Science.gov

Sample records for observed decadal variability

  1. Decadal to centennial variability of the Atlantic from observations and models

    NASA Astrophysics Data System (ADS)

    Delworth, Thomas L.; Zhang, Rong; Mann, Michael E.

    Some aspects of multidecadal Atlantic climate variability, and its impact on regional and hemispheric scale climate, are reviewed. Observational analyses have documented distinct patterns of Atlantic variability with decadal (8-12 years) and multidecadal (30-80 years) time scales. Numerical models have succeeded in capturing some aspects of this observed variability, but much work remains to understand the mechanisms of the observed variability. The impacts of the variability—particularly on the multidecadal time scale—are striking, including modulation of African and Indian summer monsoon rainfall, summer climate over North America and Europe, and a potential influence on Atlantic hurricane activity. Some of the observed variability, particularly in recent decades, is likely influenced by changing radiative forcings, of both anthropogenic and natural origin. This poses an important challenge for the detection, attribution and prediction of climate change.

  2. Decadal variability of surface incident solar radiation over China: Observations, satellite retrievals, and reanalyses

    NASA Astrophysics Data System (ADS)

    Wang, Kaicun; Ma, Qian; Li, Zhijun; Wang, Jiankai

    2015-07-01

    Existing studies have shown that observed surface incident solar radiation (Rs) over China may have important inhomogeneity issues. This study provides metadata and reference data to homogenize observed Rs, from which the decadal variability of Rs over China can be accurately derived. From 1958 to 1990, diffuse solar radiation (Rsdif) and direct solar radiation (Rsdir) were measured separately, and Rs was calculated as their sum. The pyranometers used to measure Rsdif had a strong sensitivity drift problem, which introduced a spurious decreasing trend into the observed Rsdif and Rs data, whereas the observed Rsdir did not suffer from this sensitivity drift problem. From 1990 to 1993, instruments and measurement methods were replaced and measuring stations were restructured in China, which introduced an abrupt increase in the observed Rs. Intercomparisons between observation-based and model-based Rs performed in this research show that sunshine duration (SunDu)-derived Rs is of high quality and can be used as reference data to homogenize observed Rs data. The homogenized and adjusted data of observed Rs combines the advantages of observed Rs in quantifying hourly to monthly variability and SunDu-derived Rs in depicting decadal variability and trend. Rs averaged over 105 stations in China decreased at -2.9 W m-2 per decade from 1961 to 1990 and remained stable afterward. This decadal variability is confirmed by the observed Rsdir and diurnal temperature ranges, and can be reproduced by high-quality Earth System Models. However, neither satellite retrievals nor reanalyses can accurately reproduce such decadal variability over China.

  3. 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."

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

    NASA Astrophysics Data System (ADS)

    Wang, Kaicun

    2014-08-01

    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.

  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

    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.

  7. 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. PMID:26017453

  8. Decadal Variability of the Kuroshio Extension: Observations and an Eddy-Resolving Model Hindcast*

    E-print Network

    Xie, Shang-Ping

    Change, JAMSTEC, Yokohama, Japan **Earth Simulator Center, JAMSTEC, Yokohama, Japan (Manuscript received). In both the OFES hindcast and satellite altimeter observations, low-frequency sea surface height (SSH indicates that much of the SSH variability in the western North Pacific east of Japan is explained by two

  9. Interannual to decadal temperature variability in the north-west Atlantic: Observations from the MV Oleander XBT line

    NASA Astrophysics Data System (ADS)

    Forsyth, J. S. T.; Andres, M.; Gawarkiwicz, G.

    2014-12-01

    Despite convincing evidence of deep ocean warming, temperature changes over the shelves have proven difficult to quantify as most long-term records lack the spatial and temporal resolution needed to resolve shelf variability. XBT data have been collected for 37 years along a repeat track from New Jersey to Bermuda from the MV Oleander providing the resolution necessary for shelf analysis. The XBT temperature data on the shelf (onshore of the 80 m isobath) were binned with 10 km horizontal and 5 m vertical resolution to produce monthly and annually averaged temperature sections. A climatology produced from the binned data identifies key seasonal temperature features consistent with previous climatologies, showing the utility of the XBT data. Annual spatially-averaged shelf temperatures have trended upwards since the beginning of the record in 1977 (0.025 C/yr), with recent trends (i.e., since 2002, 0.10 C/yr) substantially larger than the overall 37- year trend. Comparison of composite sections for the most anomalous years suggests that the interannual variability in the spatially-averaged temperatures is most heavily influenced by temperature anomalies near the shelf break. The spatially-averaged temperature anomalies are not correlated with annually-averaged coastal sea level anomalies from tide gauges at zero lag, which suggest that interannual variability in coastal sea level is not due to thermo steric effects. However, a strong positive correlation is found between 2-year lagged temperature anomalies and coastal sea level anomalies. This relationship is most pronounced for the shelf break temperature anomalies, with the strongest 2-year lag correlations found in winter and spring. Connections between the observed interannual to decadal temperature variability on the shelf and variability in the AMOC are being investigated in an ongoing effort to better understand open-ocean/shelf interactions in the Northwest Atlantic.

  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-stomatal deposition but failed to explain the inter-annual differences, suggesting that some still unknown mechanisms might be involved in determining the inter-annual variability. Model calculation was performed to evaluate the potential sink strength of the chemical reactions of ozone with sesquiterpenes in the canopy air space, which revealed that sesquiterpenes in typical amounts at the site were unlikely to cause significant ozone loss in canopy air space. The results clearly showed the importance of several non-stomatal removal mechanisms. Unknown chemical compounds or processes correlating with monoterpene concentrations, including potentially reactions at the surfaces, contribute to non-stomatal sink term.

  11. The Astronomer Who Came in from the Cold: The Evolution of Observing Variable Stars Over Three Decades at Appalachian State's Dark Sky Observatory (Abstract)

    NASA Astrophysics Data System (ADS)

    Caton, D. B.

    2013-12-01

    (Abstract only) Variable star research has been my main work from my Ph.D. dissertation work through three decades of research at our Appalachian State University Dark Sky Observatory. I will present a review of that work and the evolution of technology that took me from in situ observing with a photometer in a cold dome to remote and automatic CCD observing today. The research targets included RS CVn stars, apsidal motion eclipsing binaries, Trojan planets, and exoplanets in binaries.

  12. 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.

    2012-05-01

    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. Canopy-level ozone flux measurements were analysed for deposition characteristics and partitioning into stomatal and non-stomatal fractions, focusing 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 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 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). Model calculation was performed to evaluate the potential sink strength of the chemical reactions of ozone with sesquiterpenes in the canopy air space, which revealed that sesquiterpenes in typical amounts at the site were unlikely to cause significant ozone loss in canopy air space. This was also confirmed by the statistical analysis that did not link measured sesquiterpene concentration with ozone deposition. It was concluded that chemical reactions with monoterpenes, or other removal mechanisms such as surface reactions, play a role as ozone non-stomatal sink inside canopy.

  13. 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

    2015-06-01

    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.

  14. 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.

  15. Decadal variability of the Indian Ocean dipole

    NASA Astrophysics Data System (ADS)

    Ashok, Karumuri; Chan, Wing-Le; Motoi, Tatsuo; Yamagata, Toshio

    2004-12-01

    Using the Simple Ocean Data Assimilation (SODA), NCEP/NCAR reanalysis and the GISST datasets from 1950-1999, and an atmosphere-ocean coupled general circulation model, we explored the possible existence of decadal Indian Ocean Dipole (IOD) variability for the first time. We find that there are strong decadal IOD events, and that the time series of the decadal IOD and decadal ENSO indices are not well correlated. The simulated decadal signal of the IOD index is highly correlated with the 20°C isotherm depth anomaly, indicating that ocean dynamics is involved in the decadal IOD. It is also associated with the zonal wind anomaly. We suggest that the decadal IOD in the tropics is interpreted as decadal modulation of the interannual IOD events.

  16. Elements of tropical Pacific decadal variability 

    E-print Network

    Fuckar, Neven-Stjepan

    2003-01-01

    The evolution of decadal variability in the tropical Pacific is investigated using a global assimilation reanalysis. At the nexus of this study are monthly means of an ocean general circulation model coupled with a data assimilation routine...

  17. 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:

  18. 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 to the slower vertical descent in the model during spring.

  19. 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

  20. Solar forcing synchronizes decadal North Atlantic climate variability

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    Quasi-decadal variability in solar irradiance has been suggested to have substantial effects on Earth’s climate at regional scales. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the Arctic Oscillation/North Atlantic Oscillation which maximizes by a lag of a few years due to ocean-atmosphere coupling processes. However this relationship has not yet been supported by climate model simulations with realistic observed forcings. Its detection is further complicated since quasi-decadal fluctuations of the North Atlantic Oscillation can be intrinsically generated by the coupled ocean-atmosphere system.In this study we compare two fully coupled multi-decadal ocean-atmosphere chemistry-climate simulations which either include or suppress solar forcing variability. While the North Atlantic Oscillation index displays a quasi-decadal variability mode in both experiments, the one including the 11-year solar cycle shows a statistically significant solar/North Atlantic Oscillation index coherency lagged by 1-2 years. Atmospheric dynamical investigations further suggest that the 11-year solar cycle synchronizes the internally generated quasi-decadal North Atlantic Oscillation variability through the downward propagation of the solar signal from the upper stratosphere to the surface. Our results point out that both solar UV forcing as well as air-sea interaction processes are key influencing factors of quasi-decadal natural climate variability.

  1. 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 to describe the connection between shocks and food prices, and to demonstrate the importance of these metrics in overall outcomes in food-insecure communities.

  2. Origin of Quasi-decadal North Atlantic Oscillation Variability

    NASA Astrophysics Data System (ADS)

    Reintges, Annika; Latif, Mojib; Park, Wonsun

    2015-04-01

    The North Atlantic Oscillation (NAO) is the leading mode of internal atmospheric variability in the North Atlantic sector. It depicts significant quasi-decadal variability that is well documented, but the underlying mechanism is still under discussion. Other quantities in the North Atlantic sector such as sea surface temperature (SST) exhibit variability on a similar timescale. Here we present results from a global climate model which simulates the quasi-decadal NAO and North Atlantic SST variability consistent with observations. The quasi-decadal NAO variability is suggested to originate from large-scale air-sea interactions, where the Atlantic Meridional Overturning Circulation (AMOC) basically sets the timescale. Wind-driven ocean circulation changes provide a fast positive feedback on North Atlantic SST through anomalous Ekman currents and the establishment of an "intergyre" gyre. A delayed negative feedback on SST is accomplished through surface heat flux-driven changes of the AMOC and associated heat transport. The results stress the importance of both wind-induced and thermohaline-induced changes in the ocean circulation for quasi-decadal climate variability in the North Atlantic sector.

  3. 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.

  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. Decadal Variability of Surface Incident Solar Radiation over China

    NASA Astrophysics Data System (ADS)

    Wang, Kaicun

    2015-04-01

    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. This study provides metadata and reference data to investigate the observed variability of Rs in China. From 1958 to 1990, diffuse solar radiation (Rsdif) and direct solar radiation (Rsdir) was measured separately in China, from which Rs was calculated a sum. However, pyranometers used to measure Rsdif had a strong sensitivity drift problem, which introduced a spurious decreasing trend to Rsdif and Rs measurements. The observed Rsdir did not suffer from such sensitivity drift problem. From 1990 to 1993, the old instruments were replaced and measuring stations were relocated in China, which introduced an abrupt increase in the observed Rs. After 1993, Rs was measured by solid black thermopile pyranometers. Comprehensive comparisons between observation-based and model-based Rs performed in this research have shown that sunshine duration (SunDu)-derived Rs is of high quality and provide accurate estimate of decadal variability of Rs over China. SunDu-derived Rs averaged over 105 stations in China decreased at -2.9 W m-2 per decade from 1961 to 1990 and remained stable afterward. This decadal variability has been confirmed by the observed Rsdir, independent studies on aerosols and diurnal temperature range, and can be reproduced by certain high-quality earth system models. However, neither satellite retrievals (the Global Energy and Water Exchanges Project Surface Radiation Budget (GEWEX SRB)) nor reanalyses (ERA-Interim and Modern-Era Retrospective analysis for Research and Applications (MERRA)) can accurately reproduce such decadal variability of Rs over China for their exclusion of annual variability of tropospheric aerosols.

  6. 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

  7. Solar forcing synchronizes decadal North Atlantic climate variability

    PubMed Central

    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

  8. 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

  9. Decadal modulation of global surface temperature by internal climate variability

    NASA Astrophysics Data System (ADS)

    Dai, Aiguo; Fyfe, John C.; Xie, Shang-Ping; Dai, Xingang

    2015-06-01

    Despite a steady increase in atmospheric greenhouse gases (GHGs), global-mean surface temperature (T) has shown no discernible warming since about 2000, in sharp contrast to model simulations, which on average project strong warming. The recent slowdown in observed surface warming has been attributed to decadal cooling in the tropical Pacific, intensifying trade winds, changes in El Niño activity, increasing volcanic activity and decreasing solar irradiance. Earlier periods of arrested warming have been observed but received much less attention than the recent period, and their causes are poorly understood. Here we analyse observed and model-simulated global T fields to quantify the contributions of internal climate variability (ICV) to decadal changes in global-mean T since 1920. We show that the Interdecadal Pacific Oscillation (IPO) has been associated with large T anomalies over both ocean and land. Combined with another leading mode of ICV, the IPO explains most of the difference between observed and model-simulated rates of decadal change in global-mean T since 1920, and particularly over the so-called `hiatus' period since about 2000. We conclude that ICV, mainly through the IPO, was largely responsible for the recent slowdown, as well as for earlier slowdowns and accelerations in global-mean T since 1920, with preferred spatial patterns different from those associated with GHG-induced warming or aerosol-induced cooling. Recent history suggests that the IPO could reverse course and lead to accelerated global warming in the coming decades.

  10. Variability in 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.

    2015-09-01

    A detailed analysis of the polar ozone loss processes during 10 recent Antarctic winters is presented with high-resolution MIMOSA-CHIM (Modèle Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection avec CHIMie) model simulations and high-frequency polar vortex observations from the Aura microwave limb sounder (MLS) instrument. The high-frequency measurements and simulations help to characterize the winters and assist the interpretation of interannual variability better than either data or simulations alone. Our model results for the Antarctic winters of 2004-2013 show that chemical ozone loss starts in the edge region of the vortex at equivalent latitudes (EqLs) of 65-67° 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, when all EqLs (65-83° S) show a 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 per sunlit hour) in July and 4-5 ppbv sh-1 in August-mid-September, while they drop rapidly to 0 by mid-October. In the middle stratosphere, the loss rates are about 3-5 ppbv sh-1 in July-August and October at 675 K. 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 to the slower vertical descent in the model during spring.

  11. 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.

  12. 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, the changes of the strength of the subtropical high and the associated surface wind are dynamically consistent with the distribution of local SST anomalies, suggesting the importance of the atmospheric forcing in the decadal time scale. The decadal mode also presents a weak summer monsoon in its positive phase, which reduces the moisture supply from the equatorial Atlantic and the Amazon Basin and results in negative rainfall anomalies over the central Andes and Gran Chaco. The long-term trend shows decrease of rainfall from the northwest coast to the southeast subtropical region and a southward shift of Atlantic ITCZ that leads to increased rainfall over northern and eastern Brazil. Our result shows a close link of this mode to the observed SST warming trend over the subtropical South Atlantic and a remote connection to the interdecadal SST variation over the extratropical North Atlantic found in previous studies.

  13. Variable stars across the observational HR diagram

    E-print Network

    Laurent Eyer; Nami Mowlavi

    2007-12-21

    An overview of pulsating variable stars across the observational Hertzprung-Russel (HR) diagram is presented, together with a summary of their global properties. The HR diagram is presented with a third colour-coded dimension, visualizing the fraction of variable, the amplitude of variability or the period of variability. The distribution of variable stars in the other observational diagrams, such as the Period-Amplitude diagram, is also presented. Some of the progresses performed in the field of variable stars during the last decade are briefly summarized, and future projects that will improve our knowledge of variable stars are mentioned.

  14. 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.

  15. Predictability of Pacific Decadal Climate Variability and Climate Impacts (Invited)

    NASA Astrophysics Data System (ADS)

    Newman, M.

    2013-12-01

    Predictability of Pacific sea surface temperature (SST) climate variations and climate impacts on time scales of 1-10 years is discussed, using a global linear inverse model (LIM) as an empirical benchmark for decadal surface temperature forecast skill. Constructed from the observed simultaneous and 1-yr lag covariability statistics of annually averaged sea surface temperature (SST) and surface (2 m) land temperature global anomalies during 1901-2009, the LIM has hindcast skill for leads of 2-5 yr and 6-9 yr comparable to and sometimes even better than skill of the phase 5 of the Coupled Model Intercomparison Project (CMIP5) model hindcasts initialized annually over the period 1960-2000 and has skill far better than damped persistence (e.g., a local univariate AR1 process). Pronounced similarity in geographical variations of skill between LIM and CMIP5 hindcasts suggests similarity in their sources of skill as well, supporting additional evaluation of LIM predictability. For forecast leads above 1-2 yr, LIM skill almost entirely results from three nonorthogonal patterns: one corresponding to the secular trend and two more, each with about 10-yr decorrelation time scales but no trend, that represent most of the predictable portions of the Atlantic multidecadal oscillation (AMO) and Pacific decadal oscillation (PDO) indices, respectively. In contrast, for forecasts greater than about two years, ENSO acts as noise and degrades forecast skill. These results suggest that current coupled model decadal forecasts may not yet have much skill beyond that captured by multivariate, predictably linear dynamics. A particular focus will be on the predictability of the PDO, which represents the dominant mode of Pacific decadal SST variability. The PDO is shown to represent a few different physical processes, including wind-driven changes of SSTs that can occur either due to daily weather variability or to tropical forcing, and variations in the North Pacific western boundary current region. These different processes represent increasingly longer time scales but are largely unrelated, and it is their combination that may produce regime-like behavior. The question of whether the PDO represents a response to climate forcing rather than a forcing of climate variability is thus key to an understanding of what impacts, if any, the PDO has on North American climate. Finally, in many disciplines, a climate index such as the PDO is a black box to be used as input for system sensitivity tests. But just because the PDO may represent the most predictable SST variation does not mean that it must always have the greatest climate impact. How climate impact assessment will be improved with an end-to-end approach where neither the climate predictability problem nor the systems sensitivity problem is treated in isolation is an essential but largely unanswered question. That is, rather than ask how sensitive our system is to a pre-specified climate pattern, or what climate patterns are most predictable, it may be better to ask what climate impacts on systems are most predictable.

  16. A perspective on decadal climate variability and predictability

    NASA Astrophysics Data System (ADS)

    Latif, Mojib; Keenlyside, Noel S.

    2011-09-01

    The global surface air temperature record of the last 150 years is characterized by a long-term warming trend, with strong multidecadal variability superimposed. Similar multidecadal variability is also seen in other (societal important) parameters such as Sahel rainfall or Atlantic hurricane activity. The existence of the multidecadal variability makes climate change detection a challenge, since global warming evolves on a similar timescale. The ongoing discussion about a potential anthropogenic signal in the Atlantic hurricane activity is an example. A lot of work was devoted during the last years to understand the dynamics of the multidecadal variability, and external and internal mechanisms were proposed. This review paper focuses on two aspects. First, it describes the mechanisms for internal variability using a stochastic framework. Specific attention is given to variability of the Atlantic Meridional Overturning Circulation (AMOC), which is likely the origin of a considerable part of decadal variability and predictability in the Atlantic Sector. Second, the paper discusses decadal predictability and the factors limiting its realization. These include a poor understanding of the mechanisms involved and large biases in state-of-the-art climate models. Enhanced model resolution, improved subgrid scale parameterisations, and the inclusion of additional climate subsystems, such as a resolved stratosphere, may help overcome these limitations.

  17. 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.

  18. 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 parameters of the Weibull PDF. This allowed us to derive a linear model to estimate the annual power output from those parameters, which results especially useful when no wind power data is available.

  19. 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.

  20. 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.

  1. 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).

  2. 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.

  3. Decadal monitoring of variables by the AAVSO community

    NASA Astrophysics Data System (ADS)

    Henden, Arne A.

    2014-06-01

    The American Association of Variable Stars has been in existence for over 100 years. First performing monitoring and follow-up observations for Harvard College astronomers, the organization has expanded into following thousands of variables with a wide variety of instrumentation, as well as participating in the discovery of transient objects and the data-mining of survey catalogs. Several examples of how long, continuous, homogeneous light curves can yield astrophysical results not possible with short lifetime surveys will be given.

  4. 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."

  5. The Contribution of Internal and Model Variabilities to the Uncertainty in CMIP5 Decadal Climate Predictions

    E-print Network

    Strobach, Ehud

    2015-01-01

    Decadal climate predictions, which are initialized with observed conditions, are characterized by two main sources of uncertainties--internal and model variabilities. Using an ensemble of climate model simulations from the CMIP5 decadal experiments, we quantified the total uncertainty associated with these predictions and the relative importance of each source. Annual and monthly averages of the surface temperature and wind components were considered. We show that different definitions of the anomaly results in different conclusions regarding the variance of the ensemble members. However, some features of the uncertainty are common to all the measures we considered. We found that over decadal time scales, there is no considerable increase in the uncertainty with time. 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. The uncertainty of the surface temperature prediction is dom...

  6. 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.

  7. Dynamical and biogeochemical control on the decadal variability of ocean carbon fluxes

    NASA Astrophysics Data System (ADS)

    Séférian, R.; Bopp, L.; Swingedouw, D.; Servonnat, J.

    2013-04-01

    Several recent observation-based studies suggest that ocean anthropogenic carbon uptake has slowed down due to the impact of anthropogenic forced climate change. However, it remains unclear whether detected changes over the recent time period can be attributed to anthropogenic climate change or rather to natural climate variability (internal plus naturally forced variability) alone. One large uncertainty arises from the lack of knowledge on ocean carbon flux natural variability at the decadal time scales. To gain more insights into decadal time scales, we have examined the internal variability of ocean carbon fluxes in a 1000 yr long preindustrial simulation performed with the Earth System Model IPSL-CM5A-LR. Our analysis shows that ocean carbon fluxes exhibit low-frequency oscillations that emerge from their year-to-year variability in the North Atlantic, the North Pacific, and the Southern Ocean. In our model, a 20 yr mode of variability in the North Atlantic air-sea carbon flux is driven by sea surface temperature variability and accounts for ~40% of the interannual regional variance. The North Pacific and the Southern Ocean carbon fluxes are also characterised by decadal to multi-decadal modes of variability (10 to 50 yr) that account for 20-40% of the interannual regional variance. These modes are driven by the vertical supply of dissolved inorganic carbon through the variability of Ekman-induced upwelling and deep-mixing events. Differences in drivers of regional modes of variability stem from the coupling between ocean dynamics variability and the ocean carbon distribution, which is set by large-scale secular ocean circulation.

  8. Dynamical and biogeochemical control on the decadal variability of ocean carbon fluxes

    NASA Astrophysics Data System (ADS)

    Séférian, R.; Bopp, L.; Swingedouw, D.; Servonnat, J.

    2012-12-01

    Several recent observation-based studies suggest that ocean anthropogenic carbon uptake has slowed down due to the impact of anthropogenic forced climate change. However, it remains unclear if detected changes over the recent time period can really be attributed to anthropogenic climate change or to natural climate variability (internal plus naturally forced variability). One large uncertainty arises from the lack of knowledge on ocean carbon flux natural variability at the decadal time scales. To gain more insights into decadal time scales, we have examined the internal variability of ocean carbon fluxes in a 1000-yr long preindustrial simulation performed with the Earth System Model IPSL-CM5A-LR. Our analysis shows that ocean carbon fluxes exhibit low-frequency oscillations that emerge from their year-to-year variability in the North Atlantic, the North Pacific, and the Southern Ocean. In our model, a 20-yr mode of variability in the North Atlantic air-sea carbon flux is driven by sea surface temperature variability and accounts for ~40% of the interannual regional variance. The North Pacific and the Southern Ocean carbon fluxes are also characterized by decadal to multi-decadal modes of variability (10 to 50 yr) that account for 30-40% of the interannual regional variance. But these modes are driven by the vertical supply of dissolved inorganic carbon through the variability of Ekman-induced upwelling and deep-mixing events. Differences in drivers of regional modes of variability stem from the coupling between ocean dynamics variability and the ocean carbon distribution, which is set by large-scale secular ocean circulation.

  9. Decadal to bi-decadal rainfall variation in the western Pacific: A footprint of South Pacific decadal variability?

    NASA Astrophysics Data System (ADS)

    Hsu, Huang-Hsiung; Chen, Yun-Lan

    2011-02-01

    Decadal to bi-decadal rainfall variation in the Western Pacific during July-October in the second half of the 20th century was identified in this study. This 10-20-year quasi-periodic oscillation was found associated with the leading sea surface temperature (SST) pattern in the South Pacific, which is called the 10-20-year South Pacific (inter) Decadal Oscillation (SPDO). It is suggested that the 10-20-year fluctuation of the SPDO resulted in significant decadal to bi-decadal rainfall variation along the western Pacific coast. The anomalous divergent circulations were likely driven by the SSTA (SST anomaly) and resulted in the anomalous rainfall in Eastern Australia and the Maritime Continent. It is conjectured that the SSTA in the Western South Pacific led to an anomalous Hadley-like circulation in the Western Pacific and indirectly affected the convection activity in the Philippine Sea, which in turn impacted the rainfall in the Philippines, Taiwan and Korea.

  10. 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.

  11. Long-term climate change in the Mediterranean region in the midst of decadal variability

    NASA Astrophysics Data System (ADS)

    Mariotti, Annarita; Pan, Yutong; Zeng, Ning; Alessandri, Andrea

    2015-03-01

    Long-term climate change and decadal variability in the Mediterranean region during 1860-2100 are investigated based on observational data and the newly available Coupled Model Intercomparison Project—Phase 5 (CMIP5) experiments. Observational records show that decadal variability and a general tendency for annual-mean conditions to be warmer and drier have characterized the Mediterranean during 1860-2005. Consistency with CMIP5 model simulations including greenhouse gases (GHG), as well as anthropogenic aerosols and natural forcings, suggest that forced changes have characterized aspects of Mediterranean climate during this period. Future GHG-forced change will take place in the midst of decadal variability, both internal and forced, as it has occurred in the past. However, future rates of forced warming and drying over the Mediterranean are projected to be higher than in the past century. The degree to which forced change and internal variability will matter depends on the climatic quantity being considered. For surface air temperature and Mediterranean Sea annual-mean evaporation and surface freshwater fluxes, variability and forced change have become comparable and the forced signal has already emerged from internal variability. For quantities with large internal variability and relatively small forced signal such as precipitation, forced change will emerge later on in the twenty-first century over selected regions and seasons. Regardless, the probability distribution of future precipitation anomalies is progressively shifting towards drier conditions. Overall, results highlight that both mean projected forced change and the variability that will accompany forced mean change should be considered in the development of future climate outlooks.

  12. Pacific decadal variability in the view of linear equatorial wave theory

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J. B.; Cane, M. A.

    2006-12-01

    It has recently been proposed, within the framework of the linear shallow water equations, that tropical Pacific decadal variability can be accounted for by basin modes with eigenperiods of 10 to 20 years, amplifying a mid- latitude wind forcing with an essentially white spectrum (Cessi and Louazel 2001; Liu 2003). We question this idea here, using a different formalism of linear equatorial wave theory. We compute the Green's function for the wind forced response of a linear equatorial shallow water ocean, and use the results of Cane and Moore (1981) to obtain a compact, closed form expression for the motion of the equatorial thermocline, which applies to all frequencies lower than seasonal. At very low frequencies (decadal timescales), we recover the planetary geostrophic solution used by Cessi and Louazel (2001), as well as the equatorial wave solution of Liu (2003), and give a formal explanation for this convergence. Using this more general solution to explore more realistic wind forcings, we come to a different interpretation of the results. We find that the equatorial thermocline is inherently more sensitive to local than to remote wind forcing, and that planetary Rossby modes only weakly alter the spectral characteristics of the response. Tropical winds are able to generate a strong equatorial response with periods of 10 to 20 years, while midlatitude winds can only do so for periods longer than about 50 years. Since the decadal pattern of observed winds shows similar amplitude for tropical and midlatitude winds, we conclude that the latter are unlikely to be responsible for the observed decadal tropical Pacific SST variability. References : Cane, M. A., and Moore, D. W., 1981: A note on low-frequency equatorial basin modes. J. Phys. Oceanogr., 11(11), 1578 1584. Cessi, P., and Louazel, S., 2001: Decadal oceanic response to stochastic wind forcing. J. Phys. Oceanogr., 31, 3020 3029. Liu, Z., 2003: Tropical ocean decadal variability and resonance of planetary wave basin modes. J. Clim., 16(18), 1539 1550.

  13. 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

    2015-05-01

    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 period of observations or using a more realistic model of decadal variability to assess the real-time decadal predictability.

  14. 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.

  15. Looking for the role of the ocean in tropical Atlantic decadal climate variability. 12

    E-print Network

    Columbia University

    Looking for the role of the ocean in tropical Atlantic decadal climate variability. 12 Richard that the role of the ocean in tropical Atlantic decadal climate variability is largely passive and damping) of the tropical Atlantic Ocean varies in broad spatial patterns and on a variety of timescales. For example

  16. Looking for the role of the ocean in tropical Atlantic decadal climate variability.12

    E-print Network

    Columbia University

    Looking for the role of the ocean in tropical Atlantic decadal climate variability.12 Richard of the ocean in tropical Atlantic decadal climate variability is largely passive and damping. Di erences) of the tropical Atlantic Ocean varies in broad spatial patterns and on a variety of timescales. For example

  17. Regional circulation around New Caledonia from two decades of observations

    NASA Astrophysics Data System (ADS)

    Cravatte, Sophie; Kestenare, Elodie; Eldin, Gérard; Ganachaud, Alexandre; Lefèvre, Jérôme; Marin, Frédéric; Menkes, Christophe; Aucan, Jérôme

    2015-08-01

    The regional and near-coastal circulation around New Caledonia is investigated using a compilation of more than 20 years of observations. Velocity profiles acquired by Shipboard Acoustic Doppler Current Profiler (SADCP) during 109 research cruises and ship transits since 1991 are analyzed and compared with absolute geostrophic currents inferred from hydrographic profiles and Argo floats drifts. In addition, altimetric surface currents are used to explore the variability of the circulation at various timescales. By making the best use of the strength of these various observations, this study provides an unprecedented detailed picture of the mean circulation around New Caledonia and of its variability in the upper layers. New Caledonia, together with the Vanuatu Archipelago and the Fiji Islands, acts as a 750-km long obstacle to the westward South Equatorial Current (SEC) entering the Coral Sea. On average, the SEC bifurcates against New Caledonia's east coast into a northwestward boundary current, the East Caledonian Current, beginning east of the Loyalty Islands and extending to at least 1000 m depth, and into a weak southeastward current. The latter, the Vauban Current, flows into the Loyalty channel against the mean trade winds where it extends to at least 500 m depth. It is highly variable at intraseasonal timescales; it often reverses and its variability is mainly driven by incoming mesoscale eddies east and south of New Caledonia. West of the Island, the southeastward Alis Current of New Caledonia (ACNC) flows along the reef slope in the 0-150 m layer. It overlays a weaker northwestward current, creating an unusual coastal circulation reminiscent of the current system along the Australian west coast. The ACNC is a persistent feature of the observations, even if its transport is also strongly modulated by the presence of offshore eddies. This study highlights the fact, if needed, that a snapshot view of the currents provided by a single transect can be strongly impacted by mesoscale eddies, and should be put into context, e.g. by using simultaneous altimetric data.

  18. Decadal variability of global ocean significant wave height

    NASA Astrophysics Data System (ADS)

    Zheng, Chongwei; Zhou, Lin; Shi, Weilai; Li, Xin; Huang, Chaofan

    2015-10-01

    This paper presents the long-term climate changes of significant wave height (Hs) in 1958-2001 over the entire global ocean using the 45-year European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA-40) wave data. The linear trends in Hs and regional and seasonal differences of the linear trends for Hs were calculated. Results show that the Hs exhibits a significant increasing trend of about 4.6 cm decade-1 in the global ocean as a whole over the last 44 years. The Hs changes slowly during the periods 1958-1974 and 1980-1991, while it increases consistently during the periods 1975-1980 and 1995-1998. The Hs reaches its lowest magnitude in 1975, with annual average wave height about 2 m. In 1992, the Hs has the maximum value of nearly 2.60 m. The Hs in most ocean waters has a significant increasing trend of 2-14 cm decade-1 over the last 44 years. The linear trend exhibits great regional differences. Areas with strong increasing trend of Hs are mainly distributed in the westerlies of the southern Hemisphere and the northern Hemisphere. Only some small areas show obvious decreasing in Hs. The long-term trend of Hs in DJF (December, January, February) and MAM (March, April, May) is much more stronger than that in JJA (June, July, August) and SON (September, October, November). The linear trends of the Hs in different areas are different in different seasons; for instance, the increasing trend of Hs in the westerlies of the Pacific Ocean mainly appears in MAM and DJF.

  19. 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 African population to climate change. In order to put the findings of the synthesis in an historical perspective and to analyse the decadal scale variability and trends, runoff observations and modelled runoff from LPJML were also used.

  20. Extreme Space Weather Events Observed Through the Decades

    NASA Astrophysics Data System (ADS)

    Denig, W. F.

    2014-12-01

    Well before satellite observations provided exquisite information regarding the variability of the space environment the research community had to rely on cruder techniques, by today's standards, for monitoring the sun-earth system. These early techniques included published reports of aurora at low latitudes, signatures in daily magnetograms, ionospheric soundings, ground-based observations of the sun, and variations in the cosmic ray background. This talk will focus on extreme space weather events that have occurred during the last eighty years or so. We will first establish how we define an extreme geo-effective event by using the Ap-star magnetic classification scheme of Allen [see Allen and Wilkinson in Solar-Terrestrial Predictions-IV, 1992]. For the top ten events we will then present representative examples of datasets available at the time used by the scientific community to support their research objectives.

  1. Mechanisms for decadal scale variability in a simulated Atlantic meridional overturning circulation

    NASA Astrophysics Data System (ADS)

    Medhaug, I.; Langehaug, H. R.; Eldevik, T.; Furevik, T.; Bentsen, M.

    2012-07-01

    Variability in the Atlantic Meridional Overturning Circulation (AMOC) has been analysed using a 600-year pre-industrial control simulation with the Bergen Climate Model. The typical AMOC variability has amplitudes of 1 Sverdrup (1 Sv = 106 m3 s-1) and time scales of 40-70 years. The model is reproducing the observed dense water formation regions and has very realistic ocean transports and water mass distributions. The dense water produced in the Labrador Sea (1/3) and in the Nordic Seas, including the water entrained into the dense overflows across the Greenland-Scotland Ridge (GSR; 2/3), are the sources of North Atlantic Deep Water (NADW) forming the lower limb of the AMOC's northern overturning. The variability in the Labrador Sea and the Nordic Seas convection is driven by decadal scale air-sea fluxes in the convective region that can be related to opposite phases of the North Atlantic Oscillation. The Labrador Sea convection is directly linked to the variability in AMOC. Linkages between convection and water mass transformation in the Nordic Seas are more indirect. The Scandinavian Pattern, the third mode of atmospheric variability in the North Atlantic, is a driver of the ocean's poleward heat transport (PHT), the overall constraint on northern water mass transformation. Increased PHT is both associated with an increased water mass exchange across the GSR, and a stronger AMOC.

  2. Investigating the role of the Sun, the quasi-biennial oscillation, and the pacific decadal oscillation on decadal climate variability of the stratosphere

    NASA Astrophysics Data System (ADS)

    Kren, Andrew Charles

    Assessing and distinguishing between natural climate variability and anthropogenic forcing, and quantifying their relative contributions to climate change is a formidable challenge. Understanding how variations in the Sun and natural modes of variability affect the climate system will aid future climate projections. The Sun is Earth's primary source of energy, providing a global average irradiance that is four orders of magnitude greater than the largest secondary energy source, Earth's interior heat flux. Variations in the Sun occur both in the total solar irradiance and solar spectral irradiance (SSI), impacting the ocean, troposphere, and stratosphere via atmospheric winds, temperature, and planetary waves. Yet one of the difficulties in assessing the solar response is the fact that several internal modes of variability are present which can prevent accurate detection. The response of the stratosphere to the combined interaction of the Quasi-Biennial Oscillation (QBO) and the solar cycle was investigated using the Whole Atmosphere Community Climate Model (WACCM). Transient and fully coupled simulations that included observed greenhouse gases, varying SSI, and an internally generated QBO, were analyzed. A persistent wintertime solar response in the polar vortex when stratifying by QBO phase was not found. Results contradict conclusions drawn from observational data over the period 1953-2012. The Pacific Decadal Oscillation (PDO) is defined as the leading mode of sea surface temperature variability in the North Pacific, oscillating on decadal timescales. Changes in the PDO are linked to changes in precipitation, temperature, sea-level pressure, and sea-level height changes. Here we show in WACCM that the PDO also influences the stratosphere, with a weaker polar vortex in the positive PDO phase, which has implications for decadal prediction. Some evidence also points to possible modulation of the PDO by the solar cycle, which may provide an additional pathway for the Sun to impact decadal climate.

  3. 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.

  4. 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 increasing evaporation and transpiration processes. Second, annual variability in streamflow is not statistically correlated with annual temperature variability but appears to be highly correlated with annual precipitation variability. This implies that on a year-to-year basis, changes in streamflow volumes are directly affected by precipitation and not temperature. Future development of a predictive streamflow model will need to take into consideration these two processes to obtain accurate results. In order to extend predictive skill to the multi-year scale relationships between precipitation, temperature and persistent climate indices such as the Pacific Decadal Oscillation, Atlantic Multidecadal Oscillation and El Nino/Southern Oscillation will need to be examined.

  5. Photometric variability in earthshine observations.

    PubMed

    Langford, Sally V; Wyithe, J Stuart B; Turner, Edwin L

    2009-04-01

    The identification of an extrasolar planet as Earth-like will depend on the detection of atmospheric signatures or surface non-uniformities. In this paper we present spatially unresolved flux light curves of Earth for the purpose of studying a prototype extrasolar terrestrial planet. Our monitoring of the photometric variability of earthshine revealed changes of up to 23% per hour in the brightness of Earth's scattered light at around 600 nm, due to the removal of specular reflection from the view of the Moon. This variability is accompanied by reddening of the spectrum and results from a change in surface properties across the continental boundary between the Indian Ocean and Africa's east coast. Our results based on earthshine monitoring indicate that specular reflection should provide a useful tool in determining the presence of liquid water on extrasolar planets via photometric observations. PMID:19344309

  6. Observations of solar irradiance variability

    SciTech Connect

    Willson, R.C.; Janssen, M..; Hudson, H.S.; Chapman, G.A.; Bulkis, S.

    1981-02-13

    High-precision measurements of total solar irradiance, made by the active cavity radiometer irradiance monitor on the Solar Maximum Mission satellite, show the irradiance to have been variable throughout the first 153 days of observations. The corrected data resolve orbit-to-orbit variations with uncertainties as small as 0.001 percent. Irradiance fluctuations are typical of a band-limited noise spectrum with high-frequency cutoff near 0.15 day/sup -1/; their amplitudes about the mean value of 1368.31 watts per square meter approach +- 0.05 percent. Two large decreases in irradiance of up to 0.2 percent lasting about 1 week are highly correlated with the development of sunspot groups. The magnitude and time scale of the irradiance variability suggest that considerable energy storage occurs within the convection zone in solar active regions.

  7. Observations of solar irradiance variability.

    PubMed

    Willson, R C; Gulkis, S; Janssen, M; Hudson, H S; Chapman, G A

    1981-02-13

    High-precision measurements of total solar irradiance, made by the active cavity radiometer irradiance monitor on the Solar Maximum Mission satellite, show the irradiance to have been variable throughout the first 153 days of observations. The corrected data resolve orbit-to-orbit variations with uncertainties as small as 0.001 percent. Irradiance fluctuations are typical of a band-limited noise spectrum with high-frequency cutoff near 0.15 day(-1) their amplitudes about the mean value of 1368.31 watts per square meter approach +/- 0.05 percent. Two large decreases in irrradiance of up to 0.2 percent lasting about 1 week are highly correlated with the development of sunspot groups. The magnitude and time scale of the irradiance variability suggest that considerable energy storage occurs within the convection zone in solar active regions. PMID:17776650

  8. Polar lightning and decadal-scale cloud variability on Jupiter.

    PubMed

    Baines, Kevin H; Simon-Miller, Amy A; Orton, Glenn S; Weaver, Harold A; Lunsford, Allen; Momary, Thomas W; Spencer, John; Cheng, Andrew F; Reuter, Dennis C; Jennings, Donald E; Gladstone, G R; Moore, Jeffrey; Stern, S Alan; Young, Leslie A; Throop, Henry; Yanamandra-Fisher, Padma; Fisher, Brendan M; Hora, Joseph; Ressler, Michael E

    2007-10-12

    Although lightning has been seen on other planets, including Jupiter, polar lightning has been known only on Earth. Optical observations from the New Horizons spacecraft have identified lightning at high latitudes above Jupiter up to 80 degrees N and 74 degrees S. Lightning rates and optical powers were similar at each pole, and the mean optical flux is comparable to that at nonpolar latitudes, which is consistent with the notion that internal heat is the main driver of convection. Both near-infrared and ground-based 5-micrometer thermal imagery reveal that cloud cover has thinned substantially since the 2000 Cassini flyby, particularly in the turbulent wake of the Great Red Spot and in the southern half of the equatorial region, demonstrating that vertical dynamical processes are time-varying on seasonal scales at mid- and low latitudes on Jupiter. PMID:17932285

  9. Decadal Climate Variability: Economic Implications in Agriculture and Water in the Missouri River Basin 

    E-print Network

    Fernandez Cadena, Mario

    2013-07-23

    Economic research on climate and productivity effects of ocean phenomena has mostly focused on interannual cases such as the El Niño Southern Oscillation. Here Decadal climate variability (DCV) refers to ocean related climate influences of duration...

  10. Influence of Mean State on Climate Variability at Interannual and Decadal Time Scales 

    E-print Network

    Zhu, Xiaojie

    2013-05-17

    This dissertation reports on studies on the role of the mean state in modulating climate variability at interannual and decadal time scales. In the atmosphere, the nonlinear superposition of mean flow and anomalous flow has important implications...

  11. Variability of western Amazon dry-season precipitation extremes: importance of decadal fluctuations and implications for predictability

    NASA Astrophysics Data System (ADS)

    Fernandes, K.; Baethgen, W.; Verchot, L. V.; Giannini, A.; Pinedo-Vasquez, M.

    2014-12-01

    A complete assessment of climate change projections requires understanding the combined effects of decadal variability and long-term trends and evaluating the ability of models to simulate them. The western Amazon severe droughts of the 2000s were the result of a modest drying trend enhanced by reduced moisture transport from the tropical Atlantic. Most of the WA dry-season precipitation decadal variability is attributable to decadal fluctuations of the north-south gradient (NSG) in Atlantic sea surface temperature (SST). The observed WA and NSG decadal co-variability is well reproduced in Global Climate Models (GCMs) pre-industrial control (PIC) and historical (HIST) experiments that were part of the Intergovernmental Panel on Climate Change fifth assessment report (IPCC-AR5). This suggests that unforced or natural climate variability, characteristic of the PIC simulations, determines the nature of this coupling, as the results from HIST simulations (forced with greenhouse gases (GHG) and natural and anthropogenic aerosols) are comparable in magnitude and spatial distribution. Decadal fluctuation in the NSG also determines shifts in the probability of repeated droughts and pluvials in WA, as there is a 65% chance of 3 or more years of droughts per decade when NSG>0 compared to 18% when NSG<0. The HIST and PIC model simulations also reproduce the observed shifts in probability distribution of droughts and pluvials as a function of the NSG decadal phase, suggesting there is great potential for decadal predictability based on GCMs. Persistence of the current NSG positive phase may lead to continuing above normal frequencies of western Amazon dry-season droughts.

  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. OCEAN CIRCULATION. Observing the Atlantic Meridional Overturning Circulation yields a decade of inevitable surprises.

    PubMed

    Srokosz, M A; Bryden, H L

    2015-06-19

    The importance of the Atlantic Meridional Overturning Circulation (AMOC) heat transport for climate is well acknowledged. Climate models predict that the AMOC will slow down under global warming, with substantial impacts, but measurements of ocean circulation have been inadequate to evaluate these predictions. Observations over the past decade have changed that situation, providing a detailed picture of variations in the AMOC. These observations reveal a surprising degree of AMOC variability in terms of the intraannual range, the amplitude and phase of the seasonal cycle, the interannual changes in strength affecting the ocean heat content, and the decline of the AMOC over the decade, both of the latter two exceeding the variations seen in climate models. PMID:26089521

  15. Decadal variability in biogeochemical models: Comparison with a 50-year ocean colour dataset

    NASA Astrophysics Data System (ADS)

    Henson, Stephanie A.; Raitsos, Dionysios; Dunne, John P.; McQuatters-Gollop, Abigail

    2009-11-01

    Assessing the skill of biogeochemical models to hindcast past variability is challenging, yet vital in order to assess their ability to predict biogeochemical change. However, the validation of decadal variability is limited by the sparsity of consistent, long-term biological datasets. The Phytoplankton Colour Index (PCI) product from the Continuous Plankton Recorder survey, which has been sampling the North Atlantic since 1948, is an example of such a dataset. Converting the PCI to chlorophyll values using SeaWiFS data allows a direct comparison with model output. Here we validate decadal variability in chlorophyll from the GFDL TOPAZ model. The model demonstrates skill at reproducing interannual variability, but cannot simulate the regime shifts evident in the PCI data. Comparison of the model output, data and climate indices highlights under-represented processes that it may be necessary to include in future biogeochemical models in order to accurately simulate decadal variability in ocean ecosystems.

  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 period/events considered. The joint SST + SSS nudging applied everywhere is the most efficient approach. It ensures that the right water masses are formed at the right surface density, the subsequent circulation, subduction and deep convection further transporting them at depth. The results of this study underline the potential key role of SSS for decadal predictability and further make the case for sustained large-scale observations of this field.

  17. 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.

  18. Observations of Interesting Cataclysmic Variables

    NASA Astrophysics Data System (ADS)

    Dai, Zhibin; Szkody, Paula; Garnavich, Peter M.; Kennedy, Mark

    2015-01-01

    Cataclysmic Variables (CVs) comprise one category of active mass transfer binaries containing a white dwarf accreting from an orbiting late main-sequence companion. Undoubtedly, non-magnetic CVs, intermediate polars and polars constitute a powerful probe of the structure of accretion onto white dwarfs and the theories of angular momentum loss, which elucidate the long-term evolution leading to the formation of these short period compact binaries. Combining photometric and spectroscopic data from space and ground telescopes can lead to novel discoveries. The SDSS survey provided a large dataset of spectra of different types of CVs. Followup photometry and spectroscopy is still underway to determine the unique properties of the objects identified as CVs. The Kepler program provided the first look at the variability of CVs over a continuous timescale of months. The extension of the program to the K2 fields allows further sets of CVs to be explored. We present some interesting results for several new CVs found in the SDSS and Kepler surveys which include their behavior during quiescence and outburst. These observations further demonstrate the complexities of CVs. This research was partially funded by CAS visiting scholar grant, NSF grant AST-1008734 and NASA grant HST-GO12870.

  19. Holocene Multi-Decadal to Millennial-Scale Hydrologic Variability on the South American Altiplano

    NASA Astrophysics Data System (ADS)

    Fritz, S. C.; Baker, P. A.; Ekdahl, E.; Burns, S.

    2006-12-01

    On orbital timescales, lacustrine sediment records in the tropical central Andes show massive changes in lake level due to mechanisms related to global-scale drivers, varying at precessional timescales. Here we use stable isotopic and diatom records from two lakes in the Lake Titicaca drainage basin to reconstruct multi- decadal to millennial scale precipitation variability during the last 7000 to 8000 years. The records are tightly coupled at multi-decadal to millennial scales with each other and with lake-level fluctuations in Lake Titicaca, indicating that the lakes are recording a regional climate signal. A quantitative reconstruction of precipitation from stable isotopic data indicates that the central Andes underwent significant wet to dry alternations at multi- centennial frequencies with an amplitude of 30 to 40% of total precipitation. A strong millennial-scale component, similar in duration to periods of increased ice rafted debris flux in the North Atlantic, is observed in both lake records, suggesting that tropical North Atlantic sea-surface temperature (SST) variability may partly control regional precipitation. No clear relationship is evident between these records and the inferred ENSO history from Lago Pallcacocha in the northern tropical Andes. In the instrumental period, regional precipitation variability on inter-annual timescales is clearly influenced by Pacific modes; for example, most El Ninos produce dry and warm conditions in this part of the central Andes. However, on longer timescales, the control of tropical Pacific modes is less clear. Our reconstructions suggest that the cold intervals of the Holocene Bond events are periods of increased precipitation in the central Andes, thus indicating an anti-phasing of precipitation variation in the southern tropics of South America relative to the Northern Hemisphere monsoon region.

  20. 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.

  1. HERSCHEL OBSERVATIONS OF CATACLYSMIC VARIABLES

    SciTech Connect

    Harrison, Thomas E.; Hamilton, Ryan T.; Tappert, Claus; Hoffman, Douglas I.; Campbell, Ryan K. E-mail: rthamilt@nmsu.edu E-mail: dhoffman@ipac.caltech.edu

    2013-01-01

    We have used the PACS instrument on the Herschel Space Observatory to observe eight cataclysmic variables at 70 and 160 {mu}m. Of these eight objects, only AM Her was detected. We have combined the Herschel results with ground-based, Spitzer, and WISE observations to construct spectral energy distributions for all of the targets. For the two dwarf novae in the sample, SS Cyg and U Gem, we find that their infrared luminosities are completely dominated by their secondary stars. For the two highly magnetic 'polars' in our survey, AM Her and EF Eri, we find that their mid-infrared excesses, previously attributed to circumbinary dust emission, can be fully explained by cyclotron emission. The WISE light curves for both sources show large, orbitally modulated variations that are identically phased to their near-IR light curves. We propose that significant emission from the lowest cyclotron harmonics (n {<=} 3) is present in EF Eri and AM Her. Previously, such emission would have been presumed to be optically thick, and not provide significant orbitally modulated flux. This suggests that the accretion onto polars is more complicated than assumed in the simple models developed for these two sources. We develop a model for the near-/mid-IR light curves for WZ Sge with an L2 donor star that shows that the ellipsoidal variations from its secondary star are detected. We conclude that none of the targets surveyed have dusty circumbinary disks.

  2. Added-value from initialization in predictions of Atlantic multi-decadal variability

    NASA Astrophysics Data System (ADS)

    García-Serrano, J.; Guemas, V.; Doblas-Reyes, F. J.

    2015-05-01

    Identifying regions sensitive to external radiative changes, including anthropogenic (sulphate aerosols and greenhouse gases) and natural (volcanoes and solar variations) forcings, is important to formulate actionable information at multi-year time-scales. Internally-generated climate variability can overcome this radiative forcing, especially at regional level, so that detecting the areas for this potential dominance is likewise critical for decadal prediction. This work aims to clarify where each contribution has the largest effect on North Atlantic sea surface temperature (SST) predictions in relation to the Atlantic multi-decadal variability (AMV). Initialized decadal hindcasts and radiatively-forced historical simulations from the fifth phase of the Climate Model Intercomparison Project are analysed to assess multi-year skill of the AMV. The initialized hindcasts reproduce better the phase of the AMV index fluctuations. The radiatively-forced component consists of a residual positive trend, although its identification is ambiguous. Initialization reduces the inter-model spread when estimating the level of AMV skill, thus reducing its uncertainty. Our results show a skilful performance of the initialized hindcasts in capturing the AMV-related SST anomalies over the subpolar gyre and Labrador Sea regions, as well as in the eastern subtropical basin, and the inability of the radiatively-forced historical runs to simulate the horseshoe-like AMV signature over the North Atlantic. Initialization outperforms empirical predictions based on persistence beyond 1-4 years ahead, suggesting that ocean dynamics play a role in the AMV predictability beyond the thermal inertia. The initialized hindcasts are also more skilful at reproducing the observed AMV teleconnection to the West African monsoon. The impact of the start date frequency is also described, showing that the standard of 5-year interval between start dates yields the main features of the AMV skill that are robustly detected in hindcasts with yearly start date sampling. This work updates previous studies, complementing them, and concludes that skilful initialized multi-model forecasts of the AMV-related climate variability can be formulated, improving uninitialized projections, until 3-6 years ahead.

  3. 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.

  4. 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. PMID:26667904

  5. 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-order Taylor series analysis of wind speed, SST, near-surface stability and relative humidity variations around climatology to gauge the importance of these components. We find that the MERRA-2 evaporation record is strongly influenced by the availability of wind speed and humidity from passive microwave imagers beginning in the late 1980s as well as by the SST record. The trend over the period 1980 to present is nearly 10%. AMIP or the ERA-20C trends are much smaller. We find that ENSO-related signals involving both wind speed and thermodynamic variability remain the primary signal in the latter and are confirmed by satellite retrievals. We present uncertainty estimates based on the various data sources and discuss the implications for GEWEX water and energy budget science challenges.

  6. The GEOS Association of Variable Star Observers

    NASA Astrophysics Data System (ADS)

    Hambsch, F.-J.; LeBorgne, J.-F.; Poretti, E.; GEOS association

    2012-06-01

    (Abstract only) Groupe Européen d'Observation Stellaire (GEOS) is an astronomical association created in the 1970s to promote research among amateurs in Europe. We started in Belgium, France, and Italy, later extended to Spain, Switzerland, and Germany, and more recently, added U.S. amateurs. The basic idea was that amateurs should themselves extract scientific information from their observations (visually at first and later electronically) and publish their results. Some GEOS members have become professional astronomers and the amateur-professional collaboration has strengthened over the years. From the beginning, it has been clear that the study of variable stars is a privileged topic where such projects can develop. Since the 1980s GEOS members have published a number of scientific papers, even in refereed professional journals. Presently, observations are mainly done using CCD cameras though visual measurements still exist. In the past decade our main development has been the creation of a public RR Lyr star maxima database. This is a unique tool for the study of RR Lyr stars, as it enables the user to follow period variations since a star's discovery, some over 100 years ago. In parallel to the database, a project called "GEOS RR Lyr survey" was designed. Its aims include: first, add significantly more maxima timings of the brightest RR Lyr stars essentially using robotic telescopes; second, study fainter understudied stars to refine their period and find new stars which exhibit the so-called Blazhko effect; third, characterize the Blazhko effect, one of our main research topics. Other variable stars are also studied: eclipsing binaries, d Scuti stars, and so on. GEOS has a good cooperation with other variable star associations, mainly BAV and AAVSO.

  7. Three Essays on Economic and Societal Implications of Decadal Climate Variability and Fishery Management 

    E-print Network

    Huang, Pei

    2015-07-02

    climate patterns for an extended time period (Mehta 1998; Mantua and Hare 2002; Wang and Mehta 2008; McCabe et al. 2008). These DCV phenomena have been found to affect 2 agricultural productivity in crop simulation studies (Mehta, Rosenberg... to the ENSO and NAO, another category of ocean-related climate variability is called decadal climate variability, which lasts a longer period of time (Mehta, Rosenberg, and Mendoza 2011). More and more evidence shows that climate 4 anomalies...

  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 to seasonal variability of Arctic sea ice albedo S. Agarwal,1,2

    E-print Network

    Wettlaufer, John S.

    Decadal to seasonal variability of Arctic sea ice albedo S. Agarwal,1,2 W. Moon,2 and J. S for model studies of albedo parameteriza- tions and sensitivities. Citation: Agarwal, S., W. Moon, and J. S of insitu measure- ments highlights the importance of combining field and space based methods to examine

  10. Variability of the Kuroshio Extension Jet, Recirculation Gyre, and Mesoscale Eddies on Decadal Time Scales

    E-print Network

    Qiu, Bo

    Variability of the Kuroshio Extension Jet, Recirculation Gyre, and Mesoscale Eddies on Decadal Time-frequency changes and the interconnections of the Kuroshio Extension (KE) jet, its southern recirculation gyre, and their mesoscale eddy field. The dominant signal is characterized by the steady weakening of the KE jet/recirculation

  11. 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 land areas and a bimodal annual cycle with the major rainy season during MAM (often called the ``long rains'' by local people) and the second during OND (the "short rains"). To explore these distinctive features, we use the ERA-Interim Re-Analysis data to analyze the associated annual cycles of atmospheric convective stability, circulation and moisture budget. The atmosphere over East Africa is found to be convectively stable, in general, year-round but with an annual cycle dominated by the surface moist static energy (MSE), which is in phase with the precipitation annual cycle. Throughout the year, the atmospheric circulation is dominated by a pattern of convergence near the surface, divergence in the lower troposphere and convergence again at upper levels. Consistently, the convergence of the vertically integrated moisture flux is mostly negative across the year, but becomes weakly positive in the two rainy seasons. It is suggested the semi-arid/arid climate in East Africa and its bimodal rainfall annual cycle can be explained by the ventilation mechanism, in which the atmospheric convective stability over East Africa is controlled by the import of low MSE air from the relatively cool Indian Ocean off the coast and the cold winter hemisphere. During the rainy seasons, however, the off-coast SST increases (and is warmest during the long rains season) and the northerly or southerly weakens, and consequently the air imported into East Africa becomes less stable. The MSE framework is then applied to study the coupling-induced bias of the East African rainfall annual cycle often found in CMIP3/5 coupled models that overestimates the OND rainfall and underestimates the MAM rainfall, by comparing the historical (coupled) and the AMIP runs (SST-forced) for each model. It is found that a warm north and cold south SST bias over the Indian Ocean induced in coupled models is responsible for the dry MAM rainfall bias over East Africa while the ocean dynamics induced warm west and cold east SST bias over the Indian Ocean contributes to the wet OND rainfall bias in

  12. Linkage between the Pacific Decadal Oscillation and the low frequency variability of the Pacific Subtropical Cell

    NASA Astrophysics Data System (ADS)

    Hong, Lingya; Zhang, Liping; Chen, Zhaohui; Wu, Lixin

    2014-06-01

    The decadal variability of Pacific Subtropical Cell (STC) and its linkages with the Pacific Decadal Oscillation (PDO) are investigated in the present study based on a Simple Ocean Data Assimilation (SODA 2.2.4). It is found that, on decadal time scales, the western boundary and interior pycnocline transports are anticorrelated and the variation of the interior component is more significant, which is consistent with previous studies. The decadal variability of STC in the Northern Hemisphere is found to be strongly associated with PDO. Associated with a positive (negative) phase of PDO, the relaxation (acceleration) of the northeast trades slows down (spins up) the STC within a few years through baroclinic adjustment in conjunction with the subduction of the cold (warm) mixed-layer anomalies in the extratropics. The cold (warm) water is then injected into the thermocline and advected further southwestward to the tropics along the isopycnal surfaces, leading to the slowdown (spin-up) of STC due to zonal pressure gradient change at low latitude. Along with the STC weakening (strengthening), a significant warming (cold) anomaly appears in the tropics and it is advected to the midlatitude by the Kuroshio and North Pacific currents, thus feeding back to the atmosphere over the North Pacific. In contrast to the Northern Hemisphere, it is found the STC in the south only passively responds to the PDO. The mechanism found here highlights the role of the STC advection of extratropical anomalies to the tropics and horizontal gyre advection of the tropical anomalies to the extratropics in decadal variability of the STC and PDO.

  13. 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.

  14. 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

  15. Rule-based System Architecting of Earth Observing Systems: The Earth Science Decadal Survey

    E-print Network

    de Weck, Olivier L.

    Rule-based System Architecting of Earth Observing Systems: The Earth Science Decadal Survey Daniel satellite systems, and applies it to the Earth Science Decadal Survey. The architecting problem In 2004, the NASA Office of Earth Science, the National Oceanic and Atmospheric Administration (NOAA

  16. 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

  17. Holocene Decadal to Multidecadal Hydrologic Variability in the Everglades: Climate and Implications for Ecosystem Management

    NASA Astrophysics Data System (ADS)

    Moses, C. S.; Anderson, W. T.; Saunders, C.; Rebenack, C.

    2009-12-01

    The Florida Everglades are a complex, unique ecosystem. Adding to the complexity, a system of canals and gates control the flow of waters from central Florida southward into the Everglades, and ultimately Florida Bay and the Gulf of Mexico. With south Florida’s distinct wet and dry seasons, the hydrology has driven ecosystem evolution over the last 4-5 kya. However, since the 1920s the water content of the Everglades has largely been anthropogenically modulated, with the exception of the natural variability of evaporation and precipitation over the large area south of the Tamiami Trail. Because of the incredibly flat nature of the Everglades, small changes in the freshwater balance have substantial impacts on the diversity and distribution of organisms. Decadal and multidecadal variability in precipitation, hurricane incidence, and sea level rise all have important effects on the ecosystem. During the instrumental record, the natural precipitation across south Florida has been strongly influenced by combinations of the Atlantic Multidecadal Oscillation, Pacific Decadal Oscillation, and ENSO. Here we discuss evidence of natural climate variability impacts on the ecosystem beyond the anthropogenic hydrological controls. Proxy environmental data from seeds, charcoal, and trees, plus the sparse, but available, instrumental records provide evidence of changes in the ecosystem over the Holocene, and suggest considerations for future management.

  18. Rule-Based System Architecting of Earth Observing Systems: Earth Science Decadal Survey

    E-print Network

    Selva, Daniel

    This paper presents a methodology to explore the architectural trade space of Earth observing satellite systems, and applies it to the Earth Science Decadal Survey. The architecting problem is formulated as a combinatorial ...

  19. Hiatuses in global warming: the role of volcanic eruptions and Pacific decadal variability

    NASA Astrophysics Data System (ADS)

    Maher, Nicola; England, Matthew; Gupta, Alexander Sen; McGregor, Shayne

    2015-04-01

    The latest generation of climate model simulations is used to investigate hiatuses in global warming. Large tropical volcanic eruptions are found to cause decade long hiatus periods consistently across the models. These eruptions not only cool the globe to cause hiatus decades, but are also found to influence modes of Indo-Pacific variability. Specifically we find an increased probability of an initial positive Indian Ocean Dipole / El Niño-like response followed by a La Niña-like cooling in the third Southern Hemisphere summer after the eruption, which may increase the persistence of the post-volcanic global cooling anomaly. We further demonstrate that most non-volcanic hiatuses across CMIP5 models are associated with enhanced cooling in the equatorial eastern Pacific, linked to a transition to the negative phase of the Interdecadal Pacific Oscillation. Finally, two future scenarios are investigated to determine the likelihood of hiatus periods occurring under different rates of greenhouse gas emissions. Under high rates of greenhouse gas emissions there is little chance of a hiatus decade occurring beyond 2030, even in the event of a large volcanic eruption.

  20. Interannual to decadal oxygen variability in the mid-depth water masses of the eastern North Atlantic

    NASA Astrophysics Data System (ADS)

    Stendardo, Ilaria; Kieke, Dagmar; Rhein, Monika; Gruber, Nicolas; Steinfeldt, Reiner

    2015-01-01

    The detection of multi-decadal trends in the oceanic oxygen content and its possible attribution to global warming is protracted by the presence of a substantial amount of interannual to decadal variability, which hitherto is poorly known and characterized. Here we address this gap by studying interannual to decadal changes of the oxygen concentration in the Subpolar Mode Water (SPMW), the Intermediate Water (IW) and the Mediterranean Outflow Water (MOW) in the eastern North Atlantic. We use data from a hydrographic section located in the eastern North Atlantic at about 48°N repeated 12 times over a period of 19 years from 1993 through 2011, with a nearly annual resolution up to 2005. Despite a substantial amount of year-to-year variability, we observe a long-term decrease in the oxygen concentration of all three water masses, with the largest changes occurring from 1993 to 2002. During that time period, the trends were mainly caused by a contraction of the subpolar gyre associated with a northwestward shift of the Subpolar Front (SPF) in the eastern North Atlantic. This caused SPMW to be ventilated at lighter densities and its original density range being invaded by subtropical waters with substantially lower oxygen concentrations. The contraction of the subpolar gyre reduced also the penetration of IW of subpolar origin into the region in favor of an increased northward transport of IW of subtropical origin, which is also lower in oxygen. The long-term oxygen changes in the MOW were mainly affected by the interplay between circulation and solubility changes. Besides the long-term signals, mesoscale variability leaves a substantial imprint as well, affecting the water column over at least the upper 1000 m and laterally by more than 400 km. Mesoscale eddies induced changes in the oxygen concentration of a magnitude that can substantially alias analyses of long-term changes based on repeat hydrographic data that are being collected at intervals of typically 10 years.

  1. 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

    Land surface phenological cycles of vegetation greening and browning are influenced by variability in climatic forcing. Quantitative information on phenological cycles and their variability 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 reoccurring patterns. Yet, 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, the driest inhabited continent with one of the most variable rainfall climates in the world and vast areas of dryland systems. Detailed and internally consistent studies investigating phenological cycles and their response to climate variability across the entire continent designed specifically for Australian dryland conditions are missing. To fill this knowledge gap and to advance phenological research, we used existing methods more effectively to study geographic and climate-driven variability in phenology over Australia. We linked derived phenological metrics with rainfall and the Southern Oscillation Index (SOI). We based our analysis on Enhanced Vegetation Index (EVI) data from the MODerate Resolution Imaging Spectroradiometer (MODIS) from 2000 to 2013, which included extreme drought and wet years. We conducted a continent-wide investigation of the link between phenology and climate variability 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 variability in phenological cycles. Phenological cycle peaks occurred not only during the austral summer but at any time of the year, and their timing varied by more than a month in the interior of the 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.

  2. Dynamics and mechanisms of decadal variability of the Pacific-South America mode over the 20th century

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Ma, Hao; Wu, Lixin

    2015-08-01

    In this paper, decadal variability 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-decadal variability with distinct timescales between 3-8 and 10-18 years, respectively. The decadal variability 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 decadal variability of the PSA mode.

  3. 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

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system designed to study Earth's climate variability with unprecedented absolute radiometric accuracy and SI traceability. Observation System Simulation Experiments (OSSEs) were developed using GCM output and MODTRAN to simulate CLARREO reflectance measurements during the 21st century as a design tool for the CLARREO hyperspectral shortwave imager. With OSSE simulations of hyperspectral reflectance, Feldman et al. [2011a,b] found that shortwave reflectance is able to detect changes in climate variables during the 21st century and improve time-to-detection compared to broadband measurements. The OSSE has been a powerful tool in the design of the CLARREO imager and for understanding the effect of climate change on the spectral variability of reflectance, but it is important to evaluate how well the OSSE simulates the Earth's present-day spectral variability. For this evaluation we have used hyperspectral reflectance measurements from the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), a shortwave spectrometer that was operational between March 2002 and April 2012. To study the spectral variability of SCIAMACHY-measured and OSSE-simulated reflectance, we used principal component analysis (PCA), a spectral decomposition technique that identifies dominant modes of variability in a multivariate data set. Using quantitative comparisons of the OSSE and SCIAMACHY PCs, we have quantified how well the OSSE captures the spectral variability of Earth?s climate system at the beginning of the 21st century relative to SCIAMACHY measurements. These results showed that the OSSE and SCIAMACHY data sets share over 99% of their total variance in 2004. Using the PCs and the temporally distributed reflectance spectra projected onto the PCs (PC scores), we can study the temporal variability of the observed and simulated reflectance spectra. Multivariate time 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.

  4. A Robust Decision-Making Technique for Water Management under Decadal Scale Climate Variability

    NASA Astrophysics Data System (ADS)

    Callihan, L.; Zagona, E. A.; Rajagopalan, B.

    2013-12-01

    Robust decision making, a flexible and dynamic approach to managing water resources in light of deep uncertainties associated with climate variability at inter-annual to decadal time scales, is an analytical framework that detects when a system is in or approaching a vulnerable state. It provides decision makers the opportunity to implement strategies that both address the vulnerabilities and perform well over a wide range of plausible future scenarios. A strategy that performs acceptably over a wide range of possible future states is not likely to be optimal with respect to the actual future state. The degree of success--the ability to avoid vulnerable states and operate efficiently--thus depends on the skill in projecting future states and the ability to select the most efficient strategies to address vulnerabilities. This research develops a robust decision making framework that incorporates new methods of decadal scale projections with selection of efficient strategies. Previous approaches to water resources planning under inter-annual climate variability combining skillful seasonal flow forecasts with climatology for subsequent years are not skillful for medium term (i.e. decadal scale) projections as decision makers are not able to plan adequately to avoid vulnerabilities. We address this need by integrating skillful decadal scale streamflow projections into the robust decision making framework and making the probability distribution of this projection available to the decision making logic. The range of possible future hydrologic scenarios can be defined using a variety of nonparametric methods. Once defined, an ensemble projection of decadal flow scenarios are generated from a wavelet-based spectral K-nearest-neighbor resampling approach using historical and paleo-reconstructed data. This method has been shown to generate skillful medium term projections with a rich variety of natural variability. The current state of the system in combination with the probability distribution of the projected flow ensembles enables the selection of appropriate decision options. This process is repeated for each year of the planning horizon--resulting in system outcomes that can be evaluated on their performance and resiliency. The research utilizes the RiverSMART suite of software modeling and analysis tools developed under the Bureau of Reclamation's WaterSMART initiative and built around the RiverWare modeling environment. A case study is developed for the Gunnison and Upper Colorado River Basins. The ability to mitigate vulnerability using the framework is gauged by system performance indicators that measure the ability of the system to meet various water demands (i.e. agriculture, environmental flows, hydropower etc.). Options and strategies for addressing vulnerabilities include measures such as conservation, reallocation and adjustments to operational policy. In addition to being able to mitigate vulnerabilities, options and strategies are evaluated based on benefits, costs and reliability. Flow ensembles are also simulated to incorporate mean and variance from climate change projections for the planning horizon and the above robust decision-making framework is applied to evaluate its performance under changing climate.

  5. 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.

    2014-09-01

    Land surface phenological cycles of vegetation greening and browning are influenced by variability in climatic forcing. Quantitative spatial information on phenological cycles and their variability 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 variable 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 variability are missing. To fill this knowledge gap, we developed an algorithm to characterize phenological cycles, and analyzed geographic and climate-driven variability 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 variability 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, predominantly over natural land cover and particularly in floodplain and wetland areas. Integrated greenness of the phenological cycles (surrogate of vegetation productivity) showed positive anomalies of more than 2 standard deviations over most of eastern Australia in 2009-2010, which coincided with the transition from the El Niño-induced decadal droughts to flooding caused by La Niña.

  6. A model data comparison of different classes of LSW and interannual to decadal variability in a FESOM model setup

    NASA Astrophysics Data System (ADS)

    Scholz, Patrick; Lohmann, Gerrit; Ionita, Monica; Kieke, Dagmar; Rhein, Monika

    2013-04-01

    The climate in the Atlantic region is essentially influenced by the Atlantic meridional overturning circulation (AMOC) which carries warm waters into northern latitudes and returns cold deep water southward across the equator. In the Labrador Sea basin a major component of the cold limb of the Atlantic meridional overturning circulation (AMOC) is formed. The intermediate water mass that is part of this deep convection process is the Labrador Sea Water (LSW) which can be separated into two different classes: the deep LSW (dLSW) and the less dense upper LSW (uLSW). Both LSW modes are formed by convection, accompanied by a strong surface cooling during winter conditions, which leads to an increase in the near-surface density and to an unstable stratification and a homogenization of the water column. In this study we simulated the deep-water formation in the Labrador Sea using the Finite-Element Sea-Ice Ocean Model (FESOM) in a global model setup with regional focus on the Labrador Sea and Greenland Sea. We evaluated the capability of the model setup to reproduce a realistic deep water formation in the Labrador Sea by analyzing the modeled Labrador Sea hydrography and we compared the modeled and observational derived dLSW and uLSW layer thicknesses for the time interval 1958-2007. It is shown that the model is able to reproduce different phases in the temporal evolution of the potential density, temperature and salinity, which are known in observational data. Based on composite maps of the thermal and haline contributions to the surface density flux we can prove that the central Labrador Sea in the model is dominated by the thermal contributions of the surface density flux, while the haline contributions are limited to the branch of the Labrador Sea Boundary Current system, where they are dominated from the haline contributions of sea ice melting and formation. Our model results feature a shielding of the central Labrador Sea from the haline contributions by the Labrador Sea Boundary Current system. Furthermore we investigated modes of interannual to decadal variability for the period 1958-2004 and attributed the general variability in the model to the atmospheric forcing and to internal modes of the ocean system. Based on a North Atlantic Deep Water (NADW) index defined for a normal and random forced FESOM run, where the interannual to decadal atmospheric variability in the random forced run is replaced by white noise, we identify modes of interannual to quasi-decadal variability of 7yr and 14yr, respectively. The origin of the 14yr variability is attributed to the atmospheric forcing, while the 7yr variability is linked to internal modes of the ocean. To further isolate the horizontal, but also the vertical variability in the model, we apply a principal oscillation pattern analysis in a three dimensional context. Two exceptional stable interannual modes are captured by the POP analysis and their variability is attributed to a propagating Rossby wave structure.

  7. Dynamical Role of Mode Water Ventilation in Decadal Variability in the Central Subtropical Gyre of the North Pacific*

    E-print Network

    Xie, Shang-Ping

    Dynamical Role of Mode Water Ventilation in Decadal Variability in the Central Subtropical Gyre and weakening of the STCC because of var- iations in mode water ventilation. The changes in mode water can are characteristic of changes in mode water ventilation. Indeed, this natural mode of STCC variability is excited

  8. Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

    NASA Astrophysics Data System (ADS)

    Fischer, G.; Romero, O.; Merkel, U.; Donner, B.; Iversen, M.; Nowald, N.; Ratmeyer, V.; Ruhland, G.; Klann, M.; Wefer, G.

    2015-11-01

    A more than two-decadal 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 variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal 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 observed 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 high fluxes in the following cold La Niña phase. Bakun (1990) suggested an intensification of coastal upwelling due to increased winds ("Bakun upwelling intensification hypothesis", Cropper et al., 2014) and global change. We did not observe an increase of any flux component off Cape Blanc during the past two and a half decades which might support this hypothesis. Furthermore, fluxes of mineral dust did not show any positive or negative trends over time which would have suggested enhanced desertification or "Saharan greening" during the last few decades.

  9. Decadal to pentadecadal variability of intermediate water temperature in the Sea of Okhotsk: An ice-ocean coupled model simulation

    NASA Astrophysics Data System (ADS)

    Nakanowatari, T.; Uchimoto, K.; Nakamura, T.; Mitsudera, H.; Ohshima, K. I.

    2010-12-01

    An ice-ocean coupled model with atmospheric thermal and wind stress forcings was used to examine the effects of variable atmospheric forcing on the interannual variability of the intermediate-water temperature in the Sea of Okhotsk. The simulated intermediate-water temperature has variability mainly at decadal to multidecadal time scales. The atmospheric thermal forcing affects the intermediate water temperature through the ventilation in the northern part of the Okhotsk Sea related to wintertime sea ice formation over the northwestern shelf region. The sea ice formation is sensitive to the upwind air temperature anomalies, which is related to the cold outbreaks from the Eurasia continent. On the other hand, the wind stress forcing affects the intermediate water temperature through the in- and outflow strength of the Okhotsk Sea with the North Pacific. The in/outflow is explained by the subarctic gyre circulation change related to the Aleutian low strength. The trend analysis indicates that both kinds of atmospheric forcing tend to warm the intermediate water temperature for the past 50 years. Thus, our model simulation suggests that the observed warming trend of the intermediate water temperature in the Sea of Okhotsk is caused by the weakening meridional overturning circulation as well as the intensification of the wind driven in/outflow.

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

    PubMed Central

    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.

    2007-01-01

    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. PMID:17578928

  11. Decadal surface water quality trends under variable climate, land use, and hydrogeochemical setting in Iowa, USA

    USGS Publications Warehouse

    Green, Christopher T.; Bekins, Barbara A.; Kalkhoff, Stephen J.; Hirsch, Robert M.; Liao, Lixia; Barnes, Kimberlee K.

    2014-01-01

    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 variability of annual precipitation. To examine the effects of these changes, surface water quality was analyzed in 10 major Iowa Rivers. Several decades 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 decades in peripheral basins of Iowa, and may be obscured in the central basins where extreme flows strongly affect annual concentration trends.

  12. Variability Statistics for Galaxies Observed by Kepler

    NASA Astrophysics Data System (ADS)

    Fanelli, Michael N.; Marcum, Pamela M.; Van Cleve, Jeffrey E.

    2016-01-01

    The Kepler / K2 telescope combines high photometric precision with near-continuous observing cadence, permitting a unique perspective on the optical / near-IR variability 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 observed during the Kepler prime mission: ~1200 individual light curves of ~150 targeted galaxies observed during Quarters 3-10 and ~1000 light curves of galaxies observed 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 observed occurrence rate of nuclear variability 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 variability 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 observed for the entire mission (Q2-16). Our previous result is confirmed using this expanded dataset; only a few percent of galaxies show variability above 0.5 millimag. Several systems exhibiting activity in other bands, or via their optical spectra, show no measurable variations in the Kepler band. We also provide some preliminary variability estimates from K2 data.

  13. Decadal Variability and Temperature Trends in the Middle Atmosphere From Historical Rocketsonde Data

    NASA Technical Reports Server (NTRS)

    Dunkerton, Timothy J.

    2000-01-01

    Observational 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 decade and the amplitude of the decadal 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.

  14. Satellite Observations to Benefit Science and Society: Recommended Missions for the Next Decade

    NASA Astrophysics Data System (ADS)

    Committee On Earth Science; Applications From Space

    Satellite Observations to Benefit Science and Society: Recommended Missions for the Next Decade brings the next ten years into focus for the Earth and environmental science community with a prioritized agenda of space programs, missions, and supporting activities that will best serve scientists in the next decade. These missions will address a broad range of societal needs, such as more reliable weather forecasts, early earthquake warnings, and improved pollution management, benefiting both scientific discovery and the health and well-being of society. Based on the 2007 book, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, this book explores each of the seventeen recommended missions in detail, identifying launch dates, responsible agencies, estimated cost, scientific and public benefits, and more. Printed entirely in color, the book features rich photographs and illustrations, tables, and graphs that will keep the attention of scientists and non-scientists alike.

  15. Two decades of ice melt reconstruction in Greenland and Antarctica from time-variable gravity

    NASA Astrophysics Data System (ADS)

    Talpe, M.; Nerem, R. S.; Lemoine, F. G.

    2014-12-01

    In this study, we present a record of ice-sheet melt derived from space-borne gravity that spans over two decades—beyond the time-frame of the GRACE mission. GRACE fields are merged with conventional tracking data (SLR/DORIS) spanning 1992 to the present. They are provided as weekly global fields of degree and order five without C50 and S50 but with C61 and S61. Their multi-decade timespan complements the monthly fields of GRACE of degree and order 60 that start in 2003 and will end when the GRACE mission terminates. The two datasets are combined via an empirical orthogonal function analysis, whereby the conventional tracking data temporal modes are obtained by fitting the SLR/DORIS coefficients to the GRACE spatial modes via linear least squares. Combining those temporal modes with GRACE spatial modes yields the reconstructed global gravity fields. The error budget of the reconstructions is composed of three components: the SLR/DORIS covariances, the errors estimated from the assumption that GRACE spatial modes can be mapped over the SLR/DORIS timeframe, and the covariances from the least squares fit applied to obtain the SLR/DORIS temporal modes. The reconstructed surface mass changes in Greenland and Antarctica, predominantly captured in the first mode, show a rate of mass loss that is increasing since 1992. The trend of mass changes in Greenland over various epochs match with an overarching study assembling altimetry, gravimetry, and interferometry estimates of ice-sheet balance over a 1992-2011 time-frame [Shepherd et al., 2012]. Antarctica shows a trend that is different because of updated GIA models [A et al., 2013] compared to the other studies. We will also show regional mass changes over various other basins, as well as the influence of each SLR/DORIS coefficient on the reconstructions. The consistency of these results underscores the possibility of using low-resolution SLR/DORIS time-variable gravity solutions as a way to continuously monitor the behavior of the polar ice-sheets in the absence of GRACE. Shepherd, A., et al. (2012), Science 338, 1183. A, G., J. Wahr, and S. Zhong (2013), GJI 192, 557.

  16. Decadal Scale Variability in sub Antarctic Surface and Intermediate Water Properties Across the Laschamp Geomagnetic Excursion at ODP Site 1233

    NASA Astrophysics Data System (ADS)

    Foerde, A.; Kleiven, H. F.; Ninnemann, U. S.

    2007-12-01

    Here we report decadally resolved planktonic and benthic foraminiferal oxygen isotopic proxy reconstructions of surface and intermediate ocean properties across the Laschamp geomagnetic excursion (32-43 ka) from Ocean Drilling Program (ODP) Site 1233 (41°00'S, 74°27'W, 838m) on the Chilean continental margin. The sedimentation rates at this site spanning MIS 3 (~2.2 m/kyr) allow us to nominally achieve a temporal resolution of less than 20 years with 4cm sample spacing. Site 1233 is located on the northern margin of the Antarctic Circumpolar Current (ACC) and the seafloor lies in the core of Antarctic Intermediate Water (AAIW). Thus the site is ideally situated to reconstruct both near surface and AAIW variability in the high southern latitudes. The clearly defined Laschamp event in our core provides a stratigraphic reference for comparing the relative rate and timing of abrupt changes observed at our site to those observed globally. Our initial foraminiferal oxygen isotopic results show that variations in intermediate ocean properties and climate of the southeast Pacific closely align with those recorded in the EPICA ice core from Dronning Maud Land on millennial and even centennial timescales. The broad coherence of the observed Antarctic signal supports the concept of hemispheric thermal asynchrony on millennial timescales. The extension of this climate signal into the intermediate ocean demonstrates that AAIW is extremely sensitive and responds rapidly to climate variability in its source region on a broad spectrum of timescales. Using the Laschamp as a reference point, we compare the timing of our AAIW changes to those in other regions to evaluate the importance of AAIW in propagating climate signals.

  17. A Generalized Stability Analysis of the AMOC in Earth System Models: Implication for Decadal Variability and Abrupt Climate Change

    SciTech Connect

    Fedorov, Alexey V.; Fedorov, Alexey

    2015-01-14

    The central goal of this research project was to understand the mechanisms of decadal and multi-decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) as related to climate variability 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 variability to the factors that determine AMOC predictability in the Earth system models, to the stability and variability of the AMOC in past climates.

  18. Interannual to Decadal Variability of Atlantic Water in the Nordic and Adjacent Seas

    NASA Technical Reports Server (NTRS)

    Carton, James A.; Chepurin, Gennady A.; Reagan, James; Haekkinen, Sirpa

    2011-01-01

    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 decadal variability 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.

  19. Have Aerosols Caused the Observed Atlantic Multidecadal Variability?

    E-print Network

    Zhang, Rong

    Identifying the prime drivers of the twentieth-century multidecadal variability in the Atlantic Ocean is crucial for predicting how the Atlantic will evolve in the coming decades and the resulting broad impacts on weather ...

  20. An observational evidence of decrease in Indian summer monsoon rainfall in the recent three decades of global warming era

    NASA Astrophysics Data System (ADS)

    Naidu, C. V.; Dharma Raju, A.; Satyanarayana, G. Ch.; Vinay Kumar, P.; Chiranjeevi, G.; Suchitra, P.

    2015-04-01

    The variability of summer monsoon over India has been studied using the subdivisional rainfall amounts for the period 1871-2012, upper air temperatures, Sea Surface Temperatures [SSTs] and zonal wind components for the period 1953-2012. It is observed that the rainfall activity over India during the last three decades has decreased. CRU [Climate Research Unit] and GPCP [Global Precipitation Climatology Project] rainfall data sets also exhibit a declined rainfall activity over a major part of India. This decrease in rainfall is associated with the decrease in the north-south SST gradient over the North Indian Ocean as well as monsoon circulation over India and neighborhood. Further, a decrease in the soil moisture over a major part of India is observed in the warming environment.

  1. Geostationary atmospheric composition observations from the NASA Decadal Survey GEO-CAPE mission

    NASA Astrophysics Data System (ADS)

    Edwards, D. P.; Jacob, D. J.; Al-Saadi, J. A.; Iraci, L. T.

    2012-12-01

    This paper discusses the science definition work that is being performed in preparation for the NASA Decadal 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 observations 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 decade.

  2. Impact of the river nutrient load variability on the North Aegean ecosystem functioning over the last decades

    NASA Astrophysics Data System (ADS)

    Tsiaras, K. P.; Petihakis, G.; Kourafalou, V. H.; Triantafyllou, G.

    2014-02-01

    The impact of river load variability on the North Aegean ecosystem functioning over the last decades (1980-2000) was investigated by means of a coupled hydrodynamic/biogeochemical model simulation. Model results were validated against available SeaWiFS Chl-a and in situ data. The simulated food web was found dominated by small cells, in agreement with observations, with most of the carbon channelled through the microbial loop. Diatoms and dinoflagellates presented a higher relative abundance in the more productive coastal areas. The increased phosphate river loads in the early 80s resulted in nitrogen and silicate deficiency in coastal, river-influenced regions. Primary production presented a decreasing trend for most areas. During periods of increased phosphate/nitrate inputs, silicate deficiency resulted in a relative decrease of diatoms, triggering an increase of dinoflagellates. Such an increase was simulated in the late 90s in the Thermaikos Gulf, in agreement with the observed increased occurrence of Harmful Algal Blooms. Microzooplankton was found to closely follow the relative increase of dinoflagellates under higher nutrient availability, showing a faster response than mesozooplankton. Sensitivity simulations with varying nutrient river inputs revealed a linear response of net primary production and plankton biomass. A stronger effect of river inputs was simulated in the enclosed Thermaikos Gulf, in terms of productivity and plankton composition, showing a significant increase of dinoflagellates relative abundance under increased nutrient loads.

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

    E-print Network

    Behavior of tropopause height and atmospheric temperature in models, reanalyses, and observations 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

  4. Decadal-Scale Tropical North Atlantic Climate Variability Recorded in Slow Growing Cape Verde Corals

    NASA Astrophysics Data System (ADS)

    Moses, C. S.; Swart, P. K.; Dodge, R. E.; Helmle, K. P.; Thorrold, S.

    2002-12-01

    The decadal to century scale climate variability 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 (?13C and ?18O) and minor elements (Sr, Mg, and Ba). The ?18O signal present in these corals shows a distinct relationship to the TNA over the better part of the last 100 years. In addition, the ?18O 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 accurately used as a tool to study both the intensity and duration of SST and SSTA cycles as far back as the 1880's.

  5. Observed cold season changes in a Fennoscandian fell area over the past three decades.

    PubMed

    Kivinen, Sonja; Rasmus, Sirpa

    2015-04-01

    We studied trends and variability in snow and climate characteristics in 1978-2012 in the Värriötunturit fell area, northern Finland. Cold season changes were examined using long-term observational 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 observed in October-December and in April. Snow depths decreased particularly in forests at lower altitudes but not in treeless areas at higher altitudes. Interannual variability (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 observations 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

  6. North Pacific Decadal Variability in the GEOS-5 Atmosphere-Ocean Model

    NASA Technical Reports Server (NTRS)

    Achuthavarier, Deepthi; Schubert, Siegfried D.; Vikhliaev, Yury V.

    2013-01-01

    This study examines the mechanisms of the Pacific decadal 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 observations, 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.

  7. Interannual Variability in the Observed Circulation

    NASA Technical Reports Server (NTRS)

    White, G. H.

    1984-01-01

    An observational study of the relative roles of transient eddies and the time-mean flow in maintaining the momentum balance and in forcing vertical motion illuminated the role of time-mean secondary circulations forced by transient eddies. These secondary circulations transport westerly momentum from the upper to the lowr troposphere in the storm tracks, accelerating surface westerlies and making the time-mean flow more barotropic. An investigation of teleconnections in the Southern Hemisphere revealed a zonal wavenumber 3 pattern of low-frequency variability in the winterime midlatitudes and a land-ocean seesaw during summer. An observational comparison of the Northern Hemisphere winters found substantial differences in circulation patterns. The circulation changes may have been associated with substantial changes in low-frequency transient eddies in the Pacific, perhaps related to barotropic instability in the exit region of the Asian jet. Changes in the baroclinicity of the low-level flow appeared to be associated with changes in the storm tracks, while changes in the transient eddies appeared to play a minor role in interannual differences in the zonal momentum balance or in the forcing of vertical motion.

  8. Climatic controls on the interannual to decadal variability in Saudi Arabian dust activity: Toward the development of a seasonal dust prediction model

    NASA Astrophysics Data System (ADS)

    Yu, Yan; Notaro, Michael; Liu, Zhengyu; Wang, Fuyao; Alkolibi, Fahad; Fadda, Eyad; Bakhrjy, Fawzieh

    2015-03-01

    The observed 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 decadal variability. The previously identified positive trend in remotely sensed aerosol optical depth since 2000 is shown to be a segment of the decadal oscillation in dust activity, according to long-duration station record. Regression and correlation analyses reveal that the interannual variability 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 variability 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. Decadal variability 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 decadal dust variability, 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.

  9. Corrected mu_delta for Stars of Hipparcos Catalogue from Independent Latitude Observations over Many Decades

    NASA Astrophysics Data System (ADS)

    Damljanovic, G.; Milic, I. S.

    2011-06-01

    During the last century, there were many so-called independent latitude (IL) stations with the observations which were included into data of a few international organizations (like Bureau International de l'Heure - BIH, International Polar Motion Service - IPMS) and the Earth rotation programmes for determining the Earth Orientation Parameters - EOP. Because of this, nowadays, there are numerous astrometric ground-based observations (made over many decades) of some stars included in the Hipparcos Catalogue (ESA 1997). We used these latitude data for the inverse investigations - to improve the proper motions in declination ?_{?} of the mentioned Hipparcos stars. We determined the corrections ??_{?} and investigated agreement of our ?_{?} and those from the catalogues Hipparcos and new Hipparcos (van Leeuwen 2007). To do this we used the latitude variations of 7 stations (Belgrade, Blagoveschtschensk, Irkutsk, Poltava, Pulkovo, Warsaw and Mizusawa), covering different intervals in the period 1904.7 - 1992.0, obtained with 6 visual and 1 floating zenith telescopes (Mizusawa). On the other hand, with regard that about two decades have elapsed since the Hipparcos ESA mission observations (the epoch of Hipparcos catalogue is 1991.25), the error of apparent places of Hipparcos stars has increased by nearly 20 mas because of proper motion errors. Also, the mission lasted less than four years which was not enough for a sufficient accuracy of proper motions of some stars (such as double or multiple ones). Our method of calculation, and the calculated ?_{?} for the common IL/Hipparcos stars are presented here. We constructed an IL catalogue of 1200 stars: there are 707 stars in the first part (with at least 20 years of IL observations) and 493 stars in the second one (less than 20 years). In the case of ?_{&delta}; of IL stars observed at some stations (Blagoveschtschensk, Irkutsk, Mizusawa, Poltava and Pulkovo) we find the formal errors less than the corresponding Hipparcos ones and for some of them (stations Blagoveschtschensk and Irkutsk) even less than the new Hipparcos ones.

  10. Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux Variability on Daily Through Decadal Time Scales

    NASA Technical Reports Server (NTRS)

    Romanski, Joy; Romanou, Anastasia; Bauer, Michael; Tselioudis, George

    2013-01-01

    We analyze daily wintertime cyclone variability 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 observations. 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 observed 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.

  11. Decadal covariability of Atlantic SSTs and western Amazon dry-season hydroclimate in observations and CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Fernandes, Katia; Giannini, Alessandra; Verchot, Louis; Baethgen, Walter; Pinedo-Vasquez, Miguel

    2015-08-01

    The unusual severity and return time of the 2005 and 2010 dry-season droughts in western Amazon is attributed partly to decadal climate fluctuations and a modest drying trend. Decadal variability of western Amazon hydroclimate is highly correlated to the Atlantic sea surface temperature (SST) north-south gradient (NSG). Shifts of dry and wet events frequencies are also related to the NSG phase, with a 66% chance of 3+ years of dry events per decade when NSG > 0 and 19% when NSG < 0. The western Amazon and NSG decadal covariability is well reproduced in general circulation models (GCMs) historical (HIST) and preindustrial control (PIC) experiments of the Coupled Model Intercomparison Project Phase 5 (CMIP5). The HIST and PIC also reproduce the shifts in dry and wet events probabilities, indicating potential for decadal predictability based on GCMs. Persistence of the current NSG positive phase favors above normal frequency of western Amazon dry events in coming decades.

  12. An Overview of the Impacts of Pacific Decadal Climate Variability on Marine Ecosystems

    NASA Astrophysics Data System (ADS)

    Mantua, N.

    2006-12-01

    Over the past few decades a wealth of evidence has pointed to strong associations between multi-decadal climate changes and marine ecosystem changes in the Pacific. The period from the late 1970's through the mid-1990's, for example, saw sustained high productivity for most Pacific salmon at the northern end of their range coinciding with sustained low productivity for Pacific salmon at the southern end of their range. It is now recognized that this "north-south inverse production pattern" for Pacific salmon played out over much of the 20th Century in response to Pacific Decadal climate variations. There is abundant direct and indirect evidence for decadal scale climate impacts on many other Pacific marine species, including (among others) sardines and anchovies in the Humboldt and California Currents, and pollock and crab in the Bering Sea. In special cases, interdecadal ecosystem changes have been termed "ecosystem regime shifts", wherein evidence points to large-scale ecosystem restructuring at both lower and upper trophic levels. Understanding the mechanisms linking decadal variations in climate to ecosystems has proven to be a major challenge, and the lack of understanding poses a serious barrier to predicting ecosystem changes at the time-space scales important to resource managers and the fishing industry.

  13. Multi-decadal variability and trends in the El Niño-Southern Oscillation and tropical Pacific fisheries implications

    NASA Astrophysics Data System (ADS)

    Harrison, D. E.; Chiodi, Andrew M.

    2015-03-01

    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 variability 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 decades, another issue is the extent to which trends over these recent decades 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 decades is very similar to that of the early decades of the record, suggesting that ENSO has not fundamentally changed over the period of large increase in atmospheric CO2. However, the strong multi-decadal variability in ENSO is reflected in decades with quite different levels of ENSO effects on the ecosystem. Many multi-decadal subsets of the full record have statistically significant trends, using standard analysis techniques. These multi-decadal trends are not; however, representative of the record-length trend, nor are they a useful basis for projecting conditions in subsequent decades. 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 continue into future decades or be indicative of deterministic changes to the system. Analysis of the Southern Oscillation Index, another common ENSO index, but one that has been directly measured for fewer years than has Darwin, yields similar results.

  14. Geomagnetic storms during the last decade: Cluster and Double Star observations (Invited)

    NASA Astrophysics Data System (ADS)

    Escoubet, C.; Taylor, M. G.; Masson, A.; Laakso, H. E.; Liu, Z.; Goldstein, M. L.

    2013-12-01

    The launch of the Cluster spacecraft almost coincided with one of the largest geomagnetic storm of the last decade, 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 observed many geomagnetic storms and could observe, 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 observed by Cluster and Double Star in the last decade to illustrate how the magnetosphere was affected. We have observed 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.

  15. CLARREO Cornerstone of the Earth Observing System: Measuring Decadal Change Through Accurate Emitted Infrared and Reflected Solar Spectra and Radio Occultation

    NASA Technical Reports Server (NTRS)

    Sandford, Stephen P.

    2010-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is one of four Tier 1 missions recommended by the recent NRC Decadal 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 decadal change observations 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 decadal change observations 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 observations sensitive to a wide range of key decadal change variables. The required accuracy levels are determined so that climate trend signals can be detected against a background of naturally occurring variability. Climate system natural variability 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 decadal 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 the large time/space scale averages that are key to understanding decadal changes.

  16. Decadal Challenges in Ground-Based Observations for Solar and Space Physics (Invited)

    NASA Astrophysics Data System (ADS)

    Robinson, R. M.

    2013-12-01

    Ground-based observations of the sun and near-Earth space have long provided the fundamental information needed to achieve a better understanding of the coupled Sun-Earth system and the processes responsible for solar activity and its effects on Earth's magnetosphere, ionosphere, and atmosphere. Observations based on both active and passive radio wave and optical techniques provide measurements throughout Earth's atmosphere, geospace, the heliosphere, and the Sun. Although the number of observing instruments, the capabilities of the instruments, and the variety of ground-based assets continue to open new frontiers and enable scientific discoveries, gaps still exist, not only in terms of the spatial coverage of the measurements, but also in the properties of the system that are observed and the cadence and frequency of the observations. Fortunately, new technologies have provided the tools by which these challenges can be overcome. This is an opportune time to develop an integrated strategy for development, deployment, operation, and data analysis of ground-based assets. These include, for example, advanced networking technologies, crowd-sourced data acquisition, and multi-use observational platforms. Ground-based observations can also be optimized through the development of smart sensors, that operate at low power and are easily deployable, reconfigurable, and remotely operable. Furthermore, the data from ground-based observations will be collected, archived, and disseminated in ways that will enable effective and productive data mining, image and pattern recognition, cross-correlation among diverse data sets, and broadly-based collaborative research. These capabilities are especially important as we attempt to understand the system aspects of the solar-terrestrial environment. The next decade will undoubtedly see new understanding and discoveries resulting from improved and expanded ground-based instruments, as well as in their strategic deployment and operation.

  17. Highlights from a Decade of OMI-TOMS Total Ozone Observations on EOS Aura

    NASA Technical Reports Server (NTRS)

    Haffner, David P.; Bhartia, Pawan K.; McPeters, Richard D.; Joiner, Joanna; Ziemke, Jerald R.; Vassilkov, Alexander; Labow, Gordon J.; Chiou, Er-Woon

    2014-01-01

    Total ozone measurements from OMI have been instrumental in meeting Aura science objectives. In the last decade, 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 decade, we finally highlight how ozone observations from EOS Aura are playing an important role in new ozone mapping missions.

  18. Watershed-scale response of groundwater recharge to inter-annual and inter-decadal variability in precipitation (Alberta, Canada)

    NASA Astrophysics Data System (ADS)

    Hayashi, Masaki; Farrow, Christopher R.

    2014-12-01

    Groundwater recharge sets a constraint on aquifer water balance in the context of water management. Historical data on groundwater and other relevant hydrological processes can be used to understand the effects of climatic variability on recharge, but such data sets are rare. The climate of the Canadian prairies is characterized by large inter-annual and inter-decadal variability in precipitation, which provides opportunities to examine the response of groundwater recharge to changes in meteorological conditions. A decadal study was conducted in a small (250 km2) prairie watershed in Alberta, Canada. Relative magnitude of annual recharge, indicated by water-level rise, was significantly correlated with a combination of growing-season precipitation and snowmelt runoff, which drives depression-focussed infiltration of meltwater. Annual precipitation was greater than vapour flux at an experimental site in some years and smaller in other years. On average precipitation minus vapour flux was 10 mm y-1, which was comparable to the magnitude of watershed-scale groundwater recharge estimated from creek baseflow. Average baseflow showed a distinct shift from a low value (4 mm y-1) in 1982-1995 to a high value (15 mm y-1) in 2003-2013, indicating the sensitivity of groundwater recharge to a decadal-scale variability of meteorological conditions.

  19. On the mechanisms of decadal variability of the North Pacific Gyre Oscillation over the 20th century

    NASA Astrophysics Data System (ADS)

    Yi, Daling Li; Zhang, Liping; Wu, Lixin

    2015-09-01

    The decadal variability 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) variability in SODA, with a north-south dipole structure over the northeast Pacific. SSH anomalies in this region exhibit distinct decadal variability 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 decadal time scale. The limitation of current study is also discussed.

  20. A Decade of Volcanic Observations from Aura and the A-Train

    NASA Technical Reports Server (NTRS)

    Carn, Simon A.; Krotkov, Nickolay Anatoly; Yang, Kai; Krueger, Arlin J.; Hughes, Eric J.; Wang, Jun; Flower, Verity; Telling, Jennifer

    2014-01-01

    Aura observations have made many seminal contributions to volcanology. Prior to the Aura launch, satellite observations 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 decade of Aura observations of volcanic activity and look ahead to the future of volcanic observations from space.

  1. Mapping of decadal middle Adriatic oceanographic variability and its relation to the BiOS regime

    NASA Astrophysics Data System (ADS)

    Mihanovi?, Hrvoje; Vilibi?, Ivica; Duni?, Natalija; Å epi?, Jadranka

    2015-08-01

    We analyzed long-term time series of temperature, salinity, and dissolved oxygen (DO) concentrations collected along the Palagruža Sill transect (middle Adriatic) between 1952 and 2010. The data have been mostly collected on seasonal basis, allowing for extraction of seasonal signal from the series. By applying Self-Organizing Maps (SOM) method, a kind of unsupervised neural network method, the processes on a decadal time scale emerged as the most relevant for changes of oceanographic properties in the middle Adriatic area. Sensitivity studies revealed that oceanographic patterns obtained by SOM were not sensitive to shortening of time series, to removal of data from one station or to removal of DO from the analysis. Simultaneous SOM-based mapping of sea surface heights in the northern Ionian Sea, with these heights serving as a proxy for the Adriatic-Ionian Bimodal Oscillating System (BiOS), revealed asymmetry between anticyclonic and cyclonic BiOS patterns and correlated the decadal oscillations in the middle Adriatic with the reversals in the BiOS circulation regimes. These reversals are found to either rapidly change oceanographic properties in the middle Adriatic (e.g., during the Eastern Mediterranean Transient) or to change them with a time lag of 2-3 years. The mapped connections may be used for a short-time (a few years) forecasting of the Adriatic oceanographic properties or for mapping future climate decadal oscillations as seen by ocean climate models.

  2. A decade of high-resolution radio observations of GRS1915+105

    NASA Astrophysics Data System (ADS)

    Rushton, A.; Spencer, R. E.; Pooley, G.; Trushkin, S.

    2010-02-01

    The radio emitting X-ray binary GRS1915+105 shows a wide variety of X-ray and radio states. We present a decade of monitoring observations, with the Rossi X-ray Timing Explorer-All Sky Monitor and the Ryle Telescope, in conjunction with high-resolution radio observations using Multi-Element Radio-Linked Interferometer Network and the The Very Long Baseline Array. Linear polarization at 1.4 and 1.6GHz has been spatially resolved in the radio jets, on a scale of ~150 mas and at flux densities of a few mJy. Depolarization of the core occurs during radio flaring, associated with the ejection of relativistic knots of emission. We have identified the ejection at four epochs of X-ray flaring. Assuming no deceleration, proper motions of 16.5 to 27 mas per day have been observed, supporting the hypothesis of a varying angle to the line of sight per ejection, perhaps in a precessing jet.

  3. Can we reconcile our understanding of the atmospheric methane budget over the past decades with atmospheric observations?

    NASA Astrophysics Data System (ADS)

    Bruhwiler, L. M.; Matthews, E.

    2007-12-01

    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 variability, 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 decades against network observations 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 observed interannual variability in the observations. We will show results from a multi-decade 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-Sampling and GMD network observations, and our new estimates of methane sources.

  4. Surface salinity variability in the northern North Atlantic during recent decades

    E-print Network

    in the subpolar gyre within 2 years. This is because the role of deep convection is to mix down the net fresh, the deep mixing (which drives overturning changes) is forced by heat flux variability so that weak subpolar water input received by the high latitudes. Hence, at the lack of widespread deep mixing, a signal

  5. Shoreline variability from days to decades: Results of long-term video imaging

    NASA Astrophysics Data System (ADS)

    Pianca, C.; Holman, R.; Siegle, E.

    2015-03-01

    The present work characterizes the time-space scales of variability 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 variability, 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 variability, 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 variability that is coherent with the annual forcing but becomes insignificant in the longshore-average.

  6. Decadal Variability in the Formation of the North Pacific Subtropical Mode Water: Oceanic versus Atmospheric Control

    E-print Network

    Qiu, Bo

    of the recirculation gyre. By analyzing the air­sea flux data from the NCEP­NCAR reanalysis project, little correlation. Inside the Kuroshio Extension (KE) recirculation gyre where STMW forms, the dominant signal, during which time high regional eddy variability infuses high-PV KE water into the recirculation gyre

  7. Mechanisms of internally generated decadal-to-multidecadal variability of SST in the Atlantic Ocean in a coupled GCM

    NASA Astrophysics Data System (ADS)

    Chen, Hua; Schneider, Edwin K.; Wu, Zhiwei

    2015-05-01

    Mechanisms of the internally generated decadal-to-multidecadal variability 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 variability in the control simulation is predominantly forced by noise. The local noise forcing is found to be responsible for the SST variability in the Atlantic Ocean, with noise heat flux and noise wind stress playing a critical role. The control run Atlantic multidecadal variability (AMV) index is decomposed into interannual, decadal 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 decadal 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 decadal mode is more likely to be forced by noise heat flux. For both multidecadal and decadal modes, the atmospheric response to SST, including the SST-forced heat flux and SST-forced wind stress, acts as a damping.

  8. Decadal wave power variability in the North-East Atlantic and North Sea

    NASA Astrophysics Data System (ADS)

    Santo, H.; Taylor, P. H.; Woollings, T.; Poulson, S.

    2015-06-01

    Estimation of the long-term behavior of wave climate is crucial for harnessing wave energy in a cost-effective way. Previous studies have linked wave heights to the north-south atmospheric pressure anomalies in the North Atlantic, suggesting that the wave climate fluctuates as a response to changes in zonal circulation in the atmosphere. We identify changes in wave power in the North-East Atlantic that are strongly correlated to the dominant pressure anomalies, the North Atlantic Oscillation (NAO), and other modes. We present a reconstructed wave power climate for 1665-2005, using a combination of known and proxy indices for the NAO and other modes. Our reconstruction shows high interannual and multidecadal variability, which makes wave energy prediction challenging. This variability should be considered in any long-term reliability analysis for wave energy devices and in power scheme economics.

  9. Collaborative Research: Separating Forced and Unforced Decadal Predictability in Models and Observations

    SciTech Connect

    Tippett, Michael K.

    2014-04-09

    This report is a progress report of the accomplishments of the research grant “Collaborative Research: Separating Forced and Unforced Decadal 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 decadal time scales, distinguish these components from forced predictable components, and to assess the reliability of model predictions of these components. Components of unforced decadal 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 decadal predictability have large APT, so maximizing APT ensures that components with decadal 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 decadal predictability. This methodology will be applied to the decadal hindcasts generated by the CMIP5 project to assess the reliability of model projections. The question of whether anthropogenic forcing changes decadal predictability, or gives rise to new forms of decadal predictability, also will be investigated.

  10. INTRA-ANNUAL TO INTER-DECADAL VARIABILITY IN THE UPPER COLORADO HYDROCLIMATOLOGY: DIAGNOSIS, FORECASTING AND

    E-print Network

    water resources including agriculture, water supply, energy and environmental considerations with the limited observational record. This approach provides the ability to generate a richer variety of drought

  11. Oxygen minimum zone of the open Arabian Sea: variability of oxygen and nitrite from daily to decadal time scales

    NASA Astrophysics Data System (ADS)

    Banse, K.; Naqvi, S. W. A.; Narvekar, P. V.; Postel, J. R.; Jayakumar, D. A.

    2013-09-01

    The oxygen minimum zone (OMZ) of the Arabian Sea is the thickest of the three oceanic OMZs, which is of global biogeochemical significance because of denitrification in the upper part leading to N2 and N2O production. The residence time of the OMZ water is believed to be less than a decade. The upper few hundred meters of this zone are nearly anoxic but non-sulfidic and still support animal (metazoan) pelagic life, possibly as a result of episodic injections of O2 by physical processes. The very low O2 values obtained with the new STOX sensor in the eastern tropical South Pacific probably also characterize the Arabian Sea OMZ, but there is no apparent reason as to why the temporal trends of the historic data should not hold. We report on discrete measurements of dissolved O2 and NO2-, besides temperature and salinity, made between 1959 and 2004 well below the tops of the sharp pycno- and oxyclines near 150, 200, 300, 400, and 500 m depth. We assemble nearly all O2 determinations (originally, 849 values, 695 in the OMZ) by the visual endpoint detection of the iodometric Winkler procedure, which in our data base yields about 0.04 mL L-1 (∼2 ?M) O2 above the endpoint from modern automated titration methods. We find 632 values acceptable (480 from 150 stations in the OMZ). The data are grouped in zonally-paired boxes of 1° lat. and 2° long. centered at 8°, 10°, 12°, 15°, 18°, 20°, and 21° N along 65° E and 67° E. The latitudes of 8-12° N, outside the OMZ, are only treated in passing. The principal results are as follows: (1) an O2 climatology for the upper OMZ reveals a marked seasonality at 200 to 500 m depth with O2 levels during the northeast monsoon and spring intermonsoon season elevated over those during the southwest monsoon season (median difference, 0.08 mL L-1 [3.5 ?M]). The medians of the slopes of the seasonal regressions of O2 on year for the NE and SW monsoon seasons are -0.0043 and -0.0019 mL L-1 a-1, respectively (-0.19 and -0.08 ?M a-1; n = 10 and 12, differing at p = 0.01); (2) four decades of statistically significant decreases of O2 between 15° and 20° N but a trend to a similar increase near 21° N are observed. The balance of the mechanisms that more or less annually maintain the O2 levels are still uncertain. At least between 300 and 500 m the annual reconstitution of the decrease is inferred to be due to lateral, isopycnal re-supply of O2, while at 200 (250?) m it is diapycnal, most likely by eddies. Similarly, recent models show large vertical advection of O2 well below the pycno-cum-oxycline. The spatial (within drift stations) and temporal (daily) variability in hydrography and chemistry is large also below the principal pycnocline. The seasonal change of hydrography is considerable even at 500 m. There is no trend in the redox environment for a quarter of a century at a GEOSECS station near 20° N. In the entire OMZ the slopes on year within seasons for the quite variable NO2- (taken as an indicator of active denitrification) do not show a clear pattern. Also, future O2 or nutrient budgets for the OMZ should not be based on single cruises or sections obtained during one season only. Steady state cannot be assumed any longer for the intermediate layers of the central Arabian Sea.

  12. Decadal hindcasts initialized using observed surface wind stress: Evaluation and prediction out to 2024

    NASA Astrophysics Data System (ADS)

    Thoma, Malte; Greatbatch, Richard J.; Kadow, Christopher; Gerdes, Ruediger

    2015-08-01

    We use surface air temperature to evaluate the decadal forecast skill of the fully coupled Max Planck Institut Earth System Model (MPI-ESM) initialized using only surface wind stress applied to the ocean component of the model (Modini: Model initialization by partially coupled spin-up). Our analysis shows that the greenhouse gas forcing alone results in a significant forecast skill on the 2-5 and 6-9 year range even for uninitialized hindcasts. For the first forecast year, the forecast skill of Modini is generally comparable with previous initialization procedures applied to MPI-ESM. But only Modini is able to generate a significant skill (correlation) in the tropical Pacific for a 2-5 year (and to a lesser extent for a 6-9 year) hindcast. Modini is also better able to capture the observed hiatus in global warming in hindcast mode than the other methods. Finally, we present forecasts for 2015 and the average of years 2016-2019 and 2020-2024, predicting an end to the hiatus.

  13. Modelling the response of cyanobacteria to pH-variability on seasonal to decadal time scales

    NASA Astrophysics Data System (ADS)

    Hofmeister, Richard; Hinners, Jana; Hense, Inga

    2015-04-01

    Cyanobacteria blooms regularly occurred in the Baltic Sea during the last decades. The possible effects of increasing temperatures and eutrophication on cyanobacteria have been already investigated. This model study concentrates on the combined effect of expected temperature increase and ocean acidification on cyanobacteria blooms in the Baltic Sea. We make use of an established model system that comprises the life cycle model of cyanobacteria (CLC) and a biogeochemical model (ERGOM), a carbon chemistry model, and the water column model GOTM. These models are modularly coupled through the framework for aquatic biogeochemical models (FABM). In the CLC model, the cyanobacteria growth is dependent on the sea water pH following the results of experimental studies. The numerical experiments are forced by the output of a regional climate model (RCAO) for the period 1960-2100. A number of simulations are performed for different configurations of the coupled ecosystem, in order to estimate the effect of acidification and the effect of seasonally varying pH on the cyanobacteria bloom. Our simulation experiments show that cyanobacteria growth is stimulated by the increase of temperature in the future, while the blooms' strength decreases in the second half of the 21th century due to ocean acidification. The magnitude and trend of cyanobacteria concentrations are also affected by the seasonal variations of pH. Overall, the results show that the combined effect of the climate stressors, warming and acidification, on the cyanobacteria bloom is weak.

  14. Variations of the Arabian Sea nitrogen cycle: trend or decadal variability?

    NASA Astrophysics Data System (ADS)

    Gaye, Birgit; Tim, Rixen; Böll, Anna; Wiggert, Jerry

    2015-04-01

    Warmer periods of the Holocene have been characterized by a northward shift of the intertropical convergence zone (ITCZ), especially in the South Asian Monsoon sector, thereby increasing the strength and northward extension of monsoon rains. Marine sediments record increased monsoonal upwelling in the Arabian Sea during such warming periods associated with increased denitrification in the oxygen minimum zone. A similar increase can be expected due to anthropogenic warming as it may have a strong impact on Central Asia where feed-back mechanisms of stronger summer warming such as melting of glaciers and reduced albedo may increase summer monsoon strength and thus upwelling and productivity in the Arabian Sea. Models have so far had difficulties to simulate the ITCZ fluctuation in the monsoon area and to make reasonable predictions of its response to global warming. Recent data analyses showed a decrease of oxygen and an increase of nitrite concentrations in the northern part of the Arabian Sea during the last 50 years which could be related to a strengthening of the summer monsoon. To identify whether recent changes in productivity, sea surface temperatures and denitrification are related to decadal fluctuations or global warming trends, we take a comprehensive, multi-disciplinary approach that makes use of the available remote sensing records, nutrient data, and sediment trap as well as high resolution sedimentary records.

  15. Decadal changes of water properties in the Aral Sea observed by MODIS-Aqua

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Wang, Menghua

    2015-07-01

    Twelve-year satellite observations 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(?) 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 variability and significant interannual changes were observed 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 variability, 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.

  16. A decadal observation of vegetation dynamics using multi-resolution satellite images

    NASA Astrophysics Data System (ADS)

    Chiang, Yang-Sheng; Chen, Kun-Shan; Chu, Chang-Jen

    2012-10-01

    Vegetation cover not just affects the habitability of the earth, but also provides potential terrestrial mechanism for mitigation of greenhouse gases. This study aims at quantifying such green resources by incorporating multi-resolution satellite images from different platforms, including Formosat-2(RSI), SPOT(HRV/HRG), and Terra(MODIS), to investigate vegetation fractional cover (VFC) and its inter-/intra-annual variation in Taiwan. Given different sensor capabilities in terms of their spatial coverage and resolution, infusion of NDVIs at different scales was used to determine fraction of vegetation cover based on NDVI. Field campaign has been constantly conducted on a monthly basis for 6 years to calibrate the critical NDVI threshold for the presence of vegetation cover, with test sites covering IPCC-defined land cover types of Taiwan. Based on the proposed method, we analyzed spatio- temporal changes of VFC for the entire Taiwan Island. A bimodal sequence of VFC was observed for intra-annual variation based on MODIS data, with level around 5% and two peaks in spring and autumn marking the principal dual-cropping agriculture pattern in southwestern Taiwan. Compared to anthropogenic-prone variation, the inter-annual VFC (Aug.-Oct.) derived from HRV/HRG/RSI reveals that the moderate variations (3%) and the oscillations were strongly linked with regional climate pattern and major disturbances resulting from extreme weather events. Two distinct cycles (2002-2005 and 2005-2009) were identified in the decadal observations, with VFC peaks at 87.60% and 88.12% in 2003 and 2006, respectively. This time-series mapping of VFC can be used to examine vegetation dynamics and its response associated with short-term and long-term anthropogenic/natural events.

  17. A decade of oceanographic variability in summertime near Elephant Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Amos, Anthony F.

    2001-10-01

    The oceanography of near-surface (to 750 m) summertime waters surrounding the Elephant Island area of the South Shetland Islands has been surveyed each year from 1990 to 1999 as part of the U.S. Antarctic Marine Living Resources (AMLR) program. Using data from a grid of conductivity-temperature-depth stations occupied twice each summer and surface meteorological data collected continuously in the survey area, the mean (and annual departures from the mean) hydrography, circulation, and overlying wind field have been determined. The area is an important krill fishing ground and includes several water mass zones and a major frontal boundary. Differences between middle and late summer ("seasonal") conditions and interannual variability have been investigated. The mean summer condition is quite representative of conditions encountered in each of the 10 years, and little change occurs from middle to late summer, other than a warming of Antarctic Surface Water, including the Winter Water temperature minimum at 100 m, but there is no discernible trend from middle to late summer at the depth of the Circumpolar Deep Water. Interannual variability of sea temperature, winds, and sea level pressure as measured during these surveys showed no correlation with a sea ice index and a recently devised pressure index, the Drake Passage Oscillation Index (DPOI) [Naganobu et al., 1999], despite the correlations found in that study between AMLR chlorophyll a and krill recruitment indices, sea ice, and the DPOI. No correlation was found between DPOI and annual summertime sea temperature, wind, and surface pressure anomalies in the survey area. The implication is that global-scale climatic oscillations with periodicities measured in years may not be adequately detected by small-scale oceanographic surveys even though the surveys may extend over several years unless the surveys are specifically designed for that purpose.

  18. Influence of climate variability versus change at multi-decadal time scales on hydrological extremes

    NASA Astrophysics Data System (ADS)

    Willems, Patrick

    2014-05-01

    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 decades, 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 still 8% for series of 25 years lengths. Methods for bias correction are demonstrated. The definition of "bias" depends on a number of factors, which needs further debate in the hydrological and water engineering community. References: Willems P. (2013), 'Multidecadal oscillatory behaviour of rainfall extremes in Europe', Climatic Change, 120(4), 931-944 Willems, P. (2013). 'Adjustment of extreme rainfall statistics accounting for multidecadal climate oscillations', Journal of Hydrology, 490, 126-133 Willems, P., Olsson, J., Arnbjerg-Nielsen, K., Beecham, S., Pathirana, A., Bülow Gregersen, I., Madsen, H., Nguyen, V-T-V. (2012), 'Impacts of climate change on rainfall extremes and urban drainage', IWA Publishing, 252p., Paperback Print ISBN 9781780401256; Ebook ISBN 9781780401263

  19. The decadal variability of the tropical Indian Ocean SST-the South Asian High relation: CMIP5 model study

    NASA Astrophysics Data System (ADS)

    Qu, X.; Huang, G.

    2015-07-01

    Based on Coupled Model Intercomparison Project phase 5 (CMIP5) models, present study investigates the decadal variability of the tropical Indian Ocean (TIO) sea surface temperature (SST)-the South Asian High (SAH) relation (hereafter TSR) as well as its responses to the global warming. Out of the 17 CMIP5 models, only one (GFDL-CM3) reproduces reasonably the influence of the TIO SST on the SAH. In the historical simulations of GFDL-CM3, the TSR features fluctuations modulated by the western Pacific SST and the Indian subcontinent precipitation. When the TIO warming is accompanied by warm western Pacific, the western Pacific SST-induced tropospheric warming propagates westwards, warms the troposphere surrounding the Indian Ocean, enhances SAH and leads to higher TSR; when accompanied by not so warmed western Pacific, the TSR is lower. While, if the TIO warming is accompanied by negative rainfall anomalies over the Indian subcontinent, the rainfall-induced upper-troposphere cyclone over the subtropical Asia weakens the response of the SAH and leads to lower TSR; if not accompanied by negative rainfall anomalies, the TSR is higher. The decadal variability of the TSR is not subject to the global warming. In RCP45 and RCP85 scenarios, the TSR is also not directly affected by global warming. The rainfall over the Indian subcontinent is still a factor modulating the TSR. While, the western Pacific SST is invalid in the influences of the TIO SST on the SAH.

  20. Observing Decadal Trends in Atmospheric Feedbacks and Climate Change with Zeus and CLARREO

    NASA Astrophysics Data System (ADS)

    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.

    2012-12-01

    New technologies for observing decadal 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 observations, the basis for which has been established by definition of the CLARREO mission in the 2007 NRC "Decadal 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 Zeus. A key aspect of the Zeus ARI instrument is the On-orbit Verification and Test System (OVTS) for verifying its accuracy by reference to International Standards (SI) and testing on orbit. The OVTS includes an On-orbit Absolute Radiance Standard (OARS), which is a high emissivity cavity blackbody that can be operated over a wide range of temperatures to verify ARI calibration. The OARS uses multiple small phase change cells to establish its fundamental temperature scale to better than 5 mK absolute and a broad-band heated-halo source for monitoring its cavity spectral emissivity throughout the mission. A Quantum Cascade Laser (QCL) is also used by the OVTS to monitor the ARI instrument spectral lineshape and the emissivity of its calibration blackbody relative to that of the OARS. The ARI radiance measurements will also be tested for other systematic errors on orbit (non-linearity, polarization effects, and stray light). Through especially careful attention to accuracy, proven on orbit, Zeus EVI will provide the first irrefutable benchmark measurements of the Earth's emitted spectral radiance with accuracy exceeding 0.1 K 3 sigma. In addition, Zeus will serve as a reference standard for operational advanced sounders and will enable fundamental improvements in our capability to document climate trends and to forecast climate and weather.

  1. Multi-decadal variability of ice extent in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Vinje, T.; Colony, R.

    2003-04-01

    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 observed and logged sea-ice conditions and ice edge location. These shipboard observations 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 observational 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 observations and the associated time series of solar total irradiance (1600-2000). Major features of historical sea-ice extent are seen in the Sun’s total irradiance.

  2. 30-Year Satellite Record Reveals Contrasting Arctic and Antarctic Decadal Sea Ice Variability

    NASA Technical Reports Server (NTRS)

    Cavalieri, D. J.; Parkinson, C. L.; Vinnikov, K. Y.

    2003-01-01

    A 30-year satellite record of sea ice extents derived mostly from satellite microwave radiometer observations 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 observed in early visible and infrared satellite images.

  3. One decade of thermohaline variability in the deep western Mediterranean Sea (2004-2014)

    NASA Astrophysics Data System (ADS)

    Schroeder, Katrin; Ismail, S. Ben; Bryden, Harry; Borghini, Mireno; Sparnocchia, Stefania; Chiggiato, Jacopo; Ribotti, Alberto

    2015-04-01

    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 observed 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.

  4. FUSE observations of Luminous Blue Variables

    NASA Astrophysics Data System (ADS)

    Iping, Rosina C.; Sonneborn, George; Massa, Derck L.

    P Cyg, AG Car, HD 5980 and ? Car were observed 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 observations of P Cyg and AG Car, both spectral type B2pe, are very similar. The atmospheres of both ? 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 ? Car, however, does not agree very well with existing model spectra.

  5. Coupled decadal variability of the North Atlantic Oscillation, regional rainfall and karst spring discharges in the Campania region (southern Italy)

    NASA Astrophysics Data System (ADS)

    De Vita, P.; Allocca, V.; Manna, F.; Fabbrocino, S.

    2012-05-01

    Thus far, studies on climate change have focused mainly on the variability of the atmospheric and surface components of the hydrologic cycle, investigating the impact of this variability on the environment, especially with respect to the risks of desertification, droughts and floods. Conversely, the impacts of climate change on the recharge of aquifers and on the variability of groundwater flow have been less investigated, especially in Mediterranean karst areas whose water supply systems depend heavily upon groundwater exploitation. In this paper, long-term climatic variability and its influence on groundwater recharge were analysed by examining decadal 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, from 1921 to 2010, using 18 rain gauges and 9 air temperature stations with the most continuous functioning. The time series of the winter NAO index and of the discharges of 3 karst springs, selected from those feeding the major aqueducts systems, were collected for the same period. Regional normalised indexes of the precipitation, air temperature and karst spring discharges were calculated, and different methods were applied to analyse the related time series, including long-term trend analysis using smoothing numerical techniques, cross-correlation and Fourier analysis. The investigation of the normalised indexes highlighted the existence of long-term complex periodicities, from 2 to more than 30 yr, with differences in average values of up to approximately ±30% for precipitation and karst spring discharges, which were both strongly correlated with the winter NAO index. Although the effects of the North Atlantic Oscillation (NAO) had already been demonstrated in the long-term precipitation and streamflow patterns of different European countries and Mediterranean areas, the results of this study allow for the establishment of a link between a large-scale atmospheric cycle and the groundwater recharge of carbonate karst aquifers. Consequently, the winter NAO index could also be considered as a proxy to forecast the decadal variability of groundwater flow in Mediterranean karst areas.

  6. Oxygen minimum zone of the open Arabian Sea: variability of oxygen and nitrite from daily to decadal timescales

    NASA Astrophysics Data System (ADS)

    Banse, K.; Naqvi, S. W. A.; Narvekar, P. V.; Postel, J. R.; Jayakumar, D. A.

    2014-04-01

    The oxygen minimum zone (OMZ) of the Arabian Sea is the thickest of the three oceanic OMZ. It is of global biogeochemical significance because of denitrification in the upper part leading to N2 and N2O production. The residence time of OMZ water is believed to be less than a decade. The upper few hundred meters of this zone are nearly anoxic but non-sulfidic and still support animal (metazoan) pelagic life, possibly as a result of episodic injections of O2 by physical processes. We report on discrete measurements of dissolved O2 and NO2-, temperature and salinity made between 1959 and 2004 well below the tops of the sharp pycnocline and oxycline near 150, 200, 300, 400, and 500 m depth. We assemble nearly all O2 determinations (originally there were 849 values, 695 of which came from the OMZ) by the visual endpoint detection of the iodometric Winkler procedure, which in our data base yields about 0.04 mL L-1 (~ 2 ?M) O2 above the endpoint from modern automated titration methods. We acknowledge that much lower (nanomolar) O2 values have been measured recently with the STOX (Switchable Trace amount OXygen) sensor in the eastern tropical South Pacific, and that similar conditions may also prevail in the Arabian Sea OMZ. In spite of the error in O2 measurements at vanishingly low levels, we argue that the temporal trends of the historic data should still hold. We find 632 values acceptable (480 from 150 stations in the OMZ). The data are grouped in zonally paired boxes of 1° lat. and 2° long. centered at 8, 10, 12, 15, 18, 20, and 21° N along 65 and 67° E. The latitudes of 8-12° N, outside the OMZ, are treated in passing. The principal results are as follows: (1) an O2 climatology for the upper OMZ reveals a marked seasonality at 200 to 500 m depth with O2 levels during the northeast monsoon and spring intermonsoon seasons elevated over those during the southwest monsoon season (median difference, 0.08 mL L-1 [~ 3.5 ?M]). The medians of the slopes of the seasonal regressions of O2 on year for each of the NE and SW monsoon seasons are -0.0043 and -0.0019 mL L-1 a-1, respectively (-0.19 and -0.08 ?M a-1; n = 10 and 12, differing at p = 0.01); (2) four decades of statistically significant decreases of O2 between 15 and 20° N but an opposing trend toward an increase near 21° N are observed. The mechanisms of the balance that more or less annually maintain the O2 levels are still uncertain. At least between 300 and 500 m, the replenishment is inferred to be due to isopycnal re-supply of O2, while at 200 (or 250?) m it is diapycnal, most likely by eddies. Similarly, recent models show large vertical advection of O2 well below the pycnoclines and oxyclines. The NO2- distribution, taken as an indicator of active NO3- reduction, does not show a trend in the redox environment for a quarter of a century at a GEOSECS station near 20° N. In the entire OMZ, the regression slopes on year within seasons for the rather variable NO2- do not present a clear pattern but by other measures tended to an increase of NO2-. Vertical net hauls collect resident animal (metazoan) pelagic life in the NO2- maximum of the OMZ at O2 levels well below the lower limit of the Winkler titration; the extremely low O2 content is inferred from the presence of NO2- believed to be produced through microbial NO3- reduction. Instead of the difficult measurement by the STOX sensor, the relation between the very low O2 inferred from presence of NO2- and mesozooplankton should be studied with 100 to 150 L bottles rather than nets. The spatial (within drift stations) and temporal (daily) variability in hydrography and chemistry is large also below the principal pycnocline. The seasonal change of hydrography is considerable even at 500 m depth. Future O2 or nutrient budgets for the OMZ must not be based on single cruises or sections obtained during one season only. Steady state cannot be assumed any longer for the intermediate layers of the central Arabian Sea.

  7. Bayesian Network Models for Local Dependence among Observable Outcome Variables

    ERIC Educational Resources Information Center

    Almond, Russell G.; Mulder, Joris; Hemat, Lisa A.; Yan, Duanli

    2009-01-01

    Bayesian network models offer a large degree of flexibility for modeling dependence among observables (item outcome variables) from the same task, which may be dependent. This article explores four design patterns for modeling locally dependent observations: (a) no context--ignores dependence among observables; (b) compensatory context--introduces…

  8. An 1800-yr record of decadal-scale hydroclimatic variability in the upper Arkansas River basin from bristlecone pine

    USGS Publications Warehouse

    Woodhouse, C.A.; Pederson, G.T.; Gray, S.T.

    2011-01-01

    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 variability. 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 decadal-scale moisture variability 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.

  9. Variability of the Tropical Atlantic and Pacific SSS Minimum Zones in the Last Three Decades and Their Relations to the ITCZ and NECC

    NASA Astrophysics Data System (ADS)

    Delcroix, T. C.; Tchilibou, M. L.; Alory, G.; Reverdin, G. P.; Arnault, S.

    2014-12-01

    This study focuses on the time-space variability of the low Sea Surface Salinity (SSS) waters located from the West to the East within about 2°N-12°N in the Atlantic and Pacific oceans. The analysis is based on a combination of in situ SSS observations collected in the last three decades from voluntary observing ships, TAO/TRITON and PIRATA moorings, Argo floats and (few) CTD profiles. We show that the mean position of the Atlantic and Pacific low SSS waters is tightly related to the local minimum in Evaporation minus Precipitation (E-P) budget linked to the Inter Tropical Convergence Zones (ITCZ) and to salt transport by the eastward flowing North Equatorial Counter Current (NECC). We also show via EOF analyses that the meridional position of this SSS minimum varies both at seasonal time scale, with a northernmost position in boreal summer, and at interannual time scale in relation with ENSO and the Atlantic meridional mode, with however subtle differences in timing between the western, central and eastern basins. The role of the ITCZ-related E-P budget and NECC-related salt advection in these seasonal and interannual changes is examined. We further document the long-term meridional migration of these low SSS waters in the last three decades and discuss whether or not it is consistent with the expected global change effects.

  10. Understanding interannual, decadal level variability in paralytic shellfish poisoning toxicity in the Gulf of Maine: the HAB Index

    PubMed Central

    Anderson, Donald M.; Couture, Darcie A.; Kleindinst, Judith L.; Keafer, Bruce A.; McGillicuddy, Dennis J.; Martin, Jennifer L.; Richlen, Mindy L.; Hickey, J. Michael; Solow, Andrew R.

    2013-01-01

    A major goal in harmful algal bloom (HAB) research has been to identify mechanisms underlying interannual variability in bloom magnitude and impact. Here the focus is on variability 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 variability in overall toxicity between individual years as well as long-term, decadal 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 others. This statistical underpinning can guide efforts to identify physical and/or biological mechanisms underlying the patterns revealed by the HAB Index. Although A. fundyense cyst survey data (limited to 9 years) do not span the entire interval of the shellfish toxicity records, this analysis leads us to hypothesize that major changes in the abundance of A. fundyense cysts may be a primary factor contributing to the decadal trends in shellfish toxicity in this region. The HAB Index approach taken here is simple but represents a novel and potentially useful tool for resource managers in many areas of the world subject to toxic HABs. PMID:24948849

  11. Understanding interannual, decadal level variability in paralytic shellfish poisoning toxicity in the Gulf of Maine: the HAB Index.

    PubMed

    Anderson, Donald M; Couture, Darcie A; Kleindinst, Judith L; Keafer, Bruce A; McGillicuddy, Dennis J; Martin, Jennifer L; Richlen, Mindy L; Hickey, J Michael; Solow, Andrew R

    2014-05-01

    A major goal in harmful algal bloom (HAB) research has been to identify mechanisms underlying interannual variability in bloom magnitude and impact. Here the focus is on variability 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 variability in overall toxicity between individual years as well as long-term, decadal 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 others. This statistical underpinning can guide efforts to identify physical and/or biological mechanisms underlying the patterns revealed by the HAB Index. Although A. fundyense cyst survey data (limited to 9 years) do not span the entire interval of the shellfish toxicity records, this analysis leads us to hypothesize that major changes in the abundance of A. fundyense cysts may be a primary factor contributing to the decadal trends in shellfish toxicity in this region. The HAB Index approach taken here is simple but represents a novel and potentially useful tool for resource managers in many areas of the world subject to toxic HABs. PMID:24948849

  12. Understanding interannual, decadal level variability in paralytic shellfish poisoning toxicity in the Gulf of Maine: The HAB Index

    NASA Astrophysics Data System (ADS)

    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.

    2014-05-01

    A major goal in harmful algal bloom (HAB) research has been to identify mechanisms underlying interannual variability in bloom magnitude and impact. Here the focus is on variability 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 variability in overall toxicity between individual years as well as long-term, decadal 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 others. This statistical underpinning can guide efforts to identify physical and/or biological mechanisms underlying the patterns revealed by the HAB Index. Although A. fundyense cyst survey data (limited to 9 years) do not span the entire interval of the shellfish toxicity records, this analysis leads us to hypothesize that major changes in the abundance of A. fundyense cysts may be a primary factor contributing to the decadal trends in shellfish toxicity in this region. The HAB Index approach taken here is simple but represents a novel and potentially useful tool for resource managers in many areas of the world subject to toxic HABs.

  13. Einstein x-ray observations of cataclysmic variables

    SciTech Connect

    Mason, K.O.; Cordova, F.A.

    1982-01-01

    Observations 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 variable stars (CVs). The high sensitivity of the Einstein instrumentation has permitted study of their short timescale variability and spectra. The data are adding significantly to our knowledge of the accretion process in cataclysmic variables and forcing some revision in our ideas concerning the origin of the optical variability in these stars.

  14. Improving flood prediction by assimilation of the distributed streamflow observations with variable uncertainty and intermittent behavior

    NASA Astrophysics Data System (ADS)

    Mazzoleni, Maurizio; Alfonso, Leonardo; Solomatine, Dimitri

    2015-04-01

    Data assimilation techniques have been used in the last decades to integrate water measurements for physical sensors in mathematical model in order to improve flood prediction. Parallel to this, the continued technological improvement has stimulated the spread of low-cost sensors used to infer hydrological variables in a more distributed way but less accurately. The main goal of this study is to demonstrate how assimilation of streamflow observations having variable uncertainty and intermittent characteristics can improve flood prediction using hydrological model. The methodology is applied in the Brue catchment, South West of England. The catchment is divided in small sub-basins, about 2km2 resolution, in order to represent the spatial variability of the streamflow observations by means of a semi-distributed Kalinin-Milyukov-Nash Cascade model. The measured precipitation values are used as perfect forecast input in the hydrological model. Then, an Ensemble Kalman filter is implemented and adapted to account for streamflow observations having random uncertainty and coming at irregular time steps. Due to the fact that distributed observations are not available within the Brue basin, synthetic streamflow values are generated. The results show how streamflow observations having variable uncertainty can improve the flood prediction according to the location from which these observations are coming. Overall, streamflow observations coming from low cost sensors can be integrated with physical sensors observation to improve flood prediction. This study is part of the FP7 European Project WeSenseIt Citizen Water Observatory (www.http://wesenseit.eu/).

  15. Links between the Big Dry in Australia and hemispheric multi-decadal climate variability - implications for water resource management

    NASA Astrophysics Data System (ADS)

    Verdon-Kidd, D. C.; Kiem, A. S.; Moran, R.

    2014-06-01

    Southeast Australia (SEA) experienced a protracted drought during the mid-1990s until early 2010 (known as the Big Dry or Millennium Drought) that resulted in serious environmental, social and economic effects. This paper analyses a range of historical climate data sets to place the recent drought into context in terms of Southern Hemisphere inter-annual to multi-decadal hydroclimatic variability. The findings indicate that the recent Big Dry in SEA is in fact linked to the widespread Southern Hemisphere climate shift towards drier conditions that began in the mid-1970s. However, it is shown that this link is masked because the large-scale climate drivers responsible for drying in other regions of the mid-latitudes since the mid-1970s did not have the same effect on SEA during the mid- to late 1980s and early 1990s. More specifically, smaller-scale synoptic processes resulted in elevated autumn and winter rainfall (a crucial period for SEA hydrology) during the mid- to late 1980s and early 1990s, which punctuated the longer-term drying. From the mid-1990s to 2010 the frequency of the synoptic processes associated with elevated autumn/winter rainfall decreased, resulting in a return to drier than average conditions and the onset of the Big Dry. The findings presented in this paper have marked implications for water management and climate attribution studies in SEA, in particular for understanding and dealing with "baseline" (i.e. current) hydroclimatic risks.

  16. Near-infrared observations of the variable crab nebula

    NASA Astrophysics Data System (ADS)

    Yamamoto, M.; Mori, K.; Shibata, S.; Tsujimoto, M.; Misawa, T.; Burrows, D.; Kawai, N.

    We present three near-infrared NIR observations of the Crab Nebula obtained with CISCO on the Subaru Telescope and Quick Infrared Camera on the University of HAWAII 88 inch Telescope The observations were performed on 2004 September 2005 February and 2005 October and were coordinated with X-ray observations obtained with the Chandra X-ray observatory within 10 days As shown in previous optical and X-ray monitoring observations outward-moving wisps and variable knots are detected also in our NIR observations The NIR variations are closely correlated with variations in the X-ray observations indicating that both variations are driven by the same physical process We discuss the origin of NIR-emitting particles based on the temporal variations as well as the spectral energy distributions of each variable component

  17. North Atlantic atmospheric and ocean inter-annual variability over the past fifty years - Dominant patterns and decadal shifts

    NASA Astrophysics Data System (ADS)

    Hauser, Tristan; Demirov, Entcho; Zhu, Jieshun; Yashayaev, Igor

    2015-03-01

    The atmosphere and ocean of the North Atlantic have undergone significant changes in the past century. To understand these changes, their mechanisms, and their regional implications requires a quantitative understanding of processes in the coupled ocean and atmosphere system. Central to this understanding is the role played by the dominant patterns of ocean and atmospheric variability which define coherent variations in physical characteristics over large areas. Cluster analysis is used in this article to identify the patterns of the North Atlantic atmospheric variability in the subseasonal and interannual spectral intervals. Four dominant subseasonal weather regimes are defined using Bayesian Gaussian mixture models. All correlation patterns of the Sea Level Pressure (SLP) anomalies with the membership probability time series for the weather regimes show similarities with the dipole structure typical for the North Atlantic Oscillation (NAO). The SLP patterns of two of the regimes represent the opposite phases NAO+ and NAO-. The two other weather regimes, the Atlantic Ridge (AR) and Scandinavian-Greenland dipole (SG), have dipole spatial structures with the northern and southern centers of action shifted with respect to the NAO pattern. These two patterns define blocking structures over Scandinavia and near the southern tip of Greenland, respectively. The storm tracks typical for the four regimes resemble the well known paths for positive/negative phases of NAO for the NAO+/NAO- weather regimes, and paths influenced by blocking off the south Greenland tip for AR and over Scandinavia for SG. The correlation patterns of momentum and heat fluxes to the ocean for the four regimes have tripole structures with positive (warm) downward heat flux anomalies over the Subpolar North Atlantic (SPNA) for the NAO- and the AR and negative heat flux anomalies over the SPNA for the NAO+. The downward heat flux anomalies associated with the SG are negative over the Labrador Sea and 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 decadal 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 decadal variability 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.

  18. Bayesian adaptive estimation under a random cost of observation associated with each observable variable #

    E-print Network

    Jyväskylä, University of

    Bayesian adaptive estimation under a random cost of observation associated with each observable to Bayesian adaptive estimation. We extend the framework to situations where each observable variable is associated with a certain random cost of observation and consider the goal of maximizing the expected utility

  19. Bayesian adaptive estimation under a random cost of observation associated with each observable variable

    E-print Network

    Jyväskylä, University of

    Bayesian adaptive estimation under a random cost of observation associated with each observable to Bayesian adaptive estimation. We extend the framework to situations where each observable variable is associated with a certain random cost of observation and consider the goal of maximizing the expected utility

  20. A likelihood-based comparison of CMIP5 decadal experiment runs with observations from the Atmospheric Infrared Sounder

    NASA Astrophysics Data System (ADS)

    Braverman, A. J.; Cressie, N.; Teixeira, J.

    2011-12-01

    In Braverman, Cressie, and Teixeira (2011) we introduced a new method for assessing the consistency between climate model simulations and observational time series. The method uses a moving-block bootstrap to simulate the probability density function (pdf) of a statistic from a model-generated time series. The pdf evaluated at the value of a statistic computed from the observations can be thought of as an empirical likelihood. If the climate models are all considered to be equally likely a priori, then posterior probabilities of the models given the observational statistics are proportional to the likelihoods. These posterior probabilities given an indication of which models are most consistent with the observed data record. We have applied this method to CNRM-CM5 and CanCM4 runs from the CMIP5 decadal experiment suite using observations from NASA's AIRS instrument. In this talk, we report the results of these comparisons.

  1. A decade of Rossi X-ray Timing Explorer Seyfert observations: An RXTE Seyfert spectral database

    NASA Astrophysics Data System (ADS)

    Mattson, Barbara Jo

    2008-10-01

    With over forty years of X-ray observations, we should have a grasp on the X- ray nature of active galactic nuclei (AGN). The unification model of Antonucci and Miller (1985) offered a context for understanding observations by defining a "typical" AGN geometry, with observed spectral differences explained by line- of-sight effects. However, the emerging picture is that the central AGN is more complex than unification alone can describe. We explore the unified model with a systematic X-ray spectral study of bright Seyfert galaxies observed by the Rossi X-Ray Timing Explorer (RXTE) over its first 10 years. We develop a spectral-fit database of 821 time-resolved spectra from 39 Seyfert galaxies fitted to a model describing the effects of an X-ray power-law spectrum reprocessed and absorbed by material in the central AGN region. We observe a relationship between radio and X-ray properties for Seyfert 1s, with the spectral parameters differing between radio-loud and radio-quiet Seyfert 1s. We also find a complex relationship between the Fe K equivalent width ( EW ) and the power-law photon index (Gamma) for the Seyfert 1s, with a correlation for the radio-loud sources and an anti-correlation for the radio- quiet sources. These results can be explained if X-rays from the relativistic jet in radio-loud sources contribute significantly to the observed spectrum. We observe scatter in the EW-Gamma relationship for the Seyfert 2s, suggesting complex environments that unification alone cannot explain. We see a strong correlation between Gamma and the reflection fraction ( R ) in the Seyfert 1 and 2 samples, but modeling degeneracies are present, so this relationship cannot be trusted as instructive of the AGN physics. For the Seyfert 1 sample, we find an anticorrelation between EW and the 2 to 10 keV luminosity ( L x ), also known as the X-ray Baldwin effect. This may suggest that higher luminosity sources contain less material or may be due to a time-lag effect. We do not observe the previously reported relationship between Gamma and the ratio of L x to the Eddington luminosity.

  2. Monitoring multi-decadal satellite earth observation of soil moisture using era-land global land water resources dataset

    NASA Astrophysics Data System (ADS)

    Albergel, Clement; Dorigo, Wouter; Balsamo, Gianpaolo; de Rosnay, Patricia; Muñoz-Sabater, Joaquin; Isaksen, Lars; Brocca, Luca; de Jeu, Richard; Wagner, Wolfgang

    2014-05-01

    It has been widely recognized that soil moisture is one of the main drivers of the water, energy and carbon cycles. It is a crucial variable for Numerical Weather Prediction (NWP) and climate projections because it plays a key role in hydro-meteorological processes. A good representation of soil moisture conditions can help improving the forecasting of precipitation, temperature, droughts and floods. For many applications global or continental scale soil moisture maps are needed. As a consequence, a signi?cant amount of studies have been conducted to obtain such information. For that purpose, land surface modeling, remote sensing techniques or a combination of both through Land Data Assimilation Systems are used. Assessing the quality of these products is required and for instance, the release of a new -long term- harmonized soil moisture product (SM-MW hereafter) from remote sensing within the framework of the European Space Agency's Water Cycle Multi-mission Observation Strategy (WACMOS) and Climate Change Initiative (CCI) projects in 2012 (more information at http://www.esa-soilmoisture-cci.org/) triggered several evaluation activities. The typical validation approach for model and satellite based data products is to compare them to in situ observations. However the evaluation of soil moisture products using ground measurements is not trivial. Even if in the recent years huge efforts were made to make such observations available in contrasting biomes and climate conditions, long term and large scale ground measurements networks are still sparse. Additionally, different networks will present different characteristics (e.g. measurement methods, installation depths and modes, calibration techniques, measurement interval, and temporal and spatial coverage). Finally using in situ measurements, the quality of retrieved soil moisture can be accurately assessed for the locations of the stations. That is why it is of interest to conceive new validation methods, complementing the existing soil moisture networks. To do so Land Surface Models (LSM) can be used to upscale the in situ surface soil moisture observations and complete the evaluation of satellite derived products, assuming that land surface models, forced with high quality atmospheric forcing data, adequately capture the soil moisture temporal dynamic. In this study, SM-MW is first evaluated using ground measurements of soil moisture over 2007-2010. Along with SM-MW, soil moisture from two revised re-analyses; ERA-Land, an update of the land surface component of the ERA-Interim reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) and MERRA-Land, an enhanced land surface data product based on MERRA reanalysis by the National Aeronautics and Space Administration (NASA) were evaluated, also. In situ measurements from almost 200 stations from five networks in different countries (USA, Spain, France, China and Australia) were considered. Then soil moisture from ERA-Land, is used to monitor at a global scale the consistency of SM-MW over multi-decadal time period (1980-2010).

  3. Interannual and Decadal Variability of Ocean Surface Latent Heat Flux as Seen from Passive Microwave Satellite Algorithms

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Jackson, Darren L.; Wick, Gary A.; Roberts, Brent; Miller, Tim L.

    2007-01-01

    Ocean surface turbulent fluxes are critical links in the climate system since they mediate energy exchange between the two fluid systems (ocean and atmosphere) whose combined heat transport determines the basic character of Earth's climate. Deriving physically-based latent and sensible heat fluxes from satellite is dependent on inferences of near surface moisture and temperature from coarser layer retrievals or satellite radiances. Uncertainties in these "retrievals" propagate through bulk aerodynamic algorithms, interacting as well with error properties of surface wind speed, also provided by satellite. By systematically evaluating an array of passive microwave satellite algorithms, the SEAFLUX project is providing improved understanding of these errors and finding pathways for reducing or eliminating them. In this study we focus on evaluating the interannual variability of several passive microwave-based estimates of latent heat flux starting from monthly mean gridded data. The algorithms considered range from those based essentially on SSM/I (e.g. HOAPS) to newer approaches that consider additional moisture information from SSM/T-2 or AMSU-B and lower tropospheric temperature data from AMSU-A. On interannual scales, variability arising from ENSO events and time-lagged responses of ocean turbulent and radiative fluxes in other ocean basins (as well as the extratropical Pacific) is widely recognized, but still not well quantified. Locally, these flux anomalies are of order 10-20 W/sq m and present a relevant "target" with which to verify algorithm performance in a climate context. On decadal time scales there is some evidence from reanalyses and remotely-sensed fluxes alike that tropical ocean-averaged latent heat fluxes have increased 5-10 W/sq m since the early 1990s. However, significant uncertainty surrounds this estimate. Our work addresses the origin of these uncertainties and provides statistics on time series of tropical ocean averages, regional space / time correlation analysis, and separation of contributions by variations in wind and near surface humidity deficit. Comparison to variations in reanalysis data sets is also provided for reference.

  4. Ginga and ROSAT observations of the cataclysmic variable S193

    NASA Technical Reports Server (NTRS)

    Szkody, Paula; Garnavich, Peter; Castelaz, Michael; Makino, F.

    1994-01-01

    The cataclysmic variable S193 was observed with the Ginga and ROSAT satellites, along with ground-based optical observations. The bremsstrahlung temperatures and the column densities derived from these two observations are noticeably different. However, since the observations were separated by 3 yr and took place at different optical magnitudes, it is not clear whether this is related to an intrinsic change in the system or to a two component source of X-rays. While the X-ray data are not sufficient to accomplish a detailed analysis for periodicities, the Ginga data place an upper limit of 40% on the amplitude of any sinusoidal modulation.

  5. GINGA and ROSAT observations of the cataclysmic variable S193

    NASA Astrophysics Data System (ADS)

    Szkody, Paula; Garnavich, Peter; Castelaz, Michael; Makino, F.

    1994-06-01

    The cataclysmic variable S193 was observed with the Ginga and ROSAT satellites, along with ground-based optical observations. The bremsstrahlung temperatures and the column densities derived from these two observations are noticeably different. However, since the observations were separated by 3 yr and took place at different optical magnitudes, it is not clear whether this is related to an intrinsic change in the system or to a two component source of X-rays. While the X-ray data are not sufficient to accomplish a detailed analysis for periodicities, the Ginga data place an upper limit of 40% on the amplitude of any sinusoidal modulation.

  6. Trends and variability in East African rainfall and temperature observations

    NASA Astrophysics Data System (ADS)

    Seregina, Larisa; Ermert, Volker; Fink, Andreas H.; Pinto, Joaquim G.

    2014-05-01

    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 variability 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 variability in the recent past and to understand its causes. Climate variability 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 variability of temperature and rainfall and their trends with the focus on most recent decades. In the follow-up, statistical and dynamical analyses are conducted to quantify the local impact of pertinent large-scale modes of climate variability (Indian Ocean Zonal Mode, El Niño Southern Oscillation, Sea Surface Temperature of the Indian Ocean).

  7. Frequency Dependence of Short Period Seismic Noise from Two Decades of Observations at Warramunga Seismic Array (WRA), Australia

    NASA Astrophysics Data System (ADS)

    Gal, M.; Reading, A. M.; Ellingsen, S. P.; Koper, K. D.; Tkalcic, H.; Hemer, M. A.

    2014-12-01

    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 observation 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 decades. We use data recorded over two decades (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 decades. We observe, 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 decades. b) Displays the surface waves paths of incoming Rayleigh (red) and leaky Rayleigh (blue) waves. c) Shows source locations from back projected body wave arrivals.

  8. Changes in SO2 and NO2 Pollution over the Past Decade Observed by Aura OMI

    NASA Astrophysics Data System (ADS)

    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.

    2014-12-01

    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 observed 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 observed 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 observed 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.

  9. Sea Surface Height Variability Observed by Pressure-recording Inverted

    E-print Network

    Rhode Island, University of

    Sea Surface Height Variability Observed by Pressure-recording Inverted Echo Sounders and Satellite echo sounders (PIESs) 7 moored profilers 48 profiling floats 1 moored surface buoy (KEO buoy) #12;03/07/08 Park/URI 3 PIES (Pressure-recording Inverted Echo Sounder) Emits 12 kHz sound pulses Measures - round

  10. Observed Low Frequency Variability of the Brazil Current Front

    NASA Astrophysics Data System (ADS)

    Goni, G. J.; Bringas Gutierrez, F.; Di Nezio, P. N.

    2012-12-01

    The Brazil Current is a weak western boundary current, the southwest component of the South Atlantic subtropical gyre, which is the main conduit of upper ocean waters in the region. We report her the observed low frequency variability of the Brazil Current front using satellite-derived sea height anomaly and sea surface temperature observations during the 1993-2008 period. The variability of the front is studied in terms of the separation of the Brazil Current front from the continental shelf break. During the study period, estimates of this parameter indicate a shift to the south of approximately 1.5 degrees. Statistically significant changes are not observed in the geostrophic transport of the Brazil and Malvinas currents suggesting that the low-frequency changes of the Brazil Current front are governed by different mechanisms than the seasonal variability of these surface currents. Surface drifter trajectories as well as simulations using synthetic drifters are consistent with the observed shift to the south of the Brazil Current front. Trends of eddy kinetic energy, sea height anomaly, sea surface temperature and wind stress curl are also in agreement with the variability reported here. Wavelet transform analysis revealed an interesting change in the periodicity of the separation of the Brazil Current front from the continental shelf break from annual to bi-annual during 2003. Longer records together with comprehensive numerical experiments will ultimately be needed to determine the origin of these changes.

  11. Observed low frequency variability of the Brazil Current front

    NASA Astrophysics Data System (ADS)

    Goni, Gustavo Jorge; Bringas, Francis; Dinezio, Pedro Nicolas

    2011-10-01

    The Brazil Current is a weak western boundary current, the southwest component of the South Atlantic subtropical gyre, which is the main conduit of upper ocean waters in the region. The objective of this work is to report on observed low frequency variability of the Brazil Current front using satellite-derived sea height anomaly and sea surface temperature observations during the 1993-2008 period. The variability of the front is studied in terms of the separation of the Brazil Current front from the continental shelf break. During the study period, estimates of this parameter vary 6 degrees in latitude, and the mean monthly estimates exhibit a shift to the south of approximately 1.5 degrees. Statistically significant changes are not observed in the geostrophic transport of the Brazil and Malvinas currents, suggesting that the low-frequency changes of the Brazil Current front are governed by different mechanisms than the seasonal variability of these surface currents. Surface drifter trajectories and simulations using synthetic drifters are consistent with the observed shift to the south of the Brazil Current front. Trends of eddy kinetic energy, sea height anomaly, sea surface temperature and wind stress curl are also in agreement with the variability reported here. Wavelet transform analysis revealed interesting changes in the periodicity of the latitude of separation of the Brazil Current front from the continental shelf break, with periods ranging from semiannual to biannual. Longer records, together with comprehensive numerical experiments, will ultimately be needed to determine the origin of these changes.

  12. Observed climate variability and change of relevance to the biosphere

    E-print Network

    Dai, Aiguo

    Observed climate variability and change of relevance to the biosphere David R. Easterling, Thomas R the current instrumental evidence regarding climate variations and change during the 20th century emphasizing are addressed: (1) Is the climate getting warmer, (2) is the hydrologic cycle changing, and (3) is the climate

  13. 6) Midlatitude stratospheric variability and sudden stratospheric a) Observations

    E-print Network

    Lott, Francois

    in the vortex shape and location Nut it almost never disappear The air masses in the polar stratosphere stays1 6) Midlatitude stratospheric variability and sudden stratospheric warmings a) Observations b, one map every 3 days, NCEP data This is the Arctic Polar vortex Note how its deformation occurs over

  14. Coral Luminescence Identifies the Pacific Decadal Oscillation as a Primary Driver of River Runoff Variability Impacting the Southern Great Barrier Reef

    PubMed Central

    Rodriguez-Ramirez, Alberto; Grove, Craig A.; Zinke, Jens; Pandolfi, John M.; Zhao, Jian-xin

    2014-01-01

    The Pacific Decadal Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere variability on decadal time scales. While precipitation and river flow variability 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 variability (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 decadal variability 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 variability 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 variability. PMID:24416214

  15. The IRIS Data Management Center: Enabling Access to Observational Time Series Spanning Decades

    NASA Astrophysics Data System (ADS)

    Ahern, T.; Benson, R.; Trabant, C.

    2009-04-01

    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 observing 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 observational 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 are of acceptably high quality. The formats and data structures used by the seismological community are esoteric. IRIS and its FDSN partners are developing web services that can transform the data holdings to structures that are more easily used by broader scientific communities. For instance, atmospheric scientists are interested in using global observations of microbarograph data but that community does not understand the methods of applying instrument corrections to the observations. Web processing services under development at IRIS will transform these data in a manner that allows direct use within such analysis tools as MATLAB® already in use by that community. By continuing to develop web-service based methods of data discovery and access, IRIS is enabling broader access to its data holdings. We currently support data discovery using many of the Open Geospatial Consortium (OGC) web mapping services. We are involved in portal technologies to support data discovery and distribution for all data from the EarthScope project. We are working with computer scientists at several universities including the University of Washington as part of a DataNet proposal and we intend to enhance metadata, further develop ontologies, develop a Registry Service to aid in the discovery of data sets and services, and in general improve the semantic interoperability of the data managed at the IRIS DMC. Finally IRIS has been identified as one of four scientific organizations that the External Research Division of Microsoft wants to work with in the development of web services and specifically with the development of a scientific workflow engine. More specific details of current and future developments at the IRIS DMC will be included in this presentation.

  16. Intraseasonal Variability Of Tropical And South Atlantic - Observation And Modeling

    NASA Astrophysics Data System (ADS)

    de Camargo, R.

    2007-05-01

    Intraseasonal variability 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 variability and the correspondent co- variability with atmosphere were evaluated in terms of SST and surface wind anomaly fields and their cross wavelet transforms, both for observations and modeled results. Observations related to the tropical area revealed that: (i) the presence of intrinsic ocean intraseasonal variability (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 variability 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.

  17. Decadal-to-Millennial Oceanographic Variability Along the Antarctic Peninsula: ODP Site 1098 Demonstrates Strong Solar Forcing Signals In The Southern Ocean

    NASA Astrophysics Data System (ADS)

    Dunbar, R. B.; Ravelo, A. C.; Domack, E.; Leventer, A.

    2002-12-01

    The Antarctic Peninsula is highly sensitive to climate change and is currently experiencing rapid and unusual warming. In 1998, the Ocean Drilling Program triple-cored the Palmer Deep (site 1098: 64o51'S, 64o12'W), a large depression off the west coast of the Antarctic Peninsula, to examine Holocene oceanographic variability. More than 50 m of diatomaceous muds and oozes and muddy diamictons were recovered, comprising the first high resolution, continuous, Late Pleistocene through Holocene sediment record from the Antarctic continental margin. As part of a multi-proxy analysis of the site 1098 cores, we analyzed biogenic opal, organic C and N concentrations, and 13C/12C and 15N/14N isotopic ratios of sedimentary organic matter every 2.5-3 cm downcore (1600 samples, sample interval of about 8 years). We interpret the main changes in these downcore parameters as indicating substantial changes in productivity. In particular, we note that 1) that the lowest productivity of the Holocene occurred during the past 2.5 kyrs b.p., 2) Holocene variability in productivity is large, about a factor of 3, 3) A mid-Holocene productivity maximum is coeval with many mid- and low-latitude Holocene paleoclimate records, and 4) evidence for solar forcing at decadal to centennial periods is strong as is the evidence for precessional forcing over millennial timescales. Given the modern link between sea ice and net annual primary production along the Antarctic margin, it seems likely that episodes of enhanced productivity, both during the middle Holocene and during centennial productivity peaks were associated with reduced ice cover. We explore several mechanisms by which sea ice cover might respond in an fashion consistent with our observations: 1) reduced westerly winds (less evaporative cooling), 2) South Pacific gyre Spin-up (less pole-equator T contrast), 3) more local warm deep water upwelling. It is possible that the basic ENSO dynamic we know from studies of interannual variability in the Pacific also regulates climate change at decadal to millennial timescales. The answer awaits a more complete synthesis of additional Holocene land and marine records but we note that the strongest Southern Oscillation atmospheric pressure anomaly in the Southern Ocean is in the Bellingshausen/Amundsen seas, upwind from our Antarctic Peninsula study site.

  18. Characteristics of IR variable stars as observed from orbit

    NASA Technical Reports Server (NTRS)

    Maran, S. P.; Heinsheimer, T. F.; Stocker, T. L.; Chapman, R. D.; Hobbs, R. W.; Michalitsanos, A. G.

    1976-01-01

    A selection of infrared variable stars was studied at wavelength 2.7 microns during 1971-1975 with data from U.S. Air Force satellites. Stars observed in this program are classified as long-period variable stars, semiregular variables, and irregular variables and are among the strongest stellar sources at this wavelength. In addition, a few new, as yet unclassified variable 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 variable 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.

  19. The reflection of two past outbursts of Sagittarius A* observed by Chandra during the last decade

    E-print Network

    Clavel, Maïca; Goldwurm, A; Morris, M R; Ponti, G; Soldi, S; Trap, G

    2014-01-01

    The supermassive black hole at the Galactic center, Sagittarius A*, has experienced periods of higher activity in the past. The reflection of these past outbursts is observed in the molecular material surrounding the black hole but reconstructing its precise lightcurve is difficult since the distribution of the clouds along the line of sight is poorly constrained. Using Chandra high-resolution data collected from 1999 to 2011 we studied both the 6.4 keV and the 4-8 keV emission of the region located between Sgr A* and the Radio Arc, characterizing its variations down to 15" angular scale and 1-year time scale. The emission from the molecular clouds in the region varies significantly, showing either a 2-year peaked emission or 10-year linear variations. This is the first time that such fast variations are measured. Based on the cloud parameters, we conclude that these two behaviors are likely due to two distinct past outbursts of Sgr A* during which its luminosity rose to at least 10^39 erg/s.

  20. Religious education and midlife observance are associated with dementia three decades later in Israeli men

    PubMed Central

    Beeri, Michal Schnaider; Davidson, Michael; Silverman, Jeremy M.; Schmeidler, James; Springer, Ramit Ravona; Noy, Shlomo; Goldbourt, Uri

    2010-01-01

    Objective The aim of the study was to examine the association of religious education and observance 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

  1. The Earth Observing One (EO-1) Satellite Mission: Over a Decade in Space

    NASA Technical Reports Server (NTRS)

    Middleton, Elizabeth M.; Ungar, Stephen G.; Mandl, Daniel J.; Ong, Lawrence; Frye, Stuart W.; Campbell, Petya E.; Landis, David R.; Pollack, Nathan H.

    2013-01-01

    The Earth Observing One (EO-1) satellite was launched in November 2000 as a technology demonstration mission with an estimated 1-year lifespan. It has now successfully completed 12 years of high spatial resolution imaging operations from low Earth orbit. EO-1's two main instruments, Hyperion and the Advanced Land Imager (ALI), have both served as prototypes for new generation satellite missions. ALI, an innovative multispectral instrument, is the forerunner of the Operational Land Imager (OLI) onboard the Landsat Data Continuity Mission's (LDCM) Landsat-8 satellite, recently launched in Feb. 2013. Hyperion, a hyperspectral instrument, serves as the heritage orbital spectrometer for future global platforms, including the proposed NASA Hyperspectral Infrared Imager (HyspIRI) and the forthcoming (in 2017) German satellite, EnMAP. This JSTARS Special Issue is dedicated to EO-1. This paper serves as an introduction to the Hyperion and ALI instruments, their capabilities, and the important contributions this mission has made to the science and technology communities. This paper also provides an overview of the EO-1 mission, including the several operational phases which have characterized its lifetime. It also briefly describes calibration and validation activities, and gives an overview of the spin-off technologies, including disaster monitoring and new Web-based tools which can be adapted for use in future missions.

  2. MISR Decadal Observations of Mineral Dust: Property Characterization and Climate Applications

    NASA Technical Reports Server (NTRS)

    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

    2012-01-01

    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 observations 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.

  3. Variability of Arctic Sea Ice as Determined from Satellite Observations

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    1999-01-01

    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 variability. 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 variability of the ice, the frequency of ice coverage, and the length of the sea ice season. The data reveal marked regional and interannual variabilities, 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% / decade 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 variability, 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.

  4. A DECADE OF SOLAR TYPE III RADIO BURSTS OBSERVED BY THE NANCAY RADIOHELIOGRAPH 1998-2008

    SciTech Connect

    Saint-Hilaire, P.; Vilmer, N.; Kerdraon, A.

    2013-01-01

    We present a statistical survey of almost 10,000 radio type III bursts observed 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.

  5. Contrasting aerosol trends over South Asia during the last decade based on MODIS observations

    NASA Astrophysics Data System (ADS)

    Kaskaoutis, D. G.; Kharol, S. K.; Sinha, P. R.; Singh, R. P.; Badarinath, K. V. S.; Mehdi, W.; Sharma, M.

    2011-08-01

    Atmospheric aerosols over south Asia constitute a major environmental and climate issue. Thus, extensive land and cruise campaigns have been conducted over the area focusing on investigating the aerosol properties and climate implications. Except from the ground-based instrumentation, several studies dealt with analyzing the aerosol properties from space, focusing mainly on the spatial distribution of the aerosol optical depth (AOD) and possible feedbacks of aerosols on the monsoon system. However, except from some works using ground-based instrumentation or satellite observations over a specific region, there is lack of studies dealing with monitoring of the aerosol trend over south Asia. The present work analyzes the variations and trends in aerosol load over south Asia using Terra-MODIS AOD550 data in the period 2000-2009. Overall, an increasing trend of 10.17 % in AOD is found over whole south Asia, which exhibits large spatio-temporal variation. More specifically, the AOD550 increasing trend is more pronounced in winter, and especially over northern India. The present study shows an evidence of a decreasing AOD550 trend over the densely-populated Indo-Gangetic Plains (IGP) during the period April-September, which has never been reported before. This decreasing trend is not statistically significant and leads to an AOD change of -0.01 per year in June, when the dust activity is at its maximum. The AOD decrease seems to be attributed to weakness of dust activity in the northwest of India, closely associated with expansion of the vegetated areas and increase in precipitation over the Thar desert. Similarly, GOCART simulations over south Asia show a pronounced decreasing trend in dust AOD in accordance with MODIS. However, much more analysis and longer dataset are required for establishing this evidence.

  6. Observational Evidence for a Decade-long climate optimum near the Hesperian/Amazonian Transition

    NASA Astrophysics Data System (ADS)

    Parsons, R.; Moore, J. M.; Howard, A. D.

    2012-12-01

    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 observations, 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 topographic highs sourced either from polar ice redistributed during high obliquity, or by one or more outflow channel water release events. The atmospheric temperature gradient required to generate preferential ice deposition on topographic highs implies a much thicker (few hundred millibars [7]) atmosphere. Next, a significant (perhaps, brief) global warming event melted these snowpacks. Likely warming mechanisms include the formation of a ~100 km impact crater or a short-lived SO2 greenhouse generated from a rapid, voluminous volcanic dike injection such as that which formed Sirenum Fossae [8]. [1] Grant, J., & Wilson, S. (2011), Geophys. Res. Lett., 38. [2] Smart, G. (1984), J. Hydraulic Eng., 110, 267-276. [3] Meyer-Peter, E. & Mueller, R. (1948) in Int. Assoc. for Hydraul. Struct. Res., vol. 2, pp. 39-64, Stockholm. [4] Parker, G., Klingeman, P. & McLean, D. (1982) J. Hydraul. Eng., 108(HY4), 544-571. [5] Ribberink, J. S. (1998), Coastal Eng., 34, 59-82. [6] Silberman, E., Einstein, H., Hinds, J., Powell, R., et al. (1963), J. Hydraul. Eng., 89(HY2), 97-143. [7] Wordsworth, R., Forget, F., Millour, E., Head, J., Madeleine, J.-B. & Charnay, B. (submitted), Icarus. [8] Wilson, L., & Head, J. (2002), J. Geophys. Res., 107.

  7. Seasonal to Decadal Variability in the Upper Ocean Scattering Layer in Drake Passage in Relation to Atmospheric and Oceanic Forcing

    NASA Astrophysics Data System (ADS)

    Chereskin, T. K.; Koenig, Z.

    2012-12-01

    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 observational 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 observed, consistent with krill behavior. Significant geographic variations are present on both seasonal and interannual time scales. Interannual variability 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 present study and proposed sampling to address them will also be discussed.

  8. Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining decadal-scale biological variability.

    PubMed

    Litzow, Michael A; Mueter, Franz J; Hobday, Alistair J

    2014-01-01

    In areas of the North Pacific that are largely free of overfishing, climate regime shifts - abrupt changes in modes of low-frequency climate variability - are seen as the dominant drivers of decadal-scale ecological variability. We assessed the ability of leading modes of climate variability [Pacific Decadal 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 decadal-scale (1965-2008) patterns of climatic and biological variability across two North Pacific ecosystems (Gulf of Alaska and Bering Sea). Our response variables 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 variability 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 variability. However, when the residual climate trend and a time series of commercial fishery catches were used as additional candidate variables, 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 variable for explaining biology PC1 variability, and commercial catch the most important variable for biology PC2. Patterns of climate sensitivity and exploitation history for taxa strongly associated with biology PC1-2 suggest plausible mechanistic explanations for these modeling results. Our findings suggest that, even in the absence of overfishing and in areas strongly influenced by internal climate variability, climate regime shift effects can only be understood in the context of other ecosystem perturbations. PMID:23996901

  9. Simulating Lake-Groundwater Interactions During Decadal Climate Cycles: Accounting For Variable Lake Area In The Watershed

    NASA Astrophysics Data System (ADS)

    Virdi, M. L.; Lee, T. M.

    2009-12-01

    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-decadal 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 observed 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 period. Groundwater flows simulated using daily time steps over a 10-year period were used to describe the relationship between climate, the size of the groundwater catchment, and the relative importance of groundwater inflow to the lake water budget. Modeling approaches used in this study should be applicable to other surface-water bodies such as wetlands and playa lakes. Lake Starr watershed (depressions from sinkholes)

  10. Observability of Antarctic Surface Temperature Variations on Decadal Time Scales, With High Spatial Resolution, Using Satellite Observations of Thermal Microwave Emission and Sparse Ground Measurements

    NASA Astrophysics Data System (ADS)

    Winebrenner, D. P.

    2001-12-01

    Knowledge of Antarctic surface temperature variations in space and time is presently based on instrumental records and interpretation of ice cores, both of which are, by practical necessity, sparse point measurements. The sufficiency of spatial sampling by such measurements remains uncertain. Spatially extensive satellite observations of 0.8 cm-wavelength (37 GHz) thermal emission can be interpreted in terms of snow surface temperature to address this problem, but such interpretation is presently limited in two important respects: (1) interpretation is restricted to regions of space and time near instrumental or other independent temperature data that are needed to infer an effective microwave emissivity; and (2) the record of suitable observations extends back only 22 years, a duration which is short compared to the timescale of many prospective temperature variations of interest. The first limitation can be addressed by estimating long-term (centennial-scale) mean surface temperature independently from satellite observations of 4.5 cm-wavelength (6.7 GHz) emission. I present the essential physical and observational validation for this estimation, and show how, together with the shorter wavelength observations, the estimation can be used to characterize microwave emissivity at 0.8 cm-wavelength (for a simplified, though usefully approximate model in which firn properties are independent of depth within the range from which the shorter-wavelength emission originates). The second limitation can be addressed using emission observations at wavelengths longer than 0.8 cm - in particular, emission at 1.8 cm - and longer-wavelengths (i.e., frequencies of 19 GHz and lower) carries information on temperature variations on decadal scales. I present a simple calculation that shows how this occurs, and note approximate agreement of the calculation with recent results by Shuman and by Fahnestock and co-workers. The underlying physics thus supports, in principle, the use of existing and prospective satellite microwave emission observations to characterize ice sheet temperature variations during a significant part of the 20th century - the key question is whether available accuracies compare well with the expected magnitudes of such temperature variations. I address this question using basic but modern geostatistical methods to estimate the accuracy of "calibration" of the satellite temperature estimates using sparse ground observations. From this follows directly an assessment of the observability of Antarctic surface temperature variations on decadal time scales, both with present data and with data likely to become available in the next decade.

  11. Forced and Natural Atlantic Multidecadal Variabilities in Observations and Coupled Ocean- Atmosphere Models

    NASA Astrophysics Data System (ADS)

    Ting, M.; Kushnir, Y.; Li, C.

    2007-05-01

    The recent increase in both the intensity and frequency of the Atlantic hurricane activities and the rapid increase in Greenland ice sheet melting have raised an extremely urgent question as to what causes these abrupt changes in climate. The most relevant scientific question is the relative contribution of those caused by the natural climate variabilities and those due to anthropogenic forcing. If both effects are important, then the next question is to determine the phase of the natural oscillation, so one can correctly predict what we can expect for the next decades given the anthropogenic climate change. This study examines the different methods to detect and separate the natural and forced components of the most prominent multidecadal variabilities in observations: the so called Atlantic Multdecadal Oscillation or AMO.

  12. Long-term Solar Irradiance Variability: 1984-1989 Observations

    NASA Technical Reports Server (NTRS)

    Lee, Robert B., III

    1990-01-01

    Long-term variability in the total solar irradiance has been observed in the Earth Radiation Budget Experiment (ERBE) solar monitor measurements. The monitors have been used to measure the irradiance from the Earth Radiation Budget Satellite (ERBS) and the National Oceanic and Atmospheric Administration NOAA-9 and NOAA-10 spacecraft platforms since October 25, 1984, January 23, 1985, and October 22, 1986, respectively. Before September 1986, the ERBS irradiance values were found to be decreasing -0.03 percent per year. This period was marked by decreasing solar magnetic activity. Between September 1986 and mid-1989, the irradiance values increased approximately 0.1 percent. The latter period was marked by increasing solar activity which was associated with the initiations of the sunspot cycle number 22 and of a new 22-year Hale solar magnetic cycle. Therefore, long-term solar-irradiance variability appears to be correlated directly with solar activity. The maximum smoothed sunspot number occurred during September 1989, according to the Sunspot Index Data Center. Therefore, the recent irradiance increasing trend should disappear during early 1990 and change into a decreasing trend if the observed irradiance variability is correlated more so with the 11-year sunspot cycle than the 22-year Hale cycle. The ERBE irradiance values are presented and compared with sunspot activity for the 1984 to 1989 period. The ERBE values are compared with those available from the Nimbus-7 and Solar Maximum Mission spacecraft experiments.

  13. Constraints on Variability of Brightness and Surface Magnetism on Time Scales of Decades to Centuries in the Sun and Sun-Like Stars: A Source of Potential Terrestrial Climate Variability

    NASA Technical Reports Server (NTRS)

    Baliunas, Sallie L.; Sharber, James (Technical Monitor)

    2001-01-01

    These four points summarize our work to date. (1) Conciliation of solar and stellar photometric variability. Previous research by us and colleagues suggested that the Sun might at present be showing unusually low photometric variability 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 decades to centuries. However, our results indicate the contrary: the Sun's observed short-term (seasonal) and longterm (year-to-year) brightness variations closely agree with observed 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). Variable 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 variable 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 cloudy, which in turn allows more solar radiation to reach the Earth's surface. (4) Natural variability in an ocean-atmosphere climate model. We use a 14-region, 6-layer, global thermo-hydrodynamic ocean-atmosphere model to study natural climate variability. All the numerical experiments were performed with no change in the prescribed external boundary conditions (except for the seasonal cycle of the Sun's tilt angle). Therefore, the observed inter-annual variability is of an internal kind. The model results are helpful toward the understanding of the role of nonlinearity in climate change. We have demonstrated a range of possible climate behaviors using our newly developed ocean-atmosphere model. These include climate configurations with no interannual variability, with multi-year periodicities, with continuous chaos, or with chaotically occuring transitions between two discrete substrates. These possible modes of climate behavior are all possible for the real climate, as well as the model. We have shown that small temporary climate influences can trigger shifts both in the mean climate, and among these different types of behavior. Such shifts are not only theoretically plausible, as shown here and elsewhere; they are omnipresent in the climate record on time scales from several years to the age of the Earth. This has two apparently opposite implications for the possibility of anthropogenic global warming. First, any warming which might occur as a result of human influence would be only a fraction of the small-to-large unpredictable natural changes and changes which result from other external causes. On the other hand, small temporary influences such as human influence do have the potential of causing large permanent shifts in mean climate and interannual variability.

  14. New Observations of Accretion Phenomena in Magnetic Cataclysmic Variables

    NASA Astrophysics Data System (ADS)

    Buckley, D. A. H.; Potter, S. B.; Kotze, E.; Kotze, M.; Breytenbach, H.

    2014-01-01

    We present an overview of the ongoing observational, theoretical and modelling work on magnetically controlled accretion phenomena in magnetic cataclysmic variables. With SAAO's high speed polarimeter, HIPPO, we have discovered polarized Quasi-Periodic Oscillations, on a timescale of several minutes. We have investigated various scenarios in which such QPOs can be created, all of them requiring some interaction between the ballistic accretion flow and the magnetic field of the accreting white dwarf. With high speed photometry, including observations with SALT, we are investigating the nature of high frequency QPOs (~sub-few seconds) from the accretion shocks in mCVs. We also present some high speed photometric observations revealing the magnetic accretion spots on the accreting White Dwarfs. Developments in the use of Doppler tomography are also presented. Our new "inside-out" visualization gives an alternative way of calculating Doppler tomograms that can better emphasize the ballistic and magnetically confined accretion flows.

  15. Decadal to millennial-scale variability in sea ice, primary productivity, and Pacific-Water inflow in the Chukchi/East Siberian Sea area (Arctic Ocean)

    NASA Astrophysics Data System (ADS)

    Stein, Ruediger; Fahl, Kirsten; Matthiessen, Jens; Méheust, Marie; Nam, Seung-il; Niessen, Frank; Schade, Inka; Schreck, Michael; Wassmuth, Saskia; Xiao, Xiaotong

    2014-05-01

    Sea-ice is an essential component of the global climate system and, especially, the Polar Oceans. An alarming decrease in term of sea-ice concentration, thickness and duration, has been observed in the Arctic Ocean and its marginal seas over the last 30 years. Thus, understanding the processes controlling modern sea-ice variability and reconstructing paleo-sea-ice extent and variability in polar regions have become of great interest for the international scientific community during the last years. Here, we present new proxy records determined in sediment cores from the East Siberian Sea (RV Polarstern Expedition ARK-XXIII/3 in 2008; Core PS72/350) and from the Chukchi Sea (RV Araon Expedition ARA2B in 2011; Core ARA2B-1A, -1B). These records, including organic-geochemical bulk parameters, specific biomarkers (IP25 and sterols; PIP25; for recent reviews see Stein et al., 2012; Belt and Müller, 2013), biogenic opal, mineralogical data as well as high-resolution XRF scanning data, give new insight into the short-term (decadal-, centennial- to millennial-scale) variability in sea-ice, primary productivity and Pacific-Water inflow during Holocene times. Maximum concentrations of phytoplankton biomarkers and biogenic opal were determined between 8.5 and 4 kyrs. BP, suggesting enhanced primary productivity triggered by increased inflow of nutrient-rich Pacific Water (and/or an increased nutrient input due to an ice-edge position). Short-lived peak values in productivity might be related to strong pulses of Pacific-Water input during this time period (cf., Ortiz et al., 2009). A seasonal sea-ice cover was present in the Chukchi Sea throughout the last 10 kyrs. During the last 3-4 kyrs. BP, the sea-ice cover significantly extended. References Belt, S.T. and Müller, J., 2013. The Arctic sea ice biomarker IP25: a review of current understanding, recommendations for future research and applications in palaeo sea ice reconstructions. Quaternary Science Review 73, 9-25. Ortiz, J. D., Polyak, L., Grebmeier, J. M., Darby, D., Eberl D. D., Naidu, S., Nof, D., 2009. Provenance of Holocene sediment on the Chukchi-Alaskan margin based on combined diffuse spectral reflectance and quantitative X-Ray Diffraction analysis. Global and Planetary Change 68, pp.73-84. Stein, R., Fahl, K., and Müller, J., 2012. Proxy Reconstruction of Cenozoic Arctic Ocean Sea-Ice History - from IRD to IP25. Polarforschung 82, 37-71.

  16. Building on Decades of Research on the McMurdo Volcanic Group, Antarctica: A Geologic Field Guide to Observation Hill

    NASA Astrophysics Data System (ADS)

    Pound, K. S.; Panter, K. S.

    2008-12-01

    Based on more than four decades of research on the rocks of the Erebus Volcanic Province of the McMurdo Volcanic Group, a geologic field guide to the Observation Hill walking tracks near McMurdo Station, Antarctica has been developed. The geologic field guide was an outcome of questions generated by: (1) Teachers participating in the Andrill Research Immersion for Science Educators (ARISE) program; (2) McMurdo Station support staff, as well as (3) Geoscientists with specialties outside volcanology and petrology. Whilst these individuals are acutely aware of the more than a century of references to Observation Hill in exploration literature, there was little in the way of easily-accessible information about the geologic history of Hut Point and Observation Hill, as well as other nearby volcanoes (e.g. Mt. Erebus, White and Black Islands) and larger scale geologic features (e.g. Transantarctic Mountains) that can be seen from the vantage point of Observation Hill. Questions also focused on smaller scale features of the landscape (e.g. patterned ground) and textures and minerals observed in volcanic rocks exposed on the trails. In order to encompass the wide-ranging background of the audience and facilitate access, the field guide will be available in three formats: (1) A downloadable MP3 file, which includes the general information and stop-by- stop information; (2) A double-sided paper brochure that provides a relatively simple, easier-to-digest guide to views and geologic features; (3) A Google Earth Layer that includes access to the MP3 files and the paper brochure, as well as additional geologic information. Links to the field guide can be found at http://www.andrill.org/education.

  17. Interannual to decadal climate variability of sea salt aerosols in the coupled climate model CESM1.0

    NASA Astrophysics Data System (ADS)

    Xu, Li; Pierce, David W.; Russell, Lynn M.; Miller, Arthur J.; Somerville, Richard C. J.; Twohy, Cynthia H.; Ghan, Steven J.; Singh, Balwinder; Yoon, Jin-Ho; Rasch, Philip J.

    2015-02-01

    This study examines multiyear climate variability associated with sea salt aerosols and their contribution to the variability of shortwave cloud forcing (SWCF) using a 150 year simulation for preindustrial conditions of the Community Earth System Model version 1.0. The results suggest that changes in sea salt and related cloud and radiative properties on interannual timescales are dominated by the El Niño-Southern Oscillation cycle. Sea salt variability on longer (interdecadal) timescales is associated with low-frequency variability in the Pacific Ocean similar to the Interdecadal Pacific Oscillation but does not show a statistically significant spectral peak. A multivariate regression suggests that sea salt aerosol variability may contribute to SWCF variability in the tropical Pacific, explaining up to 20-30% of the variance in that region. Elsewhere, there is only a small sea salt aerosol influence on SWCF through modifying cloud droplet number and liquid water path that contributes to the change of cloud effective radius and cloud optical depth (and hence cloud albedo), producing a multiyear aerosol-cloud-wind interaction.

  18. Subtropical Gyre Variability Observed by Ocean Color Satellites

    NASA Technical Reports Server (NTRS)

    McClain, Charles R.; Signorini, Sergio R.; Christian, James R.

    2002-01-01

    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 variability 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 variability 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 variability 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 variability 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 observed to be shrinking over this period, while the South Pacific, South Atlantic, and South Indian Ocean gyres appear to be expanding.

  19. Decadal hindcasts with MPI-ESM initialized from coupled assimilation of oceanic observations and atmospheric re-analysis data

    NASA Astrophysics Data System (ADS)

    Brune, Sebastian; Pohlmann, Holger; Nerger, Lars; Müller, Wolfgang; Baehr, Johanna

    2015-04-01

    We present a set of decadal hindcast simulations initialized from a coupled assimilation of oceanic sub-surface observations and atmospheric re-analysis data within the same model. In the global coupled Max Planck Institute for Meteorology Earth System Model (MPI-ESM), we assimilate ocean observations using the singular evolutive ensemble Kalman filter (SEIK) and atmospheric re-analysis data using simple nudging. Our set of hindcast simulations consists of yearly initializations between 1960 to 2014, with 8 ensemble members each. This set of hindcast simulations from the SEIK-nudged assimilation is compared against a set of hindcasts simulations where both ocean an atmosphere are nudged to re-analysis data. In the assimilation experiments, we find for surface temperature, the nudged assimilation experiment in closer agreement with observations than the SEIK-nudged assimilation experiment. In contrast, the hindcasts initialized from the SEIK-nudged assimilation experiment improve over the hindcasts initialized from the nudged assimilation experiment for global mean surface temperature, and in particular for the Northeast Atlantic and for the lead years 1 to 3. In terms of the Atlantic meridional overturning circulation (AMOC), which has not been assimilated directly, we find that the SEIK-nudged assimilation experiment is closer to observations (26°N, 2004 to 2013) than the nudged assimilation experiment. We also investigate the hindcast skill for the AMOC in both experiments. Our initial results suggest that the subtle changes from the SEIK assimilation compared to the nudged assimilation in the ocean component of the coupled MPI-ESM do not necessarily degrade but even regionally improve hindcast skill.

  20. Decadal variability of the biosphere, the climate, and the carbon cycle in a coupled atmosphere-biosphere model, CCM3-IBIS.

    NASA Astrophysics Data System (ADS)

    Delire, C.; Foley, J.; Coe, M.

    2003-04-01

    We analyze a 500-year run of the coupled atmosphere, dynamic vegetation and soil model CCM3-IBIS that presents different slow modes of variability in the climate, vegetation and carbon cycle. IBIS (Foley et al., 1996; Kucharik et al., 2000) is a dynamic vegetation model that describes the physical, physiological and ecological processes occurring in vegetation and soils in a coherent and mechanistic way. The model includes land-surface physics, canopy physiology, plant phenology, vegetation dynamics and competition, and carbon cycling. We coupled IBIS to the NCAR CCM3 at a T31 resolution (~3.75o x 3.75o). We ran a 500-year equilibrium simulation of the 'present day' climate imposing a constant atmospheric CO2 concentration of 350 ppm and fixed sea-surface temperatures. A spectral analysis shows that the precipitation, the leaf area index of the vegetation, the net primary productivity and the heterotrophic respiration present slow modes of variation at decadal timescales. Because we ran CCM3-IBIS with fixed sea-surface temperatures, this detected variability can only be attributed to changes in vegetation structure and functioning. A comparison with a similar run with fixed vegetation confirm this hypothesis. Transition zones between vegetation types like the Sahel contribute the most to the slow variability. This study shows that feedbacks between vegetation dynamics, the carbon cycle and the atmosphere alone can produce internal variability at decadal scale.

  1. Decadal Variability of the Biosphere, the Climate, and the Carbon Cycle in a Coupled Atmosphere-Biosphere Model, CCM3-IBIS.

    NASA Astrophysics Data System (ADS)

    Delire, C.; Foley, J.; Coe, M. T.

    2002-12-01

    We analyze a 500-year run of the coupled atmosphere, dynamic vegetation and soil model CCM3-IBIS that presents different slow modes of variability in the climate, vegetation and carbon cycle. IBIS (Foley et al., 1996; Kucharik et al., 2000) is a dynamic vegetation model that describes the physical, physiological and ecological processes occurring in vegetation and soils in a coherent and mechanistic way. The model includes land-surface physics, canopy physiology, plant phenology, vegetation dynamics and competition, and carbon cycling. We coupled IBIS to the NCAR CCM3 at a T31 resolution (~3.75o x 3.75o). We ran a 500-year equilibrium simulation of the 'present day' climate imposing a constant atmospheric CO2 concentration of 350 ppm and fixed sea-surface temperatures. A spectral analysis shows that the precipitation, the leaf area index of the vegetation, the net primary productivity and the heterotrophic respiration present slow modes of variation at decadal timescales. Because we ran CCM3-IBIS with fixed sea-surface temperatures, this detected variability can only be attributed to changes in vegetation structure and functioning. A comparison with a similar run with fixed vegetation confirm this hypothesis. Transition zones between vegetation types like the Sahel contribute the most to the slow variability. This study shows that feedbacks between vegetation dynamics, the carbon cycle and the atmosphere alone can produce internal variability at decadal scale.

  2. Decadal variability of upper ocean heat content in the Pacific: Responding to the 11-year solar cycle

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Yan, Shuangxi; Qiao, Fangli

    2015-12-01

    Ocean heat content anomaly (OHCa) time series in some areas of the Pacific are significantly correlated with the total solar irradiance (TSI). Using the composite mean-difference method, we determined the mean response of OHCa in the upper-700 m of the ocean to the TSI. Among the high solar response areas, we figure out two regions, one in the tropical mid-Pacific and the other in the western Pacific, where the OHCa present decadal variations, but different phases. The variation in phase of the solar response indicates that there exists an agency for the OHCa's response to TSI.

  3. Analysis of Kepler Observations of ASAS Variable Stars

    NASA Astrophysics Data System (ADS)

    Pezzato, Jacklyn M.; Mighell, Kenneth J.

    2016-01-01

    We present preliminary results of a study that compares the performance of period-finding algorithms when using data gathered by ground-based telescopes to their performance when using data gathered by space-based telescopes. In order to make this comparison, the periods reported by the All Sky Automated Survey (ASAS) Catalog for Variable Stars in the Kepler Field of View, a study that identified targets for the Kepler Mission before its launch, were compared to periods determined by this study. Only targets that were identified in the ASAS Catalog and later observed by the Kepler Mission were selected for analysis, for a total of 599 targets. The observations gathered by the Kepler Mission were analyzed using three period-finding algorithms: the Lafler-Kinman algorithm, the Analysis of Variance algorithm, and the Conditional Entropy algorithm. These three algorithms analyzed the light curves of each target, and one of the periods produced was selected to be compared to the period found by the ASAS Catalog. The analysis of the two data sets highlights issues with the performance of period finding algorithms with ground-based data, leading to crude period estimates for all targets with periods longer than 10 days. Since the Large Synoptic Scanning Telescope (LSST), due for first light in 2020, will have a similar observation schedule to that of the ASAS survey, similar issues can be expected with the analysis of LSST data for some types of long period variables, like semiregulars), that have periods longer than 10 days. Pezzato was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  4. Decadal Variability of the Indo-Pacific Warm Pool and Its Association with Atmospheric and Oceanic Variability in the NCEPNCAR and SODA Reanalyses

    E-print Network

    Variability in the NCEP­NCAR and SODA Reanalyses HUI WANG* AND VIKRAM M. MEHTA The Center for Research­2001) SST, and the NCEP­NCAR atmospheric and Simple Ocean Data Assimilation (SODA) oceanic reanalysis data

  5. Advancing Variable Star Astronomy: The Centennial History of the American Association of Variable Star Observers

    NASA Astrophysics Data System (ADS)

    Williams, Thomas R.; Saladyga, Michael

    2011-05-01

    Preface; Part I. Pioneers in Variable Star Astronomy Prior to 1909: 1. The emergence of variable star astronomy - a need for observations; 2. A need for observers; 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 Observational Science - The Arne Henden Era: 21. Bridging the gap; 22. Accelerating the science - the Henden era begins; Epilogue; Appendices; Index.

  6. Multi-Decadal Aerosol Variations from 1980 to 2009: A Perspective from Observations and a Global Model

    NASA Technical Reports Server (NTRS)

    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.

    2014-01-01

    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 observations 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 decades, 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.

  7. Hydrological variability from gauging stations and simulated SWOT data, for major French rivers over the past decades

    NASA Astrophysics Data System (ADS)

    Chevalier, Laetitia; Laignel, Benoit; Turki, Imen; Lyard, Florent; Lion, Christine

    2014-05-01

    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 variability 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 variability: 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 variability 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

  8. Monitoring ? Scuti Variables with Coordinated Observing of Small Telescopes

    NASA Astrophysics Data System (ADS)

    Hintz, E.; Jeffery, E.; Walter, L.

    2001-12-01

    Beginning with a Research Experience for Teachers (RET) program this past summer a research effort has been started that will allow undergraduates to collaborate with high school students in monitoring a number of bright variable stars of the ? Scuti variety. This program will make use of the Brigham Young University 16" David Derrick Telescope and 8" Ferdinand Feghoot Telescope along with a new 10" Meade LX-200 installed at Payson High School. The initial targets for this program include DQ Cephei, DX Ceti, V474 Monocerotis, V376 Persei, ? Scuti, and V966 Herculis. Spectroscopic follow-up observations will be made at the 1.2-m Telescope of the Dominion Astrophysical Observatory in Victoria, B.C., Canada. We hope this program will lay the ground work for additional small telescopes at high schools throughout Utah. Preliminary results will be presented. Research Partially supported by NSF REU Program PHY-9988852

  9. Sea Ice Variability in the Sea of Okhotsk from Passive Microwave Satellite Observations

    NASA Technical Reports Server (NTRS)

    Cavalieri, Donald J.; Zukor, Dorothy (Technical Monitor)

    2000-01-01

    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 observations 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 variability 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%/decade), in contrast to the rate of decrease of -33.3+/-0.7x10(exp 3) sq km/yr (-2.7%/decade) for the Northern Hemisphere as a whole. There is large regional sea ice extent variability 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%/decade) and 1.2+/-0.5xl0(exp 3) sq km/yr (17.1%/decade), 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%/decade) 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.

  10. Field Observations of Soil Moisture Variability across Scales

    NASA Technical Reports Server (NTRS)

    Famiglietti, James S.; Ryu, Dongryeol; Berg, Aaron A.; Rodell, Matthew; Jackson, Thomas J.

    2008-01-01

    In this study, over 36,000 ground-based soil moisture measurements collected during the SGP97, SGP99, SMEX02, and SMEX03 field campaigns were analyzed to characterize the behavior of soil moisture variability across scales. The field campaigns were conducted in Oklahoma and Iowa in the central USA. The Oklahoma study region is sub-humid with moderately rolling topography, while the Iowa study region is humid with low-relief topography. The relationship of soil moisture standard deviation, skewness and the coefficient of variation versus mean moisture content was explored at six distinct extent scales, ranging from 2.5 m to 50 km. Results showed that variability generally increases with extent scale. The standard deviation increased from 0.036 cm3/cm3 at the 2.5-m scale to 0.071 cm3/cm3 at the 50-km scale. The log standard deviation of soil moisture increased linearly with the log extent scale, from 16 m to 1.6 km, indicative of fractal scaling. The soil moisture standard deviation versus mean moisture content exhibited a convex upward relationship at the 800-m and 50-km scales, with maximum values at mean moisture contents of roughly 0.17 cm3/cm3 and 0.19 cm3/cm3, respectively. An empirical model derived from the observed behavior of soil moisture variability was used to estimate uncertainty in the mean moisture content for a fixed number of samples at the 800-m and 50-km scales, as well as the number of ground-truth samples needed to achieve 0.05 cm3/cm3 and 0.03 cm3/cm3 accuracies. The empirical relationships can also be used to parameterize surface soil moisture variations in land surface and hydrological models across a range of scales. To our knowledge, this is the first study to document the behavior of soil moisture variability over this range of extent scales using ground-based measurements. Our results will contribute not only to efficient and reliable satellite validation, but also to better utilization of remotely sensed soil moisture products for enhanced modeling and prediction.

  11. Interannual and Seasonal Variability of Biomass Burning Emissions Constrained by Satellite Observations

    NASA Technical Reports Server (NTRS)

    Duncan, Bryan N.; Martin, Randall V.; Staudt, Amanda C.; Yevich, Rosemarie; Logan, Jennifer A.

    2003-01-01

    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 variability 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 observations 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 variability 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 decades, but that there is significant interannual variability.

  12. Observed Variability of the Solar Mg II h Spectral Line

    NASA Astrophysics Data System (ADS)

    Schmit, D.; Bryans, P.; De Pontieu, B.; McIntosh, S.; Leenaarts, J.; Carlsson, M.

    2015-10-01

    The Mg ii h&k doublet are two of the primary spectral lines observed 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 variability 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 observed structure and formation of the Mg ii profiles observed by IRIS.

  13. Multi-decadal Variability of Flood Risk in Southwestern Canadian Prairie Rivers as Characterized by the PDO and ENSO

    NASA Astrophysics Data System (ADS)

    Gurrapu, S.; St Jacques, J. M.; Sauchyn, D.; Hodder, K. R.

    2014-12-01

    The 2013 floods across southern Alberta, Canada, are considered to be one of the worst natural disasters in recent Canadian history. This region is highly vulnerable to flooding during spring as the frozen ground restricts infiltration and the melting snow directly contributes to streamflow. Studies have concluded that the 2013 floods in Alberta were a result of heavier snowpack from winter precipitation and higher amounts of spring precipitation as rain over the eastern slopes of the Rockies. Although this flood is considered to be less than the 100-year flood of the region, the effects were economically devastating. The return periods of floods are generally determined under the assumption that the annual peak flow series are independent and identically distributed (i.i.d.). However, researchers have demonstrated that this assumption is not valid in Australia and that the i.i.d. assumption can lead to under- or over-estimation of the true long-term flood risk. The Pacific Decadal Oscillation (PDO) and the El Niño-Southern Oscillation (ENSO) have a strong impact on western Canadian hydroclimate via teleconnections. The negative phase of the PDO and La Niña typically produce heavier snowpack across the prairies compared to that during the positive phase of PDO and El Niño. In this study, we explore the connections between the PDO, ENSO and the peak annual streamflow in southwestern Canadian prairie rivers. Daily averaged annual peak flow records from 22 rivers were stratified according to the PDO phases and ENSO states and fit to the Log-Pearson III (LP3) distribution. We determined that the flood risk is significantly higher in the negative phase of the PDO and is enhanced during La Niña episodes within the negative PDO phase. To ensure these results were not due to sampling error or unequal record lengths, a regional index approach was also employed, which confirmed these results. Our results are important for the optimal planning and design of flood control structures, transportation infrastructure, and water distribution systems, etc.

  14. GLIMPSE Proper: Mid-Infrared Observations of Proper Motion and Variability Towards Galactic Center

    NASA Astrophysics Data System (ADS)

    Benjamin, Robert; Babler, Brian; Churchwell, Ed; Clarkson, Will; Kirkpatrick, Davy; Meade, Marilyn; Whitney, Barbara

    2015-10-01

    We propose to re-image 43.4 square degrees of the Galactic center to measure the proper motions of over fifteen million sources within 5 degrees of Galactic center over the last decade. This stellar sample will be over 20 times larger than the previous optical ground-based measurements and will allow us to constrain the anisotropic stellar velocity dispersion as a function of direction and distance as well as test previous claims of streaming motions associated with the near/far side of the Galactic bar, the X-shaped bar, and the vertically thin extended Long Bar. Not only will this be the largest Galactic bulge proper motion survey to date, it will also be the most uniform as mid-infrared observations are minimally affected by extinction over most of the region. We also expect to find at least 150 high proper motion stars (>100 mas/yr) which could be substellar objects and possible microlensing candidates against the crowded Galactic bulge. We will put constraints on the current production rate of hyper-velocity stars thought to be formed in binary interactions with the supermassive black hole of the Galaxy. Finally, we will be able to identify many new variable stars, particularly in the central 2x1.5 degree region of the Galaxy which has only been observed in a single epoch with Spitzer; we expect to find 1000 new sources with variability amplitudes greater than 0.2 mag.

  15. Multiwavelength Observations of Short-Timescale Variability in NGC 4151. IV. Analysis of Multiwavelength Continuum Variability

    NASA Astrophysics Data System (ADS)

    Edelson, R. A.; Alexander, T.; Crenshaw, D. M.; Kaspi, S.; Malkan, M. A.; Peterson, B. M.; Warwick, R. S.; Clavel, J.; Filippenko, A. V.; Horne, K.; Korista, K. T.; Kriss, G. A.; Krolik, J. H.; Maoz, D.; Nandra, K.; O'Brien, P. T.; Penton, S. V.; Yaqoob, T.; Albrecht, P.; Alloin, D.; Ayres, T. R.; Balonek, T. J.; Barr, P.; Barth, A. J.; Bertram, R.; Bromage, G. E.; Carini, M.; Carone, T. E.; Cheng, F.-Z.; Chuvaev, K. K.; Dietrich, M.; Dultzin-Hacyan, D.; Gaskell, C. M.; Glass, I. S.; Goad, M. R.; Hemar, S.; Ho, L. C.; Huchra, J. P.; Hutchings, J.; Johnson, W. N.; Kazanas, D.; Kollatschny, W.; Koratkar, A. P.; Kovo, O.; Laor, A.; MacAlpine, G. M.; Magdziarz, P.; Martin, P. G.; Matheson, T.; McCollum, B.; Miller, H. R.; Morris, S. L.; Oknyanskij, V. L.; Penfold, J.; Perez, E.; Perola, G. C.; Pike, G.; Pogge, R. W.; Ptak, R. L.; Qian, B.-C.; Recondo-Gonzalez, M. C.; Reichert, G. A.; Rodriguez-Espinoza, J. M.; Rodriguez-Pascual, P. M.; Rokaki, E. L.; Roland, J.; Sadun, A. C.; Salamanca, I.; Santos-Lleo, M.; Shields, J. C.; Shull, J. M.; Smith, D. A.; Smith, S. M.; Snijders, M. A. J.; Stirpe, G. M.; Stoner, R. E.; Sun, W.-H.; Ulrich, M.-H.; van Groningen, E.; Wagner, R. M.; Wagner, S.; Wanders, I.; Welsh, W. F.; Weymann, R. J.; Wilkes, B. J.; Wu, H.; Wurster, J.; Xue, S.-J.; Zdziarski, A. A.; Zheng, W.; Zou, Z.-L.

    1996-10-01

    This paper combines data from the three preceding papers in order to analyze the multi-wave-band variability and spectral energy distribution of the Seyfert I galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths; The strongest variatIons were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA = 6%) variations (uncorrelated with those at lower energies) were seen at soft gamma ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 A. These data do not probe extreme ultraviolet (1200 A to 0.1 keV) or hard X ray (2-50 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of <~ 0.15 day between 1275 A and the other ultraviolet bands, <~0.3 day between 1275 A and 1.5 keV, and <~1 day between 1275 and 512 A. These tight limits represent more than an order of magnitude improvement over those determined in previous multi wave band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (a <= -2.5). If photons emitted at a "primary" wave band are absorbed by nearby material and "reprocessed" to produce emission at a secondary wave band, causality arguments require that variations in the secondary band follow those in the primary band. The tight interband correlation and limits on the ultraviolet and medium-energy X-ray lags indicate that the reprocessing region is smaller than ~0.15 lt-day in size. After correcting for strong (a factor of ~> 15) line-of-sight absorption, the medium-energy X-ray luminosity variations appear adequate to drive the ultraviolet/optical variations. However the medium-energy X-ray NVA is 2- 4 times that in the ultraviolet, and the single-epoch absorption- corrected X-ray/gamma ray luminosity is only about one third of that of the ultraviolet optical/infrared, suggesting that at most about a third of the total low energy flux could be reprocessed high-energy emission. The strong wavelength dependence of the ultraviolet NVAs is consistent with an origin in an accretion disk, with the variable emission coming from the hotter inner regions and nonvariable emission from the cooler outer regions. These data, when combined with the results of disk fits indicate a boundary between these regions near a radius of order R ~ 0.07 lt-day. No interband lag would be expected, as reprocessing (and thus propagation between regions) need not occur, and the orbital timescale of 1 day is consistent with the observed variability timescale. However, such a model does not immediately explain the good correlation between ultraviolet and X-ray variations.

  16. Systematic attribution of observed Southern Hemisphere circulation trends to external forcing and internal variability

    NASA Astrophysics Data System (ADS)

    Franzke, C. L. E.; O'Kane, T. J.; Monselesan, D. P.; Risbey, J. S.; Horenko, I.

    2015-09-01

    A critical question in the global warming debate concerns the causes of the observed trends of the Southern Hemisphere (SH) atmospheric circulation over recent decades. 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 observational forcing data or have mixed external forcing with indices of internal climate variability 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 decades using a non-stationary clustering method applied to both reanalysis and observational 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 observational 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.

  17. Systematic attribution of observed southern hemispheric circulation trends to external forcing and internal variability

    NASA Astrophysics Data System (ADS)

    Franzke, C. L. E.; O'Kane, T. J.; Monselesan, D. P.; Risbey, J. S.; Horenko, I.

    2015-04-01

    A critical question in the global warming debate concerns the causes of the observed trends of the Southern Hemisphere (SH) atmospheric circulation over recent decades. 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 observational forcing data or have mixed external forcing with indices of internal climate variability 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 decades using a non-stationary clustering method applied to both reanalysis and observational 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 observational 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.

  18. Systematic Attribution of Observed Southern Hemispheric Circulation Trends to External Forcing and Internal Variability

    NASA Astrophysics Data System (ADS)

    Franzke, Christian; O'Kane, Terence; Monselesan, Didier; Risbey, James; Horenko, Illia

    2015-04-01

    A critical question in the global warming debate concerns the causes of the observed trends of the Southern Hemisphere (SH) atmospheric circulation over recent decades. 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 observational forcing data or have mixed external forcing with indices of internal climate variability 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 decades using a non-stationary clustering method applied to both reanalysis and observational forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing summer SH circulation trends, we show observational 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.

  19. Surface Wind Observational Database in North Eastern North America: Quality Control Procedure and Climatological Variability

    NASA Astrophysics Data System (ADS)

    Lucio-Eceiza, Etor E.; Fidel González-Rouco, J.; Navarro, Jorge; Hidalgo, Ángela; Conte, Jorge; Beltrami, Hugo

    2015-04-01

    This work summarizes the design and application of a Quality Control (QC) procedure for an observational surface wind database located in North Eastern North America. It also presents some insights of the long-term climatological variability 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 variability, placing particular emphasis on the detection of unrealistic low wind speed records with the help of regional references; high variability 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 decadal variability of the monthly surface wind field in such a vast and orographically complex region as the North Eastern North America is explored. Several decades of quality observations allow for the calibration of a statistical downscaling method based on Canonical Correlation Analysis. The method relates the main large-scale atmospheric circulation modes over the North Atlantic with the regional wind field. The relations are centered over the extended seasons of summer and winter. These seasons present interesting distinct dynamical features such as the frequent passage of tropical storms and hurricanes during summer and strong mid-latitude winter storms.

  20. Follow up Observations of SDSS and CRTS Candidate Cataclysmic Variables

    NASA Astrophysics Data System (ADS)

    Szkody, Paula; Everett, Mark E.; Howell, Steve B.; Landolt, Arlo U.; Bond, Howard E.; Silva, David R.; Vasquez-Soltero, Stephanie

    2014-10-01

    We present photometry and spectroscopy of 11 and 35 potential cataclysmic variables, 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. Based on observations obtained with the Apache Point Observatory (APO) 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.

  1. Are stress drop and rupture velocity of earthquakes independent? Insight from observed ground motion variability

    NASA Astrophysics Data System (ADS)

    Causse, Mathieu; Song, Seok Goo

    2015-09-01

    We demonstrate that the variability of the peak ground acceleration (PGA) generated by earthquakes can be simply related to the variability of stress drop (??), rupture velocity (Vr) and their correlation. By compiling recent observations of variability of ?? and Vr, we show that the hypothesis of independence between ?? and Vr leads to an overestimation of the PGA variability. We suggest that ?? and Vr must be anticorrelated so as to match recent observations of PGA variability.

  2. Multi-decadal aerosol variations from 1980 to 2009: a perspective from observations and a global model

    NASA Astrophysics Data System (ADS)

    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.

    2014-04-01

    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 observations 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 decades, because opposite trends in different land regions cancel each other out in the global average, and changes over large open oceans are negligible. This highlights the necessity for regional-scale assessment of aerosols and their climate impacts, as global-scale average values can obscure important regional changes.

  3. Seasonal to Decadal-Scale Variability in Satellite Ocean Color and Sea Surface Temperature for the California Current System

    NASA Technical Reports Server (NTRS)

    Mitchell, B. Greg; Kahru, Mati; Marra, John (Technical Monitor)

    2002-01-01

    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 observations. 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.

  4. A new direction for Antarctic ice cores: reconstructing Pacific decadal variability and Australian drought history from the Law Dome ice core.

    NASA Astrophysics Data System (ADS)

    Vance, Tessa; Roberts, Jason; Plummer, Chris; Kiem, Anthony; van Ommen, Tas

    2015-04-01

    Decadal scale SST oscillations in the Pacific significantly influence rainfall variability and drought risk across and beyond the Pacific region. Understanding long-term decadal 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 decadal variability 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 decadal-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-droughts during the medieval period. Knowledge of the occurrence, duration and frequency of such mega-droughts will greatly improve drought risk assessment in Australia. Importantly, this new IPO reconstruction will help with assessing climate risk over the longer term in the wider Pacific Basin, particularly in the data-sparse Southern Hemisphere. In addition, the hydrological application of producing an annually dated drought record to calculate long-term drought risk represents a new use of Antarctic ice core records.

  5. An objective analysis of the observed spatial structure of the tropical Indian Ocean SST variability

    E-print Network

    Dommenget, Dietmar

    An objective analysis of the observed spatial structure of the tropical Indian Ocean SST 2010 Ó Springer-Verlag 2010 Abstract The observed interannual Indian Ocean sea surface temperature (SST of the multivariate SST variability. The Indian Ocean SST variability is marked by relatively weak SST variability

  6. Observing Simulated Cepheid Variable Stars in an Introductory Astronomy Lab.

    ERIC Educational Resources Information Center

    Flesch, Terry R.

    1979-01-01

    Describes an exercise developed by the author to help college students to become familiar with the technique of photoelectric photometry of variable stars and permits each student to work with data he or she has personally obtained. (HM)

  7. Coupled ocean-atmosphere model system for studies of interannual-to-decadal climate variability over the North Pacific Basin and precipitation over the Southwestern United States

    SciTech Connect

    Lai, Chung-Chieng A.

    1997-10-01

    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-decadal climate variability 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.

  8. Final Report for UW-Madison Portion of DE-SC0005301, "Collaborative Project: Pacific Decadal Variability and Central Pacific Warming El Niño in a Changing Climate"

    SciTech Connect

    Vimont, Daniel

    2014-06-13

    This project funded two efforts at understanding the interactions between Central Pacific ENSO events, the mid-latitude atmosphere, and decadal variability in the Pacific. The first was an investigation of conditions that lead to Central Pacific (CP) and East Pacific (EP) ENSO events through the use of linear inverse modeling with defined norms. The second effort was a modeling study that combined output from the National Center for Atmospheric Research (NCAR) Community Atmospheric Model (CAM4) with the Battisti (1988) intermediate coupled model. The intent of the second activity was to investigate the relationship between the atmospheric North Pacific Oscillation (NPO), the Pacific Meridional Mode (PMM), and ENSO. These two activities are described herein.

  9. 1 2010 Heliophysics Decadal ReviewScience with a X-ray Microcalorimeter White Paper Science Objectives for an X-Ray Microcalorimeter Observing the Sun

    E-print Network

    Savin, Daniel Wolf

    1 2010 Heliophysics Decadal ReviewScience with a X-ray Microcalorimeter White Paper Science Objectives for an X-Ray Microcalorimeter Observing the Sun J. Martin Laming1 §, J. Adams3 , D. Alexander8 , M We present the science case for a broadband X-ray imager with high-resolution spectroscopy, including

  10. Six-decade temporal change and seasonal decomposition of climate variables in Lake Dianchi watershed (China): stable trend or abrupt shift?

    NASA Astrophysics Data System (ADS)

    Zhou, Jing; Liang, Zhongyao; Liu, Yong; Guo, Huaicheng; He, Dan; Zhao, Lei

    2015-01-01

    Meteorological trend analysis is a useful tool for understanding climate change and can provide useful information on the possibility of future change. Lake Dianchi is the sixth largest freshwater body in China with serious eutrophication. Algal blooms outbreak was proven to be closely associated with some climatic factors in Lake Dianchi. It is therefore essential to explore the trends of climatic time series to understand the mechanism of climate change on lake eutrophication. We proposed an integrated method of Mann-Kendall (MK) test, seasonal-trend decomposition using locally weighted regression (LOESS) (STL), and regime shift index (RSI) to decompose the trend analysis and identify the stable and abrupt changes of some climate variables from 1951 to 2009. The variables include mean air temperature (Tm), maximum air temperatures (Tmax), minimum air temperatures (Tmin), precipitation (Prec), average relative humidity (Hum), and average wind speed (Wind). The results showed that (a) annual Tm, Tmax, and Tmin have a significant increasing trend with the increasing rates of 0.26, 0.15and 0.43 °C per decade, respectively; (b) annual precipitation has an insignificant decreasing trend with the decreasing rate of 3.17 mm per decade; (c) annual Hum has a significant decreasing trend in all seasons; and (d) there are two turning points for temperature rise around 1980 and 1995 and two abrupt change periods for precipitation with the extreme points appearing in 1963 and 1976. Temperature rise and precipitation decline in summer and autumn as well as wind speed decrease after the 1990s may be an important reason for algal blooms outbreak in Lake Dianchi. This study was expected to provide foundation and reference for regional water resource management.

  11. Pacific Decadal Variability in the Southern Indian Ocean: A 1 ky Interdecadal Pacific Oscillation and Australian Megadrought Reconstruction from Law Dome, East Antarctica.

    NASA Astrophysics Data System (ADS)

    Vance, T.; Roberts, J. L.; Plummer, C. T.; Kiem, A.; van Ommen, T. D.

    2014-12-01

    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 Decadal 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 variability and drought risk across and beyond the Pacific region on multi-decadal timescales, thus an understanding of long-term IPO/PDO variability 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 irrigation in Australia, was on the brink of ecosystem collapse. Clearly, decadal-scale droughts of the 'Big Dry' kind have occurred regularly in Australia's past. This new reconstruction will help with assessing drought risk over the longer term in the Pacific Basin, particularly in the data-sparse Southern Hemisphere.

  12. Variability of Primary Production and Surface Albedo along Desert-steppe Ecotone based on Satellite Observation

    NASA Astrophysics Data System (ADS)

    Jia, G.; Wang, H.; Zhou, Y.

    2009-12-01

    Vegetation in desert-steppe ecotone is sensitive to fluctuation of ecohydrological conditions and human disturbances such as increasing pressure of grazing by domestic herbivores. Temperatures are increasing, and higher associated rates of evaporation will likely bring drier conditions that lead sparser and less productive vegetation in those areas if summer rainfall doesn’t increase. Meanwhile, increasing variability of vegetation cover in ecotone region may have important feedback to local climate, even to summer monsoon system. Regional climate model projects that severer water shortage, intensifier land degradation, and more frequent dust storms will likely occur over monsoon Asia in coming decades, as consequences of climatic change and increasing human pressure. To examine how primary production and energy balance were changing along the transitional zone, we analyzed satellite data time series of annually accumulative normalized difference vegetation index and spectral reflectance from several sensors. We detected the decadal trends and extremes of primary production and surface albedo, and identified areas with the greatest variability along gradients of bioclimate regimes and grazing intensity in desert-steppe ecotone in northwestern China and southern Mongolia. Here we examined satellite time series derived and fused from two satellite sensors (AVHRR and MODIS) to investigate interannual changes of primary production over the region. We applied a meta analysis of field ANPP data collected from various locations to scale up the patterns with fractional analysis of fine resolution satellite data. Increased biological production was evident in large portion of the study region, but declining vegetation growth was also observed in some areas over lowlands and edge of sandy desert. There were strong interannual variability throughout the region, with the greatest fluctuations occurred along the ecotone between semi desert and desert steppe. There was generally low production and high albedo in 1980s, coincide with declined summer rainfall, strong fluctuations in 1990s, and a slight greening trend since 1999, which is likely contributed by the combination of relatively favorable water availability and recent grazing ban policy that closed 20% of rangeland and put another 30% in rotation. There is a clear evidence of grassland recovery in enclosed rangeland, however, vegetation degradation around lowland areas and oasis due to dropping water table and increasing human pressure is also detected.

  13. Variability of Attention Processes in ADHD: Observations from the Classroom

    ERIC Educational Resources Information Center

    Rapport, Mark D.; Kofler, Michael J.; Alderson, R. Matt; Timko, Thomas M., Jr.; DuPaul, George J.

    2009-01-01

    Objective: Classroom- and laboratory-based efforts to study the attentional problems of children with ADHD are incongruent in elucidating attentional deficits; however, none have explored within- or between-minute variability in the classroom attentional processing in children with ADHD. Method: High and low attention groups of ADHD children…

  14. A Review of Direct Observation Research within the Past Decade in the Field of Emotional and Behavioral Disorders

    ERIC Educational Resources Information Center

    Adamson, Reesha M.; Wachsmuth, Sean T.

    2014-01-01

    This study reviewed prominent journals within the field of emotional and behavioral disorders to identify direct observation approaches, reported reliability statistics, and key features of direct observation. Selected journals were systematically reviewed for the past 10 years identifying and quantifying specific direct observation systems and…

  15. Malvinas Current variability as observed by satellite altimetry data

    NASA Astrophysics Data System (ADS)

    Saraceno, Martin; Artana, Camila; Bodichon, Renaud; Provost, Christine

    The Malvinas Current (MC) is the northernmost extension of the Antarctic Circumpolar Current that carries cold and nutrient-rich waters. The MC is thought to be a major source of nutrients to the SW South Atlantic. The interaction of the MC with the sloping bottom is presumably responsible for sustaining upwelling along the shelf-break. Numerical and analytical models indicate that the upwelling intensity and mean transport along the Patagonian continental shelf is modulated by the MC transport. Apart from its regional influence, the MC contributes to regulate the climate since it helps the exchange of heat and salt as is a crucial component of the Meridional Overturning Circulation. Satellite altimetry data in conjunction with in-situ data allowed monitoring the transport of the MC at 41ºS. A CNES founded program will repeat those measures and will measure at the same time currents over the continental shelf under a satellite altimetry track. First deployment of instruments will occur in November 2014. In this work we use satellite altimetry data to explore the relationship between the MC and continental shelf transports and the correspondence between the variability of the MC and the mesoscale activity in the SW South Atlantic. Results suggest that (i) the large decreases of the MC transport are associated to eddies that interact with the MC and (ii) the first mode associated to the variability of the transport over the Patagonian continental shelf is significantly correlated to the first mode of variability of the MC transport.

  16. Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations.

    PubMed

    Alvarez-Mozos, Jesús; Verhoest, Niko E C; Larrañaga, Arantzazu; Casalí, Javier; González-Audícana, María

    2009-01-01

    Radar-based surface soil moisture retrieval has been subject of intense research during the last decades. 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 observations 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 variability 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 variability and roughness temporal variations on the retrieval of soil moisture from radar observations. 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 observed roughness variability 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 variability 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. PMID:22389611

  17. Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations

    PubMed Central

    Álvarez-Mozos, Jesús; Verhoest, Niko E.C.; Larrañaga, Arantzazu; Casalí, Javier; González-Audícana, María

    2009-01-01

    Radar-based surface soil moisture retrieval has been subject of intense research during the last decades. 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 observations 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 variability 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 variability and roughness temporal variations on the retrieval of soil moisture from radar observations. 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 observed roughness variability 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 variability 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. PMID:22389611

  18. A study of temporal variability of clouds in exo-atmospheres using Earth observations as a proxy

    NASA Astrophysics Data System (ADS)

    Kopparla, Pushkar; Zhai, Albert; Zhai, Alice; Su, Hui; Jiang, Jonathan H.; Yung, Yuk Ling

    2015-11-01

    Clouds are strongly linked to the dynamics of the atmosphere, and have been observed to vary over multiple spatial scales and timescales on Earth and the planets: hourly, diurnal, seasonal, interannual and decadal. The study of such variations in exoplanetary atmospheres could only be made through lightly constrained general circulation models (GCMs). In most cases, the exoplanet itself is unresolved from its star and individual cloud patches and their variations cannot be observed. However, temporal and spatial variation of cloud fields can have significant implications for the interpreting the observed phase-curve of the lights from the star-exoplanet system, yet it remains almost wholly unconstrained. To address this issue, we model Earth as an exoplanet, to understand changes in observables due to temporal and spatial variations of clouds by leveraging the rich datasets available for Earth. In particular, the International Satellite Cloud Climatology Project (ISCCP) has compiled cloud observations on Earth in the past three decades, producing a high-resolution dataset. We perform radiative transfer calculations using cloud profiles sampled from this dataset to produce disc integrated brightness and polarization phase curves which map seasonal and interannual cloud variations. This exercise gives us the first (pseudo)-observation based constraints for temporal variability of clouds in exo-atmospheres.

  19. The influence of PMCs on water vapor and drivers behind PMC variability from SOFIE observations

    NASA Astrophysics Data System (ADS)

    Hervig, Mark E.; Siskind, David E.; Bailey, Scott M.; Russell, James M.

    2015-09-01

    Observations 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 observations. In the Southern Hemisphere PMC variability 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 observed 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 decade-1 and a water vapor increase of +0.66±0.34% decade-1 (both at 80-84 km). This cooling trend agrees with reports based on observations in the middle atmosphere at similar latitudes. The water vapor increase is lower than expected due to increasing methane, although this difference may be consistent with H2O loss due to photolysis at PMC altitudes.

  20. A Review of Global Terrestrial Evapotranspiration: Observation, Modeling, Climatology, and Climatic Variability

    NASA Astrophysics Data System (ADS)

    Wang, K.; Dickinson, R. E.

    2011-12-01

    This review provides a survey of the basic theories, observational methods, satellite retrieval algorithms and land surface models of terrestrial evapotranspiration, E (or ?E, latent heat flux), from a climatic variability perspective. We carefully examine the available observations, advancements in understanding the environmental and biological controls of ?E, and their applications to evaluate satellite algorithms and land surface models. The two basic theories to estimate ?E, Penman-Monteith equation and Monin-Obukhov similarity, are similar because the first is derived from the second under three assumptions that (1) surface energy is balanced, (2) the surface can be regard as a big leaf, and (3) atmospheric transfer coefficients for water and heat are equal. However, practical applications for these two theories differ substantially due to their sensitivity to errors of input data. There are six major methods that could provide continuous ?E observations: (1) eddy covariance, (2) Bowen ratio, (3) weighable lysimeters, (4) scintillometer, (5) surface water budget, and (6) atmosphere water budget. The first two of these methods are widely accepted and deployed to provide high quality ?E data. However, its measurements are of short duration and sparse spatial coverage, and therefore, cannot provide long-term regional or global estimates of ?E. Existing evaluations of satellite remote sensing algorithms and land surface models focus on diurnal and seasonal variation. The capability of satellite algorithms and land surface models in estimating inter-annual or decadal variation of regional ?E is still unknown. Furthermore, as a consequence of the lack of information on how to partition total E into soil evaporation, canopy evaporation and canopy transpiration, results from 10 widely accepted models give simulated ratios of global averaged vegetation transpiration to total E varying from 0.25 to 0.64 with an average of 0.42. This uncertainty therefore limits the capability of land surface models to provide the sensitivities of ?E to precipitation deficit and land cover change. The ?E from existing land surface models appears to be overly sensitive to precipitation deficits. A global average for E derived from surface water balance is about 1.3 mm per day (~38 Wm-2 for ?E). The inter-annual or decadal variations of regional ?E still have large uncertainties, whether derived from observations, satellites remote sensing or land surface models.

  1. Optimization of the transmission of observable expectation values and observable statistics in continuous-variable teleportation

    SciTech Connect

    Albano Farias, L.; Stephany, J.

    2010-12-15

    We analyze the statistics of observables in continuous-variable (CV) quantum teleportation in the formalism of the characteristic function. We derive expressions for average values of output-state observables, 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 observable 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.

  2. Kepler Observations of Rapid Optical Variability in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.; Edelson, R.; Baumgartner, W. H.; Gandhi, P.

    2012-01-01

    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 variability models but seem consistent with first order MRI theoretical calculations of accretion disk fluctuations.

  3. Observations of the sun, an ultraviolet variable star

    NASA Technical Reports Server (NTRS)

    Heath, D. F.

    1972-01-01

    The uncertainty as to whether or not the sun is a variable 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.

  4. Final Progress Report: Collaborative Research: Decadal-to-Centennial Climate & Climate Change Studies with Enhanced Variable and Uniform Resolution GCMs Using Advanced Numerical Techniques

    SciTech Connect

    Fox-Rabinovitz, M; Cote, J

    2009-06-05

    The joint U.S-Canadian project has been devoted to: (a) decadal climate studies using developed state-of-the-art GCMs (General Circulation Models) with enhanced variable 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 variable-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.

  5. An Evaluation of CMIP5 Precipitation Variability for China Relative to Observations and CMIP3

    NASA Astrophysics Data System (ADS)

    Frauenfeld, O. W.; Chen, L.

    2013-12-01

    Precipitation represents an important link between the atmosphere, hydrosphere, and biosphere and is thus a key component of the climate system. As indicated by the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), global surface air temperatures increased by 0.74°C during the 20th century, with further warming of 0.2°C/decade projected by the 2030s. Projected changes in precipitation, however, are much more variable, and exhibit more complex temporal and spatial patterns. This presentation focuses on precipitation variability based on 20 general circulation models (GCMs) participating in the fifth coupled model intercomparison project (CMIP5). Specifically, we focus on China and provide a comprehensive evaluation of the CMIP5 models compared to historical 20th century precipitation variability from two observational precipitation products: the University of East Anglia's Climatic Research Unit (CRU) time series (TS) dataset version 3.10, and the Global Precipitation Climatology Centre (GPCC) version 6. We also reassess the performance of the third CMIP (CMIP3) to quantify potential improvements in CMIP5 over the previous generation of GCMs. Finally, we provide 21st century precipitation projections for China based on three representative concentration pathways (RCP): RCP 8.5, 4.5, and 2.6. These future precipitation projections are presented in light of the observed 20th century biases in the models. We find that CMIP5 models are able to better reproduce the general spatial pattern of observed 20th century precipitation than CMIP3. However, for China as a whole, the annual precipitation magnitude is overestimated in CMIP5, more so than in CMIP3. This smaller overestimation in CMIP3 was primarily driven by a large underestimation of summer precipitation. Spatially, overestimated precipitation magnitudes are evident for most regions of China, especially along the eastern margin of the Tibetan Plateau. Over southeastern China during summer, the precipitation amounts are underestimated. The multidecadal precipitation variability in CMIP5 is muted relative to observations, but improved when compared to CMIP3. We also assess precipitation trends and correlations relative to observations, and again find better agreement for CMIP5 than for CMIP3. Both observations and models indicated precipitation increases over parts of northwestern China, and decreases over the Tibetan Plateau throughout the 20th century. However, for the southeastern and northern regions of China there is poor agreement in precipitation trends. Precipitation is projected to increase across all of China under all the three emission scenarios during the 21st century. The largest significant trend is evident for RCP 8.5, which projects a precipitation increase of 1.5 mm/year, resulting in a 16% increase in precipitation by the end of the century. The smallest increases are projected to occur under the RCP 2.6 scenario, resulting in only a +6% change by 2100. The regions of greatest precipitation increases are the Tibetan Plateau and eastern China during summer, suggesting a potential change in the monsoonal circulation in the future.

  6. Patterns and Variability in Global Ocean Chlorophyll: Satellite Observations and Modeling

    NASA Technical Reports Server (NTRS)

    Gregg, Watson

    2004-01-01

    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 decadal 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 variables that can be expected to produce the changes observed 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.

  7. Component noise variables of a light observation helicopter

    NASA Technical Reports Server (NTRS)

    Robinson, F.

    1973-01-01

    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 variables either eliminated or kept as constant as possible.

  8. Observations of changes in the dissolved CO2 system in the North Sea, in four summers of the 2001-2011 decade

    NASA Astrophysics Data System (ADS)

    Clargo, Nicola; Salt, Lesley; Thomas, Helmuth; de Baar, Hein

    2015-04-01

    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 decade. 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 decade. We find significant interannual variability, but with a consistent, notable trend in decreasing pH. We found that surface alkalinity remained relatively constant over the decade, 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 decade, with implications for future CO2 uptake.

  9. Observer variability in assessing impaired consciousness and coma.

    PubMed Central

    Teasdale, G; Knill-Jones, R; van der Sande, J

    1978-01-01

    Head-injured patients were examined by a number of observers whose assessments were compared. Considerable discrepancies occurred when overall "levels" of consciousness and coma were used, and also with some terms which are in common use. More consistent assessments were obtained by employing the "Glasgow Coma Scale," which describes eye opening, verbal behaviour, and motor responsiveness. Nurses and general surgeons were as consistent as neurosurgeons when using this scale, and it was relatively resistant to language or cultural differences between observers. The practical reliability of the Glasgow scale enhances its value, both for monitoring individual cases and for making meaningful comparisons between series of patients with acute brain damage. PMID:690637

  10. Use of Machine Learning Techniques for Iidentification of Robust Teleconnections to East African Rainfall Variability in Observations and Models

    NASA Technical Reports Server (NTRS)

    Roberts, J. Brent; Robertson, Franklin R.; Funk, Chris

    2014-01-01

    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 variability are being used to examine the societal impacts of hydrometeorological variability 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 decadal variability (PDV), and anthropogenic forcing. This study applies machine learning methods (e.g. clustering, probabilistic graphical model, nonlinear PCA) to observational datasets in an attempt to expose the importance of local and remote forcing mechanisms of East African rainfall variability. The ability of the NASA Goddard Earth Observing System (GEOS5) coupled model to capture the associated relationships will be evaluated using Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations.

  11. Decadal- to biennial scale variability of planktic foraminifera in the northeastern Arabian Sea during the last two millennia: evidence for winter monsoon forcing mechanisms

    NASA Astrophysics Data System (ADS)

    Munz, Philipp; Lückge, Andreas; Siccha, Michael; Kucera, Michal; Schulz, Hartmut

    2015-04-01

    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 variability. 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 decadal- to biennial-scale resolution record of past winter monsoon variability 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 variability. 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 Oscillation, but is at the edge of the resolution of this record. A significant harmonic 46-year cycle, however, is coherent with the winter Pacific Decadal Oscillation (PDO) index, the leading mode of sea surface temperature (SST) anomalies in the North Pacific. Cold (warm) SST in the North Pacific are associated with higher (lower) abundances of G. falconensis. Wavelet coherency analysis revealed increasing coherence on higher frequency timescales since the 1960s, suggesting that global warming could lead to a stronger linkage between winter monsoon and PDO. References: Peeters, F., and Brummer, G.-J.A.: The seasonal and vertical distribution of living planktic foraminifera in the NW Arabian Sea. In: The Tectonic and Climatic Evolution of the Arabian Sea, Clift, P.D., et al. (Eds.), Geological Society Special Publication, 195, London, pp. 463--497, 2002. Schulz, H., von Rad, U., and Ittekkot, V.: Planktic foraminifera, particle flux and oceanic productivity off Pakistan, NE Arabian Sea: modern analogues and application to the palaeoclimatic record. In: The Tectonic and Climatic Evolution of the Arabian Sea, Clift, P.D., et al. (Eds.), Geological Society Special Publication, 195, London, pp. 499--516, 2002.

  12. Follow up observations of SDSS and CRTS candidate cataclysmic variables

    SciTech Connect

    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

    2014-10-01

    We present photometry and spectroscopy of 11 and 35 potential cataclysmic variables, 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.

  13. Analysis of the Evolution of the Chemical Composition of the Atmosphere over the Past Three Decades: Comparisons of Chemistry-Climate Model Simulations with In-situ and Remote Sensing Observations

    NASA Astrophysics Data System (ADS)

    Granier, C.; Doumbia, E. H. T.; Sindelarova, K.; Tilmes, S.; Hilboll, A.; Richter, A.; Colette, A.

    2014-12-01

    Global chemistry-climate models have been used to simulate the evolution of the atmospheric composition over the past decades. These simulations have been performed in free-running and specified dynamic modes, using the Community Atmosphere Model version 4 included in the the NCAR Community Earth System Model. We have analyzed the long-term changes as well as the interannual variability of several atmospheric compounds with a focus on ozone, carbon monoxide and nitrogen dioxide. We have investigated the behavior of these species by focusing on two regions, Europe and Asia. In Europe, surface emissions have decreased significantly since the 1980s, which have led to a decrease in the concentrations of several tropospheric compounds. On the contrary, emissions in Asia have dramatically increased, particularly during the past two decades, which has resulted in large increases in the atmospheric content of several species. We have used in-situ observations of O3, CO and NO2 from the Cooperative Air Sampling Network and from network of the European monitoring and evaluation programme (EMEP) to analyze the model results in different stations in the regions under consideration. We have also compared the model results with remote sensing observations from MOPITT, OMI, GOME, GOME-2 and SCIAMACHY instruments. Results show an underestimation of modeled CO concentrations, which has also been reported by previous studies. We will also analyse the simulated O3 and NO2 concentrations through comparisons with monitoring surface stations and satellite observations.

  14. Spatial Variability of Trace Gases During DISCOVER-AQ: Planning for Geostationary Observations of Atmospheric Composition

    NASA Technical Reports Server (NTRS)

    Follette-Cook, Melanie B.; Pickering, K.; Crawford, J.; Appel, W.; Diskin, G.; Fried, A.; Loughner, C.; Pfister, G.; Weinheimer, A.

    2015-01-01

    Results from an in-depth analysis of trace gas variability in MD indicated that the variability in this region was large enough to be observable by a TEMPO-like instrument. The variability observed in MD is relatively similar to the other three campaigns with a few exceptions: CO variability in CA was much higher than in the other regions; HCHO variability in CA and CO was much lower; MD showed the lowest variability in NO2All model simulations do a reasonable job simulating O3 variability. For CO, the CACO simulations largely under over estimate the variability in the observations. The variability in HCHO is underestimated for every campaign. NO2 variability is slightly overestimated in MD, more so in CO. The TX simulation underestimates the variability 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).

  15. New HST observations of Io's time-variable UV aurora: Probing Io's magma ocean and neutral and plasma environment

    NASA Astrophysics Data System (ADS)

    Roth, L.; Saur, J.; Retherford, K. D.; Strobel, D. F.; Feldman, P. D.; Bloecker, A.; Ivchenko, N.; Kullen, A.

    2014-12-01

    We report on new Space Telescope Imaging Spectrograph (STIS) observations of Io's oxygen and sulfur UV aurora obtained during two visits with the Hubble Space Telescope (HST) in December 2013 and January 2014. Io's aurora was monitored over a full variation cycle of the Jovian magnetic field to map the temporal behavior of the bright auroral spots. The aurora oscillates around the equator roughly in correlation with the time-variable orientation of the local magnetic field of Jupiter. Magnetic field perturbations near Io measured by the Galileo spacecraft were proposed to originate from induction in an electrically conductive global magma ocean. If magnetic induction modifies Io's local magnetic field environment, it will also alter the time-variable morphology of the aurora. We analyze the observed aurora variability and compare it to theoretically predicted spot morphologies for different magma ocean properties. Additionally, we compare the global O and S aurora morphology and brightness in the new observations to a large set of previous STIS images taken over a decade ago between 1997 and 2001 and investigate long-term changes of Io's neutral and plasma environment.

  16. Combined optical and X-ray observations of variable stars

    NASA Technical Reports Server (NTRS)

    Bowyer, C. S.

    1975-01-01

    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 observations 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.

  17. Observational constraints on a variable dark energy model

    SciTech Connect

    Movahed, M. Sadegh; Rahvar, Sohrab

    2006-04-15

    We study the effect of a phenomenological parameterized quintessence model on low, intermediate and high redshift observations. At low and intermediate redshifts, we use the Gold sample of supernova Type Ia (SNIa) data and recently observed size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), to put constraint on the parameters of the quintessence model. At the high redshift, the same fitting procedure is done using WAMP data, comparing the location of acoustic peak with that obtain from the dark energy model. As a complementary analysis in a flat universe, we combine the results from the SNIa, CMB and SDSS. The best fit values for the model parameters are {omega}{sub m}=0.27{sub -0.02}{sup +0.02} (the present matter content) and w{sub 0}=-1.45{sub -0.60}{sup +0.35} (dark energy equation of state). Finally we calculate the age of universe in this model and compare it with the age of old stars and high redshift objects.

  18. Interannual Variability of OLR as Observed by AIRS and CERES

    NASA Technical Reports Server (NTRS)

    Susskind, Joel; Molnar, Gyula I.; Iredell, Lena F.; Loeb, Norman G.

    2012-01-01

    The paper examines spatial anomaly time series of Outgoing Longwave Radiation (OLR) and Clear Sky OLR (OLR(sub CLR)) as determined using observations 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 observations 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.

  19. Demographic variables for wild Asian elephants using longitudinal observations.

    PubMed

    de Silva, Shermin; Webber, C Elizabeth; Weerathunga, U S; Pushpakumara, T V; Weerakoon, Devaka K; Wittemyer, George

    2013-01-01

    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 observed 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 observed 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

  20. Demographic Variables for Wild Asian Elephants Using Longitudinal Observations

    PubMed Central

    de Silva, Shermin; Webber, C. Elizabeth; Weerathunga, U. S.; Pushpakumara, T. V.; Weerakoon, Devaka K.; Wittemyer, George

    2013-01-01

    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 observed 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 observed 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

  1. Interannual Variability of OLR as Observed by AIRS and CERES

    NASA Technical Reports Server (NTRS)

    Susskind, Joel; Molnar, Gyula; Iredell, Lena; Loeb, Norman G.

    2012-01-01

    This paper compares spatial anomaly time series of OLR (Outgoing Longwave Radiation) and OLR(sub CLR) (Clear Sky OLR) as determined using observations 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 observations 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 observed 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 of cloud cover and mid-tropospheric water vapor are both highly negatively correlated with the El Nino Index. Agreement of the AIRS and CERES OLR(sub CLR) anomaly time series is less good, which may be a result of the large sampling differences in the ensemble of cases included in each OLR(sub CLR) data set.

  2. Towards the Prediction of Decadal to Centennial Climate Processes in the Coupled Earth System Model

    SciTech Connect

    Liu, Zhengyu; Kutzbach, J.; Jacob, R.; Prentice, C.

    2011-12-05

    In this proposal, we have made major advances in the understanding of decadal and long term climate variability. (a) We performed a systematic study of multidecadal climate variability in FOAM-LPJ and CCSM-T31, and are starting exploring decadal variability in the IPCC AR4 models. (b) We develop several novel methods for the assessment of climate feedbacks in the observation. (c) We also developed a new initialization scheme DAI (Dynamical Analogue Initialization) for ensemble decadal prediction. (d) We also studied climate-vegetation feedback in the observation and models. (e) Finally, we started a pilot program using Ensemble Kalman Filter in CGCM for decadal climate prediction.

  3. Assessing the vulnerability of economic sectors to climate variability to improve the usability of seasonal to decadal climate forecasts in Europe - a preliminary concept

    NASA Astrophysics Data System (ADS)

    Funk, Daniel

    2015-04-01

    Climate variability poses major challenges for decision-makers in climate-sensitive sectors. Seasonal to decadal (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 variability 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 potential physical response of the system of concern as well as the criticality of climate-related decision-making processes. Coping capacity - in an operational context coping capacity can only reduce vulnerability if it can be applied purposeful. With respect to climate vulnerabilities this refers to the availability of suitable, usable and skillful climate information. The focus for this concept is on existing S2D climate service products and their match with user needs. The outputs of the VA are climate-impact-decision-pathways which characterize critical climate conditions, estimate the role of climate in decision-making processes and evaluate the availability and potential usability of S2D climate forecast products. A classification scheme is developed for each component of the impact-pathway to assess its specific significance. The systemic character of these schemes enables a broad application of this VA across sectors where quantitative data is limited. This concept is developed and will be tested within the context of the EU-FP7 project "European Provision Of Regional Impacts Assessments on Seasonal and Decadal Timescales" EUPORIAS.

  4. Sub-Seasonal Variability of Tropical Rainfall Observed by TRMM and Ground-based Polarimetric Radar

    NASA Astrophysics Data System (ADS)

    Dolan, Brenda; Rutledge, Steven; Lang, Timothy; Cifelli, Robert; Nesbitt, Stephen

    2010-05-01

    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), variability is driven by prevailing low-level winds. During periods of low-level easterlies, deeper and more intense convection is observed, 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 variability 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 variability 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 variability 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 variability and comparison of TRMM PR statistics with ground-based radar has been extended to other regions of the globe. The Australian Bureau of Meteorology C-band polarimetric radar C-Pol has been collecting data in Darwin, Australia for over a decade. The Darwin region affords the opportunity to look at precipitation characteristics over land and ocean, as well as variability associated with monsoon and break periods over long periods of time. The polarimetric X-band radar XPort was stationed in West Africa at a field site in Benin during the 2006 and 2007 African monsoon periods, where differences in rainfall associated with African Easterly Wave (AEW) passages and non-AEW periods can be examined. Similar comparisons between TRMM PR and ground based polarimetric radars will also be reported for these regions.

  5. Seasonal variability in global sea level observed with Geosat altimetry

    NASA Technical Reports Server (NTRS)

    Zlotnicki, V.; Fu, L.-L.; Patzert, W.

    1989-01-01

    Time changes in global mesoscale sea level variances were observed 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.

  6. Observed Multi-Decade DD and DT Z-Pinch Fusion Rate Scaling in 5 Dense Plasma Focus Fusion Machines

    SciTech Connect

    Hagen, E. C.; Lowe, D. R.; O'Brien, R.; Meehan, B. T.

    2013-06-18

    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 observed 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.

  7. Source Parameter Inversion for Recent Great Earthquakes from a Decade-long Observation of Global Gravity Fields

    NASA Technical Reports Server (NTRS)

    Han, Shin-Chan; Riva, Ricccardo; Sauber, Jeanne; Okal, Emile

    2013-01-01

    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 observation 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.

  8. Spatial variability of the dose rate from (137)Cs fallout in settlements in Russia and Belarus more than two decades after the Chernobyl accident.

    PubMed

    Bernhardsson, C; Rääf, C L; Mattsson, S

    2015-11-01

    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 decades 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 observed 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

  9. TRMM Observations of Intraseasonal Variability in Convective Regimes Over the Amazon Walter A. Petersen1

    E-print Network

    Collett Jr., Jeffrey L.

    TRMM Observations of Intraseasonal Variability in Convective Regimes Over the Amazon By Walter A that regional variability in wet-season convective structure is most evident over the southern Amazon, Mato during easterly (westerly) regimes over the southern Amazon and Mato Grosso (Altiplano, and southern

  10. Sources of Variability in Gulf of Maine Circulation, and the Observations Needed to

    E-print Network

    Pringle, James "Jamie"

    Sources of Variability in Gulf of Maine Circulation, and the Observations Needed to Model it. James in the Gulf of Maine are then quantified, with an emphasis on variability on timescales longer than tidal and the volume of water entering from the Scotian Shelf to the Gulf of Maine produce roughly comparable amounts

  11. Decadal-scale variability of diffuse CO2 emissions and seismicity revealed from long-term monitoring (1995-2013) at Mammoth Mountain, California, USA

    NASA Astrophysics Data System (ADS)

    Werner, Cynthia; Bergfeld, Deborah; Farrar, Christopher D.; Doukas, Michael P.; Kelly, Peter J.; Kern, Christoph

    2014-12-01

    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 decadal-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 observed 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 decadal 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 significantly lower than long-term emissions from hydrothermal areas such as Solfatara in Campi Flegrei, Italy (16 Mt over 28 years).

  12. Temporal and Spatial Variability of Ross polynya using Multi-Satellite Observations

    NASA Astrophysics Data System (ADS)

    Park, J.; Jo, Y. H.

    2014-12-01

    Polynyas are particularly vulnerable to not only local environmental changes, but also global climate changes through air-sea-ice interactions. In order to understand the large scales of its interactions, a temporal and spatial variation of polynyas and, areas of open water in the middle of ice shelf, around the Antarctica were analyzed based on remote sensing measurements. Especially, the polynya in the Ross Sea (Ross polynya) was analyzed, which was the largest on among the all of them around the Antarctica for last decades. Accordingly, the main purpose of this presentation is to (1) evaluate a variability of Ross polynya spatial and temporal characteristics and (2) address relationship between spatial polynya variability and global warming effect. In order to conduct research the observations from the Advanced Microwave Scanning Radiometer-EOS (AMAR-E) were used. The products (SST, wind speed, cloud vapor, atmospheric water vapor and rain rate), including sea ice extent, are from June 2002 to October 2011. Additionally, Gravity Recovery and Climate Experiment (GRACE) data sets were used to estimate mass changes in adjacent ice sheet affected by local atmospheric condition. Based on the nine year's data, research results suggest that Ross polynya normally started to appear around the end of December and persist for about 77.5 days. The extent of Ross polynya in 2011 is the largest and had a tendency to increase year after year. SST in adjacent sea has slightly decreased for the same period (as 0.054?C yr-1) due to the melting ice and variation of wind, water vapor and rain rate are 0.054 m s-1 yr-1, -0.027 mm yr-1 and 0.001 mm hr-1 yr-1, respectively. Increase land mass in the west-southern Antarctica could be the result of accumulating snow which is made of vapor induced by extended polynya. In addition, we would conduct to evaluate a correlation with characteristics of other global and local components corresponding climate change and understand that how the climate change effect have implications for Ross polynya and glacial or environmental condition in the vicinity.

  13. Comment on 'All quantum observables in a hidden-variable model must commute simultaneously'

    SciTech Connect

    Nagata, Koji

    2006-06-15

    Malley discussed [Phys. Rev. A 69, 022118 (2004)] that all quantum observables in a hidden-variable model for quantum events must commute simultaneously. In this comment, we discuss that Malley's theorem is indeed valid for the hidden-variable theoretical assumptions, which were introduced by Kochen and Specker. However, we give an example that the local hidden-variable (LHV) model for quantum events preserves noncommutativity of quantum observables. It turns out that Malley's theorem is not related to the LHV model for quantum events, in general.

  14. Comment on ``All quantum observables in a hidden-variable model must commute simultaneously"

    E-print Network

    Koji Nagata

    2008-11-13

    Malley discussed {[Phys. Rev. A {\\bf 69}, 022118 (2004)]} that all quantum observables in a hidden-variable model for quantum events must commute simultaneously. In this comment, we discuss that Malley's theorem is indeed valid for the hidden-variable theoretical assumptions, which were introduced by Kochen and Specker. However, we give an example that the local hidden-variable (LHV) model for quantum events preserves noncommutativity of quantum observables. It turns out that Malley's theorem is not related with the LHV model for quantum events, in general.

  15. Interannual variability in the atmosphere-biosphere CO2 exchange as simulated by a process-based model for the last decades

    NASA Astrophysics Data System (ADS)

    Ito, A.

    2001-05-01

    Atmosphere-biosphere CO2 exchange induces not only seasonal oscillation but also interannual change in the atmospheric CO2 concentration. Actually, in 1998, atmospheric CO2 concentration increased at a remarkably high rate, while the growth rate was apparently depressed in 1992 and 1993. Elucidating whether these anomalies were attributable to the ocean or the terrestrial biosphere is an important challenge for carbon cycle researchers. In this study, a process-based model of terrestrial carbon dynamics (Sim-CYCLE) was constructed and used to simulate the terrestrial carbon balance for the period from 1953 to 1999. Climatic variables related to ecosystem processes were derived from the U.S NCEP/NCAR-reanalysis data (T62 spatial resolution), and the Matthews's biome map was adopted. The atmospheric CO2 fertilization effect during the experimental period was also considered in the simulation analysis. Sim-CYCLE includes five carbon compartments (leaves, stems, roots, litter, and humus), and calculates fluxes among them at a monthly step, with taking environmental regulations into account. Accordingly, I could obtain a time-series of net carbon budget, i.e. net ecosystem production (NEP), on the global scale. Through the experimental period, global annual NEP exhibited a considerable interannual variability ranging from +2.0 Pg C in 1971 to ?2.5 Pg C in 1998 (SD 1.1 Pg C yr-1). Tropical ecosystems were most responsible for the interannual variability, especially in such ENSO years as 1973, 1983, and 1998. The estimated NEP anomalies were negatively correlated with surface temperature anomaly, due to the high sensitivity of respiration and decomposition to temperature. Thus, it is inferred that higher temperatures induced by the strong 1997-98 ENSO event would lead to extra CO2 emission and consequently the largest negative NEP anomaly. The estimated responsiveness of terrestrial carbon budget seems enough large to cause anomalies in atmospheric CO2 concentration. However, it should be examined (1) whether the estimated NEP anomalies are consistent with atmospheric observations and oceanic budget, and (2) whether the responsiveness seen in the interannual change is applicable to the future global change.

  16. Observations of Jupiter at 5 micron from IRTF/TEXES : latitudinal variability of disequilibrium species

    NASA Astrophysics Data System (ADS)

    Drossart, P.; Encrenaz, T.; Greathouse, T. K.; DeWitt, C.; Fouchet, T.; Janssen, M.; Gulkis, S.; Orton, G. S.; Fletcher, L.; Giles, R.; Atreya, S. K.; Boudon, V.

    2015-10-01

    Observations of Jupiter in the 5 ?m spectral window,obtained in March/April 2015 at IRTF are presented, in preparation of the arrival of the NASA/JUNO mission in 2016. Sounding of the troposphere of Jupiter below 2 bars is obtained from the observations, to search for the variability of disequilibrium species, related to deep atmospheric circulation.

  17. ROSAT all-sky survey observations of X-ray variability in cool giant stars

    NASA Technical Reports Server (NTRS)

    Haisch, Bernhard; Schmitt, J. H. M. M.

    1994-01-01

    We have identified 24 active late-type giant stars, including 11 RS CVn systems, with soft X-ray count rates high enough to allow the detection of statistically significant variability on a Roentgen Satellite (ROSAT) orbital timescale (96 minutes) as observed by the Position Sensitive Proportional Counter (PSPC) during the all-sky survey. Our sensitivity typically lies in the range of 10% - 25%, depending on the source count rate. Comparison is made to the daily, nonflare solar soft X-ray variability as observed by the Solrad satellites during solar minimum in 1969 and solar maximum in 1975. Seven of the 24 stars show significant variability; in two of these cases (HR 3922 and HR 8448) major flares were observed in which the peak count rate is enhanced by at least a factor of 3 above quiescent. While HR 3922 (G5 III) is not (yet) classified as an RS CVn star, its flare is more energetic (3 x 10(exp 31) ergs/s) than previously observed RS CVn flares. The apparently single giant HR 8167 (G8 III) also shows two flares. While one might expect to find an anticorrelation between saturated coronae and variability, we find no evidence of this: the two stars in our sample with the highest ratio of f(sub x)/f(sub v) both show variability. We also point out that Capella (G6 III + F9 III) is one of the stars manifesting variability.

  18. Constraining land carbon cycle process understanding with observations of atmospheric CO2 variability

    NASA Astrophysics Data System (ADS)

    Collatz, G. J.; Kawa, S. R.; Liu, Y.; Zeng, F.; Ivanoff, A.

    2013-12-01

    We evaluate our understanding of the land biospheric carbon cycle by benchmarking a model and its variants to atmospheric CO2 observations and to an atmospheric CO2 inversion. Though the seasonal cycle in CO2 observations is well simulated by the model (RMSE/standard deviation of observations <0.5 at most sites north of 15N and <1 for Southern Hemisphere sites) different model setups suggest that the CO2 seasonal cycle provides some constraint on gross photosynthesis, respiration, and fire fluxes revealed in the amplitude and phase at northern latitude sites. CarbonTracker inversions (CT) and model show similar phasing of the seasonal fluxes but agreement in the amplitude varies by region. We also evaluate interannual variability (IAV) in the measured atmospheric CO2 which, in contrast to the seasonal cycle, is not well represented by the model. We estimate the contributions of biospheric and fire fluxes, and atmospheric transport variability to explaining observed variability in measured CO2. Comparisons with CT show that modeled IAV has some correspondence to the inversion results >40N though fluxes match poorly at regional to continental scales. Regional and global fire emissions are strongly correlated with variability observed at northern flask sample sites and in the global atmospheric CO2 growth rate though in the latter case fire emissions anomalies are not large enough to account fully for the observed variability. We discuss remaining unexplained variability in CO2 observations in terms of the representation of fluxes by the model. This work also demonstrates the limitations of the current network of CO2 observations and the potential of new denser surface measurements and space based column measurements for constraining carbon cycle processes in models.

  19. Modulation of the Pacific Decadal Oscillation on the summer precipitation over East China: a comparison of observations to 600-years control run of Bergen Climate Model

    NASA Astrophysics Data System (ADS)

    Yu, Lei; Furevik, Tore; Otterå, Odd Helge; Gao, Yongqi

    2015-01-01

    Observations show that the summer precipitation over East China often goes through decadal variations of opposite sign over North China and the Yangtze River valley (YRV), such as the "southern flood and northern drought" pattern that occurred during the late 1970s-1990s. In this study it is shown that a modulation of the Pacific Decadal Oscillation (PDO) on the summer precipitation pattern over East China during the last century is partly responsible for this characteristic precipitation pattern. During positive PDO phases, the warm winter sea surface temperatures (SSTs) in the eastern subtropical Pacific along the western coast of North American propagate to the tropics in the following summer due to weakened oceanic meridional circulation and the existence of a coupled wind-evaporation-SST feedback mechanism, resulting in a warming in the eastern tropical Pacific Ocean (5°N-20°N, 160°W-120°W) in summer. This in turn causes a zonal anomalous circulation over the subtropical-tropical Pacific Ocean that induces a strengthened western Pacific subtropical high (WPSH) and thus more moisture over the YRV region. The end result of these events is that the summer precipitation is increased over the YRV region while it is decreased over North China. The suggested mechanism is found both in the observations and in a 600-years fully coupled pre-industrial multi-century control simulations with Bergen Climate Model. The intensification of the WPSH due to the warming in the eastern tropical Pacific Ocean was also examined in idealized SSTA-forced AGCM experiments.

  20. Broad Absorption Line Variability in Repeat Quasar Observations from the Sloan Digital Sky Survey

    E-print Network

    Lundgren, B F; Brunner, R J; Hall, P B; Schneider, D P; York, D G; Vanden Berk, D E; Brinkmann, J; Lundgren, Britt F.; Wilhite, Brian C.; Brunner, Robert J.; Hall, Patrick B.; Schneider, Donald P.; York, Donald G.; Berk, Daniel E. Vanden; Brinkmann, Jonathan

    2006-01-01

    We present a time-variability analysis of 29 broad absorption line quasars (BALQSOs) observed in two epochs by the Sloan Digital Sky Survey (SDSS). These spectra are selected from a larger sample of BALQSOs with multiple observations by virtue of exhibiting a broad CIV $\\lambda$1549 absorption trough separated from the rest frame of the associated emission peak by more than 3600 km s$^{-1}$. Detached troughs facilitate higher precision variability measurements, since the measurement of the absorption in these objects is not complicated by variation in the emission line flux. We have undertaken a statistical analysis of these detached-trough BALQSO spectra to explore the relationships between BAL features that are seen to vary and the dynamics of emission from the quasar central engine. We have measured variability within our sample, which includes three strongly variable BALs. We have also verified that the statistical behavior of the overall sample agrees with current model predictions and previous studies o...

  1. X-ray and optical variability of Seyfert 1 galaxies as observed with XMM-Newton

    E-print Network

    R. Smith; S. Vaughan

    2007-01-08

    We have examined simultaneous X-ray and optical light curves of a sample of eight nearby Seyfert 1 galaxies observed using the EPIC X-ray cameras and Optical Monitor on board XMM. The observations span ~1 day and revealed optical variability in four of the eight objects studied. In all cases, the X-ray variability amplitude exceeded that of the optical both in fractional and absolute luminosity terms. No clearly significant correlations were detected between wavebands using cross correlation analysis. We conclude that, in three of the four objects in which optical variability was detected, reprocessing mechanisms between wavebands do not dominate either the optical or X-ray variability on the time-scales probed.

  2. The regional MiKlip decadal forecast ensemble for Europe

    NASA Astrophysics Data System (ADS)

    Mieruch, S.; Feldmann, H.; Schädler, G.; Lenz, C.-J.; Kothe, S.; Kottmeier, C.

    2013-11-01

    Funded by the German Ministry for Education and Research (BMBF) a major research project called MiKlip (Mittelfristige Klimaprognose, Decadal Climate Prediction) was launched and global as well as regional predictive ensemble hindcasts have been generated. The aim of the project is to demonstrate for past climate change whether predictive models have the capability of predicting climate on time scales of decades. This includes the development of a decadal forecast system, on the one hand to support decision making for economy, politics and society for decadal time spans. On the other hand, the scientific aspect is to explore the feasibility and prospects of global and regional forecasts on decadal time scales. The focus of this paper lies on the description of the regional hindcast ensemble for Europe generated by COSMO-CLM and on the assessment of the decadal variability and predictability against observations. To measure decadal variability we remove the long term bias as well as the long term linear trend from the data. Further, we applied low pass filters to the original data to separate the decadal climate signal from high frequency noise. The decadal variability and predictability assessment is applied to temperature and precipitation data for the summer and winter half-year averages/sums. The best results have been found for the prediction of decadal temperature anomalies, i.e. we have detected a distinct predictive skill and reasonable reliability. Hence it is possible to predict regional temperature variability on decadal timescales, However, the situation is less satisfactory for precipitation. Here we have found regions showing good predictability, but also regions without any predictive skill.

  3. Upper Ocean Heat Variability and its Impact on H i I t it d St t D d l PHurricane Intensity and Structure: Decadal Progress

    E-print Network

    Kuligowski, Bob

    Enough? ( ) 2 6 0 O H C 2 6 , D pc T z d z= - #12;Hurricane Opal: A Tipping Point?p pp g (Marks, Shay and Structure: Decadal Progress Objective: To quantify the ocean's role on hurricane intensity and structure h f perspectives aimed at improving hurricane landfall forecasts. Lynn K. "Nick" ShayLynn K. Nick Shay Sponsors

  4. Broad Absorption Line Variability in Repeat Quasar Observations from the Sloan Digital Sky Survey

    E-print Network

    Britt F. Lundgren; Brian C. Wilhite; Robert J. Brunner; Patrick B. Hall; Donald P. Schneider; Donald G. York; Daniel E. Vanden Berk; Jonathan Brinkmann

    2007-02-01

    We present a time-variability analysis of 29 broad absorption line quasars (BALQSOs) observed in two epochs by the Sloan Digital Sky Survey (SDSS). These spectra are selected from a larger sample of BALQSOs with multiple observations by virtue of exhibiting a broad CIV $\\lambda$1549 absorption trough separated from the rest frame of the associated emission peak by more than 3600 km s$^{-1}$. Detached troughs facilitate higher precision variability measurements, since the measurement of the absorption in these objects is not complicated by variation in the emission line flux. We have undertaken a statistical analysis of these detached-trough BALQSO spectra to explore the relationships between BAL features that are seen to vary and the dynamics of emission from the quasar central engine. We have measured variability within our sample, which includes three strongly variable BALs. We have also verified that the statistical behavior of the overall sample agrees with current model predictions and previous studies of BAL variability. Specifically, we observe that the strongest BAL variability occurs among the smallest equivalent width features and at velocities exceeding 12,000 km s$^{-1}$, as predicted by recent disk-wind modeling.

  5. An Experimental Study of Small-Scale Variability of Radar Reflectivity Using Disdrometer Observations.

    NASA Astrophysics Data System (ADS)

    Miriovsky, Benjamin J.; Bradley, A. Allen; Eichinger, William E.; Krajewski, Witold F.; Kruger, Anton; Nelson, Brian R.; Creutin, Jean-Dominique; Lapetite, Jean-Marc; Lee, Gyu Won; Zawadzki, Isztar; Ogden, Fred L.

    2004-01-01

    Analysis of data collected by four disdrometers deployed in a 1-km2 area is presented with the intent of quantifying the spatial variability of radar reflectivity at small spatial scales. Spatial variability of radar reflectivity within the radar beam is a key source of error in radar-rainfall estimation because of the assumption that drops are uniformly distributed within the radar-sensing volume. Common experience tells one that, in fact, drops are not uniformly distributed, and, although some work has been done to examine the small-scale spatial variability of rain rates, little experimental work has been done to explore the variability of radar reflectivity. The four disdrometers used for this study include a two-dimensional video disdrometer, an X-band radar-based disdrometer, an impact-type disdrometer, and an optical spectropluviometer. Although instrumental differences were expected, the magnitude of these differences clouds the natural variability of interest. An algorithm is applied to mitigate these instrumental effects, and the variability remains high, even as the observations are integrated in time. Although one cannot explicitly quantify the spatial variability from this experiment, the results clearly show that the spatial variability of reflectivity is very large.

  6. Cassini UVIS Observations of the Io Plasma Torus. 3; Observations of Temporal and Azimuthal Variability

    NASA Technical Reports Server (NTRS)

    Steffl, A. J.; Delamere, P. A.; Bagenal, F.

    2006-01-01

    In this third paper in a series presenting observations 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 observed 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 observations. 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, observations of variations in the properties of the Io plasma torus with the System III and System IV coordinate systems.

  7. Cassini UVIS Observations of the Io Plasma Torus. III. Observations of Temporal and Azimuthal Variability

    E-print Network

    A. J. Steffl; P. A. Delamere; F. Bagenal

    2005-08-01

    In this third paper in a series presenting observations 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 function of azimuthal position. The azimuthal variation in composition is such that the mixing ratio of S II is 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 observed to have a period of 10.07 hours--1.5% longer than the System III rotation period of Jupiter, yet 1.3% shorter than the System IV period defined by Brown (1995). 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 5-25% during the UVIS observations. 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 ratio (minimum S IV mixing ratio) is aligned with a System III longitude of ~200 +/- 15 degrees, the amplitude is a factor of ~4 greater than when the variation is anti-aligned. This behavior can explain numerous, often apparently contradictory, observations of variations in the properties of the Io plasma torus with the System III and System IV coordinate systems.

  8. The Variable Optical Polarization and Fermi Observations of PMN J0948+0022

    NASA Astrophysics Data System (ADS)

    Eggen, Joseph R.; Miller, H. Richard; Maune, Jeremy D.

    2013-08-01

    We report on observations of the ?-ray and optical photopolarimetric behavior of the radio-loud, narrow-line type-1 Seyfert galaxy PMN J0948+0022 over a 27 month period. As this object has recently been suggested to represent a prototype of an emerging class of blazar-like objects, the observed properties are compared to those of blazars. We extract doubling timescales of roughly 4 hr for the optical and ?-ray bands. The rapid microvariability in the optical/near-IR, significant and variable optical polarization, and strong yet rapidly variable ?-ray emission we observe for PMN J0948+0022 are all classical observational characteristics associated with blazars. However, since these observations do not show a clear correlation between the ?-ray and optical behavior, they do not offer conclusive proof that the emissive behavior of PMN J0948+0022 is due to a relativistic jet oriented close to our line of sight.

  9. High Speed Optical Observations of Cataclysmic Variables: FL Ceti, BY Cam, and DQ Her

    NASA Astrophysics Data System (ADS)

    Mason, Paul A.; Gomez, S.; Robinson, E. L.; Andronov, I. L.; Gonzalez, R. I.

    2013-01-01

    We present photometric data on three cataclysmic variables. Broad-band CCD observations 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 variables 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 observations.

  10. Seasonal to Decadal Variations of Water Vapor in the Tropical Lower Stratosphere Observed with Balloon-Borne Cryogenic Frost Point Hygrometers

    NASA Technical Reports Server (NTRS)

    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.

    2010-01-01

    We investigated water vapor variations in the tropical lower stratosphere on seasonal, quasi-biennial oscillation (QBO), and decadal 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 observed 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 decadal 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.

  11. Essays on Applied Economics and Econometrics: Decadal Climate Variability Impacts on Cropping and Sugar-sweetened Beverage Demand of Low-income 

    E-print Network

    Jithitikulchai, Theepakorn

    2014-12-10

    This dissertation examines the economic impacts of ocean-related climate variability on U.S. crops and the effect sweetened beverage taxes would have on beverage consumption among low income food assistance program ...

  12. Sea Surface Salinity Variability from Simulations and Observations: Preparing for Aquarius

    NASA Technical Reports Server (NTRS)

    Jacob, S. Daniel; LeVine, David M.

    2010-01-01

    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 observed variable, relaxing to SST reduces the range of SSS variability 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 variability. The simulated variability scales are compared to those from near-surface argo salinity measurements.

  13. Intrinsic Variability of Beta Lyrae Observed with a Digital SLR Camera

    NASA Astrophysics Data System (ADS)

    Collins, Donald F.; Prasai, Anesh

    2009-05-01

    We show that a digital SLR (DSLR) camera (Canon XTi) follows a linear response to light exposure when images are saved in raw format. We also demonstrate its usefulness for photometry of bright variable stars such as Beta Lyrae (4.2m - 3.2m) and other bright variable stars. Mounted on stationary tripod, fitted with a standard zoom lens set at 55 mm FL at f/5.6, this camera obtains reasonably precise photometry (± 0.02m ) for bright stars. Imaging bright stars with a telescope and CCD imaging detector is hampered by rapid saturation and the lack of suitable bright comparison stars in the field of view. Subtracting the average brightness for Beta Lyrae, we can easily detect the intrinsic variability of Beta Lyrae (15%) with a period about 280 days. More such observations are requested to learn more about the period and phase of the intrinsic variability of Beta Lyrae.

  14. An Observational and Computational Variable Tagging System for Climate Change Informatics

    NASA Astrophysics Data System (ADS)

    Pouchard, L. C.; Lenhardt, W.; Branstetter, M. L.; Runciman, A.; Wang, D.; Kao, S.; King, A. W.; Climate Change Informatics Team

    2010-12-01

    As climate change science uses diverse data from observations 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 observations and model results are required. The data processing tasks associated with the simultaneous use of observation 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 variables and observational 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 Observational and Computational Variable Tagging System aims to address these challenges through facilitating the quick identification of datasets of interest across archives by associating variables with tags or keywords from a controlled vocabulary. The prototype currently offers the ability to search by tags, variable 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 variables 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 variable names and descriptions of observational and computational data from a single Web interface. Our system provides an easy-to-use cross-referencing tool to help overcome an important barrier to inter-disciplinary research in climate change science. As proof-of-concept, the tagging system targets a use case based on comparison of model results against observational data to validate trends for river stream flows in the forthcoming CCSM4. Existing climate models have no ability to account for damming and other man-made stream flow obstructions. However, observational data report on dammed rivers: there is no account of how an un-managed river would fare. One solution to this problem is to use both observational data and historical portions of model data to find regions where observed stream flow and model results are highly correlated. Based on these regions, an anticipated outcome is model refinement. Another potential outcome is the discovery of un-managed rivers that may be good candidates for correctly predicting stream flow under climate change conditions.

  15. My interest in droughts dates back to the late 1990s to Mathew Barlow's doctoral research. The related papers were among the first to observationally document the influence of Pacific decadal SST

    E-print Network

    Nigam, Sumant

    , 2001: ENSO, Pacific decadal variability and U.S. summertime precipitation, drought, and streamflow. JMy interest in droughts dates back to the late 1990s ­ to Mathew Barlow's doctoral research American droughts. Subsequent work with colleague, Alfredo Ruiz-Barradas, showed that atmospheric

  16. Hubble Space Telescope Observations of Ganymede's Time-Variable Auroral Ovals

    NASA Astrophysics Data System (ADS)

    Wennmacher, A.; Saur, J.; Duling, S.; Roth, L.; Musacchio, F. M.; Feldman, P. D.; Strobel, D. F.; Retherford, K. D.; McGrath, M. A.

    2012-12-01

    We present results of Hubble Space Telescope (HST) observations of Ganymede's auroral ovals obtained during two visits when Ganymede was located at eastern elongation. The observations were obtained on November 19, 2010 and October 1, 2011 and cover five consecutive orbits each. They were designed such that the Jovian magnetic latitudes of Ganymede span the entire possible range, i.e. Ganymede is exposed to the maximum variability of Jupiter's magnetospheric field during each visit. Our analysis shows that the auroral ovals only weakly rock in concert with the time-variable Jovian magnetic field. This weak rocking of the ovals is consistent with shielding of the time-variable field due to electromagnetic induction in a saline subsurface ocean on Ganymede.

  17. Recent advances in satellite observations of solar variability and global atmospheric ozone

    NASA Technical Reports Server (NTRS)

    Heath, D. F.

    1974-01-01

    A description is given of the temporal behavior of the sun as an ultraviolet variable star in relation to daily zonal means of atmospheric ozone from the total amount to that above the 10-mb and 4-mb pressure levels. A significant correlation has been observed between enhancements in the ultraviolet solar irradiances and terrestrial passages of the solar magnetic field sector boundary structure. However, it has not yet been possible to separate solar from the dynamical effects on the variability in the zonal means of ozone. Attention is given to global changes in ozone which have been derived from the satellite observations in terms of season, solar variability, and major stratospheric disturbances such as stratospheric warmings.

  18. Variable stars observed with the AST3-1 telescope from dome A of antarctica

    E-print Network

    Li, Gang; Liu, Xuanming

    2015-01-01

    Dome A in the Antarctic plateau is likely one of the best astronomical observing sites on Earth. The first one of three Antarctic Survey Telescope (AST3-1), a 50/68 cm Schmidt-like equatorial-mount telescope, is the first trackable telescope of China operating in Antarctica and the biggest telescope located in Antarctic inland. AST3-1 obtained huge amounts of data in 2012 and we processed the time-series parts. Here we present light curves of 29 variable stars identified from ten-day observations in 2012 with AST3-1, including 22 newly discovered variable stars. 23 of them are eclipsing binaries and the others are pulsating stars. We present the properties of the 29 variable stars, including the classifications, periods and magnitude ranges in i band. For the 17 eclipsing binaries, the phased light curves are presented with the orbital period values well determined.

  19. PRECISE HIGH-CADENCE TIME SERIES OBSERVATIONS OF FIVE VARIABLE YOUNG STARS IN AURIGA WITH MOST

    SciTech Connect

    Cody, Ann Marie; Tayar, Jamie; Hillenbrand, Lynne A.; Matthews, Jaymie M.; Kallinger, Thomas

    2013-03-15

    To explore young star variability 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. Observations 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 variability 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 observed variability. 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 variability patterns not anticipated by prior studies, and we propose that this behavior originates with the circumstellar disks. The MOST observations 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 observations.

  20. Observed interannual variability of the Atlantic meridional overturning circulation at 26.5

    E-print Network

    until mid-2010, the MOC slowed below its mean value. The annual mean from 1 April 2009 to 31 March 2010Observed interannual variability of the Atlantic meridional overturning circulation at 26.5 N G. Mc. A mooring array, nominally at 26 N between the Bahamas and the Canary Islands, deployed in Apr 2004 provides

  1. Estimating Latent Variable Interactions with Nonnormal Observed Data: A Comparison of Four Approaches

    ERIC Educational Resources Information Center

    Cham, Heining; West, Stephen G.; Ma, Yue; Aiken, Leona S.

    2012-01-01

    A Monte Carlo simulation was conducted to investigate the robustness of 4 latent variable interaction modeling approaches (Constrained Product Indicator [CPI], Generalized Appended Product Indicator [GAPI], Unconstrained Product Indicator [UPI], and Latent Moderated Structural Equations [LMS]) under high degrees of nonnormality of the observed

  2. A review of observed variability in the dayside ionosphere of Mars Paul Withers

    E-print Network

    Mendillo, Michael

    Review A review of observed variability in the dayside ionosphere of Mars Paul Withers Center dayside ionosphere available for study. Together with earlier measurements from the Viking era ionosphere and to discover new ionospheric features. The dayside ion- osphere includes the main peak, called

  3. Near-infrared observations of Nova Sco 2015 and the luminous red variable in M31

    NASA Astrophysics Data System (ADS)

    Srivastava, M.; Ashok, N. M.; Banerjee, D. P. K.; Venkataraman, V.

    2015-03-01

    Near infrared observations are reported of Nova Sco 2015 (PNV J17032620-3504140) and the luminous red variable in M31 (Nova M31N 2015-01a = MASTER J004207.99+405501.1 ) using the Mount Abu 1.2m telescope and the 1024x1024 HgCdTe NIR camera/spectrograph (NICS).

  4. Sensitivity analysis of SCHADEX extreme flood estimations to observed hydrometeorological variability

    NASA Astrophysics Data System (ADS)

    Brigode, Pierre; Bernardara, Pietro; Paquet, Emmanuel; Gailhard, Joël.; Garavaglia, Federico; Merz, Ralf; Mi?ovi?, Zoran; Lawrence, Deborah; Ribstein, Pierre

    2014-01-01

    Stochastic flood simulation methods are typically based on a rainfall probabilistic model (used for simulating continuous rainfall series or for estimating probabilities of random rainfall events) and on a rainfall-runoff model. Usually, both of these models are calibrated over observed hydrometeorological series, which may be subject to significant variability and/or nonstationarity over time. The general aim of this study is thus to propose and test a methodology for performing a sensitivity analysis of extreme flood estimations to observed hydrometeorological variability. The methodology consists of performing a set of block-bootstrap experiments: for each experiment, the data used for calibration of a particular model (e.g., the rainfall probabilistic model) is bootstrapped while the model structure and the calibration process are held constant. The SCHADEX extreme flood estimation method has been applied over six catchments located in different regions of the world. The results show first that the variability of observed rainfall hazard has the most significant impact on the extreme flood estimates. Then, consideration of different rainfall-runoff calibration periods generates a significant spread of extreme flood estimated values. Finally, the variability of the catchment saturation hazard has a nonsignificant impact on the extreme flood estimates. An important point raised by this study is the dominating role played by outliers within the observed records for extreme flood estimation.

  5. Variability in Observed and Sensor Based Estimated Optimum N Rates in Corn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent research showed that active sensors such as Crop Circle can be used to estimate in-season N requirements for corn. The objective of this research was to identify sources of variability in the observed and Crop Circle-estimated optimum N rates. Field experiments were conducted at two locations...

  6. HF radar observations of small-scale surface current variability in the Straits of Florida

    E-print Network

    Miami, University of

    HF radar observations of small-scale surface current variability in the Straits of Florida A. B-frequency Wellen radar (WERA), transmitting at 16.045 MHz, was deployed along the eastern Florida Shelf current measurements within the radar footprint along the shelf break at 86-m depth. The shallowest ADCP

  7. Observed variability of chlorophyll-a using Argo profiling floats in the southeastern Arabian Sea

    E-print Network

    Riser, Stephen C.

    Observed variability of chlorophyll-a using Argo profiling floats in the southeastern Arabian Sea M 2012 Keywords: Chlorophyll-a Oxygen minimum zone Subsurface chlorophyll maxima Wind speed Southeastern Arabian Sea Air­sea interaction a b s t r a c t The time series of temperature, salinity, chlorophyll

  8. FUSE Observations of Stellar Wind Variability in {Sk -67°166}

    NASA Astrophysics Data System (ADS)

    Fullerton, A. W.; Massa, D. L.; Howarth, I. D.; Owocki, S. P.; Prinja, R. K.; Willis, A. J.

    2000-12-01

    We present results from an 18-day campaign to monitor stellar wind variability 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 variability is evident in the resonance lines of {S 6} and {O 6}. The variations are qualitatively similar to those observed in the {Si 4} wind lines of the Galactic supergiant ? Puppis [O4 I(n)f] during a 16-day monitoring campaign with IUE. However, the FUSE observations contain more diagnostic information about the nature of the structures responsible for the observed variability. 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 variability of {O 6} traces the distribution of very hot gas. This work is based on observations 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.

  9. Multi-decadal river flow variations in France

    NASA Astrophysics Data System (ADS)

    Boé, J.; Habets, F.

    2014-02-01

    In this article, multi-decadal variations in the French hydroclimate are investigated, with a specific focus on river flows. Based on long observed series, it is shown that river flows in France generally exhibit large multi-decadal variations in the instrumental period (defined in this study as the period from 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. 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, 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. Potential multi-decadal variations in river flows in other seasons, and in particular summer, are also noted. As they are not associated with significant surface climate anomalies (i.e. temperature, precipitation) in summer, other mechanisms are investigated based on hydrological simulations. The impact of climate variations in spring on summer soil moisture, and the impact of soil moisture in summer on the runoff-to-precipitation ratio, could potentially play a role in multi-decadal summer river flow variations. The large amplitude of the multi-decadal variations in French river flows suggests that internal variability may play a very important role in the evolution of river flows during the next decades, potentially temporarily limiting, reversing or seriously aggravating the long-term impacts of anthropogenic climate change.

  10. Understanding the Long-Term Spectral Variability of Cygnus X-1 from BATSE and ASM Observations

    NASA Technical Reports Server (NTRS)

    Zdziarski, Andrzej A.; Poutanen, Juri; Paciesas, William S.; Wen, Linqing; Six, N. Frank (Technical Monitor)

    2002-01-01

    We present a spectral analysis of observations 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 variability can be explained by softening the overall spectrum with a pivot at approximately 50 keV. The observations show that there has to be another, independent variability pattern of lower amplitude where the spectral shape does not change when the luminosity changes. In the soft state, the variability is mostly caused by a variable hard (Comptonized) spectral component of a constant shape superimposed on a constant soft blackbody component. These variability patterns are in agreement with the dependence of the rms variability on the photon energy in the two states. We interpret the observed correlations in terms of theoretical Comptonization models. In the hard state, the variability 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 variability is consistent with flares of hybrid, thermal/nonthermal, plasma with variable power above a stable cold disk. Also, based on broadband pointed observations simultaneous with those of the ASM and BATSE, we find the intrinsic bolometric luminosity increases by a factor of approximately 3-4 from the hard state to the soft one, which supports models of the state transition based on a change of the accretion rate.

  11. Quantifying Spatial and Seasonal Variability in Atmospheric Ammonia with In Situ and Space-Based Observations

    NASA Technical Reports Server (NTRS)

    Pinder, Robert W.; Walker, John T.; Bash, Jesse O.; Cady-Pereira, Karen E.; Henze, Daven K.; Luo, Mingzhao; Osterman, Gregory B.; Shepard, Mark W.

    2011-01-01

    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 observations, but they have not been compared to in situ measurements. We have conducted a field campaign combining co-located surface measurements and satellite special observations 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 variability 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 observed by TES is representative of the surface measurement. We find that the TES NH3 RVMR qualitatively captures the seasonal and spatial variability 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 observation. Furthermore, we find that TES H3 RVMR captures the month-to-month variability present in the surface observations. 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.

  12. X-ray observations of selected cataclysmic variable stars using the Einstein Observatory

    NASA Technical Reports Server (NTRS)

    Cordova, F. A.; Mason, K. O.; Nelson, J. E.

    1981-01-01

    X-ray observations of 12 cataclysmic variable stars using the Einstein Observatory are reported. Nine of these stars, representing all subclasses of cataclysmic variables, 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 observed from the dwarf novae SS Cyg and U Gem during optical outburst. The X-ray and optical fluxes of the objects observed 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.

  13. Can natural variability explain observed Antarctic sea ice trends? New modeling evidence from CMIP5

    NASA Astrophysics Data System (ADS)

    Polvani, Lorenzo M.; Smith, Karen L.

    2013-06-01

    The recent observed positive trends in total Antarctic sea ice %extent are at odds with the expectation of melting sea ice in a %warming world. More problematic yet, climate models indicate that sea %ice should decrease around Antarctica in response to both increasing %greenhouse gases and stratospheric ozone depletion. The resolution of %this puzzle, we suggest, may lie in the large natural variability of %the coupled atmosphere-ocean-sea-ice system. Contrasting forced and control integrations from four state-of-the-art Coupled Model Intercomparison Project Phase 5 (CMIP5) models, we show that the observed Antarctic sea ice trend falls well within the distribution of trends arising naturally in the system, and that the forced response in the models is small compared to the natural variability. From this, we conclude that it may prove difficult to attribute the observed trends in total Antarctic sea ice to anthropogenic forcings, although some regional features might be easier to explain.

  14. New Variable Stars Discovered by the APACHE Survey. II. Results After the Second Observing Season

    NASA Astrophysics Data System (ADS)

    Damasso, M.; Gioannini, L.; Bernagozzi, A.; Bertolini, E.; Calcidese, P.; Carbognani, A.; Cenadelli, D.; Christille, J.-M.; Giacobbe, P.; Lanteri, L.; Lattanzi, M. G.; Smart, R.; Sozzetti, A.

    2015-06-01

    Routinely operating since July 2012, the APACHE survey has celebrated its second birthday. While the main goal of the project is the detection of transiting planets around a large sample of bright, nearby M dwarfs in the northern hemisphere, the APACHE large photometric database, consisting of hundreds of different fields, represents a relevant resource to search for and provide a first characterization of new variable stars. We celebrate here the conclusion of the second year of observations by reporting the discovery of 14 new variables.

  15. Decadal variability in the abundance of Pacific saury and its response to climatic/oceanic regime shifts in the northwestern subtropical Pacific during the last half century

    NASA Astrophysics Data System (ADS)

    Tian, Yongjun; Ueno, Yasuhiro; Suda, Maki; Akamine, Taturo

    2004-12-01

    Pacific saury ( Cololabis saira) is one of the most important, small-sized, pelagic fishes in the North Pacific. Using correlation analysis and principal component analysis (PCA), we examined the relationships between climatic/oceanographic indices (Asian monsoon index (MOI), Southern Oscillation Index (SOI), North Pacific Index (NPI), Arctic Oscillation Index (AOI), Pacific Decadal Oscillation (PDO) index, air temperature, wind velocity, sea surface temperature (SST), and surface current velocity (SCV) in the Kuroshio axis), and abundance/biological indices of Pacific saury (adult catch, catch per unit effort, i.e., CPUE, condition factor, and body length and larval density) in order to detect the response of Pacific saury abundance to the recent climatic/oceanic regime shifts (1976/1977, 1987/1988, and 1997/1998). Our oceanographic analyses show that notable regime shifts occurred in 1987/1988 and possibly 1997/1998 in the Kuroshio region, while the same kind of regime shift was not readily apparent there in 1976/1977. Results of our oceanographic/biological analyses show that the decadal-scale variation pattern in Pacific saury abundance responded well to the regime shifts of 1987/1988 and 1997/1998. These results indicate that only the regime shifts which occurred in the Kuroshio region can affect Pacific saury abundance. Our results also showed that the abundance and biological indices of saury significantly correlated with both the SSTs in the northwestern Kuroshio waters and the SCV in the Kuroshio axis in winter. These correlations suggest that winter oceanographic conditions in the Kuroshio region strongly affect the early survival process and determine the recruitment success of Pacific saury. The abundance of other major small pelagic species also changed greatly around 1989, suggesting that the regime shift in the late 1980s occurred in the pelagic ecosystem basin. We concluded that Pacific saury could be used as a bio-indicator of regime shifts in the northwestern subtropical Pacific.

  16. Observations of Ganymede's variable auroral ovals on leading side derived from HST/STIS

    NASA Astrophysics Data System (ADS)

    Musacchio, F. M.; Saur, J.; Roth, L.; Feldman, P. D.; Strobel, D. F.; Retherford, K. D.; McGrath, M. A.

    2014-12-01

    We investigate properties of Ganymede's FUV auroral ovals using spectral images acquired during two visits in 2010 and 2011 with Hubble's Space Telescope Imaging Spectrograph (HST/STIS campaign 12244) when Ganymede was at eastern elongation. We analyze the variability of the structure and brightness of the auroral ovals as a function of magnetic latitude. The investigation of the aurora is a diagnostic tool of the various processes, which contribute to Ganymede's complex magnetic field environment. The variability which we find consists of both, spatial inhomogeneities on the moon disk and temporal variation as a function of Ganymede's position within the current sheet of Jupiter's magnetosphere. The comparison of our results with those from previous HST/STIS observations reveals an additional temporal variability as the brightness properties vary for different elongations in different periods.

  17. A new method for observing the running states of a single-variable nonlinear system.

    PubMed

    Meng, Yu; Chen, Hong; Chen, Cheng

    2015-03-01

    In order to timely grasp a single variable nonlinear system running states, a new method called Scatter Point method is put forward in this paper. It can be used to observe or monitor the running states of a single variable nonlinear system in real-time. In this paper, the definition of the method is given at first, and then its working principle is expounded theoretically, after this, some physical experiments based on Chua's nonlinear system are conducted. At the same time, many scatter point graphs are measured by a general analog oscilloscope. The motion, number, and distribution of these scatter points shown on the oscilloscope screen can directly reflect the current states of the tested system. The experimental results further confirm that the method is effective and practical, in which the system running states are not easily lost. In addition, this method is not only suitable for single variable systems but also for multivariable systems. PMID:25833428

  18. Coherent interannual and decadal variations inthe atmosphere-ocean system

    NASA Technical Reports Server (NTRS)

    Dickey, J. O.; Marcus, S. L.; DeViron, O.

    2003-01-01

    We investigate the source of poleward propagating atmospheric zonal wind anomalies, originating at the equator and penetrating to high latitudes in both hemispheres in conjunction with ENSO [Dickey et al.,1992], and report the discovery of similar variability on decadal and longer timescales. Since atmospheric dissipation times are generally on the order of a month or less, we examine the ocean as a 'memory' source for these globally coherent anomalies. This hypothesis is substantiated by the observation of complementaryoscillation in the sea surface temperature (SST) field; further, we detect a robust decadal variability (1012 yrs)in both the SST and contemporaneous atmospheric angular momentum (AAM) series. Analyzing GISST SST data beginning in 1902, we confirm this decadal mode and find signatures of longer (multidecadal) SST variability centered in the equatorial and North Pacific.

  19. Observed tropical and extratropical modes of variability in moisture fields from climate satellite dataset

    NASA Astrophysics Data System (ADS)

    Malmusi, S.; Boccolari, M.

    2010-09-01

    Global and high resolution climate dataset taken from satellite images represents one of the most interesting sources for the monitoring and the investigation of present climate and, for short time periods (decadal), an alternative to NWP reanalysis datasets. The Satellite Application Facility on Climate Monitoring (CM-SAF) archive represents a complete global dataset since January 2004 of several daily and monthly averaged atmospheric variables such as radiative flows at surface and TOA, clouds parameters, precipitable water, surface albedo and so on. In this study CM-SAF daily data of layered precipitable water and relative humidity for a period of six years, all over the globe (with the exception of polar regions), have been analyzed. Applying teleconnectivity maps both in horizontal and in vertical, and multivariate statistics methods (EOF) to moisture fields, the appearance of principal modes of general circulation variability patterns over the tropical band (Indian peninsula, southern Africa, Australia and West Pacific Ocean) seems to have been revealed. Moreover, comparisons of precipitable water fields with surface albedo and clouds data, yet collected from CM-SAF archive, have been evaluated.

  20. High Angular Resolution Observations of Episodic Dust Emission from Long Period Variable Stars Twenty Years of Observations with the Berkeley Infrared Spatial Interferometer

    NASA Technical Reports Server (NTRS)

    Danchi, William

    2010-01-01

    Over the past twenty years the U. C. Berkeley Infrared Spatial Interferometer has observed a number of Long Period Variable stars in the mid-infrared, obtaining information on the spatial distribution of dust around these stars with resolutions of the order of a few tens of milliarcseconds. The ISI is a heterodyne interferometer operating mostly at 11.15 microns, initially with two telescopes. In the last decade, it has been taking data regularly with three telescopes, thus obtaining visibility data on three baselines and also a closure phase. Over the course of the years, the ISI has been able to measure the physical properties of the dust shells surrounding these stars, in particular the inner radii of the dust shells, as well as the temperature and density distribution. For some stars, the ISI has also made precision measurements of their diameters in the mid-infrared. Closure phase measurements have revealed asymmetries in the dust distributions around many stars. Most surprisingly the ISI data has shown evidence for substantial changes in the amount of dust on time scales of 5-10 years, rather than being directly correlated with the stellar pulsation periods, which are of the order of one year. We discuss past results and new results from the ISI that highlight the dynamic environment around these stars.

  1. Examining Soil Moisture Variability and Field Mean Estimation Methods using Nested Observations

    NASA Astrophysics Data System (ADS)

    Peterson, A.; Helgason, W.; Ireson, A. M.

    2014-12-01

    Information about soil moisture is typically required at the field scale. Direct measurements of soil moisture at this scale are not possible, though there are a number of promising indirect methods (e.g. remote sensing methods and cosmic-ray neutrons). Methods for obtaining point scale measurements of soil moisture are well established. However, variability of soil moisture, in both space and time, makes accurately determining field scale soil moisture from point measurements difficult. Understanding sub-field scale variability is a key step in determining how to upscale point measurements, and in particular to identify the minimum number of point measurements necessary to represent field scale mean soil moisture. Objectives of this study are to: (1) examine the spatial variability of soil moisture with time, and (2) compare field scale soil moisture estimation methods. Nested soil moisture measurements provided observations covering a 5002m2 area within a semi-arid prairie pasture site in southern Saskatchewan, Canada. Complementary measurements of the water balance were measured using meteorological and flux instrumentation. Spatial variability of surface and root zone soil moisture were examined using data from gridded dielectric water content probe surveys and a neutron probe array. Field scale surface soil moisture was measured at the site using a cosmic-ray neutron probe. The field scale estimation methods compared are: (1) water balance, (2) upscaling by averaging point scale measurements, (3) upscaling by identification of average representative time stable sites, and (4) extrapolation of shallow soil moisture measured by cosmic-ray neutron probe. Variability of surface soil moisture was found to be smallest under extreme dry and wet conditions, and largest during intermediate moisture conditions. Large spatial variability was found in the root zone, with soil moisture being most temporally variable closer to the surface.

  2. Variability and Predictability of Land-Atmosphere Interactions: Observational and Modeling Studies

    NASA Technical Reports Server (NTRS)

    Roads, John; Oglesby, Robert; Marshall, Susan; Robertson, Franklin R.

    2002-01-01

    The overall goal of this project is to increase our understanding of seasonal to interannual variability and predictability of atmosphere-land interactions. The project objectives are to: 1. Document the low frequency variability in land surface features and associated water and energy cycles from general circulation models (GCMs), observations and reanalysis products. 2. Determine what relatively wet and dry years have in common on a region-by-region basis and then examine the physical mechanisms that may account for a significant portion of the variability. 3. Develop GCM experiments to examine the hypothesis that better knowledge of the land surface enhances long range predictability. This investigation is aimed at evaluating and predicting seasonal to interannual variability for selected regions emphasizing the role of land-atmosphere interactions. Of particular interest are the relationships between large, regional and local scales and how they interact to account for seasonal and interannual variability, including extreme events such as droughts and floods. North and South America, including the Global Energy and Water Cycle Experiment Continental International Project (GEWEX GCIP), MacKenzie, and LBA basins, are currently being emphasized. We plan to ultimately generalize and synthesize to other land regions across the globe, especially those pertinent to other GEWEX projects.

  3. Interannual variability and climatic noise in satellite-observed outgoing longwave radiation

    NASA Astrophysics Data System (ADS)

    Short, D. A.; Cahalan, R. F.

    1983-03-01

    Upwelling-IR observations of the North Pacific by polar orbiters NOAA 3, 4, 5, and 6 and TIROS-N from 1974 to 1981 are analyzed statistically in terms of interannual variability (IAV) in monthly averages and climatic noise due to short-term weather fluctuations. It is found that although the daily variance in the observations is the same in summer and winter months, and although IAV in winter is smaller than that in summer, the climatic noise in winter is so much smaller that a greater fraction of winter anomalies are statistically significant. The smaller winter climatic noise level is shown to be due to shorter autocorrelation times. It is demonstrated that increasing averaging area does not reduce the climatic noise level, suggesting that continuing collection of high-resolution satellite IR data on a global basis is necessary if better models of short-term variability are to be constructed.

  4. The variable hard X-ray emission of NGC 4945 as observed by NuSTAR

    SciTech Connect

    Puccetti, Simonetta; Comastri, Andrea; Fiore, Fabrizio; Arévalo, Patricia; Bauer, Franz E.; Risaliti, Guido; Brandt, William N.; Luo, Bin; Stern, Daniel; Harrison, Fiona A.; Alexander, David M.; Gandhi, Poshak; Lansbury, George B.; Boggs, Steve E.; Craig, William W.; Christensen, Finn E.; Hailey, Charles J.; Koss, Michael J.; Madejski, Greg M.; Matt, Giorgio; and others

    2014-09-20

    We present a broadband (?0.5-79 keV) spectral and temporal analysis of multiple NuSTAR observations combined with archival Suzaku and Chandra data of NGC 4945, the brightest extragalactic source at 100 keV. We observe hard X-ray (>10 keV) flux and spectral variability, with flux variations of a factor of two on timescales of 20 ks. A variable primary continuum dominates the high-energy spectrum (>10 keV) in all states, while the reflected/scattered flux that dominates at E <10 keV stays approximately constant. From modeling the complex reflection/transmission spectrum, we derive a Compton depth along the line of sight of ?{sub Thomson} ? 2.9, and a global covering factor for the circumnuclear gas of ?0.15. This agrees with the constraints derived from the high-energy variability, which implies that most of the high-energy flux is transmitted rather than Compton-scattered. This demonstrates the effectiveness of spectral analysis at constraining the geometric properties of the circumnuclear gas, and validates similar methods used for analyzing the spectra of other bright, Compton-thick active galactic nuclei (AGNs). The lower limits on the e-folding energy are between 200 and 300 keV, consistent with previous BeppoSAX, Suzaku, and Swift Burst Alert Telescope observations. The accretion rate, estimated from the X-ray luminosity and assuming a bolometric correction typical of type 2 AGN, is in the range ?0.1-0.3 ?{sub Edd} depending on the flux state. The substantial observed X-ray luminosity variability of NGC 4945 implies that large errors can arise from using single-epoch X-ray data to derive L/L {sub Edd} values for obscured AGNs.

  5. Structure and variability of the Martian upper atmosphere: Ultraviolet dayglow observations by MAVEN/IUVS

    NASA Astrophysics Data System (ADS)

    Deighan, Justin; Jain, Sonal K.; Lo, Daniel Y.; Stewart, A. Ian F.; Schneider, Nicholas M.; Stiepen, Arnaud; Evans, J. Scott; Stevens, Michael H.; Yelle, Roger V.; England, Scott L.; Chaffin, Michael Scott; Crismani, Matteo; McClintock, William E.; Clarke, John T.; Holsclaw, Greg M.; Lefevre, Franck; Montmessin, Franck; Thiemann, Edward M. B.; Eparvier, Frank; Jakosky, Bruce M.

    2015-11-01

    Mars has been studied extensively at ultraviolet wavelengths starting from Mariner 6 and 7, Mariner 9, and more recently by SPICAM aboard Mars Express. The results from these measurements reveal a large variability in the composition and structure of the Martian upper atmosphere. However, due to the lack of simultaneous measurements of energy input (such as solar electromagnetic and particle flux), and limitations in the observation geometry and data itself, this variability is still not fully understood.We report a comprehensive study of Mars dayglow observations by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite, focusing on vertical and global upper atmospheric structure and seasonal variability. The dayglow emission spectra show features similar to previous UV measurements at Mars. IUVS has detected a second, low-altitude peak in the emission profile of OI 297.2 nm, confirming the prediction that the absorption of solar Lyman alpha emission is an important energy source there. We find a significant drop in thermospheric scale height and temperature between Ls = 218° and Ls = 337 - 352°, attributed primarily to the decrease in solar activity and increase in heliocentric distance. The CO2+ UVD peak intensity is well correlated with simultaneous observations of solar 17 - 22 nm irradiance at Mars by Extreme Ultraviolet Monitor (EUVM) aboard MAVEN. Variations of the derived CO2 density also exhibit significant persistent global structure with longitudinal wavenumbers 1, 2 and 3 in a fixed local solar time frame, pointing to non-migrating atmospheric tides driven by diurnal solar heating. We will present and discuss the variability in Martian UV dayglow, its dependence on solar EUV flux, and the importance of IUVS observations in our current understanding of Mars’ thermosphere.

  6. The Variable Hard X-Ray Emission of NGC4945 as Observed by NuSTAR

    NASA Technical Reports Server (NTRS)

    Puccetti, Simonetta; Comastri, Andrea; Fiore, Fabrizio; Arevalo, Patricia; Risaliti, Guido; Bauer, Franz E.; Brandt, William N.; Stern, Daniel; Harrison, Fiona A.; Alexander, David M.; Boggs, Steve E.; Christensen, Finn E.; Craig, William W.; Gandhi, Poshak; Hailey, Charles J.; Koss, Michael R.; Lansbury, George B.; Luo, Bin; Madejski, Greg M.; Matt, Giorgio; Walton, Dominic J.; Zhang, Will

    2014-01-01

    We present a broadband (approx. 0.5 - 79 keV) spectral and temporal analysis of multiple NuSTAR observations combined with archival Suzaku and Chandra data of NGC4945, the brightest extragalactic source at 100 keV. We observe hard X-ray (> 10 keV) flux and spectral variability, with flux variations of a factor 2 on timescales of 20 ksec. A variable primary continuum dominates the high energy spectrum (> 10 keV) in all the states, while the reflected/scattered flux which dominates at E< 10 keV stays approximately constant. From modelling the complex reflection/transmission spectrum we derive a Compton depth along the line of sight of Thomson approx.2.9, and a global covering factor for the circumnuclear gas of approx. 0.15. This agrees with the constraints derived from the high energy variability, which implies that most of the high energy flux is transmitted, rather that Compton-scattered. This demonstrates the effectiveness of spectral analysis in constraining the geometric properties of the circumnuclear gas, and validates similar methods used for analyzing the spectra of other bright, Compton-thick AGN. The lower limits on the e-folding energy are between 200 - 300 keV, consistent with previous BeppoSAX, Suzaku and Swift BAT observations. The accretion rate, estimated from the X-ray luminosity and assuming a bolometric correction typical of type 2 AGN, is in the range approx. 0.1 - 0.3 lambda(sub Edd) depending on the flux state. The substantial observed X-ray luminosity variability of NGC4945 implies that large errors can arise from using single-epoch X-ray data to derive L/L(sub Edd) values for obscured AGNs.

  7. Determination of the Hubble constant from observations of Cepheid variables in the galaxy M96

    E-print Network

    N. R. Tanvir; T. Shanks; H. C. Ferguson; D. R. T. Robinson

    1995-10-01

    New Hubble Space Telescope observations of Cepheid variable stars in the nearby galaxy M96 give a distance to the host galaxy group, Leo-I, of 11.6+/-0.8 Mpc. This value, used in conjunction with several reliable secondary indicators of relative distance, constrains the distances to more remote galaxy clusters, and yields a value of the Hubble constant (Ho=69+/-8 km/s/Mpc) that is independent of the velocity of the Leo-I group itself.

  8. Spectral signatures of Earth's climate variability as observed from space and diagnosed from reanalyses

    NASA Astrophysics Data System (ADS)

    Brindley, Helen; Bantges, Richard; Russell, Jacqueline; Murray, Jonathan; Harries, John

    2015-04-01

    Measurements of the Earth's spectrally resolved outgoing longwave radiation have the intrinsic information content and link to the overall energy budget that implies that they are ideal candidates to monitor the climate and detect and attribute change. Theoretical studies have shown how distinct longwave spectral signals from different climate forcing and feedback mechanisms may be derived and appear to combine with a high degree of linearity. However, an open, important question which has not yet been fully addressed concerns the exact level of short-term variability seen in observed longwave spectra. We investigate this here by exploiting the emerging radiance record available from the Infrared Atmospheric Sounding Interferometer (IASI) on the Metop-A satellite. We use five years of IASI data to assess the level of interannual variability seen in all-sky spectra at different spatial scales. Maximum variability is seen at the smallest scales investigated (10° zonal means) at northern and southern high latitudes across the centre of the 15 ?m CO2 band. As spatial scale increases, the overall magnitude of interannual variability reduces across the spectrum and the spectral shape of the variability changes. We show that the interannual variability manifested across the IASI spectra is less than 0.17 K in brightness temperature in the all-sky global annual mean, collapsing to a value of less than 0.05 K in the atmospheric window, a spectral region whose variability is dominated by fluctuations in surface and cloud properties. Spectrally integrating the IASI measurements to create pseudo broadband and window channels indicates a variation about the mean that is higher for the broadband than the window channel at the global and quasi-global scale and over the Southern Hemisphere. These findings are in agreement with observations from CERES Terra over the same period and imply that at the largest spatial scales, over the period considered here, fluctuations in mid-upper tropospheric temperatures and water vapour, and not cloud or surface temperature, play the dominant role in determining the level of interannual variability in all-sky outgoing longwave radiation. This pattern of behavior is not seen in spectra simulated using reanalysis fields that have been sub-sampled to match the Metop-A satellite track. Possible reasons for this discrepancy will be discussed in this paper.

  9. Summertime tropospheric ozone variability over the Mediterranean basin observed with IASI

    NASA Astrophysics Data System (ADS)

    Doche, Clément; Dufour, Gaëlle; Foret, Gilles; Eremenko, Maxim; Cuesta, Juan; Beekmann, Matthias

    2014-05-01

    The Mediterranean basin is one of the most sensitive regions of the world to climate change and air quality issues. The particular dynamical situation of the Mediterranean basin leads to ozone amounts in the lower troposphere of the largest ones in the Northern Hemisphere. Six years of summertime tropospheric ozone observed from IASI from 2007 to 2012 have been analyzed to document the variability of ozone over this region. In the lower troposphere a large West-East gradient is observed with an enhancement of ozone in the Eastern part of the basin. This gradient is explained by (i) the diabatic convection over the Persian Gulf during the Indian Monsoon, which induces an important subsidence of ozone rich air masses from the upper to the lower troposphere over the central Mediterranean basin; (ii) the Etesian winds which set up during summer between the Azores anticyclone to the West and the thalweg of Indian Monsoon to the East, leading to a horizontal advection of potentially ozone rich air masses from the European industrial areas. Concerning the temporal variability of ozone over the basin, the IASI observation analysis shows a summertime maximum in July in the lower troposphere. The high correlation with the 300 hPa potential vorticity indicates that the temporal variability of lower tropospheric ozone is mainly driven by vertical exchanges between the upper and the lower troposphere. Two case studies (June 2008 and June 2009) showing ozone anomalies (positive and negative) will also be presented and related to two particular meteorological situations.

  10. Identification of RR Lyrae Variables in SDSS from Single-Epoch Photometric and Spectroscopic Observations

    E-print Network

    Wilhelm, Ronald; Beers, Timothy C; Sesar, Branimir; Prieto, Carlos Alende; Carrell, Kenneth W; Lee, Young Sun; Yanny, Brian; Rockosi, Constance M; De Lee, Nathan; Armstrong, Gwen Hansford; Torrence, Stephen J

    2007-01-01

    We describe a new RR Lyrae identification technique based on out-of-phase single-epoch photometric and spectroscopic observations contained in SDSS Data Release 6 (DR-6). This technique detects variability by exploiting the large disparity between the g-r color and the strength of the hydrogen Balmer lines when the two observations are made at random phases. Comparison with a large sample of known variables in the SDSS equatorial stripe (Stripe 82) shows that the discovery efficiency for our technique is ~85%. Analysis of stars with multiple spectroscopic observations suggests a similar efficiency throughout the entire DR-6 sample. We also develop a technique to estimate the average g apparent magnitude (over the pulsation cycle) for individual RR Lyrae stars, using the for the entire sample and measured colors for each star. The resulting distances are found to have precisions of ~14%. Finally, we explore the properties of our DR-6 sample of N = 1087 variables, and recover portions of the Sagittarius Northe...

  11. Identification of RR Lyrae Variables in SDSS from Single-Epoch Photometric and Spectroscopic Observations

    E-print Network

    Ronald Wilhelm; W. Lee Powell Jr.; Timothy C. Beers; Branimir Sesar; Carlos Alende Prieto; Kenneth W. Carrell; Young Sun Lee; Brian Yanny; Constance M. Rockosi; Nathan De Lee; Gwen Hansford Armstrong; Stephen J. Torrence

    2007-12-05

    We describe a new RR Lyrae identification technique based on out-of-phase single-epoch photometric and spectroscopic observations contained in SDSS Data Release 6 (DR-6). This technique detects variability by exploiting the large disparity between the g-r color and the strength of the hydrogen Balmer lines when the two observations are made at random phases. Comparison with a large sample of known variables in the SDSS equatorial stripe (Stripe 82) shows that the discovery efficiency for our technique is ~85%. Analysis of stars with multiple spectroscopic observations suggests a similar efficiency throughout the entire DR-6 sample. We also develop a technique to estimate the average g apparent magnitude (over the pulsation cycle) for individual RR Lyrae stars, using the for the entire sample and measured colors for each star. The resulting distances are found to have precisions of ~14%. Finally, we explore the properties of our DR-6 sample of N = 1087 variables, and recover portions of the Sagittarius Northern and Southern Stream. Analysis of the distance and velocity for the Southern Stream are consistent with previously published data for blue horizontal-branch stars. In a sample near the North Galactic Polar Cap, we find evidence for the descending leading Northern arm, and a possible detection of the trailing arm.

  12. A comparison of cloud and boundary layer variables in the ECMWF forecast model with observations at Surface Heat

    E-print Network

    Jakob, Christian

    radar reflectivity estimated from the ECMWF model variables was compared with 8 mm wavelength radarA comparison of cloud and boundary layer variables in the ECMWF forecast model with observations. L Andreas,5 J. M. Intrieri,6 and T. A. Uttal6 Abstract. Cloud and boundary layer variables from

  13. Murchison Widefield Array Observations of Anomalous Variability: A Serendipitous Night-time Detection of Interplanetary Scintillation

    NASA Astrophysics Data System (ADS)

    Kaplan, D. L.; Tingay, S. J.; Manoharan, P. K.; Macquart, J. P.; Hancock, P.; Morgan, J.; Mitchell, D. A.; Ekers, R. D.; Wayth, R. B.; Trott, C.; Murphy, T.; Oberoi, D.; Cairns, I. H.; Feng, L.; Kudryavtseva, N.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Deshpande, A. A.; Gaensler, B. M.; Greenhill, L. J.; Hurley Walker, N.; Hazelton, B. J.; Johnston Hollitt, M.; Lonsdale, C. J.; McWhirter, S. R.; Morales, M. F.; Morgan, E.; Ord, S. M.; Prabu, T.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Webster, R. L.; Williams, A.; Williams, C. L.

    2015-08-01

    We present observations of high-amplitude rapid (2 s) variability toward two bright, compact extragalactic radio sources out of several hundred of the brightest radio sources in one of the 30° × 30° Murchison Widefield Array (MWA) Epoch of Reionization fields using the MWA at 155 MHz. After rejecting intrinsic, instrumental, and ionospheric origins we consider the most likely explanation for this variability to be interplanetary scintillation (IPS), likely the result of a large coronal mass ejection propagating from the Sun. This is confirmed by roughly contemporaneous observations with the Ooty Radio Telescope. We see evidence for structure on spatial scales ranging from <1000 to > {10}6 km. The serendipitous night-time nature of these detections illustrates the new regime that the MWA has opened for IPS studies with sensitive night-time, wide-field, low-frequency observations. This regime complements traditional dedicated strategies for observing IPS and can be utilized in real-time to facilitate dedicated follow-up observations. At the same time, it allows large-scale surveys for compact (arcsec) structures in low-frequency radio sources despite the 2' resolution of the array.

  14. First detection of a seasonality of stratomesospheric CO above mid-latitudes via solar FTIR measurements. Analysis of one decade of observations at the NDACC Primary Station Zugspitze

    NASA Astrophysics Data System (ADS)

    Borsdorff, T.; Sussmann, R.; Rettinger, M.

    2009-04-01

    Model studies revealed that stratomesospheric CO exhibits considerable seasonal and latitudinal variations caused by the competition between downward transport from the thermospheric production region and photochemical loss processes. A sharp latitudinal gradient with highest abundances at the North Pole was found which implies that the mid-latitude region can exhibit strong enhancements of stratomesospheric CO under conditions of large-scale planetary wave activity displacing CO enriched vortex air from North to South. Unfortunately, until now there are not enough continuous long-term measurements of stratomesospheric CO at mid-latitudes to prove this assumption. Velazco et al. [2007] reported ground-based FTIR measurements of stratomesospheric CO partial columns from several sites in the Arctic, northern and southern mid-latitudes, and Antarctica. Unfortunately, this study concluded that, generally, the mid-latitude stations show no significant annual variability of stratomesospheric CO columns. However, already early microwave observations indicated that stratomesospheric CO is about twice as large in mid-latitude winter as in summer [Clancy et al., 1982]. Obviously, there was a technical difficulty with the FTIR inversion of mid-latitude mesospheric CO in the early study by Velazco et al. [2007]. It is one aim of this paper to present a solution to this problem. Therefore, this paper describes an improved retrieval approach for ground-based FTIR stations, that is capable to derive a significant seasonal cycle of stratomesospheric CO at mid-latitudes. Coincident measurements at Zugspitze (2964 m a.s.l.) and Garmisch (744 m a.s.l.) show perfect agreement (R = 0.94) which proves that the new retrieval approach is not limited to high altitude stations, and is thus applicable to all mid-latitude stations. The first long-term series of stratomesospheric CO at mid-latitudes (42.42°N, 10.98°E) derived from ground-based FTIR spectrometry is presented (1999 to 2008). Between November and April the monthly mean time series shows column enhancements by a factor of 2.2 relative to the summer minimum of 1.64E16 cm-2 with a maximum of 3.63E16 cm-2 in February and strong year-to-year variability of up to 32 % (1 sigma). The seasonality agrees very well with the WACCM model [Garcia et al., 2007] which, however, can not reproduce measured year-to-year variability. Pronounced short time enhancements (duration of 1 to 3 days) are observed, which during winter exceed the monthly-mean background seasonality by up to 276 %. Comparison with WACCM and FTIR measurements at high-latitudes [Jones et al., 2007] reveal, that these enhancements reflect inner vortex conditions and are due to transport by planetary waves. References Clancy, R. T., D. O. Muhleman and G. L. Berge (1982), Microwave spectra of terrestrial mesospheric CO, J. Geophys. Res., 87, 5009 - 5014. Garcia, R. R., D. R. Marsh, D. E. Kinnison, B. A. Boville, and F. Sassi (2007), Simulation of secular trends in the middle atmosphere, 1950-2003, J. Geophys. Res., 112, D09301, doi: 10.1029/2006JD007485. Jones, N. B., Y. Kasai, E. Dupuy, Y. Murayama, J. Urban, B. Barret, M. Sinnhuber, A. Kagawa, T. Koshiro, P. Ricaud, and D. Murtagh (2007), Stratomesospheric CO measured by a ground-based Fourier Transform Spectrometer over Poker Flat, Alaska: Comparison with Odin/SMR and a 2-D model, J. Geophys. Res., 112, D20303, doi: 10.1029/2006JD007916. Velazco, V., S. W. Wood, M.Sinnhuber, I. Kramer, N. B. Jones, Y. Kasai, J. Notholt, T. Warneke, T. Blumenstock, F. Hase, F. J. Murcray, and O. Schrems (2007), Annual variation of strato-mesospheric carbon monoxide measured by ground-based Fourier transform infrared spectrometry, Atmos. Chem. Phys., 7, 1305-1312.

  15. LRO/LAMP Observations of Temporal Variability of Lunar Exospheric Helium During June and July 2012

    NASA Astrophysics Data System (ADS)

    Feldman, P. D.; Hurley, D. M.; Retherford, K. D.; Gladstone, R.; Stern, S. A.; Pryor, W. R.; Parker, J.

    2012-12-01

    We have previously reported on observations of the lunar helium exosphere made in January 2012 with the Lyman Alpha Mapping Project (LAMP) ultraviolet spectrograph on NASA's Lunar Reconnaissance Orbiter Mission. Those observations, of resonantly scattered He I emission at 584 Å from illuminated atmosphere against the dark lunar surface, were made over the night side of the Moon within 30 degrees of the dawn terminator. During June-July 2012 these observations were repeated, this time including both the dusk and dawn terminators. We find temporal variability of the derived surface He density as well as a strong dawn/dusk asymmetry with the He density on the dawn side approximately a factor of three higher than at corresponding longitudes on the dusk side. We again observe a factor of two decrease in surface density during the passage of the Moon through the Earth's magnetotail.

  16. Summertime tropospheric ozone variability over the Mediterranean basin observed with IASI

    NASA Astrophysics Data System (ADS)

    Doche, C.; Dufour, G.; Foret, G.; Eremenko, M.; Cuesta, J.; Beekmann, M.; Kalabokas, P.

    2014-05-01

    The Mediterranean basin is one of the most sensitive regions of the world regarding climate change and air quality. This is partly due to the singular dynamical situation of the Mediterranean basin that leads to among the highest tropospheric ozone concentrations over the Northern Hemisphere. Six years of summertime tropospheric ozone observed by the IASI instrument from 2007 to 2012 have been analysed to document the variability of ozone over this region. The satellite observations have been also examined in parallel with meteorological analyses (from ECMWF) to understand the processes that drive this variability. This work confirmed the presence of a steep west-east ozone gradient in the lower troposphere with the highest concentrations observed over the eastern part of the Mediterranean basin. This gradient is mainly explained by the diabatic convection over the Persian Gulf during the Indian Monsoon, which induces an important subsidence of ozone rich air masses from the upper to the lower troposphere over the central and the eastern Mediterranean basin: IASI observations of ozone concentrations at 3 km height show a clear summertime maximum in July that is well correlated to the maximum of downward transport of rich-ozone air masses from the upper troposphere. Even if this feature is robust over the six analyzed years, we have also investigated monthly ozone anomalies, one positive (June 2008) and one negative (June and July 2009) using daily observations of IASI. We show that the relative position and the strength of the meteorological systems (Azores anticyclone and Middle eastern depression) present over the Mediterranean are key factors to explain both the variability and the anomalies of ozone in the lower troposphere in this region.

  17. Inter-observer Variability in Esophageal Body Measurements with High Resolution Manometry among New Physician Users

    PubMed Central

    Singh, Erick; Rife, Christopher; Clayton, Steven; Naas, Peter; Nietert, Paul; Castell, Donald

    2012-01-01

    Goals To evaluate inter-observer variability among four new physician users on measures of esophageal body function. Background Esophageal high resolution manometry (HRM) allows observation of esophageal motility via pressure topography plots. Little is known about the inter-observer variability among physicians. Study Two resident and two fellow level physicians each interpreted 10 liquid swallows of 20 esophageal HRM studies (n=200 swallows) using the BioVIEW Analysis Suite (Sandhill Scientific, Inc.). Studies evaluated were from patients referred for evaluation of dysphagia but found to have normal esophageal manometry and complete liquid bolus transit. Physicians received an orientation session and reviewed recent literature. Each physician recorded contractile front velocity (CFV) and distal contractile integral (DCI) for each liquid swallow. STATISTICS: Inter-observer agreements for CFV and DCI were assessed by intraclass correlation (ICC) values. Linear correlations between measurements by two readers were assessed using linear regression modeling techniques. Results CFV and DCI values of up to 200 data points were analyzed. Four reader results for CFV and DCI showed strong agreement although stronger for DCI measures (ICC=0.94; 0.91 - 0.98) in comparison to CFV (ICC=0.79; 0.52 - 0.82). Further correlation was performed with two readers; readers 1 and 2 revealed excellent correlation for DCI (r=0.95, p<0.001) and good correlation for CFV (r=0.61, p<0.001). Conclusions With a thorough orientation session, good to excellent agreement for CFV and DCI measurements can be obtained from new physician users. CFV measures exhibit greater inter-observer variability possibly due to the artifact produced by intraesophageal pressurization. PMID:22647828

  18. Summertime tropospheric-ozone variability over the Mediterranean basin observed with IASI

    NASA Astrophysics Data System (ADS)

    Doche, C.; Dufour, G.; Foret, G.; Eremenko, M.; Cuesta, J.; Beekmann, M.; Kalabokas, P.

    2014-10-01

    The Mediterranean basin is one of the most sensitive regions in the world regarding climate change and air quality. This is partly due to the singular dynamical situation of the Mediterranean basin that leads to tropospheric-ozone concentrations that are among the highest over the Northern Hemisphere. Six years of summertime tropospheric ozone observed by the Infrared Atmospheric Sounding Interferometer (IASI) instrument from 2007 to 2012 have been analysed to document the variability of ozone over this region. The satellite observations have been examined together with meteorological analyses (from ECMWF) to understand the processes driving this variability. Our work confirmed the presence of a steep west-east ozone gradient in the lower troposphere with the highest concentrations observed over the eastern part of the Mediterranean basin. This gradient is mainly explained by diabatic convection over the Persian Gulf during the Indian monsoon season, which induces an important subsidence of ozone-rich air masses from the upper to the lower troposphere over the central and the eastern Mediterranean basin. IASI observations of ozone concentrations at a 3 km height show a clear summertime maximum in July that is well correlated to the maximum of downward transport of ozone-rich air masses from the upper troposphere. Even if this feature is robust over the six analysed years, we have also investigated monthly ozone anomalies - one positive (June 2008) and one negative (June and July 2009) - using daily IASI observations. We show that the relative position and the strength of the meteorological systems (Azores anticyclone and Middle Eastern depression) present over the Mediterranean are key factors in explaining both the variability and the anomalies of ozone in the lower troposphere in this region.

  19. Multiwavelength Observations of GX 339-4 in 1996. II. Rapid X-ray Variability

    E-print Network

    I. A. Smith; E. P. Liang

    1998-12-08

    As part of our multiwavelength campaign of GX 339-4 observations in 1996 we present the rapid X-ray variability observed July 26 using the RXTE when the source was in a hard state (= soft X-ray low state). We found that the source was extremely variable, with many bright flares. The flares have relatively symmetric time profiles. There are a few time intervals where the flux rises steadily and then drops suddenly, sometimes to a level lower than the average before the increase. Hardness ratios showed that the source was slightly softer when the flux was brighter. The power density spectra (PDS) were also complicated and we found that broken power laws do not provide adequate fits to any of them. Instead a pair of zero-centered Lorentzians gives a good general description of the shape of the PDS. We found several quasi-periodic oscillations (QPO), including some that are harmonically spaced with the most stable frequency at 0.35 Hz. While the overall rms variability of the source was close to being constant throughout the observation (29% integrating between 0.01 and 50 Hz), there is a small but significant change in the PDS shape with time. More importantly, we show that the soft 2-5 keV band is more variable than the harder 5-10 and 10-40 keV bands, which is unusual for this source and for other black hole candidates. Cross correlation functions (CCF) between these bands show that the light curve for the 10-40 keV band lags that of the 2-5 keV band by 5 msec.

  20. Observer variability in pinniped counts: Ground-based enumeration of walruses at haul-out sites

    USGS Publications Warehouse

    Udevitz, M.S.; Jay, C.V.; Cody, M.B.

    2005-01-01

    Pinnipeds are often monitored by counting individuals at haul-out sites, but the often large numbers of densely packed individuals at these sites are difficult to enumerate accurately. Errors in enumeration can induce bias and reduce precision in estimates of population size and trend. We used data from paired observers monitoring walrus haul-outs in Bristol Bay, Alaska, to quantify observer variability and assess its relative importance. The probability of a pair of observers making identical counts was 50 individuals. Mean count differences ranged up to 25% for the largest counts, depending on beach and observers. In at least some cases, there was a clear tendency for counts of one observer to be consistently greater than counts of the other observer in a pair, indicating that counts of at least one of the observers were biased. These results suggest that efforts to improve accuracy of counts will be worthwhile. However, we also found that variation among observers was relatively small compared to variation among visits to a beach so that efforts to account for other sources of variation will be more important.

  1. Time-Variable Gravity from Space: Quarter Century of Observations, Mysteries, and Prospects

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.

    2003-01-01

    Any large mass transport in the Earth system produces changes in the gravity field. Via the space geodetic technique of satellite-laser ranging in the last quarter century, the Earth's dynamic oblateness J2 (the lowest-degree harmonic component of the gravity field) has been observed to undergo a slight decrease -- until around 1998, when it switched quite suddenly to an increase trend which has continued to date. The secular decrease in J2 has long been attributed primarily to the post-glacial rebound in the mantle; the present increase signifies an even larger change in global mass distribution whose J2 effect overshadows that of the post-glacial rebound, at least over interannual timescales. Intriguing evidences have been found in the ocean water distribution, especially in the extratropical Pacific basins, that may be responsible for this J2 change. New techniques based on satellite-to-satellite tracking will yield greatly improved observations for time-variable gravity, with much higher precision and spatial resolution (i.e., much higher harmonic degrees). The most important example is the GRACE mission launched in March 2002, following the success of the CHAMP mission. In addition, although less precise than GRACE, the GPS/Meteorology constellation mission COSMIC, with 6 mini-satellites to be launched in late 2005, is expected to provide continued and complementary time-variable gravity observations. Such observations are becoming a new and powerful tool for remote sensing of geophysical fluid processes that involve larger-scale mass transports.

  2. High ultrasound variability in chronic immune-mediated neuropathies. Review of the literature and personal observations.

    PubMed

    Padua, L; Paolasso, I; Pazzaglia, C; Granata, G; Lucchetta, M; Erra, C; Coraci, D; De Franco, P; Briani, C

    2013-12-01

    Chronic immune-mediated neuropathies show high clinical variability. Diagnosis is based on clinical and neurophysiological studies, but recently ultrasound (US) of peripheral nerves has been shown to provide useful morphological information. US has already been shown to crucially influence diagnosis and clinical care in entrapment neuropathies, in traumatic nerve lesions and in tumors. The role of US in the evaluation of polyneuropathies is still not clearly defined, but increasing attention has recently been focused on the immune-mediated neuropathies and specific US measures (namely the intra- and inter-nerve cross-sectional area variability) have been developed. The aim of the current paper is to make a review of the available nerve US studies and provide data from personal observations in the most common chronic immune-mediated neuropathies. PMID:24230478

  3. Observable Effects of Dust Formation in Dynamic Atmospheres of M-type Mira Variables

    E-print Network

    M. J. Ireland; M. Scholz

    2006-01-18

    The formation of dust with temperature-dependent non-grey opacity is considered in a series of self-consistent model atmospheres at different phases of an O-rich Mira variable of mass 1.2 $M_\\odot$. Photometric and interferometric properties of these models are predicted under different physical assumptions regarding the dust formation. The iron content of the initial silicate that forms and the availability of grain nuclei are found to be critical parameters that affect the observable properties. In particular, parameters were found where dust would form at 2-3 times the average continuum photospheric radius. This work provides a consistent physical explanation for the larger apparent size of Mira variables at wavelengths shorter than 1 $\\mu$m than that predicted by dust free fundamental-mode pulsation models.

  4. PHOTOMETRY OF VARIABLE STARS FROM DOME A, ANTARCTICA: RESULTS FROM THE 2010 OBSERVING SEASON

    SciTech Connect

    Wang, Lingzhi; Zhu, Zonghong; Macri, Lucas M.; Wang, Lifan; Ashley, Michael C. B.; Lawrence, Jon S.; Luong-Van, Daniel; Storey, John W. V.; Cui, Xiangqun; Feng, Long-Long; Gong, Xuefei; Liu, Qiang; Shang, Zhaohui; Yang, Huigen; Yang, Ji; Yuan, Xiangyan; Zhou, Xu; Zhu, Zhenxi; Pennypacker, Carl R.; York, Donald G.

    2013-12-01

    We present results from a season of observations with the Chinese Small Telescope ARray, obtained over 183 days of the 2010 Antarctic winter. We carried out high-cadence time-series aperture photometry of 9125 stars with i ?< 15.3 mag located in a 23 deg{sup 2} region centered on the south celestial pole. We identified 188 variable stars, including 67 new objects relative to our 2008 observations, thanks to broader synoptic coverage, a deeper magnitude limit, and a larger field of view. We used the photometric data set to derive site statistics from Dome A. Based on two years of observations, we find that extinction due to clouds at this site is less than 0.1 and 0.4 mag during 45% and 75% of the dark time, respectively.

  5. High Resolution Radio Observations of the Nebulae of Luminous Blue Variable Stars

    NASA Astrophysics Data System (ADS)

    Mercer, Allison; Chizek, M.; Lang, C. C.; Figer, D. F.; Najarro, P.

    2006-12-01

    Luminous Blue Variable (LBV) stars represent an important, but short-lived, evolutionary phase of massive stars marked by extreme mass-loss events. The ejecta from these events appear as associated LBV nebulae (LBVN). Radio observations of the LBVN can provide insight into previous and current mass loss rates of the star, as well as the details of expansion into the surrounding ISM. Here, we report new multi-frequency, multi-configuration Very Large Array (VLA) observations of seven Galactic LBVN. We present preliminary 8.5 and 22.5 GHz results on LBVN sources AFGL2298, NaSt1, G79.29+0.46, G26.47+0.02, the Galactic Center Pistol Star, Galactic Center FMM362 and LBV 1806-20. These high-resolution observations reveal structure in the LBVN.

  6. Observational evidence of the influence of Antarctic stratospheric ozone variability on middle atmosphere dynamics

    NASA Astrophysics Data System (ADS)

    Venkateswara Rao, N.; Espy, P. J.; Hibbins, R. E.; Fritts, D. C.; Kavanagh, A. J.

    2015-10-01

    Modeling results have suggested that the circulation of the stratosphere and mesosphere in spring is strongly affected by the perturbations in heating induced by the Antarctic ozone hole. Here using both mesospheric MF radar wind observations from Rothera Antarctica (67°S, 68°W) as well as stratospheric analysis data, we present observational evidence that the stratospheric and mesospheric wind strengths are highly anti-correlated, and show their largest variability in November. We find that these changes are related to the total amount of ozone loss that occurs during the Antarctic spring ozone hole and particularly with the ozone gradients that develop between 57.5°S and 77.5°S. The results show that with increasing ozone loss during spring, winter conditions in the stratosphere and mesosphere persist longer into the summer. These results are discussed in the light of observations of the onset and duration of the Antarctic polar mesospheric cloud season.

  7. Variability in the Speed of the Brewer-Dobson Circulation as Observed by Aura/MLS

    NASA Technical Reports Server (NTRS)

    Flury, Thomas; Wu, Dong L.; Read, W. G.

    2013-01-01

    We use Aura/MLS stratospheric water vapour (H2O) measurements as tracer for dynamics and infer interannual variations in the speed of the Brewer-Dobson circulation (BDC) from 2004 to 2011. We correlate one-year time series of H2O in the lower stratosphere at two subsequent pressure levels (68 hPa, approx.18.8 km and 56 hPa, approx 19.9 km at the Equator) and determine the time lag for best correlation. The same calculation is made on the horizontal on the 100 hPa (approx 16.6 km) level by correlating the H2O time series at the Equator with the ones at 40 N and 40 S. From these lag coefficients we derive the vertical and horizontal speeds of the BDC in the tropics and extra-tropics, respectively. We observe a clear interannual variability of the vertical and horizontal branch. The variability reflects signatures of the Quasi Biennial Oscillation (QBO). Our measurements confirm the QBO meridional circulation anomalies and show that the speed variations in the two branches of the BDC are out of phase and fairly well anti-correlated. Maximum ascent rates are found during the QBO easterly phase. We also find that transport of H2O towards the Northern Hemisphere (NH) is on the average two times faster than to the Southern Hemisphere (SH) with a mean speed of 1.15m/s at 100 hPa. Furthermore, the speed towards the NH shows much more interannual variability with an amplitude of about 21% whilst the speed towards the SH varies by only 10 %. An amplitude of 21% is also observed in the variability of the ascent rate at the Equator which is on the average 0.2mm/s.

  8. The spatial-temporal variability of air-sea momentum fluxes observed at a tidal inlet

    NASA Astrophysics Data System (ADS)

    Ortiz-Suslow, D. G.; Haus, B. K.; Williams, N. J.; Laxague, N. J. M.; Reniers, A. J. H. M.; Graber, H. C.

    2015-02-01

    Coastal waters are an aerodynamically unique environment that has been little explored from an air-sea interaction point of view. Consequently, most studies must assume that open ocean-derived parameterizations of the air-sea momentum flux are representative of the nearshore wind forcing. Observations made at the New River Inlet in North Carolina, during the Riverine and Estuarine Transport experiment (RIVET), were used to evaluate the suitability of wind speed-dependent, wind stress parameterizations in coastal waters. As part of the field campaign, a small, agile research vessel was deployed to make high-resolution wind velocity measurements in and around the tidal inlet. The eddy covariance method was employed to recover direct estimates of the 10 m neutral atmospheric drag coefficient from the three-dimensional winds. Observations of wind stress angle, near-surface currents, and heat flux were used to analyze the cross-shore variability of wind stress steering off the mean wind azimuth. In general, for onshore winds above 5 m/s, the drag coefficient was observed to be two and a half times the predicted open ocean value. Significant wind stress steering is observed within 2 km of the inlet mouth, which is observed to be correlated with the horizontal current shear. Other mechanisms such as the reduction in wave celerity or depth-limited breaking could also play a role. It was determined that outside the influence of these typical coastal processes, the open ocean parameterizations generally represent the wind stress field. The nearshore stress variability has significant implications for observations and simulations of coastal transport, circulation, mixing, and general surf-zone dynamics.

  9. Inter- and Intra-Observer Variability in Prostate Definition With Tissue Harmonic and Brightness Mode Imaging

    SciTech Connect

    Sandhu, Gurpreet Kaur; Dunscombe, Peter; Meyer, Tyler; Pavamani, Simon; Khan, Rao

    2012-01-01

    Purpose: The objective of this study was to compare the relative utility of tissue harmonic (H) and brightness (B) transrectal ultrasound (TRUS) images of the prostate by studying interobserver and intraobserver variation in prostate delineation. Methods and Materials: Ten patients with early-stage disease were randomly selected. TRUS images of prostates were acquired using B and H modes. The prostates on all images were contoured by an experienced radiation oncologist (RO) and five equally trained observers. The observers were blinded to information regarding patient and imaging mode. The volumes of prostate glands and areas of midgland slices were calculated. Volumes contoured were compared among the observers and between observer group and RO. Contours on one patient were repeated five times by four observers to evaluate the intraobserver variability. Results: A one-sample Student t-test showed the volumes outlined by five observers are in agreement (p > 0.05) with the RO. Paired Student t-test showed prostate volumes (p = 0.008) and midgland areas (p = 0.006) with H mode were significantly smaller than that with B mode. Two-factor analysis of variances showed significant interobserver variability (p < 0.001) in prostate volumes and areas. Inter- and intraobserver consistency was quantified as the standard deviation of mean volumes and areas, and concordance indices. It was found that for small glands ({<=}35 cc) H mode provided greater interobserver consistency; however, for large glands ({>=}35 cc), B mode provided more consistent estimates. Conclusions: H mode provided superior inter- and intraobserver agreement in prostate volume definition for small to medium prostates. In large glands, H mode does not exhibit any additional advantage. Although harmonic imaging has not proven advantageous for all cases, its utilization seems to be judicious for small prostates.

  10. Mechanisms for Diurnal Variability of Global Tropical Rainfall Observed from TRMM

    NASA Technical Reports Server (NTRS)

    Yang, Song; Smith, Eric a.

    2006-01-01

    The behavior and various controls of diurnal variability in tropical-subtropical rainfall are investigated using Tropical Rainfall Measuring Mission (TRMM) precipitation measurements retrieved from the three level-2 TRMM standard profile algorithms for the 1998 annual cycle. Results show that diurnal variability characteristics of precipitation are consistent for all three algorithms, providing assurance that TRMM retrievals are producing consistent estimates of rainfall variability. As anticipated, most ocean areas exhibit more rainfall at night, while over most land areas, rainfall peaks during daytime; however, important exceptions are noted. The dominant feature of the oceanic diurnal cycle is a rainfall maximum in late-evening-early-morning (LE-EM) hours, while over land the dominant maximum occurs in the mid- to late afternoon (MLA). In conjunction with these maxima are pronounced seasonal variations of the diurnal amplitudes. Amplitude analysis shows that the diurnal pattern and its seasonal evolution are closely related to the rainfall accumulation pattern and its seasonal evolution. In addition, the horizontal distribution of diurnal variability indicates that for oceanic rainfall, there is a secondary MLA maximum coexisting with the LE-EM maximum at latitudes dominated by large-scale convergence and deep convection. Analogously, there is a preponderancy for an LE EM maximum over land coexisting with the stronger MLA maximum, although it is not evident that this secondary continental feature is closely associated with the large-scale circulation. Neither of the secondary maxima exhibit phase behavior that can be considered semidiurnal in nature. Diurnal rainfall variability over the ocean associated with large-scale convection is clearly an integral component of the general circulation. Phase analysis reveals differences in regional and seasonal features of the diurnal cycle, indicating that underlying forcing mechanisms differ from place to place. This is underscored by the appearance of secondary ocean maxima in the presence of large-scale convection, along with other important features. Among these, there are clear-cut differences between the diurnal variability of seasonal rainfall over the mid-Pacific and Indian Ocean Basins. The mid-Pacific exhibits double maxima in spring and winter but only LE-EM maxima in summer and autumn, while the Indian Ocean exhibits double maxima in spring and summer and only an LE-EM maximum in autumn and winter. There are also evident daytime maxima within the major large-scale marine stratocumulus regions off the west coasts of continents. The study concludes with a discussion concerning how the observational evidence either supports or repudiates possible forcing mechanisms that have been suggested to explain diurnal rainfall variability.

  11. Tropospheric carbon monoxide concentrations and variability on Venus from Venus Express/VIRTIS-M observations

    NASA Astrophysics Data System (ADS)

    Tsang, Constantine C. C.; Irwin, Patrick G. J.; Wilson, Colin F.; Taylor, Fredric W.; Lee, Chris; de Kok, Remco; Drossart, Pierre; Piccioni, Giuseppe; Bezard, Bruno; Calcutt, Simon

    2008-10-01

    We present nightside observations of tropospheric carbon monoxide in the southern hemisphere near the 35 km height level, the first from Venus Express/Visible and Infrared Thermal Imaging Spectrometer (VIRTIS)-M-IR. VIRTIS-M data from 2.18 to 2.50 ?m, with a spectral resolution of 10 nm, were used in the analysis. Spectra were binned, with widths ranging from 5 to 30 spatial pixels, to increase the signal-to-noise ratio, while at the same time reducing the total number of retrievals required for complete spatial coverage. We calculate the mean abundance for carbon monoxide at the equator to be 23 +/- 2 ppm. The CO concentration increases toward the poles, peaking at a latitude of approximately 60°S, with a mean value of 32 +/- 2 ppm. This 40% equator-to-pole increase is consistent with the values found by Collard et al. (1993) from Galileo/NIMS observations. Observations suggest an overturning in this CO gradient past 60°S, declining to abundances seen in the midlatitudes. Zonal variability in this peak value has also been measured, varying on the order of 10% (~3 ppm) at different longitudes on a latitude circle. The zonal variability of the CO abundance has possible implications for the lifetime of CO and its dynamics in the troposphere. This work has definitively established a distribution of tropospheric CO, which is consistent with a Hadley cell circulation, and placed limits on the latitudinal extent of the cell.

  12. VHE gamma-ray observations of transient and variable stellar objects with the MAGIC Telescopes

    E-print Network

    Fernández-Barral, A; Wilhelmi, E de Oña; Torres, D F; Fruck, C; Hadasch, D; López-Oramas, A; Munar-Adrover, P

    2015-01-01

    Galactic transients, X-ray and gamma-ray binaries provide a proper environment for particle acceleration. This leads to the production of gamma rays with energies reaching the GeV-TeV regime. MAGIC has carried out deep observations of different transient and variable stellar objects of which we highlight 4 of them here: LSI+61 303, MWC 656, Cygnus X-1 and SN 2014J. We present the results of those observations, including long-term monitoring of Cygnus X-1 and LSI+61 303 (7 and 8 years, respectively). The former is one of the brightest X-ray sources and best studied microquasars across a broad range of wavelengths, whose steady and variable signal was studied by MAGIC within a multiwavelength scenario. The latest results of an unique object, MWC 656, are also shown in this presentation. This source is the first high-mass X-ray binary system detected that is composed of a black hole and a Be star. Finally, we report on the observations of SN 2014J, the nearest Type Ia SN of the last 40 years. Its proximity and e...

  13. Experimental observations and numerical modeling of coupled microbial and transport processes in variably saturated sand.

    SciTech Connect

    Rockhold, Mark L.; Yarwood, R R.; Niemet, M R.; Bottomley, Peter J.; Selker, John S.

    2005-05-13

    An experimental and numerical investigation was conducted to study interactions between microbial dynamics and transport processes in variably saturated porous media. Experiments were conducted with constant, surface-applied water fluxes in duplicate, variably saturated, sand-filled columns that were uniformly inoculated with the bacterium Pseudomonas fluorescens HK44. The permeability of the sand in the columns was reduced by a factor of 45 during one week of growth on glucose. Pressure heads increased (became less negative) at all measured depths, but significant increases in the apparent volumetric water contents were only observed in the upper 5 cm of the columns, corresponding to the areas with the highest concentrations of attached bacteria. A numerical model was used to simulate the experiments. The model accounted for the processes of water flow, solute and bacterial transport, cell growth and accumulation, glucose and oxygen consumption, and gas diffusion and exchange. Observed changes in water content and pressure head were reproduced approximately using fluid-media scaling to account for an apparent surface-tension lowering effect. Reasonable correspondence was obtained between observed and simulated effluent data and final attached biomass concentration distributions using first-order reversible cell attachment and detachment kinetics with attachment rate coefficients based on particle-filtration theory, and time-dependent detachment rate coefficients. The results of this study illustrate the potential importance of using fully coupled multi-fluid flow and multi-component reactive transport equations to model coupled biogeochemical and transport processes in soils.

  14. Optical observations of 22 violently variable extragalactic sources - 1968-1986

    NASA Astrophysics Data System (ADS)

    Webb, James R.; Smith, Alex G.; Leacock, Robert J.; Fitzgibbons, Gregory L.; Gombola, Paul P.; Shepherd, David W.

    1988-02-01

    Broadband photographic observations of 22 optically violent variable (OVV) active galactic nuclei are presented. Over 3100 observations made between 1968 and 1986 at Rosemary Hill Observatory are tabulated and displayed graphically. The majority of the observations were made in either the Johnson B system or the international photographic (PG) system. Multicolor data are presented for a few objects. Descriptions of the light curves include the assignment of each OVV to an arbitrary variability subclass. The light curves, some extending over 18 yr, are analyzed for linear trends and underlying structure using linear regression and unequal-interval Fourier transform techniques. The results of the analysis for each of the 22 objects are given, and models of the light variations of 3C 120, 3C 345, and 3C 446 are presented. The models of these light curves show underlying structure with rapid variations superimposed. The time scales seen in the light curves of 3C 120, 3C 345, and 3C 446 are compared with characteristic time scales found in massive-accretion-disk models. The time scales most likely to be responsible for the optical behavior are either the viscous or the thermal time scales.

  15. Optical observations of 22 violently variable extragalactic sources - 1968-1986

    SciTech Connect

    Webb, J.R.; Smith, A.G.; Leacock, R.J.; Fitzgibbons, G.L.; Gombola, P.P.

    1988-02-01

    Broadband photographic observations of 22 optically violent variable (OVV) active galactic nuclei are presented. Over 3100 observations made between 1968 and 1986 at Rosemary Hill Observatory are tabulated and displayed graphically. The majority of the observations were made in either the Johnson B system or the international photographic (PG) system. Multicolor data are presented for a few objects. Descriptions of the light curves include the assignment of each OVV to an arbitrary variability subclass. The light curves, some extending over 18 yr, are analyzed for linear trends and underlying structure using linear regression and unequal-interval Fourier transform techniques. The results of the analysis for each of the 22 objects are given, and models of the light variations of 3C 120, 3C 345, and 3C 446 are presented. The models of these light curves show underlying structure with rapid variations superimposed. The time scales seen in the light curves of 3C 120, 3C 345, and 3C 446 are compared with characteristic time scales found in massive-accretion-disk models. The time scales most likely to be responsible for the optical behavior are either the viscous or the thermal time scales. 50 references.

  16. Quantitative Comparison of the Variability in Observed and Simulated Shortwave Reflectance

    NASA Technical Reports Server (NTRS)

    Roberts, Yolanda, L.; Pilewskie, P.; Kindel, B. C.; Feldman, D. R.; Collins, W. D.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system that has been designed to monitor the Earth's climate with unprecedented absolute radiometric accuracy and SI traceability. Climate Observation System Simulation Experiments (OSSEs) have been generated to simulate CLARREO hyperspectral shortwave imager measurements to help define the measurement characteristics needed for CLARREO to achieve its objectives. To evaluate how well the OSSE-simulated reflectance spectra reproduce the Earth s climate variability at the beginning of the 21st century, we compared the variability of the OSSE reflectance spectra to that of the reflectance spectra measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY). Principal component analysis (PCA) is a multivariate decomposition technique used to represent and study the variability of hyperspectral radiation measurements. Using PCA, between 99.7%and 99.9%of the total variance the OSSE and SCIAMACHY data sets can be explained by subspaces defined by six principal components (PCs). To quantify how much information is shared between the simulated and observed data sets, we spectrally decomposed the intersection of the two data set subspaces. The results from four cases in 2004 showed that the two data sets share eight (January and October) and seven (April and July) dimensions, which correspond to about 99.9% of the total SCIAMACHY variance for each month. The spectral nature of these shared spaces, understood by examining the transformed eigenvectors calculated from the subspace intersections, exhibit similar physical characteristics to the original PCs calculated from each data set, such as water vapor absorption, vegetation reflectance, and cloud reflectance.

  17. Constraints on Variability of Brightness and Surface Magnetism on Time Scales of Decades to Centuries in the Sun and Sun-Like Stars: A Source of Potential Terrestrial Climate Variability

    NASA Technical Reports Server (NTRS)

    Baliunas, Sallie L.; Sharber, James (Technical Monitor)

    2003-01-01

    The following summarizes the most important, results of our research: (1) Conciliation of solar and stellar photometric variability; (2) Demonstration of 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); (3) Identification of a possible climate mechanism amplifying the impact of solar ultraviolet irradiance variations; (4) Exploration of natural variability in an ocean-atmosphere climate model; (5) Presentation of a review of the sun's coronal influence on the terrestrial space environment; (6) Quantification of stellar variability as an influence on the analysis of periodic radial velocities that imply the presence of a planetary companion.

  18. Daily to decadal variability of size-fractionated iron and iron-binding ligands at the Hawaii Ocean Time-series Station ALOHA

    NASA Astrophysics Data System (ADS)

    Fitzsimmons, Jessica N.; Hayes, Christopher T.; Al-Subiai, Sherain N.; Zhang, Ruifeng; Morton, Peter L.; Weisend, Rachel E.; Ascani, François; Boyle, Edward A.

    2015-12-01

    Time-series studies of trace metals in the ocean are rare, but they are critical for evaluating both the residence times of the metals themselves and also the timescales over which the marine ecosystems that depend on micronutrient metals can change. In this paper we present two new time-series of the essential micronutrient iron (Fe) taken from the Hawaii Ocean Time-series (HOT) site, Station ALOHA (22.75°N, 158°W): a set of intermittent monthly surface samples taken from ?50 dates between 1999 and 2011 by the HOT program, and a daily-resolved sample set from summer 2012 and 2013 containing ?80 surface samples and 7 profiles to 1500 m depth. The long-term monthly climatology of surface total dissolvable Fe (TDFe) concentrations covaried with the seasonal cycle of continental Asian dust deposition at Hawaii, indicating dust as the major source of TDFe to ALOHA surface waters and a short residence time for TDFe (order ? months). During the daily summer time-series, surface Fe was most variable in the larger size fractions (>0.4 ?m particulate and 0.02-0.4 ?m colloidal) and nearly constant in the smallest (<0.02 ?m) soluble size fractions, confirming that the larger size fractions have shorter residence times with respect to scavenging/settling. The most significant Fe event lasted three days in early August and "cascaded" through the Fe size fractions from largest to smallest; lacking evidence that dust triggered this event, we correlated it with the arrival of the edge of an anticyclonic eddy and an increase in diatom abundance at ALOHA. The surface Fe-binding ligand daily time-series showed that excess ligand concentrations lagged dFe by 1-2 days, revealing a short residence time of ligands in the central North Pacific likely due to photochemical degradation. In the ferricline, the dissolved Fe (dFe) linear relationship with apparent oxygen utilization was used to establish a water column dFe:C ratio of 3.12 ± 0.11 ?mol/mol and a pre-formed dFe concentration of 0.067 ± 0.009 nmol/kg that defines the central/mode waters of Station ALOHA. Finally, in deep waters near 1200 m, where minimal temporal variation in dFe might be expected, dFe instead ranged over a factor of two in concentration (0.72-1.44 nmol/kg), driven by the intermittent passing of the Loihi hydrothermal plume through Station ALOHA. This study not only provides the largest number of Fe measurements made at a single location anywhere in the global ocean to date but also reveals the strength of time-series measurements for exploring mechanisms and timescales of biogeochemical events.

  19. Seasonal and diurnal variability of the meteor flux at high latitudes observed using PFISR

    NASA Astrophysics Data System (ADS)

    Sparks, J. J.; Janches, D.; Nicolls, M. J.; Heinselman, C. J.

    2009-05-01

    We report in this and a companion paper [Fentzke, J.T., Janches, D., Sparks, J.J., 2008. Latitudinal and seasonal variability of the micrometeor input function: A study using model predictions and observations from Arecibo and PFISR. Journal of Atmospheric and Solar-Terrestrial Physics, this issue, doi:10.1016/j.jastp.2008.07.015] a complete seasonal study of the micrometeor input function (MIF) at high latitudes using meteor head-echo radar observations performed with the Poker Flat Incoherent Scatter Radar (PFISR). This flux is responsible for a number of atmospheric phenomena; for example, it could be the source of meteoric smoke that is thought to act as condensation nuclei in the formation of ice particles in the polar mesosphere. The observations presented here were performed for full 24-h periods near the summer and winter solstices and spring and autumn equinoxes, times at which the seasonal variability of the MIF is predicted to be large at high latitudes [Janches, D., Heinselman, C.J., Chau, J.L., Chandran, A., Woodman, R., 2006. Modeling of the micrometeor input function in the upper atmosphere observed by High Power and Large Aperture Radars, JGR, 11, A07317, doi:10.1029/2006JA011628]. Precise altitude and radar instantaneous line-of-sight (radial) Doppler velocity information are obtained for each of the hundreds of events detected every day. We show that meteor rates, altitude, and radial velocity distributions have a large seasonal dependence. This seasonal variability can be explained by a change in the relative location of the meteoroid sources with respect to the observer. Our results show that the meteor flux into the upper atmosphere is strongly anisotropic and its characteristics must be accounted for when including this flux into models attempting to explain related aeronomical phenomena. In addition, the measured acceleration and received signal strength distribution do not seem to depend on season; which may suggest that these observed quantities do not have a strong dependence on entry angle.

  20. Sea Ice and Ice Temperature Variability as Observed by Microwave and Infrared Satellite Data

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    Recent reports of a retreating and thinning sea ice cover in the Arctic have pointed to a strong suggestion of significant warming in the polar regions. It is especially important to understand what these reports mean in light of the observed global warning and because the polar regions are expected to be most sensitive to changes in climate. To gain insight into this phenomenon, co-registered ice concentrations and surface temperatures derived from two decades of satellite microwave and infrared data have been processed and analyzed. While observations from meteorological stations indicate consistent surface warming in both regions during the last fifty years, the last 20 years of the same data set show warming in the Arctic but a slight cooling in the Antarctic. These results are consistent with the retreat in the Arctic ice cover and the advance in the Antarctic ice cover as revealed by historical satellite passive microwave data. Surface temperatures derived from satellite infrared data are shown to be consistent within 3 K with surface temperature data from the limited number of stations. While not as accurate, the former provides spatially detailed changes over the twenty year period. In the Arctic, for example, much of the warming occurred in the Beaufort Sea and the North American region in 1998 while slight cooling actually happened in parts of the Laptev Sea and Northern Siberia during the same time period. Big warming anomalies are also observed during the last five years but a periodic cycle of about ten years is apparent suggesting a possible influence of the North Atlantic Oscillation. In the Antarctic, large interannual and seasonal changes are also observed in the circumpolar ice cover with regional changes showing good coherence with surface temperature anomalies. However, a mode 3 is observed to be more dominant than the mode 2 wave reported in the literature. Some of these spatial and temporal changes appear to be influenced by the Antarctic Circumpolar Wave (ACW) and changes in coastal polynya activities.

  1. Microwave radiometer observations of interannual water vapor variability and vertical structure over a tropical station

    NASA Astrophysics Data System (ADS)

    Renju, R.; Suresh Raju, C.; Mathew, Nizy; Antony, Tinu; Krishna Moorthy, K.

    2015-05-01

    The intraseasonal and interannual characteristics and the vertical distribution of atmospheric water vapor from the tropical coastal station Thiruvananthapuram (TVM) located in the southwestern region of the Indian Peninsula are examined from continuous multiyear, multifrequency microwave radiometer profiler (MRP) measurements. The accuracy of MRP for precipitable water vapor (PWV) estimation, particularly during a prolonged monsoon period, has been demonstrated by comparing with the PWV derived from collocated GPS measurements based on regression model between PWV and GPS wet delay component which has been developed for TVM station. Large diurnal and intraseasonal variations of PWV are observed during winter and premonsoon seasons. There is large interannual PWV variability during premonsoon, owing to frequent local convection and summer thunderstorms. During monsoon period, low interannual PWV variability is attributed to the persistent wind from the ocean which brings moisture to this coastal station. However, significant interannual humidity variability is seen at 2 to 6 km altitude, which is linked to the monsoon strength over the station. Prior to monsoon onset over the station, the specific humidity increases up to 5-10 g/kg in the altitude region above 5 km and remains consistently so throughout the active spells.

  2. An observational and modeling study of the regional impacts of climate variability

    NASA Astrophysics Data System (ADS)

    Horton, Radley M.

    Climate variability has large impacts on humans and their agricultural systems. Farmers are at the center of this agricultural network, but it is often agricultural planners---regional planners, extension agents, commodity groups and cooperatives---that translate climate information for users. Global climate models (GCMs) are a leading tool for understanding and predicting climate and climate change. Armed with climate projections and forecasts, agricultural planners adapt their decision-making to optimize outcomes. This thesis explores what GCMs can, and cannot, tell us about climate variability and change at regional scales. The question is important, since high-quality regional climate projections could assist farmers and regional planners in key management decisions, contributing to better agricultural outcomes. To answer these questions, climate variability and its regional impacts are explored in observations and models for the current and future climate. The goals are to identify impacts of observed variability, assess model simulation of variability, and explore how climate variability and its impacts may change under enhanced greenhouse warming. Chapter One explores how well Goddard Institute for Space Studies (GISS) atmospheric models, forced by historical sea surface temperatures (SST), simulate climatology and large-scale features during the exceptionally strong 1997--1999 El Nino Southern Oscillation (ENSO) cycle. Reasonable performance in this 'proof of concept' test is considered a minimum requirement for further study of variability in models. All model versions produce appropriate local changes with ENSO, indicating that with correct ocean temperatures these versions are capable of simulating the large-scale effects of ENSO around the globe. A high vertical resolution model (VHR) provides the best simulation. Evidence is also presented that SST anomalies outside the tropical Pacific may play a key role in generating remote teleconnections even during El Nino events. Based on the results from Chapter One, the analysis is expanded in several ways in Chapter Two. To gain a more complete and statistically meaningful understanding of ENSO, a 25 year time period is used instead of a single event. To gain a fuller understanding of climate variability, additional patterns are analyzed. Finally analysis is conducted at the regional scales that are of interest to farmers and agricultural planners. Key findings are that GISS ModelE can reproduce: (1) the spatial pattern associated with two additional related modes, the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO); (2) rainfall patterns in Indonesia; and (3) dynamical features such as sea level pressure (SLP) gradients and wind in the study regions. When run in coupled mode, the same model reproduces similar modes spatially but with reduced variance and weak teleconnections. Since Chapter Two identified Western Indonesia as the region where GCMs hold the most promise for agricultural applications, in Chapter Three a finer spatial and temporal scale analysis of ENSO's effects is presented. Agricultural decision-making is also linked to ENSO's climate effects. Early rainy season precipitation and circulation, and same-season planting and harvesting dates, are shown to be sensitive to ENSO. The locus of ENSO convergence and rainfall anomalies is shown to be near the axis of rainy season establishment, defined as the 6--8 mm/day isohyet, an approximate threshold for irrigated rice cultivation. As the axis tracks south and east between October and January, so do ENSO anomalies. Circulation anomalies associated with ENSO are shown to be similar to those associated with rainfall anomalies, suggesting that long lead-time ENSO forecasts may allow more adaptation than 'wait and see' methods, with little loss of forecast skill. Additional findings include: (1) rice and corn yields are lower (higher) during dry (wet) trimesters and El Nino (La Nina) years; and (2) a statistically significant negative relationship exists between malaria cases and ENSO. The fi

  3. Cassini UVIS Observations of the Io Plasma Torus. 4; Modeling Temporal and Azimuthal Variability

    NASA Technical Reports Server (NTRS)

    Steffl, A. J.; Delamere, P. A.; Bagenal, F.

    2008-01-01

    In this fourth paper in a series, we present a model of the remarkable temporal and azimuthal variability of the Io plasma torus observed during the Cassini encounter with Jupiter. Over a period of three months, the Cassini Ultraviolet Imaging Spectrograph (UVIS) observed a dramatic variaton in the average torus composition. Superimposed on this long-term variation, is a 10.07-hour periodicity caused by azimuthal variation in plasma composition subcorotating relative to System III longitude. Quite surprisingly, the amplitude of the azimuthal variation appears to be modulated at the beat frequency between the System III period and the observed 10.07-hour period. Previously, we have successfully modeled the months-long compositional change by supposing a factor of three increase in the amount of material supplied to Io's extended neutral clouds. Here, we extend our torus chemistry model to include an azimuthal dimension. We postulate the existence of two azimuthal variations in the number of superthermal electrons in the torus: a primary variation that subcorotates with a period of 10.07 hours and a secondary variation that remains fixed in System III longitude. Using these two hot electron variations, our model can reproduce the observed temporal and azimuthal variations observed by Cassini UVIS.

  4. Cassini UVIS Observations of the Io Plasma Torus. IV. Modeling Temporal and Azimuthal Variability

    E-print Network

    A. J. Steffl; P. A. Delamere; F. Bagenal

    2007-09-19

    In this fourth paper in a series, we present a model of the remarkable temporal and azimuthal variability of the Io plasma torus observed during the Cassini encounter with Jupiter. Over a period of three months, the Cassini Ultraviolet Imaging Spectrograph (UVIS) observed a dramatic variation in the average torus composition. Superimposed on this long-term variation, is a 10.07-hour periodicity caused by an azimuthal variation in plasma composition subcorotating relative to System III longitude. Quite surprisingly, the amplitude of the azimuthal variation appears to be modulated at the beat frequency between the System III period and the observed 10.07-hour period. Previously, we have successfully modeled the months-long compositional change by supposing a factor of three increase in the amount of material supplied to Io's extended neutral clouds. Here, we extend our torus chemistry model to include an azimuthal dimension. We postulate the existence of two azimuthal variations in the number of super-thermal electrons in the torus: a primary variation that subcorotates with a period of 10.07 hours and a secondary variation that remains fixed in System III longitude. Using these two hot electron variations, our model can reproduce the observed temporal and azimuthal variations observed by Cassini UVIS.

  5. Ocean variability east of Mindanao: Mooring observations at 7°N, revisited

    NASA Astrophysics Data System (ADS)

    Kashino, Yuji; Ueki, Iwao; Sasaki, Hedeharu

    2015-04-01

    Two subsurface moorings were deployed east of Mindanao Island, the Philippines, at 7°01'N, 126°55'E and 7°01'N, 127°46'E, at the location of the inshore and offshore cores of the Mindanao Undercurrent (MUC) suggested by past studies, from September 2011 to October 2012 and March 2013. A steady northward undercurrent, the MUC, was not confirmed by these observations, not only at the location of its inshore core but also of the offshore core. The observed mean flow at the mooring sites seems to be part of an anticyclonic eddy rather than the MUC. A particle-tracking experiment using a high-resolution general circulation model output showed that the northward mean flow, called the MUC by past studies, was too weak to advect water to the north. The Mindanao Current during 2011-2012 was weaker than during 1999-2002 because the sea surface height in the Philippine Sea during 2011-2012 was lower than that during 1999-2002. Intraseasonal variability with periods of 50-100 days was observed at the mooring sites, comparable to the previous observations during 1999-2002. Westward signal propagations were observed with periods and speeds of 50 days and 0.20 m s-1 at 300 m depth and of 60-72 days and 0.11-0.14 m s-1 at 960 m depth.

  6. HST/FOS Eclipse Observations of the Nova-like Cataclysmic Variable UX Ursae Majoris

    E-print Network

    C. Knigge; K. S. Long; R. A. Wade; R. Baptista; K. Horne; I. Hubeny; R. G. M. Rutten

    1998-01-21

    [abridged abstract] We present and analyze Hubble Space Telescope observations of the eclipsing nova-like cataclysmic variable UX UMa obtained with the Faint Object Spectrograph. Two eclipses each were observed with the G160L grating (covering the ultraviolet waveband) in August of 1994 and with the PRISM (covering the near-ultraviolet to near-infrared) in November of the same year. The system was 50% brighter in November than in August, which, if due to a change in the accretion rate, indicates a fairly substantial increase in Mdot_acc by >~ 50%. Model disk spectra constructed as ensembles of stellar atmospheres provide poor descriptions of the observed post-eclipse spectra, despite the fact that UX UMa's light should be dominated by the disk at this time. Suitably scaled single temperature model stellar atmospheres with T_eff = 12,500-14,500 K actually provide a better match to both the ultraviolet and optical post-eclipse spectra. Evidently, great care must be taken in attempts to derive accretion rates from comparisons of disk models to observations. One way to reconcile disk models with the observed post-eclipse spectra is to postulate the presence of a significant amount of optically thin material in the system. Such an optically thin component might be associated with the transition region (``chromosphere'') between the disk photosphere and the fast wind from the system, whose presence has been suggested by Knigge & Drew (1997).

  7. IUE and Voyager Observations of the Unusual Cataclysmic Variable S193

    NASA Astrophysics Data System (ADS)

    Szkody, Paula; Garnavich, Peter; Holberg, Jay; Silber, Andrew; Pastwick, Lora

    1997-06-01

    UV observations of S193 were obtained with Voyager and the IUE satellite during both high and low states of this unusual object. Voyager only detected the source during the high state, where the continuum looks similar to the novalike IX Vela and dwarf novae at outburst. The IUE spectra at the high state show deep absorption lines, but the line ratios are not typical of disk cataclysmic variables at outburst. They are most similar to V795 Her and the SW Sex star PG0859+415. At the low state, only CIV and MgII are in emission, while the deep absorptions at SiIII and NV persist. The spectra at this state are most similar to the intermediate polar candidate H0551-819. The UV observations of S193 provide further circumstantial evidence for the existence of a disk and a magnetic white dwarf in an intermediate polar system.

  8. The Positions, Colors, and Photometric Variability of Pluto's Small Satellites from HST Observations 2005-2006

    E-print Network

    S. A. Stern; M. J. Mutchler; H. A. Weaver; A. J. Steffl

    2006-05-02

    Pluto's two small satellites, temporarily designated S/2005 P 1 and S/2005 P 2, were observed on four dates (15.1 and 18.1 May 2005, 15.7 February 2006, and 2.8 March 2006) using the Hubble Space Telescope's (HST) Advanced Camera for Surveys (ACS). Here we collect together the astrometric positions of these two satellites (henceforth P1 and P2), as well as a single color measurement for each satellite and initial constraints on their photometric variability obtained during these observations. We find that both satellites have essentially neutral (grey) reflectivities, like Charon. We also find that neither satellite exhibited strong photometric variation, which might suggest that P1 and P2 are toward the large end of their allowable size range, and therefore may have far lower reflectivities than Charon.

  9. First XMM-Newton observations of a Cataclysmic Variable I: Timing studies of OY Car

    E-print Network

    Gavin Ramsay; Tracey Poole; Keith Mason; France Cordova; William Priedhorsky; Alice Breeveld; Rudi Much; Julian Osborne; Dirk Pandel; Stephen Potter; Jennifer West; Peter Wheatley

    2000-10-18

    We present XMM-Newton observations of the eclipsing, disc accreting, cataclysmic variable OY Car which were obtained as part of the performance verification phase of the mission. The star was observed 4 days after an outburst and then again 5 weeks later when it was in a quiescent state. There is a quasi-stable modulation of the X-rays at ~2240 sec, which is most prominent at the lowest energies. We speculate that this may be related to the spin period of the white dwarf. The duration of the eclipse ingress and egress in X-rays is 20--30 sec. This indicates that the bulk of the X-ray emission originates from the boundary layer which has a negligible height above the surface of the white dwarf. The eclipse profile implies a white dwarf of mass M_{1}=0.9-1.1Msun and a secondary star of M_{2}=0.08-0.11Msun.

  10. Investigating soil controls on soil moisture spatial variability: Numerical simulations and field observations

    NASA Astrophysics Data System (ADS)

    Wang, Tiejun; Franz, Trenton E.; Zlotnik, Vitaly A.; You, Jinsheng; Shulski, Martha D.

    2015-05-01

    Due to its complex interactions with various processes and factors, soil moisture exhibits significant spatial variability across different spatial scales. In this study, a modeling approach and field observations were used to examine the soil control on the relationship between mean (? bar) and standard deviation (??) of soil moisture content. For the numerical experiments, a 1-D vadose zone model along with van Genuchten parameters generated by pedotransfer functions was used for simulating soil moisture dynamics under different climate and surface conditions. To force the model, hydrometeorological and physiological data that spanned over three years from five research sites within the continental US were used. The modeling results showed that under bare surface conditions, different forms of the ? bar -?? relationship as observed in experimental studies were produced. For finer soils, a positive ? bar -?? relationship gradually changed to an upward convex and a negative one from arid to humid conditions; whereas, a positive relationship existed for coarser soils, regardless of climatic conditions. The maximum ?? for finer soils was larger under semiarid conditions than under arid and humid conditions, while the maximum ?? for coarser soils increased with increasing precipitation. Moreover, vegetation tended to reduce ? bar and ??, and thus affected the ? bar -?? relationship. A sensitivity analysis was also conducted to examine the controls of different van Genuchten parameters on the ? bar -?? relationship under bare surface conditions. It was found that the residual soil moisture content mainly affected ?? under dry conditions, while the saturated soil moisture content and the saturated hydraulic conductivity largely controlled ?? under wet conditions. Importantly, the upward convex ? bar -?? relationship was mostly caused by the shape factor n that accounts for pore size distribution. Finally, measured soil moisture data from a semiarid region were retrieved from the Automated Weather Data Network. The observed moisture data showed that based on soil texture, a positive ? bar -?? relationship existed for sandy soils, while an upward convex one was observed for silty soils. The difference in the observed ? bar -sigma? relationship can be attributed to the differences in water holding capacities between sand and silt, which is consistent with the modeling results. The field data also revealed that increasing spatial variability in soil texture led to increased variability in soil moisture (e.g., the maximum ??). Therefore, the effect of soil texture for verifying remotely sensed soil moisture products should be considered.

  11. Overview of observations from the RADAGAST experiment in Niamey, Niger: Meteorology and thermodynamic variables

    SciTech Connect

    Slingo, A.; Bharmal, N.; Robinson, G. J.; Settle, Jeff; Allan, R. P.; White, H. E.; Lamb, Peter J.; Lele, M.; Turner, David D.; McFarlane, Sally A.; Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Miller, Mark

    2008-10-17

    An overview is presented of the meteorological and thermodynamic data obtained during the RADAGAST experiment in Niamey, Niger, in 2006. RADAGAST (Radiative Atmospheric Divergence using ARM Mobile Facility, GERB data and AMMA STations), combined data from the Atmospheric Radiation Measurement (ARM) Program Mobile Facility (AMF) at Niamey airport with broadband satellite data from the Geostationary Earth Radiation Budget (GERB) instrument on Meteosat-8. The experiment was conducted in collaboration with the African Monsoon Multidisciplinary Analysis (AMMA) project. The focus in this paper is on the variations through the year of key surface and atmospheric variables. The seasonal advance and retreat of the InterTropical Front (ITF) and the seasonal changes in near-surface variables and precipitation in 2006 are discussed and contrasted with the behavior in 2005 and with long-term averages. Observations from the AMF at Niamey airport are used to document the evolution of near-surface variables and of the atmosphere above the site. There are large seasonal changes in these variables, from the arid and dusty conditions typical of the dry season to the much moister and more cloudy wet season accompanying the arrival and intensification of the West African monsoon. Back trajectories show the origin of the air sampled at Niamey and profiles for selected case studies from rawinsondes and from a MicroPulse Lidar at the AMF site reveal details of typical atmospheric structures. Radiative fluxes and divergences are discussed in the second part of this overview and the subsequent papers in this special section explore other aspects of the measurements and of the associated modeling.

  12. Can we explain the observed methane variability after the Mount Pinatubo eruption?

    NASA Astrophysics Data System (ADS)

    Bând?, N.; Krol, M.; van Weele, M.; van Noije, T.; Le Sager, P.; Röckmann, T.

    2015-07-01

    The CH4 growth rate in the atmosphere showed large variations after the Pinatubo eruption in June 1991. A decrease of more than 10 ppb yr-1 in the growth rate over the course of 1992 was reported and a partial recovery in the following year. Although several reasons have been proposed to explain the evolution of CH4 after the eruption, their contributions to the observed variations are not yet resolved. CH4 is removed from the atmosphere by the reaction with tropospheric OH, which in turn is produced by O3 photolysis under UV radiation. The CH4 removal after the Pinatubo eruption might have been affected by changes in tropospheric UV levels due to the presence of stratospheric SO2 and sulfate aerosols, and due to enhanced ozone depletion on Pinatubo aerosols. The perturbed climate after the eruption also altered both sources and sinks of atmospheric CH4. Furthermore, CH4 concentrations were influenced by other factors of natural variability in that period, such as ENSO and biomass burning events. Emissions of CO, NOX and NMVOCs also affected CH4 concentrations indirectly by influencing tropospheric OH levels. Potential drivers of CH4 variability are investigated using the TM5 global chemistry model. The contribution that each driver had to the global CH4 variability during the period 1990 to 1995 is quantified. We find that a decrease of 8-10 ppb yr-1 CH4 is explained by a combination of the above processes. However, the timing of the minimum growth rate is found 6-9 months later than observed. The long-term decrease in CH4 growth rate over the period 1990 to 1995 is well captured and can be attributed to an increase in OH concentrations over this time period. Potential uncertainties in our modelled CH4 growth rate include emissions of CH4 from wetlands, biomass burning emissions of CH4 and other compounds, biogenic NMVOC and the sensitivity of OH to NMVOC emission changes. Two inventories are used for CH4 emissions from wetlands, ORCHIDEE and LPJ, to investigate the role of uncertainties in these emissions. Although the higher climate sensitivity of ORCHIDEE improves the simulated CH4 growth rate change after Pinatubo, none of the two inventories properly captures the observed CH4 variability in this period.

  13. Variability and budget of CO2 in Europe: analysis of the CAATER airborne campaigns - Part 1: Observed variability

    NASA Astrophysics Data System (ADS)

    Xueref-Remy, I.; Messager, C.; Filippi, D.; Nedelec, P.; Ramonet, M.; Paris, J. D.; Ciais, P.

    2010-02-01

    Atmospheric airborne measurements of CO2 are very well-suited to estimate the time varying distribution of carbon sources and sinks at the regional scale. We present here an analysis of two cross-European airborne campaigns that have been carried out on 23-26 May 2001 (CAATER 1) and 2-3 October 2002 (CAATER 2) over Western Europe. The area covered during CAATER 1 (respectively CAATER 2) was comprised between longitude 4° W to 14° E and latitude 44° N to 52° N (respectively longitude 1° E to 17° E and latitude 46° N to 52° N). High precision in-situ CO2, CO and Radon 222 measurements have been recorded. Flasks samples have been collected during both campaigns to cross-validate the in-situ data. During CAATER 1 (respectively CAATER 2), the mean CO2 concentration was 370.1±4 ppm (respectively 371.7±5 ppm). A HYSPLIT backtrajectories analysis shows that during CAATER 1, dominant winds were blowing from the north-west. In the planetary boundary layer (PBL) airmasses got contaminated over Benelux and Western Germany by pollution from these high urbanized areas, reaching about 380 ppm. Air masses passing over rural areas are depleted in CO2 because of the photosynthesis activity of the land cover vegetation, as low as 355 ppm. During CAATER 2, the backtrajectory analysis shows that airmasses were distributed among the 4 sectors. Airmasses got enriched in CO2 and CO when passing above polluted spots in Germany but also in Poland, as these countries are known to hold part of the most polluting plants based on coal consumption, the so-called "dirty thirty" from WWF. Simultaneous measurements of in-situ CO2 and CO combined to backtrajectories helped us to discriminate the role of fossil fuel emissions from over CO2 sources. The ?CO/?CO2 ratios (R2=0.33 to 0.88, slopes=2.42 to 10.37), calculated for polluted airmasses originating from different countries/regions, matched quite well national inventories, showing that the airborne measurements can help to identify the role of fossil fuel sources even several days/hundreds of kms further in the PBL. CO2 observations have been compared to surrounding ground stations measurements, confirming that the stations located near the ground (ex. CBW, WES, HUN) are representative of the local scale, while those located in the free troposphere (FT) are representative of atmospheric CO2 on a regional scale of a few hundred kilometers (ex. CMN). Stations located several 100 km away measure CO2 concentrations different from a few ppm, indicating the existence of a gradient of a few ppm in the free troposphere. Observations at stations located on top of small mountains (ex. SCH, PUY) match or not the airborne data whether they sample air from the FT or air coming up from the valley. Finally, the analysis of the CO2 vertical variability conducted on the 14 profiles recorded per campaign shows that is at least 5 to 8 times higher in the PBL (4 ppm and 5.7 ppm for CAATER 1 and CAATER 2, respectively) than in the FT (0.5 ppm and 1.1 ppm for CAATER 1 and CAATER 2, respectively). The CO2 jump between the PBL and the FT equals 3.7 ppm for the first campaign and -0.3 ppm for the second campaign. A very striking zonal CO2 gradient of about 11 ppm could be observed in the mid-troposphere during CAATER 2, with higher concentrations in the West than in the East. This gradient could originate from differences in atmospheric mixing, ground emission rates or a earlier beginning of the Fall in the west. More airborne campaigns are currently under analysis in the framework of the CARBOEUROPE-IP project to better assess the role of these different hypothesis. In a companion paper (Xueref-Remy et al., 2010), a comparison of vertical profiles from observations and several modeling frameworks is conducted for both campaigns. An attempt to calculate CO2 fluxes during CAATER 1 using CO2 and Radon-222 observations and modeling tools is also carried out.

  14. Observed interannual variability of near-surface salinity in the Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Pant, Vimlesh; Girishkumar, M. S.; Udaya Bhaskar, T. V. S.; Ravichandran, M.; Papa, Fabrice; Thangaprakash, V. P.

    2015-05-01

    An in situ gridded data of salinity, comprising Argo and CTD profiles, has been used to study the interannual variability of near-surface salinity (within 30 m from sea surface) in the Bay of Bengal (BoB) during the years 2005-2013. In addition to the broad agreement with earlier studies on the north-to-south gradient of surface salinity and general features of seasonal variability of salinity, the data also revealed few episodes of enhanced freshening in the BoB. The observations showed distinct anomalous low salinity (< 2 psu) waters in the northern BoB during June-February of the years 2006-2007 (Y67), 2011-2012 (Y12), and 2012-2013 (Y23). The anomalous freshening during these years showed similar life cycle, such as, it starts in the northern BoB during July-September of current summer and extends up to February-March of next winter with a southward propagation. Analysis showed that the oceanic and atmospheric conditions associated with positive Indian Ocean Dipole (pIOD) lead to these freshening events, and IOD rather than El Niño/Southern Oscillation (ENSO) controls the interannual variability of salinity in the BoB. The mixed layer salt budget analysis indicated the dominant role of local fresh water flux (horizontal advection) on the observed salinity tendency during summer (winter) monsoon season. Enhanced precipitation associated with pIOD lead to enhanced freshening in northern BoB during June-September, which remained to this region with prevailing summer monsoon circulation. The weakening or absence of southward east India coastal current (EICC) during October-December of these freshening years trapped anomalous freshwater in the northern BoB.

  15. Observational Sensitivity to Climate Variability using AIRS/Aqua and MERRA

    NASA Astrophysics Data System (ADS)

    Hearty, T. J.; Fetzer, E.; Tian, B.; Yung, Y. L.; Vollmer, B.; Savtchenko, A. K.; Smith, P. M.; Theobald, M.; Ostrenga, D.

    2011-12-01

    The El Nino Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) are two of the largest climate variabilities seen in AIRS observations of temperature, water vapor, and clouds. Numerous climate feedbacks are involved in these oscillations. We examine these oscillations using observations from the Atmospheric Infrared Sounder (AIRS) and the Modern Era Retrospective-Analysis for Research and Applications (MERRA). Since sampling can be an issue for infrared satellites in low earth orbit, we examine the MERRA data sampled at the AIRS space-time locations both with and without the AIRS quality control. We estimate the sampling bias of an AIRS climatology and the atmospheric conditions where AIRS has a lower sampling rate and examine the apparent differences in the ENSO and NAO based on the different sampling. While the AIRS temperature and water vapor sampling biases are small at low latitudes, they can be more than a few degrees in temperature and 10 percent in water vapor at higher latitudes. While these numbers are small they can be important for understanding climate variability.

  16. Monitoring Atlantic overturning circulation variability with GRACE-type ocean bottom pressure observations - a sensitivity study

    NASA Astrophysics Data System (ADS)

    Bentel, K.; Landerer, F. W.; Boening, C.

    2015-08-01

    The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism for large-scale northward heat transport and thus plays an important role for global climate. Relatively warm water is transported northward in the upper layers of the North Atlantic Ocean, and after cooling at subpolar latitudes, sinks down and is transported back south in the deeper limb of the AMOC. The utility of in-situ ocean bottom pressure (OBP) observations to infer AMOC changes at single latitudes has been characterized in recent literature using output from ocean models. We extend the analysis and examine the utility of space-based observations of time-variable gravity and the inversion for ocean bottom pressure to monitor AMOC changes and variability between 20 and 60° N. Consistent with previous results, we find a strong correlation between the AMOC signal and OBP variations, mainly along the western slope of the Atlantic basin. We then use synthetic OBP data - smoothed and filtered to resemble the resolution of the GRACE gravity mission - and reconstruct geostrophic AMOC transport. Due to the coarse resolution of GRACE-like OBP fields, we find that leakage of signal across the step slopes of the ocean basin is a significant challenge at certain latitudes. However, overall, the inter-annual AMOC anomaly time series can be recovered from 20 years of monthly GRACE-like OBP fields with errors less than 1 Sverdrup.

  17. SABER Observations of the OH Meinel Airglow Variability Near the Mesopause

    NASA Technical Reports Server (NTRS)

    Marsh, Daniel R.; Smith, Anne K.; Mlynczak, Martin G.

    2005-01-01

    The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, one of four on board the TIMED satellite, observes the OH Meinel emission at 2.0 m that peaks near the mesopause. The emission results from reactions between members of the oxygen and hydrogen chemical families that can be significantly affected by mesopause dynamics. In this study we compare SABER measurements of OH Meinel emission rates and temperatures with predictions from a 3-dimensional chemical dynamical model. In general, the model is capable of reproducing both the observed diurnal and seasonal OH Meinel emission variability. The results indicate that the diurnal tide has a large effect on the overall magnitude and temporal variation of the emission in low latitudes. This tidal variability is so dominant that the seasonal cycle in the nighttime emission depends very strongly on the local time of the analysis. At higher latitudes, the emission has an annual cycle that is due mainly to transport of oxygen by the seasonally reversing mean circulation.

  18. Lack of uniform trends but increasing spatial variability in observed Indian rainfall extremes

    SciTech Connect

    Ghosh, Subimal; Das, Debasish; Kao, Shih-Chieh; Ganguly, Auroop R

    2012-01-01

    Recent studies disagree on how rainfall extremes over India have changed in space and time over the past half century, as well as on whether the changes observed are due to global warming or regional urbanization. Although a uniform and consistent decrease in moderate rainfall has been reported, a lack of agreement about trends in heavy rainfall may be due in part to differences in the characterization and spatial averaging of extremes. Here we use extreme value theory to examine trends in Indian rainfall over the past half century in the context of long-term, low-frequency variability.We show that when generalized extreme value theory is applied to annual maximum rainfall over India, no statistically significant spatially uniform trends are observed, in agreement with previous studies using different approaches. Furthermore, our space time regression analysis of the return levels points to increasing spatial variability of rainfall extremes over India. Our findings highlight the need for systematic examination of global versus regional drivers of trends in Indian rainfall extremes, and may help to inform flood hazard preparedness and water resource management in the region.

  19. X-ray observations of a large sample of cataclysmic variable stars using the Einstein Observatory

    NASA Technical Reports Server (NTRS)

    Cordova, F. A.; Mason, K. O.

    1984-01-01

    This paper presents the results of an X-ray survey of 31 known or suspected cataclysmic variables. Eighteen of these close binary systems are detected with inferred luminosities in the 0.1-4.0 keV band of between 10 to the 30th and 10 to the 32nd erg/sec. The majority have relatively hard X-ray spectra (kT greater than 2 keV) irrespective of luminosity state. Of seven dwarf novae observed during optical outbursts only U Gem exhibited enhanced ultrasoft X-ray emission (kT of about 10 eV) in addition to weak, hard X-ray emission. Variability of the X-ray flux is observed in many of these stars, on time-scales ranging from tens of seconds to hours. The contribution to the flux from extended X-ray emission is investigated for SU UMa and GK Per. Several possibilities for the origin of the hard X-rays are considered.

  20. Quantifying the diurnal variability of deep convection in the Congo basin using satellite observations, global and regional models.

    NASA Astrophysics Data System (ADS)

    White, Bethan; Kipling, Zak; Taylor, Sarah; Stier, Philip

    2015-04-01

    Convection transports moisture, momentum, heat and aerosols through the troposphere, and so the temporal variability of convection is a major driver of global weather and climate. The diurnal cycle of convection is associated with large variations in solar forcing and the ability of models to represent this cycle shows how well they represent radiative transfer and surface heat exchanges, as well as boundary layer, convective and cloud processes. Global models and some numerical weather prediction (NWP) models fail to capture the observed diurnal cycle of convection (Yang and Slingo, 2001; Stratton and Stirling, 2012), while the ability of cloud-resolving models (CRMs) to represent the diurnal cycle is strongly dependent on horizontal resolution. The Congo basin is home to some of the most intense convective activity on the planet, yet has been the focus of very few previous studies, especially when compared to the neighbouring, relatively well-understood West African climate system. Ground-based observations of convection and precipitation in the Congo region are sparse, and there has been a sharp decline in the number of rain gauges in the region over the past few decades (Washington, 2013). In this study we use a variety of tools to quantify the diurnal cycle of deep convection over the Congo including satellite observations, a global model both with and without a new convective parameterisation, and a regional convection-permitting model. This approach allows us to evaluate our simulations despite the lack of in-situ observational data. In contrast to the static picture provided by polar-orbiting satellites, the geostationary SEVIRI instrument provides continuous, high time resolution observations of cloud properties over a large area. It has the additional advantage of providing coverage of the Congo Basin, at a spatial resolution of between 3 and 5km. The CLAAS (Cloud Property Dataset Using SEVIRI) product is used to quantify the diurnal cycle of convective cloud top temperatures across the region. In global models, the mass-flux convection parameterisations commonly used limit our ability to represent the microphysics of convective clouds. We use ECHAM both with and without a new parameterisation (CCFM, the Convective Cloud Field Model), which represents a spectrum of convective updraughts in each grid box, allowing the microphysics to take account of the explicitly-simulated distributions of cloud area, cloud height and vertical velocity. High-resolution convection-permitting simulations are performed with the WRF model using a 2-moment bulk microphysics scheme. We quantify the diurnal cycle of convection and precipitation in the region on timescales much longer than those usually studied with high-resolution models. In addition, the use of CCFM in the global model allows us to compare the frequency distribution of convective precipitation rates in ECHAM with those from WRF. Comparing data from satellite observations, global and high-resolution models enables us to quantify the diurnal variability of deep convection in the Congo basin and evaluate our results against observations, providing a more comprehensive analysis of the diurnal cycle than has previously been shown, and also giving new insight into a region that has previously seen little investigation.

  1. Spurious One-Month and One-Year Periods in Visual Observations of Variable Stars

    NASA Astrophysics Data System (ADS)

    Percy, J. R.

    2015-12-01

    Visual observations of variable stars, when time-series analyzed with some algorithms such as DC-DFT in vstar, show spurious periods at or close to one synodic month (29.5306 days), and also at about a year, with an amplitude of typically a few hundredths of a magnitude. The one-year periods have been attributed to the Ceraski effect, which was believed to be a physiological effect of the visual observing process. This paper reports on time-series analysis, using DC-DFT in vstar, of visual observations (and in some cases, V observations) of a large number of stars in the AAVSO International Database, initially to investigate the one-month periods. The results suggest that both the one-month and one-year periods are actually due to aliasing of the stars' very low-frequency variations, though they do not rule out very low-amplitude signals (typically 0.01 to 0.02 magnitude) which may be due to a different process, such as a physiological one. Most or all of these aliasing effects may be avoided by using a different algorithm, which takes explicit account of the window function of the data, and/or by being fully aware of the possible presence of and aliasing by very low-frequency variations.

  2. Observation of oligotrophic gyre variability in the south Indian Ocean: Environmental forcing and biological response

    NASA Astrophysics Data System (ADS)

    Jena, Babula; Sahu, Shanghamitra; Avinash, Kumar; Swain, Debadatta

    2013-10-01

    Expansion of oligotrophic ocean gyre and widespread reduction of phytoplankton biomass will have severe environmental and ecological effect since phytoplankton accounts for half of the global primary production, which forms the trophic base for marine ecosystem. Analysis of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) derived chlorophyll-a (Chl-a) datasets (1998-2010) suggested significant expansion of South Indian Ocean oligotrophic gyre (SOG) at average annual rate of 4.46%/yr (r=0.66, p=0.013). The annual trend of SOG expansion was accompanied with the significantly declining trend of Chl-a concentration (-1.36%/yr, or -0.0007±0.0001 mg m-3/yr, r=0.76, p=0.002). Environmental parameters such as sea surface temperature (SST) and meridional wind stress (?y) were found to be the most accountable factors controlling the variability of Chl-a/gyre area. Nevertheless, SST was the dominant predictor of biological response (explains more than 60% of Chl-a variability). This study suggests that the observed trend of SOG expansion and accompanied decline in Chl-a concentration is principally due to SST warming (0.05±0.01 °C/yr, r=0.83, p=0.0008) and weakening of wind stress (?) mainly meridional wind stress component, ?y (-0012 Pa/yr, r=0.86, p=0.004). Additionally, the SST trend map showed more than 80% of the SOG area is warming significantly under circumstance of overall gain of net heat flux by the sea surface. Analysis of these climate variables suggests decreased mixing and enhanced stratification in the SOG which reduces nutrient supply to sunlit zone; consequently resulting in low phytoplankton biomass, and gyre expansion. In addition, the sea-level rise observed in SOG (0.48±0.05 cm/yr) is much higher than the global estimates (0.18±0.05 cm/yr) reported in the Intergovernmental Panel on Climate Change report, 2007. The variability in Chl-a concentration was also studied with respect to leading climate oscillators.

  3. Aerosol variability and atmospheric transport in the Himalayan region from CALIOP 2007-2010 observations

    NASA Astrophysics Data System (ADS)

    Bucci, S.; Cagnazzo, C.; Cairo, F.; Di Liberto, L.; Fierli, F.

    2014-05-01

    This work quantifies the spatial distribution of different aerosol types, their seasonal variability and sources.The analysis of four years of CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) vertically resolved aerosol data allows the identification of spatial patterns of desert dust and carbonaceous particles in different atmospheric layers. Clusters of Lagrangian back trajectories highlight the transport pathways from source regions during the dusty spring season. The analysis shows a prevalence of dust; at low heights it occurs frequently (up to 70% of available observations) and is distributed north of the Tibetan Plateau with a main contribution from the Gobi and Taklamakan deserts, and west of the Tibetan Plateau, originating from the deserts of southwest Asia and advected by the Westerlies. Above the Himalayas the dust amount is minor but still not negligible (occurrence around 20%) and mainly affected by the transport from more distant deserts sources (Sahara and Arabian Peninsula). Carbonaceous aerosol, produced mainly in northern India and eastern China, is subject to shorter-range transport and is indeed observed closer to the sources, while there is a limited amount reaching the top of the plateau. Data analysis reveals a clear seasonal variability in the frequencies of occurrence for the main aerosol types; dust is regulated principally by the monsoon dynamics, with maximal occurrence in spring. We also highlight relevant interannual differences, showing a larger presence of aerosol in the region during 2007 and 2008. The characterization of the aerosol spatial and temporal distribution in terms of observational frequency is a key piece of information that can be directly used for the evaluation of global aerosol models.

  4. Observing Tropospheric Chemistry and Climate Variables from Geostationary Orbit With SIRAS-G

    NASA Astrophysics Data System (ADS)

    Johnson, B. R.; Kampe, T. U.

    2005-12-01

    Understanding the impact of pollution on regional, continental, and global scales imposes unique challenges for spaceborne observations. The variability in tropospheric chemistry, source strengths, and transport results in sub-hourly temporal variation, and produces small-scale variations in the vertical and horizontal distribution of trace gases. Current spaceborne observation from low earth orbit have demonstrated the capability to measure tropospheric trace gases from space but are limited to a twice daily observation. Improving the depiction of diurnal variations requires observations from geosynchronous orbit. The Spaceborne Infrared Atmospheric Sounder from Geosynchronous Earth Orbit (SIRAS-G) is being developed under the NASA Instrument Incubator Program to meet this need. SIRAS-G will enable high temporal, spatial, and spectral resolution observations of temperature, water, ozone, aerosol, cloud and surface properties, and important trace gas concentrations such as CO, CH4, N2O and SO2. The spaceborne instrument concept measures thermal emission in 2048 spectral channels over the wavelength range from 3.75 to 15 microns with a nominal resolving power of 1400. The constraints imposed on instrument mass, power and volume by a geosynchronous mission drives the instrument design toward more compact, and less complex optical systems. The system employs a wide field-of-view hyperspectral infrared optical system that splits incoming radiation to four separate grating spectrometer channels. Combined with large 2-D infrared detector arrays, this system provides simultaneous high-resolution spectral and spatial imaging over a large region with a nominal 4x4 km ground resolution. The longer observation times from geosynchronous orbit enable the necessary high signal to noise. However, the longer integration time makes the sensor more sensitive to slowly varying platform motion or mechanical disturbances generated by the instrument or spacecraft subsystems. This leads to a spectral registration problem for imaging filter wheel radiometers or Fourier transform spectrometer. The imaging grating spectrometer, by virtue of its simultaneous collection of spectral information, is significantly less sensitive to disturbances.

  5. Observation of X-ray variability in the BL Lac object 1ES1959+65

    E-print Network

    Berrie Giebels; Elliott D. Bloom; Warren Focke; Gary Godfrey; Greg Madejski; Kaice T. Reilly; Pablo M. Saz Parkinson; Ganya Shabad; Reba M. Bandyopadhyay; Gilbert G. Fritz; Paul Hertz; Michael P. Kowalski; Michael P. Kowalski; Michael N. Lovellette; Paul S. Ray; Michael T. Wolff; Kent S. Wood; Daryl J. Yentis; Jeffrey D. Scargle

    2002-03-20

    This paper reports X-ray spectral observations of a relatively nearby z = 0.048 BL Lacertae (BL Lac) object 1ES1959+650, which is a potential TeV emitter. The observations include 31 short pointings made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS), and 17 pointings by the PCA on board the Rossi X-ray Timing Explorer (RXTE). Most of these observations were spaced by less than 1 day. \\es was detected by the ARGOS USA detector in the range 1-16 keV, and by the PCA in the 2-16 keV range but at different times. During the closely spaced RXTE observations beginning on 2000 July 28, an ending of one flare and a start of another are visible, associated with spectral changes, where the photon index Gamma ranges between ~ 1.4 and 1.7, and the spectrum is harder when the source is brighter. This implies that 1ES1959 is an XBL-type blazar, with the X-ray emission likely to originate via the synchrotron process. The USA observations reveal another flare that peaked on 2000 November 14 and doubled the flux within a few days, again associated with spectral changes of the same form. The spectral variability correlated with the flux and timing characteristics of this object that are similar to those of other nearby BL Lacs, and suggest relativistic beaming with a Doppler factor delta > 1.6 and magnetic fields of the order of a few mG. We also suggest that the steady component of the X-ray emission -- present in this object as well as in other XBLs -- may be due to the large-scale relativistic jet (such as measured by Chandra in many radio-loud AGN), but pointing very closely to our line of sight.

  6. A Decade of Growth

    NASA Technical Reports Server (NTRS)

    Johnson, Nicholas L.; Anzz-Meador, Phillip D.

    2001-01-01

    This paper examines the Space Surveillance Network catalog's growth in low Earth orbit (LEO) and the geosynchronous Earth orbit (GEO) over the decade 1990-2000. During this time, innovative space utilization concepts, e.g. the Iridium and Globalstar commercial communication satellite constellations, have increased the public's consciousness of space. At the same time, however, these constellations have increased spatial density per 10 km altitude bin by factors of two and three respectively. While not displaying as spectacular a growth in spatial density, other regions of space have grown steadily in terms of number, mass, size, and operational lifetime. In this work we categorize launch traffic by type (e.g. payload, rocket body, operational debris, fragmentation debris, or anomalous debris), mass, and size so as to present the observed growth numerically, in terms of mass, and in terms of cross-sectional area. GEO traffic is further categorized by operational longitude. Because growth itself defines only the instantaneous environment, we also examine the higher-order derivatives of growth. In addition, we compare the last decade's growth with modeling results to illustrate the subtle effects of inclination, eccentricity, and size, in addition to spatial densities, on estimating the collision probability. We identify those regions of space most subject to accidental collision.

  7. The response of glaciers to intrinsic climate variability: observations and models of late-Holocene variations in the

    E-print Network

    Roe, Gerard

    The response of glaciers to intrinsic climate variability: observations and models of late glacier variations due to natural climate variability and those due to true climate change is crucial for the interpretation and attribution of past glacier changes, and for the expectations of future changes. We explore

  8. PACIFIC DECADAL VARIABILITY: STRUCTURE AND MECHANISMS

    E-print Network

    Maryland at College Park, University of

    tests and/or correlations with non-physical data, say, biological productivity. Expectation of ocean-atmosphere data sets; the analysis will be designed such that all major modes of Pacific low the influence of SST anomalies on local and remote near-surface circulation and fluxes at different stages

  9. Simulated and observed trends in key variables of the Arctic marine carbon cycle

    NASA Astrophysics Data System (ADS)

    Goris, Nadine; Heinze, Christoph; Lauvset, Siv; Petrenko, Dmitry; Pozdnyakov, Dmitry; Schwinger, Jörg

    2013-04-01

    For the Arctic region, a thorough monitoring of the marine carbon cycle is important, as the general "polar amplification" of climate change also translates into the biogeochemical realm. As compared to the global ocean, the sink for human-produced CO2 is fairly small in the Arctic Ocean itself. Nevertheless, it is important to follow up this Arctic sink as a further control of the regional carbon budget and to record changes in the marine carbon cycle on the way towards a "blue Arctic". Since observations on the Arctic are rare, the EU FP7 MONARCH-A project tries to enable adequate descriptions of the status and evolution of the Arctic region Earth system components by generating time series of observation datasets and model hindcasts. In terms of the marine carbon cycle, this analysis focuses mainly on the key variables pCO2 and primary productivity. For oceanic pCO2, the comprehensive data-sets SOCAT and LDEO were combined, while measurements of atmospheric CO2 were collected from the GLOBALVIEW-CO2 data integration project. Monthly Primary Production fields were retrieved from the sensors MODIS and SeaWiFs. In order to get an overall picture of the behavior and trends of those key variables, in addition the physical-biogeochemical model MICOM-HAMOCC-M was employed. The investigation showed that both oceanic and atmospheric pCO2 are consistent variables which have a regular annual cycle and a similar behaviour all over the Arctic for both model and data. In contrast, primary production shows an irregular annual cycle in both range and form, varying over the Arctic. While a few well distributed measurement stations with continuous observations are sufficient to get a comprehensive picture for consistent variables like pCO2, it is relatively difficult and costly to get a comprehensive record of non-consistent variables. Since the provided data-set for primary production covers a relatively short time-scale, it was neither possible to confidently validate the model nor to determine significant trends. Widespread measurements for at least 40 years are needed to capture both different regional behavior and associated trends stressing the value of the existing spatially comprehensive Arctic datasets of primary production and the importance of continuing the sensor-retrievals in the following years. The measurement stations of atmospheric CO2 provide a good characterization of CO2 with continuous measurement on a few, well distributed locations and allow for a confident data-model comparison all over the Arctic, while the coverage of the LDEO/SOCAT database allows for confident statements about the trends of oceanic pCO2 in the region between 60oW and 30oE. Here, the validated model MICOM-HAMOCC-M simulates a fast rising oceanic CO2 partial pressure leading to an accelerated decrease in ocean CO2 uptake in the Arctic.

  10. Detecting and Interpreting Variable Interactions in Observational Ornithology Data Daria Sorokina, Rich Caruana, Mirek Riedewald, Wesley M. Hochachka, Steve Kelling

    E-print Network

    Riedewald, Mirek

    Detecting and Interpreting Variable Interactions in Observational Ornithology Data Daria Sorokina University, Boston, MA. mirek@ccs.neu.edu §Cornell Lab of Ornithology, Ithaca, NY. {wmh6, stk2}@cornell

  11. ROSAT observations of cataclysmic variables: A search for the boundary layer emission

    NASA Technical Reports Server (NTRS)

    Vrtilek, S. D.; Silber, A.; Raymond, J. C.; Patterson, J.

    1994-01-01

    Many cataclysmic variables (CVs) and low-mass X-ray binaries show He II line emission at wavelength 1640 and wavelength 4686. As recombination lines of an ion requiring 55 eV for ionization, these lines cannot be attributed to gravitational heating in the disk but could be due to reprocessed 55-280 eV X-rays which may be produced in a boundary layer at the disk/star surface. We undertook a search for this soft component using the Positon Sensitve Proportional Counter (PSPC) on ROSAT. The photon fluxes we observe are not sufficient to produce the He II wavelength 1640 fluxes observed by IUE. If we assume that the X-ray luminosity is due to emission from a boundary layer, then the observed quiescent luminosity is one-quarter of the total accretion luminosity as determined by optical and ultraviolet observations rather than the one-half that is predicted by some theories. An additional very soft component (e.g. an approximately equal 10-20 eV blackbody) could provide sufficient photons in the 0.055-0.100 keV band to produce the observed He II fluxes and contribute the additional luminosity from the boundary layer while remaining hidden to the PSPC and IUE. Alternatively, the high He II line fluxes could be evidence for high-temperature collisionally ionized material. We also find evidence for line emission at approximately equal 0.9 keV consistent with L-shell emission from highly ionized iron.

  12. HST/STIS observation of Ganymede's aurora: Investigating the variability of the auroral ovals

    NASA Astrophysics Data System (ADS)

    Musacchio, Fabrizio; Saur, Joachim; Roth, Lorenz; Duling, Stefan; Feldman, Paul D.; Strobel, Darrell F.; Retherford, Kurt D.; McGrath, Melissa A.

    2014-05-01

    We analyze the variability of Ganymede's FUV auroral ovals using spectral images acquired during two visits in 2010 and 2011 with Hubble's Space Telescope Imaging Spectrograph (HST/STIS) when Ganymede was at eastern elongation. The observed electron-impact-excited auroral emissions from Ganymede's O2 atmosphere are thought to be driven by electron acceleration by strong field-aligned currents at the separatrix, i.e., at the boundary area between open and closed magnetic field lines of Ganymede's mini-magnetosphere. The location of the auroral ovals correlates with the intersection of this separatrix and the satellite's surface and therefore strongly depends on the interaction between Ganymede's magnetic field and atmosphere with the local time-variable plasma environment. In our study we particularly analyze the latitudinal positions of the auroral ovals in order to better understand the correlation with the plasma environment. The HST campaign was designed such that the full range of Ganymede's magnetic-latitudinal positions within Jupiter's current sheet is covered. We provide a mapping of auroral emission distribution and study the auroral brightness as a function of Ganymede's position in Jupiter's magnetosphere.

  13. The Geminga Pulsar: Soft X-Ray Variability and an EUVE Observation

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.; Martin, Christopher; Marshall, Herman L.; Oliversen, Ronald (Technical Monitor)

    2001-01-01

    We observed the Geminga pulsar with the EUVE satellite, detecting pulsed emission in the Deep Survey imager. Joint spectral fits of the EUVE flux with ROSAT PSPC data are consistent with thermal plus power-law models in which the thermal component makes the dominant contribution to the soft X-ray flux seen by EUVE and ROSAT. The data are consistent with blackbody emission of T = (4 - 6) x 10(exp 5) K over most of the surface of the star at the measured parallax distance of 160 pc. Although model atmospheres are more realistic, and can fit the data with effective temperatures a factor of 2 lower, current data would not discriminate between these and blackbody models. We also find evidence for variability of Geminga's soft X-ray pulse shape. Narrow dips in the light curve that were present in 1991 had largely disappeared in 1993/1994, causing the pulsed fraction to decline from 32% to 18%. If the dips are attributed to cyclotron resonance scattering by an e1 plasma on closed magnetic field lines, then the process that resupplies that plasma must be variable.

  14. The Geminga Pulsar: Soft X-Ray Variability and an EUVE Observation

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.; Martin, Christopher; Marshall, Herman L.

    1996-01-01

    We observed the Geminga pulsar with the EUVE satellite, detecting pulsed emission in the Deep Survey imager. Joint spectral fits of the EUVE flux with ROSAT PSPC data are consistent with thermal plus power-law models in which the thermal component makes the dominant contribution to the soft X-ray flux seen by EUVE and ROSAT. The data are consistent with blackbody emission of T = (4-6) x 10(exp 5) K over most of the surface of the star at the measured parallax distance of 160 pc. Although model atmospheres are more realistic, and can fit the data with effective temperatures a factor of 2 lower, current data would not discriminate between these and blackbody models. We also find evidence for variability of Geminga's soft X-ray pulse shape. Narrow dips in the light curve that were present in 1991 had largely disappeared in 1993/1994, causing the pulsed fraction to decline from 32% to 18%. If the dips are attributed to cyclotron resonance scattering by an e(+/-) plasma on closed magnetic field lines, then the process that resupplies that plasma must be variable.

  15. An observational study of ice effects on Nelson River estuarine variability, Hudson Bay, Canada

    NASA Astrophysics Data System (ADS)

    Wang, Ruixue; McCullough, Greg K.; Gunn, Geoffrey G.; Hochheim, Klaus P.; Dorostkar, Abbas; Sydor, Kevin; Barber, David G.

    2012-09-01

    Many estuaries in high latitude regions are subjected to seasonally ice-covered conditions. However, ice effects on estuarine variability have received limited scientific attention and remain poorly understood. In this paper, an 11-month mooring record is used to examine seasonal variation of estuarine hydrodynamics in the Nelson River estuary (NRE), Hudson Bay (HB), in northern Canada. We show that ice cover strongly affects tidal amplitudes, velocities and phases in the NRE. In the mid-winter, the M2 tidal amplitude and consequently the tidal range are significantly reduced due to under-ice friction in HB, while conversely the M2 tidal velocity is amplified due to reduction of cross-section of the channel by formation of fast ice. A stronger surface seaward residual flow observed in the winter indicates that the formation of fast ice could also enhance the residual circulation. Suspended sediment concentration in the river mouth is reduced, also possibly due to the formation of fast ice that protects shallow nearshore shoals from erosion. This study demonstrates the importance of ice effects on estuarine variability and the complexity of processes in a seasonally ice-covered estuary.

  16. Ultraviolet, visual, and infrared observations of the WC7 variable HD 193793

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, E. L.; Savage, B. D.; Sitko, M. L.

    1982-01-01

    Low-resolution IUE data are used to explore the ultraviolet extinction toward the Wolf-Rayet star HD 193793 and to search for ultraviolet variability that might relate to the infrared variability. High-dispersion IUE observations are used to investigate the nature of the stellar wind of the star and to search for anomalies in the interstellar line spectrum that might be expected to be found toward a star that has recently formed a dust shell. Finally, the ultraviolet and new visual and infrared data are combined to investigate the full energy distribution of this unusual source. The energy distribution is found to extend from 0.12 to 12.5 microns, and the ultraviolet data suggest a normal WC-7 type star. A wind terminal speed of about 3000 km/s is implied by the data, as well as an E(B-V) value of 0.85. The dereddened ultraviolet to visual energy distribution is consistent with a star having effective temperature of about 43,000 K.

  17. Implication of observed cloud variability for parameterizations of microphysical and radiative transfer processes in climate models

    NASA Astrophysics Data System (ADS)

    Huang, D.; Liu, Y.

    2014-12-01

    The effects of subgrid cloud variability on grid-average microphysical rates and radiative fluxes are examined by use of long-term retrieval products at the Tropical West Pacific (TWP), Southern Great Plains (SGP), and North Slope of Alaska (NSA) sites of the Department of Energy's Atmospheric Radiation Measurement (ARM) Program. Four commonly used distribution functions, the truncated Gaussian, Gamma, lognormal, and Weibull distributions, are constrained to have the same mean and standard deviation as observed cloud liquid water content. The PDFs are then used to upscale relevant physical processes to obtain grid-average process rates. It is found that the truncated Gaussian representation results in up to 30% mean bias in autoconversion rate whereas the mean bias for the lognormal representation is about 10%. The Gamma and Weibull distribution function performs the best for the grid-average autoconversion rate with the mean relative bias less than 5%. For radiative fluxes, the lognormal and truncated Gaussian representations perform better than the Gamma and Weibull representations. The results show that the optimal choice of subgrid cloud distribution function depends on the nonlinearity of the process of interest and thus there is no single distribution function that works best for all parameterizations. Examination of the scale (window size) dependence of the mean bias indicates that the bias in grid-average process rates monotonically increases with increasing window sizes, suggesting the increasing importance of subgrid variability with increasing grid sizes.

  18. Interannual variability of the regional CO2 and CH4 fluxes estimated with GOSAT observations

    NASA Astrophysics Data System (ADS)

    Maksyutov, Shamil; Takagi, Hiroshi; Kim, Heon-Sook; Saito, Makoto; Mabuchi, Kazuo; Matsunaga, Tsuneo; Ito, Akihiko; Belikov, Dmitry; Oda, Tomohiro; Valsala, Vinu; Morino, Isamu; Yoshida, Yukio; Yokota, Tatsuya

    2014-05-01

    GOSAT Level 4 products - monthly regional surface flux estimates by inverse modeling from CO2 and CH4 GOSAT column-averaged mixing ratios and ground-based observational data using a global atmospheric transport model - have been updated recently to cover the 2-year period starting June 2009. This temporal extension provides look at the interannual flux variability including events of CO2 and CH4 emissions from a large-scale climate anomaly and resultant forest fires in Russia in 2010. Higher emissions of CO2 and CH4 in western Russia in the summer of 2010 are estimated when GOSAT observations are also included in the inverse modeling compared to just using ground-based data. The estimated summer emissions in 2010 are also higher than in the same season of the adjacent years. GOSAT compliments the ground-based networks by observing the concentration response to emissions closer to fire locations, resulting in the inverse models identifying emission regions more accurately. Elsewhere, GOSAT-aided flux estimates point to higher CH4 emissions (compared to ground-based only estimates) in the remote sub-tropical regions of the South America, Africa and South-East Asia. Higher emissions over South America can be attributed to biomass burning and anthropogenic sources, while in South-East Asia those are likely to be caused by agriculture and natural ecosystems.

  19. Time-Variable Gravity from Space: Quarter Century of Observations, Mysteries, and Prospects

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.

    2003-01-01

    Any large mass transport in the Earth system produces changes in the gravity field. Via the space geodetic technique of satellite-laser ranging in the last quarter century, the Earth s dynamic oblateness J2 (the lowest-degree harmonic component of the gravity field) has been observed to undergo a slight decrease - until around 1998, when it switched quite suddenly to an increase trend which has continued to date. The secular decrease in J2 has long been attributed primarily to the post-glacial rebound in the mantle; the present increase signifies an even larger change in global mass distribution whose J2 effect overshadows that of the post-glacial rebound, at least over interannual timescales. Intriguing evidences have been found in the ocean water distribution, especially in the extratropical Pacific basins, that may be responsible for this 52 change. New techniques based on satellite-to-satellite tracking will yield greatly improved observations for time-variable gravity, with much higher precision and spatial resolution @e., much higher harmonic degrees). The most important example is the GRACE mission launched in March 2002, following the success of the CHAMP mission. Such observations are becoming a new and powerful tool for remote sensing of geophysical fluid processes that involve larger-scale mass transports.

  20. Time-Variable Gravity from Space: Quarter Century of Observations, Mysteries, and Prospects

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.; Boy, John-Paul

    2003-01-01

    Any large mass transport in the Earth system produces changes in the gravity field. Via the space geodetic technique of satellite-laser ranging in the last quarter century, the Earth's dynamic oblateness J2 (the lowest-degree harmonic component of the gravity field) has been observed to undergo a slight decrease -- until around 1998, when it switched quite suddenly to an increase trend which has continued to 2001 before sharply turning back to the value which it is "supposed to be"!. The secular decrease in J2 has long been attributed primarily to the post-glacial rebound in the mantle; the present increase signifies an even larger change in global mass distribution whose J2 effect overshadows that of the post-glacial rebound, at least over interannual timescales. Intriguing evidences have been found in the ocean water distribution, especially in the extratropical Pacific basins, that may be responsible for this J2 change. New techniques based on satellite-to-satellite tracking will yield greatly improved observations for time-variable gravity, with much higher precision and spatial resolution (i.e., much higher harmonic degrees). The most important example is the GRACE mission launched in March 2002, following the success of the CHAMP mission. Such observations are becoming a new and powerful tool for remote sensing of geophysical fluid processes that involve larger-scale mass transports.

  1. Why weight? Modelling sample and observational level variability improves power in RNA-seq analyses

    PubMed Central

    Liu, Ruijie; Holik, Aliaksei Z.; Su, Shian; Jansz, Natasha; Chen, Kelan; Leong, Huei San; Blewitt, Marnie E.; Asselin-Labat, Marie-Liesse; Smyth, Gordon K.; Ritchie, Matthew E.

    2015-01-01

    Variations in sample quality are frequently encountered in small RNA-sequencing experiments, and pose a major challenge in a differential expression analysis. Removal of high variation samples reduces noise, but at a cost of reducing power, thus limiting our ability to detect biologically meaningful changes. Similarly, retaining these samples in the analysis may not reveal any statistically significant changes due to the higher noise level. A compromise is to use all available data, but to down-weight the observations from more variable samples. We describe a statistical approach that facilitates this by modelling heterogeneity at both the sample and observational levels as part of the differential expression analysis. At the sample level this is achieved by fitting a log-linear variance model that includes common sample-specific or group-specific parameters that are shared between genes. The estimated sample variance factors are then converted to weights and combined with observational level weights obtained from the mean–variance relationship of the log-counts-per-million using ‘voom’. A comprehensive analysis involving both simulations and experimental RNA-sequencing data demonstrates that this strategy leads to a universally more powerful analysis and fewer false discoveries when compared to conventional approaches. This methodology has wide application and is implemented in the open-source ‘limma’ package. PMID:25925576

  2. Long-period humidity variability in the Arctic atmosphere from upper-air observations

    NASA Astrophysics Data System (ADS)

    Agurenko, A.; Khokhlova, A.

    2014-12-01

    Under climate change, atmospheric water content also tends to change. This gives rise to changes in the amount of moisture transferred, clouds and precipitation, as well as in hydrological regime. This work analyzes seasonal climatic characteristics of precipitated water in the Arctic atmosphere, by using 1972-2011 data from 55 upper-air stations located north of 60°N. Regions of maximum and minimum mean values and variability trends are determined. In the summer, water amount is shown to increase in nearly the whole of the latitudinal zone. The comparison with the similar characteristics of reanalysis obtained by the other authors shows a good agreement. Time variation in the atmosphere moisture transport crossing 70°N, which is calculated from observation data, is presented and compared with model results. The work is supported by the joint EC ERA.Net RUS and Russian Fundamental Research Fund Project "Arctic Climate Processes Linked Through the Circulation of the Atmosphere" (ACPCA) (project 12-05-91656-???_?).

  3. XMM-NEWTON AND OPTICAL OBSERVATIONS OF CATACLYSMIC VARIABLES FROM THE SLOAN DIGITAL SKY SURVEY

    SciTech Connect

    Hilton, Eric J.; Szkody, Paula; Mukadam, Anjum; Henden, Arne; Dillon, William; Schmidt, Gary D. E-mail: szkody@astro.washington.edu

    2009-03-15

    We report on XMM-Newton and optical results for six cataclysmic variables that were selected from Sloan Digital Sky Survey (SDSS) spectra because they showed strong He II emission lines, indicative of being candidates for containing white dwarfs with strong magnetic fields. While high X-ray background rates prevented optimum results, we are able to confirm SDSS J233325.92+152222.1 as an intermediate polar from its strong pulse signature at 21 minutes and its obscured hard X-ray spectrum. Ground-based circular polarization and photometric observations were also able to confirm SDSS J142256.31 - 022108.1 as a polar with a period near 4 hr. Photometry of SDSS J083751.00+383012.5 and SDSS J093214.82+495054.7 solidifies the orbital period of the former as 3.18 hr and confirms the latter as a high-inclination system with deep eclipses.

  4. Interannual variability of the Mediterranean outflow observed in Espartel sill, western Strait of Gibraltar

    NASA Astrophysics Data System (ADS)

    GarcíA-Lafuente, J.; Delgado, J.; SáNchez RomáN, A.; Soto, J.; Carracedo, L.; DíAz Del RíO, G.

    2009-10-01

    Four-year time series of observations in Espartel sill at the western part of the Strait of Gibraltar have been analyzed in order to investigate the variability of the Mediterranean outflow. It is assumed that the observed variability comes from the changing properties of the dense waters that are located at the maximum depth from where they can be uplifted in the upstream basin (Alborán Sea, inside the Mediterranean Sea) and evacuated through the strait. From this perspective, the following three mechanisms are investigated: (1) the replenishment of the deep basin by newly formed Western Mediterranean Deep Water that, depending on its density, can either uplift old resident waters or lay above them leaving in any case a cold signature in the temperature series; (2) the presence/absence of the energetic anticyclonic gyres in the Alborán Sea, particularly the western one, which can transfer momentum to the underlying Mediterranean vein and provide it with additional energy to ascend over the sills of the strait; and (3) the meteorologically enhanced flows that follow the rapid changes of atmospheric pressure over the western Mediterranean basin, which would be able to aspire deeper waters residing in the upstream basin. The three mechanisms act on different timescales, from annual in case (1) to monthly in case (2) to weekly in case (3) although these two latter are modulated annually by the seasonal prevalence of the western Alborán gyre in summer and of the strong meteorologically driven fluctuations in winter. The mechanisms overlap at annual timescales making it difficult to separate out the different contributions.

  5. Trend and variability in observed hydrometeorological extremes in the Lake Victoria basin

    NASA Astrophysics Data System (ADS)

    Nyeko-Ogiramoi, P.; Willems, P.; Ngirane-Katashaya, G.

    2013-05-01

    SummaryIn the Lake Victoria basin hydrology, trend analysis has mainly been limited to the mean of the hydrological variable without explicit consideration of extremes, which are very crucial in understanding the behaviour of disastrous hydrometeorological events. Since the effects of climate change are unleashed, more through the occurrence of extremes, analysis of both monotonic and cyclic trends in hydrological extremes is very crucial. The presence of a significant linear trend, in a long-term hydrometeorological record of extremes, may provide evidence of a shift from the natural trend to that which is enhanced by, for example, anthropogenic forcing. In addition, cyclic trends analysis of hydrological extremes provides information on the cyclic behaviour of the extreme anomalies that have occurred over and above the natural climate variability and may link them to past consequences and their drivers. Analysis of long term records of extremes for rainfall, temperature and streamflows for selected stations in the Lake Victoria basin, were carried out based on a linear trend test, to detect significant monotonic trends, and quantile perturbation analysis, to detect significant temporal extreme anomalies. In addition, correlations between change in rainfall extremes and that for the other extremes, as well as sunspot maxima, were investigated. The findings indicated that extremes in the Lake Victoria basin are, generally, experiencing positive linear trends. Albeit positive trend was generally demonstrated, the presence of significant linear trend was manifested in the extremes of the data obtained from the stations located in the northern and eastern parts of the Lake Victoria basin. This may suggest that the monotony in the positive trend is a result of an ever increasing and consistent external enhancement of the natural climate agitation. The latter has implications for flood risks if the trend persists in the near future. The cyclic analysis of the behaviour of extremes indicated that the 1940s and the 1970s experienced significantly low extremes. Furthermore, the higher significant anomalies for the 1990s, compared to that for the 1960s, may suggest a more intense enhancement of the change in the natural variability in the recent climate. Correlation between change in the extremes for rainfall and that of the minimum daily temperature was demonstrated to be stronger (c.f. maximum temperature and sunspot maxima) implying that if such correlation persists in the future then change in the extremes of daily minimum temperature can be used as an indicator for the change in rainfall extremes. The investigation of the correlations between climate indices/solar activity and hydrometeorological extremes suggests that oceanic and solar influences are part of the explanation of the variability observed in rainfall and temperatures extremes in the Lake Victoria basin.

  6. Low-Level Cloud Variability over the Equatorial Cold Tongue in Observations and Models

    NASA Technical Reports Server (NTRS)

    Mansbach, David K.; Norris, Joel R.

    2007-01-01

    A fourth paper now in press is, Low-level cloud variability over the equatorial cold tongue in observations and models, by D. K. Mansbach and J. R. Norris (2007, J. Climate). This study examined cloud and meteorological observations from satellite, surface, and reanalysis datasets and fount that monthly anomalies in low-level cloud amount and near-surface temperature advection are strongly negatively correlated on the southern side of the equatorial Pacific cold tongue. This inverse correlation occurs independently of relationships between cloud amount and sea surface temperature (SST) or lower tropospheric static stability (LTS) and the combination of advection plus SST or LTS explains significantly more interannual cloud variability in a multilinear regression than does SST or LTS alone. Warm anomalous advection occurs when the equatorial cold tongue is well defined and the southeastern Pacific trade winds bring relatively warm air over colder water. Ship meteorological reports and soundings show that the atmospheric surface layer becomes stratified under these conditions, thus inhibiting the upward mixing of moisture needed to sustain cloudiness against subsidence and entrainment drying. Cold anomalous advection primarily occurs when the equatorial cold tongue is weak or absent and the air-sea temperature difference is substantially negative. These conditions favor a more convective atmospheric boundary layer, greater cloud amount, and less frequent occurrence of clear sky. Examination of output from global climate models developed by the Geophysical Fluid Dynamics Laboratory (GFDL) and the National Center for Atmospheric Research (NCAR) indicates that both models generally fail to simulate the cloud-advection relationships observed on the northern and southern sides of the equatorial cold tongue. Although the GFDL atmosphere model does reproduce the expected signs of cloud-advection correlations when forced with prescribed historical SST variations, it does not consistently do so when coupled to an ocean model. The NCAR model has difficulty reproducing the observed correlations in both atmosphere-only and coupled versions. This suggests that boundary layer cloud parameterizations could be improved through better representation of the effects of advection over varying SST.

  7. Radar Observations of Convective System Variability in Relationship to African Easterly Waves during the 2006 AMMA Special Observing Period

    E-print Network

    Williams, Earle R.

    A radar-based analysis of the structure, motion, and rainfall variability of westward-propagating squall-line mesoscale convective systems (SLMCSs) in Niamey, Niger, during the African Monsoon Multidisciplinary Activities ...

  8. Interannual Variability of the Tropical Energy Balance: Reconciling Observations and Models

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Fitzjarrald, D. E.; Goodman, H. Michael (Technical Monitor)

    2000-01-01

    Since the beginning of the World Climate Research Program's Global Precipitation Climatology Project (GPCP) satellite remote sensing of precipitation has made dramatic improvements, particularly for tropical regions. Data from microwave and infrared sensors now form the most critical input to precipitation data sets and can be calibrated with surface gauges to so that the strengths of each data source can be maximized in some statistically optimal sense. Recent availability of the TRMM (Tropical Rainfall Measuring Mission) has further aided in narrowing uncertainties in rainfall over the tropics and subtropics. Although climate modeling efforts have long relied on space-based precipitation estimates for validation, we now are in a position to make more quantitative assessments of model performance, particularly in tropical regions. An integration of the CCM3 using observed SSTs as a lower boundary condition is used to examine how well this model responds to ENSO forcing in terms of anomalous precipitation. An integration of the NCEP spectral model used for the Reanalysis-11 effort is also examined. This integration is run with specified SSTs, but no data assimilation. Our analysis focuses on two aspects. First are the spatial anomalies that are indicative of dislocations in Hadley and Walker circulations. Second, we consider the ability of models to replicate observed increases in oceanic precipitation that are noted in satellite observations for large ENSO events. Finally, we consider a slab ocean version of the CCM3 model with prescribed ocean heat transports that mimic upwelling anomalies, but which still allows the surface energy balance to be predicted. This less restrictive experiment is used to understand why model experiments with specified SSTs seem to have noticeably less interannual variability than do the satellite precipitation observations.

  9. Kelvin wave variability in the upper stratosphere observed in SBUV ozone data. [SBUV (solar backscatter ultraviolet)

    SciTech Connect

    Randel, W.J.; Gille, J.C. )

    1991-11-01

    The signatures of equatorially trapped Kelvin waves in the upper stratosphere are analyzed in Solar Backscatter Ultraviolet (SBUV) ozone data over the years 1979-86. Comparisons are first made with contemporaneous Limb Infrared Monitor of the Stratosphere (LIMS) ozone data to validate the SBUV Kelvin wave signatures. SBUV and LIMS data both show coherent Kelvin wave oscillations in the upper stratosphere, where ozone is photochemically controlled, and mirrors the temperature fluctuations associated with Kelvin waves; however, SBUV data underestimate wave amplitudes by 20%-60%. Furthermore, transport-induced Kelvin wave patterns in the lower stratosphere are not observed in SBUV data. The eight years of SBUV data reveal the regular occurrence of eastward-propagating zonal wave 1-2 Kelvin waves with periods in the range of 5-15 days. These data show a strong semiannual modulation of Kelvin wave activity, as documented previously in rocketsonde observations. Eight-year-average ensemble spectra are compared to the semiannual oscillation (SAO) in stratospheric zonal winds; a seasonal asymmetry in the strength of Kelvin waves is found, which mimics that observed in the zonal winds. There is a near exact phasing of maxima in wave variance with the strongest easterly zonal winds, i.e., when the wind acceleration is near zero; this argues that Kelvin waves are not a determining factor in the westerly acceleration phase. An exception is found near the stratopause in January when Kelvin wave maxima coincide with strong westerly acceleration. Interannual variability of Kelvin waves is studied in relation to that of the stratospheric zonal winds. No consistent relationship with the quasi-biennial oscillation (QBO) in the lower stratosphere is observed, and correlations with upper stratospheric winds are weak or nonexistent. 35 refs., 11 figs., 1 tab.

  10. Observational and Theoretical Constraints on the Formation and Evolution of Cataclysmic Variables in Globular Clusters

    NASA Astrophysics Data System (ADS)

    Knigge, C.

    2006-08-01

    I will present a critical overview of recent theoretical and observational results regarding the formation and evolution of cataclysmic variables (CVs) in globular clusters (GCs). The overarching goal will be to assess whether the properties of the observed cluster CV population are consistent with expectations based on theoretical predictions and/or direct comparisons to the field CV population. As a starting point, I will take an inventory of the known CV population in GCs, compare its properties to the field CV population and consider to what extent selection effects may be responsible for the differences between them. I will also explore whether physical differences (e.g. in metallicity or primary magnetic field strength) can plausibly explain the observational differences between the two populations. I will go on to consider theoretical predictions for the properties of cluster CVs and show that they depend strongly on the adopted binary evolution recipes (such as the treatment of magnetic braking). This implies that disagreements between predictions and observations of cluster binaries need not imply inadequacies in the treatment of dynamical interactions; they may equally well point to problems with binary evolution prescriptions. This is a serious worry: for example, it is well known that the canonical CV evolution scenario is in serious conflict with several key properties of the field CV population. In a cluster setting, the impact of an erroneous prescription would be exacerbated further by the feedback between stellar dynamics and binary evolution. I will finally consider how to move forward. In particular, I will present results from a recent attempt to empirically calibrate the angular momentum loss (AML) law for field CVs. This AML prescription can be implemented in theoretical models. I will also emphasize the potential of GC surveys to provide CV samples at known distances and with well-understood selection effects. In this sense, GC samples can actually be much cleaner than field CV samples.

  11. Decadal changes in the equatorial Pacific circulation 

    E-print Network

    Urizar, S. Cristina

    2002-01-01

    An ocean general circulation model with data assimilation is used to analyze the decadal changes in the tropical Pacific Ocean circulation. Results indicate that the variability in the Equatorial Undercurrent (EUC) and subtropical cells (STC) have...

  12. Water Cycle Missions for the Next Decade

    NASA Astrophysics Data System (ADS)

    Houser, P. R.

    2013-12-01

    The global water cycle describes the circulation of water as a vital and dynamic substance in its liquid, solid, and vapor phases as it moves through the atmosphere, oceans and land. Life in its many forms exists because of water, and modern civilization depends on learning how to live within the constraints imposed by the availability of water. The scientific challenge posed by the need to observe the global water cycle is to integrate in situ and space-borne observations to quantify the key water-cycle state variables and fluxes. The vision to address that challenge is a series of Earth observation missions that will measure the states, stocks, flows, and residence times of water on regional to global scales followed by a series of coordinated missions that will address the processes, on a global scale, that underlie variability and changes in water in all its three phases. The accompanying societal challenge is to foster the improved use of water data and information as a basis for enlightened management of water resources, to protect life and property from effects of extremes in the water cycle. A major change in thinking about water science that goes beyond its physics to include its role in ecosystems and society is also required. Better water-cycle observations, especially on the continental and global scales, will be essential. Water-cycle predictions need to be readily available globally to reduce loss of life and property caused by water-related natural hazards. Building on the 2007 Earth Science Decadal Survey, NASA's Plan for a Climate-Centric Architecture for Earth Observations and Applications from Space , and the 2012 Chapman Conference on Remote Sensing of the Terrestrial Water Cycle, a workshop was held in April 2013 to gather wisdom and determine how to prepare for the next generation of water cycle missions in support of the second Earth Science Decadal Survey. This talk will present the outcomes of the workshop including the intersection between science questions, technology readiness and satellite design optimization. A series of next-generation water cycle mission working groups were proposed and white papers, designed to identify capacity gaps and inform NASA were developed. The workshop identified several visions for the next decade of water cycle satellite observations, and developed a roadmap and action plan for developing the foundation for these missions. Achieving this outcome will result in optimized community investments and better functionality of these future missions, and will help to foster broader range of scientists and professionals engaged in water cycle observation planning and development around the country, and the world.

  13. Ancient Observations Reveal How a Variable Sun Has Changed the Earth's Climate

    NASA Astrophysics Data System (ADS)

    Pang, K. D.; Yau, K. K.

    2004-12-01

    The Sun, once thought to be constant, has actually undergone nine long brightness cycles in the past 1800 years. Although these luminosity changes were < 1%, they have clearly influenced in the Earth's climate. For example, during the Maunder (Solar) Minimum between 1645 and 1715, sunspots were rarely seen, indicative of a weak Sun. Astronomers at Mt. Wilson, e.g., Hale, Nicholson and Wilson, have linked the luminosity changes to solar magnetic cycles, and similar behaviors in Sun-like stars. Others have elucidated the Sun-climate connection. For example, Eddy suggested that the enfeebled Sun was responsible for the cold climate of the Little Ice Age. The estimated average global temperature then was half a degree Centigrade lower than that prevailed in the 1970's (Lean, Geophys. Res. Lett. 22, 3195, 1995). Yau researched East Asian historical sunspot records, and found that there were seven Maunder-like solar minima before 1600 (Quart. J. Roy. Astron. Soc. 29, 175, 1988). The earliest was in the third century, and the Sporer Minimum occurred in 1400-1600. These findings agree with analyses of historical records of aurora sightings. Energetic electrons and protons emitted by an active Sun create auroras on Earth. When sunspots were rare auroras were, likewise, seldom seen. Minima in sunspot/aurora sightings are, in turn, coincident with peaks in long-term carbon-14 and beryllium-10 records. The radioisotopes are made high in atmosphere by cosmic rays. Their production is low when strong solar magnetic storms deflect such rays from the Solar System, and vice versa (Pang and Yau, Eos 83, No. 43, 481, 2002). Pang analyzed Chinese historical weather records, and discovered that periods of severely cold climate coincide with the Maunder and Sporer Minima. Lakes and rivers froze up, seas icebound, unseasonable frosts killed crops, and famines were widespread during these cold spells, consistent with general circulation model hindcast of contemporary winter conditions for China (Shindell, Science 294, 2149, 2001). Although variable solar luminosity is important, other strong forces also drive the Earth's climate system. These include greenhouse warming, volcanic eruptions, and changing ocean current systems, e.g., the El Nino. The solar variations, however, act over periods ranging from decades to centuries.

  14. Diurnal Variability of the Hydrologic Cycle and Radiative Fluxes: Comparisons Between Observation and a GCM

    NASA Technical Reports Server (NTRS)

    Lin, Xin; Randall, David A.; Fowler, Laura D.

    2000-01-01

    The simulated diurnal cycle is in many ways an ideal test bed for new physical parameterizations. The purpose of this paper is to compare observations from the Tropical Rainfall Measurement Mission, the Earth Radiation Budget Experiment, the International Satellite Cloud Climatology Project, the Clouds and the Earth's Radiant Energy System Experiment, and the Anglo-Brazilian Amazonian Climate Observation Study with the diurnal variability of the Amazonian hydrologic cycle and radiative energy budget as simulated by the Colorado State University general circulation model, and to evaluate improvements and deficiencies of the model physics. The model uses a prognostic cumulus kinetic energy (CKE) to relax the quasi-equilibrium closure of the Arakawa-Schubert cumulus parameterization. A parameter, alpha, is used to relate the CKE to the cumulus mass flux. This parameter is expected to vary with cloud depth, mean shear, and the level of convective activity, but up to now a single constant value for all cloud types has been used. The results of the present study show clearly that this approach cannot yield realistic simulations of both the diurnal cycle and the monthly mean climate state. Improved results are obtained using a version of the model in which alpha is permitted to vary with cloud depth.

  15. Improved VAS regression soundings of mesoscale temperature structure observed during the 1982 atmospheric variability experiment

    NASA Technical Reports Server (NTRS)

    Chesters, Dennis; Keyser, Dennis A.; Larko, David E.; Uccellini, Louis W.

    1987-01-01

    An Atmospheric Variability Experiment (AVE) was conducted over the central U.S. in the spring of 1982, collecting radiosonde date to verify mesoscale soundings from the VISSR Atmospheric Sounder (VAS) on the GOES satellite. Previously published VAS/AVE comparisons for the 6 March 1982 case found that the satellite retrievals scarcely detected a low level temperature inversion or a mid-tropospheric cold pool over a special mesoscale radiosonde verification network in north central Texas. The previously published regression and physical retrieval algorithms did not fully utilize VAS' sensitivity to important subsynoptic thermal features. Therefore, the 6 March 1982 case was reprocessed adding two enhancements to the VAS regression retrieval algorithm: (1) the regression matrix was determined using AVE profile data obtained in the region at asynoptic times, and (2) more optimistic signal-to-noise statistical conditioning factors were applied to the VAS temperature sounding channels. The new VAS soundings resolve more of the low level temperature inversion and mid-level cold pool. Most of the improvements stems from the utilization of asynoptic radiosonde observations at NWS sites. This case suggests that VAS regression soundings may require a ground-based asynoptic profiler network to bridge the gap between the synoptic radiosonde network and the high resolution geosynchronous satellite observations during the day.

  16. A SURVEY OF FAR ULTRAVIOLET SPECTROSCOPIC EXPLORER OBSERVATIONS OF CATACLYSMIC VARIABLES

    SciTech Connect

    Froning, Cynthia S.; Long, Knox S.; Gaensicke, Boris; Szkody, Paula E-mail: long@stsci.edu E-mail: szkody@alicar.astro.washington.edu

    2012-03-01

    During its lifetime, the Far Ultraviolet Spectroscopic Explorer (FUSE) was used to observe 99 cataclysmic variables (CVs) in 211 separate observations. Here, we present a survey of the moderate-resolution (R {approx_equal} 10, 000), far-ultraviolet (905-1188 A), time-averaged FUSE spectra of CVs. The FUSE spectra are morphologically diverse. They show contributions from the accretion disk, the disk chromosphere, disk outflows, and the white dwarf (WD), but the relative contribution of each component varies widely as a function of CV subtype, orbital period and evolutionary state, inclination, mass accretion rate, and magnetic field strength of the WD. The data reveal information about the structure, temperature, density and mass flow rates of the disk and disk winds, the temperature of the WD and the effects of ongoing accretion on its structure, and the long-term response of the systems to disk outbursts. The complete atlas of time-averaged FUSE spectra of CVs is available at the Multimission Archive at Space Telescope Science Institute as a High Level Science Product.

  17. Ten years of satellite observations reveal highly variable sulphur dioxide emissions at Anatahan Volcano, Mariana Islands

    NASA Astrophysics Data System (ADS)

    McCormick, Brendan; Popp, Christoph; Andrews, Benjamin; Cottrell, Elizabeth

    2015-07-01

    Satellite remote sensing enables continuous multiyear observations of volcanic activity in remote settings. Anatahan (Mariana Islands) is a remote volcano in the western North Pacific. Available ground-based measurements of sulphur dioxide (SO2) gas emissions at Anatahan place it among thelargest volcanic SO2 sources worldwide. These ground-based measurements, however, are restricted to eruptive intervals. Anatahan's activity since 2003 has been dominated temporally by prolonged periods of quiescence. Using 10 years of satellite observations from OMI, AIRS, SCIAMACHY, and GOME-2, we report highly variable SO2 emissions within and between eruptive and quiescent intervals at Anatahan. We find close correspondence between levels of activity reported at the volcano and levels of SO2 emissions detected from space. Eruptive SO2 emission rates have a mean value of ˜6400 t d-1, but frequently are in excess of 20,000 t d-1. Conversely, SO2 emissions during quiescent intervals are below the detection limit of space-based sensors and therefore are not likely to exceed ˜300 t d-1. We show that while Anatahan occupies a quiescent state for 85% of the past 10 years, only ˜15% of total SO2 emissions over this interval occur during quiescence, with the remaining ˜85% released in short duration but intense syn-eruptive degassing. We propose that the integration of multiyear satellite data sets and activity histories are a powerful complement to targeted ground-based campaign measurements in better describing the long-term degassing behavior of remote volcanoes.

  18. A distance to the galaxy NGC4258 from observations of Cepheid variable stars.

    PubMed

    Maoz, E; Newman, J A; Ferrarese, L; Stetson, P B; Zepf, S E; Davis, M; Freedman, W L; Madore, B F

    1999-09-23

    Cepheid variable stars pulsate in a way that is correlated with their intrinsic luminosity, making them useful as 'standard candles' for determining distances to galaxies; the potential systematic uncertainties in the resulting distances have been estimated to be only 8-10%. They have played a crucial role in establishing the extragalactic distance scale and hence the value of the Hubble constant. Here we report observations of Cepheids in the nearby galaxy NGC4258; the distance calculated from the Cepheids is 8.1 +/- 0.4 Mpc, where the uncertainty does not include possible systematic errors. There is an independently determined geometric distance to this galaxy of 7.2 +/- 0.5 Mpc, based on the observed proper motions of water masers orbiting the central black hole; the distances differ by 1.3sigma. If the maser-based distance is adopted and the Cepheid distance scale revised accordingly, the derived value of the Hubble constant would increase by 12 +/- 9%, while the expansion age of the Universe would decrease by the same amount. PMID:16862105

  19. Thermal Evolution and Radiative Output of Solar Flares Observed by the EUV Variability Experiment (EVE)

    NASA Technical Reports Server (NTRS)

    Chamberlin, P. C.; Milligan, R. O.; Woods, T. N.

    2012-01-01

    This paper describes the methods used to obtain the thermal evolution and radiative output during solar flares as observed by the Extreme u ltraviolet Variability Experiment (EVE) onboard the Solar Dynamics Ob servatory (SDO). Presented and discussed in detail are how EVE measur ements, due to its temporal cadence, spectral resolution and spectral range, can be used to determine how the thermal plasma radiates at v arious temperatures throughout the impulsive and gradual phase of fla res. EVE can very accurately determine the radiative output of flares due to pre- and in-flight calibrations. Events are presented that sh ow the total radiated output of flares depends more on the flare duration than the typical GOES X-ray peak magnitude classification. With S DO observing every flare throughout its entire duration and over a la rge temperature range, new insights into flare heating and cooling as well as the radiative energy release in EUV wavelengths support exis ting research into understanding the evolution of solar flares.

  20. Sensitivity of global terrestrial carbon cycle dynamics to variability in satellite-observed burned area

    NASA Astrophysics Data System (ADS)

    Poulter, Benjamin; Cadule, Patricia; Cheiney, Audrey; Ciais, Philippe; Hodson, Elke; Peylin, Philippe; Plummer, Stephen; Spessa, Allan; Saatchi, Sassan; Yue, Chao; Zimmermann, Niklaus E.

    2015-02-01

    Fire plays an important role in terrestrial ecosystems by regulating biogeochemistry, biogeography, and energy budgets, yet despite the importance of fire as an integral ecosystem process, significant advances remain to improve its prognostic representation in carbon cycle models. To recommend and to help prioritize model improvements, this study investigates the sensitivity of a coupled global biogeography and biogeochemistry model, LPJ, to observed burned area measured by three independent satellite-derived products, GFED v3.1, L3JRC, and GlobCarbon. Model variables are compared with benchmarks that include pantropical aboveground biomass, global tree cover, and CO2 and CO trace gas concentrations. Depending on prescribed burned area product, global aboveground carbon stocks varied by 300 Pg C, and woody cover ranged from 50 to 73 Mkm2. Tree cover and biomass were both reduced linearly with increasing burned area, i.e., at regional scales, a 10% reduction in tree cover per 1000 km2, and 0.04-to-0.40 Mg C reduction per 1000 km2. In boreal regions, satellite burned area improved simulated tree cover and biomass distributions, but in savanna regions, model-data correlations decreased. Global net biome production was relatively insensitive to burned area, and the long-term land carbon sink was robust, ~2.5 Pg C yr-1, suggesting that feedbacks from ecosystem respiration compensated for reductions in fuel consumption via fire. CO2 transport provided further evidence that heterotrophic respiration compensated any emission reductions in the absence of fire, with minor differences in modeled CO2 fluxes among burned area products. CO was a more sensitive indicator for evaluating fire emissions, with MODIS-GFED burned area producing CO concentrations largely in agreement with independent observations in high latitudes. This study illustrates how ensembles of burned area data sets can be used to diagnose model structures and parameters for further improvement and also highlights the importance in considering uncertainties and variability in observed burned area data products for model applications.