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Sample records for observed decadal variability

  1. Sub-decadal North Atlantic Oscillation variability in observations and the Kiel Climate Model

    NASA Astrophysics Data System (ADS)

    Reintges, Annika; Latif, Mojib; Park, Wonsun

    2016-07-01

    The North Atlantic Oscillation (NAO) is the dominant mode of winter climate variability in the North Atlantic sector. The corresponding index varies on a wide range of timescales, from days and months to decades and beyond. Sub-decadal NAO variability has been well documented, but the underlying mechanism is still under discussion. Other indices of North Atlantic sector climate variability such as indices of sea surface and surface air temperature or Arctic sea ice extent also exhibit pronounced sub-decadal variability. Here, we use sea surface temperature and sea level pressure observations, and the Kiel Climate Model to investigate the dynamics of the sub-decadal NAO variability. The sub-decadal NAO variability is suggested to originate from dynamical large-scale air-sea interactions. The adjustment of the Atlantic Meridional Overturning Circulation to previous surface heat flux variability provides the memory of the coupled mode. The results stress the role of coupled feedbacks in generating sub-decadal North Atlantic sector climate variability, which is important to multiyear climate predictability in that region.

  2. North Atlantic Current variability as observed by two decades of XBT measurements

    NASA Astrophysics Data System (ADS)

    Hüttl-Kabus, Sabine; Klein, Birgit

    2010-05-01

    In the framework of the German contribution to the Ship-of-Opportunity program (SOOP) temperature measurements in the North Atlantic have been carried out since 1988. The timeseries of XBT measurements along the AX-03 line (English channel to Grand Banks, continuing to Halifax or New York) is without major interruptions and will be used to investigate interannual to decadal temperature changes in the highly variable transition region between the subtropical and subpolar gyre. Along the western part of the section changes of the separation latitude of the North Atlantic Current (NAC) are observed, showing a tendency for warmer waters to penetrate farther north between 1999-2006 compared to the period 1988-1998. However, interannual variability is on the same order of magnitude and masks the signal in some years. Based on XBT data only it is impossible to distinguish if the 1999-2006 warming is a trend or decadal variability. The variability in the eastern basin reveals a qualitative similar behavior, although with smaller variability amplitudes. Combining both findings the observations indicate a basinwide northward shift of the NAC and the subtropical gyre until 2006. Heat content changes at the western boundary amount to about 5*109 J/m2, along the eastern boundary to about 2*109 J/m2. Applying XBT fall rate corrections to the original data does not reveal a significant change of the variability behavior.

  3. Observed decadal variability of southern African rainfall, their teleconnections, and uncertainties

    NASA Astrophysics Data System (ADS)

    Dieppois, Bastien; Pohl, Benjamin; Rouault, Mathieu; New, Mark; Lawler, Damian; Keenlyside, Noel

    2016-04-01

    This study examines for the first time the changing characteristics of summer and winter southern African rainfall, and their teleconnections with large-scale climate through the dominant timescales of variability. The summer and winter rainfall indices exhibit three significant timescales of variability over the 20th century: interdecadal (15-28 year), quasi-decadal (8-13 year) and interannual (2-8 year). Teleconnections with global sea-surface temperature and atmospheric circulation anomalies, which have been established here using different data sets, are different for each timescale. Uncertainty related to the choice of observed-based SST and reanalysis data sets appears stronger over the winter rainfall region and at the interdecadal timescale. However, only SST and atmospheric anomalies which show an agreement greater than 90% between data sets, or between the members of the reanalysis, have been described. Tropical/subtropical teleconnections emerge as the main driver of summer rainfall variability. Thus, shifts in the Walker circulation are linked to the El Niño Southern Oscillation (ENSO) and, at decadal timescales, to decadal ENSO-like patterns related to the Pacific Decadal Oscillation and the Interdecadal Pacific Oscillation. These global changes in the upper-zonal circulation interact with asymmetric ocean-atmospheric modifications between the South Atlantic and South Indian Oceans; together these lead to shift in the South Indian Convergence Zone, and a modulation of the development of convective rain bearing systems over southern Africa in summer. Such regional changes, embedded in quasi-annular geopotential patterns, consist of easterly moisture fluxes from the Mascarene High, which dominate southerly moisture fluxes from the St Helena High. Winter rainfall variability is more influenced by mid-latitude atmospheric variability, in particular the Southern Annular Mode, but interactions with ENSO remain, especially in the subtropics. Asymmetrical

  4. Tides and Decadal Variability

    NASA Technical Reports Server (NTRS)

    Ray, Richard D.

    2003-01-01

    This paper reviews the mechanisms by which oceanic tides and decadal variability in the oceans are connected. We distinguish between variability caused by tides and variability observed in the tides themselves. Both effects have been detected at some level. The most obvious connection with decadal timescales is through the 18.6-year precession of the moon's orbit plane. This precession gives rise to a small tide of the same period and to 18.6-year modulations in the phase and amplitudes of short-period tides. The 18.6-year "node tide" is very small, no more than 2 cm anywhere, and in sea level data it is dominated by the ocean's natural Variability. Some authors have naively attributed climate variations with periods near 19 years directly to the node tide, but the amplitude of the tide is too small for this mechanism to be operative. The more likely explanation (Loder and Garrett, JGR, 83, 1967-70, 1978) is that the 18.6-y modulations in short-period tides, especially h e principal tide M2, cause variations in ocean mixing, which is then observed in temperature and other climatic indicators. Tidally forced variability has also been proposed by some authors, either in response to occasional (and highly predictable) tidal extremes or as a nonlinear low-frequency oscillation caused by interactions between short-period tides. The former mechanism can produce only short-duration events hardly more significant than normal tidal ranges, but the latter mechanism can in principle induce low-frequency oscillations. The most recent proposal of this type is by Keeling and Whorf, who highlight the 1800-year spectral peak discovered by Bond et al. (1997). But the proposal appears contrived and should be considered, in the words of Munk et al. (2002), "as the most likely among unlikely candidates."

  5. Measurement Biases Explain Discrepancies between the Observed and Simulated Decadal Variability of Surface Incident Solar Radiation

    PubMed Central

    Wang, Kaicun

    2014-01-01

    Observations have reported a widespread dimming of surface incident solar radiation (Rs) from the 1950s to the 1980s and a brightening afterwards. However, none of the state-of-the-art earth system models, including those from the Coupled Model Intercomparison Project phase 5 (CMIP5), could successfully reproduce the dimming/brightening rates over China. We find that the decadal variability of observed Rs may have important errors due to instrument sensitivity drifting and instrument replacement. While sunshine duration (SunDu), which is a robust measurement related to Rs, is nearly free from these problems. We estimate Rs from SunDu with a method calibrated by the observed Rs at each station. SunDu-derived Rs declined over China by −2.8 (with a 95% confidence interval of −1.9 to −3.7) W m−2 per decade from 1960 to 1989, while the observed Rs declined by −8.5 (with a 95% confidence interval of −7.3 to −9.8) W m−2 per decade. The former trend was duplicated by some high-quality CMIP5 models, but none reproduced the latter trend. PMID:25142756

  6. Ocean impact on decadal Atlantic climate variability revealed by sea-level observations.

    PubMed

    McCarthy, Gerard D; Haigh, Ivan D; Hirschi, Joël J-M; Grist, Jeremy P; Smeed, David A

    2015-05-28

    Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres--the intergyre region. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures, but in the coupled system we describe, there are compensating effects. In this case, the negative AMO is associated with a continued acceleration of sea-level rise along the northeast coast of the United States.

  7. Ocean impact on decadal Atlantic climate variability revealed by sea-level observations

    NASA Astrophysics Data System (ADS)

    McCarthy, Gerard D.; Haigh, Ivan D.; Hirschi, Joël J.-M.; Grist, Jeremy P.; Smeed, David A.

    2015-05-01

    Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres--the intergyre region. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures, but in the coupled system we describe, there are compensating effects. In this case, the negative AMO is associated with a continued acceleration of sea-level rise along the northeast coast of the United States.

  8. On the variability of Pacific Ocean tides at seasonal to decadal time scales: Observed vs modelled

    NASA Astrophysics Data System (ADS)

    Devlin, Adam Thomas

    forward in time to the predicted sea level in 2100. Results suggest that stations with large positive combined A-TATs produce total water levels that are greater than those predicted by an increase in MSL alone, increasing the chances of high-water events. Part II examines the mechanisms behind the yearly (TAT) variability in the Western Tropical Pacific Ocean. Significant amplitude TATs are found at more than half of 26 gauges for each of the two strongest tidal constituents, K1 (diurnal) and M2 (semidiurnal). For the lesser constituents analyzed (O1 and S2), significant trends are observed at ten gauges. Part III analyzes the seasonal behavior of tides (STATs) at twenty tide gauges in the Southeast Asian waters, which exhibit variation by 10 -- 30% of mean tidal amplitudes. A barotropic ocean tide model that considers the seasonal effects of MSL, stratification, and geostrophic and Ekman velocity is used to explain the observed seasonal variability in tides due to variations in monsoon-influenced climate forcing, with successful results at about half of all gauges. The observed changes in tides are best explained by the influence of non-tidal velocities (geostrophic and Ekman), though the effect of changing stratification is also an important secondary causative mechanism. From the results of these surveys and investigations, it is concluded that short-term fluctuations in MSL and tidal properties at multiple time scales may be as important in determining the state of future water levels as the long-term trends. Global explanations for the observed tidal behavior have not been found in this study; however, significant regional explanations are found at the yearly time scale in the Solomon Sea, and at the seasonal time scale in Southeast Asia. It is likely that tidal sensitivity to annual and seasonal variations in MSL at other locations also are driven by locally specific processes, rather than factors with basin-wide coherence. (Abstract shortened by ProQuest.).

  9. Decadal-Scale Variability of The Mesosphere And Lower Thermosphere As Observed by SABER/TIMED From 2002 to 2014

    NASA Astrophysics Data System (ADS)

    Yee, J. H.

    2014-12-01

    In this paper, we will analyze over a decade of SABER/TIMED observations to quantify and interpret the decadal-scale variability of temperature, composition, and airglow intensity, including those associated with the 11-year solar cycle (SC) and long-term anthropogenic change (AC), of the Mesosphere and Lower Thermosphere (MLT). The MLT is an interface and buffer between the Sun, interplanetary space, and the magnetosphere above and the atmosphere below and plays a uniquely important role in the solar-terrestrial system. The MLT sensitivities to solar cycle activity and long-term changes will be extracted using the multiple regression technique from12+ years of SABER/TIMED observations (2002 to 2014). Accuracies of the extracted SC and AC sensitivities will be assessed and discussed in terms of our analysis technique, the proxies we used, and the noise, drift and length of the data we used in the study.

  10. Ozone deposition into a boreal forest over a decade of observations: evaluating deposition partitioning and driving variables

    NASA Astrophysics Data System (ADS)

    Rannik, Ü.; Altimir, N.; Mammarella, I.; Bäck, J.; Rinne, J.; Ruuskanen, T. M.; Hari, P.; Vesala, T.; Kulmala, M.

    2012-12-01

    This study scrutinizes a decade-long series of ozone deposition measurements in a boreal forest in search for the signature and relevance of the different deposition processes. The canopy-level ozone flux measurements were analysed for deposition characteristics and partitioning into stomatal and non-stomatal fractions, with the main focus on growing season day-time data. Ten years of measurements enabled the analysis of ozone deposition variation at different time-scales, including daily to inter-annual variation as well as the dependence on environmental variables and concentration of biogenic volatile organic compounds (BVOC-s). Stomatal deposition was estimated by using multi-layer canopy dispersion and optimal stomatal control modelling from simultaneous carbon dioxide and water vapour flux measurements, non-stomatal was inferred as residual. Also, utilising the big-leaf assumption stomatal conductance was inferred from water vapour fluxes for dry canopy conditions. The total ozone deposition was highest during the peak growing season (4 mm s-1) and lowest during winter dormancy (1 mm s-1). During the course of the growing season the fraction of the non-stomatal deposition of ozone was determined to vary from 26 to 44% during day time, increasing from the start of the season until the end of the growing season. By using multi-variate analysis it was determined that day-time total ozone deposition was mainly driven by photosynthetic capacity of the canopy, vapour pressure deficit (VPD), photosynthetically active radiation and monoterpene concentration. The multi-variate linear model explained the high portion of ozone deposition variance on daily average level (R2 = 0.79). The explanatory power of the multi-variate model for ozone non-stomatal deposition was much lower (R2 = 0.38). The set of common environmental variables and terpene concentrations used in multivariate analysis were able to predict the observed average seasonal variation in total and non

  11. Re-Examination of the Observed Decadal Variability of Earth Radiation Budget Using Altitude-Corrected ERBE/ERBS Nonscanner WFOV Data

    NASA Technical Reports Server (NTRS)

    Wong, Takmeng; Wielicki, Bruce A.; Lee, Robert B.; Smith, G. Louis; Bush, Kathryn A.

    2005-01-01

    This paper gives an update on the observed decadal variability of Earth Radiation Budget using the latest altitude-corrected Earth Radiation Budget Experiment (ERBE)/Earth Radiation Budget Satellite (ERBS) Nonscanner Wide Field of View (WFOV) instrument Edition3 dataset. The effects of the altitude correction are to modify the original reported decadal changes in tropical mean (20N to 20S) longwave (LW), shortwave (SW), and net radiation between the 1980s and the 1990s from 3.1/-2.4/-0.7 to 1.6/-3.0/1.4 Wm(sup -2) respectively. In addition, a small SW instrument drift over the 15-year period was discovered during the validation of the WFOV Edition3 dataset. A correction was developed and applied to the Edition3 dataset at the data user level to produce the WFOV Edition3_Rev1 dataset. With this final correction, the ERBS Nonscanner observed decadal changes in tropical mean LW, SW, and net radiation between the 1980s and the 1990s now stand at 0.7/-2.1/1.4 Wm(sup -2), respectively, which are similar to the observed decadal changes in the HIRS Pathfinder OLR and the ISCCP FD record; but disagree with the AVHRR Pathfinder ERB record. Furthermore, the observed interannual variability of near-global ERBS WFOV Edition3_Rev1 net radiation is found to be remarkably consistent with the latest ocean heat storage record for the overlapping time period of 1993 to 1999. Both data sets show variations of roughly 1.5 Wm(sup -2) in planetary net heat balance during the 1990s.

  12. Atlantic forcing of Pacific decadal variability

    NASA Astrophysics Data System (ADS)

    Kucharski, Fred; Ikram, Farah; Molteni, Franco; Farneti, Riccardo; Kang, In-Sik; No, Hyun-Ho; King, Martin P.; Giuliani, Graziano; Mogensen, Kristian

    2016-04-01

    This paper investigates the Atlantic Ocean influence on equatorial Pacific decadal variability. Using an ensemble of simulations, where the ICTPAGCM ("SPEEDY") is coupled to the NEMO/OPA ocean model in the Indo-Pacific region and forced by observed sea surface temperatures in the Atlantic region, it is shown that the Atlantic Multidecadal Oscillation (AMO) has had a substantial influence on the equatorial Pacific decadal variability. According to AMO phases we have identified three periods with strong Atlantic forcing of equatorial Pacific changes, namely (1) 1931-1950 minus 1910-1929, (2) 1970-1989 minus 1931-1950 and (3) 1994-2013 minus 1970-1989. Both observations and the model show easterly surface wind anomalies in the central Pacific, cooling in the central-eastern Pacific and warming in the western Pacific/Indian Ocean region in events (1) and (3) and the opposite signals in event (2). The physical mechanism for these responses is related to a modification of the Walker circulation because a positive (negative) AMO leads to an overall warmer (cooler) tropical Atlantic. The warmer (cooler) tropical Atlantic modifies the Walker circulation, leading to rising (sinking) and upper-level divergence (convergence) motion in the Atlantic region and sinking (rising) motion and upper-level convergence (divergence) in the central Pacific region.

  13. Variability of Antarctic ozone loss in the last decade (2004-2013): high resolution simulations compared to Aura MLS observations

    NASA Astrophysics Data System (ADS)

    Kuttippurath, J.; Godin-Beekmann, S.; Lefèvre, F.; Santee, M. L.; Froidevaux, L.; Hauchecorne, A.

    2014-11-01

    A detailed analysis of the polar ozone loss processes during ten recent Antarctic winters is presented with high resolution Mimosa-Chim model simulations and high frequency polar vortex observations from the Aura Microwave Limb Sounder (MLS) instrument. Our model results for the Antarctic winters 2004-2013 show that chemical ozone loss starts in the edge region of the vortex at equivalent latitudes (EqLs) of 65-69° S in mid-June/July. The loss progresses with time at higher EqLs and intensifies during August-September over the range 400-600 K. The loss peaks in late September/early October, where all EqLs (65-83°) show similar loss and the maximum loss (>2 ppmv [parts per million by volume]) is found over a broad vertical range of 475-550 K. In the lower stratosphere, most winters show similar ozone loss and production rates. In general, at 500 K, the loss rates are about 2-3 ppbv sh-1 (parts per billion by volume/sunlit hour) in July and 4-5 ppbv sh-1 in August/mid-September, while they drop rapidly to zero by late September. In the middle stratosphere, the loss rates are about 3-5 ppbv sh-1 in July-August and October at 675 K. It is found that the Antarctic ozone hole (June-September) is controlled by the halogen cycles at about 90-95% (ClO-ClO, BrO-ClO, and ClO-O) and the loss above 700 K is dominated by the NOx cycle at about 70-75%. On average, the Mimosa-Chim simulations show that the very cold winters of 2005 and 2006 exhibit a maximum loss of ~3.5 ppmv around 550 K or about 149-173 DU over 350-850 K and the warmer winters of 2004, 2010, and 2012 show a loss of ~2.6 ppmv around 475-500 K or 131-154 DU over 350-850 K. The winters of 2007, 2008, and 2011 were moderately cold and thus both ozone loss and peak loss altitudes are between these two ranges (3 ppmv around 500 K or 150 ± 10 DU). The modeled ozone loss values are in reasonably good agreement with those estimated from Aura MLS measurements, but the model underestimates the observed ClO, largely due

  14. Enceladus Plumes: Causes of Decadal Variability

    NASA Astrophysics Data System (ADS)

    Ingersoll, Andrew P.; Ewald, Shawn P.

    2016-10-01

    The Enceladus plumes have decreased over the decade that Cassini has been observing them. This long-term variation is superposed on the much shorter-term variation tied to the position of Enceladus in its orbit around Saturn. The observations are ISS and VIMS images, which reveal the particles in the plumes but not the gas. The decadal variability largely consists of a 2-fold decline in the mass of plume material, but there is a hint of a recent turnaround. Here we offer three hypotheses, each with its strengths and weaknesses, to explain the long-term variability. The first is seasonal change, from summer to fall in the southern hemisphere. The loss of sunlight could increase the build-up of ice around the tiger stripes. The weakness is that the sunlight is likely to have a small effect, e.g., decreasing the sublimation rate of the ice by only ~1 cm/year. The second hypothesis is a statistical fluctuation in the number of active plumes, which tend to turn themselves off due to build-up of ice at the throat of the vent. The weakness is that the plumes are likely to fluctuate independently, and if there are ~100 plumes, their sum will only fluctuate by 10%. The third hypothesis is that the variation is part of a well-known decadal cycle of orbital eccentricity, which varies by ±2.5% around a mean of 0.0047. The peak eccentricity occurred in 2009-2010, and the minimum occurred in 2015. Since eccentricity controls the short-term orbital cycle variations, it could also control the longer-term decadal variations. The weakness is that the eccentricity variation is small, from 0.0046 to 0.0048. It is not certain that such a small variation could cause a 2-fold variation in the strength of the plumes. An independent study, still in its infancy, is the possibility that liquid water reaches the surface during part of the orbital cycle.

  15. Decadal Variability of Clouds and Comparison with Climate Model Simulations

    NASA Astrophysics Data System (ADS)

    Su, H.; Shen, T. J.; Jiang, J. H.; Yung, Y. L.

    2014-12-01

    An apparent climate regime shift occurred around 1998/1999, when the steady increase of global-mean surface temperature appeared to hit a hiatus. Coherent decadal variations are found in atmospheric circulation and hydrological cycles. Using 30-year cloud observations from the International Satellite Cloud Climatology Project, we examine the decadal variability of clouds and associated cloud radiative effects on surface warming. Empirical Orthogonal Function analysis is performed. After removing the seasonal cycle and ENSO signal in the 30-year data, we find that the leading EOF modes clearly represent a decadal variability in cloud fraction, well correlated with the indices of Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). The cloud radiative effects associated with decadal variations of clouds suggest a positive cloud feedback, which would reinforce the global warming hiatus by a net cloud cooling after 1998/1999. Climate model simulations driven by observed sea surface temperature are compared with satellite observed cloud decadal variability. Copyright:

  16. Processes Understanding of Decadal Climate Variability

    NASA Astrophysics Data System (ADS)

    Prömmel, Kerstin; Cubasch, Ulrich

    2016-04-01

    The realistic representation of decadal climate variability in the models is essential for the quality of decadal climate predictions. Therefore, the understanding of those processes leading to decadal climate variability needs to be improved. Several of these processes are already included in climate models but their importance has not yet completely been clarified. The simulation of other processes requires sometimes a higher resolution of the model or an extension by additional subsystems. This is addressed within one module of the German research program "MiKlip II - Decadal Climate Predictions" (http://www.fona-miklip.de/en/) with a focus on the following processes. Stratospheric processes and their impact on the troposphere are analysed regarding the climate response to aerosol perturbations caused by volcanic eruptions and the stratospheric decadal variability due to solar forcing, climate change and ozone recovery. To account for the interaction between changing ozone concentrations and climate a computationally efficient ozone chemistry module is developed and implemented in the MiKlip prediction system. The ocean variability and air-sea interaction are analysed with a special focus on the reduction of the North Atlantic cold bias. In addition, the predictability of the oceanic carbon uptake with a special emphasis on the underlying mechanism is investigated. This addresses a combination of physical, biological and chemical processes.

  17. Pacific Decadal Climate Variability and Predictability

    NASA Astrophysics Data System (ADS)

    Kirtman, B.

    2006-12-01

    The current understanding of decadal variability in both the tropical and extra-tropical Pacific is presented. Modeling studies into causes of mid-latitude ocean variability often focus on to what extent the variability involves coupled ocean-atmosphere feedbacks versus the uncoupled response to atmospheric stochastic white noise forcing. The coupled feedbacks are either viewed as a generalization of the Hasselman (1976) theory to include local air-sea interactions, which could amplify the low frequency response without any preferred time scale or as involving a "delayed oscillator" due to ocean memory whereby the variability has some preferred time scale. Generally, the coupled air-sea feedbacks are stable requiring atmospheric stochastic forcing, and the inclusion of ocean dynamics is thought to enhance the variability. The uncoupled stochastic forcing of the ocean includes a number of proposed physical mechanisms for the preferred low frequency. These mechanisms include oceanic advection processes associated with the mid-latitude gyre, an atmospheric pattern of forcing with a preferred length scale or position, the dynamical adjustment of the extra-tropical ocean circulation via long baroclinic Rossby waves, and Ekman pumping. Another possibility is that tropical forcing via some atmospheric "bridge" acts as a source of North Pacific decadal variations, which may or may not be amplified by coupled feedbacks. The amplitude and frequency of ENSO exhibits variations on decadal timescales. Whether these variations are driven by low frequency variability in the tropical Pacific mean state or are just sampling issues associated with some sort of random walk process has been the subject of some debate. Accordingly, the current literature includes a number of studies proposing mechanisms for the decadal variability of the tropical Pacific, and, as a counter argument, studies examining the null hypothesis that the amplitude and frequency variations are simply related to

  18. Decadal variability in the Eastern North Atlantic

    NASA Astrophysics Data System (ADS)

    Köllner, Manuela; Klein, Birgit; Kieke, Dagmar; Klein, Holger; Rhein, Monika; Roessler, Achim; Denker, Claudia

    2016-04-01

    The strong warming and salinification of the Eastern North Atlantic starting in the mid 1990s has been attributed to a westward contraction of the subpolar gyre and stronger inflow of waters from the subtropical gyre. Temporal changes in the shape and strength of the two gyres have been related to the major mode of atmospheric variability in the Atlantic sector, the NAO. Hydrographic conditions along the Northwest European shelf are thus the result of different processes such as variations in transports, varying relative contributions of water masses from the two gyres and property trends in the source water masses. We examine the decadal variability in the eastern North Atlantic based on Argo data from 2000-2015 and have constructed time series for four water masses (Subpolar Mode Water (SPMW), Intermediate Water (IW), upper Labrador Sea Water (uLSW) and deep Labrador Sea Water (dLSW)) at selected locations along the Northwest European shelf. Data from the Rockall Trough and the Iceland Basin are chosen to represent advective pathways in the subpolar gyre at two major branches of the North Atlantic Current towards the Nordic Seas and the Arctic Ocean. Temporal variability of subtropical waters transported northward along the eastern boundary is studied at Goban Spur around 48°N. The Argo data are extended in time with long-term hydrographic observations such as the Extended Ellet Line data and other climatological sources in the region. For the study of transport fluctuations time series from the RACE (Regional circulation and Global change) program (2012-2015) and predecessor programs have been used. These programs have monitored the subpolar gyre in the western basin and provide time series of transports and hydrographic anomalies from moored instruments at the western flank of the Mid Atlantic Ridge (MAR). First results show that the temperatures and salinities remained at high levels for the upper waters (SPMW and IW) until 2010 and have been decreasing since

  19. A decade of SETI observations

    NASA Technical Reports Server (NTRS)

    Dixon, R. S.

    1986-01-01

    A full time dedicated search for extraterrestrial radio signals of intelligent origin has been in progress at the Ohio State University Radio Observatory since 1973. The radio telescope has a collecting area of 2200 square meters, which is equivalent to a circular dish 175 feet in diameter. The search concentrates on a 500 kHz bandwidth centered on the 1420 MHz hydrogen line, Doppler corrected to the galactic standard of rest. A large portion of the sky visible from Ohio was searched, with particulat emphasis on the galactic center region and the M31 Andromeda galaxy. The survey is largely computer automated, and all data reduction is done in real time. Two distinct populations of signals were detected. The first is a relatively small number of signals which persist for over a minute and which are clearly extraterrestrial in origin. The second is the large number of signals which persist less than 10 seconds whose locations are anticorrelated with the galactic plane but show clumps along the galactic axis. None of these signals were observed to recur, despite repeated observations. The cause of these signals were not determined.

  20. Multi-decadal climate variability, New South Wales, Australia.

    PubMed

    Franks, S W

    2004-01-01

    Traditional hydrological risk estimation has treated the observations of hydro-climatological extremes as being independent and identically distributed, implying a static climate risk. However, recent research has highlighted the persistence of multi-decadal epochs of distinct climate states across New South Wales (NSW), Australia. Climatological studies have also revealed multi-decadal variability in the magnitude and frequency of El Niño/Southern Oscillation (ENSO) impacts. In this paper, examples of multi-decadal variability are presented with regard to flood and drought risk. The causal mechanisms for the observed variability are then explored. Finally, it is argued that the insights into climate variability provide (a) useful lead time for forecasting seasonal hydrological risk, (b) a strong rationale for a new framework for hydrological design and (c) a strong example of natural climate variability for use in the testing of General Circulation Models of climate change.

  1. Multi-decadal climate variability, New South Wales, Australia.

    PubMed

    Franks, S W

    2004-01-01

    Traditional hydrological risk estimation has treated the observations of hydro-climatological extremes as being independent and identically distributed, implying a static climate risk. However, recent research has highlighted the persistence of multi-decadal epochs of distinct climate states across New South Wales (NSW), Australia. Climatological studies have also revealed multi-decadal variability in the magnitude and frequency of El Niño/Southern Oscillation (ENSO) impacts. In this paper, examples of multi-decadal variability are presented with regard to flood and drought risk. The causal mechanisms for the observed variability are then explored. Finally, it is argued that the insights into climate variability provide (a) useful lead time for forecasting seasonal hydrological risk, (b) a strong rationale for a new framework for hydrological design and (c) a strong example of natural climate variability for use in the testing of General Circulation Models of climate change. PMID:15195429

  2. Decadal variability in the oxygen inventory of North Atlantic subtropical underwater captured by sustained, long-term oceanographic time series observations

    NASA Astrophysics Data System (ADS)

    Montes, Enrique; Muller-Karger, Frank E.; Cianca, Andrés.; Lomas, Michael W.; Lorenzoni, Laura; Habtes, Sennai

    2016-03-01

    Historical observations of potential temperature (θ), salinity (S), and dissolved oxygen concentrations (O2) in the tropical and subtropical North Atlantic (0-500 m; 0-40°N, 10-90°W) were examined to understand decadal-scale changes in O2 in subtropical underwater (STUW). STUW is observed at four of the longest, sustained ocean biogeochemical and ecological time series stations, namely, the CArbon Retention In A Colored Ocean (CARIACO) Ocean Time Series Program (10.5°N, 64.7°W), the Bermuda Atlantic Time-series Study (BATS; 31.7°N, 64.2°W), Hydrostation "S" (32.1°N, 64.4°W), and the European Station for Time-series in the Ocean, Canary Islands (ESTOC; 29.2°N, 15.5°W). Observations over similar time periods at CARIACO (1996-2013), BATS (1988-2011), and Hydrostation S (1980-2013) show that STUW O2 has decreased approximately 0.71, 0.28, and 0.37 µmol kg-1 yr-1, respectively. No apparent change in STUW O2 was observed at ESTOC over the course of the time series (1994-2013). Ship observation data for the tropical and subtropical North Atlantic archived at NOAA National Oceanographic Data Center show that between 1980 and 2013, STUW O2 (upper ~300 m) declined 0.58 µmol kg-1 yr-1 in the southeastern Caribbean Sea (10-15°N, 60-70°W) and 0.68 µmol kg-1 yr-1 in the western subtropical North Atlantic (30-35°N, 60-65°W). A declining O2 trend was not observed in the eastern subtropical North Atlantic (25-30°N, 15-20°W) over the same period. Most of the observed O2 loss seems to result from shifts in ventilation associated with decreased wind-driven mixing and a slowing down of STUW formation rates, rather than changes in diffusive air-sea O2 gas exchange or changes in the biological oceanography of the North Atlantic. Variability of STUW O2 showed a significant relationship with the wintertime (January-March) Atlantic Multidecadal Oscillation index (AMO, R2 = 0.32). During negative wintertime AMO years trade winds are typically stronger between 10°N and 30

  3. Food Price Volatility and Decadal Climate Variability

    NASA Astrophysics Data System (ADS)

    Brown, M. E.

    2013-12-01

    The agriculture system is under pressure to increase production every year as global population expands and more people move from a diet mostly made up of grains, to one with more meat, dairy and processed foods. Weather shocks and large changes in international commodity prices in the last decade have increased pressure on local food prices. This paper will review several studies that link climate variability as measured with satellite remote sensing to food price dynamics in 36 developing countries where local monthly food price data is available. The focus of the research is to understand how weather and climate, as measured by variations in the growing season using satellite remote sensing, has affected agricultural production, food prices and access to food in agricultural societies. Economies are vulnerable to extreme weather at multiple levels. Subsistence small holders who hold livestock and consume much of the food they produce are vulnerable to food production variability. The broader society, however, is also vulnerable to extreme weather because of the secondary effects on market functioning, resource availability, and large-scale impacts on employment in trading, trucking and wage labor that are caused by weather-related shocks. Food price variability captures many of these broad impacts and can be used to diagnose weather-related vulnerability across multiple sectors. The paper will trace these connections using market-level data and analysis. The context of the analysis is the humanitarian aid community, using the guidance of the USAID Famine Early Warning Systems Network and the United Nation's World Food Program in their response to food security crises. These organizations have worked over the past three decades to provide baseline information on food production through satellite remote sensing data and agricultural yield models, as well as assessments of food access through a food price database. Econometric models and spatial analysis are used

  4. Advances in Understanding Decadal Climate Variability

    NASA Technical Reports Server (NTRS)

    Busalaacchi, Antonio J.

    1998-01-01

    Recently, a joint Brazil-France-U.S. program, known as PIRATA (Pilot Research moored Array in the Tropical Atlantic), was proposed to begin the deployment of moored measurement platforms in the tropical Atlantic in order to enhance the existing observational data base and subsequent understanding of the processes by which the ocean and atmosphere couple in key regions of the tropical Atlantic Ocean. Empirical studies have suggested that there are strong relationships between tropical Atlantic upper ocean variability, SST, ocean-atmosphere coupling and regional climate variability. During the early 1980's a coordinated set of surface wind, subsurface thermal structure, and subsurface current observations were obtained as part of the U.S.-France SEQUAL- FOCAL process experiment designed to observe the seasonal response of the tropical Atlantic Ocean to surface forcing. Since that time, however, the observational data base for the tropical Atlantic Ocean has disintegrated to a few shiptracks measuring ocean temperatures and a small collection of tide gauge stations measuring sea level. A more comprehensive set of observations, modeling and empirical studies is now in order to make progress on understanding the regional climate variability. The proposed PIRATA program will use mooring platforms similar to the tropical Pacific Ocean TAO array to measure surface fluxes of momentum and heat and the corresponding changes in the upper ocean thermal structure. It is anticipated that the oceanic data from this monitoring array will also be used in a predictive mode for initialization studies of regional coupled climate models. Of particular interest are zonal and meridional modes of ocean-atmosphere variability within the tropical Atlantic basin that have significant impacts on the regional climate of the bordering continents.

  5. Advances in Understanding Decadal Climate Variability

    NASA Technical Reports Server (NTRS)

    Busalacchi, Antonio J.

    1999-01-01

    Recently, a joint Brazil-France-U.S. program, known as PIRATA (Pilot Research moored Array in the Tropical Atlantic), was proposed to begin the deployment of moored measurement platforms in the tropical Atlantic in order to enhance the existing observational data base and subsequent understanding of the processes by which the ocean and atmosphere couple in key regions of the tropical Atlantic Ocean. Empirical studies have suggested that there are strong relationships between tropical Atlantic upper ocean variability, SST, ocean-atmosphere coupling and regional climate variability. During the early 1980's a coordinated set of surface wind, subsurface thermal structure, and subsurface current observations were obtained as part of the U.S.-France SEQUAL-FOCAL process experiment designed to observe the seasonal response of the tropical Atlantic Ocean to surface forcing. Since that time, however, the observational data base for the tropical Atlantic Ocean has disintegrated to a few ship-tracks measuring ocean temperatures and a small collection of tide gauge stations measuring sea level. A more comprehensive set of observations, modeling and empirical studies is now in order to make progress on understanding the regional climate variability. The proposed PIRATA program will use mooring platforms similar to the tropical Pacific Ocean TAO array to measure surface fluxes of momentum and heat and the corresponding changes in the upper ocean thermal structure. It is anticipated that the oceanic data from this monitoring array will also be used in a predictive mode for initialization studies of regional coupled climate models. Of particular interest are zonal and meridional modes of ocean-atmosphere variability within the tropical Atlantic basin that have significant impacts on the regional climate of the bordering continents.

  6. Westerly Wind Bursts, ENSO Asymmetry, and Tropical Pacific Decadal Variability

    NASA Astrophysics Data System (ADS)

    Levine, A. F. Z.; McPhaden, M. J.

    2014-12-01

    Over the past half century, epochs of enhanced and suppressed ENSO activity have coincided with changes in mean trade wind strength (tropical Pacific mean state) and westerly wind burst variability. Previous research has considered this westerly wind burst variability as state-dependent noise forcing for ENSO. In agreement with the observations, we find that in the current generation of coupled climate models, the westerly wind burst variability is highly correlated with decadal and multi-decadal scale Pacific mean state variability as well as ENSO variability. However, precisely how concurrent changes to ENSO, the tropical Pacific mean state, and westerly wind burst variability is still an open question. Our previous research has shown that there is a relationship between the magnitude of the state-dependence of the noise forcing and ENSO amplitude asymmetry (i.e. that the El Nino events have a larger temperature anomaly than the La Nina events) . In turn, ENSO amplitude asymmetry can produce a signal on the tropical Pacific mean state on multi-decadal timescales. Here, we develop a systematic method to investigate the hypothesis that the inherent randomness of the state-dependent noise forcing of ENSO can explain the coincident changes in ENSO variability and the tropical Pacific mean state, using a hierarchy of coupled models, from conceptual to intermediate to coupled GCMs.

  7. Decadal-scale climate variability in the tropical and North Pacific during the 1970s and 1980s: Observations and model results

    SciTech Connect

    Graham, N.E.

    1994-08-01

    An abrupt change in the large-scale boreal winter circulation pattern over the North Pacific was observed during the mid-1970s. This paper presents a variety of observed data and model results to describe the climate shift, and to understand some of the links within the coupled climate system that produced, it. Five main findings are emphasized: (1) evidence of abrupt, simultaneous, and apparently related changes can be found in many fields and in many model results; the climate shift is not an artifact, (2) over the tropical Pacific the climate change represents a shift in the state of the coupled ocean-atmosphere system, some aspects of which resemble features associated with El Nino episodes. However, the shift in state is not well characterized as due to a change in the frequency of intensity of El Nino episodes; it is better described as a change in background mean state, (3) When forced with observed SSTs, both a very simple atmospheric model and a full general circulation model (GCM) qualitatively simulate aspects of the decadalscale shift over the tropical Pacific, (4) when forced with observed surface wind stress, two ocean models of the tropical Pacific, in which surface heat fluxes are parameterized as Newtonian damping, reproduce some aspects of the near-equatorial decadal SST signal. However, the models do not reproduce the large changes in SST observed at higher latitudes of the tropical Pacific. suggesting that altered surface heat fluxes dominated in producing these changes, and (5) an important new finding of this study is the success of a GCM in reproducing important aspects of the observed mid-1970s shift in winter northern hemisphere circulation. Comparative analyses of the observed and GCM simulated circulation suggest the altered patterns of tropical Pacific SST and convection were important in forcing the changes in the mid-latitude circulation, a finding corroborated by recent GCM experiments. 70 refs., 18 figs.

  8. Solar forcing synchronizes decadal North Atlantic climate variability.

    PubMed

    Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas

    2015-01-01

    Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth's regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1-2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface. PMID:26369503

  9. Solar forcing synchronizes decadal North Atlantic climate variability.

    PubMed

    Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas

    2015-09-15

    Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth's regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1-2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface.

  10. Contribution of solar radiation to decadal temperature variability over land

    PubMed Central

    Wang, Kaicun; Dickinson, Robert E.

    2013-01-01

    Global air temperature has become the primary metric for judging global climate change. The variability of global temperature on a decadal timescale is still poorly understood. This paper examines further one suggested hypothesis, that variations in solar radiation reaching the surface (Rs) have caused much of the observed decadal temperature variability. Because Rs only heats air during the day, its variability is plausibly related to the variability of diurnal temperature range (daily maximum temperature minus its minimum). We show that the variability of diurnal temperature range is consistent with the variability of Rs at timescales from monthly to decadal. This paper uses long comprehensive datasets for diurnal temperature range to establish what has been the contribution of Rs to decadal temperature variability. It shows that Rs over land globally peaked in the 1930s, substantially decreased from the 1940s to the 1970s, and changed little after that. Reduction of Rs caused a reduction of more than 0.2 °C in mean temperature during May to October from the 1940s through the 1970s, and a reduction of nearly 0.2 °C in mean air temperature during November to April from the 1960s through the 1970s. This cooling accounts in part for the near-constant temperature from the 1930s into the 1970s. Since then, neither the rapid increase in temperature from the 1970s through the 1990s nor the slowdown of warming in the early twenty-first century appear to be significantly related to changes of Rs. PMID:23980136

  11. Two decades of ocean CO2 sink and variability

    NASA Astrophysics Data System (ADS)

    Le QuÉRÉ, C.; Aumont, O.; Bopp, L.; Bousquet, P.; Ciais, P.; Francey, R.; Heimann, M.; Keeling, C. D.; Keeling, R. F.; Kheshgi, H.; Peylin, P.; Piper, S. C.; Prentice, I. C.; Rayner, P. J.

    2003-04-01

    Atmospheric CO2 has increased at a nearly identical average rate of 3.3 and 3.2 Pg C yr-1 for the decades of the 1980s and the 1990s, in spite of a large increase in fossil fuel emissions from 5.4 to 6.3 Pg C yr-1. Thus, the sum of the ocean and land CO2 sinks was 1 Pg C yr-1 larger in the 1990s than in to the 1980s. Here we quantify the ocean and land sinks for these two decades using recent atmospheric inversions and ocean models. The ocean and land sinks are estimated to be, respectively, 0.3 (0.1 to 0.6) and 0.7 (0.4 to 0.9) Pg C yr-1 larger in the 1990s than in the 1980s. When variability less than 5 yr is removed, all estimates show a global oceanic sink more or less steadily increasing with time, and a large anomaly in the land sink during 1990-1994. For year-to-year variability, all estimates show 1/3 to 1/2 less variability in the ocean than on land, but the amplitude and phase of the oceanic variability remain poorly determined. A mean oceanic sink of 1.9 Pg C yr-1 for the 1990s based on O2 observations corrected for ocean outgassing is supported by these estimates, but an uncertainty on the mean value of the order of ±0.7 Pg C yr-1 remains. The difference between the two decades appears to be more robust than the absolute value of either of the two decades.

  12. A Decade of Satellite Ocean Color Observations

    NASA Technical Reports Server (NTRS)

    McClain, Charles R.

    2009-01-01

    After the successful Coastal Zone Color Scanner (CZCS, 1978-1986), demonstration that quantitative estimations of geophysical variables such as chlorophyll a and diffuse attenuation coefficient could be derived from top of the atmosphere radiances, a number of international missions with ocean color capabilities were launched beginning in the late 1990s. Most notable were those with global data acquisition capabilities, i.e., the Ocean Color and Temperature Sensor (OCTS 1996-1997), the Sea-viewing Wide Field-of-view Sensor (SeaWiFS, United States, 1997-present), two Moderate Resolution Imaging Spectroradiometers, (MODIS, United States, Terra/2000-present and Aqua/2002-present), the Global Imager (GLI, Japan, 2002-2003), and the Medium Resolution Imaging Spectrometer (MERIS, European Space Agency, 2002-present). These missions have provided data of exceptional quality and continuity, allowing for scientific inquiries into a wide variety of marine research topics not possible with the CZCS. This review focuses on the scientific advances made over the past decade using these data sets.

  13. Decadal Record of Satellite Carbon Monoxide Observations

    NASA Astrophysics Data System (ADS)

    Worden, Helen; Deeter, Merritt; Frankenberg, Christian; George, Maya; Nichitiu, Florian; Worden, John; Aben, Ilse; Bowman, Kevin; Clerbaux, Cathy; Coheur, Pierre-Francois; de Laat, Jos; Warner, Juying; Drummond, James; Edwards, David; Gille, John; Hurtmans, Daniel; Ming, Luo; Martinez-Alonso, Sara; Massie, Steven; Pfister, Gabriele

    2013-04-01

    Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, chemical production, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern hemispheres along with regional trends for E. China, E. USA, Europe and India. Measurement and sampling methods for each of the instruments are discussed, and we show diagnostics for systematic errors in MOPITT trends. We find that all the satellite observations are consistent with a modest decreasing trend around -1%/year in total column CO over the Northern hemisphere for this time period. Decreasing trends in total CO column are observed for the United States, Europe and E. China with more than 2σ significance. For India, the trend is also decreasing, but smaller in magnitude and less significant. Decreasing trends in surface CO have also been observed from measurements in the U.S. and Europe. Although less information is available for surface CO in China, there is a decreasing trend reported for Beijing. Some of the interannual variability in the observations can be explained by global fire emissions, and there may be some evidence of the global financial crisis in late 2008 to early 2009. But the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.

  14. Interannual and Decadal Variability of Summer Rainfall over South America

    NASA Technical Reports Server (NTRS)

    Zhou, Jiayu; Lau, K.-M.

    1999-01-01

    Using the CPC (Climate Prediction Center) Merged Analysis of Precipitation product along with the Goddard Earth Observing System reanalysis and the Climate Analysis Center sea surface temperature (SST) data, we conduct a diagnostic study of the interannual and decadal scale variability of summer rainfall over South America. Results show three leading modes of rainfall variation identified with interannual, decadal, and long-term trend variability. Together, these modes explain more than half the total variance. The first mode is highly correlated with El Nino/southern oscillation (ENSO), showing severe drought over Northeast Brazil and copious rainfall over the Ecuador coast and the area of Uruguay-Southern Brazil in El Nino years. This pattern is attributed to the large scale zonal shift of the Walker circulation and local Hadley cell anomaly induced by positive (negative) SST anomaly over the eastern (western) equatorial Pacific. In El Nino years, two convective belts indicated by upper tropospheric velocity potential trough and mid-tropospheric rising motion, which are somewhat symmetric about the equator, extend toward the northeast and the southeast into the tropical North and South Atlantic respectively. Sandwiched between the ascent is a region of descending motion over Northeast Brazil. The southern branch of the anomalous Hadley cell is dynamically linked to the increase of rainfall over Uruguay-Southern Brazil. The regional response of anomalous circulation shows a stronger South American summer monsoon and an enhanced (weakened) subtropical high over the South Atlantic (South Pacific) Ocean. The decadal variation displays a meridional shift of the Intertropical Convergence Zone (ITCZ), which is tie to the anomalous cross-equatorial SST gradient over the Atlantic and the eastern Pacific. In conjunction with this mode is a large scale mass swing between the polar regions and midlatitudes in both hemispheres. Over the South Atlantic and the South Pacific

  15. A simple coupled model of tropical Atlantic decadal climate variability

    NASA Astrophysics Data System (ADS)

    Kushnir, Yochanan; Seager, Richard; Miller, Jennifer; Chiang, John C. H.

    2002-12-01

    A linear, zonally averaged model of the interaction between the tropical Atlantic (TA) atmosphere and ocean is presented. A balance between evaporation and meridional heat advection in the mixed layer determines the sea surface temperature tendency. The atmosphere is a fixed-depth, sub-cloud layer in which the specific humidity anomaly is determined by a steady-state balance between evaporation, meridional advection, and a parameterized humidity exchange with the free atmosphere. When the model is integrated, forced with observed surface wind anomalies from 1965 to the present, its simulation of the observed sea surface temperature (SST) is realistic and comparable to a simulation with a full ocean GCM. A statistical representation of surface winds and their relationship to the SST gradient across the equator is used to formulate and test a coupled model of their regional variability. Forced on both sides of the equator, in the trade-wind regions, with ``white-noise'' windspeed perturbations, the SST-wind relationship in the near-equatorial region feeds back positively on existing SST anomalies and gives rise to decadal variability.

  16. Evidencing decadal and interdecadal hydroclimatic variability over the Central Andes

    NASA Astrophysics Data System (ADS)

    Segura, Hans; Carlo Espinoza, Jhan; Junquas, Clementine; Takahashi, Ken

    2016-09-01

    In this study we identified a significant low frequency variability (8 to 20 years) that characterizes the hydroclimatology over the Central Andes. Decadal-interdecadal variability is related to the central-western Pacific Ocean (R 2 = 0.50) and the zonal wind at 200 hPa above the Central Andes (R 2 = 0.66). These two oceanic-atmospheric variables have a dominant decadal-interdecadal variability, and there is a strong relationship between them at a low frequency time scale (R 2 = 0.66). During warming decades in the central-western Pacific Ocean, westerlies are intensified at 200 hPa above the Central Andes, which produce decadal periods of hydrological deficit over this region. In contrast, when the central-western Pacific Ocean is cooler than usual, easterly anomalies prevail over the Central Andes, which are associated with decades of positive hydrological anomalies over this region. Our results indicate that impacts of El Niño on hydrology over the Central Andes could be influenced by the low frequency variability documented in this study.

  17. Two Decades (almost) of Keck Observations of Io

    NASA Astrophysics Data System (ADS)

    De Pater, I.; Davies, A. G.; de Kleer, K.

    2015-12-01

    We have regularly observed Io with the 10-m Keck Telescope since 1998, initially using the speckle imaging technique, and switching to Adaptive Optics techniques when this became available in 2001. In this talk we will discuss several eruptions that we witnessed, and present 20-30 year timelines of thermal emission from Pele, Pillan, Janus Patera, Kanehekili Fluctus, and Loki Patera, updating timelines in recent publications [1, 2] with additional Keck adaptive optics data obtained between 2002 and 2015. These new timelines are the most comprehensive plots ever produced of the volcanic thermal emission variability for these or any other locations on Io, utilizing data from multiple ground- and space-based assets. Our continuing multi-decadal observing program forms the basis for charting the variability of Io's volcanic activity, of great importance for understanding the evolution of the Galilean satellite system, and with the expectation of new missions to the jovian system in the next decade. Acknowledgements: This research is in part supported by NSF grant AST-1313485 to UC Berkeley. AGD is supported by a grant from the NASA OPR Program. References: [1] Davies et al. (2012) Icarus, 221, 466-470. [2] Rathbun and Spencer (2010) Icarus, 209, 625-630.

  18. Exploring the impact of CMIP5 model biases on the simulation of North Atlantic decadal variability

    NASA Astrophysics Data System (ADS)

    Menary, Matthew B.; Hodson, Daniel L. R.; Robson, Jon I.; Sutton, Rowan T.; Wood, Richard A.; Hunt, Jonathan A.

    2015-07-01

    Instrumental observations, paleoproxies, and climate models suggest significant decadal variability within the North Atlantic subpolar gyre (NASPG). However, a poorly sampled observational record and a diversity of model behaviors mean that the precise nature and mechanisms of this variability are unclear. Here we analyze an exceptionally large multimodel ensemble of 42 present-generation climate models to test whether NASPG mean state biases systematically affect the representation of decadal variability. Temperature and salinity biases in the Labrador Sea covary and influence whether density variability is controlled by temperature or salinity variations. Ocean horizontal resolution is a good predictor of the biases and the location of the dominant dynamical feedbacks within the NASPG. However, we find no link to the spectral characteristics of the variability. Our results suggest that the mean state and mechanisms of variability within the NASPG are not independent. This represents an important caveat for decadal predictions using anomaly assimilation methods.

  19. Decadal-Interdecadal SST Variability and Regional Climate Teleconnections

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Weng, H.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Dominant modes of decadal and interdecadal SST variability and their impacts on summertime rainfall variability over East Asia and the North America are studied. Two dominant modes of interdecadal SST variability, one associated with El Nino-like warming in the global oceans and one with an east-west seesaw variation in the equatorial Pacific have been identified. The first mode is associated in part with a long-term warming trend in the topical oceans and cooling over the northern Pacific. The second mode suggests an westward shift and strengthening of the Walker circulation from 1960s to the 1980s. Over East Asian, the first SST mode is correlated with reduced rainfall in northern China and excessive rainfall in central China. This SST mode is also associated with the tendency for increased rainfall over the midwest region, and reduced rainfall over the east Coast of the US. The results suggest a teleconnection pattern which links the occurrences of drought and floods over the Asian monsoon and the US summertime time climate. This teleconnection is likely to be associated with decadal variability of the East Asian jetstream, which are affected by strong land surface heating over the Siberian region, as well as El Nino-like SST forcings. The occurrences of major droughts and floods in the East Asian and US continent in recent decades are discussed in light of the above teleconnection patterns.

  20. Interannual to Decadal Variability of Outflow from the Labrador Sea

    NASA Astrophysics Data System (ADS)

    Visbeck, M.; Fischer, J.; Zantopp, R.; Nunes, N.

    2010-12-01

    A decade of weak convection in the Labrador Sea associated with decreasing water mass transformation, in combination with advective and eddy fluxes into the convection area, caused significant warming of the deep waters in both the central Labrador Sea and boundary current system along the Labrador shelf break. The connection to the export of Deep Water was studied based on moored current meter stations between 1998 and 2009 at the exit of the Labrador Sea, near the shelf break at 53 ° N. More than 100 year-long current meter records have been analyzed with respect to high frequency variability, decaying from the surface to the bottom layer, and for the annual mean flow, showing intra- to interannual variability but no detectable decadal trend in the strength of the deep and near bottom flow out of the Labrador Sea.

  1. Interannual to Decadal Variability of Ocean Evaporation as Viewed from Climate Reanalyses

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Bosilovich, Michael G.; Roberts, Jason B.; Wang, Hailan

    2015-01-01

    Questions we'll address: Given the uncoupled framework of "AMIP" (Atmosphere Model Inter-comparison Project) experiments, what can they tell us regarding evaporation variability? Do Reduced Observations Reanalyses (RedObs) using Surface Fluxes and Clouds (SFC) pressure (and wind) provide a more realistic picture of evaporation variability? What signals of interannual variability (e.g. El Nino/Southern Oscillation (ENSO)) and decadal variability (Interdecadal Pacific Oscillation (IPO)) are detectable with this hierarchy of evaporation estimates?

  2. Decadal variability of tropical tropopause temperature and its relationship to the Pacific Decadal Oscillation

    NASA Astrophysics Data System (ADS)

    Wang, Wuke; Matthes, Katja; Omrani, Nour-Eddine; Latif, Mojib

    2016-07-01

    Tropopause temperatures (TPTs) control the amount of stratospheric water vapour, which influences chemistry, radiation and circulation in the stratosphere, and is also an important driver of surface climate. Decadal variability and long-term trends in tropical TPTs as well as stratospheric water vapour are largely unknown. Here, we present for the first time evidence, from reanalysis and state-of-the-art climate model simulations, of a link between decadal variability in tropical TPTs and the Pacific Decadal Oscillation (PDO). The negative phase of the PDO is associated with anomalously cold sea surface temperatures (SSTs) in the tropical east and central Pacific, which enhance the zonal SST gradient across the equatorial Pacific. The latter drives a stronger Walker Circulation and a weaker Hadley Circulation, which leads to less convection and subsequently a warmer tropopause over the central equatorial Pacific. Over the North Pacific, positive sea level pressure anomalies occur, which damp vertical wave propagation into the stratosphere. This in turn slows the Brewer-Dobson circulation, and hence warms the tropical tropopause, enabling more water vapour to enter the stratosphere. The reverse chain of events holds for the positive phase of the PDO. Such ocean-troposphere-stratosphere interactions may provide an important feedback on the Earth’s global surface temperature.

  3. Decadal variability of tropical tropopause temperature and its relationship to the Pacific Decadal Oscillation

    PubMed Central

    Wang, Wuke; Matthes, Katja; Omrani, Nour-Eddine; Latif, Mojib

    2016-01-01

    Tropopause temperatures (TPTs) control the amount of stratospheric water vapour, which influences chemistry, radiation and circulation in the stratosphere, and is also an important driver of surface climate. Decadal variability and long-term trends in tropical TPTs as well as stratospheric water vapour are largely unknown. Here, we present for the first time evidence, from reanalysis and state-of-the-art climate model simulations, of a link between decadal variability in tropical TPTs and the Pacific Decadal Oscillation (PDO). The negative phase of the PDO is associated with anomalously cold sea surface temperatures (SSTs) in the tropical east and central Pacific, which enhance the zonal SST gradient across the equatorial Pacific. The latter drives a stronger Walker Circulation and a weaker Hadley Circulation, which leads to less convection and subsequently a warmer tropopause over the central equatorial Pacific. Over the North Pacific, positive sea level pressure anomalies occur, which damp vertical wave propagation into the stratosphere. This in turn slows the Brewer-Dobson circulation, and hence warms the tropical tropopause, enabling more water vapour to enter the stratosphere. The reverse chain of events holds for the positive phase of the PDO. Such ocean-troposphere-stratosphere interactions may provide an important feedback on the Earth’s global surface temperature. PMID:27404090

  4. Decadal variability of tropical tropopause temperature and its relationship to the Pacific Decadal Oscillation.

    PubMed

    Wang, Wuke; Matthes, Katja; Omrani, Nour-Eddine; Latif, Mojib

    2016-01-01

    Tropopause temperatures (TPTs) control the amount of stratospheric water vapour, which influences chemistry, radiation and circulation in the stratosphere, and is also an important driver of surface climate. Decadal variability and long-term trends in tropical TPTs as well as stratospheric water vapour are largely unknown. Here, we present for the first time evidence, from reanalysis and state-of-the-art climate model simulations, of a link between decadal variability in tropical TPTs and the Pacific Decadal Oscillation (PDO). The negative phase of the PDO is associated with anomalously cold sea surface temperatures (SSTs) in the tropical east and central Pacific, which enhance the zonal SST gradient across the equatorial Pacific. The latter drives a stronger Walker Circulation and a weaker Hadley Circulation, which leads to less convection and subsequently a warmer tropopause over the central equatorial Pacific. Over the North Pacific, positive sea level pressure anomalies occur, which damp vertical wave propagation into the stratosphere. This in turn slows the Brewer-Dobson circulation, and hence warms the tropical tropopause, enabling more water vapour to enter the stratosphere. The reverse chain of events holds for the positive phase of the PDO. Such ocean-troposphere-stratosphere interactions may provide an important feedback on the Earth's global surface temperature. PMID:27404090

  5. Multi-decadal Variability of the Wind Power Output

    NASA Astrophysics Data System (ADS)

    Kirchner Bossi, Nicolas; García-Herrera, Ricardo; Prieto, Luis; Trigo, Ricardo M.

    2014-05-01

    The knowledge of the long-term wind power variability is essential to provide a realistic outlook on the power output during the lifetime of a planned wind power project. In this work, the Power Output (Po) of a market wind turbine is simulated with a daily resolution for the period 1871-2009 at two different locations in Spain, one at the Central Iberian Plateau and another at the Gibraltar Strait Area. This is attained through a statistical downscaling of the daily wind conditions. It implements a Greedy Algorithm as classificator of a geostrophic-based wind predictor, which is derived by considering the SLP daily field from the 56 ensemble members of the longest homogeneous reanalysis available (20CR, 1871-2009). For calibration and validation purposes we use 10 years of wind observations (the predictand) at both sites. As a result, a series of 139 annual wind speed Probability Density Functions (PDF) are obtained, with a good performance in terms of wind speed uncertainty reduction (average daily wind speed MAE=1.48 m/s). The obtained centennial series allow to investigate the multi-decadal variability of wind power from different points of view. Significant periodicities around the 25-yr frequency band, as well as long-term linear trends are detected at both locations. In addition, a negative correlation is found between annual Po at both locations, evidencing the differences in the dynamical mechanisms ruling them (and possible complementary behavior). Furthermore, the impact that the three leading large-scale circulation patterns over Iberia (NAO, EA and SCAND) exert over wind power output is evaluated. Results show distinct (and non-stationary) couplings to these forcings depending on the geographical position and season or month. Moreover, significant non-stationary correlations are observed with the slow varying Atlantic Multidecadal Oscillation (AMO) index for both case studies. Finally, an empirical relationship is explored between the annual Po and the

  6. Societal Adaptation to Decadal Climate Variability in the United States

    NASA Astrophysics Data System (ADS)

    Rosenberg, Norman J.; Mehta, Vikram M.; Olsen, J. Rolf; von Storch, Hans; Varady, Robert G.; Hayes, Michael J.; Wilhite, Donald

    2007-10-01

    CRCES Workshop on Societal Impacts of Decadal Climate Variability in the United States, 26-28 April 2007, Waikoloa, Hawaii The search for evidence of decadal climatic variability (DCV) has a very long history. In the past decade, a research community has coalesced around a series of roughly biennial workshops that have emphasized description of past DCV events; their causes and their ``teleconnections'' responsible for droughts, floods, and warm and cold spells around the world; and recently, the predictability of DCV events. Researchers studying climate change put great emphasis on prospective impacts, but the DCV community has yet to do so. To begin rectifying this deficiency, a short but ambitious workshop was convened in Waikoloa, near Kona, Hawaii, from 26-28 April 2007. This workshop, sponsored by the Center for Research on the Changing Earth System (CRCES), NOAA, the U.S. Geological Survey, and the U.S. Army Corps of Engineers, brought together climatologists and sectoral specialists representing agriculture, water resources, economics, the insurance industry, and developing country interests.

  7. Atmospheric Blocking and Atlantic Multi-Decadal Ocean Variability

    NASA Technical Reports Server (NTRS)

    Haekkinen, Sirpa; Rhines, Peter B.; Worthlen, Denise L.

    2011-01-01

    Based on the 20th century atmospheric reanalysis, winters with more frequent blocking, in a band of blocked latitudes from Greenland to Western Europe, are found to persist over several decades and correspond to a warm North Atlantic Ocean, in-phase with Atlantic multi-decadal ocean variability. Atmospheric blocking over the northern North Atlantic, which involves isolation of large regions of air from the westerly circulation for 5 days or more, influences fundamentally the ocean circulation and upper ocean properties by impacting wind patterns. Winters with clusters of more frequent blocking between Greenland and western Europe correspond to a warmer, more saline subpolar ocean. The correspondence between blocked westerly winds and warm ocean holds in recent decadal episodes (especially, 1996-2010). It also describes much longer-timescale Atlantic multidecadal ocean variability (AMV), including the extreme, pre-greenhouse-gas, northern warming of the 1930s-1960s. The space-time structure of the wind forcing associated with a blocked regime leads to weaker ocean gyres and weaker heat-exchange, both of which contribute to the warm phase of AMV.

  8. Atmospheric Blocking and Atlantic Multi-Decadal Ocean Variability

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.

    2011-01-01

    Atmospheric blocking over the northern North Atlantic involves isolation of large regions of air from the westerly circulation for 5-14 days or more. From a recent 20th century atmospheric reanalysis (1,2) winters with more frequent blocking persist over several decades and correspond to a warm North Atlantic Ocean, in-phase with Atlantic multi-decadal ocean variability (AMV). Ocean circulation is forced by wind-stress curl and related air/sea heat exchange, and we find that their space-time structure is associated with dominant blocking patterns: weaker ocean gyres and weaker heat exchange contribute to the warm phase of AMV. Increased blocking activity extending from Greenland to British Isles is evident when winter blocking days of the cold years (1900-1929) are subtracted from those of the warm years (1939-1968).

  9. Surface Salinity Variability in the North Atlantic During Recent Decades

    NASA Technical Reports Server (NTRS)

    Haekkinen, Sirpa

    2001-01-01

    The sea surface salinity (SSS) variability in the North Atlantic is investigated using numerical model simulations for the last 50 years based on atmospheric forcing variability from Comprehensive Atmosphere Ocean Data Set (COADS) and National Center for Environmental Prediction / National Center for Atmospheric Research (NCEP/NCAR) Reanalysis. The largest interannual and longer term variability occurs in two regions: the Labrador Sea and the North Equatorial Countercurrent (NECC) region. In both regions the seasonality of the surface salinity variability is prominent with the maximum standard deviation occurring in the summer/fall period. In the Labrador Sea the summer SSS anomalies far exceed those of wintertime in amplitude. The interannual SSS variability in the subpolar gyre can be attributed to two factors: excess ice melt and heat flux (i.e. deep mixing) variations. On the other hand, heat flux variability can also lead to meridional overturning changes on decadal time scales such that weak overturning is manifested in fresh surface conditions in the subpolar gyre. The overturning changes also influence the NECC region SSS variability. Moreover, the subpolar freshening events are expected to occur during the negative phase of North Atlantic Oscillation which is associated with a weak wintertime surface heat loss in the subpolar gyre. No excess sea ice melt or precipitation is necessary for the formation of the fresh anomalies, because with the lack of wide-spread deep mixing, the fresh water that would be expected based on climatology, would accumulate at the surface. Thus, the fresh water 'conveyor' in the Atlantic operates via the overturning circulation such that deep mixing inserts fresh water while removing heat from the water column.

  10. Multi-decadal Variability of Indian Summer Monsoon in CMIP5 Models

    NASA Astrophysics Data System (ADS)

    Sandeep, S.; Ravindran, A.

    2013-12-01

    The multi-decadal variability of Indian Summer Monsoon (ISM) Rainfall in the fifth phase Coupled Model Inter-comparison Project (CMIP5) climate model simulations is analyzed. Recent studies, suggest a slight weakening of the Indian precipitation as assessed from CMIP3 simulations. The ISM rainfall simulated by CMIP5 runs with all historical forcing (AF) also suggest a strong multi-decadal weakening trend in ISM precipitation during 1901 - 2005. Further, the decadal scale variability in ISM land precipitation in multi model ensemble of AF simulations is fairly comparable with the observed variability. However, these simulations show patterns of regional variability and trends within the monsoon domain. The CMIP5 ensembles with natural variability alone and those with only Green House Gas (GHG) forcing could not reproduce the observed variability in ISM precipitation. This suggests strong influence of anthropogenic aerosols on multi-decadal variability in ISM precipitation, which is consistent with previous findings. Further investigation revealed that the weakening of zonal winds in AF simulations, possibly due to aerosol induced weakening in land-ocean thermal contrast, resulted in reduced moisture transport from ocean to the land. The trends and variability of ISM in multi model ensemble of CMIP5 simulations will be discussed in detail.

  11. Drivers of decadal variability in the Tasman Sea

    NASA Astrophysics Data System (ADS)

    Sloyan, Bernadette M.; O'Kane, Terence J.

    2015-05-01

    In this study, we compare optimally interpolated monthly time series Tasman Sea XBT data and a comprehensive set of ocean data assimilation models forced by atmospheric reanalysis to investigate the stability of the Tasman Sea thermocline and the transport variability of the East Australian Current (EAC), the Tasman Front, and EAC-extension. We find that anomalously weaker EAC transport at 25°S corresponds to an anomalously weaker Tasman Front and anomalously stronger EAC-extension. We further show that, post about 1980 and relative to the previous 30 years, the anomalously weaker EAC transport at 25°S is associated with large-scale changes in the Tasman Sea; specifically stronger stratification above the thermocline, larger thermocline temperature gradients, and enhanced energy conversion. Significant correlations are found between the Maria Island station Sea Surface Temperature (SST) variability and stratification, thermocline temperature gradient, and baroclinic energy conversion suggesting that nonlinear dynamical responses to variability in the basin-scale wind stress curl are important drivers of decadal variability in the Tasman Sea. We further show that the stability of the EAC is linked, via the South Caledonian Jet, to the stability of the pan-basin subtropical South Pacific Ocean "storm track."

  12. Extratropical Control of Recent Tropical Pacific Decadal Climate Variability: A relay teleconnection

    NASA Astrophysics Data System (ADS)

    Wu, L.; Liu, Z.; Li, C.

    2006-12-01

    Observations indicate that recent tropical Pacific decadal climate variability tends to originate from the extratropical North Pacific through a relay teleconnection of a fast coupled ocean-atmosphere process and a slow oceanic tunnel. A coupled ocean-atmosphere model, forced by the observed decadal wind in the extratropical North Pacific, explicitly demonstrates that extratropical decadal sea surface temperature (SST) anomalies may propagate to the tropics through a coupled wind-evaporative-SST (WES) feedback. The WES feedback can not only lead to a nearly synchronous change of equatorial SST, but also force a delayed adjustment of the meridional overturning circulation in the upper ocean to further sustain the tropical SST change.

  13. Stochastically-forced Decadal Variability in Australian Rainfall

    NASA Astrophysics Data System (ADS)

    Taschetto, A.

    2015-12-01

    Iconic Australian dry and wet periods were driven by anomalous conditions in the tropical oceans, such as the worst short-term drought in the southeast in 1982 associated with the strong El Niño and the widespread "Big Wet" in 1974 linked with a La Niña event. The association with oceanic conditions makes droughts predictable to some extent. However, prediction can be difficult when there is no clear external forcing such as El Niños. Can dry spells be triggered and maintained with no ocean memory? In this study, we investigate the potential role of internal multi-century atmospheric variability in controlling the frequency, duration and intensity of long-term dry and wet spells over Australia. Two multi-century-scale simulations were performed with the NCAR CESM: (1) a fully-coupled simulation (CPLD) and (2) an atmospheric simulation forced by a seasonal SST climatology derived from the coupled experiment (ACGM). Results reveal that droughts and wet spells can indeed be generated by internal variability of the atmosphere. Those internally generated events are less severe than those forced by oceanic variability, however the duration of dry and wet spells longer than 3 years is comparable with and without the ocean memory. Large-scale ocean modes of variability seem to play an important role in producing continental-scale rainfall impacts over Australia. While the Pacific Decadal Oscillation plays an important role in generating droughts in the fully coupled model, perturbations of monsoonal winds seem to be the main trigger of dry spells in the AGCM case. Droughts in the mid-latitude regions such as Tasmania can be driven by perturbations in the Southern Annular Mode, not necessarily linked to oceanic conditions even in the fully-coupled model. The mechanisms behind internally-driven mega-droughts and mega-wets will be discussed.

  14. Causes of Decadal Climate Variability over the North Pacific and North America.

    PubMed

    Latif, M; Barnett, T P

    1994-10-28

    The cause of decadal climate variability over the North Pacific Ocean and North America is investigated by the analysis of data from a multidecadal integration with a state-of-the-art coupled ocean-atmosphere model and observations. About one-third of the low-frequency climate variability in the region of interest can be attributed to a cycle involving unstable air-sea interactions between the subtropical gyre circulation in the North Pacific and the Aleutian low-pressure system. The existence of this cycle provides a basis for long-range climate forecasting over the western United States at decadal time scales. PMID:17793457

  15. Causes of decadal climate variability over the North Pacific and North America

    SciTech Connect

    Latif, M. ); Barnett, T.P. )

    1994-10-28

    The cause of decadal climate variability over the North Pacific Ocean and North America is investigated by the analysis of data from a multidecadal integration with a state-of-the-art coupled ocean-atmosphere model and observations. About one-third of the low-frequency climate variability in the region of interest can be attributed to a cycle involving unstable air-sea interactions between the subtropical gyre circulation in the North Pacific and the Aleutian low-pressure system. The existence of this cycle provides a basis for long-range climate forecasting over the western United States at decadal time scales. 17 refs., 5 figs.

  16. Multi-decadal water resource variations in France : connexion with the Altantic Multidecadal Variability

    NASA Astrophysics Data System (ADS)

    Habets, F.; Boe, J.; Dayon, G.

    2015-12-01

    Hydrological cycles have strong temporal variations. Analysis of the long-term observations can help detect trends that may be consistent with theses projected in the context of climate change and thus help awareness of stakeholders. However, one must remain cautious on the analysis of these trends when they are estimated on the basis of a few decades, because the water cycle can have strong multi-decadal variations. Indeed, in France, long observed series shown that river flows generally exhibit large multidecadal variation since the late 19th century to the present, especially in spring. Differences of means between 21 yr periods of the 20th century as large as 40% are indeed found for many gauging stations. Such multi decadal variations were also found on glaciers, but are difficult to detect on the groundwater resource, which might be linked to the recharge processes. Multi-decadal spring river flow variations are associated with variations in spring precipitation and temperature. These multi-decadal variations in precipitation are themselves found to be driven by large-scale atmospheric circulation, more precisely by a multi-decadal oscillation in a sea level pressure dipole between western Europe and the eastern Atlantic. It is suggested that the Atlantic Multidecadal Variability (AMV), the main mode of multi-decadal variability in the North Atlantic-Europe sector, controls those variations in large-scale circulation and is therefore the main ultimate driver of multi-decadal variations in spring river flows.Impact of such teleconnection for the management of the water resource is important, since the threshold alert used by stakeholder vary also at multi decadal scale. Moreover, such natural variabilities are not well reproduced by climate model, especially because of weak teleconnection between the simulated AMV and the simulated precipitation over France. Statistical methods could help correct such bias, and are currently assessed on the 20th century.

  17. Greenhouse warming, decadal variability, or El Nino? An attempt to understand the anomalous 1990s

    SciTech Connect

    Latif, M.; Eckert, C.; Kleeman, R.

    1997-09-01

    The dominant variability modes in the Tropics are investigated and contrasted with the anomalous situation observed during the last few years. The prime quantity analyzed is anomalous sea surface temperature (SST) in the region 30{degrees}S-60{degrees}N. Additionally, observed tropical surface wind stress fields were investigated. Further tropical atmospheric information was derived from a multidecadal run with an atmospheric general circulation model that was forced by the same SSTs. The tropical SST variability can be characterized by three modes: an interannual mode [the El Nino-Southern Oscillation (ENSO)], a decadal mode, and a trend or unresolved ultra-low-frequency variability. 48 refs., 20 figs.

  18. Decadal climate variability over the North Pacific and North America: Dynamics and predictability

    SciTech Connect

    Latif, M.; Barnett, T.P.

    1996-10-01

    The dynamics and predictability of decadal climate variability over the North Pacific and North America are investigated by analyzing various observation datasets and the output of a state of the art coupled ocean-atmosphere general circulation model that was integrated for 125 years. Both the observations and model results support the picture that the decadal variability in the regional of interest is based on a cycle involving unstable ocean-atmosphere interactions over the North Pacific. The period of this cycle is of the order of a few decades. The cycle involves the two major circulation regimes in the North Pacific climate system, the subtropical ocean gyre, and the Aleutian low. 41 refs., 18 figs.

  19. Extratropical control of recent tropical Pacific decadal climate variability: a relay teleconnection

    NASA Astrophysics Data System (ADS)

    Wu, Lixin; Liu, Zhengyu; Li, Chun; Sun, Yan

    2007-01-01

    Observations indicate that recent tropical Pacific decadal climate variability tends to be associated with the extratropical North Pacific through a relay teleconnection of a fast coupled ocean-atmosphere bridge and a slow oceanic tunnel. A coupled ocean-atmosphere model, forced by the observed decadal wind in the extratropical North Pacific, explicitly demonstrates that extratropical decadal sea surface temperature (SST) anomalies may propagate to the tropics through a coupled wind-evaporative-SST (WES) feedback. The WES feedback cannot only lead to a nearly synchronous change of tropical SST, but also force a delayed adjustment of the meridional overturning circulation in the upper ocean to further sustain the tropical SST change. The study further suggests that the extratropical tropical teleconnection provides a positive feedback to sustain the decadal changes in both the tropical and extratropical North Pacific.

  20. Role of the North Pacific sea surface temperature in the East Asian winter monsoon decadal variability

    NASA Astrophysics Data System (ADS)

    Sun, Jianqi; Wu, Sha; Ao, Juan

    2016-06-01

    In this study, a possible mechanism for the decadal variability in the East Asian winter monsoon (EAWM) is proposed. Specifically, the North Pacific sea surface temperature (SST) may play an important role. An analysis of the observations shows that the North Pacific SST has a remarkable decadal pattern whose phase shifted around the mid-1980s. This North Pacific SST decadal pattern can weaken the East Asian trough and enhance the North Pacific Oscillation through changing air-sea interactions over the North Pacific. The weak East Asian trough enhances the zonal circulation and weakens the meridional circulation over East Asia, consequently leading to a weaker southward cold surge and East Asia warming around the mid-1980s. The numerical experiment further confirms the pronounced physical processes. In addition, over the longer period of 1871-2012, the indices of the EAWM and North Pacific SST decadal pattern are also highly consistent on the decadal timescale, which further confirms the impact of the North Pacific SST decadal pattern on the EAWM decadal variability.

  1. Evidence for Large Decadal Variability in the Tropical Mean Radiative Energy Budget

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Wong, Takmeng; Allan, Richard; Slingo, Anthony; Kiehl, Jeffrey T.; Soden, Brian J.; Gordon, C. T.; Miller, Alvin J.; Yang, Shi-Keng; Randall, David R.; Arnold, James E. (Technical Monitor)

    2001-01-01

    It is widely assumed that variations in the radiative energy budget at large time and space scales are very small. We present new evidence from a compilation of over two decades of accurate satellite data that the top-of-atmosphere (TOA) tropical radiative energy budget is much more dynamic and variable than previously thought. We demonstrate that the radiation budget changes are caused by changes In tropical mean cloudiness. The results of several current climate model simulations fall to predict this large observed variation In tropical energy budget. The missing variability in the models highlights the critical need to Improve cloud modeling in the tropics to support Improved prediction of tropical climate on Inter-annual and decadal time scales. We believe that these data are the first rigorous demonstration of decadal time scale changes In the Earth's tropical cloudiness, and that they represent a new and necessary test of climate models.

  2. An Observation from Liver Biopsies Two Decades Post-Fontan.

    PubMed

    Evans, William N; Acherman, Ruben J; Reardon, Leigh C; Galindo, Alvaro; Rothman, Abraham; Ciccolo, Michael L; Carrillo, Sergio A; Winn, Brody J; Yumiaco, Noel S; Restrepo, Humberto

    2016-08-01

    This brief report describes an observation from liver biopsy results in nonfailing Fontan patients, currently in their second postoperative decade. In three patients, with either atriopulmonary or atrioventricular connections and functional left ventricles, we found no portal fibrosis. In contrast, we found portal fibrosis in three clinically similar, nonfailing Fontan patients with lateral tunnel connections and functional left ventricles. We recognize the results may be secondary to chance; nevertheless, we speculate about possible relevancy.

  3. Decade of balloon observations of auroral X-rays

    SciTech Connect

    Venkatesan, D.; Vij, K.K.

    1981-01-01

    The paper describes balloon observations of bremsstrahlung X-rays carried out by the University of Calgary over the past decade which deal with morphological studies of auroral electron precipitation. The program concentrated on the understanding of the correlation between parent electrons and secondary X-rays, the study of microbursts, east-west and north-south extent of electron precipitation, and precipitation during pulsating auroras.

  4. Arctic decadal variability: An auto-oscillatory system of heat and fresh water exchange

    NASA Astrophysics Data System (ADS)

    Dukhovskoy, Dmitry S.; Johnson, Mark A.; Proshutinsky, Andrey

    2004-02-01

    This paper presents a mechanism of decadal variability in the Artic Ocean-GIN Sea (Greenland, Iceland and Norwegian Seas) atmosphere-ice-ocean system. We hypothesize that Arctic variability is regulated by heat and freshwater exchange between the Arctic Ocean and the GIN Sea. The interaction between basins is weak during anticyclonic circulation regimes (low AO/NAO) and strong during cyclonic circulation regimes (high AO/NAO). Regime shifts are controlled by the system itself through oceanic and atmospheric gradients (dynamic height and surface air temperature) that increase during the anticyclonic regime and decrease during the cyclonic regime. This conceptual mechanism for Arctic decadal variability has been reproduced in a model experiment. Both model results and observational data support the suggested mechanism.

  5. The Relative Contribution of Internal and Model Variabilities to the Uncertainty in Decadal Climate Predictions

    NASA Astrophysics Data System (ADS)

    Strobach, Ehud; Bel, Golan

    2016-04-01

    Decadal climate predictions, which are initialized with observed conditions, are characterized by two main sources of uncertainties--internal and model variabilities. The former is due to the sensitivity of the models to the initial conditions, and the latter is due to the different predictions of different models. There is not much that can be done to reduce the internal variability; however, there are several methods for reducing the model variability--for example, using an ensemble weighted according to the past performance of the models rather than an equally weighted ensemble. Quantifying the contribution of each of these sources can help in assessing the potential reduction of the total uncertainty of these climate predictions. We used an ensemble of climate model simulations, from the CMIP5 decadal experiments, that includes different climate models and several initializations for each of the models, to analyze the uncertainties on a decadal time scale. Time series of the monthly and annual means of the surface temperature and wind components were established for the variability analysis. The analysis focused on the contributions of the internal and model variabilities and the total uncertainty. We found that different definitions of the anomaly resulted in different conclusions regarding the variability of the ensemble. However, some features of the uncertainty were common to all the anomalies we considered. In particular, we found that (i) over decadal time scales, there is no considerable increase in the uncertainty with time; (ii) the model variability is more sensitive to the annual cycle than the internal variability (this, in turn, results in a maximal uncertainty during the winter in the northern hemisphere); (iii) the uncertainty of the surface temperature prediction is dominated by the model variability, whereas the uncertainty of the surface wind components is determined by both the model and the internal variabilities. Analysis of the spatial

  6. Decadal-scale Holocene climate variability in the Nordic seas

    NASA Astrophysics Data System (ADS)

    Koc, N.; Andersen, C.; Andrews, J.; Jennings, A.

    2003-04-01

    Sea-surface temperatures (SST) at decadal resolution have been reconstructed from core MD 95-2011, core MD 99-2269 and core BS88-6-5A based on diatom transfer functions. Core MD 95-2011 is located on the Vöring Plateau (66^o58.18N; 07^o38.36E, 1050 m water depth) along the main axis of the northward flowing warm Atlantic water. It is, therefore, in an ideal position to monitor changes in the northward heat flux to northwestern Europe. Core MD 99-2269 is located in the deep Hunafloi trough, off N Iceland (66^o37.53N; 20^o51.16W, 365 m water depth). Today the core lies under the influence of the Irminger current, but it also may be influenced by the cold East Greenland current (EGC) as the Polar front migrates eastward. Core BS88-6-5A is located on the East Greenland shelf (67^o07.54N; 30^o54.26W, 707 m water depth) and is influenced by the EGC. The cores has been dated by AMS C-14 and Pb 210 isotope profiles. SST variations are estimated by means of 3 different diatom transfer function methods. Results indicate a division of the Holocene into three periods and a climate development in step with the decreasing Northern Hemisphere insolation. However, regional differences between the surface currents occur regarding both timing and magnitude of changes. Superimposed on the general Holocene cooling trend there is a high frequency SST variability, which is in the order of 1--1.5 degrees C for the Vöring Plateau and the East Greenland shelf, and 2.5--3 degrees C for the North Iceland shelf. There is clear evidence for late Holocene climatic events such as the "Little Ice Age" and the "Medieval Warm Period". Timing of late Holocene climatic events at the eastern versus western Nordic Seas will be discussed.

  7. Estimating the limit of decadal-scale climate predictability using observational data

    NASA Astrophysics Data System (ADS)

    Ding, Ruiqiang; Li, Jianping

    2016-04-01

    Current coupled atmosphere-ocean general circulation models (CGCMs) can not simulate decadal variability well, and model errors would have a significant impact on the estimation of decadal predictability. In this study, the nonlinear local Lyapunov exponent (NLLE) method is adopted to estimate the limit of decadal predictability based on 9-yr low-pass filtered sea surface temperature (SST) and sea level pressure (SLP) observations. The results show that the limit of decadal predictability of the SST field is relatively large in the North Atlantic, North Pacific, Southern Ocean, tropical Indian Ocean, and western North Pacific, exceeding 7 years at most locations in these regions. In contrast, the limit of the SST field is relatively small in the tropical central-eastern Pacific (4-6 years). Similar to the SST field, the SLP field has a relatively large limit of decadal predictability over the Antarctic, North Pacific, and tropical Indian Ocean (>6 years). In addition, a relatively large limit of decadal predictability of the SLP field also occurs over the land regions of Africa, India, and South America. Distributions of the limit of decadal predictability of both the SST and SLP fields are almost consistent with those of their intensity and persistence on decadal timescales. By examining the limit of decadal predictability of several major climate modes, we found that the limit of decadal predictability of the Pacific Decadal Oscillation (PDO) is about 9 years, slightly lower than that of the Atlantic Multidecadal Oscillation (AMO) (about 11 years). In contrast, the Northern and Southern Annular Modes (NAM and SAM) have limits of decadal predictability of about 4 and 9 years, respectively. However, the above limits estimated using time-filtered data may overestimate the predictability of decadal variability due to the use of time filtering. Filtered noise with the same spectral characteristics as the PDO and AMO, has a predictability of about 3 years. Future work

  8. Estimating the limit of decadal-scale climate predictability using observational data

    NASA Astrophysics Data System (ADS)

    Ding, Ruiqiang; Li, Jianping; Zheng, Fei; Feng, Jie; Liu, Deqiang

    2016-03-01

    Current coupled atmosphere-ocean general circulation models can not simulate decadal variability well, and model errors would have a significant impact on the estimation of decadal predictability. In this study, the nonlinear local Lyapunov exponent method is adopted to estimate the limit of decadal predictability based on 9-year low-pass filtered sea surface temperature (SST) and sea level pressure (SLP) observations. The results show that the limit of decadal predictability of the SST field is relatively large in the North Atlantic, North Pacific, Southern Ocean, tropical Indian Ocean, and western North Pacific, exceeding 7 years at most locations in these regions. In contrast, the limit of the SST field is relatively small in the tropical central-eastern Pacific (4-6 years). Similar to the SST field, the SLP field has a relatively large limit of decadal predictability over the Antarctic, North Pacific, and tropical Indian Ocean (>6 years). In addition, a relatively large limit of decadal predictability of the SLP field also occurs over the land regions of Africa, India, and South America. Distributions of the limit of decadal predictability of both the SST and SLP fields are almost consistent with those of their intensity and persistence on decadal timescales. By examining the limit of decadal predictability of several major climate modes, we found that the limit of decadal predictability of the Pacific decadal oscillation (PDO) is about 9 years, slightly lower than that of the Atlantic multidecadal oscillation (AMO) (about 11 years). In contrast, the northern and southern annular modes have limits of decadal predictability of about 4 and 9 years, respectively. However, the above limits estimated using time-filtered data may overestimate the predictability of decadal variability due to the use of time filtering. Filtered noise with the same spectral characteristics as the PDO and AMO, has a predictability of about 3 years. Future work is required with a longer

  9. Climate variability in the North Atlantic on decadal and multi-decadal time scales: A numerical study

    NASA Astrophysics Data System (ADS)

    Cheng, Wei

    The goal of this work is to understand the mechanisms that drive the decadal and multi-decadal climate variability in the North Atlantic. Natural climate variability on these particular time scales occupies a central position in discussions of anthropogenic climate changes, but many aspects related, to this issue are still poorly understood. The major tool used in this study is a coupled general circulation model consisting of the NCAR CCM3 and the Miami Isopycnic Coordinate Ocean Model. The simulated decadal variability in the North Atlantic is dominated by a tri-pole pattern in sea surface temperature and a North Atlantic Oscillation (NAO) pattern in sea level pressure. The associated oceanic fluctuations are characterized by a delayed subtropical gyre response to anomalou's NAO surface wind stress forcing and advection of SST anomalies originating near the western boundary into the interior ocean. Separate ocean-alone experiments suggest that the SST variability can not be attributed solely to passive response of the ocean to atmospheric thermal forcing. It is also found that a quasi-oscillatory fluctuation of the thermohaline circulation (THC) in the North Atlantic ocean with an approximate time scale of 30 years is present in the coupled but not in uncoupled simulations. The latter were forced with either Newtonian relaxation boundary conditions (based on a monthly climatology of the atmospheric state variables such as the surface air temperature and surface specific humidity) or with imposed monthly varying heat and fresh water flux conditions. These results suggest that the variability of the THC in this model is neither an ocean internal phenomenon nor a passive response of the ocean to atmospheric forcing. Rather, it is a coupled process involving both the ocean and the atmosphere. The THC oscillation appears to be driven by surface heat flux forcings while the effects of surface fresh water fluxes are secondary. Two delay effects are crucial for

  10. Teleconnections force interannual-to-decadal tidal variability in the Lagoon of Venice (northern Adriatic)

    NASA Astrophysics Data System (ADS)

    Zanchettin, D.; Rubino, A.; Traverso, P.; Tomasino, M.

    2009-04-01

    In the present investigation, for the first time, fundamental characteristics of autumn and winter average sequences of sea level heights (SLH) that were recorded in the Lagoon of Venice (northern Adriatic, in the Mediterranean Sea) during the period 1872-2004 are investigated. Interannual-to-decadal variability of Venetian SLH is found to reflect the variability of the most prominent Euro-Atlantic teleconnections (EATs). In particular, the North Atlantic Oscillation (NAO), the East Atlantic/Western Russian, and the Scandinavian patterns are found to contribute to generate the ˜5-year, ˜8-year and ˜22-year peaks that dominate the spectra of seasonal Venetian SLH. Among the possible oceanic and atmospheric phenomena downscaling interannual-to-decadal large-scale atmospheric signals into the observed variability in the Venetian SLH, we explore inverse barometer effect, wind-driven setup, and the thermohaline circulation of both the Adriatic and the Mediterranean seas. All these phenomena are assessed to display some of the typical features of the shared interannual-to-decadal variability of both Venetian SLH and EATs. Our analysis shows also that the decadal variability of winter Venetian SLH is closely linked with variations in solar activity: in particular, the winter SLH multidecadal pattern is found to be correlated, with very high statistical confidence, to the Hale Cycles pattern (˜22 years), which describes the series of sunspot cycles with alternating opposite polarity. The marked signature of Hale Cycles on the leading mode of multidecadal sea level pressure winter variability (which is practically indistinguishable from the inverse wintertime NAO) is also detailed to further support the hypothesis of a Sun-Venetian SLH association.

  11. IUE observations of young variables

    NASA Technical Reports Server (NTRS)

    Gahm, G. F.

    1981-01-01

    A number of far UV spectrograms of young variable stars have become available through observations with the IUE satellite. Several T Tauri stars and Herbig type Be- and Ae-stars in dark nebulae were observed and spectrograms of a total of 17 stars, which were considered to be very young pre-main-sequence stars, were collected. In many of these cases only part of the spectral region available at the IUE is covered and there are examples where large spectral regions are severely underexposed. With a few exceptions, the stars have been observed with the low resolution cameras, providing spectra resolutions of 6 to 7 A.

  12. Evidence for multiple drivers of North Atlantic multi-decadal climate variability using CMIP5 models

    NASA Astrophysics Data System (ADS)

    Terray, L.

    2012-12-01

    Observed North Atlantic Ocean surface temperatures have changed in a non-monotonic and non-uniform fashion over the last century. While future North Atlantic decadal-to-multi-decadal climate change will be driven by a combination of internal variability and anthropogenic as well as natural forcings, the relative importance of these effects is still unclear for the 20th century [Ting et al., 2009; Knight 2009; Ottera et al. 2010; DelSole et al., 2011; Booth et al. 2012]. Here we assess the relative roles of greenhouses gases, anthropogenic aerosols, natural forcings and internal variability to the North Atlantic surface temperature decadal fluctuations using CMIP5 multi-model historical simulations driven by estimates of observed external forcings. While the latter are the main source of decadal variability in the tropics and subtropics, there is a large contribution from the unforced component to subpolar Atlantic variations. Reconstruction of forced response patterns suggests that anthropogenic forcings are the main causes of the accelerated warming of the last three decades while internal variability has a dominant contribution to the early 20th-century temperature multi-decadal swings and recent abrupt changes in the subpolar Atlantic. Significant inter-model spread with regard to the spatial response patterns to anthropogenic forcing leads to substantial uncertainty as to robust attribution statements for the mid-to-late 20th century North Atlantic warm and cold periods. Comparing internal variability from preindustrial simulations with that estimated from the observed residual after removing the best estimate of the total forced response leads to a consistency metric which allows to identify models with a biased forced response.; CMIP5 multi-model ratio (ρ_LF) of the externally forced -natural and anthropogenic- variance, σ_EF to the total variance, σ_T, of fluctuations with a period greater than 10 years. Stippling indicates regions where the null

  13. Decadal variability in PMCs and implications for changing temperature and water vapor in the upper mesosphere

    NASA Astrophysics Data System (ADS)

    Hervig, Mark E.; Berger, Uwe; Siskind, David E.

    2016-03-01

    Observations of polar mesospheric clouds (PMC) from the solar backscatter ultraviolet (SBUV) satellite instruments are used to characterize variability and trends from 1979 to 2014. The SBUV PMC record indicates decadal oscillations during the 1980s and 1990s, which are expected to result from the 11 year solar cycle. This oscillation is absent in the recent decade, however, and we speculate that solar cycle effects at PMC altitudes during the 1980s and 1990s may have been fortuitously amplified by stratospheric warming due to volcanic eruptions which occurred near solar maximum. SBUV trend results are compared with temperature, water vapor, and PMCs from the Mesospheric Ice Microphysics and Transport (MIMAS) model. Both SBUV and the model indicate positive trends in PMC vertically integrated water content (IWC), which increase toward higher latitudes. Using analysis of Solar Occultation for Ice Experiment (SOFIE) observations, the SBUV IWC trends are expressed in terms of the underlying changes in temperature and water vapor in the upper mesosphere. SBUV indicates cooling trends that increase toward higher latitudes (-0.5 ± 0.2 K decade-1 at 77°N), consistent with the MIMAS model and scant observations. SBUV indicates increasing water vapor in the Northern Hemisphere upper mesosphere (0.07 ± 0.03 ppmv decade-1 at 77°N, insignificant in the Southern Hemisphere), with values that are consistent with MIMAS but less than expected due to increasing methane.

  14. Estimating decadal variability in sea level from tide gauge records: an application to the North Sea.

    NASA Astrophysics Data System (ADS)

    Riva, R.; Frederikse, T.; Slobbe, C.; Broerse, T.; Verlaan, M.

    2015-12-01

    One of the primary observational datasets of sea level is represented by the tide gauge record. We propose a new method to estimate trends and variability on decadal time scales from tide gauge data by using a state space formulation, which couples the direct observations to a predefined state space model by using a Kalman filter. The model consists of a time-varying trend and seasonal cycle, and variability induced by several physical processes, such as wind, atmospheric pressure changes and teleconnection patterns. This model has two advantages over the classical least-squares method that uses regression to explain variations due to known processes: a seasonal cycle with time-varying phase and amplitude can be estimated, and the trend is allowed to vary over time. This time-varying trend consists of a secular trend and low-frequency variance that is not explained by any other term in the model. As a test case, we have used tide gauge data from stations around the North Sea over the period 1980-2013. We compare a model that only estimates a trend with two models that also remove intra-annual variability: one by means of time series of wind stress and sea level pressure, and one by using a two-dimensional hydrodynamic model. Explaining variability significantly improves the accuracy of the found decadal variability signal, where the best results are obtained with the hydrodynamic model. We find a consistent decadal sea level signal in the North Sea, which significantly influences estimates of a linear trend over the 34-year period.

  15. The leading modes of decadal SST variability in the Southern Ocean in CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Dommenget, Dietmar

    2016-09-01

    The leading modes of Sea Surface Temperature variability in the Southern Ocean on decadal and even larger time scales are analysed using Coupled Model Intercomparison Project 5 (CMIP5) model simulations and observations. The analysis is based on Empirical Orthogonal Function modes of the CMIP5 model super ensemble. We compare the modes from the CMIP5 super ensemble against several simple null hypotheses, such as isotropic diffusion (red noise) and a Slab Ocean model, to investigate the sources of decadal variability and the physical processes affecting the characteristics of the modes. The results show three main modes in the Southern Ocean: the first and most dominant mode on interannual to decadal time scales is an annular mode with largest amplitudes in the Pacific, which is strongly related to atmospheric forcing by the Southern Annular Mode and El Nino Southern Oscillation. The second mode is an almost basin wide monopole pattern, which has pronounced multi-decadal and longer time scales variability. It is firstly inducted by the Wave-3 patterns in the atmosphere and further developed via ocean dynamics. The third mode is a dipole pattern in the southern Pacific that has a pronounced peak in the power spectrum at multi-decadal time scales. All three leading modes found in the CMIP5 super model have distinct patterns and time scale behaviour that can not be explained by simple stochastic null hypothesis, thus all three leading modes are ocean-atmosphere coupled modes and are likely to be substantially influenced or driven by ocean dynamical processes.

  16. Atmospheric response to Arctic sea ice loss moderated by (multi-) decadal ocean variability

    NASA Astrophysics Data System (ADS)

    Screen, J.; Francis, J. A.; Osborne, J. M.; Collins, M.

    2015-12-01

    Increasing evidence suggests that ongoing reductions of Arctic sea ice may affect various aspects of Northern Hemisphere weather and climate. Many of these linkages have been hypothesized based on statistical associations found in observations; however, it is difficult to unambiguously assign causality and to separate the influences of multiple interconnected processes in the climate system using observations alone. Modeling studies offer a way forward for understanding and isolating the physical processes underlying observed relationships. The atmospheric response to Arctic sea ice loss is often estimated through atmospheric general circulation model (AGCM) simulations with prescribed sea ice and sea surface temperature (SST) conditions. Typically, global SSTs are held to climatological-mean values. It is well known however, that (multi-) decadal ocean variability has a strong influence on the mean atmospheric state and thus, the atmospheric response to sea ice loss may be sensitive to the phase of (multi-) decadal ocean variability (i.e., be state dependent). Here we explore the atmospheric response to Arctic sea ice loss under different phases of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), using 8 ensembles of AGCM simulations; with extensive and reduced Arctic sea ice applied alongside PDO-, PDO+, AMO- and AMO+ SST anomalies. Preliminary analyses suggest, amongst other things: 1) an enhanced Arctic winter warming response during PDO- compared to PDO+; and 2) during AMO- sea ice loss forces a wintertime ridge-trough pattern over North America, with warmer conditions over the west and colder conditions over the east, compared to the response to identical sea ice loss during AMO+. The largest observed losses of Arctic sea ice have occurred since ~2000 during predominantly PDO- and AMO+. The possible implications of the recent switch to PDO+ in 2014, and an eventual return to AMO+ in coming decades, will be discussed.

  17. The Leading Modes of Decadal SST Variability in the Southern Ocean in CMIP5 Simulations

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Dommenget, Dietmar

    2016-04-01

    The leading modes of Sea Surface Temperature (SST) variability in the Southern Ocean on decadal and even larger time scales are analysed using Coupled Model Intercomparison Project 5 (CMIP5) model simulations and observations. We compare the modes from the CMIP5 super ensemble against several simple null hypotheses, such as isotropic diffusion (red noise) and a Slab Ocean model, to investigate the sources of decadal variability and the physical processes affecting the characteristics of the modes. The results show three main modes in the Southern Ocean: the first and most dominant mode on interannual to decadal time scales is an annular mode with largest amplitudes in the Pacific, which is strongly related to atmospheric forcing by the Southern Annular Mode (SAM) and El Nino Southern Oscillation (ENSO). The second mode is an almost basin wide monopole pattern, which has pronounced multi-decadal and longer time scales variability. It is firstly inducted by the Wave-3 patterns in the atmosphere and further developed via ocean dynamics. The third mode is a dipole pattern in the southern Pacific that has a pronounced peak in the power spectrum at multi-decadal time scales. All three leading modes found in the CMIP5 super model have distinct patterns and time scale behaviour that can not be explained by simple stochastic null hypothesis, thus all three leading modes are ocean-atmospheric coupled modes and are likely to be substantially influenced or driven by ocean dynamical processes. The mechanism of the basin-wide mode is further analysed based on a series of idealized experiments. The results show that the monopole mode has a two-step power spectrum, with a first spectral increase on interannual time scale and a second higher up level on the multi-decadal to centennial time scales. Ocean dynamics, especially the ocean advection, transport the anomalous signals, connect the entire ocean and lead to the homogeneous-like spatial pattern even under stochastic

  18. Decadal variability of NAO during the last millennium inferred from Saharan dust in Alpine ice

    NASA Astrophysics Data System (ADS)

    Schwikowski, Margit; Sigl, Michael; Gäggeler, Heinz W.; Gabrieli, Jacopo; Barbante, Carlo; Boutron, Claude

    2010-05-01

    Interannual variability of North African atmospheric dust is strongly linked to drought conditions in the Sahel and to the winter North Atlantic Oscillation (NAO). Dust generation and transport are enhanced during winter NAO(+) phases when the North African dust source regions are controlled by high pressure situations leading to less precipitation, and thus to stronger wind erosion of soil material. However, direct Saharan dust observations are limited to the last decades only. Here, we present a first highly resolved ice core record of Saharan dust from the Alps, spanning the last 1,000 years. We focus thereby on concentrations of Fe, Al, Sr, and Ca which are typical elements present in long-range transported Saharan dust. We show that the mineral dust transport to the Southern Alps is primarily controlled by drought conditions in Northern Africa and by the winter NAO. Mean dust concentrations of the last 20 years are unprecedented in the context of the last 1,000 years. These elevated Saharan dust concentrations are consistent with the observed widespread increase in dustiness and dust storm frequencies over Northern Africa from direct measurements or from satellite based observations over the last decades. In contrast, between AD 1050 and 1400, when persistent arid conditions in the main source regions of dust in Northern Africa were deduced from tree-ring data and linked to a pervasive positive NAO mode over centuries, no according imprint is recorded in the ice core mineral dust record. We assume that the low-frequency variability of the tree-ring based reconstruction of Moroccan droughts (which also form the basis for the NAO reconstruction) is biased by the method applied to remove the non-climatic growth trends from the tree-ring series. Based on the ice core data we suggest that decadal-scale variability of the NAO (Moroccan droughts) prevailed over the last 1,000 years.

  19. Decadal Variability of Tropical Cyclone Annual Frequency in Different Ocean Basins

    NASA Astrophysics Data System (ADS)

    Zhao, Y.

    2015-12-01

    Yating Zhao1, Jing Jiang1 1 School of Atmospheric Sciences, Nanjing University Nanjing 210093 China Abstract: Tropical cyclone, one of the most severe global natural disasters, causes massive casualties and economic losses every year, greatly influences the rapid development of the modern society. Using hurricane best track data from JTWC and TPC we investigate the decadal variations of TC activities. Our research indicates that the variability of TC frequency of different ocean basins (North Indian Ocean (NIO), Northwest Pacific Ocean (WP), Northeast Pacific Ocean (NEP), North Atlantic Ocean (NA) and South Hemisphere (SH)) all have significant decadal periods, and these decadal signals have something connect with the Pacific Decadal Oscillation (PDO), which acting as the background, modulating and influencing the synoptic scale weather systems. Through diagnosing the oceanic and atmospheric circulation in different stages of PDO, we find that, as the PDO signal transmits through the Pacific Ocean, the atmospheric circulation changes accordingly all over the tropical ocean. And they influence the dynamic conditions in the troposphere and promote or restrain the tropical cyclone activities in these areas. In another word, in the positive phase of PDO, there are much more (less) TC activities observed over the NEP (NA, WP, NIO, SH), which very likely due to the favorable (unfavorable) environmental factors, such as higher (lower) SST, weaker (stronger) vertical wind shear, higher (lower) relative humidity in the middle level of troposphere, and low level positive (negative) vorticity in the local area. Meanwhile, what should be noted is that the primary environmental factor could be very different in different ocean basin. Keywords: tropical cyclone, decadal variability, PDO

  20. Decadal variability of chlorophyll a in the South China Sea: a possible mechanism

    NASA Astrophysics Data System (ADS)

    Liu, Fenfen; Chen, Chuqun; Zhan, Haigang

    2012-11-01

    Four climatologies on a monthly scale (January, April, May and November) of chlorophyll a within the South China Sea (SCS) were calculated using a Coastal Zone Color Scanner (CZCS) (1979-1983) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (1998-2002). We analyzed decadal variability of chlorophyll a by comparing the products of the two observation periods. The relationships of variability in chlorophyll a with sea surface wind speed (SSW), sea surface temperature (SST), wind stress (WS), and mixed layer depth (MLD) were determined. The results indicate that there is obvious chlorophyll a decadal variability in the SCS. The decadal chlorophyll a presents distinct seasonal variability in characteristics, which may be as a result of various different dynamic processes. The negative chlorophyll a concentration anomaly in January was associated with the warming of SST and a shallower MLD. Generally, there were higher chlorophyll a concentrations in spring during the SeaWiFS period compared with the CZCS period. However, the chlorophyll a concentration exhibits some regional differences during this season, leading to an explanation being diffi cult. The deepened MLD may have contributed to the positive chlorophyll a concentration anomalies from the northwestern Luzon Island to the northeastern region of Vietnam during April and May. The increases of chlorophyll a concentration in northwestern Borneo during May may be because the stronger SSW and higher WS produce a deeper mixed layer and convective mixing, leading to high levels of nutrient concentrations. The higher chlorophyll a off southeastern Vietnam may be associated with the advective transport of the colder water extending from the Karimata Strait to southeastern Vietnam.

  1. Decadal variability in coupled sea-ice-thermohaline circulation systems

    SciTech Connect

    Yang, J.; Neelin, J.D.

    1997-12-01

    An interdecadal oscillation in a coupled ocean-ice system was identified in a previous study. This paper extends that study to further examine the stability of the oscillation and the sensitivity of its frequency to various parameters and forcing fields. Three models are used: (i) an analytical box model; (ii) a two-dimensional model for the ocean thermohaline circulation (THC) coupled to a thermodynamic ice model, as in the authors` previous study; and (iii) a three-dimensional ocean general circulation model (OGCM) coupled to a similar ice model. The box model is used to elucidate the essential feedbacks that give rise to this oscillation and to identify the most important parameters and processes that determine the period. The counted model becomes more stable toward low coupling, greater diffusion, and weaker THC feedback. Nonlinear effects in the sea-ice model become important in the higher ocean-ice coupling regime where the effective sea-ice damping associated with this nonlinearity stabilizes the model. The 3D OGCM is used to test this coupled ocean-ice mechanism in a more realistic model setting. This model generates an interdecadal oscillation whose characteristics and phase relations among the model variables are similar to the oscillation obtained in the 2D models. The major difference is that the oscillation frequency is considerably lower. The difference can be explained in terms of the analytical box model solution in which the period of oscillation depends on the rate of anomalous density production by melting/cooling of sea ice per SST anomaly, times the rate of warming/cooling by anomalous THC heat advection per change in density anomaly. The 3D model has a smaller THC response to high-latitude density perturbations than the 2D model, and anomalous velocities in the 3D case tend to follow the mean isotherms so anomalous heat advection is reduced. This slows the ocean-ice feedback process, leading to the longer oscillation period. 36 refs., 27 figs.

  2. IUE observations of cataclysmic variable

    NASA Technical Reports Server (NTRS)

    Szkody, Paula

    1993-01-01

    Twenty two approved International Ultraviolet Explorer (IUE) programs were studied over a 14 year period. These programs are listed. The observations and subsequent analysis centered on cataclysmic variables (close binaries with a late main sequence star transferring material to a primary white dwarf via an accretion disk). The early studies highlighted the flux distribution of the accretion disk at outburst and quiescence, while later studies accomplished time-resolved observations throughout the orbital cycles, the study of the outflowing winds present at outburst, the study of the white dwarf in those systems with low accretion rate. There are 39 publications resulting from this work which are listed. These results include those for individual systems (Stepanian's star, Lanning 10, AM Her, MV Lyr, TV Col, VW Hyi, T Leo, IR Gem, TT Ari, Z Cam, BV Pup, IP Peg, PG1030+590, V1315 Aql, SW UMa, V426 Oph, WZ Sge, BY Cam, and U Gem) as well as review articles in journals and publications from reviews at meetings that summarize the impact of IUE on the study of accretion disks, white dwarfs, and hot spots resulting from stream impact as well as magnetic accretion columns.

  3. IUE observations of cataclysmic variable

    NASA Astrophysics Data System (ADS)

    Szkody, Paula

    1993-06-01

    Twenty two approved International Ultraviolet Explorer (IUE) programs were studied over a 14 year period. These programs are listed. The observations and subsequent analysis centered on cataclysmic variables (close binaries with a late main sequence star transferring material to a primary white dwarf via an accretion disk). The early studies highlighted the flux distribution of the accretion disk at outburst and quiescence, while later studies accomplished time-resolved observations throughout the orbital cycles, the study of the outflowing winds present at outburst, the study of the white dwarf in those systems with low accretion rate. There are 39 publications resulting from this work which are listed. These results include those for individual systems (Stepanian's star, Lanning 10, AM Her, MV Lyr, TV Col, VW Hyi, T Leo, IR Gem, TT Ari, Z Cam, BV Pup, IP Peg, PG1030+590, V1315 Aql, SW UMa, V426 Oph, WZ Sge, BY Cam, and U Gem) as well as review articles in journals and publications from reviews at meetings that summarize the impact of IUE on the study of accretion disks, white dwarfs, and hot spots resulting from stream impact as well as magnetic accretion columns.

  4. Interannual and decadal-scale variability of soil moisture and water resources in Africa

    NASA Astrophysics Data System (ADS)

    Thomas, E.; Jung, M.; Wattenbach, M.; Heinke, J.; Weber, U.

    2013-12-01

    Within water scarce regions such as the African continent, water availability is a fundamental factor for both ecosystems and human population. In particular the various ecoregions are highly vulnerable to climate change as seen in the recent drought in 2011, which affected the entire East African region and forced severe food crises causing the death of thousands of people. Several climate change scenarios associated with the expected population growth revealed an additional pressure on water availability, water accessibility and water demand in Africa in the future. In order to prevent, adapt and to mitigate climate change impacts (e.g. increasing water scarcity in the future) on soil moisture variability and water resources synthesis of its recent variations are extremely important. Unfortunately, there is currently no synthesis that highlights recent variations of soil moisture and fresh water resources in Africa. The aim of the study is to identify regions with large inter annual variability as well as decadal scale variability (trend, trend changes) of soil moisture and water resources. Hence, especially patterns of soil moisture and water resources variability will be demonstrated and implications in terms of vulnerability will be further discussed. The study comprises three different data sources: point measurements, remote sensing datasets and modelling results. Soil moisture observations from passive microwave radiometry (TRMM, AMSRE-E) and GRACE-derived terrestrial water storage were applied to locate areas which show a large inter annual variability. Supplementary, water level fluctuations from SAR altimetry (LEGOS/GOHS, ENVISAT) and in-situ runoff observations (SA FRIEND) provided by the Global Runoff Data Centre were used to confirm the encountered patterns of soil moisture and water resources variability. The spatial map of inter annual variability was subsequently overlaid by population density and land use data to assess the vulnerability of the

  5. Decadal variability in the occurrence of wintertime haze in central eastern China tied to the Pacific Decadal Oscillation.

    PubMed

    Zhao, Sen; Li, Jianping; Sun, Cheng

    2016-01-01

    Haze is a serious issue in China with increasing concerns, and understanding the factors driving decadal-scale variations in haze occurrence is relevant for government policymaking. Using a comprehensive observational haze dataset, we demonstrate notable decadal fluctuations in the number of haze days (HD) during winter in central eastern China, showing a decline since the mid-1980s. The leading mode of the wintertime HD features an increasing trend for 1959-2012 in eastern China, highly correlated with China's gross domestic product (GDP) that represents increasing trend of pollutant emissions, and to a lesser extent meteorological factors. The second mode shows decadal variations in central eastern China associated with Pacific Decadal Oscillation (PDO). Observations and numerical simulations suggest that Mongolia High and corresponding descending motion tend to be enhanced (weakened) in central eastern China during the positive (negative) phase of PDO. With PDO shifting towards a negative phase, the weakened Mongolia High and ascending anomalies make the air unstable and conduce to the spread of pollutants, leading to the decline in the wintertime HD over central eastern China since the mid-1980s. Based on above physical mechanisms, a linear model based on PDO and GDP metrics provided a good fit to the observed HD. PMID:27282140

  6. Decadal variability in the occurrence of wintertime haze in central eastern China tied to the Pacific Decadal Oscillation

    PubMed Central

    Zhao, Sen; Li, Jianping; Sun, Cheng

    2016-01-01

    Haze is a serious issue in China with increasing concerns, and understanding the factors driving decadal-scale variations in haze occurrence is relevant for government policymaking. Using a comprehensive observational haze dataset, we demonstrate notable decadal fluctuations in the number of haze days (HD) during winter in central eastern China, showing a decline since the mid-1980s. The leading mode of the wintertime HD features an increasing trend for 1959–2012 in eastern China, highly correlated with China’s gross domestic product (GDP) that represents increasing trend of pollutant emissions, and to a lesser extent meteorological factors. The second mode shows decadal variations in central eastern China associated with Pacific Decadal Oscillation (PDO). Observations and numerical simulations suggest that Mongolia High and corresponding descending motion tend to be enhanced (weakened) in central eastern China during the positive (negative) phase of PDO. With PDO shifting towards a negative phase, the weakened Mongolia High and ascending anomalies make the air unstable and conduce to the spread of pollutants, leading to the decline in the wintertime HD over central eastern China since the mid-1980s. Based on above physical mechanisms, a linear model based on PDO and GDP metrics provided a good fit to the observed HD. PMID:27282140

  7. Decadal variability in the occurrence of wintertime haze in central eastern China tied to the Pacific Decadal Oscillation

    NASA Astrophysics Data System (ADS)

    Zhao, Sen; Li, Jianping; Sun, Cheng

    2016-06-01

    Haze is a serious issue in China with increasing concerns, and understanding the factors driving decadal-scale variations in haze occurrence is relevant for government policymaking. Using a comprehensive observational haze dataset, we demonstrate notable decadal fluctuations in the number of haze days (HD) during winter in central eastern China, showing a decline since the mid-1980s. The leading mode of the wintertime HD features an increasing trend for 1959–2012 in eastern China, highly correlated with China’s gross domestic product (GDP) that represents increasing trend of pollutant emissions, and to a lesser extent meteorological factors. The second mode shows decadal variations in central eastern China associated with Pacific Decadal Oscillation (PDO). Observations and numerical simulations suggest that Mongolia High and corresponding descending motion tend to be enhanced (weakened) in central eastern China during the positive (negative) phase of PDO. With PDO shifting towards a negative phase, the weakened Mongolia High and ascending anomalies make the air unstable and conduce to the spread of pollutants, leading to the decline in the wintertime HD over central eastern China since the mid-1980s. Based on above physical mechanisms, a linear model based on PDO and GDP metrics provided a good fit to the observed HD.

  8. Decadal variability in the occurrence of wintertime haze in central eastern China tied to the Pacific Decadal Oscillation.

    PubMed

    Zhao, Sen; Li, Jianping; Sun, Cheng

    2016-06-10

    Haze is a serious issue in China with increasing concerns, and understanding the factors driving decadal-scale variations in haze occurrence is relevant for government policymaking. Using a comprehensive observational haze dataset, we demonstrate notable decadal fluctuations in the number of haze days (HD) during winter in central eastern China, showing a decline since the mid-1980s. The leading mode of the wintertime HD features an increasing trend for 1959-2012 in eastern China, highly correlated with China's gross domestic product (GDP) that represents increasing trend of pollutant emissions, and to a lesser extent meteorological factors. The second mode shows decadal variations in central eastern China associated with Pacific Decadal Oscillation (PDO). Observations and numerical simulations suggest that Mongolia High and corresponding descending motion tend to be enhanced (weakened) in central eastern China during the positive (negative) phase of PDO. With PDO shifting towards a negative phase, the weakened Mongolia High and ascending anomalies make the air unstable and conduce to the spread of pollutants, leading to the decline in the wintertime HD over central eastern China since the mid-1980s. Based on above physical mechanisms, a linear model based on PDO and GDP metrics provided a good fit to the observed HD.

  9. Seasonal-to-Interannual Variability of Southeastern South America in CMIP5 Decadal Hindcasts

    NASA Astrophysics Data System (ADS)

    Gonzalez, P. L.; Goddard, L. M.

    2011-12-01

    To face the increasing demand of near-term climate information, CMIP5 has designed a set of decadal hindcasts that explore the effect of initializing the models with information about the current state of the climate system. The idea is that some skill for the next year-to-decade may be gained if one can predict aspects of the natural internal variability of the climate system in addition to the anthropogenic trend. Preliminary results suggest that these hindcasts have some additional skill in the North Atlantic Ocean, which is likely associated with Atlantic multi-decadal variability, and in the tropical Pacific Ocean, which may reflect the decadal-scale component of ENSO. Southeastern South America (SESA) is a potentially interesting region to explore in these hindcasts, especially for precipitation. Over the 20th century this region experienced large trends, showed decadal-scale variability, and also exhibited strong seasonal-to-interannual variability, mainly due to an ENSO teleconnection. In this presentation we will discuss whether near-term climate projections for the area can benefit from initialized decadal hindcasts. In particular, we will explore if the hindcasts capture the main features of seasonal-to-interannual variability in SESA, even if we cannot expect to predict the exact timing of this variability years in advance. In particular, we examine the low-frequency modulation of ENSO-teleconnections in the region, and the extent to which these are tied to decadal-scale changes in the oceanic circulation.

  10. Drivers of annual to decadal streamflow variability in the lower Colorado River Basin

    NASA Astrophysics Data System (ADS)

    Lambeth-Beagles, R. S.; Troch, P. A.

    2010-12-01

    The Colorado River is the main water supply to the southwest region. As demand reaches the limit of supply in the southwest it becomes increasingly important to understand the dynamics of streamflow in the Colorado River and in particular the tributaries to the lower Colorado River. Climate change may pose an additional threat to the already-scarce water supply in the southwest. Due to the narrowing margin for error, water managers are keen on extending their ability to predict streamflow volumes on a mid-range to decadal scale. Before a predictive streamflow model can be developed, an understanding of the physical drivers of annual to decadal streamflow variability in the lower Colorado River Basin is needed. This research addresses this need by applying multiple statistical methods to identify trends, patterns and relationships present in streamflow, precipitation and temperature over the past century in four contributing watersheds to the lower Colorado River. The four watersheds selected were the Paria, Little Colorado, Virgin/Muddy, and Bill Williams. Time series data over a common period from 1906-2007 for streamflow, precipitation and temperature were used for the initial analysis. Through statistical analysis the following questions were addressed: 1) are there observable trends and patterns in these variables during the past century and 2) if there are trends or patterns, how are they related to each other? The Mann-Kendall test was used to identify trends in the three variables. Assumptions regarding autocorrelation and persistence in the data were taken into consideration. Kendall’s tau-b test was used to establish association between any found trends in the data. Initial results suggest there are two primary processes occurring. First, statistical analysis reveals significant upward trends in temperatures and downward trends in streamflow. However, there appears to be no trend in precipitation data. These trends in streamflow and temperature speak to

  11. Interannual to Multi-Decadal Variability of Indo-Pacific SST

    NASA Astrophysics Data System (ADS)

    Slawinska, J.; Giannakis, D.

    2014-12-01

    Low-frequency (decadal to centennial) modes of ocean are important components of climate variability. With the rise of supercomputers, these modes are inferred often from long-term climate simulations after being preprocessed by low-pass filtering. Notably, the few modes that are consistently found in many climate models differ significantly, even in frequency, as every model has biases and model errors. At the same time, validation of the extracted signals against observations is limited by the time span of the observational record (e.g., sea surface temperature and sea ice extent observed during the satellite era), which is oftentimes shorter than the timescales of interest and also significantly altered by anthropogenic factors. More importantly, due to preprocessing as well as the subsequent data analysis techniques (such as EOFs), the results have frequently ambiguous physical interpretation. Here, we investigate Indo-Pacific Ocean variability from 1300 control run of CCSM4. For that, we apply recently introduced technique called Nonlinear Laplacian Spectral Analysis (NLSA, Giannakis and Majda 2012). Through this technique, drawbacks associated with ad-hoc filtering are avoided as the extracted signals span many temporal scales without preprocessing the input data, enabling detection of low-frequency and intermittent modes not previously accessible with classical EOF-based approaches. Here, we identify spatiotemporal modes covering multiple scales of interest, including several intraseasonal modes such as ENSO, the Indian Ocean Dipole, and Tropical Biennial Oscillation, revealing refined linkages between these patterns. Additionally, the amplitudes of these patterns are modulated by low-frequency envelopes whose character can in certain cases be related to patterns of decadal or longer variability which are also identified. As such, our study unambiguously clarifies interdependencies between intraseasonal modes which are sometimes treated in the climate

  12. Interannual to decadal variability of circulation in the northern Japan/East Sea, 1958-2006

    NASA Astrophysics Data System (ADS)

    Stepanov, Dmitry; Stepanova, Victoriia; Gusev, Anatoly

    2015-04-01

    We use a numerical ocean model INMOM (Institute of Numerical Mathematics Ocean Model) and atmospheric forcing data extracted from the CORE (Coordinated Ocean Reference Experiments) dataset and reconstruct a circulation in the Japan/East Sea (JES) from 1958 to 2006 and its interannual and decadal variability in the intermediate and abyssal layers in the northern JES. It is founded that the circulation is cyclonic over the course of a climatological year. The circulation increases in spring and decreases in autumn. We analyzes the relative vorticity (RV) averaged over the Japan Basin (JB) and show that the variability is characterized by the interannual oscillations (2.3, 3.7 and 4.7 years) and decadal variability (9.5 and 14.3 years). The spectrum structure of the average RV variability does not change with depth; however, the energy of the decadal oscillations decreases in contrast to that of the interannual oscillations. We analyze monthly anomalies of the wind stress curl and sensible heat flux and reveal that interannual variability (3-4 years) of the circulation over the JB result from 4-year variability of the wind stress curl. In contrast, the decadal variability (period of 9.5 years) of the circulation over the JB is generated by both the wind stress curl and the decadal variability in deep convection.

  13. Reconciling two alternative mechanisms behind bi-decadal variability in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Ortega, Pablo; Mignot, Juliette; Swingedouw, Didier; Sévellec, Florian; Guilyardi, Eric

    2015-09-01

    Understanding the preferential timescales of variability in the North Atlantic, usually associated with the Atlantic meridional overturning circulation (AMOC), is essential for the prospects for decadal prediction. However, the wide variety of mechanisms proposed from the analysis of climate simulations, potentially dependent on the models themselves, has stimulated the debate of which processes take place in reality. One mechanism receiving increasing attention, identified both in idealized models and observations, is a westward propagation of subsurface buoyancy anomalies that impact the AMOC through a basin-scale intensification of the zonal density gradient, enhancing the northward transport via thermal wind balance. In this study, we revisit a control simulation from the Institut Pierre-Simon Laplace Coupled Model 5A (IPSL-CM5A), characterized by a strong AMOC periodicity at 20 years, previously explained by an upper ocean-atmosphere-sea ice coupled mode driving convection activity south of Iceland. Our study shows that this mechanism interacts constructively with the basin-wide propagation in the subsurface. This constructive feedback may explain why bi-decadal variability is so intense in this coupled model as compared to others.

  14. Estimating decadal variability in sea level from tide gauge records: An application to the North Sea

    NASA Astrophysics Data System (ADS)

    Frederikse, Thomas; Riva, Riccardo; Slobbe, Cornelis; Broerse, Taco; Verlaan, Martin

    2016-03-01

    One of the primary observational data sets of sea level is represented by the tide gauge record. We propose a new method to estimate variability on decadal time scales from tide gauge data by using a state space formulation, which couples the direct observations to a predefined state space model by using a Kalman filter. The model consists of a time-varying trend and seasonal cycle, and variability induced by several physical processes, such as wind, atmospheric pressure changes and teleconnection patterns. This model has two advantages over the classical least-squares method that uses regression to explain variations due to known processes: a seasonal cycle with time-varying phase and amplitude can be estimated, and the trend is allowed to vary over time. This time-varying trend consists of a secular trend and low-frequency variability that is not explained by any other term in the model. As a test case, we have used tide gauge data from stations around the North Sea over the period 1980-2013. We compare a model that only estimates a trend with two models that also remove intra-annual variability: one by means of time series of wind stress and sea level pressure, and one by using a two-dimensional hydrodynamic model. The last two models explain a large part of the variability, which significantly improves the accuracy of the estimated time-varying trend. The best results are obtained with the hydrodynamic model. We find a consistent low-frequency sea level signal in the North Sea, which can be linked to a steric signal over the northeastern part of the Atlantic.

  15. Pacific Decadal Variability and Central Pacific Warming El Niño in a Changing Climate

    SciTech Connect

    Di Lorenzo, Emanuele

    2015-02-27

    This research aimed at understanding the dynamics controlling decadal variability in the Pacific Ocean and its interactions with global-scale climate change. The first goal was to assess how the dynamics and statistics of the El Niño Southern Oscillation and the modes of Pacific decadal variability are represented in global climate models used in the IPCC. The second goal was to quantify how decadal dynamics are projected to change under continued greenhouse forcing, and determine their significance in the context of paleo-proxy reconstruction of long-term climate.

  16. Reconstructing the subsurface ocean decadal variability using surface nudging in a perfect model framework

    NASA Astrophysics Data System (ADS)

    Servonnat, Jérôme; Mignot, Juliette; Guilyardi, Eric; Swingedouw, Didier; Séférian, Roland; Labetoulle, Sonia

    2015-01-01

    Initialising the ocean internal variability for decadal predictability studies is a new area of research and a variety of ad hoc methods are currently proposed. In this study, we explore how nudging with sea surface temperature (SST) and salinity (SSS) can reconstruct the three-dimensional variability of the ocean in a perfect model framework. This approach builds on the hypothesis that oceanic processes themselves will transport the surface information into the ocean interior as seen in ocean-only simulations. Five nudged simulations are designed to reconstruct a 150 years "target" simulation, defined as a portion of a long control simulation. The nudged simulations differ by the variables restored to, SST or SST + SSS, and by the area where the nudging is applied. The strength of the heat flux feedback is diagnosed from observations and the restoring coefficients for SSS use the same time-scale. We observed that this choice prevents spurious convection at high latitudes and near sea-ice border when nudging both SST and SSS. In the tropics, nudging the SST is enough to reconstruct the tropical atmosphere circulation and the associated dynamical and thermodynamical impacts on the underlying ocean. In the tropical Pacific Ocean, the profiles for temperature show a significant correlation from the surface down to 2,000 m, due to dynamical adjustment of the isopycnals. At mid-to-high latitudes, SSS nudging is required to reconstruct both the temperature and the salinity below the seasonal thermocline. This is particularly true in the North Atlantic where adding SSS nudging enables to reconstruct the deep convection regions of the target. By initiating a previously documented 20-year cycle of the model, the SST + SSS nudging is also able to reproduce most of the AMOC variations, a key source of decadal predictability. Reconstruction at depth does not significantly improve with amount of time spent nudging and the efficiency of the surface nudging rather depends on the

  17. Prioritizing Global Observations Along Essential Climate Variables

    NASA Astrophysics Data System (ADS)

    Bojinski, Stephan; Richter, Carolin

    2010-12-01

    The Global Climate Observing System (GCOS) Secretariat, housed within the World Meteorological Organization, released in August 2010 updated guidance for priority actions worldwide in support of observations of GCOS Essential Climate Variables (ECVs). This guidance states that full achievement of the recommendations in the 2010 Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (http://www.wmo.int/pages/prog/gcos/Publications/gcos­138.pdf) is required to ensure that countries are able to understand and predict climate change and its impacts and manage their response throughout the 21st century and beyond. GCOS is sponsored by the United Nations and the International Council for Science (ICSU) and is an internationally coordinated network of observing systems and a program of activities that support and improve the network, which is designed to meet evolving national and international requirements for climate observations. One of the main objectives of GCOS is to sustain observations into the future to allow evaluation of how climate is changing, so that informed decisions can be made on prevention, mitigation, and adaptation strategies. GCOS priorities are based on the belief that observations are crucial to supporting the research needed to refine understanding of the climate system and its changes, to initialize predictions on time scales out to decades, and to develop the models used to make these predictions and longer­term scenario-based projections. Observations are also needed to assess social and economic vulnerabilities and to support related actions needed across a broad range of societal sectors by underpinning emerging climate services.

  18. Sahel decadal rainfall variability and the role of model horizontal resolution

    NASA Astrophysics Data System (ADS)

    Vellinga, Michael; Roberts, Malcolm; Vidale, Pier Luigi; Mizielinski, Matthew S.; Demory, Marie-Estelle; Schiemann, Reinhard; Strachan, Jane; Bain, Caroline

    2016-01-01

    Substantial low-frequency rainfall fluctuations occurred in the Sahel throughout the twentieth century, causing devastating drought. Modeling these low-frequency rainfall fluctuations has remained problematic for climate models for many years. Here we show using a combination of state-of-the-art rainfall observations and high-resolution global climate models that changes in organized heavy rainfall events carry most of the rainfall variability in the Sahel at multiannual to decadal time scales. Ability to produce intense, organized convection allows climate models to correctly simulate the magnitude of late-twentieth century rainfall change, underlining the importance of model resolution. Increasing model resolution allows a better coupling between large-scale circulation changes and regional rainfall processes over the Sahel. These results provide a strong basis for developing more reliable and skilful long-term predictions of rainfall (seasons to years) which could benefit many sectors in the region by allowing early adaptation to impending extremes.

  19. Interannual-decadal variability of wintertime mixed layer depths in the North Pacific detected by an ensemble of ocean syntheses

    NASA Astrophysics Data System (ADS)

    Toyoda, Takahiro; Fujii, Yosuke; Kuragano, Tsurane; Kosugi, Naohiro; Sasano, Daisuke; Kamachi, Masafumi; Ishikawa, Yoichi; Masuda, Shuhei; Sato, Kanako; Awaji, Toshiyuki; Hernandez, Fabrice; Ferry, Nicolas; Guinehut, Stéphanie; Martin, Matthew; Andrew Peterson, K.; Good, Simon A.; Valdivieso, Maria; Haines, Keith; Storto, Andrea; Masina, Simona; Köhl, Armin; Yin, Yonghong; Shi, Li; Alves, Oscar; Smith, Gregory; Chang, You-Soon; Vernieres, Guillaume; Wang, Xiaochun; Forget, Gael; Heimbach, Patrick; Wang, Ou; Fukumori, Ichiro; Lee, Tong; Zuo, Hao; Balmaseda, Magdalena

    2015-08-01

    The interannual-decadal variability of the wintertime mixed layer depths (MLDs) over the North Pacific is investigated from an empirical orthogonal function (EOF) analysis of an ensemble of global ocean reanalyses. The first leading EOF mode represents the interannual MLD anomalies centered in the eastern part of the central mode water formation region in phase opposition with those in the eastern subtropics and the central Alaskan Gyre. This first EOF mode is highly correlated with the Pacific decadal oscillation index on both the interannual and decadal time scales. The second leading EOF mode represents the MLD variability in the subtropical mode water (STMW) formation region and has a good correlation with the wintertime West Pacific (WP) index with time lag of 3 years, suggesting the importance of the oceanic dynamical response to the change in the surface wind field associated with the meridional shifts of the Aleutian Low. The above MLD variabilities are in basic agreement with previous observational and modeling findings. Moreover the reanalysis ensemble provides uncertainty estimates. The interannual MLD anomalies in the first and second EOF modes are consistently represented by the individual reanalyses and the amplitudes of the variabilities generally exceed the ensemble spread of the reanalyses. Besides, the resulting MLD variability indices, spanning the 1948-2012 period, should be helpful for characterizing the North Pacific climate variability. In particular, a 6-year oscillation including the WP teleconnection pattern in the atmosphere and the oceanic MLD variability in the STMW formation region is first detected.

  20. Decadal Air-Sea Interaction in the North Atlantic Based on Observations and Modeling Results

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa

    1998-01-01

    The decadal, 12-14 year, cycle observed in the North Atlantic SST and tide gauge data was examined using the NCEP/NCAR reanalyses, COADS data and an ocean model simulation. Besides this decadal mode, a shorter, subdecadal period of about 8 years exists in tide gauge data north of 40N, in the subpolar SST and in the winter North Atlantic Oscillation (NAO) index and in subpolar winter heat flux values. The decadal cycle is a well separated mode in a singular spectrum analysis (SSA) for a time series of SST EOF mode 1 with a center over the Gulf Stream extension. Tide gauge and SST data are consistent in that both show a significant subdecadal periodicity exclusively in the subpolar gyre, but in subtropics the 12-14 year period is the prominent, but nonstationary, decadal signal. The main finding of this study is that this 12-14 year cycle can be constructed based on the leading mode of the surface heat flux. This connection to the surface heat flux implicates the participation of the thermohaline circulation in the decadal cycle. During the cycle starting from the positive index phase of NAO, SST and oceanic heat content anomalies are created in subtropics due to local heat flux and intensification of the thermohaline circulation. The anomalies advect to the subpolar gyre where they are amplified by local heat flux and are part of the negative feedback of thermohaline circulation on itself. Consequently the oceanic thermohaline circulation slows down and the opposite cycle starts. The oscillatory nature would not be possible without the active atmospheric participation in the cycle, because it provides the unstable interaction through heat flux, without it, the oceanic mode would be damped. This analysis suggests that the two principal modes of heat flux variability, corresponding to patterns similar to North Atlantic Oscillation (NAO) and Western Atlantic (WA), are part of the same decadal cycle and an indirect measure of the north-south movement of the storm tracks.

  1. A decade of progress in observing and modelling Antarctic subglacial water systems.

    PubMed

    Fricker, Helen A; Siegfried, Matthew R; Carter, Sasha P; Scambos, Ted A

    2016-01-28

    In the decade since the discovery of active Antarctic subglacial water systems by detection of subtle surface displacements, much progress has been made in our understanding of these dynamic systems. Here, we present some of the key results of observations derived from ICESat laser altimetry, CryoSat-2 radar altimetry, Operation IceBridge airborne laser altimetry, satellite image differencing and ground-based continuous Global Positioning System (GPS) experiments deployed in hydrologically active regions. These observations provide us with an increased understanding of various lake systems in Antarctica: Whillans/Mercer Ice Streams, Crane Glacier, Recovery Ice Stream, Byrd Glacier and eastern Wilkes Land. In several cases, subglacial water systems are shown to control ice flux through the glacier system. For some lake systems, we have been able to construct more than a decade of continuous lake activity, revealing internal variability on time scales ranging from days to years. This variability indicates that continuous, accurate time series of altimetry data are critical to understanding these systems. On Whillans Ice Stream, our results from a 5-year continuous GPS record demonstrate that subglacial lake flood events significantly change the regional ice dynamics. We also show how models for subglacial water flow have evolved since the availability of observations of lake volume change, from regional-scale models of water routeing to process models of channels carved into the subglacial sediment instead of the overlying ice. We show that progress in understanding the processes governing lake drainage now allows us to create simulated lake volume time series that reproduce time series from satellite observations. This transformational decade in Antarctic subglacial water research has moved us significantly closer to understanding the processes of water transfer sufficiently for inclusion in continental-scale ice-sheet models.

  2. Two centuries of coherent decadal climate variability across the Pacific North American region

    NASA Astrophysics Data System (ADS)

    Sanchez, S. C.; Charles, C. D.; Carriquiry, J. D.; Villaescusa, J. A.

    2016-09-01

    The decadal variability of the Pacific Ocean and North American hydroclimate are subjects of immediate concern for society, yet the length of the instrumental record limits full mechanistic understanding of this variability. Here we introduce a 178 year, seasonally resolved coral oxygen isotopic record from Clarion Island (18°N, 115°W), a sampling a subtropical region that is strongly influenced by the decadal-scale fluctuations of the North Pacific Gyre Oscillation and a region that serves as a critical locus for the communication of climate anomalies with the tropics. This Mexican Pacific coral record is highly correlated to coral records from the central tropical Pacific and tree ring records from western North America. Significant changes in the amplitude of oceanic decadal variability in the early nineteenth century are mirrored in the drought reconstructions in western North America. The spatial manifestation of this relationship was relatively invariant, despite notable changes in the climatic mean state.

  3. Global Ocean Evaporation: How Well Can We Estimate Interannual to Decadal Variability?

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Bosilovich, Michael G.; Roberts, Jason B.; Wang, Hailan

    2015-01-01

    Evaporation from the world's oceans constitutes the largest component of the global water balance. It is important not only as the ultimate source of moisture that is tied to the radiative processes determining Earth's energy balance but also to freshwater availability over land, governing habitability of the planet. Here we focus on variability of ocean evaporation on scales from interannual to decadal by appealing to three sources of data: the new MERRA-2 (Modern-Era Retrospective analysis for Research and Applications -2); climate models run with historical sea-surface temperatures, ice and atmospheric constituents (so-called AMIP experiments); and state-of-the-art satellite retrievals from the Seaflux and HOAPS (Hamburg Ocean-Atmosphere Parameters and Fluxes from Satellite) projects. Each of these sources has distinct advantages as well as drawbacks. MERRA-2, like other reanalyses, synthesizes evaporation estimates consistent with observationally constrained physical and dynamical models-but data stream discontinuities are a major problem for interpreting multi-decadal records. The climate models used in data assimilation can also be run with lesser constraints such as with SSTs and sea-ice (i.e. AMIPs) or with additional, minimal observations of surface pressure and marine observations that have longer and less fragmentary observational records. We use the new ERA-20C reanalysis produced by ECMWF embodying the latter methodology. Still, the model physics biases in climate models and the lack of a predicted surface energy balance are of concern. Satellite retrievals and comparisons to ship-based measurements offer the most observationally-based estimates, but sensor inter-calibration, algorithm retrieval assumptions, and short records are dominant issues. Our strategy depends on maximizing the advantages of these combined records. The primary diagnostic tool used here is an analysis of bulk aerodynamic computations produced by these sources and uses a first

  4. Analysis and modeling of decadal and long-term variability of coastal California summer temperature changes

    NASA Astrophysics Data System (ADS)

    Sequera, Pedro

    Summer average daily maximum temperature (Tmax) trends for 1950-2010 were calculated for 241 locations along all of California by use of daily max temperatures from NWS Coop sites to understand the spatial and temporal variabilities of the previously reported summer coastal-cooling. Results show that coastal-cooling appears almost continuously throughout the California coast in locations open to marine air penetrations for the period of 1970-2010. Correlations with the Pacific Decadal Oscillation (PDO) Index show that coastal-cooling disappears during the increasing PDO period (1950-1985). The most influential factor(s) on California summer coastal temperatures, i.e., Greenhouse Gas (GHG) warming, PDO and changes in Land Cover/Land Use (LCLU), were determined through numerical atmospheric modeling using the Weather Research & Forecasting (WRF) model. Combined results from observations, reanalysis and modeling lead to the conclusion that PDO is the main mechanism of decadal variability of California summer temperatures, dominating over global GHG-warming effects. PDO affects both coastal and inland temperatures by controlling the position and intensity of the two dominating global circulation patterns on California summer: the semi-permanent Pacific High Pressure System and the continental Thermal-Low. Coastal cooling will rise on decreasing PDO periods, where the warming of inland regions and cooling of nearshore Sea Surface Temperatures (SSTs) results in an increase in sea-breeze activity. Coastal-warming results in increasing periods of the PDO. Global warming induced by GHG and hyper-urbanization were found to be major sources of coastal warming over complete PDO cycles (1950-2010).

  5. Decadal-scale thermohaline variability in the Atlantic sector of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Hutchinson, K.; Swart, S.; Meijers, A.; Ansorge, I.; Speich, S.

    2016-05-01

    An enhanced Altimetry Gravest Empirical Mode (AGEM), including both adiabatic and diabatic trends, is developed for the Antarctic Circumpolar Current (ACC) south of Africa using updated hydrographic CTD sections, Argo data, and satellite altimetry. This AGEM has improved accuracy compared to traditional climatologies and other proxy methods. The AGEM for the Atlantic Southern Ocean offers an ideal technique to investigate the thermohaline variability over the past two decades in a key region for water mass exchanges and transformation. In order to assess and attribute changes in the hydrography of the region, we separate the changes into adiabatic and diabatic components. Integrated over the upper 2000 dbar of the ACC south of Africa, results show mean adiabatic changes of 0.16 ± 0.11°C decade-1 and 0.006 ± 0.014 decade-1, and diabatic differences of -0.044 ± 0.13°C decade-1 and -0.01 ± 0.017 decade-1 for temperature and salinity, respectively. The trends of the resultant AGEM, that include both adiabatic and diabatic variability (termed AD-AGEM), show a significant increase in the heat content of the upper 2000 dbar of the ACC with a mean warming of 0.12 ± 0.087°C decade-1. This study focuses on the Antarctic Intermediate Water (AAIW) mass where negative diabatic trends dominate positive adiabatic differences in the Subantarctic Zone (SAZ), with results indicating a cooling (-0.17°C decade-1) and freshening (-0.032 decade-1) of AAIW in this area, whereas south of the SAZ positive adiabatic and diabatic trends together create a cumulative warming (0.31°C decade-1) and salinification (0.014 decade-1) of AAIW.

  6. Dynamical response of the North Pacific Ocean to the tropical variability and its decadal modulation

    NASA Astrophysics Data System (ADS)

    Nonaka, M.; Taguchi, B.; Schneider, N.

    2015-12-01

    While teleconnections from the tropical Pacific to the North Pacific sea surface temperature are well known, the dynamical response of the North Pacific Ocean to the tropical atmosphere-ocean variability is not well investigated. Based on observed and reanalysis data, we investigate this link through a correlation analysis using the indices of Nino3, Nino3.4, and El Nino Modoki Index (EMI). The simultaneous correlation maps of the wind-stress curl indicate that the signal associated with EMI in the eastern North Pacific is stronger than the counterparts with Nino3 and Nino3.4. Responding to these signals in wind-stress curl, sea surface height (SSH) anomalies develop following EMI, but almost no SSH responses are found to Nino3 and Nino3.4. As El Nino Modoki lasts for a longer period than canonical El Nino, the stronger wind-stress curl signal to EMI drives the ocean more persistently, and induces substantial SSH signals. The induced SSH signals propagate westward to the western boundary region around 35N, affecting variability in the Kuroshio Extension, which might further exert feedback on the atmosphere aloft. The teleconnection from EMI to the North Pacific, however, was not found before the 1990s, indicating its clear decadal modulation.

  7. Associations of decadal to multidecadal sea-surface temperature variability with Upper Colorado River flow

    USGS Publications Warehouse

    McCabe, G.J.; Betancourt, J.L.; Hidalgo, H.G.

    2007-01-01

    The relations of decadal to multidecadal (D2M) variability in global sea-surface temperatures (SSTs) with D2M variability in the flow of the Upper Colorado River Basin (UCRB) are examined for the years 1906-2003. Results indicate that D2M variability of SSTs in the North Atlantic, North Pacific, tropical Pacific, and Indian Oceans is associated with D2M variability of the UCRB. A principal components analysis (with varimax rotation) of detrended and 11-year smoothed global SSTs indicates that the two leading rotated principal components (RPCs) explain 56% of the variability in the transformed SST data. The first RPC (RPC1) strongly reflects variability associated with the Atlantic Multidecadal Oscillation and the second RPC (RPC2) represents variability of the Pacific Decadal Oscillation, the tropical Pacific Ocean, and Indian Ocean SSTs. Results indicate that SSTs in the North Atlantic Ocean (RPC1) explain as much of the D2M variability in global SSTs as does the combination of Indian and Pacific Ocean variability (RPC2). These results suggest that SSTs in all of the oceans have some relation with flow of the UCRB, but the North Atlantic may have the strongest and most consistent association on D2M time scales. Hydroclimatic persistence on these time scales introduces significant nonstationarity in mean annual streamflow, with critical implications for UCRB water resource management. ?? 2007 American Water Resources Association.

  8. Optimal nonlinear excitation of decadal variability of the North Atlantic thermohaline circulation

    NASA Astrophysics Data System (ADS)

    Zu, Ziqing; Mu, Mu; Dijkstra, Henk A.

    2013-11-01

    Nonlinear development of salinity perturbations in the Atlantic thermohaline circulation (THC) is investigated with a three-dimensional ocean circulation model, using the conditional nonlinear optimal perturbation method. The results show two types of optimal initial perturbations of sea surface salinity, one associated with freshwater and the other with salinity. Both types of perturbations excite decadal variability of the THC. Under the same amplitude of initial perturbation, the decadal variation induced by the freshwater perturbation is much stronger than that by the salinity perturbation, suggesting that the THC is more sensitive to freshwater than salinity perturbation. As the amplitude of initial perturbation increases, the decadal variations become stronger for both perturbations. For salinity perturbations, recovery time of the THC to return to steady state gradually saturates with increasing amplitude, whereas this recovery time increases remarkably for freshwater perturbations. A nonlinear (advective) feedback between density and velocity anomalies is proposed to explain these characteristics of decadal variability excitation. The results are consistent with previous ones from simple box models, and highlight the importance of nonlinear feedback in decadal THC variability.

  9. Decadal variability of the Turner Angle in the Mediterranean Sea and its implications for double diffusion

    NASA Astrophysics Data System (ADS)

    Meccia, Virna L.; Simoncelli, Simona; Sparnocchia, Stefania

    2016-08-01

    The physical reanalysis component of the Mediterranean Forecasting System is used to construct a high-resolution three-dimensional atlas of the Turner Angle. An assessment of the model quality shows a maximum degree of agreement with observations in the water column between 150 and 1000 m depth. The mean state of the favourable conditions for double diffusion processes is evaluated and the recent decadal variability is studied in terms of changes in the water mass properties. The results show that approximately 50% of the Mediterranean Sea is favourable to double diffusion processes, from which around 47% is associated with salt fingering. The Tyrrhenian, Ionian and southwestern Mediterranean are the most vulnerable basins to salt fingering, and the strongest processes can occur in the Tyrrhenian deep waters. Diffusive convection is most likely to occur in the Ionian, Aegean and eastern Mediterranean at vertical levels deeper than 1000 m. The observed gradual warming and salinification of the Mediterranean after 1997 decreased and increased the possibilities of the occurrence of salt fingers and double diffusive convections, respectively. The climatological atlas that is presented in this paper provides a three-dimensional picture of the regions that are either doubly stable or favourable to double diffusion instability and allows for the characterization of the diffusive properties of the water masses.

  10. The amplitude of decadal to multidecadal variability in precipitation simulated by state-of-the-art climate models

    NASA Astrophysics Data System (ADS)

    Ault, T. R.; Cole, J. E.; St. George, S.

    2012-11-01

    We assess the magnitude of decadal to multidecadal (D2M) variability in Climate Model Intercomparison Project 5 (CMIP5) simulations that will be used to understand, and plan for, climate change as part of the Intergovernmental Panel on Climate Change's 5th Assessment Report. Model performance on D2M timescales is evaluated using metrics designed to characterize the relative and absolute magnitude of variability at these frequencies. In observational data, we find that between 10% and 35% of the total variance occurs on D2M timescales. Regions characterized by the high end of this range include Africa, Australia, western North America, and the Amazon region of South America. In these areas D2M fluctuations are especially prominent and linked to prolonged drought. D2M fluctuations account for considerably less of the total variance (between 5% and 15%) in the CMIP5 archive of historical (1850-2005) simulations. The discrepancy between observation and model based estimates of D2M prominence reflects two features of the CMIP5 archive. First, interannual components of variability are generally too energetic. Second, decadal components are too weak in several key regions. Our findings imply that projections of the future lack sufficient decadal variability, presenting a limited view of prolonged drought and pluvial risk.

  11. Climate-informed stochastic hydrological modeling: Incorporating decadal-scale variability using paleo data

    NASA Astrophysics Data System (ADS)

    Henley, B.; Thyer, M.; Kuczera, G.

    2012-04-01

    A hierarchical framework for incorporating modes of climate variability into stochastic simulations of hydrological data is developed, termed the climate-informed multi-time scale stochastic (CIMSS) framework. To characterize long-term variability for the first level of the hierarchy, paleoclimate and instrumental data describing the Interdecadal Pacific Oscillation (IPO) and the Pacific Decadal Oscillation (PDO) are analyzed. A new paleo IPO-PDO time series dating back 440 yr is produced, combining seven IPO-PDO paleo sources using an objective smoothing procedure to fit low-pass filters to individual records. The paleo data analysis indicates that wet/dry IPO-PDO states have a broad range of run lengths, with 90% between 3 and 33 yr and a mean of 15 yr. Model selection techniques were used to determine a suitable stochastic model to simulate these run lengths. The Markov chain model, previously used to simulate oscillating wet/dry climate states, was found to underestimate the probability of wet/dry periods >5 yr, and was rejected in favor of a gamma distribution. For the second level of the hierarchy, a seasonal rainfall model is conditioned on the simulated IPO-PDO state. Application to two high quality rainfall sites close to water supply reservoirs found that mean seasonal rainfall in the IPO-PDO dry state was 15%-28% lower than the wet state. The model was able to replicate observed statistics such as seasonal and multi-year accumulated rainfall distributions and interannual autocorrelations for the case study sites. In comparison, an annual lag-one autoregressive AR(1) model was unable to adequately capture the observed rainfall distribution within separate IPO-PDO states. Furthermore, analysis of the impact of the CIMSS framework on drought risk analysis found that short-term drought risks conditional on IPO/PDO state were far higher than the traditional AR(1) model.

  12. Interannual variability and decadal trends in carbon exchange at the Harvard Forest EMS site

    NASA Astrophysics Data System (ADS)

    Munger, J.. W.; Wofsy, S. C.; Moorcroft, P. R.; Medvigy, D.

    2009-04-01

    The Harvard Forest EMS site in a mixed deciduous forest in central Massachusetts has been measuring carbon, water, and energy fluxes since 1992. Above-ground biomass, litter input, and tree mortality have been measured since 1995. The forest at this site has consistently been a net sink for carbon over the measurement period with annual uptake rates of 1.0 to > 5.Mg-C ha-1y-1. Carbon uptake rates show a significant increasing trend, despite the forest being 75- 110 years old. There were parallel increases in midsummer photosynthetic capacity at high light level (21.5-31.5 mole m-2s-1), woody biomass (101-115 Mg-C ha-1from 1993-2005, mostly due to growth of one species, red oak), and peak leaf area index (4.5-5.5 m2m-2from 1998-2005). These long-term trends were interrupted in 1998 by sharp declines in photosynthetic capacity, net ecosystem exchange (NEE) of CO2, and other parameters, followed by recovery over the next 3 years. The dip in 1998 could not be directly attributed to any one cause, though leaf expansion in the spring appeared to stall during a period of unfavorable weather, and did not recover later in the summer. Annual increment of above-ground woody biomass has followed the trend in NEE with 1 year offset implying that spring wood growth is supplied by carbon fixed in the previous year. An empirical model of carbon fluxes based on mean temperature and light response functions and observed phenology represents the hourly to seasonal patterns in carbon fluxes but can not adequately account for interannual variability or the long-term trends in carbon uptake. A structured ecosystem model (ED2) that represented both canopy-scale physiology and long-term dynamics of tree growth, mortality, and species composition was able to simulate interannual variability over decadal intervals better than the empirical model based on mean responses could. These results imply that direct effects of climate variability only partially account for interannual variability in

  13. The role of Atlantic Multi-decadal Oscillation in the global mean temperature variability

    NASA Astrophysics Data System (ADS)

    Chylek, Petr; Klett, James D.; Dubey, Manvendra K.; Hengartner, Nicolas

    2016-02-01

    The global mean 1900-2015 warming simulated by 42 Coupled Models Inter-comparison Project, phase 5 (CMIP5) climate models varies between 0.58 and 1.70 °C. The observed warming according to the NASA GISS temperature analysis is 0.95 °C with a 1200 km smoothing radius, or 0.86 °C with a 250 km smoothing radius. The projection of the future 2015-2100 global warming under a moderate increase of anthropogenic radiative forcing (RCP4.5 scenario) by individual models is between 0.7 and 2.3 °C. The CMIP5 climate models agree that the future climate will be warmer; however, there is little consensus as to how large the warming will be (reflected by an uncertainty of over a factor of three). A parsimonious statistical regression model with just three explanatory variables [anthropogenic radiative forcing due to greenhouse gases and aerosols (GHGA), solar variability, and the Atlantic Multi-decadal Oscillation (AMO) index] accounts for over 95 % of the observed 1900-2015 temperature variance. This statistical regression model reproduces very accurately the past warming (0.96 °C compared to the observed 0.95 °C) and projects the future 2015-2100 warming to be around 0.95 °C (with the IPCC 2013 suggested RCP4.5 radiative forcing and an assumed cyclic AMO behavior). The AMO contribution to the 1970-2005 warming was between 0.13 and 0.20 °C (depending on which AMO index is used) compared to the GHGA contribution of 0.49-0.58 °C. During the twenty-first century AMO cycle the AMO contribution is projected to remain the same (0.13-0.20 °C), while the GHGA contribution is expected to decrease to 0.21-0.25 °C due to the levelling off of the GHGA radiative forcing that is assumed according to the RCP4.5 scenario. Thus the anthropogenic contribution and natural variability are expected to contribute about equally to the anticipated global warming during the second half of the twenty-first century for the RCP4.5 trajectory.

  14. The role of Atlantic Multi-decadal Oscillation in the global mean temperature variability

    DOE PAGES

    Chylek, Petr; Klett, James D.; Dubey, Manvendra K.; Hengartner, Nicolas

    2016-02-20

    We simulated the global mean 1900–2015 warming by 42 Coupled Models Inter-comparison Project, phase 5 (CMIP5) climate models varies between 0.58 and 1.70 °C. The observed warming according to the NASA GISS temperature analysis is 0.95 °C with a 1200 km smoothing radius, or 0.86 °C with a 250 km smoothing radius. The projection of the future 2015–2100 global warming under a moderate increase of anthropogenic radiative forcing (RCP4.5 scenario) by individual models is between 0.7 and 2.3 °C. The CMIP5 climate models agree that the future climate will be warmer; however, there is little consensus as to how largemore » the warming will be (reflected by an uncertainty of over a factor of three). Moreover, a parsimonious statistical regression model with just three explanatory variables [anthropogenic radiative forcing due to greenhouse gases and aerosols (GHGA), solar variability, and the Atlantic Multi-decadal Oscillation (AMO) index] accounts for over 95 % of the observed 1900–2015 temperature variance. This statistical regression model reproduces very accurately the past warming (0.96 °C compared to the observed 0.95 °C) and projects the future 2015–2100 warming to be around 0.95 °C (with the IPCC 2013 suggested RCP4.5 radiative forcing and an assumed cyclic AMO behavior). The AMO contribution to the 1970–2005 warming was between 0.13 and 0.20 °C (depending on which AMO index is used) compared to the GHGA contribution of 0.49–0.58 °C. During the twenty-first century AMO cycle the AMO contribution is projected to remain the same (0.13–0.20 °C), while the GHGA contribution is expected to decrease to 0.21–0.25 °C due to the levelling off of the GHGA radiative forcing that is assumed according to the RCP4.5 scenario. Therefore, the anthropogenic contribution and natural variability are expected to contribute about equally to the anticipated global warming during the second half of the twenty-first century for the RCP4.5 trajectory.« less

  15. South Pacific Decadal Variability Since the 1790s and Changes in Earth Surface Temperature

    NASA Astrophysics Data System (ADS)

    Linsley, B. K.; Wu, H. C.; Dassie, E. P.; Schrag, D. P.

    2014-12-01

    Changes in oceanic heat storage may be partly responsible for the most recent stall (or hiatus) in rising Earth surface temperatures since ~2000 C.E. Instrumental data indicates that this most recent stall is coincident with a phase reversal of the North Pacific Decadal Oscillation (PDO). The main locations for this heat exchange with the atmosphere appear to be the tropical and mid-latitude regions of the surface ocean, primarily in the Pacific. We have been investigating poorly understood decadal surface ocean variability in the South Pacific Convergence Zone (SPCZ) region. Despite very sparse instrumental water temperature data in the South Pacific to define the decadal changes at the sea surface and in the upper water column, the available data suggests a disproportionately large role of the Southwest Pacific in decadal-scale changes in heat sequestration. We have generated coral Sr/Ca-derived sea surface temperature (SST) time-series extending back to 1791 C.E. from Fiji, Tonga and Rarotonga (FTR) in the SPCZ region of the subtropical Southwest Pacific and show that decadal-scale SST fluctuations in this broad region are concurrent with the PDO at least since ~1930 C.E. Beginning in the mid-20th century, when more reliable instrumental temperature and ocean heat content data exist, decades of warmer South Pacific subtropical SST co-occur with elevated South Pacific upper ocean (0-700m) heat content. These decadal-scale South Pacific warming events coincide with decadal-scale stalls or plateaus in rising global temperatures. Cross wavelet coherence analysis reveals an increase in the frequency of decadal SST variability from a period near 30 years throughout the 1800s to ~20 years in the later half of the 20th century. Our results provide strong supporting evidence that decadal-scale changes in global surface temperatures are in-part, related to heat storage in the upper water column in the subtropical Pacific. Our results also suggest that decadal-scale stalls

  16. Variability of Ocean Heat Uptake: Reconciling Observations and Models

    SciTech Connect

    AchutaRao, K M; Santer, B D; Gleckler, P J; Taylor, K; Pierce, D; Barnett, T; Wigley, T L

    2005-05-05

    This study examines the temporal variability of ocean heat uptake in observations and in climate models. Previous work suggests that coupled Atmosphere-Ocean General Circulation Models (A-OGCMs) may have underestimated the observed natural variability of ocean heat content, particularly on decadal and longer timescales. To address this issue, we rely on observed estimates of heat content from the 2004 World Ocean Atlas (WOA-2004) compiled by Levitus et al. (2005). Given information about the distribution of observations in WOA-2004, we evaluate the effects of sparse observational coverage and the infilling that Levitus et al. use to produce the spatially-complete temperature fields required to compute heat content variations. We first show that in ocean basins with limited observational coverage, there are important differences between ocean temperature variability estimated from observed and infilled portions of the basin. We then employ data from control simulations performed with eight different A-OGCMs as a test-bed for studying the effects of sparse, space- and time-varying observational coverage. Subsampling model data with actual observational coverage has a large impact on the inferred temperature variability in the top 300 and 3000 meters of the ocean. This arises from changes in both sampling depth and in the geographical areas sampled. Our results illustrate that subsampling model data at the locations of available observations increases the variability, reducing the discrepancy between models and observations.

  17. Simulated and observed variability in ocean temperature and heat content.

    PubMed

    Achutarao, K M; Ishii, M; Santer, B D; Gleckler, P J; Taylor, K E; Barnett, T P; Pierce, D W; Stouffer, R J; Wigley, T M L

    2007-06-26

    Observations show both a pronounced increase in ocean heat content (OHC) over the second half of the 20th century and substantial OHC variability on interannual-to-decadal time scales. Although climate models are able to simulate overall changes in OHC, they are generally thought to underestimate the amplitude of OHC variability. Using simulations of 20th century climate performed with 13 numerical models, we demonstrate that the apparent discrepancy between modeled and observed variability is largely explained by accounting for changes in observational coverage and instrumentation and by including the effects of volcanic eruptions. Our work does not support the recent claim that the 0- to 700-m layer of the global ocean experienced a substantial OHC decrease over the 2003 to 2005 time period. We show that the 2003-2005 cooling is largely an artifact of a systematic change in the observing system, with the deployment of Argo floats reducing a warm bias in the original observing system.

  18. The Hydroclimate of East Africa: Seasonal cycle, Decadal Variability, and Human-induced Climate Change

    NASA Astrophysics Data System (ADS)

    Yang, Wenchang

    The hydroclimate of East Africa shows distinctive variabilities on seasonal to decadal time scales and poses a great challenge to climatologists attempting to project its response to anthropogenic emissions of greenhouse gases (GHGs). Increased frequency and intensity of droughts over East Africa in recent decades raise the question of whether the drying trend will continue into the future. To address this question, we first examine the decadal variability of the East African rainfall during March--May (MAM, the major rainy season in East Africa) and assess how well a series of models simulate the observed features. Observational results show that the drying trend during MAM is associated with decadal natural variability of sea surface temperature (SST) variations over the Pacific Ocean. The multimodel mean of the SST-forced, Coupled Model Intercomparison Project Phase 5 (CMIP5) AMIP experiment models reproduces both the climatological annual cycle and the drying trend in recent decades. The fully coupled models from the CMIP5 historical experiment, however, have systematic errors in simulating the East African rainfall annual cycle by underestimating the MAM rainfall while overestimating the October--December (OND, the second rainy season in East Africa) rainfall. The multimodel mean of the historical coupled runs of the MAM rainfall anomalies, which is the best estimate of the radiatively-forced change, shows a weak wetting trend associated with anthropogenic forcing. However, the SST anomaly pattern associated with the MAM rainfall has large discrepancies with the observations. The errors in simulating the East African hydroclimate with coupled models raise questions about how reliable model projections of future East African climate are. This motivates a fundamental study of why East African climate is the way it is and why coupled models get it wrong. East African hydroclimate is characterized by a dry annual mean climatology compared to other deep tropical

  19. A decadally delayed response of the tropical Pacific to Atlantic multidecadal variability

    NASA Astrophysics Data System (ADS)

    Zanchettin, Davide; Bothe, Oliver; Graf, Hans F.; Omrani, Nour-Eddine; Rubino, Angelo; Jungclaus, Johann H.

    2016-01-01

    North Atlantic sea surface temperature anomalies are known to affect tropical Pacific climate variability and El Niño-Southern Oscillation (ENSO) through thermocline adjustment in the equatorial Pacific Ocean. Here coupled climate simulations featuring repeated idealized cycles of the Atlantic Multidecadal Oscillation (AMO) generated by nudging its tropical branch demonstrate that the tropical Pacific response to the AMO also entails a substantial decadally delayed component. The simulations robustly show multidecadal fluctuations in central equatorial Pacific sea surface temperatures lagging the AMO by about three decades and a subdecadal cold-to-warm transition of the tropical Pacific mean state during the AMO's cooling phase. The interplay between out-of-phase responses of seawater temperature and salinity in the western Pacific and associated density anomalies in local thermocline waters emerge as crucial factors of remotely driven multidecadal variations of the equatorial Pacific climate. The delayed AMO influences on tropical Pacific dynamics could help understanding past and future ENSO variability.

  20. Decadal and Lower Frequency South Pacific Climate Variability Since 1619 AD from Replicated Coral Records

    NASA Astrophysics Data System (ADS)

    Linsley, B. K.; Wellington, G. M.; Kaplan, A.; Demenocal, P. B.

    2004-12-01

    both influenced to varying degrees by the South Pacific Convergence Zone (SPCZ) one explanation for the \\delta18O trend is that the SPCZ has been intensifying over the last 200 years with increasing cloud cover and rainfall as the surface ocean warmed. On decadal-interdecadal time-scales, comparison of the Fiji and Rarotonga coral \\delta18O series to other coral \\delta18O records from New Caledonia and the Great Barrier Reef indicates that some interdecadal climate shifts apparently were related to changes in the SPCZ and others apparently were unrelated to the SPCZ. This observation suggests the possibility that decadal-interdecadal climate variability in the South Pacific has multiple sources, and may at times be related to higher latitude South Pacific processes.

  1. Associations of multi-decadal sea-surface temperature variability with US drought

    USGS Publications Warehouse

    McCabe, G.J.; Betancourt, J.L.; Gray, S.T.; Palecki, M.A.; Hidalgo, H.G.

    2008-01-01

    Recent research suggests a link between drought occurrence in the conterminous United States (US) and sea surface temperature (SST) variability in both the tropical Pacific and North Atlantic Oceans on decadal to multidecadal (D2M) time scales. Results show that the Atlantic Multidecadal Oscillation (AMO) is the most consistent indicator of D2M drought variability in the conterminous US during the 20th century, but during the 19th century the tropical Pacific is a more consistent indicator of D2 M drought. The interaction between El Nin??o-Southern Oscillation (ENSO) and the AMO explain a large part of the D2M drought variability in the conterminous US. More modeling studies are needed to reveal possible mechanisms linking low-frequency ENSO variability and the AMO with drought in the conterminous US. ?? 2007 Elsevier Ltd and INQUA.

  2. A decadal microwave record of tropical air temperature from AMSU-A/aqua observations

    NASA Astrophysics Data System (ADS)

    Shi, Yuan; Li, King-Fai; Yung, Yuk L.; Aumann, Hartmut H.; Shi, Zuoqiang; Hou, Thomas Y.

    2013-09-01

    Atmospheric temperature is one of the most important climate variables. This observational study presents detailed descriptions of the temperature variability imprinted in the 9-year brightness temperature data acquired by the Advanced Microwave Sounding Unit-Instrument A (AMSU-A) aboard Aqua since September 2002 over tropical oceans. A non-linear, adaptive method called the Ensemble Joint Multiple Extraction has been employed to extract the principal modes of variability in the AMSU-A/Aqua data. The semi-annual, annual, quasi-biennial oscillation (QBO) modes and QBO-annual beat in the troposphere and the stratosphere have been successfully recovered. The modulation by the El Niño/Southern oscillation (ENSO) in the troposphere was found and correlates well with the Multivariate ENSO Index. The long-term variations during 2002-2011 reveal a cooling trend (-0.5 K/decade at 10 hPa) in the tropical stratosphere; the trend below the tropical tropopause is not statistically significant due to the length of our data. A new tropospheric near-annual mode (period ~1.6 years) was also revealed in the troposphere, whose existence was confirmed using National Centers for Environmental Prediction Reanalysis air temperature data. The near-annual mode in the troposphere is found to prevail in the eastern Pacific region and is coherent with a near-annual mode in the observed sea surface temperature over the Warm Pool region that has previously been reported. It remains a challenge for climate models to simulate the trends and principal modes of natural variability reported in this work.

  3. What has driven the interannual variability of atmospheric methane concentrations over the last three decades?

    NASA Astrophysics Data System (ADS)

    Coulon, A.; Stenke, A.; Peter, T.

    2015-12-01

    Atmospheric methane (CH4) is the second most anthropogenic greenhouse gas (IPCC, 2013). Observations of methane concentrations at the surface from the last three decades show puzzling fluctuations; from the early 1980s they indicate a nearly constant increase of 8.7 ppbv/year until 2000, including a slowdown after 1990. After a period of about eight years with near zero growh rates, methane concentrations have again been rising since 2007 (Sussmann et al., 2012). Simulations forced with prescribed meteorological fields have been performed for the 1980-2010 period using the chemistry-climate model (CCM) SOCOL. 48 methane tracers have been included in SOCOL and used together with flux boundary conditions for CH4 to allow the tracking of methane emissions from different source categories, such as wetlands, rice paddies, ruminants, industry…, as well as geographical regions. These new simulations provide an innovative way to better understand methane variability, both in terms of emission changes and changes in tropospheric OH, which is investigated with a tracer based on methyl chloroform emissions. An analysis of the tracers elucidates the impact of different emission source categories for different time periods. For 1980-1990, positive gobal methane growth rates result from increasing anthropogenic emissions over Europe, India, and China. A decrease of anthropogenic emissions over Europe after 1990 is consistent with the slow down in the global methane growth rate for 1990-2000. During this period short-lived events such as the eruption of Mount Pinatubo and the strong 1997-1998 El-Niño also affect global methane concentrations, largely by a decrease in wetlands emissions during 1992 and high levels of biomass burning in tropical Asia, respectively. The near-zero trend is maintained after 2000 because of reduced natural emissions, again from wetlands. After 2005, our simulations show a positive global methane growth rate, in agreement with the observations, due

  4. Vegetation dynamics and climate variability in West Africa at seasonal- decadal Scales

    NASA Astrophysics Data System (ADS)

    Xue, Y.; Song, G.; Cox, P.

    2011-12-01

    New evidence emerged from satellite data analyses and modeling study indicate that patterns of vegetation spatial distribution and vegetation structure are important in the soil-vegetation-atmosphere system (SVAS) and including a fully coupled dynamic vegetation/climate process is of imminent important in increasing our understanding and predictive capabilities of the SVAS. We apply the Simplified Simple Biosphere Model version 4/Top-down Representation of Interactive Foliage and Flora Including Dynamics Model (SSiB4/TRIFFID) to investigate the interactions between vegetation dynamics and climate variability for West Africa. The TRIFFID is a dynamic vegetation model, in which the relevant vegetation spatial distribution and structure are modeled based on the surface carbon balance. SSiB4 is a biophysical model based on surface water and energy balance and produces carbon assimilation rate for TRIFFID. The offline SSiB2, which uses specified vegetation spatial distribution and vegetation structure with no inter-annual and decadal variability, and SSiB4/TRIFFID are integrated using the observed precipitation and reanalysis-based meteorological forcing from 1948 to 2006 with 1 degree horizontal resolution over West Africa. West Africa is a diverse climatic and ecosystem region and suffered the most severe and longest drought in the world during the Twentieth Century since the later 1960s. The simulation results indicate that the SSiB4/TRIFFID model was able to produce reasonable vegetation spatial distributions, generally consistent with the products derived from satellites and with the Sahel drought in the 1970s and the 1980s and the partial recovery in the 1990s and the 2000s. The SSiB4/TRIFFID and SSIB2 results show quite different spatial patterns and vegetation structure, which lead to differences in surface net radiation, latent and sensible heat flux partitioning, soil moisture and runoff distribution, and carbon cycles at seasonal and inter-decadal time scales

  5. Decadal-Scale Rainfall Variability in Guam over the Common Era

    NASA Astrophysics Data System (ADS)

    Lindzey, K.; Partin, J. W.; Quinn, T. M.; Jenson, J. W.; Shen, C.; Banner, J. L.; lin, K.; Hardt, B. F.

    2012-12-01

    Guam is located in the Western Pacific Warm Pool (WPWP), a region of the ocean where seasonal sea surface temperatures > 28°C provide a major source of heat and water vapor to the atmosphere. Rainfall data from islands in the WPWP are limited in time and space in the pre-satellite era. Instrumental rainfall records are available from Guam from 1948 to the present. These instrumental records contain evidence of inter-decadal variations of 1-1.4 m of wet season rainfall over ~20 year periods. Rainfall proxies that overlap with, and extend beyond, the instrumental period are needed to capture the spectrum of natural rainfall variability. We use variations in stalagmite δ18O from Cool Cave in southern Guam as a proxy for rainfall variability from 2010 back to 460 CE. Our preliminary age model is based on two U-series disequilibrium dates and the time of collection. The preliminary stalagmite δ18O rainfall reconstruction is continuous back to 980 CE, has an average temporal resolution of 4 years per data point, and is dominated by inter-decadal variability (20-40 year period) in δ18O of 0.8-2.2‰. The δ18O rainfall reconstruction contains no clear centennial-scale extrema associated with the Little Ice Age or the Medieval Climate Anomaly; nor any correlation with the Pacific Decadal Oscillation (in agreement with the instrumental record of rainfall). Additional U/Th dates are needed, however, to reduce age model uncertainties. The Guam stalagmite δ18O record suggests that internal climate variability, and not external solar forcing, controls rainfall variability in this region of the WPWP.

  6. Behavior of tropopause height and atmospheric temperature in models, reanalyses, and observations: Decadal changes

    NASA Astrophysics Data System (ADS)

    Santer, B. D.; Sausen, R.; Wigley, T. M. L.; Boyle, J. S.; Achutarao, K.; Doutriaux, C.; Hansen, J. E.; Meehl, G. A.; Roeckner, E.; Ruedy, R.; Schmidt, G.; Taylor, K. E.

    2003-01-01

    We examine changes in tropopause height, a variable that has hitherto been neglected in climate change detection and attribution studies. The pressure of the lapse rate tropopause, pLRT, is diagnosed from reanalyses and from integrations performed with coupled and uncoupled climate models. In the National Centers for Environmental Prediction (NCEP) reanalysis, global-mean pLRT decreases by 2.16 hPa/decade over 1979-2000, indicating an increase in the height of the tropopause. The shorter European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis has a global-mean pLRT trend of -1.13 hPa/decade over 1979-1993. Simulated pLRT trends over the past several decades are consistent with reanalysis results. Superimposed on the overall increase in tropopause height in models and reanalyses are pronounced height decreases following the eruptions of El Chichón and Pinatubo. Interpreting these pLRT results requires knowledge of both T(z), the initial atmospheric temperature profile, and ΔT(z), the change in this profile in response to external forcing. T(z) has a strong latitudinal dependence, as does ΔT(z) for forcing by well-mixed greenhouse gases and stratospheric ozone depletion. These dependencies help explain why overall tropopause height increases in reanalyses and observations are amplified toward the poles. The pronounced increases in tropopause height in the climate change integrations considered here indicate that even AGCMs with coarse vertical resolution can resolve relatively small externally forced changes in tropopause height. The simulated decadal-scale changes in pLRT are primarily thermally driven and are an integrated measure of the anthropogenically forced warming of the troposphere and cooling of the stratosphere. Our algorithm for estimating pLRT (based on a thermal definition of tropopause height) is sufficiently sensitive to resolve these large-scale changes in atmospheric thermal structure. Our results indicate that the simulated

  7. Climate-informed stochastic hydrological modeling: Incorporating decadal-scale variability using paleoclimate data

    NASA Astrophysics Data System (ADS)

    Henley, B. J.; Thyer, M. A.; Kuczera, G. A.

    2012-12-01

    A hierarchical framework for incorporating modes of climate variability into stochastic simulations of hydrological data is developed, termed the climate-informed multi-time scale stochastic (CIMSS) framework. To characterize long-term variability for the first level of the hierarchy, paleoclimate and instrumental data describing the Interdecadal Pacific Oscillation (IPO) and the Pacific Decadal Oscillation (PDO) are analyzed. A new paleo IPO-PDO time series dating back 440 yrs is produced, combining seven IPO-PDO paleo sources using an objective smoothing procedure to fit low-pass filters to individual records. The paleo data analysis indicates that wet/dry IPO-PDO states have a broad range of run-lengths, with 90% between 3 and 33 yr and a mean of 15 yr. Model selection techniques were used to determine a suitable stochastic model to simulate these run-lengths. The Markov chain model, previously used to simulate oscillating wet/dry climate states, was found to underestimate the probability of wet/dry periods >5 yr, and was rejected in favor of a gamma distribution. For the second level of the hierarchy, a seasonal rainfall model is conditioned on the simulated IPO-PDO state. Application to two high-quality rainfall sites close to water supply reservoirs found that mean seasonal rainfall in the IPO-PDO dry state was 15%-28% lower than the wet state. The model was able to replicate observed statistics such as seasonal and multi-year accumulated rainfall distributions and interannual autocorrelations for the case study sites. In comparison, an annual lag-one autoregressive AR(1) model was unable to adequately capture the observed rainfall distribution within separate IPO-PDO states. Furthermore, analysis of the impact of the CIMSS framework on drought risk analysis found that short-term drought risks conditional on IPO/PDO state were considerably higher than the traditional AR(1) model.hort-term conditional water supply drought risks for the CIMSS and AR(1) models

  8. Missing pieces of the puzzle: understanding decadal variability of Sahel Rainfall

    NASA Astrophysics Data System (ADS)

    Vellinga, Michael; Roberts, Malcolm; Vidale, Pier-Luigi; Mizielinski, Matthew; Demory, Marie-Estelle; Schiemann, Reinhard; Strachan, Jane; Bain, Caroline

    2015-04-01

    The instrumental record shows that substantial decadal fluctuations affected Sahel rainfall from the West African monsoon throughout the 20th century. Climate models generally underestimate the magnitude of decadal Sahel rainfall changes compared to observations. This shows that the processes that control low-frequency Sahel rainfall change are misrepresented in most CMIP5-era climate models. Reliable climate information of future low-frequency rainfall changes thus remains elusive. Here we identify key processes that control the magnitude of the decadal rainfall recovery in the Sahel since the mid-1980s. We show its sensitivity to model resolution and physics in a suite of experiments with global HadGEM3 model configurations at resolutions between 130-25 km. The decadal rainfall trend increases with resolution and at 60-25 km falls within the observed range. Higher resolution models have stronger increases of moisture supply and of African Easterly wave activity. Easterly waves control the occurrence of strong organised rainfall events which carry most of the decadal trend. Weak rainfall events occur too frequently at all resolutions and at low resolution contribute substantially to the decadal trend. All of this behaviour is seen across CMIP5, including future scenarios. Additional simulations with a global 12km version of HadGEM3 show that treating convection explicitly dramatically improves the properties of Sahel rainfall systems. We conclude that interaction between convective scale and global scale processes is key to decadal rainfall changes in the Sahel. This work is distributed under the Creative Commons Attribution 3.0 Unported License together with an author copyright. This license does not conflict with the regulations of the Crown Copyright.Crown Copyright

  9. EUVE Observations of Nonmagnetic Cataclysmic Variables

    SciTech Connect

    Mauche, C W

    2001-09-05

    The authors summarize EUVE's contribution to the study of the boundary layer emission of high accretion-rate nonmagnetic cataclysmic variables, especially the dwarf novae SS Cyg, U Gem, VW Hyi, and OY Car in outburst. They discuss the optical and EUV light curves of dwarf nova outbursts, the quasi-coherent oscillations of the EUV flux of SS Cyg, the EUV spectra of dwarf novae, and the future of EUV observations of cataclysmic variables.

  10. Decadal variability in Gulf of Mexico sea surface temperatures since 1734 CE

    NASA Astrophysics Data System (ADS)

    DeLong, K. L.; Maupin, C. R.; Flannery, J. A.; Quinn, T. M.; lin, K.; Shen, C.

    2012-12-01

    The Gulf of Mexico is a major source of moisture to North America and is a source region for the Gulf Stream, which transports ocean heat northward. Sea surface temperature (SST) variations on centennial to millennial time scales have been documented for this region using paleoceanographic proxies; however, records capable of resolving decadal to subannual variability are lacking. Here we present 274 years of monthly-resolved SST variations derived from records of strontium-to-calcium ratios (Sr/Ca) extracted from four Siderastrea siderea cores recovered from coral colonies within the Dry Tortugas National Park (24°42‧N, 82°48‧W) in the Gulf of Mexico. We find no significant difference in mean Sr/Ca among these cores and significant correlation between cores (r ≥ 0.90, p ≤ 0.05 for monthly). The cross-dated chronology, determined by counting annual bands and correlating Sr/Ca variations, agrees with four 230Th dates within ±2σ analytical precision. Calibration and verification of our multi-core coral Sr/Ca record with local temperature records reveals high agreement (Sr/Ca = -0.042 SST + 10.074, R2 = 0.96; σregression = 0.70°C, 1σ), similar to those reported for single cores from this location. We find winter SSTs tend to be more variable than summer SSTs (0.99 and 0.81°C, 1σ; respectively) with periodic intervals of 10 to 15 years with cooler summer temperatures. The average reconstructed SST during the Little Ice Age (LIA; 1734-1880 CE) is colder (-0.82°C) than that during the late twentieth century (1971-2000 CE). The amplitude of decadal-scale variability (1 to 2.5°C) in the LIA is larger compared to similar scale variability in the twentieth century. The secular trend and decadal-scale variability in our reconstruction is broadly similar to an ~ decadally-resolved (~12 years/sample) Mg/Ca record from planktic foraminifer in the northern Gulf of Mexico (Richey et al., 2007), thus further confirming the reconstructed patterns of temperature

  11. Multi-Decadal Modulations in the Variability of the East Asian Summer Monsoon

    NASA Astrophysics Data System (ADS)

    Nakamura, H.; Machimura, T.; Ogawa, S.; Kosaka, Y.; Nishii, K.; Miyasaka, T.

    2015-12-01

    The East Asian summer monsoon fluctuates from its climatological activity on monthly and interannual time scales, and the most dominant pattern of the variability is known as the Pacific-Japan (PJ) pattern. Characterized by a meridional teleconnection in anomalous activity of the Meiyu/Baiu rainband, tropical storms and a surface subtropical anticyclone (the Bonin High) in between, the PJ pattern exerts substantial influence on summertime climatic conditions over East Asia and the western North Pacific. Despite the recent warming trend observed in its background state, no assessment thus far has been made on how substantially the PJ has undergone, if any, multi-decadal modulations in its structure and/or dominance. Through an EOF analysis applied to a new dataset of global atmospheric reanalysis (JRA-55), the predominance of the PJ pattern is confirmed as being extracted in the leading EOF of lower-tropospheric monthly vorticity anomalies over 55 recent years. Both efficient barotropic/baroclinic energy conversion from the climatological-mean state and efficient generation of available potential energy through anomalous convective activity over the tropical western Pacific are shown to be essential for the maintenance of the monthly atmospheric anomalies of the PJ pattern over the entire 55-year period. At the same time, however, the same EOF analysis as above but applied separately to each of the sub-periods reveals a distinct signature of long-term modulations in amplitude and thus the dominance of the PJ pattern. While being extracted in the first EOF up to the 1980s, the PJ pattern is extracted in the second EOF in the period since the 1990s with marked reductions in both the variance fraction explained and the efficiency of energy conversion/generation. The resultant modulations of the summertime meridional teleconnection are also discussed with implications for future changes.

  12. Mountain hemlock growth responds to climatic variability at annual and decadal time scales

    USGS Publications Warehouse

    Peterson, D.W.; Peterson, D.L.

    2001-01-01

    Improved understanding of tree growth responses to climate is needed to model and predict forest ecosystem responses to current and future climatic variability. We used dendroecological methods to study the effects of climatic variability on radial growth of a subalpine conifer, mountain hemlock (Tsuga mertensiana). Tree-ring chronologies were developed for 31 sites, spanning the latitudinal and elevational ranges of mountain hemlock in the Pacific Northwest. Factor analysis was used to identify common patterns of inter-annual growth variability among the chronologies, and correlation and regression analyses were used to identify climatic factors associated with that variability. Factor analysis identified three common growth patterns, representing groups of sites with different climate-growth relationships. At high-elevation and midrange sites in Washington and northern Oregon, growth was negatively correlated with spring snowpack depth, and positively correlated with growth-year summer temperature and the winter Pacific Decadal Oscillation index (PDO). In southern Oregon, growth was negatively correlated with spring snowpack depth and previous summer temperature, and positively correlated with previous summer precipitation. At the low-elevation sites, growth was mostly insensitive to annual climatic variability but displayed sensitivity to decadal variability in the PDO opposite to that found at high-elevation sites. Mountain hemlock growth appears to be limited by late snowmelt, short growing seasons, and cool summer temperatures throughout much of its range in the Pacific Northwest. Earlier snowmelt, higher summer temperatures, and lower summer precipitation in southern Oregon produce conditions under which growth is limited by summer temperature and/or soil water availability. Increasing atmospheric CO2 concentrations could produce warmer temperatures and reduced snowpack depths in the next century. Such changes would likely increase mountain hemlock growth

  13. Swithin St. Cleeve: Variable Star Observer

    NASA Astrophysics Data System (ADS)

    Weitzenhoffer, K.

    1986-12-01

    THomas Hardy's romance "Two on a Tower" is the first novel to use an astronomical background as its unifying theme and the first to cast an astronomer in the role of protagonist. One subplot of the novel concerns Swithin St. Cleeve's quest for fame through his observations of variable stars. Despite a number of observational and instrumental setbacks, he makes an amazing discovery about variable stars, one he is certain will excite the astronomical world. But before he can get the news into print, another astronomer announces that very discover and takes from St. Cleeve the fame he thought would be his.

  14. Temporal and climatic variables in naturalistic observation.

    PubMed

    Russell, M B; Bernal, M E

    1977-01-01

    Home-observation data on 5- to 7-yr-old boys collected over 2 yr were examined for systematic variations in rates of desirable and undesirable behaviors associated with several temporal and climatic variables. Significant effects associated with time of day, day of the week, precipitation, and temperature were found. No significant effects on the naturalistic observation data were found for environmental factors associated with lunar phase. It was noted that the correlational nature of the findings did not obviate the necessity for control of the influence of temporal and climatic variables. Several methodological strategies for such control were discussed.

  15. Tropical Atlantic Impacts on the Decadal Climate Variability of the Tropical Ocean and Atmosphere.

    NASA Astrophysics Data System (ADS)

    Li, X.; Xie, S. P.; Gille, S. T.; Yoo, C.

    2015-12-01

    Previous studies revealed atmospheric bridges between the tropical Pacific, Atlantic, and Indian Ocean. In particular, several recent works indicate that the Atlantic sea surface temperature (SST) may contribute to the climate variability over the equatorial Pacific. Inspired by these studies, our work aims at investigating the impact of the tropical Atlantic on the entire tropical climate system, and uncovering the physical dynamics under these tropical teleconnections. We first performed a 'pacemaker' simulation by restoring the satellite era tropical Atlantic SST changes in a fully coupled model - the CESM1. Results reveal that the Atlantic warming heats the Indo-Western Pacific and cools the Eastern Pacific, enhances the Walker circulation and drives the subsurface Pacific to a La Niña mode, contributing to 60-70% of the above tropical changes in the past 30 years. The same pan-tropical teleconnections have been validated by the statistics of observations and 106 CMIP5 control simulations. We then used a hierarchy of atmospheric and oceanic models with different complexities, to single out the roles of atmospheric dynamics, atmosphere-ocean fluxes, and oceanic dynamics in these teleconnections. With these simulations we established a two-step mechanism as shown in the schematic figure: 1) Atlantic warming generates an atmospheric deep convection and induces easterly wind anomalies over the Indo-Western Pacific in the form of Kelvin waves, and westerly wind anomalies over the eastern equatorial Pacific as Rossby waves, in line with Gill's solution. This circulation changes warms the Indo-Western Pacific and cools the Eastern Pacific with the wind-evaporation-SST effect, forming a temperature gradient over the Indo-Pacific basins. 2) The temperature gradient further generates a secondary atmospheric deep convection, which reinforces the easterly wind anomalies over the equatorial Pacific and enhances the Walker circulation, triggering the Pacific to a La Ni

  16. Hydrologic Sensitivities of Upper Indus Basin (North Pakistan) Rivers to Multi-Decadal Climatic Variability

    NASA Astrophysics Data System (ADS)

    Farhan, S. B.; Zhang, Y.; Ma, Y.; Haifeng, G.; Jilani, R.; Hashmi, D.; Rasul, G.

    2014-12-01

    Thermal inputs play a vital role in the management and seasonal distribution of stream-flows particularly in snow and glacier fed basins, therefore the signatures of the recent climate trends can also be observed in various hydrological variables in those basins. Upper Indus Basin (UIB) is located in the western part of Tibetan Plateau, and most of its flows are dependent on snow- and glacier-melt produced water, thus the analyses of historical stream-flows and climatic indicators in the snow-melt dominated rivers of UIB was carried out, which points towards an advance in the spring flow onset time over the past few decades. Trend results reveal that warm temperature spells in spring have occurred much earlier in recent years, which explains in part the trend in the timing of spring peak stream-flows owing to earlier occurrence of snow melt onset. The observed increase in spring stream-flows and decrease in summer stream-flows suggests a broad shift of snow-melt yield and spring peak flows. These trends are found to be strongest at lower elevations basins where winter temperatures are closer to the melting point, even modest variation in temperatures are capable to enforce large shifts in the basin hydrologic feedback. In addition, it appears that in recent years due to winter and spring warming, more of the precipitation is falling as rain rather than snow particularly in late winter and early spring seasons, consequently it is speculated that this shift in precipitation ratio (snow vs rain) and early warming spells might also affect local (basin-scale) Albedo via early recession and systematic decrease of snow cover area, which tends in lowering Albedo from an increased fraction of snow-free area, which instigate positive feedback on radiative balance that can perhaps causes local-scale heat redistribution, which collectively in turn augmented winter and early spring stream-flows in those basins. These observed hydro-climatological trends over UIB can have

  17. Ocean surface temperature variability: large model-data differences at decadal and longer periods.

    PubMed

    Laepple, Thomas; Huybers, Peter

    2014-11-25

    The variability of sea surface temperatures (SSTs) at multidecadal and longer timescales is poorly constrained, primarily because instrumental records are short and proxy records are noisy. Through applying a new noise filtering technique to a global network of late Holocene SST proxies, we estimate SST variability between annual and millennial timescales. Filtered estimates of SST variability obtained from coral, foraminifer, and alkenone records are shown to be consistent with one another and with instrumental records in the frequency bands at which they overlap. General circulation models, however, simulate SST variability that is systematically smaller than instrumental and proxy-based estimates. Discrepancies in variability are largest at low latitudes and increase with timescale, reaching two orders of magnitude for tropical variability at millennial timescales. This result implies major deficiencies in observational estimates or model simulations, or both, and has implications for the attribution of past variations and prediction of future change. PMID:25385623

  18. Ocean surface temperature variability: Large model–data differences at decadal and longer periods

    PubMed Central

    Laepple, Thomas; Huybers, Peter

    2014-01-01

    The variability of sea surface temperatures (SSTs) at multidecadal and longer timescales is poorly constrained, primarily because instrumental records are short and proxy records are noisy. Through applying a new noise filtering technique to a global network of late Holocene SST proxies, we estimate SST variability between annual and millennial timescales. Filtered estimates of SST variability obtained from coral, foraminifer, and alkenone records are shown to be consistent with one another and with instrumental records in the frequency bands at which they overlap. General circulation models, however, simulate SST variability that is systematically smaller than instrumental and proxy-based estimates. Discrepancies in variability are largest at low latitudes and increase with timescale, reaching two orders of magnitude for tropical variability at millennial timescales. This result implies major deficiencies in observational estimates or model simulations, or both, and has implications for the attribution of past variations and prediction of future change. PMID:25385623

  19. Interannual and decadal variability and trends in upper ocean temperatures in the North Pacific Ocean

    SciTech Connect

    White, W.B.; Cayan, D.R.

    1994-12-31

    Temperature profiles from the surface to 400 m deployed over the North Pacific Ocean for the 45 years from 1950--1994 are mapped onto a coarse grid each month, allowing trends in the upper ocean temperature to be estimated. Only temperature profiles distributed from 20{degree}N-60{degree}N are used, these subjected to rigorous scientific quality control. Two parameters are chosen to be representative of the upper ocean thermal structure; i.e., sea surface temperature (SST) and heat storage over the upper 400 m (HS400). Mapping of SST and HS400 is conducted monthly, with optimal interpolation utilizing a priori estimates of the covariance structure of the anomalous fields determined by White. This yields a time sequence of 540 monthly maps for each parameter over this 45-year period. Examining these time sequences for decadal variability and trends finds their magnitude and sign to change substantially as a function of geographical location over the North Pacific Ocean. For example, all along the west coast of North America, both SST and HS400 warmed during the past 45 years. But, in the middle of the North Pacific Ocean, both parameters cooled over this period. The average SST and HS400 over the entire domain from 20{degree}-60{degree}N did not show a trend. Rather, decadal variability dominated the time sequence, with the 1950`s colder than normal, the 1960`s near normal, the 1970`s warmer than normal, the 1980`s colder than normal, and the 1990`s warmer than normal. This natural decadal variability obscures any possible anthropogenic warming due to increased greenhouse gas concentrations in the atmosphere over this period.

  20. Variability and Trends in the Global Water Cycle Based on Multi-Decadal Earth Science Data Record

    NASA Astrophysics Data System (ADS)

    Wood, E. F.; Coccia, G.; Pan, M.; Sheffield, J.

    2014-12-01

    Documentation of the global water cycle and its evolution over time has been a primary scientific goal of the Global Energy and Water Exchanges Project, and is fundamental to providing a benchmark for the present climate, to document inter-annual variability and global change impacts, and to validate models. In developed countries, observation systems that include in-situ, remote sensing and modeled data can provide long-term, consistent and generally high quality datasets of water cycle variables. In less developed, data sparse regions, in situ data alone are insufficient to develop a comprehensive picture of how the water cycle is changing, and strategies that merge in-situ, model and satellite observations within a framework that results in consistent water cycle records is essential. This presentation will utilize newly developed, multi-decadal water and energy cycles data sets to analyze and advance our understanding of the role of the terrestrial hydrosphere in Earth's climate system. The data sets include a 60-year global water cycle dataset developed through a NASA-sponsored multi-institutional effort under the NASA MEaSUREs program, multi-model terrestrial evapotranspiration data sets coordinated under the GEWEX Data and Assessments Panel (GDAP) as part of the LandFlux initiative, and ocean evaporation under SeaFlux. The foundations of the datasets are a variety of independent large-scale datasets of the hydrologic variables that are used to bridge the gap between sparse in-situ observations, including remote-sensing based retrievals, observation-forced hydrologic modeling, and weather model reanalyses. Analyses are carried out across a range of temporal and spatial scales from monthly to annual and decadal, and from ~250 river basins to continental and global scales, and will address long-standing GEWEX science questions that include (i) quantifying the nature and extent of changes (trends and variability) to the terrestrial hydrosphere over the last 60

  1. Temporal Variability of Observed and Simulated Hyperspectral Earth Reflectance

    NASA Technical Reports Server (NTRS)

    Roberts, Yolanda; Pilewskie, Peter; Kindel, Bruce; Feldman, Daniel; Collins, William D.

    2012-01-01

    series analysis of the PC scores using techniques such as Singular Spectrum Analysis (SSA) and Multichannel SSA will provide information about the temporal variability of the dominant variables. Quantitative comparison techniques can evaluate how well the OSSE reproduces the temporal variability observed by SCIAMACHY spectral reflectance measurements during the first decade of the 21st century. PCA of OSSE-simulated reflectance can also be used to study how the dominant spectral variables change on centennial scales for forced and unforced climate change scenarios. To have confidence in OSSE predictions of the spectral variability of hyperspectral reflectance, it is first necessary for us to evaluate the degree to which the OSSE simulations are able to reproduce the Earth?s present-day spectral variability.

  2. Land surface phenological response to decadal climate variability across Australia using satellite remote sensing

    NASA Astrophysics Data System (ADS)

    Broich, M.; Huete, A.; Tulbure, M. G.; Ma, X.; Xin, Q.; Paget, M.; Restrepo-Coupe, N.; Davies, K.; Devadas, R.; Held, A.

    2014-05-01

    continent. The phenological cycle peak magnitude and integrated greenness were most significantly correlated with monthly SOI within the preceding 12 months. Correlation patterns occurred primarily over north-eastern Australia and within the MDB predominantly over natural land cover and particularly in floodplain and wetland areas. Integrated greenness of the phenological cycles (surrogate of productivity) showed positive anomalies of more than two standard deviations over most of eastern Australia in 2009-2010, which coincided with the transition between the El Niño induced decadal droughts to flooding caused by La Niña. The quantified spatial-temporal variability in phenology across Australia in response to climate variability presented here provides important information for land management and climate change studies and applications.

  3. Links between central Greenland stable isotopes, blocking and extreme climate variability over Europe at decadal to multidecadal time scales

    NASA Astrophysics Data System (ADS)

    Rimbu, N.; Lohmann, G.; Werner, M.; Ionita, M.

    2016-10-01

    The link between central Greenland stable oxygen isotopes, atmospheric blocking frequency and cold temperature extremes at decadal to multidecadal time scales is investigated using observed and proxy data as well as model experiments. A composite analysis reveals that positive stable isotope anomalies in central Greenland are associated with enhanced blocking activity in the Atlantic European region. Several indices of blocking activity in the Atlantic European region are higher correlated with central Greenland stable isotope time series than with the North Atlantic Oscillation indices both in observations and model simulation. Furthermore, the blocking frequency anomaly pattern associated with central Greenland stable isotope variability is similar to the blocking anomaly pattern associated with the Atlantic Multidecadal Oscillation. A composite analysis reveals that stable isotope variations in central Greenland are related to a large-scale pattern in the frequency of extreme low temperature events with significant positive anomalies over Europe and a southwest to northeast dipolar pattern over Asia. During observational period central Greenland isotope records, blocking and extreme temperature indices over Europe show enhanced variability 10-30 and 50-70 years. Similar quasi-periodicities dominate the spectrum of central Greenland isotope variability during the last millennium. We argue that long-term variations of climate extreme indices over Europe and Asia, as derived from observational data, can be put into a long-term perspective using central Greenland stable isotope ice core records.

  4. Simulated decadal variability of the meridional overturning circulation across the A25-Ovide section

    NASA Astrophysics Data System (ADS)

    DesbruyèRes, Damien; Thierry, Virginie; Mercier, Herlé

    2013-01-01

    Abstract<span class="hlt">Decadal</span> changes of the meridional overturning circulation (MOC) at the A25-Ovide section between Portugal and Greenland are investigated in a numerical simulation forced by atmospheric reanalysis data for the period 1965-2004. The intensity, composition, and structure of the upper MOC limb are assessed using a Lagrangian analysis tool. Its mean transport is fed by water masses of two distinct origins: the subtropics and the Labrador Sea. Two vertical overturning cells are consequently identified: a subtropical cell connecting low and high latitudes (12 Sv, 1 Sv = 106 m3 s-1) and a cell internal to the subpolar gyre (4 Sv). The <span class="hlt">decadal</span> MOC <span class="hlt">variability</span> is associated with synchronized transport changes of the subtropical and subpolar inflow within the North Atlantic Current (NAC). The varying strength of the MOC is further related to changes in the upper horizontal transport distribution. When the MOC is in a strong phase (early 1990s), the northern branch of the NAC in the Iceland Basin is strong while the southern branch at the Rockall Trough entrance is relatively weak. The inverse situation holds for a persistent weak MOC state (1970s). Contrary to the conclusions of earlier studies, <span class="hlt">variability</span> in the strength and shape of the subpolar gyre does not stand as the main driver of the changing NAC structure, which is largely induced by the horizontal <span class="hlt">variability</span> of the subtropical inflow. Additionally, the recently shown intrusion of subtropical waters into the northeastern Atlantic (late 1960s, early 1980s, and 2000s) are shown to primarily occur during periods of weak MOC circulation at A25-Ovide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7811D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7811D"><span id="translatedtitle">Simulated <span class="hlt">Decadal</span> <span class="hlt">Variability</span> of the Meridional Overturning Circulation across the A25-Ovide section</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Desbruyères, Damien; Thierry, Virginie; Mercier, Herlé</p> <p>2013-04-01</p> <p><span class="hlt">Decadal</span> changes of the Meridional Overturning Circulation (MOC) at the A25-Ovide section between Portugal and Greenland are investigated in a numerical simulation forced by atmospheric reanalysis data for the period 1965-2004. The intensity, composition and structure of the upper MOC limb are assessed using a Lagrangian analysis tool. Its mean transport is fed by water masses of two distinct origins: the subtropics and the Labrador Sea. Two vertical overturning cells are consequently identified: a subtropical cell connecting low and high latitudes (12 Sv, 1 Sv = 106 m3 s^-1) and a cell internal to the subpolar gyre (4 Sv). The <span class="hlt">decadal</span> MOC <span class="hlt">variability</span> is associated with synchronized transport changes of the subtropical and subpolar inflow within the North Atlantic Current (NAC). The varying strength of the MOC is further related to changes in the upper horizontal transport distribution. When the MOC is in a strong phase (early 1990's), the northern branch of the NAC in the Iceland Basin is strong while the southern branch at the Rockall Trough entrance is relatively weak. The inverse situation holds for a persistent weak MOC state (1970's). Contrary to the conclusions of earlier studies, <span class="hlt">variability</span> in the strength and shape of the subpolar gyre does not stand as the main driver of the changing NAC structure, which is largely induced by the horizontal <span class="hlt">variability</span> of the subtropical inflow. Additionally, the recently shown intrusion of subtropical waters into the Northeastern Atlantic (late 1960's, early 1980's and 2000's) are shown to primarily occur during periods of weak MOC circulation at A25-Ovide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22711907F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22711907F"><span id="translatedtitle"><span class="hlt">Variability</span> Statistics for Galaxies <span class="hlt">Observed</span> by Kepler</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fanelli, Michael N.; Marcum, Pamela M.; Van Cleve, Jeffrey E.</p> <p>2016-01-01</p> <p>The Kepler / K2 telescope combines high photometric precision with near-continuous <span class="hlt">observing</span> cadence, permitting a unique perspective on the optical / near-IR <span class="hlt">variability</span> of galactic systems. In particular, Kepler / K2 data can be exploited to quantify the amplitude of AGN signals in galaxy cores, to directly address this question - What fraction of galactic nuclei are active at any given time ? Alternatively stated, this question becomes - What is the duty cycle for supermassive black hole accretion of sufficient strength to produce a detectable optical signal ? Additionally, the quasi-continuous cadence provides the capability to detect low-level episodic variations from the central AGN, highly luminous stars and other compact objects.Previously we reported on analysis of a subset of the complete galaxy dataset <span class="hlt">observed</span> during the Kepler prime mission: ~1200 individual light curves of ~150 targeted galaxies <span class="hlt">observed</span> during Quarters 3-10 and ~1000 light curves of galaxies <span class="hlt">observed</span> serendipitously by the exoplanet program from Q2 through Q16. Based on an average of 8 quarters of data for ~300 systems and excluding systems specifically targeted as AGNs, we found that the <span class="hlt">observed</span> occurrence rate of nuclear <span class="hlt">variability</span> in galaxies with amplitude > 1 millimag is ~2-3%, a value which is ~ 2-3 times smaller than previous estimates from ground-based monitoring.Here we provide an update on galactic nuclear <span class="hlt">variability</span> statistics using an expanded dataset from the Kepler Prime mission. We combine the previous data with 1200 light curves for ~200 targeted systems from Q11-16 and ~800 additional light curves found in the exoplanet program. These data are the longest continuous time series for galaxies ever obtained - some systems were <span class="hlt">observed</span> for the entire mission (Q2-16). Our previous result is confirmed using this expanded dataset; only a few percent of galaxies show <span class="hlt">variability</span> above 0.5 millimag. Several systems exhibiting activity in other bands, or via their optical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPSC....9...62F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPSC....9...62F"><span id="translatedtitle">Seasonal Evolution of Saturn's Polar Atmosphere from a <span class="hlt">Decade</span> of Cassini/CIRS <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fletcher, L. N.; Sinclair, J. A.; Irwin, P. G. J.; Giles, R. S.; Orton, G. S.; Hesman, B. E.; Hurley, J.; Bjoraker, G. L.; Simon, A. A.</p> <p>2014-04-01</p> <p>Saturn's polar regions are subjected to extreme insolation variations over its 29.5 year orbit due to the gas giant's 26-degree axial tilt, causing seasonal changes to the thermal structure, chemistry, dynamics and cloud properties of the polar environments. Cassini's high inclination orbits permit detailed scrutiny of Saturn's high latitudes in a dataset that now spans a <span class="hlt">decade</span> (a third of a Saturn year, 2004-2014), five years either side of the northern spring equinox in 2009. Thermal infrared Cassini/CIRS spectra (7-16 μm) from all mission phases are inverted to determine the rate of change of polar temperatures, wind shears, tropospheric phosphine (as a tracer of vertical mixing) and stratospheric hydrocarbons (tracers of middle atmospheric circulation and chemistry). Cassini's unique vantage point allows us to track these parameters as the summer southern pole receded into autumn and the winter northern pole emerged into spring sunlight. Results show the most rapid changes to temperature and composition occurring poleward of 70o in each hemisphere, in excess of expectations from simple radiative climate models. Small cyclonic vortices persist at both poles throughout theCassini mission, while the broad stratospheric vortices are seasonally <span class="hlt">variable</span>. The signature of the northern hexagon is still present in the tropospheric thermal structure. At the time of writing, an infraredbright polar vortex is beginning to emerge at the northern spring pole, consistent with the historical record of Saturn <span class="hlt">observations</span> from the 1980s (previous northern spring, [4]).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H13C1120T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H13C1120T"><span id="translatedtitle"><span class="hlt">Decadal</span> climatic <span class="hlt">variability</span> and regional weather simulation: stochastic nature of forest fuel moisture and climatic forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsinko, Y.; Johnson, E. A.; Martin, Y. E.</p> <p>2014-12-01</p> <p>Natural range of <span class="hlt">variability</span> of forest fire frequency is of great interest due to the current changing climate and seeming increase in the number of fires. The <span class="hlt">variability</span> of the annual area burned in Canada has not been stable in the 20th century. Recently, these changes have been linked to large scale climate cycles, such as Pacific <span class="hlt">Decadal</span> Oscillation (PDO) phases and El Nino Southern Oscillation (ENSO). The positive phase of the PDO was associated with the increased probability of hot dry spells leading to drier fuels and increased area burned. However, so far only one historical timeline was used to assess correlations between the natural climate oscillations and forest fire frequency. To counteract similar problems, weather generators are extensively used in hydrological and agricultural modeling to extend short instrumental record and to synthesize long sequences of daily weather parameters that are different from but statistically similar to historical weather. In the current study synthetic weather models were used to assess effects of alternative weather timelines on fuel moisture in Canada by using Canadian Forest Fire Weather Index moisture codes and potential fire frequency. The <span class="hlt">variability</span> of fuel moisture codes was found to increase with the increased length of simulated series, thus indicating that the natural range of <span class="hlt">variability</span> of forest fire frequency may be larger than that calculated from available short records. It may be viewed as a manifestation of a Hurst effect. Since PDO phases are thought to be caused by diverse mechanisms including overturning oceanic circulation, some of the lower frequency signals may be attributed to the long term memory of the oceanic system. Thus, care must be taken when assessing natural <span class="hlt">variability</span> of climate dependent processes without accounting for potential long-term mechanisms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020194','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020194"><span id="translatedtitle">Mesoscale disturbance and ecological response to <span class="hlt">decadal</span> climatic <span class="hlt">variability</span> in the American Southwest</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Swetnam, T.W.; Betancourt, J.L.</p> <p>1998-01-01</p> <p>Ecological responses to climatic <span class="hlt">variability</span> in the Southwest include regionally synchronized fires, insect outbreaks, and pulses in tree demography (births and deaths). Multicentury, tree-ring reconstructions of drought, disturbance history, and tree demography reveal climatic effects across scales, from annual to <span class="hlt">decadal</span>, and from local (<102 km2) to mesoscale (104-106 km2). Climate-disturbance relations are more <span class="hlt">variable</span> and complex than previously assumed. During the past three centuries, mesoscale outbreaks of the western spruce budworm (Choristoneura occidentalis) were associated with wet, not dry episodes, contrary to conventional wisdom. Regional fires occur during extreme droughts but, in some ecosystems, antecedent wet conditions play a secondary role by regulating accumulation of fuels. Interdecadal changes in fire-climate associations parallel other evidence for shifts in the frequency or amplitude of the Southern Oscillation (SO) during the past three centuries. High interannual, fire-climate correlations (r = 0.7 to 0.9) during specific <span class="hlt">decades</span> (i.e., circa 1740-80 and 1830-60) reflect periods of high amplitude in the SO and rapid switching from extreme wet to dry years in the Southwest, thereby entraining fire occurrence across the region. Weak correlations from 1780 to 1830 correspond with a decrease in SO frequency or amplitude inferred from independent tree-ring width, ice core, and coral isotope reconstructions. Episodic dry and wet episodes have altered age structures and species composition of woodland and conifer forests. The scarcity of old, living conifers established before circa 1600 suggests that the extreme drought of 1575-95 had pervasive effects on tree populations. The most extreme drought of the past 400 years occurred in the mid-twentieth century (1942-57). This drought resulted in broadscale plant dieoffs in shrublands, woodlands, and forests and accelerated shrub invasion of grasslands. Drought conditions were broken by the post</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcDyn..66.1317L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcDyn..66.1317L"><span id="translatedtitle">The eddy-dipole mode interaction and the <span class="hlt">decadal</span> <span class="hlt">variability</span> of the Kuroshio Extension system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luo, Dehai; Feng, Shaohua; Wu, Lixin</p> <p>2016-10-01</p> <p>In this paper, the physical cause of why the eddy kinetic energy (EKE) in the upstream Kuroshio Extension (KE) region is strong (weak) during a large (small) jet meandering period is studied by using the satellite altimeter data and constructing an eddy-dipole mode interaction theory from a reduced gravity shallow water wave quasi-geostrophic vorticity equation. It is found that the large KE jet meander corresponds to a large-scale positive-over-negative dipole SSH anomaly (KED- mode, hereafter), a double-branch jet with a weak strength and a strong EKE in the upstream KE region, while the small jet meander corresponds to a negative-over-positive dipole anomaly (KED+ mode, hereafter), a strong single-branch jet, and a weak EKE. Further diagnostics using this new eddy-dipole mode interaction theory reveals that the horizontal advection and KED deformation field can change the eddy activity in the upstream KE region. When the KED- mode is amplified by mesoscale eddies, the EKE grows by extracting energy from the KED- deformation (shearing and stretching) field and due to a reduced eastward advection, thus showing a high EKE level during the KED- mode (large jet meander) episode. In contrast, when the KED+ mode is intensified, the kinetic energy of the eddy weakens by losing its energy to the KED+ deformation field and by an enhanced eastward advection, thus showing a low EKE level during the KED+ mode (small jet meander) episode. Because the KED mode shows a clear <span class="hlt">decadal</span> variation due to the modulation of the Pacific <span class="hlt">Decadal</span> Oscillation, both the KE jet and EKE exhibit inevitably a distinct <span class="hlt">decadal</span> <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcDyn.tmp...76L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcDyn.tmp...76L"><span id="translatedtitle">The eddy-dipole mode interaction and the <span class="hlt">decadal</span> <span class="hlt">variability</span> of the Kuroshio Extension system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luo, Dehai; Feng, Shaohua; Wu, Lixin</p> <p>2016-09-01</p> <p>In this paper, the physical cause of why the eddy kinetic energy (EKE) in the upstream Kuroshio Extension (KE) region is strong (weak) during a large (small) jet meandering period is studied by using the satellite altimeter data and constructing an eddy-dipole mode interaction theory from a reduced gravity shallow water wave quasi-geostrophic vorticity equation. It is found that the large KE jet meander corresponds to a large-scale positive-over-negative dipole SSH anomaly (KED- mode, hereafter), a double-branch jet with a weak strength and a strong EKE in the upstream KE region, while the small jet meander corresponds to a negative-over-positive dipole anomaly (KED+ mode, hereafter), a strong single-branch jet, and a weak EKE. Further diagnostics using this new eddy-dipole mode interaction theory reveals that the horizontal advection and KED deformation field can change the eddy activity in the upstream KE region. When the KED- mode is amplified by mesoscale eddies, the EKE grows by extracting energy from the KED- deformation (shearing and stretching) field and due to a reduced eastward advection, thus showing a high EKE level during the KED- mode (large jet meander) episode. In contrast, when the KED+ mode is intensified, the kinetic energy of the eddy weakens by losing its energy to the KED+ deformation field and by an enhanced eastward advection, thus showing a low EKE level during the KED+ mode (small jet meander) episode. Because the KED mode shows a clear <span class="hlt">decadal</span> variation due to the modulation of the Pacific <span class="hlt">Decadal</span> Oscillation, both the KE jet and EKE exhibit inevitably a distinct <span class="hlt">decadal</span> <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002GeoRL..29.1351B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002GeoRL..29.1351B"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> of the North Pacific Polar Front: Subsurface warming versus surface cooling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belkin, Igor; Krishfield, Richard; Honjo, Susumu</p> <p>2002-05-01</p> <p>Over 200 hydrographic sections are used to trace the Polar Front defined as the southern boundary of the ``pure'' subarctic stratification with a pronounced, extremely cold, subsurface temperature minimum underlain by a temperature maximum. The front extends from 40°N off Japan to 57°N in the Gulf of Alaska where it retroflects and continues WSW with the Alaskan Stream. The front's <span class="hlt">decadal</span> <span class="hlt">variability</span> from 1977-1999 is examined along 150°E, 170°E, 175.5°E, and 180°E. At these longitudes the front is relatively stable, except for 170°E, where it shifts north-south by 400 km every 6 years. Most time series reveal a subsurface warming of ~1°C per <span class="hlt">decade</span>, and a surface cooling, of the front. Since the subsurface temperature minimum is a remnant of winter convection, the subsurface warming signals an amelioration of the winter climate, whereas the summer climate becomes colder.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PASP..110..906H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PASP..110..906H"><span id="translatedtitle"><span class="hlt">Observations</span> of Three Suspected Cataclysmic <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoard, D. W.; Wachter, S.</p> <p>1998-08-01</p> <p>We have obtained photometric and spectroscopic <span class="hlt">observations</span> of the suspected cataclysmic <span class="hlt">variable</span> stars VW Tucanae, Phe 1, and Scl 2. VW Tuc and Phe 1 are confirmed as cataclysmic <span class="hlt">variables</span> (CVs). VW Tuc has the spectrum of a ``normal,'' disk-accreting CV. Phe 1 is a double-lined spectroscopic binary that may have a short orbital period-a time-resolved spectroscopic study of the kinematics in this system could have important implications to the understanding of CV structure and evolution. Scl 2 appears to be a non-CV composed of a late-type dwarf emission (dMe) star with a (noninteracting) white dwarf or hot subdwarf companion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22425506','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22425506"><span id="translatedtitle">Black Sea biogeochemistry: response to <span class="hlt">decadal</span> atmospheric <span class="hlt">variability</span> during 1960-2000 inferred from numerical modeling.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>He, Yunchang; Stanev, Emil V; Yakushev, Evgeniy; Staneva, Joanna</p> <p>2012-06-01</p> <p>The long-term <span class="hlt">variability</span> of the physical and biochemical structure of oxic and suboxic layers in the Black Sea was studied using a one-dimensional coupled hydrophysical and biogeochemical model. The focus was on the correlation between atmospheric forcing (2 m air temperature and dew point temperature, surface level pressure, surface wind) affected by the North Atlantic Oscillation in and the regional responses. The quality of model performance was demonstrated using <span class="hlt">observed</span> vertical and temporal distribution of biogeochemical <span class="hlt">variables</span>. It was shown that during 1960-2000, the long-term <span class="hlt">variability</span> of simulated winter-mean SST in the Black Sea correlated reasonably well with the <span class="hlt">variability</span> of 2 m air temperature. Furthermore, the thermal state of the upper ocean impacted largely on the <span class="hlt">variability</span> of biogeochemical <span class="hlt">variables</span>, such as oxygen, nitrate and phytoplankton concentration. The tele-connection between North Atlantic Oscillation and Black Sea biogeochemistry was manifested in a different way for the specific time-interval 1960-2000; the corresponding regime shifts were thus associated with the large scale forcing. One such extreme event occurred in 1976 leading to a pronounced shift in the oxygen and hydrogen sulfide state. PMID:22425506</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...46.3657Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...46.3657Z"><span id="translatedtitle">Dynamics and mechanisms of <span class="hlt">decadal</span> <span class="hlt">variability</span> of the Pacific-South America mode over the 20th century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Li; Ma, Hao; Wu, Lixin</p> <p>2016-06-01</p> <p>In this paper, <span class="hlt">decadal</span> <span class="hlt">variability</span> of the Pacific-South America (PSA) mode is examined from year 1871 to 2008 based on the newly developed ocean and atmosphere reanalysis products. The PSA mode, mirroring the Pacific-North America mode in the Northern Hemisphere, emerges as the second EOF mode of 500 mb geopotential height anomalies. The mode displays substantial interannual-<span class="hlt">decadal</span> <span class="hlt">variability</span> with distinct timescales between 3-8 and 10-18 years, respectively. The <span class="hlt">decadal</span> <span class="hlt">variability</span> of the PSA mode is found to be associated with the coupled ocean-atmosphere interaction over the subtropical South and tropical Pacific. The subduction of the subtropical temperature anomalies in the South Pacific in conjunction with the tropical-subtropical atmospheric teleconnection plays important role in the <span class="hlt">decadal</span> <span class="hlt">variability</span> of the PSA mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1904169','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1904169"><span id="translatedtitle">Simulated and <span class="hlt">observed</span> <span class="hlt">variability</span> in ocean temperature and heat content</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>AchutaRao, K. M.; Ishii, M.; Santer, B. D.; Gleckler, P. J.; Taylor, K. E.; Barnett, T. P.; Pierce, D. W.; Stouffer, R. J.; Wigley, T. M. L.</p> <p>2007-01-01</p> <p><span class="hlt">Observations</span> show both a pronounced increase in ocean heat content (OHC) over the second half of the 20th century and substantial OHC <span class="hlt">variability</span> on interannual-to-<span class="hlt">decadal</span> time scales. Although climate models are able to simulate overall changes in OHC, they are generally thought to underestimate the amplitude of OHC <span class="hlt">variability</span>. Using simulations of 20th century climate performed with 13 numerical models, we demonstrate that the apparent discrepancy between modeled and <span class="hlt">observed</span> <span class="hlt">variability</span> is largely explained by accounting for changes in <span class="hlt">observational</span> coverage and instrumentation and by including the effects of volcanic eruptions. Our work does not support the recent claim that the 0- to 700-m layer of the global ocean experienced a substantial OHC decrease over the 2003 to 2005 time period. We show that the 2003–2005 cooling is largely an artifact of a systematic change in the <span class="hlt">observing</span> system, with the deployment of Argo floats reducing a warm bias in the original <span class="hlt">observing</span> system. PMID:17578928</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JGRC..120.7166W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JGRC..120.7166W&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> in seawater pH in the West Pacific: Evidence from coral δ11B records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Gangjian; Wang, Zhibing; Ke, Ting; Liu, Ying; Deng, Wenfeng; Chen, Xuefei; Xu, Jifeng; Zeng, Ti; Xie, Luhua</p> <p>2015-11-01</p> <p>Long-term seawater pH records are essential for evaluating the rates of ocean acidification (OA) driven by anthropogenic emissions. Widespread, natural <span class="hlt">decadal</span> <span class="hlt">variability</span> in seawater pH superimposes on the long-term anthropogenic variations, likely influencing the OA rates estimated from the pH records. Here, we report a record of annual seawater pH estimated using the δ11B proxy over the past 159 years reconstructed from a Porites coral collected to the east of Hainan Island in the northern South China Sea (SCS). By coupling this time series with previously reported long-term seawater pH records in the West Pacific, the <span class="hlt">decadal</span> <span class="hlt">variability</span> in seawater pH records and its possible driving mechanisms were investigated. The results indicate that large <span class="hlt">decadal</span> <span class="hlt">variability</span> in seawater pH has occurred off eastern Hainan Island over the past 159 years, in agreement with previous records. The Qiongdong upwelling system, which controls nutrient supplies, regulates surface water productivity, and is driven by the East Asian summer monsoon, is the primary control of this <span class="hlt">decadal</span> <span class="hlt">variability</span>, while terrestrial inputs appear not influence significantly. Meanwhile the impacts of the Pacific <span class="hlt">Decadal</span> Oscillation (PDO) and the El Nino and Southern Oscillation (ENSO) systems on seawater pH off eastern Hainan Island is likely limited. In contrast, the PDO is the main factor to influence the <span class="hlt">decadal</span> seawater pH <span class="hlt">variability</span> offshore the East Australia, while the mechanism controlling the <span class="hlt">decadal</span> seawater pH <span class="hlt">variability</span> in Guam is not clear yet. Meanwhile, The rate of decrease in seawater pH estimated from coral records are significantly different in different regions and over different time spans, which may reflect a combination of natural <span class="hlt">decadal</span> <span class="hlt">variability</span> in seawater pH and long-term variations. Therefore, understanding the mechanisms driving natural <span class="hlt">variability</span> in seawater pH is important for improving estimates of ocean acidification rates driven by anthropogenic emissions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014BGeo...11.5181B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014BGeo...11.5181B"><span id="translatedtitle">Land surface phenological response to <span class="hlt">decadal</span> climate <span class="hlt">variability</span> across Australia using satellite remote sensing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Broich, M.; Huete, A.; Tulbure, M. G.; Ma, X.; Xin, Q.; Paget, M.; Restrepo-Coupe, N.; Davies, K.; Devadas, R.; Held, A.</p> <p>2014-09-01</p> <p>Land surface phenological cycles of vegetation greening and browning are influenced by <span class="hlt">variability</span> in climatic forcing. Quantitative spatial information on phenological cycles and their <span class="hlt">variability</span> is important for agricultural applications, wildfire fuel accumulation, land management, land surface modeling, and climate change studies. Most phenology studies have focused on temperature-driven Northern Hemisphere systems, where phenology shows annually recurring patterns. However, precipitation-driven non-annual phenology of arid and semi-arid systems (i.e., drylands) received much less attention, despite the fact that they cover more than 30% of the global land surface. Here, we focused on Australia, a continent with one of the most <span class="hlt">variable</span> rainfall climates in the world and vast areas of dryland systems, where a detailed phenological investigation and a characterization of the relationship between phenology and climate <span class="hlt">variability</span> are missing. To fill this knowledge gap, we developed an algorithm to characterize phenological cycles, and analyzed geographic and climate-driven <span class="hlt">variability</span> in phenology from 2000 to 2013, which included extreme drought and wet years. We linked derived phenological metrics to rainfall and the Southern Oscillation Index (SOI). We conducted a continent-wide investigation and a more detailed investigation over the Murray-Darling Basin (MDB), the primary agricultural area and largest river catchment of Australia. Results showed high inter- and intra-annual <span class="hlt">variability</span> in phenological cycles across Australia. The peak of phenological cycles occurred not only during the austral summer, but also at any time of the year, and their timing varied by more than a month in the interior of the continent. The magnitude of the phenological cycle peak and the integrated greenness were most significantly correlated with monthly SOI within the preceding 12 months. Correlation patterns occurred primarily over northeastern Australia and within the MDB</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016BGeo...13.3071F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016BGeo...13.3071F"><span id="translatedtitle">Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: <span class="hlt">variability</span> on seasonal to <span class="hlt">decadal</span> timescales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, Gerhard; Romero, Oscar; Merkel, Ute; Donner, Barbara; Iversen, Morten; Nowald, Nico; Ratmeyer, Volker; Ruhland, Götz; Klann, Marco; Wefer, Gerold</p> <p>2016-05-01</p> <p>A more than two-<span class="hlt">decadal</span> sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analysed with respect to deep ocean mass fluxes, flux components and their <span class="hlt">variability</span> on seasonal to <span class="hlt">decadal</span> timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on <span class="hlt">decadal</span> timescales. High winter fluxes of biogenic silica (BSi), used as a measure of marine production (mostly by diatoms) largely correspond to a positive North Atlantic Oscillation (NAO) index (December-March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004-2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter and occasionally in summer/autumn enhanced particle sedimentation and carbon export on short timescales via the ballasting effect. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) might have weakened the relationships between fluxes and large-scale climatic oscillations. As phytoplankton biomass is high throughout the year, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by incorporating dust into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was <span class="hlt">observed</span> for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all bulk fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997-1999 where low fluxes were obtained for almost 1 year during the warm El Niño and high fluxes in the following cold La Niña phase. For <span class="hlt">decadal</span> timescales, Bakun (1990) suggested an intensification of coastal upwelling</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998JCli...11.3128S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998JCli...11.3128S&link_type=ABSTRACT"><span id="translatedtitle">Mesoscale Disturbance and Ecological Response to <span class="hlt">Decadal</span> Climatic <span class="hlt">Variability</span> in the American Southwest.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swetnam, Thomas W.; Betancourt, Julio L.</p> <p>1998-12-01</p> <p>Ecological responses to climatic <span class="hlt">variability</span> in the Southwest include regionally synchronized fires, insect outbreaks, and pulses in tree demography (births and deaths). Multicentury, tree-ring reconstructions of drought, disturbance history, and tree demography reveal climatic effects across scales, from annual to <span class="hlt">decadal</span>, and from local (<102 km2) to mesoscale (104-106 km2). Climate-disturbance relations are more <span class="hlt">variable</span> and complex than previously assumed. During the past three centuries, mesoscale outbreaks of the western spruce budworm (Choristoneura occidentalis) were associated with wet, not dry episodes, contrary to conventional wisdom. Regional fires occur during extreme droughts but, in some ecosystems, antecedent wet conditions play a secondary role by regulating accumulation of fuels. Interdecadal changes in fire-climate associations parallel other evidence for shifts in the frequency or amplitude of the Southern Oscillation (SO) during the past three centuries. High interannual, fire-climate correlations (r = 0.7 to 0.9) during specific <span class="hlt">decades</span> (i.e., circa 1740-80 and 1830-60) reflect periods of high amplitude in the SO and rapid switching from extreme wet to dry years in the Southwest, thereby entraining fire occurrence across the region. Weak correlations from 1780 to 1830 correspond with a decrease in SO frequency or amplitude inferred from independent tree-ring width, ice core, and coral isotope reconstructions.Episodic dry and wet episodes have altered age structures and species composition of woodland and conifer forests. The scarcity of old, living conifers established before circa 1600 suggests that the extreme drought of 1575-95 had pervasive effects on tree populations. The most extreme drought of the past 400 years occurred in the mid-twentieth century (1942-57). This drought resulted in broadscale plant dieoffs in shrublands, woodlands, and forests and accelerated shrub invasion of grasslands. Drought conditions were broken by the post</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCC...6..856S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCC...6..856S"><span id="translatedtitle">Contribution of sea-ice loss to Arctic amplification is regulated by Pacific Ocean <span class="hlt">decadal</span> <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Screen, James A.; Francis, Jennifer A.</p> <p>2016-09-01</p> <p>The pace of Arctic warming is about double that at lower latitudes--a robust phenomenon known as Arctic amplification. Many diverse climate processes and feedbacks cause Arctic amplification, including positive feedbacks associated with diminished sea ice. However, the precise contribution of sea-ice loss to Arctic amplification remains uncertain. Through analyses of both <span class="hlt">observations</span> and model simulations, we show that the contribution of sea-ice loss to wintertime Arctic amplification seems to be dependent on the phase of the Pacific <span class="hlt">Decadal</span> Oscillation (PDO). Our results suggest that, for the same pattern and amount of sea-ice loss, consequent Arctic warming is larger during the negative PDO phase relative to the positive phase, leading to larger reductions in the poleward gradient of tropospheric thickness and to more pronounced reductions in the upper-level westerlies. Given the oscillatory nature of the PDO, this relationship has the potential to increase skill in <span class="hlt">decadal</span>-scale predictability of the Arctic and sub-Arctic climate. Our results indicate that Arctic warming in response to the ongoing long-term sea-ice decline is greater (reduced) during periods of the negative (positive) PDO phase. We speculate that the <span class="hlt">observed</span> recent shift to the positive PDO phase, if maintained and all other factors being equal, could act to temporarily reduce the pace of wintertime Arctic warming in the near future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PrOce..62...33M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PrOce..62...33M"><span id="translatedtitle">Annual and <span class="hlt">decadal</span> <span class="hlt">variability</span> in the western subtropical North Atlantic: signal characteristics and sampling methodologies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Molinari, Robert L.</p> <p>2004-07-01</p> <p>Upper ocean (above 750 m) temperature structure of the northwestern subtropical Atlantic, including the Gulf Stream and a recirculation gyre south of the Stream, is characterized using primarily bathythermograph (BT) data collected between 1950 and 2003. Geostrophic calculations, using mean temperature-salinity relationships to compute dynamic height, are used to estimate velocities and transports. The mean annual Gulf Stream transport at 72° W relative to 750 m, 36.1 Sv, is approximately equal to the sum of the transport of the Florida Current, 32.0 Sv, and a shallow recirculation gyre described by Wang and Koblinsky [Journal of Physical Oceanography 26 (1996) 2462-2479], 5.5 Sv. The annual cycle of geostrophic transport relative to 750 m at 72° W is in phase with both an earlier published annual cycle of transport relative to 2000 m derived from hydrographic <span class="hlt">observations</span> and the annual cycle of Florida Current transport measured indirectly by a submarine cable (i.e., maximum transports are <span class="hlt">observed</span> in the summer and minimum in the fall, early winter). However, simple Sverdrup dynamics are inadequate to explain these cycles as maximum Sverdrup transports extend from winter to summer, while <span class="hlt">observed</span> transports are minimum (maximum) in fall/winter (summer). The annual cycles derived from the BT data of the size of the shallow southern recirculation gyre, Gulf Stream position and upper layer transport (relative to 300 m) are in phase (maximum size, northern position and transport in fall) and consistent with the WK results derived from altimetry. However, the shallower annual cycles are out of phase with the deeper signals (i.e., maximum for the former (latter) are <span class="hlt">observed</span> in fall (summer)). <span class="hlt">Decadal</span> signals after 1965 in Gulf Stream position, geostrophic transport relative to 450 m, and the size of a recirculation gyre south of the Stream are approximately in phase as <span class="hlt">observed</span> for the annual signal. This gyre and the shallow WK gyre exhibit the same horizontal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JSR....93..118F&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JSR....93..118F&link_type=ABSTRACT"><span id="translatedtitle">High marsh foraminiferal assemblages' response to intra-<span class="hlt">decadal</span> and multi-<span class="hlt">decadal</span> precipitation <span class="hlt">variability</span>, between 1934 and 2010 (Minho, NW Portugal)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fatela, Francisco; Moreno, João; Leorri, Eduardo; Corbett, Reide</p> <p>2014-10-01</p> <p>Foraminiferal assemblages of Caminha tidal marshes have been studied since 2002 revealing a peculiar dominance of brackish species, such as Haplophragmoides manilaensis, Haplophragmoides wilberti, Haplophragmoides sp., Pseudothurammina limnetis and Trochamminita salsa/irregularis in the high marshes of the Minho and the Coura lower estuaries. The assemblage composition reflects low salinity conditions, despite the short distance to the estuarine mouth (~ 4 km). However, in May 2010, the presence of salt marsh species Trochammina inflata and Jadammina macrescens became very significant, likely a result of 5 consecutive dry years and a corresponding salinity rise in sediment pore water. Correspondence analysis (CA) groups the surface samples according to their marsh zone, showing a positive correlation with the submersion time of each sampling point. The brackish and normal salinity foraminiferal species appear separated in the CA. This <span class="hlt">observation</span> was applied to the top 10 cm of a high marsh sediment core that corresponds to the period of instrumental record of precipitation and river flow in the Minho region. We found that river flow strongly correlates with precipitation in the Lima and Minho basins. The longer precipitation record was, therefore, used to interpret the foraminiferal assemblages' <span class="hlt">variability</span>. Three main phases were distinguished along ca. 80 years of precipitation data: 1) negative anomalies from 1934 to 1957; 2) positive anomalies from 1958 to 1983; and 3) negative anomalies from 1984 to 2010. This last dryer period exhibits the precipitation maximum and the greatest amplitude of rainfall values. High marsh foraminifera reveals a fast response to these short-term shifts; low salinity species relative abundance increases when precipitation increases over several <span class="hlt">decades</span>, as well as in the same <span class="hlt">decade</span>, in the years of heavy rainfall of dryer periods. High marsh foraminifera records the increase of freshwater flooding and seepage by 1) decreasing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014WRR....50.2425G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014WRR....50.2425G&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Decadal</span> surface water quality trends under <span class="hlt">variable</span> climate, land use, and hydrogeochemical setting in Iowa, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Green, Christopher T.; Bekins, Barbara A.; Kalkhoff, Stephen J.; Hirsch, Robert M.; Liao, Lixia; Barnes, Kimberlee K.</p> <p>2014-03-01</p> <p>Understanding how nitrogen fluxes respond to changes in agriculture and climate is important for improving water quality. In the midwestern United States, expansion of corn cropping for ethanol production led to increasing N application rates in the 2000s during a period of extreme <span class="hlt">variability</span> of annual precipitation. To examine the effects of these changes, surface water quality was analyzed in 10 major Iowa Rivers. Several <span class="hlt">decades</span> of concentration and flow data were analyzed with a statistical method that provides internally consistent estimates of the concentration history and reveals flow-normalized trends that are independent of year-to-year streamflow variations. Flow-normalized concentrations of nitrate+nitrite-N decreased from 2000 to 2012 in all basins. To evaluate effects of annual discharge and N loading on these trends, multiple conceptual models were developed and calibrated to flow-weighted annual concentrations. The recent declining concentration trends can be attributed to both very high and very low discharge in the 2000s and to the long (e.g., 8 year) subsurface residence times in some basins. Dilution of N and depletion of stored N occurs in years with high discharge. Reduced N transport and increased N storage occurs in low-discharge years. Central Iowa basins showed the greatest reduction in flow-normalized concentrations, likely because of smaller storage volumes and shorter residence times. Effects of land-use changes on the water quality of major Iowa Rivers may not be noticeable for years or <span class="hlt">decades</span> in peripheral basins of Iowa, and may be obscured in the central basins where extreme flows strongly affect annual concentration trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70100468','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70100468"><span id="translatedtitle"><span class="hlt">Decadal</span> surface water quality trends under <span class="hlt">variable</span> climate, land use, and hydrogeochemical setting in Iowa, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Green, Christopher T.; Bekins, Barbara A.; Kalkhoff, Stephen J.; Hirsch, Robert M.; Liao, Lixia; Barnes, Kimberlee K.</p> <p>2014-01-01</p> <p>Understanding how nitrogen fluxes respond to changes in agriculture and climate is important for improving water quality. In the midwestern United States, expansion of corn cropping for ethanol production led to increasing N application rates in the 2000s during a period of extreme <span class="hlt">variability</span> of annual precipitation. To examine the effects of these changes, surface water quality was analyzed in 10 major Iowa Rivers. Several <span class="hlt">decades</span> of concentration and flow data were analyzed with a statistical method that provides internally consistent estimates of the concentration history and reveals flow-normalized trends that are independent of year-to-year streamflow variations. Flow-normalized concentrations of nitrate+nitrite-N decreased from 2000 to 2012 in all basins. To evaluate effects of annual discharge and N loading on these trends, multiple conceptual models were developed and calibrated to flow-weighted annual concentrations. The recent declining concentration trends can be attributed to both very high and very low discharge in the 2000s and to the long (e.g., 8 year) subsurface residence times in some basins. Dilution of N and depletion of stored N occurs in years with high discharge. Reduced N transport and increased N storage occurs in low-discharge years. Central Iowa basins showed the greatest reduction in flow-normalized concentrations, likely because of smaller storage volumes and shorter residence times. Effects of land-use changes on the water quality of major Iowa Rivers may not be noticeable for years or <span class="hlt">decades</span> in peripheral basins of Iowa, and may be obscured in the central basins where extreme flows strongly affect annual concentration trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1812286S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1812286S"><span id="translatedtitle">External forcing as a source for the <span class="hlt">observed</span> multi-<span class="hlt">decadal</span> relation between AMV and the Indian summer monsoon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Svendsen, Lea; Luo, Feifei; Sankar, Syam; Gao, Yongqi; Keenlyside, Noel; Vareed Joseph, Porathur; Johannessen, Ola</p> <p>2016-04-01</p> <p>The instrumental records show a significant positive correlation between the Atlantic multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> (AMV) and the Indian summer monsoon (ISM) rainfall, where a positive (negative) AMV is associated with more (less) ISM rainfall. We have used both proxy reconstruction and twelve models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to investigate if the <span class="hlt">observed</span> AMV-ISM relation is a persistent internal climate signal or externally forced. A comparison of several annual resolution proxy records both from the Atlantic and for the ISM show that the multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> in both indices is persistent, but the link between them is not. The correlation between the two regions is weak, and even negative in some periods, before the instrumental time period. The analysis of CMIP5 simualtions is consistent with these results. While none of the CMIP5 models investigated simulate the significant AMV-ISM connection in the pre-industrial control simulations with fixed external forcing, three of the models reproduce the relation in the 20th century historical simulations with transient forcing. In these models external forcing is linked to the mid-to-upper tropospheric temperature pattern with a strengthened land-ocean contrast over South Asia, consistent with an enhanced ISM, as well as the evolution of AMV. We conclude that the significant AMV-ISM relation found in the <span class="hlt">observations</span> after the industrial revolution may be associated with external forcing, rather than being internal climate <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000112946','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000112946"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">Variability</span> and Temperature Trends in the Middle Atmosphere From Historical Rocketsonde Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dunkerton, Timothy J.</p> <p>2000-01-01</p> <p><span class="hlt">Observational</span> studies were performed using historical rocketsonde data to investigate long-term temperature trends, solar-cycle variations, and interactions between tropical and extratropical latitudes in the middle atmosphere. Evidence from tropical, subtropical, and midlatitude North American rocketsonde stations indicated a consistent downward trend over 25 years, with a solar cycle component superposed. The trend is about -1.4 to -2.0 K per <span class="hlt">decade</span> and the amplitude of the <span class="hlt">decadal</span> oscillation is about 1.1 K. Prior to trend derivation it was necessary for us to correct temperatures for aerodynamic heating in the early years. The empirically derived correction profile agrees well with a theoretical profile of Krumins and Lyons. A study was also performed of the correlation between equatorial winds and north polar temperatures in winter, showing that the entire stratospheric wind profile near the equator -- including the quasi-biennial oscillation (QBO) and stratopause semiannual oscillation (SAO) -- is important to the extratropical flow, not merely the QBO component as previously thought. A strong correlation was discovered between winter polar temperatures and equatorial winds in the upper stratosphere during the preceding September, suggesting a role for the second cycle of the SAO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGD....1217643F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGD....1217643F"><span id="translatedtitle">Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: <span class="hlt">variability</span> on seasonal to <span class="hlt">decadal</span> timescales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, G.; Romero, O.; Merkel, U.; Donner, B.; Iversen, M.; Nowald, N.; Ratmeyer, V.; Ruhland, G.; Klann, M.; Wefer, G.</p> <p>2015-11-01</p> <p>A more than two-<span class="hlt">decadal</span> sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analyzed with respect to deep ocean mass fluxes, flux components and their <span class="hlt">variability</span> on seasonal to <span class="hlt">decadal</span> timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on <span class="hlt">decadal</span> timescales possibly linked to the Atlantic Multidedadal Oscillation (AMO). High winter fluxes of biogenic silica (BSi), used as a measure of marine production mostly by diatoms largely correspond to a positive North Atlantic Oscillation (NAO) index during boreal winter (December-March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004-2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter but also in summer/fall enhanced particle sedimentation and carbon export on rather short timescales via the ballasting effect, thus leading to these episodic sedimentation events. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) weakened the relationships between fluxes and larger scale climatic oscillations. As phytoplankton biomass is high throughout the year in our study area, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by being incorporated into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was <span class="hlt">observed</span> for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997-1999 where low fluxes were obtained for almost one year during the warm El Niño and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17354457','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17354457"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> in growth of the Caribbean spiny lobster Panulirus argus (Decapoda: Paniluridae) in Cuban waters.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de León, Maria Estela; Martínez, Juana López; Cota, Daniel Lluch; Vázquez, Sergio Hernández; Rafael, Puga</p> <p>2005-01-01</p> <p>Annual von Bertalanffy growth parameters of the Caribbean spiny lobster (Panulirus argus) in Cuban waters were estimated from a long term study (40 years) by length-based methods ELEFAN and the new version of SLCA. Data of around 800 000 lobsters (with carapace length ranging 14 to 199mm) were randomly sampled in artificial shelters (a non selective fishing gear very common in the lobster fishery), through the field monitory program established for this species since 1963 in 14 localities of southwestern Cuban shelf. The software ELEFAN showed problems to converge in an optimal combination of the instantaneous growth coefficient (K) and the asymptotic length (Linfinity) of the von Bertalanffy equation, whereas the new SLCA software produced value estimates of K between 0.20 and 0.27 year(-1) and values of Linfinity between 177 and 190 mm carapace length, all within the range reported in the literature. The standardized anomalies of both parameters showed the presence of cycles along the analyzed time series. <span class="hlt">Decadal</span> <span class="hlt">variability</span> in growth parameters was revealed through the spectral analysis indicating cycles of 16 and 20 years for K and of 16 years for Linfinity. The incidence of some factors such as biomass and temperature that modulate growth in this crustacean was explored, using a nonlinear multiple regression model. These combined factors explained 33% and 69% of the <span class="hlt">variability</span> of K and Linfinity respectively. The growth coefficient appeared to be maximum with annual mean sea surface temperature of 28. 1 degrees C and the largest Linfinity is reached at a annual men biomass level of 23,000 t. These results should be the basis to understand the Cuban lobster population dynamics. PMID:17354457</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/12269739','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/12269739"><span id="translatedtitle"><span class="hlt">Decadal</span> and shorter period <span class="hlt">variability</span> of surf zone water quality at Huntington Beach, California.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boehm, A B; Grant, S B; Kim, J H; Mowbray, S L; McGee, C D; Clark, C D; Foley, D M; Wellman, D E</p> <p>2002-09-15</p> <p>The concentration of fecal indicator bacteria in the surf zone at Huntington Beach, CA, varies over time scales that span at least 7 orders of magnitude, from minutes to <span class="hlt">decades</span>. Sources of this <span class="hlt">variability</span> include historical changes in the treatment and disposal of wastewater and dry weather runoff, El Niño events, seasonal variations in rainfall, spring-neap tidal cycles, sunlight-induced mortality of bacteria, and nearshore mixing. On average, total coliform concentrations have decreased over the past 43 years, although point sources of shoreline contamination (storm drains, river outlets, and submarine outfalls) continue to cause transiently poor water quality. These transient point sources typically persist for 5-8 yr and are modulated by the phase of the moon, reflecting the influence of tides on the sourcing and transport of pollutants in the coastal ocean. Indicator bacteria are very sensitive to sunlight therefore, the time of day when samples are collected can influence the outcome of water quality testing. These results demonstrate that coastal water quality is forced by a complex combination of local and external processes and raise questions about the efficacy of existing marine bathing water monitoring and reporting programs. PMID:12269739</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://elibrary.unm.edu/sora/JFO/v053n02/p0159-p0167.pdf','USGSPUBS'); return false;" href="http://elibrary.unm.edu/sora/JFO/v053n02/p0159-p0167.pdf"><span id="translatedtitle"><span class="hlt">Observer</span> <span class="hlt">variability</span> in estimating numbers: An experiment</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Erwin, R.M.</p> <p>1982-01-01</p> <p>Census estimates of bird populations provide an essential framework for a host of research and management questions. However, with some exceptions, the reliability of numerical estimates and the factors influencing them have received insufficient attention. Independent of the problems associated with habitat type, weather conditions, cryptic coloration, ete., estimates may vary widely due only to intrinsic differences in <span class="hlt">observers</span>? abilities to estimate numbers. Lessons learned in the field of perceptual psychology may be usefully applied to 'real world' problems in field ornithology. Based largely on dot discrimination tests in the laboratory, it was found that numerical abundance, density of objects, spatial configuration, color, background, and other <span class="hlt">variables</span> influence individual accuracy in estimating numbers. The primary purpose of the present experiment was to assess the effects of <span class="hlt">observer</span>, prior experience, and numerical range on accuracy in estimating numbers of waterfowl from black-and-white photographs. By using photographs of animals rather than black dots, I felt the results could be applied more meaningfully to field situations. Further, reinforcement was provided throughout some experiments to examine the influence of training on accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811148L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811148L"><span id="translatedtitle"><span class="hlt">Observations</span> of Atlantic overturning <span class="hlt">variability</span> and latitudinal coherence with GRACE time-<span class="hlt">variable</span> gravity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Landerer, Felix; Wiese, David; Bentel, Katrin; Watkins, Michael; Boening, Carmen</p> <p>2016-04-01</p> <p>The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism of pole-ward planetary heat transport. Concerns about AMOC changes imply the need for a continuous, large-scale <span class="hlt">observation</span> capability to detect and monitor changes on interannual to <span class="hlt">decadal</span> time scales. Here we present measurements of AMOC component transport changes directly obtained from time-<span class="hlt">variable</span> gravity <span class="hlt">observations</span> of the Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 until now. Recent improvements at JPL of monthly gravity field retrievals allow the detection of AMOC-related interannual bottom pressure anomalies and in turn LNADW transport estimates. In the Atlantic at 26N, these GRACE AMOC estimates are in good agreement with those from the Rapid Climate Change-Meridional Overturning Circulation and Heatflux Array (RAPID/MOCHA) . We extend the GRACE-based estimates of AMOC <span class="hlt">variability</span> from the Southern Ocean to the Northern sinking branch to assess meridional coherence and discuss challenges of the GRACE <span class="hlt">observing</span> system. Our results highlight the efficacy and utility of space-gravimetry for <span class="hlt">observing</span> AMOC variations to evaluate latitudinal coherency and long-term <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.207..228W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.207..228W"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> in core surface flows deduced from geomagnetic observatory monthly means</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Whaler, K. A.; Olsen, N.; Finlay, C. C.</p> <p>2016-10-01</p> <p>Monthly means of the magnetic field measurements at ground observatories are a key data source for studying temporal changes of the core magnetic field. However, when they are calculated in the usual way, contributions of external (magnetospheric and ionospheric) origin may remain, which make them less favourable for studying the field generated by dynamo action in the core. We remove external field predictions, including a new way of characterizing the magnetospheric ring current, from the data and then calculate revised monthly means using robust methods. The geomagnetic secular variation (SV) is calculated as the first annual differences of these monthly means, which also removes the static crustal field. SV time-series based on revised monthly means are much less scattered than those calculated from ordinary monthly means, and their variances and correlations between components are smaller. On the annual to <span class="hlt">decadal</span> timescale, the SV is generated primarily by advection in the fluid outer core. We demonstrate the utility of the revised monthly means by calculating models of the core surface advective flow between 1997 and 2013 directly from the SV data. One set of models assumes flow that is constant over three months; such models exhibit large and rapid temporal variations. For models of this type, less complex flows achieve the same fit to the SV derived from revised monthly means than those from ordinary monthly means. However, those obtained from ordinary monthly means are able to follow excursions in SV that are likely to be external field contamination rather than core signals. Having established that we can find models that fit the data adequately, we then assess how much temporal <span class="hlt">variability</span> is required. Previous studies have suggested that the flow is consistent with torsional oscillations (TO), solid body-like oscillations of fluid on concentric cylinders with axes aligned along the Earth's rotation axis. TO have been proposed to explain <span class="hlt">decadal</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.tmp..225W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.tmp..225W"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> in core surface flows deduced from geomagnetic observatory monthly means</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Whaler, K. A.; Olsen, N.; Finlay, C. C.</p> <p>2016-07-01</p> <p>Monthly means of the magnetic field measurements at ground observatories are a key data source for studying temporal changes of the core magnetic field. However, when they are calculated in the usual way, contributions of external (magnetospheric and ionospheric) origin may remain, which make them less favourable for studying the field generated by dynamo action in the core. We remove external field predictions, including a new way of characterising the magnetospheric ring current, from the data and then calculate revised monthly means using robust methods. The geomagnetic secular variation (SV) is calculated as the first annual differences of these monthly means, which also removes the static crustal field. SV time series based on revised monthly means are much less scattered than those calculated from ordinary monthly means, and their variances and correlations between components are smaller. On the annual to <span class="hlt">decadal</span> timescale, the SV is generated primarily by advection in the fluid outer core. We demonstrate the utility of the revised monthly means by calculating models of the core surface advective flow between 1997 and 2013 directly from the SV data. One set of models assumes flow that is constant over three months; such models exhibit large and rapid temporal variations. For models of this type, less complex flows achieve the same fit to the SV derived from revised monthly means than those from ordinary monthly means. However, those obtained from ordinary monthly means are able to follow excursions in SV that are likely to be external field contamination rather than core signals. Having established that we can find models that fit the data adequately, we then assess how much temporal <span class="hlt">variability</span> is required. Previous studies have suggested that the flow is consistent with torsional oscillations (TO), solid body-like oscillations of fluid on concentric cylinders with axes aligned along the Earth's rotation axis. TO have been proposed to explain <span class="hlt">decadal</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1110658S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1110658S"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> of freshwater and heat content in the subpolar North Atlantic: the role of intergyre exchange processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scheinert, M.; Böning, C. W.; Biastoch, A.</p> <p>2009-04-01</p> <p>Recent studies of ocean <span class="hlt">observations</span> have advanced the hypothesis that an increased northward flow of subtropical Intermediate Water has added a large amount of salt to the eastern subpolar North Atlantic and the Nordic Seas during the the last <span class="hlt">decade</span>. The advection of subtropical waters is not only suspected to have reversed the prominent freshening trend in the Subpolar Gyre during the 1960s to mid-1990s, but there is also some evidence for a conspicuous warming that has accompanied the salinification. Although there is some consensus about the coherence of this event with the state of the atmospheric forcing (NAO), only little is known about the physical mechanisms and its reverberation in the meridional net heat transport. Using a global ocean sea-ice model, we show here that the <span class="hlt">decadal</span> <span class="hlt">variability</span> of both the subpolar freshwater and heat content for the period 1960-2000 can be mostly explained by the shallow meridional exchange of heat and salt with the subtropical North Atlantic. We corroborate the theory of a time dependent northward flow of warm haline water through the West European Basin; the model experiments show these meridional fluxes in the inter-gyre regime between 45°-50° to be governed primarily by changes in the wind stress curl. Due to the leading role of local forcing effects the meridional heat transport in this latitude band is not coherent with heat transport <span class="hlt">variability</span> further south; in contrast to the subtropical North Atlantic, there is no close linkage between the heat transport and the meridional overturning circulation (MOC).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110023540','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110023540"><span id="translatedtitle">Interannual to <span class="hlt">Decadal</span> <span class="hlt">Variability</span> of Atlantic Water in the Nordic and Adjacent Seas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carton, James A.; Chepurin, Gennady A.; Reagan, James; Haekkinen, Sirpa</p> <p>2011-01-01</p> <p>Warm salty Atlantic Water is the main source water for the Arctic Ocean and thus plays an important role in the mass and heat budget of the Arctic. This study explores interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span> of Atlantic Water properties in the Nordic Seas area where Atlantic Water enters the Arctic, based on a reexamination of the historical hydrographic record for the years 1950-2009, obtained by combining multiple data sets. The analysis shows a succession of four multi-year warm events where temperature anomalies at 100m depth exceed 0.4oC, and three cold events. Three of the four warm events lasted 3-4 years, while the fourth began in 1999 and persists at least through 2009. This most recent warm event is anomalous in other ways as well, being the strongest, having the broadest geographic extent, being surface-intensified, and occurring under exceptional meteorological conditions. Three of the four warm events were accompanied by elevated salinities consistent with enhanced ocean transport into the Nordic Seas, with the exception of the event spanning July 1989-July 1993. Of the three cold events, two lasted for four years, while the third lasted for nearly 14 years. Two of the three cold events are associated with reduced salinities, but the cold event of the 1960s had elevated salinities. The relationship of these events to meteorological conditions is examined. The results show that local surface heat flux variations act in some cases to reinforce the anomalies, but are too weak to be the sole cause.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRC..11611035C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRC..11611035C"><span id="translatedtitle">Interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span> of Atlantic Water in the Nordic and adjacent seas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carton, James A.; Chepurin, Gennady A.; Reagan, James; HäKkinen, Sirpa</p> <p>2011-11-01</p> <p>Warm salty Atlantic Water is the main source water for the Arctic Ocean and thus plays an important role in the mass and heat budget of the Arctic. This study explores interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span> of Atlantic Water properties in the Nordic Seas area where Atlantic Water enters the Arctic, based on a reexamination of the historical hydrographic record for the years 1950-2009, obtained by combining multiple data sets. The analysis shows a succession of four multiyear warm events where temperature anomalies at 100 m depth exceed 0.4°C, and three cold events. Three of the four warm events lasted 3-4 years, while the fourth began in 1999 and persists at least through 2009. This most recent warm event is anomalous in other ways as well, being the strongest, having the broadest geographic extent, being surface-intensified, and occurring under exceptional meteorological conditions. Three of the four warm events were accompanied by elevated salinities consistent with enhanced ocean transport into the Nordic Seas, with the exception of the event spanning July 1989-July 1993. Of the three cold events, two lasted for 4 years, while the third lasted for nearly 14 years. Two of the three cold events are associated with reduced salinities, but the cold event of the 1960s had elevated salinities. The relationship of these events to meteorological conditions is examined. The results show that local surface heat flux variations act in some cases to reinforce the anomalies, but are too weak to be the sole cause.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950047289&hterms=coupled+model+atmosphere+ocean+circulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcoupled%2Bmodel%2Batmosphere%2Bocean%2Bcirculation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950047289&hterms=coupled+model+atmosphere+ocean+circulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcoupled%2Bmodel%2Batmosphere%2Bocean%2Bcirculation"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> of the Tropical Atlantic Ocean Surface Temperature in shipboard measurements and in a Global Ocean-Atmosphere model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mehta, Vikram M.; Delworth, Thomas</p> <p>1995-01-01</p> <p>Sea surface temperature (SST) <span class="hlt">variability</span> was investigated in a 200-yr integration of a global model of the coupled oceanic and atmospheric general circulations developed at the Geophysical Fluid Dynamics Laboratory (GFDL). The second 100 yr of SST in the coupled model's tropical Atlantic region were analyzed with a variety of techniques. Analyses of SST time series, averaged over approximately the same subregions as the Global Ocean Surface Temperature Atlas (GOSTA) time series, showed that the GFDL SST anomalies also undergo pronounced quasi-oscillatory <span class="hlt">decadal</span> and multidecadal <span class="hlt">variability</span> but at somewhat shorter timescales than the GOSTA SST anomalies. Further analyses of the horizontal structures of the <span class="hlt">decadal</span> timescale <span class="hlt">variability</span> in the GFDL coupled model showed the existence of two types of <span class="hlt">variability</span> in general agreement with results of the GOSTA SST time series analyses. One type, characterized by timescales between 8 and 11 yr, has high spatial coherence within each hemisphere but not between the two hemispheres of the tropical Atlantic. A second type, characterized by timescales between 12 and 20 yr, has high spatial coherence between the two hemispheres. The second type of <span class="hlt">variability</span> is considerably weaker than the first. As in the GOSTA time series, the multidecadal <span class="hlt">variability</span> in the GFDL SST time series has approximately opposite phases between the tropical North and South Atlantic Oceans. Empirical orthogonal function analyses of the tropical Atlantic SST anomalies revealed a north-south bipolar pattern as the dominant pattern of <span class="hlt">decadal</span> <span class="hlt">variability</span>. It is suggested that the bipolar pattern can be interpreted as <span class="hlt">decadal</span> <span class="hlt">variability</span> of the interhemispheric gradient of SST anomalies. The <span class="hlt">decadal</span> and multidecadal timescale <span class="hlt">variability</span> of the tropical Atlantic SST, both in the actual and in the GFDL model, stands out significantly above the background 'red noise' and is coherent within each of the time series, suggesting that specific sets of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011JGRD..11620121H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011JGRD..11620121H&link_type=ABSTRACT"><span id="translatedtitle">A dynamical fingerprint of tropical Pacific sea surface temperatures on the <span class="hlt">decadal</span>-scale <span class="hlt">variability</span> of cool-season Arctic precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hegyi, Bradley M.; Deng, Yi</p> <p>2011-10-01</p> <p>The temporal and spatial characteristics of <span class="hlt">decadal</span>-scale <span class="hlt">variability</span> in the Northern Hemisphere (NH) cool-season (October-March) Arctic precipitation are identified from both the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) and the Global Precipitation Climatology Project (GPCP) precipitation data sets. This <span class="hlt">decadal</span> <span class="hlt">variability</span> is shown to be partly connected to the <span class="hlt">decadal</span>-scale variations in tropical central Pacific sea surface temperatures (SSTs) that are primarily associated with a <span class="hlt">decadal</span> modulation of the El Niño-Southern Oscillation (ENSO), i.e., transitions between periods favoring typical eastern Pacific warming (EPW) events and periods favoring central Pacific warming (CPW) events. Regression and composite analyses reveal that increases of central Pacific SSTs drive a stationary Rossby wave train that destructively interferes with the wave number-1 component of the extratropical planetary wave. This destructive interference is opposite to the mean effect of typical EPW on the extratropical planetary wave. It leads to suppressed upward propagation of wave energy into the polar stratosphere, a stronger stratospheric polar vortex, and a tendency toward a positive phase of the Arctic Oscillation (AO). The positive AO tendency is synchronized on the <span class="hlt">decadal</span> scale with a poleward shift of the NH storm tracks, particularly in the North Atlantic. Storm track variations further induce changes in the amount of moisture transported into the Arctic by synoptic eddies. The fluctuations in the eddy moisture transport ultimately contribute to the <span class="hlt">observed</span> <span class="hlt">decadal</span>-scale variations in the total Arctic precipitation in the NH cool season.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMOS42B..01R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMOS42B..01R"><span id="translatedtitle"><span class="hlt">Variability</span> in a Multi-<span class="hlt">Decadal</span> Record of Ocean Acidification in Surface Waters of the U.S. Northeast Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rebuck, N. D.; Hare, J. A.; Mulholland, M. R.; Bernhardt, P. W.; Staryk, C. J.</p> <p>2011-12-01</p> <p>Multiple shelf-wide surveys of the Northeast Shelf of the United States, from the Gulf of Maine through the Mid-Atlantic Bight, were conducted as part of the NOAA Marine Resources Monitoring, Assessment, and Prediction Program (MARMAP) and the Northeast Monitoring Program (NEMP). <span class="hlt">Observations</span> including pH, total alkalinity, temperature, and salinity were collected from 1973-1984. These historical data were compared to recent data collected as part of a joint NASA/NOAA project (CliVEC) as part of the NOAA Ocean Acidification Program. A preliminary comparison of the historical surface waters suggests that interannual <span class="hlt">variability</span> in the carbonate system is approximately equal in magnitude to the expected multi-<span class="hlt">decadal</span> changes. Where geographically comparable data exist for the MARMAP era and recent surveys, changes appear to be dominated by varying water masses, however salinity normalized DIC in the Mid-Atlantic Bight appears to have increased proportional to other published global averages. Ongoing studies of carbonate chemistry in the region will benefit from the availability of this retrospective baseline of the carbonate system and a greater understanding of the seasonal, interannual, and interdecadal <span class="hlt">variability</span>. Determining the proximal causes of differences between acidification on the Northeast Shelf and the global average is a necessary component of future ecological modeling studies and regional management in this biologically productive and economically valuable region.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A32G..03G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A32G..03G"><span id="translatedtitle">Santa Ana Winds of Southern California: Their Climatology and <span class="hlt">Variability</span> Spanning 6.5 <span class="hlt">Decades</span> from Regional Dynamical Modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guzman-Morales, J.; Gershunov, A.</p> <p>2015-12-01</p> <p>Santa Ana Winds (SAWs) are an integral feature of the regional climate of Southern California/Northern Baja California region. In spite of their tremendous episodic impacts on the health, economy and mood of the region, climate-scale behavior of SAW is poorly understood. In the present work, we identify SAWs in mesoscale dynamical downscaling of a global reanalysis product and construct an hourly SAW catalogue spanning 65 years. We describe the long-term SAW climatology at relevant time-space resolutions, i.e, we developed local and regional SAW indices and analyse their <span class="hlt">variability</span> on hourly, daily, annual, and multi-<span class="hlt">decadal</span> timescales. Local and regional SAW indices are validated with available anemometer <span class="hlt">observations</span>. Characteristic behaviors are revealed, e.g. the SAW intensity-duration relationship. At interdecadal time scales, we find that seasonal SAW activity is sensitive to prominent large-scale low-frequency modes of climate <span class="hlt">variability</span> rooted in the tropical and north Pacific ocean-atmosphere system that are also known to affect the hydroclimate of this region. Lastly, we do not find any long-term trend in SAW frequency and intensity as previously reported. Instead, we identify a significant long-term trend in SAW behavior whereby contribution of extreme SAW events to total seasonal SAW activity has been increasing at the expense of moderate events. These findings motivate further investigation on SAW evolution in future climate and its impact on wildfires.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A23J..01E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A23J..01E"><span id="translatedtitle">Geostationary atmospheric composition <span class="hlt">observations</span> from the NASA <span class="hlt">Decadal</span> Survey GEO-CAPE mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edwards, D. P.; Jacob, D. J.; Al-Saadi, J. A.; Iraci, L. T.</p> <p>2012-12-01</p> <p>This paper discusses the science definition work that is being performed in preparation for the NASA <span class="hlt">Decadal</span> Survey GEO-CAPE mission. To serve the atmospheric composition community, GEO-CAPE will make a suite of trace gas and aerosol measurements from geostationary orbit concentrating on North America with high spatiotemporal resolution. This will provide unique insights into pollutant sources, transport, chemical transformations and climate impact. In addition to significantly improved understanding of the underlying processes determining atmospheric composition, GEO-CAPE <span class="hlt">observations</span> will also find direct societal application for air quality management and forecasting. The paper will also discuss the potential phased implementation of this mission as a series of hosted payloads, and GEO-CAPE as the U.S. contribution to a constellation of geostationary platforms to achieve continuous coverage at northern mid-latitudes by the turn of the <span class="hlt">decade</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010AGUFMGC13E..04C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010AGUFMGC13E..04C&link_type=ABSTRACT"><span id="translatedtitle">Modeling the Temperature Responses to Spectral Solar <span class="hlt">Variability</span> on <span class="hlt">Decadal</span> and Centennial Time Scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cahalan, R. F.; Wen, G.; Pilewskie, P.; Harder, J. W.</p> <p>2010-12-01</p> <p>Atmospheric temperature responses to <span class="hlt">decadal</span> solar variations are computed for two scenarios of solar spectral irradiance (SSI), SIM-based out-of-phase and proxy-based in-phase variations, using a time-dependent radiative-convective model (RCM), and also GISS modelE (GCM.) For both scenarios and both models, maximum responses occur in upper stratosphere, decreasing downward to the surface. Upper stratospheric temperature peak-to-peak responses to out-of-phase forcing are ~0.6 K in RCM and ~0.9 K over tropics in GCM, ~5x as large as responses to in-phase forcing. Stratospheric responses are in-phase with TSI (Total Solar Irradiance). Modeled upper stratospheric temperature responses to SIM-based forcing are similar to 11-year temperature variations <span class="hlt">observed</span> with HALOE (Halogen Occultation Experiment). For both RCM and GCM, surface responses to the two scenarios are significantly smaller than stratospheric responses. On centennial timescales, SSI variations are poorly known. However, two scenarios of reconstructed TSI, one based on 11-year cycle with background [Lean 2000] and the other on flux transport with much less background [Wang, Lean, and Sheeley, 2005], provide a potential range of TSI variations. We apply phase relations among different SSI bands both from SIM <span class="hlt">observations</span> and proxy reconstructions to the two scenarios of historical TSI to derive associated historical SSI, which then drives the RCM. The updated atmosphere and ocean mixed coupled RCM including diffusion to deep-ocean provide a first order estimate of temperature responses to SSI variations on centennial time scales. We discuss potential mechanisms for atmosphere-ocean and stratosphere-troposphere couplings responsible for the climate responses to spectral solar variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1167250','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1167250"><span id="translatedtitle">A Generalized Stability Analysis of the AMOC in Earth System Models: Implication for <span class="hlt">Decadal</span> <span class="hlt">Variability</span> and Abrupt Climate Change</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fedorov, Alexey V.</p> <p>2015-01-14</p> <p>The central goal of this research project was to understand the mechanisms of <span class="hlt">decadal</span> and multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> of the Atlantic Meridional Overturning Circulation (AMOC) as related to climate <span class="hlt">variability</span> and abrupt climate change within a hierarchy of climate models ranging from realistic ocean models to comprehensive Earth system models. Generalized Stability Analysis, a method that quantifies the transient and asymptotic growth of perturbations in the system, is one of the main approaches used throughout this project. The topics we have explored range from physical mechanisms that control AMOC <span class="hlt">variability</span> to the factors that determine AMOC predictability in the Earth system models, to the stability and <span class="hlt">variability</span> of the AMOC in past climates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ClDy..tmp...46Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ClDy..tmp...46Y&link_type=ABSTRACT"><span id="translatedtitle">Space-time <span class="hlt">variability</span> of Indonesian rainfall at inter-annual and multi-<span class="hlt">decadal</span> time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yanto; Rajagopalan, Balaji; Zagona, Edith</p> <p>2016-01-01</p> <p>We investigated the space-time <span class="hlt">variability</span> of wet (Nov-Apr) and dry (May-Oct) season rainfall over Indonesia, using monthly gridded rainfall data from the University of East Angela Climatic Research Unit covering the period 1901-2012. Three complimentary techniques were employed—(1) principal component analysis to identify the dominant modes of <span class="hlt">variability</span>, (2) wavelet spectral analysis to identify the spectral characteristics of the leading modes and their coherence with large scale climate <span class="hlt">variables</span> and (3) Bayesian Dynamical Linear Model (BDLM) to quantify the temporal <span class="hlt">variability</span> of the association between rainfall modes and climate <span class="hlt">variables</span>. In the dry season when the Inter Tropical Convergence Zone (ITCZ) is to the north of the equator the leading two principal components (PCs) explain close to 50 % of the rainfall. In the wet season the ITCZ moves to the south and the leading PCs explain close to 30 % of the variance. El Niño Southern Oscillation (ENSO) is the driver of the leading modes of rainfall <span class="hlt">variability</span> during both seasons. We find asymmetry in the teleconnections of ENSO to high and low rainfall years in the dry season. Furthermore, ENSO and the leading PCs of rainfall have spectral coherence in the inter-annual band (2-8 years) over the entire period of record and in the multi-<span class="hlt">decadal</span> (8-16 years) band in post-1980 years. In addition, during the 1950-1980 period the second mode of <span class="hlt">variability</span> in both seasons has a strong relationship with Pacific <span class="hlt">Decadal</span> Oscillation. The association between ENSO and the leading mode of Indonesian rainfall has strengthened in recent <span class="hlt">decades</span>, more so during dry season. These inter-annual and multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> of Indonesian rainfall modulated by Pacific climate drivers has implications for rainfall and hydrologic predictability important for water resources management.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014QSRv..105...86B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014QSRv..105...86B"><span id="translatedtitle">High resolution sedimentary record of dinoflagellate cysts reflects <span class="hlt">decadal</span> <span class="hlt">variability</span> and 20th century warming in the Santa Barbara Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bringué, Manuel; Pospelova, Vera; Field, David B.</p> <p>2014-12-01</p> <p>We present a continuous record of dinoflagellate cysts from a core of laminated sediments collected in the Santa Barbara Basin (SBB), off Southern California. The core spans the last ∼260 years and is analysed at biennial (two-year) resolution. Variations in dinoflagellate cyst assemblages are compared with 20th century historical changes, and are used to examine changes in primary productivity and species composition, which are bound to the <span class="hlt">variability</span> in upwelling and sea-surface temperature (SST) in the region. Cysts produced by heterotrophic dinoflagellates dominate the assemblages. In particular, Brigantedinium spp. (on average 64.2% of the assemblages) are commonly associated with high levels of primary productivity, typically <span class="hlt">observed</span> under active upwelling conditions, when nutrient supply is higher. Other heterotrophic taxa such as cysts of Protoperidinium americanum, Protoperidinium fukuyoi, Protoperidinium minutum and Archaeperidinium saanichi, all Echinidinium species, Quinquecuspis concreta and Selenopemphix undulata are more abundant in the early part of the record (∼1750s-1870s). These taxa are generally associated with high primary productivity and are <span class="hlt">observed</span> predominantly during intervals marked by relatively <span class="hlt">variable</span> conditions of SST, stratification and nutrient loading. The 20th century is marked by an increase in several species of autotrophic affinity, primarily Lingulodinium machaerophorum and Spiniferites ramosus. In recent surface sediments from the region, these species are more abundant in the Southern California Bight, and they are associated with conditions of relaxed upwelling in the SBB (typically <span class="hlt">observed</span> during summer and fall), when SST is higher and nutrient supply is moderate. Their increasing concentrations since the early 20th century reflect warmer SST and possibly stronger stratification during the warmest season. Taken together, the changes in cyst assemblages provide further evidence that persistently warmer conditions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFMPP62A0316M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFMPP62A0316M"><span id="translatedtitle"><span class="hlt">Decadal</span>-Scale Tropical North Atlantic Climate <span class="hlt">Variability</span> Recorded in Slow Growing Cape Verde Corals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moses, C. S.; Swart, P. K.; Dodge, R. E.; Helmle, K. P.; Thorrold, S.</p> <p>2002-12-01</p> <p>The <span class="hlt">decadal</span> to century scale climate <span class="hlt">variability</span> of the tropical North Atlantic has major implications for both neighboring coastal and inland areas. Changes in patterns of sea surface temperature (SST) and SST anomalies (SSTA) in the tropical North Atlantic are known to affect rainfall in Florida, South America, and sub-Saharan Africa, as well as the number of major hurricanes formed in the Atlantic. Because of the significance of these connections, it is important to further increase our predictive capacity for the recognition of trends and cycles in tropical North Atlantic SST and SSTA. Located at 15° N latitude off the west coast of sub-Saharan Africa, the Cape Verde Islands are an ideal geographic location to search for records of the Tropical North Atlantic Index (TNA). Such patterns are present in proxy indicators of climate (O, C, Sr/Ca and Mg/Ca) recorded in the skeletons of slow growing corals, such as Siderastrea radians, found in Cape Verde (growth rate = 1-2 mm/yr). These corals represent an archive for SST and SSTA records that exceed the instrumental period of the eastern tropical North Atlantic. We cored corals from several different locations within the Cape Verde archipelago and analyzed them for stable isotopes (δ13C and δ18O) and minor elements (Sr, Mg, and Ba). The δ18O signal present in these corals shows a distinct relationship to the TNA over the better part of the last 100 years. In addition, the δ18O record in several of these corals also records the onset of the latest Sahel (11°-18° N in Africa) drought which began in 1970. The Sr/Ca and Mg/Ca records of these corals indicate a slight warming of the waters around Cape Verde during the last 100 years, as well as accurately recording the El Niño events of 1982-83 and 1997-98. The correlations present between the records in these corals and the known instrumental record for the eastern tropical North Atlantic suggests that the fluctuations recorded in the proxy indicators may be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18..785J&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18..785J&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Decadal</span> trend of precipitation and temperature patterns and impacts on snow-related <span class="hlt">variables</span> in a semiarid region, Sierra Nevada, Spain.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>José Pérez-Palazón, María; Pimentel, Rafael; Herrero, Javier; José Polo, María</p> <p>2016-04-01</p> <p>, with the exception of the average annual mean and maximum daily temperature. In the case of the snow-related <span class="hlt">variables</span>, no significant trends are <span class="hlt">observed</span> at this time scale; nonetheless, a global decreasing rate is predominant in most of the <span class="hlt">variables</span>. The torrential events are more frequent in the last <span class="hlt">decades</span> of the study period, with an apparently increasing associated dispersion. This study constitutes a first sound analysis of the long-term <span class="hlt">observed</span> trends of the snow regime in this area under the context of increasing temperature and decreasing precipitation regimes. The results highlight the complexity of non-linearity in environmental processes in Mediterranean regions, and point out to a significant shift in the precipitation and temperature regime, and thus on the snow-affected hydrological <span class="hlt">variables</span> in the study area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010cosp...38.1704C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010cosp...38.1704C&link_type=ABSTRACT"><span id="translatedtitle">Modeling the Climate Responses to Spectral Solar <span class="hlt">Variability</span> on <span class="hlt">Decadal</span> and Centennial Time Scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cahalan, Robert; Wen, Guoyong; Pilewskie, Peter; Harder, Jerald</p> <p></p> <p>We apply two scenarios of external forcing, namely the SIM-based out-of-phase variations and the proxy-based in-phase variations, as input to a time-dependent radiative-convective model (RCM), and also to the GISS modelE GCM, to compute climate responses to solar variation on <span class="hlt">decadal</span> time scale. We find that the maximum temperature response occurs in the upper stratosphere, while temperature response decreases downward to the surface for both scenarios, and both models. The upper stratospheric temperature peak-to-peak responses to out-of-phase solar forcing are 0.6 K in RCM and 0.9 K over the tropical region in GCM simulations, a factor of 5 times as large as responses to in-phase solar forcing. Stratospheric responses are in-phase with TSI (Total Solar Irradiance) variations. The modeled upper stratospheric temperature responses to the SORCE SIM <span class="hlt">observed</span> SSI (Spectral Solar Irradiance) forcing are similar to the HALOE (Halogen Occultation Experiment) <span class="hlt">observed</span> 11-year temperature variations. Surface responses to the two SSI scenarios are small for both RCM and GCM studies, as compared to the stratospheric responses. Though solar irradiance variations on centennial time scale are not well known, the two sce-narios of reconstructed TSI time series (i.e., the one based on 11-year cycle with background [Lean 2000] and the other one from flux transport that has much less background component [Wang, Lean, and Sheeley, 2005]) provide potential range of variations of TSI on centennial time scale. We apply phase relations among different spectral irradiance bands both from SIM <span class="hlt">observation</span> and proxy reconstructions to the two scenarios of historical TSI to derive the as-sociated historical SSI. The historical SSI is used to drive the RCM. The updated atmosphere and ocean mixed coupled RCM including diffusion to deep-ocean will provide the first order estimate of temperature response to SSI variation on centennial time scales. We anticipate the stratosphere, troposphere, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008E%26PSL.270...86K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008E%26PSL.270...86K"><span id="translatedtitle">Spatial <span class="hlt">variability</span> in subsurface warming over the last three <span class="hlt">decades</span>; insight from repeated borehole temperature measurements in The Netherlands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kooi, Henk</p> <p>2008-06-01</p> <p>Subsurface temperatures around the world are changing in response to accelerated surface atmospheric temperature (SAT) rise, but are also impacted by other natural and anthropogenic changes in surface environmental conditions which alter the surface energy balance. Improved understanding of the latter influences is important for geothermal climate applications and to generate a comprehensive knowledge-framework of subsurface warming, including inherent spatial <span class="hlt">variability</span>. Here I examine sixteen wells in a relatively small area in The Netherlands, each with two available temperature logs recorded some three <span class="hlt">decades</span> apart. Temperature differences of the log pairs reveal marked differences in subsurface warming amongst the wells for this time period. Forward modelling of the <span class="hlt">observed</span> temperature changes, using surface air temperature (SAT) forcing, shows that a considerable part of this inter-site <span class="hlt">variability</span> may be caused by inter-site differences in thermal properties and groundwater flow conditions. However, for some of the wells these factors are insufficient, implying contributions from non-SAT-driven changes in ground surface temperature (GST). In one case an anomalous decrease in GST can be linked to back-growth of the canopy after forest cutting. For another well site, GST warming has been less than SAT warming in the absence of apparent changes in surface conditions, indicating local, subtle influences on the surface energy balance independent of SAT. The results demonstrate that repeated borehole temperature logging resolves key uncertainties and ambiguities pertaining to interpretation of individual temperature logs. The study further highlights the importance of establishing high-quality borehole temperature databases, also for these relatively complex settings with dynamic and <span class="hlt">variable</span> surface conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1329071','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1329071"><span id="translatedtitle">Collaborative Proposal: Improving <span class="hlt">Decadal</span> Prediction of Arctic Climate <span class="hlt">Variability</span> and Change Using a Regional Arctic System Model (RASM)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cassano, John</p> <p>2011-05-15</p> <p>The primary outcome of the project was the development of the Regional Arctic System Model (RASM) and evaluation of its individual model components, coupling among them and fully coupled model results. Overall, we have demonstrated that RASM produces realistic mean and seasonal surface climate as well as its interannual and <span class="hlt">decadal</span> <span class="hlt">variability</span> and trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C42B..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C42B..08W"><span id="translatedtitle">Spatio-temporal <span class="hlt">Variability</span> of Arctic Sea Ice from Days to <span class="hlt">Decades</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wettlaufer, J. S.; Agarwal, S.</p> <p>2014-12-01</p> <p>We examine the daily satellite retrievals of Arctic sea-ice extent over three <span class="hlt">decades</span>. The Arctic basin is divided into 14 different regions and we study how the Arctic wide <span class="hlt">observations</span> emerge from these regional trends. In order to capture all possible time scales, the temporal dynamics within each spatial region, and in the basin as a whole, are treated as a multifractal. Our approach is Multi-Fractal Temporally Weighted Detrended Fluctuation Analysis (MF-TWDFA), which captures long time scales that are not accessible by standard DFA or MF-DFA and are by definition not part of a procedure that assumes the dynamics are described by an order one auto-regressive process. We examine how the eastern, western, central and the marginal seas control the longest time scales and what processes are responsible for the responses found in the data. Of particular interest is how regions with substantial seasonality contribute to the basin-wide dynamics of the system. The importance of this is intertwined with the general problem of how and when the Arctic may pass on to a state in which the ice cover is seasonal. The transition from a perennial state to a seasonal ice cover is the persistent state of affairs in the marginal regions of the ice cover, which constitute 10 of the 14 subregions, whereas the remaining 4 are in various stages of partial ice cover at various times of the year. In this manner, we use sub-basins as laboratories for the entire basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013019','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013019"><span id="translatedtitle">North Pacific <span class="hlt">Decadal</span> <span class="hlt">Variability</span> in the GEOS-5 Atmosphere-Ocean Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Achuthavarier, Deepthi; Schubert, Siegfried D.; Vikhliaev, Yury V.</p> <p>2013-01-01</p> <p>This study examines the mechanisms of the Pacific <span class="hlt">decadal</span> oscillation (PDO) in the GEOS-5 general circulation model. The model simulates a realistic PDO pattern that is resolved as the first empirical orthogonal function (EOF) of winter sea surface temperature (SST). The simulated PDO is primarily forced by Aleutian low through Ekman transport and surface fluxes, and shows a red spectrum without any preferred periodicity. This differs from the <span class="hlt">observations</span>, which indicate a greater role of El Nino-Southern Oscillation (ENSO) forcing, and likely reflects the too short time scale of the simulated ENSO. The geostrophic transport in response to the Aleutian low is limited to the Kuroshio-Oyashio Extension, and is unlikely the main controlling factor in this model, although it reinforces the Ekman-induced SST anomalies. The delay between the Aleutian low and the PDO is relatively short (1 year) suggesting that the fast Ekman response (rather than Rossby wave propagation) sets the SST pattern immediately following an Aleutian low fluctuation. The atmospheric feedback (response to the SST) is only about 25 of the forcing and never evolves into an Aleutian low completely, instead projecting onto the North Pacific Oscillation (NPO), a meridional dipole in sea level pressure (SLP). The lack of preferred periodicity and weak atmospheric response bothindicate a coupled oscillation is an unlikely mechanism for the PDO in this model. In agreement with recent studies, the NPO is correlated with the North Pacific Gyre Oscillation (NPGO), which is another leading EOF of the North Pacific SST. A possible connection between the PDO and the NPGO is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008PalOc..23.2219L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008PalOc..23.2219L&link_type=ABSTRACT"><span id="translatedtitle">Interdecadal-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> from multicoral oxygen isotope records in the South Pacific Convergence Zone region since 1650 A.D.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Linsley, Braddock K.; Zhang, Peipei; Kaplan, Alexey; Howe, Stephen S.; Wellington, Gerard M.</p> <p>2008-06-01</p> <p>In the South Pacific, interdecadal-<span class="hlt">decadal</span> oceanic and atmospheric <span class="hlt">variability</span>, referred to as the Interdecadal Pacific Oscillation (IPO), is most pronounced in the South Pacific Convergence Zone (SPCZ) salinity front region. Here we have used annual average oxygen isotope (δ18O) time series from five coral cores collected from Fiji and Tonga in this region to construct a Fiji-Tonga Interdecadal-<span class="hlt">Decadal</span> Pacific Oscillation (F-T IDPO) index of low-frequency (>9 and <55 years) climate <span class="hlt">variability</span> back to 1650 A.D. We first demonstrate the consistency between this F-T IDPO index and a mean sea level (MSL) pressure-based SPCZ position index (SPI) (1891-2000), thus verifying the ability of coral δ18O to record past interdecadal-<span class="hlt">decadal</span> climatic variations in this region back to 1891. The F-T IDPO index is then shown to be synchronous with the IPO index (1856-2000), suggesting that this coral-based index effectively represents the interdecadal-<span class="hlt">decadal</span> scale climate variance back to 1650. The regularity of the F-T IDPO index indicates that interdecadal-<span class="hlt">decadal</span> <span class="hlt">variability</span> in the SPCZ region has been relatively constant over the past 350 years with a mean frequency of ˜20 years (variance peaks near 11 and 35 years). There is a consistent antiphase correlation of the F-T IDPO index and the interdecadal-<span class="hlt">decadal</span> components in equatorial Pacific coral δ18O series from Maiana and Palmyra. This <span class="hlt">observation</span> indicates that the eastward expansion (westward contraction) of the eastern salinity front of the Western Pacific Warm Pool (WPWP) occurs simultaneously (±<1 year) with the westward (eastward) shift of the SPCZ salinity front during positive IPO (negative IPO) phases. This is the same relationship <span class="hlt">observed</span> during the phases of the El Niño Southern Oscillation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140011835','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140011835"><span id="translatedtitle">Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux <span class="hlt">Variability</span> on Daily Through <span class="hlt">Decadal</span> Time Scales</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Romanski, Joy; Romanou, Anastasia; Bauer, Michael; Tselioudis, George</p> <p>2013-01-01</p> <p>We analyze daily wintertime cyclone <span class="hlt">variability</span> in the central and eastern Mediterranean during 1958-2001, and identify four distinct cyclone states, corresponding to the presence or absence of cyclones in each basin. Each cyclone state is associated with wind flows that induce characteristic patterns of cooling via turbulent (sensible and latent) heat fluxes in the eastern Mediterranean basin and Aegean Sea. The relative frequency of occurrence of each state determines the heat loss from the Aegean Sea during that winter, with largest heat losses occurring when there is a storm in the eastern but not central Mediterranean (eNOTc), and the smallest occurring when there is a storm in the central but not eastern Mediterranean (cNOTe). Time series of daily cyclone states for each winter allow us to infer Aegean Sea cooling for winters prior to 1985, the earliest year for which we have daily heat flux <span class="hlt">observations</span>. We show that cyclone states conducive to Aegean Sea convection occurred in 1991/1992 and 1992/1993, the winters during which deep water formation was <span class="hlt">observed</span> in the Aegean Sea, and also during the mid-1970s and the winters of 1963/1964 and 1968/1969. We find that the eNOTc cyclone state is anticorrelated with the North Atlantic Oscillation (NAO) prior to 1977/1978. After 1977/1978, the cNOTe state is anticorrelated with both the NAO and the North Caspian Pattern (NCP), showing that the area of influence of large scale atmospheric teleconnections on regional cyclone activity shifted from the eastern to the central Mediterranean during the late 1970s. A trend toward more frequent occurrence of the positive phase of the NAO produced less frequent cNOTe states since the late 1970s, increasing the number of days with strong cooling of the Aegean Sea surface waters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatGe...9..590M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatGe...9..590M"><span id="translatedtitle">Antarctic sea-ice expansion between 2000 and 2014 driven by tropical Pacific <span class="hlt">decadal</span> climate <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meehl, Gerald A.; Arblaster, Julie M.; Bitz, Cecilia M.; Chung, Christine T. Y.; Teng, Haiyan</p> <p>2016-08-01</p> <p>Antarctic sea-ice extent has been slowly increasing in the satellite record that began in 1979. Since the late 1990s, the increase has accelerated, but the average of all climate models shows a decline. Meanwhile, the Interdecadal Pacific Oscillation, an internally generated mode of climate <span class="hlt">variability</span>, transitioned from positive to negative, with an average cooling of tropical Pacific sea surface temperatures, a slowdown of the global warming trend and a deepening of the Amundsen Sea Low near Antarctica that has contributed to regional circulation changes in the Ross Sea region and expansion of sea ice. Here we show that the negative phase of the Interdecadal Pacific Oscillation in global coupled climate models is characterized by anomalies similar to the <span class="hlt">observed</span> sea-level pressure and near-surface 850 hPa wind changes near Antarctica since 2000 that are conducive to expanding Antarctic sea-ice extent, particularly in the Ross Sea region in all seasons, involving a deepening of the Amundsen Sea Low. These atmospheric circulation changes are shown to be mainly driven by precipitation and convective heating anomalies related to the Interdecadal Pacific Oscillation in the equatorial eastern Pacific, with additional contributions from convective heating anomalies in the South Pacific convergence zone and tropical Atlantic regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH33C..07E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH33C..07E"><span id="translatedtitle">Geomagnetic storms during the last <span class="hlt">decade</span>: Cluster and Double Star <span class="hlt">observations</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Escoubet, C.; Taylor, M. G.; Masson, A.; Laakso, H. E.; Liu, Z.; Goldstein, M. L.</p> <p>2013-12-01</p> <p>The launch of the Cluster spacecraft almost coincided with one of the largest geomagnetic storm of the last <span class="hlt">decade</span>, well known as the "Bastille Day" storm, on 14-15 July 2000. Planned on 15 July, the launch was aborted a few minutes before due to a thunderstorm that had hit the Baikonour cosmodrome and made a disruption in the communication lines with the rocket. The launch took place the day after, on 16 July 2000. Our US colleagues had warned us about the storm and recommended not to launch on 15 July. Given the facts that (1) Cluster was built to study the effects of space weather and geomagnetic storms and (2) that the Russian launch authorities were not concerned for the Soyuz rocket, it was decided to go ahead with the launch. The launch was fine and, after a second launch less than a month later, the four Cluster spacecraft were put successfully in their 4x19 RE polar orbit. Since then, Cluster has <span class="hlt">observed</span> many geomagnetic storms and could <span class="hlt">observe</span>, for the first time with a constellation of four spacecraft, the dynamics induced in the magnetosphere by coronal mass ejections or interplanetary shocks coming from the Sun. In this talk we will use storms <span class="hlt">observed</span> by Cluster and Double Star in the last <span class="hlt">decade</span> to illustrate how the magnetosphere was affected. We have <span class="hlt">observed</span> large compressions of the magnetosphere, distortions of the polar cusp, acceleration of particles associated with chorus and ULF waves, intensification of the ring current imaged by energetic neutral atom imagers, oxygen outflow from polar regions, and tail current sheet motions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.C41A0484H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.C41A0484H"><span id="translatedtitle">The Nature of the <span class="hlt">Decadal</span> <span class="hlt">Variability</span> of Surface Climate Over the North Atlantic Ocean --- --- Coupled Ocean-Atmosphere-Sea Ice Interaction Organized by Damped Ocean Mode</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, F.; Liu, Z.</p> <p>2008-12-01</p> <p>The nature of the <span class="hlt">observed</span> 11-14 year <span class="hlt">decadal</span> <span class="hlt">variability</span> of the surface climate over the North Atlantic Ocean is investigated using the Fast Ocean Atmosphere Model (FOAM) and its data-atmosphere configuration. A 14-16 year damped ocean mode, characterized by the <span class="hlt">decadal</span> <span class="hlt">variability</span> of Atlantic Meridional Overturning Circulation (AMOC), is found to be able to organize coupled ocean--atmosphere-- sea ice interaction in the North Atlantic and produce the <span class="hlt">decadal</span> <span class="hlt">variability</span> of the surface climate in this region. In the coupled simulation, two physical processes were found to be critical. The SAT-convection feedback is the local effect of SAT on oceanic convections in the Labrador Sea. Under cold episodes of surface climate in the North Atlantic, the damped ocean mode is pushed to its "positive" mode when the cold air induces stronger convective activity in the Labrador Sea. The stronger convections produce more vigorous AMOC and more heat transport into the subpolar North Atlantic and generates warmer SST and SAT. This gives rise to the warm episodes of surface climate. The sea ice-convection feedback is the effect of salinity anomaly on oceanic convections. The aforementioned warmer SAT induces more sea ice melting and results in low sea surface salinity in the northern subpolar gyre, especially in Irminger Sea. After the low salinity is transported into Labrador Sea, it suppresses local convective activity and acts jointly with SAT-convection feedback to switch the damped ocean mode into its "negative" mode. The damped ocean mode was uncovered in the stochastic atmospheric simulation and found to be responsible for the <span class="hlt">decadal</span> time scale in the coupled simulations. However, the stochastic atmospheric simulation fails maintaining the <span class="hlt">decadal</span> <span class="hlt">variability</span> of ocean temperature and salinity in the North Atlantic both at surface and subsurface. In fact, given the insurmountable damping effect of the stochastic atmosphere, it is impossible to sustain the <span class="hlt">decadal</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=302477','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=302477"><span id="translatedtitle">Intra- to Multi-<span class="hlt">Decadal</span> Temperature <span class="hlt">Variability</span> over the Continental United States: 1896-2012</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-<span class="hlt">decadal</span> (IMD) time windows containing significant ranking sequences in U.S. climate division temperature data. The simplicity of the ORR procedure’s output – a time series’ most significant non-overlapping periods of high o...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GML...tmp...33C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GML...tmp...33C"><span id="translatedtitle">German Bight residual current <span class="hlt">variability</span> on a daily basis: principal components of multi-<span class="hlt">decadal</span> barotropic simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Callies, Ulrich; Gaslikova, Lidia; Kapitza, Hartmut; Scharfe, Mirco</p> <p>2016-08-01</p> <p>Time <span class="hlt">variability</span> of Eulerian residual currents in the German Bight (North Sea) is studied drawing on existing multi-<span class="hlt">decadal</span> 2D barotropic simulations (1.6 km resolution) for the period Jan. 1958-Aug. 2015. Residual currents are calculated as 25 h means of velocity fields stored every hour. Principal component analysis (PCA) reveals that daily variations of these residual currents can be reasonably well represented in terms of only 2-3 degrees of freedom, partly linked to wind directions. The daily data refine monthly data already used in the past. Unlike existing classifications based on subjective assessment, numerical principal components (PCs) provide measures of strength and can directly be incorporated into more comprehensive statistical data analyses. Daily resolution in particular fits the time schedule of data sampled at the German Bight long-term monitoring station at Helgoland Roads. An example demonstrates the use of PCs and corresponding empirical orthogonal functions (EOFs) for the interpretation of short-term variations of these local <span class="hlt">observations</span>. On the other hand, monthly averaging of the daily PCs enables to link up with previous studies on longer timescales.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP31C1889C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP31C1889C"><span id="translatedtitle"><span class="hlt">Decadal</span> and Centennial <span class="hlt">Variability</span> of Wet and Dry in China since Medieval Warm Period Detected from High Resolution Speleothem Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chu, P. C.; Li, H.</p> <p>2011-12-01</p> <p>High-resolution δ18O data (yearly) since AD 900 from six caves (Dongge, Furong, Heshang, Wanxiang, Buddha, Shihua) in China was analyzed to detect <span class="hlt">decadal</span> and centennial <span class="hlt">variability</span> of wet/dry in the Asian Monsoon region. The empirical mode decomposition method (Huang et al., 1998) was used to obtain trends for the six cave data. The nine-year running average was conducted on the detrened data (Δδ18O, called anomaly) to filter out high-frequency fluctuation such as the interannual <span class="hlt">variability</span>. Mean values of anomaly for each cave were calculated for 5 periods: (1) medieval warm period (MWD, AD 900 -AD 1100), (2) little ice age phase-1 (LIA-1, AD 1250 - AD 1550), (3) little ice age phase-2 (LIA-2, AD 1550 - AD 1850), (4) modern period-1 (MD-1, AD 1850 - AD 1950), and (5) modern period-2 (MD-2, AD 1950-2000). Anomalies in MWP and LIA-2 has opposite signs: negative anomaly (strong monsoon) in MWP and positive anomaly (weak monsoon) in LIA-2 in (Dongge, Wanxiang) cave data otherwise in (Budda, Furong, Heshang, Shihua) cave data. In LIA-1, all the six caves have positive anomalies (weak monsoon). In MD-1 (AD 1850-AD 1950), all the six caves have negative anomalies; and in MD-2 (AD 1950 - AD 2000), all the caves except Buddha have negative anomalies. It implies strong monsoon with global warming trend. Spectral analysis was also conducted on the detrended data of the six caves. The above <span class="hlt">observational</span> studies show the following results: (1) Monsoon strength has spatial variations; (2) Stronger monsoon occurred under both warm and cold climatic conditions. One should not use the relationship of warm condition, i.e., stronger summer monsoon to interpret monsoonal climates in short time scales (less than centennial scale); and (3) Monsoon strengthening continues.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RSPSA.47260376S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RSPSA.47260376S"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> of extreme wave height representing storm severity in the northeast Atlantic and North Sea since the foundation of the Royal Society</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santo, H.; Taylor, P. H.; Gibson, R.</p> <p>2016-09-01</p> <p>Long-term estimation of extreme wave height remains a key challenge because of the short duration of available wave data, and also because of the possible impact of climate <span class="hlt">variability</span> on ocean waves. Here, we analyse storm-based statistics to obtain estimates of extreme wave height at locations in the northeast Atlantic and North Sea using the NORA10 wave hindcast (1958-2011), and use a 5 year sliding window to examine temporal <span class="hlt">variability</span>. The <span class="hlt">decadal</span> <span class="hlt">variability</span> is correlated to the North Atlantic oscillation and other atmospheric modes, using a six-term predictor model incorporating the climate indices and their Hilbert transforms. This allows reconstruction of the historic extreme climate back to 1661, using a combination of known and proxy climate indices. Significant <span class="hlt">decadal</span> <span class="hlt">variability</span> primarily driven by the North Atlantic oscillation is <span class="hlt">observed</span>, and this should be considered for the long-term survivability of offshore structures and marine renewable energy devices. The analysis on wave climate reconstruction reveals that the variation of the mean, 99th percentile and extreme wave climates over <span class="hlt">decadal</span> time scales for locations close to the dominant storm tracks in the open North Atlantic are comparable, whereas the wave climates for the rest of the locations including the North Sea are rather different.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5046986','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5046986"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> of extreme wave height representing storm severity in the northeast Atlantic and North Sea since the foundation of the Royal Society</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Taylor, P. H.; Gibson, R.</p> <p>2016-01-01</p> <p>Long-term estimation of extreme wave height remains a key challenge because of the short duration of available wave data, and also because of the possible impact of climate <span class="hlt">variability</span> on ocean waves. Here, we analyse storm-based statistics to obtain estimates of extreme wave height at locations in the northeast Atlantic and North Sea using the NORA10 wave hindcast (1958–2011), and use a 5 year sliding window to examine temporal <span class="hlt">variability</span>. The <span class="hlt">decadal</span> <span class="hlt">variability</span> is correlated to the North Atlantic oscillation and other atmospheric modes, using a six-term predictor model incorporating the climate indices and their Hilbert transforms. This allows reconstruction of the historic extreme climate back to 1661, using a combination of known and proxy climate indices. Significant <span class="hlt">decadal</span> <span class="hlt">variability</span> primarily driven by the North Atlantic oscillation is <span class="hlt">observed</span>, and this should be considered for the long-term survivability of offshore structures and marine renewable energy devices. The analysis on wave climate reconstruction reveals that the variation of the mean, 99th percentile and extreme wave climates over <span class="hlt">decadal</span> time scales for locations close to the dominant storm tracks in the open North Atlantic are comparable, whereas the wave climates for the rest of the locations including the North Sea are rather different. PMID:27713662</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DSRII.113....9H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DSRII.113....9H"><span id="translatedtitle">Multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> and trends in the El Niño-Southern Oscillation and tropical Pacific fisheries implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harrison, D. E.; Chiodi, Andrew M.</p> <p>2015-03-01</p> <p>Extremes of the El Niño-Southern Oscillation (ENSO) are known to have various socio-economic impacts, including effects on several Pacific fisheries. The 137-year-long record of Darwin sea-level pressure offers a uniquely long-term perspective on ENSO and provides important insight into various aspects of interannual to century-scale <span class="hlt">variability</span> that affects these fisheries. One particular issue of interest is whether there is a centennial-scale (or longer) trend that can be expected to alter the future distributions of these fisheries. Since most tropical Pacific fishery records are no longer than a few <span class="hlt">decades</span>, another issue is the extent to which trends over these recent <span class="hlt">decades</span> are a good basis for detecting the presence of long-term (e.g., centennial-scale) deterministic changes, and perhaps thereby projecting future conditions. We find that the full 137-yr trend cannot be distinguished from zero with 95% confidence, and also that the ENSO variance in recent <span class="hlt">decades</span> is very similar to that of the early <span class="hlt">decades</span> of the record, suggesting that ENSO has not fundamentally changed over the period of large increase in atmospheric CO2. However, the strong multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> in ENSO is reflected in <span class="hlt">decades</span> with quite different levels of ENSO effects on the ecosystem. Many multi-<span class="hlt">decadal</span> subsets of the full record have statistically significant trends, using standard analysis techniques. These multi-<span class="hlt">decadal</span> trends are not; however, representative of the record-length trend, nor are they a useful basis for projecting conditions in subsequent <span class="hlt">decades</span>. Trend statistical significance is not a robust foundation for speculation about the future. We illustrate how the difficulties involved in determining whether a trend is statistically significant or not mean that, even after careful consideration, an unexpectedly large number of trends may reach standard statistical significance levels over the time spans for which many newer records are available, but still not</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000358','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000358"><span id="translatedtitle">Highlights from a <span class="hlt">Decade</span> of OMI-TOMS Total Ozone <span class="hlt">Observations</span> on EOS Aura</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Haffner, David P.; Bhartia, Pawan K.; McPeters, Richard D.; Joiner, Joanna; Ziemke, Jerald R.; Vassilkov, Alexander; Labow, Gordon J.; Chiou, Er-Woon</p> <p>2014-01-01</p> <p>Total ozone measurements from OMI have been instrumental in meeting Aura science objectives. In the last <span class="hlt">decade</span>, OMI has extended the length of the TOMS total ozone record to over 35 years to monitor stratospheric ozone recovery. OMI-TOMS total ozone measurements have also been combined synergistically with measurements from other Aura instruments and MLS in particular, which provides vertically resolved information that complements the total O3 mapping capability of OMI. With this combined approach, the EOS Aura platform has produced more accurate and detailed measurements of tropospheric ozone. This has led in turn to greater understanding of the sources and transport of tropospheric ozone as well as its radiative forcing effect. The combined use of OMI and MLS data was also vital to the analysis of the severe Arctic ozone depletion event of 2011. The quality of OMI-TOMS total O3 data used in these studies is the result of several factors: a mature and well-validated algorithm, the striking stability of the OMI instrument, and OMI's hyperspectral capabilities used to derive cloud pressures. The latter has changed how we think about the effects of clouds on total ozone retrievals. We will discuss the evolution of the operational V8.5 algorithm and provide an overview and motivation for V9. After reviewing results and developments of the past <span class="hlt">decade</span>, we finally highlight how ozone <span class="hlt">observations</span> from EOS Aura are playing an important role in new ozone mapping missions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000707','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000707"><span id="translatedtitle">A <span class="hlt">Decade</span> of Volcanic <span class="hlt">Observations</span> from Aura and the A-Train</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carn, Simon A.; Krotkov, Nickolay Anatoly; Yang, Kai; Krueger, Arlin J.; Hughes, Eric J.; Wang, Jun; Flower, Verity; Telling, Jennifer</p> <p>2014-01-01</p> <p>Aura <span class="hlt">observations</span> have made many seminal contributions to volcanology. Prior to the Aura launch, satellite <span class="hlt">observations</span> of volcanic degassing (e.g., from TOMS) were mostly restricted to large eruptions. However, the vast majority of volcanic gases are released during quiescent 'passive' degassing between eruptions. The improved sensitivity of Aura OMI permitted the first daily, space-borne measurements of passive volcanic SO2 degassing, providing improved constraints on the source locations and magnitude of global SO2 emissions for input to atmospheric chemistry and climate models. As a result of this unique sensitivity to volcanic activity, OMI data were also the first satellite SO2 measurements to be routinely used for volcano monitoring at several volcano observatories worldwide. Furthermore, the Aura OMI SO2 data also offer unprecedented sensitivity to volcanic clouds in the UTLS, elucidating the transport, fate and lifetime of volcanic SO2 and providing critical input to aviation hazard mitigation efforts. Another major advance has been the improved vertical resolution of volcanic clouds made possible by synergy between Aura and other A-Train instruments (e.g., AIRS, CALIPSO, CloudSat), advanced UV SO2 altitude retrievals, and inverse trajectory modeling of detailed SO2 cloud maps. This altitude information is crucial for climate models and aviation hazards. We will review some of the highlights of a <span class="hlt">decade</span> of Aura <span class="hlt">observations</span> of volcanic activity and look ahead to the future of volcanic <span class="hlt">observations</span> from space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19820031091&hterms=Calcium+Signaling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DCalcium%2BSignaling','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19820031091&hterms=Calcium+Signaling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DCalcium%2BSignaling"><span id="translatedtitle">Discovery and <span class="hlt">observation</span> of BY Draconis <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bopp, B. W.; Noah, P. V.; Klimke, A.; Africano, J.</p> <p>1981-01-01</p> <p>The discovery of BY Draconis <span class="hlt">variables</span> was efficiently accomplished by a spectroscopic survey of dK-M stars for weak H-alpha emissions, using 1-2 A resolution. The four BY Dra <span class="hlt">variables</span> discovered are all spectroscopic binaries with P values lower than about 10 d, in light of which, it is noted that the onset of high surface activity and appearance of H-alpha emission occur sharply at v(equator) of approximately 5 km/sec. At v(equator) of about 3 km/sec, dK-M stars have low levels of surface activity. It is found that while there is a range of Ca II emission strength, and only the strongest emitters of this line are BY Dra and/or flare stars, the H-alpha feature changes abruptly to an emission feature signaling the onset of flaring and/or the BY Dra syndrome. An increase of the rotation rate above v(equator) 5 km/sec does not appear to increase the level of surface activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.1739Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.1739Y"><span id="translatedtitle">Climatic controls on the interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span> in Saudi Arabian dust activity: Toward the development of a seasonal dust prediction model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Yan; Notaro, Michael; Liu, Zhengyu; Wang, Fuyao; Alkolibi, Fahad; Fadda, Eyad; Bakhrjy, Fawzieh</p> <p>2015-03-01</p> <p>The <span class="hlt">observed</span> climatic controls on springtime and summertime Saudi Arabian dust activities during 1975-2012 are analyzed, leading to development of a seasonal dust prediction model. According to empirical orthogonal function analysis, dust storm frequency exhibits a dominantly homogeneous pattern across Saudi Arabia, with distinct interannual and <span class="hlt">decadal</span> <span class="hlt">variability</span>. The previously identified positive trend in remotely sensed aerosol optical depth since 2000 is shown to be a segment of the <span class="hlt">decadal</span> oscillation in dust activity, according to long-duration station record. Regression and correlation analyses reveal that the interannual <span class="hlt">variability</span> in Saudi Arabian dust storm frequency is regulated by springtime rainfall across the Arabian Peninsula and summertime Shamal wind intensity. The key drivers of Saudi Arabian dust storm <span class="hlt">variability</span> are identified. Winter-to-spring La Niña enhances subsequent spring dust activity by decreasing rainfall across the country's primary dust source region, the Rub' al Khali Desert. A relatively cool tropical Indian Ocean favors frequent summer dust storms by producing an anomalously anticyclonic circulation over the central Arabian Peninsula, which enhances the Shamal wind. <span class="hlt">Decadal</span> <span class="hlt">variability</span> in Saudi Arabian dust storm frequency is associated with North African rainfall and Sahel vegetation, which regulate African dust emissions and transport to Saudi Arabia. Mediterranean sea surface temperatures (SSTs) also regulate <span class="hlt">decadal</span> dust <span class="hlt">variability</span>, likely through their influence on Sahel rainfall and Shamal intensity. Using antecedent-accumulated rainfall over the Arabian Peninsula and North Africa, and Mediterranean SSTs, as low-frequency predictors, and tropical eastern Pacific and tropical Indian Ocean SSTs as high-frequency predictors, Saudi Arabia's seasonal dust activity is well predicted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1227122','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1227122"><span id="translatedtitle">Collaborative Research. Separating Forced and Unforced <span class="hlt">Decadal</span> Predictability in Models and <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>DelSole, Timothy</p> <p>2015-08-31</p> <p>The purpose of the proposed research was to identify unforced predictable components on <span class="hlt">decadal</span> time scales, distinguish these components from forced predictable components, and to assess the reliability of model predictions of these components. The question of whether anthropogenic forcing changes <span class="hlt">decadal</span> predictability, or gives rise to new forms of <span class="hlt">decadal</span> predictability, also will be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9003Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9003Z"><span id="translatedtitle">An updated set of nutations derived from the reanalysis of 3.5 <span class="hlt">decades</span> VLBI <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, Ping; Koot, Laurence; Rivoldini, Attilio; Dehant, Veronique</p> <p>2016-04-01</p> <p>The global VLBI <span class="hlt">observation</span> started in the 1979. After that the qualities of the measurements are continuously improving by taking into account various instrumental and environmental effects. The MHB2000 models was introduced in 2002 (Mathews, et.al. 2002, [1]) and it has a good agreement (5 μas) on the short period nutation series (<400 days) with the values derived from 2 <span class="hlt">decades</span> (1979-2000) VLBI data while a higher uncertainties up to 56 μas for those longer periods (>400 days) nutation series (Herring et.al. 2002). In MHB2000, the forcing frequencies of the nutation series are solved by least-squares fitting to the VLBI data in frequency domain. Koot et al. (2008), have processed another similar set of nutation series by inversing the time series of VLBI data (1984-2005) using a Bayesian approach. In the present work, we will repeat both approaches using the up-to-date 3.5 <span class="hlt">decades</span> VLBI <span class="hlt">observations</span> (1980-2014) meanwhile paying more attention on the results of longer period (>400 days). Finally some features of Earth's interior structure will be discussed based on the determined nutation series. [1] Mathews, P.M., Herring, T.A. & Buffett, B.A., 2002. Modeling of nutation and precession: new nutation series for nonrigid Earth and insights into the Earth's interior, J. Geophys. Res., 107, 2068, doi: 10.1029/2001JB000390. [2] Herring, T. A., P. M. Mathews, and B. A. Buffett, Modeling of nutation and precession: Very long baseline interferometry results, J. Geophys. Res., 107, B4, 2069, doi: 10.1029/2001JB000165, 2002 [3] Koot, L., Rivoldini, A., de Viron, O. & Dehant, V., 2008. Estimation of Earth interior parameters from a Bayesian inversion of very long baseline interferometry nutation time series, J. Geophys. Res., 113, 8414, doi: 10.1029/2007JB005409.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6752V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6752V"><span id="translatedtitle">A new centennial index to study the Western North Pacific Monsoon <span class="hlt">decadal</span> <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vega, Inmaculada; Gómez-Delgado, F. de Paula; Gallego, David; Ribera, Pedro; Peña-Ortiz, Cristina; García-Herrera, Ricardo</p> <p>2016-04-01</p> <p>The concept of the Western North Pacific Summer Monsoon (WNPSM) appeared for the first time in 1987. It is, unlike the Indian Summer Monsoon (ISM) and the East Asian summer monsoon (EASM), an oceanic monsoon mostly driven by the meridional gradient of sea surface temperature. Its circulation is characterized by a northwest-southeast oriented monsoon trough with intense precipitation and low-level southwesterlies and upper-tropospheric easterlies in the region [100°-130° E, 5°-15°N]. Up to now, the primary index to characterize the WNPSM has been the Western North Pacific Monsoon Index (WNPMI) which covers the 1949-2013 period. The original WNPMI was defined as the difference of 850-hPa westerlies between two regions: D1 [5°-15°N, 100°-130°E] and D2 [20°-30°N, 110°-140°E]. Both domains are included in the main historical ship routes circumnavigating Asia for hundreds of years. Many of the logbooks of these ships have been preserved in historical archives and they usually contain daily <span class="hlt">observations</span> of wind force and direction. Therefore, it has been possible to compute a new index of instrumental character, which reconstructs the WNPSM back to the middle of the 19th Century, by using solely historical wind direction records preserved in logbooks. We define the monthly Western North Pacific Directional Index (WNPDI) as the sum of the persistence of the low-level westerly winds in D1 and easterly winds in D2. The advantages of this new index are its nature (instrumental) and its length (1849-2013), which is 100 years longer than the WNPMI (which was based on reanalysis data). Our WNPDI shows a high correlation (r=+0.87, p<0.01) with the previous WNPMI in summer for the 1949-2009 period, thus allowing to study the multidecadal <span class="hlt">variability</span> of the WNPSM in a more robust way. Our results show that the WNPDI has a strong impact on the precipitation in densely populated areas in South-East Asia, such as the Philippines or the west coast of Myanmar where the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817989P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817989P"><span id="translatedtitle">Mean SST bias and <span class="hlt">variability</span> at inter-annual and <span class="hlt">decadal</span> time-scales in CMIP5 models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polo, Irene; Villamayor, Julian; Rodriguez-Fonseca, Belen; Mohino, Elsa; Losada, Teresa</p> <p>2016-04-01</p> <p>Analysis of model systematic errors in Sea Surface Temperature (SST) has generally focused on local processes and particular basins. Mean warm bias over the south subtropical upwelling systems in coupled models are largely studied and local cloud cover, alongshore winds and ocean stratification are pointed out as the responsible processes. Mean errors have impacts on the <span class="hlt">variability</span> but this is less understood. In this study we try to understand the relation between mean global SST biases and how models perform the <span class="hlt">variability</span> at different time-scales. To this end, we calculate the SST <span class="hlt">variability</span> modes for 18 models in the preindustrial control CMIP5 experiment. We first analyse the seasonality of those modes and the inter-model differences. Associated parameters are confronted with the mean SST bias <span class="hlt">variability</span> among models, thus we conclude how realistic models simulate the <span class="hlt">variability</span> depending on the mean SST bias. Preliminary results suggest that models with cooler (warmer) that average SST mean bias over the southern hemisphere reproduce better (worse) the Inter-<span class="hlt">Decadal</span> Pacific <span class="hlt">variability</span>. Similar mean bias pattern has an effect on the skill for reproducing Pacific El Nino and Atlantic Nino modes. Finally an inter-model SST bias <span class="hlt">variability</span> mode is found relating errors over the southern upwelling systems with cloud cover around 60S and equatorial precipitation shift. This mode is able to summarize some features in relation with inter-<span class="hlt">decadal</span> to inter-annual <span class="hlt">variability</span> in CMIP5 models and thus represents a potential tool to understand the wider picture in relation to SST biases and future projections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JGRB..114.0A12K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JGRB..114.0A12K"><span id="translatedtitle">Northern Cascadia episodic tremor and slip: A <span class="hlt">decade</span> of tremor <span class="hlt">observations</span> from 1997 to 2007</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kao, Honn; Shan, Shao-Ju; Dragert, Herb; Rogers, Garry</p> <p>2009-11-01</p> <p>We analyze continuous seismic and GPS records collected in the last <span class="hlt">decade</span> (1997-2007) to establish the most comprehensive <span class="hlt">observational</span> basis for northern Cascadia episodic tremor and slip (ETS) events. A simple "ETS scale" system, using a combination of a letter and a digit, is proposed to quantitatively characterize the spatial and temporal dimensions of ETS events. Clear correlation between GPS and tremor signals is <span class="hlt">observed</span> for all A/B class episodes, but the GPS signature is less obvious for minor ones. Regular ETS recurrence can be established only for A/B class episodes in southern Vancouver Island. Halting and jumping are very common in ETS migration patterns, and along-strike migration can happen in both directions. A prominent tremor gap is <span class="hlt">observed</span> in midisland around 49.5°N. This gap coincides with the epicenters of the only two large earthquakes beneath Vancouver Island. ETS tremors also tend to occur in places where the local seismicity is relatively sparse. The tremor depth distribution shows a peak in the 25-35 km range where strong seismic reflectors (i.e., the E layer) are documented. Detailed waveform analysis confirms the existence of shallow tremors above the currently interpreted plate interface. Our results suggest that a significant portion of the tremor activity and perhaps associated shearing are taking place along well-developed structures such as the E layer, while fewer tremor bursts are generated elsewhere in response to the induced stress variation throughout the source volume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.6114Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.6114Y"><span id="translatedtitle">On the mechanisms of <span class="hlt">decadal</span> <span class="hlt">variability</span> of the North Pacific Gyre Oscillation over the 20th century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yi, Daling Li; Zhang, Liping; Wu, Lixin</p> <p>2015-09-01</p> <p>The <span class="hlt">decadal</span> <span class="hlt">variability</span> of the North Pacific gyre oscillation (NPGO) over the 20th century is examined from a long-term integration of the Simple Ocean Data Assimilation (SODA) reanalysis. The NPGO is reflected by the second dominant pattern of sea surface height (SSH) <span class="hlt">variability</span> in SODA, with a north-south dipole structure over the northeast Pacific. SSH anomalies in this region exhibit distinct <span class="hlt">decadal</span> <span class="hlt">variability</span> with a significant spectrum peak at approximately 18 years. The upper-ocean heat budget reveals that this dipole structure associated with the NPGO is predominantly due to the anomalous Ekman pumping and Ekman advection induced by the surface wind. The NPGO mode in SODA reanalysis originates from atmosphere stochastic noise (North Pacific Oscillation) which has a meridional dipole pattern but no preferred time scale. The oceanic planetary wave, particularly the advective baroclinic mode, integration of atmospheric stochastic noise leads to a spatial resonance with preferred <span class="hlt">decadal</span> time scale. The limitation of current study is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25001240','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25001240"><span id="translatedtitle"><span class="hlt">Observed</span> cold season changes in a Fennoscandian fell area over the past three <span class="hlt">decades</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kivinen, Sonja; Rasmus, Sirpa</p> <p>2015-04-01</p> <p>We studied trends and <span class="hlt">variability</span> in snow and climate characteristics in 1978-2012 in the Värriötunturit fell area, northern Finland. Cold season changes were examined using long-term <span class="hlt">observational</span> data on snow depths, meteorological data, large-scale climate indices, and reindeer herders' experiences with difficult snow conditions. Snow depths declined, and temperatures increased significantly over the study period, with the largest changes <span class="hlt">observed</span> in October-December and in April. Snow depths decreased particularly in forests at lower altitudes but not in treeless areas at higher altitudes. Interannual <span class="hlt">variability</span> (but not the trends) in snow depths could be partially linked to large-scale climate indices. A majority of difficult reindeer grazing conditions were related to deep snow in the winter or spring. Our <span class="hlt">observations</span> suggest that shortened duration of snow cover may facilitate reindeer grazing, whereas potentially more frequent formation of ice layers and mold growth on pastures in the future is disadvantageous for reindeer husbandry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25001240','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25001240"><span id="translatedtitle"><span class="hlt">Observed</span> cold season changes in a Fennoscandian fell area over the past three <span class="hlt">decades</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kivinen, Sonja; Rasmus, Sirpa</p> <p>2015-04-01</p> <p>We studied trends and <span class="hlt">variability</span> in snow and climate characteristics in 1978-2012 in the Värriötunturit fell area, northern Finland. Cold season changes were examined using long-term <span class="hlt">observational</span> data on snow depths, meteorological data, large-scale climate indices, and reindeer herders' experiences with difficult snow conditions. Snow depths declined, and temperatures increased significantly over the study period, with the largest changes <span class="hlt">observed</span> in October-December and in April. Snow depths decreased particularly in forests at lower altitudes but not in treeless areas at higher altitudes. Interannual <span class="hlt">variability</span> (but not the trends) in snow depths could be partially linked to large-scale climate indices. A majority of difficult reindeer grazing conditions were related to deep snow in the winter or spring. Our <span class="hlt">observations</span> suggest that shortened duration of snow cover may facilitate reindeer grazing, whereas potentially more frequent formation of ice layers and mold growth on pastures in the future is disadvantageous for reindeer husbandry. PMID:25001240</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A51A0082S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A51A0082S"><span id="translatedtitle">Atmospheric <span class="hlt">Variability</span> of CO2 impact on space <span class="hlt">observation</span> Requirements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swanson, A. L.; Sen, B.; Newhart, L.; Segal, G.</p> <p>2009-12-01</p> <p>If International governments are to reduce GHG levels by 80% by 2050, as recommended by most scientific bodies concerned with avoiding the most hazardous changes in climate, then massive investments in infrastructure and new technology will be required over the coming <span class="hlt">decades</span>. Such an investment will be a huge commitment by governments and corporations, and while it will offer long-term dividends in lower energy costs, a healthier environment and averted additional global warming, the shear magnitude of upfront costs will drive a call for a monitoring and verification system. Such a system will be required to offer accountability to signatories of governing bodies, as well as, for the global public. Measuring the average global distribution of CO2 is straight forward, as exemplified by the long running station measurements managed by NOAA’s Global Monitoring Division that includes the longterm Keeling record. However, quantifying anthropogenic and natural source/sink distributions and atmospheric mixing have been much more difficult to constrain. And, yet, an accurate accounting of all anthropogenic source strengths is required for Global Treaty verification. The only way to accurately assess Global GHG emissions is to construct an integrated system of ground, air and space based <span class="hlt">observations</span> with extensive chemical modeling capabilities. We look at the measurement requirements for the space based component of the solutions. To determine what space sensor performance requirements for ground resolution, coverage, and revisit, we have analyzed regional CO2 distributions and <span class="hlt">variability</span> using NASA and NOAA aircraft flight campaigns. The results of our analysis are presented as variograms showing average spatial <span class="hlt">variability</span> over several Northern Hemispheric regions. There are distinct regional differences with the starkest contrast between urban versus rural and Coastal Asia versus Coastal US. The results suggest specific consequences on what spatial and temporal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AAS...19913306I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AAS...19913306I"><span id="translatedtitle">FUSE <span class="hlt">Observations</span> of Luminous Blue <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iping, R. C.; Sonneborn, G.</p> <p>2001-12-01</p> <p>P-Cygni, AG Carinae, S-Doradus and Eta Carinae were <span class="hlt">observed</span> with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. FUSE covers the spectral range 905 to 1187 Angstroms at a resolution of 0.05 Angstroms. In this paper we explore in what way the LBV's are similar and in what way they are different. For Eta Car the <span class="hlt">observed</span> flux at 1160 A, is 4E-12 erg/cm2/s/A. This is 20X larger than <span class="hlt">observed</span> by STIS/E140M at the same wavelength through a 0.2"x0.2" aperture. The flux level declines toward the Lyman limit where converging molecular and atomic hydrogen features completely blanket the spectrum. The shape of the spectrum shortward of 1110 Angstroms is dominated by strong absorption bands of interstellar molecular hydrogen. In addition to many strong interstellar atomic species, the spectrum contains several prominent P-Cygni features, including C III 1175, S IV 1063-73, Si III 1113, and N I 1134. The lines are broad with unsaturated absorption troughs, implying that the wind is patchy and/or only partly covers the UV emitting surface. The wind absorption extends to -1000 km/s. The large far ultraviolet flux levels at 1150-1180 A, relative to those <span class="hlt">observed</span> by HST/STIS, imply that the <span class="hlt">observed</span> far-UV spectrum is formed in an extended 1-2 arcsec diameter UV scattering envelope. The far-UV spectra of P Cygni and AG Carinae are very similar and indicate a cooler atmosphere than Eta Car and S Dor. There is very good agreement between the FUSE spectrum of P Cygni and a model atmosphere computed by Hillier with his code CMFGEN. This work has been supported in part by NASA grants NAG5-8631 to Catholic University of America and NAS5-32985 to Johns Hopkins University.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AAS...21812202B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AAS...21812202B"><span id="translatedtitle">Chandra Watches Over A <span class="hlt">Decade</span> Of <span class="hlt">Variability</span> In M31 Globular Clusters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barnard, Robin; Li, Z.; Garcia, M.; Murray, S.</p> <p>2011-05-01</p> <p>The central region of M31 has been monitored with Chandra > 120 times over the last 11 years. In this region we find X-ray sources corresponding to 35 out of 420 globular clusters; these are highly likely to be X-ray binaries. We have created long-term, calibrated lightcurves for all 35 sources, and will present highlights of our <span class="hlt">variability</span> survey. We have detected significant <span class="hlt">variability</span> in all the sources with 0.3-10 keV luminosity > 2x10E+36 erg/s. Since the emission spectra of background active galaxies often resemble those of X-ray binaries, the long term <span class="hlt">variability</span> will be a valuable tool for identifying X-ray binaries in the remaining 400 sources in our field. This work is funded by Chandra grant GO9-0100X and HST grant GO-1101.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003IAUS..212..208I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003IAUS..212..208I"><span id="translatedtitle">FUSE <span class="hlt">observations</span> of Luminous Blue <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iping, Rosina C.; Sonneborn, George; Massa, Derck L.</p> <p></p> <p>P Cyg, AG Car, HD 5980 and η Car were <span class="hlt">observed</span> with the Far Ultraviolet Spectroscopic Explorer ( FUSE) satellite. FUSE covers the spectral range from 980 Å to 1187 Å at a resolution of 0.05 Å. In this paper we discuss the far-UV properties of these LBVs and explore their similarities and differences. The FUSE <span class="hlt">observations</span> of P Cyg and AG Car, both spectral type B2pe, are very similar. The atmospheres of both η Car and HD 5980 appear to be somewhat hotter and have much higher ionization stages (Si IV, S IV, and P V) in the FUSE spectrum than P Cyg and AG Car. There is a very good agreement between the FUSE spectrum of P Cygni and the model atmosphere computed by John Hillier with his code CMFGEN. The FUSE spectrum of η Car, however, does not agree very well with existing model spectra.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110012422','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110012422"><span id="translatedtitle">CLARREO Cornerstone of the Earth <span class="hlt">Observing</span> System: Measuring <span class="hlt">Decadal</span> Change Through Accurate Emitted Infrared and Reflected Solar Spectra and Radio Occultation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sandford, Stephen P.</p> <p>2010-01-01</p> <p>The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is one of four Tier 1 missions recommended by the recent NRC <span class="hlt">Decadal</span> Survey report on Earth Science and Applications from Space (NRC, 2007). The CLARREO mission addresses the need to provide accurate, broadly acknowledged climate records that are used to enable validated long-term climate projections that become the foundation for informed decisions on mitigation and adaptation policies that address the effects of climate change on society. The CLARREO mission accomplishes this critical objective through rigorous SI traceable <span class="hlt">decadal</span> change <span class="hlt">observations</span> that are sensitive to many of the key uncertainties in climate radiative forcings, responses, and feedbacks that in turn drive uncertainty in current climate model projections. These same uncertainties also lead to uncertainty in attribution of climate change to anthropogenic forcing. For the first time CLARREO will make highly accurate, global, SI-traceable <span class="hlt">decadal</span> change <span class="hlt">observations</span> sensitive to the most critical, but least understood, climate forcings, responses, and feedbacks. The CLARREO breakthrough is to achieve the required levels of accuracy and traceability to SI standards for a set of <span class="hlt">observations</span> sensitive to a wide range of key <span class="hlt">decadal</span> change <span class="hlt">variables</span>. The required accuracy levels are determined so that climate trend signals can be detected against a background of naturally occurring <span class="hlt">variability</span>. Climate system natural <span class="hlt">variability</span> therefore determines what level of accuracy is overkill, and what level is critical to obtain. In this sense, the CLARREO mission requirements are considered optimal from a science value perspective. The accuracy for <span class="hlt">decadal</span> change traceability to SI standards includes uncertainties associated with instrument calibration, satellite orbit sampling, and analysis methods. Unlike most space missions, the CLARREO requirements are driven not by the instantaneous accuracy of the measurements, but by accuracy in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.2159P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.2159P"><span id="translatedtitle">Shoreline <span class="hlt">variability</span> from days to <span class="hlt">decades</span>: Results of long-term video imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pianca, C.; Holman, R.; Siegle, E.</p> <p>2015-03-01</p> <p>The present work characterizes the time-space scales of <span class="hlt">variability</span> and forcing dependencies of a unique 26 year record of daily to hourly shoreline data from a steep beach at Duck, North Carolina. Shoreline positions over a 1500 m alongshore span were estimated using a new algorithm called ASLIM based on fitting the band of high light intensity in time exposure images to a local Gaussian fit, with a subsequent Kalman filter to reduce noise and uncertainty. Our findings revealed that the shoreline change at long times scales dominates seasonal <span class="hlt">variability</span>, despite that wave forcing had only 2% variance at interannual frequencies. The shoreline response presented 66% of the variance at interannual scales. These results were not expected since from wave forcing it would have been expected that the shoreline response should similarly lack interannual <span class="hlt">variability</span>, but we found it to be dominated by this scale. The alongshore-mean shoreline time series revealed no significant annual cycle. However, there are annual oscillations in the shoreline response that are coherent with wave forcing and deserves further explanations. The pier was found to have a significant influence on shoreline behavior since restricts the seasonal longshore transport between the sides, resulting in a seasonally reversing sediment accumulation. Thus, there is a significant annual peak in shoreline <span class="hlt">variability</span> that is coherent with the annual forcing but becomes insignificant in the longshore-average.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.3241R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.3241R"><span id="translatedtitle">Does mesoscale matters in <span class="hlt">decadal</span> changes <span class="hlt">observed</span> in the northern Canary upwelling system?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Relvas, P.; Luís, J.; Santos, A. M. P.</p> <p>2009-04-01</p> <p>The Western Iberia constitutes the northern limb of the Canary Current Upwelling System, one of the four Eastern Boundary Upwelling Systems of the world ocean. The strong dynamic link between the atmosphere and the ocean makes these systems highly sensitive to global change, ideal to monitor and investigate its effects. In order to investigate <span class="hlt">decadal</span> changes of the mesoscale patterns in the Northern Canary upwelling system (off Western Iberia), the field of the satellite-derived sea surface temperature (SST) trends was built at the pixel scale (4x4 km) for the period 1985-2007, based on the monthly mean data from the Advanced Very High Resolution Radiometer (AVHRR) on board NOAA series satellites, provided by the NASA Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the Jet Propulsion Laboratory. The time series were limited to the nighttime passes to avoid the solar heating effect and a suite of procedures were followed to guarantee that the temperature trends were not biased towards the seasonally more abundant summer data, when the sky is considerably clear. A robust linear fit was applied to each individual pixel, crossing along the time the same pixel in all the processed monthly mean AVHRR SST images from 1985 until 2007. The field of the SST trends was created upon the slopes of the linear fits applied to each pixel. Monthly mean SST time series from the one degree enhanced International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and from near-shore measurements collected on a daily basis by the Portuguese Meteorological Office (IM) are also used to compare the results and extend the analysis back until 1960. A generalized warming trend is detected in the coastal waters off Western Iberia during the last <span class="hlt">decades</span>, no matter which data set we analyse. However, significant spatial differences in the warming rates are <span class="hlt">observed</span> in the satellite-derived SST trends. Remarkably, off the southern part of the Western Iberia the known</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.B52C..03B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.B52C..03B"><span id="translatedtitle">Can we reconcile our understanding of the atmospheric methane budget over the past <span class="hlt">decades</span> with atmospheric <span class="hlt">observations</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bruhwiler, L. M.; Matthews, E.</p> <p>2007-12-01</p> <p>The balance of methane in the atmosphere is determined by surface emission, and losses due to uptake in soils and reaction with the hydroxyl radical. The atmospheric abundance of methane has risen by about a factor of three since pre-industrial times, but the growth rate has decreased substantially since the 1990's. Thus, global atmospheric methane appears to have equilibrated to around 1780 ppb subject to considerable interannual <span class="hlt">variability</span>, the causes of which are not well-understood. Methane emissions are expected to increase in the future due to increases in fossil fuel use and possible changes in wetlands at high-latitudes, and it is therefore important to test our understanding of the methane budget over the last two <span class="hlt">decades</span> against network <span class="hlt">observations</span> of atmospheric methane. Issues of interest are whether we can match the rise in methane over the 1980's, whether we can explain the decrease in growth rate during the 1990's, and whether we are able to simulate the <span class="hlt">observed</span> interannual <span class="hlt">variability</span> in the <span class="hlt">observations</span>. We will show results from a multi-<span class="hlt">decade</span> model simulation using analyzed meteorology from the ERA-40 reanalysis over this period. New times series of methane sources for 1980 through the early 2000's are used in the simulation. Anthropogenic sources include fossil fuels with a total of 7 fuel-process emission combinations associated with mining, processing, transport and distribution of coal, natural gas and oil; ruminant animals and manure based on regionally-representative profiles of bovine populations ; landfills including the impact of on- site methane capture; and irrigated rice cultivation based on seasonal rice-cropping calendars. Natural sources we include are biomass burning from the GFED emission data base, oceans, termites, and natural wetlands using a multiple-regression model derived from a process-based model. If time permits, we will also show preliminary results of a methane data assimilation using the Cooperative Air</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT........16U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT........16U"><span id="translatedtitle"><span class="hlt">Observational</span> studies of highly evolved cataclysmic <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Uthas, Helena</p> <p>2011-05-01</p> <p>According to standard evolutionary theory for cataclysmic <span class="hlt">variables</span> (CVs), angular momentum loss drives CVs to initially evolve from longer to shorter orbital periods until a minimum period is reached (approx 80 min). At roughly this stage, the donors becomes degenerate, expand in size, and the systems move towards longer Porb. Theory predicts that 70% of all CVs should have passed their minimum period and have sub-stellar donors, but until recently, no such systems were known. I present one CV showing evidence of harbouring a sub-dwarf donor, SDSS J1507+52. Due to the system's unusually short Porb of about 65 min, and very high space velocity, two origins for SDSS J1507+52 have been proposed; either the system was formed from a young WD/brown-dwarf binary, or the system is a halo CV. In order to distinguish between these two theories, I present UV spectroscopy and find a metallicity consistent with halo origin. Systems close to Pmin are expected to have low accretion rates. Some of these CVs show absorption in their spectra, implying that the underlying WD is exposed. This yields a rare opportunity to study the WD in a CV. I introduce two new systems showing WD signatures in their light curves and spectra, SDSS J1457+51 and BW Scl. Despite the fact that CVs close to Pmin should be faint, we find systems that are much too bright for their Porb. Such a system is T Pyx - a recurrent nova with an unusually high accretion rate and a photometrically determined Porb < 2 hr. T Pyx is about 2 times brighter than any other CV at its period. However, to confirm its evolutionary status, a more reliable period determination is needed. Here, I present a spectroscopic study, confirming T Pyx as a short-period CV. In this thesis, I discuss what implications these systems may have on the current understanding of CV evolution, and the importance of studying individual systems in general.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1127130','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1127130"><span id="translatedtitle">Collaborative Research: Separating Forced and Unforced <span class="hlt">Decadal</span> Predictability in Models and <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tippett, Michael K.</p> <p>2014-04-09</p> <p>This report is a progress report of the accomplishments of the research grant “Collaborative Research: Separating Forced and Unforced <span class="hlt">Decadal</span> Predictability in Models and Observa- tions” during the period 1 May 2011- 31 August 2013. This project is a collaborative one between Columbia University and George Mason University. George Mason University will submit a final technical report at the conclusion of their no-cost extension. The purpose of the proposed research is to identify unforced predictable components on <span class="hlt">decadal</span> time scales, distinguish these components from forced predictable components, and to assess the reliability of model predictions of these components. Components of unforced <span class="hlt">decadal</span> predictability will be isolated by maximizing the Average Predictability Time (APT) in long, multimodel control runs from state-of-the-art climate models. Components with <span class="hlt">decadal</span> predictability have large APT, so maximizing APT ensures that components with <span class="hlt">decadal</span> predictability will be detected. Optimal fingerprinting techniques, as used in detection and attribution analysis, will be used to separate variations due to natural and anthropogenic forcing from those due to unforced <span class="hlt">decadal</span> predictability. This methodology will be applied to the <span class="hlt">decadal</span> hindcasts generated by the CMIP5 project to assess the reliability of model projections. The question of whether anthropogenic forcing changes <span class="hlt">decadal</span> predictability, or gives rise to new forms of <span class="hlt">decadal</span> predictability, also will be investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003DSRII..50.2449B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003DSRII..50.2449B&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> in abundances of the dominant euphausiid species in southern sectors of the California Current</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brinton, Edward; Townsend, Annie</p> <p>2003-08-01</p> <p>Euphausiid abundance data from broadly based California Cooperative Oceanic Fisheries Investigation surveys in California and Baja California sectors of the California Current provided a time series distinguishing periodic, rhythmic and irregular species patterns. Comparisons with environmental indexes indicate significant correlations with warm-water species, most notably in coastal Nyctiphanes simplex. Oceanic warm-water species were similarly, but less extremely, allied with an index. Coastal warm-water N. simplex was uncommon off southern California before the atmospheric regime shift of the 1970s. It assumed a post-1978 pattern of rhythmic biannual abundance increases and decreases during 1981-2000. The near-tropical oceanic Euphausia eximia and Pacific Central subtropicals patterned similarly, but was more periodic than rhythmic. Euphausia pacifica, the most dominant and broadly ranging Euphausia species, peaked at irregular but distinct bi-<span class="hlt">decadal</span> abundances during 6 strong La Niña episodes. The peaks uniformly collapsed by 90%, becoming El Niño-associated minima. The cold-water coastal northern species Thysanoessa spinifera frequently ranged far south off Baja California before 1960 but became limited to Central California in the 1980s. The importance of T. spinifera off the Californias is small compared with northern regions, but it extends to southern upwelling centers contributing to dominance, here, by cold-water euphausiids. <span class="hlt">Decadal</span> periodicity of species abundances decreased in the 1990s, when trends became more common. Differences among sectors were minimal between the two Californias, but were often distinct between southern California and Central Baja California. Species abundances, comparing pre- and post-climate shift species averages, differed insignificantly for all species when logarithmic values were used. With arithmetic values, most 1977-1998 average values were the greater, but with large standard deviations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.U31B..02K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.U31B..02K"><span id="translatedtitle">Northern Cascadia Episodic Tremor and Slip: A <span class="hlt">Decade</span> of <span class="hlt">Observations</span> from 1997 to 2007</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kao, H.; Shan, S.; Dragert, H.; Rogers, G.; Ito, Y.</p> <p>2008-12-01</p> <p>We analyze continuous seismic and GPS records collected in the last <span class="hlt">decade</span> (1997-2007) to establish the most comprehensive <span class="hlt">observational</span> basis for northern Cascadia episodic tremor and slip (ETS) events. A simple ¡§ETS scale¡¨ system, using a combination of a letter and a digit, is proposed to quantitatively characterize the spatial and temporal dimensions of ETS events. Clear correlation between GPS and tremor signals is <span class="hlt">observed</span> for all major episodes with lateral dimension >150 km (i.e., A- or B-class), but the GPS signature is less obvious for minor ones. Regular ETS recurrence can be established only for A-/B-class episodes in southern Vancouver Island. Halting and jumping are very common in ETS migration patterns, and along-strike migration can happen in both directions. A prominent tremor gap is <span class="hlt">observed</span> in mid island around 49.5N. This gap coincides with the epicenters of the only two large documented crustal earthquakes in the region. ETS tremors also tend to occur in places where the local seismicity is relatively sparse. The tremor depth distribution shows a peak in the 25-35 km range where strong seismic reflectors (i.e., the E- layer) are documented. Existence of tremors in the vicinity of E-layer is also confirmed by an independent waveform analysis. More significantly, we have found a few very-low-frequency earthquakes (VLFE) at the depth of E-layer showing low-angle thrust faulting mechanisms. Our results suggest that a significant portion of the tremor activity and perhaps associated shearing are taking place along well-developed structures such as the E-layer, while a reduced number of tremor bursts are generated elsewhere in response to induced stress variation throughout the source volume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...46.1517C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...46.1517C"><span id="translatedtitle">Mechanisms of internally generated <span class="hlt">decadal</span>-to-multidecadal <span class="hlt">variability</span> of SST in the Atlantic Ocean in a coupled GCM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Hua; Schneider, Edwin K.; Wu, Zhiwei</p> <p>2016-03-01</p> <p>Mechanisms of the internally generated <span class="hlt">decadal</span>-to-multidecadal <span class="hlt">variability</span> of SST in the Atlantic Ocean are investigated in a long control simulation of the Community Climate System Model version 3 with constant external forcing. The interactive ensemble (IE) coupling strategy, with an ensemble of atmospheric GCMs (AGCM) coupled to an ocean model, a sea-ice model and a land model, is used to diagnose the roles of various processes in the coupled GCM (CGCM). The noise components of heat flux, wind stress and fresh water flux of the control simulation, determined from the CGCM surface fluxes by subtracting the SST-forced surface fluxes, estimated as the ensemble mean of AGCM simulations, are applied at the ocean surface of the IE in different regions and in different combinations. The IE simulations demonstrate that the climate <span class="hlt">variability</span> in the control simulation is predominantly forced by noise. The local noise forcing is found to be responsible for the SST <span class="hlt">variability</span> in the Atlantic Ocean, with noise heat flux and noise wind stress playing a critical role. The control run Atlantic multidecadal <span class="hlt">variability</span> (AMV) index is decomposed into interannual, <span class="hlt">decadal</span> and multidecadal modes based on the ensemble empirical mode decomposition. The AMV multidecadal mode, a combination of 50- and 100-year modes, is examined in detail. The North Atlantic Oscillation (NAO) pattern in the atmosphere, dominated by the noise component, forces the multidecadal mode through noise heat flux and noise wind stress. The noise wind stress forcing on the multidecadal mode is associated with ocean dynamics, including gyre adjustment and the Atlantic Meridional Overturning Circulation (AMOC). The AMV <span class="hlt">decadal</span> mode is also found to be related to noise NAO forcing. The associated ocean dynamics are connected with both noise heat flux and noise wind stress, but the AMOC related to the <span class="hlt">decadal</span> mode is more likely to be forced by noise heat flux. For both multidecadal and <span class="hlt">decadal</span> modes, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026788','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026788"><span id="translatedtitle">Tree-ring based reconstructions of interannual to <span class="hlt">decadal</span> scale precipitation <span class="hlt">variability</span> for northeastern Utah since 1226 A.D.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Gray, S.T.; Jackson, S.T.; Betancourt, J.L.</p> <p>2004-01-01</p> <p>Samples from 107 pin??on pines (Pinus edulis) at four sites were used to develop a proxy record of annual (June to June) precipitation spanning the 1226 to 2001 AD interval for the Uinta Basin Watershed of northeastern Utah. The reconstruction reveals significant precipitation <span class="hlt">variability</span> at interannual to <span class="hlt">decadal</span> scales. Single-year dry events before the instrumental period tended to be more severe than those after 1900. In general, <span class="hlt">decadal</span> scale dry events were longer and more severe prior to 1900. In particular, dry events in the late 13th, 16th, and 18th Centuries surpass the magnitude and duration of droughts seen in the Uinta Basin after 1900. The last four <span class="hlt">decades</span> of the 20th Century also represent one of the wettest periods in the reconstruction. The proxy record indicates that the instrumental record (approximately 1900 to the Present) underestimates the potential frequency and severity of severe, sustained droughts in this area, while over representing the prominence of wet episodes. In the longer record, the empirical probability of any <span class="hlt">decadal</span> scale drought exceeding the duration of the 1954 through 1964 drought is 94 percent, while the probability for any wet event exceeding the duration of the 1965 through 1999 wet spell is only 1 percent. Hence, estimates of future water availability in the Uinta Basin and forecasts for exports to the Colorado River, based on the 1961 to 1990 and 1971 to 2000 "normal" periods, may be overly optimistic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GeoRL..3623611D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GeoRL..3623611D"><span id="translatedtitle">Freshwater fluxes in the East Greenland Current: A <span class="hlt">decade</span> of <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Steur, L.; Hansen, E.; Gerdes, R.; Karcher, M.; Fahrbach, E.; Holfort, J.</p> <p>2009-12-01</p> <p>Over a <span class="hlt">decade</span> of mooring measurements in the western Fram Strait at 78°50‧N shows that the annual mean liquid freshwater flux (FWF) in the East Greenland Current is relatively constant at -1274 ± 453 km3 yr-1 (-40.4 ± 14.4 mSv) despite the fact that the annual mean total volume transport of the EGC has more than doubled since 2001. This is shown to be due to an increase of the transport in the deeper ocean and the fact that the largest FW content is present on the East Greenland shelf and not in the core of the EGC. In order to capture the FWF on the shelf modeling results of NAOSIM are included showing that a mean contribution of FWF on the shelf of at least -807 ± 357 km3 yr-1 (-25.6 ± 11.3 mSv) should be added to the FWF obtained for the EGC. When compared to the extra input of freshwater required to account for the 1960-1990 freshening of the northern North Atlantic, the <span class="hlt">observed</span> variations in the 1998-2008 EGC liquid freshwater fluxes are small.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.458.2063K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.458.2063K"><span id="translatedtitle">Evolving into a remnant: optical <span class="hlt">observations</span> of SN 1978K at three <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuncarayakti, H.; Maeda, K.; Anderson, J. P.; Hamuy, M.; Nomoto, K.; Galbany, L.; Doi, M.</p> <p>2016-05-01</p> <p>We present new optical <span class="hlt">observations</span> of the supernova SN 1978K, obtained in 2007 and 2014 with the Very Large Telescope. We discover that the supernova has not faded significantly, even more than three <span class="hlt">decades</span> after its explosion. The spectrum exhibits numerous narrow (FWHM ≲600 km s-1) emission lines, indicating that the supernova blastwave is persistently interacting with dense circumstellar material (CSM). Evolution of emission lines indicates that the supernova ejecta is slowly progressing through the reverse shock, and has not expanded past the outer edge of the circumstellar envelope. We demonstrate that the CSM is not likely to be spherically distributed, with mass of ≲1 M⊙. The progenitor mass loss rate is estimated as ≳0.01 M⊙ yr-1. The slowly fading late-time light curve and spectra show striking similarity with SN 1987A, indicating that a rate at which the CSM is being swept-up by the blastwave is gradually decaying and SN 1978K is undergoing similar evolution to become a remnant. Due to its proximity (4 Mpc), SN 1978K serves as the next best example of late-time supernova evolution after SN 1987A.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUSMSA41A..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUSMSA41A..01S"><span id="translatedtitle">Mesosphere and Lower Thermosphere Winds from space: A <span class="hlt">decade</span> and a half of <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skinner, W. R.; Niciejewski, R.; Gell, D. A.; Cooper, M.; Marshall, A. R.; Solomon, S. C.; Wu, Q.; Killeen, T. L.; Ortland, D. A.</p> <p>2006-05-01</p> <p>Continuous space borne <span class="hlt">observations</span> of the mesosphere and lower thermosphere wind field have now been made for more than 14 years. Wind measurements commenced in late 1991 with two wind sensing instrument on the UARS spacecraft (HRDI and WINDII) and continue to the present with the TIDI instrument on TIMED. The HRDI and WINDII instruments operated simultaneously during much of the operational life of UARS and have been extensively validated. Both TIDI and HRDI obtained measurements from 2002 to 2005 providing a very desirable three year overlap to cross calibrate the instruments. The length of this combined data set permits study of the inter-annual <span class="hlt">variability</span> of this part of the atmosphere. This paper discusses some of longer term phenomena that have been studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPSC....9...86F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPSC....9...86F"><span id="translatedtitle">A <span class="hlt">Decade</span> of Cassini Radio Science <span class="hlt">Observations</span> of the Saturn System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>French, R.; Armstrong, J.; Flasar, M.; Iess, L.; Kliore, A.; Marouf, E.; McGhee, C.; Nagy, A.; Rappaport, N.; Schinder, P.; Tortora, P.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischmann, D.; Kahan, D.</p> <p>2014-04-01</p> <p>The Cassini Radio Science Subsystem (RSS) on board the Cassini spacecraft has returned a wealth ofinformation about the Saturn system during its first <span class="hlt">decade</span> of <span class="hlt">observations</span>. The instrumentation is quite versatile, operating in up to three wavelengths simultaneously (S, X, and Ka bands), and tied to a very stable frequency standard either on board or uplinked to the spacecraft from a maser-controlled transmitter as part of the Deep Space Network. Over the course of the mission so far, dozens of occultations by Saturn's rings have been <span class="hlt">observed</span>, revealing the detailed structure and scattering properties of the rings at sub-km resolution. A companion set of atmospheric occultations by Saturn and Titan have provided detailed vertical profiles of the temperature of the neutral atmosphere and the electron density of the ionosphere, spanning a range of latitudes and a significant fraction of a Saturn season. Operatin in a bistatic mode, the RSS instrument has transmitted signals to the surface of Titan at the specular point such that the reflected signal is received on the earth, revealing the dielectric properties of Titan's surface. Finally, exquisitely accurate measurements of the gravitationally induced Dopper shift of the RSS transmitted signal have provided measurements of the gravitations fields and probes of the internal structure of several of Saturn's major satellites, most notably indicating the presence of sub-surface oceans on both Titan and Enceladus. During the upcoming three-year finale of the Cassini mission, highlights of the remaining RSS science objectives include high- SNR measurements of the rings at their most favorable geometry of the entire Cassini orbital tour, and a set of close orbital fly-bys of Saturn itself, enabling the determination of the planet's gravitational field to an accuracy comparable to that expected for the Juno mission to Jupiter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.4687S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.4687S"><span id="translatedtitle"><span class="hlt">Decadal</span> changes of water properties in the Aral Sea <span class="hlt">observed</span> by MODIS-Aqua</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shi, Wei; Wang, Menghua</p> <p>2015-07-01</p> <p>Twelve-year satellite <span class="hlt">observations</span> between 2002 and 2013 from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the satellite Aqua are used to quantitatively assess the water property changes in the Aral Sea. The shortwave infrared (SWIR) atmospheric correction algorithm is required and used to derive normalized water-leaving radiance spectra nLw(λ) in the Aral Sea. We used radiance ratio nLw(555)/nLw(443) as a surrogate to characterize the spatial and temporal variations of chlorophyll-a (Chl-a) in the Aral Sea. Both seasonal <span class="hlt">variability</span> and significant interannual changes were <span class="hlt">observed</span> when the Aral Sea desiccated between 2002 and 2013. All three separated regions of the Aral Sea show increased nLw(555)/nLw(443) ratio (a surrogate for Chl-a) and the diffuse attenuation coefficient at the wavelength of 490 nm (Kd(490)) during the fall season. Of the three regions, the North Aral Sea has had the least interannual <span class="hlt">variability</span>, while South-East (SE) Aral Sea experienced drastic changes. Waters in the SE Aral Sea are the most turbid with significantly higher Kd(490) than those in the other two subregions. Kd(490) gradually increased from ˜2 m-1 in 2002 to ˜3.5 m-1 after 2008 in the SE Aral Sea. In comparison, both radiance ratio nLw(555)/nLw(443) and Kd(490) were relatively stable for the North Aral Sea. In the South-West (SW) Aral Sea, however, nLw(555)/nLw(443) values reached peaks in the fall of 2007 and 2010. A possible link between the Aral Sea water property change and the regional climate variation is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002JCli...15.1855N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002JCli...15.1855N"><span id="translatedtitle">Interannual and <span class="hlt">Decadal</span> Modulations Recently <span class="hlt">Observed</span> in the Pacific Storm Track Activity and East Asian Winter Monsoon.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, Hisashi; Izumi, Takuya; Sampe, Takeaki</p> <p>2002-07-01</p> <p>Interannual <span class="hlt">variability</span> of the North Pacific storm track <span class="hlt">observed</span> over 17 recent winters is documented. The local storm track activity is measured by a meridional flux of sensible heat associated with the lower-tropospheric subweekly fluctuations. The interannual <span class="hlt">variability</span> in the heat flux over the northwestern (NW) Pacific is found to be strongest in midwinter. The first empirical orthogonal function of the interannual <span class="hlt">variability</span> in midwinter captures the <span class="hlt">decadal</span> tendency toward the enhanced storm track activity in midwinter over the NW Pacific, in association with the <span class="hlt">decadal</span> weakening of the east Asian winter monsoon (Siberian high) and the Aleutian low that occurred in the late 1980s. The most marked signature of this enhancement is that the midwinter minimum in the storm track activity, which had been apparent in the early to mid-1980s, almost disappeared afterward. As opposed to linear theory of baroclinic instability, the enhanced activity occurred despite the weakening of the Pacific jet. As the excessively strong westerlies weakened, the eddy temperature field tended to become better correlated with the eddy meridional and vertical velocities, suggesting that eddy structure tends to become more efficient in converting the mean-flow available potential energy into eddy kinetic energy for growth. The weakened jet also acted to prolong the residence time for migratory eddies in the baroclinic zone, which seemingly overcompensated the effect of the reduced mean-flow baroclinicity but appeared to be of secondary importance. Over the Far East, tropospheric warming to the north of the weakened jet appears to be associated with an anomalous overturning in the thermally direct sense, which is not attributable to the feedback from the concomitant enhancement in the local storm track activity.Over the NW Pacific, the enhanced poleward heat transport by the intensified storm track tended to be compensated by the reduced transport by the weakened monsoonal flow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1413559B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413559B"><span id="translatedtitle">How does natural climate <span class="hlt">variability</span> on <span class="hlt">decadal</span> timescales affect timeseries analysis?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brisson, E.; van Lipzig, N. P. M.</p> <p>2012-04-01</p> <p>The world meteorological organization (WMO) defined the classical length of climate analysis to be 30 years. Even if this definition allows the uniformity of climate studies, such 30 years period might not be appropriate for different reasons. One example is the presence of non-stationary processes in a time-serie such as the solar cycle or the NAO. Another example is the computational constraints inherent to convection resolving climate simulation that often results in shorter time period integrations. To identify the minimum length required for climate integrations, it is essential to know the uncertainty related to the natural climate <span class="hlt">variability</span>. The objective of this study is to assess this uncertainty of using a time-limited period for climate analysis with an application to precipitation in Belgium. The precipitation weather generator approach is used for the production of synthetic time-series from which the time-average and the return value are derived. The weather generator integrates three main components, i) a 5th order Markov that models the occurrence of dry, wet and extremely wet days, ii) a gamma generalized linear model that reproduces the amplitude of wet events and iii) a gamma Pareto generalized linear model that reproduces the amplitude of extreme events. These three models use quasi-periodic signal derived from an empirical mode decomposition analysis, as predictors to reproduce cycle signal such as solar cycle, NAO, ENSO, etc... From these models 10000 synthetic time-series are produced allowing the derivation of the uncertainty of the time-averaged and the return value of precipitation. This method has been applied to evaluate the uncertainty related to natural climate <span class="hlt">variability</span> over a 10 years period. It was found that it represents 10% and 20% of respectively the time-averaged and the return value of daily precipitation in Belgium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611711W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611711W"><span id="translatedtitle">Influence of climate <span class="hlt">variability</span> versus change at multi-<span class="hlt">decadal</span> time scales on hydrological extremes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Willems, Patrick</p> <p>2014-05-01</p> <p>Recent studies have shown that rainfall and hydrological extremes do not randomly occur in time, but are subject to multidecadal oscillations. In addition to these oscillations, there are temporal trends due to climate change. Design statistics, such as intensity-duration-frequency (IDF) for extreme rainfall or flow-duration-frequency (QDF) relationships, are affected by both types of temporal changes (short term and long term). This presentation discusses these changes, how they influence water engineering design and decision making, and how this influence can be assessed and taken into account in practice. The multidecadal oscillations in rainfall and hydrological extremes were studied based on a technique for the identification and analysis of changes in extreme quantiles. The statistical significance of the oscillations was evaluated by means of a non-parametric bootstrapping method. Oscillations in large scale atmospheric circulation were identified as the main drivers for the temporal oscillations in rainfall and hydrological extremes. They also explain why spatial phase shifts (e.g. north-south variations in Europe) exist between the oscillation highs and lows. Next to the multidecadal climate oscillations, several stations show trends during the most recent <span class="hlt">decades</span>, which may be attributed to climate change as a result of anthropogenic global warming. Such attribution to anthropogenic global warming is, however, uncertain. It can be done based on simulation results with climate models, but it is shown that the climate model results are too uncertain to enable a clear attribution. Water engineering design statistics, such as extreme rainfall IDF or peak or low flow QDF statistics, obviously are influenced by these temporal variations (oscillations, trends). It is shown in the paper, based on the Brussels 10-minutes rainfall data, that rainfall design values may be about 20% biased or different when based on short rainfall series of 10 to 15 years length, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.2198S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.2198S"><span id="translatedtitle">Interannual and sub-<span class="hlt">decadal</span> <span class="hlt">variability</span> in hydrography and nutrient concentrations in the Cariaco Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scranton, Mary; Taylor, Gordon; Muller-Karger, Frank; Lorenzoni, Laura; Montes, Enrique; Fanning, Kent; Thunell, Robert; Benitez-Nelson, Claudia; Astor, Yrene; Varela, Ramon</p> <p>2014-05-01</p> <p>The Cariaco Basin is a deep (1400 m) permanently anoxic depression on the Venezuelan continental margin. First studied in the mid-1950s, it is the site of one of the longest time series of biogeochemical data in the ocean and for the past 18 years has been intensively studied by US and Venezuelan scientists through the CARIACO Ocean Times Series program. Although the basin's geochemistry was originally thought to be in steady state, data from CARIACO have demonstrated both long term trends and short term <span class="hlt">variability</span> in hydrography and nutrients at all depths. These trends are influenced by a number of factors including changes in the position of the ITCZ, the exchange of water between the Caribbean and the Cariaco Basin, and by changes in terrestrial influence. The long term trends include warming of surface waters by more than 1oC in 18 years, increases in surface fCO2 (2.95 +/- 0.43 micro-atmospheres kg-1 y-1) and nDIC (1.89 +/- 0.45 micromole kg-1 y-1), decreases in pH (0.0025 +/- 0.0004 y-1), and shifts in plankton community structure. Short-term <span class="hlt">variability</span> includes fluctuations in the depth and salinity of Subtropical Underwater and depth of the oxic/anoxic interface, changes in the depth and frequency of intrusions of oxygen-containing water into mid-depths, and episodic transport of terrestrial material into the basin after earthquakes or high precipitation events. Our results show that at least the upper 300-400 m of the water column is periodically (but not continuously) ventilated by water from the open Caribbean. Nutrient concentrations in the deep basin have increased steadily with time in a proportion reflective of the elemental ratios in the settling organic matter, although N:P ratios in the water column (for dissolved ammonium and phosphate in the sulfidic zone the ratio is approximately 16:1) differ from ratios for the accumulating nutrients (11:1) and the settling flux (approximately 5:1 to 12.5:1). This difference is likely due to long</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714427E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714427E"><span id="translatedtitle"><span class="hlt">Decadal</span> slowdown in global air temperature rise triggered by <span class="hlt">variability</span> in the Atlantic Meridional Overturning Circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>England, Matthew H.</p> <p>2015-04-01</p> <p>Various explanations have been proposed for the recent slowdown in global surface air temperature (SAT) rise, either involving enhanced ocean heat uptake or reduced radiation reaching Earth's surface. Among the mechanisms postulated involving enhanced ocean heat uptake, past work has argued for both a Pacific and Atlantic origin, with additional contributions from the Southern Ocean. Here we examine the mechanisms driving 'hiatus' periods originating out of the Atlantic Ocean. We show that while Atlantic-driven hiatuses are entirely plausible and consistent with known climate feedbacks associated with <span class="hlt">variability</span> 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.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFM.A21E0116R&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFM.A21E0116R&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Observing</span> <span class="hlt">Decadal</span> Trends in Atmospheric Feedbacks and Climate Change with Zeus and CLARREO</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Revercomb, H. E.; Best, F. A.; Knuteson, R. O.; Tobin, D. C.; Taylor, J. K.; Gero, P.; Adler, D. P.; Pettersen, C.; Mulligan, M.; Tobin, D. C.</p> <p>2012-12-01</p> <p>New technologies for <span class="hlt">observing</span> <span class="hlt">decadal</span> trends in atmospheric feedbacks and climate change from space have been recently demonstrated via a NASA Instrument Incubator Program (IIP) project of our group and the Anderson Group of Harvard University. Using these new technologies, a mission named Zeus has been proposed to the first NASA Earth Venture Instruments opportunity (EVI-1). Zeus would provide a low cost mechanism to initiate a new era in high spectral resolution IR climate Benchmark and Intercalibration <span class="hlt">observations</span>, the basis for which has been established by definition of the CLARREO mission in the 2007 NRC "<span class="hlt">Decadal</span> Survey" and by the Science Definition Team established by NASA LaRC to further the full blown CLARREO mission. Zeus EVI is a low-cost, low-risk, and high-value EVI mission that will deploy an Absolute Radiance Interferometer (ARI) instrument to measure absolute spectrally resolved infrared radiance over much of the Earth-emitted spectrum with ultra-high accuracy (<0.1 K 3-sigma brightness temperature). Zeus makes use of broad spectral coverage (3.7-50 microns) and high spectral resolution (<1 cm-1) to provide benchmark products for climate trending with much higher information content than traditional spectrally-integrated measurements. While ARI requirements for accuracy and spectral properties are demanding, the overall instrument is relatively simple and low-cost because of the limited requirements on spatial sampling (25-100 km nadir-only footprints spaced at < 250 km) and on noise performance (climate products are created by combining many samples). The orbit chosen for Zeus must provide coverage immune to time-of-day sampling errors. Because of its relatively high rate of precession, an attractive baseline option for Zeus EVI is the 51.6 degrees inclination orbit of the International Space Station (ISS). For Zeus deployment on the ISS, higher latitude climate benchmark information will be obtained from operational sounders intercalibrated by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.......88V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.......88V"><span id="translatedtitle">Multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> of ice extent in the Barents Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vinje, T.; Colony, R.</p> <p>2003-04-01</p> <p>The European Arctic has been explored and commercially exploited for more than 400 years. In 1596, Willem Barentsz sailed the northern Barents Sea reporting on sea-ice extent and on the large number of whales found along the ice edge. By the early 17th century, an extensive and sophisticated whaling industry had developed in northern Spitzbergen. The whale hunters systematically <span class="hlt">observed</span> and logged sea-ice conditions and ice edge location. These shipboard <span class="hlt">observations</span> provide sea-ice extent information throughout the Nordic Seas and the western Barents for much of the 17th and 18th centuries. In 1850, Norway began extensive whale/seal hunting along the ice edge, stretching from Iceland to Novaya Zemlya. The records of sea-ice conditions and extent were archived by the Norwegian Polar Research Institute and are now placed in the ACSYS Historical Ice Chart Database. The annual April and August latitude of sea-ice extent in the western Barents is constructed for the period 1730-2000. The early part of the record (1730-1790) suggests April and August ice conditions similar to the modern era. However, just at the end of the 18th century, the sea-ice moved 300 km southward of its previous mean position. For the next 200 years (1800-2000), sea ice cover in the western Barents has steadily receded to its present state. Covariance studies offer insight into the processes controlling sea-ice extent and serve to bound the <span class="hlt">observational</span> errors. The instrumental temperature record is mostly limited to the past 150-years. During this period, we estimate the correlation between Northern Hemisphere mean temperature and August sea-ice extent at r = 0.80 (using 7-year running means). Temperature records from central England are available from 1700, as are proxy temperature based data boreholes from the Greenland Ice Sheet Project. Again, significant covariance is found. The most provocative data come from sun spot <span class="hlt">observations</span> and the associated time series of solar total irradiance</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030102176','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030102176"><span id="translatedtitle">30-Year Satellite Record Reveals Contrasting Arctic and Antarctic <span class="hlt">Decadal</span> Sea Ice <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cavalieri, D. J.; Parkinson, C. L.; Vinnikov, K. Y.</p> <p>2003-01-01</p> <p>A 30-year satellite record of sea ice extents derived mostly from satellite microwave radiometer <span class="hlt">observations</span> reveals that the Arctic sea ice extent decreased by 0.30+0.03 x 10(exp 6) square kilometers per 10 yr from 1972 through 2002, but by 0.36 plus or minus 0.05 x 10(exp 6) square kilometers per 10yr from 1979 through 2002, indicating an acceleration of 20% in the rate of decrease. In contrast, the Antarctic sea ice extent decreased dramatically over the period 1973-1977, then gradually increased. Over the full 30-year period, the Antarctic ice extent decreased by 0.15 plus or minus 0.08 x 10(exp 6) square kilometers per 10 yr. The trend reversal is attributed to a large positive anomaly in Antarctic sea ice extent in the early 1970's, an anomaly that apparently began in the late 1960's, as <span class="hlt">observed</span> in early visible and infrared satellite images.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..114T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..114T"><span id="translatedtitle">The <span class="hlt">Decadal</span> <span class="hlt">Variability</span> of Cosmic Ray Flux Outside of a Grand Solar Maximum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomas, Simon; Owens, Mathew; Lockwood, Mike</p> <p>2016-04-01</p> <p>Galactic cosmic ray (GCR) flux is modulated by changes in the Sun's magnetic field. In the long-term, GCRs flux at Earth varies in a 22-year cycle. <span class="hlt">Observing</span> time-series of GCR flux we see a pattern of 'flat topped' and 'spiked topped' peaks. It is thought that differing drift patterns for when the northern solar pole is predominantly positive (qA>0) to when the northern pole is negative (qA<0) cause this difference in modulation. We demonstrate a link between GCR modulation and long-term changes in the intensity and structure of the large-scale heliospheric magnetic field, particularly during the declining phase of consecutive solar cycles. Using reconstructions of the heliospheric field from geomagnetic data, we demonstrate that this cause of GCR modulation is only present in cycles during the recent Grand Solar Maximum and not during the weaker period of activity prior to it. We therefore suggest that the current decline in solar activity will result in different long-term patterns in GCR data to those <span class="hlt">observed</span> during the space-age which would be important for the planning of space-based missions. Finally, we compare our results to ice-core data (found to display the 22-year variation) to further explore how the 22-year cycle varies between different solar activity periods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..12.2455C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..12.2455C&link_type=ABSTRACT"><span id="translatedtitle">Temperature Responses to Spectral Solar <span class="hlt">Variability</span> on <span class="hlt">Decadal</span> and Centennial Time Scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cahalan, Robert; Wen, Guoyong; Pilewskie, Peter; Harder, Jerald</p> <p>2010-05-01</p> <p>We apply two scenarios of 11-year solar spectral forcing, namely SIM-based out-of-phase variations and proxy-based in-phase variations, as input to a time-dependent radiative-convective model (RCM), and also to the GISS modelE GCM. For both scenarios, and both models, we find that the maximum temperature response occurs in the upper stratosphere, and temperature responses decrease downward to the surface. The upper stratospheric temperature peak-to-peak responses to out-of-phase solar forcing are ~0.6 K in RCM and ~0.9 K over the tropical region in GCM simulations, a factor of ~5 times as large as responses to in-phase solar forcing. Stratospheric responses are in-phase with TSI (Total Solar Irradiance) variations. The modeled upper stratospheric temperature response to the SORCE SIM <span class="hlt">observed</span> SSI (Spectral Solar Irradiance) forcing resembles 11-year temperature variations <span class="hlt">observed</span> with HALOE (Halogen Occultation Experiment). Surface responses to the two SSI scenarios are small for both RCM and GCM studies, as compared to stratospheric responses. Though solar irradiance variations on centennial time scale are not well known, the two scenarios of reconstructed TSI time series (i.e., one based on 11-year cycles with background [Lean 2000] and the second from flux transport that has much less background change [Wang, Lean, and Sheeley, 2005]) provide a range of variations of TSI on centennial time scales. We apply phase relations among different spectral irradiance bands both from SIM <span class="hlt">observation</span> and proxy reconstructions to the two scenarios of historical TSI. The spectral solar forcing is used to drive the RCM. The updated atmosphere and ocean mixed coupled RCM including diffusion to deep-ocean provides a first-order estimate of climate response. We report the different responses of stratosphere, troposphere, and ocean surface to these 4 scenarios of centennial spectral solar forcing. We further discuss the mechanisms for atmosphere-ocean and stratosphere</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1715700S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1715700S"><span id="translatedtitle">One <span class="hlt">decade</span> of thermohaline <span class="hlt">variability</span> in the deep western Mediterranean Sea (2004-2014)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schroeder, Katrin; Ismail, S. Ben; Bryden, Harry; Borghini, Mireno; Sparnocchia, Stefania; Chiggiato, Jacopo; Ribotti, Alberto</p> <p>2015-04-01</p> <p>Recent intense deep water formation events in the western Mediterranean have produced a huge amount of a new deep water. Significantly warmer and saltier than previously, it substituted the resident deep water. The deep structure and properties began to change after winter 2004/2005 and the water rapidly spread towards the interior of the basin, in the direction of the Strait of Gibraltar and within the Tyrrhenian Sea. The changes <span class="hlt">observed</span> over the past 10 years are substantial: since 2004 we witnessed increases in deep water temperature and salinity 3-4 times faster than during 1961-2004. The possible impacts these changes could have on a global scale are still an open issue.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS43B..08L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS43B..08L"><span id="translatedtitle"><span class="hlt">Observed</span> <span class="hlt">decadal</span> ocean warming (2005-2014) and its contribution to the top of atmosphere energy budget</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Llovel, W.; Terray, L.</p> <p>2015-12-01</p> <p>Quantifying ocean heat content and its change is essential for understanding the response of the climate system to radiative forcing because the oceans are the dominant reservoir of heat on Earth. Here we investigate the 2005-2014 ocean heat content change inferred by Argo gridded products provided by three different groups. Overall, we demonstrate a good agreement among the different products despite a few discrepancies at global and regional scales. We found a <span class="hlt">decadal</span> increase of ocean heat content of 8.19 +/- 0.68 J/yr. This corresponds to an ocean heat uptake of 0.74 +/- 0.06 W/m2, in good agreement with the IPCC-AR5 estimate report of 0.71W/m2 for 1993-2010. As the Argo coverage is not perfect (coastal regions, marginal seas and semi-enclosed seas are not well sampled by the floats), we compare the global ocean heat content (0-2000m) with and without the aforementioned regions using the ORAS4 ocean reanalysis and find no significant differences between the two estimates. We then show that the Southern hemisphere explains about 90% of the net global ocean heat content increase during 2005-2014 while the Northern hemisphere shows large interannual <span class="hlt">variability</span> and explains only 10% of the net increase. We also find that the maximum warming is centered at 40°S with two main structures located in the Indian and Pacific oceans, suggesting a possible heat penetration due to the wind-driven mean ocean circulation. We finally compare the annually averaged ocean heating rates with the net TOA flux inferred by CERES and the atmospheric reanalysis ERA-Interim. We find that ocean heating rates show large interannual <span class="hlt">variability</span> associated with a large spread around the mean estimate (based on the three gridded T/S products). We confirm that the mean ocean heating rate is comparable to the net TOA flux for the last <span class="hlt">decade</span> within <span class="hlt">observational</span> uncertainties. However, we find a discrepancy for 2013 that could be due to unsampled regions and/or the significant contribution to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950008093','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950008093"><span id="translatedtitle">FRESIP project <span class="hlt">observations</span> of cataclysmic <span class="hlt">variables</span>: A unique opportunity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Howell, Steve B.</p> <p>1994-01-01</p> <p>FRESIP Project <span class="hlt">observations</span> of cataclysmic <span class="hlt">variables</span> would provide unique data sets. In the study of known cataclysmic <span class="hlt">variables</span> they would provide extended, well sampled temporal photometric information and in addition, they would provide a large area deep survey; obtaining a complete magnitude limited sample of the galaxy in the volume cone defined by the FRESIP field of view.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Almond&pg=5&id=EJ879637','ERIC'); return false;" href="http://eric.ed.gov/?q=Almond&pg=5&id=EJ879637"><span id="translatedtitle">Bayesian Network Models for Local Dependence among <span class="hlt">Observable</span> Outcome <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Almond, Russell G.; Mulder, Joris; Hemat, Lisa A.; Yan, Duanli</p> <p>2009-01-01</p> <p>Bayesian network models offer a large degree of flexibility for modeling dependence among <span class="hlt">observables</span> (item outcome <span class="hlt">variables</span>) from the same task, which may be dependent. This article explores four design patterns for modeling locally dependent <span class="hlt">observations</span>: (a) no context--ignores dependence among <span class="hlt">observables</span>; (b) compensatory context--introduces…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.H11H..04N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.H11H..04N"><span id="translatedtitle">Three <span class="hlt">Decades</span> of Field Experiments Show Minimal <span class="hlt">Variability</span> in Maximum Preferential Flow Speed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nimmo, J. R.</p> <p>2005-12-01</p> <p>Evaluation of about 50 published field tests shows that the maximum transport speed in macropores and other preferential channels varies surprisingly little. The tests differ substantially: in type of medium, including fractured rock and various soil textures; in travel distance, ranging from less than 1 to more than 1000 m; in type of tracer; and in vertical or horizontal flow direction. One factor that significantly affects transport speed is the supply of water that generates the flow. Continuous application of water at the land surface, such as ponding or steady irrigation, as opposed to a sporadic supply such as natural rainfall, causes preferential flow that is faster and that varies less among studies. For continuously supplied water, nearly all <span class="hlt">observations</span> of maximum transport speed fall between 1 and 100 m/d, suggesting that a value in that range could serve as a guideline for expected transport speed under comparable conditions. For sporadically applied water, if transport speeds are adjusted by a factor equal to the fraction of time during which water is applied, the adjusted values also fall in a range of about 1 to 100 m/d. Results suggest that in some common modes of preferential flow, certain mechanisms tend to compensate for factors that would normally cause substantial differences in flow rate. For example, an increase in water content within an unsaturated fracture may not affect the speed of solute transport in thick films if the greater water content is accommodated not by changing film thickness but by covering a larger portion of fracture-wall surface. The generalization that certain transport speeds are predictable to a large extent from water input conditions may improve the reliability and ease of predicting worst-case contaminant travel times and other quantities of hydrologic importance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.5800P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.5800P"><span id="translatedtitle"><span class="hlt">Observations</span> and simulations of the ionospheric lunar tide: Seasonal <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pedatella, N. M.</p> <p>2014-07-01</p> <p>The seasonal <span class="hlt">variability</span> of the ionospheric lunar tide is investigated using a combination of Constellation <span class="hlt">Observing</span> System for Meteorology, Ionosphere, and Climate (COSMIC) <span class="hlt">observations</span> and thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM) simulations. The present study focuses on the seasonal <span class="hlt">variability</span> of the lunar tide in the ionosphere and its potential connection to the occurrence of stratosphere sudden warmings (SSWs). COSMIC maximum F region electron density (NmF2) and total electron content <span class="hlt">observations</span> reveal a primarily annual variation of the ionospheric lunar tide, with maximum amplitudes occurring at low latitudes during December-February. Simulations of the lunar tide climatology in TIME-GCM display a similar annual <span class="hlt">variability</span> as the COSMIC <span class="hlt">observations</span>. This leads to the conclusion that the annual <span class="hlt">variability</span> of the lunar tide in the ionosphere is not solely due to the occurrence of SSWs. Rather, the annual <span class="hlt">variability</span> of the lunar tide in the ionosphere is generated by the seasonal <span class="hlt">variability</span> of the lunar tide at E region altitudes. However, compared to the <span class="hlt">observations</span>, the ionospheric lunar tide annual <span class="hlt">variability</span> is weaker in the climatological simulations which is attributed to the occurrence of SSWs during the majority of the years included in the <span class="hlt">observations</span>. Introducing a SSW into the TIME-GCM simulation leads to an additional enhancement of the lunar tide during Northern Hemisphere winter, increasing the lunar tide annual <span class="hlt">variability</span> and resulting in an annual <span class="hlt">variability</span> that is more consistent with the <span class="hlt">observations</span>. The occurrence of SSWs can therefore potentially bias lunar tide climatologies, and it is important to consider these effects in studies of the lunar tide in the atmosphere and ionosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5234906','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5234906"><span id="translatedtitle">Einstein x-ray <span class="hlt">observations</span> of cataclysmic <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mason, K.O.; Cordova, F.A.</p> <p>1982-01-01</p> <p><span class="hlt">Observations</span> with the imaging x-ray detectors on the Einstein Observatory have led to a large increase in the number of low luminosity x-ray sources known to be associated with cataclysmic <span class="hlt">variable</span> stars (CVs). The high sensitivity of the Einstein instrumentation has permitted study of their short timescale <span class="hlt">variability</span> and spectra. The data are adding significantly to our knowledge of the accretion process in cataclysmic <span class="hlt">variables</span> and forcing some revision in our ideas concerning the origin of the optical <span class="hlt">variability</span> in these stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....5192O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....5192O"><span id="translatedtitle">The evolution of heat anomalies in a coupled ocean-atmosphere GCM and the implications for North Atlantic <span class="hlt">decadal</span> climate <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Old, C.; Haines, K.</p> <p>2003-04-01</p> <p><span class="hlt">Observational</span> records show that over pentadal and <span class="hlt">decadal</span> timescales, heat anomalies form and decay in the North Atlantic Ocean. Due to the oceans capacity to store heat, long-term heat anomalies may feedback into the atmosphere through surface-flux processes producing a change in the climatic pattern. Similarly, changes in climate may change the oceans heat content, which can potentially alter the large-scale thermohaline circulation patterns. Hence an understanding of the evolution of oceanic heat anomalies will help determine the role of ocean-atmosphere thermal coupling in <span class="hlt">decadal</span> scale climate <span class="hlt">variability</span>. Gösta Walin (Tellus, 1982) developed a novel method for studying the thermal processes within a closed ocean basin through the sorting of water volumes into temperature classes. This allows the transformation rates of water between temperature classes due to advection in and out of the region, surface forcing and internal processes (mixing and diffusion) to be quantified independently. We apply this method to 100 years of monthly averaged data taken from the 1000-year control run of the Hadley Centres coupled ocean-atmosphere climate model, HADCM3. The closed basin formed by the North Atlantic / Arctic Oceans extending from the Equator to the North Pole, with the Artic Ocean being bound by the Bering Strait, forms the transformation basin studied. The results presented are interpreted in terms of the filtered anomalous transformations about the 100-year mean transformations. It will be shown that the model produces significant anomalous transformations over <span class="hlt">decadal</span> time-scales, and that one of the key factors in the anomalous transformations is the variation in the position of the isotherm outcroppings at the sea-surface, in contrast with the variations in the air-sea fluxes. These findings will be discussed in terms of the causes of <span class="hlt">decadal</span> climate <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcMod..97...65D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcMod..97...65D"><span id="translatedtitle">North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part II: Inter-annual to <span class="hlt">decadal</span> <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Danabasoglu, Gokhan; Yeager, Steve G.; Kim, Who M.; Behrens, Erik; Bentsen, Mats; Bi, Daohua; Biastoch, Arne; Bleck, Rainer; Böning, Claus; Bozec, Alexandra; Canuto, Vittorio M.; Cassou, Christophe; Chassignet, Eric; Coward, Andrew C.; Danilov, Sergey; Diansky, Nikolay; Drange, Helge; Farneti, Riccardo; Fernandez, Elodie; Fogli, Pier Giuseppe; Forget, Gael; Fujii, Yosuke; Griffies, Stephen M.; Gusev, Anatoly; Heimbach, Patrick; Howard, Armando; Ilicak, Mehmet; Jung, Thomas; Karspeck, Alicia R.; Kelley, Maxwell; Large, William G.; Leboissetier, Anthony; Lu, Jianhua; Madec, Gurvan; Marsland, Simon J.; Masina, Simona; Navarra, Antonio; Nurser, A. J. George; Pirani, Anna; Romanou, Anastasia; Salas y Mélia, David; Samuels, Bonita L.; Scheinert, Markus; Sidorenko, Dmitry; Sun, Shan; Treguier, Anne-Marie; Tsujino, Hiroyuki; Uotila, Petteri; Valcke, Sophie; Voldoire, Aurore; Wang, Qiang; Yashayaev, Igor</p> <p>2016-01-01</p> <p>Simulated inter-annual to <span class="hlt">decadal</span> <span class="hlt">variability</span> and trends in the North Atlantic for the 1958-2007 period from twenty global ocean - sea-ice coupled models are presented. These simulations are performed as contributions to the second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II). The study is Part II of our companion paper (Danabasoglu et al., 2014) which documented the mean states in the North Atlantic from the same models. A major focus of the present study is the representation of Atlantic meridional overturning circulation (AMOC) <span class="hlt">variability</span> in the participating models. Relationships between AMOC <span class="hlt">variability</span> and those of some other related <span class="hlt">variables</span>, such as subpolar mixed layer depths, the North Atlantic Oscillation (NAO), and the Labrador Sea upper-ocean hydrographic properties, are also investigated. In general, AMOC <span class="hlt">variability</span> shows three distinct stages. During the first stage that lasts until the mid- to late-1970s, AMOC is relatively steady, remaining lower than its long-term (1958-2007) mean. Thereafter, AMOC intensifies with maximum transports achieved in the mid- to late-1990s. This enhancement is then followed by a weakening trend until the end of our integration period. This sequence of low frequency AMOC <span class="hlt">variability</span> is consistent with previous studies. Regarding strengthening of AMOC between about the mid-1970s and the mid-1990s, our results support a previously identified <span class="hlt">variability</span> mechanism where AMOC intensification is connected to increased deep water formation in the subpolar North Atlantic, driven by NAO-related surface fluxes. The simulations tend to show general agreement in their temporal representations of, for example, AMOC, sea surface temperature (SST), and subpolar mixed layer depth <span class="hlt">variabilities</span>. In particular, the <span class="hlt">observed</span> <span class="hlt">variability</span> of the North Atlantic SSTs is captured well by all models. These findings indicate that simulated <span class="hlt">variability</span> and trends are primarily dictated by the atmospheric datasets which</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP51A1815M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP51A1815M"><span id="translatedtitle">Late Holocene (0-1.2 ka BP) centennial to <span class="hlt">decadal</span> time scales surface and deep water <span class="hlt">variability</span> in the North Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moffa Sanchez, P.; Hall, I. R.; Barker, S.; Thornalley, D. J.</p> <p>2011-12-01</p> <p>The subpolar North Atlantic is a key region for understanding climate <span class="hlt">variability</span>, as it is one of the world's main localities of deepwater formation. On <span class="hlt">decadal</span> to multidecadal time-scales two interrelated modes of natural climate <span class="hlt">variability</span> have been identified that contribute to changes <span class="hlt">observed</span> in the recent North Atlantic climate system (mostly through their impact on the Atlantic Meridional Overturning Circulation, AMOC): the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO). The Medieval Climatic Anomaly (MCA) and the Little Ice Age (LIA) have often been highlighted as a good example of the impact of climate oscillations on society. Although the causality of these intervals still remains controversial, a commonly cited explanation is a weak solar trigger which was amplified and transmitted globally through positive feedbacks, possibly including some internal climatic modes (such as the NAO/AMO) and the AMOC. In this study, sediment cores RAPiD-35-25B and RAPiD-17-5P recovered from the Eirik Drift (south of Greenland) and Björn Drift (Iceland Basin) respectively, are used to produce multi-proxy reconstructions of some of the main constituents of the AMOC at sub-<span class="hlt">decadal</span> to multidecadal resolution during the last 1.2 ka BP. Near-bottom flow speed reconstructions based on the sortable silt mean grain size proxy show multidecadal <span class="hlt">variability</span> in both of the Nordic Overflows. In particular, the Iceland Scotland Overflow Water vigour presents a range of <span class="hlt">decadal</span> to centennial periodicities similar to the AMO (55 years) and deVries solar cycles (200 years). Additionally, surface water reconstructions from multi-species planktonic foraminiferal δ18O, Mg/Ca and assemblage counts reveal changes in the properties of the North Atlantic Current and summer season stratification of the upper water column in the Eastern Labrador Sea, with a possible common link to changes in Subpolar Gyre dynamics. As yet, no clear consensus has emerged as to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70033816','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70033816"><span id="translatedtitle">An 1800-yr record of <span class="hlt">decadal</span>-scale hydroclimatic <span class="hlt">variability</span> in the upper Arkansas River basin from bristlecone pine</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Woodhouse, C.A.; Pederson, G.T.; Gray, S.T.</p> <p>2011-01-01</p> <p>Bristlecone pine trees are exceptionally long-lived, and with the incorporation of remnant material have been used to construct multi-millennial length ring-width chronologies. These chronologies can provide valuable information about past temperature and moisture <span class="hlt">variability</span>. In this study, we outline a method to build a moisture-sensitive bristlecone chronology and assess the robustness and consistency of this sensitivity over the past 1200. yr using new reconstructions of Arkansas River flow (AD 1275-2002 and 1577-2002) and the summer Palmer Drought Sensitivity Index. The chronology, a composite built from parts of three collections in the central Rocky Mountains, is a proxy for <span class="hlt">decadal</span>-scale moisture <span class="hlt">variability</span> for the past 18 centuries. Since the sample size is small in some portions of the time series, the chronology should be considered preliminary; the timing and duration of drought events are likely the most robust characteristics. This chronology suggests that the region experienced increased aridity during the medieval period, as did much of western North America, but that the timing and duration of drought episodes within this period were somewhat different from those in other western locations, such as the upper Colorado River basin. ?? 2010 University of Washington.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DSRII.103..264A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DSRII.103..264A"><span id="translatedtitle">Understanding interannual, <span class="hlt">decadal</span> level <span class="hlt">variability</span> in paralytic shellfish poisoning toxicity in the Gulf of Maine: The HAB Index</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, Donald M.; Couture, Darcie A.; Kleindinst, Judith L.; Keafer, Bruce A.; McGillicuddy, Dennis J., Jr.; Martin, Jennifer L.; Richlen, Mindy L.; Hickey, J. Michael; Solow, Andrew R.</p> <p>2014-05-01</p> <p>A major goal in harmful algal bloom (HAB) research has been to identify mechanisms underlying interannual <span class="hlt">variability</span> in bloom magnitude and impact. Here the focus is on <span class="hlt">variability</span> in Alexandrium fundyense blooms and paralytic shellfish poisoning (PSP) toxicity in Maine, USA, over 34 years (1978-2011). The Maine coastline was divided into two regions - eastern and western Maine, and within those two regions, three measures of PSP toxicity (the percent of stations showing detectable toxicity over the year, the cumulative amount of toxicity per station measured in all shellfish (mussel) samples during that year, and the duration of measurable toxicity) were examined for each year in the time series. These metrics were combined into a simple HAB Index that provides a single measure of annual toxin severity across each region. The three toxin metrics, as well as the HAB Index that integrates them, reveal significant <span class="hlt">variability</span> in overall toxicity between individual years as well as long-term, <span class="hlt">decadal</span> patterns or regimes. Based on different conceptual models of the system, we considered three trend formulations to characterize the long-term patterns in the Index - a three-phase (mean-shift) model, a linear two-phase model, and a pulse-decline model. The first represents a “regime shift” or multiple equilibria formulation as might occur with alternating periods of sustained high and low cyst abundance or favorable and unfavorable growth conditions, the second depicts a scenario of more gradual transitions in cyst abundance or growth conditions of vegetative cells, and the third characterizes a ”sawtooth” pattern in which upward shifts in toxicity are associated with major cyst recruitment events, followed by a gradual but continuous decline until the next pulse. The fitted models were compared using both residual sum of squares and Akaike's Information Criterion. There were some differences between model fits, but none consistently gave a better fit than the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5702487','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5702487"><span id="translatedtitle"><span class="hlt">Observation</span> of possible mode switching in three semiregular <span class="hlt">variable</span> stars</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cadmus, R.R. Jr.; Willson, L.A.; Sneden, C.; Mattei, J.A. Iowa State Univ. of Science and Technology, Ames Texas Univ., Austin American Association of Variable Star Observers, Cambridge, MA )</p> <p>1991-03-01</p> <p>Both the amplitude and period of the light variations of the semiregular long-period <span class="hlt">variables</span> RV And, S Aql, and U Boo dramaticaly decreased, and then suddenly increased, in recent years. These <span class="hlt">observations</span>, in conjunction with spectroscopic data, suggest that these stars may have switched from fundamental to overtone pulsation and back again. Theoretical models are consistent with both the photometric and spectroscopic <span class="hlt">observations</span>. The similarity between the longer-period oscillations of these stars and the behavior of Mira <span class="hlt">variables</span> supports the conclusion that the Miras are fundamental-mode pulsators. 14 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6088S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6088S"><span id="translatedtitle">Trends and <span class="hlt">variability</span> in East African rainfall and temperature <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seregina, Larisa; Ermert, Volker; Fink, Andreas H.; Pinto, Joaquim G.</p> <p>2014-05-01</p> <p>The economy of East Africa is highly dependent on agriculture, leading to a strong vulnerability of local society to fluctuations in seasonal rainfall amounts, including extreme events. Hence, the knowledge about the evolution of seasonal rainfall under future climate conditions is crucial. Rainfall regimes over East Africa are influenced by multiple factors, including two monsoon systems, several convergence zones and the Rift Valley lakes. In addition, local conditions, like topography, modulate the large-scale rainfall pattern. East African rainfall <span class="hlt">variability</span> is also influenced by various teleconnections like the Indian Ocean Zonal Mode and El Niño Southern Oscillation. Regarding future climate projections, regional and global climate models partly disagree on the increase or decrease of East African rainfall. The specific aim of the present study is the acquirement of historic data from weather stations in East Africa (Kenya, Tanzania, Ruanda and Uganda), the use of gridded satellite (rainfall) products (ARC2 and TRMM), and three-dimensional atmospheric reanalysis (e.g., ERA-Interim) to quantify climate <span class="hlt">variability</span> in the recent past and to understand its causes. Climate <span class="hlt">variability</span> and trends, including changes in extreme events, are evaluated using ETCCDI climate change and standardized precipitation indices. These climate indices are determined in order to investigate the <span class="hlt">variability</span> of temperature and rainfall and their trends with the focus on most recent <span class="hlt">decades</span>. In the follow-up, statistical and dynamical analyses are conducted to quantify the local impact of pertinent large-scale modes of climate <span class="hlt">variability</span> (Indian Ocean Zonal Mode, El Niño Southern Oscillation, Sea Surface Temperature of the Indian Ocean).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814041S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814041S"><span id="translatedtitle">Potential impacts of a future Grand Solar Minimum on <span class="hlt">decadal</span> regional climate change and interannual hemispherical climate <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spiegl, Tobias; Langematz, Ulrike</p> <p>2016-04-01</p> <p>The political, technical and socio-economic developments of the next <span class="hlt">decades</span> will determine the magnitude of 21st century climate change, since they are inextricably linked to future anthropogenic greenhouse gas emissions. To assess the range of uncertainty that is related to these developments, it is common to assume different emission scenarios for 21st climate projections. While the uncertainties associated with the anthropogenic greenhouse gas forcing have been studied intensely, the contribution of natural climate drivers (particularly solar <span class="hlt">variability</span>) to recent and future climate change are subject of intense debate. The past 1,000 years featured at least 5 excursions (lasting 60-100 years) of exceptionally low solar activity, induced by a weak magnetic field of the Sun, so called Grand Solar Minima. While the global temperature response to such a decrease in solar activity is assumed to be rather small, nonlinear mechanisms in the climate system might amplify the regional temperature signal. This hypothesis is supported by the last Grand Solar Minimum (the Maunder Minimum, 1645-1715) which coincides with the Little Ice Age, an epoch which is characterized by severe cold and hardship over Europe, North America and Asia. The long-lasting minimum of Solar Cycle 23 as well as the overall weak maximum of Cycle 24 reveal the possibility for a return to Grand Solar Minimum conditions within the next <span class="hlt">decades</span>. The quantification of the implications of such a projected decrease in solar forcing is of ultimate importance, given the on-going public discussion of the role of carbon dioxide emissions for global warming, and the possible role a cooling due to decreasing solar activity could be ascribed to. Since there is still no clear consensus about the actual strength of the Maunder Minimum, we used 3 acknowledged solar reconstruction datasets that show significant differences in both, total solar irradiance (TSI) and spectral irradiance (SSI) to simulate a future</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983PASP...95..427D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983PASP...95..427D"><span id="translatedtitle">New <span class="hlt">observations</span> of six RV Tauri and SRd <span class="hlt">variable</span> stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>DuPuy, D. L.; Allwright, J. W. B.; Dawson, D. W.; Africano, J. L.</p> <p>1983-07-01</p> <p>Differential photoelectric <span class="hlt">observations</span> in the b and y filters of the four-color system have been obtained of five known or questionable RV Tau <span class="hlt">variable</span> stars and one SRd <span class="hlt">variable</span>, using the 1.2-meter telescope at Cloudcroft Observatory. These <span class="hlt">observations</span> spanned roughly 180 days for TT Oph and V564 Oph, with 40 to 50 <span class="hlt">observations</span> each (every fourth night on the average). The other four stars, (TX Aql, DW Peg, EI Peg, and Z Sex) were all <span class="hlt">observed</span> an average of 13 nights, spanning roughly 100 nights. One to three cycles were covered for each star. V564 Oph displayed an unusual asymmetric deep minimum in its light curve. TT Oph has adhered closely to its light elements (61.08 d) over the past 43 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NHESS..16..469M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NHESS..16..469M"><span id="translatedtitle">Variations in water storage in China over recent <span class="hlt">decades</span> from GRACE <span class="hlt">observations</span> and GLDAS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mo, X.; Wu, J. J.; Wang, Q.; Zhou, H.</p> <p>2016-02-01</p> <p>We applied Gravity Recovery and Climate Experiment (GRACE) Tellus products in combination with Global Land Data Assimilation System (GLDAS) simulations and data from reports, to analyze variations in terrestrial water storage (TWS) in China as a whole and eight of its basins from 2003 to 2013. Amplitudes of TWS were well restored after scaling, and showed good correlations with those estimated from models at the basin scale. TWS generally followed variations in annual precipitation; it decreased linearly in the Huai River basin (-0.56 cm yr-1) and increased with fluctuations in the Changjiang River basin (0.35 cm yr-1), Zhujiang basin (0.55 cm yr-1) and southeast rivers basin (0.70 cm yr-1). In the Hai River basin and Yellow River basin, groundwater exploitation may have altered TWS's response to climate, and TWS kept decreasing until 2012. Changes in soil moisture storage contributed over 50 % of variance in TWS in most basins. Precipitation and runoff showed a large impact on TWS, with more explained TWS in the south than in the north. North China and southwest rivers region exhibited long-term TWS depletions. TWS has increased significantly over recent <span class="hlt">decades</span> in the middle and lower reaches of Changjiang River, southeastern coastal areas, as well as the Hoh Xil, and the headstream region of the Yellow River in the Tibetan Plateau. The findings in this study could be helpful to climate change impact research and disaster mitigation planning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800006719','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800006719"><span id="translatedtitle">X-ray <span class="hlt">variability</span> <span class="hlt">observed</span> with HEAO A-1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Friedman, H.</p> <p>1979-01-01</p> <p>Results from the HEAO A-1 instrument which <span class="hlt">observed</span> X-ray source <span class="hlt">variability</span> over a wide range of accessible timescales are surveyed. The objects <span class="hlt">observed</span> include quasars, BL Lacertae, and active galactic nuclei. A high sensitivity search for X-ray pulsars, known black hole candidates, period fluctuation in binary pulsars, and X-ray and gamma ray bursts are among the topics covered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A42E..07D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A42E..07D"><span id="translatedtitle">How well can interannual to <span class="hlt">decadal</span>-scale <span class="hlt">variability</span> in stratospheric ozone and water vapor be quantified using limb-based satellite measurements?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davis, S. M.; Rosenlof, K. H.; Hurst, D. F.; Hassler, B.; Read, W. G.</p> <p>2015-12-01</p> <p>Vertical profiles of ozone and humidity from the upper troposphere to stratosphere have been retrieved from a number of limb sounding and solar occultation satellite instruments since the 1980's. In particular, measurements from the SAGE instruments, UARS MLS, UARS HALOE, and most recently Aura MLS, have provided overlapping data since 1984. In order to quantify interannual- to <span class="hlt">decadal</span>-scale <span class="hlt">variability</span> in water vapor and ozone, it is necessary to have a uniform and homogenous record over the period of interest. With this in mind, we merged the aforementioned satellite measurements to create the Stratospheric Water and Ozone Satellite Homogenized (SWOOSH) data set, which contains vertically resolved zonal-mean (2.5°) monthly-mean water vapor and ozone concentration at levels covering the stratosphere. In this presentation, we describe the process of merging the satellite data sets, which involves adjusting the data to a reference measurement using offsets calculated from coincident <span class="hlt">observations</span> taken during instrument overlap periods. Uncertainties associated with individual measurement precision, geophysical <span class="hlt">variability</span>, and the merging process are quantified and compared to one another. We show that while the SWOOSH data can be used to quantify interannual <span class="hlt">variability</span>, quantifying long-term trends in SWOOSH is complicated by the various sources of uncertainty, as well as by potential drifts of individual instruments. The issue of satellite-derived trends is discussed in relation to the long-term record of balloon-borne frostpoint hygrometer measurements from Boulder, CO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AAS...204.3513S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AAS...204.3513S"><span id="translatedtitle"><span class="hlt">Observing</span> Blazar <span class="hlt">Variability</span>: The GTN-AAVSO Collaboration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spear, G.; Price, A.; Plait, P.; Graves, T.; Cominsky, L.; Mattei, J.</p> <p>2004-05-01</p> <p>The NASA/EPO group at Sonoma State University is creating the GLAST Ground-Based Telescope Network (GTN). The GTN is a series of telescopes and <span class="hlt">observers</span> which will support the science and education goals of NASA's Gamma-Ray Large Area Space Telescope. The GTN is a collaboration with the American Association of <span class="hlt">Variable</span> Star <span class="hlt">Observers</span> (AAVSO), other amateurs, schools, and professionals. GLAST will <span class="hlt">observe</span> gamma rays from high-energy sources such as blazars. The ground-based telescopes will <span class="hlt">observe</span> GLAST targets to provide a multi-year baseline of <span class="hlt">variability</span> characteristics. During the mission the network will <span class="hlt">observe</span> these targets simultaneously with GLAST to provided multi-wavelength coverage. Because of recent improvements in the sensitivity of CCD detectors and the improved reliability of computer controlled (robotic) telescopes, amateurs and students can now obtain professional quality data, and can make substantial contributions to the science goals of space observatories such as GLAST. Because of the unpredictability of blazar <span class="hlt">variability</span> it is important to obtain as many <span class="hlt">observations</span> as possible. A distributed network of committed <span class="hlt">observers</span> is ideally suited. Indeed, such a network is essential to accumulate the data needed to ultimately understand the <span class="hlt">variability</span> mechanism and the production of the gamma rays in this type of active galaxy. Amateurs are ideally suited to provide this type of coverage while professionals are finding it increasingly difficult to obtain telescope time on small telescopes. We will describe the resource materials and tutorials that are available through the GTN and the AAVSO, the GTN blazar image archive, the AAVSO international database of magnitudes, and the various levels of contributions to provide the required science data. We will also show comparisons of blazar data accumulated by professionals, by the AAVSO, and by students. Finally we will provide a status report for the 0.3 meter robotic telescope system being</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUSMOS23C..04D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUSMOS23C..04D"><span id="translatedtitle">Intraseasonal <span class="hlt">Variability</span> Of Tropical And South Atlantic - <span class="hlt">Observation</span> And Modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Camargo, R.</p> <p>2007-05-01</p> <p>Intraseasonal <span class="hlt">variability</span> on the Tropical and South Atlantic has been analyzed through the use of SST and surface wind data respectively from TMI and QuikScat satellite missions and also through numerical modeling on basin scale with Princeton Ocean Model. The intrinsic intraseasonal ocean <span class="hlt">variability</span> and the correspondent co- <span class="hlt">variability</span> with atmosphere were evaluated in terms of SST and surface wind anomaly fields and their cross wavelet transforms, both for <span class="hlt">observations</span> and modeled results. <span class="hlt">Observations</span> related to the tropical area revealed that: (i) the presence of intrinsic ocean intraseasonal <span class="hlt">variability</span> (30-40 days) mainly from July to October associated to TIW activity with strong influence over surface winds, i.e., dominance of ocean over atmosphere in longer intraseasonal periods and (ii) atmospheric driven intraseasonal ocean <span class="hlt">variability</span> from February to May with smaller intraseasonal periods. Besides, the extra-tropical areas with permanent strong temperature gradients (Brazil-Malvinas Confluence as well as Agulhas Current) presented a similar behavior, but not necessarily during the same months. In a general way, the numerical experiments with POM with 0.5 degree resolution could capture the intrinsic ocean behavior in both tropical and extra-tropical regions, which means that the physical mechanism has been well represented by the model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19770053166&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Variable%2Bstars%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19770053166&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Variable%2Bstars%2529"><span id="translatedtitle">Characteristics of IR <span class="hlt">variable</span> stars as <span class="hlt">observed</span> from orbit</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maran, S. P.; Heinsheimer, T. F.; Stocker, T. L.; Chapman, R. D.; Hobbs, R. W.; Michalitsanos, A. G.</p> <p>1976-01-01</p> <p>A selection of infrared <span class="hlt">variable</span> stars was studied at wavelength 2.7 microns during 1971-1975 with data from U.S. Air Force satellites. Stars <span class="hlt">observed</span> in this program are classified as long-period <span class="hlt">variable</span> stars, semiregular <span class="hlt">variables</span>, and irregular <span class="hlt">variables</span> and are among the strongest stellar sources at this wavelength. In addition, a few new, as yet unclassified <span class="hlt">variable</span> stars were identified during the course of the investigation. Time scales of reproducible variations range from a few weeks to a few years, and amplitudes of variation are as large as a factor of three for stars with periods of order one year. The minimum infrared flux density of a long-period star repeats accurately from one cycle to the next, whereas the maximum flux density was found to be unstable. The correlation of 2.7 micron and radio emission line data from one, well-studied long-period <span class="hlt">variable</span> is consistent with the hypothesis that the H2O and OH circumstellar masers are saturated, if pumped by the stellar infrared flux near 2.7 microns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990064613&hterms=Arctic+Sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DArctic%2BSea','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990064613&hterms=Arctic+Sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DArctic%2BSea"><span id="translatedtitle"><span class="hlt">Variability</span> of Arctic Sea Ice as Determined from Satellite <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.</p> <p>1999-01-01</p> <p>The compiled, quality-controlled satellite multichannel passive-microwave record of polar sea ice now spans over 18 years, from November 1978 through December 1996, and is revealing considerable information about the Arctic sea ice cover and its <span class="hlt">variability</span>. The information includes data on ice concentrations (percent areal coverages of ice), ice extents, ice melt, ice velocities, the seasonal cycle of the ice, the interannual <span class="hlt">variability</span> of the ice, the frequency of ice coverage, and the length of the sea ice season. The data reveal marked regional and interannual <span class="hlt">variabilities</span>, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 sq km, while individual regions experienced much greater percent variations, for instance, with the Greenland Sea having a range of 740,000 - 1,110,000 sq km in its yearly maximum ice coverage. In spite of the large variations from year to year and region to region, overall the Arctic ice extents showed a statistically significant, 2.80% / <span class="hlt">decade</span> negative trend over the 18.2-year period. Ice season lengths, which vary from only a few weeks near the ice margins to the full year in the large region of perennial ice coverage, also experienced interannual <span class="hlt">variability</span>, along with spatially coherent overall trends. Linear least squares trends show the sea ice season to have lengthened in much of the Bering Sea, Baffin Bay, the Davis Strait, and the Labrador Sea, but to have shortened over a much larger area, including the Sea of Okhotsk, the Greenland Sea, the Barents Sea, and the southeastern Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3458S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3458S"><span id="translatedtitle">Two centuries of <span class="hlt">observed</span> atmospheric <span class="hlt">variability</span> and change over the North Sea region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; van Oldenborgh, Geert Jan; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard</p> <p>2015-04-01</p> <p>Situated in northwestern Europe, the North Sea region is under influence of air masses from subtropical to arctic origin, and thus exhibits significant natural climate <span class="hlt">variability</span>. As the land areas surrounding the North Sea are densely populated, climate change is an important issue in terms of e.g. coastal protection, fishery and trade. This study is part of the NOSCCA initiative (North Sea Region Climate Change Assessment) and presents <span class="hlt">observed</span> <span class="hlt">variability</span> and changes in atmospheric parameters during the last roughly 200 years. Circulation patterns show considerable <span class="hlt">decadal</span> <span class="hlt">variability</span>. In recent <span class="hlt">decades</span>, a northward shift of storm tracks and increased cyclonic activity has been <span class="hlt">observed</span>. There is also an indication of increased persistence of weather types. The wind climate is dominated by large multidecadal <span class="hlt">variability</span>, and no robust long-term trends can be identified in the available datasets. There is a clear positive trend in near-surface temperatures, in particular during spring and winter. Over the region as a whole, no clear long-term precipitation trends are visible, although regional indications exist for an increased risk of extreme precipitation events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011HESSD...811233D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011HESSD...811233D"><span id="translatedtitle">Coupled <span class="hlt">decadal</span> <span class="hlt">variability</span> of the North Atlantic Oscillation, regional rainfall and spring discharges in the Campania region (Southern Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Vita, P.; Allocca, V.; Manna, F.; Fabbrocino, S.</p> <p>2011-12-01</p> <p>Climate change is one of the issues most debated by the scientific community with a special focus to the combined effects of anthropogenic modifications of the atmosphere and the natural climatic cycles. Various scenarios have been formulated in order to forecast the global atmospheric circulation and consequently the <span class="hlt">variability</span> of the global distribution of air temperature and rainfall. The effects of climate change have been analysed with respect to the risks of desertification, droughts and floods, remaining mainly limited to the atmospheric and surface components of the hydrologic cycle. Consequently the impact of the climate change on the recharge of regional aquifers and on the groundwater circulation is still a challenging topic especially in those areas whose aqueduct systems depend basically on springs or wells, such as the Campania region (Southern Italy). In order to analyse the long-term climatic <span class="hlt">variability</span> and its influence on groundwater circulation, we analysed <span class="hlt">decadal</span> patterns of precipitation, air temperature and spring discharges in the Campania region (Southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, in the period from 1921 to 2010, choosing 18 rain gauges and 9 air temperature stations among those with the most continuous functioning as well as arranged in a homogeneous spatial distribution. Moreover, for the same period, we gathered the time series of the winter NAO index (December to March mean) and of the discharges of the Sanità spring, belonging to an extended carbonate aquifer (Cervialto Mount) located in the central-eastern area of the Campania region, as well as of two other shorter time series of spring discharges. The hydrogeological features of this aquifer, its relevance due to the feeding of an important regional aqueduct system, as well as the unique availability of a long-lasting time series of spring discharges, allowed us to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.132..197H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.132..197H"><span id="translatedtitle">North Atlantic atmospheric and ocean inter-annual <span class="hlt">variability</span> over the past fifty years - Dominant patterns and <span class="hlt">decadal</span> shifts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hauser, Tristan; Demirov, Entcho; Zhu, Jieshun; Yashayaev, Igor</p> <p>2015-03-01</p> <p> positive over the eastern SPNA. The long term impact of the weather regimes on the regional climate is characterized by their distribution; i.e. the frequency of occurrence and persistence in time of each of them. Four typical distributions of the weather regimes are identified in this study which are associated with four dominant spatial interannual patterns representing the phases of two asymmetrical "modes". The first two patterns have the spatial structures of positive and negative phases of the North Atlantic Oscillation (NAO). The third and fourth patterns, here referred to as G+ and G-, define the opposite phases of a mode, that has a spatial structure defined by three centers found over Florida, south of Greenland and over Scandinavia. The NAO+ interannual patterns are associated with negative anomalies of the surface downward heat flux and ocean heat content over the SPNA. The NAO- and G+ are associated with positive anomalies of heat flux and ocean heat content. In the 1960s the dominant NAO- and G+ interannual patterns favored warmer than normal atmospheric and ocean temperatures over the SPNA. The winters in the late 1980s and early 1990s over the SPNA were colder than normal. This <span class="hlt">decadal</span> shift in the atmospheric state between 1970s and 1980s was associated with a change in the dominant interannual patterns towards NAO+ and G- in the late 1980s and early 1990s. The recent warming of the SPNA since the mid-1990s was related to dominance of the G+/G- interannual patterns in the distribution of interannual patterns probability membership. Our analysis suggests that this <span class="hlt">decadal</span> <span class="hlt">variability</span> was associated with long term shifts in atmospheric behavior over the SPNA that can be described by a change in the 1980s of the distribution of membership probabilities for the interannual patterns. Within the interannual pattern phase space, this change is characterized with a shift from the NAO-/G+/G- subspace in the 1950 and 1960s, towards NAO+/G+/G- since the mid 1980s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A41G0148Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A41G0148Y"><span id="translatedtitle">Climatic controls of the interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span> in Saudi Arabian dust activity: Towards the development of a seasonal prediction tool</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Y.; Notaro, M.; Liu, Z.; Alkolibi, F.; Fadda, E.; Bakhrjy, F.</p> <p>2013-12-01</p> <p>Atmospheric dust significantly influences the climate system, as well as human life in Saudi Arabia. Skillful seasonal prediction of dust activity with climatic <span class="hlt">variables</span> will help prevent some negative social impacts of dust storms. Yet, the climatic regulators on Saudi Arabian dust activity remain largely unaddressed. Remote sensing and station <span class="hlt">observations</span> show consistent seasonal cycles in Saudi Arabian dust activity, which peaks in spring and summer. The climatic controls on springtime and summertime Saudi Arabian dust activity during 1975-2010 are studied using <span class="hlt">observational</span> and reanalysis data. Empirical Orthogonal Function (EOF) of the <span class="hlt">observed</span> Saudi Arabian dust storm frequency shows a dominant homogeneous pattern across the country, which has distinct interannual and <span class="hlt">decadal</span> variations, as revealed by the power spectrum. Regression and correlation analyses reveal that Saudi Arabian dust activity is largely tied to precipitation on the Arabian Peninsula in spring and northwesterly (Shamal) wind in summer. On the seasonal-interannual time scale, warm El Niño-Southern Oscillation (ENSO) phase (El Niño) in winter-to-spring inhibits spring dust activity by increasing the precipitation over the Rub'al Khali Desert, a major dust source region on the southern Arabian Peninsula; warm ENSO and warm Indian Ocean Basin Mode (IOBM) in winter-to-spring favor less summer dust activity by producing anomalously low sea-level pressure over eastern north Africa and Arabian Peninsula, which leads to the reduced Shamal wind speed. The <span class="hlt">decadal</span> variation in dust activity is likely associated with the Atlantic Multidecadal Oscillation (AMO), which impacts Sahel rainfall and North African dust, and likely dust transport to Saudi Arabia. The Pacific <span class="hlt">Decadal</span> Oscillation (PDO) and tropical Indian Ocean SST also have influence on the <span class="hlt">decadal</span> variation in Saudi Arabian dust activity, by altering precipitation over the Arabian Peninsula and summer Shamal wind speed. Using eastern</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013JGRA..118.4534M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013JGRA..118.4534M&link_type=ABSTRACT"><span id="translatedtitle">A <span class="hlt">decade</span>-long climatology of terdiurnal tides using TIMED/SABER <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moudden, Y.; Forbes, J. M.</p> <p>2013-07-01</p> <p>In this paper, we globally characterize the solar terdiurnal tide in the 80-110 km region of Earth's atmosphere through analysis of 10 years of temperature measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry instrument on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics spacecraft. The Sun-synchronous ("migrating") component (TW3), which is longitude-independent and achieves maximum amplitudes of order of 5 K (10 K) at 90 km (110 km), not too different than the 7-15 K amplitudes that are typical of the migrating diurnal and semidiurnal tides in this region. Significant longitude <span class="hlt">variability</span> (˜ 20-25%) in terdiurnal temperature amplitudes also exists, which is decomposed into zonal wave number components. The largest of these (TE1, TW4, and TW5) reveal distinct seasonal-latitudinal and height versus latitude patterns and interannual consistency. In addition, it is demonstrated that these particular components vary in ways that suggest that they originate from nonlinear interactions between diurnal and semidiurnal tides, specifically between DE3 and SW2 for TE1, between DW2 and SW2 for TW4, and between DW1 and SW4 for TW5. We also demonstrate that the terdiurnal tides derived here are not influenced to any significant degree by aliasing due to the presence of other waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AcAau..57..520S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AcAau..57..520S"><span id="translatedtitle">High resolution earth <span class="hlt">observation</span> satellites and services in the next <span class="hlt">decade</span> a European perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schreier, Gunter; Dech, Stefan</p> <p>2005-07-01</p> <p>Projects to use very high resolution optical satellite sensor data started in the late 90s and are believed to be the major driver for the commercialisation of earth <span class="hlt">observation</span>. The global political security situation and updated legislative frameworks created new opportunities for high resolution, dual use satellite systems. In addition to new optical sensors, very high resolution synthetic aperture radars will become in the next few years an important component in the imaging satellite fleet. The paper will review the development in this domain so far, and give perspectives on future emerging markets and opportunities. With dual-use satellite initiatives and new political frameworks agreed between the European Commission and the European Space Agency (ESA), the European market becomes very attractive for both service suppliers and customers. The political focus on "Global Monitoring for Environment and Security" (GMES) and the "European Defence and Security Policy" drive and amplify this demand which ranges from low resolution climate monitoring to very high resolution reconnaissance tasks. In order to create an operational and sustainable GMES in Europe by 2007, the European infrastructure need to be adapted and extended. This includes the ESA SENTINEL and OXYGEN programmes, aiming for a fleet of earth <span class="hlt">observation</span> satellites and an open and operational earth <span class="hlt">observation</span> ground segment. The harmonisation of national and regional geographic information is driven by the European Commission's INSPIRE programme. The necessary satellite capacity to complement existing systems in the delivery of space based data required for GMES is currently under definition. Embedded in a market with global competition and in the global political framework of a Global Earth <span class="hlt">Observation</span> System of Systems, European companies, agencies and research institutions are now contributing to this joint undertaking. The paper addresses the chances, risks and options for the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A33I3309K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A33I3309K"><span id="translatedtitle">Changes in SO2 and NO2 Pollution over the Past <span class="hlt">Decade</span> <span class="hlt">Observed</span> by Aura OMI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krotkov, N. A.; Li, C.; Lamsal, L. N.; Celarier, E. A.; Marchenko, S. V.; Swartz, W.; Bucsela, E. J.; Fioletov, V.; McLinden, C. A.; Joiner, J.; Bhartia, P. K.; Duncan, B. N.; Dickerson, R. R.</p> <p>2014-12-01</p> <p>The Ozone Monitoring Instrument (OMI), a NASA partnership with the Netherlands and Finland, flies on the EOS Aura satellite and uses reflected sunlight to measure two critical atmospheric trace gases, nitrogen dioxide (NO2) and sulfur dioxide (SO2), characterizing daily air quality. Both gases and the secondary pollutants they produce (particulate matter, PM2.5, and tropospheric ozone) are among USEPA designated criteria pollutants, posing serious threats to human health and the environment (e.g., acid rain, plant damage, and reduced visibility). A new generation of the OMI standard SO2 and NO2 products (based on critically improved DOAS spectral fitting for NO2 and innovative Principal Component Analysis method for SO2) provides a valuable dataset for studying anthropogenic pollution on local to global scales. Here we highlight some of the OMI <span class="hlt">observed</span> long-term changes in air quality over several regions. Over the US, average NO2 and SO2 pollution levels have decreased dramatically as a result of both technological improvements (e.g., catalytic converters on cars) and stricter regulations of emissions. We see continued decline in NO2 and SO2 pollution over Europe. Over China OMI <span class="hlt">observed</span> a ~ 60% increase in NO2 pollution between 2005 and 2013, despite a temporary reversal of the growing trend due to both 2008 Olympic Games and the economic recession in 2009. Chinese SO2 pollution seems to have stabilized since peaking in 2007, probably due to government efforts to curb SO2 emissions from the power sector. We have also <span class="hlt">observed</span> large increases in both SO2 and NO2 pollution particularly in Eastern India where a number of new large coal power plants have been built in recent years. We expect that further improvements in the OMI NO2 and SO2 products will allow more robust quantification of long-term trends in local to global air quality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AAN...471....1W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AAN...471....1W"><span id="translatedtitle">Cataclysmic <span class="hlt">variables</span> to be monitored for HST <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waagen, Elizabeth O.</p> <p>2012-09-01</p> <p>Drs. Boris Gaensicke (Warwick University), Joseph Patterson (Columbia University, Center for Backyard Astrophysics), and Arne Henden (AAVSO), on behalf of a consortium of 16 astronomers, requested the help of AAVSO <span class="hlt">observers</span> in monitoring the ~40 cataclysmic <span class="hlt">variables</span> in support of Hubble Space Telescope <span class="hlt">observations</span> in the coming months. The HST COS (Cosmic Origins Spectrograph) will be carrying out far-ultraviolet spectroscopy of ~40 CVs sequentially, with the aim to measure the temperatures, atmospheric compositions, rotation rates, and eventually masses of their white dwarfs. The primary purpose of the monitoring is to know whether each target is in quiescence immediately prior to the <span class="hlt">observation</span> window; if it is in outburst it will be too bright for the HST instrumentation. Based on the information supplied by the AAVSO, the HST scheduling team will make the decision (usually) the evening before the scheduled <span class="hlt">observing</span> time as to whether to go forward with the HST <span class="hlt">observations</span>. For CCD <span class="hlt">observers</span>, simultaneous photometry [shortly before, during, and after the HST <span class="hlt">observations</span>] would be ideal. B filter would be best for a light curve, although for the magnitude estimates, V would be best. Finder charts may be created using the AAVSO <span class="hlt">Variable</span> Star Plotter (http://www.aavso.org/vsp). <span class="hlt">Observations</span> should be submitted to the AAVSO International Database. If the target is seen in outburst, please contact the AAVSO immediately and post a message to the <span class="hlt">Observations</span> and Campaigns & <span class="hlt">Observations</span> Reports forum (http://www.aavso.org/forum). This campaign will run the better part of a year or longer. See full Alert Notice for more details and list of objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.2630A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.2630A"><span id="translatedtitle">The IRIS Data Management Center: Enabling Access to <span class="hlt">Observational</span> Time Series Spanning <span class="hlt">Decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahern, T.; Benson, R.; Trabant, C.</p> <p>2009-04-01</p> <p>The Incorporated Research Institutions for Seismology (IRIS) is funded by the National Science Foundation (NSF) to operate the facilities to generate, archive, and distribute seismological data to research communities in the United States and internationally. The IRIS Data Management System (DMS) is responsible for the ingestion, archiving, curation and distribution of these data. The IRIS Data Management Center (DMC) manages data from more than 100 permanent seismic networks, hundreds of temporary seismic deployments as well as data from other geophysical <span class="hlt">observing</span> networks such as magnetotelluric sensors, ocean bottom sensors, superconducting gravimeters, strainmeters, surface meteorological measurements, and in-situ atmospheric pressure measurements. The IRIS DMC has data from more than 20 different types of sensors. The IRIS DMC manages approximately 100 terabytes of primary <span class="hlt">observational</span> data. These data are archived in multiple distributed storage systems that insure data availability independent of any single catastrophic failure. Storage systems include both RAID systems of greater than 100 terabytes as well as robotic tape robots of petabyte capacity. IRIS performs routine transcription of the data to new media and storage systems to insure the long-term viability of the scientific data. IRIS adheres to the OAIS Data Preservation Model in most cases. The IRIS data model requires the availability of metadata describing the characteristics and geographic location of sensors before data can be fully archived. IRIS works with the International Federation of Digital Seismographic Networks (FDSN) in the definition and evolution of the metadata. The metadata insures that the data remain useful to both current and future generations of earth scientists. Curation of the metadata and time series is one of the most important activities at the IRIS DMC. Data analysts and an automated quality assurance system monitor the quality of the incoming data. This insures data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JAVSO..40...24B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAVSO..40...24B"><span id="translatedtitle">Anne S. Young: Professor and <span class="hlt">Variable</span> Star <span class="hlt">Observer</span> Extraordinaire</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bracher, K.</p> <p>2012-06-01</p> <p>One of the original eight members of the AAVSO, but not well known today, was Professor Anne Sewell Young of Mount Holyoke College. Miss Young taught there for thirty-seven years, and trained many women astronomers during the first third of the 20th century. This paper will attempt to present her life as an inspiring teacher, as well as a contributor of more than 6,500 <span class="hlt">variable</span> star <span class="hlt">observations</span> to the AAVSO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.2218T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.2218T"><span id="translatedtitle">A large increase in U.S. methane emissions over the past <span class="hlt">decade</span> inferred from satellite data and surface <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turner, A. J.; Jacob, D. J.; Benmergui, J.; Wofsy, S. C.; Maasakkers, J. D.; Butz, A.; Hasekamp, O.; Biraud, S. C.</p> <p>2016-03-01</p> <p>The global burden of atmospheric methane has been increasing over the past <span class="hlt">decade</span>, but the causes are not well understood. National inventory estimates from the U.S. Environmental Protection Agency indicate no significant trend in U.S. anthropogenic methane emissions from 2002 to present. Here we use satellite retrievals and surface <span class="hlt">observations</span> of atmospheric methane to suggest that U.S. methane emissions have increased by more than 30% over the 2002-2014 period. The trend is largest in the central part of the country, but we cannot readily attribute it to any specific source type. This large increase in U.S. methane emissions could account for 30-60% of the global growth of atmospheric methane seen in the past <span class="hlt">decade</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPD....44...09S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPD....44...09S"><span id="translatedtitle">A <span class="hlt">Decade</span> of Solar Type III Radio Bursts <span class="hlt">Observed</span> by the Nancay Radioheliograph 1998-2008</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saint-Hilaire, Pascal; Vilmer, N.; Kerdraon, A.</p> <p>2013-07-01</p> <p>We present a statistical survey of almost 10'000 radio type III bursts <span class="hlt">observed</span> by the Nancay Radioheliograph from 1998 to 2008, covering nearly a full solar cycle. In particular, sources sizes, positions, and fluxes were examined. We find an east-west asymmetry in source positions that could be attributed to a ~6 degrees eastward tilt of the magnetic field, that source FWHM sizes s roughly follow a solar-cycle-averaged distribution dN/ds = 14 ν-3.3s-4 arcmin-1 day-1, and that source fluxes closely follow a solar-cycle-averaged dN/dS = 0.34 ν-2.9 S-1.7 sfu-1 day-1 distribution (when ν is in GHz, s in arcminutes, and S in sfu). Fitting a barometric density profile yields a temperature of 0.6 MK, while a solar wind-like h-2) density profile yields a density of 1.2 × 106 cm-3 at an altitude of 1 Rs, assuming harmonic emission. Finally, the flux distribution combined with rough radiative efficiency estimates hint at the possibility that escaping electron beams might carry as much energy away from the corona as is introduced into it by nanoflare-accelerated electrons.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2911134','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2911134"><span id="translatedtitle">Religious education and midlife <span class="hlt">observance</span> are associated with dementia three <span class="hlt">decades</span> later in Israeli men</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Beeri, Michal Schnaider; Davidson, Michael; Silverman, Jeremy M.; Schmeidler, James; Springer, Ramit Ravona; Noy, Shlomo; Goldbourt, Uri</p> <p>2010-01-01</p> <p>Objective The aim of the study was to examine the association of religious education and <span class="hlt">observance</span> with dementia among participants in the Israeli Ischemic Heart Disease study. Study Design and Setting We assessed dementia in 1,890 participants among 2,604 survivors of 10,059 participants in the Israeli Ischemic Heart Disease study, a longitudinal investigation of the incidence and risk factors for cardiovascular disease among Jewish male civil servants in Israel. Face-to-face interviews were conducted with 651 subjects identified as possibly demented by the Modified Telephone Interview for Cognitive Status. Results Of 1,628 subjects included in this analysis (mean age 82 at assessment), 308 (18.9%) had dementia. The prevalence rates of dementia (and odds ratios (ORs) relative to those with exclusively religious education, adjusted for age, area of birth, and socioeconomic status) were 27.1% for those with exclusively religious education, 12.6% (OR=0.49) for those with mixed education, and 16.1% (OR=0.76) for those with secular education. For religious self-definition and practice, the prevalence rates were 9.7%, 17.7%, 14.1%, 19.3%, and 28.8% for categories from least to most religious (ORs relative to the most religious: 0.43, 0.67, 0.48, 0.55). Conclusions Examining lifestyles associated with religiosity might shed light onto environmental risks for dementia. Mechanisms underlying these associations remain elusive. PMID:18538995</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20150005603&hterms=mineral&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmineral','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20150005603&hterms=mineral&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmineral"><span id="translatedtitle">MISR <span class="hlt">Decadal</span> <span class="hlt">Observations</span> of Mineral Dust: Property Characterization and Climate Applications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kalashnikova, Olga V.; Garay, Michael J.; Sokolik, Irina; Kahn, Ralph A.; Lyapustin, A.; Diner, David J.; Lee, Jae N.; Torres, Omar; Leptoukh, Gregory G.; Sabbah, Ismail</p> <p>2012-01-01</p> <p>The Multi-angle Imaging SpectroRadiometer (MISR) provides a unique, independent source of data for studying dust emission and transport. MISR's multiple view angles allow the retrieval of aerosol properties over bright surfaces, and such retrievals have been shown to be sensitive to the non-sphericity of dust aerosols over both land and water. MISR stereographic views of thick aerosol plumes allow height and instantaneous wind derivations at spatial resolutions of better than 1.1 km horizontally and 200m vertically. We will discuss the radiometric and stereo-retrieval capabilities of MISR specifically for dust, and demonstrate the use of MISR data in conjunction with other available satellite <span class="hlt">observations</span> for dust property characterization and climate studies.First, we will discuss MISR non-spherical (dust) fraction product over the global oceans. We will show that over the Atlantic Ocean, changes in the MISR-derived non-spherical AOD fraction illustrate the evolution of dust during transport. Next, we will present a MISR satellite perspective on dust climatology in major dust source regions with a particular emphasis on the West Africa and Middle East and discuss MISR's unique strengths as well as current product biases. Finally, we will discuss MISR dust plume product and climatological applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S41A4408G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S41A4408G"><span id="translatedtitle">Frequency Dependence of Short Period Seismic Noise from Two <span class="hlt">Decades</span> of <span class="hlt">Observations</span> at Warramunga Seismic Array (WRA), Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gal, M.; Reading, A. M.; Ellingsen, S. P.; Koper, K. D.; Tkalcic, H.; Hemer, M. A.</p> <p>2014-12-01</p> <p>The analysis of the seismic ambient noise field has recently received increased attention owing to its success in mapping the Earth's shallow and deep structures. The origin of the passive seismic wavefield is associated with deep ocean and coastal regions where ocean waves, under certain conditions, can excite seismic waves (microseisms) that propagate as surface and body waves. Previous seismological studies mainly focused on the <span class="hlt">observation</span> of the strongest microseisms that are associated with the frequency range 0.1-0.3Hz. In our study, we focus on short period microseisms (0.325-0.725Hz) and examine the frequency dependant wave field and temporal variations over two <span class="hlt">decades</span>. We use data recorded over two <span class="hlt">decades</span> (1991-2012) from the Warramunga array (WRA) in central Australia. The analysis is carried out using IAS Capon beamforming that shows robust estimates of slowness and backazimuth, and is able to resolve multiple wave arrivals. Continuous data records are divided into one hour long recordings and evaluated for multiple arrivals in 8 separate frequency bands. We find multiple surface and body wave sources, which display seasonality and frequency dependence and remain stationary for two <span class="hlt">decades</span>. We <span class="hlt">observe</span>, for surface waves, that Rayleigh waves dominate for low frequencies while higher frequencies show a transition to leaky Rayleigh waves. The strong stationarity of the signal over multiple years, supports the suggestion that bathymetry and other site effects, such as coast line geometry, create favourable conditions for the generation of ocean induced surface waves. For body waves, source locations are identified in deep ocean regions for low frequencies and in shallow waters for higher frequencies. We further discuss correlation between arrivals and a WAVEWATCH III ocean wave hindcast for strong events. Fig 1: a) Shows the slowness of strongest incoming arrivals for 1 hour of WRA data over two <span class="hlt">decades</span>. b) Displays the surface waves paths of incoming</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22167329','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22167329"><span id="translatedtitle">A <span class="hlt">DECADE</span> OF SOLAR TYPE III RADIO BURSTS <span class="hlt">OBSERVED</span> BY THE NANCAY RADIOHELIOGRAPH 1998-2008</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Saint-Hilaire, P.; Vilmer, N.; Kerdraon, A.</p> <p>2013-01-01</p> <p>We present a statistical survey of almost 10,000 radio type III bursts <span class="hlt">observed</span> by the Nancay Radioheliograph from 1998 to 2008, covering nearly a full solar cycle. In particular, sources sizes, positions, and fluxes were examined. We find an east-west asymmetry in source positions that could be attributed to a 6 Degree-Sign {+-} 1 Degree-Sign eastward tilt of the magnetic field, that source FWHM sizes s roughly follow a solar-cycle-averaged distribution (dN/ds) Almost-Equal-To 14 {nu}{sup -3.3} s {sup -4} arcmin{sup -1} day{sup -1}, and that source fluxes closely follow a solar-cycle-averaged (dN/ds {sub {nu}}) Almost-Equal-To 0.34 {nu}{sup -2.9} S {sup -1.7} {sub {nu}} sfu{sup -1} day{sup -1} distribution (when {nu} is in GHz, s in arcminutes, and S {sub {nu}} in sfu). Fitting a barometric density profile yields a temperature of 0.6 MK, while a solar wind-like ({proportional_to}h {sup -2}) density profile yields a density of 1.2 Multiplication-Sign 10{sup 6} cm{sup -3} at an altitude of 1 R{sub S} , assuming harmonic emission. Finally, we found that the solar-cycle-averaged radiated type III energy could be similar in magnitude to that radiated by nanoflares via non-thermal bremsstrahlung processes, and we hint at the possibility that escaping electron beams might carry as much energy away from the corona as is introduced into it by accelerated nanoflare electrons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFMOS41A1990D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFMOS41A1990D&link_type=ABSTRACT"><span id="translatedtitle">Using <span class="hlt">Observations</span> and Climate Models to Investigate Recent <span class="hlt">Variability</span> in Upper Ocean Warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Durack, P. J.; Gleckler, P. J.; Guilyardi, E.; Landerer, F. W.</p> <p>2015-12-01</p> <p>The global ocean is responsible for storing more than 90% of the heat associated with <span class="hlt">observed</span> greenhouse-gas-attributed warming. Our previous work used multiple in-situ estimates as well as altimetry in conjunction with a large suite of climate models to quantify how estimates of global upper-ocean warming since 1970 are likely biased low. This apparent underestimation, consistent with earlier studies, was attributed to poor <span class="hlt">observational</span> coverage of the Southern Hemisphere. Recent 2006-2013 Argo ocean heat content (OHC) change estimates have placed 67-98% of increased heat in the Southern Hemisphere. The new estimates contrast markedly to long-term evaluations that place only 35-49% of the warming since 1970 in the Southern Hemisphere - even though the Southern Hemisphere contains more than 60% of the upper ocean volume. Although unforced <span class="hlt">variability</span> is likely to play a larger role on resolved trends over this shorter time period, results from climate models provide one mechanism for investigating the role of <span class="hlt">variability</span> across time scales. Extending our previous work, we investigate the hemispheric distribution of OHC using a number of <span class="hlt">observed</span> change estimates along with a large suite of CMIP5 model simulations. We consider changes over <span class="hlt">decadal</span> (Argo) to multi-<span class="hlt">decadal</span> (multi-platform) time scales and contrast the <span class="hlt">observation</span>-based hemispheric partitioning of OHC changes to a distribution of results from individual model simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70162171','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70162171"><span id="translatedtitle">Lake oxygen isotopes as recorders of North American Rocky Mountain hydroclimate: Holocene patterns and <span class="hlt">variability</span> at multi-<span class="hlt">decadal</span> to millennial time scales</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Anderson, Lesleigh; Max Berkelhammer,; Barron, John A.; Steinman, Byron A.; Finney, Bruce P.; Abbott, Mark B.</p> <p>2016-01-01</p> <p>Lake sediment oxygen isotope records (calcium carbonate-δ18O) in the western North American Cordillera developed during the past <span class="hlt">decade</span> provide substantial evidence of Pacific ocean–atmosphere forcing of hydroclimatic <span class="hlt">variability</span> during the Holocene. Here we present an overview of 18 lake sediment δ18O records along with a new compilation of lake water δ18O and δ2H that are used to characterize lake sediment sensitivity to precipitation-δ18O in contrast to fractionation by evaporation. Of the 18 records, 14 have substantial sensitivity to evaporation. Two records reflect precipitation-δ18O since the middle Holocene, Jellybean and Bison Lakes, and are geographically positioned in the northern and southern regions of the study area. Their comparative analysis indicates a sequence of time-varying north–south precipitation-δ18O patterns that is evidence for a highly non-stationary influence by Pacific ocean–atmosphere processes on the hydroclimate of western North America. These <span class="hlt">observations</span> are discussed within the context of previous research on North Pacific precipitation-δ18O based on empirical and modeling methods. The Jellybean and Bison Lake records indicate that a prominent precipitation-δ18O dipole (enriched-north and depleted-south) was sustained between ~ 3.5 and 1.5 ka, which contrasts with earlier Holocene patterns, and appears to indicate the onset of a dominant tropical control on North Pacific ocean–atmosphere dynamics. This remains the state of the system today. Higher frequency reversals of the north–south precipitation-δ18O dipole between ~ 2.5 and 1.5 ka, and during the Medieval Climate Anomaly and the Little Ice Age, also suggest more varieties of Pacific ocean–atmosphere modes than a single Pacific <span class="hlt">Decadal</span> Oscillation (PDO) type analogue. Results indicate that further investigation of precipitation-δ18O patterns on short (<span class="hlt">observational</span>) and long (Holocene) time scales is needed to improve our understanding of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GPC...137..131A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GPC...137..131A"><span id="translatedtitle">Lake oxygen isotopes as recorders of North American Rocky Mountain hydroclimate: Holocene patterns and <span class="hlt">variability</span> at multi-<span class="hlt">decadal</span> to millennial time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, Lesleigh; Berkelhammer, Max; Barron, John A.; Steinman, Byron A.; Finney, Bruce P.; Abbott, Mark B.</p> <p>2016-02-01</p> <p>Lake sediment oxygen isotope records (calcium carbonate-δ18O) in the western North American Cordillera developed during the past <span class="hlt">decade</span> provide substantial evidence of Pacific ocean-atmosphere forcing of hydroclimatic <span class="hlt">variability</span> during the Holocene. Here we present an overview of 18 lake sediment δ18O records along with a new compilation of lake water δ18O and δ2H that are used to characterize lake sediment sensitivity to precipitation-δ18O in contrast to fractionation by evaporation. Of the 18 records, 14 have substantial sensitivity to evaporation. Two records reflect precipitation-δ18O since the middle Holocene, Jellybean and Bison Lakes, and are geographically positioned in the northern and southern regions of the study area. Their comparative analysis indicates a sequence of time-varying north-south precipitation-δ18O patterns that is evidence for a highly non-stationary influence by Pacific ocean-atmosphere processes on the hydroclimate of western North America. These <span class="hlt">observations</span> are discussed within the context of previous research on North Pacific precipitation-δ18O based on empirical and modeling methods. The Jellybean and Bison Lake records indicate that a prominent precipitation-δ18O dipole (enriched-north and depleted-south) was sustained between ~ 3.5 and 1.5 ka, which contrasts with earlier Holocene patterns, and appears to indicate the onset of a dominant tropical control on North Pacific ocean-atmosphere dynamics. This remains the state of the system today. Higher frequency reversals of the north-south precipitation-δ18O dipole between ~ 2.5 and 1.5 ka, and during the Medieval Climate Anomaly and the Little Ice Age, also suggest more varieties of Pacific ocean-atmosphere modes than a single Pacific <span class="hlt">Decadal</span> Oscillation (PDO) type analogue. Results indicate that further investigation of precipitation-δ18O patterns on short (<span class="hlt">observational</span>) and long (Holocene) time scales is needed to improve our understanding of the processes that drive</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.P23A1922P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.P23A1922P"><span id="translatedtitle"><span class="hlt">Observational</span> Evidence for a <span class="hlt">Decade</span>-long climate optimum near the Hesperian/Amazonian Transition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parsons, R.; Moore, J. M.; Howard, A. D.</p> <p>2012-12-01</p> <p>Hesperian to Amazonian-aged valleys (HAVs) are predominantly found in the southern equatorial and mid-latitudes of Mars and form parallel to dendritic networks. These features record a significant warming of the regional/global climate which may have been associated with outflow channel formation and/or a period of alluvial fan deposition in Margaritifer Terra [1]. HAVs are distinct from older valley networks in both their age and morphology and they provide a window into the past climate conditions and potential water sources which formed them. Using quantitative geomorphic analysis we calculate the expected range of timescales, water volumes, precipitation rates and atmospheric conditions which contributed to HAV formation. In Newton crater (40oS, -159oE) we measured valley widths, depths, slopes and alluvial fan volumes. These <span class="hlt">observations</span>, when combined with a set of terrestrial sediment transport prediction functions [2,3,4,5], allow us to calculate an expected duration of fluvial activity ranging from 0.1 to 10 years for water-filled channel depths ranging between 20 and 130 cm, and median sediment grain size ranging from 1 mm to 10 cm. The water volume required to form a single HAV in Newton crater ranges between 1.8 and 5.7~km3 based on the Darcy-Weisbach equation [6] in combination with the aforementioned range in channel depths, grain sizes and formation timescales. These results imply water runoff rates of between 1 to 10~cm/day over a typical, 300~km2, drainage area. Such a high runoff rate and short formation time suggest a brief, dramatic regional to global climate excursion. The source of water which formed these features remains unclear, but it must have been released at the aforementioned rates, and was widely distributed within each drainage catchment, and regionally over Newton crater and the southern highlands. HAV formation was likely a two-step process involving, first, the deposition of a 10s of meters thick regional snowpack along</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.V11F2574B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V11F2574B"><span id="translatedtitle"><span class="hlt">Variability</span> of the stratospheric aerosol layer due to volcanic eruptions in the last <span class="hlt">decade</span>: Odin-OSIRIS measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bourassa, A. E.; Degenstein, D. A.</p> <p>2011-12-01</p> <p>Recently reported measurements show that an increasing trend in the stratospheric aerosol layer during the last <span class="hlt">decade</span> can be attributed in a large part to a series of relatively minor lower stratospheric volcanic eruptions. The limb scatter measurements of the stratospheric aerosol extinction coefficient made by the OSIRIS instrument on the Odin satellite show evidence of several eruptions, both tropical and at high latitude, which have a significant impact on the stratospheric aerosol layer. The extent and duration of the stratospheric impact of these eruptions is explored in this work. The measurements, which have daily, nearly global coverage, show that these minor eruptions, particularly those in the tropics, have increased the magnitude of stratospheric aerosol optical depth by more than 5% per year at mid-latitudes. Additionally, the measurements show that a measureable increase in aerosol optical depth is <span class="hlt">observed</span> in the tropics in the months following the eruption of two high latitude eruptions, namely Kasatochi Volcano in 2008 and Sarychev Peak in 2009.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A41C0074W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A41C0074W"><span id="translatedtitle">Analysis of Marine Stratocumulus Drizzle <span class="hlt">Variability</span> Using In Situ <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Witte, M.; Chuang, P. Y.; Rossiter, D.</p> <p>2013-12-01</p> <p>Precipitation is an important factor in the dynamics and large-scale organization of marine stratocumulus, yet it remains poorly understood. We aim to elucidate the factors driving the amount and <span class="hlt">variability</span> of marine stratocumulus drizzle using in situ <span class="hlt">observations</span>. We use aircraft measurements from two regions: a) in the near-coastal region of Monterey, CA during the Physics of Stratocumulus Top (POST) project from July and August 2008 and b) in the near-coastal region of Iquique, Chile during the VAMOS Ocean-Cloud-Atmosphere-Land Study (VOCALS) from October 2008. Using these two different projects, we examine whether or not changes in conditions such as boundary layer depth, cloud top liquid water content, aerosol or drop concentrations, turbulence strength and inversion strength affect drizzle amount and <span class="hlt">variability</span>. Interpreting which of these factors tend to associate most closely with various measures of drizzle intensity and <span class="hlt">variability</span> will give insight into processes relevant to both precipitation formation and maintenance, and hopefully help explain how stratocumulus organize into the large-scale cellular patterns <span class="hlt">observed</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24416214','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24416214"><span id="translatedtitle">Coral luminescence identifies the Pacific <span class="hlt">Decadal</span> Oscillation as a primary driver of river runoff <span class="hlt">variability</span> impacting the southern Great Barrier Reef.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rodriguez-Ramirez, Alberto; Grove, Craig A; Zinke, Jens; Pandolfi, John M; Zhao, Jian-xin</p> <p>2014-01-01</p> <p>The Pacific <span class="hlt">Decadal</span> Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere <span class="hlt">variability</span> on <span class="hlt">decadal</span> time scales. While precipitation and river flow <span class="hlt">variability</span> in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence <span class="hlt">variability</span> (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and <span class="hlt">decadal</span> <span class="hlt">variability</span> of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the <span class="hlt">variability</span> in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3885547','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3885547"><span id="translatedtitle">Coral Luminescence Identifies the Pacific <span class="hlt">Decadal</span> Oscillation as a Primary Driver of River Runoff <span class="hlt">Variability</span> Impacting the Southern Great Barrier Reef</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rodriguez-Ramirez, Alberto; Grove, Craig A.; Zinke, Jens; Pandolfi, John M.; Zhao, Jian-xin</p> <p>2014-01-01</p> <p>The Pacific <span class="hlt">Decadal</span> Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere <span class="hlt">variability</span> on <span class="hlt">decadal</span> time scales. While precipitation and river flow <span class="hlt">variability</span> in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence <span class="hlt">variability</span> (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and <span class="hlt">decadal</span> <span class="hlt">variability</span> of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the <span class="hlt">variability</span> in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate <span class="hlt">variability</span>. PMID:24416214</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006656','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006656"><span id="translatedtitle">Atmospheric CO2 <span class="hlt">Variability</span> <span class="hlt">Observed</span> From ASCENDS Flight Campaigns</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lin, Bing; Browell, Edward; Campbell, Joel; Choi, Yonghoon; Dobler, Jeremy; Fan, Tai-Fang; Harrison, F. Wallace; Kooi, Susan; Liu, Zhaoyan; Meadows, Byron; Nehrir, Amin; Obland, Michael; Plant, James; Yang, Melissa</p> <p>2015-01-01</p> <p>Significant atmospheric CO2 variations on various spatiotemporal scales were <span class="hlt">observed</span> during ASCENDS flight campaigns. For example, around 10-ppm CO2 changes were found within free troposphere in a region of about 200x300 sq km over Iowa during a summer 2014 flight. Even over extended forests, about 2-ppm CO2 column <span class="hlt">variability</span> was measured within about 500-km distance. For winter times, especially over snow covered ground, relatively less horizontal CO2 <span class="hlt">variability</span> was <span class="hlt">observed</span>, likely owing to minimal interactions between the atmosphere and land surface. Inter-annual variations of CO2 drawdown over cornfields in the Mid-West were found to be larger than 5 ppm due to slight differences in the corn growing phase and meteorological conditions even in the same time period of a year. Furthermore, considerable differences in atmospheric CO2 profiles were found during winter and summer campaigns. In the winter CO2 was found to decrease from about 400 ppm in the atmospheric boundary layer (ABL) to about 392 ppm above 10 km, while in the summer CO2 increased from 386 ppm in the ABL to about 396 ppm in free troposphere. These and other CO2 <span class="hlt">observations</span> are discussed in this presentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950053165&hterms=lake+precipitation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlake%2Bprecipitation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950053165&hterms=lake+precipitation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlake%2Bprecipitation"><span id="translatedtitle"><span class="hlt">Decadal</span>-to-centennial-scale climate <span class="hlt">variability</span>: Insights into the rise and fall of the Great Salt Lake</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mann, Michael E.; Lall, Upmanu; Saltzman, Barry</p> <p>1995-01-01</p> <p>We demonstrate connections between <span class="hlt">decadal</span> and secular global climatic variations, and historical variations in the volume of the Great Salt Lake. The <span class="hlt">decadal</span> variations correspond to a low-frequency shifting of storm tracks which influence winter precipitation and explain nearly 18% of the interannual and longer-term variance in the record of monthly volume change. The secular trend accounts for a more modest approximately 1.5% of the variance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008A%26A...486..293B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008A%26A...486..293B"><span id="translatedtitle">INTEGRAL <span class="hlt">observations</span> of the <span class="hlt">variability</span> of OAO 1657-415</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barnstedt, J.; Staubert, R.; Santangelo, A.; Ferrigno, C.; Horns, D.; Klochkov, D.; Kretschmar, P.; Kreykenbohm, I.; Segreto, A.; Wilms, J.</p> <p>2008-07-01</p> <p>Context: The Galactic Plane Scan (GPS) was one of the core <span class="hlt">observation</span> programmes of the INTEGRAL satellite. The highly <span class="hlt">variable</span> accreting pulsar OAO 1657-415 was frequently <span class="hlt">observed</span> within the GPS. Aims: We investigate the spectral and timing properties of OAO 1657-415 and their <span class="hlt">variability</span> on short and long time scales in the energy range 6-160 keV. Methods: Using standard extraction tools and custom software for extracting INTEGRAL data we analysed energy-resolved light curves with a time resolution of one second - mainly data of the ISGRI instrument. We also analysed phase-averaged broad band spectra - including JEM-X spectra - and pulse-phase resolved spectra of ISGRI. Results: During the time covered by the INTEGRAL <span class="hlt">observations</span>, the pulse period evolution shows an initial spin-down, which is followed by an equally strong spin-up. In combining our results with historical pulse period measurements (correcting them for orbital variation) and with stretches of continuous <span class="hlt">observations</span> by BATSE, we find that the long-term period evolution is characterised by a long-term spin-up overlayed by sets of relative spin-down/spin-up episodes, which appear to repeat quasi-periodically on a 4.8 yr time scale. We measure an updated local ephemeris and confirm the previously determined orbital period with an improved accuracy. The spectra clearly change with pulse phase. The spectrum measured during the main peak of the pulse profile is particularly hard. We do not find any evidence of a cyclotron line, wether in the phase-averaged spectrum or in phase-resolved spectra. Based on <span class="hlt">observations</span> with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, and Spain), the Czech Republic, and Poland and with the participation of Russia and the US.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1311528','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1311528"><span id="translatedtitle"><span class="hlt">Variability</span> of expert <span class="hlt">observers</span> in evaluating the optic disc.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lichter, P R</p> <p>1976-01-01</p> <p>A significant amount of <span class="hlt">variability</span> exists between <span class="hlt">observers</span> in designating cup/diac (C/D) ratios. Further, different methods are used for evaluating the size of the cup. On method uses a combination of contour and color, the other specifically measures contour and pallor separately. This study confirms that these methods yeild different numerical results. Interestingly, the "cupping/pallor" <span class="hlt">observers</span> show no significant difference among one another in C/D determination which may support the notion that cupping <span class="hlt">observations</span> are more consistent than "standard" C/D ratios. Though both groups feel the cup is larger on stereo compared to monocular viewing, the "cupping/pallor" group demonstrated much greater differences in this regard. However, the evaluation of pallor by the latter group corresponded closely to the C/D ratios of the "standard" group both for nonstereo and stereo. An individual <span class="hlt">observer</span> is reasonably consistent on repeat evaluation, but at times, inconsistency is quite substantial. These inconsistencies lead to the conclusion that C/D ratios are an inexact method of recording the status of a disc. Except for considerable changes over time, this numerical method is probably not reliable in checking for small disc changes. However, the disc alone can provide clues as to whether it is physiologic or pathologic. Nevertheless, even with expert <span class="hlt">observers</span>, significant <span class="hlt">variability</span> exists in interpretation of an optic disc in this regard. Individuals who evaluate the disc cup by cupping and pallor tend to call discs more pathologic than other <span class="hlt">observers</span>. The clinical implications of this study suggest that certain <span class="hlt">observers</span> are more accurate than others and certain discs are more easily evaluated than others. Yet, no one method seems foolproof and no specific criteria can as yet distinguish a normal from an abnormal disc. Stereo color transparencies are evaluated more accurately than are nonstereo color prints. Vessel detail and pallor patterns are probably the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.G43B1044W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.G43B1044W"><span id="translatedtitle"><span class="hlt">Decadal</span>-scale sea level rise acceleration along the Florida Atlantic coast and its relations to sea level <span class="hlt">variability</span> along the Florida Current</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wdowinski, S.; Thompson, P. R.; Mitchum, G. T.; Park, J.</p> <p>2015-12-01</p> <p>The US Atlantic coast is one of the most vulnerable areas to sea level rise (SLR) due to its low elevation, large population concentrations, and economic importance. Further vulnerability arises from accelerating rates of SLR, which began in the early 2000's and caused a significant increase in flooding frequency in several coastal communities. Several studies have suggested that the accelerating SLR rates are due to the slowing down of the Atlantic Meridional Overturning Circulation, in particular, a weakening of the Gulf Stream (GS). However, there are no direct <span class="hlt">observations</span> that link the GS conditions and high sea levels along the coast. In this study we use satellite altimetry, tide gauge, and Florida Current (FC) cable data to explore possible relations between the recent SLR rate increase along the Florida Atlantic coast and various dynamical processes in the GS/FC system. Preliminary calculations indicate a good agreement between coastal sea level and nearshore altimetry series (R = 0.76-0.8) suggesting that SSH gradients from altimetry may be useful for assessing the dynamics associated with the coastal sea level change. Here we focus on spatio-temporal SSH changes along the two satellite passes located closest to the Florida Atlantic coast. Our results indicate an intriguing transition in SSH behavior around 2004-5. Prior to 2004, anomalous low coastal SSH events (strong FC) occurred every 3-5 years in correlation with warm ENSO events. After 2004, the strong relationship between ENSO and the gradient across the FC vanishes, while the mean sea level across the current increases. The <span class="hlt">observed</span> SSH anomaly transition around 2004-5 correlates well with the initiation of accelerated rates of coastal SLR, suggesting that the <span class="hlt">decadal</span> scale SLR acceleration has occurred during weak FC conditions. However, the forcing of this transition and the role of mean sea level <span class="hlt">variability</span>, which is of comparable magnitude to <span class="hlt">variability</span> in the gradient, remain unexplained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817779C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817779C"><span id="translatedtitle">Existence and inter-<span class="hlt">decadal</span> changes of the Antarctic Circumpolar Wave during the last 142 years and its relationship to large scale modes of <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cerrone, Dario; Fusco, Giannetta; Cotroneo, Yuri; Simmonds, Ian; Budillon, Giorgio</p> <p>2016-04-01</p> <p>The Southern Ocean is the region of the world ocean bordering on Antarctica over which important exchanges between the atmosphere, the ocean and the sea ice take place. Here, the strong and nearly unhindered eastward flow of the Antarctic Circumpolar Current (ACC) plays an important control on mean global climate as it transmits climate anomalies around the globe. Features of interannual <span class="hlt">variability</span> have been often <span class="hlt">observed</span> to propagate eastward around the Southern Ocean with the circumpolar flow in form of a system of coupled anomalies, known as the Antarctic Circumpolar Wave (ACW). In the present study, using a 142-year series of a composite dataset (850hPa geopotential height, sea level pressure, sea surface temperature, surface meridional wind, surface air temperature) spanning from 1871-2012, the presence of ACWs was investigated. Results show the presence of the ACW before the mid-1950s and interdecadal changes in its <span class="hlt">variability</span>. Modifications in strength and speed of circumpolar wave have also been <span class="hlt">observed</span> in connection with large-scale climate changes. CEOF analyses on the same period confirmed that the ACW becomes apparent when there is a constructive combination between the Pacific-South America pattern and the subantarctic zonal wavenumber-3 (ZW3). The analyses also quantify the role played by El-Niño Southern Oscillation (ENSO) teleconnections for the appearance of the ACW. The composite dataset and various climate indices have been also used to diagnose interactions among the Southern Annular Mode (SAM), ENSO and ZW3 circulation patterns on interannual and sub-<span class="hlt">decadal</span> scales. Results show that SAM and ENSO patterns interact with each other modulating ACW anomalies in the western and central south Pacific Ocean on interannual scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020080613','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020080613"><span id="translatedtitle">Subtropical Gyre <span class="hlt">Variability</span> <span class="hlt">Observed</span> by Ocean Color Satellites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McClain, Charles R.; Signorini, Sergio R.; Christian, James R.</p> <p>2002-01-01</p> <p>The subtropical gyres of the world are extensive, coherent regions that occupy about 40% of the surface of the earth. Once thought to be homogeneous and static habitats, there is increasing evidence that mid-latitude gyres exhibit substantial physical and biological <span class="hlt">variability</span> on a variety of time scales. While biological productivity within these oligotrophic regions may be relatively small, their immense size makes their total contribution significant. Global distributions of dynamic height derived from satellite altimeter data, and chlorophyll concentration derived from satellite ocean color data, show that the dynamic center of the gyres, the region of maximum dynamic height where the thermocline is deepest, does not coincide with the region of minimum chlorophyll concentration. The physical and biological processes by which this distribution of ocean properties is maintained, and the spatial and temporal scales of <span class="hlt">variability</span> associated with these processes, are analyzed using global surface chlorophyll-a concentrations, sea surface height, sea surface temperature and surface winds from operational satellite and meteorological sources, and hydrographic data from climatologies and individual surveys. Seasonal and interannual <span class="hlt">variability</span> in the areal extent of the subtropical gyres are examined using 8 months (November 1996 - June 1997) of OCTS and nearly 5 years (September 1997 - June 02) of SeaWiFS ocean color data and are interpreted in the context of climate <span class="hlt">variability</span> and measured changes in other ocean properties (i.e., wind forcing, surface currents, Ekman pumping, and vertical mixing). The North Pacific and North Atlantic gyres are <span class="hlt">observed</span> to be shrinking over this period, while the South Pacific, South Atlantic, and South Indian Ocean gyres appear to be expanding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C42A..02P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C42A..02P"><span id="translatedtitle">Trends and <span class="hlt">Variability</span> in <span class="hlt">Observed</span> Runoff from Land Terminating Glaciers in Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petersen, D.; Ahlstrom, A. P.</p> <p>2015-12-01</p> <p>The Greenland ice sheet is losing mass at an accelerated rate with both surface melting and iceberg discharge increasing notably over the last <span class="hlt">decade</span>. The impact of Greenland ice sheet mass loss on the ongoing global sea level rise has raised concern and a better understanding of the reaction of the ice sheet to a future warmer climate is needed. Yet, <span class="hlt">observational</span> records of surface melting have so far only been in the form of stake readings or short-term discharge measurements. Here we present continuous, long-term <span class="hlt">observations</span> of discharge from pro-glacial lake Tasersiaq in West Greenland (66.3°N, 50.4°W) whose drainage basin extends over around 8500 km2 of which around 80% is ice covered (by Greenland Ice Sheet and local glaciers). The discharge time series covers the period from 1975 to 2014 and gives insight into the hydrological system's reaction to climatic forcing, e.g. a clear impact from major volcanic eruptions is <span class="hlt">observed</span>. Over the entire data period a significant positive trend of 0.06 km3/yr in annual discharge is seen, where the median annual discharge is 2.50 km3. In addition to the trend in annual discharge a large and increasing year-to-year <span class="hlt">variability</span> is <span class="hlt">observed</span>. We examine both discharge trend and <span class="hlt">variability</span> in the context of atmospheric circulation patterns and indicators of climate <span class="hlt">variability</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS53E..05C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS53E..05C"><span id="translatedtitle">Seasonal to <span class="hlt">Decadal</span> <span class="hlt">Variability</span> in the Upper Ocean Scattering Layer in Drake Passage in Relation to Atmospheric and Oceanic Forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chereskin, T. K.; Koenig, Z.</p> <p>2012-12-01</p> <p>The surface shoaling of nutrient-rich waters poleward across the Antarctic Circumpolar Current is responsible for the elevated productivity of the Southern Ocean. Over the last half century, the Southern Ocean has been warming at a faster rate than the global ocean as a whole. In particular, the Antarctic Peninsula region has undergone rapid atmospheric warming, significant glacial retreat and a decrease in seasonal sea ice extent, impacting krill and its predators. Improving knowledge of the Southern Ocean is a high priority for understanding the effects of climate change, but the harsh environment poses substantial <span class="hlt">observational</span> challenges. The U.S. Antarctic Research and Supply Vessel Laurence M. Gould crosses Drake Passage 2-4 times per month in all seasons, collecting underway data on transits between Punta Arenas, Chile and Palmer Station, Antarctica. High-resolution measurements of upper ocean temperature, salinity, velocity and acoustic backscatter, along with concurrent meteorological, surface water CO2 and nutrient measurements have been routinely acquired since the late 1990s. This study makes use of 238 acoustic Doppler current profiler (ADCP) transects collected over a 12-year period to remotely sense the characteristics of the near-surface scattering layer, which at 153.6 kHz is dominated by macrozooplankton. Although the primary use of the shipboard ADCP is to measure ocean currents, the measured acoustic backscatter has provided valuable insights into the depth distributions, vertical migration behaviors and even life cycles of dominant biological scatterers. Diel vertical migration and a well defined annual cycle are <span class="hlt">observed</span>, consistent with krill behavior. Significant geographic variations are present on both seasonal and interannual time scales. Interannual <span class="hlt">variability</span> is linked to two main climate modes, the El Niño-Southern Oscillation and the Southern Annular Mode, as well as to variations in seasonal sea ice extent. Limitations of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A23B0287L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A23B0287L"><span id="translatedtitle">Atmospheric CO2 <span class="hlt">Variability</span> <span class="hlt">Observed</span> during ASCENDS Flight Campaigns</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, B.; Browell, E. V.; Campbell, J. F.; Choi, Y.; Dobler, J. T.; Fan, T. F.; Harrison, F. W.; Kooi, S. A.; Liu, Z.; Meadows, B.; Nehrir, A. R.; Obland, M. D.; Plant, J.; Yang, M. M.</p> <p>2015-12-01</p> <p>Accurate <span class="hlt">observations</span> of atmospheric CO2 with a space-based lidar system, such as for the NASA ASCENDS mission, will improve knowledge of global CO2 distribution and <span class="hlt">variability</span> and increase the confidence in predictions of future climate changes. To prepare for the ASCENDS mission, the NASA Langley Research Center and Exelis Inc. (now part of Harris Corp.) have been collaborating in the development and evaluation of an Intensity-Modulated Continuous-Wave (IM-CW) lidar approach for measuring atmospheric CO2 from space. Two airborne IM-CW lidars operating in the 1.57-mm CO2 absorption band have been developed and flight tested to demonstrate precise atmospheric CO2 column measurements. A total of 14 flight campaigns have been conducted with the two lidar and in-situ CO2 measurement systems. Significant atmospheric CO2 variations on various spatiotemporal scales were <span class="hlt">observed</span> during these campaigns. For example, around 10-ppm CO2 changes were found within free troposphere in a region of about 200×300 km2 over Iowa during a summer 2014 flight. Even over extended forests, about 2-ppm CO2 column <span class="hlt">variability</span> was measured within about 500-km distance. For winter times, especially over snow covered ground, relatively less horizontal CO2 <span class="hlt">variability</span> was <span class="hlt">observed</span>, likely owing to minimal interactions between the atmosphere and land surface. Inter-annual variations of CO2 drawdown over cornfields in the Mid-West were found to be larger than 5 ppm due to slight differences in the corn growing phase and meteorological conditions even in the same time period of a year. Furthermore, considerable differences in atmospheric CO2 profiles were found during winter and summer campaigns. In the winter CO2 was found to decrease from about 400 ppm in the atmospheric boundary layer (ABL) to about 392 ppm above 10 km, while in the summer CO2 increased from 386 ppm in the ABL to about 396 ppm in free troposphere. These and other CO2 <span class="hlt">observations</span> are discussed in this presentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20010015246&hterms=surface+area&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsurface%2Barea','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010015246&hterms=surface+area&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsurface%2Barea"><span id="translatedtitle">Satellite <span class="hlt">Observed</span> <span class="hlt">Variability</span> in Antarctic and Arctic Surface Temperatures and Their Correlation to Open Water Areas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.; Zukor, Dorothy (Technical Monitor)</p> <p>2000-01-01</p> <p>Recent studies using meterological station data have indicated that global surface air temperature has been increasing at a rate of 0.05 K/<span class="hlt">decade</span>. Using the same set of data but for stations in the Antarctic and Arctic regions (>50 N) only, the increases in temperature were 0.08, and 0.22 K/<span class="hlt">decade</span>, when record lengths of 100 and 50 years, respectively, were used. To gain insights into the increasing rate of warming, satellite infrared and passive microwave <span class="hlt">observations</span> over the Arctic region during the last 20 years were processed and analyzed. The results show that during this period, the ice extent in the Antarctic has been increasing at the rate of 1.2% per <span class="hlt">decade</span> while the surface temperature has been decreasing at about 0.08 K per <span class="hlt">decade</span>. Conversely, in the Northern Hemisphere, the ice extent has been decreasing at a rate of 2.8% per <span class="hlt">decade</span>, while the surface temperatures have been increasing at the rate of 0.38 K per <span class="hlt">decade</span>. In the Antarctic, it is surprising that there is a short term trend of cooling during a global period of warming. Very large anomalies in open water areas in the Arctic were <span class="hlt">observed</span> especially in the western region, that includes the Beaufort Sea, where the <span class="hlt">observed</span> open water area was about 1x10(exp 6) sq km, about twice the average for the region, during the summer of 1998. In the eastern region, that includes the Laptev Sea, the area of open water was also abnormally large in the summer of 1995. Note that globally, the warmest and second warmest years in this century, were 1998 and 1995, respectively. The data, however, show large spatial <span class="hlt">variability</span> with the open water area distribution showing a cyclic periodicity of about ten years, which is akin to the North Atlantic and Arctic Oscillations. This was <span class="hlt">observed</span> in both western and eastern regions but with the phase of one lagging the other by about two years. This makes it difficult to interpret what the trends really mean. But although the record length of satellite data is still</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFMPP51E1360K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFMPP51E1360K"><span id="translatedtitle">Solar vs. Tidal Forcing of Centennial to <span class="hlt">Decadal</span> Scale <span class="hlt">Variability</span> in Marine Sedimentary Records from the Western Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirkwood, G.; Domack, E.; Brachfeld, S.</p> <p>2004-12-01</p> <p>Prior studies on Holocene marine sediments from the Antarctic Peninsula, including ODP Site 1098 and USAP N. B. Palmer jumbo piston cores have revealed pronounced multi-century scale variations within a number of paleoenvironmental proxies. In order to fully understand the exact timing of this signal an ultra-high resolution jumbo piston core from the Schollaert Drift was correlated with the well-known Palmer Deep record. A precise and accurate radiocarbon chronology is now available from the former site that utilizes in-situ mollusks, rather than bulk organic matter. The resulting time series spans the last 5000 years over the 20 m length of core NBP99-03 JPC28 and the surface stratigraphy of kasten core NBP01-07 KC8. The corrected and calibrated ages (with an applied reservoir correction of 1170 years) of 10 mollusks dated by the National Ocean Sciences Accelerator Mass Spectrometry Facility and the University of Arizona TAMS facility were used to construct an age-depth profile for JPC28 and KC8. A linear trend (R2 value of 0.993) of the age-depth profile was used to extrapolate the constant time interval between magnetic susceptibility measurements, which were analyzed every 1 cm. Dominant periods in the upper 10 m of the time series were identified using the Arand Spectral Analysis Package (Howell, 2001). This analysis revealed a single pronounced maxima at 160 years, which is inconsistent with the dominant periods found in time series of climate proxies from other sites on the western side of the Antarctic Peninsula. In particular, periods of 200 and 400 years, which are dominant in the Palmer Deep site (Warner and Domack, 2002), are not present in the Schollaert Drift. The spectral peaks derived from the two records are significantly different at the 95% confidence level. The cycles in the Palmer Deep record have been associated with solar <span class="hlt">variability</span>, where as the 160 year cycle in the Schollaert Drift is close to a 180 year cycle in tidal forces (Keeling</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000070387&hterms=earth+surface+dynamics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dearth%2Bsurface%2Bdynamics','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000070387&hterms=earth+surface+dynamics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dearth%2Bsurface%2Bdynamics"><span id="translatedtitle"><span class="hlt">Observations</span> of Land Surface <span class="hlt">Variability</span> Using Passive Microwave Sensing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Njoku, Eni G.</p> <p>1999-01-01</p> <p>Understanding the global <span class="hlt">variability</span> of land surface wetness (soil moisture), skin temperature, and related surface fluxes of heat and moisture is key to assessing the importance of the land surface in influencing climate. The feasibility of producing model estimates of these quantities is being studied as part of the International Satellite Land Surface Climatology Project (ISLSCP) Global Soil Wetness Project (GSWP). In the GSWP approach, meteorological <span class="hlt">observations</span> and analyses are used to drive global circulation models. Satellite measurements can provide independent estimates of key land surface parameters that are needed for initializing and validating the climate models and for monitoring long-term change. Satellite <span class="hlt">observations</span> of the land surface can also be assimilated into soil models to estimate moisture in the root zone. In our research, passive microwave satellite data recorded during 1978-1987 from the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) are being used to examine spatial and temporal trends in surface soil moisture, vegetation, and temperature. These data include <span class="hlt">observations</span> at C and X bands (6.6 and 10.7 GHz), which are not available on the current Special Sensor Microwave/Imager (SSM/I) and are precursors to data that will become available from the Advanced Microwave Scanning Radiometer (AMSR) on Advanced Earth <span class="hlt">Observing</span> Satellite (ADEOS-II) and Earth <span class="hlt">Observing</span> System (EOS) PM1 in the year 2000. A chart shows a time-series of SMMR-derived surface temperature, T-e and surface soil moisture M, retrieved on a 0.5 deg x 0.5 deg grid and further averaged over a 4 deg x 10 deg study region in the African Sahel. Also shown are National Center for Environmental Prediction (NCEP) model outputs of surface temperature, T-sfc, and soil wetness, Soil-w. The <span class="hlt">variables</span> have been scaled to have similar dynamic ranges on the plots. The NCEP data from the NCEP Reanalysis Project are monthly averages on a 2.5 deg x 2.5 deg grid averaged over</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.H23B0954V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.H23B0954V"><span id="translatedtitle">Simulating Lake-Groundwater Interactions During <span class="hlt">Decadal</span> Climate Cycles: Accounting For <span class="hlt">Variable</span> Lake Area In The Watershed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Virdi, M. L.; Lee, T. M.</p> <p>2009-12-01</p> <p>The volume and extent of a lake within the topo-bathymetry of a watershed can change substantially during wetter and drier climate cycles, altering the interaction of the lake with the groundwater flow system. Lake Starr and other seepage lakes in the permeable sandhills of central Florida are vulnerable to climate changes as they rely exclusively on rainfall and groundwater for inflows in a setting where annual rainfall and recharge vary widely. The groundwater inflow typically arrives from a small catchment area bordering the lake. The sinkhole origin of these lakes combined with groundwater pumping from underlying aquifers further complicate groundwater interactions. Understanding the lake-groundwater interactions and their effects on lake stage over multi-<span class="hlt">decadal</span> climate cycles is needed to manage groundwater pumping and public expectation about future lake levels. The interdependence between climate, recharge, changing lake area and the groundwater catchment pose unique challenges to simulating lake-groundwater interactions. During the 10-year study period, Lake Starr stage fluctuated more than 13 feet and the lake surface area receded and expanded from 96 acres to 148 acres over drier and wetter years that included hurricanes, two El Nino events and a La Nina event. The recently developed Unsaturated Zone Flow (UZF1) and Lake (LAK7) packages for MODFLOW-2005 were used to simulate the changing lake sizes and the extent of the groundwater catchment contributing flow to the lake. The lake area was discretized to occupy the largest surface area at the highest <span class="hlt">observed</span> stage and then allowed to change size. Lake cells convert to land cells and receive infiltration as receding lake area exposes the underlying unsaturated zone to rainfall and recharge. The unique model conceptualization also made it possible to capture the dynamic size of the groundwater catchment contributing to lake inflows, as the surface area and volume of the lake changed during the study</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CliPa..12.1243B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CliPa..12.1243B"><span id="translatedtitle">Interannual and (multi-)<span class="hlt">decadal</span> <span class="hlt">variability</span> in the sedimentary BIT index of Lake Challa, East Africa, over the past 2200 years: assessment of the precipitation proxy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buckles, Laura K.; Verschuren, Dirk; Weijers, Johan W. H.; Cocquyt, Christine; Blaauw, Maarten; Sinninghe Damsté, Jaap S.</p> <p>2016-05-01</p> <p>The branched vs. isoprenoid tetraether (BIT) index is based on the relative abundance of branched tetraether lipids (brGDGTs) and the isoprenoidal GDGT crenarchaeol. In Lake Challa sediments the BIT index has been applied as a proxy for local monsoon precipitation on the assumption that the primary source of brGDGTs is soil washed in from the lake's catchment. Since then, microbial production within the water column has been identified as the primary source of brGDGTs in Lake Challa sediments, meaning that either an alternative mechanism links BIT index variation with rainfall or that the proxy's application must be reconsidered. We investigated GDGT concentrations and BIT index variation in Lake Challa sediments at a <span class="hlt">decadal</span> resolution over the past 2200 years, in combination with GDGT time-series data from 45 monthly sediment-trap samples and a chronosequence of profundal surface sediments.Our 2200-year geochemical record reveals high-frequency <span class="hlt">variability</span> in GDGT concentrations, and therefore in the BIT index, superimposed on distinct lower-frequency fluctuations at multi-<span class="hlt">decadal</span> to century timescales. These changes in BIT index are correlated with changes in the concentration of crenarchaeol but not with those of the brGDGTs. A clue for understanding the indirect link between rainfall and crenarchaeol concentration (and thus thaumarchaeotal abundance) was provided by the <span class="hlt">observation</span> that surface sediments collected in January 2010 show a distinct shift in GDGT composition relative to sediments collected in August 2007. This shift is associated with increased bulk flux of settling mineral particles with high Ti / Al ratios during March-April 2008, reflecting an event of unusually high detrital input to Lake Challa concurrent with intense precipitation at the onset of the principal rain season that year. Although brGDGT distributions in the settling material are initially unaffected, this soil-erosion event is succeeded by a massive dry-season diatom bloom in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22127076','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22127076"><span id="translatedtitle"><span class="hlt">OBSERVATIONS</span> OF THERMAL FLARE PLASMA WITH THE EUV <span class="hlt">VARIABILITY</span> EXPERIMENT</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Warren, Harry P.; Doschek, George A.; Mariska, John T.</p> <p>2013-06-20</p> <p>One of the defining characteristics of a solar flare is the impulsive formation of very high temperature plasma. The properties of the thermal emission are not well understood, however, and the analysis of solar flare <span class="hlt">observations</span> is often predicated on the assumption that the flare plasma is isothermal. The EUV <span class="hlt">Variability</span> Experiment (EVE) on the Solar Dynamics Observatory provides spectrally resolved <span class="hlt">observations</span> of emission lines that span a wide range of temperatures (e.g., Fe XV-Fe XXIV) and allow for thermal flare plasma to be studied in detail. In this paper we describe a method for computing the differential emission measure distribution in a flare using EVE <span class="hlt">observations</span> and apply it to several representative events. We find that in all phases of the flare the differential emission measure distribution is broad. Comparisons of EVE spectra with calculations based on parameters derived from the Geostationary Operational Environmental Satellites soft X-ray fluxes indicate that the isothermal approximation is generally a poor representation of the thermal structure of a flare.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23996901','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23996901"><span id="translatedtitle">Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining <span class="hlt">decadal</span>-scale biological <span class="hlt">variability</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Litzow, Michael A; Mueter, Franz J; Hobday, Alistair J</p> <p>2014-01-01</p> <p>In areas of the North Pacific that are largely free of overfishing, climate regime shifts - abrupt changes in modes of low-frequency climate <span class="hlt">variability</span> - are seen as the dominant drivers of <span class="hlt">decadal</span>-scale ecological <span class="hlt">variability</span>. We assessed the ability of leading modes of climate <span class="hlt">variability</span> [Pacific <span class="hlt">Decadal</span> Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), Arctic Oscillation (AO), Pacific-North American Pattern (PNA), North Pacific Index (NPI), El Niño-Southern Oscillation (ENSO)] to explain <span class="hlt">decadal</span>-scale (1965-2008) patterns of climatic and biological <span class="hlt">variability</span> across two North Pacific ecosystems (Gulf of Alaska and Bering Sea). Our response <span class="hlt">variables</span> were the first principle component (PC1) of four regional climate parameters [sea surface temperature (SST), sea level pressure (SLP), freshwater input, ice cover], and PCs 1-2 of 36 biological time series [production or abundance for populations of salmon (Oncorhynchus spp.), groundfish, herring (Clupea pallasii), shrimp, and jellyfish]. We found that the climate modes alone could not explain ecological <span class="hlt">variability</span> in the study region. Both linear models (for climate PC1) and generalized additive models (for biology PC1-2) invoking only the climate modes produced residuals with significant temporal trends, indicating that the models failed to capture coherent patterns of ecological <span class="hlt">variability</span>. However, when the residual climate trend and a time series of commercial fishery catches were used as additional candidate <span class="hlt">variables</span>, resulting models of biology PC1-2 satisfied assumptions of independent residuals and out-performed models constructed from the climate modes alone in terms of predictive power. As measured by effect size and Akaike weights, the residual climate trend was the most important <span class="hlt">variable</span> for explaining biology PC1 <span class="hlt">variability</span>, and commercial catch the most important <span class="hlt">variable</span> for biology PC2. Patterns of climate sensitivity and exploitation history for taxa strongly associated with biology</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23996901','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23996901"><span id="translatedtitle">Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining <span class="hlt">decadal</span>-scale biological <span class="hlt">variability</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Litzow, Michael A; Mueter, Franz J; Hobday, Alistair J</p> <p>2014-01-01</p> <p>In areas of the North Pacific that are largely free of overfishing, climate regime shifts - abrupt changes in modes of low-frequency climate <span class="hlt">variability</span> - are seen as the dominant drivers of <span class="hlt">decadal</span>-scale ecological <span class="hlt">variability</span>. We assessed the ability of leading modes of climate <span class="hlt">variability</span> [Pacific <span class="hlt">Decadal</span> Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), Arctic Oscillation (AO), Pacific-North American Pattern (PNA), North Pacific Index (NPI), El Niño-Southern Oscillation (ENSO)] to explain <span class="hlt">decadal</span>-scale (1965-2008) patterns of climatic and biological <span class="hlt">variability</span> across two North Pacific ecosystems (Gulf of Alaska and Bering Sea). Our response <span class="hlt">variables</span> were the first principle component (PC1) of four regional climate parameters [sea surface temperature (SST), sea level pressure (SLP), freshwater input, ice cover], and PCs 1-2 of 36 biological time series [production or abundance for populations of salmon (Oncorhynchus spp.), groundfish, herring (Clupea pallasii), shrimp, and jellyfish]. We found that the climate modes alone could not explain ecological <span class="hlt">variability</span> in the study region. Both linear models (for climate PC1) and generalized additive models (for biology PC1-2) invoking only the climate modes produced residuals with significant temporal trends, indicating that the models failed to capture coherent patterns of ecological <span class="hlt">variability</span>. However, when the residual climate trend and a time series of commercial fishery catches were used as additional candidate <span class="hlt">variables</span>, resulting models of biology PC1-2 satisfied assumptions of independent residuals and out-performed models constructed from the climate modes alone in terms of predictive power. As measured by effect size and Akaike weights, the residual climate trend was the most important <span class="hlt">variable</span> for explaining biology PC1 <span class="hlt">variability</span>, and commercial catch the most important <span class="hlt">variable</span> for biology PC2. Patterns of climate sensitivity and exploitation history for taxa strongly associated with biology</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......224H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......224H"><span id="translatedtitle"><span class="hlt">Observations</span> and Modeling of Temporal <span class="hlt">Variability</span> in Slow Slip Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hawthorne, Jessica Cleary</p> <p></p> <p> <span class="hlt">observed</span> stress drops. We also investigate simulated back-propagating fronts. These are small regions of high slip rate that propagate in the opposite direction of the longer-term propagation, back through the region that has already slipped. Such fronts have been inferred from tremor <span class="hlt">observations</span>. The modeled fronts propagate much more slowly than the <span class="hlt">observed</span> ones. For the modeled fronts to reach the speeds indicated by the <span class="hlt">observations</span>, the slip distribution in the slow slip event would have to be highly heterogeneous in space and time. Even if we added significant spatial heterogeneity to the modeled interface, it would be different for our model to reproduce some aspects of the <span class="hlt">observations</span>. On the other hand, in the final <span class="hlt">observational</span> component of this thesis, we show that slow slip does exhibit significant temporal heterogeneity on timescales shorter than one day. Such <span class="hlt">variability</span> is frequently <span class="hlt">observed</span> in tremor but is difficult to <span class="hlt">observe</span> in slow slip because geodetic <span class="hlt">observations</span> have limited resolution. We look for short-timescale variations in slow slip that are correlated with variations in tremor amplitude. We find that, on average, the tremor amplitude and the slow slip moment rate are correlated on timescales between 15 minutes and 16 hours. The aseismic moment rate changes by at least a factor of 2 on timescales shorter than 4 hours.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011avsa.book.....W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011avsa.book.....W&link_type=ABSTRACT"><span id="translatedtitle">Advancing <span class="hlt">Variable</span> Star Astronomy: The Centennial History of the American Association of <span class="hlt">Variable</span> Star <span class="hlt">Observers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williams, Thomas R.; Saladyga, Michael</p> <p>2011-05-01</p> <p>Preface; Part I. Pioneers in <span class="hlt">Variable</span> Star Astronomy Prior to 1909: 1. The emergence of <span class="hlt">variable</span> star astronomy - a need for <span class="hlt">observations</span>; 2. A need for <span class="hlt">observers</span>; Part II. The Founding of the AAVSO - The William Tyler Olcott Era: 3. The amateur's amateur; 4. Amateurs in the service of science; Part III. The Leon Campbell Era: 5. Leon Campbell to the rescue; 6. Formalizing relationships; 7. The Pickering Memorial Endowment; 8. Fading of the Old Guard; 9. Growing pains and distractions; Part IV. The Service Bureau - The Margaret Mayall Era: 10. Learning about independence; 11. Eviction from Harvard College Observatory; 12. Actions and reactions; 13. In search of a home; 14. Survival on Brattle Street; 15. AAVSO achievements; 16. Breathing room on Concord Avenue; Part V. Analysis and Science: The Janet Mattei Era: 17. The growth of a director; 18. Learning the ropes the hard way; 19. Managing with renewed confidence; 20. Expanding the scientific charter; Part VI. Accelerating <span class="hlt">Observational</span> Science - The Arne Henden Era: 21. Bridging the gap; 22. Accelerating the science - the Henden era begins; Epilogue; Appendices; Index.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811239I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811239I"><span id="translatedtitle">Climate and polar motion during the GRACE <span class="hlt">observing</span> period: 2002-2015: Implications for <span class="hlt">decadal</span> scale oscillations during the 20th Century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivins, Erik; Adhikari, Surendra; Larour, Eric</p> <p>2016-04-01</p> <p>The motion of the Earth's pole in space has been <span class="hlt">observed</span> with great accuracy for the last 115 years. The angular variations of the pole position away from its mean are a well explained at annual and 434-day periods. Variations at annual periods are caused by changes in the mass and angular momentum forced by all Earth surface changes that have near seasonality. The 434-day period is explained as a resonance between the cumulative driving forces having periods near the Chandler wobble free eigenmode of the Earth and is well understood theoretically. The Earth also has a longer-term drift that is explained primarily as a response to the ice age changes in the moments of inertial of the Earth. However, there has been a long-standing search for the origins of pole variations that have a period near 10 years. Using GRACE space gravimetry we show that ice mass losses from Greenland and Antarctica, and when combined with changes in continental hydrology, explain almost all the main features of interannual time scale polar wander. The discovery has broad interdisciplinary implications, as we show that <span class="hlt">decadal</span> scale pole variations are directly linked to global changes continental water. The energy sources for these pole position changes are, therefore, likely to be associated with <span class="hlt">decadal</span> scale ocean and atmospheric oscillations that also drive 20th Century on-land wet-dry oscillations at <span class="hlt">decadal</span>-scale across the globe. <span class="hlt">Variability</span> in pole position, therefore, offers a tool for assessing past stability of our climate, and for the future, now faced with an increased intensity in the water cycle and more vulnerable to ice sheet instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP51C..02Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP51C..02Y"><span id="translatedtitle"><span class="hlt">Decadal</span>- and Centennial-Scale <span class="hlt">Variability</span> in Sea Surface Temperature in Beppu Bay in Japan During the Last 2900 Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, M.; Kuwae, M.; Abe, M.; Ichikawa, N.</p> <p>2012-12-01</p> <p>We generated 8-year-resolution records of paleotemperatures using UK37‧ and TEX86 and discuss the <span class="hlt">decadal</span> and centennial changes in winter and summer sea surface temperatures (SSTs) in Beppu Bay, Kyushu Island, Japan. Beppu Bay is a silled basin filled with oxygen-deficient bottom water. Because of anoxic environment, organic matter is well preserved in sediments and bioturbation is limited. Fourteen piston and gravity cores were retrieved at the center of the basin. Correlation of cores was conducted using sand and silt seams, and the age-depth model was created by wiggle-matching of forty-two AMS radiocarbon dates from bivalve mollusk shells and excess Pb-210 and Cs-137 concentrations. The sedimentation rates were 230-300 cm/ky. TEX86 and UK37‧ records show different patterns, but both have a similar multi-<span class="hlt">decadal</span> periodicity. The temperature estimated by TEX86 at the core-top sample is lower than mean annual SST, implying that TEX86 reflects the SST weighted in winter. That by UK37‧ corresponds to the SST weighted in summer. UK37‧ shows multi-<span class="hlt">decadal</span> and centennial-scale variation interrupted by frequent short-term cool periods. The periods corresponded to volcanic eruptions recorded in a Greenland ice core. TEX86 shows multi-<span class="hlt">decadal</span> variation that is consistent with a proxy PDO record reconstructed from North American tree-rings. Beppu Bay sediments are a good climate archive to provide high-resolution summer and winter SST records in the northwestern Pacific region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010111482','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010111482"><span id="translatedtitle">Constraints on <span class="hlt">Variability</span> of Brightness and Surface Magnetism on Time Scales of <span class="hlt">Decades</span> to Centuries in the Sun and Sun-Like Stars: A Source of Potential Terrestrial Climate <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baliunas, Sallie L.; Sharber, James (Technical Monitor)</p> <p>2001-01-01</p> <p>These four points summarize our work to date. (1) Conciliation of solar and stellar photometric <span class="hlt">variability</span>. Previous research by us and colleagues suggested that the Sun might at present be showing unusually low photometric <span class="hlt">variability</span> compared to other sun-like stars. Those early results would question the suitability of the technique of using sun-like stars as proxies for solar irradiance change on time scales of <span class="hlt">decades</span> to centuries. However, our results indicate the contrary: the Sun's <span class="hlt">observed</span> short-term (seasonal) and longterm (year-to-year) brightness variations closely agree with <span class="hlt">observed</span> brightness variations in stars of similar mass and age. (2) We have demonstrated an inverse correlation between the global temperature of the terrestrial lower troposphere, inferred from the NASA Microwave Sounding Unit (MSU) radiometers, and the total area of the Sun covered by coronal holes from January 1979 to present (up to May 2000). <span class="hlt">Variable</span> fluxes of either solar charged particles or cosmic rays, or both, may influence the terrestrial tropospheric temperature. The geographical pattern of the correlation is consistent with our interpretation of an extra-terrestrial charged particle forcing. (3) Possible climate mechanism amplifying the impact of solar ultraviolet irradiance variations. The key points of our proposed climate hypersensitivity mechanism are: (a) The Sun is more <span class="hlt">variable</span> in the UV (ultraviolet) than in the visible. However, the increased UV irradiance is mainly absorbed in the lower stratosphere/upper troposphere rather than at the surface. (b) Absorption in the stratosphere raises the temperature moderately around the vicinity of the tropopause, and tends to stabilize the atmosphere against vertical convective/diffusive transport, thus decreasing the flux of heat and moisture carried upward from surface. (c) The decrease in the upward convection of heat and moisture tends to raise the surface temperature because a drier upper atmosphere becomes less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22525320','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22525320"><span id="translatedtitle"><span class="hlt">OBSERVED</span> <span class="hlt">VARIABILITY</span> OF THE SOLAR Mg II h SPECTRAL LINE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schmit, D.; Pontieu, B. De; Bryans, P.; McIntosh, S.; Leenaarts, J.; Carlsson, M.</p> <p>2015-10-01</p> <p>The Mg ii h and k doublet are two of the primary spectral lines <span class="hlt">observed</span> by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double-Gaussian model to fit the Mg ii h profile for a full-Sun mosaic data set taken on 2014 August 24. We use the ensemble of high-quality profile fits to conduct a statistical study on the <span class="hlt">variability</span> of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well as h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles that do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared to predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core that is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the <span class="hlt">observed</span> structure and formation of the Mg ii profiles <span class="hlt">observed</span> by IRIS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...811..127S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...811..127S"><span id="translatedtitle"><span class="hlt">Observed</span> <span class="hlt">Variability</span> of the Solar Mg II h Spectral Line</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmit, D.; Bryans, P.; De Pontieu, B.; McIntosh, S.; Leenaarts, J.; Carlsson, M.</p> <p>2015-10-01</p> <p>The Mg ii h&k doublet are two of the primary spectral lines <span class="hlt">observed</span> by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double-Gaussian model to fit the Mg ii h profile for a full-Sun mosaic data set taken on 2014 August 24. We use the ensemble of high-quality profile fits to conduct a statistical study on the <span class="hlt">variability</span> of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well as h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles that do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared to predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core that is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the <span class="hlt">observed</span> structure and formation of the Mg ii profiles <span class="hlt">observed</span> by IRIS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JCli...12.3181B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JCli...12.3181B"><span id="translatedtitle">Interannual to <span class="hlt">Decadal</span> <span class="hlt">Variability</span> in Climate and the Glacier Mass Balance in Washington, Western Canada, and Alaska*.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bitz, C. M.; Battisti, D. S.</p> <p>1999-11-01</p> <p>The authors examine the net winter, summer, and annual mass balance of six glaciers along the northwest coast of North America, extending from Washington State to Alaska. The net winter (NWB) and net annual (NAB) mass balance anomalies for the maritime glaciers in the southern group, located in Washington and British Columbia, are shown to be positively correlated with local precipitation anomalies and storminess (defined as the rms of high-passed 500-mb geopotential anomalies) and weakly and negatively correlated with local temperature anomalies. The NWB and NAB of the maritime Wolverine glacier in Alaska are also positively correlated with local precipitation, but they are positively correlated with local winter temperature and negatively correlated with local storminess. Hence, anomalies in mass balance at Wolverine result mainly from the change in moisture that is being advected into the region by anomalies in the averaged wintertime circulation rather than from a change in storminess. The patterns of the wintertime 500-mb circulation and storminess anomalies associated with years of high NWB in the southern glacier group are similar to those associated with low NWB years at the Wolverine glacier, and vice versa.The <span class="hlt">decadal</span> ENSO-like climate phenomenon discussed by Zhang et al. has a large impact on the NWB and NAB of these maritime glaciers, accounting for up to 35% of the variance in NWB. The 500-mb circulation and storminess anomalies associated with this <span class="hlt">decadal</span> ENSO-like mode resemble the Pacific-North American pattern, as do 500-mb composites of years of extreme NWB of South Cascade glacier in Washington and of Wolverine glacier in Alaska. Hence, the <span class="hlt">decadal</span> ENSO-like mode affects precipitation in a crucial way for the NWB of these glaciers. Specifically, the <span class="hlt">decadal</span> ENSO-like phenomenon strongly affects the storminess over British Columbia and Washington and the moisture transported by the seasonally averaged circulation into maritime Alaska. In contrast</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20010023033&hterms=Okhotsk+Sea+of&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3D%2528%2528Okhotsk%252C%2BSea%2529%2Bof%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010023033&hterms=Okhotsk+Sea+of&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3D%2528%2528Okhotsk%252C%2BSea%2529%2Bof%2529"><span id="translatedtitle">Sea Ice <span class="hlt">Variability</span> in the Sea of Okhotsk from Passive Microwave Satellite <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cavalieri, Donald J.; Zukor, Dorothy (Technical Monitor)</p> <p>2000-01-01</p> <p>The Sea of Okhotsk, located between 50 and 60 N, is bounded by the Kamchatka Peninsula, Siberia, Sakhalin Island, and the Kuril Island chain and is the largest midlatitude seasonal sea ice zone in the Northern Hemisphere. The winter sea ice cover begins to form in November and expands to cover most of the sea by March. Over the following three months, the ice retreats with only small ice-covered areas remaining by the beginning of June. The sea is ice free or nearly ice free on average for six months of the year, from June through November. The recent compilation of a consistent, long-term record of Northern Hemisphere sea ice extents based on passive microwave satellite <span class="hlt">observations</span> from the Nimbus 7 Scanning Multichannel Microwave Radiometer and from four Defense Meteorological Satellite Program Special Sensor Microwave Imagers provides the basis for assessing long-term sea ice extent <span class="hlt">variability</span> in the Sea of Okhotsk. Analysis of this 20-year data record (1979-1998) shows that based on yearly averages the overall extent of the Sea of Okhotsk ice cover is decreasing at the rate of -8.1+/-2.1x10(exp 3) sq km/yr (-17.2%/<span class="hlt">decade</span>), in contrast to the rate of decrease of -33.3+/-0.7x10(exp 3) sq km/yr (-2.7%/<span class="hlt">decade</span>) for the Northern Hemisphere as a whole. There is large regional sea ice extent <span class="hlt">variability</span> of the Arctic ice cover. Two of the nine Arctic regions analyzed, the Bering Sea and the Gulf of St. Lawrence, show increases of 0.8+/-1.4xl0(exp 3) sq km/yr (2.7%/<span class="hlt">decade</span>) and 1.2+/-0.5xl0(exp 3) sq km/yr (17.1%/<span class="hlt">decade</span>), respectively. Interestingly, the Sea of Okhotsk and the Gulf of St. Lawrence show about equal percentage changes, but of opposite sign. The Sea of Okhotsk exhibits its greatest percent decrease (-24.3%/<span class="hlt">decade</span>) during spring (April-June). The year of maximum winter sea ice extent for the Sea of Okhotsk was 1979, whereas the minimum winter sea ice extent occurred in 1984.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC11D1028L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC11D1028L"><span id="translatedtitle">The Parana paradox: can a model explain the <span class="hlt">decadal</span> impacts of climate <span class="hlt">variability</span> and land-cover change?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, E.; Moorcroft, P. R.; Livino, A.; Briscoe, J.</p> <p>2013-12-01</p> <p>Since the 1970s, despite a decrease in rainfall, flow in the Parana river has increased. This paradox is explored using the Ecosystem Demography (ED) model. If there were no change in land cover, the modeled runoff decreased from the 1970s to the 2000s by 11.8% (with 1970 land cover) or 18.8% (with 2008 land cover). When the model is run holding climate constant, the <span class="hlt">decadal</span> average of the modeled runoff increased by 24.4% (with the 1970s climate) or by 33.6% (with 2000s climate). When the model is run allowing both the actual climate and land-cover changes, the model gives an increase in the <span class="hlt">decadal</span> average of runoff by 8.5%. This agrees well with 10.5% increase in the actual stream flow as measured at Itaipu. There are three main conclusions from this work. First, the ED model is able to explain a major, paradoxical, reality in the Parana basin. Second, it is necessary to take into account both climate and land use changes when exploring past or future changes in river flows. Third, the ED model, now coupled with a regional climate model (i.e., EDBRAMS), is a sound basis for exploring likely changes in river flows in major South American rivers.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AJ....152....5D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AJ....152....5D"><span id="translatedtitle">Cataclysmic <span class="hlt">Variables</span> <span class="hlt">Observed</span> During K2 Campaigns 0 and 1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dai, Zhibin; Szkody, Paula; Garnavich, Peter M.; Kennedy, Mark</p> <p>2016-07-01</p> <p>There are 15 cataclysmic <span class="hlt">variables</span> (CVs) <span class="hlt">observed</span> in the first two campaigns of the K2 mission. In this paper, the eight CVs showing distinct features are analyzed in detail. Among these eight, modulations during quiescence are evident at the known orbital periods in the SU UMa stars QZ Vir and RZ Leo, and at our newly determined orbital periods for 1RXS J0632+2536 and WD 1144+011. The periodogram analysis for the quiescent light curve of QZ Vir reveals multi-period modulations and the coexistence of orbital and superhump periods. The phased orbital light curves for the other three CVs in quiescence display wide (about half cycle) and shallow (<0.5 mag) eclipse features. Besides these modulations, their quiescent light curves reveal several transient events: a sudden decrease of system light in 1RXS J0632+2536, a low-level flare-like event in QZ Vir, a short brightening event in RZ Leo, and a temporary disappearance of the orbital modulation in WD 1144+011. The two known dwarf novae UV Gem and TW Vir and the CVs USNO-B1.01144-00115322 and CSS 130516:111236:111236.7+002807 show outbursts, including one complete and three incomplete normal outbursts and two complete superoutbursts. An incomplete but typical normal outburst confirms the dwarf nova identification of the USNO-B1.01144-00115322. The one complete normal outburst in UV Gem may provide the orbital period, since its modulations are shorter than the previously <span class="hlt">observed</span> superhump period. The superoutburst of CSS 130516:111236.7+002807, along with the corresponding superhump period, indicates that this object is an SU UMa star. The derived superhump period of CSS 130516:111236:111236.7+002807 is 1.44 hr, implying that this new SU UMa star is close to the period minimum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSA13B1955B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSA13B1955B"><span id="translatedtitle">Ionospheric <span class="hlt">Variability</span> as <span class="hlt">Observed</span> by the CTECS and CORISS Sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bishop, R. L.; Redding, M.; Straus, P. R.</p> <p>2013-12-01</p> <p>The Compact Total Electron Content Sensor (CTECS) is a GPS radio occultation instrument designed for cubesat platforms that utilizes a COTS receiver, modified firmware, and a custom designed antenna. CTECS was placed on the Pico Satellite Solar Cell Testbed 2 (PSSC2) nanosat that was installed on the Space Shuttle Atlantis (STS-135). PSSC2 was successfully released from the shuttle on 20 July 2011 near 380 km altitude. Because of attitude control and power issues, only 13.5 hours of data was collected during its approximately 5-month mission life. The C/NOFS Occultation Receiver for Ionospheric Sensing and Specification (CORISS) GPS radio occultation sensor on the C/NOFS satellite has collected data nearly continuously from May 2008 to June 2013. Both CTECS and CORISS obtain Total Electron Content and scintillation data. In this presentation the CTECS data is first validated against CORISS and available ground-based <span class="hlt">observations</span>. Then combining the CTECS and CORISS data, low and mid latitude ionospheric <span class="hlt">variability</span> including scintillation events is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSA42A..01D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSA42A..01D"><span id="translatedtitle">C/NOFS <span class="hlt">Observations</span> of Longitudinal Ionospheric <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de la Beaujardiere, O.; Huang, C.; Colman, J. J.; Roddy, P.; Dao, E.; Kelley, M. C.; Crowley, G.; Pfaff, R. F.</p> <p>2012-12-01</p> <p>Launched at a 13 degrees inclination, the Communication/Navigation Outage Forecasting System (C/NOFS) satellite samples all longitudes during each orbit. C/NOFS is thus ideal for studying how the ionospheric ambient density and scintillation-producing irregularities vary with longitude. Irregularities maximize in frequency and amplitude in the America to Africa sector. It has been suggested that waves generated by tropospheric convection propagate upward and launch secondary waves that are responsible for triggering the instability that gives rise to equatorial plasma bubbles. Lightning frequency can be used as a proxy for tropospheric convection regions. We thus examine the possibility that the longitudinal <span class="hlt">variability</span> is related to the occurrence of lightning, since the frequency of lightning in the equatorial regions is largest in Africa and then South America. We also present simultaneous data from C/NOFS and from the TID Detector Built in Texas (TIDDBIT) system newly installed in Peru. The purpose is to investigate a possible relationship between C/NOFS ionospheric irregularities and the waves <span class="hlt">observed</span> below the F-peak by TIDDBIT. C/NOFS can also be used to investigate longitudinal changes in the ambient density. For example, as the solar cycle increased, the F-peak height increased. Close to perigee (400 km), C/NOFS was often below the F-peak. Preliminary analysis suggests that the F-peak altitude varies with longitude and is highest in the America to Africa sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy..tmp..273X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy..tmp..273X"><span id="translatedtitle">West African monsoon <span class="hlt">decadal</span> <span class="hlt">variability</span> and surface-related forcings: second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xue, Yongkang; De Sales, Fernando; Lau, William K.-M.; Boone, Aaron; Kim, Kyu-Myong; Mechoso, Carlos R.; Wang, Guiling; Kucharski, Fred; Schiro, Kathleen; Hosaka, Masahiro; Li, Suosuo; Druyan, Leonard M.; Sanda, Ibrah Seidou; Thiaw, Wassila; Zeng, Ning; Comer, Ruth E.; Lim, Young-Kwon; Mahanama, Sarith; Song, Guoqiong; Gu, Yu; Hagos, Samson M.; Chin, Mian; Schubert, Siegfried; Dirmeyer, Paul; Ruby Leung, L.; Kalnay, Eugenia; Kitoh, Akio; Lu, Cheng-Hsuan; Mahowald, Natalie M.; Zhang, Zhengqiu</p> <p>2016-06-01</p> <p>The second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II) is designed to improve understanding of the possible roles and feedbacks of sea surface temperature (SST), land use land cover change (LULCC), and aerosols forcings in the Sahel climate system at seasonal to <span class="hlt">decadal</span> scales. The project's strategy is to apply prescribed <span class="hlt">observationally</span> based anomaly forcing, i.e., "idealized but realistic" forcing, in simulations by climate models. The goal is to assess these forcings' effects in producing/amplifying seasonal and <span class="hlt">decadal</span> climate <span class="hlt">variability</span> in the Sahel between the 1950s and the 1980s, which is selected to characterize the great drought period of the last century. This is the first multi-model experiment specifically designed to simultaneously evaluate such relative contributions. The WAMME II models have consistently demonstrated that SST forcing is a major contributor to the twentieth century Sahel drought. Under the influence of the maximum possible SST forcing, the ensemble mean of WAMME II models can produce up to 60 % of the precipitation difference during the period. The present paper also addresses the role of SSTs in triggering and maintaining the Sahel drought. In this regard, the consensus of WAMME II models is that both Indian and Pacific Ocean SSTs greatly contributed to the drought, with the former producing an anomalous displacement of the Intertropical Convergence Zone before the WAM onset, and the latter mainly contributes to the summer WAM drought. The WAMME II models also show that the impact of LULCC forcing on the Sahel climate system is weaker than that of SST forcing, but still of first order magnitude. According to the results, under LULCC forcing the ensemble mean of WAMME II models can produces about 40 % of the precipitation difference between the 1980s and the 1950s. The role of land surface processes in responding to and amplifying the drought is also identified. The results suggest that catastrophic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.H33M..01G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.H33M..01G&link_type=ABSTRACT"><span id="translatedtitle">Effects of <span class="hlt">variable</span> climate, land use, and hydrogeochemical setting on <span class="hlt">decadal</span> surface water quality trends, Iowa, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Green, C. T.; Bekins, B. A.; Kalkhoff, S.; Hirsch, R. M.; Liao, L.; Barnes, K.</p> <p>2013-12-01</p> <p>Nitrogen fluxes from agricultural lands are a major concern for ecological health and water quality. Understanding how these fluxes respond to changes in agricultural practices and climatic variations is important for improving water quality in agricultural settings. In the midwestern USA, intensification of corn cropping as a result of ethanol production led to increases in N application rates in the 2000s during a period including both extreme dry and wet conditions. To examine the effect of these recent changes, a study was conducted on surface water quality in 10 major Iowa Rivers. Long term (~20 to 30 years) water quality and flow data were analyzed with Weighted Regression on Time, Discharge and Season (WRTDS), a statistical method that provides internally consistent estimates of the concentration history and reveals <span class="hlt">decadal</span> trends that are independent of random variations of stream flow from seasonal averages. Trends of surface water quality showed constant or decreasing flow-normalized concentrations of nitrate+nitrite-N from 2000 to 2012 in all basins. To evaluate effects of annual discharge and N loading on these trends, multiple conceptual models were developed and calibrated to annual concentrations. The recent declining concentration trends can be attributed to both very high and very low discharge in the 2000's and to the long (e.g. 8-year) subsurface residence times in some basins. Dilution of surface water nitrate and depletion of stored nitrate may occur in years with very high discharge. Limited transport of N to surface water and accumulation of stored N may occur in years with very low discharge. Central Iowa basins showed the greatest reduction in concentrations, likely because extensive tile drainage results in smaller storage volumes and shorter residence times, and the glacial sediments are naturally reducing. Effects of agricultural intensification from ethanol production and other factors will likely be delayed for years or <span class="hlt">decades</span> in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013029','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013029"><span id="translatedtitle">Multi-<span class="hlt">Decadal</span> Aerosol Variations from 1980 to 2009: A Perspective from <span class="hlt">Observations</span> and a Global Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chin, Mian; Diehl, T.; Tan, Q.; Prospero, J. M.; Kahn, R. A.; Remer, L. A.; Yu, H.; Sayer, A. M.; Bian, H.; Geogdzhayev, I. V.; Holben, B. N.; Howell, S. G.; Huebert, B. J.; Hsu, N. C.; Kim, D.; Kucsera, T. L.; Levy, R. C.; Mishchenko, M. I.; Pan, X.; Quinn, P. K.; Schuster, G. L.; Streets, D. G.; Strode, S. A.; Torres, O.; Zhao, X.-P.</p> <p>2014-01-01</p> <p>Aerosol variations and trends over different land and ocean regions during 1980-2009 are analyzed with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and <span class="hlt">observations</span> from multiple satellite sensors and ground-based networks. Excluding time periods with large volcanic influences, the tendency of aerosol optical depth (AOD) and surface concentration over polluted land regions is consistent with the anthropogenic emission changes.The largest reduction occurs over Europe, and regions in North America and Russia also exhibit reductions. On the other hand, East Asia and South Asia show AOD increases, although relatively large amount of natural aerosols in Asia makes the total changes less directly connected to the pollutant emission trends. Over major dust source regions, model analysis indicates that the dust emissions over the Sahara and Sahel respond mainly to the near-surface wind speed, but over Central Asia they are largely influenced by ground wetness. The decreasing dust trend in the tropical North Atlantic is most closely associated with the decrease of Sahel dust emission and increase of precipitation over the tropical North Atlantic, likely driven by the sea surface temperature increase. Despite significant regional trends, the model-calculated global annual average AOD shows little changes over land and ocean in the past three <span class="hlt">decades</span>, because opposite trends in different regions cancel each other in the global average. This highlights the need for regional-scale aerosol assessment, as the global average value conceals regional changes, and thus is not sufficient for assessing changes in aerosol loading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7334C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7334C"><span id="translatedtitle">Hydrological <span class="hlt">variability</span> from gauging stations and simulated SWOT data, for major French rivers over the past <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chevalier, Laetitia; Laignel, Benoit; Turki, Imen; Lyard, Florent; Lion, Christine</p> <p>2014-05-01</p> <p>This study was carried out in the framework of the program Surface Water and Ocean Topography (SWOT) associated to the National Center of Space Studies (CNES). Basing on discharge measurements, and simulated Surface Water and Ocean Topography (SWOT) data, we have investigated the hydrological <span class="hlt">variability</span> of the main French rivers (Seine, Loire, Garonne and Rhône) by the use of a minimum, maximum and mean annual discharge analyses, Loess and wavelet approach (continuous wavelet analyses and wavelet coherence analyses). Results show (i) strong coherence between the four watershed discharges, varying between 73% and 92% and (ii) three different periods for hydrological <span class="hlt">variability</span>: before 1970, between 1970 and 1990, and after 1990. From these results, simulated SWOT data and discharges are compared for these three periods using same analyses. Simulated SWOT data are obtained by re-sampling river discharges from the SWOT crossing time calculated. Simulated SWOT data can reproduce the hydrological <span class="hlt">variability</span> of rivers despite number of SWOT passages (from two to four). These results are validated by coherence wavelet, which underlines coherence higher than 90% between simulated SWOT data and in-situ discharge. However, the results indicate that simulated SWOT data don't reproduce exactly the minimum and maximum annual discharge: (i) maximum annual SWOT data are underestimated and (ii) minimum annual SWOT data are overestimated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040111406&hterms=Biomass&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DBiomass','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040111406&hterms=Biomass&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DBiomass"><span id="translatedtitle">Interannual and Seasonal <span class="hlt">Variability</span> of Biomass Burning Emissions Constrained by Satellite <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Duncan, Bryan N.; Martin, Randall V.; Staudt, Amanda C.; Yevich, Rosemarie; Logan, Jennifer A.</p> <p>2003-01-01</p> <p>We present a methodology for estimating the seasonal and interannual variation of biomass burning designed for use in global chemical transport models. The average seasonal variation is estimated from 4 years of fire-count data from the Along Track Scanning Radiometer (ATSR) and 1-2 years of similar data from the Advanced Very High Resolution Radiometer (AVHRR) World Fire Atlases. We use the Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) data product as a surrogate to estimate interannual <span class="hlt">variability</span> in biomass burning for six regions: Southeast Asia, Indonesia and Malaysia, Brazil, Central America and Mexico, Canada and Alaska, and Asiatic Russia. The AI data set is available from 1979 to the present with an interruption in satellite <span class="hlt">observations</span> from mid-1993 to mid-1996; this data gap is filled where possible with estimates of area burned from the literature for different regions. Between August 1996 and July 2000, the ATSR fire-counts are used to provide specific locations of emissions and a record of interannual <span class="hlt">variability</span> throughout the world. We use our methodology to estimate mean seasonal and interannual variations for emissions of carbon monoxide from biomass burning, and we find that no trend is apparent in these emissions over the last two <span class="hlt">decades</span>, but that there is significant interannual <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Variable+AND+stars&id=EJ200250','ERIC'); return false;" href="http://eric.ed.gov/?q=Variable+AND+stars&id=EJ200250"><span id="translatedtitle"><span class="hlt">Observing</span> Simulated Cepheid <span class="hlt">Variable</span> Stars in an Introductory Astronomy Lab.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Flesch, Terry R.</p> <p>1979-01-01</p> <p>Describes an exercise developed by the author to help college students to become familiar with the technique of photoelectric photometry of <span class="hlt">variable</span> stars and permits each student to work with data he or she has personally obtained. (HM)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JAVSO..24..129W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JAVSO..24..129W"><span id="translatedtitle">Mythological Evidence for Ancient <span class="hlt">Observations</span> of <span class="hlt">Variable</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilk, Stephen R.</p> <p></p> <p>I suggest that the <span class="hlt">variability</span> of Algol was known in pre-classical Greece, and that knowledge of its period is reflected in the myth of Perseus. Moreover, knowledge of the <span class="hlt">variability</span> of Algol, Mira, delta Cephei, and gamma Cassiopeiae accounts for all their parent constellations being associated in the same myth as antagonists of Perseus. Finally, I propose alternative interpretations of the same constellations which show their influence upon classical myth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NPGD....2..675F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NPGD....2..675F"><span id="translatedtitle">Systematic attribution of <span class="hlt">observed</span> southern hemispheric circulation trends to external forcing and internal <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franzke, C. L. E.; O'Kane, T. J.; Monselesan, D. P.; Risbey, J. S.; Horenko, I.</p> <p>2015-04-01</p> <p>A critical question in the global warming debate concerns the causes of the <span class="hlt">observed</span> trends of the Southern Hemisphere (SH) atmospheric circulation over recent <span class="hlt">decades</span>. Secular trends have been identified in the frequency of occurrence of circulation regimes, namely the positive phase of the Southern Annular Mode (SAM) and the hemispheric wave 3 pattern which is associated with blocking. Previous studies into the causes of these secular trends have either been purely model based, have not included <span class="hlt">observational</span> forcing data or have mixed external forcing with indices of internal climate <span class="hlt">variability</span> impeding a systematic and unbiased attribution of the causes of the secular trends. Most model studies also focused mainly on the austral summer season. However, the changes to the storm tracks have occurred in all seasons and particularly in the austral winter and early spring when mid-latitude blocking is most active and stratospheric ozone should not a play a role. Here we systematically attribute the secular trends over the recent <span class="hlt">decades</span> using a non-stationary clustering method applied to both reanalysis and <span class="hlt">observational</span> forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing austral summer SH circulation trends, we show <span class="hlt">observational</span> evidence that anthropogenic greenhouse gas concentrations have been the major driver of these secular trends in the SAM and blocking when all seasons are considered. Our results suggest that the recovery of the ozone hole might delay the signal of global warming less strongly than previously thought and that effects from all seasons are likely crucial in understanding the causes of the secular trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2614F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2614F"><span id="translatedtitle">Systematic Attribution of <span class="hlt">Observed</span> Southern Hemispheric Circulation Trends to External Forcing and Internal <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franzke, Christian; O'Kane, Terence; Monselesan, Didier; Risbey, James; Horenko, Illia</p> <p>2015-04-01</p> <p>A critical question in the global warming debate concerns the causes of the <span class="hlt">observed</span> trends of the Southern Hemisphere (SH) atmospheric circulation over recent <span class="hlt">decades</span>. Secular trends have been identified in the frequency of occurrence of circulation regimes, namely the positive phase of the Southern Annular Mode (SAM) and the hemispheric wave 3 pattern which is associated with blocking. Previous studies into the causes of these secular trends have either been purely model based, have not included <span class="hlt">observational</span> forcing data or have mixed external forcing with indices of internal climate <span class="hlt">variability</span> impeding a systematic and unbiased attribution of the causes of the secular trends. Most model studies also focused mainly on the austral summer season. However, the changes to the storm tracks have occurred in all seasons and particularly in the winter and early spring when mid-latitude blocking is most active and stratospheric ozone plays no role. Here we systematically attribute the secular trends over the recent <span class="hlt">decades</span> using a non-stationary clustering method applied to both reanalysis and <span class="hlt">observational</span> forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing summer SH circulation trends, we show <span class="hlt">observational</span> evidence that anthropogenic greenhouse gas concentrations have been the major driver of these secular trends in the SAM and blocking when all seasons are considered. Our results suggest that the recovery of the ozone hole might delay the signal of global warming less strongly than previously thought and that seasonal effects are likely crucial in understanding the causes of the secular trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NPGeo..22..513F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NPGeo..22..513F"><span id="translatedtitle">Systematic attribution of <span class="hlt">observed</span> Southern Hemisphere circulation trends to external forcing and internal <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franzke, C. L. E.; O'Kane, T. J.; Monselesan, D. P.; Risbey, J. S.; Horenko, I.</p> <p>2015-09-01</p> <p>A critical question in the global warming debate concerns the causes of the <span class="hlt">observed</span> trends of the Southern Hemisphere (SH) atmospheric circulation over recent <span class="hlt">decades</span>. Secular trends have been identified in the frequency of occurrence of circulation regimes, namely the positive phase of the Southern Annular Mode (SAM) and the hemispheric wave-3 pattern which is associated with blocking. Previous studies into the causes of these secular trends have either been purely model based, have not included <span class="hlt">observational</span> forcing data or have mixed external forcing with indices of internal climate <span class="hlt">variability</span> impeding a systematic and unbiased attribution of the causes of the secular trends. Most model studies also focused mainly on the austral summer season. However, the changes to the storm tracks have occurred in all seasons and particularly in the austral winter and early spring when midlatitude blocking is most active and stratospheric ozone should not play a role. Here we systematically attribute the secular trends over the recent <span class="hlt">decades</span> using a non-stationary clustering method applied to both reanalysis and <span class="hlt">observational</span> forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing austral summer SH circulation trends, we show <span class="hlt">observational</span> evidence that anthropogenic greenhouse gas concentrations have been the major driver of these secular trends in the SAM and blocking when all seasons are considered. Our results suggest that the recovery of the ozone hole might delay the signal of global warming less strongly than previously thought and that effects from all seasons are likely crucial in understanding the causes of the secular trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6738L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6738L"><span id="translatedtitle">Surface Wind <span class="hlt">Observational</span> Database in North Eastern North America: Quality Control Procedure and Climatological <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lucio-Eceiza, Etor E.; Fidel González-Rouco, J.; Navarro, Jorge; Hidalgo, Ángela; Conte, Jorge; Beltrami, Hugo</p> <p>2015-04-01</p> <p>This work summarizes the design and application of a Quality Control (QC) procedure for an <span class="hlt">observational</span> surface wind database located in North Eastern North America. It also presents some insights of the long-term climatological <span class="hlt">variability</span> over the region. The database consists of 527 sites (487 land stations and 40 buoys) with varying resolutions of hourly, 3 hourly and 6 hourly data, compiled from three different source institutions. The records span from 1940 to 2010 and cover an approximate spatial extension of 2.2 × 106 km2. The QC process is composed of different phases focused either on problems related with the providing source institutions or measurement errors. Due to the size of the data set, a great effort has been made on the automation of the procedures. A number of problems are associated with data management and data conventions: unification of measurement units and recording times due to the variety of institutional sources; detection of erroneous data sequence duplications within a station or among different ones; and detection of errors related with physically unrealistic data measurements. From the other hand there is a variety of treated instrumental errors: problems related with low <span class="hlt">variability</span>, placing particular emphasis on the detection of unrealistic low wind speed records with the help of regional references; high <span class="hlt">variability</span> related erroneous records; wind speed biases on week to monthly timescales and homogenization of wind direction records. As a result, around 1.7% of wind speed records and 0.4% of wind direction records have been deleted, making a combined total of 1.9% of removed records. Around 2.4% of wind direction data have been also corrected. The already quality controlled database allows for subsequent climatological analyses. The intra and inter <span class="hlt">decadal</span> <span class="hlt">variability</span> of the monthly surface wind field in such a vast and orographically complex region as the North Eastern North America is explored. Several <span class="hlt">decades</span> of quality</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6423S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6423S"><span id="translatedtitle">Two centuries of <span class="hlt">observed</span> atmospheric <span class="hlt">variability</span> and change over the North Sea region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard; Woollings, Tim</p> <p>2016-04-01</p> <p>In the upcoming North Sea Region Climate Change Assessment (NOSCCA), we present a synthesis of current knowledge about past, present and possible future climate change in the North Sea region. A climate change assessment from published scientific work has been conducted as a kind of regional IPCC report, and a book has been produced that will be published by Springer in 2016. In the framework of the NOSCCA project, we examine past and present studies of <span class="hlt">variability</span> and changes in atmospheric <span class="hlt">variables</span> within the North Sea region over the instrumental period, roughly the past 200 years, based on <span class="hlt">observations</span> and reanalyses. The <span class="hlt">variables</span> addressed in this presentation are large-scale circulation, pressure and wind, surface air temperature, precipitation and radiative properties (clouds, solar radiation, and sunshine duration). While air temperature over land, not unexpectedly, has increased everywhere in the North Sea region, with strongest trends in spring and in the north of the region, a precipitation increase has been <span class="hlt">observed</span> in the north and a decrease in the south of the region. This pattern goes along with a north-eastward shift of storm tracks and is in agreement with climate model projections under enhanced greenhouse gas concentrations. For other <span class="hlt">variables</span>, it is not obvious which part of the <span class="hlt">observed</span> changes may be due to anthropogenic activities and which is internally forced. It remains also unclear to what extent atmospheric circulation over the North Sea region is influenced by distant factors, in particular Arctic sea-ice decline in recent <span class="hlt">decades</span>. There are indications of an increase in the number of deep cyclones (but not in the total number of cyclones), while storminess since the late 19th century shows no robust trends. The persistence of circulation types appears to have increased over the last century, and consequently, there is an indication for 'more extreme' extreme events. However, changes in extreme weather events are difficult to assess</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AdAtS..33..852R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AdAtS..33..852R"><span id="translatedtitle">Spatiotemporal <span class="hlt">variability</span> of methane over the Amazon from satellite <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ribeiro, Igor Oliveira; de Souza, Rodrigo Augusto Ferreira; Andreoli, Rita Valéria; Kayano, Mary Toshie; Costa, Patrícia dos Santos</p> <p>2016-07-01</p> <p>The spatiotemporal <span class="hlt">variability</span> of the greenhouse gas methane (CH4) in the atmosphere over the Amazon is studied using data from the space-borne measurements of the Atmospheric Infrared Sounder on board NASA's AQUA satellite for the period 2003-12. The results show a pronounced <span class="hlt">variability</span> of this gas over the Amazon Basin lowlands region, where wetland areas occur. CH4 has a well-defined seasonal behavior, with a progressive increase of its concentration during the dry season, followed by a decrease during the wet season. Concerning this <span class="hlt">variability</span>, the present study indicates the important role of ENSO in modulating the <span class="hlt">variability</span> of CH4 emissions over the northern Amazon, where this association seems to be mostly linked to changes in flooded areas in response to ENSO-related precipitation changes. In this region, a CH4 decrease (increase) is due to the El Niño-related (La Niña-related) dryness (wetness). On the other hand, an increase (decrease) in the biomass burning over the southeastern Amazon during very dry (wet) years explains the increase (decrease) in CH4 emissions in this region. The present analysis identifies the two main areas of the Amazon, its northern and southeastern sectors, with remarkable interannual variations of CH4. This result might be useful for future monitoring of the variations in the concentration of CH4, the second-most important greenhouse gas, in this area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ACP....14.3657C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ACP....14.3657C"><span id="translatedtitle">Multi-<span class="hlt">decadal</span> aerosol variations from 1980 to 2009: a perspective from <span class="hlt">observations</span> and a global model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chin, M.; Diehl, T.; Tan, Q.; Prospero, J. M.; Kahn, R. A.; Remer, L. A.; Yu, H.; Sayer, A. M.; Bian, H.; Geogdzhayev, I. V.; Holben, B. N.; Howell, S. G.; Huebert, B. J.; Hsu, N. C.; Kim, D.; Kucsera, T. L.; Levy, R. C.; Mishchenko, M. I.; Pan, X.; Quinn, P. K.; Schuster, G. L.; Streets, D. G.; Strode, S. A.; Torres, O.; Zhao, X.-P.</p> <p>2014-04-01</p> <p>Aerosol variations and trends over different land and ocean regions from 1980 to 2009 are analyzed with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and <span class="hlt">observations</span> from multiple satellite sensors and available ground-based networks. Excluding time periods with large volcanic influence, aerosol optical depth (AOD) and surface concentration over polluted land regions generally vary with anthropogenic emissions, but the magnitude of this association can be dampened by the presence of natural aerosols, especially dust. Over the 30-year period in this study, the largest reduction in aerosol levels occurs over Europe, where AOD has decreased by 40-60% on average and surface sulfate concentrations have declined by a factor of up to 3-4. In contrast, East Asia and South Asia show AOD increases, but the relatively high level of dust aerosols in Asia reduces the correlation between AOD and pollutant emission trends. Over major dust source regions, model analysis indicates that the change of dust emissions over the Sahara and Sahel has been predominantly driven by the change of near-surface wind speed, but over Central Asia it has been largely influenced by the change of the surface wetness. The decreasing dust trend in the North African dust outflow region of the tropical North Atlantic and the receptor sites of Barbados and Miami is closely associated with an increase of the sea surface temperature in the North Atlantic. This temperature increase may drive the decrease of the wind velocity over North Africa, which reduces the dust emission, and the increase of precipitation over the tropical North Atlantic, which enhances dust removal during transport. Despite significant trends over some major continental source regions, the model-calculated global annual average AOD shows little change over land and ocean in the past three <span class="hlt">decades</span>, because opposite trends in different land regions cancel each other out in the global average, and changes over</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020045387','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020045387"><span id="translatedtitle">Seasonal to <span class="hlt">Decadal</span>-Scale <span class="hlt">Variability</span> in Satellite Ocean Color and Sea Surface Temperature for the California Current System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mitchell, B. Greg; Kahru, Mati; Marra, John (Technical Monitor)</p> <p>2002-01-01</p> <p>Support for this project was used to develop satellite ocean color and temperature indices (SOCTI) for the California Current System (CCS) using the historic record of CZCS West Coast Time Series (WCTS), OCTS, WiFS and AVHRR SST. The ocean color satellite data have been evaluated in relation to CalCOFI data sets for chlorophyll (CZCS) and ocean spectral reflectance and chlorophyll OCTS and SeaWiFS. New algorithms for the three missions have been implemented based on in-water algorithm data sets, or in the case of CZCS, by comparing retrieved pigments with ship-based <span class="hlt">observations</span>. New algorithms for absorption coefficients, diffuse attenuation coefficients and primary production have also been evaluated. Satellite retrievals are being evaluated based on our large data set of pigments and optics from CalCOFI.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy..tmp..171C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy..tmp..171C"><span id="translatedtitle">Rainfall <span class="hlt">variability</span> and trends of the past six <span class="hlt">decades</span> (1950-2014) in the subtropical NW Argentine Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castino, F.; Bookhagen, B.; Strecker, M. R.</p> <p>2016-04-01</p> <p>The eastern flanks of the Central Andes are characterized by deep convection, exposing them to hydrometeorological extreme events, often resulting in floods and a variety of mass movements. We assessed the spatiotemporal pattern of rainfall trends and the changes in the magnitude and frequency of extreme events (≥95th percentile) along an E-W traverse across the southern Central Andes using rain-gauge and high-resolution gridded datasets (CPC-uni and TRMM 3B42 V7). We generated different climate indices and made three key <span class="hlt">observations</span>: (1) an increase of the annual rainfall has occurred at the transition between low (<0.5 km) and intermediate (0.5-3 km) elevations between 1950 and 2014. Also, rainfall increases during the wet season and, to a lesser degree, decreases during the dry season. Increasing trends in annual total amounts characterize the period 1979-2014 in the arid, high-elevation southern Andean Plateau, whereas trend reversals with decreasing annual total amounts were found at low elevations. (2) For all analyzed periods, we <span class="hlt">observed</span> small or no changes in the median values of the rainfall-frequency distribution, but significant trends with intensification or attenuation in the 95th percentile. (3) In the southern Andean Plateau, extreme rainfall events exhibit trends towards increasing magnitude and, to a lesser degree, frequency during the wet season, at least since 1979. Our analysis revealed that low (<0.5 km), intermediate (0.5-3 km), and high-elevation (>3 km) areas respond differently to changing climate conditions, and the transition zone between low and intermediate elevations is characterized by the most significant changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3806845','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3806845"><span id="translatedtitle">Temperature <span class="hlt">Variability</span> during Delirium in ICU Patients: An <span class="hlt">Observational</span> Study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>van der Kooi, Arendina W.; Kappen, Teus H.; Raijmakers, Rosa J.; Zaal, Irene J.; Slooter, Arjen J. C.</p> <p>2013-01-01</p> <p>Introduction Delirium is an acute disturbance of consciousness and cognition. It is a common disorder in the intensive care unit (ICU) and associated with impaired long-term outcome. Despite its frequency and impact, delirium is poorly recognized by ICU-physicians and –nurses using delirium screening tools. A completely new approach to detect delirium is to use monitoring of physiological alterations. Temperature <span class="hlt">variability</span>, a measure for temperature regulation, could be an interesting component to monitor delirium, but whether temperature regulation is different during ICU delirium has not yet been investigated. The aim of this study was to investigate whether ICU delirium is related to temperature <span class="hlt">variability</span>. Furthermore, we investigated whether ICU delirium is related to absolute body temperature. Methods We included patients who experienced both delirium and delirium free days during ICU stay, based on the Confusion Assessment method for the ICU conducted by a research- physician or –nurse, in combination with inspection of medical records. We excluded patients with conditions affecting thermal regulation or therapies affecting body temperature. Daily temperature <span class="hlt">variability</span> was determined by computing the mean absolute second derivative of the temperature signal. Temperature <span class="hlt">variability</span> (primary outcome) and absolute body temperature (secondary outcome) were compared between delirium- and non-delirium days with a linear mixed model and adjusted for daily mean Richmond Agitation and Sedation Scale scores and daily maximum Sequential Organ Failure Assessment scores. Results Temperature <span class="hlt">variability</span> was increased during delirium-days compared to days without delirium (βunadjusted=0.007, 95% confidence interval (CI)=0.004 to 0.011, p<0.001). Adjustment for confounders did not alter this result (βadjusted=0.005, 95% CI=0.002 to 0.008, p<0.001). Delirium was not associated with absolute body temperature (βunadjusted=-0.03, 95% CI=-0.17 to 0.10, p=0.61). This</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.3905B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.3905B"><span id="translatedtitle">Southern Ocean deep convection in global climate models: A driver for <span class="hlt">variability</span> of subpolar gyres and Drake Passage transport on <span class="hlt">decadal</span> timescales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behrens, Erik; Rickard, Graham; Morgenstern, Olaf; Martin, Torge; Osprey, Annette; Joshi, Manoj</p> <p>2016-06-01</p> <p>We investigate the individual and joint <span class="hlt">decadal</span> <span class="hlt">variability</span> of Southern Ocean state quantities, such as the strength of the Ross and Weddell Gyres, Drake Passage transport, and sea ice area, using the National Institute of Water and Atmospheric Research UK Chemistry and Aerosols (NIWA-UKCA) model and CMIP5 models. <span class="hlt">Variability</span> in these quantities is stimulated by strong deep reaching convective events in the Southern Ocean, which produce an Antarctic Bottom Water-like water mass and affect the large-scale meridional density structure in the Southern Ocean. An increase in the (near) surface stratification, due to freshwater forcing, can be a precondition for subsequent strong convection activity. The combination of enhanced-gyre driven sea ice and freshwater export, as well as ongoing subsurface heat accumulation, lead to a time lag between changes in oceanic freshwater and heat content. This causes an ongoing weakening of the stratification until sudden strong mixing events emerge and the heat is released to the atmosphere. We find that strong convection reduces sea ice cover, weakens the subpolar gyres, increases the meridional density gradient and subsequently results in a positive Drake Passage transport anomaly. Results of available CMIP5 models confirm that <span class="hlt">variability</span> in sea ice, Drake Passage transport, and the Weddell Gyre strength is enhanced if models show strong open ocean convective events. Consistent relationships between convection, sea ice, Drake Passage transport, and Ross Gyre strength <span class="hlt">variability</span> are evident in most models, whether or not they host open ocean convection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhRvE..67e6216Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhRvE..67e6216Z"><span id="translatedtitle">Direct <span class="hlt">observation</span> of homoclinic orbits in human heart rate <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Żebrowski, J. J.; Baranowski, R.</p> <p>2003-05-01</p> <p>Homoclinic trajectories of the interbeat intervals between contractions of ventricles of the human heart are identified. The interbeat intervals are extracted from 24-h Holter ECG recordings. Three such recordings are discussed in detail. Mappings of the measured consecutive interbeat intervals are constructed. In the second and in some cases in the fourth iterate of the map of interbeat intervals homoclinic trajectories associated with a hyperbolic saddle are found. The homoclinic trajectories are often persistent for many interbeat intervals, sometimes spanning many thousands of heartbeats. Several features typical for homoclinic trajectories found in other systems were identified, including a signature of the gluing bifurcation. The homoclinic trajectories are present both in recordings of heart rate <span class="hlt">variability</span> obtained from patients with an increased number of arrhythmias and in cases in which the sinus rhythm is dominant. The results presented are a strong indication of the importance of deterministic nonlinear instabilities in human heart rate <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70031802','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70031802"><span id="translatedtitle">High nutrient pulses, tidal mixing and biological response in a small California estuary: <span class="hlt">Variability</span> in nutrient concentrations from <span class="hlt">decadal</span> to hourly time scales</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Caffrey, J.M.; Chapin, T.P.; Jannasch, H.W.; Haskins, J.C.</p> <p>2007-01-01</p> <p>Elkhorn Slough is a small estuary in Central California, where nutrient inputs are dominated by runoff from agricultural row crops, a golf course, and residential development. We examined the <span class="hlt">variability</span> in nutrient concentrations from <span class="hlt">decadal</span> to hourly time scales in Elkhorn Slough to compare forcing by physical and biological factors. Hourly data were collected using in situ nitrate analyzers and water quality data sondes, and two <span class="hlt">decades</span> of monthly monitoring data were analyzed. Nutrient concentrations increased from the mid 1970s to 1990s as pastures and woodlands were converted to row crops and population increased in the watershed. Climatic <span class="hlt">variability</span> was also a significant factor controlling interannual nutrient <span class="hlt">variability</span>, with higher nutrient concentrations during wet than drought years. Elkhorn Slough has a Mediterranean climate with dry and rainy seasons. Dissolved inorganic nitrogen (DIN) concentrations were relatively low (10-70 ??mol L-1) during the dry season and high (20-160 ??mol L-1) during the rainy season. Dissolved inorganic phosphorus (DIP) concentrations showed the inverse pattern, with higher concentrations during the dry season. Pulsed runoff events were a consistent feature controlling nitrate concentrations during the rainy season. Peak nitrate concentrations lagged runoff events by 1 to 6 days. Tidal exchange with Monterey Bay was also an important process controlling nutrient concentrations, particularly near the mouth of the Slough. Biological processes had the greatest effect on nitrate concentrations during the dry season and were less important during the rainy season. While primary production was enhanced by nutrient pulses, chlorophyll a concentrations were not. We believe that the generally weak biological response compared to the strong physical forcing in Elkhorn Slough occurred because the short residence time and tidal mixing rapidly diluted nutrient pulses. ?? 2006 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ECSS...71..368C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ECSS...71..368C"><span id="translatedtitle">High nutrient pulses, tidal mixing and biological response in a small California estuary: <span class="hlt">Variability</span> in nutrient concentrations from <span class="hlt">decadal</span> to hourly time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caffrey, Jane M.; Chapin, Thomas P.; Jannasch, Hans W.; Haskins, John C.</p> <p>2007-02-01</p> <p>Elkhorn Slough is a small estuary in Central California, where nutrient inputs are dominated by runoff from agricultural row crops, a golf course, and residential development. We examined the <span class="hlt">variability</span> in nutrient concentrations from <span class="hlt">decadal</span> to hourly time scales in Elkhorn Slough to compare forcing by physical and biological factors. Hourly data were collected using in situ nitrate analyzers and water quality data sondes, and two <span class="hlt">decades</span> of monthly monitoring data were analyzed. Nutrient concentrations increased from the mid 1970s to 1990s as pastures and woodlands were converted to row crops and population increased in the watershed. Climatic <span class="hlt">variability</span> was also a significant factor controlling interannual nutrient <span class="hlt">variability</span>, with higher nutrient concentrations during wet than drought years. Elkhorn Slough has a Mediterranean climate with dry and rainy seasons. Dissolved inorganic nitrogen (DIN) concentrations were relatively low (10-70 μmol L -1) during the dry season and high (20-160 μmol L -1) during the rainy season. Dissolved inorganic phosphorus (DIP) concentrations showed the inverse pattern, with higher concentrations during the dry season. Pulsed runoff events were a consistent feature controlling nitrate concentrations during the rainy season. Peak nitrate concentrations lagged runoff events by 1 to 6 days. Tidal exchange with Monterey Bay was also an important process controlling nutrient concentrations, particularly near the mouth of the Slough. Biological processes had the greatest effect on nitrate concentrations during the dry season and were less important during the rainy season. While primary production was enhanced by nutrient pulses, chlorophyll a concentrations were not. We believe that the generally weak biological response compared to the strong physical forcing in Elkhorn Slough occurred because the short residence time and tidal mixing rapidly diluted nutrient pulses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730007141','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730007141"><span id="translatedtitle"><span class="hlt">Observations</span> of the sun, an ultraviolet <span class="hlt">variable</span> star</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Heath, D. F.</p> <p>1972-01-01</p> <p>The uncertainty as to whether or not the sun is a <span class="hlt">variable</span> star in that region of the ultraviolet which is absorbed in the mesosphere and stratosphere led to an experiment with acronym MUSE, Monitor of Ultraviolet Solar Energy. The experiment was first flown on an Aerobee rocket in August 1966 and subsequently on Nimbus 3 and 4 in April 1969 and April 1970 respectively. The basic philosophy behind the design of the experiment was to provide an instrument which would not require a solar pointing mechanism and at the same time would be capable of high radiometric accuracy for long periods in space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120013038','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120013038"><span id="translatedtitle">Kepler <span class="hlt">Observations</span> of Rapid Optical <span class="hlt">Variability</span> in Active Galactic Nuclei</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mushotzky, R. F.; Edelson, R.; Baumgartner, W. H.; Gandhi, P.</p> <p>2012-01-01</p> <p>Over three quarters in 2010 - 2011, Kepler monitored optical emission from four active galactic nuclei (AGN) with approx 30 min sampling, > 90% duty cycle and approx < 0.1% repeatability. These data determined the AGN optical fluctuation power spectral density functions (PSDs) over a wide range in temporal frequency. Fits to these PSDs yielded power law slopes of -2.6 to -3.3, much steeper than typically seen in the X-rays. We find evidence that individual AGN exhibit intrinsically different PSD slopes. The steep PSD fits are a challenge to recent AGN <span class="hlt">variability</span> models but seem consistent with first order MRI theoretical calculations of accretion disk fluctuations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21528851','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21528851"><span id="translatedtitle">Optimization of the transmission of <span class="hlt">observable</span> expectation values and <span class="hlt">observable</span> statistics in continuous-<span class="hlt">variable</span> teleportation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Albano Farias, L.; Stephany, J.</p> <p>2010-12-15</p> <p>We analyze the statistics of <span class="hlt">observables</span> in continuous-<span class="hlt">variable</span> (CV) quantum teleportation in the formalism of the characteristic function. We derive expressions for average values of output-state <span class="hlt">observables</span>, in particular, cumulants which are additive in terms of the input state and the resource of teleportation. Working with a general class of teleportation resources, the squeezed-bell-like states, which may be optimized in a free parameter for better teleportation performance, we discuss the relation between resources optimal for fidelity and those optimal for different <span class="hlt">observable</span> averages. We obtain the values of the free parameter of the squeezed-bell-like states which optimize the central momenta and cumulants up to fourth order. For the cumulants the distortion between in and out states due to teleportation depends only on the resource. We obtain optimal parameters {Delta}{sub (2)}{sup opt} and {Delta}{sub (4)}{sup opt} for the second- and fourth-order cumulants, which do not depend on the squeezing of the resource. The second-order central momenta, which are equal to the second-order cumulants, and the photon number average are also optimized by the resource with {Delta}{sub (2)}{sup opt}. We show that the optimal fidelity resource, which has been found previously to depend on the characteristics of input, approaches for high squeezing to the resource that optimizes the second-order momenta. A similar behavior is obtained for the resource that optimizes the photon statistics, which is treated here using the sum of the squared differences in photon probabilities of input versus output states as the distortion measure. This is interpreted naturally to mean that the distortions associated with second-order momenta dominate the behavior of the output state for large squeezing of the resource. Optimal fidelity resources and optimal photon statistics resources are compared, and it is shown that for mixtures of Fock states both resources are equivalent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4703K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4703K"><span id="translatedtitle">Spatial Analysis of Weather-induced Annual and <span class="hlt">Decadal</span> Average Yield <span class="hlt">Variability</span> as Modeled by EPIC for Rain-fed Wheat in Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khabarov, Nikolay; Balkovic, Juraj; Schmid, Erwin; Schwartz, Alexander; Obersteiner, Michael; Azevedo, Ligia B.</p> <p>2016-04-01</p> <p>In our analysis we evaluate the accuracy of near-term (<span class="hlt">decadal</span>) average crop yield assessments as supported by the biophysical crop growth model EPIC. A spatial assessment of averages and <span class="hlt">variability</span> has clear practical implications for agricultural producers and investors concerned with an estimation of the basic stochastic characteristics of a crop yield distribution. As a reliable weather projection for a time period of several years will apparently remain a challenge in the near future, we have employed the existing gridded datasets on historical weather as a best proxy for the current climate. Based on different weather inputs to EPIC, we analyzed the model runs for the rain-fed wheat for 1968-2007 employing AgGRID/GGCMI simulations using harmonized inputs and assumptions (weather datasets: GRASP and Princeton). We have explored the <span class="hlt">variability</span> of historical ten-year yield averages in the past forty years as modeled by the EPIC model, and found that generally the ten-year average yield <span class="hlt">variability</span> is less than 20% ((max-min)/average), whereas there are mid/low yielding areas with a higher ten-years average <span class="hlt">variability</span> of 20-50%. The location of these spots of high <span class="hlt">variability</span> differs between distinctive model-weather setups. Assuming that historical weather can be used as a proxy of the weather in the next ten years, a best possible EPIC-based assessment of a ten-year average yield is a range of 20% width ((max-min)/average). For some mid/low productive areas the range is up to 50% wide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.4344V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.4344V"><span id="translatedtitle">A new direction for Antarctic ice cores: reconstructing Pacific <span class="hlt">decadal</span> <span class="hlt">variability</span> and Australian drought history from the Law Dome ice core.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vance, Tessa; Roberts, Jason; Plummer, Chris; Kiem, Anthony; van Ommen, Tas</p> <p>2015-04-01</p> <p><span class="hlt">Decadal</span> scale SST oscillations in the Pacific significantly influence rainfall <span class="hlt">variability</span> and drought risk across and beyond the Pacific region. Understanding long-term <span class="hlt">decadal</span> SST behavior in the Pacific is necessary to assess past and future climate, particularly drought risk. However, short instrumental records through much of the Pacific region, in particular the South Pacific, make such assessments difficult. A new reconstruction of Pacific <span class="hlt">decadal</span> <span class="hlt">variability</span> covering the last millennium has been produced from the Law Dome ice core, a high snow accumulation site in East Antarctica. The Law Dome ice core samples (at sub-annual resolution) a broad mid-latitude swathe of the Indian and South West Pacific region. This region exhibits wind speed and direction anomalies that are coherent with the phase of the Interdecadal Pacific Oscillation (IPO), an index measuring the <span class="hlt">decadal</span>-scale Pacific SST state. This is the first millennial length IPO reconstruction and is based on the annual accumulation (snowfall) and sub-annual sea salt (wind proxy) records from Law Dome. To demonstrate the versatility of this new IPO reconstruction, we used it to explore drought history in eastern Australia, a region where drought risk is elevated during IPO positive phases. To do this, we super-imposed the 1000 year IPO reconstruction on a Law Dome proxy for eastern Australian rainfall (previously shown to represent rainfall with high significance during IPO positive phases (r =0.406-0.677, p <0.0001-0.01). Eight 'mega-droughts' (dry periods >5 years duration) were identified over the last millennium. Six mega-droughts occurred between AD 1000-1320 including one 39 y drought (AD 1174-1212). Water resources and infrastructure planning in Australia has been based on very limited statistical certainty around drought risk due to the short (~100 year) instrumental record and lack of rainfall proxies. This study shows that, similar to SW North America, Australia also experienced mega</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JHyd..536..426N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JHyd..536..426N"><span id="translatedtitle">Inter-annual to inter-<span class="hlt">decadal</span> streamflow <span class="hlt">variability</span> in Quebec and Ontario in relation to dominant large-scale climate indices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nalley, D.; Adamowski, J.; Khalil, B.; Biswas, A.</p> <p>2016-05-01</p> <p>The impacts of large-scale climate oscillations on hydrological systems and their <span class="hlt">variability</span> have been documented in different parts of the world. Since hydroclimatic data are known to exhibit non-stationary characteristics, spectral analyses such as wavelet transforms are very useful in extracting time-frequency information from such data. As Canadian studies, particularly those of regions east of the Prairies, using wavelet transform-based methods to draw links between relevant climate indices [e.g., the El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the Pacific <span class="hlt">Decadal</span> Oscillation (PDO)] and streamflow <span class="hlt">variability</span> are not common, this study aims to analyze such relationships for the southern regions of Quebec and Ontario. Monthly and annual streamflow data with a record length of 55 years were used to capture streamflow <span class="hlt">variability</span> at intra-annual, inter-annual and inter-<span class="hlt">decadal</span> scales. The continuous wavelet transform spectra of monthly streamflow data revealed consistent significant 6- and 12-month periodicities, which are likely associated with strong seasonality factors. Its annual counterparts showed four different significant periodicities: up to 4 years, 4-6 years, 6-8 years, and greater than 8 years - all of which occurred after the late 1960s/early 1970s. Wavelet coherence analyses show that the influence of ENSO and NAO at the inter-annual scale occurs at 2-6 year periodicities, and the influence of PDO occur at periodicities up to 8 years and exceeding 16 years. Correlations between these climate indices and streamflow were computed to determine the time delay of streamflow response to the influence of ENSO, NAO, and PDO. The lag times ranged from 6-48 months (for monthly data) and 1-4 years (for annual data). This research contributes to our understanding of streamflow <span class="hlt">variability</span> over the southern parts of Quebec and Ontario, and the role of ENSO, NAO, and PDO phenomena on this <span class="hlt">variability</span>. These relationships can</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740012549','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740012549"><span id="translatedtitle">Component noise <span class="hlt">variables</span> of a light <span class="hlt">observation</span> helicopter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robinson, F.</p> <p>1973-01-01</p> <p>A test program was conducted to isolate and evaluate the individual noise sources of a light helicopter. To accomplish this, the helicopter was mounted on a special test rig, at a 6-foot skid height, in a simulated hover. The test rig contained by dynamometer for absorbing engine power and an exhaust silencing system for reducing engine noise. This test set-up allowed the various components of the helicopter to be run and listened to individually or in any combination. The sound pressure level was recorded at a point 200 feet from the helicopter as the component parameters were systematically varied. The tests were conducted in an open area, during the middle of the night, with no wind, and with all other known <span class="hlt">variables</span> either eliminated or kept as constant as possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1214798A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1214798A"><span id="translatedtitle">Ozone column content <span class="hlt">variability</span> at the Kishinev site from satellite retrievals and ground <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aculinin, Alexandr; Smicov, Vladimir</p> <p>2010-05-01</p> <p>It is analyzed <span class="hlt">variability</span> of the total ozone content (TOC) in column of atmosphere by using ozone retrievals from satellite platform and from direct ground <span class="hlt">observations</span> at the Kishinev site, Moldova (47.00N; 28.56E). Direct ground <span class="hlt">observations</span> of the TOC are regular carried out by Atmospheric Research Group (ARG), Institute of Applied Physics at the ground-based solar radiation monitoring station, Kishinev site, by using of hand-held ozonemeter MICROTOPS II. TOC measurements started since 2003. Data of ozone <span class="hlt">observations</span> are presented at the research group web-site http://arg.phys.asm.md. Satellite TOC dataset at specific coordinates of Kishinev site was derived by using linear interpolation of the parent gridded databases from TOMS (1979-2004) and OMI (2005-2008) <span class="hlt">observations</span>. It was established that relative difference of TOC between periods from 1979 to 1983 and from 2004 to 2008 was -5.16 %. Data were processed by applying of 5-year averaging "window". For a period from 1979 to 2008 statistical estimation of linear trend of the TOC was -2.08% per <span class="hlt">decade</span>. Climatic norm of TOC for this period was equal to 335 DU. Variation of ozone column content at Kishinev site shows it seasonal character with maximum of the order of ~378 DU (in March and April) and with minimum of the order of ~289 DU (in October). The largest and lowest range of oscillations of monthly means of the TOC retrieved for Kishinev site from TOMS and OMI <span class="hlt">observations</span> in the course of the period from 1979 to 2008 were ~ 102 DU (in February) and ~29 DU (in October). Extremely low and high values of the TOC ever registered for Kishinev site from TOMS and OMI <span class="hlt">observations</span> were ~ 209 DU (on December 1, 1999) and ~ 532 DU (on March 3, 1988). It was shown that ARG ground <span class="hlt">observations</span> give overestimated TOC values in comparison with the TOMS and OMI <span class="hlt">observations</span> from satellite platforms. Relative differences or biases (in %) between satellite and ARG ground <span class="hlt">observations</span> of the TOC at Kishinev site were</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A31C0058S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A31C0058S"><span id="translatedtitle"><span class="hlt">Decadal</span> changes in all and clear-sky shortwave radiation from high spatial resolution satellite-derived and ground-based <span class="hlt">observations</span> over Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanchez-Lorenzo, A.; Enriquez-Alonso, A.; Wild, M.; Trentmann, J.; Sanchez-Romero, A.; Posselt, R.; Hakuba, M. Z.; Bartok, B.; Vicente-Serrano, S. M.; Calbo Angrill, J.</p> <p>2015-12-01</p> <p>Trends of all-sky downward surface shortwave radiation (SSR) from high-spatial resolution satellite-derived data over Europe from 1983 to 2010 are first presented. The results show a widespread (i.e., non-local dimension) brightening in the major part of Europe, especially since the mid-1990s and in springtime. There is a mean increase of SSR of around 2 Wm-2 per <span class="hlt">decade</span> over the whole Europe, which, taking into account that the satellite-derived product lacks of aerosol variations, can be related to a decrease in the cloud radiative effects over Europe. The reported increase in SSR is slightly lower than the obtained using high-quality ground-based series over Europe. Secondly, clear-sky SSR estimates have been derived as the result of the difference between ground-based and satellite-derived all-sky SSR data (i.e., this latter lacking direct aerosol effects). The results highlight that these residual series can be useful to estimate clear-sky SSR trends, pointing to a significant increase during the period 1983-2010, with higher rates of around 2 Wm-2 per <span class="hlt">decade</span> over central and eastern Europe. This increase in clear-sky SSR is mainly due to a strong increase from the mid-1980s to the late 1990s, possibly linked to a decrease in anthropogenic emissions and a recovery from the El Chichón and Pinatubo volcanic eruptions. These results are in line with <span class="hlt">observations</span> and other estimates of clear-sky SSR (e.g., by making use of sunshine duration records), as well as reported anthropogenic aerosol emissions and concentrations in Europe. Overall, from the results of this study it can be concluded that around one third of the brightening trend in Europe from 1983 to 2010 can be explained by direct aerosol effects, whereas the other two third is related to clouds, i.e. via changes in natural cloud <span class="hlt">variability</span> and/or aerosol indirect effect on clouds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030067741&hterms=spatiotemporal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dspatiotemporal','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030067741&hterms=spatiotemporal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dspatiotemporal"><span id="translatedtitle">Spatiotemporal <span class="hlt">Variability</span> and Propagation of Equatorial Noise <span class="hlt">Observed</span> by Cluster</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Santolik, O.; Pickett, J. S.; Gurnett, D. A.; Maksimovic, M.; Cornilleau-Wehrlin, N.</p> <p>2002-01-01</p> <p>We report a multipoint case study of the electromagnetic equatorial noise <span class="hlt">observed</span> by the Cluster project. High-resolution data were measured in three close points in space located in the morning sector of the outer plasmasphere. We demonstrate a narrow latitudinal extent of the emissions with a typical width of 2 degrees, centered near the minimum-B equator. Power spectra recorded by the different satellites show a complex structure of emission lines whose relative intensities and positions vary at timescales of 1-2 min and/or at spatial scales of tens of wavelengths. These lines do not match harmonics of the local proton cyclotron frequency, as it would be expected if the waves are generated by energetic ions and <span class="hlt">observed</span> near the source region. We bring <span class="hlt">observational</span> evidence that the waves propagate with a significant radial component and thus can propagate from a distant generation region located at different radial distances where ion cyclotron frequencies match the <span class="hlt">observed</span> fine structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AAS...218.9802B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AAS...218.9802B"><span id="translatedtitle">Anne S. Young: Professor and <span class="hlt">Variable</span> Star <span class="hlt">Observer</span> Extraordinaire</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bracher, Katherine</p> <p>2011-05-01</p> <p>Anne Sewell Young (1871-1961) was one of the eight original members of the AAVSO, to which she contributed more than 6500 <span class="hlt">observations</span> over 33 years. She also taught astronomy for 37 years at Mount Holyoke College; among her students was Helen Sawyer Hogg. This paper will look at her life and career both at Mount Holyoke and with the AAVSO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/534525','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/534525"><span id="translatedtitle">Coupled ocean-atmosphere model system for studies of interannual-to-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> over the North Pacific Basin and precipitation over the Southwestern United States</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lai, Chung-Chieng A.</p> <p>1997-10-01</p> <p>This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The ultimate objective of this research project is to make understanding and predicting regional climate easier. The long-term goals of this project are (1) to construct a coupled ocean-atmosphere model (COAM) system, (2) use it to explore the interannual-to-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> over the North Pacific Basin, and (3) determine climate effects on the precipitation over the Southwestern United States. During this project life, three major tasks were completed: (1) Mesoscale ocean and atmospheric model; (2) global-coupled ocean and atmospheric modeling: completed the coupling of LANL POP global ocean model with NCAR CCM2+ global atmospheric model; and (3) global nested-grid ocean modeling: designed the boundary interface for the nested-grid ocean models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22342105','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22342105"><span id="translatedtitle">Follow up <span class="hlt">observations</span> of SDSS and CRTS candidate cataclysmic <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Szkody, Paula; Vasquez-Soltero, Stephanie; Everett, Mark E.; Silva, David R.; Howell, Steve B.; Landolt, Arlo U.; Bond, Howard E. E-mail: dsilva@noao.edu E-mail: landolt@rouge.phys.lsu.edu</p> <p>2014-10-01</p> <p>We present photometry and spectroscopy of 11 and 35 potential cataclysmic <span class="hlt">variables</span>, respectively, from the Sloan Digital Sky Survey, the Catalina Real-Time Transient Survey, and vsnet alerts. The photometry results include quasi-periodic oscillations during the decline of V1363 Cyg, nightly accretion changes in the likely Polar (AM Herculis binary) SDSS J1344+20, eclipses in SDSS J2141+05 with an orbital period of 76 ± 2 minutes, and possible eclipses in SDSS J2158+09 at an orbital period near 100 minutes. Time-resolved spectra reveal short orbital periods near 80 minutes for SDSS J0206+20, 85 minutes for SDSS J1502+33, and near 100 minutes for CSS J0015+26, RXS J0150+37, SDSS J1132+62, SDSS J2154+15, and SDSS J2158+09. The prominent He II line and velocity amplitude of SDSS J2154+15 are consistent with a Polar nature for this object, while the absence of this line and a low velocity amplitude argue against this classification for RXS J0150+37. Single spectra of 10 objects were obtained near outburst and the rest near quiescence, confirming the dwarf novae nature of these objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15676481','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15676481"><span id="translatedtitle">Sex differences in strength - some <span class="hlt">observations</span> on their <span class="hlt">variability</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pheasant, S T</p> <p>1983-09-01</p> <p>One hundred and twelve datasets, which allowed a direct comparison of the strengths of men and women, were located in the published literature. For each of these, three indices of sex difference were calculated: the ratio of the mean female strength to the mean male (F/M), the proportion of the total variance in strength attributable to sex (R(2)) and the "percentage of chance encounters between members of the opposite sex in which the female is stronger" (%CEFS). Sex difference was shown to be very <span class="hlt">variable</span>, the values of these indices being both task and population specific. An experiment was conducted in which male and female subjects gripped and turned knurled cylindrical handles of 10, 30, 50 and 70 mm diameter. Maximum isometric torques were recorded. Sex differences became more pronounced as handle size increased. The optimal handle-size was 50 mm for both male and female subjects. Data concerning whole body exertion (Pheasant et al, 1982) were also analysed for sex differences. It was concluded that very similar tests of strength could exhibit very different levels of sex difference. The task or equipment designer should not make assumptions about sex differences in strength for a particular action, but should rely on empirical investigation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JGRC..110.5018A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JGRC..110.5018A"><span id="translatedtitle">Interannual and <span class="hlt">decadal</span> <span class="hlt">variability</span> of the western Pacific sea surface condition for the years 1787-2000: Reconstruction based on stable isotope record from a Guam coral</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Asami, Ryuji; Yamada, Tsutomu; Iryu, Yasufumi; Quinn, Terrence M.; Meyer, Christopher P.; Paulay, Gustav</p> <p>2005-05-01</p> <p>We present a monthly resolved, 213-year stable isotope time series from a coral from Guam (13°N, 145°E), which is located on the northern edge of the western Pacific warm pool. Oxygen isotopic composition of the coral skeleton (δ18Ocoral) shows seasonal, interannual, and <span class="hlt">decadal</span> <span class="hlt">variability</span>, which documents significant oceanographic changes related to thermal and hydrologic variations in this region. The δ18Ocoral anomaly reflects sea surface temperature (SST) anomaly and sea surface salinity (SSS) anomaly with significant r values of -0.69 and 0.49, respectively, which are strongly linked to oceanographic changes that occur during El Niño-Southern Oscillation (ENSO) warm and cool phases. We identified 46 ENSO warm (El Niño) and 53 cool phases (La Niña) in the coral record, which are consistent with those phases reconstructed by Niño 3.4 SST anomaly. Spectral analyses of the δ18Ocoral anomaly record for the years 1790-1999 identified significant peaks around ˜3 to ˜7 years. These results indicate that the Guam coral has recorded ENSO periodicity. The δ18Ocoral anomaly shows <span class="hlt">decadal</span> <span class="hlt">variability</span> of ˜15- to ˜45-year periodicity with significant shifts (<0.2‰) from warmer to cooler condition and vice versa. An accumulative decrease in δ18Ocoral time series may imply ˜0.75°C warming of SST and ˜0.23‰ freshening of seawater δ18O, corresponding to a decrease of SSS by ˜0.85, in the northwestern tropical Pacific over the last 2 centuries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AAS...218.9704K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AAS...218.9704K"><span id="translatedtitle"><span class="hlt">Variable</span> Star <span class="hlt">Observing</span> with the Bradford Robotic Telescope</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinne, Richard C. S.</p> <p>2011-05-01</p> <p>With the recent addition of Johnson BVRI filters on the Bradford Robotic Telescope's 24 sq. arc minute camera, this scope has become a possibility to be considered when monitoring certain stars such as LPVs. This presentation will examine the mechanics of <span class="hlt">observing</span> with the BRT and show examples of work that has been done by the author and how that data has been reduced using VPhot.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9638E..0OT','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9638E..0OT"><span id="translatedtitle"><span class="hlt">Observations</span> of SST diurnal <span class="hlt">variability</span> in the South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tu, Qianguang; Pan, Delu; Hao, Zengzhou; Chen, Jianyu</p> <p>2015-10-01</p> <p>In this study, a 3-hourly time resolution gap free sea surface temperature (SST) analysis is generated to resolve the diurnal cycle in the South China Sea (SCS, 0°-25°N, 100°-125°E).It takes advantage of hourly geostationary satellite MTSAT <span class="hlt">observations</span> and combines three infrared and two microwave polar satellite <span class="hlt">observations</span> at different local times. First, all the data are classified into eight SST datasets at 3 hour intervals and then remapped to 0.05°resolution grids. A series of critical quality control is done to remove the outliers.Then bias adjustment is applied to the polar satellite <span class="hlt">observations</span> with reference to the MTSAT data. Finally, the six satellites SST data are blended by using the optimal interpolated algorithm. The 3-hourly blended SST is compared against buoy measurements. It shows a good agreement that the biases do not exceed 0.2 °C and root mean square errors range from 0.5 to 0.65 °C. A typical diurnal cycle similar to sine wave is <span class="hlt">observed</span>. The minimum SST occurs at around 0600h and warming peak occurring between 1300h and 1500h local solar time and then decrease in the late afternoon, tapering off at night on March 13, 2008 for example. The frequency of diurnal warming events derived from four years of the blended SST provides solid statistics to investigate the seasonal and spatial distributions of the diurnal warming in the SCS. The sea surface diurnal warming tends to appear more easily in spring, especially in the coastal regions than other seasons and the central regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JASTP.132..124H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JASTP.132..124H&link_type=ABSTRACT"><span id="translatedtitle">The influence of PMCs on water vapor and drivers behind PMC <span class="hlt">variability</span> from SOFIE <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hervig, Mark E.; Siskind, David E.; Bailey, Scott M.; Russell, James M.</p> <p>2015-09-01</p> <p><span class="hlt">Observations</span> from the Solar Occultation For Ice Experiment (SOFIE) are used to quantify relationships between polar mesospheric clouds (PMC) and their environment. Dehydration due to ice growth is found to be greatest ∼1.8 km above the height of peak ice mass density on average, and H2O enhancement due to sublimation is greatest near the bottom of the PMC layer. The dehydration and hydration layers contain a similar amount of H2O, although less than is found in ice layers, a difference that may be due to meridional transport. Because PMCs modify the surrounding water vapor, PMC-H2O relationships can be misleading and recommendations are made for dealing with this issue. The dependence of PMCs on water vapor and temperature was quantified, accounting for the effects of ice on water vapor. The approach examined inter-annual variations and considered the subset of PMCs detected by the Solar Backscatter Ultraviolet (SBUV) instruments, which are less sensitive than SOFIE. Results in the Northern Hemisphere indicate that PMC variations are dominated by temperature, but that a combination of temperature and water vapor provides the best explanation of the <span class="hlt">observations</span>. In the Southern Hemisphere PMC <span class="hlt">variability</span> is attributed primarily to temperature, with water vapor playing a minor role. The subset of SBUV PMCs are found to be one third as sensitive to changing temperature as the entire PMC population <span class="hlt">observed</span> by SOFIE. Finally, an approach is presented which allows temperature and water vapor anomalies to be estimated from various PMC data sets such as SBUV. Using recently reported SBUV PMC trends at 64-74°N latitude with the results of this study indicates a cooling trend of -0.27±0.14 K <span class="hlt">decade</span>-1 and a water vapor increase of +0.66±0.34% <span class="hlt">decade</span>-1 (both at 80-84 km). This cooling trend agrees with reports based on <span class="hlt">observations</span> in the middle atmosphere at similar latitudes. The water vapor increase is lower than expected due to increasing methane, although this</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=literature+AND+review+AND+journal&pg=2&id=EJ1042328','ERIC'); return false;" href="http://eric.ed.gov/?q=literature+AND+review+AND+journal&pg=2&id=EJ1042328"><span id="translatedtitle">A Review of Direct <span class="hlt">Observation</span> Research within the Past <span class="hlt">Decade</span> in the Field of Emotional and Behavioral Disorders</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Adamson, Reesha M.; Wachsmuth, Sean T.</p> <p>2014-01-01</p> <p>This study reviewed prominent journals within the field of emotional and behavioral disorders to identify direct <span class="hlt">observation</span> approaches, reported reliability statistics, and key features of direct <span class="hlt">observation</span>. Selected journals were systematically reviewed for the past 10 years identifying and quantifying specific direct <span class="hlt">observation</span> systems and…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19760030096&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Variable%2Bstars%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19760030096&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Variable%2Bstars%2529"><span id="translatedtitle">Combined optical and X-ray <span class="hlt">observations</span> of <span class="hlt">variable</span> stars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bowyer, C. S.</p> <p>1975-01-01</p> <p>Questions concerning the optical identification of X-ray sources are considered. There are now a total of eight optically identified galactic X-ray sources. Of these eight, five are definitely established as binaries. The nature of the other three sources remains unknown. Studies of U Geminorum conducted on the basis of optical and X-ray <span class="hlt">observations</span> are also discussed. From the upper limit to the accretion rate for U Gem obtained with the aid of soft X-ray data, it is seen that most of the mass flow in U Gem is lost from the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JAVSO..40..435K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAVSO..40..435K"><span id="translatedtitle"><span class="hlt">Variable</span> Star <span class="hlt">Observing</span> with the Bradford Robotic Telescope</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinne, R. C. S.</p> <p>2012-06-01</p> <p>(Abstract only) The Bradford Robotic Telescope (BRT) is a collection of telescopes and other instruments located on Mount Teide, Tenerife, Canary Islands; this resource is available to all for use at no cost (http://www.telescope.org/info/BRT_information). With the recent addition of Johnson BVRI filters on the BRT's 24 square arc minute camera, this telescope has become a resource to be considered when monitoring certain stars such as LPVs. This presentation will examine the mechanics of <span class="hlt">observing</span> with the BRT and show examples of work that has been done by the author and how those data have been reduced using VPhot.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFM.A33E3244V&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFM.A33E3244V&link_type=ABSTRACT"><span id="translatedtitle">Pacific <span class="hlt">Decadal</span> <span class="hlt">Variability</span> in the Southern Indian Ocean: A 1 ky Interdecadal Pacific Oscillation and Australian Megadrought Reconstruction from Law Dome, East Antarctica.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vance, T.; Roberts, J. L.; Plummer, C. T.; Kiem, A.; van Ommen, T. D.</p> <p>2014-12-01</p> <p>The Interdecadal Pacific Oscillation (IPO) is a multidecadal mode of Pacific basin SST anomalies, and is the basin-wide, bi-hemispheric expression of the Pacific <span class="hlt">Decadal</span> Oscillation (PDO). The two indices are highly correlated, but the extent to which they are merely low frequency ENSO is debated. Nonetheless, the IPO/PDO significantly influences interannual rainfall <span class="hlt">variability</span> and drought risk across and beyond the Pacific region on multi-<span class="hlt">decadal</span> timescales, thus an understanding of long-term IPO/PDO <span class="hlt">variability</span> will help with assessing past and future drought risk. A new and highly accurate 1 ky IPO reconstruction has been produced from the Law Dome ice core (East Antarctica). Law Dome is a high accumulation site on the coast of Antarctica in the Indian Ocean sector of the Southern Ocean, and the Law Dome record is directly related to atmospheric anomalies across a broad mid-latitude swathe of this region. The reconstruction utilizes both the accumulation (snowfall) and sea salt (wind proxy) records to produce a reconstruction that is highly calibrated to the instrumental IPO record from 1870-2009 and shows excellent skill (reduction of error value of 0.86). We then super-imposed the 1 ky IPO on a Law Dome proxy for rainfall in eastern subtropical Australia (previously shown to represent rainfall with high significance during IPO positive phases (r =0.406-0.677, p <0.0001-0.01) to identify eight Australian 'mega-droughts' (dry periods >5 y duration) over the last millennium. Six mega-droughts occur between AD 1000-1320 including one 39 y drought (AD 1174-1212). Water resources and infrastructure planning in Australia has been based on very limited statistical certainty around drought risk due to the short instrumental record and lack of rainfall proxies. A recent drought (the 'Big Dry' ~1995-2009) brought both agricultural and urban water supplies to critically low levels, while the Murray-Darling Basin river system, which provides 65% of the water used for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24376581','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24376581"><span id="translatedtitle">Demographic <span class="hlt">variables</span> for wild Asian elephants using longitudinal <span class="hlt">observations</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de Silva, Shermin; Webber, C Elizabeth; Weerathunga, U S; Pushpakumara, T V; Weerakoon, Devaka K; Wittemyer, George</p> <p>2013-01-01</p> <p>Detailed demographic data on wild Asian elephants have been difficult to collect due to habitat characteristics of much of the species' remaining range. Such data, however, are critical for understanding and modeling population processes in this endangered species. We present data from six years of an ongoing study of Asian elephants (Elephas maximus) in Uda Walawe National Park, Sri Lanka. This relatively undisturbed population numbering over one thousand elephants is individually monitored, providing cohort-based information on mortality and reproduction. Reproduction was seasonal, such that most births occurred during the long inter-monsoon dry season and peaked in May. During the study, the average age at first reproduction was 13.4 years and the 50(th) percentile inter-birth interval was approximately 6 years. Birth sex ratios did not deviate significantly from parity. Fecundity was relatively stable throughout the <span class="hlt">observed</span> reproductive life of an individual (ages 11-60), averaging between 0.13-0.17 female offspring per individual per year. Mortalities and injuries based on carcasses and disappearances showed that males were significantly more likely than females to be killed or injured through anthropogenic activity. Overall, however, most <span class="hlt">observed</span> injuries did not appear to be fatal. This population exhibits higher fecundity and density relative to published estimates on other Asian elephant populations, possibly enhanced by present range constriction. Understanding the factors responsible for these demographic dynamics can shed insight on the future needs of this elephant population, with probable parallels to other populations in similar settings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130013062','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130013062"><span id="translatedtitle">Interannual <span class="hlt">Variability</span> of OLR as <span class="hlt">Observed</span> by AIRS and CERES</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Susskind, Joel; Molnar, Gyula I.; Iredell, Lena F.; Loeb, Norman G.</p> <p>2012-01-01</p> <p>The paper examines spatial anomaly time series of Outgoing Longwave Radiation (OLR) and Clear Sky OLR (OLR(sub CLR)) as determined using <span class="hlt">observations</span> from CERES Terra and AIRS over the time period September 2002 through June 2011. We find excellent agreement of the two OLR data sets in almost every detail down to the x11deg spatial grid point level. The extremely close agreement of OLR anomaly time series derived from <span class="hlt">observations</span> by two different instruments implies high stability of both sets of results. Anomalies of global mean, and especially tropical mean, OLR are shown to be strongly correlated with an El Nino index. These correlations explain that the recent global and tropical mean decreases in OLR over the time period studied are primarily the result of a transition from an El Nino condition at the beginning of the data record to La Nina conditions toward the end of the data period. We show that the close correlation of mean OLR anomalies with the El Nino Index can be well accounted for by temporal changes of OLR within two spatial regions, one to the east of, and one to the west of, the NOAA Nino-4 region. Anomalies of OLR in these two spatial regions are both strongly correlated with the El Nino Index as a result of the strong anti-correlation of anomalies of cloud cover and mid-tropospheric water vapor in these two regions with the El Nino Index.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24376581','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24376581"><span id="translatedtitle">Demographic <span class="hlt">variables</span> for wild Asian elephants using longitudinal <span class="hlt">observations</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de Silva, Shermin; Webber, C Elizabeth; Weerathunga, U S; Pushpakumara, T V; Weerakoon, Devaka K; Wittemyer, George</p> <p>2013-01-01</p> <p>Detailed demographic data on wild Asian elephants have been difficult to collect due to habitat characteristics of much of the species' remaining range. Such data, however, are critical for understanding and modeling population processes in this endangered species. We present data from six years of an ongoing study of Asian elephants (Elephas maximus) in Uda Walawe National Park, Sri Lanka. This relatively undisturbed population numbering over one thousand elephants is individually monitored, providing cohort-based information on mortality and reproduction. Reproduction was seasonal, such that most births occurred during the long inter-monsoon dry season and peaked in May. During the study, the average age at first reproduction was 13.4 years and the 50(th) percentile inter-birth interval was approximately 6 years. Birth sex ratios did not deviate significantly from parity. Fecundity was relatively stable throughout the <span class="hlt">observed</span> reproductive life of an individual (ages 11-60), averaging between 0.13-0.17 female offspring per individual per year. Mortalities and injuries based on carcasses and disappearances showed that males were significantly more likely than females to be killed or injured through anthropogenic activity. Overall, however, most <span class="hlt">observed</span> injuries did not appear to be fatal. This population exhibits higher fecundity and density relative to published estimates on other Asian elephant populations, possibly enhanced by present range constriction. Understanding the factors responsible for these demographic dynamics can shed insight on the future needs of this elephant population, with probable parallels to other populations in similar settings. PMID:24376581</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3869725','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3869725"><span id="translatedtitle">Demographic <span class="hlt">Variables</span> for Wild Asian Elephants Using Longitudinal <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>de Silva, Shermin; Webber, C. Elizabeth; Weerathunga, U. S.; Pushpakumara, T. V.; Weerakoon, Devaka K.; Wittemyer, George</p> <p>2013-01-01</p> <p>Detailed demographic data on wild Asian elephants have been difficult to collect due to habitat characteristics of much of the species’ remaining range. Such data, however, are critical for understanding and modeling population processes in this endangered species. We present data from six years of an ongoing study of Asian elephants (Elephas maximus) in Uda Walawe National Park, Sri Lanka. This relatively undisturbed population numbering over one thousand elephants is individually monitored, providing cohort-based information on mortality and reproduction. Reproduction was seasonal, such that most births occurred during the long inter-monsoon dry season and peaked in May. During the study, the average age at first reproduction was 13.4 years and the 50th percentile inter-birth interval was approximately 6 years. Birth sex ratios did not deviate significantly from parity. Fecundity was relatively stable throughout the <span class="hlt">observed</span> reproductive life of an individual (ages 11–60), averaging between 0.13–0.17 female offspring per individual per year. Mortalities and injuries based on carcasses and disappearances showed that males were significantly more likely than females to be killed or injured through anthropogenic activity. Overall, however, most <span class="hlt">observed</span> injuries did not appear to be fatal. This population exhibits higher fecundity and density relative to published estimates on other Asian elephant populations, possibly enhanced by present range constriction. Understanding the factors responsible for these demographic dynamics can shed insight on the future needs of this elephant population, with probable parallels to other populations in similar settings. PMID:24376581</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994TellB..46..294A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994TellB..46..294A"><span id="translatedtitle">Pattern of annual snow accumulation along a west Greenland flow line: no significant change <span class="hlt">observed</span> during recent <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anklin, Martin; Stauffer, Bernhard; Geis, Klaus; Wagenbach, Dietmar</p> <p>1994-09-01</p> <p>At 10 positions on a traverse along a West Greenland flow line, shallow drillings and pit studies were performed in summer 1990. Continuous in situ hydrogen peroxide analyses on these samples allowed the seasonal firn stratigraphy to be established and thus to collect seasonally adjusted subsamples from the core in the field. The mean annual accumulation rate decreases from about 440mm water equivalent at the western sites T9 and T13 to about 250mm at the central positions T41 and Crête. Most of the prominent inter-annual changes of the surface mass balance appear to be well preserved over the area investigated. A comparison of the accumulation rates of the last <span class="hlt">decades</span> with earlier measurements along the same Greenland flow line shows no significant change in accumulation rates during the last forty years. Further, there is no significant evidence for a pronounced increase in the Greenland surface mass balance as suggested by satellite altimetry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120012822','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120012822"><span id="translatedtitle">Interannual <span class="hlt">Variability</span> of OLR as <span class="hlt">Observed</span> by AIRS and CERES</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Susskind, Joel; Molnar, Gyula; Iredell, Lena; Loeb, Norman G.</p> <p>2012-01-01</p> <p>This paper compares spatial anomaly time series of OLR (Outgoing Longwave Radiation) and OLR(sub CLR) (Clear Sky OLR) as determined using <span class="hlt">observations</span> from CERES Terra and AIRS over the time period September 2002 through June 2011. Both AIRS and CERES show a significant decrease in global mean and tropical mean OLR over this time period. We find excellent agreement of the anomaly time-series of the two OLR data sets in almost every detail, down to 1 deg X 1 deg spatial grid point level. The extremely close agreement of OLR anomaly time series derived from <span class="hlt">observations</span> by two different instruments implies that both sets of results must be highly stable. This agreement also validates to some extent the anomaly time series of the AIRS derived products used in the computation of the AIRS OLR product. The paper also examines the correlations of anomaly time series of AIRS and CERES OLR, on different spatial scales, as well as those of other AIRS derived products, with that of the NOAA Sea Surface Temperature (SST) product averaged over the NOAA Nino-4 spatial region. We refer to these SST anomalies as the El Nino Index. Large spatially coherent positive and negative correlations of OLR anomaly time series with that of the El Nino Index are found in different spatial regions. Anomalies of global mean, and especially tropical mean, OLR are highly positively correlated with the El Nino Index. These correlations explain that the recent global and tropical mean decreases in OLR over the period September 2002 through June 2011, as <span class="hlt">observed</span> by both AIRS and CERES, are primarily the result of a transition from an El Nino condition at the beginning of the data record to La Nina conditions toward the end of the data period. We show that the close correlation of global mean, and especially tropical mean, OLR anomalies with the El Nino Index can be well accounted for by temporal changes of OLR within two spatial regions which lie outside the NOAA Nino-4 region, in which anomalies</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900033471&hterms=Barometers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBarometers','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900033471&hterms=Barometers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBarometers"><span id="translatedtitle">Seasonal <span class="hlt">variability</span> in global sea level <span class="hlt">observed</span> with Geosat altimetry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zlotnicki, V.; Fu, L.-L.; Patzert, W.</p> <p>1989-01-01</p> <p>Time changes in global mesoscale sea level variances were <span class="hlt">observed</span> with satellite altimetry between November 1986 and March 1988, showing significant, geographically coherent seasonal patterns. The NE Pacific and NE Atlantic variances show the most reliable patterns, higher than their yearly averages in both the fall and winter. The response to wind forcing appears as the major contributor to the NE Pacific and Atlantic signals; errors in the estimated inverse barometer response due to errors in atmospheric pressure, residual orbit errors, and errors in sea state bias are evaluated and found to be negligible contributors to this particular signal. The equatorial regions also show significant seasonal patterns, but the uncertainties in the wet tropospheric correction prevent definitive conclusions. The western boundary current changes are very large but not statistically significant. Estimates of the regression coefficient between sea level and significant wave height, an estimate of the sea state bias correction, range between 2.3 and 2.9 percent and vary with the type of orbit correction applied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22389611','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22389611"><span id="translatedtitle">Influence of Surface Roughness Spatial <span class="hlt">Variability</span> and Temporal Dynamics on the Retrieval of Soil Moisture from SAR <span class="hlt">Observations</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alvarez-Mozos, Jesús; Verhoest, Niko E C; Larrañaga, Arantzazu; Casalí, Javier; González-Audícana, María</p> <p>2009-01-01</p> <p>Radar-based surface soil moisture retrieval has been subject of intense research during the last <span class="hlt">decades</span>. However, several difficulties hamper the operational estimation of soil moisture based on currently available spaceborne sensors. The main difficulty experienced so far results from the strong influence of other surface characteristics, mainly roughness, on the backscattering coefficient, which hinders the soil moisture inversion. This is especially true for single configuration <span class="hlt">observations</span> where the solution to the surface backscattering problem is ill-posed. Over agricultural areas cultivated with winter cereal crops, roughness can be assumed to remain constant along the growing cycle allowing the use of simplified approaches that facilitate the estimation of the moisture content of soils. However, the field scale spatial <span class="hlt">variability</span> and temporal variations of roughness can introduce errors in the estimation of soil moisture that are difficult to evaluate. The objective of this study is to assess the impact of roughness spatial <span class="hlt">variability</span> and roughness temporal variations on the retrieval of soil moisture from radar <span class="hlt">observations</span>. A series of laser profilometer measurements were performed over several fields in an experimental watershed from September 2004 to March 2005. The influence of the <span class="hlt">observed</span> roughness <span class="hlt">variability</span> and its temporal variations on the retrieval of soil moisture is studied using simulations performed with the Integral Equation Model, considering different sensor configurations. Results show that both field scale roughness spatial <span class="hlt">variability</span> and its temporal variations are aspects that need to be taken into account, since they can introduce large errors on the retrieved soil moisture values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040081225&hterms=Chlorophyll&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DChlorophyll','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040081225&hterms=Chlorophyll&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DChlorophyll"><span id="translatedtitle">Patterns and <span class="hlt">Variability</span> in Global Ocean Chlorophyll: Satellite <span class="hlt">Observations</span> and Modeling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gregg, Watson</p> <p>2004-01-01</p> <p>Recent analyses of SeaWiFS data have shown that global ocean chlorophyll has increased more than 4% since 1998. The North Pacific ocean basin has increased nearly 19%. These trend analyses follow earlier results showing <span class="hlt">decadal</span> declines in global ocean chlorophyll and primary production. To understand the causes of these changes and trends we have applied the newly developed NASA Ocean Biogeochemical Assimilation Model (OBAM), which is driven in mechanistic fashion by surface winds, sea surface temperature, atmospheric iron deposition, sea ice, and surface irradiance. The model utilizes chlorophyll from SeaWiFS in a daily assimilation. The model has in place many of the climatic <span class="hlt">variables</span> that can be expected to produce the changes <span class="hlt">observed</span> in SeaWiFS data. This enables us to diagnose the model performance, the assimilation performance, and possible causes for the increase in chlorophyll. A full discussion of the changes and trends, possible causes, modeling approaches, and data assimilation will be the focus of the seminar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5354921','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5354921"><span id="translatedtitle">Stable Auroral Red arc occurrences detected by the Pacific Northwest Laboratory photometer network: A <span class="hlt">decade</span> of <span class="hlt">observations</span>, 1978--1988</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Slater, D.W.; Kleckner, E.W.</p> <p>1989-11-01</p> <p>Using data obtained from a network of all-sky scanning photometers designed to operate routinely for long periods of time, a comprehensive inspection of <span class="hlt">observations</span> covering the time period 1978--1988 has revealed features that we interpret to be Stable Auroral Red (SAR) arcs during 250 nighttime <span class="hlt">observing</span> periods. These arcs result from high temperature within the ionospheric electron gas that is maintained by slow leakage of energy from the earth's magnetosphere. A listing of these events, the most complete available for this time interval, is presented for the purpose of complementing <span class="hlt">observations</span> reported for earlier dates. This listing is composed of location of the <span class="hlt">observing</span> photometer, date, time, photometric intensity, and location (as defined by the earth's magnetic coordinate system). The intent is to make these <span class="hlt">observations</span> available to a broad range of researchers and thereby initiate further investigations of these features. 22 refs., 3 figs., 2 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7646A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7646A"><span id="translatedtitle">Surface solar radiation <span class="hlt">variability</span> over Eastern Mediterranean: A high spatial resolution view from satellite and ground-based <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexandri, Georgia; Georgoulias, Aristeidis K.; Meleti, Charikleia; Balis, Dimitris</p> <p>2013-04-01</p> <p>Surface Solar Radiation (SSR) has been measured for <span class="hlt">decades</span> from ground-based <span class="hlt">observations</span> for several spots around the planet. On the other hand, during the last <span class="hlt">decades</span>, satellite <span class="hlt">observations</span> made possible the assessment of the spatial <span class="hlt">variability</span> of the SSR at a global as well as regional scale. In this study, a detailed view of the SSR spatiotemporal <span class="hlt">variability</span> is presented at a high spatial resolution, focusing on the region of Eastern Mediterranean. This is a region of particular interest since it is affected by aerosols of various origins (continental, sea, dust and biomass burning particles) and encloses countries with significant socioeconomical changes during the last <span class="hlt">decades</span>. The SSR satellite data used in this study have been obtained from the Satellite Application Facility on Climate Monitoring (CM SAF) (www.cmsaf.eu). The CM SAF SSR dataset is based on reflections in the visible channel of Meteosat First Generation, has a spatial resolution of 0.03ox0.03o and spans from 1983 to 2005. The satellite <span class="hlt">observations</span> are validated against ground-based measurements for the city of Thessaloniki, a coastal city of ~1 million inhabitants in northern Greece, situated in the heart of Eastern Mediterranean. Measurements from two pyranometers, an Eppley Precision pyranometer (1983-1992) and a Kipp & Zonen CM-11 pyranometer (1993-2005), both located at the center of the city, were homogenized and a uniform time series for the 23 year period was constructed. SSR was also calculated with the use of MODIS level-2 aerosol and cloud satellite data for the region of Thessaloniki and the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. These new satellite-based results are compared to both CM SAF and ground-based <span class="hlt">observations</span> in order to examine whether SBDART and MODIS could be further used for the investigation of the spatial patterns of SSR in the area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmRe.172..126P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmRe.172..126P"><span id="translatedtitle"><span class="hlt">Variability</span> in solar irradiance <span class="hlt">observed</span> at two contrasting Antarctic sites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petkov, Boyan H.; Láska, Kamil; Vitale, Vito; Lanconelli, Christian; Lupi, Angelo; Mazzola, Mauro; Budíková, Marie</p> <p>2016-05-01</p> <p>The features of erythemally weighted (EW) and short-wave downwelling (SWD) solar irradiances, <span class="hlt">observed</span> during the spring-summer months of 2007-2011 at Johann Gregor Mendel (63°48‧S, 57°53‧W, 7 m a.s.l.) and Dome Concordia (75°06‧S, 123°21‧E, 3233 m a.s.l.) stations, placed at the Antarctic coastal region and on the interior plateau respectively, have been analysed and compared to each other. The EW and SWD spectral components have been presented by the corresponding daily integrated values and were examined taking into account the different geographic positions and different environmental conditions at both sites. The results indicate that at Mendel station the surface solar irradiance is strongly affected by the changes in the cloud cover, aerosols and albedo that cause a decrease in EW between 20% and 35%, and from 0% to 50% in SWD component, which contributions are slightly lower than the seasonal SWD variations evaluated to be about 71%. On the contrary, the changes in the cloud cover features at Concordia station produce only a 5% reduction of the solar irradiance, whilst the seasonal oscillations of 94% turn out to be the predominant mode. The present analysis leads to the conclusion that the variations in the ozone column cause an average decrease of about 46% in EW irradiance with respect to the value found in the case of minimum ozone content at each of the stations. In addition, the ratio between EW and SWD spectral components can be used to achieve a realistic assessment of the radiation amplification factor that quantifies the relationship between the atmospheric ozone and the surface UV irradiance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211648C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211648C"><span id="translatedtitle">Nonlinear and stochastic effects in ENSO <span class="hlt">variability</span>: From <span class="hlt">observations</span> to intermediate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chekroun, Mickael David; Kondrashov, Dmitri; Neelin, David; Ghil, Michael</p> <p>2010-05-01</p> <p>The El-Nino/Southern-Oscillation (ENSO) phenomenon dominates interannual climate signals in and around the Tropical Pacific and affects the atmospheric circulation and air-sea interaction over many parts of the globe. <span class="hlt">Observational</span> campaigns over the last <span class="hlt">decades</span> have helped infer the most relevant processes, time scales and spatial patterns. A hierarchy of models has been developed to understand these processes and their interaction. These models have been, by-and-large, either deterministic and nonlinear or stochastic and linear, and have been applied to the prediction of future <span class="hlt">variability</span> as well. The purpose of our work is to combine these two complementary points of view, and thus account for (i) the most robust and relevant aspects of the <span class="hlt">observations</span>; (ii) the advances in understanding the nonlinear, deterministic interactions between the largest and most energetic scales; and (iii) the impact of small-scale ("noise") and remote ("external") processes. The main thrust of our approach is based on the concepts and tools of the theory of random dynamical systems (RDS). So far, two of the co-authors (MC & MG), in collaboration with E. Simonnet, have successfully applied RDS theory to, and described in detail the random attractors of several idealized climate models, such as the Lorenz (JAS, 1963) model of convection and the ENSO model of Timmermann and Jin (GRL, 2002). In the present work, we are extending these results to more detailed and realistic models, on the way to their eventual application to IPCC-class general circulation models (GCMs). Specifically, we address here two classes of such intermediate models. The first class is that of nonlinear inverse models derived by empirical mode reduction (EMR), as developed by two of the co-authors (MG and DK), in collaboration with S. Kravtsov, A. W. Robertson and others. In particular, we are studying the random attractor of the ENSO model derived in 2005 from sea surface temperature data over the past century</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150023592','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150023592"><span id="translatedtitle">Spatial <span class="hlt">Variability</span> of Trace Gases During DISCOVER-AQ: Planning for Geostationary <span class="hlt">Observations</span> of Atmospheric Composition</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Follette-Cook, Melanie B.; Pickering, K.; Crawford, J.; Appel, W.; Diskin, G.; Fried, A.; Loughner, C.; Pfister, G.; Weinheimer, A.</p> <p>2015-01-01</p> <p>Results from an in-depth analysis of trace gas <span class="hlt">variability</span> in MD indicated that the <span class="hlt">variability</span> in this region was large enough to be <span class="hlt">observable</span> by a TEMPO-like instrument. The <span class="hlt">variability</span> <span class="hlt">observed</span> in MD is relatively similar to the other three campaigns with a few exceptions: CO <span class="hlt">variability</span> in CA was much higher than in the other regions; HCHO <span class="hlt">variability</span> in CA and CO was much lower; MD showed the lowest <span class="hlt">variability</span> in NO2All model simulations do a reasonable job simulating O3 <span class="hlt">variability</span>. For CO, the CACO simulations largely under over estimate the <span class="hlt">variability</span> in the <span class="hlt">observations</span>. The <span class="hlt">variability</span> in HCHO is underestimated for every campaign. NO2 <span class="hlt">variability</span> is slightly overestimated in MD, more so in CO. The TX simulation underestimates the <span class="hlt">variability</span> in each trace gas. This is most likely due to missing emissions sources (C. Loughner, manuscript in preparation).Future Work: Where reasonable, we will use these model outputs to further explore the resolvability from space of these key trace gases using analyses of tropospheric column amounts relative to satellite precision requirements, similar to Follette-Cook et al. (2015).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140007330','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140007330"><span id="translatedtitle">Use of Machine Learning Techniques for Iidentification of Robust Teleconnections to East African Rainfall <span class="hlt">Variability</span> in <span class="hlt">Observations</span> and Models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roberts, J. Brent; Robertson, Franklin R.; Funk, Chris</p> <p>2014-01-01</p> <p>Providing advance warning of East African rainfall variations is a particular focus of several groups including those participating in the Famine Early Warming Systems Network. Both seasonal and long-term model projections of climate <span class="hlt">variability</span> are being used to examine the societal impacts of hydrometeorological <span class="hlt">variability</span> on seasonal to interannual and longer time scales. The NASA / USAID SERVIR project, which leverages satellite and modeling-based resources for environmental decision making in developing nations, is focusing on the evaluation of both seasonal and climate model projections to develop downscaled scenarios for using in impact modeling. The utility of these projections is reliant on the ability of current models to capture the embedded relationships between East African rainfall and evolving forcing within the coupled ocean-atmosphere-land climate system. Previous studies have posited relationships between variations in El Niño, the Walker circulation, Pacific <span class="hlt">decadal</span> <span class="hlt">variability</span> (PDV), and anthropogenic forcing. This study applies machine learning methods (e.g. clustering, probabilistic graphical model, nonlinear PCA) to <span class="hlt">observational</span> datasets in an attempt to expose the importance of local and remote forcing mechanisms of East African rainfall <span class="hlt">variability</span>. The ability of the NASA Goddard Earth <span class="hlt">Observing</span> System (GEOS5) coupled model to capture the associated relationships will be evaluated using Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/953845','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/953845"><span id="translatedtitle">Final Progress Report: Collaborative Research: <span class="hlt">Decadal</span>-to-Centennial Climate & Climate Change Studies with Enhanced <span class="hlt">Variable</span> and Uniform Resolution GCMs Using Advanced Numerical Techniques</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fox-Rabinovitz, M; Cote, J</p> <p>2009-06-05</p> <p>The joint U.S-Canadian project has been devoted to: (a) <span class="hlt">decadal</span> climate studies using developed state-of-the-art GCMs (General Circulation Models) with enhanced <span class="hlt">variable</span> and uniform resolution; (b) development and implementation of advanced numerical techniques; (c) research in parallel computing and associated numerical methods; (d) atmospheric chemistry experiments related to climate issues; (e) validation of regional climate modeling strategies for nested- and stretched-grid models. The <span class="hlt">variable</span>-resolution stretched-grid (SG) GCMs produce accurate and cost-efficient regional climate simulations with mesoscale resolution. The advantage of the stretched grid approach is that it allows us to preserve the high quality of both global and regional circulations while providing consistent interactions between global and regional scales and phenomena. The major accomplishment for the project has been the successful international SGMIP-1 and SGMIP-2 (Stretched-Grid Model Intercomparison Project, phase-1 and phase-2) based on this research developments and activities. The SGMIP provides unique high-resolution regional and global multi-model ensembles beneficial for regional climate modeling and broader modeling community. The U.S SGMIP simulations have been produced using SciDAC ORNL supercomputers. Collaborations with other international participants M. Deque (Meteo-France) and J. McGregor (CSIRO, Australia) and their centers and groups have been beneficial for the strong joint effort, especially for the SGMIP activities. The WMO/WCRP/WGNE endorsed the SGMIP activities in 2004-2008. This project reflects a trend in the modeling and broader communities to move towards regional and sub-regional assessments and applications important for the U.S. and Canadian public, business and policy decision makers, as well as for international collaborations on regional, and especially climate related issues.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmEn.124..119Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmEn.124..119Z"><span id="translatedtitle">Impact of synoptic weather patterns and inter-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> on air quality in the North China Plain during 1980-2013</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Yang; Ding, Aijun; Mao, Huiting; Nie, Wei; Zhou, Derong; Liu, Lixia; Huang, Xin; Fu, Congbin</p> <p>2016-01-01</p> <p>Potential relationships between air quality, synoptic weather patterns, and the East Asian Monsoon (EAM) over the North China Plain (NCP) were examined during the time period of 1980-2013 using a weather typing technique and ground-based air pollution index (API) data from three cities: Beijing, Tianjin and Shijiazhuang. Using the Kirchhofer method, circulation patterns during the 34-yr study period were classified into 5 categories, which were further used to understand the quantitative relationship between weather and air quality in NCP. The highest API values were associated with a stagnant weather condition when wide-spread stable conditions controlled most part of NCP, while westerly and southerly wind flowed over the northern and eastern part of this region, resulting in both the regional transport and local build-up of air pollutants. Under the continuous control of this weather pattern, API values were found to increase at a rate of 8.5 per day on average. Based on the qualitative and quantitative analysis, a significant correlation was found between the strength of EAM and inter-annual <span class="hlt">variability</span> of frequencies of the weather patterns. The strengthening of summer/winter monsoon could increase the frequency of occurrence of cyclone/anticyclone related weather patterns. Time series of climate-induced <span class="hlt">variability</span> in API over the 34 years were reconstructed based on the quantitative relationship between API and predominant weather patterns during 2001-2010. Significant connections between EAM and reconstructed API were found on both the inter-annual and inter-<span class="hlt">decadal</span> scales. In winter and summer, strengthening/weakening of EAM, which was generally associated with the change of the representative circulation patterns, could improve/worsen air quality in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS23C2033P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS23C2033P"><span id="translatedtitle">Evidence For <span class="hlt">Decadal</span> and Century Scale Climate and Oceanic <span class="hlt">Variability</span> in the Guaymas Basin, Gulf of California, Over the Last Millenium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pineda, L.; Ravelo, A. C.; Aiello, I. W.; Stewart, Z.; Sauthoff, W.</p> <p>2015-12-01</p> <p>Linda Pineda1Ana Christina Ravelo2Ivano Aiello3Zach Stewart2Wilson Sauthoff2 Earth and Planetary Sciences Department, UCSC Ocean Sciences Department, UCSC Moss Landing Marine Lab Natural climate change affects coastal water resources, human land use, and marine biological productivity. In particular, the seasonal migration of the Intertropical Convergence Zone (ITCZ) is influenced by changes in global-scale temperature and pressure gradients and is responsible for spatial changes in summertime rainfall in Mesoamerica impacting regional water resources and the strength of upwelling. In October 2014, aboard the Research Vessel El Puma, a 3.9 meter long core (G14-P12) was recovered from the Northeast flank of the Guaymas Basin in the Gulf of California within the oxygen minimum zone (27˚52.11'N, 111˚41.51'W, water depth of 677m) to investigate changes in seasonal upwelling and Central Mexico rainfall over the last ~1000 years. The age model was developed using Pb210, C14 and lamination counting. The time interval includes the Little Ice Age and the Medieval Warm Period. Biological productivity and precipitation proxy records were produced using an X-Ray Fluorescence (XRF) core-scanner and a color line scanner to generate a record of bulk chemistry and color reflectance. The records indicate marked <span class="hlt">decadal</span> and centennial scale <span class="hlt">variability</span> in the lithologic composition of the sediment superimposed on millimeter-scale <span class="hlt">variability</span> that reflects the presence of seasonally laminated sediments. Nitrogen isotopic and nitrogen weight % measurements were used, in combination with the scanned data, to interpret changes in nitrate utilization and biological productivity. These new records will have broad implications on the link between regional coastal environmental conditions in the Gulf of California and global climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B51D0465H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B51D0465H"><span id="translatedtitle">Two <span class="hlt">decades</span> of historical phenology <span class="hlt">observations</span> of African tropical tree species: exploring the past to predict the futur</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hufkens, K.; Kosmala, M.; Ewango, C.; Richardson, A. D.; Beeckman, H.</p> <p>2015-12-01</p> <p>African tropical forests cover ~630 million ha, store up to 66 Pg of carbon and represent a significant carbon sink (0.34Pg C yr-1 ). As such African tropical forests provide an important negative feedback to the global carbon cycle. Unlike temperate forests, tropical forests lack sharp temperature and photoperiod cues to constrain phenology and growth. Therefore, events such as seasonal leaf abscission and reproductive life cycles are often driven by changes in water availability. With future climate predictions expecting a warmer, and especially drier tropical Africa, it is likely we will see concomitant changes in tree growth and phenology.As tropical trees show a high degree of phenological plasticity depending on the severity of the dry season, intermittent water stress or the location of an individual in the canopy structure. As such, frequent and long term <span class="hlt">observations</span> are key to characterize tropical tree phenology. Here I use two long term historical phenology records of weekly <span class="hlt">observations</span>, some digitized within the context of a citizen science project (http://junglerhythms.org/), to explore differences in tree phenology between two sites (Luki and Yangambi, DR Congo) with contrasting climate regimes within the Congo basin. I describe variation in leaf, flower and fruit phenology across similar species at both locations in relation to complementary historical climatological <span class="hlt">observations</span>. I further discuss the potential implications of changing phenology under future climate conditions as phenological changes could alter both ecosystem demography and growing season length providing important feedbacks to the climate system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..12.7753D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..12.7753D&link_type=ABSTRACT"><span id="translatedtitle">Sub-Seasonal <span class="hlt">Variability</span> of Tropical Rainfall <span class="hlt">Observed</span> by TRMM and Ground-based Polarimetric Radar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dolan, Brenda; Rutledge, Steven; Lang, Timothy; Cifelli, Robert; Nesbitt, Stephen</p> <p>2010-05-01</p> <p>Studies of tropical precipitation characteristics from the TRMM-LBA and NAME field campaigns using ground-based polarimetric S-band data have revealed significant differences in microphysical processes occurring in the various meteorological regimes sampled in those projects. In TRMM-LMA (January-February 1999 in Brazil; a TRMM ground validation experiment), <span class="hlt">variability</span> is driven by prevailing low-level winds. During periods of low-level easterlies, deeper and more intense convection is <span class="hlt">observed</span>, while during periods of low-level westerlies, weaker convection embedded in widespread stratiform precipitation is common. In the NAME region (North American Monsoon Experiment, summer 2004 along the west coast of Mexico), strong terrain <span class="hlt">variability</span> drives differences in precipitation, with larger drops and larger ice mass aloft associated with convection occurring over the coastal plain compared to convection over the higher terrain of the Sierra Madre Occidental, or adjacent coastal waters. Comparisons with the TRMM precipitation radar (PR) indicate that such sub-seasonal <span class="hlt">variability</span> in these two regions are not well characterized by the TRMM PR reflectivity and rainfall statistics. TRMM PR reflectivity profiles in the LBA region are somewhat lower than S-Pol values, particularly in the more intense easterly regime convection. In NAME, mean reflectivities are even more divergent, with TRMM profiles below those of S-Pol. In both regions, the TRMM PR does not capture rain rates above 80 mm hr-1 despite much higher rain rates estimated from the S-Pol polarimetric data, and rain rates are generally lower for a given reflectivity from TRMM PR compared to S-Pol. These differences between TRMM PR and S-Pol may arise from the inability of Z-R relationships to capture the full <span class="hlt">variability</span> of microphysical conditions or may highlight problems with TRMM retrievals over land. In addition to the TRMM-LBA and NAME regions, analysis of sub-seasonal precipitation <span class="hlt">variability</span> and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711910C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711910C"><span id="translatedtitle"><span class="hlt">Observations</span> of changes in the dissolved CO2 system in the North Sea, in four summers of the 2001-2011 <span class="hlt">decade</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clargo, Nicola; Salt, Lesley; Thomas, Helmuth; de Baar, Hein</p> <p>2015-04-01</p> <p>Since the industrial revolution, atmospheric concentrations of carbon dioxide (CO2) have risen dramatically, largely due to the combustion of fossil fuels, changes in land-use patterns and the production of cement. The oceans have absorbed a large amount of this CO2, with resulting impacts on ocean chemistry. Coastal seas play a significant role in the mitigation of anthropogenic atmospheric CO2 as they contribute approximately 10-30% of global primary productivity despite accounting for only 7% of the surface area. The North Sea is a perfect natural laboratory in which to study the CO2 system as it consists of two biogeochemically distinct regions displaying both oceanic and relatively coastal behaviour. It has also been identified as a continental shelf pump with respect to CO2, transporting it to the deeper waters of the North Atlantic. Large scale forcing has been shown to have a significant impact on the CO2 system over varying time scales, often masking the effects of anthropogenic influence. Here, we present data from the North Sea spanning the 2001-2011 <span class="hlt">decade</span>. In order to investigate the dynamics of the dissolved CO2 system in this region in the face of climate change, four basin-wide cruises were conducted during the summers of 2001, 2005, 2008 and 2011. The acquired Dissolved Inorganic Carbon (DIC) and alkalinity data were then used to fully resolve the carbon system in order to assess trends over the 2001-2011 <span class="hlt">decade</span>. We find significant interannual <span class="hlt">variability</span>, but with a consistent, notable trend in decreasing pH. We found that surface alkalinity remained relatively constant over the <span class="hlt">decade</span>, whereas DIC increased, indicating that the pH decline is DIC-driven. We also found that the partial pressure of CO2 (pCO2) increased faster than concurrent atmospheric CO2 concentrations, and that the CO2 buffering capacity of the North Sea decreased over the <span class="hlt">decade</span>, with implications for future CO2 uptake.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.A33G..01R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.A33G..01R"><span id="translatedtitle">Outcomes of an International Coordination Workshop to Understand Aerosol <span class="hlt">Observability</span> Capabilities and Requirements for the Next <span class="hlt">Decade</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reid, J. S.; Benedetti, A.; Colarco, P. R.; Carmichael, G. R.; Icap Team</p> <p>2010-12-01</p> <p>In late April 2010 roughly 15 developers for many of the world’s operational numerical weather prediction centers with aerosol forecasting mandates met with an equal number of representatives of satellite data providers to discuss aerosol <span class="hlt">observability</span> issues facing the next generation of aerosol forecast and modeling systems. While the last 3 years has seen rapid operational implementation of aerosol and pollution models around the world, the key to further development of these models is aerosol <span class="hlt">observational</span> data from satellites for model evaluation and data assimilation. However, while the dynamical meteorology community has a well developed near real-time <span class="hlt">observing</span> system to support forecasting, the aerosol community is only beginning to address the problem. This meeting was the first ever to combine the lead aerosol developers and remote sensing data providers from around the globe in discussing state-of-the-art technologies and operational requirements for aerosol forecasting. Participants included: operational centers representatives of ECMWF, FNMOC, JMA, NCEP, and UKMO; remote sensing data providers from EUMETSAT, ESA, JAXA, NASA, and NOAA NESDIS; and additional developers from NASA GMAO, NGST, NOAA, NRL, and several universities. Indeed, the smooth transition from the NASA EOS/A-Train into the international constellation of multi-model, multi-sensor products which satisfy both research and operational communities will require coordination among all of the above participants. In this paper, we provide an overview of important meeting outcomes that should interest the broader atmospheric composition community, including an overview of future satellite and ground systems and their capabilities, key definitions of operational diction, desires for error metrics, specialized product development, and customer outreach and research product delivery. These outcomes are already effecting CONOPS at major data and forecasting sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AnGeo..34..801H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AnGeo..34..801H"><span id="translatedtitle">Ozone and temperature <span class="hlt">decadal</span> responses to solar <span class="hlt">variability</span> in the stratosphere and lower mesosphere, based on measurements from SABER on TIMED</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Frank T.; Mayr, Hans G.; Russell, James M., III; Mlynczak, Martin G.</p> <p>2016-09-01</p> <p>We have derived ozone and temperature responses to solar <span class="hlt">variability</span> over a solar cycle, from 2002 to 2014 at 20-60 km and 48° S-48° N, based on data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. Simultaneous results for ozone and temperature with this kind of spatial coverage have not been previously available, and they provide the opportunity to study correlations between ozone and temperature responses. In previous studies, there has not been general agreement on the details or, at times, even the broad behavior of the responses to <span class="hlt">decadal</span> solar <span class="hlt">variability</span>. New results from a different dataset should supply new information on this important and interesting subject. A multiple regression is applied to obtain responses as a function of the solar 10.7 cm flux. Positive responses mean that they are larger at solar maximum than at solar minimum of the solar cycle. Both ozone and temperature responses are found be positive or negative, depending on location. Generally, from ˜ 25 to 60 km, the ozone and temperature responses are mostly out of phase (negatively correlated) with each other as a function of solar <span class="hlt">variability</span>, with some exceptions in the lower altitudes. These negative correlations are maintained even though the individual ozone (temperature) responses can change signs as a function of altitude and latitude, because the corresponding temperature (ozone) responses change signs in step with each other. From ˜ 50 to 60 km, ozone responses are relatively small, varying from ˜ -1 to ˜ 2 % 100 sfu-1 (solar flux units), while temperature responses can approach ˜ 2 °K 100 sfu-1. From ˜ 25 to ˜ 40 km, the ozone responses have become mostly positive at all latitudes and approach a maximum of ˜ 5 % 100 sfu-1 near the Equator and ˜ 30-35 km. In contrast, at low latitudes, the temperature responses have become negative but also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713144M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713144M"><span id="translatedtitle"><span class="hlt">Decadal</span>- to biennial scale <span class="hlt">variability</span> of planktic foraminifera in the northeastern Arabian Sea during the last two millennia: evidence for winter monsoon forcing mechanisms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Munz, Philipp; Lückge, Andreas; Siccha, Michael; Kucera, Michal; Schulz, Hartmut</p> <p>2015-04-01</p> <p>The Asian monsoon system is controlling the hydrologic cycle, and thus the agricultural and economic prosperity of the worlds most densely populated region. Strong and moisture-laden winds from the southwest induce upwelling and significant productivity in the western Arabian Sea during boreal summer. During boreal winter, weaker dry and cold surface winds from the northeast nourish ocean productivity mainly in the northeastern Arabian Sea. Instrumental records spanning the last century are too short to understand how the monsoon system reacts to external forcing mechanisms and to accurately determine its natural <span class="hlt">variability</span>. Compared to the summer monsoon component, the dynamics of the winter monsoon are virtually unknown, due to the lack of adequate archives that are affected only by winter conditions. Here we present a <span class="hlt">decadal</span>- to biennial-scale resolution record of past winter monsoon <span class="hlt">variability</span> over the last two millennia, based on census counts of planktic foraminifera from two laminated sediment cores collected offshore Pakistan. One shorter box core (SO90-39KG) spans the last 250 years with an average ~2-year resolution, whereas the longer piston core (SO130-275KL) spans the last 2,100 years with a 10-year resolution. We use Globigerina falconensis as a faunal indicator for winter conditions, a species that is most abundant during winter in the NE Arabian Sea (Peeters and Brummer, 2002; Schulz et al., 2002). Our results show that during the past 2,100 years G. falconensis varied with significant periodicities centered on ˜ 60, ˜ 53, ˜ 40, ˜ 34 and ˜ 29 years per cycle. Some of these periods closely match cycles that are known from proxy records of solar irradiance, suggesting a solar forcing on winter monsoon <span class="hlt">variability</span>. During the past 250 years G. falconensis varied in correlation with the (11-year) Schwabe and the (22-year) Hale solar cycles. Furthermore, a significant ˜ 7 year cyclicity could indicate a teleconnection to the El Niño Southern</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22810602K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22810602K"><span id="translatedtitle">The American Association of <span class="hlt">Variable</span> Star <span class="hlt">Observers</span> as a Professional-Amateur Astronomical Community of practice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kafka, Stella; 6173540484</p> <p>2016-06-01</p> <p>The AAVSO was formed in 1911 as a group of US-based amateur <span class="hlt">observers</span> obtaining data in support of professional astronomy projects. Now, it has evolved into an International Organization with members and <span class="hlt">observers</span> in all continents, contributing photometry to a public database of about 22,000 <span class="hlt">variable</span> objects. I will present main aspects of the association and how it has evolved with time to a premium resource for <span class="hlt">variable</span> star research. I will also discuss current projects and opportunities for Professional-Amateur collaborations within the AAVSO, building a stronger international community of <span class="hlt">variable</span> star <span class="hlt">observers</span>!</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApJ...762...60S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApJ...762...60S"><span id="translatedtitle">A <span class="hlt">Decade</span> of Solar Type III Radio Bursts <span class="hlt">Observed</span> by the Nançay Radioheliograph 1998-2008</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saint-Hilaire, P.; Vilmer, N.; Kerdraon, A.</p> <p>2013-01-01</p> <p>We present a statistical survey of almost 10,000 radio type III bursts <span class="hlt">observed</span> by the Nançay Radioheliograph from 1998 to 2008, covering nearly a full solar cycle. In particular, sources sizes, positions, and fluxes were examined. We find an east-west asymmetry in source positions that could be attributed to a 6° ± 1° eastward tilt of the magnetic field, that source FWHM sizes s roughly follow a solar-cycle-averaged distribution (dN/ds) ≈ 14 ν-3.3 s -4 arcmin-1 day-1, and that source fluxes closely follow a solar-cycle-averaged (dN/ds ν) ≈ 0.34 ν-2.9 S -1.7 ν sfu-1 day-1 distribution (when ν is in GHz, s in arcminutes, and S ν in sfu). Fitting a barometric density profile yields a temperature of 0.6 MK, while a solar wind-like (vproph -2) density profile yields a density of 1.2 × 106 cm-3 at an altitude of 1 RS , assuming harmonic emission. Finally, we found that the solar-cycle-averaged radiated type III energy could be similar in magnitude to that radiated by nanoflares via non-thermal bremsstrahlung processes, and we hint at the possibility that escaping electron beams might carry as much energy away from the corona as is introduced into it by accelerated nanoflare electrons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3739040','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3739040"><span id="translatedtitle">Improvements in <span class="hlt">observed</span> and relative survival in follicular grade 1-2 lymphoma during 4 <span class="hlt">decades</span>: the Stanford University experience</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tan, Daryl; Horning, Sandra J.; Hoppe, Richard T.; Levy, Ronald; Rosenberg, Saul A.; Sigal, Bronislava M.; Warnke, Roger A.; Natkunam, Yasodha; Han, Summer S.; Yuen, Alan; Plevritis, Sylvia K.</p> <p>2013-01-01</p> <p>Recent studies report an improvement in overall survival (OS) of patients with follicular lymphoma (FL). Previously untreated patients with grade 1 to 2 FL treated at Stanford University from 1960-2003 were identified. Four eras were considered: era 1, pre-anthracycline (1960-1975, n = 180); era 2, anthracycline (1976-1986, n = 426); era 3, aggressive chemotherapy/purine analogs (1987-1996, n = 471); and era 4, rituximab (1997-2003, n = 257). Clinical characteristics, patterns of care, and survival were assessed. <span class="hlt">Observed</span> OS was compared with the expected OS calculated from Berkeley Mortality Database life tables derived from population matched by gender and age at the time of diagnosis. The median OS was 13.6 years. Age, gender, and stage did not differ across the eras. Although primary treatment varied, event-free survival after the first treatment did not differ between eras (P = .17). Median OS improved from 11 years in eras 1 and 2 to 18.4 years in era 3 and has not yet been reached for era 4 (P < .001), with no suggestion of a plateau in any era. These improvements in OS exceeded improvements in survival in the general population during the same period. Several factors, including better supportive care and effective therapies for relapsed disease, are likely responsible for this improvement. PMID:23777769</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990MNRAS.242P...9M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990MNRAS.242P...9M"><span id="translatedtitle">WHT <span class="hlt">observations</span> of cataclysmic <span class="hlt">variables</span> in globular clusters. II - The CV candidates in M71</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Machin, G.; Allington-Smith, J.; Callanan, P. J.; Charles, P. A.; Hassall, B. J. M.; Mason, K. O.; Mukai, K.; Naylor, T.; Smale, A. P.; van Paradijs, J.</p> <p>1990-01-01</p> <p>Results are presented from photometric and spectroscopic <span class="hlt">observations</span> of the six UV-bright objects in M71 which Richer and Fahlman (1988) proposed as candidate cataclysmic <span class="hlt">variables</span>. It is found that the two brightest of these candidates are probably hot subdwarfs. It is suggested that the remaining candidates are more likely to be white dwarfs and subdwarfs than cataclysmic <span class="hlt">variables</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=logistic+AND+regression+AND+model&pg=5&id=EJ733800','ERIC'); return false;" href="http://eric.ed.gov/?q=logistic+AND+regression+AND+model&pg=5&id=EJ733800"><span id="translatedtitle">Mixed-Effects Logistic Regression Models for Indirectly <span class="hlt">Observed</span> Discrete Outcome <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Vermunt, Jeroen K.</p> <p>2005-01-01</p> <p>A well-established approach to modeling clustered data introduces random effects in the model of interest. Mixed-effects logistic regression models can be used to predict discrete outcome <span class="hlt">variables</span> when <span class="hlt">observations</span> are correlated. An extension of the mixed-effects logistic regression model is presented in which the dependent <span class="hlt">variable</span> is a latent…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.2980H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.2980H"><span id="translatedtitle">Geodetic <span class="hlt">observations</span> of postseismic creep in the <span class="hlt">decade</span> after the 1999 Izmit earthquake, Turkey: Implications for a shallow slip deficit</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hussain, Ekbal; Wright, Tim J.; Walters, Richard J.; Bekaert, David; Hooper, Andrew; Houseman, Gregory A.</p> <p>2016-04-01</p> <p>The relationship between aseismic slip and tectonic loading is important for understanding both the pattern of strain accumulation along a fault and its ability to generate large earthquakes. We investigate the spatial distribution and temporal evolution of aseismic creep on the western North Anatolian Fault (NAF) using time series analysis of Envisat interferometric synthetic aperture radar (InSAR) data, covering the full extent of the 1999 Izmit and Düzce earthquake ruptures and spanning 2002-2010. Discontinuities in the line-of-sight velocity across the fault imply that fault creep reaches the Earth's surface at an average fault-parallel rate of ˜5 mm/yr along an ˜80 km section of the NAF. By combining InSAR and published GPS velocities, we are able to extract the vertical and east-west components of motion and show that the Adapazari basin is subsiding at a rate of ˜6 mm/yr. Vertical motions have biased previous estimates of creep in this region. The displacement time series close to the fault is consistent with an afterslip model based on rate-and-state friction, which predicts a rapid deceleration in fault creep rate after the Izmit earthquake to a near-steady state ˜5 mm/yr after 5 years. Projecting our model 200 years into the future we find that the cumulative displacement of 1-1.3 m is insufficient to account for the shallow coseismic slip deficit <span class="hlt">observed</span> in previous studies. Distributed off-fault deformation in the shallow crust or transient episodes of faster slip are likely required to release some of the long-term strain during the earthquake cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006625','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006625"><span id="translatedtitle">Nearly a <span class="hlt">Decade</span> of CALIPSO <span class="hlt">Observations</span> of Asian and Saharan Dust Properties Near Source and Transport Regions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Omar, Ali H.; Liu, Z.; Tackett, J.; Vaughan, M.; Trepte, C.; Winker, D.; H. Yu,</p> <p>2015-01-01</p> <p>The lidar on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite <span class="hlt">Observations</span> (CALIPSO) mission, makes robust measurements of dust and has generated a length of record that is significant both seasonally and inter-annually. We exploit this record to determine a multi-year climatology of the properties of Asian and Saharan dust, in particular seasonal optical depths, layer frequencies, and layer heights of dust gridded in accordance with the Level 3 data products protocol, between 2006-2015. The data are screened using standard CALIPSO quality assurance flags, cloud aerosol discrimination (CAD) scores, overlying features and layer properties. To evaluate the effects of transport on the morphology, vertical extent and size of the dust layers, we compare probability distribution functions of the layer integrated volume depolarization ratios, geometric depths and integrated attenuated color ratios near the source to the same distributions in the far field or transport region. CALIPSO is collaboration between NASA and Centre National D'études Spatiales (CNES), was launched in April 2006 to provide vertically resolved measurements of cloud and aerosol distributions. The primary instrument on the CALIPSO satellite is the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), a near-nadir viewing two-wavelength polarization-sensitive instrument. The unique nature of CALIOP measurements make it quite challenging to validate backscatter profiles, aerosol type, and cloud phase, all of which are used to retrieve extinction and optical depth. To evaluate the uncertainty in the lidar ratios, we compare the values computed from dust layers overlying opaque water clouds, considered nominal, with the constant lidar ratio value used in the CALIOP algorithms for dust. We also explore the effects of noise on the CALIOP retrievals at daytime by comparing the distributions of the properties at daytime to the nighttime distributions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A52F..08O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A52F..08O"><span id="translatedtitle">Nearly a <span class="hlt">Decade</span> of CALIPSO <span class="hlt">Observations</span> of Asian and Saharan Dust Properties near Source and Transport Regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Omar, A. H.; Tackett, J. L.; Liu, Z.; Vaughan, M. A.; Trepte, C. R.; Winker, D. M.; Yu, H.</p> <p>2015-12-01</p> <p>The lidar on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite <span class="hlt">Observations</span> (CALIPSO) mission, makes robust measurements of dust and has generated a length of record that is significant both seasonally and inter-annually. We exploit this record to determine a multi-year climatology of the properties of Asian and Saharan dust, in particular seasonal optical depths, layer frequencies, and layer heights of dust gridded in accordance with the Level 3 data products protocol between 2006 and 2015. The data are screened using standard CALIPSO quality assurance flags, cloud aerosol discrimination (CAD) scores, overlying features and layer properties. To evaluate the effects of transport on small-scale phenomena such as morphology, vertical extent and size of the dust layers, we compare probability distribution functions of the layer integrated volume depolarization ratios, geometric depths and integrated attenuated color ratios near the source to the same distributions in the far field or transport region. CALIPSO is collaboration between NASA and Centre National d'Études Spatiales (CNES), was launched in April 2006 to provide vertically resolved measurements of cloud and aerosol distributions. The primary instrument on the CALIPSO satellite is the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), a near-nadir viewing two-wavelength polarization-sensitive instrument. The unique nature of CALIOP measurements make it quite challenging to validate backscatter profiles, aerosol type, and cloud phase, all of which are used to retrieve extinction and optical depth. To evaluate the uncertainty in the lidar ratios, we compare the values computed from dust layers overlying opaque water clouds, considered nominal, with the constant lidar ratio value used in the CALIOP algorithms for dust. We also explore the effects of noise on the CALIOP retrievals at daytime by comparing the distributions of the properties at daytime to the nighttime distributions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140016841','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140016841"><span id="translatedtitle">Source Parameter Inversion for Recent Great Earthquakes from a <span class="hlt">Decade</span>-long <span class="hlt">Observation</span> of Global Gravity Fields</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Han, Shin-Chan; Riva, Ricccardo; Sauber, Jeanne; Okal, Emile</p> <p>2013-01-01</p> <p>We quantify gravity changes after great earthquakes present within the 10 year long time series of monthly Gravity Recovery and Climate Experiment (GRACE) gravity fields. Using spherical harmonic normal-mode formulation, the respective source parameters of moment tensor and double-couple were estimated. For the 2004 Sumatra-Andaman earthquake, the gravity data indicate a composite moment of 1.2x10(exp 23)Nm with a dip of 10deg, in agreement with the estimate obtained at ultralong seismic periods. For the 2010 Maule earthquake, the GRACE solutions range from 2.0 to 2.7x10(exp 22)Nm for dips of 12deg-24deg and centroid depths within the lower crust. For the 2011 Tohoku-Oki earthquake, the estimated scalar moments range from 4.1 to 6.1x10(exp 22)Nm, with dips of 9deg-19deg and centroid depths within the lower crust. For the 2012 Indian Ocean strike-slip earthquakes, the gravity data delineate a composite moment of 1.9x10(exp 22)Nm regardless of the centroid depth, comparing favorably with the total moment of the main ruptures and aftershocks. The smallest event we successfully analyzed with GRACE was the 2007 Bengkulu earthquake with M(sub 0) approx. 5.0x10(exp 21)Nm. We found that the gravity data constrain the focal mechanism with the centroid only within the upper and lower crustal layers for thrust events. Deeper sources (i.e., in the upper mantle) could not reproduce the gravity <span class="hlt">observation</span> as the larger rigidity and bulk modulus at mantle depths inhibit the interior from changing its volume, thus reducing the negative gravity component. Focal mechanisms and seismic moments obtained in this study represent the behavior of the sources on temporal and spatial scales exceeding the seismic and geodetic spectrum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1087698','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1087698"><span id="translatedtitle"><span class="hlt">Observed</span> Multi-<span class="hlt">Decade</span> DD and DT Z-Pinch Fusion Rate Scaling in 5 Dense Plasma Focus Fusion Machines</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hagen, E. C.; Lowe, D. R.; O'Brien, R.; Meehan, B. T.</p> <p>2013-06-18</p> <p>Dense Plasma Focus (DPF) machines are in use worldwide or a wide variety of applications; one of these is to produce intense, short bursts of fusion via r-Z pinch heating and compression of a working gas. We have designed and constructed a series of these, ranging from portable to a maximum energy storage capacity of 2 MJ. Fusion rates from 5 DPF pulsed fusion generators have been measured in a single laboratory using calibrated activation detectors. Measured rates range from ~ 1015 to more than 1019 fusions per second have been measured. Fusion rates from the intense short (20 – 50 ns) periods of production were inferred from measurement of neutron production using both calibrated activation detectors and scintillator-PMT neutron time of flight (NTOF) detectors. The NTOF detectors are arranged to measure neutrons versus time over flight paths of 30 Meters. Fusion rate scaling versus energy and current will be discussed. Data showing <span class="hlt">observed</span> fusion cutoff at D-D fusion yield levels of approximately 1*1012, and corresponding tube currents of ~ 3 MA will be shown. Energy asymmetry of product neutrons will also be discussed. Data from the NTOF lines of sight have been used to measure energy asymmetries of the fusion neutrons. From this, center of mass energies for the D(d,n)3He reaction are inferred. A novel re-entrant chamber that allows extremely high single pulse neutron doses (> 109 neutrons/cm2 in 50 ns) to be supplied to samples will be described. Machine characteristics and detector types will be discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3703F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3703F"><span id="translatedtitle">Assessing the vulnerability of economic sectors to climate <span class="hlt">variability</span> to improve the usability of seasonal to <span class="hlt">decadal</span> climate forecasts in Europe - a preliminary concept</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Funk, Daniel</p> <p>2015-04-01</p> <p>Climate <span class="hlt">variability</span> poses major challenges for decision-makers in climate-sensitive sectors. Seasonal to <span class="hlt">decadal</span> (S2D) forecasts provide potential value for management decisions especially in the context of climate change where information from present or past climatology loses significance. However, usable and decision-relevant tailored climate forecasts are still sparse for Europe and successful examples of application require elaborate and individual producer-user interaction. The assessment of sector-specific vulnerabilities to critical climate conditions at specific temporal scale will be a great step forward to increase the usability and efficiency of climate forecasts. A concept for a sector-specific vulnerability assessment (VA) to climate <span class="hlt">variability</span> is presented. The focus of this VA is on the provision of usable vulnerability information which can be directly incorporated in decision-making processes. This is done by developing sector-specific climate-impact-decision-pathways and the identification of their specific time frames using data from both bottom-up and top-down approaches. The structure of common VA's for climate change related issues is adopted which envisages the determination of exposure, sensitivity and coping capacity. However, the application of the common vulnerability components within the context of climate service application poses some fundamental considerations: Exposure - the effect of climate events on the system of concern may be modified and delayed due to interconnected systems (e.g. catchment). The critical time-frame of a climate event or event sequence is dependent on system-internal thresholds and initial conditions. But also on decision-making processes which require specific lead times of climate information to initiate respective coping measures. Sensitivity - in organizational systems climate may pose only one of many factors relevant for decision making. The scope of "sensitivity" in this concept comprises both the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP21D..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP21D..07C"><span id="translatedtitle"><span class="hlt">Decadal</span>-scale Climate <span class="hlt">Variability</span> on the Central Iranian Plateau Spanning the So-called 4.2 ka BP Drought Event</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carolin, S.; Walker, R. T.; Henderson, G. M.; Maxfield, L.; Ersek, V.; Sloan, A.; Talebian, M.; Fattahi, M.; Nezamdoust, J.</p> <p>2015-12-01</p> <p>The influence of climate on the growth and development of ancient civilizations throughout the Holocene remains a topic of heated debate. The 4.2 ka BP global-scale mid-to-low latitude aridification event (Walker et al., 2012) in particular has incited various correlation proposals. Some authors suggest that this event may have led to the collapse of the Akkadian empire in Mesopotamia, one of the first empires in human history, as well as to changes among other Early Bronze Age societies dependent on cereal agriculture (eg. Staubwasser and Weiss, 2006). Other authors remain doubtful of the impact of environmental factors on the collapse of past societies (eg. Middleton, 2012). While coincident timing of an environmental event with archeological evidence does not necessitate a causation, a comprehensive understanding of climate <span class="hlt">variability</span> in the ancient Near East is nonetheless an essential component to resolving the full history of early human settlements. Paleoclimate data on the Central Iranian Plateau, a region rich with ancient history, is exceptionally sparse compared to other areas. Many karst locations are found throughout the region, however, setting the stage for the development of several high-resolution, accurate and precisely-dated climate proxy records if a correlation between the chemistry of semi-arid speleothem samples and climate is resolved. Here we present a 5.1-3.7 ka BP record of <span class="hlt">decadal</span>-scale stalagmite stable isotope and trace metal <span class="hlt">variability</span>. The stalagmite was collected in Gol-e zard cave (35.8oN, 52.0oE), ~100 km NE of Tehran on the southern flank of the Alborz mountain range (2530masl). The area currently receives ~270mm mean annual precipitation, with more than 90% of precipitation falling within the wet season (November-May). We use GNIP data from Tehran and local and regional meteorological data to resolve the large-scale mechanisms forcing isotopic variations in rainwater over Gol-e zard cave. We discuss possible transformation of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMS...161...26C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMS...161...26C"><span id="translatedtitle">Developing priority <span class="hlt">variables</span> ("ecosystem Essential Ocean <span class="hlt">Variables</span>" - eEOVs) for <span class="hlt">observing</span> dynamics and change in Southern Ocean ecosystems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Constable, Andrew J.; Costa, Daniel P.; Schofield, Oscar; Newman, Louise; Urban, Edward R.; Fulton, Elizabeth A.; Melbourne-Thomas, Jessica; Ballerini, Tosca; Boyd, Philip W.; Brandt, Angelika; de la Mare, Willaim K.; Edwards, Martin; Eléaume, Marc; Emmerson, Louise; Fennel, Katja; Fielding, Sophie; Griffiths, Huw; Gutt, Julian; Hindell, Mark A.; Hofmann, Eileen E.; Jennings, Simon; La, Hyoung Sul; McCurdy, Andrea; Mitchell, B. Greg; Moltmann, Tim; Muelbert, Monica; Murphy, Eugene; Press, Anthony J.; Raymond, Ben; Reid, Keith; Reiss, Christian; Rice, Jake; Salter, Ian; Smith, David C.; Song, Sun; Southwell, Colin; Swadling, Kerrie M.; Van de Putte, Anton; Willis, Zdenka</p> <p>2016-09-01</p> <p>Reliable statements about <span class="hlt">variability</span> and change in marine ecosystems and their underlying causes are needed to report on their status and to guide management. Here we use the Framework on Ocean <span class="hlt">Observing</span> (FOO) to begin developing ecosystem Essential Ocean <span class="hlt">Variables</span> (eEOVs) for the Southern Ocean <span class="hlt">Observing</span> System (SOOS). An eEOV is a defined biological or ecological quantity, which is derived from field <span class="hlt">observations</span>, and which contributes significantly to assessments of Southern Ocean ecosystems. Here, assessments are concerned with estimating status and trends in ecosystem properties, attribution of trends to causes, and predicting future trajectories. eEOVs should be feasible to collect at appropriate spatial and temporal scales and are useful to the extent that they contribute to direct estimation of trends and/or attribution, and/or development of ecological (statistical or simulation) models to support assessments. In this paper we outline the rationale, including establishing a set of criteria, for selecting eEOVs for the SOOS and develop a list of candidate eEOVs for further evaluation. Other than habitat <span class="hlt">variables</span>, nine types of eEOVs for Southern Ocean taxa are identified within three classes: state (magnitude, genetic/species, size spectrum), predator-prey (diet, foraging range), and autecology (phenology, reproductive rate, individual growth rate, detritus). Most candidates for the suite of Southern Ocean taxa relate to state or diet. Candidate autecological eEOVs have not been developed other than for marine mammals and birds. We consider some of the spatial and temporal issues that will influence the adoption and use of eEOVs in an <span class="hlt">observing</span> system in the Southern Ocean, noting that existing operations and platforms potentially provide coverage of the four main sectors of the region - the East and West Pacific, Atlantic and Indian. Lastly, we discuss the importance of simulation modelling in helping with the design of the <span class="hlt">observing</span> system in the long</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1211601','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1211601"><span id="translatedtitle">Amplitude <span class="hlt">Variability</span> in gamma Dor and delta Sct Stars <span class="hlt">Observed</span> by Kepler</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Guzik, Joyce Ann; Kosak, Mary Katherine; Bradley, Paul Andrew; Jackiewicz, Jason</p> <p>2015-08-17</p> <p>The NASA Kepler spacecraft data revealed a large number of new multimode nonradially pulsating gamma Dor and delta Sct <span class="hlt">variable</span> stars. The Kepler high-precision long time-series photometry makes it possible to study amplitude variations of the frequencies, and recent literature on amplitude and frequency variations in nonradially pulsating <span class="hlt">variables</span> is summarized. Several methods are applied to study amplitude <span class="hlt">variability</span> in about a dozen gamma Doradus or delta Scuti candidate <span class="hlt">variable</span> stars <span class="hlt">observed</span> for several quarters as part of the Kepler Guest <span class="hlt">Observer</span> program. The magnitude and timescale of the amplitude variations are discussed, along with the presence or absence of correlations between amplitude variations for different frequencies of a given star. Proposed causes of amplitude spectrum <span class="hlt">variability</span> that will require further investigation are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20080032403&hterms=Io&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DIo','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20080032403&hterms=Io&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DIo"><span id="translatedtitle">Cassini UVIS <span class="hlt">Observations</span> of the Io Plasma Torus. 3; <span class="hlt">Observations</span> of Temporal and Azimuthal <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Steffl, A. J.; Delamere, P. A.; Bagenal, F.</p> <p>2006-01-01</p> <p>In this third paper in a series presenting <span class="hlt">observations</span> by the Cassini Ultraviolet Imaging Spectrometer (UVIS) of the Io plasma torus, we show remarkable, though subtle, spatio-temporal variations in torus properties. The Io torus is found to exhibit significant, near sinusoidal variations in ion composition as a functions of azimuthal position. The azimuthal variation in composition is such that the mixing ratio of S II us strongly correlated with the mixing ratio of S III and the equatorial electron density and strongly anti-correlated with the mixing ratios of both S IV and O II and the equatorial electron temperature. Surprisingly, the azimuthal variation in ion composition is <span class="hlt">observed</span> to have a period of 10.07 h -- 1.5% longer than the System III rotation period of Jupiter, yet 1.3% shorter than the System UV period defined by [Brown, M. E., 1995. J. Geophys. Res. 100, 21683-21696]. Although the amplitude of the azimuthal variation of S III and O II remained in the range of 2-5%, the amplitude of the S II and S IV compositional variation ranged between 5 and 25% during the UVIS <span class="hlt">observations</span>. Furthermore, the amplitude of the azimuthal variations of S II and S IV appears to be modulated by its location in System III longitude, such that when the region of maximum S II mixing ration (minimum S IV mixing ratio) is aligned with a System III longitude of 200 deg +/-, the amplitude is a factor of 4 greater than when the variation is anti-aligned. This behavior can explain numerous, often apparently contradictory, <span class="hlt">observations</span> of variations in the properties of the Io plasma torus with the System III and System IV coordinate systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26245870','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26245870"><span id="translatedtitle">Spatial <span class="hlt">variability</span> of the dose rate from (137)Cs fallout in settlements in Russia and Belarus more than two <span class="hlt">decades</span> after the Chernobyl accident.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bernhardsson, C; Rääf, C L; Mattsson, S</p> <p>2015-11-01</p> <p>Radionuclides from the 1986 Chernobyl accident were released and dispersed during a limited period of time, but under widely varying weather conditions. As a result, there was a high geographical variation in the deposited radioactive fallout per unit area over Europe, depending on the released composition of fission products and the weather during the 10 days of releases. If the plume from Chernobyl coincided with rain, then the radionuclides were unevenly distributed on the ground. However, large variations in the initial fallout also occurred locally or even on a meter scale. Over the ensuing years the initial deposition may have been altered further by different weathering processes or human activities such as agriculture, gardening, and decontamination measures. Using measurements taken more than two <span class="hlt">decades</span> after the accident, we report on the inhomogeneous distribution of the ground deposition of the fission product (137)Cs and its influence on the dose rate 1 m above ground, on both large and small scales (10ths of km(2) - 1 m(2)), in the Gomel-Bryansk area close to the border between Belarus and Russia. The dose rate from the deposition was <span class="hlt">observed</span> to vary by one order of magnitude depending on the size of the area considered, whether human processes were applied to the surface or not, and on location specific properties (e.g. radionuclide migration in soil). PMID:26245870</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26245870','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26245870"><span id="translatedtitle">Spatial <span class="hlt">variability</span> of the dose rate from (137)Cs fallout in settlements in Russia and Belarus more than two <span class="hlt">decades</span> after the Chernobyl accident.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bernhardsson, C; Rääf, C L; Mattsson, S</p> <p>2015-11-01</p> <p>Radionuclides from the 1986 Chernobyl accident were released and dispersed during a limited period of time, but under widely varying weather conditions. As a result, there was a high geographical variation in the deposited radioactive fallout per unit area over Europe, depending on the released composition of fission products and the weather during the 10 days of releases. If the plume from Chernobyl coincided with rain, then the radionuclides were unevenly distributed on the ground. However, large variations in the initial fallout also occurred locally or even on a meter scale. Over the ensuing years the initial deposition may have been altered further by different weathering processes or human activities such as agriculture, gardening, and decontamination measures. Using measurements taken more than two <span class="hlt">decades</span> after the accident, we report on the inhomogeneous distribution of the ground deposition of the fission product (137)Cs and its influence on the dose rate 1 m above ground, on both large and small scales (10ths of km(2) - 1 m(2)), in the Gomel-Bryansk area close to the border between Belarus and Russia. The dose rate from the deposition was <span class="hlt">observed</span> to vary by one order of magnitude depending on the size of the area considered, whether human processes were applied to the surface or not, and on location specific properties (e.g. radionuclide migration in soil).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JVGR..289...51W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JVGR..289...51W"><span id="translatedtitle"><span class="hlt">Decadal</span>-scale <span class="hlt">variability</span> of diffuse CO2 emissions and seismicity revealed from long-term monitoring (1995-2013) at Mammoth Mountain, California, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Werner, Cynthia; Bergfeld, Deborah; Farrar, Christopher D.; Doukas, Michael P.; Kelly, Peter J.; Kern, Christoph</p> <p>2014-12-01</p> <p>Mammoth Mountain, California, is a dacitic volcano that has experienced several periods of unrest since 1989. The onset of diffuse soil CO2 emissions at numerous locations on the flanks of the volcano began in 1989-1990 following an 11-month period of heightened seismicity. CO2 emission rates were measured yearly from 1995 to 2013 at Horseshoe Lake (HSL), the largest tree kill area on Mammoth Mountain, and measured intermittently at four smaller degassing areas around Mammoth from 2006 to 2013. The long-term record at HSL shows <span class="hlt">decadal</span>-scale variations in CO2 emissions with two peaks in 2000-2001 and 2011-2012, both of which follow peaks in seismicity by 2-3 years. Between 2000 and 2004 emissions gradually declined during a seismically quiet period, and from 2004 to 2009 were steady at ~ 100 metric tonnes per day (t d- 1). CO2 emissions at the four smaller tree-kill areas also increased by factors of 2-3 between 2006 and 2011-2012, demonstrating a mountain-wide increase in degassing. Delays between the peaks in seismicity and degassing have been <span class="hlt">observed</span> at other volcanic and hydrothermal areas worldwide, and are thought to result from an injection of deep CO2-rich fluid into shallow subsurface reservoirs causing a pressurization event with a delayed transport to the surface. Such processes are consistent with previous studies at Mammoth, and here we highlight (1) the mountain-wide response, (2) the characteristic delay of 2-3 years, and (3) the roughly <span class="hlt">decadal</span> reoccurrence interval for such behavior. Our best estimate of total CO2 degassing from Mammoth Mountain was 416 t d- 1 in 2011 during the peak of emissions, over half of which was emitted from HSL. The cumulative release of CO2 between 1995 and 2013 from diffuse emissions is estimated to be ~ 2-3 Mt, and extrapolation back to 1989 gives ~ 4.8 Mt. This amount of CO2 release is similar to that produced by the mid-sized (VEI 3) 2009 eruption of Redoubt Volcano in Alaska (~ 2.3 Mt over 11 months), and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APh....80....8G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APh....80....8G"><span id="translatedtitle">Optimal strategies for <span class="hlt">observation</span> of active galactic nuclei <span class="hlt">variability</span> with Imaging Atmospheric Cherenkov Telescopes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giomi, Matteo; Gerard, Lucie; Maier, Gernot</p> <p>2016-07-01</p> <p><span class="hlt">Variable</span> emission is one of the defining characteristic of active galactic nuclei (AGN). While providing precious information on the nature and physics of the sources, <span class="hlt">variability</span> is often challenging to <span class="hlt">observe</span> with time- and field-of-view-limited astronomical observatories such as Imaging Atmospheric Cherenkov Telescopes (IACTs). In this work, we address two questions relevant for the <span class="hlt">observation</span> of sources characterized by AGN-like <span class="hlt">variability</span>: what is the most time-efficient way to detect such sources, and what is the <span class="hlt">observational</span> bias that can be introduced by the choice of the <span class="hlt">observing</span> strategy when conducting blind surveys of the sky. Different <span class="hlt">observing</span> strategies are evaluated using simulated light curves and realistic instrument response functions of the Cherenkov Telescope Array (CTA), a future gamma-ray observatory. We show that strategies that makes use of very small <span class="hlt">observing</span> windows, spread over large periods of time, allows for a faster detection of the source, and are less influenced by the <span class="hlt">variability</span> properties of the sources, as compared to strategies that concentrate the <span class="hlt">observing</span> time in a small number of large <span class="hlt">observing</span> windows. Although derived using CTA as an example, our conclusions are conceptually valid for any IACTs facility, and in general, to all observatories with small field of view and limited duty cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3570187','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3570187"><span id="translatedtitle">Inter-<span class="hlt">observer</span> and intra-<span class="hlt">observer</span> <span class="hlt">variability</span> in immunohistochemical detection of endometrial stromal plasmacytes in chronic endometritis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>KITAYA, KOTARO; YASUO, TADAHIRO</p> <p>2013-01-01</p> <p>Chronic endometritis (CE) is an unusual endometrial inflammation characterized by stromal plasmacyte infiltration. CE is easily missed due to its subtle symptoms and demanding histopathological examinations. Although the immunohistochemistry for the plasmacyte marker CD138 has facilitated the detection of endometrial stromal plasmacytes, the accuracy and biases of this method for CE diagnosis remain poorly understood. The aim of this study was to investigate the inter- and intra-<span class="hlt">observer</span> <span class="hlt">variability</span> in the immunohistochemical detection of stromal plasmacytes in the human endometrium. A total of 80 CE and 20 non-pathological archival hematoxylin-stained endometrial preparations with or without immunostaining for CD138 were evaluated independently by two experienced <span class="hlt">observers</span> and two inexperienced <span class="hlt">observers</span>. Endometrial stromal plasmacytes in unit areas were counted in the hematoxylin-stained and CD138-immunostained preparations. Each preparation was subdivided into 11 categories by every five plasmacyte counts. The second evaluation was performed four weeks after the first evaluation. The immunohistochemical detection method was superior to conventional histopathological evaluation in both the inter- and intra-<span class="hlt">observer</span> agreement, irrespective of the experience level of the <span class="hlt">observers</span>. The linear weighted κ coefficient for intra-<span class="hlt">observer</span> agreement was higher in the experienced <span class="hlt">observers</span> than in the inexperienced <span class="hlt">observers</span>. The inter-<span class="hlt">observer</span> agreement among the four <span class="hlt">observers</span> by the immunohistochemical detection method was similarly good between the first and second evaluation. There was no significant inter- or intra-<span class="hlt">observer</span> <span class="hlt">variability</span> in the paired comparison of the individual samples. These findings validate the use of immunohistochemistry for CD138 as an accurate and less biased diagnostic tool for CE. PMID:23407614</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009CoAst.160....2L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009CoAst.160....2L&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Observations</span> of candidate oscillating eclipsing binaries and two newly discovered pulsating <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liakos, A.; Niarchos, P.</p> <p>2009-03-01</p> <p>CCD <span class="hlt">observations</span> of 24 eclipsing binary systems with spectral types ranging between A0-F0, candidate for containing pulsating components, were obtained. Appropriate exposure times in one or more photometric filters were used so that short-periodic pulsations could be detected. Their light curves were analyzed using the Period04 software in order to search for pulsational behaviour. Two new <span class="hlt">variable</span> stars, namely GSC 2673-1583 and GSC 3641-0359, were discov- ered as by-product during the <span class="hlt">observations</span> of eclipsing <span class="hlt">variables</span>. The Fourier analysis of the <span class="hlt">observations</span> of each star, the dominant pulsation frequencies and the derived frequency spectra are also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8041M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8041M"><span id="translatedtitle">Volcanic forcing in <span class="hlt">decadal</span> forecasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ménégoz, Martin; Doblas-Reyes, Francisco; Guemas, Virginie; Asif, Muhammad; Prodhomme, chloe</p> <p>2016-04-01</p> <p>Volcanic eruptions can significantly impact the climate system, by injecting large amounts of particles into the stratosphere. By reflecting backward the solar radiation, these particles cool the troposphere, and by absorbing the longwave radiation, they warm the stratosphere. As a consequence of this radiative forcing, the global mean surface temperature can decrease by several tenths of degrees. However, large eruptions are also associated to a complex dynamical response of the climate system that is particularly tricky do understand regarding the low number of available <span class="hlt">observations</span>. <span class="hlt">Observations</span> seem to show an increase of the positive phases of the Northern Atlantic Oscillation (NAO) the two winters following large eruptions, associated to positive temperature anomalies over the Eurasian continent. The summers following large eruptions are generally particularly cold, especially over the continents of the Northern Hemisphere. Overall, it is really challenging to forecast the climate response to large eruptions, as it is both modulated by, and superimposed to the climate background conditions, largely driven themselves by internal <span class="hlt">variability</span> at seasonal to <span class="hlt">decadal</span> scales. This work describes the additional skill of a forecast system used for seasonal and <span class="hlt">decadal</span> predictions when it includes <span class="hlt">observed</span> volcanic forcing over the last <span class="hlt">decades</span>. An idealized volcanic forcing that could be used for real-time forecasts is also evaluated. This work consists in a base for forecasts that will be performed in the context of the next large volcanic eruption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC53B1057T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC53B1057T"><span id="translatedtitle">Two <span class="hlt">Decades</span> of <span class="hlt">Variability</span> in Nutrient Budgets for Ice-Covered, Closed Basin Lakes in the McMurdo Dry Valleys, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Truhlar, A. M.; Gooseff, M. N.; McKnight, D. M.; Priscu, J. C.; Doran, P. T.</p> <p>2013-12-01</p> <p>The McMurdo Dry Valleys (MCM) of Antarctica represent one of the world's driest deserts. A collection of permanently ice-covered lakes in the MCM provide an important refuge for microorganisms. Thus, it is of interest to understand the nutrient dynamics of these lakes and how these dynamics have changed over time. One to two <span class="hlt">decade</span>-long records of physical, chemical, and biological characteristics in the East Lobe of Lake Bonney (ELB), Lake Fryxell (FRX), and Lake Hoare (HOR) allowed for development of annual nutrient budgets and analysis of possible causes of <span class="hlt">variability</span>. Annual nutrient budgets were built by accounting for total seasonal streamflow and average seasonal nutrient concentration in streamflow, as well as nutrient diffusion across the chemocline, which roughly coincides with the bottom of the photic zone. Unaccounted-for changes in nutrient content were assumed to be caused by processes internal to the lake. Changes to the proportion of lake volume in the photic zone, seasonal streamflow, and biological activity, represented by chlorophyll-a (CHL) concentration, were considered as potential explanations. For all three lakes, nutrient diffusion either into or out of the photic zone was minimal compared to nutrient inputs from streamflow. The sole exception to this was NH4 inputs to FRX; for eight of the nine years considered, diffusive inputs of NH4 to the photic zone were greater than streamflow inputs. In most cases, internal processes appeared to dominate over streamflow inputs; this is likely because seasonal streamflow represented less than 8% of the photic zone volume in all three lakes. Three exceptions to this trend were the phosphorus budget in ELB, and the NH4 and NO3 budgets in HOR; in these cases, streamflow inputs represented a notable portion of the annual nutrient budgets. The MCM lakes decreased in volume from the early 1990s to the early 2000s; they have since been increasing in volume. The volume of the photic zone was positively</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.H21H1294W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.H21H1294W"><span id="translatedtitle"><span class="hlt">Decadal</span> dynamics of lake inundation areas in the Yangtze Basin downstream from the Three Gorges Reservoir (TGR) - consequences from climate <span class="hlt">variability</span> or from the TGR water modulation?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, J.; Sheng, Y.; Tong, T. D.</p> <p>2012-12-01</p> <p>The central and lower reach of Yangtze Basin is the host of over 75% of Chinese freshwater lakes in area. Statuses of these lakes (e.g., size, level, and gradient) are closely associated with water levels and discharge from the Yangtze main stem and tributaries. This study presents a systematic diagnosis of the <span class="hlt">decadal</span> (2000 - 2012) dynamics of lake inundation areas in this region, in response to local climate <span class="hlt">variability</span> and upstream water level modulation from the Three Gorges Reservoir (TGR). We aim to investigate two overarching questions: i) How did inundation areas of the downstream lakes change before vs. after the initial TGR impounding (June, 2003)? ii) How much has water level modulation from the TGR altered the seasonality and annual trends of downstream lake areas in comparison to the contribution of natural precipitation? Existing literature on the interaction between TGR and downstream lakes was limited to individual lake cases and lacking contextual comparison with the surrounding tributary watersheds and lake systems. This study targeted 118 lakes larger than 25 km2 across the entire hydrologic watershed downstream from the TGR. Covering a total area of ~15,100 km2, these lakes constitute 80% of the total lake surface in the studied downstream basin. Based on their discriminant relationships with the Yangtze River (the main stem), these lakes were classified into three categories: (I) in the floodplain and freely connected to the Yangtze River; (II) in the floodplain but outflows to the Yangtze River artificially controlled (i.g., by sluice gates); and (III) beyond the floodplain. Lake areas in Classes I & II are considered to be influenced by the Yangtze River level. Daily-to-monthly areas of each studied lake was mapped using MODIS Terra imagery consecutively from February, 2000 to February, 2012. The combined lake inundation area from either Class I or II indicate a significant decline trend after the initial impounding event in late June, 2003</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013IJSyS..44.1934C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013IJSyS..44.1934C"><span id="translatedtitle">Impulsive <span class="hlt">observers</span> with <span class="hlt">variable</span> update intervals for Lipschitz nonlinear time-delay systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Wu-Hua; Li, Dan-Xia; Lu, Xiaomei</p> <p>2013-10-01</p> <p>This article is concerned with the design of impulsive <span class="hlt">observers</span> with <span class="hlt">variable</span> update intervals for Lipschitz nonlinear systems with delays in state. Discontinuous Lyapunov function/funtional approaches are developed to analyse the stability of error dynamics. Delay-independent sufficient conditions for uniform exponential stability of the error dynamics over <span class="hlt">variable</span> update intervals are derived in terms of linear matrix inequalities (LMIs). When these LMIs are feasible, the <span class="hlt">observer</span> gain matrix can be solved numerically with an LMI-based optimisation algorithm. Numerical examples are provided to show the efficiency of the proposed approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AAS...22140102M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AAS...22140102M"><span id="translatedtitle">High Speed Optical <span class="hlt">Observations</span> of Cataclysmic <span class="hlt">Variables</span>: FL Ceti, BY Cam, and DQ Her</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mason, Paul A.; Gomez, S.; Robinson, E. L.; Andronov, I. L.; Gonzalez, R. I.</p> <p>2013-01-01</p> <p>We present photometric data on three cataclysmic <span class="hlt">variables</span>. Broad-band CCD <span class="hlt">observations</span> of FL Ceti, BY Cam, and DQ Her were obtained with 1-3s integrations at the Otto Struve, 2.1m, Telescope of McDonald Observatory. High speed optical photometry reveals details in these cataclysmic <span class="hlt">variables</span> not possible using longer time integrations. In FL Ceti, the shortest period eclipsing polar known, the eclipse of two separate well localized accretion regions is resolved. In BY Cam and DQ Her, the spin period of the white dwarf is revealed. We discuss model constrains provided by these <span class="hlt">observations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.6829Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.6829Y"><span id="translatedtitle">Effect of subtropical mode water on the <span class="hlt">decadal</span> <span class="hlt">variability</span> of the subsurface transport through the Luzon Strait in the western Pacific Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Kai; Qu, Tangdong; Dong, Changming; Yan, Youfang</p> <p>2015-10-01</p> <p>Analysis of the 62 year hindcast outputs from an eddy-resolving ocean general circulation model shows a good correspondence of the Luzon Strait subsurface transport to the Pacific <span class="hlt">Decadal</span> Oscillation (PDO) index on a <span class="hlt">decadal</span> time scale, with the latter leading by about 5 years. The backward particle tracing experiments indicate that the part of the subsurface water in the Luzon Strait generated by the subduction processes comes from the Subtropical Mode Water (STMW). The model results also show a strong PDO signal in the subduction rate, as well as the subsurface low potential vorticity (PV), in the formation region of the STMW, and these <span class="hlt">decadal</span> signals can be traced all the way to the Luzon Strait as PV anomalies follow the subtropical gyre circulation in about 5 years. The PV anomalies from the STMW affect the subsurface net transport in the Luzon Strait through changing the subsurface density structure and then zonal velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24266463','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24266463"><span id="translatedtitle">Detecting and estimating continuous-<span class="hlt">variable</span> entanglement by local orthogonal <span class="hlt">observables</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Chengjie; Yu, Sixia; Chen, Qing; Oh, C H</p> <p>2013-11-01</p> <p>Entanglement detection and estimation are fundamental problems in quantum information science. Compared with discrete-<span class="hlt">variable</span> states, for which lots of efficient entanglement detection criteria and lower bounds of entanglement measures have been proposed, the continuous-<span class="hlt">variable</span> entanglement is much less understood. Here we shall present a family of entanglement witnesses based on continuous-<span class="hlt">variable</span> local orthogonal <span class="hlt">observables</span> (CVLOOs) to detect and estimate entanglement of Gaussian and non-Gaussian states, especially for bound entangled states. By choosing an optimal set of CVLOOs, our entanglement witness is equivalent to the realignment criterion and can be used to detect bound entanglement of a class of 2+2 mode Gaussian states. Via our entanglement witness, lower bounds of two typical entanglement measures for arbitrary two-mode continuous-<span class="hlt">variable</span> states are provided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110015263','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110015263"><span id="translatedtitle">Sea Surface Salinity <span class="hlt">Variability</span> from Simulations and <span class="hlt">Observations</span>: Preparing for Aquarius</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jacob, S. Daniel; LeVine, David M.</p> <p>2010-01-01</p> <p>Oceanic fresh water transport has been shown to play an important role in the global hydrological cycle. Sea surface salinity (SSS) is representative of the surface fresh water fluxes and the upcoming Aquarius mission scheduled to be launched in December 2010 will provide excellent spatial and temporal SSS coverage to better estimate the net exchange. In most ocean general circulation models, SSS is relaxed to climatology to prevent model drift. While SST remains a well <span class="hlt">observed</span> <span class="hlt">variable</span>, relaxing to SST reduces the range of SSS <span class="hlt">variability</span> in the simulations (Fig.1). The main objective of the present study is to simulate surface tracers using a primitive equation ocean model for multiple forcing data sets to identify and establish a baseline SSS <span class="hlt">variability</span>. The simulated <span class="hlt">variability</span> scales are compared to those from near-surface argo salinity measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMIN11B1078P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMIN11B1078P"><span id="translatedtitle">An <span class="hlt">Observational</span> and Computational <span class="hlt">Variable</span> Tagging System for Climate Change Informatics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pouchard, L. C.; Lenhardt, W.; Branstetter, M. L.; Runciman, A.; Wang, D.; Kao, S.; King, A. W.; Climate Change Informatics Team</p> <p>2010-12-01</p> <p>As climate change science uses diverse data from <span class="hlt">observations</span> and computational results to model and validate earth systems from global to local scale, understand complex processes, and perform integrated assessments, adaptable and accessible information systems that integrate these <span class="hlt">observations</span> and model results are required. The data processing tasks associated with the simultaneous use of <span class="hlt">observation</span> and modeling data are time-consuming because scientists are typically familiar with one or the other, but rarely both. Each data domain has its own portal, its own metadata formats, and its own query-building methods for obtaining datasets. The exact definition of <span class="hlt">variables</span> and <span class="hlt">observational</span> parameters may require substantial searches for unfamiliar topics. The dearth of formal descriptions such as ontologies compounds the problem and negatively impacts the advancement of science for each aspect of studying climate change. Our <span class="hlt">Observational</span> and Computational <span class="hlt">Variable</span> Tagging System aims to address these challenges through facilitating the quick identification of datasets of interest across archives by associating <span class="hlt">variables</span> with tags or keywords from a controlled vocabulary. The prototype currently offers the ability to search by tags, <span class="hlt">variable</span> names, and annotations. Names, plain text descriptions, units, dimensions, and a link to each dataset are returned. The information is aggregated from various locations at the source of origin. Keywords from NASA’s Global Change Master Directory provide built-in suggestions for tags. These features ensure accuracy and disambiguation. For the target application, the system tags <span class="hlt">variables</span> and stores data from the Community Climate System Model (CCSM), International Boundary Water Commission, US Geological Survey, National Oceanic and Atmospheric Administration, and NASA. Our tagging system allows users to identify <span class="hlt">variable</span> names and descriptions of <span class="hlt">observational</span> and computational data from a single Web interface. Our system</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988Icar...73...80J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988Icar...73...80J"><span id="translatedtitle">The <span class="hlt">observed</span> day-to-day <span class="hlt">variability</span> of Mars atmospheric water vapor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jakosky, B. M.; Zurek, R. W.; La Pointe, M. R.</p> <p>1988-01-01</p> <p>The present evaluation of Viking water column abundance measurements of the Martian atmosphere notes <span class="hlt">observed</span> changes to be due to atmospheric water vapor vertical column abundance variations, as well as to apparent changes resulting from abundance changes of atmospheric aerosols, relative vertical distribution changes of water vapor and aerosol, or systematic viewing-geometry variations. <span class="hlt">Variability</span> noted in several major regions by visible and thermal-IR <span class="hlt">observations</span> is found to very accurately coincide with the occurrence of water ice clouds and hazes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFMPP24A..04D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFMPP24A..04D&link_type=ABSTRACT"><span id="translatedtitle">Evolution of Interannual and <span class="hlt">Decadal</span>/Interdecadal <span class="hlt">variability</span> of the SPCZ since the late 18th century using a network of Fiji coral δ18O time-series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dassie, E. P.; Linsley, B. K.; Correge, T.; Wu, H. C.; Lemley, G. M.; Cabioch, G.</p> <p>2012-12-01</p> <p> interannual and D/I coral δ18O <span class="hlt">variability</span> from equatorial sites in the Pacific (e.g. Maiana). Collectively, our results from the SPCZ region reflect the validity of the coral δ18O composite to track regional climatic <span class="hlt">variability</span> at both interannual and <span class="hlt">decadal</span>/interdecadal timescales. From the late 18th century to the late 19th century the D/I band dominates the Fiji composite while the ENSO-band amplitude is relatively small. Starting around 1885, this tendency reverses and we <span class="hlt">observed</span> a drastic decrease in the D/I signal amplitude, with its variance reduced by more than 50%, while the ENSO-band signal increases progressively in amplitude toward the present, reaching unprecedented values during the mid-20th century. This switch around 1885 A.D. is unique over the last 250 years and may correspond to a reorganization of Pacific-wide climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22130868','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22130868"><span id="translatedtitle">PRECISE HIGH-CADENCE TIME SERIES <span class="hlt">OBSERVATIONS</span> OF FIVE <span class="hlt">VARIABLE</span> YOUNG STARS IN AURIGA WITH MOST</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cody, Ann Marie; Tayar, Jamie; Hillenbrand, Lynne A.; Matthews, Jaymie M.; Kallinger, Thomas</p> <p>2013-03-15</p> <p>To explore young star <span class="hlt">variability</span> on a large range of timescales, we have used the MOST satellite to obtain 24 days of continuous, sub-minute cadence, high-precision optical photometry on a field of classical and weak-lined T Tauri stars (TTSs) in the Taurus-Auriga star formation complex. <span class="hlt">Observations</span> of AB Aurigae, SU Aurigae, V396 Aurigae, V397 Aurigae, and HD 31305 reveal brightness fluctuations at the 1%-10% level on timescales of hours to weeks. We have further assessed the <span class="hlt">variability</span> properties with Fourier, wavelet, and autocorrelation techniques, identifying one significant period per star. We present spot models in an attempt to fit the periodicities, but find that we cannot fully account for the <span class="hlt">observed</span> <span class="hlt">variability</span>. Rather, all stars exhibit a mixture of periodic and aperiodic behavior, with the latter dominating stochastically on timescales less than several days. After removal of the main periodicity, periodograms for each light curve display power-law trends consistent with those seen for other young accreting stars. Several of our targets exhibited unusual <span class="hlt">variability</span> patterns not anticipated by prior studies, and we propose that this behavior originates with the circumstellar disks. The MOST <span class="hlt">observations</span> underscore the need for investigation of TTS light variations on a wide range of timescales in order to elucidate the physical processes responsible; we provide guidelines for future time series <span class="hlt">observations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000AAS...197.0802F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AAS...197.0802F"><span id="translatedtitle">FUSE <span class="hlt">Observations</span> of Stellar Wind <span class="hlt">Variability</span> in {Sk -67°166}</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fullerton, A. W.; Massa, D. L.; Howarth, I. D.; Owocki, S. P.; Prinja, R. K.; Willis, A. J.</p> <p>2000-12-01</p> <p>We present results from an 18-day campaign to monitor stellar wind <span class="hlt">variability</span> in {Sk -67°166} (HDE 269698), an O4 If+ star in the Large Magellanic Cloud, with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Optical depth enhancements that progress from blue to red through the absorption trough are prominent in all unsaturated P Cygni profiles, particularly the resonance doublets of {S 4} and {P 5}. Related <span class="hlt">variability</span> is evident in the resonance lines of {S 6} and {O 6}. The variations are qualitatively similar to those <span class="hlt">observed</span> in the {Si 4} wind lines of the Galactic supergiant ζ Puppis [O4 I(n)f] during a 16-day monitoring campaign with IUE. However, the FUSE <span class="hlt">observations</span> contain more diagnostic information about the nature of the structures responsible for the <span class="hlt">observed</span> <span class="hlt">variability</span>. In particular, the relative amplitudes of the variations in {S 4} and {S 6} provide the first empirical constraint on the ionization equilibrium of these structures in an O star wind, while the <span class="hlt">variability</span> of {O 6} traces the distribution of very hot gas. This work is based on <span class="hlt">observations</span> made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1030607','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1030607"><span id="translatedtitle">Towards the Prediction of <span class="hlt">Decadal</span> to Centennial Climate Processes in the Coupled Earth System Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Liu, Zhengyu; Kutzbach, J.; Jacob, R.; Prentice, C.</p> <p>2011-12-05</p> <p>In this proposal, we have made major advances in the understanding of <span class="hlt">decadal</span> and long term climate <span class="hlt">variability</span>. (a) We performed a systematic study of multidecadal climate <span class="hlt">variability</span> in FOAM-LPJ and CCSM-T31, and are starting exploring <span class="hlt">decadal</span> <span class="hlt">variability</span> in the IPCC AR4 models. (b) We develop several novel methods for the assessment of climate feedbacks in the <span class="hlt">observation</span>. (c) We also developed a new initialization scheme DAI (Dynamical Analogue Initialization) for ensemble <span class="hlt">decadal</span> prediction. (d) We also studied climate-vegetation feedback in the <span class="hlt">observation</span> and models. (e) Finally, we started a pilot program using Ensemble Kalman Filter in CGCM for <span class="hlt">decadal</span> climate prediction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020068102&hterms=ph&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dph','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020068102&hterms=ph&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dph"><span id="translatedtitle">Understanding the Long-Term Spectral <span class="hlt">Variability</span> of Cygnus X-1 from BATSE and ASM <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zdziarski, Andrzej A.; Poutanen, Juri; Paciesas, William S.; Wen, Linqing; Six, N. Frank (Technical Monitor)</p> <p>2002-01-01</p> <p>We present a spectral analysis of <span class="hlt">observations</span> of Cygnus X-1 by the RXTE/ASM (1.5-12 keV) and CGRO/BATSE (20-300 keV), including about 1200 days of simultaneous data. We find a number of correlations between intensities and hardnesses in different energy bands from 1.5 keV to 300 keV. In the hard (low) spectral state, there is a negative correlation between the ASM 1.5-12 keV flux and the hardness at any energy. In the soft (high) spectral state, the ASM flux is positively correlated with the ASM hardness (as previously reported) but uncorrelated with the BATSE hardness. In both spectral states, the BATSE hardness correlates with the flux above 100 keV, while it shows no correlation with the flux in the 20-100 keV range. At the same time, there is clear correlation between the BATSE fluxes below and above 100 keV. In the hard state, most of the <span class="hlt">variability</span> can be explained by softening the overall spectrum with a pivot at approximately 50 keV. The <span class="hlt">observations</span> show that there has to be another, independent <span class="hlt">variability</span> pattern of lower amplitude where the spectral shape does not change when the luminosity changes. In the soft state, the <span class="hlt">variability</span> is mostly caused by a <span class="hlt">variable</span> hard (Comptonized) spectral component of a constant shape superimposed on a constant soft blackbody component. These <span class="hlt">variability</span> patterns are in agreement with the dependence of the rms <span class="hlt">variability</span> on the photon energy in the two states. We interpret the <span class="hlt">observed</span> correlations in terms of theoretical Comptonization models. In the hard state, the <span class="hlt">variability</span> appears to be driven mostly by changing flux in seed photons Comptonized in a hot thermal plasma cloud with an approximately constant power supply. In the soft state, the <span class="hlt">variability</span> is consistent with flares of hybrid, thermal/nonthermal, plasma with <span class="hlt">variable</span> power above a stable cold disk. Also, based on broadband pointed <span class="hlt">observations</span> simultaneous with those of the ASM and BATSE, we find the intrinsic bolometric luminosity increases by a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2393438','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2393438"><span id="translatedtitle">Structured <span class="hlt">observations</span> of hygiene behaviours in Burkina Faso: validity, <span class="hlt">variability</span>, and utility.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Curtis, V.; Cousens, S.; Mertens, T.; Traore, E.; Kanki, B.; Diallo, I.</p> <p>1993-01-01</p> <p>The use of <span class="hlt">observation</span> techniques has been promoted for the study of hygiene practices; however, questions still remain about the validity and repeatability of such techniques. In this article we compare data on hygiene behaviours obtained from questionnaires with data obtained using a structured <span class="hlt">observation</span> approach and examine the repeatability of structured <span class="hlt">observations</span> of behaviours and spot <span class="hlt">observations</span> of environmental conditions. Poor agreement between questionnaire responses and <span class="hlt">observations</span> was found for child defecation and stool disposal practices (kappa statistic: 0.25 and 0.28, respectively). There was evidence of over-reporting of "good" behaviours (P < 0.0001). Repeated <span class="hlt">observations</span> of child defecation and stool disposal behaviours showed better agreement (kappa statistic: 0.76 and 0.62, respectively) based on small sample sizes. These findings suggest that our questionnaire data are less valid than data obtained by direct <span class="hlt">observation</span>. However, different approaches to questioning may be less prone to over-reporting of "good" behaviours than our approach. Further research into the validity of different forms of question is warranted. Behaviours and conditions related to hygiene vary. <span class="hlt">Observations</span> may be useful in determining the frequency of different behaviours/conditions in the community. However, individual practices may be too <span class="hlt">variable</span> to assign individuals to exposed and non-exposed groups for the purpose of identifying links with health outcomes. Further studies on the <span class="hlt">variability</span> of behaviours and the repeatability of <span class="hlt">observations</span> are therefore needed. PMID:8440034</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Geomo.257...75M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Geomo.257...75M"><span id="translatedtitle">Multi-<span class="hlt">decadal</span> shoreline changes on Takú Atoll, Papua New Guinea: <span class="hlt">Observational</span> evidence of early reef island recovery after the impact of storm waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mann, Thomas; Westphal, Hildegard</p> <p>2016-03-01</p> <p>Hurricanes, tropical cyclones and other high-magnitude events are important steering mechanisms in the geomorphic development of coral reef islands. Sandy reef islands located outside the storm belts are strongly sensitive to the impact of occasional high-magnitude events and show abrupt, commonly erosive geomorphic change in response to such events. Based on the interpretation of remote sensing data, it is well known that the process of landform recovery might take several <span class="hlt">decades</span> or even longer. However, despite the increasing amount of scientific attention towards short- and long-term island dynamics, the lack of data and models often prevent a robust analysis of the timing and nature of recovery initiation. Here we show how natural island recovery starts immediately after the impact of a high-magnitude event. We analyze multi-temporal shoreline changes on Takú Atoll, Papua New Guinea and combine our findings with a unique set of published field <span class="hlt">observations</span> (Smithers and Hoeke, 2014). Trends of shoreline change since 1943 and changes in planform island area indicate a long-term accretionary mode for most islands. Apparent shoreline instability is detected for the last <span class="hlt">decade</span> of analysis, however this can be explained by the impact of storm waves in December 2008 that (temporarily?) masked the long-term trend. The transition from negative to positive rates of change in the aftermath of this storm event is indicative of inherent negative feedback processes that counteract short-term changes in energy input and represent the initiation of island recovery. Collectively, our results support the concept of dynamic rather than static reef islands and clearly demonstrate how short-term processes can influence interpretations of medium-term change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6360S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6360S"><span id="translatedtitle"><span class="hlt">Decadal</span> changes in downward shortwave radiation from a satellite-derived CM SAF product and ground-based <span class="hlt">observations</span> over Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanchez-Lorenzo, Arturo; Wild, Martin; Trentmann, Jörg; Enriquez-Alonso, Aaron; Pfeifroth, Uwe; Manara, Veronica</p> <p>2016-04-01</p> <p>Trends of downward shortwave radiation (DSR) from high-spatial resolution satellite-derived data over Europe since 1983 are first presented based on a Satellite Application Facility on Climate Monitoring (CM SAF) surface radiation data set, which is derived from the Meteosat geostationary satellites. The results show a widespread brightening in the major part of Europe, especially since the mid-1990s and in springtime. There is a mean increase of SSR of around 2 Wm-2 per <span class="hlt">decade</span> over the whole Europe, which, taking into account that the satellite-derived product lacks of aerosol variations, can be related to a decrease in the cloud radiative effects over Europe. The reported increase in SSR is slightly lower than the obtained using high-quality ground-based series over Europe. Secondly, residual series have been derived as the result of the difference between ground-based and satellite-derived all-sky SSR data. The residual mean series points to a significant increase during the period 1983-2010, with higher rates of around 2 Wm-2 per <span class="hlt">decade</span> over central and eastern Europe. The spatial variation of these residual time series seem to be in line with <span class="hlt">observed</span> clear-sky SSR and anthropogenic aerosol loading trends and are not just explained by inhomogeneities in the satellite-derived product. This increase in the residual series is mainly due to a strong increase from the mid-1980s to the late 1990s, thus possibly linked to a decrease in anthropogenic emissions and a recovery from the El Chichón and Pinatubo volcanic eruptions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20110007974&hterms=hidrologia&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dhidrologia','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20110007974&hterms=hidrologia&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dhidrologia"><span id="translatedtitle">Seasonal to <span class="hlt">Decadal</span> Variations of Water Vapor in the Tropical Lower Stratosphere <span class="hlt">Observed</span> with Balloon-Borne Cryogenic Frost Point Hygrometers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fujiwara, M.; Voemel, H.; Hasebe, F.; Shiotani, M.; Ogino, S.-Y.; Iwasaki, S.; Nishi, N.; Shibata, T.; Shimizu, K.; Nishimoto, E.; ValverdeCanossa, J. M.; Selkirk, H. B.; Oltmans, S. J.</p> <p>2010-01-01</p> <p>We investigated water vapor variations in the tropical lower stratosphere on seasonal, quasi-biennial oscillation (QBO), and <span class="hlt">decadal</span> time scales using balloon-borne cryogenic frost point hygrometer data taken between 1993 and 2009 during various campaigns including the Central Equatorial Pacific Experiment (March 1993), campaigns once or twice annually during the Soundings of Ozone and Water in the Equatorial Region (SOWER) project in the eastern Pacific (1998-2003) and in the western Pacific and Southeast Asia (2001-2009), and the Ticosonde campaigns and regular sounding at Costa Rica (2005-2009). Quasi-regular sounding data taken at Costa Rica clearly show the tape recorder signal. The <span class="hlt">observed</span> ascent rates agree well with the ones from the Halogen Occultation Experiment (HALOE) satellite sensor. Average profiles from the recent five SOWER campaigns in the equatorial western, Pacific in northern winter and from the three Ticosonde campaigns at Costa Rica (10degN) in northern summer clearly show two effects of the QBO. One is the vertical displacement of water vapor profiles associated with the QBO meridional circulation anomalies, and the other is the concentration variations associated with the QBO tropopause temperature variations. Time series of cryogenic frost point hygrometer data averaged in a lower stratospheric layer together with HALOE and Aura Microwave Limb Sounder data show the existence of <span class="hlt">decadal</span> variations: The mixing ratios were higher and increasing in the 1990s, lower in the early 2000s, and probably slightly higher again or recovering after 2004. Thus linear trend analysis is not appropriate to investigate the behavior of the tropical lower stratospheric water vapor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS11A1989L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS11A1989L"><span id="translatedtitle">A large ensemble of 1/4° ocean/sea-ice hindcasts to characterize the stochastic character of the ocean <span class="hlt">variability</span> at interannual-to-<span class="hlt">decadal</span> timescales.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leroux, S.; Penduff, T.; Bessières, L.; Brankart, J. M.; Molines, J. M.; Terray, L.</p> <p>2015-12-01</p> <p>In the perspective of the future CMIP exercise, turbulent Ocean Global Circulation Models (at about 1/4° resolution) are progressively replacing laminar OGCMs (2° to 1°) in ocean-atmosphere coupled systems. Unlike in laminar models, a substantial intrinsic and chaotic <span class="hlt">variability</span> spontaneously emerges in turbulent OGCMs under climatological forcing, cascading up to multidecadal timescales. To which extent may this chaotic low-frequency intrinsic <span class="hlt">variability</span> (LFIV) be modified or paced by an interannually-varying atmosphere ? The objective of the OCCIPUT project is to perform an ensemble of 50 global 1/4˚ ocean hindcasts (1958-2014) driven by the same reanalyzed atmospheric forcing, after perturbation of their initial conditions. This ensemble provides the first opportunity to extract and study both the intrinsic and the forced components of the oceanic <span class="hlt">variability</span>, and to measure the actual constraint exerted by the atmosphere on this <span class="hlt">variability</span>. We have analyzed a smaller regional ensemble hindcast (10 members, 20 years) run over the North Atlantic as a "pilot experiment" and we will illustrate the imprint of the LFIV, and compare its amplitude with the atmospherically-forced <span class="hlt">variability</span>, on various ocean quantities relevant for the climate system: Sea-Surface Height (SSH) and Temperature (SST), Heat-Content and Atlantic Meridional Overturning Circulation (AMOC). We find that: - in the turbulent areas like the Gulf Stream, the intrinsic part of the <span class="hlt">variability</span> on interannual timescales dominates the <span class="hlt">variability</span> driven by the atmosphere, - for a basin-wide integrated quantity like the AMOC, at 26.5N, the intrinsic <span class="hlt">variability</span> is about 30 % of the magnitude of the forced <span class="hlt">variability</span> on interannual timescales. Some preliminary results will also be presented from the first years of the global 50-member ensemble which is currently being performed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AAN...422....1W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AAN...422....1W"><span id="translatedtitle"><span class="hlt">Observing</span> Campaign on Hubble's First <span class="hlt">Variable</span> in M31: M31_V1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waagen, Elizabeth O.</p> <p>2010-07-01</p> <p>An <span class="hlt">observing</span> campaign is being carried out on M31_V1, the first <span class="hlt">variable</span> star discovered in M31 by Edwin Hubble. The Hubble Heritage Team, with Dr. Keith Noll (STScI) as P.I., plans to <span class="hlt">observe</span> M31_V1 with HST, and needs to know the phase of this Cepheid <span class="hlt">variable</span>. Although basic parameters are known for this star, no recent photometry exists, so <span class="hlt">observations</span> are required to generate current phase information. In 1925 Edwin Hubble published a note in The Observatory (vol. 48, 139) on "Cepheids in Spiral Nebulae." In 1929, he published a seminal paper in the Astrophysical Journal (vol. 69, 103), "A Spiral Nebula as a Stellar System, Messier 31." This paper discussed in detail the galaxy and the 50 <span class="hlt">variable</span> stars he found in its outer regions. Hubble remarked that the 40 Cepheids found showed the period-luminosity relationship in a conspicuous manner, enabling distance to the galaxy to be calculated. Furthermore, he said that the results of his calculations supported the value determined by Harlow Shapley of the zero point of the period-luminosity relation. This confirmation of the zero point had significant implications for future extragalactic distance determinations. As the first of the <span class="hlt">variables</span> on Hubble's list, V1, a Cepheid, is a historical curiosity. M31_V1 is magnitude 19.4V. B-V = +1.28, period is 30.41 days, and amplitude ~ 1.2 magnitudes in B, likely smaller in V. Five nights of data obtained by Arne Henden, AAVSO, show that the <span class="hlt">variable</span> appears to have peaked on 2010 June 19 at about R=18 and as of July 2 was on its way down. It is recommended that <span class="hlt">observers</span> use either an Rc filter or <span class="hlt">observe</span> unfiltered. About an hour or more of exposure per integration will be required to reach S/N = 20, depending on your equipment and sky brightness; multiple exposures and stacking might be necessary to avoid saturating the background. The field is not crowded, and the <span class="hlt">variable</span> itself is not blended. Contamination from the M31 background should n! ot be prohibitive</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AAS...210.1301W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AAS...210.1301W"><span id="translatedtitle"><span class="hlt">Observation</span> Of New <span class="hlt">Variable</span> Stars In The Field Of Open Cluster M23</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilkerson, Jeffrey A.; Brown, T. S.; Frank, K. A.; Joshi, U.; Lacoul, B. K.; Rengstorf, N. P.; Schiefelbein, A. M.</p> <p>2007-05-01</p> <p>In 2002 a program of surveying regions containing bright open star clusters was initiated using the <span class="hlt">observing</span> facilities at Luther College. As part of this program the half degree square field containing open cluster M23 was <span class="hlt">observed</span> in 2003, 2005 and 2006, resulting in approximately 45,000 2.5-second images, 45,000 3.5-second images and 65,000 5.0-second images. The data set contains images from 94 nights spanning a time range from JD 2452810 to JD 2454005. We have searched for stellar <span class="hlt">variability</span> on timescales from seconds to years in approximately 1600 stars in this field. Unambiguous <span class="hlt">variability</span> is apparent in 30 stars ranging in magnitude from about 10 to 17. Twenty-eight of these stars have not been previously reported as <span class="hlt">variable</span>. Seven of the stars are eclipsing binaries, including two apparent W UMa-type contact binaries and one additional eclipsing binary with a period shorter than 0.6 days. The remaining 23 <span class="hlt">variables</span> are red pulsating stars with long periods. Most of these stars have amplitudes smaller than two magnitudes and periods between 200 and 400 days. Thus, they are likely Semi-Regular <span class="hlt">variables</span>. We present celestial coordinates, estimated amplitude and estimated period for each of these stars, as well as several selected light curves. Finally, we have performed low-precision BVRI photometry of the field and have placed most of the <span class="hlt">observed</span> <span class="hlt">variables</span> on color magnitude diagrams. We are grateful for support from the Roy J. Carver Charitable Trust and the R. J. McElroy Trust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20120000700&hterms=livestock+pollution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dlivestock%2Bpollution','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20120000700&hterms=livestock+pollution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dlivestock%2Bpollution"><span id="translatedtitle">Quantifying Spatial and Seasonal <span class="hlt">Variability</span> in Atmospheric Ammonia with In Situ and Space-Based <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pinder, Robert W.; Walker, John T.; Bash, Jesse O.; Cady-Pereira, Karen E.; Henze, Daven K.; Luo, Mingzhao; Osterman, Gregory B.; Shepard, Mark W.</p> <p>2011-01-01</p> <p>Ammonia plays an important role in many biogeochemical processes, yet atmospheric mixing ratios are not well known. Recently, methods have been developed for retrieving NH3 from space-based <span class="hlt">observations</span>, but they have not been compared to in situ measurements. We have conducted a field campaign combining co-located surface measurements and satellite special <span class="hlt">observations</span> from the Tropospheric Emission Spectrometer (TES). Our study includes 25 surface monitoring sites spanning 350 km across eastern North Carolina, a region with large seasonal and spatial <span class="hlt">variability</span> in NH3. From the TES spectra, we retrieve a NH3 representative volume mixing ratio (RVMR), and we restrict our analysis to times when the region of the atmosphere <span class="hlt">observed</span> by TES is representative of the surface measurement. We find that the TES NH3 RVMR qualitatively captures the seasonal and spatial <span class="hlt">variability</span> found in eastern North Carolina. Both surface measurements and TES NH3 show a strong correspondence with the number of livestock facilities within 10 km of the <span class="hlt">observation</span>. Furthermore, we find that TES H3 RVMR captures the month-to-month <span class="hlt">variability</span> present in the surface <span class="hlt">observations</span>. The high correspondence with in situ measurements and vast spatial coverage make TES NH3 RVMR a valuable tool for understanding regional and global NH3 fluxes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19810050794&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Variable%2Bstars%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19810050794&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Variable%2Bstars%2529"><span id="translatedtitle">X-ray <span class="hlt">observations</span> of selected cataclysmic <span class="hlt">variable</span> stars using the Einstein Observatory</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cordova, F. A.; Mason, K. O.; Nelson, J. E.</p> <p>1981-01-01</p> <p>X-ray <span class="hlt">observations</span> of 12 cataclysmic <span class="hlt">variable</span> stars using the Einstein Observatory are reported. Nine of these stars, representing all subclasses of cataclysmic <span class="hlt">variables</span>, were detected. Their fluxes range from 2 x 10 to the -13th to 1 x 10 to the -11th ergs/sq cm-s in the energy interval 0.16-4.5 keV. The spectra of all the sources detected are relatively hard (kT not less than 5 keV). There is no evidence for an ultrasoft emission component (kT of about 50 eV) such as has been <span class="hlt">observed</span> from the dwarf novae SS Cyg and U Gem during optical outburst. The X-ray and optical fluxes of the objects <span class="hlt">observed</span> can be understood in terms of differences in mass accretion rate if the accreting stars in these close binary systems possess a weak magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/263567','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/263567"><span id="translatedtitle"><span class="hlt">Observations</span> of regional and local <span class="hlt">variability</span> in the optical properties of maritime clouds</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>White, A.B.</p> <p>1996-04-01</p> <p>White and Fairall (1995) calculated the optical properties of the marine boundary layer (MBL) clouds <span class="hlt">observed</span> during the Atlantic Stratocumulus Transition Experiment (ASTEX) and compared their results with the results obtained by Fairall et al. for the MBL clouds <span class="hlt">observed</span> during the First International Satellite Climatology Program (ISSCP) Regional Experiment (FIRE). They found a factor of two difference in the optical depth versus liquid water relationship that applies to the clouds <span class="hlt">observed</span> in each case. In the present study, we present evidence to support this difference. We also investigate the local <span class="hlt">variability</span> exhibited in the ASTEX optical properties using measurements of the boundary layer aerosol concentration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6662H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6662H"><span id="translatedtitle">Interplay of oxygen and hydrography in the eastern tropical North Atlantic on <span class="hlt">decadal</span> to multi-<span class="hlt">decadal</span> time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hahn, Johannes; Brandt, Peter; Schmidtko, Sunke; Krahmann, Gerd</p> <p>2016-04-01</p> <p>Ocean <span class="hlt">observations</span> in the oxygen minimum zone (OMZ) of the eastern tropical North Atlantic (ETNA) are analyzed to study <span class="hlt">decadal</span> oxygen <span class="hlt">variability</span>. Corresponding changes in hydrography are discussed and associated with changes in the circulation and ventilation. The data set consists of repeat shipboard hydrographic, oxygen and velocity <span class="hlt">observations</span> along 23°W as well as of three multi-year long moored <span class="hlt">observations</span> both acquired during the last <span class="hlt">decade</span>. It is examined in comparison to historic hydrographic data on a <span class="hlt">decadal</span> to multi-<span class="hlt">decadal</span> time scale perspective. During the last <span class="hlt">decade</span>, a strong deoxygenation was <span class="hlt">observed</span> at depth of the deep oxycline representing a shallowing of the ETNA OMZ, while oxygen increased below in the OMZ core. Both trends are superimposed with a moderate multi-<span class="hlt">decadal</span> oxygen decrease over the whole depth range. Water mass analysis indicates that this dipole pattern in the <span class="hlt">decadal</span> oxygen <span class="hlt">variability</span> is associated with a shift in the ventilation pathways having their origin either in the northern or southern hemisphere. The <span class="hlt">decadal</span> and multi-<span class="hlt">decadal</span> oxygen trend is implemented in the oxygen budget for the ETNA OMZ, which is based on recent estimates of oxygen consumption as well as lateral and diapycnal diffusive oxygen supply. The change in the residual of this oxygen budget derived from multi-<span class="hlt">decadal</span> and <span class="hlt">decadal</span> oxygen trend patterns indicates a shallower wind-driven near-surface circulation during the last <span class="hlt">decade</span> compared to the period before. In contrast, the latitudinally alternating zonal jets that were suggested to generally weaken since the 70ies might have intensified during the last <span class="hlt">decade</span> providing the enhanced oxygen supply at the core depth of the OMZ.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AIPC.1553...69M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AIPC.1553...69M&link_type=ABSTRACT"><span id="translatedtitle">Towards identification of relevant <span class="hlt">variables</span> in the <span class="hlt">observed</span> aerosol optical depth bias between MODIS and AERONET <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malakar, N. K.; Lary, D. J.; Gencaga, D.; Albayrak, A.; Wei, J.</p> <p>2013-08-01</p> <p>Measurements made by satellite remote sensing, Moderate Resolution Imaging Spectroradiometer (MODIS), and globally distributed Aerosol Robotic Network (AERONET) are compared. Comparison of the two datasets measurements for aerosol optical depth values show that there are biases between the two data products. In this paper, we present a general framework towards identifying relevant set of <span class="hlt">variables</span> responsible for the <span class="hlt">observed</span> bias. We present a general framework to identify the possible factors influencing the bias, which might be associated with the measurement conditions s