earth tide. Similar precision is achieved for the zonal harmonic of degree 3. The precision obtained for the fourth degree zonal harmonic reflects more closely the accuracy expected from the level of noise in the orbital solutions.

A statistical examination of Nimbus 7 SMMR data and remote sensing of sea surface temperature, liquid water content in the atmosphere and surfaces wind speed

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Wang, I.; Chang, A. T. C.; Gloersen, P.

1982-01-01

Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) brightness temperature measurements over the global oceans have been examined with the help of statistical and empirical techniques. Such analyses show that zonal averages of brightness temperature measured by SMMR, over the oceans, on a large scale are primarily influenced by the water vapor in the atmosphere. Liquid water in the clouds and rain, which has a much smaller spatial and temporal scale, contributes substantially to the variability of the SMMR measurements within the latitudinal zones. The surface wind not only increases the surface emissivity but through its interactions with the atmosphere produces correlations, in the SMMR brightness temperature data, that have significant meteorological implications. It is found that a simple meteorological model can explain the general characteristics of the SMMR data. With the help of this model methods to infer over the global oceans, the surface temperature, liquid water content in the atmosphere, and surface wind speed are developed. Monthly mean estimates of the sea surface temperature and surface winds are compared with the ship measurements. Estimates of liquid water content in the atmosphere are consistent with earlier satellite measurements.

Titan Surface Temperatures as Measured by Cassini CIRS

NASA Technical Reports Server (NTRS)

Jennings, Donald E.; Flasar, F.M.; Kunde, V.G.; Nixon, C.A.; Romani, P.N.; Samuelson, R.E.; Coustenis, A.; Courtin, R.

2009-01-01

Thermal radiation from the surface of Titan reaches space through a spectral window of low opacity at 19-microns wavelength. This radiance gives a measure of the brightness temperature of the surface. Composite Infrared Spectrometer' (CIRS) observations from Cassini during its first four years at Saturn have permitted latitude mapping of zonally averaged surface temperatures. The measurements are corrected for atmospheric opacity using the dependence of radiance on emission angle. With the more complete latitude coverage and much larger dataset of CIRS we have improved upon the original results from Voyager IRIS. CIRS measures the equatorial surface brightness temperature to be 93.7+/-0.6 K, the same as the temperature measured at the Huygens landing site. The surface brightness temperature decreases by 2 K toward the south pole and by 3 K toward the north pole. The drop in surface temperature between equator and north pole implies a 50% decrease in methane saturation vapor pressure and relative humidity; this may help explain the large northern lakes. The H2 mole fraction is derived as a by-product of our analysis and agrees with previous results. Evidence of seasonal variation in surface and atmospheric temperatures is emerging from CIRS measurements over the Cassini mission.

Meridional displacement of the Antarctic Circumpolar Current

PubMed Central

Gille, Sarah T.

2014-01-01

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 meridional 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

A search for solar related changes in tropospheric weather

NASA Technical Reports Server (NTRS)

Mohanakumar, K.

1989-01-01

The possibility that solar variations associated with the 11-year solar cycle may be the cause of the changes in tropospheric weather and climate has been the subject to scientific investigation for several decades. Meteorologists are greatly concerned with the changes in tropospheric phenomena. An attempt was made to find solar activity related changes in tropospheric weather, by the modulation of the quasi-biennial oscillation (QBO) of zonal wind at 50 mb. Rainfall and surface temperature data for a period of about three solar cycles, 1953 to 1988, from various stations in the Indian subcontinent were utilized. By extension, a possible teleconnection was looked for between the temperature changes in middle atmospheric levels and surface temperature when the data are stratified according to east or west phase of the QBO. The temperature data were averaged for January and February to represent the winter temperature and for July and August to represent the summer temperature.

Relationship between eastern tropical Pacific cooling and recent trends in the Southern Hemisphere zonal-mean circulation

NASA Astrophysics Data System (ADS)

Clem, Kyle R.; Renwick, James A.; McGregor, James

2017-07-01

During 1979-2014, eastern tropical Pacific sea surface temperatures significantly cooled, which has generally been attributed to the transition of the Pacific Decadal Oscillation to its negative phase after 1999. We find the eastern tropical Pacific cooling to be associated with: (1) an intensified Walker Circulation during austral summer (December-February, DJF) and autumn (March-May, MAM); (2) a weakened South Pacific Hadley cell and subtropical jet during MAM; and (3) a strengthening of the circumpolar westerlies between 50 and 60°S during DJF and MAM. Observed cooling in the eastern tropical Pacific is linearly congruent with 60-80 % of the observed Southern Hemisphere positive zonal-mean zonal wind trend between 50 and 60°S during DJF ( 35 % of the interannual variability), and around half of the observed positive zonal-mean zonal wind trend during MAM ( 15 % of the interannual variability). Although previous studies have linked the strengthened DJF and MAM circumpolar westerlies to stratospheric ozone depletion and increasing greenhouse gases, we note that the continuation of the positive SAM trends into the twenty-first century is partially associated with eastern tropical Pacific cooling, especially during MAM when zonal wind anomalies associated with eastern tropical Pacific cooling project strongly onto the observed trends. Outside of DJF and MAM, eastern tropical Pacific cooling is associated with opposing zonal wind anomalies over the Pacific and Indian sectors, which we infer is the reason for the absence of significant positive SAM trends outside of DJF and MAM despite significant eastern tropical Pacific cooling seen during all seasons.

Direct phase measurement in zonal wavefront reconstruction using multidither coherent optical adaptive technique.

PubMed

Liu, Rui; Milkie, Daniel E; Kerlin, Aaron; MacLennan, Bryan; Ji, Na

2014-01-27

In traditional zonal wavefront sensing for adaptive optics, after local wavefront gradients are obtained, the entire wavefront can be calculated by assuming that the wavefront is a continuous surface. Such an approach will lead to sub-optimal performance in reconstructing wavefronts which are either discontinuous or undersampled by the zonal wavefront sensor. Here, we report a new method to reconstruct the wavefront by directly measuring local wavefront phases in parallel using multidither coherent optical adaptive technique. This method determines the relative phases of each pupil segment independently, and thus produces an accurate wavefront for even discontinuous wavefronts. We implemented this method in an adaptive optical two-photon fluorescence microscopy and demonstrated its superior performance in correcting large or discontinuous aberrations.

Soil dust aerosols and wind as predictors of seasonal meningitis incidence in Niger.

PubMed

Pérez García-Pando, Carlos; Stanton, Michelle C; Diggle, Peter J; Trzaska, Sylwia; Miller, Ron L; Perlwitz, Jan P; Baldasano, José M; Cuevas, Emilio; Ceccato, Pietro; Yaka, Pascal; Thomson, Madeleine C

2014-07-01

Epidemics of meningococcal meningitis are concentrated in sub-Saharan Africa during the dry season, a period when the region is affected by the Harmattan, a dry and dusty northeasterly trade wind blowing from the Sahara into the Gulf of Guinea. We examined the potential of climate-based statistical forecasting models to predict seasonal incidence of meningitis in Niger at both the national and district levels. We used time series of meningitis incidence from 1986 through 2006 for 38 districts in Niger. We tested models based on data that would be readily available in an operational framework, such as climate and dust, population, and the incidence of early cases before the onset of the meningitis season in January-May. Incidence was used as a proxy for immunological state, susceptibility, and carriage in the population. We compared a range of negative binomial generalized linear models fitted to the meningitis data. At the national level, a model using early incidence in December and averaged November-December zonal wind provided the best fit (pseudo-R2 = 0.57), with zonal wind having the greatest impact. A model with surface dust concentration as a predictive variable performed indistinguishably well. At the district level, the best spatiotemporal model included zonal wind, dust concentration, early incidence in December, and population density (pseudo-R2 = 0.41). We showed that wind and dust information and incidence in the early dry season predict part of the year-to-year variability of the seasonal incidence of meningitis at both national and district levels in Niger. Models of this form could provide an early-season alert that wind, dust, and other conditions are potentially conducive to an epidemic.

Impacts of the IOD-associated temperature and salinity anomalies on the intermittent equatorial undercurrent anomalies

NASA Astrophysics Data System (ADS)

Li, Junde; Liang, Chujin; Tang, Youmin; Liu, Xiaohui; Lian, Tao; Shen, Zheqi; Li, Xiaojing

2017-11-01

The study of Equatorial Undercurrent (EUC) has attracted a broad attention in recent years due to its strong response and feedback to the Indian Ocean Dipole. In this paper, we first produce a high-quality simulation of three-dimensional temperature, salinity and zonal current simulation from 1982 to 2014, using a high-resolution ocean general circulation model. On this basis, with two sensitivity experiments, we investigate the role of temperature and salinity anomalies in driving and enhancing the EUC during the positive IOD events by examining the variation of the EUC seasonal cycle and diagnosing the zonal momentum budget along the equatorial Indian Ocean. Our results show that during January-March, the EUC can appear along the entire equatorial Indian Ocean in all years, but during August-November, the EUC can appear and reach the eastern Indian Ocean only during the positive IOD events. The zonal momentum budget analysis indicates that the pressure gradient force contributes most to the variation of the eastward acceleration of zonal currents in the subsurface. During the positive IOD events, strong negative subsurface temperature anomalies exist in the eastern Indian Ocean, with negative surface salinity anomalies in the central and eastern Indian Ocean, resulting in a large pressure gradient force to drive EUC during the August-November. Further, the results of two sensitivity experiments indicate that the temperature anomalies significantly impact the pressure gradient force, playing a leading role in driving the EUC, while the surface salinity anomalies can secondarily help to intensify the eastward EUC through increasing the zonal density gradient in the eastern Indian Ocean and impacting the vertical momentum advection in the subsurface.

Anomalously Strong and Rapid Drying of the Tropical Lower Stratosphere in 2016: Connections to Both the QBO and ENSO

NASA Astrophysics Data System (ADS)

Hurst, D. F.; Davis, S. M.; Rosenlof, K. H.; Lambert, A.; Read, W. G.; Hall, E.; Jordan, A. F.

2017-12-01

Variations in tropical lower stratospheric water vapor are generally attributable to annual cycles in the Brewer-Dobson circulation and inter-annual phenomenon like the quasi-biennial oscillation (QBO) and the El Niño Southern Oscillation (ENSO). Extremes in tropical lower stratospheric water vapor (SWV) occur when these annual and inter-annual changes are constructively superimposed. The atypical progression of the 2015-16 QBO led to a strong and rapid cooling of the tropical lower stratosphere during 2016. From December 2015 to November 2016, monthly tropical mean (15°S-15°N) coldpoint temperature (CPT) anomalies decreased 3.2°C, from 1.1 to -2.1°C. Accordingly, monthly tropical mean SWV anomalies at 83 hPa dropped 1.9 ppm, from 0.85 to -1.05 ppm. This decline in SWV anomalies is equivalent to 40% of the long-term December average tropical abundance of SWV at 83 hPa. The 2016 decreases in tropical anomalies of both CPTs and SWV were not zonally uniform, with average Eastern Hemisphere reductions greater by 2°C and 0.9 ppm (50%), respectively. Since the QBO typically has a zonally uniform effect on tropical CPTs, this implies a zonally non-uniform mechanism like ENSO also influenced CPTs during 2016. The transition of ENSO from strong El Niño to weak La Niña conditions in 2016 would induce this zonal non-uniformity by shifting convective activity from the Eastern Pacific to the Western Pacific and Indian Ocean regions. Evidence indicates the simultaneous cooling of tropical CPTs by both the QBO and ENSO during 2016 rapidly dried the tropical lower stratosphere with anomalous strength, especially in the Eastern Hemisphere.

Tomographic Imaging of the Suns Interior

NASA Technical Reports Server (NTRS)

Kosovichev, A. G.

1996-01-01

A new method is presented of determining the three-dimensional sound-speed structure and flow velocities in the solar convection zone by inversion of the acoustic travel-time data recently obtained by Duvall and coworkers. The initial inversion results reveal large-scale subsurface structures and flows related to the active regions, and are important for understanding the physics of solar activity and large-scale convection. The results provide evidence of a zonal structure below the surface in the low-latitude area of the magnetic activity. Strong converging downflows, up to 1.2 km/s, and a substantial excess of the sound speed are found beneath growing active regions. In a decaying active region, there is evidence for the lower than average sound speed and for upwelling of plasma.

Present-day secular variations in the zonal harmonics of earth's geopotential

NASA Technical Reports Server (NTRS)

Mitrovica, J. X.; Peltier, W. R.

1993-01-01

The mathematical formulation required for predicting secular variation in the geopotential is developed for the case of a spherically symmetric, self-gravitating, viscoelastic earth model and an arbitrary surface load which can include a gravitational self-consistent ocean loading component. The theory is specifically applied to predict the present-day secular variation in the zonal harmonics of the geopotenial arising from the surface mass loading associated with the late Pleistocene glacial cycles. A procedure is outlined in which predictions of the present-day geopotential signal due to the late Pleistocene glacial cycles may be used to derive bounds on the net present-day mass flux from the Antarctic and Greenland ice sheets to the local oceans.

External Influences on Modeled and Observed Cloud Trends

NASA Technical Reports Server (NTRS)

Marvel, Kate; Zelinka, Mark; Klein, Stephen A.; Bonfils, Celine; Caldwell, Peter; Doutriaux, Charles; Santer, Benjamin D.; Taylor, Karl E.

2015-01-01

Understanding the cloud response to external forcing is a major challenge for climate science. This crucial goal is complicated by intermodel differences in simulating present and future cloud cover and by observational uncertainty. This is the first formal detection and attribution study of cloud changes over the satellite era. Presented herein are CMIP5 (Coupled Model Intercomparison Project - Phase 5) model-derived fingerprints of externally forced changes to three cloud properties: the latitudes at which the zonally averaged total cloud fraction (CLT) is maximized or minimized, the zonal average CLT at these latitudes, and the height of high clouds at these latitudes. By considering simultaneous changes in all three properties, the authors define a coherent multivariate fingerprint of cloud response to external forcing and use models from phase 5 of CMIP (CMIP5) to calculate the average time to detect these changes. It is found that given perfect satellite cloud observations beginning in 1983, the models indicate that a detectable multivariate signal should have already emerged. A search is then made for signals of external forcing in two observational datasets: ISCCP (International Satellite Cloud Climatology Project) and PATMOS-x (Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmospheres - Extended). The datasets are both found to show a poleward migration of the zonal CLT pattern that is incompatible with forced CMIP5 models. Nevertheless, a detectable multivariate signal is predicted by models over the PATMOS-x time period and is indeed present in the dataset. Despite persistent observational uncertainties, these results present a strong case for continued efforts to improve these existing satellite observations, in addition to planning for new missions.

Laboratory modeling of multiple zonal jets on the polar beta-plane

NASA Astrophysics Data System (ADS)

Afanasyev, Y.

2011-12-01

Zonal jets observed in the oceans and atmospheres of planets are studied in a laboratory rotating tank. The fluid layer in the rotating tank has parabolic free surface and dynamically simulates the polar beta-plane where the Coriolis parameter varies quadratically with distance from the pole. Velocity and surface elevation fields are measured with an optical altimetry method (Afanasyev et al., Exps Fluids 2009). The flows are induced by a localized buoyancy source along radial direction. The baroclinic flow consisting of a field of eddies propagates away from the source due West and forms zonal jets (Fig. 1). Barotropic jets ahead of the baroclinic flow are formed by radiation of beta plumes. Inside the baroclinic flow the jets flow between the chains of eddies. Experimental evidence of so-called noodles (baroclinic instability mode with motions in the radial, North-South direction) theoretically predicted by Berloff et al. (JFM, JPO 2009) was found in our experiments. Beta plume radiation mechanism and the mechanism associated with the instability of noodles are likely to contribute to formation of jets in the baroclinic flow.

Zonal wind indices to reconstruct United States winter precipitation during El Niño

NASA Astrophysics Data System (ADS)

Farnham, D. J.; Steinschneider, S.; Lall, U.

2017-12-01

The highly discussed 2015/16 El Niño event, which many likened to the similarly strong 1997/98 El Niño event, led to precipitation impacts over the continental United States (CONUS) inconsistent with general expectations given past events and model-based forecasts. This presents a challenge for regional water managers and others who use seasonal precipitation forecasts who previously viewed El Niño events as times of enhanced confidence in seasonal water availability and flood risk forecasts. It is therefore useful to understand the extent to which wintertime CONUS precipitation during El Niño events can be explained by seasonal sea surface temperature heating patterns and the extent to which the precipitation is a product of natural variability. In this work, we define two seasonal indices based on the zonal wind field spanning from the eastern Pacific to the western Atlantic over CONUS that can explain El Niño precipitation variation spatially throughout CONUS over 11 historic El Niño events from 1950 to 2016. The indices reconstruct El Niño event wintertime (Jan-Mar) gridded precipitation over CONUS through cross-validated regression much better than the traditional ENSO sea surface temperature indices or other known modes of variability. Lastly, we show strong relationships between sea surface temperature patterns and the phases of the zonal wind indices, which in turn suggests that some of the disparate CONUS precipitation during El Niño events can be explained by different heating patterns. The primary contribution of this work is the identification of intermediate variables (in the form of zonal wind indices) that can facilitate further studies into the distinct hydroclimatic response to specific El Niño events.

Validity of the "Laplace Swindle" in Calculation of Giant-Planet Gravity Fields

NASA Astrophysics Data System (ADS)

Hubbard, William B.

2014-11-01

Jupiter and Saturn have large rotation-induced distortions, providing an opportunity to constrain interior structure via precise measurement of external gravity. Anticipated high-precision gravity measurements close to the surfaces of Jupiter (Juno spacecraft) and Saturn (Cassini spacecraft), possibly detecting zonal harmonics to J10 and beyond, will place unprecedented requirements on gravitational modeling via the theory of figures (TOF). It is not widely appreciated that the traditional TOF employs a formally nonconvergent expansion attributed to Laplace. This suspect expansion is intimately related to the standard zonal harmonic (J-coefficient) expansion of the external gravity potential. It can be shown (Hubbard, Schubert, Kong, and Zhang: Icarus, in press) that both Jupiter and Saturn are in the domain where Laplace's "swindle" works exactly, or at least as well as necessary. More highly-distorted objects such as rapidly spinning asteroids may not be in this domain, however. I present a numerical test for the validity and precision of TOF via polar "audit points". I extend the audit-point test to objects rotating differentially on cylinders, obtaining zonal harmonics to J20 and beyond. Models with only low-order differential rotation do not exhibit dramatic effects in the shape of the zonal harmonic spectrum. However, a model with Jupiter-like zonal winds exhibits a break in the zonal harmonic spectrum above about J10, and generally follows the more shallow Kaula power rule at higher orders. This confirms an earlier result obtained by a different method (Hubbard: Icarus 137, 357-359, 1999).

Trends in the Zonal Winds over the Southern Ocean from the NCEP/NCAR Reanalysis and Scatterometers

NASA Astrophysics Data System (ADS)

Richman, J. G.

2002-12-01

The winds over the Southern Ocean for the entire 54-year (1948-2001) period of the NCEP/NCAR Reanalysis have been decomposed into Principal Components (Empirical Orthogonal Functions). The first EOF describes 83 percent of the variance in the zonal wind. The loading of the EOF shows the predominately westerly surface flow with strongest winds in the Indian sector of the Southern Ocean. The structure of this EOF is similar to the Southern Annular Mode (SAM) identified by Thompson, et al 2000. The amplitude of this EOF reveals a large trend of 4.42 cm/s/yr in the strength of the zonal wind corresponding to a nearly 50 percent increase in the wind stress over the Southern Ocean. Such a trend, if real, would be important in the dynamics of the Antarctic Circumpolar Current (ACC). Recent studies by Gille, et al. (2001), Olbers and Ivchenko (2001) and Gent et al. (2001) have shown that the transport of the ACC is correlated to the variability in the zonal wind with a monotonic increase in the transport with increasing zonal wind strength. However, errors in the data assimilation scheme for surface pressure observations on the Antarctic continent appears to have caused a spurious trend in the sea level pressure south of 40S of -0.2 hPa/yr (Hines, et al. 2000 and Marshall, 2002). The sea level pressure difference between 40S and 60S has risen by 8 hPa over the same period. This sea level pressure difference is used as a proxy for the strength of the zonal winds. Thus, the trend in the zonal wind EOF amplitude may be an artifact of model errors in the NCEP Reanalysis. To check this trend, we analyzed scatterometer winds over the Southern Ocean from the SEASAT, ERS (1 and 2), NSCAT and QuikScat satellites. The scatterometer data is not used in the NCEP Reanalysis and, thus, is an independent estimate of the winds. The SEASAT Scatterometer (SASS) operated for 90 days in July-September, 1978, while the ERS, NSCAT and QuikScat scatterometers provide a continuous dataset from September 1992 through the present. The zonal winds for the combined ERS/NSCAT dataset were decomposed into Principal Components, similar to the NCEP winds. The first EOF describes 78 percent of the variance in the zonal wind. The loading of the EOF is nearly identical in structure to the loading of the NCEP EOF, and the correlation between the amplitudes is 0.93 for the coincident period. The trend in the scatterometer winds is 3.9 cm/s/yr for the eight years, which is not significantly different from the 4.4 cm /s/yr trend of the NCEP winds. The three months of SASS data were projected onto the scatterometer EOF and the amplitudes compared to the long-term NCEP amplitudes. The agreement between the scatterometer amplitudes and the NCEP is remarkable. The comparison between the scatterometer winds and NCEP Reanalysis winds suggests that the trend towards increasing zonal winds is real. The increasing zonal winds over the Southern Ocean may lead to a substantial increase in the transport of the ACC over the past 50 years.

Zonally Averaged Carbon Dioxide Concentration from Earth Mid-Troposphere at Different Latitudes, 2002 to 2013

NASA Image and Video Library

2013-05-22

This plot shows the concentration of carbon dioxide in Earth mid-troposphere at various latitudes as measured by NASA Aqua satellite. The colored lines represent different latitude bands that circle Earth, called zones.

Extreme pressure differences at 0900 NZST and winds across New Zealand

NASA Astrophysics Data System (ADS)

Salinger, M. James; Griffiths, Georgina M.; Gosai, Ashmita

2005-07-01

Trends in extremes in station daily sea-level pressure differences at 0900 NZST are examined, and extreme daily wind gusts, across New Zealand, since the 1960s. Annual time series were examined (with indices of magnitude and frequency over threshold percentiles) from the daily indices selected. These follow from earlier indices of normalized monthly mean sea-level pressure differences between station pairs, except the daily indices are not normalized. The frequency statistics quantify the number of extreme zonal (westerly and easterly), or extreme meridional (southerly or northerly), pressure gradient events. The frequency and magnitude of extreme westerly episodes has increased slightly over New Zealand, with a significant increase in the westerly extremes to the south of New Zealand. In contrast, the magnitude and frequency of easterly extremes has decreased over New Zealand, but increased to the south, with some trends weakly significant. The frequency and magnitude of daily southerly extremes has decreased significantly in the region.Extreme daily wind gust events at key climate stations in New Zealand and at Hobart, Australia, are highly likely to be associated with an extreme daily pressure difference. The converse was less likely to hold: extreme wind gusts were not always observed on days with extreme daily pressure difference, probably due to the strong influence that topography has on localized station winds. Significant correlations exist between the frequency indices and both annual-average mean sea-level pressures around the Australasian region and annual-average sea surface temperature (SST) anomalies in the Southern Hemisphere. These correlations are generally stronger for indices of extreme westerly or extreme southerly airflows. Annual-average pressures in the Tasman Sea or Southern Ocean are highly correlated to zonal indices (frequency of extreme westerlies). SST anomalies in the NINO3 region or on either side of the South Island are significantly correlated with the frequency of extreme westerly airflows.

The dynamical core of the Aeolus 1.0 statistical-dynamical atmosphere model: validation and parameter optimization

NASA Astrophysics Data System (ADS)

Totz, Sonja; Eliseev, Alexey V.; Petri, Stefan; Flechsig, Michael; Caesar, Levke; Petoukhov, Vladimir; Coumou, Dim

2018-02-01

We present and validate a set of equations for representing the atmosphere's large-scale general circulation in an Earth system model of intermediate complexity (EMIC). These dynamical equations have been implemented in Aeolus 1.0, which is a statistical-dynamical atmosphere model (SDAM) and includes radiative transfer and cloud modules (Coumou et al., 2011; Eliseev et al., 2013). The statistical dynamical approach is computationally efficient and thus enables us to perform climate simulations at multimillennia timescales, which is a prime aim of our model development. Further, this computational efficiency enables us to scan large and high-dimensional parameter space to tune the model parameters, e.g., for sensitivity studies.Here, we present novel equations for the large-scale zonal-mean wind as well as those for planetary waves. Together with synoptic parameterization (as presented by Coumou et al., 2011), these form the mathematical description of the dynamical core of Aeolus 1.0.We optimize the dynamical core parameter values by tuning all relevant dynamical fields to ERA-Interim reanalysis data (1983-2009) forcing the dynamical core with prescribed surface temperature, surface humidity and cumulus cloud fraction. We test the model's performance in reproducing the seasonal cycle and the influence of the El Niño-Southern Oscillation (ENSO). We use a simulated annealing optimization algorithm, which approximates the global minimum of a high-dimensional function.With non-tuned parameter values, the model performs reasonably in terms of its representation of zonal-mean circulation, planetary waves and storm tracks. The simulated annealing optimization improves in particular the model's representation of the Northern Hemisphere jet stream and storm tracks as well as the Hadley circulation.The regions of high azonal wind velocities (planetary waves) are accurately captured for all validation experiments. The zonal-mean zonal wind and the integrated lower troposphere mass flux show good results in particular in the Northern Hemisphere. In the Southern Hemisphere, the model tends to produce too-weak zonal-mean zonal winds and a too-narrow Hadley circulation. We discuss possible reasons for these model biases as well as planned future model improvements and applications.

Comparison between SAGE II and ISCCP high-level clouds. 1: Global and zonal mean cloud amounts

NASA Technical Reports Server (NTRS)

Liao, Xiaohan; Rossow, William B.; Rind, David

1995-01-01

Global high-level clouds identified in Stratospheric Aerosol and Gas Experiment II (SAGE II) occultation measurements for January and July in the period 1985 to 1990 are compared with near-nadir-looking observations from the International Satellite Cloud Climatology Project (ISCCP). Global and zonal mean high-level cloud amounts from the two data sets agree very well, if clouds with layer extinction coefficients of less than 0.008/km at 1.02 micrometers wavelength are removed from the SAGE II results and all detected clouds are interpreted to have an average horizontal size of about 75 km along the 200 km transimission path length of the SAGE II observations. The SAGE II results are much more sensitive to variations of assumed cloud size than to variations of detection threshold. The geographical distribution of cloud fractions shows good agreement, but systematic regional differences also indicate that the average cloud size varies somewhat among different climate regimes. The more sensitive SAGE II results show that about one third of all high-level clouds are missed by ISCCP but that these clouds have very low optical thicknesses (less than 0.1 at 0.6 micrometers wavelength). SAGE II sampling error in monthly zonal cloud fraction is shown to produce no bias, to be less than the intraseasonal natural variability, but to be comparable with the natural variability at longer time scales.

Coherency Between Volume Transport in the Antarctic Circumpolar Current and Southern Hemisphere Winds

NASA Astrophysics Data System (ADS)

Makowski, Jessica; Chambers, Don; Bonin, Jennifer

2013-04-01

Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). The OBP observations from the Gravity Recovery and Climate Experiment (GRACE) will be used to calculate transport along the 150°E longitude choke point, between Antarctica and Australia. We will examine whether zonally averaged wind stress, wind stress curl, or local zonal winds are more coherent with zonal mass transport variability. Preliminary studies suggest that seasonal variation in transport across 150°E is more correlated with winds along and north of the northern front of the ACC: the Sub Tropical front (STF). It also appears that interannual variations in transport along 150°E are related to wind variations south of the STF and centered south of the Sub Antarctic Front (SAF). We have observed a strong anti-correlation across the SAF, in the Indian Ocean, which suggests wind stress curl may also be responsible for transport variations. Preliminary results will be presented.

Understanding the double peaked El Niño in coupled GCMs

NASA Astrophysics Data System (ADS)

Graham, Felicity S.; Wittenberg, Andrew T.; Brown, Jaclyn N.; Marsland, Simon J.; Holbrook, Neil J.

2017-03-01

Coupled general circulation models (CGCMs) simulate a diverse range of El Niño-Southern Oscillation behaviors. "Double peaked" El Niño events—where two separate centers of positive sea surface temperature (SST) anomalies evolve concurrently in the eastern and western equatorial Pacific—have been evidenced in Coupled Model Intercomparison Project version 5 CGCMs and are without precedent in observations. The characteristic CGCM double peaked El Niño may be mistaken for a central Pacific warming event in El Niño composites, shifted westwards due to the cold tongue bias. In results from the Australian Community Climate and Earth System Simulator coupled model, we find that the western Pacific warm peak of the double peaked El Niño event emerges due to an excessive westward extension of the climatological cold tongue, displacing the region of strong zonal SST gradients towards the west Pacific. A coincident westward shift in the zonal current anomalies reinforces the western peak in SST anomalies, leading to a zonal separation between the warming effect of zonal advection (in the west Pacific) and that of vertical advection (in the east Pacific). Meridional advection and net surface heat fluxes further drive growth of the western Pacific warm peak. Our results demonstrate that understanding historical CGCM El Niño behaviors is a necessary precursor to interpreting projections of future CGCM El Niño behaviors, such as changes in the frequency of eastern Pacific El Niño events, under global warming scenarios.

Using a zonal atmospheric model to test biogeophysical feedback-caused drought in the subtropical desert

DOE Office of Scientific and Technical Information (OSTI.GOV)

Potter, G.L.; MacCracken, M.C.; Ellsaesser, H.W.

1975-08-01

Recent interest in the cause of the sub-Sahara drought has initiated several investigations implying possible anthropogenic origin through increased surface albedo due to reduced plant cover from overgrazing. Results of two integrations of the Zonal Atmospheric Model (ZAM2) are presented, differing only in the prescribed surface albedo for the subtropical land masses of the northern hemisphere. These studies were initiated to determine whether an albedo change alone can bring about such dramatic impacts on local precipitation rates as have been implied. Preliminary results indicate that an albedo change can affect the climate, not just at the latitude of change butmore » also at other latitudes due to various atmospheric feedback mechanisms. (auth)« less

Troposphere-stratosphere (surface-55 km) monthly winter general circulation statistics for the Northern Hemisphere Interannual variations

NASA Technical Reports Server (NTRS)

Geller, M. A.; Wu, M.-F.; Gelman, M. E.

1984-01-01

Individual monthly mean general circulation statistics for the Northern Hemisphere winters of 1978-79, 1979-80, 1980-81, and 1981-82 are examined for the altitude region from the earth's surface to 55 km. Substantial interannual variability is found in the mean zonal geostrophic wind; planetary waves with zonal wavenumber one and two; the heat and momentum fluxes; and the divergence of the Eliassen-Palm flux. These results are compared with previous studies by other workers. This variability in the monthly means is examined further by looking at both time-latitude sections at constant pressure levels and time-height sections at constant latitudes. The implications of this interannual variability for verifying models and interpreting observations are discussed.

Elevated Ozone in the Troposphere over the Atlantic and Pacific Oceans in the Northern Hemisphere

NASA Technical Reports Server (NTRS)

Chandra, S.; Ziemke, J. R.; Tie, Xuexi

2003-01-01

Tropospheric column ozone (TCO) is derived from differential measurements of total column ozone from Nimus-7 and Earth Probe TOMS, and stratospheric column ozone from the Microwave Limb Sounder instrument on the Upper Atmospheric Research Satellite. It is shown that TCO during summer months over the Atlantic and Pacific Oceans at northern mid-latitudes is about the same (50-60 Dobson Units) as over the continents of North America, Europe and Asia, where surface emissions of nitrogen oxides from industrial sources, biomass and biofuel burning and biogenic emissions are significantly larger. This nearly uniform zonal variation in TCO is modulated by surface topography of the Rocky and Himalayan mountains and Tibetan Plateau where TCO is reduced by 20-30 Dobson Units. The zonal characteristics of TCO derived from satellite measurements are well simulated by a global chemical transport model called MOZART-2 (Model of Ozone and Related Chemical Tracers, version 2). The model results are analyzed to delineate the relative importance of various processes contributing to observed zonal characteristics of TCO, and they are shown that the surface emission of NOx contributes about 50% of the TCO at northern mid-latitudes, especially over the continents of North America, Europe and Asia. The result of TCO derived from TOMS and the analysis from MOZART-2 indicate that TCO is a very useful tool to study tropospheric O3 pollution resulting from surface emissions of pollutants.

Statistically Assessing Time-Averaged and Paleosecular Variation Field Models Against Paleomagnetic Directional Data Sets. Can Likely non-Zonal Features be Detected in a Robust way ?

NASA Astrophysics Data System (ADS)

Hulot, G.; Khokhlov, A.

2007-12-01

We recently introduced a method to rigorously test the statistical compatibility of combined time-averaged (TAF) and paleosecular variation (PSV) field models against any lava flow paleomagnetic database (Khokhlov et al., 2001, 2006). Applying this method to test (TAF+PSV) models against synthetic data produced from those shows that the method is very efficient at discriminating models, and very sensitive, provided those data errors are properly taken into account. This prompted us to test a variety of published combined (TAF+PSV) models against a test Bruhnes stable polarity data set extracted from the Quidelleur et al. (1994) data base. Not surprisingly, ignoring data errors leads all models to be rejected. But taking data errors into account leads to the stimulating conclusion that at least one (TAF+PSV) model appears to be compatible with the selected data set, this model being purely axisymmetric. This result shows that in practice also, and with the data bases currently available, the method can discriminate various candidate models and decide which actually best fits a given data set. But it also shows that likely non-zonal signatures of non-homogeneous boundary conditions imposed by the mantle are difficult to identify as statistically robust from paleomagnetic directional data sets. In the present paper, we will discuss the possibility that such signatures could eventually be identified as robust with the help of more recent data sets (such as the one put together under the collaborative "TAFI" effort, see e.g. Johnson et al. abstract #GP21A-0013, AGU Fall Meeting, 2005) or by taking additional information into account (such as the possible coincidence of non-zonal time-averaged field patterns with analogous patterns in the modern field).

Convective organization in the Pacific ITCZ: Merging OLR, TOVS, and SSM/I information

NASA Technical Reports Server (NTRS)

Hayes, Patrick M.; Mcguirk, James P.

1993-01-01

One of the most striking features of the planet's long-time average cloudiness is the zonal band of concentrated convection lying near the equator. Large-scale variability of the Intertropical Convergence Zone (ITCZ) has been well documented in studies of the planetary spatial scales and seasonal/annual/interannual temporal cycles of convection. Smaller-scale variability is difficult to study over the tropical oceans for several reasons. Conventional surface and upper-air data are virtually non-existent in some regions; diurnal and annual signals overwhelm fluctuations on other time scales; and analyses of variables such as geopotential and moisture are generally less reliable in the tropics. These problems make the use of satellite data an attractive alternative and the preferred means to study variability of tropical weather systems.

On the vertical distribution of water vapor in the Martian tropics

NASA Technical Reports Server (NTRS)

Haberle, Robert M.

1988-01-01

Although measurements of the column abundance of atmospheric water vapor on Mars have been made, measurements of its vertical distribution have not. How water is distributed in the vertical is fundamental to atmosphere-surface exchange processes, and especially to transport within the atmosphere. Several lines of evidence suggest that in the lowest several scale heights of the atmosphere, water vapor is nearly uniformly distributed. However, most of these arguments are suggestive rather than conclusive since they only demonstrate that the altitude to saturation is very high if the observed amount of water vapor is distributed uniformly. A simple argument is presented, independent of the saturation constraint, which suggests that in tropical regions, water vapor on Mars should be very nearly uniformly mixed on an annual and zonally averaged basis.

Newton vs. Munchhausen in upper-troposphere dynamics

NASA Astrophysics Data System (ADS)

Bergmann, Juan Carlos

2010-05-01

Atmospheric angular momentum (AM) balance depends crucially on the existence and magnitude of the planetary-scale AM transport by 'eddies' in the upper troposphere. Its divergence has to provide the torque, which is necessary to realise the upper-troposphere branch of meridional circulation. (In the boundary layer, the torque is provided by surface-friction.) The torques in neighbouring circulation cells are opposed, so that the AM transport mediates a torque-interaction between the circulation cells. This interaction corresponds to a clear requirement of Newton's Third Law: torques (forces) exist only in interaction with other bodies, and their sum is equal to zero. In Münchhausen's physics, force (and torque) exists without interaction: In a famous tale, Münchhausen saves himself (and his horse!) from drowning in a swamp-hole by pulling himself up at his hair. Münchhausen-physics situations arise in the dynamical analysis of the torque exerted by a single eddy and in analysis of the cause for the AM transport of the single eddy. The local AM transport of the single eddy is defined by the difference in zonal velocity between the pole-ward and equator-ward branches (Δu) multiplied with meridional velocity-magnitude (¦v¦). For the average over many eddies, it transforms to the average product of the deviations of zonal and meridional velocities from their local averages (, eddy-correlation; the complete formulations include the local radius of rotation but it is omitted here for simplicity reasons). This definition is phenomenological but not dynamical. In dynamical analysis it turns out that the torque-related zonal equation of motion of an AM-transporting single eddy can be formulated without torque-interaction with other bodies (torque-free eddy). Newton III implies also the phenomenological torque (transport divergence -δ(¦v¦Δu)/δy) to be zero for this case because there is no partner of torque-interaction. However, the dynamically torque-free single eddy has an unavoidable 'transport' divergence - especially in the turning-region of the meridional motion. Thus, there is a phenomenological 'torque' (non-zero 'transport' divergence) without torque-interaction - a classical Münchhausen situation! The dynamical cause of phenomenological 'AM transport' and associated phenomenological 'torques' of the dynamically torque-free single eddy is 'hidden' in the non-torque-related meridional equation of motion for steady-state: δv-δ t = - u δv-δx - vδv-δ y - f u(x) + Fy(x) = 0 . Strong variation of the meridional pressure-gradient force Fy(x) (no torque!) over the eddy-path (longitude x) produces varying zonal velocities u(x) that are falsely interpreted as 'AM transport' on the phenomenological level (the 'advective' terms are negligible outside the eddy's turning regions). Thus, creation and destruction of phenomenological 'AM transport' (Δu) in a single eddy do not originate from torque-interaction with other bodies - another classical Münchhausen situation! Should the previous analysis be ignored in favour of maintaining the 'established' ideas of upper-troposphere dynamics or should there be an effort to formulate new ideas that are in accordance with Newtonian physics?

Empirical wind model for the middle and lower atmosphere. Part 1: Local time average

NASA Technical Reports Server (NTRS)

Hedin, A. E.; Fleming, E. L.; Manson, A. H.; Schmidlin, F. J.; Avery, S. K.; Franke, S. J.

1993-01-01

The HWM90 thermospheric wind model was revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating zonal and meridional wind profiles representative of the climatological average for various geophysical conditions. Gradient winds from CIRA-86 plus rocket soundings, incoherent scatter radar, MF radar, and meteor radar provide the data base and are supplemented by previous data driven model summaries. Low-order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, and longitude (stationary wave 1). The model represents a smoothed compromise between the data sources. Although agreement between various data sources is generally good, some systematic differences are noted, particularly near the mesopause. Root mean square differences between data and model are on the order of 15 m/s in the mesosphere and 10 m/s in the stratosphere for zonal wind, and 10 m/s and 4 m/s, respectively, for meridional wind.

Low-latitude zonal and vertical ion drifts seen by DE 2

NASA Technical Reports Server (NTRS)

Coley, W. R.; Heelis, R. A.

1989-01-01

Horizontal and vertical ion drift data from the DE 2 spacecraft have been used to determine average zonal and vertical plasma flow (electric field) characteristics in the +/- 26-deg dip latitude region during a time of high solar activity. The 'average data' local time profile for an apex height bin centered at 400 km indicates westward plasma flow from 0600 to 1900 solar local time ((SLT) with a maximum westward velocity of 80 m/s in the early afternoon. There is a sharp change to eastward flow at approximately 1900 hours with an early evening peak of 170 m/s. A secondary nighttime maximum exists at 0430 SLT preceeding the reversal to westward flow. This profile is in good agreement with Jicamarca, Peru, radar measurements made under similar solar maximum conditions. Haramonic analysis indicates a net superrotation which is strongest at lower apex altitudes. The diurnal term is dominant, but higher order terms through the quatradiurnal are significant.

Climate warming due to increasing atmospheric CO2 - Simulations with a multilayer coupled atmosphere-ocean seasonal energy balance model

NASA Technical Reports Server (NTRS)

Li, Peng; Chou, Ming-Dah; Arking, Albert

1987-01-01

The transient response of the climate to increasing CO2 is studied using a modified version of the multilayer energy balance model of Peng et al. (1982). The main characteristics of the model are described. Latitudinal and seasonal distributions of planetary albedo, latitude-time distributions of zonal mean temperatures, and latitudinal distributions of evaporation, water vapor transport, and snow cover generated from the model and derived from actual observations are analyzed and compared. It is observed that in response to an atmospheric doubling of CO2, the model reaches within 1/e of the equilibrium response of global mean surface temperature in 9-35 years for the probable range of vertical heat diffusivity in the ocean. For CO2 increases projected by the National Research Council (1983), the model's transient response in annually and globally averaged surface temperatures is 60-75 percent of the corresponding equilibrium response, and the disequilibrium increases with increasing heat diffusivity of the ocean.

Results of a zonally truncated three-dimensional model of the Venus middle atmosphere

NASA Technical Reports Server (NTRS)

Newman, M.

1992-01-01

Although the equatorial rotational speed of the solid surface of Venus is only 4 m s(exp-1), the atmospheric rotational speed reaches a maximum of approximately 100 m s(exp-1) near the equatorial cloud top level (65 to 70 km). This phenomenon, known as superrotation, is the central dynamical problem of the Venus atmosphere. We report here the results of numerical simulations aimed at clarifying the mechanism for maintaining the equatorial cloud top rotation. Maintenance of an equatorial rotational speed maximum above the surface requires waves or eddies that systematically transport angular momentum against its zonal mean gradient. The zonally symmetric Hadley circulation is driven thermally and acts to reduce the rotational speed at the equatorial cloud top level; thus wave or eddy transport must counter this tendency as well as friction. Planetary waves arising from horizontal shear instability of the zonal flow (barotropic instability) could maintain the equatorial rotation by transporting angular momentum horizontally from midlatitudes toward the equator. Alternatively, vertically propagating waves could provide the required momentum source. The relative motion between the rotating atmosphere and the pattern of solar heating, which as a maximum where solar radiation is absorbed near the cloud tops, drives diurnal and semidiurnal thermal tides that propagate vertically away from the cloud top level. The effect of this wave propagation is to transport momentum toward the cloud top level at low latitudes and accelerate the mean zonal flow there. We employ a semispectral primitive equation model with a zonal mean flow and zonal wavenumbers 1 and 2. These waves correspond to the diurnal and semidiurnal tides, but they can also be excited by barotropic or baroclinic instability. Waves of higher wavenumbers and interactions between the waves are neglected. Symmetry about the equator is assumed, so the model applies to one hemisphere and covers the altitude range 30 to 110 km. Horizontal resolution is 1.5 deg latitude, and vertical resolution is 1.5 km. Solar and thermal infrared heating, based on Venus observations and calculations drive the model flow. Dissipation is accomplished mainly by Rayleigh friction, chosen to produce strong dissipation above 85 km in order to absorb upward propagating waves and limit extreme flow velocities there, yet to give very weak Rayleigh friction below 70 km; results in the cloud layer do not appear to be sensitive to the Rayleigh friction. The model also has weak vertical diffusion, and very weak horizontal diffusion, which has a smoothing effect on the flow only at the two grid points nearest the pole.

Multidecadal Changes in Near-Global Cloud Cover and Estimated Cloud Cover Radiative Forcing

NASA Technical Reports Server (NTRS)

Norris, Joel

2005-01-01

The first paper was Multidecadal changes in near-global cloud cover and estimated cloud cover radiative forcing, by J. R. Norris (2005, J. Geophys. Res. - Atmos., 110, D08206, doi: lO.l029/2004JD005600). This study examined variability in zonal mean surface-observed upper-level (combined midlevel and high-level) and low-level cloud cover over land during 1971-1 996 and over ocean during 1952-1997. These data were averaged from individual synoptic reports in the Extended Edited Cloud Report Archive (EECRA). Although substantial interdecadal variability is present in the time series, long-term decreases in upper-level cloud cover occur over land and ocean at low and middle latitudes in both hemispheres. Near-global upper-level cloud cover declined by 1.5%-sky-cover over land between 1971 and 1996 and by 1.3%-sky-cover over ocean between 1952 and 1997. Consistency between EECRA upper-level cloud cover anomalies and those from the International Satellite Cloud Climatology Project (ISCCP) during 1984-1 997 suggests the surface-observed trends are real. The reduction in surface-observed upper-level cloud cover between the 1980s and 1990s is also consistent with the decadal increase in all-sky outgoing longwave radiation reported by the Earth Radiation Budget Satellite (EMS). Discrepancies occur between time series of EECRA and ISCCP low-level cloud cover due to identified and probable artifacts in satellite and surface cloud data. Radiative effects of surface-observed cloud cover anomalies, called "cloud cover radiative forcing (CCRF) anomalies," are estimated based on a linear relationship to climatological cloud radiative forcing per unit cloud cover. Zonal mean estimated longwave CCRF has decreased over most of the globe. Estimated shortwave CCRF has become slightly stronger over northern midlatitude oceans and slightly weaker over northern midlatitude land areas. A long-term decline in the magnitude of estimated shortwave CCRF occurs over low-latitude land and ocean, but comparison with EMS all-sky reflected shortwave radiation during 1985-1997 suggests this decrease may be underestimated.

Surface radiation fluxes in transient climate simulations

NASA Astrophysics Data System (ADS)

Garratt, J. R.; O'Brien, D. M.; Dix, M. R.; Murphy, J. M.; Stephens, G. L.; Wild, M.

1999-01-01

Transient CO 2 experiments from five coupled climate models, in which the CO 2 concentration increases at rates of 0.6-1.1% per annum for periods of 75-200 years, are used to document the responses of surface radiation fluxes, and associated atmospheric properties, to the CO 2 increase. In all five models, the responses of global surface temperature and column water vapour are non-linear and fairly tightly constrained. Thus, global warming lies between 1.9 and 2.7 K at doubled, and between 3.1 and 4.1 K at tripled, CO 2, whilst column water vapour increases by between 3.5 and 4.5 mm at doubled, and between 7 and 8 mm at tripled, CO 2. Global cloud fraction tends to decrease by 1-2% out to tripled CO 2, mainly the result of decreases in low cloud. Global increases in column water, and differences in these increases between models, are mainly determined by the warming of the tropical oceans relative to the middle and high latitudes; these links are emphasised in the zonal profiles of warming and column water vapour increase, with strong water vapour maxima in the tropics. In all models the all-sky shortwave flux to the surface S↓ (global, annual average) changes by less than 5 W m -2 out to tripled CO 2, in some cases being essentially invariant in time. In contrast, the longwave flux to the surface L↓ increases significantly, by 25 W m -2 typically at tripled CO 2. The variations of S↓ and L↓ (clear-sky and all-sky fluxes) with increase in CO 2 concentration are generally non-linear, reflecting the effects of ocean thermal inertia, but as functions of global warming are close to linear in all five models. This is best illustrated for the clear-sky downwelling fluxes, and the net radiation. Regionally, as illustrated in zonal profiles and global distributions, greatest changes in both S↓ and L↓ are the result primarily of local maxima in warming and column water vapour increases.

On statistical irregularity of stratospheric warming occurrence during northern winters

NASA Astrophysics Data System (ADS)

Savenkova, Elena N.; Gavrilov, Nikolai M.; Pogoreltsev, Alexander I.

2017-10-01

Statistical analysis of dates of warming events observed during the years 1981-2016 at different stratospheric altitudes reveals their non-uniform distributions during northern winter months with maxima at the beginning of January, at the end of January - beginning of February and at the end of February. Climatology of zonal-mean zonal wind, deviations of temperature from its winter-averaged values, and planetary wave (PW) characteristics at high and middle northern latitudes in the altitude range from the ground up to 60 km is studied using the database of meteorological reanalysis MERRA. Climatological temperature deviations averaged over the 60-90°N latitudinal bands reveal cooler and warmer layers descending due to seasonal changes during the polar night. PW amplitudes and upward Eliassen-Palm fluxes averaged over 36 years have periodical maxima with the main maximum at the beginning of January at altitudes 40-50 km. During the above-mentioned intervals of more frequent occurrence of stratospheric warming events, maxima of PW amplitudes and Eliassen-Palm fluxes, also minima of eastward winds in the high-latitude northern stratosphere have been found. Climatological intra-seasonal irregularities of stratospheric warming dates could indicate reiterating phases of stratospheric vacillations in different years.

Multiproxy Reduced-Dimension Reconstruction of Holocene Tropical Pacific SST Fields and Indian Monsoon Variability

NASA Astrophysics Data System (ADS)

Gill, E.; Rajagopalan, B.; Molnar, P. H.; Marchitto, T. M., Jr.; Kushnir, Y.

2016-12-01

We develop a multiproxy reduced-dimension methodology that blends magnesium calcium (Mg/Ca) and alkenone (UK'37) paleo sea surface temperature (SST) records from the eastern and western equatorial Pacific to recreate snapshots of full field SSTs and zonal wind anomalies from 10 to 2 ka BP in 2000-year increments. In the reconstruction, the zonal SST difference (average west Pacific SST minus average east Pacific SST) is largest at 10 ka (0.26°C), with coldest SST anomalies of -0.9°C in the eastern equatorial Pacific and concurrent easterly maximum zonal wind anomalies of 7 m s-1 throughout the central Pacific. From 10 to 2 ka, the entire equatorial Pacific warms, but at a faster rate in the east than in the west. These patterns are broadly consistent with previous inferences of reduced El Niño-Southern Oscillation variability associated with a cooler and/or "La Niña-like" state during the early to middle Holocene. At present there is a strong negative correlation between tropical pacific SSTs and Indian summer monsoon strength. Assuming ENSO-monsoon teleconnections were the same during early Holocene, we would expect a cooler tropical Pacific to enhance the summer Indian monsoon. To test this idea, we used the same tropical Pacific SST proxy records and a similar reduced-dimension technique to reconstruct fields of Arabian Sea wind-stress curl and Indian summer monsoon precipitation. Reconstructions for 10 ka reveal wind-stress curl anomalies of 30% greater than present day off the coastlines of Oman and Yemen, which suggest greater coastal upwelling and an enhanced monsoon jet during this time. Spatial rainfall reconstructions reveal the greatest difference in precipitation at 10 ka over the core monsoon region ( 20-60% greater than present day). Specifically, reconstructions from 10 ka reveal 40-60% greater rainfall over North West India, a region home to abundant paleo-lake records spanning the Holocene but is at present remarkably dry ( 200-450 mm of annual rainfall). These findings advance the hypothesis that teleconnections from the tropical Pacific contributed to, if not accounted for, greater early to middle Holocene wetness over India as recorded by various (e.g., cave, lacustrine, river discharge) paleoclimate proxies throughout the monsoon region.

Observations of cloud liquid water path over oceans: Optical and microwave remote sensing methods

NASA Technical Reports Server (NTRS)

Lin, Bing; Rossow, William B.

1994-01-01

Published estimates of cloud liquid water path (LWP) from satellite-measured microwave radiation show little agreement, even about the relative magnitudes of LWP in the tropics and midlatitudes. To understand these differences and to obtain more reliable estimate, optical and microwave LWP retrieval methods are compared using the International Satellite Cloud Climatology Project (ISCCP) and special sensor microwave/imager (SSM/I) data. Errors in microwave LWP retrieval associated with uncertainties in surface, atmosphere, and cloud properties are assessed. Sea surface temperature may not produce great LWP errors, if accurate contemporaneous measurements are used in the retrieval. An uncertainty of estimated near-surface wind speed as high as 2 m/s produces uncertainty in LWP of about 5 mg/sq cm. Cloud liquid water temperature has only a small effect on LWP retrievals (rms errors less than 2 mg/sq cm), if errors in the temperature are less than 5 C; however, such errors can produce spurious variations of LWP with latitude and season. Errors in atmospheric column water vapor (CWV) are strongly coupled with errors in LWP (for some retrieval methods) causing errors as large as 30 mg/sq cm. Because microwave radiation is much less sensitive to clouds with small LWP (less than 7 mg/sq cm) than visible wavelength radiation, the microwave results are very sensitive to the process used to separate clear and cloudy conditions. Different cloud detection sensitivities in different microwave retrieval methods bias estimated LWP values. Comparing ISCCP and SSM/I LWPs, we find that the two estimated values are consistent in global, zonal, and regional means for warm, nonprecipitating clouds, which have average LWP values of about 5 mg/sq cm and occur much more frequently than precipitating clouds. Ice water path (IWP) can be roughly estimated from the differences between ISCCP total water path and SSM/I LWP for cold, nonprecipitating clouds. IWP in the winter hemisphere is about 3 times the LWP but only half the LWP in the summer hemisphere. Precipitating clouds contribute significantly to monthly, zonal mean LWP values determined from microwave, especially in the intertropical convergence zone (ITCZ), because they have almost 10 times the liquid water (cloud plus precipitation) of nonprecipitating clouds on average. There are significant differences among microwave LWP estimates associated with the treatment of precipitating clouds.

Biohazards Assessment in Large-Scale Zonal Centrifugation

PubMed Central

Baldwin, C. L.; Lemp, J. F.; Barbeito, M. S.

1975-01-01

A study was conducted to determine the biohazards associated with use of the large-scale zonal centrifuge for purification of moderate risk oncogenic viruses. To safely and conveniently assess the hazard, coliphage T3 was substituted for the virus in a typical processing procedure performed in a National Cancer Institute contract laboratory. Risk of personnel exposure was found to be minimal during optimal operation but definite potential for virus release from a number of centrifuge components during mechanical malfunction was shown by assay of surface, liquid, and air samples collected during the processing. High concentration of phage was detected in the turbine air exhaust and the seal coolant system when faulty seals were employed. The simulant virus was also found on both centrifuge chamber interior and rotor surfaces. Images PMID:1124921

Bounded relative motion under zonal harmonics perturbations

NASA Astrophysics Data System (ADS)

Baresi, Nicola; Scheeres, Daniel J.

2017-04-01

The problem of finding natural bounded relative trajectories between the different units of a distributed space system is of great interest to the astrodynamics community. This is because most popular initialization methods still fail to establish long-term bounded relative motion when gravitational perturbations are involved. Recent numerical searches based on dynamical systems theory and ergodic maps have demonstrated that bounded relative trajectories not only exist but may extend up to hundreds of kilometers, i.e., well beyond the reach of currently available techniques. To remedy this, we introduce a novel approach that relies on neither linearized equations nor mean-to-osculating orbit element mappings. The proposed algorithm applies to rotationally symmetric bodies and is based on a numerical method for computing quasi-periodic invariant tori via stroboscopic maps, including extra constraints to fix the average of the nodal period and RAAN drift between two consecutive equatorial plane crossings of the quasi-periodic solutions. In this way, bounded relative trajectories of arbitrary size can be found with great accuracy as long as these are allowed by the natural dynamics and the physical constraints of the system (e.g., the surface of the gravitational attractor). This holds under any number of zonal harmonics perturbations and for arbitrary time intervals as demonstrated by numerical simulations about an Earth-like planet and the highly oblate primary of the binary asteroid (66391) 1999 KW4.

Impact of Surface Emissions to the Zonal Variability of Tropical Tropospheric Ozone and Carbon Monoxide for November 2004

NASA Technical Reports Server (NTRS)

Bowman, K. W.; Jones, D.; Logan, J.; Worden, H.; Boersma, F.; Chang, R.; Kulawik, S.; Osterman, G.; Worden, J.

2008-01-01

The chemical and dynamical processes governing the zonal variability of tropical tropospheric ozone and carbon monoxide are investigated for November 2004 using satellite observations, in-situ measurements, and chemical transport models in conjunction with inverse-estimated surface emissions. Vertical ozone profile estimates from the Tropospheric Emission Spectrometer (TES) and ozone sonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network show the so called zonal 'wave-one' pattern, which is characterized by peak ozone concentrations (70-80 ppb) centered over the Atlantic, as well as elevated concentrations of ozone over Indonesia and Australia (60-70 ppb) in the lower troposphere. Observational evidence from TES CO vertical profiles and Ozone Monitoring Instrument (OMI) NO2 columns point to regional surface emissions as an important contributor to the elevated ozone over Indonesia. This contribution is investigated with the GEOS-Chem chemistry and transport model using surface emission estimates derived from an optimal inverse model, which was constrained by TES and Measurements Of Pollution In The Troposphere (MOPITT) CO profiles (Jones et al., 2007). These a posteriori estimates, which were over a factor of 2 greater than climatological emissions, reduced differences between GEOS-Chem and TES ozone observations by 30-40% and led to changes in GEOS-Chem upper tropospheric ozone of up to 40% over Indonesia. The remaining residual differences can be explained in part by upper tropospheric ozone produced from lightning NOx in the South Atlantic. Furthermore, model simulations from GEOS-Chem indicate that ozone over Indonesian/Australian is more sensitive to changes in surface emissions of NOx than ozone over the tropical Atlantic.

Mechanism for Surface Warming in the Equatorial Pacific during 1994-95

NASA Technical Reports Server (NTRS)

Rienecker, Michele M.; Borovikov, Anna; Schopf, Paul S.

1999-01-01

Mechanisms controlling the variation in sea surface temperature warm event in the equatorial Pacific were investigated through ocean model simulations. In addition, the mechanisms of the climatological SST cycle were investigated. The dominant mechanisms governing the seasonal cycle of SST vary significantly across the basin. In the western Pacific the annual cycle of SST is primarily in response to external heat flux. In the central basin the magnitude of zonal advection is comparable to that of the external heat flux. In the eastern basin the role of zonal advection is reduced and the vertical mixing is more important. In the easternmost equatorial Pacific the vertical entrainment contribution is as large as that of vertical diffusion. The model estimate of the vertical mixing contribution to the mixed layer heat budget compared well with estimates obtained by analysis of observations using the same diagnostic vertical mixing scheme. During 1994- 1995 the largest positive SST anomaly was observed in the mid-basin and was related to reduced latent heat flux due to weak surface winds. In the western basin the initial warming was related to enhanced external heating and reduced cooling effects of both vertical mixing and horizontal advection associated with weaker than usual wind stress. In the eastern Pacific where winds were not significantly anomalous throughout 1994-1995, only a moderate warm surface anomaly was detected. This is in contrast to strong El Nino events where the SST anomaly is largest in the eastern basin and, as shown by previous studies, the anomaly is due to zonal advection rather than anomalous surface heat flux. The end of the warm event was marked by cooling in July 1995 everywhere across the equatorial Pacific.

Modulation of Bjerknes feedback on the decadal variations in ENSO predictability

NASA Astrophysics Data System (ADS)

Zheng, Fei; Fang, Xiang-Hui; Zhu, Jiang; Yu, Jin-Yi; Li, Xi-Chen

2016-12-01

Clear decadal variations exist in the predictability of the El Niño-Southern Oscillation (ENSO), with the most recent decade having the lowest ENSO predictability in the past six decades. The Bjerknes Feedback (BF) intensity, which dominates the development of ENSO, has been proposed to determine ENSO predictability. Here we demonstrate that decadal variations in BF intensity are largely a result of the sensitivity of the zonal winds to the zonal sea level pressure (SLP) gradient in the equatorial Pacific. Furthermore, the results show that during low-ENSO predictability decades, zonal wind anomalies over the equatorial Pacific are more linked to SLP variations in the off-equatorial Pacific, which can then transfer this information into surface temperature and precipitation fields through the BF, suggesting a weakening in the ocean-atmosphere coupling in the tropical Pacific. This result indicates that more attention should be paid to off-equatorial processes in the prediction of ENSO.

Trapped waves on the mid-latitude β-plane

NASA Astrophysics Data System (ADS)

Paldor, Nathan; Sigalov, Andrey

2008-08-01

A new type of approximate solutions of the Linearized Shallow Water Equations (LSWE) on the mid-latitude β-plane, zonally propagating trapped waves with Airy-like latitude-dependent amplitude, is constructed in this work, for sufficiently small radius of deformation. In contrast to harmonic Poincare and Rossby waves, these newly found trapped waves vanish fast in the positive half-axis, and their zonal phase speed is larger than that of the corresponding harmonic waves for sufficiently large meridional domains. Our analysis implies that due to the smaller radius of deformation in the ocean compared with that in the atmosphere, the trapped waves are relevant to observations in the ocean whereas harmonic waves typify atmospheric observations. The increase in the zonal phase speed of trapped Rossby waves compared with that of harmonic ones is consistent with recent observations that showed that Sea Surface Height features propagated westwards faster than the phase speed of harmonic Rossby waves.

Global, Hemispheric, and Zonal Temperature Deviations Derived From a 63-Station Radiosonde Network

DOE Data Explorer

Angell, J. K. [NOAA, Air Resources Laboratory

2011-01-01

Surface temperatures and thickness-derived temperatures from a 63-station, globally distributed radiosonde network have been used to estimate global, hemispheric, and zonal annual and seasonal temperature deviations. Most of the temperature values used were column-mean temperatures, obtained from the differences in height (thickness) between constant-pressure surfaces at individual radiosonde stations. The pressure-height data before 1980 were obtained from published values in Monthly Climatic Data for the World. Between 1980 and 1990, Angell used data from both the Climatic Data for the World and the Global Telecommunications System (GTS) Network received at the National Meteorological Center. Between 1990 and 1995, the data were obtained only from GTS, and since 1995 the data have been obtained from National Center for Atmospheric Research files. The data are evaluated as deviations from the mean based on the interval 1958-1977. The station deviations have been averaged (with equal weighting) to obtain annual and seasonal temperature deviations for the globe, the Northern and Southern Hemispheres, and the following latitudinal zones: North (60° N-90° N) and South (60° S-90° S) Polar; North (30° N-60° N) and South (30° S-60° S) Temperate; North (10° N-30° N) and South (10° S-30° S) Subtropical; Tropical(30° S-30° N); and Equatorial (10° S-10° N). The seasonal calculations are for the standard meteorological seasons (i.e., winter is defined as December, January, and February; spring is March, April, and May, etc.) and the annual calculations are for December through the following November (i.e., for the four meteorological seasons). For greater details, see Angell and Korshover (1983) and Angell (1988, 1991)

Mechanisms of Robust Future Spring Drying in the Southwest U.S. in CMIP5 Models

NASA Astrophysics Data System (ADS)

Ting, M.; Seager, R.; Li, C.; Liu, H.

2017-12-01

The net surface water budget, precipitation minus evaporation (P-E), shows a clear seasonal cycle in the American Southwest with net gain of surface water (positive P-E) in the cold half of the year (October to March) and net loss of water (negative P-E) in the warmer half (April - September), with June and July being the driest time of the year. There is a significant shift of the summer drying toward earlier in the year under CO2 warming scenario, resulting in substantial spring drying (MAM) of the American Southwest, from the near-term future (2021 - 2040) to the end of the current Century with gradually increasing magnitude. While the spring drying has been identified in previous studies, its mechanism has not been fully addressed. Using moisture budget analysis, we found that the drying is mainly due to decreased mean moisture convergence, partially compensated by the increase in transient eddy moisture flux convergence. The decreased mean moisture convergence is further separated into those due to changes in circulation (dynamic changes) and changes in atmospheric moisture content (thermodynamic changes). The drying is found to be dominated by the thermodynamic driven changes in column averaged moisture convergence, due mainly to increased dry zonal advection caused by the climatological land-ocean thermal contrast, rather than by the well-known "dry gets drier" mechanism. Furthermore, the enhanced dry advection in the warming climate is dominated by the robust zonal mean atmospheric warming, thus the spring drying in Southwest US is very robust. We also discuss reasons this future drying is particularly strong in the spring as compared to the other seasons.

Atmospheric thermal structure and cloud features in the southern hemisphere of Venus as retrieved from VIRTIS/VEX radiation measurements

NASA Astrophysics Data System (ADS)

Haus, R.; Kappel, D.; Arnold, G.

2014-04-01

Thermal structure and cloud features in the atmosphere of Venus are investigated using spectroscopic nightside measurements recorded by the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) aboard ESA’s Venus Express mission in the moderate resolution infrared mapping channel (M-IR, 1-5 μm). New methodical approaches and retrieval results for the northern hemisphere have been recently described by Haus et al. (Haus, R., Kappel, D., Arnold, G. [2013]. Planet. Space Sci. 89, 77-101. http://dx.doi.org/10.1016/j.pss.2013.09.020). Now, southern hemisphere maps of mesospheric temperature and cloud parameter fields are presented that cover variations with altitude, latitude, local time, and mission time. Measurements from the entire usable data archive are utilized comprising radiation spectra recorded during eight Venus solar days between April 2006 and October 2008. Zonal averages of retrieved temperature altitude profiles in both hemispheres are very similar and give evidence of global N-S axial symmetry of atmospheric temperature structure. Cold collar and warmer polar vortex regions exhibit the strongest temperature variability with standard deviations up to 8.5 K at 75°S and 63 km altitude compared with about 1.0 K at low and mid latitudes above 75 km. The mesospheric temperature field strongly depends on local time. At altitudes above about 75 km, the atmosphere is warmer in the second half of night, while the dawn side at lower altitudes is usually colder than the dusk side by about 8 K. Local minimum temperature of 220 K occurs at 03:00 h local time at 65 km and 60°S. Temperature standard deviation at polar latitudes is particularly large near midnight. Temperature variability with solar longitude is forced by solar thermal tides with a dominating diurnal component. The influence of observed cloud parameter changes on retrieved mesospheric zonal average temperature structure is moderate and does not exceed 2-3 K at altitudes between 60 and 75 km. The mesospheric thermal structure was essentially stable with Julian date between 2006 and 2008. Global N-S axial symmetry is also observed in cloud structures. Cloud top altitude at 1 μm slowly decreases from 71 km at the equator to 70 km at 45-50° and rapidly drops poleward of 50°. It reaches 61 km over both poles. Average particle size in the vertical cloud column increases from mid latitudes toward the poles and also toward the equator resulting in minimum and maximum zonal average cloud opacities of about 32 and 42 and a planetary average of 36.5 at 1 μm. Zonal averages of cloud features are similar at different solar days, but variations with local time are very complex and inseparably associated with the superrotation of the clouds.

Geographical analysis of equatorial plasma bubbles by GPS and nightglow measurements

NASA Astrophysics Data System (ADS)

Nade, D. P.; Shetti, D. J.; Sharma, A. K.; Taori, A.; Chavan, G. A.; Patil, P. T.; Ghodpage, R. N.; Gurav, O. B.; Nikte, S. S.

2015-11-01

This work about the zonal drift velocity and signature of equatorial plasma bubbles (EPBs) by measurements of global positioning system (GPS) receiver and all sky imager (ASI) operating in India, at the low latitude region. The optical and radio observations have been made from Kolhapur (16.8° N, 74.2° E) and Hyderabad (17.37°N, 78.48°E), respectively. The zonal drift velocity of EPBs has estimated using images of nightglow OI 630.0 nm emission recorded by ASI at Kolhapur. The measurements of total electron content (TEC) using the GPS have carried from the nearby station, Hyderabad. When depletions occurred about 00:37 h (IST) in TEC, the EPBs were found to occur about 5:30 h in optical data of OI 630.0 nm emission. This work focuses on simultaneous measurements of TEC and intensity of OI 630.0 nm emissions for EPBs during nighttime. The occurrence period of EPBs in TEC and OI 630.0 nm has found to be different. To study this difference, the zonal drift velocity of EPBs has established. The averaged eastward velocity of EPBs was found to be 138 m/s. The calculated values of zonal drift velocities are well correlated with that of the empirical model values. This work may be helpful in finding the growth of EPBs over low latitude.

Numerical aspects and implementation of a two-layer zonal wall model for LES of compressible turbulent flows on unstructured meshes

NASA Astrophysics Data System (ADS)

Park, George Ilhwan; Moin, Parviz

2016-01-01

This paper focuses on numerical and practical aspects associated with a parallel implementation of a two-layer zonal wall model for large-eddy simulation (LES) of compressible wall-bounded turbulent flows on unstructured meshes. A zonal wall model based on the solution of unsteady three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations on a separate near-wall grid is implemented in an unstructured, cell-centered finite-volume LES solver. The main challenge in its implementation is to couple two parallel, unstructured flow solvers for efficient boundary data communication and simultaneous time integrations. A coupling strategy with good load balancing and low processors underutilization is identified. Face mapping and interpolation procedures at the coupling interface are explained in detail. The method of manufactured solution is used for verifying the correct implementation of solver coupling, and parallel performance of the combined wall-modeled LES (WMLES) solver is investigated. The method has successfully been applied to several attached and separated flows, including a transitional flow over a flat plate and a separated flow over an airfoil at an angle of attack.

Modeling the effects of UV variability and the QBO on the troposphere-stratosphere system. Part II: The troposphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rind, D.; Balachandran, N.K.

1995-08-01

Results of experiments with a GCM involving changes in UV input ({plus_minus} 25%, {plus_minus}5% at wavelengths below 0.3 {mu}) and simulated equatorial QBO are presented, with emphasis on the tropospheric response. The QBO and UV changes alter the temperature in the lower stratosphere/upper troposphere warms, tropospheric eddy energy is reduced, leading to extratropical tropospheric cooling of some 0.5{degrees}C on the zonal average, and surface temperature changes up to {plus_minus}5{degrees}C locally. Opposite effects occur when the extratropical lower stratosphere/upper troposphere cools. Cooling or warming of the comparable region in the Tropics decreases/increases static stability, accelerating/decelerating the Hadley circulation. Tropospheric dynamical changesmore » are on the order of 5%. The combined UV/QBO effect in the troposphere results from its impact on the middle atmosphere; in the QBO east phase, more energy is refracted to higher latitudes, due to the increased horizontal shear of the zonal wind, but with increased UV, this energy propagates preferentially out of the polar lower stratosphere, in response to the increased vertical shear of the zonal winds; therefore, it is less effective in warming the polar lower stratosphere. Due to their impacts on planetary wave generation and propagation, all combinations of UV and QBO phases affect the longitudinal patterns of tropospheric temperatures and geopotential heights. The modeled perturbations often agree qualitatively with observations and are of generally similar orders of magnitude. The results are sensitive to the forcing employed. In particular, the nature of the tropospheric response depends upon the magnitude (and presumably wavelength) of the solar irradiance perturbation. The results of the smaller UV variations ({plus_minus}5%) are more in agreement with observations, showing clear differences between the UV impact in the east and west QBO phase. 34 refs., 15 figs., 3 tabs.« less

EFFECTS OF NON-METHANE HYDROCARBONS ON LOWER STRATOSPHERIC AND UPPER TROPOSPHERIC 2-D ZONAL AVERAGE MODEL CLIMATOLOGY. (R826384)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Baseline predictability of daily east Asian summer monsoon circulation indices

NASA Astrophysics Data System (ADS)

Ai, Shucong; Chen, Quanliang; Li, Jianping; Ding, Ruiqiang; Zhong, Quanjia

2017-05-01

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 meridional wind shear (about 5 days). The initial error of EASM indices defined by SLP difference and meridional 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 meridional 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 meridional 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 meridional 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 types of EASM indices does not show coherent interannual fluctuations.

Evolution of the Antarctic polar vortex in spring: Response of a GCM to a prescribed Antarctic ozone hole

NASA Technical Reports Server (NTRS)

Boville, B. A.; Kiehl, J. T.; Briegleb, B. P.

1988-01-01

The possible effect of the Antartic ozone hole on the evolution of the polar vortex during late winter and spring using a general circulation model (GCM) is examined. The GCM is a version of the NCAR Community Climate Model whose domain extends from the surface to the mesosphere and is similar to that described on Boville and Randel (1986). Ozone is not a predicted variable in the model. A zonally averaged ozone distribution is specified as a function of latitude, pressure and month for the radiation parameterization. Rather that explicitly address reasons for the formation of the ozone hole, researchers postulate its existence and ask what effect it has on the subsequent evolution of the vortex. The evolution of the model when an ozone hole is imposed is then discussed.

Two dimensional wavefront retrieval using lateral shearing interferometry

NASA Astrophysics Data System (ADS)

Mancilla-Escobar, B.; Malacara-Hernández, Z.; Malacara-Hernández, D.

2018-06-01

A new zonal two-dimensional method for wavefront retrieval from a surface under test using lateral shearing interferometry is presented. A modified Saunders method and phase shifting techniques are combined to generate a method for wavefront reconstruction. The result is a wavefront with an error below 0.7 λ and without any global high frequency filtering. A zonal analysis over square cells along the surfaces is made, obtaining a polynomial expression for the wavefront deformations over each cell. The main advantage of this method over previously published methods is that a global filtering of high spatial frequencies is not present. Thus, a global smoothing of the wavefront deformations is avoided, allowing the detection of deformations with relatively small extensions, that is, with high spatial frequencies. Additionally, local curvature and low order aberration coefficients are obtained in each cell.

Zonally asymmetric response of the Southern Ocean mixed-layer depth to the Southern Annular Mode

NASA Astrophysics Data System (ADS)

Sallée, J. B.; Speer, K. G.; Rintoul, S. R.

2010-04-01

Interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface. The depth of this layer is determined by wind forcing and heating from the atmosphere. Variations in mixed-layer depth affect the rate of exchange between the atmosphere and deeper ocean, the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton. However, the response of the Southern Ocean mixed layer to changes in the atmosphere is not well known. Here we analyse temperature and salinity data from Argo profiling floats to show that the Southern Annular Mode (SAM), the dominant mode of atmospheric variability in the Southern Hemisphere, leads to large-scale anomalies in mixed-layer depth that are zonally asymmetric. From a simple heat budget of the mixed layer we conclude that meridional winds associated with departures of the SAM from zonal symmetry cause anomalies in heat flux that can, in turn, explain the observed changes of mixed-layer depth and sea surface temperature. Our results suggest that changes in the SAM, including recent and projected trends attributed to human activity, drive variations in Southern Ocean mixed-layer depth, with consequences for air-sea exchange, ocean sequestration of heat and carbon, and biological productivity.

Characteristics and Mechanisms of Zonal Oscillation of Western Pacific Subtropical High in Summer

NASA Astrophysics Data System (ADS)

Guan, W.; Ren, X.; Hu, H.

2017-12-01

The zonal oscillation of the western Pacific subtropical high (WPSH) influences the weather and climate over East Asia significantly. This study investigates the features and mechanisms of the zonal oscillation of the WPSH during summer on subseasonal time scales. The zonal oscillation index of the WPSH is defined by normalized subseasonal geopotential height anomaly at 500hPa averaged over the WPSH's western edge (110° - 140°E, 10° - 30°N). The index shows a predominant oscillation with a period of 10-40 days. Large positive index indicates a strong anticyclonic anomaly over East Asia and its coastal region south of 30°N at both 850hPa and 500hPa. The WPSH stretches more westward accompanied by warmer SST anomalies beneath the western edge of the WPSH. Meanwhile, above-normal precipitation is seen over the Yangtze-Huaihe river basin and below-normal precipitation over the south of the Yangtze River. Negative index suggests a more eastward position of WPSH. The anomalies in circulation and SST for negative index are almost the mirror image of those for the positive index. In early summer, the zonal shift of the WPSH is affected by both the East Asia/Pacific (EAP) teleconnection pattern and the Silk road pattern (SRP). The positive (negative) phase of the EAP pattern is characterized by a low-level anticyclonic (cyclonic) anomaly over the subtropical western Pacific, indicating the western extension (eastward retreat) of the WPSH. Comparing with the EAP pattern, the SRP forms an upper-level anticyclonic (cyclonic) anomaly in mid-latitudes of East Asia, and then leads to the westward (eastward) movement of the WPSH. In late summer, the zonal shift of the WPSH is mainly affected by the EAP pattern, because the EAP pattern in late summer is stronger than that in early summer. The zonal shift of the WPSH is also influenced by the subseasonal air-sea interaction locally. During the early stage of WPSH's westward stretch, the local SST anomaly in late summer is colder than that in early summer. This forms a more favorable condition for the increasing of local anticyclonic anomaly. Thus, the anticyclonic anomaly in late summer is stronger than that in early summer.

Ockham's Razorblade Shaving Wind-Induced Circulation

NASA Astrophysics Data System (ADS)

Bergmann, Juan Carlos

2010-05-01

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 circulation 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 meridional 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 circulation 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. Meridional 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 meridional 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 circulation, where mechanical forcing is caused by the pressure-fields that result from differential heating/cooling and therefore ‘automatically' comprise the entire circulation system. Wind-caused oceanic flow is exclusively generated by frictional wind-forces at the surface, and other processes in the ocean are not causally connected hereto. In absence of continents it is quite difficult to ‘find' the corresponding forcing for the meridional return-flows - and it can definitely not be wind-force-caused - very strange! The fact that the wind-induced circulation can only be closed by the action of other processes, which are not causally connected to wind-forces, demonstrates that something must be fundamentally wrong. The singularity at the equator and the extreme down-welling in the equatorial belt indicate an additional severe problem that can only be avoided if zonal wind-stress is completely excluded. Escape to additional assumptions is similar to the introduction of the epicycles in order to explain the planets' retrograde motion in maintaining geocentric cosmology. Should the previous analysis be ignored in favour of maintaining the ‘established' ideas of wind-induced circulation or should there be an effort to formulate new ideas that provide closed and balanced circulation without employing other processes than wind-forces?

Climatology of water vapor in the upper troposphere and lower stratosphere determined from Sage 2 observations

NASA Technical Reports Server (NTRS)

Chiou, Er-Woon; McCormick, M. P.

1994-01-01

The purpose of this paper is to present a vertically-resolved global climatology of water vapor in the upper troposphere and lower stratosphere based on multi-year SAGE 2 observations. Seasonally averaged zonal mean profiles are illustrated in terms of both mixing ration and relative humidity.

Measurements of wind vectors, eddy momentum transports, and energy conversions in Jupiter's atmosphere from Voyager 1 images

NASA Astrophysics Data System (ADS)

Beebe, R. F.; Ingersoll, A. P.; Hunt, G. E.; Mitchell, J. L.; Muller, J.-P.

1980-01-01

Voyager 1 narrow-angle images were used to obtain displacements of features down to 100 to 200 km in size over intervals of 10 hours. A global map of velocity vectors and longitudinally averaged zonal wind vectors as functions of the latitude, is presented and discussed

Cloud level winds from UV and IR images obtained by VMC onboard Venus Express

NASA Astrophysics Data System (ADS)

Khatuntsev, Igor; Patsaeva, Marina; Titov, Dmitri; Ignatiev, Nikolay; Turin, Alexander; Bertaux, Jean-Loup

2017-04-01

During eight years Venus Monitoring Camera (VMC) [1] onboard the Venus Express orbiter has observed the upper cloud layer of Venus. The largest set of images was obtained in the UV (365 nm), visible (513 nm) and two infrared channels - 965 nm and 1010 nm. The UV dayside images were used to study the atmospheric circulation at the Venus cloud tops [2], [3]. Mean zonal and meridional profiles of winds and their variability were derived from cloud tracking of UV images. In low latitudes the mean retrograde zonal wind at the cloud top (67±2 km) is about 95 m/s with a maximum of about 102 m/s at 40-50°S. Poleward from 50°S the zonal wind quickly fades out with latitude. The mean poleward meridional wind slowly increases from zero value at the equator to about 10 m/s at 50°S. Poleward from this latitude, the absolute value of the meridional component monotonically decreases to zero at the pole. The VMC observations suggest clear diurnal signature in the wind field. They also indicate a long term trend for the zonal wind speed at low latitudes to increase from 85 m/s in the beginning of the mission to 110 m/s by the middle of 2012. The trend was explained by influence of the surface topography on the zonal flow [4]. Cloud features tracking in the IR images provided information about winds in the middle cloud deck (55±4 km). In the low and middle latitudes (5-65°S) the IR mean retrograde zonal velocity is about 68-70 m/s. In contrast to poleward flow at the cloud tops, equatorward motions dominate in the middle cloud with maximum speed of 5.8±1.2 m/s at latitude 15°S. The meridional speed slowly decreases to 0 at 65-70°S. At low latitudes the zonal and meridional speed demonstrate long term variations. Following [4] we explain the observed long term trend of zonal and meridional components by the influence of surface topography of highland region Aphrodite Terra on dynamic processes in the middle cloud deck through gravity waves. Acknowledgements: I.V. Khatuntsev, M.V. Patsaeva, N.I. Ignatiev, J.-L. Bertaux were supported by the Ministry of Education and Science of Russian Federation grant 14.W03.31.0017. References: [1] Markiewicz W. J. et al.: Venus Monitoring Camera for Venus Express // Planet. Space Sci., 55(12), 1701-1711. doi:10.1016/j.pss.2007.01.004, 2007. [2] Khatuntsev I.V. et al.: Cloud level winds from the Venus Express Monitoring Camera imaging // Icarus, 226, 140-158. 2013. [3] Patsaeva M.V. et al.: The relationship between mesoscale circulation and cloud morphology at the upper cloud level of Venus from VMC/Venus Express // Planet. Space Sci., 113(08), 100-108, doi:10.1016/j.pss.2015.01.013, 2015. [4] Bertaux J.-L. et al.: Influence of Venus topography on the zonal wind and UV albedo at cloud top level: The role of stationary gravity waves // J. Geophys. Res. Planets, 121, 1087-1101, doi:10.1002/2015JE004958, 2016.

Substorm-related thermospheric density and wind disturbances derived from CHAMP observations

NASA Astrophysics Data System (ADS)

Ritter, P.; Lühr, H.; Doornbos, E.

2010-06-01

The input of energy and momentum from the magnetosphere is most efficiently coupled into the high latitude ionosphere-thermosphere. The phenomenon we are focusing on here is the magnetospheric substorm. This paper presents substorm related observations of the thermosphere derived from the CHAMP satellite. With its sensitive accelerometer the satellite can measure the air density and zonal winds. Based on a large number of substorm events the average high and low latitude thermospheric response to substorm onsets was deduced. During magnetic substorms the thermospheric density is enhanced first at high latitudes. Then the disturbance travels at an average speed of 650 m/s to lower latitudes, and 3-4 h later the bulge reaches the equator on the night side. Under the influence of the Coriolis force the travelling atmospheric disturbance (TAD) is deflected westward. In accordance with present-day atmospheric models the disturbance zonal wind velocities during substorms are close to zero near the equator before midnight and attain moderate westward velocities after midnight. In general, the wind system is only weakly perturbed (Δvy<20 m/s) by substorms.

Nimbus-7 Stratospheric and Mesospheric Sounder (SAMS) experiment data user's guide

NASA Technical Reports Server (NTRS)

Taylor, F. W.; Rodgers, C. D.; Nutter, S. T.; Oslik, N.

1989-01-01

The Stratospheric and Mesospheric Sounder (SAMS) aboard Nimbus-7 observes infrared radiation from the atmospheric limb. Global upper atmosphere temperature profiles and vertical concentrations of H2O, NO, N2O, CH4 and CO2 are derived from these measurements. The status of all channels was carefully monitored. Temperature and composition were retrieved from the measurements by linearizing the direct equation about an a priori profile and using an optimum statistical estimator to find the most likely solution. The derived temperature and composition profiles are archived on two tape products whose file structure and record formats are described in detail. The gridded retrieved temperature tape (GRID-T) contains daily day and night average temperatures at 62 pressure levels in a 2.5 degree latitude by 10 degree longitude grid extending from 67.5 degrees N to 50 degrees S. The zonal mean methane and nitrous oxide composition tape (ZMT-G) contains zonal mean day and night average CH4 and N2O mixing ratios at 31 pressure levels for 2.5 degrees latitude zones extending from 67.5 degrees N to 50 degrees S.

Variability in daily, zonal mean lower-stratospheric temperatures

NASA Technical Reports Server (NTRS)

Christy, John R.; Drouilhet, S. James, Jr.

1994-01-01

Satellite data from the microwave sounding unit (MSU) channel 4, when carefully merged, provide daily zonal anomalies of lower-stratosphere temperature with a level of precision between 0.01 and 0.08 C per 2.5 deg latitude band. Global averages of these daily zonal anomalies reveal the prominent warming events due to volcanic aerosol in 1982 (El Chichon) and 1991 (Mt. Pinatubo), which are on the order of 1 C. The quasibiennial oscillation (QBO) may be extracted from these zonal data by applying a spatial filter between 15 deg N and 15 deg S latitude, which resembles the meridional curvature. Previously published relationships between the QBO and the north polar stratospheric temperatures during northern winter are examined but were not found to be reproduced in the MSU4 data. Sudden stratospheric warmings in the north polar region are represented in the MSU4 data for latitudes poleward of 70 deg N. In the Southern Hemisphere, there appears to be a moderate relationship between total ozone concentration and MSU4 temperatures, though it has been less apparent in 1991 and 1992. In terms of empirical modes of variability, the authors find a strong tendency in EOF 1 (39.2% of the variance) for anomalies in the Northern Hemisphere polar regions to be counterbalanced by anomalies equatorward of 40 deg N and 40 deg S latitudes. In addition, most of the modes revealed significant power in the 15-20 day period band.

Modeling Study of Mesospheric Planetary Waves: Genesis and Characteristics

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G.; Talaat, E. L.; Porter, H. S.; Chan, K. L.

2003-01-01

In preparation for the measurements from the TIMED mission and coordinated ground based observations, we discuss results for the planetary waves (PWs) that appear in our Numerical Spectral Model (NSM). The present model accounts for a tropospheric heat source in the zonal mean (m = 0), which reproduces qualitatively the observed zonal jets near the tropopause and the accompanying reversal in the latitudinal temperature variations. We discuss the PWs that are solely generated internally, i.e., without the explicit excitation sources related to tropospheric convection or topography. Our analysis shows that PWs are not produced when the zonally averaged heat source into the atmosphere is artificially suppressed, and that the PWs generally are significantly weaker when the tropospheric source is not applied. Instabilities associated with the zonal mean temperature, pressure and wind fields, which still need to be explored, are exciting PWs that have amplitudes in the mesosphere comparable to those observed. Three classes of PWs are generated in the NSM. (1) Rossby waves, (2) Rossby gravity waves propagating westward at low latitudes, and (3) Eastward propagating equatorial Kelvin waves. A survey of the PWs reveals that the largest wind amplitudes tend to occur below 80 km in the winter hemisphere, but above that altitude they occur in the summer hemisphere where the amplitudes can approach 50 meters per second. It is shown that the non-migrating tides in the mesosphere, generated by non-linear coupling between migrating tides and PWs, are significantly larger for the model with the tropospheric heat source.

Geophysics, Oceanography

NASA Technical Reports Server (NTRS)

Halpern, D.; Wentz, F.

1993-01-01

Development of decade-long time series of global surface wind measurements for studies ofseasonal-to-interannual climate variability presents unique challenges for space- borne instrumentationbecause of the necessity to combine data sets of 3- to 5-year lifetimes. Before the first Special SensorMicrowave Imager (SSMI), which was launched on the Defence Meteorological Satellite Program(DMSP) F8 spacecraft in July 1987, stopped recording wind speed in December 1991, another SSMIwas launched on DMSP F10 in December 1991. Interpretation of the 1987 - 1993 composite timeseries is dependent upon the space and time characteristics of the differences between concurrent F8and F10 SSMI measurements. This paper emphasizes large geographical regions and 1-month timescale. The F8-F10 area-weighted difference between 60 degrees S and 60 degrees S during 305 daysof 1991 (-0.12 m s^(-1)) was comparable to the year-to-year wind speed variations during 1988-1991. The 10 degree-zonal averaged monthly mean F8-F10 difference was negative (positive) forwind speeds less (greater) than 7.9 m s^(-1), reaching - 0.43(0.32) m s^(-1) at 5(10) m s^(-1). The10 degree-zonal averaged monthly mean F8-F10 bias had considerable variations throughout the yearand between 60 degrees S - 60 degrees N, with the largest temporal variation (1.4 m s^(-1)) in the 50degrees - 60 degrees N region from February to April. The 1991 average value of the monthly meanroot-mean-square (rms) difference between F8 and F10 daily wind speeds in 10 degree-longitudinalbands was 2.0 m s^(-1) over 60 degrees S - 60 degrees N, the amplitude of the annual cycle of therms difference was largest in the northern hemisphere middle latitudes, and the rms difference wasrelated to the wind speed (e.g., at 6 and 10 m s^(-1), the rms difference was 1.7 and 2.7 m s^(-1),respectively). The relationship between monthly mean 1/3 degrees x 1/3 degrees F8-F10 SSMI windspeed differences and integrated water vapor and liquid water content in the atmosphere is discussed.

Variability simulations with a steady, linearized primitive equations model

NASA Technical Reports Server (NTRS)

Kinter, J. L., III; Nigam, S.

1985-01-01

Solutions of the steady, primitive equations on a sphere, linearized about a zonally symmetric basic state are computed for the purpose of simulating monthly mean variability in the troposphere. The basic states are observed, winter monthly mean, zonal means of zontal and meridional velocities, temperatures and surface pressures computed from the 15 year NMC time series. A least squares fit to a series of Legendre polynomials is used to compute the basic states between 20 H and the equator, and the hemispheres are assumed symmetric. The model is spectral in the zonal direction, and centered differences are employed in the meridional and vertical directions. Since the model is steady and linear, the solution is obtained by inversion of a block, pente-diagonal matrix. The model simulates the climatology of the GFDL nine level, spectral general circulation model quite closely, particularly in middle latitudes above the boundary layer. This experiment is an extension of that simulation to examine variability of the steady, linear solution.

Feedback process responsible for intermodel diversity of ENSO variability

NASA Astrophysics Data System (ADS)

An, Soon-Il; Heo, Eun Sook; Kim, Seon Tae

2017-05-01

The origin of the intermodel diversity of the El Niño-Southern Oscillation (ENSO) variability is investigated by applying a singular value decomposition (SVD) analysis between the intermodel tropical Pacific sea surface temperature anomalies (SSTA) variance and the intermodel ENSO stability index (BJ index). The first SVD mode features an ENSO-like pattern for the intermodel SSTA variance (74% of total variance) and the dominant thermocline feedback (TH) for the BJ index (51%). Intermodel TH is mainly modified by the intermodel sensitivity of the zonal thermocline gradient response to zonal winds over the equatorial Pacific (βh), and the intermodel βh is correlated higher with the intermodel off-equatorial wind stress curl anomalies than the equatorial zonal wind stress anomalies. Finally, the intermodel off-equatorial wind stress curl is associated with the meridional shape and intensity of ENSO-related wind patterns, which may cause a model-to-model difference in ENSO variability by influencing the off-equatorial oceanic Rossby wave response.

On radiating baroclinic instability of zonally varying flow

NASA Technical Reports Server (NTRS)

Finley, Catherine A.; Nathan, Terrence R.

1993-01-01

A quasi-geostrophic, two-layer, beta-plane model is used to study the baroclinic instability characteristics of a zonally inhomogeneous flow. It is assumed that the disturbance varied slowly in the cross-stream direction, and the stability problem was formulated as a 1D initial value problem. Emphasis is placed on determining how the vertically averaged wind, local maximum in vertical wind shear, and length of the locally supercritical region combine to yield local instabilities. Analysis of the local disturbance energetics reveals that, for slowly varying basic states, the baroclinic energy conversion predominates within the locally unstable region. Using calculations of the basic state tendencies, it is shown that the net effect of the local instabilities is to redistribute energy from the baroclinic to the barotropic component of the basic state flow.

Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding.

PubMed

Lin, Po-Cheng; I, Lin

2016-02-01

We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow.

Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding

NASA Astrophysics Data System (ADS)

Lin, Po-Cheng; I, Lin

2016-02-01

We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow.

Three dimensional model calculations of the global dispersion of high speed aircraft exhaust and implications for stratospheric ozone loss

NASA Technical Reports Server (NTRS)

Douglass, Anne R.; Rood, Richard B.; Jackman, Charles H.; Weaver, Clark J.

1994-01-01

Two-dimensional (zonally averaged) photochemical models are commonly used for calculations of ozone changes due to various perturbations. These include calculating the ozone change expected as a result of change in the lower stratospheric composition due to the exhaust of a fleet of supersonic aircraft flying in the lower stratosphere. However, zonal asymmetries are anticipated to be important to this sort of calculation. The aircraft are expected to be restricted from flying over land at supersonic speed due to sonic booms, thus the pollutant source will not be zonally symmetric. There is loss of pollutant through stratosphere/troposphere exchange, but these processes are spatially and temporally inhomogeneous. Asymmetry in the pollutant distribution contributes to the uncertainty in the ozone changes calculated with two dimensional models. Pollutant distributions for integrations of at least 1 year of continuous pollutant emissions along flight corridors are calculated using a three dimensional chemistry and transport model. These distributions indicate the importance of asymmetry in the pollutant distributions to evaluation of the impact of stratospheric aircraft on ozone. The implications of such pollutant asymmetries to assessment calculations are discussed, considering both homogeneous and heterogeneous reactions.

SPCZ Zonal Events and Downstream Influence on Surface Ocean Conditions in the Indonesian Throughflow Region: Implications for SPCZ Mean Position Effects on the ITF

NASA Astrophysics Data System (ADS)

Linsley, B. K.; Wu, H. C.; Rixen, T.; Charles, C. D.; Gordon, A. L.; Moore, M.

2017-12-01

Seasonal surface freshening of the Makassar Strait, the main conduit of the Indonesian Throughflow (ITF), is a key factor controlling the temperature and salinity characteristics of ITF transport to the Indian Ocean. Here we present a 262-year reconstruction of seasonal sea-surface-salinity (SSS) variability from 1742-2004 C.E. using coral oxygen isotope (δ18O) records from the central Makassar Strait. Our record reveals persistent seasonal freshening and also years with significant truncations of seasonal freshening that correlate exactly with South Pacific Convergence Zone (SPCZ) zonal events >4,000 km to the east. During these newly identified events, the SPCZ dramatically rotates 15° north to near the equator and stronger westward flowing South Pacific boundary currents transport salty water north across the equator and force higher salinity water through the Makassar Strait in February-May halting the normal seasonal freshening in the strait. By these teleconnections, our Makassar coral δ18O series provides the first record of the recurrence interval of these zonal SPCZ events and demonstrates that they have occurred on a semi-regular basis since the mid-1700s. The deeper time implications of these results suggest that long-term changes in the position of the SPCZ and ITCZ in the central equatorial Pacific would affect Pacific western boundary currents and the transport of South Pacific water north across the equator and into the ITF. Preliminary results and plans underway to evaluate this hypothesis over the last 2.5 Ma will also be presented.

Sensitivity of Coupled Tropical Pacific Model Biases to Convective Parameterization in CESM1

NASA Astrophysics Data System (ADS)

Woelfle, M. D.; Yu, S.; Bretherton, C. S.; Pritchard, M. S.

2018-01-01

Six month coupled hindcasts show the central equatorial Pacific cold tongue bias development in a GCM to be sensitive to the atmospheric convective parameterization employed. Simulations using the standard configuration of the Community Earth System Model version 1 (CESM1) develop a cold bias in equatorial Pacific sea surface temperatures (SSTs) within the first two months of integration due to anomalous ocean advection driven by overly strong easterly surface wind stress along the equator. Disabling the deep convection parameterization enhances the zonal pressure gradient leading to stronger zonal wind stress and a stronger equatorial SST bias, highlighting the role of pressure gradients in determining the strength of the cold bias. Superparameterized hindcasts show reduced SST bias in the cold tongue region due to a reduction in surface easterlies despite simulating an excessively strong low-level jet at 1-1.5 km elevation. This reflects inadequate vertical mixing of zonal momentum from the absence of convective momentum transport in the superparameterized model. Standard CESM1simulations modified to omit shallow convective momentum transport reproduce the superparameterized low-level wind bias and associated equatorial SST pattern. Further superparameterized simulations using a three-dimensional cloud resolving model capable of producing realistic momentum transport simulate a cold tongue similar to the default CESM1. These findings imply convective momentum fluxes may be an underappreciated mechanism for controlling the strength of the equatorial cold tongue. Despite the sensitivity of equatorial SST to these changes in convective parameterization, the east Pacific double-Intertropical Convergence Zone rainfall bias persists in all simulations presented in this study.

Salty Anomalies Forced by Central American Gap Winds: Aquarius Observations

NASA Astrophysics Data System (ADS)

Grodsky, S. A.; Carton, J.; Bentamy, A.

2014-12-01

Although upwelling normally doesn't have direct impact on the sea surface salinity (SSS), we present observational evidence of upwelling-induced SSS patterns off the Pacific Central American coast. This area is characterized by stable near-surface salinity stratification that is produced by the mixed layer dilution by local rainfall. Here the fresh and warm mixed layer is periodically disrupted by the gap wind-induced uplifts of colder and saltier water. Aquarius SSS data capture these high SSS events. In boreal winter when the intense gap winds are frequent, two tongues of anomalously salty water develop off the Gulfs of Tehuantepec and Papagayo. During that season the average SSS in the meridionally oriented Tehuantepec tongue is about 0.4 psu saltier than background SSS. The zonally elongated Papagayo tongue stands out even more strongly, being 1 to 2 psu saltier than SSS in the neighboring Panama Bight. The spatial locations and orientations of these salty tongues closely correspond to the locations and orientations of the cool SST tongues suggesting they have similar governing mechanisms.

GCM simulations of volcanic aerosol forcing. I - Climate changes induced by steady-state perturbations

NASA Technical Reports Server (NTRS)

Pollack, James B.; Rind, David; Lacis, Andrew; Hansen, James E.; Sato, Makiko; Ruedy, Reto

1993-01-01

The response of the climate system to a temporally and spatially constant amount of volcanic particles is simulated using a general circulation model (GCM). The optical depth of the aerosols is chosen so as to produce approximately the same amount of forcing as results from doubling the present CO2 content of the atmosphere and from the boundary conditions associated with the peak of the last ice age. The climate changes produced by long-term volcanic aerosol forcing are obtained by differencing this simulation and one made for the present climate with no volcanic aerosol forcing. The simulations indicate that a significant cooling of the troposphere and surface can occur at times of closely spaced multiple sulfur-rich volcanic explosions that span time scales of decades to centuries. The steady-state climate response to volcanic forcing includes a large expansion of sea ice, especially in the Southern Hemisphere; a resultant large increase in surface and planetary albedo at high latitudes; and sizable changes in the annually and zonally averaged air temperature.

Dependence of Arctic climate on the latitudinal position of stationary waves and to high-latitudes surface warming

NASA Astrophysics Data System (ADS)

Shin, Yechul; Kang, Sarah M.; Watanabe, Masahiro

2017-12-01

Previous studies suggest large uncertainties in the stationary wave response under global warming. Here, we investigate how the Arctic climate responds to changes in the latitudinal position of stationary waves, and to high-latitudes surface warming that mimics the effect of Arctic sea ice loss under global warming. To generate stationary waves in an atmospheric model coupled to slab ocean, a series of experiments is performed where the thermal forcing with a zonal wavenumber-2 (with zero zonal-mean) is prescribed at the surface at different latitude bands in the Northern Hemisphere. When the stationary waves are generated in the subtropics, the cooling response dominates over the warming response in the lower troposphere due to cloud radiative effects. Then, the low-level baroclinicity is reduced in the subtropics, which gives rise to a poleward shift of the eddy driven jet, thereby inducing substantial cooling in the northern high latitudes. As the stationary waves are progressively generated at higher latitudes, the zonal-mean climate state gradually becomes more similar to the integration with no stationary waves. These differences in the mean climate affect the Arctic climate response to high-latitudes surface warming. Additional surface heating over the Arctic is imposed to the reference climates in which the stationary waves are located at different latitude bands. When the stationary waves are positioned at lower latitudes, the eddy driven jet is located at higher latitude, closer to the prescribed Arctic heating. As baroclinicity is more effectively perturbed, the jet shifts more equatorward that accompanies a larger reduction in the poleward eddy transport of heat and momentum. A stronger eddy-induced descending motion creates greater warming over the Arctic. Our study calls for a more accurate simulation of the present-day stationary wave pattern to enhance the predictability of the Arctic warming response in a changing climate.

Treatment of Articular Cartilage Defects in the Goat with Frozen Versus Fresh Osteochondral Allografts: Effects on Cartilage Stiffness, Zonal Composition, and Structure at Six Months

PubMed Central

Pallante, Andrea L.; Görtz, Simon; Chen, Albert C.; Healey, Robert M.; Chase, Derek C.; Ball, Scott T.; Amiel, David; Sah, Robert L.; Bugbee, William D.

2012-01-01

Background: Understanding the effectiveness of frozen as compared with fresh osteochondral allografts at six months after surgery and the resultant consequences of traditional freezing may facilitate in vivo maintenance of cartilage integrity. Our hypothesis was that the state of the allograft at implantation affects its performance after six months in vivo. Methods: The effect of frozen as compared with fresh storage on in vivo allograft performance was determined for osteochondral allografts that were transplanted into seven recipient goats and analyzed at six months. Allograft performance was assessed by examining osteochondral structure (cartilage thickness, fill, surface location, surface degeneration, and bone-cartilage interface location), zonal cartilage composition (cellularity, matrix content), and cartilage biomechanical function (stiffness). Relationships between cartilage stiffness or cartilage composition and surface degeneration were assessed with use of linear regression. Results: Fresh allografts maintained cartilage load-bearing function, while also maintaining zonal organization of cartilage cellularity and matrix content, compared with frozen allografts. Overall, allograft performance was similar between fresh allografts and nonoperative controls. However, cartilage stiffness was approximately 80% lower (95% confidence interval [CI], 73% to 87%) in the frozen allografts than in the nonoperative controls or fresh allografts. Concomitantly, in frozen allografts, matrix content and cellularity were approximately 55% (95% CI, 22% to 92%) and approximately 96% (95% CI, 94% to 99%) lower, respectively, than those in the nonoperative controls and fresh allografts. Cartilage stiffness correlated positively with cartilage cellularity and matrix content, and negatively with surface degeneration. Conclusions: Maintenance of cartilage load-bearing function in allografts is associated with zonal maintenance of cartilage cellularity and matrix content. In this animal model, frozen allografts displayed signs of failure at six months, with cartilage softening, loss of cells and matrix, and/or graft subsidence, supporting the importance of maintaining cell viability during allograft storage and suggesting that outcomes at six months may be indicative of long-term (dys)function. Clinical Relevance: Fresh versus frozen allografts represent the “best versus worst” conditions with respect to chondrocyte viability, but “difficult versus simple” with respect to acquisition and distribution. The outcomes described from these two conditions expand the current understanding of in vivo cartilage remodeling and describe structural properties (initial graft subsidence), which may have implications for impending graft failure. PMID:23138239

The seasonal march of the equatorial Pacific upper-ocean and its El Niño variability

NASA Astrophysics Data System (ADS)

Gasparin, Florent; Roemmich, Dean

2017-08-01

Based on two modern data sets, the climatological seasonal march of the upper-ocean is examined in the equatorial Pacific for the period 2004-2014, because of its large contribution to the total variance, its relationship to El Niño, and its unique equatorial wave phenomena. Argo provides a broadscale view of the equatorial Pacific upper-ocean based on subsurface temperature and salinity measurements for the period 2004-2015, and satellite altimetry provides synoptic observations of the sea surface height (SSH) for the period 1993-2015. Using either 11-year (1993-2003/2004-2014) time-series for averaging, the seasonal Rossby waves stands out clearly and eastward intraseasonal Kelvin wave propagation is strong enough in individual years to leave residuals in the 11-year averages, particularly but not exclusively, during El Niño onset years. The agreement of altimetric SSH minus Argo steric height (SH) residuals with GRACE ocean mass estimates confirms the scale-matching of in situ variability with that of satellite observations. Surface layer and subsurface thermohaline variations are both important in determining SH and SSH basin-wide patterns. The SH/SSH October-November maximum in the central-eastern Pacific is primarily due to a downward deflection of the thermocline (∼20 m), causing a warm subsurface anomaly (>1 °C), in response to the phasing of downwelling intraseasonal Kelvin and seasonal Rossby waves. Compared with the climatology, the stronger October-November maximum in the 2004-2014 El Niño composites is due to higher intraseasonal oscillations and interannual variability. Associated with these equatorial wave patterns along the thermocline, the western warm/fresh pool waters move zonally at interannual timescales through zonal wind stress and pressure gradient fluctuations, and cause substantial fresh (up to 0.6 psu) and warm (∼1 °C higher than the climatology) anomalies in the western-central Pacific surface-layer during the El Niño onset year, and of the opposite sign during the termination year. These El Niño-related patterns are then analyzed focusing on the case of the onset of the strong 2015/2016 episode, and are seen to be around two times larger than that in the 2004-2014 El Niño composites. The present work exploits the capabilities of Argo and altimetry to update and improve the description of the physical state of the equatorial Pacific upper-ocean, and provides a benchmark for assessing the accuracy of models in representing equatorial Pacific variability.

Assessment of a 3-D boundary layer code to predict heat transfer and flow losses in a turbine

NASA Technical Reports Server (NTRS)

Anderson, O. L.

1984-01-01

Zonal concepts are utilized to delineate regions of application of three-dimensional boundary layer (DBL) theory. The zonal approach requires three distinct analyses. A modified version of the 3-DBL code named TABLET is used to analyze the boundary layer flow. This modified code solves the finite difference form of the compressible 3-DBL equations in a nonorthogonal surface coordinate system which includes coriolis forces produced by coordinate rotation. These equations are solved using an efficient, implicit, fully coupled finite difference procedure. The nonorthogonal surface coordinate system is calculated using a general analysis based on the transfinite mapping of Gordon which is valid for any arbitrary surface. Experimental data is used to determine the boundary layer edge conditions. The boundary layer edge conditions are determined by integrating the boundary layer edge equations, which are the Euler equations at the edge of the boundary layer, using the known experimental wall pressure distribution. Starting solutions along the inflow boundaries are estimated by solving the appropriate limiting form of the 3-DBL equations.

Decomposing variations of geopotential height in the troposphere and stratosphere into stationary and travelling waves

NASA Astrophysics Data System (ADS)

Guryanov, Vladimir; Eliseev, Alexey

2016-07-01

The ERA-Interim geopotential height in the Northern Hemisphere from November to March, 1992-2015 in the layer from between pressure levels 1000 mb and 1 mb is expanded into stationary and travelling zonal waves with zonal wavenumbers, k, from 1 to 10, and with periods, T, from 2 to 156 days (the so called Hayashi spectra). Among the studied waves, the largest amplitude is attained by the stationary and travelling waves with zonal wavenumber k=1 and with periods from 3 to 4 weeks in the upper stratosphere over the latitudinal belt 60-70oN. The stationary waves with k from 1 to 3 and with T from 2 to 3 weeks are most pronounced in the stratosphere. In turn, the largest amplitudes of the travelling waves with zonal wavenumbers k ≥ 5 are found in the troposphere. The dominant periods of the latter waves are about 1 week or slightly higher, and this dominant period basically decrease with increasing wavenumber. In the upper stratosphere, the eastward travelling waves generally dominate over westward ones. The only exception is the longest zonal mode with k=1, for which the amplitude of the westward travelling wave is larger than that for the eastward one. The period of the travelling waves dominating in the upper stratosphere is close to 3 weeks. In the upper troposphere, the amplitudes of the eastward waves with k from 4 to 10 is several-fold larger than those for their westward counterparts. The latter is reflected in the larger average wavenumber of the eastward travelling wave in comparison to that of the westarward one. The period of the gravest of the dominant travelling waves in the upper troposphere is close to one week, and it decreases to 2-4 days for the dominant travelling waves with k=8-10.

Geometrical constraint on the localization of deep water formation

NASA Astrophysics Data System (ADS)

Ferreira, D.; Marshall, J.

2008-12-01

That deep water formation occurs in the North Atlantic and not North Pacific is one of the most notable features of the present climate. In an effort to build a system able to mimic such basic aspects of climate using a minimal description, we study here the influence of ocean geometry on the localization of deep water formation. Using the MIT GCM, two idealized configurations of an ocean-atmosphere-sea ice climate system are studied: Drake and Double-Drake. In Drake, one narrow barrier extends from the North Pole to 35°S while, in Double-Drake, two such barriers set 90° apart join at the North Pole to delimit a Small and a Large basin. Despite the different continental configurations, the two climates are strikingly similar in the zonal average (almost identical heat and fresh water transports, and meridional overturning circulation). However, regional circulations in the Small and Large basins exhibit distinctive Atlantic-like and Pacific-like characteristics: the Small basin is warmer and saltier than the Large one, concentrates dense water formation and deep overturning circulation and achieve the largest fraction of the northward ocean heat transport. We show that the warmer temperature and higher evaporation over the Small basin is not its distinguishing factor. Rather, it is the width of the basin in relation to the zonal fetch of the precipitation pattern. This generates a deficit/excess of precipitation over the Small/Large basin: a fraction of the moisture evaporated from the Small basin is transported zonally and rains out over the Large basin. This creates a salt contrast between the 2 basins, leading to the localization of deep convection in the salty Small basin. Finally, given on the broad similarities between the Double-Drake and real World, we suggest that many gross features that define the present climate are a consequence of 2 asymmetries: a meridional asymmetry (a zonally unblocked southern/blocked northern ocean) and a zonal one (a small and a large basin in the northern hemisphere).

Intermittency in flux driven kinetic simulations of trapped ion turbulence

NASA Astrophysics Data System (ADS)

Darmet, G.; Ghendrih, Ph.; Sarazin, Y.; Garbet, X.; Grandgirard, V.

2008-02-01

Flux driven kinetic transport is analysed for deeply trapped ion turbulence with the code GYSELA. The main observation is the existence of a steady state situation with respect to the statistics, in particular the balance between the injected energy and the time averaged energy flowing out through the outer edge boundary layer. The temperature is characterised by a very bursty behaviour with a skewed PDF. Superimposed to these short time scale fluctuations, one finds a regime with a strong increase of the zonal flows and a quenching of the turbulent energy. During this phase of such a predator-prey cycle, the core temperature rapidly increases while the edge temperature gradually decreases. The end of this reduced transport regime is governed by the onset of turbulence that governs large relaxation events, and a strong modification of the zonal flow pattern.

Residual zonal flows in tokamaks and stellarators at arbitrary wavelengths

NASA Astrophysics Data System (ADS)

Monreal, Pedro; Calvo, Iván; Sánchez, Edilberto; Parra, Félix I.; Bustos, Andrés; Könies, Axel; Kleiber, Ralf; Görler, Tobias

2016-04-01

In the linear collisionless limit, a zonal potential perturbation in a toroidal plasma relaxes, in general, to a non-zero residual value. Expressions for the residual value in tokamak and stellarator geometries, and for arbitrary wavelengths, are derived. These expressions involve averages over the lowest order particle trajectories, that typically cannot be evaluated analytically. In this work, an efficient numerical method for the evaluation of such expressions is reported. It is shown that this method is faster than direct gyrokinetic simulations performed with the Gene and EUTERPE codes. Calculations of the residual value in stellarators are provided for much shorter wavelengths than previously available in the literature. Electrons must be treated kinetically in stellarators because, unlike in tokamaks, kinetic electrons modify the residual value even at long wavelengths. This effect, that had already been predicted theoretically, is confirmed by gyrokinetic simulations.

Differential rotation in Jupiter: A comparison of methods

NASA Astrophysics Data System (ADS)

Wisdom, J.; Hubbard, W. B.

2016-03-01

Whether Jupiter rotates as a solid body or has some element of differential rotation along concentric cylinders is unknown. But Jupiter's zonal wind is not north/south symmetric so at most some average of the north/south zonal winds could be an expression of cylinders. Here we explore the signature in the gravitational moments of such a smooth differential rotation. We carry out this investigation with two general methods for solving for the interior structure of a differentially rotating planet: the CMS method of Hubbard (Hubbard, W.B. [2013]. Astrophys. J. 768, 1-8) and the CLC method of Wisdom (Wisdom, J. [1996]. Non-Perturbative Hydrostatic Equilibrium. http://web.mit.edu/wisdom/www/interior.pdf). The two methods are in remarkable agreement. We find that for smooth differential rotation the moments do not level off as they do for strong differential rotation.

An assessment of satellite temperature distributions used to derive the net diabatic transport for zonally averaged models of the middle atmosphere

NASA Technical Reports Server (NTRS)

Remsberg, Ellis E.; Bhatt, Praful P.; Miles, Thomas

1994-01-01

Determinations of the zonally averaged and diabatically derived residual mean circulation (RMC) are particularly sensitive to the assumed zonal mean temperature distribution used as input. Several different middle atmosphere satellite temperature distributions have been employed in models and are compared here: a 4-year (late 1978 to early 1982) National Meteorological Center (NMC) climatology, the Barnett and Corney (or BC) climatology, and the 7 months of Nimbus 7 limb infrared monitor of the stratosphere (LIMS) temperatures. All three climatologies are generally accurate below the 10 hPa level, but there are systematic differences between them of up to +/-5 K in the upper stratosphere and lower mesosphere. The NMC/LIMS differences are evaluated using time series of rocketsonde and reconstructed satellite temperatures at station locations. Much of those biases can be explained by the differing vertical resolutions for the satellite-derived temperatures; the time series of reconstructed LIMS profiles have higher resolution and are more accurate. Because the LIMS temperatures are limited to just two full seasons, one cannot obtain monthly RMCs from them for an annual model calculation. Two alternate monthly climatologies are examined briefly: the 4-year Nimbus 7 stratospheric and mesospheric sounder (SAMS) temperatures and for the mesosphere the distribution from the Solar Mesosphere Explorer (SME), both of which are limb viewers of medium vertical resolution. There are also differences of the order of +/-5 K for those data sets. It is concluded that a major source of error in the determination of diabatic RMCs is a persistent pattern of temperature bias whose characteristics vary according to the vertical resolution of each individual climatology.

Climatology of the quasi-2-day waves observed in the MLS/Aura measurements (2005-2014)

NASA Astrophysics Data System (ADS)

Pancheva, Dora; Mukhtarov, Plamen; Siskind, David E.

2018-06-01

The paper presents the climatology and interannual variability of both eastward- and westward-propagating ∼2-day waves (QTDW) observed in the MLS/Aura geopotential height data for a period of 10 full years (2005-2014). The climatology of the QTDWs has been studied in two steps: (i) by using average 2D-wavelet spectra both the dominant modes of variability and how these modes vary in time and space have been determined, and (ii) by applying a 2D decomposition procedure, where all planetary waves are simultaneously extracted from the data, the average global spatio-temporal distributions of all defined by the 2D-wavelet analysis modes have been obtained. It is found that the westward-propagating waves at mid-high latitudes have zonal wave numbers 2, 3 and 4 and are observed mainly in summer hemisphere. Two different types of eastward-propagating waves have been identified: (i) waves at mid-high latitudes with zonal wave numbers 2 and 3 observed in the winter hemisphere, and (ii) waves observed predominantly over the equator with zonal wave number 2, which do not have a well-defined seasonal variability but show some enhancement in both solstices. While the climatological features of the MLS/Aura QTDWs for the considered period are robust the interannual variations have to be adopted cautiously. The primary reason is that the length of the considered period of 10 years is not enough for finding clear variability pattern. The only long-term variability which appears to have some robustness is that of the W3 wave in the Southern Hemisphere where the influence of the solar cycle has been distinguished.

On the fast zonal transport of the STS-121 space shuttle exhaust plume in the lower thermosphere

NASA Astrophysics Data System (ADS)

Yue, Jia; Liu, Han-Li; Meier, R. R.; Chang, Loren; Gu, Sheng-Yang; Russell, James, III

2013-03-01

Meier et al. (2011) reported rapid eastward transport of the STS-121 space shuttle (launch: July 4, 2006) main engine plume in the lower thermosphere, observed in hydrogen Lyman α images by the GUVI instrument onboard the TIMED satellite. In order to study the mechanism of the rapid zonal transport, diagnostic tracer calculations are performed using winds from the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) simulation of July, 2006. It is found that the strong eastward jet at heights of 100-110 km, where the exhaust plume was deposited, results in a persistent eastward tracer motion with an average velocity of 45 m/s. This is generally consistent with, though faster than, the prevailing eastward shuttle plume movement with daily mean velocity of 30 m/s deduced from the STS-121 GUVI observation. The quasi-two-day wave (QTDW) was not included in the numerical simulation because it was found not to be large. Its absence, however, might be partially responsible for insufficient meridional transport to move the tracers away from the fast jet in the simulation. The current study and our model results from Yue and Liu (2010) explain two very different shuttle plume transport scenarios (STS-121 and STS-107 (launch: January 16, 2003), respectively): we conclude that lower thermospheric dynamics is sufficient to account for both very fast zonal motion (zonal jet in the case of STS-121) and very fast meridional motion to polar regions (large QTDW in the case of STS-107).

An ocean dynamical thermostat—dominant in observations, absent in climate models

NASA Astrophysics Data System (ADS)

Coats, S.; Karnauskas, K. B.

2016-12-01

The pattern of sea surface temperature (SST) in the tropical Pacific Ocean is coupled to the Walker circulation, necessitating an understanding of how this pattern will change in response to anthropogenic radiative forcing. State-of-the-art climate models from the Coupled Model Intercomparison Project phase 5 (CMIP5) overwhelmingly project a decrease in the tropical Pacific zonal SST gradient over the coming century. This decrease in the zonal SST gradient is a response of the ocean to a weakening Walker circulation in the CMIP5 models, a consequence of the mass and energy balances of the hydrologic cycle identified by Held and Soden (2006). CMIP5 models, however, are not able to reproduce the observed increase in the zonal SST gradient between 1900-2013 C.E., which we argue to be robust using advanced statistical techniques and new observational datasets. While the observed increase in the zonal SST gradient is suggestive of the ocean dynamical thermostat mechanism of Clement et al. (1996), a strengthening Equatorial Undercurrent (EUC) also contributes to eastern equatorial Pacific cooling. Importantly, the strengthening EUC is a response of the ocean to a seasonal weakening of the Walker circulation and thus can reconcile disparate observations of changes to the atmosphere and ocean in the equatorial Pacific. CMIP5 models do not capture the magnitude of this response of the EUC to anthropogenic radiative forcing potentially because of biases in the sensitivity of the EUC to changes in zonal wind stress, like the weakening Walker circulation. Consequently, they project a continuation of the opposite to what has been observed in the real world, with potentially serious consequences for projected climate impacts that are influenced by the tropical Pacific.

Changes in atmospheric circulation between solar maximum and minimum conditions in winter and summer

NASA Astrophysics Data System (ADS)

Lee, Jae Nyung

2008-10-01

Statistically significant climate responses to the solar variability are found in Northern Annular Mode (NAM) and in the tropical circulation. This study is based on the statistical analysis of numerical simulations with ModelE version of the chemistry coupled Goddard Institute for Space Studies (GISS) general circulation model (GCM) and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The low frequency large scale variability of the winter and summer circulation is described by the NAM, the leading Empirical Orthogonal Function (EOF) of geopotential heights. The newly defined seasonal annular modes and its dynamical significance in the stratosphere and troposphere in the GISS ModelE is shown and compared with those in the NCEP/NCAR reanalysis. In the stratosphere, the summer NAM obtained from NCEP/NCAR reanalysis as well as from the ModelE simulations has the same sign throughout the northern hemisphere, but shows greater variability at low latitudes. The patterns in both analyses are consistent with the interpretation that low NAM conditions represent an enhancement of the seasonal difference between the summer and the annual averages of geopotential height, temperature and velocity distributions, while the reverse holds for high NAM conditions. Composite analysis of high and low NAM cases in both the model and observation suggests that the summer stratosphere is more "summer-like" when the solar activity is near a maximum. This means that the zonal easterly wind flow is stronger and the temperature is higher than normal. Thus increased irradiance favors a low summer NAM. A quantitative comparison of the anti-correlation between the NAM and the solar forcing is presented in the model and in the observation, both of which show lower/higher NAM index in solar maximum/minimum conditions. The summer NAM in the troposphere obtained from NCEP/NCAR reanalysis has a dipolar zonal structure with maximum variability over the Asian monsoon region. The corresponding EOF in ModelE has a qualitatively similar structure but with less variability in the Asian monsoon region which is displaced eastward of its observed position. In both the NCEP/NCAR reanalysis and the GISS GCM, the negative anomalies associated with the NAM in the Euro-Atlantic and Aleutian island regions are enhanced in the solar minimum conditions, though the results are not statistically significant. The difference of the downward propagation of NAM between solar maximum and solar minimum is shown with the NCEP/NCAR reanalysis. For the winter NAM, a much greater fraction of stratospheric circulation perturbations penetrate to the surface in solar maximum conditions than in minimum conditions. This difference is more striking when the zonal wind direction in the tropics is from the west: when equatorial 50 hPa winds are from the west, no stratospheric signals reach the surface under solar minimum conditions, while over 50 percent reach the surface under solar maximum conditions. This work also studies the response of the tropical circulation to the solar forcing in combination with different atmospheric compositions and with different ocean modules. Four model experiments have been designed to investigate the role of solar forcing in the tropical circulation: one with the present day (PD) greenhouse gases and aerosol conditions, one with the preindustrial (PI) conditions, one with the doubled minimum solar forcing, and finally one with the hybrid-isopycnic ocean model (HYCOM). The response patterns in the tropical humidity and in the vertical motion due to solar forcing are season dependent and spatially heterogeneous. The tropical humidity response from the model experiments are compared with the corresponding differences obtained from the NCEP/NCAR reanalysis with all years and with non-ENSO years. Both the model and the reanalysis consistently show that the specific humidity is significantly greater in the convective region in solar maximum compared to solar minimum for January and July. The column integrated humidity in all the model experiments with different composition, different solar forcing, and different ocean module, increased with solar forcing in the tropical band over the Atlantic sector in both seasons. The model's humidity response pattern is generally consistent with the paleoclimate records indicating increased precipitation near the equator that decreases at subtropical to middle latitudes with increased solar output. The differences in the zonally averaged vertical velocities indicate that the ascending branch of the Hadley cell is enhanced and shifted northward, and that the descending branch is weakened and shifted northward in the solar MAX simulation in January. The downward branch of the Hadley cell is strengthened in MAX in July. A possible link of climate response in midlatitudes to solar forcing is also presented by showing changes in zonal mean wind, changes in temperature gradient, and changes in E-P flux.

GCM simulations of cold dry Snowball Earth atmospheres

NASA Astrophysics Data System (ADS)

Voigt, A.; Held, I.; Marotzke, J.

2009-12-01

We use the full-physics atmospheric general circulation 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 circulation 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 circulation 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 meridional 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 Hadley circulation, at least in its upper tropospheric branch. Suppressing vertical diffusion of horizontal momentum above 850 hPa leads to a stronger Hadley circulation. This behaviour cannot be understood from axisymmetric models of the atmosphere, nor idealized atmospheric general circulation models, which both predict a weakening of the Hadley circulation when the vertical viscosity is decreased globally. We find that enabling the diurnal cycle does not change tropical annual-mean surface temperatures but significantly strengthens the Hadley circulation, which increases by 33% for equinoctial and by 50% during solstitial insolation conditions compared to simulations without diurnal cycle. Including the seasonal cycle results in a ''reversed'' annual-mean Hadley circulation with subsiding motion at the equator and ascending motion around 15N/S, a manifestation of the extreme seasonality of Snowball Earth atmospheres due to the low thermal inertia of the sea-ice surface. The impact of the seasonal cycle on the tropical annual-mean surface is a straightforward consequence of changes in insolation distribution: as annual-mean incoming shortwave radiation at the equator reduces by 18 Wm-2 for enabled seasonal cycle, tropical annual-mean surface temperatures decrease from 221 K to 217 K.

High-Precision Simulation of the Gravity Field of Rapidly-Rotating Barotropes in Hydrostatic Equilibrium

NASA Astrophysics Data System (ADS)

Hubbard, W. B.

2013-12-01

The so-called theory of figures (TOF) uses potential theory to solve for the structure of highly distorted rotating liquid planets in hydrostatic equilibrium. TOF is noteworthy both for its antiquity (Maclaurin 1742) and its mathematical complexity. Planned high-precision gravity measurements near the surfaces of Jupiter and Saturn (possibly detecting signals ~ microgal) will place unprecedented requirements on TOF, not because one expects hydrostatic equilibrium to that level, but because nonhydrostatic components in the surface gravity, at expected levels ~ 1 milligal, must be referenced to precise hydrostatic-equilibrium models. The Maclaurin spheroid is both a useful test of numerical TOF codes (Hubbard 2012, ApJ Lett 756:L15), and an approach to an efficient TOF code for arbitrary barotropes of variable density (Hubbard 2013, ApJ 768:43). For the latter, one trades off vertical resolution by replacing a continuous barotropic pressure-density relation with a stairstep relation, corresponding to N concentric Maclaurin spheroids (CMS), each of constant density. The benefit of this trade-off is that two-dimensional integrals over the mass distributions at each interface are reduced to one-dimensional integrals, quickly and accurately evaluated by Gaussian quadrature. The shapes of the spheroids comprise N level surfaces within the planet and at its surface, are gravitationally coupled to each other, and are found by self-consistent iteration, relaxing to a final configuration to within the computer's precision limits. The angular and radial variation of external gravity (using the usual geophysical expansion in multipole moments) can be found to the limit of typical floating point precision (~ 1.e-14), much better than the expected noise/signal for either the Juno or Cassini gravity experiments. The stairstep barotrope can be adjusted to fit a prescribed continuous or discontinuous interior barotrope, and can be made to approximate it to any required precision by increasing N. One can insert a higher density of CMSs toward the surface of an interior model in order to more accurately model high-order gravitational moments. The magnitude of high-order moments predicted by TOF declines geometrically with order number, and falls below the magnitude of expected non-hydrostatic terms produced by interior dynamics at ~ order 10 and above. Juno's sensitivity is enough to detect tidal gravity signals from Galilean satellites. The CMS method can be generalized to predict tidal zonal and tesseral terms consistent with an interior model fitted to measured zonal harmonics. For this purpose, two-dimensional Gaussian quadrature is necessary at each CMS interface. However, once the model is relaxed to equilibrium, one need not refit the model to the average zonal harmonics because of the smallness of the tidal terms. I will describe how the CMS method has been validated through comparisons with standard TOF models for which fully or partially analytic solutions exist, as well as through consistency checks. At this stage in software development in preparation for Jupiter orbit, we are focused on increasing the speed of the code in order to more efficiently search the parameter space of acceptable Jupiter interior models, as well as to interface it with advanced hydrogen-helium equations of state.

Middle Atmosphere Program. Handbook for MAP, Volume 5

NASA Technical Reports Server (NTRS)

Sechrist, C. F., Jr. (Editor)

1982-01-01

The variability of the stratosphere during the winter in the Northern Hemisphere is considered. Long term monthly mean 30-mbar maps are presented that include geopotential heights, temperatures, and standard deviations of 15 year averages. Latitudinal profiles of mean zonal winds and temperatures are given along with meridional time sections of derived quantities for the winters 1965/66 to 1980/81.

The zonally averaged transport characteristics of the atmosphere as determined by a general circulation model

NASA Technical Reports Server (NTRS)

Plumb, R. A.

1985-01-01

Two dimensional modeling has become an established technique for the simulation of the global structure of trace constituents. Such models are simpler to formulate and cheaper to operate than three dimensional general circulation models, while avoiding some of the gross simplifications of one dimensional models. Nevertheless, the parameterization of eddy fluxes required in a 2-D model is not a trivial problem. This fact has apparently led some to interpret the shortcomings of existing 2-D models as indicating that the parameterization procedure is wrong in principle. There are grounds to believe that these shortcomings result primarily from incorrect implementations of the predictions of eddy transport theory and that a properly based parameterization may provide a good basis for atmospheric modeling. The existence of these GCM-derived coefficients affords an unprecedented opportunity to test the validity of the flux-gradient parameterization. To this end, a zonally averaged (2-D) model was developed, using these coefficients in the transport parameterization. Results from this model for a number of contrived tracer experiments were compared with the parent GCM. The generally good agreement substantially validates the flus-gradient parameterization, and thus the basic principle of 2-D modeling.

Calculation of the radiative heat exchange in a conical cavity of complex configuration with an absorptive medium

NASA Technical Reports Server (NTRS)

Surinov, Y. A.; Fedyanin, V. E.

1975-01-01

The generalized zonal method is used to calculate the distribution of the temperature factor on the lateral surface of a conical cavity of complex configuration (a Laval nozzle) containing an absorptive medium. The highest values of the radiation density occur on the converging part of the lateral surface of the complex conical cavity (Laval nozzle).

Transonic Navier-Stokes wing solution using a zonal approach. Part 1: Solution methodology and code validation

NASA Technical Reports Server (NTRS)

Flores, J.; Gundy, K.; Gundy, K.; Gundy, K.; Gundy, K.; Gundy, K.

1986-01-01

A fast diagonalized Beam-Warming algorithm is coupled with a zonal approach to solve the three-dimensional Euler/Navier-Stokes equations. The computer code, called Transonic Navier-Stokes (TNS), uses a total of four zones for wing configurations (or can be extended to complete aircraft configurations by adding zones). In the inner blocks near the wing surface, the thin-layer Navier-Stokes equations are solved, while in the outer two blocks the Euler equations are solved. The diagonal algorithm yields a speedup of as much as a factor of 40 over the original algorithm/zonal method code. The TNS code, in addition, has the capability to model wind tunnel walls. Transonic viscous solutions are obtained on a 150,000-point mesh for a NACA 0012 wing. A three-order-of-magnitude drop in the L2-norm of the residual requires approximately 500 iterations, which takes about 45 min of CPU time on a Cray-XMP processor. Simulations are also conducted for a different geometrical wing called WING C. All cases show good agreement with experimental data.

New observations of Yanai waves and equatorial inertia-gravity waves in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Farrar, J. T.; Durland, T.

2011-12-01

In the 1970's and 1980's, there was a great deal of research activity on near-equatorial variability at periods of days to weeks associated with oceanic equatorial inertia-gravity waves and Yanai waves. At that time, the measurements available for studying these waves were much more limited than today: most of the available observations were from island tide gauges and a handful of short mooring records. We use more than a decade of the extensive modern data record from the TAO/TRITON mooring array in the Pacific Ocean to re-examine the internal-wave climate in the equatorial Pacific, with a focus on interpretation of the zonal-wavenumber/frequency spectrum of surface dynamic height relative to 500-m depth. Many equatorial-wave meridional modes can be identified, for both the first and second baroclinic mode. We also estimated zonal-wavenumber/frequency spectra for the zonal and meridional wind stress components. The location and extent of spectral peaks in dynamic height is readily rationalized using basic, linear theory of forced equatorial waves and the observed wind stress spectrum.

Evaluating the effect of oceanic striations on biogeochemistry in the eastern South Pacific

NASA Astrophysics Data System (ADS)

Auger, P. A.; Belmadani, A.; Donoso, D.; Hormazabal, S.

2017-12-01

In recent years, quasi-zonal mesoscale jet-like features or striations have been ubiquitously detected in the time-mean circulation of the world ocean using satellite altimetry and in situ data. Most likely the result of some organization of the mesoscale eddy field such as preferred eddy tracks, these striations may be able to advect and mix physical properties. Yet, their impact on biogeochemistry has not been assessed yet. Off central Chile, the interaction between striations and sharp background gradients of biogeochemical properties may spatially structure biogeochemistry, with potential implications for marine ecosystems. For instance, striations may affect the mean horizontal distribution of surface phytoplankton biomass in the coastal transition zone (CTZ), or the structure and variability of the oxygen-minimum zone (OMZ). Here, we evaluate the expression of striations in satellite records of ocean color and in a set of numerically simulated biogeochemical tracers off central Chile (chlorophyll, carbon, primary production, oxygen, nutrients), averaged over the surface productive layer, the OMZ at intermediate depths or the water column. A multi-decadal hindcast simulation of the physical-biogeochemical dynamics was run over the period 1984-2013 using the ROMS-PISCES (for Regional Oceanic Modeling System - Pelagic Interactions Scheme for Carbon and Ecosystem Studies) platform at an eddy-resolving resolution. Satellite data and model outputs are spatially high-pass filtered to remove the large-scale signal and evaluate the match between striations and biogeochemical tracer anomalies in the model and observations. The effect of striations on the mean shape of the zonal gradient of phytoplankton biomass in the CTZ between eutrophic coastal waters and oligotrophic offshore waters is then deduced. The fraction of tracer anomalies due to striations is quantified, and the structuring roles of stationary and transient striations are respectively explored by matching striations and biogeochemical tracers on moving frames of variable widths from 6 months to several years.

Examining Changes to the Madden-Julian Oscillation in a Warmer Climate Using CMIP5 Models

NASA Astrophysics Data System (ADS)

Rushley, Stephanie

Five models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) that reasonably represent the Madden-Julian Oscillation (MJO) are used to examine the response of the MJO to greenhouse gas induced warming. Changes in the MJO's amplitude, zonal scale, and phase speed are examined using daily-mean precipitation during boreal winter (November to April) when the MJO is strongest. The MJO precipitation variance increases with tropics mean surface temperature. However, the westward moving waves of the same temporal and spatial scales increase at about the same rate, suggesting that the maintenance mechanism for the MJO does not change with warming. On the other hand, a robust increase in phase speed of the MJO is found with a rate of 5-12% per degree of surface warming. The robust increase in the MJO phase speed are examined using the linear moisture wave theory of Adames and Kim (2016). In this theory, the MJO phase speed is determined by the horizontal moisture gradient in the lower troposphere, the gross dry stability, the convective moisture adjustment timescale, and zonal wavenumber of the MJO. All CMIP5 models examined show an increase in the horizontal humidity gradient, the gross dry stability and the convective moisture adjustment timescale, while exhibiting a decrease in the zonal wavenumber of the MJO. The increase in the horizontal humidity gradient and zonal scale of the MJO act to increase the speed of the MJO by enhancing horizontal moisture advection associated with the MJO, while the gross dry stability and convective moisture adjustment timescale act to slow down the MJO by dampening the horizontal moisture advection process. In all the models, the combined effects of the four key parameters act to speed up the MJO, matching the calculated phase speed changes with warming in the models.

On the contribution of G20 and G30 in the Time-Averaged Paleomagnetic Field: First results from a new Giant Gaussian Process inverse modeling approach

NASA Astrophysics Data System (ADS)

Khokhlov, A.; Hulot, G.; Johnson, C. L.

2013-12-01

It is well known that the geometry of the recent time-averaged paleomagnetic field (TAF) is very close to that of a geocentric axial dipole (GAD). However, many TAF models recovered from averaging lava flow paleomagnetic directional data (the most numerous and reliable of all data) suggest that significant additional terms, in particular quadrupolar (G20) and octupolar (G30) zonal terms, likely contribute. The traditional way in which most such TAF models are recovered uses an empirical estimate for paleosecular variation (PSV) that is subject to limitations imposed by the limited age information available for such data. In this presentation, we will report on a new way to recover the TAF, using an inverse modeling approach based on the so-called Giant Gaussian Process (GGP) description of the TAF and PSV, and various statistical tools we recently made available (see Khokhlov and Hulot, Geophysical Journal International, 2013, doi: 10.1093/gji/ggs118). First results based on high quality data published from the Time-Averaged Field Investigations project (see Johnson et al., G-cubed, 2008, doi:10.1029/2007GC001696) clearly show that both the G20 and G30 terms are very well constrained, and that optimum values fully consistent with the data can be found. These promising results lay the groundwork for use of the method with more extensive data sets, to search for possible additional non-zonal departures of the TAF from the GAD.

The Huygens Doppler Wind Experiment: Ten Years Ago

NASA Astrophysics Data System (ADS)

Bird, Michael; Dutta-Roy, Robin; Dzierma, Yvonne; Atkinson, David; Allison, Michael; Asmar, Sami; Folkner, William; Preston, Robert; Plettemeier, Dirk; Tyler, Len; Edenhofer, Peter

2015-04-01

The Huygens Doppler Wind Experiment (DWE) achieved its primary scientific goal: the derivation of Titan's vertical wind profile from the start of Probe descent to the surface. The carrier frequency of the ultra-stable Huygens radio signal at 2040 MHz was recorded using special narrow-band receivers at two large radio telescopes on Earth: the Green Bank Telescope in West Virginia and the Parkes Radio Telescope in Australia. Huygens drifted predominantly eastward during the parachute descent, providing the first in situ confirmation of Titan's prograde super-rotational zonal winds. A region of surprisingly weak wind with associated strong vertical shear reversal was discovered within the range of altitudes from 65 to 100 km. Below this level, the zonal wind subsided monotonically from 35 m/s to about 7 km, at which point it reversed direction. The vertical profile of the near-surface winds implies the existence of a planetary boundary layer. Recent results on Titan atmospheric circulation within the context of the DWE will be reviewed.

Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events.

PubMed

Mann, Michael E; Rahmstorf, Stefan; Kornhuber, Kai; Steinman, Byron A; Miller, Sonya K; Coumou, Dim

2017-03-27

Persistent episodes of extreme weather in the Northern Hemisphere summer have been shown to be associated with the presence of high-amplitude quasi-stationary atmospheric Rossby waves within a particular wavelength range (zonal wavenumber 6-8). The underlying mechanistic relationship involves the phenomenon of quasi-resonant amplification (QRA) of synoptic-scale waves with that wavenumber range becoming trapped within an effective mid-latitude atmospheric waveguide. Recent work suggests an increase in recent decades in the occurrence of QRA-favorable conditions and associated extreme weather, possibly linked to amplified Arctic warming and thus a climate change influence. Here, we isolate a specific fingerprint in the zonal mean surface temperature profile that is associated with QRA-favorable conditions. State-of-the-art ("CMIP5") historical climate model simulations subject to anthropogenic forcing display an increase in the projection of this fingerprint that is mirrored in multiple observational surface temperature datasets. Both the models and observations suggest this signal has only recently emerged from the background noise of natural variability.

SUPERGRANULES AS PROBES OF THE SUN'S MERIDIONAL CIRCULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hathaway, David H., E-mail: david.hathaway@nasa.gov

2012-11-20

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 meridional circulation by cross-correlating maps of the Doppler velocity signal using a series of successively longer time lags between maps. We find that the poleward meridional 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 meridional 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 meridional return flow and illustrates the power of using supergranules to probe the Sun's internal dynamics.« less

Comparison of horizontal winds from the LIMS satellite instrument with rocket measurements

NASA Technical Reports Server (NTRS)

Smith, A. K.; Bailey, P. L.

1985-01-01

Statistical results are given for a comparison between horizontal geostrophic winds computed from satellite height data and all available in situ rocket wind soundings during a 7-month period. The satellite data are the daily mapped fields from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) instrument, which extend from 100 to 0.1 mbar. Results indicate that in both the tropics and the extratropical Northern Hemisphere, the average zonal and meridional wind speeds agree to within 2-4 m/s throughout the stratosphere. The rms differences are much larger, with values of 5-10 m/s in the lower stratosphere, increasing to 20-40 m/s in the lower mesosphere. Time series show that LIMS and rocketsonde zonal wind speeds show coherent variations with temporal periods of 1-2 weeks and more, and both exhibit irregular variations on time scales of less than one week.

Present-day Antarctic climatology of the NCAR Community Climate Model Version 1

NASA Technical Reports Server (NTRS)

Tzeng, Ren-Yow; Bromwich, David H.; Parish, Thomas R.

1993-01-01

The ability of the NCAR Community Climate Model Version 1 (CCM1) with R 15 resolution to simulate the present-day climate of Antarctica was evaluated using the five-year seasonal cycle output produced by the CCM1 and comparing the model results with observed horizontal syntheses and point data. The results showed that the CCM1 with R 15 resolution can simulate to some extent the dynamics of Antarctic climate on the synoptic scale as well as some mesoscale features. The model can also simulate the phase and the amplitude of the annual and semiannual variation of the temperature, sea level pressure, and zonally averaged zonal (E-W) wind. The main shortcomings of the CCM1 model are associated with the model's anomalously large precipitation amounts at high latitudes, due to the tendency of the scheme to suppress negative moisture values.

Drift-wave turbulence and zonal flow generation.

PubMed

Balescu, R

2003-10-01

Drift-wave turbulence in a plasma is analyzed on the basis of the wave Liouville equation, describing the evolution of the distribution function of wave packets (quasiparticles) characterized by position x and wave vector k. A closed kinetic equation is derived for the ensemble-averaged part of this function by the methods of nonequilibrium statistical mechanics. It has the form of a non-Markovian advection-diffusion equation describing coupled diffusion processes in x and k spaces. General forms of the diffusion coefficients are obtained in terms of Lagrangian velocity correlations. The latter are calculated in the decorrelation trajectory approximation, a method recently developed for an accurate measure of the important trapping phenomena of particles in the rugged electrostatic potential. The analysis of individual decorrelation trajectories provides an illustration of the fragmentation of drift-wave structures in the radial direction and the generation of long-wavelength structures in the poloidal direction that are identified as zonal flows.

Zonal harmonic model of Saturn's magnetic field from Voyager 1 and 2 observations

NASA Technical Reports Server (NTRS)

Connerney, J. E. P.; Ness, N. F.; Acuna, M. H.

1982-01-01

An analysis of the magnetic field of Saturn is presented which takes into account both the Voyager 1 and 2 vector magnetic field observations. The analysis is based on the traditional spherical harmonic expansion of a scale potential to derive the magnetic field within 8 Saturn radii. A third-order zonal harmonic model fitted to Voyager 1 and 2 observations is found to be capable of predicting the magnetic field characteristics at one encounter based on those observed at another, unlike models including dipole and quadrupole terms only. The third-order model is noted to lead to significantly enhanced polar surface field intensities with respect to dipole models, and probably represents the axisymmetric part of a complex dynamo field.

ENSO and East Asian winter monsoon relationship modulation associated with the anomalous northwest Pacific anticyclone

NASA Astrophysics Data System (ADS)

Kim, Ji-Won; An, Soon-Il; Jun, Sang-Yoon; Park, Hey-Jin; Yeh, Sang-Wook

2017-08-01

Using observational datasets and numerical model experiments, the mechanism on the slowly varying change in the relationship between the El Niño-Southern Oscillation (ENSO) and the East Asian winter monsoon (EAWM) is investigated. The decadal-window (11-, 15-, and 21-year) moving correlations show a significant change in the boreal wintertime ENSO-EAWM relationship between two sub-periods of 1976‒1992 and 1997‒2013. Such recent change in ENSO-EAWM relationship is mainly attributed to the changes in the intensity and zonal location of the anomalous lower-tropospheric northwest Pacific anticyclone (NWP-AC). NWP-AC commonly develops near the region of the Philippine Sea during the ENSO's peak phase and plays an important role of bridging the tropical convection and mid-latitude teleconnection. On one hand, the intensity of the NWP-AC is influenced by the interdecadal variation in a linkage between ENSO and the Indian Ocean sea surface temperature (SST) variability, referring that a strong connection between the Pacific and Indian Oceans results in the strengthening of NWP-AC response to ENSO. On the other hand, the zonal displacement of the NWP-AC is associated with the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). That is, the tropical Pacific mean state (i.e., zonal SST gradient between climatologically warm western Pacific and cold eastern Pacific)—strengthened by either the negative PDO phase or the positive AMO phase—drives the anomalous ENSO-induced convection to be shifted to the west. With this westward shift, the zonal center of the NWP-AC also migrates westward over the Philippine Islands and exerts stronger connection between ENSO and EAWM. In contrast, the relaxed zonal SST contrast associated with either the positive PDO phase or the negative AMO phase tends to exhibit weaker ENSO-EAWM relationship via both of eastward shifted zonal centers of the anomalous ENSO-induced convection and the NWP-AC. Finally, a series of the numerical experiments conducted by an atmospheric general circulation model supports the observational findings.

On the Variation of Zonal Gravity Coefficients of a Giant Planet Caused by Its Deep Zonal Flows

NASA Astrophysics Data System (ADS)

Kong, Dali; Zhang, Keke; Schubert, Gerald

2012-04-01

Rapidly rotating giant planets are usually marked by the existence of strong zonal flows at the cloud level. If the zonal flow is sufficiently deep and strong, it can produce hydrostatic-related gravitational anomalies through distortion of the planet's shape. This paper determines the zonal gravity coefficients, J 2n , n = 1, 2, 3, ..., via an analytical method taking into account rotation-induced shape changes by assuming that a planet has an effective uniform density and that the zonal flows arise from deep convection and extend along cylinders parallel to the rotation axis. Two different but related hydrostatic models are considered. When a giant planet is in rigid-body rotation, the exact solution of the problem using oblate spheroidal coordinates is derived, allowing us to compute the value of its zonal gravity coefficients \\bar{J}_{2n}, n=1,2,3, \\dots, without making any approximation. When the deep zonal flow is sufficiently strong, we develop a general perturbation theory for estimating the variation of the zonal gravity coefficients, \\Delta {J}_{2n}={J}_{2n}-\\bar{J}_{2n}, n=1,2,3, \\dots, caused by the effect of the deep zonal flows for an arbitrarily rapidly rotating planet. Applying the general theory to Jupiter, we find that the deep zonal flow could contribute up to 0.3% of the J 2 coefficient and 0.7% of J 4. It is also found that the shape-driven harmonics at the 10th zonal gravity coefficient become dominant, i.e., \\Delta {J}_{2n} \\,{\\ge}\\, \\bar{J}_{2n} for n >= 5.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Staten, Paul; Reichler, Thomas; Lu, Jian

Tropospheric circulation shifts have strong potential to impact surface climate. But the magnitude of these shifts in a changing climate, and the attending regional hydrological changes, are difficult to project. Part of this difficulty arises from our lack of understanding of the physical mechanisms behind the circulation shifts themselves. In order to better delineate circulation shifts and their respective causes, we decompose the circulation response into (1) the "direct" response to radiative forcings themselves, and (2) the "indirect" response to changing sea surface temperatures. Using ensembles of 90-day climate model simulations with immediate switch-on forcings, including perturbed greenhouse gas concentrations,more » stratospheric ozone concentrations, and sea surface temperatures, we document the direct and indirect transient responses of the zonal mean general circulation, and investigate the roles of previously proposed mechanisms in shifting the midlatitude jet. We find that both the direct and indirect wind responses often begin in the lower stratosphere. Changes in midlatitude eddies are ubiquitous and synchronous with the midlatitude zonal wind response. Shifts in the critical latitude of wave absorption on either flank of the jet are not indicted as primary factors for the poleward shifting jet, although we see some evidence for increasing equatorward wave reflection over the southern hemisphere in response to sea surface warming. Mechanisms for the northern hemisphere jet shift are less clear.« less

The impact of wave-induced Coriolis-Stokes forcing on satellite-derived ocean surface currents

NASA Astrophysics Data System (ADS)

Hui, Zhenli; Xu, Yongsheng

2016-01-01

Ocean surface currents estimated from the satellite data consist of two terms: Ekman currents from the wind stress and geostrophic currents from the sea surface height (SSH). But the classical Ekman model does not consider the wave effects. By taking the wave-induced Coriolis-Stokes forcing into account, the impact of waves (primarily the Stokes drift) on ocean surface currents is investigated and the wave-modified currents are formed. The products are validated by comparing with OSCAR currents and Lagrangian drifter velocity. The result shows that our products with the Stokes drift are better adapted to the in situ Lagrangian drifter currents. Especially in the Southern Ocean region (40°S-65°S), 90% (91%) of the zonal (meridional) currents have been improved compared with currents that do not include Stokes drift. The correlation (RMSE) in the Southern Ocean has also increased (decreased) from 0.78 (13) to 0.81 (10.99) for the zonal component and 0.76 (10.87) to 0.79 (10.09) for the meridional component. This finding provides the evidence that waves indeed play an important role in the ocean circulation, and need to be represented in numerical simulations of the global ocean circulation. This article was corrected on 10 FEB 2016. See the end of the full text for details.

Laboratory study of forced rotating shallow water turbulence

NASA Astrophysics Data System (ADS)

Espa, Stefania; Di Nitto, Gabriella; Cenedese, Antonio

2011-12-01

During the last three decades several authors have studied the appearance of multiple zonal jets in planetary atmospheres and in the Earths oceans. The appearance of zonal jets has been recovered in numerical simulations (Yoden & Yamada, 1993), laboratory experiments (Afanasyev & Wells, 2005; Espa et al., 2008, 2010) and in field measurements of the atmosphere of giant planets (Galperin et al., 2001). Recent studies have revealed the presence of zonation also in the Earths oceans, in fact zonal jets have been found in the outputs of Oceanic General Circulation Models-GCMs (Nakano & Hasumi, 2005) and from the analysis of satellite altimetry observations (Maximenko et al., 2005). In previous works (Espa et al., 2008, 2010) we have investigated the impact of the variation of the rotation rate and of the fluid depth on jets organization in decaying and forced regimes. In this work we show results from experiments performed in a bigger domain in which the fluid is forced continuously. The experimental set-up consists of a rotating tank (1m in diameter) where the initial distribution of vorticity has been generated via the Lorentz force in an electromagnetic cell. The latitudinal variation of the Coriolis parameter has been simulated by the parabolic profile assumed by the free surface of the rotating fluid. Flow measurements have been performed using an image analysis technique. Experiments have been performed changing the tank rotation rate and the fluid thickness. We have investigated the flow in terms of zonal and radial flow pattern, flow variability and jet scales.

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, G.; Abarbanel, H.; Carruthers, P.

If the current growth rate in the use of fossil fuels continues at 4.3% per year, then the CO/sub 2/ concentration in the atmosphere can be expected to double by about 2035 provided the current partition of CO/sub 2/ between the atmosphere, biosphere, and oceans is maintained as is the current mix of fuels. Slower rates of anticipated growth of energy use lead to a doubling of the carbon content of the atmosphere sometime in the period 2040 to 2060. This report addresses the questions of the sources of atmospheric CO/sub 2/; considers distribution of the present CO/sub 2/ amongmore » the atmospheric, oceanic, and biospheric reservoir; and assesses the impact on climate as reflected by the average ground temperature at each latitude of significant increases in atmospheric CO/sub 2/. An analytic model of the atmosphere was constructed (JASON Climate Model). Calculation with this zonally averaged model shows an increase of average surface temperature of 2.4/sup 0/ for a doubling of CO/sub 2/. The equatorial temperature increases by 0.7/sup 0/K, while the poles warm up by 10 to 12/sup 0/K. The warming of climate will not necessarily lead to improved living conditions everywhere. Changes in sea level, in agricultural productivity, and in water availability can be anticipated, but the dimensions of their economic, political, or social consequences can not.« less

Arctic Amplification and the Northward shift of a new Greenland melting record

NASA Astrophysics Data System (ADS)

Tedesco, Marco; Mote, Thomas; Fettweis, Xavier; Hanna, Edward; Booth, James; Jeyaratnam, Jeyavinoth; Datta, Rajashree; Briggs, Kate

2016-04-01

Large-scale atmospheric circulation controls the mass and energy balance of the Greenland ice sheet through its impact on radiative budget, runoff and accumulation. Using reanalysis data and the outputs of a regional climate model, here we show that the persistence of an exceptional atmospheric ridge, centred over the Arctic Ocean was responsible for a northward shift of surface melting records over Greenland, and for increased accumulation in the south during the summer of 2015. Concurrently, new records of mean monthly zonal winds at 500 hPa and of the maximum latitude of ridge peaks of the 5700±50 m isohypse over the Arctic were also set. An unprecedented (1948 - 2015) and sustained jet stream easterly flow promoted enhanced runoff, increased surface temperatures and decreased albedo in northern Greenland, while inhibiting melting in the south. The exceptional 2015 summer Arctic atmospheric conditions are consistent with the anticipated effects of Arctic Amplification, including slower zonal winds and increased jet stream wave amplitude. Properly addressing the impact of Arctic Amplification on surface runoff of the Greenland ice sheet is crucial for rigorously quantifying its contribution to current and future sea level rise, and the relative impact of freshwater discharge on the surrounding ocean.

UNDERSTANDING SOLAR TORSIONAL OSCILLATIONS FROM GLOBAL DYNAMO MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guerrero, G.; Smolarkiewicz, P. K.; Pino, E. M. de Gouveia Dal

2016-09-01

The phenomenon of solar “torsional oscillations” (TO) represents migratory zonal flows associated with the solar cycle. These flows are observed on the solar surface and, according to helioseismology, extend through the convection zone. We study the origin of the TO using results from a global MHD simulation of the solar interior that reproduces several of the observed characteristics of the mean-flows and magnetic fields. Our results indicate that the magnetic tension (MT) in the tachocline region is a key factor for the periodic changes in the angular momentum transport that causes the TO. The torque induced by the MT atmore » the base of the convection zone is positive at the poles and negative at the equator. A rising MT torque at higher latitudes causes the poles to speed up, whereas a declining negative MT torque at the lower latitudes causes the equator to slow-down. These changes in the zonal flows propagate through the convection zone up to the surface. Additionally, our results suggest that it is the magnetic field at the tachocline that modulates the amplitude of the surface meridional flow rather than the opposite as assumed by flux-transport dynamo models of the solar cycle.« less

Connections Between the Spring Breakup of the Southern Hemisphere Polar Vortex, Stationary Waves, and Air-sea Roughness

NASA Technical Reports Server (NTRS)

Garfinkel, Chaim I.; Oman, Luke David; Barnes, Elizabeth A.; Waugh, Darryn W.; Hurwitz, Margaret H.; Molod, Andrea M.

2013-01-01

A robust connection between the drag on surface-layer winds and the stratospheric circulation is demonstrated in NASA's Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM). Specifically, an updated parameterization of roughness at the air-sea interface, in which surface roughness is increased for moderate wind speeds (4ms to 20ms), leads to a decrease in model biases in Southern Hemispheric ozone, polar cap temperature, stationary wave heat flux, and springtime vortex breakup. A dynamical mechanism is proposed whereby increased surface roughness leads to improved stationary waves. Increased surface roughness leads to anomalous eddy momentum flux convergence primarily in the Indian Ocean sector (where eddies are strongest climatologically) in September and October. The localization of the eddy momentum flux convergence anomaly in the Indian Ocean sector leads to a zonally asymmetric reduction in zonal wind and, by geostrophy, to a wavenumber-1 stationary wave pattern. This tropospheric stationary wave pattern leads to enhanced upwards wave activity entering the stratosphere. The net effect is an improved Southern Hemisphere vortex: the vortex breaks up earlier in spring (i.e., the spring late-breakup bias is partially ameliorated) yet is no weaker in mid-winter. More than half of the stratospheric biases appear to be related to the surface wind speed biases. As many other chemistry climate models use a similar scheme for their surface layer momentum exchange and have similar biases in the stratosphere, we expect that results from GEOSCCM may be relevant for other climate models.

Approximate Co-Location of Precipitation and Low-Level Westerlies in Tropical Monthly Means

NASA Technical Reports Server (NTRS)

Choa, Winston C.; Chen, Baode

1999-01-01

In summer monsoon regions the monthly mean precipitation regions coincide approximately well with regions of westerlies at low-levels. An included chart shows a 15-year (1979-1993) mean August 850 hPa zonal wind from NCEP/NCAR reanalysis dataset and Xie-Arkin precipitation. It shows a region of westerlies covering most of Northern Indian Ocean and extending to northwestern Pacific. This region coincides well with the region with precipitation greater than 6 mm/day. Obviously the coincidence is not exact; the region of larges; zonal wind in the Arabian Sea is in a region of relatively low precipitation and is far from the region of maximum precipitation in Bay of Bengal. Also, in a zonally averaged sense between 40E and 140E, the latitude of maximum precipitation is slightly higher than that of the maximum zonal wind. Low-level westerlies are also found in regions west of Central America and in western Africa north of the equator. These regions are also closely associated with precipitation centers. Across equator from these westerlies regions there are regions of strong easterlies. Also, on their poleward side the westerly regions are flanked by weaker easterly regions. In February, similar observation can be found in the Australian monsoon area and in South America monsoon region; again the regions of westerlies coincide well with regions of maximum precipitation. As in the northern hemisphere, the maximum precipitation is found to the cast of the maximum zonal wind. The two maxima lie almost at the same latitude with that of the westerlies slightly closer to the equator. In the non-monsoon seasons the low- level westerlies can also be found in the tropical precipitation regions, the longitudinal range of the westerlies is undiminished and the speed of the westerlies is not much weaker than that found in February. The interpretation of these observational facts is the goal of this investigation. The approach taken is numerical simulation with the Goddard Earth Observation Systems atmospheric general circulation model, and its aqua-planet version, combined with theoretical arguments.

Thermal zonal winds in the Venus mesosphere from the Venus Express temperature soundings

NASA Astrophysics Data System (ADS)

Piccialli, Arianna; Titov, Dmitri; Tellmann, Silvia; Migliorini, Alessandra; Read, Peter; Grassi, Davide; Paetzold, Martin; Haeusler, Bernd; Piccioni, Giuseppe; Drossart, Pierre

The Venus mesosphere (60-100 km altitude) is a transition region characterized by extremely complex dynamics: strong retrograde zonal winds dominate in the troposphere and lower meso-sphere while a solar-antisolar circulation can be observed in the upper mesosphere. The super-rotation extends from the surface up to the cloud top (˜65 km altitude) with wind speeds of only a few meters per second near the surface and reaching a maximum value of ˜100 m s-1 at cloud top, corresponding to a rotation period of ˜4 Earth days (˜60 times faster than Venus itself). The solar-antisolar circulation is driven by the day-night contrast in solar heating, and occurs above 110 km altitude with speeds of 120 m s-1 . The processes responsible for maintain-ing the zonal super-rotation in the lower atmosphere and its transition to the solar-antisolar circulation in the upper atmosphere are still poorly understood (Schubert et al.,2007). Different techniques have been used to obtain direct observations of wind at various altitudes: tracking of clouds in ultraviolet (UV) and near infrared (NIR) images give information on wind speeds at the cloud top (Moissl et al., 2009; Sanchez-Lavega et al., 2008) and within the clouds (˜47 km, ˜61 km) (Sanchez-Lavega et al., 2008) while ground-based measurements of Doppler shifts in the CO2 band at 10 µm (Sornig et al., 2008) and in several CO millimiter lines (Rengel et al., 2008) provide wind speeds above the clouds up to ˜110 km altitude. The deep atmosphere from the surface up to the cloud top has been investigated through the Doppler tracking of descent probes and balloons (Counselman et al., 1980; Kerzhanovich and Limaye, 1985). In the mesosphere, between 45-85 km of altitude, where direct observations of wind are not possible, the zonal wind field can be derived from the vertical temperature structure using a special approximation of the thermal wind equation: based on cyclostrophic balance. Previous studies (Leovy, 1973; Newman et al., 1984) showed that on a slowly rotating planet, like Venus, strong zonal winds at the cloud top can be described by a cyclostrophic balance in which the equatorward component of centrifugal force is balanced by the meridional pressure gradient. This equation gives a possibility to reconstruct the zonal wind if the temperature field is known, together with a suitable boundary condition on u. Two experiments onboard Venus Express are sounding the temperature structure of the Venus mesosphere: VIRTIS sounds the Venus Southern hemisphere in the altitude range 65-90 km with a very good spatial and temporal coverage (Grassi et al., 2008) and the Northern hemi-sphere but with more limited coverage; VeRa observes both northern and southern hemispheres between 40-90 km altitude with a vertical resolution of ˜500 m (Tellmann et al., 2008). Here we present zonal thermal winds derived applying cyclostrophic balance from VIRTIS and VeRa temperature retrievals. The main features of the retrieved winds are: (1) a midlatitude jet with a maximum speed up to 140 ± 15 m s-1 which occurs around 50° S latitude at 70 km altitude; (2) the fast decrease of the wind speed from 60° S toward the pole; (3) the decrease of the wind speed with increasing height above the jet (Piccialli et al., 2008). Cyclostrophic winds show satisfactory agreement with the cloud-tracked winds derived from the Venus Monitoring Camera (VMC/VEx) UV images, although a disagreement is observed at the equator and near the pole due to the breakdown of the cyclostrophic approximation. From zonal thermal winds the Richardson number has been evaluated. In good agreement with previous studies (Allison et al., 1994), we have found that the atmosphere is dominated by convection from ˜45 km altitude up to the cloud top. A high value of Richardson number has been determined, cor-responding to the midlatitude jet and indicating a highly stable atmosphere. Verification of the necessary condition for barotropic instability implies that barotropic instability may occur on the poleward side of the midlatitude jet where planetary waves are expected to play an important role in the maintenance of the circulation.

Synoptic backgrounds of the widest wildfire in Mazandaran Province of Iran during December 11-13, 2010

NASA Astrophysics Data System (ADS)

Ghavidel, Yousef; Farajzadeh, Manuchehr; Khaleghi Babaei, Meysam

2016-12-01

In this paper, atmospheric origins of the widest wildfire in Mazandaran province on 11-13th of December, 2010 have been investigated. Data sets of this research include maximum daily temperature (MDT), minimum relative humidity (MRH) of terrestrial stations, dynamic and thermodynamic features of the atmosphere, Gridded data sets of Self-Calibrated Palmer drought severity index (SCPDSI) and global drought dataset standardized precipitation-evapotranspiration index (SPEI) and data related to the time and the extent of the wildfire. The ``environmental to circulation'' approach to synoptic classification has been used to investigate relationships between local-scale surface environment (wildfire) and the synoptic-scale atmospheric circulation conditions. Results of study show that during the 3-day wide wildfire, the average of MDT and the MRH was significantly different from the long-term average. During the aforementioned wildfire, the average of MDT in Mazandaran province was 26 °C and the average of MRH was reported 35 %. The long-term average of MDT and the MRH in Mazandaran province during 3 days of wildfire was 12.3 °C and 68 %, respectively. Therefore, the MDT has a positive abnormality of 13.7 °C and the MRH has a negative abnormality of 33 %. In addition, monthly SCPDSI and SPEI indicated severe drought conditions at December 2010 in Mazandaran. Analysis of SLP maps shows that during the 3-day fire, a pressure center of 1110 hPa on Persian Gulf and a very low-pressure center on Turkey and Asia Minor were created. Normally, this event has caused the pressure gradient and warm and dry air advection from Arabian Peninsula to higher longitudes, particularly Mazandaran province. Consequently, the MDT increased and the wildfire of Mazandaran forest took place in an area of 220 ha. Zonal wind maps signify the weakness of Zonal wind and meridional wind maps show the southern direction of meridional wind flow during the wide wildfire. Moreover, Omega maps prove that during the aforementioned wildfire, the Omega flow has been positive and the warm air flow has subsidence. This made the infusion of warm air and increased the MDT substantially and consequently the wildfire occurrence was facilitated. Temperature advection maps showed that in the level of 1000 hPa, the warm air blowing source is originated from Arabian Peninsula, in the level of 850 hPa from the Arabian Peninsula and Iraq and in the level of 700 and 500 hPa from Ethiopia, Arabian Peninsula and Iraq. The Hybrid-Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model outputs confirm the synoptic mechanisms for the discussed wildfire.

A low-order model of the equatorial ocean-atmosphere system

NASA Astrophysics Data System (ADS)

Legnani, Roberto

A low order model of the equatorial ocean-atmosphere coupled system is presented. The model atmosphere includes a hydrological cycle with cloud-radiation interaction. The model ocean is based on mixed layer dynamics with a parameterization of entrainment processes. The coupling takes place via transfer to momentum, sensible heat, latent heat and short wave and long wave radiation through the ocean surface. The dynamical formulation is that of the primitive equations of an equatorial beta-plane, with zonally periodic and meridionally infinite geometry. The system is expanded into the set of normal modes pertinent to the linear problem and severly truncated to a few modes; 54 degrees of freedom are retained. Some nonlinear terms of the equations are evaluated in physical space and then projected onto the functional space; other terms are evaluated directly in the functional space. Sensitivity tests to variations of the parameters are performed, and some results from 10-year initial value simulations are presented. The model is capable of supporting oscillations of different time scales, ranging from a few days to a few years; it prefers a particular zonally asymmetric state, but temporarily switches to a different (opposite) zonally asymmetric state in an event-like fashion.

a Low-Order Model of the Equatorial Ocean-Atmosphere System.

NASA Astrophysics Data System (ADS)

Legnani, Roberto

A low order model of the equatorial ocean-atmosphere coupled system is presented. The model atmosphere includes a hydrological cycle with cloud-radiation interaction. The model ocean is based on mixed layer dynamics with a parameterization of entrainment processes. The coupling takes place via transfer to momentum, sensible heat, latent heat and short -wave and long-wave radiation through the ocean surface. The dynamical formulation is that of the primitive equations of an equatorial beta-plane, with zonally periodic and meridionally infinite geometry. The system is expanded into the set of normal modes pertinent to the linear problem and severely truncated to a few modes; 54 degrees of freedom are retained. Some nonlinear terms of the equations are evaluated in physical space and then projected onto the functional space; other terms are evaluated directly in the functional space. Sensitivity tests to variations of the parameters are performed, and some results from 10-year initial value simulations are presented. The model is capable of supporting oscillations of different time scales, ranging from a few days to a few years; it prefers a particular zonally asymmetric state, but temporarily switches to a different (opposite) zonally asymmetric state in an event-like fashion.

A theory of self-organized zonal flow with fine radial structure in tokamak

NASA Astrophysics Data System (ADS)

Zhang, Y. Z.; Liu, Z. Y.; Xie, T.; Mahajan, S. M.; Liu, J.

2017-12-01

The (low frequency) zonal flow-ion temperature gradient (ITG) wave system, constructed on Braginskii's fluid model in tokamak, is shown to be a reaction-diffusion-advection system; it is derived by making use of a multiple spatiotemporal scale technique and two-dimensional (2D) ballooning theory. For real regular group velocities of ITG waves, two distinct temporal processes, sharing a very similar meso-scale radial structure, are identified in the nonlinear self-organized stage. The stationary and quasi-stationary structures reflect a particular feature of the poloidal group velocity. The equation set posed to be an initial value problem is numerically solved for JET low mode parameters; the results are presented in several figures and two movies that show the spatiotemporal evolutions as well as the spectrum analysis—frequency-wave number spectrum, auto power spectrum, and Lissajous diagram. This approach reveals that the zonal flow in tokamak is a local traveling wave. For the quasi-stationary process, the cycle of ITG wave energy is composed of two consecutive phases in distinct spatiotemporal structures: a pair of Cavitons growing and breathing slowly without long range propagation, followed by a sudden decay into many Instantons that carry negative wave energy rapidly into infinity. A spotlight onto the motion of Instantons for a given radial position reproduces a Blob-Hole temporal structure; the occurrence as well as the rapid decay of Caviton into Instantons is triggered by zero-crossing of radial group velocity. A sample of the radial profile of zonal flow contributed from 31 nonlinearly coupled rational surfaces near plasma edge is found to be very similar to that observed in the JET Ohmic phase [J. C. Hillesheim et al., Phys. Rev. Lett. 116, 165002 (2016)]. The theory predicts an interior asymmetric dipole structure associated with the zonal flow that is driven by the gradients of ITG turbulence intensity.

A two-dimensional study of ethane and propane oxidation in the troposphere

NASA Technical Reports Server (NTRS)

Kanakidou, M.; Valentin, K. M.; Crutzen, P. J.; Singh, H. B.

1991-01-01

The chemistry of ethane and propane is studied using a global two-dimensional 'zonally averaged' height- and latitude-dependent tropospheric model. The purpose of the study is to derive theoretical estimates of the seasonal and latitudinal distributions of a variety of intermediate organic compounds formed by the photochemical oxidation of C2H6 and C3H8. It is shown that C2H6 and C3H8 emitted at rates of 16 Tg C2H6/a and 23 Tg C3H8/a do not affect the overall photochemistry of the troposphere significantly. Major global effects on O3 and OH concentrations are suggested to be coming from the formation of peroxyacetyl nitrate by the interactions of NOx with other hydrocarbons with strong and spatially correlated anthropogenic or natural sources at the earth's surface. It is pointed out that attention should be given to organic nitrates produced by the oxidation of NMHC other than C2H6 and C3H8.

Response of the global climate to changes in atmospheric chemical composition due to fossil fuel burning

NASA Technical Reports Server (NTRS)

Cess, R. D.; Hameed, S.; Hogan, J. S.

1980-01-01

Tropospheric ozone and methane might increase in the future as the result of increasing anthropogenic emissions of CO, NOx and CH4 due to fossil fuel burning. Since O3 and CH4 are both greenhouse gases, increases in their concentrations could augment global warming due to larger future amounts of atmospheric CO2. To test this possible climatic impact, a zonal energy-balance climate model has been combined with a vertically-averaged tropospheric chemical model. The latter model includes all relevant chemical reactions which affect species derived from H2O, O2, CH4 and NOx. The climate model correspondingly incorporates changes in the infrared heating of the surface-troposphere system resulting from chemically induced changes in tropospheric ozone and methane. This coupled climate-chemical model indicates that global climate is sensitive to changes in emissions of CO, NOx and CH4, and that future increases in these emissions could enhance global warming due to increasing atmospheric CO2.

Atlas of Seasonal Means Simulated by the NSIPP 1 Atmospheric GCM. Volume 17

NASA Technical Reports Server (NTRS)

Suarez, Max J. (Editor); Bacmeister, Julio; Pegion, Philip J.; Schubert, Siegfried D.; Busalacchi, Antonio J. (Technical Monitor)

2000-01-01

This atlas documents the climate characteristics of version 1 of the NASA Seasonal-to-Interannual Prediction Project (NSIPP) Atmospheric General Circulation Model (AGCM). The AGCM includes an interactive land model (the Mosaic scheme), and is part of the NSIPP coupled atmosphere-land-ocean model. The results presented here are based on a 20-year (December 1979-November 1999) "ANIIP-style" integration of the AGCM in which the monthly-mean sea-surface temperature and sea ice are specified from observations. The climate characteristics of the AGCM are compared with the National Centers for Environmental Prediction (NCEP) and the European Center for Medium-Range Weather Forecasting (ECMWF) reanalyses. Other verification data include Special Sensor Microwave/Imager (SSNM) total precipitable water, the Xie-Arkin estimates of precipitation, and Earth Radiation Budget Experiment (ERBE) measurements of short and long wave radiation. The atlas is organized by season. The basic quantities include seasonal mean global maps and zonal and vertical averages of circulation, variance/covariance statistics, and selected physics quantities.

Free Flow Zonal Electrophoresis for Fractionation of Plant Membrane Compartments Prior to Proteomic Analysis.

PubMed

Barkla, Bronwyn J

2018-01-01

Free flow zonal electrophoresis (FFZE) is a versatile, reproducible, and potentially high-throughput technique for the separation of plant organelles and membranes by differences in membrane surface charge. It offers considerable benefits over traditional fractionation techniques, such as density gradient centrifugation and two-phase partitioning, as it is relatively fast, sample recovery is high, and the method provides unparalleled sample purity. It has been used to successfully purify chloroplasts and mitochondria from plants but also, to obtain highly pure fractions of plasma membrane, tonoplast, ER, Golgi, and thylakoid membranes. Application of the technique can significantly improve protein coverage in large-scale proteomics studies by decreasing sample complexity. Here, we describe the method for the fractionation of plant cellular membranes from leaves by FFZE.

Pronounced zonal heterogeneity in Eocene southern high-latitude sea surface temperatures.

PubMed

Douglas, Peter M J; Affek, Hagit P; Ivany, Linda C; Houben, Alexander J P; Sijp, Willem P; Sluijs, Appy; Schouten, Stefan; Pagani, Mark

2014-05-06

Paleoclimate studies suggest that increased global warmth during the Eocene epoch was greatly amplified at high latitudes, a state that climate models cannot fully reproduce. However, proxy estimates of Eocene near-Antarctic sea surface temperatures (SSTs) have produced widely divergent results at similar latitudes, with SSTs above 20 °C in the southwest Pacific contrasting with SSTs between 5 and 15 °C in the South Atlantic. Validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites. Here, we present multiproxy data from Seymour Island, near the Antarctic Peninsula, that provides well-constrained evidence for annual SSTs of 10-17 °C (1σ SD) during the middle and late Eocene. Comparison of the same paleotemperature proxy at Seymour Island and at the East Tasman Plateau indicate the presence of a large and consistent middle-to-late Eocene SST gradient of ∼7 °C between these two sites located at similar paleolatitudes. Intermediate-complexity climate model simulations suggest that enhanced oceanic heat transport in the South Pacific, driven by deep-water formation in the Ross Sea, was largely responsible for the observed SST gradient. These results indicate that very warm SSTs, in excess of 18 °C, did not extend uniformly across the Eocene southern high latitudes, and suggest that thermohaline circulation may partially control the distribution of high-latitude ocean temperatures in greenhouse climates. The pronounced zonal SST heterogeneity evident in the Eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands.

Pronounced zonal heterogeneity in Eocene southern high-latitude sea surface temperatures

PubMed Central

Douglas, Peter M. J.; Affek, Hagit P.; Ivany, Linda C.; Houben, Alexander J. P.; Sijp, Willem P.; Sluijs, Appy; Schouten, Stefan; Pagani, Mark

2014-01-01

Paleoclimate studies suggest that increased global warmth during the Eocene epoch was greatly amplified at high latitudes, a state that climate models cannot fully reproduce. However, proxy estimates of Eocene near-Antarctic sea surface temperatures (SSTs) have produced widely divergent results at similar latitudes, with SSTs above 20 °C in the southwest Pacific contrasting with SSTs between 5 and 15 °C in the South Atlantic. Validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites. Here, we present multiproxy data from Seymour Island, near the Antarctic Peninsula, that provides well-constrained evidence for annual SSTs of 10–17 °C (1σ SD) during the middle and late Eocene. Comparison of the same paleotemperature proxy at Seymour Island and at the East Tasman Plateau indicate the presence of a large and consistent middle-to-late Eocene SST gradient of ∼7 °C between these two sites located at similar paleolatitudes. Intermediate-complexity climate model simulations suggest that enhanced oceanic heat transport in the South Pacific, driven by deep-water formation in the Ross Sea, was largely responsible for the observed SST gradient. These results indicate that very warm SSTs, in excess of 18 °C, did not extend uniformly across the Eocene southern high latitudes, and suggest that thermohaline circulation may partially control the distribution of high-latitude ocean temperatures in greenhouse climates. The pronounced zonal SST heterogeneity evident in the Eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands. PMID:24753570

The Role of Clear Sky Identification in the Study of Cloud Radiative Effects: Combine Analysis from ISCCP and the Scanner of Radiation Budget (ScaRaB)

NASA Technical Reports Server (NTRS)

Rossow, W. B.; Stubenrauch, C. J.; Briand, V.; Hansen, James E. (Technical Monitor)

2001-01-01

Since the effect of clouds on the earth's radiation balance is often estimated as the difference of net radiative fluxes at the top of the atmosphere between all situations and monthly averaged clear sky situations of the same regions, a reliable identification of clear sky is important for the study of cloud radiative effects. The Scanner for Radiation Balance (ScaRaB) radiometer on board the Russian Meteor-3/7 satellite provided earth radiation budget observations from March 1994 to February 1995 with two ERBE-Re broad-band longwave and shortwave channels. Two narrow-band channels, in the infrared atmospheric window and in the visible band, have been added to the ScaRaB instrument to improve the cloud scene identification. The International Satellite Cloud Climatology Project (ISCCP) method for cloud detection and determination of cloud and surface properties uses the same narrow-band channels as ScaRaB, but is employed to a collection of measurements at a better spatial resolution of about 5 km. By applying the original ISCCP algorithms to the ScaRaB data, the clear sky frequency is about 5% lower than the one over quasi-simultaneous original ISCCP data, an indication that the ISCCP cloud detection is quite stable. However, one would expect an about 10 to 20% smaller clear sky occurrence over the larger ScaRaB pixels. Adapting the ISCCP algorithms to the reduced spatial resolution of 60 km and to the different time sampling of the ScaRaB data leads therefore to a reduction of a residual cloud contamination. A sensitivity study with time-space collocated ScaRaB and original ISCCP data at a spatial resolution of 1deg longitude x 1deg latitude shows that the effect of clear sky identification method plays a higher role on the clear sky frequency and therefore on the statistics than on the zonal mean values of the clear sky fluxes. Nevertheless, the zonal outgoing longwave fluxes corresponding to ERBE clear sky are in general about 2 to 10 W/sq m higher than those obtained from the ScaRaB adapted ISCCP clear sky identifications. The latter are close to (about 1 W/sq m higher) fluxes corresponding to clear sky regions from original ISCCP data, whereas ScaRaB clear sky LW fluxes obtained with the original ISCCP identification lie about 1 to 2 W/sq m below. Especially in the tropics where water vapor abundance is high, the ERBE clear sky LW fluxes seem to be systematically overestimated by about 4 W/sq m, and SW fluxes are lower by about 5 to 10 W/sq m. However, the uncertainty in the analysis of monthly mean zonal cloud radiative effects is also produced by the low frequency of clear sky occurrence, illustrated when averaging over pixels or even over regions of 4deg longitude x 5deg latitude, corresponding to the spatial resolution of General Circulation Models. The systematic bias in the clear sky fluxes is not reflected in the zonal cloud radiative effects, because the clear sky regions selected by the different algorithms can occur in different geographic regions with different cloud properties.

Cause of different local time distribution in the postsunset equatorial ionospheric irregularity occurrences between June and December solstices

NASA Astrophysics Data System (ADS)

Su, S.-Y.; Chao, C. K.; Liu, C. H.

2009-04-01

Global averaged postsunset equatorial ionospheric density irregularity occurrences observed by ROCSAT during the moderate to high solar activity years of 1999 to 2004 indicate a different local time distribution between June and December solstices. The irregularity occurrences during the December solstice show a faster increase rate to peak at 2100-2200 local time, while the irregularity occurrences during the June solstice have a slower increase rate and peak one hour later in local time than that in the December solstice. The cause of such different local time distributions is attributed to a large contrast in the time of zonal drift reversal and the magnitude of postsunset vertical drift observed by ROCSAT at longitudes of large magnetic declination in the two solstices. That is, a delay in the zonal drift reversal in association with a smaller postsunset vertical drift observed at longitudes of positive magnetic declination has greatly inhibited the irregularity occurrences during the June solstice in contrast to an earlier zonal drift reversal together with a large vertical drift occurring at longitudes of negative magnetic declination to accelerate the irregularity occurrences during the December solstice. We think that the different geomagnetic field strengths that existed between the longitudes of positive and negative magnetic declinations have played a crucial role in determining the different local time distributions of irregularity occurrences for the two solstices.

Influence of large-scale zonal flows on the evolution of stellar and planetary magnetic fields

NASA Astrophysics Data System (ADS)

Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel; ENS Collaboration

2011-10-01

Zonal flows and magnetic field are present in various objects as accretion discs, stars and planets. Observations show a huge variety of stellar and planetary magnetic fields. Of particular interest is the understanding of cyclic field variations, as known from the sun. They are often explained by an important Ω-effect, i.e., by the stretching of field lines because of strong differential rotation. We computed the dynamo coefficients for an oscillatory dynamo model with the help of the test-field method. We argue that this model is of α2 Ω -type and here the Ω-effect alone is not responsible for its cyclic time variation. More general conditions which lead to dynamo waves in global direct numerical simulations are presented. Zonal flows driven by convection in planetary interiors may lead to secondary instabilities. We showed that a simple, modified version of the MagnetoRotational Instability, i.e., the MS-MRI can develop in planteray interiors. The weak shear yields an instability by its constructive interaction with the much larger rotation rate of planets. We present results from 3D simulations and show that 3D MS-MRI modes can generate wave pattern at the surface of the spherical numerical domain. Zonal flows and magnetic field are present in various objects as accretion discs, stars and planets. Observations show a huge variety of stellar and planetary magnetic fields. Of particular interest is the understanding of cyclic field variations, as known from the sun. They are often explained by an important Ω-effect, i.e., by the stretching of field lines because of strong differential rotation. We computed the dynamo coefficients for an oscillatory dynamo model with the help of the test-field method. We argue that this model is of α2 Ω -type and here the Ω-effect alone is not responsible for its cyclic time variation. More general conditions which lead to dynamo waves in global direct numerical simulations are presented. Zonal flows driven by convection in planetary interiors may lead to secondary instabilities. We showed that a simple, modified version of the MagnetoRotational Instability, i.e., the MS-MRI can develop in planteray interiors. The weak shear yields an instability by its constructive interaction with the much larger rotation rate of planets. We present results from 3D simulations and show that 3D MS-MRI modes can generate wave pattern at the surface of the spherical numerical domain. The first author thanks DFG and PlanetMag project for financial support.

Global Three-Dimensional Atmospheric Structure of the Atlantic Multidecadal Oscillation as Revealed by Two Reanalyses

NASA Astrophysics Data System (ADS)

Stuckman, Scott Seele

This study is a first documentation of the structure of the entire AMO life cycle, including extreme and transition phases, throughout the global troposphere. The extreme phase climate signature is constructed based on the strongest and most robust patterns identified by two methods (linear correlation and composite analyses), two reanalysis datasets (the National Centers for Environmental Prediction/National Center for Atmospheric Research and Twentieth Century Reanalysis, supplemented with precipitation data from the University of Delaware dataset) and data from two consecutive AMO cycles. The first characterization of the AMO transition phases uses a transition index based on the time derivative of AMO index. When trying to compare the zonal mean structure of AMO with the El Niño-Southern Oscillation (ENSO), a literature search showed the zonal mean structure of ENSO remained unpublished, despite the otherwise generally well-characterized horizontal structures. Therefore this study includes a seasonal analysis of the ENSO zonal mean structure during boreal winter (DJF) and summer (JJA). The AMO extreme phase is characterized by a blend of low and middle latitude centers of action, with the associated tilt of geopotential height anomaly patterns consistent with off-equatorial heating patterns generated by the Held idealized model. The surface climate signature is connected to the upper air with baroclinic vertical structure over the North Atlantic but barotropic structures elsewhere. The associated zonal mean circulation features three circulation cells globally with strong inter-hemispheric mixing that suggests the traditional view of the AMO involving a Northern-Southern Hemisphere asymmetry is accurate only near the surface. The AMO transition phase features a more equatorial-based climate signature and associated geopotential height anomaly patterns consistent with the Matsuno-Gill idealized model. The zonal mean circulation of the transition phases features six, rather than three, circulation cells globally. The only baroclinic structure, over North America, and several barotropic structures are positioned west of corresponding similar structures during the AMO extreme phase, suggesting an eastward evolution of climate anomalies as the AMO progresses from a cool-to-warm transition phase to warm phase. The Pacific-based climate signature resembles the IPO warm phase and it is proposed the AMO and IPO are different basin-wide expressions of a single multidecadal oscillation. The identification of an AMO transition phase climate signature distinct from the extreme phase suggests transition phases are not neutral and may provide an additional source of information for characterizing climate cycles.

Geographic distribution of zonal wind and UV albedo at cloud top level from VMC camera on Venus Express: Influence of Venus topography through stationary gravity waves vertical propagation.

NASA Astrophysics Data System (ADS)

Bertaux, Jean-Loup; Khatunstsev, Igor; Hauchecorne, Alain; Markiewicz, Wojciech; Marcq, Emmanuel; Lebonnois, Sébastien; Patsaeva, Marina; Turin, Alexander

2015-04-01

UV images (at 365 nm) of Venus cloud top collected with VMC camera on board Venus Express allowed to derive a large number of wind measurements at altitude 67±2 km from tracking of cloud features in the period 2006-2012. Both manual (45,600) and digital (391,600) individual wind measurements over 127 orbits were analyzed showing various patterns with latitude and local time. A new longitude-latitude geographic map of the zonal wind shows a conspicuous region of strongly decreased zonal wind, a remarkable feature that was unknown up to now. While the average zonal wind near equator (from 5°S to 15°s) is -100.9 m/s in the longitude range 200-330°, it reaches -83.4 m/s in the range 60-100°, a difference of 17.5 m/s. When compared to the altimetry map of Venus, it is found that the zonal wind pattern is well correlated with the underlying relief in the region of Aphrodite Terra, with a downstream shift of about 30° (˜3,200 km). We interpret this pattern as the result of stationary gravity waves produced at ground level by the up lift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to cloud top level, break there and transfer their momentum to the zonal flow. A similar phenomenon is known to operate on Earth with an influence on mesospheric winds. The LMD-GCM for Venus was run with or without topography, with and without a parameterization of gravity waves and does not display such an observed change of velocity near equator. The cloud albedo map at 365 nm varies also in longitude and latitude. We speculate that it might be the result of increased vertical mixing associated to wave breaking, and decreased abundance of the UV absorber which makes the contrast in images. The impact of these new findings on current super rotation theories remains to be assessed. This work was triggered by the presence of a conspicuous peak at 117 days in a time series of wind measurements. This is the length of the solar day as seen at the ground of Venus. Since VMC measurements are done preferably in a local time window centred on the sub-solar point, any parameter having a geographic longitude dependence will show a peak at 117 days.

Southern Hemisphere Carbon Monoxide Inferannual Variability Observed by Terra/Measurement of Pollution in the Troposphere (MOPITT)

NASA Technical Reports Server (NTRS)

Edwards, D. P.; Petron, G.; Novelli, P. C.; Emmons, L. K.; Gille, J. C.; Drummond, J. R.

2010-01-01

Biomass burning is an annual occurrence in the tropical southern hemisphere (SH) and represents a major source of regional pollution. Vegetation fires emit carbon monoxide (CO), which due to its medium lifetime is an excellent tracer of tropospheric transport. CO is also one of the few tropospheric trace gases currently observed from satellite and this provides long-term global measurements. In this paper, we use the 5 year CO data record from the Measurement Of Pollution In The Troposphere (MOPITT) instrument to examine the inter-annual variability of the SH CO loading and show how this relates to climate conditions which determine the intensity of fire sources. The MOPITT observations show an annual austral springtime peak in the SH zonal CO loading each year with dry-season biomass burning emissions in S. America, southern Africa, the Maritime Continent, and northwestern Australia. Although fires in southern Africa and S. America typically produce the greatest amount of CO, the most significant inter-annual variation is due to varying fire activity and emissions from the Maritime Continent and northern Australia. We find that this variation in turn correlates well with the El Nino Southern Oscillation precipitation index. Between 2000 and 2005, emissions were greatest in late 2002 and an inverse modeling of the MOPITT data using the MOZART chemical transport model estimates the southeast Asia regional fire source for the year August 2002 to September 2003 to be 52 Tg CO. Comparison of the MOPITT retrievals and NOAA surface network measurements indicate that the latter do not fully capture the inter-annual variability or the seasonal range of the CO zonal average concentration due to biases associated with atmospheric and geographic sampling.

Large-Scale Traveling Weather Systems in Mars’ Southern Extratropics

NASA Astrophysics Data System (ADS)

Hollingsworth, Jeffery L.; Kahre, Melinda A.

2017-10-01

Between late fall and early spring, Mars’ middle- and high-latitude atmosphere supports strong mean equator-to-pole temperature contrasts and an accompanying mean westerly polar vortex. Observations from both the MGS Thermal Emission Spectrometer (TES) and the MRO Mars Climate Sounder (MCS) indicate that a mean baroclinicity-barotropicity supports intense, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). Such extratropical weather disturbances are critical components of the global circulation as they serve as agents in the transport of heat and momentum, and generalized scalar/tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). The character of such traveling extratropical synoptic disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This Mars GCM imposes interactively-lifted and radiatively-active dust based on a threshold value of the surface stress. The model exhibits a reasonable "dust cycle" (i.e., globally averaged, a dustier atmosphere during southern spring and summer occurs). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

Large-Scale Traveling Weather Systems in Mars Southern Extratropics

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery L.; Kahre, Melinda A.

2017-01-01

Between late fall and early spring, Mars' middle- and high-latitude atmosphere supports strong mean equator-to-pole temperature contrasts and an accompanying mean westerly polar vortex. Observations from both the MGS Thermal Emission Spectrometer (TES) and the MRO Mars Climate Sounder (MCS) indicate that a mean baroclinicity-barotropicity supports intense, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). Such extratropical weather disturbances are critical components of the global circulation as they serve as agents in the transport of heat and momentum, and generalized scalar/tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). The character of such traveling extratropical synoptic disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This Mars GCM imposes interactively-lifted and radiatively-active dust based on a threshold value of the surface stress. The model exhibits a reasonable "dust cycle" (i.e., globally averaged, a dustier atmosphere during southern spring and summer occurs). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

Rossby waves and two-dimensional turbulence in a large-scale zonal jet

NASA Technical Reports Server (NTRS)

Shepherd, Theodor G.

1987-01-01

Homogeneous barotropic beta-plane turbulence is investigated, taking into account the effects of spatial inhomogeneity in the form of a zonal shear flows. Attention is given to the case of zonal flows that are barotropically stable and of larger scale than the resulting transient eddy field. Numerical simulations reveal that large-scale zonal flows alter the picture of classical beta-plane turbulence. It is found that the disturbance field penetrates to the largest scales of motion, that the larger disturbance scales show a tendency to meridional rather than zonal anisotropy, and that the initial spectral transfer rate away from an isotropic intermediate-scale source is enhanced by the shear-induced transfer associated with straining by the zonal flow.

Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events

PubMed Central

Mann, Michael E.; Rahmstorf, Stefan; Kornhuber, Kai; Steinman, Byron A.; Miller, Sonya K.; Coumou, Dim

2017-01-01

Persistent episodes of extreme weather in the Northern Hemisphere summer have been shown to be associated with the presence of high-amplitude quasi-stationary atmospheric Rossby waves within a particular wavelength range (zonal wavenumber 6–8). The underlying mechanistic relationship involves the phenomenon of quasi-resonant amplification (QRA) of synoptic-scale waves with that wavenumber range becoming trapped within an effective mid-latitude atmospheric waveguide. Recent work suggests an increase in recent decades in the occurrence of QRA-favorable conditions and associated extreme weather, possibly linked to amplified Arctic warming and thus a climate change influence. Here, we isolate a specific fingerprint in the zonal mean surface temperature profile that is associated with QRA-favorable conditions. State-of-the-art (“CMIP5”) historical climate model simulations subject to anthropogenic forcing display an increase in the projection of this fingerprint that is mirrored in multiple observational surface temperature datasets. Both the models and observations suggest this signal has only recently emerged from the background noise of natural variability. PMID:28345645

Representativeness of single lidar stations for zonally averaged ozone profiles, their trends and attribution to proxies

NASA Astrophysics Data System (ADS)

Zerefos, Christos; Kapsomenakis, John; Eleftheratos, Kostas; Tourpali, Kleareti; Petropavlovskikh, Irina; Hubert, Daan; Godin-Beekmann, Sophie; Steinbrecht, Wolfgang; Frith, Stacey; Sofieva, Viktoria; Hassler, Birgit

2018-05-01

This paper is focusing on the representativeness of single lidar stations for zonally averaged ozone profile variations over the middle and upper stratosphere. From the lower to the upper stratosphere, ozone profiles from single or grouped lidar stations correlate well with zonal means calculated from the Solar Backscatter Ultraviolet Radiometer (SBUV) satellite overpasses. The best representativeness with significant correlation coefficients is found within ±15° of latitude circles north or south of any lidar station. This paper also includes a multivariate linear regression (MLR) analysis on the relative importance of proxy time series for explaining variations in the vertical ozone profiles. Studied proxies represent variability due to influences outside of the earth system (solar cycle) and within the earth system, i.e. dynamic processes (the Quasi Biennial Oscillation, QBO; the Arctic Oscillation, AO; the Antarctic Oscillation, AAO; the El Niño Southern Oscillation, ENSO), those due to volcanic aerosol (aerosol optical depth, AOD), tropopause height changes (including global warming) and those influences due to anthropogenic contributions to atmospheric chemistry (equivalent effective stratospheric chlorine, EESC). Ozone trends are estimated, with and without removal of proxies, from the total available 1980 to 2015 SBUV record. Except for the chemistry related proxy (EESC) and its orthogonal function, the removal of the other proxies does not alter the significance of the estimated long-term trends. At heights above 15 hPa an inflection point between 1997 and 1999 marks the end of significant negative ozone trends, followed by a recent period between 1998 and 2015 with positive ozone trends. At heights between 15 and 40 hPa the pre-1998 negative ozone trends tend to become less significant as we move towards 2015, below which the lower stratosphere ozone decline continues in agreement with findings of recent literature.

The anomalous circulation associated with the ENSO-related west Pacific sea surface temperature gradient

USGS Publications Warehouse

Hoell, Andrew; Funk, Christopher C.

2013-01-01

The temporal evolution and distribution of Pacific SST as well as the near-surface tropical Pacific zonal wind, tropical divergence and vertical velocity are considerably different during ENSO events partitioned according to the strength of the WPG. Modifications to the tropical circulation result in changes to the Indo-west Pacific precipitation and vertically integrated energy budgets and are linked to strong and consistent circulation and precipitation modifications throughout the Northern Hemisphere during winter.

Influence of the 11-year solar cycle on the effects of the equatorial quasi-biennial oscillation, manifesting in the extratropical northern atmosphere

NASA Astrophysics Data System (ADS)

Sitnov, S. A.

2009-01-01

Using the longest and most reliable ozonesonde data sets grouped for four regions (Japan, Europe, as well as temperate and polar latitudes of Canada) the comparative analysis of regional responses of ozone, temperature, horizontal wind, tropopause and surface pressure on the equatorial quasi-biennial oscillation (QBO effects), manifesting in opposite phases of the 11-year solar cycle (11-yr SC) was carried out. The impact of solar cycle is found to be the strongest at the Canadian Arctic, near one of two climatological centres of polar vortex, where in solar maximum conditions the QBO signals in ozone and temperature have much larger amplitudes, embrace greater range of heights, and are maximized much higher than those in solar minimum conditions. The strengthening of the temperature QBO effect during solar maxima can explain why correlation between the 11-yr SC and polar winter stratospheric temperature is reversed in the opposite QBO phases. At the border of polar vortex the 11-yr SC also modulates the QBO effect in zonal wind, strengthening the quasi-biennial modulation of polar vortex during solar maxima that is associated with strong negative correlation between stratospheric QBO signals in zonal wind and temperature. Above Japan the QBO effects of ozone, temperature, and zonal wind, manifesting in solar maxima reveal the downward phase dynamics, reminding similar feature of the zonal wind in the equatorial stratosphere. Above Europe, the QBO effects in solar maxima reveal more similarity with those above Japan, while in solar minima with the effects obtained at the Canadian middle-latitude stations. It is revealed that the 11-yr SC influences regional QBO effects in tropopause height, tropopause temperature and surface pressure. The influence most distinctly manifest itself in tropopause characteristics above Japan. The results of the accompanying analysis of the QBO reference time series testify that in the period of 1965-2006 above 50-hPa level the duration of the QBO cycle in solar maxima is 1-3 months longer than in solar minima. The differences are more distinct at higher levels, but they are diminished with lengthening of the period.

Discrimination between mineralized and unmineralized alteration zones using primary geochemical haloes in the Darreh-Zar porphyry copper deposit in Kerman, southeastern Iran

NASA Astrophysics Data System (ADS)

Parsapoor, A.; Khalili, M.; Maghami, M.

2017-08-01

Primary geochemical haloes were studied at the Darreh-Zar porphyry Cu-deposit, southern Iran. In terms of geochemical signatures, high K2O/Na2O enrichment, HREEs and HFSE's depletion in the potassic alteration, high (La/Sm)cn, (La/Yb)cn and (Gd/Yb)cn ratios in mineralized sericitic and potassic zones and notable depletion in the REEs content in argillic alteration is recognized. Further, Mg, Li, Sc, P enrichment and W depletion can serve to separate potassic alteration from the other altered zones, while (Eu/Eu*)cn and (Ce/Ce*)cn don't show pronounced changes in different alteration zones. The coupled positive Tl, Se, S, Rb, Co, Cs, Mo, K and negative Te, Ta, Ti, Sr, Rb, As, Bi, Ga, Hf, In, Mn, Zn and Zr anomalies can be adequately used in discriminating between the mineralized zones (potassic, chlorite-sericite and sericite alterations) and the barren (propylitic zone). The behavior of the trace elements on isocon diagrams reveal that HFSEs are depleted in mineralized altered zones and display variations in the amounts in the barren facies. Zonality index in the axial direction from drill holes 146 to 124 estimates the zonality sequence as Pb-Zn-Ag-Cu-Pb-Zn in the surface horizons. The calculated zonality in five drill holes and six levels indicates that the level of 550 m at the DH 117 in the central part of the area has the highest value (0.76) for Cu. The zonality sequence from the surface to the depth is variable and can be demonstrated as follow: DH 146: Pb-Zn-Cu-Mo-Ag; DH 137: Zn-Cu-Mo-Pb-Ag; DH 117: Ag-Zn-Pb-Mo-Cu; DH: 121: Cu-Mo-Zn-Ag-Pb; DH 136: Pb-Ag-Zn-Cu-Mo; DH 124: Zn-Mo-Cu-Pb-Ag. Available data of the enrichment factors shows different enrichment for copper and molybdenum (i.e. EF > 10), selenium and silver (i.e. EF > 5), tin and LREEs (i.e. 1 < EF < 5).

A flexible climate model for use in integrated assessments

NASA Astrophysics Data System (ADS)

Sokolov, A. P.; Stone, P. H.

Because of significant uncertainty in the behavior of the climate system, evaluations of the possible impact of an increase in greenhouse gas concentrations in the atmosphere require a large number of long-term climate simulations. Studies of this kind are impossible to carry out with coupled atmosphere ocean general circulation models (AOGCMs) because of their tremendous computer resource requirements. Here we describe a two dimensional (zonally averaged) atmospheric model coupled with a diffusive ocean model developed for use in the integrated framework of the Massachusetts Institute of Technology (MIT) Joint Program on the Science and Policy of Global Change. The 2-D model has been developed from the Goddard Institute for Space Studies (GISS) GCM and includes parametrizations of all the main physical processes. This allows it to reproduce many of the nonlinear interactions occurring in simulations with GCMs. Comparisons of the results of present-day climate simulations with observations show that the model reasonably reproduces the main features of the zonally averaged atmospheric structure and circulation. The model's sensitivity can be varied by changing the magnitude of an inserted additional cloud feedback. Equilibrium responses of different versions of the 2-D model to an instantaneous doubling of atmospheric CO2 are compared with results of similar simulations with different AGCMs. It is shown that the additional cloud feedback does not lead to any physically inconsistent results. On the contrary, changes in climate variables such as precipitation and evaporation, and their dependencies on surface warming produced by different versions of the MIT 2-D model are similar to those shown by GCMs. By choosing appropriate values of the deep ocean diffusion coefficients, the transient behavior of different AOGCMs can be matched in simulations with the 2-D model, with a unique choice of diffusion coefficients allowing one to match the performance of a given AOGCM for a variety of transient forcing scenarios. Both surface warming and sea level rise due to thermal expansion of the deep ocean in response to a gradually increasing forcing are reasonably reproduced on time scales of 100-150 y. However a wide range of diffusion coefficients is needed to match the behavior of different AOGCMs. We use results of simulations with the 2-D model to show that the impact on climate change of the implied uncertainty in the rate of heat penetration into the deep ocean is comparable with that of other significant uncertainties.

Transport in zonal flows in analogous geophysical and plasma systems

NASA Astrophysics Data System (ADS)

del-Castillo-Negrete, Diego

1999-11-01

Zonal flows occur naturally in the oceans and the atmosphere of planets. Important examples include the zonal flows in Jupiter, the stratospheric polar jet in Antarctica, and oceanic jets like the Gulf Stream. These zonal flows create transport barriers that have a crucial influence on mixing and confinement (e.g. the ozone depletion in Antarctica). Zonal flows also give rise to long-lasting vortices (e.g. the Jupiter red spot) by shear instability. Because of this, the formation and stability of zonal flows and their role on transport have been problems of great interest in geophysical fluid dynamics. On the other hand, zonal flows have also been observed in fusion plasmas and their impact on the reduction of transport has been widely recognized. Based on the well-known analogy between Rossby waves in quasigeostrophic flows and drift waves in magnetically confined plasmas, I will discuss the relevance to fusion plasmas of models and experiments recently developed in geophysical fluid dynamics. Also, the potential application of plasma physics ideas to geophysical flows will be discussed. The role of shear in the suppression of transport and the effect of zonal flows on the statistics of transport will be studied using simplified models. It will be shown how zonal flows induce large particle displacements that can be characterized as Lévy flights, and that the trapping effect of vortices combined with the zonal flows gives rise to anomalous diffusion and Lévy (non-Gaussian) statistics. The models will be compared with laboratory experiments and with atmospheric and oceanographic qualitative observations.

Assessing the Importance of the Evaporation-Wind Feedback Mechanism in the Modulation of Simulated Madden-Julian Oscillations

NASA Technical Reports Server (NTRS)

Colon, Edward; Lindesay, James; Suarez, Max J.

1998-01-01

An examination of simulated Madden-Julian Oscillation (MJO) response to active and suppressed air-sea interactions is made using an aquaplanet model employing a realistic representation of the hydrologic cyle. In general, the evaporation-wind feedback (EWF) results from a coupling between tropical zonal surface wind stresses and evaporation anomalies. Recent observational and theoretical studies have questioned the significance of EWF in sustaining the predominantly wavenumber 1 eastward propagating mode commonly attributed to the interaction between large scale convergence and cumulus-scale convection (conditional instability of the second kind, CISK). To ascertain the nature of the EWF dependence on lower boundary conditions and thus quantify its effect on MJO development, a series of numerical experiments were conducted employing various zonally symmetric sea surface temperature (SST) distributions with active and suppressed EWF mechanisms. Results suggest that a correlation exists between tropical SSTs and the efficacy of the EWF in vertically redistributing heat acquired through surface wind stresses. It has been determined that the removal of the EWF is not a crucial factor in the dampening of the simulated MJO at high equatorial SSTs. The additional energy fed into the developing convective mode by the EWF selectively amplifies higher order wave modes in all numerical experiments thus boosting overall variances in oscillatory responses.

Simulations of Bluff Body Flow Interaction for Noise Source Modeling

NASA Technical Reports Server (NTRS)

Khorrami, Medi R.; Lockard David P.; Choudhari, Meelan M.; Jenkins, Luther N.; Neuhart, Dan H.; McGinley, Catherine B.

2006-01-01

The current study is a continuation of our effort to characterize the details of flow interaction between two cylinders in a tandem configuration. This configuration is viewed to possess many of the pertinent flow features of the highly interactive unsteady flow field associated with the main landing gear of large civil transports. The present effort extends our previous two-dimensional, unsteady, Reynolds Averaged Navier-Stokes computations to three dimensions using a quasilaminar, zonal approach, in conjunction with a two-equation turbulence model. Two distinct separation length-to-diameter ratios of L/D = 3.7 and 1.435, representing intermediate and short separation distances between the two cylinders, are simulated. The Mach 0.166 simulations are performed at a Reynolds number of Re = 1.66 105 to match the companion experiments at NASA Langley Research Center. Extensive comparisons with the measured steady and unsteady surface pressure and off-surface particle image velocimetry data show encouraging agreement. Both prominent and some of the more subtle trends in the mean and fluctuating flow fields are correctly predicted. Both computations and the measured data reveal a more robust and energetic shedding process at L/D = 3.7 in comparison with the weaker shedding in the shorter separation case of L/D = 1.435. The vortex shedding frequency based on the computed surface pressure spectra is in reasonable agreement with the measured Strouhal frequency.

Stable isotopes in water vapor and rainwater over Indian sector of Southern Ocean and estimation of fraction of recycled moisture.

PubMed

Rahul, P; Prasanna, K; Ghosh, Prosenjit; Anilkumar, N; Yoshimura, Kei

2018-05-15

Stable Hydrogen and Oxygen isotopic composition of water vapor, rainwater and surface seawater show a distinct trend across the latitude over the Southern Indian Ocean. Our observations on isotopic composition of surface seawater, water vapor and rainwater across a transect covering the tropical Indian Ocean to the regions of the Southern Ocean showed a strong latitudinal dependency; characterized by the zonal process of evaporation and precipitation. The sampling points were spread across diverse zones of SST, wind speed and rainfall regimes. The observed physical parameters such as sea surface temperature, wind speed and relative humidity over the oceanic regions were used in a box model calculation across the latitudes to predict the isotopic composition of water vapor under equilibrium and kinetic conditions, and compared with results from isotope enabled global spectral model. Further, we obtained the average fraction of recycled moisture across the oceanic transect latitudes as 13.4 ± 7.7%. The values of recycled fraction were maximum at the vicinity of the Inter Tropical Convergence Zone (ITCZ), while the minimum values were recorded over the region of subsidence and evaporation, at the Northern and Southern latitudes of the ITCZ. These estimates are consistent with the earlier reported recyling values.

Statistical analysis of Hasegawa-Wakatani turbulence

NASA Astrophysics Data System (ADS)

Anderson, Johan; Hnat, Bogdan

2017-06-01

Resistive drift wave turbulence is a multipurpose paradigm that can be used to understand transport at the edge of fusion devices. The Hasegawa-Wakatani model captures the essential physics of drift turbulence while retaining the simplicity needed to gain a qualitative understanding of this process. We provide a theoretical interpretation of numerically generated probability density functions (PDFs) of intermittent events in Hasegawa-Wakatani turbulence with enforced equipartition of energy in large scale zonal flows, and small scale drift turbulence. We find that for a wide range of adiabatic index values, the stochastic component representing the small scale turbulent eddies of the flow, obtained from the autoregressive integrated moving average model, exhibits super-diffusive statistics, consistent with intermittent transport. The PDFs of large events (above one standard deviation) are well approximated by the Laplace distribution, while small events often exhibit a Gaussian character. Furthermore, there exists a strong influence of zonal flows, for example, via shearing and then viscous dissipation maintaining a sub-diffusive character of the fluxes.

Dynamical component of seasonal and year-to-year changes in Antarctic and global ozone

NASA Technical Reports Server (NTRS)

Tung, Ka Kit; Yang, HU

1988-01-01

The dynamics of the ozone concetration components of the Antarctic ozone hole as related to seasonal and year-to-year temperature changes in August, September, October, and November during the 1979-1985 period is studied using a zonally averaged model in which all transport fields are fixed by input temperature data. The results suggest that, prior to 1984, both the seasonal and year-to year variability of the zonal-mean Antarctic ozone minimum and the surrounding maximum can be accounted for by temperature dynamics without invoking changes in chemical composition (e.g., chlorine content) or special chemistry. The same dynamical mechanism also accounts for the good simulation of the observed seasonal and latitudinal structure of column ozone in other parts of the world. However, chemical depletion of ozone may have become more important after 1984. The model also appears to underpredict the September ozone decline in years, leading to an underprediction of the recent minimum values in the Antarctic ozone hole.

Tropospheric jet response to Antarctic ozone depletion: An update with Chemistry-Climate Model Initiative (CCMI) models

NASA Astrophysics Data System (ADS)

Son, Seok-Woo; Han, Bo-Reum; Garfinkel, Chaim I.; Kim, Seo-Yeon; Park, Rokjin; Abraham, N. Luke; Akiyoshi, Hideharu; Archibald, Alexander T.; Butchart, N.; Chipperfield, Martyn P.; Dameris, Martin; Deushi, Makoto; Dhomse, Sandip S.; Hardiman, Steven C.; Jöckel, Patrick; Kinnison, Douglas; Michou, Martine; Morgenstern, Olaf; O’Connor, Fiona M.; Oman, Luke D.; Plummer, David A.; Pozzer, Andrea; Revell, Laura E.; Rozanov, Eugene; Stenke, Andrea; Stone, Kane; Tilmes, Simone; Yamashita, Yousuke; Zeng, Guang

2018-05-01

The Southern Hemisphere (SH) zonal-mean circulation change in response to Antarctic ozone depletion is re-visited by examining a set of the latest model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project. All models reasonably well reproduce Antarctic ozone depletion in the late 20th century. The related SH-summer circulation changes, such as a poleward intensification of westerly jet and a poleward expansion of the Hadley cell, are also well captured. All experiments exhibit quantitatively the same multi-model mean trend, irrespective of whether the ocean is coupled or prescribed. Results are also quantitatively similar to those derived from the Coupled Model Intercomparison Project phase 5 (CMIP5) high-top model simulations in which the stratospheric ozone is mostly prescribed with monthly- and zonally-averaged values. These results suggest that the ozone-hole-induced SH-summer circulation changes are robust across the models irrespective of the specific chemistry-atmosphere-ocean coupling.

Effects of the 2004 El Nino on Tropospheric Ozone and Water Vapor

NASA Technical Reports Server (NTRS)

Chandra, S.; Ziemke, J. R.; Schoeberl, M. R.; Froidevaux, L.; Read, W. G.; Levelt, P. F.; Bhartia, P. K.

2007-01-01

The global effects of the 2004 El Nino on tropospheric ozone and H2O based on Aura OM1 and MLS measurements are analyzed. Although it was a weak El Nino from a historical perspective, it produced significant changes in these parameters in tropical latitudes. Tropospheric ozone increased by 10-20% over most of the western Pacific region and decreased by about the same amount over the eastern Pacific region. H2O in the upper troposphere showed similar changes but with opposite sign. These zonal changes in tropospheric ozone and H2O are caused by the eastward shift in the Walker circulation in the tropical pacific region during El Nino. For the 2004 El Nino, biomass burning did not have a significant effect on the ozone budget in the troposphere unlike the 1997 El Nino. Zonally averaged tropospheric column ozone did not change significantly either globally or over the tropical and subtropical latitudes.

Substorm-related thermospheric density and wind disturbances

NASA Astrophysics Data System (ADS)

Ritter, P.; Luhr, H.; Doornbos, E. N.

2009-12-01

The input of energy and momentum from the magnetosphere is most efficiently coupled into the high latitude ionosphere-thermosphere. The phenomenon we are focusing on here is the magnetospheric substorm. This paper presents substorm related observations of the thermosphere derived from the CHAMP satellite. With its sensitive accelerometer the satellite can measure the air density and zonal winds. Based on a large number of substorm events the average high and low latitude thermosphere response to substorm onsets was deduced. During magnetic substorms the thermospheric density is enhanced first at high latitudes. Then the disturbance travels at sonic speed to lower latitudes, and 3-4 hours later the bulge reaches the equator on the night side. Under the influence of the Coriolis force the traveling atmospheric disturbance (TAD) is deflected westward. In accordance with present-day atmospheric models the disturbance zonal wind velocities during substorms are close to zero near the equator before midnight and attain moderate westward velocities after midnight. In general, the wind system is only weakly perturbed by substorms.

Elliptic generation of composite three-dimensional grids about realistic aircraft

NASA Technical Reports Server (NTRS)

Sorenson, R. L.

1986-01-01

An elliptic method for generating composite grids about realistic aircraft is presented. A body-conforming grid is first generated about the entire aircraft by the solution of Poisson's differential equation. This grid has relatively coarse spacing, and it covers the entire physical domain. At boundary surfaces, cell size is controlled and cell skewness is nearly eliminated by inhomogeneous terms, which are found automatically by the program. Certain regions of the grid in which high gradients are expected, and which map into rectangular solids in the computational domain, are then designated for zonal refinement. Spacing in the zonal grids is reduced by adding points with a simple, algebraic scheme. Details of the grid generation method are presented along with results of the present application, a wing-body configuration based on the F-16 fighter aircraft.

The Study Of Soil And Agrochemical Features Of Zonal Soils Of Coal Mining Enterprises In Kemerovo Region

NASA Astrophysics Data System (ADS)

Yakovchenko, M. A.; Kosolapova, A. A.; Ermolaev, V. A.

2017-01-01

The paper represents the results of the study of soil and agrochemical features of zonal soils: the grain-size composition, the content of humus, phosphorus and potassium, and heavy metals, the reaction of soil solution of the territory of the open-pit coal mine No12 of Kemerovo region in the areas of the working enterprise. The species composition of the lignose and herbaceous vegetation of the undisturbed territories has been studied. It has been revealed that the fertile soil layer of the studied areas of the open-pit coal mine is characterized as fertile but can’t be removed and stored because the surface of the whole area under study is forest-covered very much, rumpled, there are gullies and a lot of wind-fallen trees.

Saturn’s gravitational field induced by its equatorially antisymmetric zonal winds

NASA Astrophysics Data System (ADS)

Kong, Dali; Zhang, Keke; Schubert, Gerald; Anderson, John D.

2018-05-01

The cloud-level zonal winds of Saturn are marked by a substantial equatorially antisymmetric component with a speed of about 50ms‑1 which, if they are sufficiently deep, can produce measurable odd zonal gravitational coefficients ΔJ 2k+1, k = 1, 2, 3, 4. This study, based on solutions of the thermal-gravitational wind equation, provides a theoretical basis for interpreting the odd gravitational coefficients of Saturn in terms of its equatorially antisymmetric zonal flow. We adopt a Saturnian model comprising an ice-rock core, a metallic dynamo region and an outer molecular envelope. We use an equatorially antisymmetric zonal flow that is parameterized, confined in the molecular envelope and satisfies the solvability condition required for the thermal-gravitational wind equation. The structure and amplitude of the zonal flow at the cloud level are chosen to be consistent with observations of Saturn. We calculate the odd zonal gravitational coefficients ΔJ 2k+1, k = 1, 2, 3, 4 by regarding the depth of the equatorially antisymmetric winds as a parameter. It is found that ΔJ 3 is ‑4.197 × 10‑8 if the zonal winds extend about 13 000 km downward from the cloud tops while it is ‑0.765 × 10‑8 if the depth is about 4000 km. The depth/profile of the equatorially antisymmetric zonal winds can eventually be estimated when the high-precision measurements of the Cassini Grand Finale become available.

Exploring the Propagation of the Madden-Julian Oscillation (MJO) across the Maritime Continent

DTIC Science & Technology

orthogonal function analysis was developed to identify phases of thestratospheric Quasi-Biennial Oscillation (QBO) by direction and altitude of zonal wind...centers. In the troposphere, positive specifichumidity anomalies within the MJO active envelope and a near-surface moisture foot region in the lower troposphere east of the activeenvelope favor MJO propagation.

Diagnostics of the Heat Sources and Sinks of the Asiatic Monsoon and the Thermally-Forced Planetary Scale Response.

DTIC Science & Technology

1981-01-01

Scotia and the Northern Atlantic is evidence of winter monsoonal flow with polar air imoving equatorward and zonally from continental regions to the...inviscid motion must be tangent to both the entropy and energy surfaces and 2) the condition emphasized earlier in the discussion that, in the time

Turbulence, transport, and zonal flows in the Madison symmetric torus reversed-field pinch

NASA Astrophysics Data System (ADS)

Williams, Z. R.; Pueschel, M. J.; Terry, P. W.; Hauff, T.

2017-12-01

The robustness and the effect of zonal flows in trapped electron mode (TEM) turbulence and Ion Temperature Gradient (ITG) turbulence in the reversed-field pinch (RFP) are investigated from numerical solutions of the gyrokinetic equations with and without magnetic external perturbations introduced to model tearing modes. For simulations without external magnetic field perturbations, zonal flows produce a much larger reduction of transport for the density-gradient-driven TEM turbulence than they do for the ITG turbulence. Zonal flows are studied in detail to understand the nature of their strong excitation in the RFP and to gain insight into the key differences between the TEM- and ITG-driven regimes. The zonal flow residuals are significantly larger in the RFP than in tokamak geometry due to the low safety factor. Collisionality is seen to play a significant role in the TEM zonal flow regulation through the different responses of the linear growth rate and the size of the Dimits shift to collisionality, while affecting the ITG only minimally. A secondary instability analysis reveals that the TEM turbulence drives zonal flows at a rate that is twice that of the ITG turbulence. In addition to interfering with zonal flows, the magnetic perturbations are found to obviate an energy scaling relation for fast particles.

The influence of initial and surface boundary conditions on a model-generated January climatology

NASA Technical Reports Server (NTRS)

Wu, K. F.; Spar, J.

1981-01-01

The influence on a model-generated January climate of various surface boundary conditions, as well as initial conditions, was studied by using the GISS coarse-mesh climate model. Four experiments - two with water planets, one with flat continents, and one with mountains - were used to investigate the effects of initial conditions, and the thermal and dynamical effects of the surface on the model generated-climate. However, climatological mean zonal-symmetric sea surface temperature is used in all four runs over the model oceans. Moreover, zero ground wetness and uniform ground albedo except for snow are used in the last experiments.

Some effects of topography, soil moisture, and sea-surface temperature on continental precipitation as computed with the GISS coarse mesh climate model

NASA Technical Reports Server (NTRS)

Spar, J.; Cohen, C.

1981-01-01

The effects of terrain elevation, soil moisture, and zonal variations in sea/surface temperature on the mean daily precipitation rates over Australia, Africa, and South America in January were evaluated. It is suggested that evaporation of soil moisture may either increase or decrease the model generated precipitation, depending on the surface albedo. It was found that a flat, dry continent model best simulates the January rainfall over Australia and South America, while over Africa the simulation is improved by the inclusion of surface physics, specifically soil moisture and albedo variations.

Averaged model to study long-term dynamics of a probe about Mercury

NASA Astrophysics Data System (ADS)

Tresaco, Eva; Carvalho, Jean Paulo S.; Prado, Antonio F. B. A.; Elipe, Antonio; de Moraes, Rodolpho Vilhena

2018-02-01

This paper provides a method for finding initial conditions of frozen orbits for a probe around Mercury. Frozen orbits are those whose orbital elements remain constant on average. Thus, at the same point in each orbit, the satellite always passes at the same altitude. This is very interesting for scientific missions that require close inspection of any celestial body. The orbital dynamics of an artificial satellite about Mercury is governed by the potential attraction of the main body. Besides the Keplerian attraction, we consider the inhomogeneities of the potential of the central body. We include secondary terms of Mercury gravity field from J_2 up to J_6, and the tesseral harmonics \\overline{C}_{22} that is of the same magnitude than zonal J_2. In the case of science missions about Mercury, it is also important to consider third-body perturbation (Sun). Circular restricted three body problem can not be applied to Mercury-Sun system due to its non-negligible orbital eccentricity. Besides the harmonics coefficients of Mercury's gravitational potential, and the Sun gravitational perturbation, our average model also includes Solar acceleration pressure. This simplified model captures the majority of the dynamics of low and high orbits about Mercury. In order to capture the dominant characteristics of the dynamics, short-period terms of the system are removed applying a double-averaging technique. This algorithm is a two-fold process which firstly averages over the period of the satellite, and secondly averages with respect to the period of the third body. This simplified Hamiltonian model is introduced in the Lagrange Planetary equations. Thus, frozen orbits are characterized by a surface depending on three variables: the orbital semimajor axis, eccentricity and inclination. We find frozen orbits for an average altitude of 400 and 1000 km, which are the predicted values for the BepiColombo mission. Finally, the paper delves into the orbital stability of frozen orbits and the temporal evolution of the eccentricity of these orbits.

Geothermal heating enhances atmospheric asymmetries on synchronously rotating planets

NASA Astrophysics Data System (ADS)

Haqq-Misra, Jacob; Kopparapu, Ravi Kumar

2015-01-01

Earth-like planets within the liquid water habitable zone of M-type stars may evolve into synchronous rotators. On these planets, the substellar hemisphere experiences perpetual daylight while the opposing antistellar hemisphere experiences perpetual darkness. Because the night-side hemisphere has no direct source of energy, the air over this side of the planet is prone to freeze out and deposit on the surface, which could result in atmospheric collapse. However, general circulation models (GCMs) have shown that atmospheric dynamics can counteract this problem and provide sufficient energy transport to the antistellar side. Here, we use an idealized GCM to consider the impact of geothermal heating on the habitability of synchronously rotating planets. Geothermal heating may be expected due to tidal interactions with the host star, and the effects of geothermal heating provide additional habitable surface area and may help to induce melting of ice on the antistellar hemisphere. We also explore the persistence of atmospheric asymmetries between the Northern and Southern hemispheres, and we find that the direction of the meridional circulation (for rapidly rotating planets) or the direction of zonal wind (for slowly rotating planets) reverses on either side of the substellar point. We show that the zonal circulation approaches a theoretical state similar to a Walker circulation only for slowly rotating planets, while rapidly rotating planets show a zonal circulation with the opposite direction. We find that a cross-polar circulation is present in all cases and provides an additional mechanism of mass and energy transport from the substellar to antistellar point. Characterization of the atmospheres of synchronously rotating planets should include consideration of hemispheric differences in meridional circulation and examination of transport due to cross-polar flow.

The Southern Ocean's role in ocean circulation and climate transients

NASA Astrophysics Data System (ADS)

Thompson, A. F.; Stewart, A.; Hines, S.; Adkins, J. F.

2017-12-01

The ventilation of deep and intermediate density classes at the surface of the Southern Ocean impacts water mass modification and the air-sea exchange of heat and trace gases, which in turn influences the global overturning circulation and Earth's climate. Zonal variability occurs along the Antarctic Circumpolar Current and the Antarctic margins related to flow-topography interactions, variations in surface boundary conditions, and exchange with northern basins. Information about these zonal variations, and their impact on mass and tracer transport, are suppressed when the overturning is depicted as a two-dimensional (depth-latitude) streamfunction. Here we present an idealized, multi-basin, time-dependent circulation model that applies residual circulation theory in the Southern Ocean and allows for zonal water mass transfer between different ocean basins. This model efficiently determines the temporal evolution of the ocean's stratification, ventilation and overturning strength in response to perturbations in the external forcing. With this model we explore the dynamics that lead to transitions in the circulation structure between multiple, isolated cells and a three-dimensional, "figure-of-eight," circulation in which traditional upper and lower cells are interleaved. The transient model is also used to support a mechanistic explanation of the hemispheric asymmetry and phase lag associated with Dansgaard-Oeschger (DO) events during the last glacial period. In particular, the 200 year lag in southern hemisphere temperatures, following a perturbation in North Atlantic deep water formation, depends critically on the migration of Southern Ocean isopycnal outcropping in response to low-latitude stratification changes. Our results provide a self-consistent dynamical framework to explain various ocean overturning transitions that have occurred over the Earth's last 100,000 years, and motivate an exploration of these mechanisms in more sophisticated climate models.

Ultra-high field diffusion tensor imaging of articular cartilage correlated with histology and scanning electron microscopy.

PubMed

Raya, José G; Arnoldi, Andreas P; Weber, Daniel L; Filidoro, Lucianna; Dietrich, Olaf; Adam-Neumair, Silvia; Mützel, Elisabeth; Melkus, Gerd; Putz, Reinhard; Reiser, Maximilian F; Jakob, Peter M; Glaser, Christian

2011-08-01

To investigate the relationship of the different diffusion tensor imaging (DTI) parameters (ADC, FA, and first eigenvector (EV)) to the constituents (proteoglycans and collagen), the zonal arrangement of the collagen network, and mechanical loading of articular cartilage. DTI of eight cartilage-on-bone samples of healthy human patellar cartilage was performed at 17.6 T. Three samples were additionally imaged under indentation loading. After DTI, samples underwent biomechanical testing, safranin-O staining for semiquantitative proteoglycan estimation, and scanning electron microscopy (SEM) for depicting collagen architecture. From the articular surface to the bone-cartilage interface, ADC continuously decreased and FA increased. Cartilage zonal heights calculated from EVs strongly correlated with SEM-derived zonal heights (P < 0.01, r (2)=0.87). Compression reduced ADC in the superficial 30% of cartilage and increased FA in the superficial 5% of cartilage. Reorientation of the EVs indicative of collagen fiber reorientation under the indenter was observed. No significant correlation was found between ADC, FA, and compressive stiffness. Correlating ADC and FA with proteoglycan and collagen content suggests that diffusion is dominated by different depth-dependent mechanisms within cartilage. Knowledge of the spatial distribution of the DTI parameters and their variation contributes to form a database for future analysis of defective cartilage.

Mean winds and momemtum fluxes over Jicamarca, Peru, during June and August 1987

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hitchman, M.H.; Bywaters, K.W.; Fritts, D.C.

1992-12-15

Data from the mesophere-stratosphere-troposphere (MST) radar at Jicamarca, Peru, together with other available data, are used to diagnose the mean structure of winds and gravity-wave momentum fluxes from the surface to 90 km during two ten-day campaigns in June and August of 1987. In the stratosphere a layer of maximum eastward flow associated with the quasi-biennial oscillation (QBO) was seen to strengthen and descend rapidly from June to August, overlying persitent westward flow. A layer of enhanced signal return, suggestive of a turbulent layer, was observed just above the descending QBO eastward maximum. Notable zonal asymmetries were present during thismore » transition and the local meridional circulation departed form zonal-mean QBO theory. A substantial northeastward momentum flux was found below 25 km, which may be related to topographic gravity waves excited by southeastward flow across the Andes. In the lower mesosphere a relatively weak second mesopause semiannual oxcillation is confirmed. Gravity-wave zonal and meridional momentum fluxes usually opposed the flow, yielding body forces of [approximately]10-100 ms[sup [minus]1] day [sup [minus]1]. In both the lower stratosphere and mesosphere, body forces were comparable in magnitude to inferred Coriolis torques. 52 refs., 9 figs.« less

Changes in Jupiter's Zonal Wind Profile Preceding and During the Juno Mission

NASA Technical Reports Server (NTRS)

Tollefson, Joshua; Wong, Michael H.; de Pater, Imke; Simon, Amy A.; Orton, Glenn S.; Rogers, John H.; Atreya, Sushil K.; Cosentino, Richard G.; Januszewski, William; Morales-Juberias, Raul;

A new model for the (geo)magnetic power spectrum, with application to planetary dynamo radii

NASA Astrophysics Data System (ADS)

Langlais, Benoit; Amit, Hagay; Larnier, Hugo; Thébault, Erwan; Mocquet, Antoine

2014-09-01

We propose two new analytical expressions to fit the Mauersberger-Lowes geomagnetic field spectrum at the core-mantle boundary. These can be used to estimate the radius of the outer liquid core where the geodynamo operates, or more generally the radius of the planetary dynamo regions. We show that two sub-families of the geomagnetic field are independent of spherical harmonics degree n at the core-mantle boundary and exhibit flat spectra. The first is the non-zonal field, i.e., for spherical harmonics order m different from zero. The second is the quadrupole family, i.e., n+m even. The flatness of their spectra is motivated by the nearly axisymmetric time-average paleomagnetic field (for the non-zonal field) and the dominance of rotational effects in core dynamics (for the quadrupole family). We test our two expressions with two approaches using the reference case of the Earth. First we estimate at the seismic core radius the agreement between the actual spectrum and the theoretical one. Second we estimate the magnetic core radius, where the spectrum flattens. We show that both sub-families offer a better agreement with the actual spectrum compared with previously proposed analytical expressions, and predict a magnetic core radius within less than 10 km of the Earth's seismic core radius. These new expressions supersede previous ones to infer the core radius from geomagnetic field information because the low degree terms are not ignored. Our formalism is then applied to infer the radius of the dynamo regions on Jupiter, Saturn, Uranus and Neptune. The axisymmetric nature of the magnetic field of Saturn prevents the use of the non-zonal expression. For the three other planets both expressions converge and offer independent constraints on the internal structure of these planets. These non-zonal and quadrupole family expressions may be implemented to extrapolate the geomagnetic field spectrum beyond observable degrees, or to further regularize magnetic field models constructed from modern or historical observations.

SAGE Aerosol Measurements. Volume 2: 1 January - 31 December 1980

NASA Technical Reports Server (NTRS)

Mccormick, M. P.

1986-01-01

The stratospheric Aerosol and Gas Experiment (SAGE) satellite system, launched on February 18, 1979, provides profiles of aerosol extinction at wavelengths of 1.00 and 0.45 micron, ozone concentration, and nitrogen dioxide concentration. Data taken during sunset events in the form of zonal averages and seasonal averages of the aerosol extinction at 1.00 and 0.45 micron, ratios of the aerosol extinction to the molecular extinction at 1.00 micron, and ratios of the aerosol extinction at 0.45 micron to the aerosol extinction at 1.00 micron are presented. The averages for l980 are shown in tables and in profile and contour plots (as a function of altitude and latitude). In addition, temperature data provided by the National Oceanic and Atmospheric Administration (NOAA) for the time and location of each SAGE measurement are averaged and shown in a similar format.

Dynamic sea surface topography from GEOS-3 altimetry - Determination of some dominant parameters

NASA Technical Reports Server (NTRS)

Mather, R. S.; Lerch, F. J.; Rizos, C.; Masters, E. G.; Hirsch, B.

1979-01-01

The second, third and fourth degree zonal harmonics of the quasi-stationary dynamic sea surface topography can be recovered from the GEOS-3 altimetry despite the adverse levels of noise indicated by the crossover discrepancies generated from the best orbits available at the end of 1977 and the GEOS-3 altimetry. Techniques for modelling the global sea surface topography are discussed along with methods for signal recovery in the presence of significant levels of noise. The analysis also provides a means of defining the geocentricity of the system of reference used in preparing the GEOS-3 ephemeris.

Middle and long-term prediction of UT1-UTC based on combination of Gray Model and Autoregressive Integrated Moving Average

NASA Astrophysics Data System (ADS)

Jia, Song; Xu, Tian-he; Sun, Zhang-zhen; Li, Jia-jing

2017-02-01

UT1-UTC is an important part of the Earth Orientation Parameters (EOP). The high-precision predictions of UT1-UTC play a key role in practical applications of deep space exploration, spacecraft tracking and satellite navigation and positioning. In this paper, a new prediction method with combination of Gray Model (GM(1, 1)) and Autoregressive Integrated Moving Average (ARIMA) is developed. The main idea is as following. Firstly, the UT1-UTC data are preprocessed by removing the leap second and Earth's zonal harmonic tidal to get UT1R-TAI data. Periodic terms are estimated and removed by the least square to get UT2R-TAI. Then the linear terms of UT2R-TAI data are modeled by the GM(1, 1), and the residual terms are modeled by the ARIMA. Finally, the UT2R-TAI prediction can be performed based on the combined model of GM(1, 1) and ARIMA, and the UT1-UTC predictions are obtained by adding the corresponding periodic terms, leap second correction and the Earth's zonal harmonic tidal correction. The results show that the proposed model can be used to predict UT1-UTC effectively with higher middle and long-term (from 32 to 360 days) accuracy than those of LS + AR, LS + MAR and WLS + MAR.

Version 8 SBUV Ozone Profile Trends Compared with Trends from a Zonally Averaged Chemical Model

NASA Technical Reports Server (NTRS)

Rosenfield, Joan E.; Frith, Stacey; Stolarski, Richard

2004-01-01

Linear regression trends for the years 1979-2003 were computed using the new Version 8 merged Solar Backscatter Ultraviolet (SBUV) data set of ozone profiles. These trends were compared to trends computed using ozone profiles from the Goddard Space Flight Center (GSFC) zonally averaged coupled model. Observed and modeled annual trends between 50 N and 50 S were a maximum in the higher latitudes of the upper stratosphere, with southern hemisphere (SH) trends greater than northern hemisphere (NH) trends. The observed upper stratospheric maximum annual trend is -5.5 +/- 0.9 % per decade (1 sigma) at 47.5 S and -3.8 +/- 0.5 % per decade at 47.5 N, to be compared with the modeled trends of -4.5 +/- 0.3 % per decade in the SH and -4.0 +/- 0.2% per decade in the NH. Both observed and modeled trends are most negative in winter and least negative in summer, although the modeled seasonal difference is less than observed. Model trends are shown to be greatest in winter due to a repartitioning of chlorine species and the increasing abundance of chlorine with time. The model results show that trend differences can occur depending on whether ozone profiles are in mixing ratio or number density coordinates, and on whether they are recorded on pressure or altitude levels.

Predictability of Zonal Means During Boreal Summer

NASA Technical Reports Server (NTRS)

Schubert, Siegfried; Suarez, Max J.; Pegion, Philip J.; Kistler, Michael A.; Kumar, Arun; Einaudi, Franco (Technical Monitor)

2001-01-01

This study examines the predictability of seasonal means during boreal summer. The results are based on ensembles of June-July-August (JJA) simulations (started in mid May) carried out with the NASA Seasonal-to-Interannual Prediction Project (NSIPP-1) atmospheric general circulation model (AGCM) forced with observed sea surface temperatures (SSTS) and sea ice for the years 1980-1999. We find that the predictability of the JJA extra-tropical height field is primarily in the zonal mean component of the response to the SST anomalies. This contrasts with the cold season (January-February-March) when the predictability of seasonal means in the boreal extratropics is primarily in the wave component of the El Nino/Southern Oscillation (ENSO) response. Two patterns dominate the interannual variability of the ensemble mean JJA zonal mean height field. One has maximum variance in the tropical/subtropical upper troposphere, while the other has substantial variance in middle latitudes of both hemispheres. Both are symmetric with respect to the equator. A regression analysis suggests that the tropical/subtropical pattern is associated with SST anomalies in the far eastern tropical Pacific and the Indian Ocean, while the middle latitude pattern is forced by SST anomalies in the tropical Pacific just east of the dateline. The two leading zonal height patterns are reproduced in model runs forced with the two leading JJA SST patterns of variability. A comparison with observations shows a signature of the middle latitude pattern that is consistent with the occurrence of dry and wet summers over the United States. We hypothesize that both patterns, while imposing only weak constraints on extratropical warm season continental-scale climates, may play a role in the predilection for drought or pluvial conditions.

Propagating and Non-propagating Annular Modes and Principal Oscillation Patterns

NASA Astrophysics Data System (ADS)

Plumb, R. A.; Sheshadri, A.

2016-12-01

The leading "annular mode" in each hemisphere — usually defined as the dominant EOF of surface pressure or of zonal mean zonal wind variability — appears as a dipolar structure straddling the mean midlatitude jet and thus seems to describe north-south wobbling of the jet latitude. However, extratropical zonal wind anomalies frequently tend to migrate poleward. This behavior can be described by the first two EOFs, the first (AM1) being the dipolar structure, and the second (AM2) having a tripolar structure centered on the mean jet. (AM2 explains a significant amount of variance, though less than AM1.) Taken in isolation, AM1 thus describes a north-south wobbling of the jet position, while AM2 describes a strengthening and narrowing (or weakening and broadening) of the jet. However, despite the fact that they are spatially orthogonal, and their corresponding time series temporally orthogonal, AM1 and AM2 are not independent, but show significant lag-correlations which reveal the poleward propagation. The EOFs are not modes of the underlying dynamical system governing the zonal flow evolution. The true modes can be estimated using principal oscillation pattern (POP) analysis. The leading POPs manifest themselves as a pair of complex conjugate structures with conjugate eigenvalues thus, in reality, constituting a single, complex, mode that describes poleward propagating anomalies. This mode then shows up as AM1 and AM2 in EOF analyses. Even though the principal components associated with the two leading EOFs decay at different rates, each decays faster than the true mode. In the propagating regime, these facts have implications for the use of autocorrelations and cross-correlations to quantify eddy feedback and the susceptibility of the mode to external perturbations, including the response to stratospheric anomalies.

A diagnostic model to estimate winds and small-scale drag from Mars Observer PMIRR data

NASA Technical Reports Server (NTRS)

Barnes, J. R.

1993-01-01

Theoretical and modeling studies indicate that small-scale drag due to breaking gravity waves is likely to be of considerable importance for the circulation in the middle atmospheric region (approximately 40-100 km altitude) on Mars. Recent earth-based spectroscopic observations have provided evidence for the existence of circulation features, in particular, a warm winter polar region, associated with gravity wave drag. Since the Mars Observer PMIRR experiment will obtain temperature profiles extending from the surface up to about 80 km altitude, it will be extensively sampling middle atmospheric regions in which gravity wave drag may play a dominant role. Estimating the drag then becomes crucial to the estimation of the atmospheric winds from the PMIRR-observed temperatures. An interative diagnostic model based upon one previously developed and tested with earth satellite temperature data will be applied to the PMIRR measurements to produce estimates of the small-scale zonal drag and three-dimensional wind fields in the Mars middle atmosphere. This model is based on the primitive equations, and can allow for time dependence (the time tendencies used may be based upon those computed in a Fast Fourier Mapping procedure). The small-scale zonal drag is estimated as the residual in the zonal momentum equation; the horizontal winds having first been estimated from the meridional momentum equation and the continuity equation. The scheme estimates the vertical motions from the thermodynamic equation, and thus needs estimates of the diabatic heating based upon the observed temperatures. The latter will be generated using a radiative model. It is hoped that the diagnostic scheme will be able to produce good estimates of the zonal gravity wave drag in the Mars middle atmosphere, estimates that can then be used in other diagnostic or assimilation efforts, as well as more theoretical studies.

Interdecadal Change in the Tropical Pacific Precipitation Anomaly Pattern around the Late 1990s during Boreal Spring

NASA Astrophysics Data System (ADS)

Wen, Zhiping; Guo, Yuanyuan; Wu, Renguang

2017-04-01

The leading mode of boreal spring precipitation variability over the tropical Pacific experienced a pronounced interdecadal change around the late 1990s. The pattern before 1998 features positive precipitation anomalies over the equatorial eastern Pacific (EP) with positive principle component years. The counterpart after 1998 exhibits a westward shift of the positive center to the equatorial central Pacific (CP). Observational evidence shows that this interdecadal change in the leading mode of precipitation variability is closely associated with a distinctive sea surface temperature (SST) anomaly pattern. The westward shift of the anomalous precipitation center after 1998 is in tandem with a similar shift of maximum warming from the EP to CP. Diagnostic analyses based on a linear equation of the mixed layer temperature anomaly exhibit that an interdecadal enhancement of zonal advection (ZA) feedback process plays a vital role in the shift in the leading mode of both the tropical Pacific SST and the precipitation anomaly during spring. Moreover, the variability of the anomalous zonal current at the upper ocean dominates the ZA feedback change, while the mean zonal SST gradient associated with a La Niña-like pattern of the mean state only accounts for a relatively trivial proportion of the ZA feedback change. It was found that both the relatively rapid decaying of the SST anomalies in the EP and the La Niña-like mean state make it conceivable that the shift of the leading mode of the tropical precipitation anomaly only occurs in spring. In addition, the largest variance of the anomalous zonal current in spring might contribute to the unique interdecadal change in the tropical spring precipitation anomaly pattern.

Effects of finite poloidal gyroradius, shaping, and collisions on the zonal flow residuala)

NASA Astrophysics Data System (ADS)

Xiao, Yong; Catto, Peter J.; Dorland, William

2007-05-01

Zonal flow helps reduce and regulate the turbulent transport level in tokamaks. Rosenbluth and Hinton have shown that zonal flow damps to a nonvanishing residual level in collisionless [M. Rosenbluth and F. Hinton, Phys. Rev. Lett. 80, 724 (1998)] and collisional [F. Hinton and M. Rosenbluth, Plasma Phys. Control. Fusion 41, A653 (1999)] banana regime plasmas. Recent zonal flow advances are summarized including the evaluation of the effects on the zonal flow residual by plasma cross-section shaping, shorter wavelengths including those less than an electron gyroradius, and arbitrary ion collisionality relative to the zonal low frequency. In addition to giving a brief summary of these new developments, the analytic results are compared with GS2 numerical simulations [M. Kotschenreuther, G. Rewoldt, and W. Tang, Comput. Phys. Commun. 88, 128 (1991)] to demonstrate their value as benchmarks for turbulence codes.

Strong Temporal Variation Over One Saturnian Year: From Voyager to Cassini

NASA Technical Reports Server (NTRS)

Li, Liming; Achterberg, Richard K.; Conrath, Barney J.; Gierasch, Peter J.; Smith, Mark A.; Simon-Miller, Amy A.; Nixon, Conor A.; Orton, Glenn S.; Flasar, F. Michael; Jiang, Xun;

Strong Temporal Variation Over One Saturnian Year: From Voyager to Cassini

PubMed Central

Li, Liming; Achterberg, Richard K.; Conrath, Barney J.; Gierasch, Peter J.; Smith, Mark A.; Simon-Miller, Amy A.; Nixon, Conor A.; Orton, Glenn S.; Flasar, F. Michael; Jiang, Xun; Baines, Kevin H.; Morales-Juberías, Raúl; Ingersoll, Andrew P.; Vasavada, Ashwin R.; Del Genio, Anthony D.; West, Robert A.; Ewald, Shawn P.

2013-01-01

Here we report the combined spacecraft observations of Saturn acquired over one Saturnian year (~29.5 Earth years), from the Voyager encounters (1980–81) to the new Cassini reconnaissance (2009–10). The combined observations reveal a strong temporal increase of tropic temperature (~10 Kelvins) around the tropopause of Saturn (i.e., 50 mbar), which is stronger than the seasonal variability (~a few Kelvins). We also provide the first estimate of the zonal winds at 750 mbar, which is close to the zonal winds at 2000 mbar. The quasi-consistency of zonal winds between these two levels provides observational support to a numerical suggestion inferring that the zonal winds at pressures greater than 500 mbar do not vary significantly with depth. Furthermore, the temporal variation of zonal winds decreases its magnitude with depth, implying that the relatively deep zonal winds are stable with time. PMID:23934437

Planetary wave-gravity wave interactions during mesospheric inversion layer events

NASA Astrophysics Data System (ADS)

Ramesh, K.; Sridharan, S.; Raghunath, K.; Vijaya Bhaskara Rao, S.; Bhavani Kumar, Y.

2013-07-01

lidar temperature observations over Gadanki (13.5°N, 79.2°E) show a few mesospheric inversion layer (MIL) events during 20-25 January 2007. The zonal mean removed SABER temperature shows warm anomalies around 50°E and 275°E indicating the presence of planetary wave of zonal wave number 2. The MIL amplitudes in SABER temperature averaged for 10°N-15°N and 70°E-90°E show a clear 2 day wave modulation during 20-28 January 2007. Prior to 20 January 2007, a strong 2day wave (zonal wave number 2) is observed in the height region of 80-90 km and it gets largely suppressed during 20-26 January 2007 as the condition for vertical propagation is not favorable, though it prevails at lower heights. The 10 day mean zonal wind over Tirunelveli (8.7°N, 77.8°E) shows deceleration of eastward winds indicating the westward drag due to wave dissipation. The nightly mean MF radar observed zonal winds show the presence of alternating eastward and westward winds during the period of 20-26 January 2007. The two dimensional spectrum of Rayleigh lidar temperature observations available for the nights of 20, 22, and 24 January 2007 shows the presence of gravity wave activity with periods 18 min, 38 min, 38 min, and vertical wavelengths 6.4 km, 4.0 km, 6.4 km respectively. From the dispersion relation of gravity waves, it is inferred that these waves are internal gravity waves rather than inertia gravity waves with the horizontal phase speeds of ~40 m/s, ~37 m/s, and ~50 m/s respectively. Assuming the gravity waves are eastward propagating waves, they get absorbed only in the eastward local wind fields of the planetary wave thereby causing turbulence and eddy diffusion which can be inferred from the estimation of large drag force due to the breaking of gravity wave leading to the formation of large amplitude inversion events in alternate nights. The present study shows that, the mesospheric temperature inversion is caused mainly due to the gravity wave breaking and the inversion amplitude may get modulated by the interaction between gravity waves and planetary waves. The eddy diffusion associated with gravity wave drag may also cause suppression in the planetary wave activity.

The Role of Reversed Equatorial Zonal Transport in Terminating an ENSO Event

NASA Astrophysics Data System (ADS)

Chen, H. C.; Hu, Z. Z.; Huang, B.; Sui, C. H.

2016-02-01

In this study, we demonstrate that a sudden reversal of anomalous equatorial zonal current at the peaking ENSO phase triggers the rapid termination of an ENSO event. Throughout an ENSO cycle, the anomalous equatorial zonal current is strongly controlled by the concavity of the anomalous thermocline meridional structure near the equator. During the ENSO developing phase, the anomalous zonal current in the central and eastern Pacific generally enhances the ENSO growth through its zonal SST advection. In the mature phase of ENSO, however, the equatorial thermocline depth anomalies are reflected in the eastern Pacific and slowly propagate westward off the equator in both hemispheres. As a result, the concavity of the thermocline anomalies near the equator is reversed, i.e., the off-equatorial thermocline depth anomalies become higher than that on the equator for El Niño events and lower for La Niño events. This meridional change of thermocline structure reverses zonal transport rapidly in the central-to-eastern equatorial Pacific, which weakens the ENSO SST anomalies by reversed advection. More importantly, the reversed zonal mass transport weakens the existing zonal tilting of equatorial thermocline and suppresses the thermocline feedback. Both processes are concentrated in the eastern equatorial Pacific and can be effective on subseasonal time scales. These current reversal effects are built-in to the ENSO peak phase and independent of the zonal wind effect on thermocline slope. It functions as an oceanic control on ENSO evolution during both El Niño and La Niña events.

Excitation mechanism of non-migrating tides

NASA Astrophysics Data System (ADS)

Miyoshi, Yasunobu; Pancheva, Dora; Mukhtarov, Plamen; Jin, Hidekatsu; Fujiwara, Hitoshi; Shinagawa, Hiroyuki

2017-04-01

Using an atmosphere-ionosphere coupled model, the excitation source and temporal (seasonal and interannual) variations in non-migrating tides are investigated in this study. We first focus our attention on temporal variations in eastward moving diurnal tide with zonal wavenumber 3 (DE3), which is the largest of all the non-migrating tides in the mesosphere and lower thermosphere (MLT). Our simulation results indicate that upward propagation of the DE3 excited in the troposphere is sensitive to the zonal mean zonal wind in the stratosphere and mesosphere. The DE3 amplitude is enhanced in the region where the vertical shear of the zonal mean zonal wind is positive (westerly shear). Quasi-2-year variation in the DE3 amplitude in the MLT region is generated by quasi-2-year variation in the zonal mean zonal wind between 40 and 70 km, which is modulated by the stratospheric QBO. The excitation mechanisms of SW3 (westward moving semidiurnal tide with zonal wavenumber 3) and SW1 (westward moving semidiurnal tide with zonal wavenumber 1) are also investigated. During equinoxes, the SW3 and SW1 are excited by tropospheric heating (latent heat release and solar radiative heating) associated with cumulus convection in the tropics, and propagate upward into the MLT region. On the other hand, during solstices, SW3 and SW1 are generated in the winter stratosphere and mesosphere through the nonlinear interaction between the stationary planetary wave and migrating semidiurnal tide, and propagate upward to the lower thermosphere. The excitation sources of other non-migrating tides are also discussed.

Decadal slowdown in global air temperature rise triggered by variability in the Atlantic Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

England, Matthew H.

2015-04-01

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 Meridional Overturning Circulation (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.

Numerical experiments with a wind- and buoyancy-driven two-and-a-half-layer upper ocean model

NASA Astrophysics Data System (ADS)

Cherniawsky, J. Y.; Yuen, C. W.; Lin, C. A.; Mysak, L. A.

1990-09-01

We describe numerical experiments with a limited domain (15°-67°N, 65° west to east) coarse-resolution two-and-a-half-layer upper ocean model. The model consists of two active variable density layers: a Niiler and Kraus (1977) type mixed layer and a pycnocline layer, which overlays a semipassive deep ocean. The mixed layer is forced with a cosine wind stress and Haney type heat and precipitation-evaporation fluxes, which were derived from zonally averaged climatological (Levitus, 1982) surface temperatures and salinities for the North Atlantic. The second layer is forced from below with (1) Newtonian cooling to climatological temperatures and salinities at the lower boundary, (2) convective adjustment, which occurs whenever the density of the second layer is unstable with respect to climatology, and (3) mass entrainment in areas of strong upwelling, when the deep ocean ventilates through the bottom surface. The sensitivity of this model to changes in its internal (mixed layer) and external (e.g., a Newtonian coupling coefficient) parameters is investigated and compared to the results from a control experiment. We find that the model is not overly sensitive to changes in most of the parameters that were tested, albeit these results may depend to some extent on the choice of the control experiment.

Generation of zonal magnetic fields by low-frequency dispersive electromagnetic waves in a nonuniform dusty magnetoplasma.

PubMed

Shukla, P K

2004-04-01

It is shown that zonal magnetic fields can be parametrically excited by low-frequency dispersive driftlike compressional electromagnetic (DDCEM) modes in a nonuniform dusty magnetoplasma. For this purpose, we derive a pair of coupled equations which exhibits the nonlinear coupling between DDCEM modes and zonal magnetic fields. The coupled mode equations are Fourier analyzed to derive a nonlinear dispersion relation. The latter depicts that zonal magnetic fields are nonlinearly generated at the expense of the low-frequency DDCEM wave energy. The relevance of our investigation to the transfer of energy from short scale DDCEM waves to long scale zonal magnetic field structures in dark molecular clouds is discussed.

Optimisation of confinement in a fusion reactor using a nonlinear turbulence model

NASA Astrophysics Data System (ADS)

Highcock, E. G.; Mandell, N. R.; Barnes, M.

2018-04-01

The confinement of heat in the core of a magnetic fusion reactor is optimised using a multidimensional optimisation algorithm. For the first time in such a study, the loss of heat due to turbulence is modelled at every stage using first-principles nonlinear simulations which accurately capture the turbulent cascade and large-scale zonal flows. The simulations utilise a novel approach, with gyrofluid treatment of the small-scale drift waves and gyrokinetic treatment of the large-scale zonal flows. A simple near-circular equilibrium with standard parameters is chosen as the initial condition. The figure of merit, fusion power per unit volume, is calculated, and then two control parameters, the elongation and triangularity of the outer flux surface, are varied, with the algorithm seeking to optimise the chosen figure of merit. A twofold increase in the plasma power per unit volume is achieved by moving to higher elongation and strongly negative triangularity.

Dynamical excitation of the tropical Pacific Ocean and ENSO variability by Little Ice Age cooling.

PubMed

Rustic, Gerald T; Koutavas, Athanasios; Marchitto, Thomas M; Linsley, Braddock K

2015-12-18

Tropical Pacific Ocean dynamics during the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are poorly characterized due to a lack of evidence from the eastern equatorial Pacific. We reconstructed sea surface temperature, El Niño-Southern Oscillation (ENSO) activity, and the tropical Pacific zonal gradient for the past millennium from Galápagos ocean sediments. We document a mid-millennium shift (MMS) in ocean-atmosphere circulation around 1500-1650 CE, from a state with dampened ENSO and strong zonal gradient to one with amplified ENSO and weak gradient. The MMS coincided with the deepest LIA cooling and was probably caused by a southward shift of the intertropical convergence zone. The peak of the MCA (900-1150 CE) was a warm period in the eastern Pacific, contradicting the paradigm of a persistent La Niña pattern. Copyright © 2015, American Association for the Advancement of Science.

Model test of anchoring effect on zonal disintegration in deep surrounding rock masses.

PubMed

Chen, Xu-Guang; Zhang, Qiang-Yong; Wang, Yuan; Liu, De-Jun; Zhang, Ning

2013-01-01

The deep rock masses show a different mechanical behavior compared with the shallow rock masses. They are classified into alternating fractured and intact zones during the excavation, which is known as zonal disintegration. Such phenomenon is a great disaster and will induce the different excavation and anchoring methodology. In this study, a 3D geomechanics model test was conducted to research the anchoring effect of zonal disintegration. The model was constructed with anchoring in a half and nonanchoring in the other half, to compare with each other. The optical extensometer and optical sensor were adopted to measure the displacement and strain changing law in the model test. The displacement laws of the deep surrounding rocks were obtained and found to be nonmonotonic versus the distance to the periphery. Zonal disintegration occurs in the area without anchoring and did not occur in the model under anchoring condition. By contrasting the phenomenon, the anchor effect of restraining zonal disintegration was revealed. And the formation condition of zonal disintegration was decided. In the procedure of tunnel excavation, the anchor strain was found to be alternation in tension and compression. It indicates that anchor will show the nonmonotonic law during suppressing the zonal disintegration.

Model Test of Anchoring Effect on Zonal Disintegration in Deep Surrounding Rock Masses

PubMed Central

Chen, Xu-Guang; Zhang, Qiang-Yong; Wang, Yuan; Liu, De-Jun; Zhang, Ning

2013-01-01

The deep rock masses show a different mechanical behavior compared with the shallow rock masses. They are classified into alternating fractured and intact zones during the excavation, which is known as zonal disintegration. Such phenomenon is a great disaster and will induce the different excavation and anchoring methodology. In this study, a 3D geomechanics model test was conducted to research the anchoring effect of zonal disintegration. The model was constructed with anchoring in a half and nonanchoring in the other half, to compare with each other. The optical extensometer and optical sensor were adopted to measure the displacement and strain changing law in the model test. The displacement laws of the deep surrounding rocks were obtained and found to be nonmonotonic versus the distance to the periphery. Zonal disintegration occurs in the area without anchoring and did not occur in the model under anchoring condition. By contrasting the phenomenon, the anchor effect of restraining zonal disintegration was revealed. And the formation condition of zonal disintegration was decided. In the procedure of tunnel excavation, the anchor strain was found to be alternation in tension and compression. It indicates that anchor will show the nonmonotonic law during suppressing the zonal disintegration. PMID:23997683

A numerical study of the effect of geometry variation, turbulence models, and dissipation on the flow past control surfaces

NASA Technical Reports Server (NTRS)

Chaussee, Denny S.

1993-01-01

The steady 3D viscous flow past the ONERA M6 wing and a slender delta wing-body with trailing edge control surfaces has been computed. A cell-centered finite-volume Navier-Stokes patched zonal method has been used for the numerical simulation. Both diagonalized and LUSGS schemes have been implemented. Besides the standard nonplanar zonal interfacing techniques, a new virtual zone capability has been employed. For code validation, the transonic flow past the ONERA M5 wing is calculated for angles-of-attack of 3.06 deg and 5.06 deg and compared with the available experiments. The wing-body computational results are compared with experimental data for both trailing-edge flaps deflected. The experimental flow conditions are M subinfinity = 0.4, a turbulent Reynolds number of 5.41 million based on a mean aerodynamic chord of 25.959 inches, adiabatic wall, and angles-of-attack varying from 0 deg to 23.85 deg. The computational results are presented for the 23.85 deg angle-of-attack case. The effects of the base flow due to a model sting, the varying second and fourth order numerical dissipation, and the turbulence model are all considered.

The global surface temperatures of the Moon as measured by the Diviner Lunar Radiometer Experiment

NASA Astrophysics Data System (ADS)

Williams, J.-P.; Paige, D. A.; Greenhagen, B. T.; Sefton-Nash, E.

2017-02-01

The Diviner Lunar Radiometer Experiment onboard the Lunar Reconnaissance Orbiter (LRO) has been acquiring solar reflectance and mid-infrared radiance measurements nearly continuously since July of 2009. Diviner is providing the most comprehensive view of how regoliths on airless bodies store and exchange thermal energy with the space environment. Approximately a quarter trillion calibrated radiance measurements of the Moon, acquired over 5.5 years by Diviner, have been compiled into a 0.5° resolution global dataset with a 0.25 h local time resolution. Maps generated with this dataset provide a global perspective of the surface energy balance of the Moon and reveal the complex and extreme nature of the lunar surface thermal environment. Our achievable map resolution, both spatially and temporally, will continue to improve with further data acquisition. Daytime maximum temperatures are sensitive to the albedo of the surface and are ∼387-397 K at the equator, dropping to ∼95 K just before sunrise, though anomalously warm areas characterized by high rock abundances can be > 50 K warmer than the zonal average nighttime temperatures. An asymmetry is observed between the morning and afternoon temperatures due to the thermal inertia of the lunar regolith with the dusk terminator ∼30 K warmer than the dawn terminator at the equator. An increase in albedo with incidence angle is required to explain the observed decrease in temperatures with latitude. At incidence angles exceeding ∼40°, topography and surface roughness influence temperatures resulting in increasing scatter in temperatures and anisothermality between Diviner channels. Nighttime temperatures are sensitive to the thermophysical properties of the regolith. High thermal inertia (TI) materials such as large rocks, remain warmer during the long lunar night and result in anomalously warm nighttime temperatures and anisothermality in the Diviner channels. Anomalous maximum and minimum temperatures are highlighted by subtracting the zonal mean temperatures from maps. Terrains can be characterized as low or high reflectance and low or high TI. Low maximum temperatures result from high reflectance surfaces while low minimum temperatures from low-TI material. Conversely, high maximum temperatures result from dark surface, and high minimum temperatures from high-TI materials. Impact craters are found to modify regolith properties over large distances. The thermal signature of Tycho is asymmetric, consistent with an oblique impact coming from the west. Some prominent crater rays are visible in the thermal data and require material with a higher thermal inertial than nominal regolith. The influence of the formation of the Orientale basin on the regolith properties is observable over a substantial portion of the western hemisphere despite its age (∼3.8 Gyr), and may have contributed to mixing of highland and mare material on the southwest margin of Oceanus Procellarum where the gradient in radiative properties at the mare-highland contact is broad (∼200 km).

Continuous versus discontinuous albedo representations in a simple diffusive climate model

NASA Astrophysics Data System (ADS)

Simmons, P. A.; Griffel, D. H.

1988-07-01

A one-dimensional annually and zonally averaged energy-balance model, with diffusive meridional heat transport and including icealbedo feedback, is considered. This type of model is found to be very sensitive to the form of albedo used. The solutions for a discontinuous step-function albedo are compared to those for a more realistic smoothly varying albedo. The smooth albedo gives a closer fit to present conditions, but the discontinuous form gives a better representation of climates in earlier epochs.

The effect of global warming on lightning frequencies

NASA Technical Reports Server (NTRS)

Price, Colin; Rind, David

1990-01-01

The first attempt to model global lightning distributions by using the Goddard Institute for Space Studies (GISS) GCM is reported. Three sets of observations showing the relationship between lightning frequency and cloud top height are shown. Zonally averaged lightning frequency observed by satellite are compared with those calculated using the GISS GCM, and fair agreement is found. The change in lightning frequency for a double CO2 climate is calculated and found to be nearly 2.23 x 10 exp 6 extra lightning flashes per day.

Simulations of the Quasi-Biennial Oscillation and its Effect on Stratospheric H2O, CH4, and Age of Air with an Interactive Two-Dimensional Model

DTIC Science & Technology

2002-11-22

November 2002. [1] A zonally averaged photochemical–dynamical model of the middle atmosphere is used to simulate the quasi-biennial oscillation ( QBO ) and... QBO period. Comparable changes in prescribed tropical heating have a smaller effect on the QBO period. The response of tropical upwelling, and QBO ...wave forcing is smaller than in the Northern Hemisphere, increased forcing produces stronger equatorial upwelling and a longer QBO period. In the

Neutral Mass Spectrometry for Venus Atmosphere and Surface

NASA Technical Reports Server (NTRS)

Mahaffy, Paul

2005-01-01

The assignment is to make precise (better than 1 %) measurements of isotope ratios and accurate (5-10%) measurements of abundances of noble gas and to obtain vertical profiles of trace chemically active gases from above the clouds all the way down to the surface. Science measurement objectives are as follows: 1) Determine the composition of Venus atmosphere, including trace gas species and light stable isotopes; 2) Accurately measure noble-gas isotopic abundance in the atmosphere; 3) Provide descent, surface, and ascent meteorological data; 4) Measure zonal cloud-level winds over several Earth days; 5) Obtain near-IR descent images of the surface from 10-km altitude to the surface; 6) Accurately measure elemental abundances & mineralogy of a core from the surface; and 7) Evaluate the texture of surface materials to constrain weathering environment.

Analysis of Ozone Trends and Spatial Variations in the North American Lower and Middle Troposphere from a Long-term Ozone Climatology Dataset

NASA Astrophysics Data System (ADS)

Liu, J.; Tarasick, D. W.; Mao, H.; Li, Y., , Dr; Osman, M.; Zhao, T.; Jung, J.; Fioletov, V.; Moeini, O.

2017-12-01

Ozone trends and spatial variations in the North American free troposphere from the 1970s to the 2000s are characterized, based on the newly developed Trajectory-mapped Ozonesonde dataset for the Stratosphere and Troposphere (TOST). TOST uses a special domain-filling technique with forward and backward trajectory calculations to fill in spatial gaps in ozonesonde data. TOST is resolved in latitude, longitude, and altitude so it can provide new information on the long-term variations of troposheric ozone in three dimensions. . Global trend calculations with sparse and irregularly-spaced ozonesonde data must contend with the problem of how to properly weight the data in a zonal or regional average. As TOST spreads the data according to dynamic meteorological information, in a zonal or regional average it will therefore weight the data according to the meteorologically-determined area that each site samples. Through four decades, the highest ozone concentrations in the lower and middle troposphere generally appeared over the central midlatitudes of North America. Longitudinally, ozone was lowest over the southern Pacific Ocean, intermediate over the North American continent, and highest in the outflow along the east coast. The overall ozone trends in the four decades averaged over North America are positive. In particular, there has been an increasing trend at high latitudes between 50-90°N in the North American middle troposphere. Our analysis suggests that this may be caused by influences from the stratosphere and from lower latitudes during the period. The trends from TOST are compared with the original ozonesonde data at selected stations and both datasets correlate closely.

Generation of zonal flows by electrostatic drift waves in electron-positron-ion plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaladze, T. D.; I. Vekua Institute of Applied Mathematics, Tbilisi State University, 2 University Str., 0186 Tbilisi; Shad, M.

2010-02-15

Generation of large-scale zonal flows by comparatively small-scale electrostatic drift waves in electron-positron-ion plasmas is considered. The generation mechanism is based on the parametric excitation of convective cells by finite amplitude drift waves having arbitrary wavelengths (as compared with the ion Larmor radius of plasma ions at the plasma electron temperature). Temperature inhomogeneity of electrons and positrons is taken into account assuming ions to be cold. To describe the generation of zonal flow generalized Hasegawa-Mima equation containing both vector and two scalar (of different nature) nonlinearities is used. A set of coupled equations describing the nonlinear interaction of drift wavesmore » and zonal flows is deduced. Explicit expressions for the maximum growth rate as well as for the optimal spatial dimensions of the zonal flows are obtained. Enriched possibilities of zonal flow generation with different growth rates are revealed. The present theory can be used for interpretations of drift wave observations in laboratory and astrophysical plasmas.« less

The role of zonal flows in disc gravito-turbulence

NASA Astrophysics Data System (ADS)

Vanon, R.

2018-07-01

The work presented here focuses on the role of zonal flows in the self-sustenance of gravito-turbulence in accretion discs. The numerical analysis is conducted using a bespoke pseudo-spectral code in fully compressible, non-linear conditions. The disc in question, which is modelled using the shearing sheet approximation, is assumed to be self-gravitating, viscous, and thermally diffusive; a constant cooling time-scale is also considered. Zonal flows are found to emerge at the onset of gravito-turbulence and they remain closely linked to the turbulent state. A cycle of zonal flow formation and destruction is established, mediated by a slow mode instability (which allows zonal flows to grow) and a non-axisymmetric instability (which disrupts the zonal flow), which is found to repeat numerous times. It is in fact the disruptive action of the non-axisymmetric instability to form new leading and trailing shearing waves, allowing energy to be extracted from the background flow and ensuring the self-sustenance of the gravito-turbulent regime.

The role of zonal flows in disc gravito-turbulence

NASA Astrophysics Data System (ADS)

Vanon, R.

2018-04-01

The work presented here focuses on the role of zonal flows in the self-sustenance of gravito-turbulence in accretion discs. The numerical analysis is conducted using a bespoke pseudo-spectral code in fully compressible, non-linear conditions. The disc in question, which is modelled using the shearing sheet approximation, is assumed to be self-gravitating, viscous, and thermally diffusive; a constant cooling timescale is also considered. Zonal flows are found to emerge at the onset of gravito-turbulence and they remain closely linked to the turbulent state. A cycle of zonal flow formation and destruction is established, mediated by a slow mode instability (which allows zonal flows to grow) and a non-axisymmetric instability (which disrupts the zonal flow), which is found to repeat numerous times. It is in fact the disruptive action of the non-axisymmetric instability to form new leading and trailing shearing waves, allowing energy to be extracted from the background flow and ensuring the self-sustenance of the gravito-turbulent regime.

Climatology and natural variability of the global hydrologic cycle in the GLA atmospheric general circulation model

NASA Technical Reports Server (NTRS)

Lau, K.-M.; Mehta, V. M.; Sud, Y. C.; Walker, G. K.

1994-01-01

Time average climatology and low-frequency variabilities of the global hydrologic cycle (GHC) in the Goddard Laboratory for Atmospheres (GLA) general circulation model (GCM) were investigated in the present work. A 730-day experiment was conducted with the GLA GCM forced by insolation, sea surface temperature, and ice-snow undergoing climatological annual cycles. Ifluences of interactive soil moisture on time average climatology and natural variability of the GHC were also investigated by conducting 365-day experiments with and without interactive soil moisture. Insolation, sea surface temperature, and ice-snow were fixed at their July levels in the latter two experiments. Results show that the model's time average hydrologic cycle variables for July in all three experiments agree reasonably well with observations. Except in the case of precipitable water, the zonal average climates of the annual cycle experiment and the two perpetual July experiments are alike, i.e., their differences are within limits of the natural variability of the model's climate. Statistics of various components of the GHC, i.e., water vapor, evaporation, and precipitation, are significantly affected by the presence of interactive soil moisture. A long-term trend is found in the principal empirical modes of variability of ground wetness, evaporation, and sensible heat. Dominant modes of variability of these quantities over land are physically consistent with one another and with land surface energy balance requirements. The dominant mode of precipitation variability is found to be closely related to organized convection over the tropical western Pacific Ocean. The precipitation variability has timescales in the range of 2 to 3 months and can be identified with the stationary component of the Madden-Julian Oscillation. The precipitation mode is not sensitive to the presence of interactive soil moisture but is closely linked to both the rotational and divergent components of atmospheric moisture transport. The present results indicate that globally coherent natural variability of the GHC in the GLA GCM has two basic timescales in the absence of annual cycles of external forcings: a long-term trend associated with atmosphere-soil moisture interaction which affects the model atmosphere mostly over midlatitude continental regions and a large-scale 2- to 3-month variability associated with atmospheric moist processes over the western Pacific Ocean.

Unusual behavior of quiet-time zonal and vertical plasma drift velocities over Jicamarca during the recent extended solar minimum of 2008

NASA Astrophysics Data System (ADS)

Santos, Ângela M.; Abdu, Mangalathayil A.; Souza, Jonas R.; Batista, Inez S.; Sobral, José H. A.

2017-11-01

The influence of the recent deep and prolonged solar minimum on the daytime zonal and vertical plasma drift velocities during quiet time is investigated in this work. Analyzing the data obtained from incoherent scatter radar from Jicamarca (11.95° S, 76.87° W) we observe an anomalous behavior of the zonal plasma drift during June 2008 characterized by lower than usual daytime westward drift and its early afternoon reversal to eastward. As a case study the zonal drift observed on 24 June 2008 is modeled using a realistic low-latitude ionosphere simulated by the Sheffield University Plasmasphere-Ionosphere Model-INPE (SUPIM-INPE). The results show that an anomalously low zonal wind was mainly responsible for the observed anomalous behavior in the zonal drift. A comparative study of the vertical plasma drifts obtained from magnetometer data for some periods of maximum (2000-2002) and minimum solar activity (1998, 2008, 2010) phases reveal a considerable decrease on the E-region conductivity and the dynamo electric field during 2008. However, we believe that the contribution of these characteristics to the unusual behavior of the zonal plasma drift is significantly smaller than that arising from the anomalously low zonal wind. The SUPIM-INPE result of the critical frequency of the F layer (foF2) over Jicamarca suggested a lower radiation flux than that predicted by solar irradiance model (SOLAR2000) for June 2008.

Role of zonal flows in trapped electron mode turbulence through nonlinear gyrokinetic particle and continuum simulationa)

NASA Astrophysics Data System (ADS)

Ernst, D. R.; Lang, J.; Nevins, W. M.; Hoffman, M.; Chen, Y.; Dorland, W.; Parker, S.

2009-05-01

Trapped electron mode (TEM) turbulence exhibits a rich variety of collisional and zonal flow physics. This work explores the parametric variation of zonal flows and underlying mechanisms through a series of linear and nonlinear gyrokinetic simulations, using both particle-in-cell and continuum methods. A new stability diagram for electron modes is presented, identifying a critical boundary at ηe=1, separating long and short wavelength TEMs. A novel parity test is used to separate TEMs from electron temperature gradient driven modes. A nonlinear scan of ηe reveals fine scale structure for ηe≳1, consistent with linear expectation. For ηe<1, zonal flows are the dominant saturation mechanism, and TEM transport is insensitive to ηe. For ηe>1, zonal flows are weak, and TEM transport falls inversely with a power law in ηe. The role of zonal flows appears to be connected to linear stability properties. Particle and continuum methods are compared in detail over a range of ηe=d ln Te/d ln ne values from zero to five. Linear growth rate spectra, transport fluxes, fluctuation wavelength spectra, zonal flow shearing spectra, and correlation lengths and times are in close agreement. In addition to identifying the critical parameter ηe for TEM zonal flows, this paper takes a challenging step in code verification, directly comparing very different methods of simulating simultaneous kinetic electron and ion dynamics in TEM turbulence.

Using Self-Organizing Map (SOM) Clusters of Ozonesonde Profiles to Evaluate Climatologies and Create Linkages between Meteorology and Pollution

NASA Astrophysics Data System (ADS)

Stauffer, R. M.; Thompson, A. M.; Young, G. S.; Oltmans, S. J.; Johnson, B.

2016-12-01

Ozone (O3) climatologies are typically created by averaging ozonesonde profiles on a monthly or seasonal basis, either for specific regions or zonally. We demonstrate the advantages of using a statistical clustering technique, self-organizing maps (SOM), over this simple averaging, through analysis of more than 4500 sonde profiles taken from the long-term US sites at Boulder, CO; Huntsville, AL; Trinidad Head, CA; and Wallops Island, VA. First, we apply SOM to O3 mixing ratios from surface to 12 km amsl. At all four sites, profiles in SOM clusters exhibit similar tropopause height, 500 hPa height and temperature, and total and tropospheric column O3. Second, when profiles from each SOM cluster are compared to monthly O3 means, near-tropopause O3 in three of the clusters is double (over +100 ppbv) the climatological O3 mixing ratio. The three clusters include 13-16% of all profiles, mostly from winter and spring. Large mid-tropospheric deviations from monthly means are found in two highly-populated clusters that represent either distinctly polluted (summer) or clean O3 (fall-winter, high tropopause) profiles. Thus, SOM indeed appear to represent US O3 profile statistics better than conventional climatologies. In the case of Trinidad Head, SOM clusters of O3 profile data from the lower troposphere (surface-6 km amsl) can discriminate background vs polluted O3 and the meteorology associated with each. Two of nine O3 clusters exhibit thin layers ( 100s of m thick) of high O3, typically between 1 and 4 km. Comparisons between clusters and downwind, high-altitude surface O3 measurements display a marked impact of the elevated tropospheric O­­3. Days corresponding to the high O3 clusters exhibit hourly surface O3 anomalies at surface sites of +5 -10 ppbv compared to a climatology; the anomalies can last up to four days. We also explore applications of SOM to tropical ozonesonde profiles, where tropospheric O3 variability is generally smaller.

SAGE aerosol measurements. Volume 3: January 1, 1981 to November 18, 1981

NASA Technical Reports Server (NTRS)

Mccormick, M. Patrick

1987-01-01

The Stratospheric Aerosol and Gas Experiment (SAGE) satellite system, launched February 18, 1979, obtained profiles of aerosol extinction at 1.00 micron and 0.45 micron ozone concentration, and nitrogen dioxide concentration. Data taken during sunset events are presented in the form of zonal and seasonal averages of aerosol extinction of 1.00 micron and 0.45 micron, ratios of aerosol extinction to molecular extinction at 1.00 micron and ratios of aerosol extinction at 0.45 micron to aerosol extinction at 1.00 micron. Averages for 1981 are shown in tables, and in profile and contour plots (as a function of altitude and latitude). In addition, temperature data provided by NOAA for the time and location of each SAGE measurement are averaged and shown in a similar format. The stratospheric aerosol distribution for 1981 shows effects of volcanically injected material from eruptions of Ulawun, Alaid, and Pagan. Peak values of aerosol extinction at 0.45 micron and 1.00 micron were 2 to 4 times higher than typical peak values observed during near background conditions. Stratospheric aerosol optical depth values at 1.00 microns increased by a factor of about 2 from near background levels in regions of volcanic activity. During the year, these values ranged from between 0.001 and 0.006. The largest were near the location of a recent eruption. The distribution of the ratio of aerosol to molecular extinction at 1.00 microns also showed that maximum values are found in the vicinity of an eruption. These maximums varied in altitude, but remained below a height of about 25 km. No attempt has been made to give detailed explanations or interpretations of these data. The intent is to provide, in a ready-to-use visual format, representative zonal and seasonal averages of aerosol extinction data for the third calendar year of the SAGE data set to facilitate atmospheric and climatic studies.

Observed temporal variations in the Earth's gravity field from 16-year Starlette orbit analysis

NASA Technical Reports Server (NTRS)

Cheng, M. K.; Eanes, R. L.; Shum, C. K.; Schutz, B. E.; Tapley, B. D.

1992-01-01

Satellite laser ranging data to Starlette, collected during the period from 1975 to 1990, are analyzed to determine yearly values of the second degree annual (Sa) and semiannual (Ssa) tides, simultaneously with average values of other low degree and order tide parameters. The yearly fluctuations in the values for Sa and Ssa are associated with changes in the Earth's second degree zonal harmonic caused by meteorological excitation. The Starlette-determined mean values for the amplitude of the annual and semiannual variations in J2 are 32.3 x 10 exp -11 and 19.5 x 10 exp -11, respectively; while the rms about the mean values are 4.1 x 10 exp -11 and 6.3 x 10 exp -11, respectively. The annual delta-J2 is in good agreement with the value obtained from the combined effects of air mass redistribution without the oceanic inverted-barometer effects (non-IB) and hydrological change. Approximately 90 percent of the observed annual variation from Starlette is attributed to the meteorological mass redistribution occurring on the Earth's surface.

AIRS Water Vapor and Cloud Products Validate and Explain Recent Short Term Decreases in Global and Tropical OLR as Observed by CERES

NASA Technical Reports Server (NTRS)

Susskind, Joel; Molnar, Gyula; Iredell, Lena

2010-01-01

A strong equatorial SST cooling occurred from 160E westward to 120W during the period of September 2002 through August 2010, surrounded by a weaker warming ring to the west. This is the result of a transition from a strong El Nino in late 2002 to a strong La Nina in 2008. Late 2009 is characterized by the beginning of another El Nino. Average rates of change (ARC's) in 500mb specific humidity and cloud cover are in phase with those in the Sea surface temperature (SST). In the El Nino and surrounding region causing outgoing longwave radiation (OLR), to decrease significantly near the dateline and increase in the vicinity of Indonesia. Tropical OLR ARC's in these two areas cancel each other to first order. The negative zonal mean tropical OLR ARC from a drop in equatorial OLR in region 1 from 140W to 40E. This results from increasing water vapor and cloud cover in this area during La Nina with the reverse holding during El Nino.

The Formation each Winter of the Circumpolar Wave in the Sea Ice around Antarctica

NASA Technical Reports Server (NTRS)

Gloersen, Per; White, Warren B.

1999-01-01

Seeking to improve upon the visualization of the Antarctic Circumpolar Wave (ACW) , we compare a 16-year sequence of 6-month winter averages of Antarctic sea ice extents and concentrations with those of adjacent sea surface temperatures (SSTs). Here we follow SSTs around the globe along the maximum sea ice edge rather than in a zonal band equatorward of it. The results are similar to the earlier ones, but the ACWs do not propagate with equal amplitude or speed. Additionally in a sequence of 4 polar stereographic plots of these SSTs and sea ice concentrations, we find a remarkable correlation between SST minima and sea ice concentration maxima, even to the extent of matching contours across the ice-sea boundary, in the sector between 900E and the Palmer Peninsula. Based on these observations, we suggest that the memory of the ACW in the sea ice is carried from one Austral winter to the next by the neighboring SSTS, since the sea ice is nearly absent in the Austral summer.

Rossby and drift wave turbulence and zonal flows: The Charney-Hasegawa-Mima model and its extensions

NASA Astrophysics Data System (ADS)

Connaughton, Colm; Nazarenko, Sergey; Quinn, Brenda

2015-12-01

A detailed study of the Charney-Hasegawa-Mima model and its extensions is presented. These simple nonlinear partial differential equations suggested for both Rossby waves in the atmosphere and drift waves in a magnetically-confined plasma, exhibit some remarkable and nontrivial properties, which in their qualitative form, survive in more realistic and complicated models. As such, they form a conceptual basis for understanding the turbulence and zonal flow dynamics in real plasma and geophysical systems. Two idealised scenarios of generation of zonal flows by small-scale turbulence are explored: a modulational instability and turbulent cascades. A detailed study of the generation of zonal flows by the modulational instability reveals that the dynamics of this zonal flow generation mechanism differ widely depending on the initial degree of nonlinearity. The jets in the strongly nonlinear case further roll up into vortex streets and saturate, while for the weaker nonlinearities, the growth of the unstable mode reverses and the system oscillates between a dominant jet, which is slightly inclined to the zonal direction, and a dominant primary wave. A numerical proof is provided for the extra invariant in Rossby and drift wave turbulence-zonostrophy. While the theoretical derivations of this invariant stem from the wave kinetic equation which assumes weak wave amplitudes, it is shown to be relatively well-conserved for higher nonlinearities also. Together with the energy and enstrophy, these three invariants cascade into anisotropic sectors in the k-space as predicted by the Fjørtoft argument. The cascades are characterised by the zonostrophy pushing the energy to the zonal scales. A small scale instability forcing applied to the model has demonstrated the well-known drift wave-zonal flow feedback loop. The drift wave turbulence is generated from this primary instability. The zonal flows are then excited by either one of the generation mechanisms, extracting energy from the drift waves as they grow. Eventually the turbulence is completely suppressed and the zonal flows saturate. The turbulence spectrum is shown to diffuse in a manner which has been mathematically predicted. The insights gained from this simple model could provide a basis for equivalent studies in more sophisticated plasma and geophysical fluid dynamics models in an effort to fully understand the zonal flow generation, the turbulent transport suppression and the zonal flow saturation processes in both the plasma and geophysical contexts as well as other wave and turbulence systems where order evolves from chaos.

Two- and three-dimensional natural and mixed convection simulation using modular zonal models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wurtz, E.; Nataf, J.M.; Winkelmann, F.

We demonstrate the use of the zonal model approach, which is a simplified method for calculating natural and mixed convection in rooms. Zonal models use a coarse grid and use balance equations, state equations, hydrostatic pressure drop equations and power law equations of the form {ital m} = {ital C}{Delta}{sup {ital n}}. The advantage of the zonal approach and its modular implementation are discussed. The zonal model resolution of nonlinear equation systems is demonstrated for three cases: a 2-D room, a 3-D room and a pair of 3-D rooms separated by a partition with an opening. A sensitivity analysis withmore » respect to physical parameters and grid coarseness is presented. Results are compared to computational fluid dynamics (CFD) calculations and experimental data.« less

Rossby Wave Propagation into the Northern Hemisphere Stratosphere: The Role of Zonal Phase Speed

NASA Astrophysics Data System (ADS)

Domeisen, Daniela I. V.; Martius, Olivia; Jiménez-Esteve, Bernat

2018-02-01

Sudden stratospheric warming (SSW) events are to a dominant part induced by upward propagating planetary waves. While theory predicts that the zonal phase speed of a tropospheric wave forcing affects wave propagation into the stratosphere, its relevance for SSW events has so far not been considered. This study shows in a linear wave diagnostic and in reanalysis data that phase speeds tend eastward as waves propagate upward, indicating that the stratosphere preselects eastward phase speeds for propagation, especially for zonal wave number 2. This also affects SSW events: Split SSW events tend to be preceded by anomalously eastward zonal phase speeds. Zonal phase speed may indeed explain part of the increased wave flux observed during the preconditioning of SSW events, as, for example, for the record 2009 SSW event.

The volcanic signal in Goddard Institute for Space Studies three-dimensional model simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robock, A.; Liu, Y.

1994-01-01

Transient calculations of the Goddard Institute for Space Studies general circulation model for the climatic signal of volcanic eruptions are analyzed. By compositing the output for two different volcanoes for scenario A and five different volcanos for scenario B, the natural variability is suppressed and the volcanic signals are extracted. Significant global means surface air temperature cooling and precipitation reduction are found for several years following the eruptions, with larger changes in the Northern Hemisphere (NH) than in the Southern Hemisphere. The global-average temperature response lasts for more than four years, but the precipitation response disappears after three years. Themore » largest cooling in the model occurs in the NH summer of the year after spring eruptions. Significant zonal-average temperature reductions begin in the tropics immediately after the eruptions and extend to 45[degrees]S-45[degrees]N in the year after the eruptions. In the second year, cooling is still seen from 30[degrees]S to 30[degrees]N. Because of the low variability in this model as compared to the real world, these signals may appear more significant here than they would be attempting to isolate them using real data. The results suggest that volcanoes can enhance the drought in the Sahel. No evidence was found that stratospheric aerosols from the low-latitude volcanic eruptions can trigger ENSO events in this model.« less

Evaluation of the impact of observations on blended sea surface winds in a two-dimensional variational scheme using degrees of freedom

NASA Astrophysics Data System (ADS)

Wang, Ting; Xiang, Jie; Fei, Jianfang; Wang, Yi; Liu, Chunxia; Li, Yuanxiang

2017-12-01

This paper presents an evaluation of the observational impacts on blended sea surface winds from a two-dimensional variational data assimilation (2D-Var) scheme. We begin by briefly introducing the analysis sensitivity with respect to observations in variational data assimilation systems and its relationship with the degrees of freedom for signal (DFS), and then the DFS concept is applied to the 2D-Var sea surface wind blending scheme. Two methods, a priori and a posteriori, are used to estimate the DFS of the zonal ( u) and meridional ( v) components of winds in the 2D-Var blending scheme. The a posteriori method can obtain almost the same results as the a priori method. Because only by-products of the blending scheme are used for the a posteriori method, the computation time is reduced significantly. The magnitude of the DFS is critically related to the observational and background error statistics. Changing the observational and background error variances can affect the DFS value. Because the observation error variances are assumed to be uniform, the observational influence at each observational location is related to the background error variance, and the observations located at the place where there are larger background error variances have larger influences. The average observational influence of u and v with respect to the analysis is about 40%, implying that the background influence with respect to the analysis is about 60%.

On non-local energy transfer via zonal flow in the Dimits shift

NASA Astrophysics Data System (ADS)

St-Onge, Denis A.

2017-10-01

The two-dimensional Terry-Horton equation is shown to exhibit the Dimits shift when suitably modified to capture both the nonlinear enhancement of zonal/drift-wave interactions and the existence of residual Rosenbluth-Hinton states. This phenomenon persists through numerous simplifications of the equation, including a quasilinear approximation as well as a four-mode truncation. It is shown that the use of an appropriate adiabatic electron response, for which the electrons are not affected by the flux-averaged potential, results in an nonlinearity that can efficiently transfer energy non-locally to length scales of the order of the sound radius. The size of the shift for the nonlinear system is heuristically calculated and found to be in excellent agreement with numerical solutions. The existence of the Dimits shift for this system is then understood as an ability of the unstable primary modes to efficiently couple to stable modes at smaller scales, and the shift ends when these stable modes eventually destabilize as the density gradient is increased. This non-local mechanism of energy transfer is argued to be generically important even for more physically complete systems.

Mie lidar and radiosonde observations at Gadanki (13.5°N, 79.2°E) during sudden stratospheric warming of 2009

NASA Astrophysics Data System (ADS)

Sridharan, S.; Raghunath, K.; Sathishkumar, S.; Nath, D.

2011-03-01

During a major sudden stratospheric warming event (21-27 January 2009), Mie-lidar observations at Gadanki (13.5°N, 79.2°E) show persistent occurrence of cirrus clouds. Outgoing long-wave radiation averaged for 70°E-90°E, decreases to a low value (170 W/m2) on 27 January 2009 over equator indicating deep convection. The zonal mean ERA-Interim data reveal large northward and upward circulation over equatorial upper troposphere. The latitude-longitude map of ERA-Interim zonal mean potential vorticity (PV) indicates two tongues of high PV emanating from polar latitudes and extending further down to equator. Radiosonde observations at Gadanki show the presence of ∼40% relative humidity at 11-13 km and lower tropopause temperature. It is inferred that the tropical circulation change due to PV intrusion leads to deep convection, which along with high humidity and low tropopause temperature leading to the formation of persistent cirrus clouds, the occurrence frequency of which is normally less during winter season over Gadanki.

Stationary waves and slowly moving features in the night upper clouds of Venus

NASA Astrophysics Data System (ADS)

Peralta, J.; Hueso, R.; Sánchez-Lavega, A.; Lee, Y. J.; Muñoz, A. García; Kouyama, T.; Sagawa, H.; Sato, T. M.; Piccioni, G.; Tellmann, S.; Imamura, T.; Satoh, T.

2017-08-01

At the cloud top level of Venus (65-70 km altitude) the atmosphere rotates 60 times faster than the underlying surface—a phenomenon known as superrotation1,2. Whereas on Venus's dayside the cloud top motions are well determined3,4,5,6 and Venus general circulation models predict the mean zonal flow at the upper clouds to be similar on both the day and nightside2, the nightside circulation remains poorly studied except for the polar region7,8. Here, we report global measurements of the nightside circulation at the upper cloud level. We tracked individual features in thermal emission images at 3.8 and 5.0 μm obtained between 2006 and 2008 by the Visible and Infrared Thermal Imaging Spectrometer-Mapper onboard Venus Express and in 2015 by ground-based measurements with the Medium-Resolution 0.8-5.5 Micron Spectrograph and Imager at the National Aeronautics and Space Administration Infrared Telescope Facility. The zonal motions range from -110 to -60 m s-1, which is consistent with those found for the dayside but with larger dispersion6. Slow motions (-50 to -20 m s-1) were also found and remain unexplained. In addition, abundant stationary wave patterns with zonal speeds from -10 to +10 m s-1 dominate the night upper clouds and concentrate over the regions of higher surface elevation.

Interannual and intra-annual variability of rainfall in Haiti (1905-2005)

NASA Astrophysics Data System (ADS)

Moron, Vincent; Frelat, Romain; Jean-Jeune, Pierre Karly; Gaucherel, Cédric

2015-08-01

The interannual variability of annual and monthly rainfall in Haiti is examined from a database of 78 rain gauges in 1905-2005. The spatial coherence of annual rainfall is rather low, which is partly due to Haiti's rugged landscape, complex shoreline, and surrounding warm waters (mean sea surface temperatures >27 °C from May to December). The interannual variation of monthly rainfall is mostly shaped by the intensity of the low-level winds across the Caribbean Sea, leading to a drier- (or wetter-) than-average rainy season associated with easterly (or westerly) anomalies, increasing (or decreasing) winds. The varying speed of low-level easterlies across the Caribbean basin may reflect at least four different processes during the year: (1) an anomalous trough/ridge over the western edge of the Azores high from December to February, peaking in January; (2) a zonal pressure gradient between Eastern Pacific and the tropical Northern Atlantic from May/June to September, with a peak in August (i.e. lower-than-average rainfall in Haiti is associated with positive sea level pressure anomalies over the tropical North Atlantic and negative sea level pressure anomalies over the Eastern Pacific); (3) a local ocean-atmosphere coupling between the speed of the Caribbean Low Level Jet and the meridional sea surface temperature (SST) gradient across the Caribbean basin (i.e. colder-than-average SST in the southern Caribbean sea is associated with increased easterlies and below-average rainfall in Haiti). This coupling is triggered when the warmest Caribbean waters move northward toward the Gulf of Mexico; (4) in October/November, a drier- (or wetter-) than-usual rainy season is related to an almost closed anticyclonic (or cyclonic) anomaly located ENE of Haiti on the SW edge of the Azores high. This suggests a main control of the interannual variations of rainfall by intensity, track and/or recurrence of tropical depressions traveling northeast of Haiti. During this period, the teleconnection of Haitian rainfall with synchronous Atlantic and Eastern Pacific SST is at a minimum.

Modification of Jupiter's Stratosphere Three Weeks After the 2009 Impact

NASA Technical Reports Server (NTRS)

Fast, Kelly Elizabeth; Kostiuk, T.; Livengood, T. A.; Hewagama, T.; Annen, J.

2010-01-01

Infrared spectroscopy sensitive to thermal emission from Jupiter's stratosphere reveals effects persisting 3 1/2 weeks after the impact of a body in late July 2009. Measurements obtained at 11.7 microns on 2009 August 11 UT at the impact latitude of 56degS (planetocentric), using the Goddard Heterodyne Instrument for Planetary Winds and Composition (HIPWAC) mounted on the NASA Infrared Telescope facility, reveal an interval of reduced thermal continuum emission that extends approx.60deg-80deg towards planetary East of the impact site, estimated to be at 305deg longitude (System III). Retrieved stratospheric ethane mole fraction in the near vicinity of the impact site is enhanced by up to approx.60% relative to quiescent regions at this latitude. Thermal continuum emission at the impact site, and somewhat west of it, is significantly enhanced in the same spectra that retrieve enhanced ethane mole fraction. Assuming that the enhanced continuum brightness near the impact site results from thermalized aerosol debris, then continuum emission by a haze layer can be approximated by an opaque surface inserted at the 45-60 mbar pressure level in the stratosphere in an unperturbed thermal profile, setting a lower limit on the altitude of the top of the ejecta cloud at this time. The reduced continuum brightness east of the impact site can be modeled by an opaque surface near the cold tropopause, consistent with a lower altitude of ejecta/impactor-formed opacity or significantly lesser column density of opaque haze material. The physical extent of the observed region of reduced continuum implies a minimum average velocity of 21 m/s transporting material prograde (East) from the impact. Spectra acquired further East, with quiescent characteristics, imply an average zonal velocity of less than 63 m/s.

Testing for the linearity of responses to multiple anthropogenic climate forcings

NASA Astrophysics Data System (ADS)

Forest, C. E.; Stone, P. H.; Sokolov, A. P.

2001-12-01

To test whether climate forcings are additive, we compare climate model simulations in which anthropogenic forcings are applied individually and in combination. Tests are performed with different values for climate system properties (climate sensitivity and rate of heat uptake by the deep ocean) as well as for different strengths of the net aerosol forcing, thereby testing for the dependence of linearity on these properties. The MIT 2D Land-Ocean Climate Model used in this study consists of a zonally averaged statistical-dynamical atmospheric model coupled to a mixed-layer Q-flux ocean model, with heat anomalies diffused into the deep ocean. Following our previous studies, the anthropogenic forcings are the changes in concentrations of greenhouse gases (1860-1995), sulfate aerosol (1860-1995), and stratospheric and tropospheric ozone (1979-1995). The sulfate aerosol forcing is applied as a surface albedo change. For an aerosol forcing of -1.0 W/m2 and an effective ocean diffusitivity of 2.5 cm2/s, the nonlinearity of the response of global-mean surface temperatures to the combined forcing shows a strong dependence on climate sensitivity. The fractional change in decadal averages ([(Δ TG + Δ TS + Δ TO) - Δ TGSO ]/ Δ TGSO) for the 1986-1995 period compared to pre-industrial times are 0.43, 0.90, and 1.08 with climate sensitivities of 3.0, 4.5, and 6.2 oC, respectively. The values of Δ TGSO for these three cases are 0.52, 0.62, and 0.76 oC. The dependence of linearity on climate system properties, the role of climate system feedbacks, and the implications for the detection of climate system's response to individual forcings will be presented. Details of the model and forcings can be found at http://web.mit.edu/globalchange/www/.

Significant Features Found in Simulated Tropical Climates Using a Cloud Resolving Model

NASA Technical Reports Server (NTRS)

Shie, C.-L.; Tao, W.-K.; Simpson, J.; Sui, C.-H.

2000-01-01

Cloud resolving model (CRM) has widely been used in recent years for simulations involving studies of radiative-convective systems and their role in determining the tropical regional climate. The growing popularity of CRMs usage can be credited for their inclusion of crucial and realistic features such like explicit cloud-scale dynamics, sophisticated microphysical processes, and explicit radiative-convective interaction. For example, by using a two-dimensional cloud model with radiative-convective interaction process, found a QBO-like (quasibiennial oscillation) oscillation of mean zonal wind that affected the convective system. Accordingly, the model-generated rain band corresponding to convective activity propagated in the direction of the low-level zonal mean winds; however, the precipitation became "localized" (limited within a small portion of the domain) as zonal mean winds were removed. Two other CRM simulations by S94 and Grabowski et al. (1996, hereafter G96), respectively that produced distinctive quasi-equilibrium ("climate") states on both tropical water and energy, i.e., a cold/dry state in S94 and a warm/wet state in G96, have later been investigated by T99. They found that the pattern of the imposed large-scale horizontal wind and the magnitude of the imposed surface fluxes were the two crucial mechanisms in determining the tropical climate states. The warm/wet climate was found associated with prescribed strong surface winds, or with maintained strong vertical wind shears that well-organized convective systems prevailed. On the other hand, the cold/dry climate was produced due to imposed weak surface winds and weak wind shears throughout a vertically mixing process by convection. In this study, considered as a sequel of T99, the model simulations to be presented are generally similar to those of T99 (where a detailed model setup can be found), except for a more detailed discussion along with few more simulated experiments. There are twelve major experiments chosen for presentations that are introduced in section two. Several significant feature analyses regarding the rainfall properties, CAPE (Convective Available Potential Energy), cloud-scale eddies, the stability issue, the convective system propagation, relative humidity, and the effect on the quasi-equilibrium state by the imposed constant. radiation or constant surface fluxes, and etc. will be presented in the meeting. However, only three of the subjects are discussed in section three. A brief summary is concluded in the end section.

Potential application of artificial concepts to aerodynamic simulation

NASA Technical Reports Server (NTRS)

Kutler, P.; Mehta, U. B.; Andrews, A.

1984-01-01

The concept of artificial intelligence as it applies to computational fluid dynamics simulation is investigated. How expert systems can be adapted to speed the numerical aerodynamic simulation process is also examined. A proposed expert grid generation system is briefly described which, given flow parameters, configuration geometry, and simulation constraints, uses knowledge about the discretization process to determine grid point coordinates, computational surface information, and zonal interface parameters.

Inventory of File sref.t03z.pgrb212_SPC.prob_3hrly.gri

Science.gov Websites

-GWD analysis Zonal Flux of Gravity Wave Stress [prob] prob =1 002 entire atmosphere (considered as a as a single layer) VUCSH analysis Vertical U-Component Shear [prob] prob =2 004 entire atmosphere (considered as a single layer) VUCSH analysis Vertical U-Component Shear [prob] prob =3 005 surface APCP 0-3

Inventory of File sref.t03z.pgrb216_SPC.prob_3hrly.gri

Science.gov Websites

-GWD analysis Zonal Flux of Gravity Wave Stress [prob] prob =1 002 entire atmosphere (considered as a as a single layer) VUCSH analysis Vertical U-Component Shear [prob] prob =2 004 entire atmosphere (considered as a single layer) VUCSH analysis Vertical U-Component Shear [prob] prob =3 005 surface APCP 0-3

Inventory of File sref.t03z.pgrb243_SPC.prob_3hrly.gri

Science.gov Websites

-GWD analysis Zonal Flux of Gravity Wave Stress [prob] prob =1 002 entire atmosphere (considered as a as a single layer) VUCSH analysis Vertical U-Component Shear [prob] prob =2 004 entire atmosphere (considered as a single layer) VUCSH analysis Vertical U-Component Shear [prob] prob =3 005 surface APCP 0-3

CPC - Climate Weather Linkage: El Niño Southern Oscillation

Science.gov Websites

Equatorial Pacific Temperature Depth Anomalies Animation Time longitude section of Anomalous OLR 850 hecto Temperatures anomalies Time series of weekly sea surface temperatures anomalies for the 4 Niño regions Time (OLR) Pentad mean and anomalous OLR Time-longitude section of anomalous OLR 850-hPa Zonal Wind Time

Climate modeling. [for use in understanding earth's radiation budget

NASA Technical Reports Server (NTRS)

1978-01-01

The requirements for radiation measurements suitable for the understanding, improvement, and verification of models used in performing climate research are considered. Both zonal energy balance models and three dimensional general circulation models are considered, and certain problems are identified as common to all models. Areas of emphasis include regional energy balance observations, spectral band observations, cloud-radiation interaction, and the radiative properties of the earth's surface.

Disturbance zonal and vertical plasma drifts in the Peruvian sector during solar minimum phases

NASA Astrophysics Data System (ADS)

Santos, A. M.; Abdu, M. A.; Souza, J. R.; Sobral, J. H. A.; Batista, I. S.

2016-03-01

In the present work, we investigate the behavior of the equatorial F region zonal plasma drifts over the Peruvian region under magnetically disturbed conditions during two solar minimum epochs, one of them being the recent prolonged solar activity minimum. The study utilizes the vertical and zonal components of the plasma drifts measured by the Jicamarca (11.95°S; 76.87°W) incoherent scatter radar during two events that occurred on 10 April 1997 and 24 June 2008 and model calculation of the zonal drift in a realistic ionosphere simulated by the Sheffield University Plasmasphere-Ionosphere Model-INPE. Two main points are focused: (1) the connection between electric fields and plasma drifts under prompt penetration electric field during a disturbed periods and (2) anomalous behavior of daytime zonal drift in the absence of any magnetic storm. A perfect anticorrelation between vertical and zonal drifts was observed during the night and in the initial and growth phases of the magnetic storm. For the first time, based on a realistic low-latitude ionosphere, we will show, on a detailed quantitative basis, that this anticorrelation is driven mainly by a vertical Hall electric field induced by the primary zonal electric field in the presence of an enhanced nighttime E region ionization. It is shown that an increase in the field line-integrated Hall-to-Pedersen conductivity ratio (∑H/∑P), which can arise from precipitation of energetic particles in the region of the South American Magnetic Anomaly, is capable of explaining the observed anticorrelation between the vertical and zonal plasma drifts. Evidence for the particle ionization is provided from the occurrence of anomalous sporadic E layers over the low-latitude station, Cachoeira Paulista (22.67°S; 44.9°W)—Brazil. It will also be shown that the zonal plasma drift reversal to eastward in the afternoon two hours earlier than its reference quiet time pattern is possibly caused by weakening of the zonal wind system during the prolonged solar minimum period.

Surface-Wind Anomalies in North-Atlantic and North Pacific from SSM/I Observations: Influence on Temperature of Adjoining Land Regions

NASA Technical Reports Server (NTRS)

Otterman, Joseph; Atlas, R.; Ingraham, J.; Ardizzone, J.; Starr, D.; Terry, J.

1998-01-01

Surface winds over the oceans are derived from Special Sensor Microwave Imager (SSM/I) measurements, assigning direction by Variational Analysis Method (VAM). Validations by comparison with other measurements indicate highly-satisfactory data quality. Providing global coverage from 1988, the dataset is a convenient source for surface-wind climatology. In this study, the interannual variability of zonal winds is analyzed concentrating on the westerlies in North Atlantic and North Pacific, above 30 N. Interannual differences in the westerlies exceeding 10 m sec (exp -1) are observed over large regions, often accompanied by changes of the same magnitude in the easterlies below 30 N. We concentrate on February/March, since elevated temperatures, by advancing snow-melt, can produce early spring. The extremely strong westerlies in 1997 observed in these months over North Atlantic (and also North Pacific) apparently contributed to large surface-temperature anomalies in western Europe, on the order of +3 C above the climatic monthly average for England and France. At these latitudes strong positive anomalies extended in a ring around the globe. We formulated an Index of South westerlies for the North Atlantic, which can serve as an indicator for day-by-day advection effects into Europe. In comparing 1997 and 1998 with the previous years, we establish significant correlations with the temperature anomalies (one to five days later, depending on the region, and on the season). This variability of the ocean-surface winds and of the temperature anomalies on land may be related to the El Nino/La Nina oscillations. Such large temperature fluctuations over large areas, whatever the cause, can be regarded as noise in attempts to assess long-term trends in global temperature.

Geomagnetic Storm Effects in the Low- to Middle-Latitude Upper Thermosphere

NASA Technical Reports Server (NTRS)

Burns, A. G.; Killeen, T. L.; Deng, W.; Carignan, G. R.; Roble, R. G.

1995-01-01

In this paper, we use data from the Dynamics Explorer 2 (DE 2) satellite and a theoretical simulation made by using the National Center for Atmospheric Research thermosphere/ionosphere general circulation model (NCAR-TIGCM) to study storm-induced changes in the structure of the upper thermosphere in the low- to middle-latitude (20 deg-40 deg N) region of the winter hemisphere. Our principal results are as follows: (1) The winds associated with the diurnal tide weaken during geomagnetic storms, causing primarily zonally oriented changes in the evening sector, few changes in the middle of the afternoon, a combination of zonal and meridional changes in the late morning region, and mainly meridional changes early in the morning; (2) Decreases in the magnitudes of the horizontal winds associated with the diurnal tide lead to a net downward tendency in the vertical winds blowing through a constant pressure surface; (3) Because of these changes in the vertical wind, there is an increase in compressional heating (or a decrease in cooling through expansion), and thus temperatures in the low- to middle-latitudes of the winter hemisphere increase; (4) Densities of all neutral species increase on a constant height surface, but the pattern of changes in the O/N2 ratio is not well ordered on these surfaces; (5) The pattern of changes in the O/N2 ratio is better ordered on constant pressure surfaces. The increases in this ratio on constant pressure surfaces in the low- to middle-latitude, winter hemisphere are caused by a more downward tendency in the vertical winds that blow through the constant pressure surfaces. Nitrogen-poor air is then advected downward through the pressure surface, increasing the O/N2 ratio; (6) The daytime geographical distribution of the modeled increases in the O/N2 ratio on a constant pressure surface in the low- to middle-latitudes of the winter hemisphere correspond very closely with those of increases in the modeled electron densities at the F2 peak.

A preliminary comparison of Na lidar and meteor radar zonal winds during geomagnetic quiet and disturbed conditions

NASA Astrophysics Data System (ADS)

Kishore Kumar, G.; Nesse Tyssøy, H.; Williams, Bifford P.

2018-03-01

We investigate the possibility that sufficiently large electric fields and/or ionization during geomagnetic disturbed conditions may invalidate the assumptions applied in the retrieval of neutral horizontal winds from meteor and/or lidar measurements. As per our knowledge, the possible errors in the wind estimation have never been reported. In the present case study, we have been using co-located meteor radar and sodium resonance lidar zonal wind measurements over Andenes (69.27°N, 16.04°E) during intense substorms in the declining phase of the January 2005 solar proton event (21-22 January 2005). In total, 14 h of measurements are available for the comparison, which covers both quiet and disturbed conditions. For comparison, the lidar zonal wind measurements are averaged over the same time and altitude as the meteor radar wind measurements. High cross correlations (∼0.8) are found in all height regions. The discrepancies can be explained in light of differences in the observational volumes of the two instruments. Further, we extended the comparison to address the electric field and/or ionization impact on the neutral wind estimation. For the periods of low ionization, the neutral winds estimated with both instruments are quite consistent with each other. During periods of elevated ionization, comparatively large differences are noticed at the highermost altitude, which might be due to the electric field and/or ionization impact on the wind estimation. At present, one event is not sufficient to make any firm conclusion. Further study with more co-located measurements are needed to test the statistical significance of the result.

A Paleointensity-Based Test of the Geocentric Axial Dipole (GAD) Hypothesis

NASA Astrophysics Data System (ADS)

Heimpel, M. H.; Veikkolainen, T.; Evans, M. E.; Pesonen, L. J.; Korhonen, K.

2016-12-01

The GAD model is central to many aspects of geophysics, including plate tectonics and paleoclimate. However, significant departures from a GAD field over geologic time have not been ruled out, particularly for the Precambrian. Here, we investigate a test of the GAD model using published paleointensity data. Our goals are to determine if paleointensities can shed light on the validity of the GAD model, and hence to see if they provide constraints on the evolution of the geodynamo throughout earth history. Using numerical dynamo models, we show that intensity distributions can be fairly well characterized by the first three zonal Gauss coefficients (dipole, quadrupole and octupole), although time-averaging tends to broaden the range of intensities. The dynamo models indicate that the ancient core, prior to nucleation of the inner core, may have had a significant (up to 10%) contribution of the zonal octupole. We then investigate the connection between the measured paleointensities assembled in the PINT database and the GAD model by means of predicted theoretical frequency distributions for various simple models (GAD, GAD ± small zonal quadrupole or octupole components). Hitherto, paleointensities have often been analysed in terms of corresponding virtual dipole moments (VDMs). But this rather begs the question because a GAD model is assumed in order to derive a VDM. By using raw field values reported from each sampling site we eliminate dependence on the GAD hypothesis. We find that models consisting of one or two different GADs cannot explain the data, but 3- or 4-GAD models can fit the data surprisingly well, and adding a ±5% octupole significantly improves the fit.

Characteristics of equatorial plasma bubbles observed by TEC map based on ground-based GNSS receivers over South America

NASA Astrophysics Data System (ADS)

Barros, Diego; Takahashi, Hisao; Wrasse, Cristiano M.; Figueiredo, Cosme Alexandre O. B.

2018-01-01

A ground-based network of GNSS receivers has been used to monitor equatorial plasma bubbles (EPBs) by mapping the total electron content (TEC map). The large coverage of the TEC map allowed us to monitor several EPBs simultaneously and get characteristics of the dynamics, extension and longitudinal distributions of the EPBs from the onset time until their disappearance. These characteristics were obtained by using TEC map analysis and the keogram technique. TEC map databases analyzed were for the period between November 2012 and January 2016. The zonal drift velocities of the EPBs showed a clear latitudinal gradient varying from 123 m s-1 at the Equator to 65 m s-1 for 35° S latitude. Consequently, observed EPBs are inclined against the geomagnetic field lines. Both zonal drift velocity and the inclination of the EPBs were compared to the thermospheric neutral wind, which showed good agreement. Moreover, the large two-dimensional coverage of TEC maps allowed us to study periodic EPBs with a wide longitudinal distance. The averaged values observed for the inter-bubble distances also presented a clear latitudinal gradient varying from 920 km at the Equator to 640 km at 30° S. The latitudinal gradient in the inter-bubble distances seems to be related to the difference in the zonal drift velocity of the EPB from the Equator to middle latitudes and to the difference in the westward movement of the terminator. On several occasions, the distances reached more than 2000 km. Inter-bubble distances greater than 1000 km have not been reported in the literature.

A preliminary comparison of Na lidar and meteor radar zonal winds during quiet and sub-storm conditions

NASA Astrophysics Data System (ADS)

Grandhi, Kishore Kumar; Nesse Tyssøy, Hilde; Williams, Bifford P.; Stober, Gunter

2017-04-01

It is speculated that sufficiently large electric fields during geomagnetic disturbed conditions may decouple the meteor trail electron motions from the background neutral winds and leads to erroneous neutral wind estimation. As per our knowledge, the potential errors have never been reported. In the present case study, we have been using co-located meteor radar and sodium resonance lidar zonal wind measurements over Andenes (69.27oN,16.04oE) during intense sub storms in the declining phase of Jan 2005 solar proton event (21-22 Jan 2005). In total 14 hours of continuous measurements are available for the comparison, which covers both quiet and disturbed conditions. For comparison, the lidar zonal winds are averaged in meteor radar time and height bins. High cross correlations (˜0.8) are found in all height regions. The discrepancies can be explained in the light of differences in the observational volumes of the two instruments. Further, we extended the comparison to address the ionization impact on the meteor radar winds. For quiet hours, the observed meteor radar winds are quite consistent with lidar winds. While during the disturbed hours comparatively large differences are noticed at higher most altitudes. This might be due to ionization impact on meteor radar winds. At the present one event is not sufficient to make any consolidate conclusion. However, at least from this study we found some effect on the neutral wind measurements for the meteor radar. Further study with more co-located measurements are needed to test statistical significance of the result.

Analysis of solute-protein interactions and solute-solute competition by zonal elution affinity chromatography.

PubMed

Tao, Pingyang; Poddar, Saumen; Sun, Zuchen; Hage, David S; Chen, Jianzhong

2018-02-02

Many biological processes involve solute-protein interactions and solute-solute competition for protein binding. One method that has been developed to examine these interactions is zonal elution affinity chromatography. This review discusses the theory and principles of zonal elution affinity chromatography, along with its general applications. Examples of applications that are examined include the use of this method to estimate the relative extent of solute-protein binding, to examine solute-solute competition and displacement from proteins, and to measure the strength of these interactions. It is also shown how zonal elution affinity chromatography can be used in solvent and temperature studies and to characterize the binding sites for solutes on proteins. In addition, several alternative applications of zonal elution affinity chromatography are discussed, which include the analysis of binding by a solute with a soluble binding agent and studies of allosteric effects. Other recent applications that are considered are the combined use of immunoextraction and zonal elution for drug-protein binding studies, and binding studies that are based on immobilized receptors or small targets. Copyright © 2018 Elsevier Inc. All rights reserved.

Effect of external plasma flows on the interaction between turbulence and convective cells

NASA Astrophysics Data System (ADS)

Uzawa, Ken; Li, Jiquan

2005-10-01

It is widely recognized that large scale structures, such as zonal flows, streamers and also long wavelength Kelvin-Helmholtz modes are nonlinearly generated from maternal turbulence through modulational instability process and play a crucial role in regulating the transport in tokamaks. In order to control the transport, it is desirable to control such structures and/or modulational process. One of control parameters may be mean flow which intrinsically exists in tokamak plasmas. Besides the direct influence on the transport through vortex decorrelation, the mean flow may indirectly change the zonal flow generation by acting on the modulational process itself. In this work, we theoretically investigate the characteristics of zonal flow generation due to the electron temperature gradient (ETG) turbulence in the presence of long wavelength ITG driven zonal flow. This was done by extending our previous modulational analyses[1]. We have numerically analyzed the influence of mean flow on zonal flow generation. The main result is that the zonal flow generation is suppressed by the presence of the mean flow. [1]J. Li, Y. Kishimoto, Physics of Plasmas, 9, 1241 (2002)

High-fidelity simulations of unsteady civil aircraft aerodynamics: stakes and perspectives. Application of zonal detached eddy simulation

PubMed Central

Deck, Sébastien; Gand, Fabien; Brunet, Vincent; Ben Khelil, Saloua

2014-01-01

This paper provides an up-to-date survey of the use of zonal detached eddy simulations (ZDES) for unsteady civil aircraft applications as a reflection on the stakes and perspectives of the use of hybrid methods in the framework of industrial aerodynamics. The issue of zonal or non-zonal treatment of turbulent flows for engineering applications is discussed. The ZDES method used in this article and based on a fluid problem-dependent zonalization is briefly presented. Some recent landmark achievements for conditions all over the flight envelope are presented, including low-speed (aeroacoustics of high-lift devices and landing gear), cruising (engine–airframe interactions), propulsive jets and off-design (transonic buffet and dive manoeuvres) applications. The implications of such results and remaining challenges in a more global framework are further discussed. PMID:25024411

Stationary zonal flows during the formation of the edge transport barrier in the JET tokamak

DOE PAGES

Hillesheim, J. C.; Meyer, H.; Maggi, C. F.; ...

2016-02-10

In this study, high spatial resolution Doppler backscattering measurements in JET have enabled new insights into the development of the edge E r. We observe fine-scale spatial structures in the edge E r well with a wave number k rρi ≈ 0.4-0.8, consistent with stationary zonal flows, the characteristics of which vary with density. The zonal flow amplitude and wavelength both decrease with local collisionality, such that the zonal flow E x B shear increases. Above the minimum of the L-H transition power threshold dependence on density, the zonal flows are present during L mode and disappear following the H-modemore » transition, while below the minimum they are reduced below measurable amplitude during L mode, before the L-H transition.« less

Impacts of parameterized orographic drag on the Northern Hemisphere winter circulation

PubMed Central

Bechtold, Peter; Beljaars, Anton; Bozzo, Alessio; Pithan, Felix; Shepherd, Theodore G.; Zadra, Ayrton

2016-01-01

Abstract A recent intercomparison exercise proposed by the Working Group for Numerical Experimentation (WGNE) revealed that the parameterized, or unresolved, surface stress in weather forecast models is highly model‐dependent, especially over orography. Models of comparable resolution differ over land by as much as 20% in zonal mean total subgrid surface stress (τtot). The way τtot is partitioned between the different parameterizations is also model‐dependent. In this study, we simulated in a particular model an increase in τtot comparable with the spread found in the WGNE intercomparison. This increase was simulated in two ways, namely by increasing independently the contributions to τtot of the turbulent orographic form drag scheme (TOFD) and of the orographic low‐level blocking scheme (BLOCK). Increasing the parameterized orographic drag leads to significant changes in surface pressure, zonal wind and temperature in the Northern Hemisphere during winter both in 10 day weather forecasts and in seasonal integrations. However, the magnitude of these changes in circulation strongly depends on which scheme is modified. In 10 day forecasts, stronger changes are found when the TOFD stress is increased, while on seasonal time scales the effects are of comparable magnitude, although different in detail. At these time scales, the BLOCK scheme affects the lower stratosphere winds through changes in the resolved planetary waves which are associated with surface impacts, while the TOFD effects are mostly limited to the lower troposphere. The partitioning of τtot between the two schemes appears to play an important role at all time scales. PMID:27668040

Enhanced separation of membranes during free flow zonal electrophoresis in plants.

PubMed

Barkla, Bronwyn J; Vera-Estrella, Rosario; Pantoja, Omar

2007-07-15

Free flow zonal electrophoresis (FFZE) is a versatile technique that allows for the separation of cells, organelles, membranes, and proteins based on net surface charge during laminar flow through a thin aqueous layer. We have been optimizing the FFZE technique to enhance separation of plant vacuolar membranes (tonoplast) from other endomembranes to pursue a directed proteomics approach to identify novel tonoplast transporters. Addition of ATP to a mixture of endomembranes selectively enhanced electrophoretic mobility of acidic vesicular compartments during FFZE toward the positive electrode. This has been attributed to activation of the V-ATPase generating a more negative membrane potential outside the vesicles, resulting in enhanced migration of acidic vesicles, including tonoplast, to the anode (Morré, D. J.; Lawrence, J.; Safranski, K.; Hammond, T.; Morré, D. M. J. Chromatogr., A 1994, 668, 201-213). We confirm that ATP does induce a redistribution of membranes during FFZE of microsomal membranes isolated from several plant species, including Arabidopsis thaliana, Thellungiella halophila, Mesembryanthemum crystallinum, and Ananas comosus. However, we demonstrate, using V-ATPase-specific inhibitors, nonhydrolyzable ATP analogs, and ionophores to dissipate membrane potential, that the ATP-dependent migrational shift of membranes under FFZE is not due to activation of the V-ATPase. Addition of EDTA to chelate Mg2+, leading to the production of the tetravalent anionic form of ATP, resulted in a further enhancement of membrane migration toward the anode, and manipulation of cell surface charge by addition of polycations also influenced the ATP-dependent migration of membranes. We propose that ATP enhances the mobility of endomembranes by screening positive surface charges on the membrane surface.

Eastern equatorial Pacific sea surface temperature annual cycle in the Kiel climate model: simulation benefits from enhancing atmospheric resolution

NASA Astrophysics Data System (ADS)

Wengel, C.; Latif, M.; Park, W.; Harlaß, J.; Bayr, T.

2018-05-01

A long-standing difficulty of climate models is to capture the annual cycle (AC) of eastern equatorial Pacific (EEP) sea surface temperature (SST). In this study, we first examine the EEP SST AC in a set of integrations of the coupled Kiel Climate Model, in which only atmosphere model resolution differs. When employing coarse horizontal and vertical atmospheric resolution, significant biases in the EEP SST AC are observed. These are reflected in an erroneous timing of the cold tongue's onset and termination as well as in an underestimation of the boreal spring warming amplitude. A large portion of these biases are linked to a wrong simulation of zonal surface winds, which can be traced back to precipitation biases on both sides of the equator and an erroneous low-level atmospheric circulation over land. Part of the SST biases also is related to shortwave radiation biases related to cloud cover biases. Both wind and cloud cover biases are inherent to the atmospheric component, as shown by companion uncoupled atmosphere model integrations forced by observed SSTs. Enhancing atmosphere model resolution, horizontal and vertical, markedly reduces zonal wind and cloud cover biases in coupled as well as uncoupled mode and generally improves simulation of the EEP SST AC. Enhanced atmospheric resolution reduces convection biases and improves simulation of surface winds over land. Analysis of a subset of models from the Coupled Model Intercomparison Project phase 5 (CMIP5) reveals that in these models, very similar mechanisms are at work in driving EEP SST AC biases.

Impacts of parameterized orographic drag on the Northern Hemisphere winter circulation

NASA Astrophysics Data System (ADS)

Sandu, Irina; Bechtold, Peter; Beljaars, Anton; Bozzo, Alessio; Pithan, Felix; Shepherd, Theodore G.; Zadra, Ayrton

2016-03-01

A recent intercomparison exercise proposed by the Working Group for Numerical Experimentation (WGNE) revealed that the parameterized, or unresolved, surface stress in weather forecast models is highly model-dependent, especially over orography. Models of comparable resolution differ over land by as much as 20% in zonal mean total subgrid surface stress (τtot). The way τtot is partitioned between the different parameterizations is also model-dependent. In this study, we simulated in a particular model an increase in τtot comparable with the spread found in the WGNE intercomparison. This increase was simulated in two ways, namely by increasing independently the contributions to τtot of the turbulent orographic form drag scheme (TOFD) and of the orographic low-level blocking scheme (BLOCK). Increasing the parameterized orographic drag leads to significant changes in surface pressure, zonal wind and temperature in the Northern Hemisphere during winter both in 10 day weather forecasts and in seasonal integrations. However, the magnitude of these changes in circulation strongly depends on which scheme is modified. In 10 day forecasts, stronger changes are found when the TOFD stress is increased, while on seasonal time scales the effects are of comparable magnitude, although different in detail. At these time scales, the BLOCK scheme affects the lower stratosphere winds through changes in the resolved planetary waves which are associated with surface impacts, while the TOFD effects are mostly limited to the lower troposphere. The partitioning of τtot between the two schemes appears to play an important role at all time scales.

Fluid simulation of tokamak ion temperature gradient turbulence with zonal flow closure model

NASA Astrophysics Data System (ADS)

Yamagishi, Osamu; Sugama, Hideo

2016-03-01

Nonlinear fluid simulation of turbulence driven by ion temperature gradient modes in the tokamak fluxtube configuration is performed by combining two different closure models. One model is a gyrofluid model by Beer and Hammett [Phys. Plasmas 3, 4046 (1996)], and the other is a closure model to reproduce the kinetic zonal flow response [Sugama et al., Phys. Plasmas 14, 022502 (2007)]. By including the zonal flow closure, generation of zonal flows, significant reduction in energy transport, reproduction of the gyrokinetic transport level, and nonlinear upshift on the critical value of gradient scale length are observed.

Fluid simulation of tokamak ion temperature gradient turbulence with zonal flow closure model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamagishi, Osamu, E-mail: yamagisi@nifs.ac.jp; Sugama, Hideo

Nonlinear fluid simulation of turbulence driven by ion temperature gradient modes in the tokamak fluxtube configuration is performed by combining two different closure models. One model is a gyrofluid model by Beer and Hammett [Phys. Plasmas 3, 4046 (1996)], and the other is a closure model to reproduce the kinetic zonal flow response [Sugama et al., Phys. Plasmas 14, 022502 (2007)]. By including the zonal flow closure, generation of zonal flows, significant reduction in energy transport, reproduction of the gyrokinetic transport level, and nonlinear upshift on the critical value of gradient scale length are observed.

New results on equatorial thermospheric winds and temperatures from Ethiopia, Africa

NASA Astrophysics Data System (ADS)

Tesema, Fasil; Mesquita, Rafael; Meriwether, John; Damtie, Baylie; Nigussie, Melessew; Makela, Jonathan; Fisher, Daniel; Harding, Brian; Yizengaw, Endawoke; Sanders, Samuel

2017-03-01

Measurements of equatorial thermospheric winds, temperatures, and 630 nm relative intensities were obtained using an imaging Fabry-Perot interferometer (FPI), which was recently deployed at Bahir Dar University in Ethiopia (11.6° N, 37.4° E, 3.7° N magnetic). The results obtained in this study cover 6 months (53 nights of useable data) between November 2015 and April 2016. The monthly-averaged values, which include local winter and equinox seasons, show the magnitude of the maximum monthly-averaged zonal wind is typically within the range of 70 to 90 ms-1 and is eastward between 19:00 and 21:00 LT. Compared to prior studies of the equatorial thermospheric wind for this local time period, the magnitude is considerably weaker as compared to the maximum zonal wind speed observed in the Peruvian sector but comparable to Brazilian FPI results. During the early evening, the meridional wind speeds are 30 to 50 ms-1 poleward during the winter months and 10 to 25 ms-1 equatorward in the equinox months. The direction of the poleward wind during the winter months is believed to be mainly caused by the existence of the interhemispheric wind flow from the summer to winter hemispheres. An equatorial wind surge is observed later in the evening and is shifted to later local times during the winter months and to earlier local times during the equinox months. Significant night-to-night variations are also observed in the maximum speed of both zonal and meridional winds. The temperature observations show the midnight temperature maximum (MTM) to be generally present between 00:30 and 02:00 LT. The amplitude of the MTM was ˜ 110 K in January 2016 with values smaller than this in the other months. The local time difference between the appearance of the MTM and a pre-midnight equatorial wind was generally 60 to 180 min. A meridional wind reversal was also observed after the appearance of the MTM (after 02:00 LT). Climatological models, HWM14 and MSIS-00, were compared to the observations and the HWM14 model generally predicted the zonal wind observations well with the exception of higher model values by 25 ms-1 in the winter months. The HWM14 model meridional wind showed generally good agreement with the observations. Finally, the MSIS-00 model overestimated the temperature by 50 to 75 K during the early evening hours of local winter months. Otherwise, the agreement was generally good, although, in line with prior studies, the model failed to reproduce the MTM peak for any of the 6 months compared with the FPI data.

A comparison of the momentum budget in reanalysis datasets during sudden stratospheric warming events

NASA Astrophysics Data System (ADS)

Martineau, Patrick; Son, Seok-Woo; Taguchi, Masakazu; Butler, Amy H.

2018-05-01

The agreement between reanalysis datasets, in terms of the zonal-mean momentum budget, is evaluated during sudden stratospheric warming (SSW) events. It is revealed that there is a good agreement among datasets in the lower stratosphere and troposphere concerning zonal-mean zonal wind, but less so in the upper stratosphere. Forcing terms of the momentum equation are also relatively similar in the lower atmosphere, but their uncertainties are typically larger than uncertainties of the zonal-wind tendency. Similar to zonal-wind tendency, the agreement among forcing terms is degraded in the upper stratosphere. Discrepancies among reanalyses increase during the onset of SSW events, a period characterized by unusually large fluxes of planetary-scale waves from the troposphere to the stratosphere, and decrease substantially after the onset. While the largest uncertainties in the resolved terms of the momentum budget are found in the Coriolis torque, momentum flux convergence also presents a non-negligible spread among the reanalyses. Such a spread is reduced in the latest reanalysis products, decreasing the uncertainty of the momentum budget. It is also found that the uncertainties in the Coriolis torque depend on the strength of SSW events: the SSW events that exhibit the most intense deceleration of zonal-mean zonal wind are subject to larger discrepancies among reanalyses. These uncertainties in stratospheric circulation, however, are not communicated to the troposphere.

Three-pattern decomposition of global atmospheric circulation: part II—dynamical equations of horizontal, meridional and zonal circulations

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 and zonal components of global atmospheric circulation.

The 10-30-day oscillation of winter zonal wind in the entrance region of the East Asian subtropical jet and its relationship with precipitation in southern China

NASA Astrophysics Data System (ADS)

Yao, Chenyu; Huang, Qian; Zhu, Bin; Liu, Fei

2018-06-01

Using ECMWF ERA-Interim 6-h reanalysis data, zonal wind intra-seasonal oscillations (ISOs) in the entrance region of the East Asian subtropical westerly jet (EASWJ) in winter from 1979/1980 to 2012/2013 are studied. The results first show that there is an area with large ISO strength in the northwest of the EASWJ; in the key region, zonal wind has a dominant period of 10-30 days. The composite analysis reveals that zonal wind at 200 hPa in this key region has 10-30-day oscillation characteristics. On the 10-30-day time scale, the center of zonal wind anomaly moves eastward. The propagation of zonal wind oscillation relates to temperature tendencies at different latitudes. The remarkable increase (or decrease) in zonal wind in the key region is mostly determined by temperature anomalies to the north. The 10-30-day filtered temperature advection to the north of the key region leads to either a decrease or an increase in temperature; on the other hand, temperature variations south of the key region have trends opposite of the northern trends, which changes the temperature gradient. On the 10-30-day time scale, zonal wind anomalies are associated with precipitation in southern China. When there are easterly wind anomalies over the key region, precipitation occurs over the Yangtze River basin and its south. Diabatic heating during precipitation corresponds with warming to the south of the key region, which combines with the temperature advection to weaken the easterly wind and strengths the westerly wind. Then, the intra-seasonal precipitation moves to southwest China with warm advection and the enhanced westerly wind, which brings the positive relative vorticity advection there.

Regulation of electron temperature gradient turbulence by zonal flows driven by trapped electron modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asahi, Y., E-mail: y.asahi@nr.titech.ac.jp; Tsutsui, H.; Tsuji-Iio, S.

2014-05-15

Turbulent transport caused by electron temperature gradient (ETG) modes was investigated by means of gyrokinetic simulations. It was found that the ETG turbulence can be regulated by meso-scale zonal flows driven by trapped electron modes (TEMs), which are excited with much smaller growth rates than those of ETG modes. The zonal flows of which radial wavelengths are in between the ion and the electron banana widths are not shielded by trapped ions nor electrons, and hence they are effectively driven by the TEMs. It was also shown that an E × B shearing rate of the TEM-driven zonal flows is larger thanmore » or comparable to the growth rates of long-wavelength ETG modes and TEMs, which make a main contribution to the turbulent transport before excitation of the zonal flows.« less

High-fidelity simulations of unsteady civil aircraft aerodynamics: stakes and perspectives. Application of zonal detached eddy simulation.

PubMed

Deck, Sébastien; Gand, Fabien; Brunet, Vincent; Ben Khelil, Saloua

2014-08-13

This paper provides an up-to-date survey of the use of zonal detached eddy simulations (ZDES) for unsteady civil aircraft applications as a reflection on the stakes and perspectives of the use of hybrid methods in the framework of industrial aerodynamics. The issue of zonal or non-zonal treatment of turbulent flows for engineering applications is discussed. The ZDES method used in this article and based on a fluid problem-dependent zonalization is briefly presented. Some recent landmark achievements for conditions all over the flight envelope are presented, including low-speed (aeroacoustics of high-lift devices and landing gear), cruising (engine-airframe interactions), propulsive jets and off-design (transonic buffet and dive manoeuvres) applications. The implications of such results and remaining challenges in a more global framework are further discussed. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

A PRELIMINARY JUPITER MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hubbard, W. B.; Militzer, B.

In anticipation of new observational results for Jupiter's axial moment of inertia and gravitational zonal harmonic coefficients from the forthcoming Juno orbiter, we present a number of preliminary Jupiter interior models. We combine results from ab initio computer simulations of hydrogen–helium mixtures, including immiscibility calculations, with a new nonperturbative calculation of Jupiter's zonal harmonic coefficients, to derive a self-consistent model for the planet's external gravity and moment of inertia. We assume helium rain modified the interior temperature and composition profiles. Our calculation predicts zonal harmonic values to which measurements can be compared. Although some models fit the observed (pre-Juno) second-more » and fourth-order zonal harmonics to within their error bars, our preferred reference model predicts a fourth-order zonal harmonic whose absolute value lies above the pre-Juno error bars. This model has a dense core of about 12 Earth masses and a hydrogen–helium-rich envelope with approximately three times solar metallicity.« less

Theory of Fine-scale Zonal Flow Generation From Trapped Electron Mode Turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu Wang and T.S. Hahm

Most existing zonal flow generation theory has been developed with a usual assumption of qrρθ¡ << 1 (qr is the radial wave number of zonal flow, and ρθ¡ is the ion poloidal gyrora- dius). However, recent nonlinear gyrokinetic simulations of trapped electron mode (TEM) turbulence exhibit a relatively short radial scale of the zonal flows with qrρθ¡ ~ 1 [Z. Lin et al., IAEA-CN/TH/P2-8 (2006); D. Ernst et al., Phys. Plasmas 16, 055906 (2009)]. This work reports an extension of zonal flow growth calculation to this short wavelength regime via the wave kinetics approach. A generalized expression for the polarizationmore » shielding for arbitrary radial wavelength [Lu Wang and T.S. Hahm, to appear in Phys. Plasmas (2009)] which extends the Rosenbluth-Hinton formula in the long wavelength limit is applied.« less

The Asian monsoon's role in atmospheric heat transport responses to orbital and millennial-scale climate change

NASA Astrophysics Data System (ADS)

McGee, D.; Green, B.; Donohoe, A.; Marshall, J.

2015-12-01

Recent studies have provided a framework for understanding the zonal-mean position of the tropical rain belt by documenting relationships between rain belt latitude and atmospheric heat transport across the equator (Donohoe et al., 2013). Modern seasonal and interannual variability in globally-averaged rain belt position (often referred to as 'ITCZ position') reflects the interhemispheric heat balance, with the rain belt's displacement toward the warmer hemisphere directly proportional to atmospheric heat transport into the cooler hemisphere. Model simulations suggest that rain belt shifts are likely to have obeyed the same relationship with interhemispheric heat transport in response to past changes in orbital parameters, ice sheets, and ocean circulation. This relationship implies that even small (±1 degree) shifts in the mean rain belt require large changes in hemispheric heat budgets, placing tight bounds on mean rain belt shifts in past climates. This work has primarily viewed tropical circulation in two dimensions, as a pair of zonal-mean Hadley cells on either side of the rain belt that are displaced north and south by perturbations in hemispheric energy budgets, causing the atmosphere to transport heat into the cooler hemisphere. Here we attempt to move beyond this zonal-mean perspective, motivated by arguments that the Asian monsoon system, rather than the zonal-mean circulation, plays the dominant role in annual-mean heat transport into the southern hemisphere in the modern climate (Heaviside and Czaja, 2012; Marshall et al., 2014). We explore a range of climate change experiments, including simulations of North Atlantic cooling and mid-Holocene climate, to test whether changes in interhemispheric atmospheric heat transport are primarily driven by the mean Hadley circulation, the Asian monsoon system, or other regional-scale atmospheric circulation changes. The scalings that this work identifies between Asian monsoon changes and atmospheric heat transport help to provide quantitative insights into Asian monsoon variability in past climates. References cited: Donohoe, A. et al., (2013) Journal of Climate 26, 3597-3618. Heaviside, C. and Czaja, A. (2012) Quart. J. Royal Met. Soc. 139, 2181-2189. Marshall, J. et al., (2014) Climate Dynamics 42, 1967-1979.

Vertical Motion Changes Related to North-East Brazil Rainfall Variability: a GCM Simulation

NASA Astrophysics Data System (ADS)

Roucou, Pascal; Oribe Rocha de Aragão, José; Harzallah, Ali; Fontaine, Bernard; Janicot, Serge

1996-08-01

The atmospheric structure over north-east Brazil during anomalous rainfall years is studied in the 11 levels of the outputs of the Laboratoire de Météorologie Dynamique atmospheric general circulation model (LMD AGCM). Seven 19-year simulations were performed using observed sea-surface temperature (SST) corresponding to the period 1970- 1988. The ensemble mean is calculated for each month of the period, leading to an ensemble-averaged simulation. The simulated March-April rainfall is in good agreement with observations. Correlations of simulated rainfall and three SST indices relative to the equatorial Pacific and northern and southern parts of the Atlantic Ocean exhibit stronger relationships in the simulation than in the observations. This is particularly true with the SST gradient in the Atlantic (Atlantic dipole). Analyses on 200 ;hPa velocity potential, vertical velocity, and vertical integral of the zonal component of mass flux are performed for years of abnormal rainfall and positive/negative SST anomalies in the Pacific and Atlantic oceans in March-April during the rainy season over the Nordeste region. The results at 200 hPa show a convergence anomaly over Nordeste and a divergence anomaly over the Pacific concomitant with dry seasons associated with warm SST anomalies in the Pacific and warm (cold) waters in the North (South) Atlantic. During drought years convection inside the ITCZ indicated by the vertical velocity exhibits a displacement of the convection zone corresponding to a northward migration of the ITCZ. The east-west circulation depicted by the zonal divergent mass flux shows subsiding motion over Nordeste and ascending motion over the Pacific in drought years, accompanied by warm waters in the eastern Pacific and warm/cold waters in northern/southern Atlantic. Rainfall variability of the Nordeste rainfall is linked mainly to vertical motion and SST variability through the migration of the ITCZ and the east-west circulation.

Large-Scale Weather Disturbances in Mars’ Southern Extratropics

NASA Astrophysics Data System (ADS)

Hollingsworth, Jeffery L.; Kahre, Melinda A.

2015-11-01

Between late autumn and early spring, Mars’ middle and high latitudes within its atmosphere support strong mean thermal gradients between the tropics and poles. Observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports intense, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). These extratropical weather disturbances are key components of the global circulation. Such wave-like disturbances act as agents in the transport of heat and momentum, and generalized scalar/tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). The character of large-scale, traveling extratropical synoptic-period disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This Mars GCM imposes interactively lifted and radiatively active dust based on a threshold value of the surface stress. The model exhibits a reasonable "dust cycle" (i.e., globally averaged, a dustier atmosphere during southern spring and summer occurs). Compared to their northern-hemisphere counterparts, southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are examined. Simulations that adapt Mars’ full topography compared to simulations that utilize synthetic topographies emulating key large-scale features of the southern middle latitudes indicate that Mars’ transient barotropic/baroclinic eddies are highly influenced by the great impact basins of this hemisphere (e.g., Argyre and Hellas). The occurrence of a southern storm zone in late winter and early spring appears to be anchored to the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

The local and global climate forcings induced inhomogeneity of Indian rainfall.

PubMed

Nair, P J; Chakraborty, A; Varikoden, H; Francis, P A; Kuttippurath, J

2018-04-16

India is home for more than a billion people and its economy is largely based on agrarian society. Therefore, rainfall received not only decides its livelihood, but also influences its water security and economy. This situation warrants continuous surveillance and analysis of Indian rainfall. These kinds of studies would also help forecasters to better tune their models for accurate weather prediction. Here, we introduce a new method for estimating variability and trends in rainfall over different climate regions of India. The method based on multiple linear regression helps to assess contributions of different remote and local climate forcings to seasonal and regional inhomogeneity in rainfall. We show that the Indian Summer Monsoon Rainfall (ISMR) variability is governed by Eastern and Central Pacific El Niño Southern Oscillation, equatorial zonal winds, Atlantic zonal mode and surface temperatures of the Arabian Sea and Bay of Bengal, and the North East Monsoon Rainfall variability is controlled by the sea surface temperature of the North Atlantic and extratropial oceans. Also, our analyses reveal significant positive trends (0.43 mm/day/dec) in the North West for ISMR in the 1979-2017 period. This study cautions against the significant changes in Indian rainfall in a perspective of global climate change.

Winds in the Middle Cloud Deck From the Near-IR Imaging by the Venus Monitoring Camera Onboard Venus Express

NASA Astrophysics Data System (ADS)

Khatuntsev, I. V.; Patsaeva, M. V.; Titov, D. V.; Ignatiev, N. I.; Turin, A. V.; Fedorova, A. A.; Markiewicz, W. J.

2017-11-01

For more than 8 years the Venus Monitoring Camera (VMC) onboard the Venus Express orbiter performed continuous imaging of the Venus cloud layer in UV, visible and near-IR filters. We applied the correlation approach to sequences of the near-IR images at 965 nm to track cloud features and determine the wind field in the middle and lower cloud (49-57 km). From the VMC images that spanned from December of 2006 through August of 2013 we derived zonal and meridional components of the wind field. In low-to-middle latitudes (5-65°S) the velocity of the retrograde zonal wind was found to be 68-70 m/s. The meridional wind velocity slowly decreases from peak value of +5.8 ± 1.2 m/s at 15°S to 0 at 65-70°S. The mean meridional speed has a positive sign at 5-65°S suggesting equatorward flow. This result, together with the earlier measurements of the poleward flow at the cloud tops, indicates the presence of a closed Hadley cell in the altitude range 55-65 km. Long-term variations of zonal and meridional velocity components were found during 1,200 Earth days of observation. At 20° ± 5°S the zonal wind speed increases from -67.18 ± 1.81 m/s to -77.30 ± 2.49 m/s. The meridional wind gradually increases from +1.30 ± 1.82 m/s to +8.53 ± 2.14 m/s. Following Bertaux et al. (2016) we attribute this long-term trend to the influence from the surface topography on the dynamical process in the atmosphere via the upward propagation of gravity waves that became apparent in the VMC observations due to slow drift of the Venus Express orbit over Aphrodite Terra.

Time evolution of atmospheric parameters and their influence on sea level pressure over the head Bay of Bengal

NASA Astrophysics Data System (ADS)

Patra, Anindita; Bhaskaran, Prasad K.; Jose, Felix

2018-06-01

A zonal dipole in the observed trends of wind speed and significant wave height over the Head Bay of Bengal region was recently reported in the literature attributed due to the variations in sea level pressure (SLP). The SLP in turn is governed by prevailing atmospheric conditions such as local temperature, humidity, rainfall, atmospheric pressure, wind field distribution, formation of tropical cyclones, etc. The present study attempts to investigate the inter-annual variability of atmospheric parameters and its role on the observed zonal dipole trend in sea level pressure, surface wind speed and significant wave height. It reports on the aspects related to linear trend as well as its spatial variability for several atmospheric parameters: air temperature, geopotential height, omega (vertical velocity), and zonal wind, over the head Bay of Bengal, by analyzing National Centers for Environmental Prediction (NCEP) Reanalysis 2 dataset covering a period of 38 years (1979-2016). Significant warming from sea level to 200 mb pressure level and thereafter cooling above has been noticed during all the seasons. Warming within the troposphere exhibits spatial difference between eastern and western side of the domain. This led to fall in lower tropospheric geopotential height and its east-west variability, exhibiting a zonal dipole pattern across the Head Bay. In the upper troposphere, uplift in geopotential height was found as a result of cooling in higher levels (10-100 mb). Variability in omega also substantiated the observed variations in geopotential height. The study also finds weakening in the upper level westerlies and easterlies. Interestingly, a linear trend in lower tropospheric u-wind component also reveals an east-west dipole pattern over the study region. Further, the study corroborates the reported dipole in trends of sea level pressure, wind speed and significant wave height by evaluating the influence of atmospheric variability on these parameters.

The Sinuosity of Atmospheric Circulation over North America and its Relationship to Arctic Climate Change and Extreme Events

NASA Astrophysics Data System (ADS)

Vavrus, S. J.; Wang, F.; Martin, J. E.; Francis, J. A.

2015-12-01

Recent research has suggested a relationship between mid-latitude weather and Arctic amplification (AA) of global climate change via a slower and wavier extratropical circulation inducing more extreme events. To test this hypothesis and to quantify the waviness of the extratropical flow, we apply a novel application of the geomorphological concept of sinuosity (SIN) over greater North America. SIN is defined as the ratio of the curvilinear length of a geopotential height contour to the perimeter of its equivalent latitude, where the contour and the equivalent latitude enclose the same area. We use 500 hPa daily heights from reanalysis and model simulations to calculate past and future SIN. The circulation exhibits a distinct annual cycle of maximum SIN (waviness) in summer and a minimum in winter, inversely related to the annual cycle of zonal wind speed. Positive trends in SIN have emerged in recent decades during winter and summer at several latitude bands, generally collocated with negative trends in zonal wind speeds. High values of SIN coincide with many prominent extreme-weather events, including Superstorm Sandy. RCP8.5 simulations (2006-2100) project a dipole pattern of zonal wind changes that varies seasonally. In winter, AA causes inflated heights over the Arctic relative to mid-latitudes and an associated weakening (strengthening) of the westerlies north (south) of 40N. The AA signal in summer is strongest over upper-latitude land, promoting localized atmospheric ridging aloft with lighter westerlies to the south and stronger zonal winds to the north. The changes in wind speeds in both seasons are inversely correlated with SIN, indicating a wavier circulation where the flow weakens. In summer the lighter winds over much of the U. S. resemble circulation anomalies observed during extreme summer heat and drought. Such changes may be linked to enhanced heating of upper-latitude land surfaces caused by earlier snow melt during spring-summer.

Analysis of clouds and precipitation during Baiu period over the East China Sea with cloud database CTOP and precipitation database GSMaP

NASA Astrophysics Data System (ADS)

Nishi, N.; Hamada, A.; Hirose, H.; Hotta, S.; Suzuki, J.

2016-12-01

We have made a quantitative research of the clouds and precipitation during Baiu: the rainy season within the East Asia, using recent satellite observation datasets. As the precipitation dataset, we utilized the Global Satellite Mapping of Precipitation (GSMaP), whose primary source is passive microwave observations. As the cloud dataset, we used our original database CTOP, in which the cloud top height and optical depth are estimated only with the infrared split-window channels of the geostationary satellites. Lookup tables are made by training the infrared observations with the direct cloud observation by CloudSat and CALIPSO. This technique was originally developed only for the tropics but we extended it to the mid-latitude by estimating temperature at the cloud top instead of the height. We analyzed the properties of northward shift of the Baiu precipitation zone over the East China Sea. Abrupt northward shift in mid-June has already been reported. We showed here that the abrupt shift is limited to the western half of the East China Sea. We also analyzed the zonal difference of the precipitation amount in the East China Sea. In the central latitudinal range (30-33N), the amount is larger in the eastern part of the sea. There is no significant zonal contrast in both the activity of the low pressure and the front, while the sea surface temperature in the eastern part is slightly larger than in the western part. The zonal gradient is much smaller than that in the southern region near the Kuroshio Current, but may possibly affect the zonal contrast of the precipitation. By using CTOP cloud top data, we also calculated the occurrence ratio of the cloud with various thresholds of the top height. The ratio of clouds with the tops higher than 12 km in the East China Sea is clearly lower than those over the Continental area and the main Japanese islands.

The South ``West'' Pacific Convergence Zone: Large-scale feedback on atmospheric subsidence to the east

NASA Astrophysics Data System (ADS)

Widlansky, M. J.; Webster, P. J.; Hoyos, C.

2010-12-01

Three semi-permanent convective cloud bands exist in the Southern Hemisphere extending southeastward from the equator, through the tropics, and into the subtropics. The most prominent of these features occurs in the South Pacific during summer and is referred to as the South Pacific Convergence Zone (SPCZ). Similar cloud bands, with less intensity, exist in the South Indian and Atlantic basins. To the east of each convective zone is a large-scale region of atmospheric subsidence. We attempt to explain the physical mechanisms that promote the diagonal orientation of the SPCZ and also teleconnections that may exist with stratocumulus cloud cover in the southeastern Pacific. It is argued that slowly varying sea surface temperature patterns produce upper tropospheric wind fields that vary substantially in longitude (∂U/∂x). Regions where 200 hPa zonal winds decrease with longitude (i.e., negative zonal stretching deformation, or ∂U/∂x<0) reduce the group speed of the eastward propagating synoptic (3-6 day period) Rossby waves and locally increase the wave energy density. Such a region of wave accumulation occurs in the vicinity of the SPCZ (see Figure), thus providing a hypothesis for the diagonal orientation and a physical basis for earlier observations that the zone traps eastward propagating synoptic disturbances. Controlled numerical experiments and composites of observed life cycles of synoptic waves confirm that disturbances slow in the SPCZ. From the hypothesis comes a more general theory accounting for the SPCZ’s spatial orientation and the lack of disturbances to the east. December-February climatology of 200 hPa zonal winds (shading) and negative zonal stretching deformation (red contours). Large black box located at 20°S-35°S, 165°W-135°W encloses the diagonal region of the SPCZ. 240 W m-2 OLR contour outlined by blue lines.

Dominant covarying climate signals in the Southern Ocean and Antarctic Sea Ice influence during last three decades

NASA Astrophysics Data System (ADS)

Cerrone, Dario; Fusco, Giannetta; Simmonds, Ian; Aulicino, Giuseppe; Budillon, Giorgio

2017-04-01

A composite dataset (comprising geopotential height, sea surface temperature, zonal and meridional surface winds, precipitation, cloud cover, surface air temperature, latent plus sensible heat fluxes , and sea ice concentration) has been investigated with the aim of revealing the dominant timescales of variability from 1982 to 2013. Three covarying climate signals associated with variations in the sea ice distribution around Antarctica have been detected through the application of the Multiple-Taper Method with Singular Value Decomposition (MTM-SVD). Features of the established patterns of variation over the Southern Hemisphere (SH) extratropics have been identified in each of these three climate signals in the form of coupled or individual oscillations. The climate patterns considered here are the Southern Annular Mode (SAM), the Pacific-South America (PSA) teleconnection, the Semi-Annual Oscillation (SAO) and Zonal Wavenumber-3 (ZW3) mode. It is shown that most of the sea ice temporal variance is concentrated at the quasi-triennial scale resulting from the constructive superposition of the PSA and ZW3 patterns. In addition the combination of the SAM and SAO patterns is found to promote the interannual sea ice variations underlying a general change in the Southern Ocean atmospheric and oceanic circulations. These two modes of variability are also found consistent with the occurrence of the SAM+/PSA- or SAM-/PSA+ combinations, which could have favored the cooling of the sub-Antarctic and important changes in the Antarctic sea ice distribution since 2000.

On the relationship between the stratospheric quasi-biennial oscillation and the tropospheric Southern oscillation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, J.S.

1992-05-01

Two quasi-periodic oscillations in the tropical atmosphere with similar oscillation period-the stratospheric quasi-biennial and the Southern oscillations-and the relationship between these two oscillations are examined using the Principal Oscillation Pattern (POP) analysis technique. The POP analysis of the equatorial stratospheric dataset provides a compact description of the QBO. The oscillation features identified by the POP analysis, namely, the spatial structure, the characteristic times of the oscillation, and the asymmetry in downward propagation, are almost identical to those found by earlier studies using more conventional analyses. The simultaneous POP analysis of the equatorial zonal surface wind and sea surface temperature indicatesmore » a well-defined cyclic behavior of the SO. In contrast to the very regular QBO, the SO appears to be much more noisy with intermittent quiet phases. A spectral analysis of the complex POP coefficient time series and the SO index reveals a negligible correlation between the two processes. A POP analysis of the combined equatorial dataset of stratospheric wind, zonal surface wind, and SST also indicates no relation between the QBO and the SO. Two independent modes are identified, one of them completely describing the QBO and the other representing the entire SO. No linear relationship is found between the two modes either in space or in time. It is concluded that the SO and the QBO are two independent processes in the tropical atmosphere with similar time scales. 26 refs., 17 figs.« less

Zonal subdivision of marine sequences: achievements and discrepancies

NASA Astrophysics Data System (ADS)

Gladenkov, Yuri

2010-05-01

It was 150 years ago when a notion of zone was introduced into stratigraphy. By the present time zonal units with a duration of 0.3-3.0 M.y. in average have been established virtually for all systems and stages of the Phanerozoic. Their quantity reached 300. It is not a chance that zonal stratigraphy is considered to be one of the most significant achievement of the modern geology. There are different interpretations of essence and goals of zonal stratigraphy, techniques of separation of zones, and evaluation of zones as stratigraphic units. Particularly it is reflected in International Stratigraphic Guide (Murphy, Salvador, 1999), Russian Stratigraphic Code (Zhamoida, 2006), and a number of stratigraphic reports of the last years. It concerns different approaches to: (a) establishment of different types of zones (biostratigraphic zones and chronozones, oppel-zones and biohorizons, etc.); (b) assessment of spatial distribution of zones (global or provincial) and a role of sedimentological factor; (c) definition of zones as stratigraphic units (relationships with geostratigraphic units of the standard and regional scales). The latest publications show that because of the different interpretations of zones, authors should explain usage of certain type of zone (for example, when they use the terms "interval-zone" or "assemblage-zone", what limitations stem from application of datum-levels, and others). It is common opinion, that biostratigraphic zones used widely by paleontologists and stratigraphers cannot be a final goal of stratigraphy although they provide a base for solution of many important problems (definition of certain stratigraphic levels, correlation of different biofacies, and others). At the same time, the most important stratigraphic units are chronozones, which correspond to stages or phases of geological evolutio of basins and are marked by distinct fossil assemblages and other properties (magnetic and other characteristics) in the type sections. Therefore, in Russian Stratigraphic Code biostratigraphic zones are regarded as special units and chronozones as general units of integrated substantiation. Now it becomes clear that unlike chronozones, biostratigraphic zones often have diachronous boundaries and provincial but not global distribution. This is not frequently taken into account at practical correlations. A special attention should be paid to a scale of these occurrences when refining stratigraphic scales. It should not be forgotten that magneto-, litho-, and cyclostratigraphic markers should be used to assess isochronism of zonal boundaries. Many zonal reconstructions do not look faultless without such a control. If we consider zonal stratigraphy not only in applied aspect but in a wide scientific one, it fits in with the geohistorical concept of stratigraphy, which is now reflected in "dynamic", or "ecosystem", or biosphere stratigraphy (Gladenkov, 2004). Establishment of stages of geological development of the Earth and its separate parts, reconstructions of changes in the organic world at the biogeocoenotic and biospheric levels, complex study of paleobiotic assemblages are thought to be one of principal lines of stratigraphic investigations. At present discussions are being organized and experience of zonal stratigraphy is being summarized in Russia. In particular, a large book titled "Biozonal stratigraphy of the Phanerozoic in Russia" and devoted to this problem has been published recently (Koren, 2006). References 1. Gladenkov, Yu.B., 2004. Biosphere Stratigraphy (Stratigraphic Problems in the Early XXI Century). Moscow: GEOS, 120 pp. (in Russian). 2. Koren, T.N., ed., 2006. Biozonal stratigraphy of the Phanerozoic in Russia. Saint-Petersburg: VSEGEI Press, 256 рp. (in Russian). 3. Murphy, M.A., and Salvador, A., eds., 1999. International Stratigraphic Guide: An abridged version. Episodes, 22 (4): 255-271. 4. Zhamoida. A.I., ed., 2006. Russian Stratigraphic Guide (3rd Edition). Saint-Petersburg: VSEGEI Press, 95 pp. (in Russian).

Comparative Effect of Physicomechanical and Biomolecular Cues on Zone-Specific Chondrogenic Differentiation of Mesenchymal Stem Cells

PubMed Central

Moeinzadeh, Seyedsina; Shariati, Seyed Ramin Pajoum; Jabbari, Esmaiel

2016-01-01

Current tissue engineering approaches to regeneration of articular cartilage rarely restore the tissue to its normal state because the generated tissue lacks the intricate zonal organization of the native cartilage. Zonal regeneration of articular cartilage is hampered by the lack of knowledge for the relation between physical, mechanical, and biomolecular cues and zone-specific chondrogenic differentiation of progenitor cells. This work investigated in 3D the effect of TGF-β1, zone-specific growth factors, optimum matrix stiffness, and adding nanofibers on the expression of chondrogenic markers specific to the superficial, middle, and calcified zones of articular cartilage by the differentiating human mesenchymal stem cells (hMSCs). Growth factors included BMP-7, IGF-1, and hydroxyapatite (HA) for the superficial, middle, and calcified zones, respectively; optimum matrix stiffness was 80 kPa, 2.1 MPa, and 320 MPa; and nanofibers were aligned horizontal, random, and perpendicular to the gel surface. hMSCs with zone-specific cell densities were encapsulated in engineered hydrogels and cultured with or without TGF-β1, zone-specific growth factor, optimum matrix modulus, and fiber addition and cultured in basic chondrogenic medium. The expression of encapsulated cells was measured by mRNA, protein, and biochemical analysis. Results indicated that zone-specific matrix stiffness had a dominating effect on chondrogenic differentiation of hMSCs to the superficial and calcified zone phenotypes. Addition of aligned nanofibers parallel to the direction of gel surface significantly enhanced expression of Col II in the superficial zone chondrogenic differentiation of hMSCs. Conversely, biomolecular factor IGF-1 in combination with TGF-β1 had a dominating effect on the middle zone chondrogenic differentiation of hMSCs. Results of this work could potentially lead to the development of multilayer grafts mimicking the zonal organization of articular cartilage. PMID:27038568

Recent Advances in the Salinity Retrieval Algorithms for Aquarius and SMAP

NASA Astrophysics Data System (ADS)

Meissner, T.; Wentz, F. J.

2016-12-01

Our presentation discusses the latest improvements in the salinity retrievals for both Aquarius and SMAP since the last releases. The Aquarius V4.0 was released in June 2015 and the SMAP V 1.0 was released in November 2015. Upcoming releases are planned for SMAP (V 2.0) in August 2016 and for Aquarius (V 5.0) late 2017. The full 360o look capability of SMAP makes it possible to take observations from the forward and backward looking direction at the same instance of time. This two-look capability strongly aids the salinity retrievals. One of the largest spurious contaminations in the salinity retrievals is caused by the galaxy that is reflected from the ocean surface. Because in most instances the reflected galaxy appears only in either the forward or the backward look, it is possible to determine its contribution by taking the difference of the measured SMAP brightness temperatures between the two looks. Our result suggests that the surface roughness that is used in the galactic correction needs to be increased and also the strength of some of the galactic sources need to be slightly adjusted. The improved galaxy correction is getting implemented in upcoming Aquarius and SMAP salinity releases and strongly aids the mitigation of residual zonal and temporal biases that are observed in both products. Another major cause of the observed zonal biases in SMAP is the emissive SMAP mesh antenna. In order to correct for it the physical temperature of the antenna is needed. No direct measurements but only a thermal model are available. We discuss recent improvements in the correction for the emissive SMAP antenna and show how most of the zonal biases in V1.0 can be mitigated. Finally, we show that observed salty biases at higher Northern latitudes can be explained by inaccuracies in the model that is used in correcting for the absorption by atmospheric oxygen. These biases can be decreased by fine-tuning the parameters in the absorption model.

The Mass and Angular Momentum Balance of the Zonally-Averaged Global Circulation.

DTIC Science & Technology

1981-01-01

2 2SFSf F SO~ ABSTRACT (0m-l n oerse~e side Ht moeoeei md fdeutly’ by Week now"*ee Li ATTACHED hO u 47 EDI TIo OP 1 NOV6 Ies OBSOLETE UNCLASS 82 09 28...eddies, and transient circulat.@ns, respec tively. rigeree 12 and 13 displa the vertical sad meridional distribution of relat’.ve angular momentum trass...the transient component is the dominant mode of angular momentum transport in January. It is poleward at virtually all latitudes in each hemisphere

A history of presatellite investigations of the earth's radiation budget

NASA Technical Reports Server (NTRS)

Hunt, G. E.; Kandel, R.; Mecherikunnel, A. T.

1986-01-01

The history of radiation budget studies from the early twentieth century to the advent of the space age is reviewed. By the beginning of the 1960's, accurate radiative models had been developed capable of estimating the global and zonally averaged components of the radiation budget, though great uncertainty in the derived parameters existed due to inaccuracy of the data describing the physical parameters used in the model, associated with clouds, the solar radiation, and the gaseous atmospheric absorbers. Over the century, the planetary albedo estimates had reduced from 89 to 30 percent.

Temporal Decrease in Upper Atmospheric Chlorine

NASA Technical Reports Server (NTRS)

Froidevaux, L.; Livesey, N. J.; Read, W. G.; Salawitch, R. J.; Waters, J. W.; Drouin, B.; MacKenzie, I. A.; Pumphrey, H. C.; Bernath, P.; Boone, C.;

Estimations of the Global Distribution and Time Series of UV Noontime Irradiance (305, 310, 324, 380 nm, and Erythemal) from TOMS and SeaWiFS Data

NASA Technical Reports Server (NTRS)

Herman, J.

2004-01-01

The amount of UV irradiance reaching the Earth's surface is estimated from the measured cloud reflectivity, ozone, aerosol amounts, and surface reflectivity time series from 1980 to 1992 and 1997 to 2000 to estimate changes that have occurred over a 21-year period. Recent analysis of the TOMS data shows that there has been an apparent increase in reflectivity (decrease in W) in the Southern Hemisphere that is related to a calibration error in EP-TOMS. Data from the well-calibrated SeaWiFS satellite instrument have been used to correct the EP-TOMS reflectivity and UV time series. After correction, some of the local trend features seen in the N7 time series (1980 to 1992) have been continued in the combined time series, but the overall zonal average and global trends have changed. In addition to correcting the EP-TOMS radiance calibration, the use of SeaWiFS cloud data permits estimation of UV irradiance at higher spatial resolution (1 to 4 km) than is available from TOMS (100 km) under the assumption that ozone is slowly varying over a scale of 100 km. The key results include a continuing decrease in cloud cover over Europe and North America with a corresponding increase in UV and a decrease in UV irradiance near Antarctica.

Cattaraugus Creek Harbor, New York General Design Memorandum. Phase II. (Detailed Design). Volume II. Appendix E. Littoral Processes and Sedimentation in the Cattaraugus Embayment, New York. Appendix F. Sediment Transport in Cattaraugus Creek.

DTIC Science & Technology

1976-03-01

beaches than any other part of the southeastern shoreline of Lake Erie . It is the only major sand accumulation zone with the exception of Presque Isle , in...52 20. Photographs of zonal site #10. 54 21. Photograph and map of zonal site #11, Presque Isle , Pa. 57 F22. Photographs and beach profiles at zonal...site #11. 59 23. Photograph of zonal site #12, the recurved spit area on Presque Isle , Pa. 62 24. Block diagram of recurved spit area of Presque Isle

Frequency-dependent behavior of the barotropic and baroclinic modes of zonal jet variability

NASA Astrophysics Data System (ADS)

Sheshadri, A.; Plumb, R. A.

2016-12-01

Stratosphere-troposphere interactions are frequently described in terms of the leading modes of variability, i.e. the annular modes. An idealized dynamical core model is used to explore the differences between the low- and high- frequency (periods greater and less than 30 days) behavior of the first two principal components of zonal mean zonal wind and eddy kinetic energy, i.e., the barotropic/baroclinic annular modes of variability of the extratropical circulation. The modes show similar spatial characteristics in the different frequency ranges considered, however the ranking of the modes switches in some cases from one range to the other. There is some cancelation in the signatures of eddy heat flux and eddy kinetic energy in the leading low-pass and high-pass filtered zonal wind mode, partly explaining their small signature in the total. At low frequencies, the first zonal wind mode describes latitudinal shifts of both the midlatitude jet and its associated storm tracks, and the persistence of zonal wind anomalies appears to be sustained primarily by a baroclinic, rather than a barotropic, feedback. On shorter time scales, the behavior is more complicated and transient.

Numerical simulation on zonal disintegration in deep surrounding rock mass.

PubMed

Chen, Xuguang; Wang, Yuan; Mei, Yu; Zhang, Xin

2014-01-01

Zonal disintegration have been discovered in many underground tunnels with the increasing of embedded depth. The formation mechanism of such phenomenon is difficult to explain under the framework of traditional rock mechanics, and the fractured shape and forming conditions are unclear. The numerical simulation was carried out to research the generating condition and forming process of zonal disintegration. Via comparing the results with the geomechanical model test, the zonal disintegration phenomenon was confirmed and its mechanism is revealed. It is found to be the result of circular fracture which develops within surrounding rock mass under the high geostress. The fractured shape of zonal disintegration was determined, and the radii of the fractured zones were found to fulfill the relationship of geometric progression. The numerical results were in accordance with the model test findings. The mechanism of the zonal disintegration was revealed by theoretical analysis based on fracture mechanics. The fractured zones are reportedly circular and concentric to the cavern. Each fracture zone ruptured at the elastic-plastic boundary of the surrounding rocks and then coalesced into the circular form. The geometric progression ratio was found to be related to the mechanical parameters and the ground stress of the surrounding rocks.

Numerical Simulation on Zonal Disintegration in Deep Surrounding Rock Mass

PubMed Central

Chen, Xuguang; Wang, Yuan; Mei, Yu; Zhang, Xin

2014-01-01

Zonal disintegration have been discovered in many underground tunnels with the increasing of embedded depth. The formation mechanism of such phenomenon is difficult to explain under the framework of traditional rock mechanics, and the fractured shape and forming conditions are unclear. The numerical simulation was carried out to research the generating condition and forming process of zonal disintegration. Via comparing the results with the geomechanical model test, the zonal disintegration phenomenon was confirmed and its mechanism is revealed. It is found to be the result of circular fracture which develops within surrounding rock mass under the high geostress. The fractured shape of zonal disintegration was determined, and the radii of the fractured zones were found to fulfill the relationship of geometric progression. The numerical results were in accordance with the model test findings. The mechanism of the zonal disintegration was revealed by theoretical analysis based on fracture mechanics. The fractured zones are reportedly circular and concentric to the cavern. Each fracture zone ruptured at the elastic-plastic boundary of the surrounding rocks and then coalesced into the circular form. The geometric progression ratio was found to be related to the mechanical parameters and the ground stress of the surrounding rocks. PMID:24592166

Gravitational field modes GEM 3 and 4

NASA Technical Reports Server (NTRS)

Lerch, F. J.; Wagner, C. A.; Putney, B. H.; Sandson, M. L.; Brownd, J. E.; Richardson, J. A.; Taylor, W. A.

1972-01-01

A refinement in the satellite geopotential solution for a Goddard Earth Model (GEM 3) was obtained. The solution includes the addition of two low inclination satellites, SAS at 3 deg and PEOLE at 15 deg, and is based upon 27 close earth satellites containing some 400,000 observations of electronic, laser, and optical data. In addition, a new combination satellite/gravimetry solution (GEM 4) was derived. The new model includes 61 center of mass tracking station locations with data from GRARR, Laser, MOTS, Baker-Nunn, and NWL Tranet Doppler tracking sites. Improvement was obtained for the zonal coefficients of the new models and is shown by tests on the long period perturbations of the orbits. Individual zonal coefficients agree very closely among different models that contain low inclination satellites. Tests of models with surface gravity data show that the GEM 3 satellite model has significantly better agreement with the gravimetry data than the GEM 1 satellite model, and that it also has better agreement with the gravimetry data than the 1969 SAO Standard Earth 2 model.

Low-degree gravity change from GPS data of COSMIC and GRACE satellite missions

NASA Astrophysics Data System (ADS)

Lin, Tingjung; Hwang, Cheinway; Tseng, Tzu-Pang; Chao, B. F.

2012-01-01

This paper demonstrates estimation of time-varying gravity harmonic coefficients from GPS data of COSMIC and GRACE satellite missions. The kinematic orbits of COSMIC and GRACE are determined to the cm-level accuracy. The NASA Goddard's GEODYN II software is used to model the orbit dynamics of COSMIC and GRACE, including the effect of a static gravity field. The surface forces are estimated per one orbital period. Residual orbits generated from kinematic and reference orbits serve as observables to determine the harmonic coefficients in the weighted-constraint least-squares. The monthly COSMIC and GRACE GPS data from September 2006 to December 2007 (16 months) are processed to estimate harmonic coefficients to degree 5. The geoid variations from the GPS and CSR RL04 (GRACE) solutions show consistent patterns over space and time, especially in regions of active hydrological changes. The monthly GPS-derived second zonal coefficient closely resembles the SLR-derived and CSR RL04 values, and third and fourth zonal coefficients resemble the CSR RL04 values.

Tidal influence through LOD variations on the temporal distribution of earthquake occurrences

NASA Astrophysics Data System (ADS)

Varga, P.; Gambis, D.; Bizouard, Ch.; Bus, Z.; Kiszely, M.

2006-10-01

Stresses generated by the body tides are very small at the depth of crustal earth- quakes (~10^2 N/m2). The maximum value of the lunisolar stress within the depth range of earthquakes is 10^3 N/m2 (at depth of about 600 km). Surface loads, due to oceanic tides, in coastal areas are ~ 104 N/m2. These influences are however too small to affect the outbreak time of seismic events. Authors show the effect on time distribution of seismic activity due to ΔLOD generated by zonal tides for the case of Mf, Mm, Ssa and Sa tidal constituents can be much more effective to trigger earthquakes. According to this approach we show that the tides are not directly triggering the seismic events but through the generated length of day variations. That is the reason why in case of zonal tides a correlation of the lunisolar effect and seismic activity exists, what is not the case for the tesseral and sectorial tides.

Coral record of southeast Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient

PubMed Central

Zinke, J.; Hoell, A.; Lough, J. M.; Feng, M.; Kuret, A. J.; Clarke, H.; Ricca, V.; Rankenburg, K.; McCulloch, M. T.

2015-01-01

Increasing intensity of marine heatwaves has caused widespread mass coral bleaching events, threatening the integrity and functional diversity of coral reefs. Here we demonstrate the role of inter-ocean coupling in amplifying thermal stress on reefs in the poorly studied southeast Indian Ocean (SEIO), through a robust 215-year (1795–2010) geochemical coral proxy sea surface temperature (SST) record. We show that marine heatwaves affecting the SEIO are linked to the behaviour of the Western Pacific Warm Pool on decadal to centennial timescales, and are most pronounced when an anomalously strong zonal SST gradient between the western and central Pacific co-occurs with strong La Niña's. This SST gradient forces large-scale changes in heat flux that exacerbate SEIO heatwaves. Better understanding of the zonal SST gradient in the Western Pacific is expected to improve projections of the frequency of extreme SEIO heatwaves and their ecological impacts on the important coral reef ecosystems off Western Australia. PMID:26493738

A New Look at Titan's Zonal Winds from Cassini Radio Occultations

NASA Technical Reports Server (NTRS)

Flasar, F. M.; Schinder, P. J.

2012-01-01

We use the existing thirteen Cassini radio'occultation soundings to construct a meridional cross section of geopotential height vs. pressure and latitude. The assumption of balanced flow permits the construction of a similar cross section of zonal winds, from near the surface to the 0.1'mbar level. In the lower troposphere, the winds are approx.10 m/s, except within 20deg of the equator, where they are much smaller. The winds increase higher up in the troposphere to nearly 40 m/s in the tropopause region, but then decay rapidly in the lower stratosphere to near'zero values at 20 mbar (approx.80 km), reminiscent of the Huygens Doppler Wind Experiment result. This null zone extends over most latitudes, except for limited bands at mid'latitudes. Higher up in the stratosphere, the winds become larger. They are highest in the northern (winter) hemisphere. We compare the occultation results with the DWE and CIRS retrievals and discuss the similarities and differences among the data sets.

Minimal modeling of the extratropical general circulation

NASA Technical Reports Server (NTRS)

O'Brien, Enda; Branscome, Lee E.

1989-01-01

The ability of low-order, two-layer models to reproduce basic features of the mid-latitude general circulation 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 meridional modes. This minimal resolution also reproduces qualitatively realistic surface and upper-level winds and mean meridional circulations. Higher meridional resolution does not result in substantial changes in the latitudinal structure of the circulation. 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 meridional 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 circulation features that are obtained at higher resolution. The model performance improves gradually with higher resolution and is smoothly dependent on changes in external parameters.

Coral record of southeast Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient.

PubMed

Zinke, J; Hoell, A; Lough, J M; Feng, M; Kuret, A J; Clarke, H; Ricca, V; Rankenburg, K; McCulloch, M T

2015-10-23

Increasing intensity of marine heatwaves has caused widespread mass coral bleaching events, threatening the integrity and functional diversity of coral reefs. Here we demonstrate the role of inter-ocean coupling in amplifying thermal stress on reefs in the poorly studied southeast Indian Ocean (SEIO), through a robust 215-year (1795-2010) geochemical coral proxy sea surface temperature (SST) record. We show that marine heatwaves affecting the SEIO are linked to the behaviour of the Western Pacific Warm Pool on decadal to centennial timescales, and are most pronounced when an anomalously strong zonal SST gradient between the western and central Pacific co-occurs with strong La Niña's. This SST gradient forces large-scale changes in heat flux that exacerbate SEIO heatwaves. Better understanding of the zonal SST gradient in the Western Pacific is expected to improve projections of the frequency of extreme SEIO heatwaves and their ecological impacts on the important coral reef ecosystems off Western Australia.

Multisatellite systems with linear structure and their application for continuous coverage of the earth

NASA Astrophysics Data System (ADS)

Saulskiy, V. K.

2005-01-01

Multisatellite systems with linear structure (SLS) are defined, and their application for a continuous global or zonal coverage of the Earth’s surface is justified. It is demonstrated that in some cases these systems turned out to be better than usually recommended kinematically regular systems by G.V. Mozhaev, delta systems of J.G. Walker, and polar systems suggested by F.W. Gobets, L. Rider, and W.S. Adams. When a comparison is made using the criterion of a minimum radius of one-satellite coverage circle, the SLS beat the other systems for the majority of satellite numbers from the range 20 63, if the global continuous single coverage of the Earth is required. In the case of a zonal continuous single coverage of the latitude belt ±65°, the SLS are preferable at almost all numbers of satellites from 38 to 100, and further at any values up to 200 excluding 144.

Impact of asymmetry in the total ozone distribution in Antarctic region to the South Ocean ecosystem

NASA Astrophysics Data System (ADS)

Kovalenok, S.; Evtushevsky, A.; Grytsai, A.; Milinevsky, G.

2009-04-01

Impact of asymmetry in the total ozone distribution in Antarctic region to South Ocean ecosystem is studied. The existence of the considerable zonal asymmetry in total ozone distribution over Antarctica observed last decades based on the satellite TOMS measurements in 1979-2005 due to existence of quasi-stationary planetary waves in a polar stratosphere. As was shown by authors earlier in the latitudinal interval of 55-75°S in Antarctic spring months (Sep-Nov) the region of zonal total ozone minimum experienced the systematic spatial drift to the east. In the same period a minimum and maximum of quasi-stationary wave in TOC distribution are located: minimum over the Antarctic Peninsula and Weddell Sea area, and maximum in the Ross Sea area. We expect that zonal asymmetry in total ozone distribution and its long-term spatial changes should impact to South Ocean ecosystem food chain, especially in primary level. The systematic eastern shift of the quasi-stationary minimum in ozone distribution over north Weddell Sea area should cause the increased UV radiation on sea surface in comparison to Ross Sea area, where the lack of UVR should exist in spring month. To study this influence the available data of phytoplankton distribution in South Ocean in 1997-2007 were analyzed. The results of analysis in connections with Antarctic Peninsula regional climate warming are discussed. The research was partly supported by project 06BF051-12 of the National Taras Shevchenko University of Kyiv.

Stationary eddies in the Mars general circulation as simulated by the NASA-Ames GCM

NASA Technical Reports Server (NTRS)

Barnes, J. R.; Pollack, J. B.; Haberle, Robert M.

1993-01-01

Quasistationary eddies are prominent in a large set of simulations of the Mars general circulation performed with the NASA-Ames GCM. Various spacecraft observations have at least hinted at the existence of such eddies in the Mars atmosphere. The GCM stationary eddies appear to be forced primarily by the large Mars topography, and (to a much lesser degree) by spatial variations in the surface albedo and thermal inertia. The stationary eddy circulations exhibit largest amplitudes at high altitudes (above 30-40 km) in the winter extratropical regions. In these regions they are of planetary scale, characterized largely by zonal wavenumbers 1 and 2. Southern Hemisphere winter appears to be dominated by a very strong wave 1 pattern, with both waves 1 and 2 being prominent in the Northern Hemisphere winter regime. This difference seems to be basically understandable in terms of differences in the topography in the two hemispheres. The stationary eddies in the northern winter extratropics are found to increase in amplitude with dust loading. This behavior appears to be at least partly associated with changes in the structure of the zonal-mean flow that favor a greater response to wave 1 topographic forcing. There are also strong stationary eddy circulations in the tropics and in the summer hemisphere. The eddies in the summer subtropics and extratropics arc substantially stronger in southern summer than in northern summer. The summer hemisphere stationary circulations are relatively shallow and are characterized by smaller zonal scales than those in the winter extratropics.

A three-dimensional model simulation of atmospheric nitrous oxide

NASA Technical Reports Server (NTRS)

Turner, R. E.; Blackshear, W. T.; Grose, W. L.; Eckman, R. S.; Pierce, R. B.; Fairlie, T. D. A.

1992-01-01

The NASA Langley 3D GCM chemical transport model is used to investigate the distribution of atmospheric N2O up to 60 km altitude. The transport characteristics of the model is evaluated without the complications of a detailed chemical formulation for all of the relevant stratospheric minor constituents. Interpretation of the yearly average zonal mean N2O distribution in terms of transport by the yearly averaged meridional circulation and stratospheric photochemical loss indicates large regions in the Northern Hemisphere stratosphere where dynamical mixing apparently plays a large role in maintaining the N2O distribution. In these regions, slopes of the N2O mixing ratio isopleths are maintained by competition between advection by the meridional circulation acting to steepen and dynamical mixing acting to flatten the slopes.

Long-term climate change and the geochemical cycle of carbon

NASA Technical Reports Server (NTRS)

Marshall, Hal G.; Walker, James C. G.; Kuhn, William R.

1988-01-01

The response of the coupled climate-geochemical system to changes in paleography is examined in terms of the biogeochemical carbon cycle. The simple, zonally averaged energy balance climate model combined with a geochemical carbon cycle model, which was developed to study climate changes, is described. The effects of latitudinal distributions of the continents on the carbon cycle are investigated, and the global silicate weathering rate as a function of latitude is measured. It is observed that a concentration of land area at high altitudes results in a high CO2 partial pressure and a high global average temperature, and for land at low latitudes a cold globe and ice are detected. It is noted that the CO2 greenhouse feedback effect is potentially strong and has a stabilizing effect on the climate system.

Neutral winds in the polar thermosphere as measured from Dynamics Explorer

NASA Technical Reports Server (NTRS)

Killeen, T. L.; Hays, P. B.; Spencer, N. W.; Wharton, L. E.

1982-01-01

Remote sensing measurements of the meridional thermospheric neutral wind using the Fabry-Perot Interferometer on Dynamics Explorer have been combined with in-situ measurements of the zonal component using the Wind and Temperature Spectrometer on the same spacecraft. The two data sets with appropriate spatial phasing and averaging determine the vector wind along the track of the polar orbiting spacecraft. A study of fifty-eight passes over the Southern (sunlit) pole has enabled the average Universal Time dependence of the wind field to be determined for essentially a single solar local time cut. The results show the presence of a 'back-ground' wind field driven by solar EUV heating upon which is superposed a circulating wind field driven by high latitude momentum and energy sources.

Effects of eddy initial conditions on nonlinear forcing of planetary scale waves by amplifying baroclinic eddies

NASA Technical Reports Server (NTRS)

Young, Richard E.

1986-01-01

The previous study of Young and Villere concerning growth of planetary scale waves forced by wave-wave interactions of amplifying intermediate scale baroclinic eddies is extended to investigate effects of different eddy initial conditions. A global, spectral, primitive equation model is used for the calculations. For every set of eddy initial conditions considered, growth rates of planetary modes are considerably greater than growth rates computed from linear instability theory for a fixed zonally independent basic state. However, values of growth rates ranged over a factor of 3 depending on the particular set of eddy initial conditions used. Nonlinear forcing of planetary modes via wave-wave coupling becomes more important than baroclinic growth on the basic state at small values of the intermediate-scale modal amplitudes. The relative importance of direct transfer of kinetic energy from intermediate scales of motion to a planetary mode, compared to baroclinic conversion of available potential energy to kinetic energy within that planetary mode, depends on the individual case. In all cases, however, the transfer of either kinetic or available potential energy to the planetary modes was accomplished principally by wave-wave transfer from intermediate scale eddies, rather than from the zonally averaged state. The zonal wavenumber 2 planetary mode was prominent in all solutions, even in those for which eddy initial conditions were such that a different planetary mode was selectively forced at the start. General characteristics of the structural evolution of the planetary wave components of total heat and momentum flux, and modal structures themselves, were relatively insensitive to variations in eddy initial conditions, even though quantitative details varied from case to case.

Atmospheric blocking as a traffic jam in the jet stream

NASA Astrophysics Data System (ADS)

Nakamura, N.; Huang, S. Y.

2017-12-01

It is demonstrated using the ERA-Interim product that synoptic to intraseasonal variabilities of extratropical circulation in the boreal storm track regions are strongly affected by the zonal convergence of the column-integrated eastward flux of local wave activity (LWA). In particular, from the multi-year daily samples of LWA fluxes, we find that the wintertime zonal LWA flux in the jet exit regions tends to maximize for an intermediate value of column-averaged LWA. This is because an increasing LWA decelerates the zonal flow, eventually weakening the eastward advection of LWA. From theory we argue that large wave events on the decreasing side of the flux curve with increasing LWA cannot be maintained as a stable steady state. Consistent with this argument, observed states corresponding to that side of flux curve often exhibit local wave breaking and blocking events. A close parallelism exists for the traffic flow problem, in which the traffic flux (traffic density times traffic speed) is often observed to maximize for an intermediate value of traffic density. This is because the traffic speed is controlled not only by the imposed speed limit but also by the traffic density — an increasingly heavy traffic slows down the flow naturally and eventually decreases the flux. Once the flux starts to decrease with an increasing traffic density, a traffic jam kicks in suddenly (Lighthill and Whitham 1955, Richards 1956). The above idea is demonstrated by a simple conceptual model based on the equivalent barotropic PV contour design (Nakamura and Huang 2017, JAS), which predicts a threshold of blocking onset. The idea also suggests that the LWA that gives the `flux capacity,' i.e., the maximum LWA flux at a given location, is a useful predictor of local wave breaking/block formation.

An A-train climatology of extratropical cyclone clouds and precipitation

NASA Astrophysics Data System (ADS)

Naud, C. M.; Booth, J.; Del Genio, A. D.; van den Heever, S. C.; Posselt, D. J.

2016-12-01

It is demonstrated using the ERA-Interim product that synoptic to intraseasonal variabilities of extratropical circulation in the boreal storm track regions are strongly affected by the zonal convergence of the column-integrated eastward flux of local wave activity (LWA). In particular, from the multi-year daily samples of LWA fluxes, we find that the wintertime zonal LWA flux in the jet exit regions tends to maximize for an intermediate value of column-averaged LWA. This is because an increasing LWA decelerates the zonal flow, eventually weakening the eastward advection of LWA. From theory we argue that large wave events on the decreasing side of the flux curve with increasing LWA cannot be maintained as a stable steady state. Consistent with this argument, observed states corresponding to that side of flux curve often exhibit local wave breaking and blocking events. A close parallelism exists for the traffic flow problem, in which the traffic flux (traffic density times traffic speed) is often observed to maximize for an intermediate value of traffic density. This is because the traffic speed is controlled not only by the imposed speed limit but also by the traffic density — an increasingly heavy traffic slows down the flow naturally and eventually decreases the flux. Once the flux starts to decrease with an increasing traffic density, a traffic jam kicks in suddenly (Lighthill and Whitham 1955, Richards 1956). The above idea is demonstrated by a simple conceptual model based on the equivalent barotropic PV contour design (Nakamura and Huang 2017, JAS), which predicts a threshold of blocking onset. The idea also suggests that the LWA that gives the `flux capacity,' i.e., the maximum LWA flux at a given location, is a useful predictor of local wave breaking/block formation.

Interannual Variability of Martian Global Dust Storms: Simulations with a Low-Order Model of the General Circulation

NASA Technical Reports Server (NTRS)

Pankine, A. A.; Ingersoll, Andrew P.

2002-01-01

We present simulations of the interannual variability of martian global dust storms (GDSs) with a simplified low-order model (LOM) of the general circulation. The simplified model allows one to conduct computationally fast long-term simulations of the martian climate system. The LOM is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting LOM consists of 12 coupled nonlinear ordinary differential equations describing atmospheric dynamics and dust transport within the Hadley cell. The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit the output of the NASA AMES GCM and the fit is generally very good. Interannual variability of GDSs is possible in the IBM, but only when stochastic forcing is added to the model. The stochastic forcing could be provided by transient weather systems or some surface process such as redistribution of the sand particles in storm generating zones on the surface. The results are sensitive to the value of the saltation threshold, which hints at a possible feedback between saltation threshold and dust storm activity. According to this hypothesis, erodable material builds up its a result of a local process, whose effect is to lower the saltation threshold until a GDS occurs. The saltation threshold adjusts its value so that dust storms are barely able to occur.

Jupiter: New estimates of mean zonal flow at the cloud level

NASA Technical Reports Server (NTRS)

Limaye, Sanjay S.

1986-01-01

In order to reexamine the magnitude differences of the Jovian atmosphere's jets, as determined by Voyager 1 and 2 images, a novel approach is used to ascertain the zonal mean east-west component of motion. This technique is based on digital pattern matching, and is applied on pairs of mapped images to yield a profile of the mean zonal component that reproduces the exact locations of the easterly and westerly jets between + and 60 deg latitude. Results were obtained for all of the Voyager 1 and 2 cylindrical mosaics; the correlation coefficient between Voyagers 1 and 2 in mean zonal flow between + and - 60 deg latitude, determined from violet filter mosaics, is 0.998.

Time-varying zonal asymmetries in stratospheric nitrous oxide and methane

NASA Technical Reports Server (NTRS)

Gao, H.; Stanford, J. L.

1993-01-01

Previously analyses of Stratospheric And Mesospheric Sounder (SAMS) data of atmospheric constituent gases have dealt almost exclusively with zonal means (and mostly monthly means), owing perhaps to concern over data quality. The purpose of this note is to show that, with care, time-dependent zonally-asymmetric features may be recovered from the SAMS nitrous oxide and methane data. As an example, we demonstrate the existence of zonal wave-1 constituent perturbations with periods of a few weeks in the middle and upper stratosphere. When the perturbations are normalized by the constituent zonal-mean mixing ratio to compensate for the slowly varying (in both space and time) background concentration of constituents, wavepacket-like features are found over all latitudes and seasons in the three-year SAMS record. One specific low-latitude case discussed had features which appear to be consistent with constituent oscillations induced by episodic equatorial Kelvin waves. Further studies are needed to better identify the nature of the plethora of observed wave-like phenomena.

Numerical simulation of phenomenon on zonal disintegration in deep underground mining in case of unsupported roadway

NASA Astrophysics Data System (ADS)

Han, Fengshan; Wu, Xinli; Li, Xia; Zhu, Dekang

2018-02-01

Zonal disintegration phenomenon was found in deep mining roadway surrounding rock. It seriously affects the safety of mining and underground engineering and it may lead to the occurrence of natural disasters. in deep mining roadway surrounding rock, tectonic stress in deep mining roadway rock mass, horizontal stress is much greater than the vertical stress, When the direction of maximum principal stress is parallel to the axis of the roadway in deep mining, this is the main reasons for Zonal disintegration phenomenon. Using ABAQUS software to numerical simulation of the three-dimensional model of roadway rupture formation process systematically, and the study shows that when The Direction of maximum main stress in deep underground mining is along the roadway axial direction, Zonal disintegration phenomenon in deep underground mining is successfully reproduced by our numerical simulation..numerical simulation shows that using ABAQUA simulation can reproduce Zonal disintegration phenomenon and the formation process of damage of surrounding rock can be reproduced. which have important engineering practical significance.

Effect of resonant magnetic perturbations on secondary structures in drift-wave turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leconte, M.; Diamond, P. H.; CMTFO and CASS, UCSD, California 92093

2011-08-15

Recent experiments showed a decrease of long range correlations during the application of resonant magnetic perturbations (RMPs) [Y. Xu et al., Nucl. Fusion 51, 063020 (2011)]. This finding suggests that RMPs damp zonal flows. To elucidate the effect of the RMPs on zonal structures in drift wave turbulence, we construct a generalized Hasegawa-Wakatani model including RMP fields. The effect of the RMPs is to induce a linear coupling between the zonal electric field and the zonal density gradient, which drives the system to a state of electron radial force balance for large RMP amplitude. A predator-prey model coupling the primarymore » drift wave dynamics to the zonal modes evolution is derived. This model has both turbulence drive and RMP amplitude as control parameters and predicts a novel type of transport bifurcation in the presence of RMPs. The novel regime has a power threshold which increases with RMP amplitude as {gamma}{sub c}{approx}[({delta}B{sub r}/B)]{sup 2}.« less

The modulational instability in the extended Hasegawa-Mima equation with a finite Larmor radius

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallagher, S.; Hnat, B.; Rowlands, G.

2012-12-15

The effects of the finite Larmor radius on the generation of zonal flows by the four-wave modulational instability are investigated using an extended form of the Hasegawa-Mima equation. Growth rates of the zonal mode are quantified using analytical predictions from a four-mode truncated model, as well as from direct numerical simulation of the nonlinear extended Hasegawa-Mima equation. We not only consider purely zonal flows but also examine the generic oblique case and show that, for small Larmor radii, off-axis modes may become dominant. We find a key parameter M{sub {rho}} which characterises the behaviour of the system due to changesmore » in the Larmor radius. We find that, similarly to previous results obtained by changing the driving wave amplitude, two separate dynamical regimes can be accessed. These correspond to oscillatory energy transfer between zonal flows and a driving wave and the fully saturated zonal flow.« less

Gravitational Anomalies Caused by Zonal Winds in Jupiter

NASA Astrophysics Data System (ADS)

Schubert, G.; Kong, D.; Zhang, K.

2012-12-01

We present an accurate three-dimensional non-spherical numerical calculation of the gravitational anomalies caused by zonal winds in Jupiter. The calculation is based on a three-dimensional finite element method and accounts for the full effect of significant departure from spherical geometry caused by rapid rotation. Since the speeds of Jupiter's zonal winds are much smaller than that of its rigid-body rotation, our numerical calculation is carried out in two stages. First, we compute the non-spherical distributions of density and pressure at the equilibrium within Jupiter via a hybrid inverse approach by determining an a priori unknown coefficient in the polytropic equation of state that results in a match to the observed shape of Jupiter. Second, by assuming that Jupiter's zonal winds extend throughout the interior along cylinders parallel to the rotation axis, we compute gravitational anomalies produced by the wind-related density anomalies, providing an upper bound to the gravitational anomalies caused by the Jovian zonal winds.

Microwave Investigation of the Mars Atmosphere and Surface

NASA Technical Reports Server (NTRS)

Gulkis, S.; Forget, F.; Janssen, M.; Riley, A. L.; Hartogh, P.; Clancy, T.; Allen, M.; Frerking, M.

2000-01-01

The Microwave Investigation of the Mars Atmosphere and Surface Experiment (MIMAS) is designed to address two major scientific goals: 1) To understand the three dimensional general circulation of the Martian atmosphere, and 2) To understand the hydrologic cycle of water on Mars, including the time-variable sources, sinks, and atmospheric transport of water vapor. The proposed instrument is a submillimeter wave, heterodyne receiver, with both continuum and very high spectral resolution capability. A small reflector antenna will be used to feed the receiver. Instrument heritage comes from the MIRO receiver, currently under design for the ESA Rosetta Mission, and from SWAS, a NASA astrophysics mission. The instrument will be able to measure atmospheric spectral lines from both water and carbon monoxide and use these lines as tracers of atmospheric winds. Measurement objectives of MIMAS are to measure surface temperature, atmospheric temperature from the surface up to an altitude of 60 km or more, the distribution of CO and H2O in the atmosphere, and certain wind fields (zonal and meridional). The global distribution of CO, as well as temperature distributions, will be used as input data for GCMs (general circulation models). Water vapor profiles will be used to understand the sources and sinks of water on Mars and to understand how it is transported globally by the general circulation. Zonal and meridional wind fields will provide further tests of the GCMs. An important aspect of this experiment is that the temperature and humidity measurements are insensitive to dust and ice condensates thereby making the measurement capability independent of the presence of dust clouds and ice particles. Temperature measurements derived from the data can be used in conjunction with infrared measurements to determine dust profiles.

Buoyancy forcing and the MOC: insights from experiments, simulations and global models

NASA Astrophysics Data System (ADS)

White, B. L.; Passaggia, P. Y.; Zemskova, V.

2017-12-01

The driving forces behind the Meridional Overturning Circulation (MOC) have been widely debated, with wind-driven upwelling, surface buoyancy fluxes due to heating/cooling/freshwater input, and vertical diffusion due to turbulent mixing all thought to play significant roles. To explore the specific role of buoyancy forcing we present results from experiments and simulations of Horizontal Convection (HC), where a circulation is driven by differential buoyancy forcing applied along a horizontal surface. We interpret these results using energy budgets based on the local Available Potential Energy framework introduced in [Scotti and White, J. Fluid Mech., 2014]. We first describe HC experiments driven by the diffusion of salt in water across membranes localized at the surface, at Schmidt numbers {Sc}≈ 610 and Rayleigh numbers in the range 1012 < Ra=Δ b L3/(ν κ ) < 1017, where ν is the kinematic viscosity of water, κ is the diffusion coefficient of salt, L=[.5,2,5]m is the length of the different tanks and Δ b=g(ρ salt}-ρ {fresh}/ρ_{fresh is the reduced gravity difference. We show that the scaling follows a Nu ˜ Ra1/4 type scaling recently theorized by Shishkina et; al. (2016). We then present numerical results for rotating horizontal convection with a zonally re-entrant channel to represent the Southern Ocean branch of the MOC. While the zonal wind stress profile is important to the spatial pattern of the circulation, perhaps surprisingly, the energy budget shows only a weak dependence on the magnitude of the wind input, suggesting that surface APE generation by buoyancy forcing is dominant in driving the overturning circulation.

The solsticial pause on Mars: 2 modelling and investigation of causes

NASA Astrophysics Data System (ADS)

Mulholland, David P.; Lewis, Stephen R.; Read, Peter L.; Madeleine, Jean-Baptiste; Forget, Francois

2016-01-01

The martian solsticial pause, presented in a companion paper (Lewis et al., 2016), was investigated further through a series of model runs using the UK version of the LMD/UK Mars Global Climate Model. It was found that the pause could not be adequately reproduced if radiatively active water ice clouds were omitted from the model. When clouds were used, along with a realistic time-dependent dust opacity distribution, a substantial minimum in near-surface transient eddy activity formed around solstice in both hemispheres. The net effect of the clouds in the model is, by altering the thermal structure of the atmosphere, to decrease the vertical shear of the westerly jet near the surface around solstice, and thus reduce baroclinic growth rates. A similar effect was seen under conditions of large dust loading, implying that northern midlatitude eddy activity will tend to become suppressed after a period of intense flushing storm formation around the northern cap edge. Suppression of baroclinic eddy generation by the barotropic component of the flow and via diabatic eddy dissipation were also investigated as possible mechanisms leading to the formation of the solsticial pause but were found not to make major contributions. Zonal variations in topography were found to be important, as their presence results in weakened transient eddies around winter solstice in both hemispheres, through modification of the near-surface flow. The zonal topographic asymmetry appears to be the primary reason for the weakness of eddy activity in the southern hemisphere relative to the northern hemisphere, and the ultimate cause of the solsticial pause in both hemispheres. The meridional topographic gradient was found to exert a much weaker influence on near-surface transient eddies.

The coccolithophores Emiliania huxleyi and Coccolithus pelagicus: Extant populations from the Norwegian-Iceland Seas and Fram Strait

NASA Astrophysics Data System (ADS)

Dylmer, C. V.; Giraudeau, J.; Hanquiez, V.; Husum, K.

2015-04-01

The distributions of the coccolithophore species Emiliania huxleyi and Coccolithus pelagicus (heterococcolith-bearing phase) in the northern North Atlantic were investigated along two zonal transects crossing Fram Strait and the Norwegian-Iceland Sea, respectively, each conducted during both July 2011 and September-October 2007. Remote-sensing images as well as CTD and ARGO profiles were used to constrain the physico-chemical state of the surface water and surface mixed layer at the time of sampling. Strong seasonal differences in bulk coccolithophore standing stocks characterized the northern and southern transects, where the maximum values of 53×103 cells/l (fall) and 70×103 cells/l (summer), respectively, were essentially explained by E. huxleyi. This pattern confirms previous findings of a summer to fall northwestward shift in peak coccolithophore cell densities within the Nordic Seas. While depicting an overall zonal shift in high cell densities between the summer (Norwegian Sea) and fall (northern Iceland Sea) conditions, the southern transects were additionally characterized by local peak coccolithophore concentrations associated with a geographically and temporally restricted convective process (Lofoten Gyre, summer), as well as an island mass effect (in the vicinity of Jan Mayen Island, fall). Maximum coccolithophore abundances within Fram Strait were found during both seasons close to the western frontal zone (Polar and Arctic Fronts) an area of strong density gradients where physical and chemical properties of the surface mixed layer are prone to enhance phytoplankton biomass and productivity. Here, changes in species dominance from E. huxleyi in summer, to C. pelagicus in fall, were related to the strengthened influence during summer, of surface AW, as well as to high July solar irradiance, within an area usually characterized by C. pelagicus-dominated low density populations.

Zonally Asymmetric Ozone and the Morphology of the Planetary Waveguide

DTIC Science & Technology

2011-07-15

sections for the 271 troposphere , J. Atmos. Sci., 37, 2600-2616. 272 Eyring, V., et al. (2007), Multimodel projections of stratospheric ozone ...GEOPHYSICAL RESEARCH LETTERS, VOL. ???, XXXX, DOI:10.1029/, JULY 15, 2011 Zonally asymmetric ozone and the morphology of the 1 planetary waveguide...that zonally asymmetric 6 ozone (ZAO) profoundly changes the morphology of the Northern Hemisphere planetary 7 waveguide (PWG). ZAO causes the PWG to

The role of zonal flows in the saturation of multi-scale gyrokinetic turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Staebler, G. M.; Candy, J.; Howard, N. T.

2016-06-15

The 2D spectrum of the saturated electric potential from gyrokinetic turbulence simulations that include both ion and electron scales (multi-scale) in axisymmetric tokamak geometry is analyzed. The paradigm that the turbulence is saturated when the zonal (axisymmetic) ExB flow shearing rate competes with linear growth is shown to not apply to the electron scale turbulence. Instead, it is the mixing rate by the zonal ExB velocity spectrum with the turbulent distribution function that competes with linear growth. A model of this mechanism is shown to be able to capture the suppression of electron-scale turbulence by ion-scale turbulence and the thresholdmore » for the increase in electron scale turbulence when the ion-scale turbulence is reduced. The model computes the strength of the zonal flow velocity and the saturated potential spectrum from the linear growth rate spectrum. The model for the saturated electric potential spectrum is applied to a quasilinear transport model and shown to accurately reproduce the electron and ion energy fluxes of the non-linear gyrokinetic multi-scale simulations. The zonal flow mixing saturation model is also shown to reproduce the non-linear upshift in the critical temperature gradient caused by zonal flows in ion-scale gyrokinetic simulations.« less

Net Influence of an Internally Generated Guasi-biennial Oscillation on Modelled Stratospheric Climate and Chemistry

NASA Technical Reports Server (NTRS)

Hurwitz, Margaret M.; Oman, Luke David; Newman, Paul A.; Song, InSun

2013-01-01

A Goddard Earth Observing System Chemistry- Climate Model (GEOSCCM) simulation with strong tropical non-orographic gravity wave drag (GWD) is compared to an otherwise identical simulation with near-zero tropical non-orographic GWD. The GEOSCCM generates a quasibiennial oscillation (QBO) zonal wind signal in response to a tropical peak in GWD that resembles the zonal and climatological mean precipitation field. The modelled QBO has a frequency and amplitude that closely resembles observations. As expected, the modelled QBO improves the simulation of tropical zonal winds and enhances tropical and subtropical stratospheric variability. Also, inclusion of the QBO slows the meridional overturning circulation, resulting in a generally older stratospheric mean age of air. Slowing of the overturning circulation, changes in stratospheric temperature and enhanced subtropical mixing all affect the annual mean distributions of ozone, methane and nitrous oxide. Furthermore, the modelled QBO enhances polar stratospheric variability in winter. Because tropical zonal winds are easterly in the simulation without a QBO, there is a relative increase in tropical zonal winds in the simulation with a QBO. Extratropical differences between the simulations with and without a QBO thus reflect the westerly shift in tropical zonal winds: a relative strengthening of the polar stratospheric jet, polar stratospheric cooling and a weak reduction in Arctic lower stratospheric ozone.

Multiple zonal jets and convective heat transport barriers in a quasi-geostrophic model of planetary cores

NASA Astrophysics Data System (ADS)

Guervilly, C.; Cardin, P.

2017-10-01

We study rapidly rotating Boussinesq convection driven by internal heating in a full sphere. We use a numerical model based on the quasi-geostrophic approximation for the velocity field, whereas the temperature field is 3-D. This approximation allows us to perform simulations for Ekman numbers down to 10-8, Prandtl numbers relevant for liquid metals (˜10-1) and Reynolds numbers up to 3 × 104. Persistent zonal flows composed of multiple jets form as a result of the mixing of potential vorticity. For the largest Rayleigh numbers computed, the zonal velocity is larger than the convective velocity despite the presence of boundary friction. The convective structures and the zonal jets widen when the thermal forcing increases. Prograde and retrograde zonal jets are dynamically different: in the prograde jets (which correspond to weak potential vorticity gradients) the convection transports heat efficiently and the mean temperature tends to be homogenized; by contrast, in the cores of the retrograde jets (which correspond to steep gradients of potential vorticity) the dynamics is dominated by the propagation of Rossby waves, resulting in the formation of steep mean temperature gradients and the dominance of conduction in the heat transfer process. Consequently, in quasi-geostrophic systems, the width of the retrograde zonal jets controls the efficiency of the heat transfer.

The role of zonal flows in the saturation of multi-scale gyrokinetic turbulence

DOE PAGES

Staebler, Gary M.; Candy, John; Howard, Nathan T.; ...

2016-06-29

The 2D spectrum of the saturated electric potential from gyrokinetic turbulence simulations that include both ion and electron scales (multi-scale) in axisymmetric tokamak geometry is analyzed. The paradigm that the turbulence is saturated when the zonal (axisymmetic) ExB flow shearing rate competes with linear growth is shown to not apply to the electron scale turbulence. Instead, it is the mixing rate by the zonal ExB velocity spectrum with the turbulent distribution function that competes with linear growth. A model of this mechanism is shown to be able to capture the suppression of electron-scale turbulence by ion-scale turbulence and the thresholdmore » for the increase in electron scale turbulence when the ion-scale turbulence is reduced. The model computes the strength of the zonal flow velocity and the saturated potential spectrum from the linear growth rate spectrum. The model for the saturated electric potential spectrum is applied to a quasilinear transport model and shown to accurately reproduce the electron and ion energy fluxes of the non-linear gyrokinetic multi-scale simulations. Finally, the zonal flow mixing saturation model is also shown to reproduce the non-linear upshift in the critical temperature gradient caused by zonal flows in ionscale gyrokinetic simulations.« less

Cloud Inhomogeneity from MODIS

NASA Technical Reports Server (NTRS)

Oreopoulos, Lazaros; Cahalan, Robert F.

2004-01-01

Two full months (July 2003 and January 2004) of MODIS Atmosphere Level-3 data from the Terra and Aqua satellites are analyzed in order to characterize the horizontal variability of cloud optical thickness and water path at global scales. Various options to derive cloud variability parameters are discussed. The climatology of cloud inhomogeneity is built by first calculating daily parameter values at spatial scales of l degree x 1 degree, and then at zonal and global scales, followed by averaging over monthly time scales. Geographical, diurnal, and seasonal changes of inhomogeneity parameters are examined separately for the two cloud phases, and separately over land and ocean. We find that cloud inhomogeneity is weaker in summer than in winter, weaker over land than ocean for liquid clouds, weaker for local morning than local afternoon, about the same for liquid and ice clouds on a global scale, but with wider probability distribution functions (PDFs) and larger latitudinal variations for ice, and relatively insensitive to whether water path or optical thickness products are used. Typical mean values at hemispheric and global scales of the inhomogeneity parameter nu (roughly the mean over the standard deviation of water path or optical thickness), range from approximately 2.5 to 3, while for the inhomogeneity parameter chi (the ratio of the logarithmic to linear mean) from approximately 0.7 to 0.8. Values of chi for zonal averages can occasionally fall below 0.6 and for individual gridpoints below 0.5. Our results demonstrate that MODIS is capable of revealing significant fluctuations in cloud horizontal inhomogenity and stress the need to model their global radiative effect in future studies.

Reconstruction of pre-instrumental storm track trajectories across the U.S. Pacific Northwest using circulation-based field sampling of Pinus Ponderosa

NASA Astrophysics Data System (ADS)

Wise, E.; Dannenberg, M. P.

2015-12-01

The trajectory of incoming storms from the Pacific Ocean is a key influence on drought and flood regimes in western North America. Flow is typically from the west in a zonal pattern, but decadal shifts between zonal and meridional flow have been identified as key features in hydroclimatic variability over the instrumental period. In Washington and most of the Pacific Northwest, there tend to be lower-latitude storm systems that result in decreased precipitation in El Niño years. However, the Columbia Basin in central Washington behaves in opposition to the surrounding region and typically has average to above-average precipitation in El Niño years due to changing storm-track trajectories and a decreasing rain shadow effect on the leeward side of the Cascades. This direct connection between storm-track position and precipitation patterns in Washington provided an exceptional opportunity for circulation-based field sampling and chronology development. New Pinus ponderosa (Ponderosa pine) tree-ring chronologies were developed from eight sites around the Columbia Basin in Washington and used to examine year-to-year changes in moisture regimes. Results show that these sites are representative of the two distinct climate response areas. The divergence points between these two site responses allowed us to reconstruct changing precipitation patterns since the late-17th century, and to link these patterns to previously reconstructed atmospheric pressure and El Niño indices. This study highlights the potential for using synoptic climatology to inform field-based proxy collection.

A zonal method for modeling powered-lift aircraft flow fields

NASA Technical Reports Server (NTRS)

Roberts, D. W.

1989-01-01

A zonal method for modeling powered-lift aircraft flow fields is based on the coupling of a three-dimensional Navier-Stokes code to a potential flow code. By minimizing the extent of the viscous Navier-Stokes zones the zonal method can be a cost effective flow analysis tool. The successful coupling of the zonal solutions provides the viscous/inviscid interations that are necessary to achieve convergent and unique overall solutions. The feasibility of coupling the two vastly different codes is demonstrated. The interzone boundaries were overlapped to facilitate the passing of boundary condition information between the codes. Routines were developed to extract the normal velocity boundary conditions for the potential flow zone from the viscous zone solution. Similarly, the velocity vector direction along with the total conditions were obtained from the potential flow solution to provide boundary conditions for the Navier-Stokes solution. Studies were conducted to determine the influence of the overlap of the interzone boundaries and the convergence of the zonal solutions on the convergence of the overall solution. The zonal method was applied to a jet impingement problem to model the suckdown effect that results from the entrainment of the inviscid zone flow by the viscous zone jet. The resultant potential flow solution created a lower pressure on the base of the vehicle which produces the suckdown load. The feasibility of the zonal method was demonstrated. By enhancing the Navier-Stokes code for powered-lift flow fields and optimizing the convergence of the coupled analysis a practical flow analysis tool will result.

Rethinking wave-kinetic theory applied to zonal flows

NASA Astrophysics Data System (ADS)

Parker, Jeffrey

2017-10-01

Over the past two decades, a number of studies have employed a wave-kinetic theory to describe fluctuations interacting with zonal flows. Recent work has uncovered a defect in this wave-kinetic formulation: the system is dominated by the growth of (arbitrarily) small-scale zonal structures. Theoretical calculations of linear growth rates suggest, and nonlinear simulations confirm, that this system leads to the concentration of zonal flow energy in the smallest resolved scales, irrespective of the numerical resolution. This behavior results from the assumption that zonal flows are extremely long wavelength, leading to the neglect of key terms responsible for conservation of enstrophy. A corrected theory, CE2-GO, is presented; it is free of these errors yet preserves the intuitive phase-space mathematical structure. CE2-GO properly conserves enstrophy as well as energy, and yields accurate growth rates of zonal flow. Numerical simulations are shown to be well-behaved and not dependent on box size. The steady-state limit simplifies into an exact wave-kinetic form which offers the promise of deeper insight into the behavior of wavepackets. The CE2-GO theory takes its place in a hierarchy of models as the geometrical-optics reduction of the more complete cumulant-expansion statistical theory CE2. The new theory represents the minimal statistical description, enabling an intuitive phase-space formulation and an accurate description of turbulence-zonal flow dynamics. This work was supported by an NSF Graduate Research Fellowship, a US DOE Fusion Energy Sciences Fellowship, and US DOE Contract Nos. DE-AC52-07NA27344 and DE-AC02-09CH11466.

Depth and Distribution of CO2 Snow on Mars

NASA Technical Reports Server (NTRS)

Aharonson, Oded; Zuber, Maria T.; Smith, David E.; Neumann, Gregory A.

2003-01-01

The dynamic role of volatiles on the surface of Mars has been a subject of longstanding interest. In the pre-Viking era, much of the debate was necessarily addressed by theoretical considerations. A particularly influential treatment by Leighton and Murray put forth a simple model relying on solar energy balance, and led to the conclusion that the most prominent volatile exchanging with the atmosphere over seasonal cycles is carbon dioxide. Their model suggested that due to this exchange, atmospheric CO2 partial pressure is regulated by polar ice. While current thinking attributes a larger role to H2O ice than did the occasional thin polar coating this model predicted, the CO2 cycle appears to be essentially correct. There are a number of observational constraints on the seasonal exchange of surface volatiles with the atmosphere. The growth and retreat of polar CO2 frost is visible from Earth-based telescopes and from spacecraft in Mars orbit, both at visible wavelengths and in thermal IR properties of the surface. Recently, variations in Gamma ray and neutron fluxes have also been used to infer integrated changes in CO2 mass on the surface. Measurements made by Viking's Mars Atmospheric Water Detector experiment were sensitive to atmospheric H2O vapor abundance. Surface condensates and their transient nature were detected by the Viking landers. The study here is motivated by recent data collected by the Mars Global Surveyor, affording the opportunity to not only detect the lateral distribution of volatiles, but also to constrain the variable volumes of the reservoirs. We elaborate on a technique first employed by Smith et al. By examining averages of a large number of topographic measurements collected by the Mars Orbiter Laser Altimeter (MOLA), that study showed that the zonal pattern of deposition and sublimation of CO2 can be determined. In their first approach, reference surfaces were fit to all measurements in narrow latitude annuli, and the time dependent variations about those mean surfaces were examined. In their second approach, height measurements from pairs of tracks that cross on the surface were interpolated and differenced, forming a set of crossover residuals. These residuals were then examined as a function of time and latitude. The initial studies averaged over longitude to maximize signal and minimize noise in order to isolate the expected small signal. In this follow-up study we now attempt to extract the elevation change pattern also as a function of longitude, and we focus on the crossover approach.

Contribution to the study of the zonal variation of the climate aridity in central northern Sahara (Algeria)

NASA Astrophysics Data System (ADS)

Benseghier-Hadjaidji, Fatiha; Talbi, Nadjib; Derridj, Arezki

2018-05-01

The environment degradation at the level of all its compartments which we notice at present, calls us to the risks that it would underestimate the climatic and consequently bioclimatic crisis there, in the North as in the South of the Mediterranean region. To protect the environment is not a luxury. In this respect, we wondered about the zonal variation of the climate aridity at the level of three bordering climatic stations: El-Oued, Touggourt and Ouargla. These are distant from 160 km on average some of the others. For that purpose, we based ourselves on the statistical tool the software "instat +" for the estimation of the ETP (PM) and afterward the determination of the pluvio-evapotranspiration "quotient P/ETP". For this analysis, the climatic data spread out over a period of 20 years. The results allowed to specify the aridity degree of the studied zone. So, they reveal a mitigation of the aridity of the climate in Touggourt and El-Oued while the hyper-aridity distinguishes well the Ouargla region. This approach contributes to a better knowledge of the dry ecosystems. This is important to indicate it to turn better in the eremologic search later.

The effect of breaking gravity waves on the dynamics and chemistry of the mesosphere and lower thermosphere (invited review)

NASA Technical Reports Server (NTRS)

Garcia, R. R.

1986-01-01

The influence of breaking gravity waves on the dynamics and chemical composition of the 60 to 110 km region is investigated with a two dimensional model that includes a parameterization of gravity wave momentum deposition and diffusion. The dynamical model is described by Garcia and Solomon (1983) and Solomon and Garcia (1983) and includes a complete chemical scheme for the mesosphere and lower thermosphere. The parameterization of Lindzen (1981) is used to calculate the momentum deposited and the turbulent diffusion produced by the gravity waves. It is found that wave momentum deposition drives a very vigorous mean meridional circulation, produces a very cold summer mesopause and reverse the zonal wind jets above about 85 km. The seasonal variation of the turbulent diffusion coefficient is consistent with the behavior of mesospheric turbulences inferred from MST radar echoes. The large degree of consistency between model results and various types of dynamical and chemical data supports very strongly the hypothesis that breaking gravity waves play a major role in determining the zonally-averaged dynamical and chemical structure of the 60 to 110 km region of the atmosphere.

On non-local energy transfer via zonal flow in the Dimits shift

DOE PAGES

St-Onge, Denis A.

2017-10-10

The two-dimensional Terry–Horton equation is shown to exhibit the Dimits shift when suitably modified to capture both the nonlinear enhancement of zonal/drift-wave interactions and the existence of residual Rosenbluth–Hinton states. This phenomenon persists through numerous simplifications of the equation, including a quasilinear approximation as well as a four-mode truncation. It is shown that the use of an appropriate adiabatic electron response, for which the electrons are not affected by the flux-averaged potential, results in anmore » $$\\boldsymbol{E}\\times \\boldsymbol{B}$$ nonlinearity that can efficiently transfer energy non-locally to length scales of the order of the sound radius. The size of the shift for the nonlinear system is heuristically calculated and found to be in excellent agreement with numerical solutions. The existence of the Dimits shift for this system is then understood as an ability of the unstable primary modes to efficiently couple to stable modes at smaller scales, and the shift ends when these stable modes eventually destabilize as the density gradient is increased. This non-local mechanism of energy transfer is argued to be generically important even for more physically complete systems.« less

Dynamical Coupling Between the Stratosphere and the Troposphere: The Influence of External Forcings

NASA Astrophysics Data System (ADS)

Hansen, Felicitas; Matthes, Katja

2013-04-01

The dynamical coupling between the stratosphere and the troposphere is dominated by planetary waves that are generated in the troposphere by orography and land-sea contrasts. These waves travel upward into the stratosphere where they either dissipate or are reflected downward to impact the troposphere again. Through the interaction with the zonal mean flow planetary waves can induce stratospheric sudden warmings (SSWs), i.e., conditions during NH winter where the stratospheric polar vortex is disturbed so that the zonal mean zonal wind in the NH stratospheric jet becomes easterly and the polar cap meridional temperature gradient reverses. Since strong major SSWs can propagate down into the troposphere and even affect surface weather, SSWs present a strong and clear manifestation of the dynamical coupling in the stratosphere-troposphere system. We will investigate the influence of some external forcings, namely sea surface temperatures (SSTs), anthropogenic greenhouse gases and the quasi-biennial oscillation (QBO), on these coupling processes. Thereby we are interested in how the distribution of SSWs in the winter months changes due to the different forcings, whether the events evolve differently, and whether they show differences in their preconditioning, e.g. a different wave geometry. We will also investigate whether and how vertical reflective surfaces in the stratosphere, which can reflect upward propagating planetary waves, influence the evolution of SSWs. To address these questions, we performed a set of model simulations with NCAR's Community Earth System Model (CESM), a coupled model system including an interactive ocean (POP2), land (CLM4), sea ice (CICE) and atmosphere (NCAR's Whole Atmosphere Community Climate Model (WACCM)) component. Our control experiment is a 140-year simulation with the fully coupled atmosphere-ocean version of CESM. A second experiment is a 55-year simulation with only CESM's atmospheric component WACCM, a fully interactive chemistry-climate model extending from the Earth's surface through the thermosphere (about 140 km), with underlying climatological SSTs obtained from the coupled CESM control run. A third 55-year simulation is performed without the nudging of the equatorial QBO. All three simulations develop under conditions where greenhouse gases are held constant at the 1960 level. In a fourth simulations, the greenhouse gases follow the RCP8.5 scenario. From the differences of the individual simulations to the control experiment we can estimate the respective roles of SSTs, the QBO and anthropogenic greenhouse gases for the stratosphere-troposphere coupling. The model results will be compared to the Modern Era Retrospective-Analysis for Research and Applications (MERRA) dataset.

Inventory of File sref.t03z.pgrb212_SPC.prob_1hrly.grib2

Science.gov Websites

analysis Total Precipitation [prob] prob >0.25 002 cloud base U-GWD 1 hour fcst Zonal Flux of Gravity Precipitation [prob] prob >0.25 007 cloud base U-GWD 2 hour fcst Zonal Flux of Gravity Wave Stress [prob ;0.25 012 cloud base U-GWD 4 hour fcst Zonal Flux of Gravity Wave Stress [prob] prob =1 013 entire

Venus's winds and temperatures during the MESSENGER's flyby: An approximation to a three-dimensional instantaneous state of the atmosphere

NASA Astrophysics Data System (ADS)

Peralta, J.; Lee, Y. J.; Hueso, R.; Clancy, R. T.; Sandor, B. J.; Sánchez-Lavega, A.; Lellouch, E.; Rengel, M.; Machado, P.; Omino, M.; Piccialli, A.; Imamura, T.; Horinouchi, T.; Murakami, S.; Ogohara, K.; Luz, D.; Peach, D.

2017-04-01

Even though many missions have explored the Venus atmospheric circulation, its instantaneous state is poorly characterized. In situ measurements vertically sampling the atmosphere exist for limited locations and dates, while remote sensing observations provide only global averages of winds at altitudes of the clouds: 47, 60, and 70 km. We present a three-dimensional global view of Venus's atmospheric circulation from data obtained in June 2007 by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) and Venus Express spacecrafts, together with ground-based observations. Winds and temperatures were measured for heights 47-110 km from multiwavelength images and spectra covering 40°N-80°S and local times 12 h-21 h. Dayside westward winds exhibit day-to-day changes, with maximum speeds ranging 97-143 m/s and peaking at variable altitudes within 75-90 km, while on the nightside these peak below cloud tops at ˜60 km. Our results support past reports of strong variability of the westward zonal superrotation in the transition region, and good agreement is found above the clouds with results from the Laboratoire de Météorologie Dynamique (LMD) Venus general circulation model.

Response of the global climate to changes in atmospheric chemical composition due to fossil fuel burning

NASA Technical Reports Server (NTRS)

Hameed, S.; Cess, R. D.; Hogan, J. S.

1980-01-01

Recent modeling of atmospheric chemical processes (Logan et al, 1978; Hameed et al, 1979) suggests that tropospheric ozone and methane might significantly increase in the future as the result of increasing anthropogenic emissions of CO, NO(x), and CH4 due to fossil fuel burning. Since O3 and CH4 are both greenhouse gases, increases in their concentrations could augment global warming due to larger future amounts of atmospheric CO2. To test the possible climatic impact of changes in tropospheric chemical composition, a zonal energy-balance climate model has been combined with a vertically averaged tropospheric chemical model. The latter model includes all relevant chemical reactions which affect species derived from H2O, O2, CH4, and NO(x). The climate model correspondingly incorporates changes in the infrared heating of the surface-troposphere system resulting from chemically induced changes in tropospheric ozone and methane. This coupled climate-chemical model indicates that global climate is sensitive to changes in emissions of CO, NO(x) and CH4, and that future increases in these emissions could augment global warming due to increasing atmospheric CO2.

Infrared radiation parameterizations for the minor CO2 bands and for several CFC bands in the window region

NASA Technical Reports Server (NTRS)

Kratz, David P.; Chou, Ming-Dah; Yan, Michael M.-H.

1993-01-01

Fast and accurate parameterizations have been developed for the transmission functions of the CO2 9.4- and 10.4-micron bands, as well as the CFC-11, CFC-12, and CFC-22 bands located in the 8-12-micron region. The parameterizations are based on line-by-line calculations of transmission functions for the CO2 bands and on high spectral resolution laboratory measurements of the absorption coefficients for the CFC bands. Also developed are the parameterizations for the H2O transmission functions for the corresponding spectral bands. Compared to the high-resolution calculations, fluxes at the tropopause computed with the parameterizations are accurate to within 10 percent when overlapping of gas absorptions within a band is taken into account. For individual gas absorption, the accuracy is of order 0-2 percent. The climatic effects of these trace gases have been studied using a zonally averaged multilayer energy balance model, which includes seasonal cycles and a simplified deep ocean. With the trace gas abundances taken to follow the Intergovernmental Panel on Climate Change Low Emissions 'B' scenario, the transient response of the surface temperature is simulated for the period 1900-2060.

Modeling the seasonal cycle of CO2 on Mars: A fit to the Viking lander pressure curves

NASA Technical Reports Server (NTRS)

Wood, S. E.; Paige, D. A.

1992-01-01

We have constructed a more accurate Mars thermal model, similar to the one used by Leighton and Murray in 1966, which solves radiative, conductive, and latent heat balance at the surface as well as the one-dimensional heat conduction equation for 40 layers to a depth of 15 meters every 1/36 of a Martian day. The planet is divided into 42 latitude bands with a resolution of two degrees near the poles and five degrees at lower latitudes, with elevations relative to the 6.1 mbar reference areoid. This estimate of the Martian zonally averaged topography was derived primarily from radio occultations. We show that a realistic one-dimensional thermal model is able to reproduce the VL1 pressure curve reasonably well without having to invoke complicated atmospheric effects such as dust storms and polar hoods. Although these factors may cause our deduced values for each model parameter to differ from its true value, we believe that this simple model can be used as a platform to study many aspects of the Martian CO2 cycle over seasonal, interannual, and long-term climate timescales.

Characterization of Unsteady Flow Structures Near Landing-Edge Slat. Part 2; 2D Computations

NASA Technical Reports Server (NTRS)

Khorrami, Mehdi; Choudhari, Meelan M.; Jenkins, Luther N.

2004-01-01

In our previous computational studies of a generic high-lift configuration, quasi-laminar (as opposed to fully turbulent) treatment of the slat cove region proved to be an effective approach for capturing the unsteady dynamics of the cove flow field. Combined with acoustic propagation via Ffowes Williams and Hawkings formulation, the quasi-laminar simulations captured some important features of the slat cove noise measured with microphone array techniques. However. a direct assessment of the computed cove flow field was not feasible due to the unavailability of off-surface flow measurements. To remedy this shortcoming, we have undertaken a combined experiment and computational study aimed at characterizing the flow structures and fluid mechanical processes within the slat cove region. Part I of this paper outlines the experimental aspects of this investigation focused on the 30P30N high-lift configuration; the present paper describes the accompanying computational results including a comparison between computation and experiment at various angles of attack. Even through predictions of the time-averaged flow field agree well with the measured data, the study indicates the need for further refinement of the zonal turbulence approach in order to capture the full dynamics of the cove's fluctuating flow field.

Anelastic and Compressible Simulation of Moist Dynamics at Planetary Scales

NASA Astrophysics Data System (ADS)

Kurowski, M.; Smolarkiewicz, P. K.; Grabowski, W.

2015-12-01

Moist anelastic and compressible numerical solutions to the planetary baroclinic instability and climate benchmarks are compared. The solutions are obtained applying a consistent numerical framework for dis- crete integrations of the various nonhydrostatic flow equations. Moist extension of the baroclinic instability benchmark is formulated as an analog of the dry case. Flow patterns, surface vertical vorticity and pressure, total kinetic energy, power spectra, and total amount of condensed water are analyzed. The climate bench- mark extends the baroclinic instability study by addressing long-term statistics of an idealized planetary equilibrium and associated meridional transports. Short-term deterministic anelastic and compressible so- lutions differ significantly. In particular, anelastic baroclinic eddies propagate faster and develop slower owing to, respectively, modified dispersion relation and abbreviated baroclinic vorticity production. These eddies also carry less kinetic energy, and the onset of their rapid growth occurs later than for the compressible solutions. The observed differences between the two solutions are sensitive to initial conditions as they di- minish for large-amplitude excitations of the instability. In particular, on the climatic time scales, the anelastic and compressible solutions evince similar zonally averaged flow patterns with the matching meridional transports of entropy, momentum, and moisture.

Effects of plasma shaping on nonlinear gyrokinetic turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belli, E. A.; Hammett, G. W.; Dorland, W.

The effects of flux surface shape on the gyrokinetic stability and transport of tokamak plasmas are studied using the GS2 code [M. Kotschenreuther, G. Rewoldt, and W. M. Tang, Comput. Phys. Commun. 88, 128 (1995); W. Dorland, F. Jenko, M. Kotschenreuther, and B. N. Rogers, Phys. Rev. Lett. 85, 5579 (2000)]. Studies of the scaling of nonlinear turbulence with shaping parameters are performed using analytic equilibria based on interpolations of representative shapes of the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)]. High shaping is found to be a stabilizing influence on bothmore » the linear ion-temperature-gradient (ITG) instability and the nonlinear ITG turbulence. For the parameter regime studied here, a scaling of the heat flux with elongation of {chi}{approx}{kappa}{sup -1.5} or {kappa}{sup -2.0}, depending on the triangularity, is observed at fixed average temperature gradient. While this is not as strong as empirical elongation scalings, it is also found that high shaping results in a larger Dimits upshift of the nonlinear critical temperature gradient due to an enhancement of the Rosenbluth-Hinton residual zonal flows.« less

The roles of vertical mixing, solar radiation, and wind stress in a model simulation of the sea surface temperature seasonal cycle in the tropical Pacfic Ocean

NASA Technical Reports Server (NTRS)

Chen, Dake; Busalacchi, Antonio J.; Rothstein, Lewis M.

1994-01-01

The climatological seasonal cycle of sea surface temperature (SST) in the tropical Pacific is simulated using a newly developed upper ocean model. The roles of vertical mixing, solar radiation, and wind stress are investigated in a hierarchy of numerical experiments with various combinations of vertical mixing algorithms and surface-forcing products. It is found that the large SST annual cycle in the eastern equatorial Pacific is, to a large extent, controlled by the annually varying mixed layer depth which, in turn, is mainly determined by the competing effects of solar radiation and wind forcing. With the application of our hybrid vertical mixing scheme the model-simulated SST annual cycle is much improved in both amplitude and phase as compared to the case of a constant mixed layer depth. Beside the strong effects on vertical mixing, solar radiation is the primary heating term in the surface layer heat budget, and wind forcing influences SST by driving oceanic advective processes that redistribute heat in the upper ocean. For example, the SST seasonal cycle in the western Pacific basically follows the semiannual variation of solar heating, and the cycle in the central equatorial region is significantly affected by the zonal advective heat flux associated with the seasonally reversing South Equatorial Current. It has been shown in our experiments that the amount of heat flux modification needed to eliminate the annual mean SST errors in the model is, on average, no larger than the annual mean uncertainties among the various surface flux products used in this study. Whereas a bias correction is needed to account for remaining uncertainties in the annual mean heat flux, this study demonstrates that with proper treatment of mixed layer physics and realistic forcing functions the seasonal variability of SST is capable of being simulated successfully in response to external forcing without relying on a relaxation or damping formulation for the dominant surface heat flux contributions.

Titan's Surface Temperatures Maps from Cassini - CIRS Observations

NASA Astrophysics Data System (ADS)

Cottini, Valeria; Nixon, C. A.; Jennings, D. E.; Anderson, C. M.; Samuelson, R. E.; Irwin, P. G. J.; Flasar, F. M.

2009-09-01

The Cassini Composite Infrared Spectrometer (CIRS) observations of Saturn's largest moon, Titan, are providing us with the ability to detect the surface temperature of the planet by studying its outgoing radiance through a spectral window in the thermal infrared at 19 μm (530 cm-1) characterized by low opacity. Since the first acquisitions of CIRS Titan data the instrument has gathered a large amount of spectra covering a wide range of latitudes, longitudes and local times. We retrieve the surface temperature and the atmospheric temperature profile by modeling proper zonally averaged spectra of nadir observations with radiative transfer computations. Our forward model uses the correlated-k approximation for spectral opacity to calculate the emitted radiance, including contributions from collision induced pairs of CH4, N2 and H2, haze, and gaseous emission lines (Irwin et al. 2008). The retrieval method uses a non-linear least-squares optimal estimation technique to iteratively adjust the model parameters to achieve a spectral fit (Rodgers 2000). We show an accurate selection of the wide amount of data available in terms of footprint diameter on the planet and observational conditions, together with the retrieved results. Our results represent formal retrievals of surface brightness temperatures from the Cassini CIRS dataset using a full radiative transfer treatment, and we compare to the earlier findings of Jennings et al. (2009). In future, application of our methodology over wide areas should greatly increase the planet coverage and accuracy of our knowledge of Titan's surface brightness temperature. References: Irwin, P.G.J., et al.: "The NEMESIS planetary atmosphere radiative transfer and retrieval tool" (2008). JQSRT, Vol. 109, pp. 1136-1150, 2008. Rodgers, C. D.: "Inverse Methods For Atmospheric Sounding: Theory and Practice". World Scientific, Singapore, 2000. Jennings, D.E., et al.: "Titan's Surface Brightness Temperatures." Ap. J. L., Vol. 691, pp. L103-L105, 2009.

TGLF Recalibration for ITER Standard Case Parameters FY2015: Theory and Simulation Performance Target Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candy, J.

2015-12-01

This work was motivated by the observation, as early as 2008, that GYRO simulations of some ITER operating scenarios exhibited nonlinear zonal-flow generation large enough to effectively quench turbulence inside r /a ~ 0.5. This observation of flow-dominated, low-transport states persisted even as more accurate and comprehensive predictions of ITER profiles were made using the state-of-the-art TGLF transport model. This core stabilization is in stark contrast to GYRO-TGLF comparisons for modern-day tokamaks, for which GYRO and TGLF are typically in very close agreement. So, we began to suspect that TGLF needed to be generalized to include the effect of zonal-flowmore » stabilization in order to be more accurate for the conditions of reactor simulations. While the precise cause of the GYRO-TGLF discrepancy for ITER parameters was not known, it was speculated that closeness to threshold in the absence of driven rotation, as well as electromagnetic stabilization, created conditions more sensitive the self-generated zonal-flow stabilization than in modern tokamaks. Need for nonlinear zonal-flow stabilization: To explore the inclusion of a zonal-flow stabilization mechanism in TGLF, we started with a nominal ITER profile predicted by TGLF, and then performed linear and nonlinear GYRO simulations to characterize the behavior at and slightly above the nominal temperature gradients for finite levels of energy transport. Then, we ran TGLF on these cases to see where the discrepancies were largest. The predicted ITER profiles were indeed near to the TGLF threshold over most of the plasma core in the hybrid discharge studied (weak magnetic shear, q > 1). Scanning temperature gradients above the TGLF power balance values also showed that TGLF overpredicted the electron energy transport in the low-collisionality ITER plasma. At first (in Q3), a model of only the zonal-flow stabilization (Dimits shift) was attempted. Although we were able to construct an ad hoc model of the zonal flows that fit the GYRO simulations, the parameters of the model had to be tuned to each case. A physics basis for the zonal flow model was lacking. Electron energy transport at short wavelength: A secondary issue – the high-k electron energy flux – was initially assumed to be independent of the zonal flow effect. However, detailed studies of the fluctuation spectra from recent multiscale (electron and ion scale) GYRO simulations provided a critical new insight into the role of zonal flows. The multiscale simulations suggested that advection by the zonal flows strongly suppressed electron-scale turbulence. Radial shear of the zonal E×B fluctuation could not compete with the large electron-scale linear growth rate, but the k x-mixing rate of the E×B advection could. This insight led to a preliminary new model for the way zonal flows saturate both electron- and ion-scale turbulence. It was also discovered that the strength of the zonal E×B velocity could be computed from the linear growth rate spectrum. The new saturation model (SAT1), which replaces the original model (SAT0), was fit to the multiscale GYRO simulations as well as the ion-scale GYRO simulations used to calibrate the original SAT0 model. Thus, SAT1 captures the physics of both multiscale electron transport and zonal-flow stabilization. In future work, the SAT1 model will require significant further testing and (expensive) calibration with nonlinear multiscale gyrokinetic simulations over a wider variety of plasma conditions – certainly more than the small set of scans about a single C-Mod L-mode discharge. We believe the SAT1 model holds great promise as a physics-based model of the multiscale turbulent transport in fusion devices. Correction to ITER performance predictions: Finally, the impact of the SAT1model on the ITER hybrid case is mixed. Without the electron-scale contribution to the fluxes, the Dimits shift makes a significant improvement in the predicted fusion power as originally posited. Alas, including the high-k electron transport reduces the improvement, yielding a modest net increase in predicted fusion power compared to the TGLF prediction with the original SAT0 model.« less

Intraseasonal oscillation features of the South China Sea summer monsoon and its response to abnormal MJO in the tropical Indian Ocean

NASA Astrophysics Data System (ADS)

Li, Ting

2014-05-01

This paper analyzes Intraseasonal Oscillation (ISO) features and inter-annual differences of the South China Sea (SCS) Summer Monsoon (SCSSM), evolution of its Low Frequency (LF) circulation and convection fields and precipitation anomalies, and path of ISO propagation, as well as impact of MJO in tropical Indian Ocean on SCSSM ISO during 1979-2008. It is found that (1) The SCSSM ISO goes through six phases (exclusive of the weak phase) at every complete fluctuation: developing, strongest, weakening, restraining, weakest and recovering phase. Due to tropical LF convection propagating eastward and northward, the LF convection and circulation in the 1st-3rd and 4th-6th phases present the anti-phase in the Arabian Sea-West Pacific zonal band. Its corresponding rainy bands also present anti-phase roughly. The rainy band moves eastward with LF convection mainly in tropical regions in the south of 20° N, while moves northward in East Asia subtropical regions in the north of 20° N. (2) The SCSSM ISO intensity presents significant inter-annual difference. There are three stronger ISO in the stronger SCSSM ISO years. The first two oscillations propagates from the tropical Indian Ocean to the Bay of Bengal firstly, and then to SCS along the 10° -20° N zonal direction, stimulates the ISO to propagate to South China, forming a relay propagation path in meridional-zonal direction. Moreover, in the weaker SCSSM ISO years, the ISO weakens greatly and irregularly. In averaged conditions, the ISO propagates from tropical Indian Ocean to the SCS by about 20 days (one half ISO periods). (3) MJO1 (the first modal of MJO index provided by the Climate Prediction Center) averaged value in the 1st-2nd pentads of April has the negative correlation with the SCSSM ISO intensity. When MJO in tropical Indian Ocean is more active in the 1st-2nd pentads of April, it is stronger in the subsequent May to August, and the ISO also propagates strongly to the SCS, so that the SCSSM ISO strengthens. Conversely, the SCSSM ISO weakens. The abnormal MJO in the 1st-2nd pentads of April contributes to a certain theory basis to predict the subsequent SCSSM ISO intensity and analyze the abnormal rainfall in related regions.

Long term variabilities and tendencies of mesospheric lunar semidiurnal tide over Tirunelveli (8.7°N, 77.8°E)

NASA Astrophysics Data System (ADS)

Sathishkumar, S.; Sridharan, S.; Muhammed Kutty, P. V.; Gurubaran, S.

2017-10-01

The medium frequency radar deployed at Tirunelveli (8.7°N, 77.8°E), which is located near the southmost tip of peninsular India, have been providing continuous data from the year 1993 to the year 2012 that helped to study the long term tendencies in the lunar tidal variabilities over this geographic location. In the present paper we present the results of seasonal, interannual and long-term variabilities of lunar semi-diurnal tides in the upper mesosphere over Tirunelveli. The present study also includes comparison with model values. The study shows that the tidal amplitudes are larger in the meridional components of the mesospheric winds than the zonal winds. The seasonal variations of the tides are similar in both the components. The tides show maximum amplitudes of about ∼5 m/s in February/March, secondary maximum amplitudes of about ∼3 m/s in September and minimum amplitudes during summer months (May-August). The observed seasonal variation of the lunar tides do not compare well with Vial and Forbes (1994) model values, though it is consistent with earlier observations. The lunar tidal phase in meridional winds leads that in zonal winds from January to June and from September to November, while the latter leads the former during July/August. The lunar tides show large interannual variability. There are unusual amplitude enhancements in the lunar tide in meridional winds during the winters of 2006 and 2009, when major sudden stratospheric warmings (SSW) occurred at high latitude northern hemisphere, whereas zonal lunar tide does not show any clear association with the SSW. Vertical wavelengths of lunar tides in zonal and meridional wind are in the range of 20-90 km. The vertical wavelengths of lunar tides in both zonal and meridional component are smaller in June and larger in November and December. The monthly mean zonal and meridional winds are subjected to regression analysis to study the tidal response to long-period oscillations, namely, quasi-biennial oscillation (QBO), solar cycle variation and El-nino southern oscillation (ENSO). It is found the lunar tide in both zonal and meridional winds show significant QBO response, whereas zonal tide only shows significant negative response to solar cycle and positive response to ENSO. Besides, zonal tide only shows significant long-term increasing trend.

MGS Radio Science Measurements of Atmospheric Dynamics on Mars

NASA Astrophysics Data System (ADS)

Hinson, D. P.

2001-12-01

The Sun-synchronous, polar orbit of Mars Global Surveyor (MGS) provides frequent opportunities for radio occultation sounding of the neutral atmosphere. The basic result of each experiment is a profile of pressure and temperature versus planetocentric radius and geopotential. More than 4000 profiles were obtained during the 687-day mapping phase of the mission, and additional observations are underway. These measurements allow detailed characterization of planetary-scale dynamics, including stationary planetary (or Rossby) waves and transient waves produced by instability. For example, both types of dynamics were observed near 67° S during midwinter of the southern hemisphere (Ls=134° --160° ). Planetary waves are the most prominent dynamical feature in this subset of data. At zonal wave number s=1, both the temperature and geopotential fields tilt westward with increasing height, as expected for vertically-propagating planetary waves forced at the surface. The wave-2 structure is more nearly barotropic. The amplitude in geopotential height at Ls=150° increases from ~200 m near the surface to ~700 m at 10 Pa. The corresponding meridional wind speed increases from ~5 m s-1 near the surface to ~20 m s-1 at 10 Pa. Traveling ``baroclinic'' waves also appear intermittently during this interval. The dominant mode has a period of ~2 sols, s=3, and a peak amplitude of ~7 K at 300 Pa. Stong zonal variations in eddy amplitude signal the presence of a possible ``storm zone'' at 150° --330° E longitude. This talk will include other examples of these phenomena as well as comparisons with computer simulations by a Martian general circulation model (MGCM).

Climatology of the relationship of cusp-related density anomaly with zonal wind and large-scale FAC based on CHAMP observations: IMF By and solar cycle dependence

NASA Astrophysics Data System (ADS)

Kervalishvili, Guram; Lühr, Hermann

2014-05-01

We present climatology of the relationship of cusp-related density enhancement with the neutral zonal wind velocity, large-scale field-aligned current (FAC), small-scale FAC, and electron temperature using the superposed epoch analysis (SEA) method. The dependence of these variables on the interplanetary magnetic field (IMF) By component orientation and solar cycle are of particular interest. In addition, the obtained results of relative density enhancement (ρrel), zonal wind, electron temperature and FAC are subdivided into three local seasons of 130 days each: local winter (1 January ±65 days), combined equinoxes (1 April ±32 days and 1 October ±32 days), and local summer (1 July ±65 days). Our investigation is based on CHAMP satellite observations and NASA/GSFC's OMNI online data set for solar maximum (Mar/2002-2007) and minimum (Mar/2004-2009) conditions in the Northern Hemisphere. The SEA technique uses the time and location of the thermospheric mass density anomaly peaks as reference parameters. The relative amplitude of cusp-related density enhancement does on average not depend on the IMF By orientation, solar cycle phase, and local season. Also, it is apparent that the IMF By amplitude does not have a big influence on the relative amplitude of the density anomaly. Conversely, there exists a good correlation between ρrel and the negative amplitude of IMF Bz prevailing about half an hour earlier. In the cusp region, both large-scale FAC distribution and thermospheric zonal wind velocity exhibit a clear dependence on the IMF By orientation. In the case of positive (negative) IMF By there is a systematic imbalance between downward (upward) and upward (downward) FACs peaks equatorward and poleward of the reference point, respectively. The zonal wind velocity is directed towards west i.e. towards dawn in a geomagnetic latitude-magnetic local time (MLat-MLT) frame. This is true for all local seasons and solar conditions. The thermospheric density enhancements appear half way between Region 1 (R1) and Region 0 (R0) field-aligned currents, in closer proximity to the upward FAC region. In our case R0 currents are systematically weaker than R1 ones. Also, around the cusp region we find no sign of Region 2 field-aligned currents. We can conclude that there is a close spatial relationship between FACs and cusp-related density enhancements, but we cannot offer any simple functional relation between field-aligned current strength and density anomaly amplitude. There seem to be other quantities (e.g. precipitating electrons) controlling this relation. All the conclusions drawn above are true for the Northern Hemisphere. There may be differences in the Southern Hemisphere.

Three-dimensional assembly of tissue-engineered cartilage constructs results in cartilaginous tissue formation without retainment of zonal characteristics.

PubMed

Schuurman, W; Harimulyo, E B; Gawlitta, D; Woodfield, T B F; Dhert, W J A; van Weeren, P R; Malda, J

2016-04-01

Articular cartilage has limited regenerative capabilities. Chondrocytes from different layers of cartilage have specific properties, and regenerative approaches using zonal chondrocytes may yield better replication of the architecture of native cartilage than when using a single cell population. To obtain high seeding efficiency while still mimicking zonal architecture, cell pellets of expanded deep zone and superficial zone equine chondrocytes were seeded and cultured in two layers on poly(ethylene glycol)-terephthalate-poly(butylene terephthalate) (PEGT-PBT) scaffolds. Scaffolds seeded with cell pellets consisting of a 1:1 mixture of both cell sources served as controls. Parallel to this, pellets of superficial or deep zone chondrocytes, and combinations of the two cell populations, were cultured without the scaffold. Pellet cultures of zonal chondrocytes in scaffolds resulted in a high seeding efficiency and abundant cartilaginous tissue formation, containing collagen type II and glycosaminoglycans (GAGs) in all groups, irrespective of the donor (n = 3), zonal population or stratified scaffold-seeding approach used. However, whereas total GAG production was similar, the constructs retained significantly more GAG compared to pellet cultures, in which a high percentage of the produced GAGs were secreted into the culture medium. Immunohistochemistry for zonal markers did not show any differences between the conditions. We conclude that spatially defined pellet culture in 3D scaffolds is associated with high seeding efficiency and supports cartilaginous tissue formation, but did not result in the maintenance or restoration of the original zonal phenotype. The use of pellet-assembled constructs leads to a better retainment of newly produced GAGs than the use of pellet cultures alone. Copyright © 2013 John Wiley & Sons, Ltd.

Impact of aerosol microphysics on cloud optical properties and implications to atmospheric oxidation capacity

NASA Astrophysics Data System (ADS)

Luo, G.; Yu, F.

2016-12-01

GEOS-Chem, presently used by many research groups, is a state-of-the-art global 3-D model of atmospheric composition driven by assimilated meteorology from the Goddard Earth Observing System. Our comparisons of GEOS-5 cloud properties, used in photolysis rate calculation, with MODIS retrievals show that GEOS-5 underestimates cloud optical depth (COD) by a factor of more than 2 over most regions. Our further analysis indicates that the COD underestimation in the released GEOS-5 meteorology products is likely to be associated with the fact that the GEOS-5 doesn't take into account the impact of aerosol on cloud microphysics and optical properties. A new COD parameterization (called NewC thereafter), which re-calculates COD from GEOS-5 water content and GEOS-Chem simulated size-resolved particle properties, cloud condensation nuclei abundance, and cloud droplet number concentration, has been developed and incorporated into GEOS-Chem. The NewC increases the GEOS-5 derived annual mean CODs averaged between 60ºS and 60ºN from 2.0 to 4.3, in much better agreement with corresponding MODIS value of 4.3. The enhanced COD based on NewC scheme reduces global average boundary layer OH concentration by 9.8%. Zonal averaged OH is increased 3-7% above clouds due to backscattering and decreased 10-15% below clouds due to the attenuation of solar radiation. The global mean OH concentration simulated by GEOS-Chem driven by GEOS-5 COD and NewC COD are respectively12.9 × 105molec cm-3 and 12.2 × 105molec cm-3, with the latter closer to the ACCMIP multi-model estimation (11.7±1 105molec cm-3). Surface OH concentrations over major anthropogenic regions such as Eastern US, Europe, and East Asia decrease by up to -18.6%, -14.4%, and -19.9%, respectively. The relative change of surface OH concentration appears to be the largest over the Amazon rainforest, reaching up to -30%. After switching from old COD to NewC COD, GEOS-Chem simulated column HCHO and surface isoprene over Amazon region are enhanced 12% and 20%, respectively. At the Eastern United States, column HCHO and surface isoprene are enhanced 5% and 15%, respectively. Seasonal variation and regional characteristics of the impact of aerosol microphysics on cloud properties and implications to atmospheric oxidation capacity and tropospheric compositions will be discussed.

SAGE aerosol measurements. Volume 1: February 21, 1979 to December 31, 1979

NASA Technical Reports Server (NTRS)

Mccormick, M. P.

1985-01-01

The Stratospheric Aerosol and Gas Experiment (SAGE) satellite system, launched on February 18, 1979, provides profiles of aerosol extinction, ozone concentration, and nitrogen dioxide concentration between about 80 N and 80 S. Zonal averages, separated into sunrise and sunset events, and seasonal averages of the aerosol extinction at 1.00 microns and 0.45 microns ratios of the aerosol extinction to the molecular extinction at 1.00 microns, and ratios of the aerosol extinction at 0.45 microns to the aerosol extinction at 1.00 microns are given. The averages for 1979 are shown in tables and in profile and contour plots (as a function of altitude and latitude). In addition, temperature data provided by the National Oceanic and Atmospheric Administration (NOAA) for the time and location of each SAGE measurement are averaged and shown in a similar format. Typical values of the peak aerosol extinction were 0.0001 to 0.0002 km at 1.00 microns depth values for the 1.00 microns channel varied between 0.001 and 0.002 over all latitudes.

Causal impact of magnetic fluctuations in slow and fast L–H transitions at TJ-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milligen, B. Ph. van; Estrada, T.; Ascasíbar, E.

2016-07-15

This work focuses on the relationship between L–H (or L–I) transitions and MHD activity in the low magnetic shear TJ-II stellarator. It is shown that the presence of a low order rational surface in the plasma edge (gradient) region lowers the threshold density for H-mode access. MHD activity is systematically suppressed near the confinement transition. We apply a causality detection technique (based on the Transfer Entropy) to study the relation between magnetic oscillations and locally measured plasma rotation velocity (related to Zonal Flows). For this purpose, we study a large number of discharges in two magnetic configurations, corresponding to “fast”more » and “slow” transitions. With the “slow” transitions, the developing Zonal Flow prior to the transition is associated with the gradual reduction of magnetic oscillations. The transition itself is marked by a strong spike of “information transfer” from magnetic to velocity oscillations, suggesting that the magnetic drive may play a role in setting up the final sheared flow responsible for the H-mode transport barrier. Similar observations were made for the “fast” transitions. Thus, it is shown that magnetic oscillations associated with rational surfaces play an important and active role in confinement transitions, so that electromagnetic effects should be included in any complete transition model.« less

A ‘self-adjustment’ mechanism for mixed-layer heat budget in the equatorial Atlantic cold tongue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Yanyan; Wang, Bin; Huang, Wenyu

Wind forcing is one of the most important sources for the oceanic energy cycle and is especially critical to the heat budget of surface mixed layer. The sensitivity of heat budget in the equatorial Atlantic cold tongue (EACT) region (5°S–5°N, 25°W–5°E) to wind forcing and the related mechanism are explored in this study. Based on the experiments forced by different wind forcing from both reanalysis and idealized datasets, it is revealed that the contribution ratio for each of the dominant physical processes in the heat budget is insensitive (the variations within 1% of the mean) to the variations in themore » local winds (the largest variation is about 20% of the mean) over the EACT region. Therefore, a ‘self-adjustment’ mechanism exists in the mixed-layer heat budget: as local zonal winds over the EACT region strengthen (weaken), both the cooling effects of turbulent mixing and the combined warming effects of surface net heat flux and zonal advection simultaneously increase (decrease) by nearly the same percentage and thus their contribution ratios are kept constant. Finally, owing to the impact of meridional winds on each term of heat budget can be neglected, the above mechanism is also tenable under the situation when the local meridional winds change.« less

Global energetics and local physics as drivers of past, present and future monsoons

NASA Astrophysics Data System (ADS)

Biasutti, Michela; Voigt, Aiko; Boos, William R.; Braconnot, Pascale; Hargreaves, Julia C.; Harrison, Sandy P.; Kang, Sarah M.; Mapes, Brian E.; Scheff, Jacob; Schumacher, Courtney; Sobel, Adam H.; Xie, Shang-Ping

2018-06-01

Global constraints on momentum and energy govern the variability of the rainfall belt in the intertropical convergence zone and the structure of the zonal mean tropical circulation. The continental-scale monsoon systems are also facets of a momentum- and energy-constrained global circulation, but their modern and palaeo variability deviates substantially from that of the intertropical convergence zone. The mechanisms underlying deviations from expectations based on the longitudinal mean budgets are neither fully understood nor simulated accurately. We argue that a framework grounded in global constraints on energy and momentum yet encompassing the complexities of monsoon dynamics is needed to identify the causes of the mismatch between theory, models and observations, and ultimately to improve regional climate projections. In a first step towards this goal, disparate regional processes must be distilled into gross measures of energy flow in and out of continents and between the surface and the tropopause, so that monsoon dynamics may be coherently diagnosed across modern and palaeo observations and across idealized and comprehensive simulations. Accounting for zonal asymmetries in the circulation, land/ocean differences in surface fluxes, and the character of convective systems, such a monsoon framework would integrate our understanding at all relevant scales: from the fine details of how moisture and energy are lifted in the updrafts of thunderclouds, up to the global circulations.

A ‘self-adjustment’ mechanism for mixed-layer heat budget in the equatorial Atlantic cold tongue

DOE PAGES

Shi, Yanyan; Wang, Bin; Huang, Wenyu

2017-01-20

Wind forcing is one of the most important sources for the oceanic energy cycle and is especially critical to the heat budget of surface mixed layer. The sensitivity of heat budget in the equatorial Atlantic cold tongue (EACT) region (5°S–5°N, 25°W–5°E) to wind forcing and the related mechanism are explored in this study. Based on the experiments forced by different wind forcing from both reanalysis and idealized datasets, it is revealed that the contribution ratio for each of the dominant physical processes in the heat budget is insensitive (the variations within 1% of the mean) to the variations in themore » local winds (the largest variation is about 20% of the mean) over the EACT region. Therefore, a ‘self-adjustment’ mechanism exists in the mixed-layer heat budget: as local zonal winds over the EACT region strengthen (weaken), both the cooling effects of turbulent mixing and the combined warming effects of surface net heat flux and zonal advection simultaneously increase (decrease) by nearly the same percentage and thus their contribution ratios are kept constant. Finally, owing to the impact of meridional winds on each term of heat budget can be neglected, the above mechanism is also tenable under the situation when the local meridional winds change.« less

On the role of the transient eddies in maintaining the seasonal mean circulation

NASA Technical Reports Server (NTRS)

White, G. H.; Hoskins, B. J.

1984-01-01

The role of transient eddies in maintaining the observed local seasonal mean atmospheric circulation was investigated by examining the time-averaged momentum balances and omega equation, using seasonal statistics calculated from daily operational analyses by the European Centre for Medium Range Weather Forecasts. While both the Northern and Southern Hemispheres and several seasons were studied, emphasis was placed upon the Northern Hemisphere during December 1981-February 1982. The results showed that transient eddies played a secondary role in the seasonal mean zonal momentum budget and in the forcing of seasonal mean vertical and a geostrophic motion.

The dynamics of the HSCT environment. [air pollution from High Speed Civil Transport Aircraft

NASA Technical Reports Server (NTRS)

Douglass, Anne R.; Rood, Richard B.

1991-01-01

Assessments of the impact of aircraft engine exhausts on stratospheric ozone levels are currently limited to 2D zonally-averaged models which, while completely representing chemistry, involve high parameterization of transport processes. Prospective 3D models under development by NASA-Goddard will use winds from a data-assimilation procedure; the upper troposphere/lower stratosphere behavior of one such model has been verified by direct comparison of model simulations with satellite, balloon, and sonde measurements. Attention is presently given to the stratosphere/troposphere exchange and nonzonal distribution of aircraft engine exhaust.

A Numerical Study of Nonlinear Nonhydrostatic Conditional Symmetric Instability in a Convectively Unstable Atmosphere.

NASA Astrophysics Data System (ADS)

Seman, Charles J.

1994-06-01

Nonlinear nonhydrostatic conditional symmetric instability (CSI) is studied as an initial value problem using a two-dimensional (y, z)nonlinear, nonhydrostatic numerical mesoscale/cloud model. The initial atmosphere for the rotating, baroclinic (BCF) simulation contains large convective available potential energy (CAPE). Analytical theory, various model output diagnostics, and a companion nonrotating barotropic (BTNF) simulation are used to interpret the results from the BCF simulation. A single warm moist thermal initiates convection for the two 8-h simulations.The BCF simulation exhibited a very intricate life cycle. Following the initial convection, a series of discrete convective cells developed within a growing mesoscale circulation. Between hours 4 and 8, the circulation grew upscale into a structure resembling that of a squall-line mesoscale convective system (MCS). The mesoscale updrafts were nearly vertical and the circulation was strongest on the baroclinically cool side of the initial convection, as predicted by a two-dimensional Lagrangian parcel model of CSI with CAPE. The cool-side mesoscale circulation grew nearly exponentially over the last 5 h as it slowly propagated toward the warm air. Significant vertical transport of zonal momentum occurred in the (multicellular) convection that developed, resulting in local subgeostrophic zonal wind anomalies aloft. Over time, geostrophic adjustment acted to balance these anomalies. The system became warm core, with mesohigh pressure aloft and mesolow pressure at the surface. A positive zonal wind anomaly also formed downstream from the mesohigh.Analysis of the BCF simulation showed that convective momentum transport played a key role in the evolution of the simulated MCS, in that it fostered the development of the nonlinear CSI on mesoscale time scales. The vertical momentum transport in the initial deep convection generated a subgeostrophic zonal momentum anomaly aloft; the resulting imbalance in pressure gradient and Coriolis forces accelerated the meridional outflow toward the baroclinically cool side, transporting zonal momentum horizontally. The vertical (horizontal) momentum transport occurred on a convective (inertial) time scale. Taken together, the sloping convective updraft/cool side outflow represents the release of the CSI in the convectively unstable atmosphere. Further diagnostics showed that mass transports in the horizontal outflow branch ventilated the upper levels of the system, with enhanced mesoscale lifting in the core and on the leading edge of the MCS, which assisted in convective redevelopments on mesoscale time scales. Geostrophic adjustment acted to balance the convectively generated zonal momentum anomalies, thereby limiting the strength of the meridional outflow predicted by CSI theory. Circulation tendency diagnostics showed that the mesoscale circulation developed in response to thermal wind imbalances generated by the deep convection.Comparison of the BCF and BTNF simulations showed that baroclinicity enhanced mesoscale circulation growth. The BTNF circulation was more transient on mesoscale time and space scales. Overall, the BCF system produced more rainfall than the BTNF.Based on the present and past work in CSI theory, a new definition for the term `slantwise convection' is proposed.

Eastern Tropical Pacific Precipitation Response to Zonal SPCZ events

NASA Astrophysics Data System (ADS)

Durán-Quesada, A. M.; Lintner, B. R.

2014-12-01

Extreme El Niño events and warming conditions in the eastern tropical Pacific have been linked to pronounced spatial displacements of the South Pacific Convergence Zone known as "zonal SPCZ" events.. Using a global dataset of Lagrangian back trajectories computed with the FLEXPART model for the period 1980-2013, comprehensive analysis of the 3D circulation characteristics associated with the SPCZ is undertaken. Ten days history of along-trajectory specific humidity, potential vorticity and temperature are reconstructed for zonal SPCZ events as well as other states,, with differences related to El Niño intensity and development stage as well as the state of the Western Hemisphere Warm Pool. How zonal events influence precipitation over the Eastern Tropical Pacific is examined using back trajectories, reanalysis, TRMM precipitation, and additional satellite derived cloud information. It is found that SPCZ displacements are associated with enhanced convection over the Eastern Tropical Pacific in good agreement with prior work. The connection between intensification of precipitation over the eastern Tropical Pacific during zonal events and suppression of rainfall over the Maritime continent is also described.

A model of the saturation of coupled electron and ion scale gyrokinetic turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Staebler, Gary M.; Howard, Nathan T.; Candy, Jeffrey M.

A new paradigm of zonal flow mixing as the mechanism by which zonal E × B fluctuations impact the saturation of gyrokinetic turbulence has recently been deduced from the nonlinear 2D spectrum of electric potential fluctuations in gyrokinetic simulations. These state of the art simulations span the physical scales of both ion and electron turbulence. It was found that the zonal flow mixing rate, rather than zonal flow shearing rate, competes with linear growth at both electron and ion scales. A model for saturation of the turbulence by the zonal flow mixing was developed and applied to the quasilinear trappedmore » gyro-Landau fluid transport model (TGLF). The first validation tests of the new saturation model are reported in this paper with data from L-mode and high-β p regime discharges from the DIII-D tokamak. Lastly, the shortfall in the predicted L-mode edge electron energy transport is improved with the new saturation model for these discharges but additional multiscale simulations are required in order to verify the safety factor and collisionality dependencies found in the modeling.« less

A model of the saturation of coupled electron and ion scale gyrokinetic turbulence

DOE PAGES

Staebler, Gary M.; Howard, Nathan T.; Candy, Jeffrey M.; ...

2017-05-09

A new paradigm of zonal flow mixing as the mechanism by which zonal E × B fluctuations impact the saturation of gyrokinetic turbulence has recently been deduced from the nonlinear 2D spectrum of electric potential fluctuations in gyrokinetic simulations. These state of the art simulations span the physical scales of both ion and electron turbulence. It was found that the zonal flow mixing rate, rather than zonal flow shearing rate, competes with linear growth at both electron and ion scales. A model for saturation of the turbulence by the zonal flow mixing was developed and applied to the quasilinear trappedmore » gyro-Landau fluid transport model (TGLF). The first validation tests of the new saturation model are reported in this paper with data from L-mode and high-β p regime discharges from the DIII-D tokamak. Lastly, the shortfall in the predicted L-mode edge electron energy transport is improved with the new saturation model for these discharges but additional multiscale simulations are required in order to verify the safety factor and collisionality dependencies found in the modeling.« less

Seasonally-Active Water on Mars: Vapour, Ice, Adsorbate, and the Possibility of Liquid

NASA Astrophysics Data System (ADS)

Richardson, M. I.

2002-12-01

Seasonally-active water can be defined to include any water reservoir that communicates with other reservoirs on time scales of a year or shorter. It is the interaction of these water reservoirs, under the influence of varying solar radiation and in conjunction with surface and atmospheric temperatures, that determines the phase-stability field for water at the surface, and the distribution of water in various forms below, on, and above the surface. The atmosphere is the critical, dynamical link in this cycling system, and also (fortunately) one of the easiest to observe. Viking and Mars Global Surveyor observations paint a strongly asymmetric picture of the global seasonal water cycle, tied proximately to planetary eccentricity, and the existence of residual ice caps of different composition at the two poles. The northern summer experiences the largest water vapour columns, and is associated with sublimation from the northern residual water ice cap. The southern summer residual carbon dioxide ice cap is cold trap for water. Asymmetry in the water cycle is an unsolved problem. Possible solutions may involve the current timing of perihelion (the water cap resides at the pole experiencing the longer but cooler summer), the trapping of water ice in the northern hemisphere by tropical water ice clouds, and the bias in the annual-average, zonal-mean atmospheric circulation resulting from the zonal-mean difference in the elevation of the northern and southern hemispheres. Adsorbed and frozen water have proven harder to constrain. Recent Odyssey Gamma Ray Spectrometer results suggest substantial ground ice in the mid- and high-latitudes, but this water is likely below the seasonal skin depth for two reasons: the GRS results are best fit with such a model, and GCM models of the water cycle produce dramatically unrealistic atmospheric vapour distributions when such a very near surface, GRS-like distribution is initialized - ultimately removing the water to the northern and southern caps. Similar climate-models of the water cycle also do not need much exchangeable adsorbed water in order to explain the observed vapour distributions. The possibility of liquid water is tantalizing, but difficult to definitively judge. On scales greater than a meter or so, Mars is most definitely well away from the water triple point--although the surface pressure can exceed 6.1 mbars, the partial pressure of water vapor (to which the triple point refers) is at best orders of magnitude lower. Several careful studies have shown, however, that locally transient (meta-stable) liquid is possible, if the net heating of ice deposits is high enough. This process is aided if the total surface pressure exceeds 6.1mbar (this prevents boiling, or the explosive loss of vapour into the atmosphere) or if the liquid is covered by a thin ice shell, and is only possible if surface temperatures exceed 273K (for pure water, or the appropriate eutectic for brines) and if ice is present. The former challenge is much easier to meet than the latter. The melt scenario requires that ice deposited in winter must be protected from sublimation as surface temperatures increase in spring, but then exposed to the peak of solar heating in summer. Available spacecraft observations of seasonal water will be discussed with the aid of GCM model simulations, and examined in the context of water distributions and phases.

A Possible Strategy for the Use of Solar Climate Engineering

NASA Astrophysics Data System (ADS)

Ackerman, T. P.; Russotto, R. D.; Kravitz, B.

2016-12-01

The Paris accord signals an international effort to hold global temperature change below 2°C above pre-industrial levels, raising the question of what role solar climate engineering (SCE) might play in meeting this objective. However, avoiding continuing, long-term application of SCE with an ever increasing magnitude requires an "exit strategy", i. e., a plan to phase out SCE by removing stabilizing and removing CO2. Here we present results from a series of climate model runs that combine both CO2 and SCE transient forcings over a 200-year period (2000 to 2200). Our results confirm past results that maintaining both global surface air temperature (TA) and precipitation (P) at baseline levels is not feasible. They also demonstrate a quasi-linear relationship between changes in SCE and changes in P. Zonally-averaged changes in TA show, as expected, polar amplification of warming, but that enhancement scales uniformly with the change in global TA. We draw several conclusions from our results: (1) There are plausible scenarios in which SCE can be part of an integrated strategy to meet the temperature goals of the Paris accord. (2) Applying transient forcings can be used to maintain some, but not all, globally-averaged climate system variables (such as TA or P) at a prescribed baseline level. That globally-averaged stability, however, is achieved by averaging over changes in spatial distributions. These spatial changes create difficult issues regarding prediction of regional climate changes due to SCE and potential impacts on regional societies. (3) Our inability to predict interannual climate variability on the annual-to-decadal time scale suggests that it may take a decade or more to provide reliable detection and attribution of the global climate impacts of SCE following its inception (the so-called time of emergence). Furthermore, it will take much longer to determine regional impacts.

Conservative zonal schemes for patched grids in 2 and 3 dimensions

NASA Technical Reports Server (NTRS)

Hessenius, Kristin A.

1987-01-01

The computation of flow over complex geometries, such as realistic aircraft configurations, poses difficult grid generation problems for computational aerodynamicists. The creation of a traditional, single-module grid of acceptable quality about an entire configuration may be impossible even with the most sophisticated of grid generation techniques. A zonal approach, wherein the flow field is partitioned into several regions within which grids are independently generated, is a practical alternative for treating complicated geometries. This technique not only alleviates the problems of discretizing a complex region, but also facilitates a block processing approach to computation thereby circumventing computer memory limitations. The use of such a zonal scheme, however, requires the development of an interfacing procedure that ensures a stable, accurate, and conservative calculation for the transfer of information across the zonal borders.

Jovian vortices by simulated annealing

NASA Astrophysics Data System (ADS)

Morrison, P. J.; Flierl, G. R.; Swaminathan, R. V.

2017-11-01

We explore the conditions required for isolated vortices to exist in sheared zonal flows and the stability of the underlying zonal winds. This is done using the standard 2-layer quasigeostrophic model with the lower layer depth becoming infinite; however, this model differs from the usual layer model because the lower layer is not assumed to be motionless but has a steady configuration of alternating zonal flows. Steady state vortices are obtained by a simulated annealing computational method introduced in, generalized and applied in in fluid flow, and used in the context of magnetohydrodynamics in. Various cases of vortices with a constant potential vorticity anomaly atop zonal winds and the stability of the underlying winds are considered using a mix of computational and analytical techniques. U.S. Department of Energy Contract DE-FG05-80ET-53088.

Unbiased mean direction of paleomagnetic data and better estimate of paleolatitude

NASA Astrophysics Data System (ADS)

Hatakeyama, T.; Shibuya, H.

2010-12-01

In paleomagnetism, when we obtain only paleodirection data without paleointensities we calculate Fisher-mean directions (I, D) and Fisher-mean VGP positions as the description of the mean field. However, Kono (1997) and Hatakeyama and Kono (2001) indicated that these averaged directions does not show the unbiased estimated mean directions derived from the time-averaged field (TAF). Hatakeyama and Kono (2002) calculated the TAF and paleosecular variation (PSV) models for the past 5My with considering the biases due to the averaging of the nonlinear functions such as the summation of the unit vectors in the Fisher statistics process. Here we will show a zonal TAF model based on the Hatakeyama and Kono TAF model. Moreover, we will introduce the biased angles due to the PSV in the mean direction and a method for determining true paleolatitudes, which represents the TAF, from paleodirections. This method will helps tectonics studies, especially in the estimation of the accurate paleolatitude in the middle latitude regions.

User's guide for SBUV/TOMS ozone derivative products

NASA Technical Reports Server (NTRS)

Fleig, A. J.; Wellemeyer, C.; Oslik, N.; Lee, D.; Miller, J.; Magatani, R.

1984-01-01

A series of products are available derived from the total-ozone and ozone vertical profile results for the Solar Backscattered Ultraviolet/Total-Ozone Mapping Spectrometer (SBUV/TOMS) Nimbus-7 operation. Products available are (1) orbital height-latitude cross sections of the SBUV profile data, (2) daily global total ozone contours in polar coordinates, (3) daily averages of total ozone in global 5x5 degree latitude-longitude grid, (4) daily, monthly and quarterly averages of total ozone and profile data in 10 degree latitude zones, (5) tabular presentation of zonal means, (6) daily global total ozone and profile contours in polar coordinates. The ""Derivative Products User's Guide'' describes each of these products in detail, including their derivation and presentation format. Information is provided on how to order the tapes and microfilm from the National Space Science Data Center.

Trends in winter circulation over the British Isles and central Europe in twenty-first century projections by 25 CMIP5 GCMs

NASA Astrophysics Data System (ADS)

Stryhal, Jan; Huth, Radan

2018-03-01

Winter midlatitude atmospheric circulation has been extensively studied for its tight link to surface weather, and automated circulation classifications have often been used to this end. Here, eight such classifications are applied to daily sea level pressure patterns simulated by an ensemble of CMIP5 GCMs twenty-first century projections for the British Isles and central Europe in order to robustly estimate future changes in frequency, persistence, and strength of synoptic-scale circulation there. All methods are able to identify present-day biases of models reported before, such as an overestimated occurrence of zonal flow and underestimation of anticyclonic conditions and easterly advection, although the strength of these biases varies among the methods. In future, models show that the zonal flow will become more frequent while the strength of the mean flow is not projected to change. Over the British Isles, the models that better simulate the latitude of zonal flow over the historical period indicate a slight equatorward shift of westerlies in their projections, while the poleward expansion of circulation—expected in future at global scale—is apparent in those models that have large errors. Over central Europe, some classifications indicate an increase in persistence and especially in frequency of anticyclonic types, which is, however, shown to be rather an artifact of some methods than a real feature. On the other hand, the easterly flow is robustly projected to become markedly weaker in central Europe, which we hypothesize might be an important factor contributing to the projected decrease of cold extremes there.

Autumn Cooling of Western East Antarctica Linked to the Tropical Pacific

NASA Astrophysics Data System (ADS)

Clem, Kyle R.; Renwick, James A.; McGregor, James

2018-01-01

Over the past 60 years, the climate of East Antarctica cooled while portions of West Antarctica were among the most rapidly warming regions on the planet. The East Antarctic cooling is attributed to a positive trend in the Southern Annular Mode (SAM) and a strengthening of the westerlies, while West Antarctic warming is tied to zonally asymmetric circulation changes forced by the tropics. This study finds recent (post-1979) surface cooling of East Antarctica during austral autumn to also be tied to tropical forcing, namely, an increase in La Niña events. The recent increase in La Niña conditions forces a Rossby wave into the Southern Hemisphere that increases anticyclonic circulation over the South Atlantic. The South Atlantic anticyclone is associated with cold air advection, weakened northerlies, and increased sea ice concentrations across the western East Antarctic coast, which has increased the rate of cooling at Novolazarevskaya and Syowa stations after 1979. This enhanced cooling over western East Antarctica is tied more broadly to a zonally asymmetric temperature trend pattern across East Antarctica during autumn that is consistent with a tropically forced Rossby wave rather than a SAM pattern; the positive SAM pattern is associated with ubiquitous cooling across East Antarctica, which is not seen in temperature observations after 1979. We conclude that El Niño-Southern Oscillation-related circulation anomalies, particularly zonal asymmetries that locally enhance meridional wind, are an important component of East Antarctic climate variability during autumn, and future changes in tropical Pacific climate will likely have implications for East Antarctica.

Demarcating Circulation Regimes of Synchronously Rotating Terrestrial Planets within the Habitable Zone

NASA Astrophysics Data System (ADS)

Haqq-Misra, Jacob; Wolf, Eric. T.; Joshi, Manoj; Zhang, Xi; Kopparapu, Ravi Kumar

2018-01-01

We investigate the atmospheric dynamics of terrestrial planets in synchronous rotation within the habitable zone of low-mass stars using the Community Atmosphere Model. The surface temperature contrast between the day and night hemispheres decreases with an increase in incident stellar flux, which is opposite the trend seen in gas giants. We define three dynamical regimes in terms of the equatorial Rossby deformation radius and the Rhines length. The slow rotation regime has a mean zonal circulation that spans from the day to the night sides, which occurs for planets around stars with effective temperatures of 3300–4500 K (rotation period > 20 days), with both the Rossby deformation radius and the Rhines length exceeding the planetary radius. Rapid rotators have a mean zonal circulation that partially spans a hemisphere and with banded cloud formation beneath the substellar point, which occurs for planets orbiting stars with effective temperatures of less than 3000 K (rotation period < 5 days), with the Rossby deformation radius less than the planetary radius. In between is the Rhines rotation regime, which retains a thermally direct circulation from the day side to the night side but also features midlatitude turbulence-driven zonal jets. Rhines rotators occur for planets around stars in the range of 3000–3300 K (rotation period ∼5–20 days), where the Rhines length is greater than the planetary radius but the Rossby deformation radius is less than the planetary radius. The dynamical state can be observationally inferred from a comparison of the morphologies of the thermal emission phase curves of synchronously rotating planets.

Examining cross-equatorial precipitation variability in the western Indian Ocean using stalagmites from Madagascar

NASA Astrophysics Data System (ADS)

Scroxton, N.; Burns, S. J.; McGee, D.; Hardt, B. F.; Godfrey, L.; Ranivoharimanana, L.; Faina, P.

2017-12-01

The behavior of the world's monsoon systems and the position of the Inter Tropical Convergence Zone (ITCZ) resulting from large global climatic changes is reasonably well understood at orbital and millennial timescales. However, under the boundary conditions and relatively modest forcing of the last 2000 years it is not yet clear how tropical monsoon systems changed and why. The traditional schema of north-south translation of the ITCZ is being challenged by new theories relating to meridional expansion and contraction of the tropical rain belt, and/or to changes in zonal circulation patterns resembling modern El-Niño Southern Oscillation end members. Located at a hotspot of zonal and meridional climate forcing, stalagmites from the western Indian Ocean can provide new insights into past rainfall variability and uncover the driving mechanisms. Here, we present results from a new southern hemisphere speleothem record from Anjohibe cave, northwestern Madagascar, covering the last 1,700 years. We demonstrate that our quasi-annual, precisely dated, stable oxygen isotope record serves as a proxy for the strength of the northwestern Madagascan monsoon. The record shows a multi-decadal, in-phase relationship with its northern hemisphere monsoon counterpart from Oman - contrary to the expected antiphase relationship that would result from north-south ITCZ translation. At the centennial scale, the Madagascan record correlates well with precipitation records from Eastern Africa. We discuss the potential causes of western Indian Ocean precipitation coherency, and how it relates to either symmetrical changes in continental sensible heating, or to a low frequency zonal sea-surface temperature mode.

Ion Layer Separation and Equilibrium Zonal Winds in Midlatitude Sporadic E

NASA Technical Reports Server (NTRS)

Earle, G. D.; Kane, T. J.; Pfaff, R. F.; Bounds, S. R.

2000-01-01

In-situ observations of a moderately strong mid-latitude sporadic-E layer show a separation in altitude between distinct sublayers composed of Fe(+), Mg(+), and NO(+). From these observations it is possible to estimate the zonal wind field consistent with diffusive equilibrium near the altitude of the layer. The amplitude of the zonal wind necessary to sustain the layer against diffusive effects is less than 10 meters per second, and the vertical wavelength is less than 10 km.

On the Longitudinal Morphology of Zonal Irregularity Drift Measured using Networks of GPS Scintillation Monitors

NASA Astrophysics Data System (ADS)

Carrano, C. S.; Groves, K. M.; Valladares, C. E.; Delay, S. H.

2014-12-01

A complete characterization of field-aligned ionospheric irregularities responsible for the scintillation of satellite signals includes not only their spectral properties (power spectral strength, spectral index, anisotropy ratio, and outer-scale) but also their horizontal drift velocity. From a system impacts perspective, the horizontal drift velocity is important in that it dictates the rate of signal fading and also, to an extent, the level of phase fluctuations encountered by the receiver. From a physics perspective, studying the longitudinal morphology of zonal irregularity may lead to an improved understanding of the F region dynamo and regional electrodynamics at low latitudes. The irregularity drift at low latitudes is predominantly zonal and is most commonly measured by cross-correlating observations of satellite signals made by a pair of closely-spaced antennas. The AFRL-SCINDA network operates a small number of VHF spaced-antenna systems at low latitude stations for this purpose. A far greater number of GPS scintillation monitors are operated by AFRL-SCINDA (25-30) and the Low Latitude Ionospheric Sensor Network (35-50), but the receivers are situated too far apart to monitor the drift using cross-correlation techniques. In this paper, we present an alternative approach that leverages the weak scatter scintillation theory (Rino, Radio Sci., 1979) to infer the zonal irregularity drift from single-station GPS measurements of S4, sigma-phi, and the propagation geometry alone. Unlike the spaced-receiver technique, this technique requires assumptions for the height of the scattering layer (which introduces a bias in the drift estimates) and the spectral index of the irregularities (which affects the spread of the drift estimates about the mean). Nevertheless, theory and experiment show that the ratio of sigma-phi to S4 is less sensitive to these parameters than it is to the zonal drift, and hence the zonal drift can be estimated with reasonable accuracy. In this talk, we first validate the technique using spaced VHF-antenna measurements of zonal irregularity drift from the AFRL-SCINDA network. Next, we discuss preliminary results from our investigation into the longitudinal morphology of zonal irregularity drift using the AFRL-SCINDA and LISN networks of GPS scintillation monitors.

Zonal structure and variability of the Western Pacific dynamic warm pool edge in CMIP5

NASA Astrophysics Data System (ADS)

Brown, Jaclyn N.; Langlais, Clothilde; Maes, Christophe

2014-06-01

The equatorial edge of the Western Pacific Warm Pool is operationally identified by one isotherm ranging between 28° and 29 °C, chosen to align with the interannual variability of strong zonal salinity gradients and the convergence of zonal ocean currents. The simulation of this edge is examined in 19 models from the World Climate Research Program Coupled Model Intercomparison Project Phase 5 (CMIP5), over the historical period from 1950 to 2000. The dynamic warm pool edge (DWPE), where the zonal currents converge, is difficult to determine from limited observations and biased models. A new analysis technique is introduced where a proxy for DWPE is determined by the isotherm that most closely correlates with the movements of the strong salinity gradient. It can therefore be a different isotherm in each model. The DWPE is simulated much closer to observations than if a direct temperature-only comparison is made. Aspects of the DWPE remain difficult for coupled models to simulate including the mean longitude, the interannual excursions, and the zonal convergence of ocean currents. Some models have only very weak salinity gradients trapped to the western side of the basin making it difficult to even identify a DWPE. The model's DWPE are generally 1-2 °C cooler than observed. In line with theory, the magnitude of the zonal migrations of the DWPE are strongly related to the amplitudes of the Nino3.4 SST index. Nevertheless, a better simulation of the mean location of the DWPE does not necessarily improve the amplitude of a model's ENSO. It is also found that in a few models (CSIROMk3.6, inmcm and inmcm4-esm) the warm pool displacements result from a net heating or cooling rather than a zonal advection of warm water. The simulation of the DWPE has implications for ENSO dynamics when considering ENSO paradigms such as the delayed action oscillator mechanism, the Advective-Reflective oscillator, and the zonal-advective feedback. These are also discussed in the context of the CMIP5 simulations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Navarro, Alejandro Bañón, E-mail: banon@physics.ucla.edu; Jenko, Frank, E-mail: jenko@physics.ucla.edu; Teaca, Bogdan, E-mail: bogdan.teaca@coventry.ac.uk

For a Z-pinch geometry, we report on the nonlinear redistribution of free energy across scales perpendicular to the magnetic guide field, for a turbulent plasma described in the framework of gyrokinetics. The analysis is performed using a local flux-surface approximation, in a regime dominated by electrostatic fluctuations driven by the entropy mode, with both ion and electron species being treated kinetically. To explore the anisotropic nature of the free energy redistribution caused by the emergence of zonal flows, we use a polar coordinate representation for the field-perpendicular directions and define an angular density for the scale flux. Positive values formore » the classically defined (angle integrated) scale flux, which denote a direct energy cascade, are shown to be also composed of negative angular sections, a fact that impacts our understanding of the backscatter of energy and the way in which it enters the modeling of sub-grid scales for turbulence. A definition for the flux of free energy across each perpendicular direction is introduced as well, which shows that the redistribution of energy in the presence of zonal flows is highly anisotropic.« less

Influence of magnetic field configuration on magnetohydrodynamic waves in Earth's core

NASA Astrophysics Data System (ADS)

Knezek, Nicholas; Buffett, Bruce

2018-04-01

We develop a numerical model to study magnetohydrodynamic waves in a thin layer of stratified fluid near the surface of Earth's core. Past studies have been limited to using simple background magnetic field configurations. However, the choice of field distribution can dramatically affect the structure and frequency of the waves. To permit a more general treatment of background magnetic field and layer stratification, we combine finite volume and Fourier methods to describe the wave motions. We validate our model by comparisons to previous studies and examine the influence of background magnetic field configuration on two types of magnetohydrodynamic waves. We show that the structure of zonal Magnetic-Archimedes-Coriolis (MAC) waves for a dipole background field is unstable to small perturbations of the field strength in the equatorial region. Modifications to the wave structures are computed for a range of field configurations. In addition, we show that non-zonal MAC waves are trapped near the equator for realistic magnetic field distributions, and that their latitudinal extent depends upon the distribution of magnetic field strength at the CMB.

The Sensitivity of the Midlatitude Moist Isentropic Circulation on Both Sides of the Climate Model Hierarchy

NASA Astrophysics Data System (ADS)

Fajber, R. A.; Kushner, P. J.; Laliberte, F. B.

2017-12-01

In the midlatitude atmosphere, baroclinic eddies are able to raise warm, moist air from the surface into the midtroposphere where it condenses and warms the atmosphere through latent heating. This coupling between dynamics and moist thermodynamics motivates using a conserved moist thermodynamic variable, such as the equivalent potential temperature, to study the midlatitude circulation and associated heat transport since it implicitly accounts for latent heating. When the equivalent potential temperature is used to zonally average the circulation, the moist isentropic circulation takes the form of a single cell in each hemisphere. By utilising the statistical transformed Eulerian mean (STEM) circulation we are able to parametrize the moist isentropic circulation in terms of second order dynamic and moist thermodynamic statistics. The functional dependence of the STEM allows us to analytically calculate functional derivatives that reveal the spatially varying sensitivity of the moist isentropic circulation to perturbations in different statistics. Using the STEM functional derivatives as sensitivity kernels we interpret changes in the moist isentropic circulation from two experiments: surface heating in an idealised moist model, and a climate change scenario in a comprehensive atmospheric general circulation model. In both cases we find that the changes in the moist isentropic circulation are well predicted by the functional sensitivities, and that the total heat transport is more sensitive to changes in dynamical processes driving local changes in poleward heat transport than it is to thermodynamic and/or radiative processes driving changes to the distribution of equivalent potential temperature.

Propagating annular modes

NASA Astrophysics Data System (ADS)

Sheshadri, A.; Plumb, R. A.

2017-12-01

The leading "annular mode", defined as the dominant EOF of surface pressure or of zonal mean zonal wind variability, appears as a dipolar structure straddling the mean midlatitude jet and thus seems to describe north-south wobbling of the jet latitude. However, extratropical zonal wind anomalies frequently tend to migrate poleward. This behavior can be described by the first two EOFs, the first (AM1) being the dipolar structure, and the second (AM2) having a tripolar structure centered on the mean jet. Taken in isolation, AM1 thus describes a north-south wobbling of the jet position, while AM2 describes a strengthening and narrowing of the jet. However, despite the fact that they are spatially orthogonal, and their corresponding time series temporally orthogonal, AM1 and AM2 are not independent, but show significant lag-correlations which reveal the propagation. The EOFs are not modes of the underlying dynamical system governing the zonal flow evolution. The true modes can be estimated using principal oscillation pattern (POP) analysis. In the troposphere, the leading POPs manifest themselves as a pair of complex conjugate structures with conjugate eigenvalues thus, in reality, constituting a single, complex, mode that describes propagating anomalies. Even though the principal components associated with the two leading EOFs decay at different rates, each decays faster than the true mode. These facts have implications for eddy feedback and the susceptibility of the mode to external perturbations. If one interprets the annular modes as the modes of the system, then simple theory predicts that the response to steady forcing will usually be dominated by AM1 (with the longest time scale). However, such arguments should really be applied to the true modes. Experiments with a simplified GCM show that climate response to perturbations do not necessarily have AM1 structures. Implications of these results for stratosphere-troposphere interactions are explored. The POP structures are shown to be independent of any weighting (unlike the EOFs, the structures and time scales of which change substantially with pressure weighting), a fact that is particularly important for a deep system such as the troposphere and stratospere. The structure and time evolution of coupled modes of the troposphere-stratosphere system are studied.

Are Strong Zonal Winds in Giant Planets Caused by Density-Stratification?

NASA Astrophysics Data System (ADS)

Verhoeven, J.; Stellmach, S.

2012-12-01

One of the most striking features of giant planets like Jupiter and Saturn are the zonal wind patterns observed on their surfaces. The mechanism that drives this differential rotation is still not clearly identified and is currently strongly debated in the astro- and geophysics community. Different mechanisms have been proposed over the last decades. Here, a recently discovered mechanism based on background density stratification (Glatzmaier et al., 2009) is investigated. This mechanism has the potential to overcome known difficulties of previous explanations and its efficiency has been demonstrated in 2-d simulations covering equatorial planes. By performing highly resolved numerical simulations in a local Cartesian geometry, we are able to test the efficiency and functionality of this mechanism in turbulent, rotating convection in three spatial dimensions. The choice of a Cartesian model geometry naturally excludes other known mechanisms capable of producing differential rotation, thus allowing us to investigate the role of density stratification in isolation. Typically, the dynamics can be classified into two main regimes: A regime exhibiting strong zonal winds for weak to moderate thermal driving and a regime where zonal winds are largely absent in the case of a strong thermal forcing. Our results indicate that previous 2-d results must be handled with care and can only explain parts of the full 3-d behavior. We show that the density-stratification mechanism tends to operate in a more narrow parameter range in 3-d as compared to 2-d simulations. The dynamics of the regime transition is shown to differ in both cases, which renders scaling laws derived from two-dimensional studies questionable. Based on our results, we provide estimates for the importance of the density-stratification mechanism for giant planets like Jupiter (strong density stratification), for systems like the Earth's core (weak density stratification) and compare its efficiency with other suggested mechanisms for driving differential rotation. Gary A. Glatzmaier, Martha Evonuk and Tamara M. Rogers (2009), Differential rotation in giant planets maintained by density-stratified turbulent convection. Geophysical and Astrophysical Fluid Dynamics, Vol. 103, No. 1, 31-51.

Dynamically Intuitive and Potentially Predicatable Three-Dimensional Structures in the Low Frequency Flow Variability of the Extratropical Northern Hemisphere

NASA Astrophysics Data System (ADS)

Wettstein, J. J.; Li, C.; Bradshaw, S.

2016-12-01

Canonical tropospheric climate variability patterns and their corresponding indices are ubiquitous, yet a firm dynamical interpretation has remained elusive for many of even the leading extratropical patterns. Part of the lingering difficulty in understanding and predicting atmospheric low frequency variability is the fact that the identification itself of the different patterns is indistinct. This study characterizes three-dimensional structures in the low frequency variability of the extratropical zonal wind field within the entire period of record of the ERA-Interim reanalysis and suggests the foundations for a new paradigm in identifying and predicting extratropical atmospheric low-frequency variability. In concert with previous results, there is a surprisingly rich three-dimensional structure to the variance of the zonal wind field that is not (cannot be) captured by traditional identification protocols that explore covariance of pressure in the lower troposphere, flow variability in the zonal mean or, for that matter, in any variable on any planar surface. Correspondingly, many of the pressure-based canonical indices of low frequency atmospheric variability exhibit inconsistent relationships to physically intuitive reorganizations of the subtropical and polar front jets and with other forcing mechanisms. Different patterns exhibit these inconsistencies to a greater or lesser extent. The three-dimensional variance of the zonal wind field is, by contrast, naturally organized around dynamically intuitive atmospheric redistributions that have a surprisingly large amount of physically intuitive information in the vertical. These conclusions are robust in a variety of seasons and also in intra-seasonal and inter-annual explorations. Similar results and conclusions are also derived using detrended data, other reanalyses, and state-of-the-art coupled climate model output. In addition to providing a clearer perspective on the distinct three-dimensional patterns of atmospheric low frequency variability, the time evolution and potential predictability of the resultant patterns can be explored with much greater clarity because of an intrinsic link between the patterns and the requisite conservation of momentum (i.e. to the primitive equations and candidate forcing mechanisms).

Observations of planetary mixed Rossby-gravity waves in the upper stratosphere

NASA Technical Reports Server (NTRS)

Randel, William J.; Boville, Byron A.; Gille, John C.

1990-01-01

Observational evidence is presented for planetary scale (zonal wave number 1-2) mixed Rossby-gravity (MRG) waves in the equatorial upper stratosphere (35-50 km). These waves are detected in LIMS measurements as coherently propagating temperature maxima of amplitude 0.1-0.3 K, which are antisymmetric (out of phase) about the equator, centered near 10-15 deg north and south latitude. These features have vertical wavelengths of order 10-15 km, periods near 2-3 days, and zonal phase velocities close to 200 m/s. Both eastward and westward propagating waves are found, and the observed vertical wavelengths and meridional structures are in good agreement with the MRG dispersion relation. Theoretical estimates of the zonal accelerations attributable to these waves suggest they do not contribute substantially to the zonal momentum balance in the middle atmosphere.

Nonlinear saturation of the slab ITG instability and zonal flow generation with fully kinetic ions

NASA Astrophysics Data System (ADS)

Miecnikowski, Matthew T.; Sturdevant, Benjamin J.; Chen, Yang; Parker, Scott E.

2018-05-01

Fully kinetic turbulence models are of interest for their potential to validate or replace gyrokinetic models in plasma regimes where the gyrokinetic expansion parameters are marginal. Here, we demonstrate fully kinetic ion capability by simulating the growth and nonlinear saturation of the ion-temperature-gradient instability in shearless slab geometry assuming adiabatic electrons and including zonal flow dynamics. The ion trajectories are integrated using the Lorentz force, and the cyclotron motion is fully resolved. Linear growth and nonlinear saturation characteristics show excellent agreement with analogous gyrokinetic simulations across a wide range of parameters. The fully kinetic simulation accurately reproduces the nonlinearly generated zonal flow. This work demonstrates nonlinear capability, resolution of weak gradient drive, and zonal flow physics, which are critical aspects of modeling plasma turbulence with full ion dynamics.