Science.gov

Sample records for observed decadal variability

  1. Observing Interannual to Decadal Variability of Labrador Sea Outflow

    NASA Astrophysics Data System (ADS)

    Fischer, J.; Visbeck, M.; Zantopp, R.; Dengler, M.

    2009-04-01

    During the decade 1996-2008, several moored arrays were deployed over varying time intervals and positions along the western margin of the Labrador Sea. The main objective is the quantification of the water mass exports from the Labrador Sea through observation of currents (moorings, shipboard current measurements and floats) and water masses on time scales ranging from days to decades. During mooring deployments and recoveries, ship sections were occupied with CTD and ADCP/LADCP measurements, yielding transport estimates for the different layers of North Atlantic Deep Water (NADW). The western boundary transports in the Labrador Sea and their variability during 1997-99 were first presented by Fischer et al. (2004), who established the two-year mean section transports in the different isopycnal ranges of the DWBC at 53˚N and reported on intraseasonal variability of currents and transports. Recently, Dengler et al. (2006) evaluated the longer-term changes during 1996-2005 at the Labrador Sea Water level at 1500m depth and found interannual variability of the order of 10 to 20% of the mean flow at that level. While a weakening of the formation of classical Labrador Sea Water was observed during the last decade, accompanied by a reduced vertical extent of the classical LSW, the shallower and lighter LSW constituent increased considerably. During this period the mid-depth temperatures increased by 0.05°C per year in the center of the Labrador Sea as well as in the boundary current; however, there is no indication of corresponding trends in the boundary current flow. Here, the focus will be on a detailed investigation of the Deep Water export throughout the full depth range and near the exit of the Labrador Sea.

  2. 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."

  3. Measurement biases explain discrepancies between the observed and simulated decadal variability of surface incident solar radiation.

    PubMed

    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

  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.

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  8. Decadal Variability of ENSO Predictability

    NASA Astrophysics Data System (ADS)

    Wang, Guomin; Hendon, Harry H.; McPhaden, Michael J.

    2013-04-01

    Seasonal prediction of climate depends primarily on the capability to predict ENSO and its teleconnections. Seasonal predictability of ENSO derives primarily from upper ocean initial conditions, so forecast skill is limited, in part, by the quality of the ocean initial conditions available to the forecast model. Here we report on variations of ENSO forecast skill with the BoM coupled ocean-atmosphere forecast model, for which we have generated hindcasts for the period 1960-2010. It is found despite the recent dramatic increase in ocean observations (primarily from ARGO), the forecast skill for predicting ENSO events, as measured by correlation skill for Nino3 SST index, is dramatically lower in the most recent decade (2001-2010) compared to the previous two decades (1981-2000), and lower even than the earlier two decades (1960-1979) when there was a dearth of ocean observations. We argue that the low skill in the recent decade reflects a recent reduction of ENSO predictability, and this reduced predictability is attributed to decadal changes in the coupled mean state. Post 1998, the coupled mean state has not favoured ENSO variability in the central-eastern Pacific (i.e. as measured by Nino3 SST variations), but rather has promoted ENSO variability further to the west (i.e., as measured by Nino4 SST variations). The underlying mechanisms for this change in ENSO behavior and the implications for decadal prediction of ENSO and its teleconnection to the monsoon will be discussed.

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

    NASA Astrophysics Data System (ADS)

    Yee, J. H.

    2014-12-01

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

  10. 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.

  11. Water Tables, Evapotranspiration, and Climate Variability: A Decade of Observations From a Semi-Arid Riparian Ecosystem

    NASA Astrophysics Data System (ADS)

    Thibault, J. R.; Cleverly, J. R.; Dahm, C.

    2009-12-01

    Native (Rio Grande cottonwood) riparian ecosystems in the semi-arid Rio Grande floodplain of central New Mexico are threatened by hydrologic alterations and highly competitive invasive vegetation (saltcedar, Russian olive). Climate change is expected to alter surface runoff in the southwestern United States and exacerbate water scarcity. Depletions are likely to increase in this agricultural riverine corridor downstream of the rapidly growing Albuquerque metropolitan area. Long-term monitoring of shallow alluvial water tables (WTs) and evapotranspiration (ET) in native, non-native, and mixed communities along the river has provided critical information to help understand how water availability affects these ecosystems during a decade of extreme climate variability. Here, we present several observations, with implications for restoration. WTs ranged from several meters depth to flood stage and from relatively stable to highly dynamic, which can influence recruitment of native vegetation and ecosystem functioning. Annual ET declined with deeper WTs across sites, with robust correlations where WTs were dynamic. Riparian communities responded differently to drought cycles and to restorative flooding during peak runoff at the onset of the growing season. Annual ET in a native-dominated system was reduced following removal of non-native understory vegetation, but returned to previous levels when regrowth was left unmanaged. Long-term data are valuable assets that can help optimize efforts to sustain and restore native ecosystems amid the challenges of a changing climate.

  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.

    2012-12-01

    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.

  13. 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.

  14. Atlantic forcing of Pacific decadal variability

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  15. 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.

  16. 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:

  17. Pacific Decadal Climate Variability and Predictability

    NASA Astrophysics Data System (ADS)

    Kirtman, B.

    2006-12-01

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

  18. Decadal variability in Floods and Extreme Rainfall

    NASA Astrophysics Data System (ADS)

    Lall, Upmanu; Cioffi, Francesco; Devineni, Naresh; Lu, Mengqian

    2014-05-01

    Decadal variability in climate extremes associated with floods is of particular interest for infrastructure development and for insurance programs. From an analysis of US data we note that changes in insurance rates and in the construction of flood control infrastructure emerge soon after a period where there is a high incidence of regional flooding. This leads to the question of whether there is clustering in the incidence of anomalous flooding (or its absence) at decadal scales. The direct examination of this question from streamflow data is often clouded by the modification of flows by the construction of dams and other infrastructure to control floods, especially over a large river basin. Consequently, we explore the answer to this question through the analysis of both extreme rainfall and flood records. Spectral and time domain methods are used to identify the nature of decadal variability and its potential links to large scale climate.

  19. A decade of SETI observations

    NASA Technical Reports Server (NTRS)

    Dixon, R. S.

    1986-01-01

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

  20. Decadal climate variability in the eastern Caribbean

    NASA Astrophysics Data System (ADS)

    Jury, Mark R.; Gouirand, Isabelle

    2011-11-01

    Rainfall variability in the eastern Caribbean during the 20th century is analyzed using principal component analysis and singular value decomposition. In contrast to earlier studies that used seasonal data, here we employ continuous signal processing. The leading mode is a decadal oscillation related to third and fourth modes of sea level pressure (SLP) and sea surface temperatures (SST) which together identify three zones of action in the Atlantic: 35°N-20°N, 20°N-5°N, and 5°N-20°S. The ability of the ECHAM4.5 model to simulate this signal is investigated. Its decadal variability is also represented through lower-order SLP and SST modes that comprise an Atlantic tripole pattern with lower pressure east of the Caribbean. Composite analysis of high and low phases of the decadal mode reflects a cool east Pacific and a more active Atlantic Intertropical Convergence Zone during boreal summer, conditions that favor the intensification of African easterly waves. The decadal signal has strengthened since 1970, yet the three centers of action in Atlantic SST are relatively unsynchronized.

  1. Deciphering the Role of Climate and Sea-Level Changes on Observed Decadal-Scale Variability in Salt-Marsh Sedimentation.

    NASA Astrophysics Data System (ADS)

    Kolker, A. S.; Goodbred, S. L.; Cochran, J. K.; Beck, A.; Kroboth, T.

    2004-12-01

    We are investigating the controls that climate and local oceanography exert on sedimentation patterns in 4 salt marsh-estuary complexes around Long Island, New York, USA. These systems encompass a variety of physical settings, including a range of tidal conditions, wave fetches, and human influences, but are all located within one climatic regime. Within these settings, we hypothesize that sedimentation patterns in limited-fetch, mesotidal salt marshes are influenced most strongly by sea-level changes, as the system is largely steady-state under high-energy conditions and sedimentation should track the longer-term sea-level transgression. Conversely, sedimentation in microtidal systems with large fetch should better track atmospheric forcings, because marsh-surface accretion largely occurs during episodic wind and storm events. To test this hypothesis, accretion rates (cm/yr) were determined by applying a constant-flux model to profiles of excess 210Pb, which reveals temporal variation in sedimentation. Additionally, we examined the rate of mineral sediment deposition (g/cm2/yr) and rate of organic matter accumulation (g/cm2/yr). These measures yielded a chronology of sedimentation patterns ~100 years long with a temporal resolution of 2-5 years, sufficient for resolving decadal-scale oscillations. Our proxies for sea-level change come from a variety of tide gauges; including the gauge at Battery Park, NYC which covers much of the past century, as well as local tide gauges with records spanning several decades. Proxies used for atmospheric forcings include mean annual winds for the past 50 years, storm histories and Hurrel's index of the North Atlantic Oscillation, which extends for over a century. Initial results reveal clear decadal-scale variability in marsh accretion, with variations ranging 2-3 fold about the long-term mean. These oscillations are very similar in timing and magnitude to those observed for the climate proxies and sea-level records. However, initial results reveal no significant correlation between local climate proxies and tide gauge records at the scale of this study. Therefore, we suspect that independent atmospheric and oceanic drivers of marsh sedimentation exist. The relative importance of these drivers in a particular embayment will likely depend on how characteristics such as the tidal regime, wave climate and human modifications, respond to changes in their physical forcings.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Historical observations of potential temperature (θ), salinity (S), and dissolved oxygen concentrations (O2) in the tropical and subtropical North Atlantic (0-500 m; 0-40°N, 10-90°W) were examined to understand decadal-scale changes in O2 in subtropical underwater (STUW). STUW is observed at four of the longest, sustained ocean biogeochemical and ecological time series stations, namely, the CArbon Retention In A Colored Ocean (CARIACO) Ocean Time Series Program (10.5°N, 64.7°W), the Bermuda Atlantic Time-series Study (BATS; 31.7°N, 64.2°W), Hydrostation "S" (32.1°N, 64.4°W), and the European Station for Time-series in the Ocean, Canary Islands (ESTOC; 29.2°N, 15.5°W). Observations over similar time periods at CARIACO (1996-2013), BATS (1988-2011), and Hydrostation S (1980-2013) show that STUW O2 has decreased approximately 0.71, 0.28, and 0.37 µmol kg-1 yr-1, respectively. No apparent change in STUW O2 was observed at ESTOC over the course of the time series (1994-2013). Ship observation data for the tropical and subtropical North Atlantic archived at NOAA National Oceanographic Data Center show that between 1980 and 2013, STUW O2 (upper ~300 m) declined 0.58 µmol kg-1 yr-1 in the southeastern Caribbean Sea (10-15°N, 60-70°W) and 0.68 µmol kg-1 yr-1 in the western subtropical North Atlantic (30-35°N, 60-65°W). A declining O2 trend was not observed in the eastern subtropical North Atlantic (25-30°N, 15-20°W) over the same period. Most of the observed O2 loss seems to result from shifts in ventilation associated with decreased wind-driven mixing and a slowing down of STUW formation rates, rather than changes in diffusive air-sea O2 gas exchange or changes in the biological oceanography of the North Atlantic. Variability of STUW O2 showed a significant relationship with the wintertime (January-March) Atlantic Multidecadal Oscillation index (AMO, R2 = 0.32). During negative wintertime AMO years trade winds are typically stronger between 10°N and 30°N. These conditions stimulate the formation and ventilation of STUW. The decreasing trend in STUW O2 in the three decades spanning 1980 through 2013 reflects the shift from a strongly negative wintertime AMO between the mid-1980s and mid-1990s to a positive wintertime AMO observed between the mid-1990s and 2013. These changes in STUW O2 were captured by the CARIACO, BATS, and Hydrostation S time series stations. Sustained positive AMO conditions could lead to further deoxygenation in tropical and subtropical North Atlantic upper waters.

  3. Food Price Volatility and Decadal Climate Variability

    NASA Astrophysics Data System (ADS)

    Brown, M. E.

    2013-12-01

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

  4. 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.

  5. Advances in Understanding Decadal Climate Variability

    NASA Technical Reports Server (NTRS)

    Busalacchi, Antonio J.

    1999-01-01

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

  6. 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.

  7. Tropical Pacific Decadal Variability: Insights from Coupled Climate Models

    NASA Astrophysics Data System (ADS)

    Capotondi, A.

    2006-12-01

    Tropical Pacific decadal variability is examined in simulations of the 20th century performed with two different state-of-the-art climate models. The first model, CCSM3, is characterized by a regular biennial ENSO, and appears to have small-amplitude decadal variability. The second model, GFDL-CM2.1 is characterized by interannual variations with more realistic spectral characteristics, as well as decadal variations whose amplitude is comparable to the observed. One of the theories of tropical Pacific decadal variability relies upon the changes in the strength of the upper ocean overturning circulation, known as the Subtropical-Tropical Cells (STCs). The variations of the STC circulation are wind-driven, and the adjustment time for the different branches of the cells occurs at different rates: while the surface branch, consisting of the poleward Ekman transport adjusts almost instantaneously to changes in the wind, the adjustment of the equatorward thermocline flow is achieved through Rossby wave propagation, and occurs on longer timescales. Thus, the characteristics of decadal variability can be strongly affected by both the mean density structure of the ocean model as well as the characteristics of the anomalous winds. The latter factor seems to play a very important role in setting the temporal structure of ENSO. Here we examine the connections between STC transport variations and equatorial SST variations at decadal timescales in the two coupled GCMs. We then investigate the relative role of mean STC's structure and anomalous winds in determining the characteristics of the decadal SST variations in GFDL-CM2.1, and whether inaccuracies in those two factors may be responsible for the small decadal signal in CCSM3.

  8. Agulhas leakage dynamics affects decadal variability in Atlantic overturning circulation.

    PubMed

    Biastoch, A; Böning, C W; Lutjeharms, J R E

    2008-11-27

    Predicting the evolution of climate over decadal timescales requires a quantitative understanding of the dynamics that govern the meridional overturning circulation (MOC). Comprehensive ocean measurement programmes aiming to monitor MOC variations have been established in the subtropical North Atlantic (RAPID, at latitude 26.5 degrees N, and MOVE, at latitude 16 degrees N) and show strong variability on intraseasonal to interannual timescales. Observational evidence of longer-term changes in MOC transport remains scarce, owing to infrequent sampling of transoceanic sections over past decades. Inferences based on long-term sea surface temperature records, however, supported by model simulations, suggest a variability with an amplitude of +/-1.5-3 Sv (1 Sv = 10(6) m(3) s(-1)) on decadal timescales in the subtropics. Such variability has been attributed to variations of deep water formation in the sub-arctic Atlantic, particularly the renewal rate of Labrador Sea Water. Here we present results from a model simulation that suggest an additional influence on decadal MOC variability having a Southern Hemisphere origin: dynamic signals originating in the Agulhas leakage region at the southern tip of Africa. These contribute a MOC signal in the tropical and subtropical North Atlantic that is of the same order of magnitude as the northern source. A complete rationalization of observed MOC changes therefore also requires consideration of signals arriving from the south. PMID:19037313

  9. 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.

  10. 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

  11. 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

  12. Decadal Modulation of Global Surface Temperature By Internal Climate Variability

    NASA Astrophysics Data System (ADS)

    Dai, A.; Fyfe, J. C.; Xie, S. P.; Dai, X.

    2014-12-01

    Despite a steady increase in atmospheric greenhouse gases (GHGs), global-mean surface temperature (T) has shown no discernable 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 analyze 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 Inter-decadal Pacific Oscillation (IPO) has been associated with large T anomalies over both ocean and land since 1920. 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 GHG-induced warming. Recent history suggests that the IPO could reverse course and lead to accelerated global warming in the coming decades.

  13. 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

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

    PubMed

    Wang, Kaicun; Dickinson, Robert E

    2013-09-10

    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

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

    NASA Astrophysics Data System (ADS)

    Wang, Kaicun; Dickinson, Robert

    2014-05-01

    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.

  16. Decadal and interannual variability of the Indian Ocean SST

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Lakshmi; Krishnamurthy, V.

    2016-01-01

    The variability of the Indian Ocean on interannual and decadal timescales is investigated in observations, coupled model simulation and model experiment. The Indian Ocean Dipole (IOD) mode was specifically analyzed using a data-adaptive method. This study reveals one decadal mode and two interannual modes in the sea surface temperature (SST) of the IOD. The decadal mode in the IOD is associated with the Pacific Decadal Oscillation (PDO) of the North Pacific SST. The two interannual modes are related to the biennial and canonical components of El Niño-Southern Oscillation (ENSO), consistent with previous studies. This study hypothesizes that the relation between the Indian Ocean and the North Pacific on decadal scale may be through the northerly winds from the western North Pacific. The long simulation of Community Climate System Model version 4 also indicates the presence of IOD modes associated with the decadal PDO and canonical ENSO modes. However, the model fails to simulate the biennial ENSO mode in the Indian Ocean. The relation between the Indian Ocean and North Pacific Ocean is further supported by the regionally de-coupled model experiment.

  17. 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.

  18. 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.

  19. Observing Variable Stars

    NASA Astrophysics Data System (ADS)

    Good, Gerry A.

    Observing variable stars is one of the major contributions amateur astronomers make to science. There are 36,000 variable stars listed in the General Catalogue of Variable Stars, so it is clearly impossible for the limited number of professional observatories to target even the majority of them. That's where amateur astronomers come in - thousands of them turning their telescopes to the sky every night. Variable star observing is the most popular of "real science" activities for amateurs, and Gerry Good's book provides everything needed. The first part of the book provides a highly detailed account of the various classes of variable star, with examples, illustrations and physical descriptions. The second section covers practical aspects of observing, everything from preparation and planning, through observing techniques, to data management and reduction.

  20. 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.

  1. Decadal Scale Variability of the Mesosphere and Lower Thermosphere

    NASA Astrophysics Data System (ADS)

    Yee, J.

    2012-12-01

    In this paper, we will analyze over two decades of satellite observations to quantify and interpret the decadal-scale variation of temperature, composition, and airglow intensity, including the 11-year solar cycle (SC) and long-term anthropogenic change (AC) induced variability, of the Mesosphere and Lower Thermosphere (MLT). The MLT is an interface and buffer between the Sun, interplanetary space, and the magnetosphere above and the atmosphere below and plays a uniquely important role in the solar-terrestrial system. The MLT sensitivities to solar cycle and anthropogenic activities will be extracted from over 11+ years of TIMED observational data. Additional satellite observations (i.e. COSMIC, CHAMP, HALOE/UARS, SOLSTICE/UARS, SORCE) are used to (1) establish the external solar energy input variabilities, (2) determine differences between the satellite datasets and evaluate potential SABER measurement long-term degradation, and (3) extend the length of data records (up to two solar cycles) to assess how their combination refines our conclusions about SC and AC responses.

  2. Decadal Record of Satellite Carbon Monoxide Observations

    NASA Astrophysics Data System (ADS)

    Worden, H. M.; Deeter, M. N.; Frankenberg, C.; George, M.; Nichitiu, F.; Worden, J.; Aben, I.; Bowman, K. W.; Clerbaux, C.; Coheur, P.; de Laat, J.; Detweiler, R.; Drummond, J. R.; Edwards, D. P.; Gille, J. C.; Hurtmans, D.; Luo, M.; Martinez-Alonso, S.; Massie, S. T.; Pfister, G.; Warner, J. X.

    2012-12-01

    Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern hemispheres along with regional trends for E. China, E. USA, Europe and India. Measurement and sampling methods for each of the instruments are discussed. We find that all the satellite observations are consistent with a modest decreasing trend ~ -1%/year in total column CO over the Northern hemisphere for this time period. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.

  3. Decadal record of satellite carbon monoxide observations

    NASA Astrophysics Data System (ADS)

    Worden, H. M.; Deeter, M. N.; Frankenberg, C.; George, M.; Nichitiu, F.; Worden, J.; Aben, I.; Bowman, K. W.; Clerbaux, C.; Coheur, P. F.; de Laat, A. T. J.; Detweiler, R.; Drummond, J. R.; Edwards, D. P.; Gille, J. C.; Hurtmans, D.; Luo, M.; Martínez-Alonso, S.; Massie, S.; Pfister, G.; Warner, J. X.

    2013-01-01

    Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend ~ -1 % yr-1 in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.

  4. Decadal record of satellite carbon monoxide observations

    NASA Astrophysics Data System (ADS)

    Worden, H. M.; Deeter, M. N.; Frankenberg, C.; George, M.; Nichitiu, F.; Worden, J.; Aben, I.; Bowman, K. W.; Clerbaux, C.; Coheur, P. F.; de Laat, A. T. J.; Detweiler, R.; Drummond, J. R.; Edwards, D. P.; Gille, J. C.; Hurtmans, D.; Luo, M.; Martínez-Alonso, S.; Massie, S.; Pfister, G.; Warner, J. X.

    2012-09-01

    Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend ∼-1% yr-1 in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.

  5. Decadal Record of Satellite Carbon Monoxide Observations

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

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

  8. 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.

  9. 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.

  10. Processes of Decadal Climate Variability in Different Regions

    NASA Astrophysics Data System (ADS)

    Proemmel, K.; Cubasch, U.

    2014-12-01

    The realistic representation of decadal climate variability in the models is essential for the quality of decadal climate predictions. Therefore, those processes important for the realistic representation need to be found and included or improved in the climate models. This is done within the German research program "MiKlip - Decadal Predictions" (http://www.fona-miklip.de/en/) for the following processes. A new parameterization of boundary layer processes over inhomogeneous Arctic sea ice is developed. A coupled global atmosphere-ocean-sea ice system with regional refinement in the Arctic is applied. The consideration of the full-physics subsurface hydrodynamics to account for the memory effect of soil moisture is tested for different regions in Europe. The air-sea interaction is analyzed over the North Atlantic Current and Gulf Stream. Stratospheric processes and their impact on the troposphere are analyzed including tropospheric and stratospheric chemistry. The effect of large volcanic eruptions is also taken into account.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  12. Stochastic modeling of decadal variability in ocean gyres

    NASA Astrophysics Data System (ADS)

    Kondrashov, D.; Berloff, P.

    2015-03-01

    Decadal large-scale low-frequency variability of the ocean circulation due to its nonlinear dynamics remains a big challenge for theoretical understanding and practical ocean modeling. This paper presents a novel fully data driven approach that addresses this challenge. Proposed is non-Markovian low-order methodology with stochastic closure and use of mode decomposition by multichannel Singular Spectrum Analysis. The multilayer stochastic linear model is obtained from the coarse-grained eddy-resolving ocean model solution, and with high accuracy it reproduces the main statistical properties of the decadal variability. The proposed methodology does not depend on the governing fluid dynamics equations and geometry of the problem, and it can be extended to other ocean models and ultimately to the real data.

  13. Stochastic Modeling of Decadal Variability in Ocean Gyres

    NASA Astrophysics Data System (ADS)

    Kondrashov, Dmitri; Berloff, Pavel

    2015-04-01

    Decadal large-scale low-frequency variability of the ocean circulation due to its nonlinear dynamics remains a big challenge for theoretical understanding and practical ocean modeling. This paper presents a novel fully data-driven approach that addresses this challenge. We propose non-Markovian low-order methodology with stochastic closure and data-adaptive mode decomposition. The multilayer stochastic linear model is obtained from the coarse-grained eddy-resolving ocean model solution, and it reproduces with high accuracy the main statistical properties of the decadal variability. The proposed methodology does not depend on the governing fluid dynamics equations and geometry of the problem, and it can be extended to other ocean models and ultimately to the real data.

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  15. Multi-Decadal Variability of Colorado River Basin Streamflow

    NASA Astrophysics Data System (ADS)

    Nowak, K. C.; Rajagopalan, B.; Hoerling, M.; Zagona, E. A.

    2010-12-01

    Conventional water resource planning and management are based upon the assumption that past run-off records are indicative of future hydrologic conditions. The severe and sustained nature of the recent drought in the Southwestern United States has underscored the limitation of this planning approach. Furthermore, a growing collection of scientific literature indicates that anthropogenic climate change may further dry the region and strain its water resources. Thus, developing tools and strategies to address streamflow variability, is critical for effective water management in regions such as the Colorado River Basin. A crucial first step toward this end is the understanding of streamflow variability at multi-decadal time scales, driven by large scale climate features such as El Nino Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multi-decadal Oscillation (AMO), etc. Here, a systematic analysis of basin-wide natural streamflow and paleo-reconstructed flows in the Colorado River Basin is presented, using time domain principal component analysis (PCA) and spectral methods based on wavelets and a multi-taper method. The dominant patterns of variability are related to global sea surface temperatures (SSTs) to identify potential large scale climate features that drive the variability. Results indicate that the first two PCs explain approximately 60% of the total streamflow variance in the Basin. The first PC, which is a predominantly Upper Basin signal, correlates strongly with Atlantic Ocean SSTs and shows an AMO pattern, while the second PC has distinct ties to the Pacific Ocean, reminiscent of PDO and ENSO patterns. The spectral analyses of the leading PCs indicate strong coherence with the corresponding indices of the aforementioned climate forcings. The spectrum of the first PC displays a strong signal at 10-15 year and 60-70 year periodicities. Spectral analysis of paleo-reconstructed Upper Basin streamflow indicates that these periodicities are modulated, especially the decadal signal being modulated at a 75-year time scale. These results provide insight into the multi-decadal variability of Colorado River streamflow. Furthermore, they will have considerable utility in realistic simulation of near-term streamflows and consequently, efficient planning and management of water resources in the Colorado River Basin.

  16. 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.

  17. Sea level trends, interannual and decadal variability in the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Zhang, Xuebin; Church, John A.

    2012-11-01

    Linear trend analysis is commonly applied to quantify sea level change, often over short periods because of limited data availability. However, the linear trend computed over short periods is complicated by large-scale climate variability which can affect regional sea level on interannual to inter-decadal time scales. As a result, the meaning of a local linear sea level trend over the short altimeter era (since 1993; less than 20 years) is unclear, and it is not straightforward to distinguish the regional sea level changes associated with climate change from those associated with natural climate variability. In this study, we use continuous near-global altimeter measurements since 1993 to attempt to separate interannual and decadal sea level variability in the Pacific from the sea level trend. We conclude that the rapid rates of sea level rise in the western tropical Pacific found from a single variable linear regression analysis are partially due to basin-scale decadal climate variability. The negligible sea level rise, or even falling sea level, in the eastern tropical Pacific and US west coast is a result of the combination of decreasing of sea level associated with decadal climate variability and a positive sea level trend. The single variable linear regression analysis only accounts for slightly more than 20% of the observed variance, whereas a multiple variable linear regression including filtered indices of the El Nino-Southern Oscillation and the Pacific Decadal Oscillation accounts for almost 60% of the observed variance.

  18. 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.

  19. 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.

  20. 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).

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Sandeep, S.; Ravindran, A.

    2013-12-01

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

  3. 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."

  4. Evaluating SODA for Indo-Pacific Ocean decadal climate variability studies

    NASA Astrophysics Data System (ADS)

    Vargas-Hernandez, J. Mauro; Wijffels, Susan; Meyers, Gary; Holbrook, Neil J.

    2014-11-01

    Estimates of changes in upper ocean temperature, heat content, and sea level are dependent on the coverage of subsurface observations in space and time. Historically, these data are sparse, which has limited our understanding of ocean climate variability and change mechanisms. Ocean state estimates, which effectively represent a model synthesis and integration of the available observations, including internal observations in the ocean and surface forcing, help to address the inhomogeneity of sparse observations in space and time. Here we evaluate the representativeness of ocean state estimates from the Simple Ocean Data Assimilation Version 2.2.4 (SODA) data for studying Indo-Pacific Ocean decadal temperature and sea level variability over the period 1950-2007. The SODA data are evaluated against independent sea level anomalies from long-record tide gauges at Midway Island and Fremantle, reconstructed sea surface height anomalies, and sea surface height anomalies from TOPEX/Poseidon satellite altimeter observations at the decadal time scale. This study demonstrates that SODA captures the characteristic Interdecadal Pacific Oscillation (IPO) over the upper 200 m, and accurately represents these decadal changes against the independent observations. The SODA-product shows a meridional asymmetry of patterns that connect the western tropical Pacific and the Indian Ocean, apparently in relation to IPO changes. Regional sea level at the Midway Island and Fremantle tide gauges confirm this decadal connection and the relationship with the IPO. We concluded that SODA is potentially a useful tool to examine ocean decadal climate variability across the Indo-Pacific Ocean.

  5. Decadal variability in European wet and dry phases

    NASA Astrophysics Data System (ADS)

    Hänsel, Stephanie; Miketta, Wiebke; Matschullat, Jörg

    2013-04-01

    Climate varies over time and space, triggered by a large variety of processes. At continental and regional scales, numerous long-term changes in climate have been observed with profound direct and indirect influences on natural environments and the human society. This study focuses on the spatio-temporal characteristics and changes of long-lasting dry and wet spells in Europe for 1851-2010. Analysis is done for seven European sub-regions ranging from Northern Europa via Central Europe to the Mediterranean area. The decile indicator is used for precipitation time series to define long-lasting dry and wet phases that may last several months to years. Its calculation is based on three-month precipitation totals. Different decile-based thresholds are used to determine the start and the end of the respective dry or wet phase. They are calculated separately for each of the twelve three-month periods to account for the seasonal precipitation cycle. Links of this precipitation-based indicator to flood events in European catchments are examined. We noticed that during certain times, dry and wet phases, respectively, occur more frequent and last longer than during other times, where almost no event occurs. Considering all of Europe, dry phases were particularly frequent and long between 1880 and 1910, the mid-1940s to mid-1960s and in the mid 1970s, while wet phases showed a peak in occurrence from 1910 to the early 40s, from the mid-1960s to the early 1980s and from 1994 to 2010. The picture changes if individual sub-regions are considered. Opposite sub-regional trends lead to almost negligible or indifferent trends over Europe. Spatial extent and duration of dry phases have decreased noticeably and most pronounced in the second half of the 20th Century, while wet phases show increases in spatial extent and duration from 1851 to the present. Those developments are particularly pronounced in Northern Europe. Opposite trends - particularly for the second half of the 20th century - were noticed for Central Europe and the Mediterranean area. Besides those long-term trends exists a strong inter-decadal variability of the spatial coverage of dry and wet phases, respectively, within all sub-regions, indicating a relation of decile phase occurrence to long-term variations in atmospheric circulation. We explored the relationship between dry and wet phase occurrence and large-scale atmospheric circulation patterns, e.g., Hess-Brezowsky catalogue of circulation types (GWT), North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) and found some links depending on the particular sub-region. Yet, the observed links cannot simply be reduced to simple cause-effect relationships.

  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. Mechanisms of the Internally Generated Decadal-to-Multidecadal Variability in the Atlantic

    NASA Astrophysics Data System (ADS)

    Chen, H.; Schneider, E. K.

    2011-12-01

    This study investigates the mechanisms of the internally generated decadal-to-multidecadal time scale SST variability in the Atlantic, including the North Atlantic Tripole variability, the Atlantic Multidecadal Variability and the Tropical Atlantic Variability, on the basis of a 300-year 1990 control simulation (CONTROL) made with CCSM3 and in an interactive ensemble version of CCSM3 (IE-CCSM3: 6 copies of AGCM coupled to the OGCM through the flux coupler). The structures, amplitudes and time scales of these three low frequency modes from CONTROL have properties similar to the observed variability, indicating that CCSM3 is appropriate for studying their mechanisms. These modes are closely related to the variability of the Atlantic Meridional Overturning Circulation (AMOC) on decadal time scales, suggesting that all of these types of variability may be manifestations of a single decadal "mode" of variability. To understand the low frequency modes and their interaction with each other, and the interaction among different oceanic regions, we isolate weather noise forcing from other mechanisms, including the coupled feedback, the gyre circulations, wave dynamics, and AMOC. The weather noise surface fluxes, including the net heat flux, wind stress and freshwater flux, are obtained from CONTROL by removing the SST forced surface fluxes, which are averaged from an ensemble of six AGCMs forced by the CONTROL SST. The IE-CCSM3 simulations in which the specified weather noise forcing is restricted to specific regions or in which the effects of the different specified surface fluxes are isolated are carried out to determine the contributions to the Atlantic decadal modes by region and by forcing type. Our results from the weather noise forced IE-CCSM3 simulations demonstrate that weather noise is responsible for most of decadal variability in the Atlantic and reveal the interactions between the three modes.

  8. Decadal variability of rift propagation on the Amery Ice Shelf

    NASA Astrophysics Data System (ADS)

    Walker, C. C.; Bassis, J. N.; Czerwinski, R. J.; Fricker, H. A.

    2012-12-01

    The Amery Ice Shelf, East Antarctica, features five prominent rifts within 30 km of its calving front. We produce a time series of changes in rift length for the period 2002-2012 using available MODIS and MISR data. We find that all five are actively propagating, but with a complex spatio-temporal pattern of variability in which some rifts propagate in tandem while others appear to tradeoff. Temporal variability in rift propagation is dominated by large episodic bursts. These bursts, analogous to the much smaller propagation events detected from field observations, are not synchronous across all five rifts nor do the timing of propagation events exhibit any correlation with observed proxies for environmental forcing (e.g., atmospheric temperatures, sea-ice extent). However, we find that several propagation events take place after the predicted arrival from tsunamis originating in the Indian Ocean. This is especially apparent following the December 2004 Sumatra earthquake and three other earthquakes in the Sumatra/W. Indonesia area. This connection is bolstered by the observation of similar effects at other ice shelves, e.g., a large iceberg calving after the sudden propagation of two front-initiated rifts at Larsen C after the December 2004 tsunami. In comparing rift propagation at Amery with 61 rifts on 10 other ice shelves, we find that with the exception of the occasional tsunami triggered propagation event, the extreme variability on the Amery Ice Shelf is highly atypical. We postulate that the pronounced activity on the Amery is due to the fact that it last had a large calving event in 1963/64, and is approaching its pre-calved position. This suggests that the AIS is poised for another major calving event and the highly dynamic propagation we observe is the precursor to such an event. That multiple rifts exist and propagate due to structural heterogeneity and shelf geometry also makes these observations relevant to the highly fractured shells of the icy moons, which exhibit a high number of fractures and active surfaces.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  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. The first decade of RR Lyrae space photometric observations

    NASA Astrophysics Data System (ADS)

    Molnar, L.

    2016-05-01

    Space-based photometric telescopes stirred up stellar astrophysics in the last decade, and RR Lyrae stars have not been an exception from that either. The long, quasi-continuous, high-precision data from MOST, CoRoT and Kepler revealed a wealth of new insights about this well-known variable class. One of the most surprising mysteries turned out to be the apparent omnipresence of a common additional mode in all RRd and RRc stars. Moreover, fundamental- mode stars seem to populate two distinct classes, one of which is characterized by the presence of additional modes and/or modulation, and another limited to strict single-mode pulsation. The presence of additional modes and multiple modulations in RRab stars allowed us to construct Petersen diagrams for these parameters: while the pulsation modes show clear structures according to period ratios, there seems to be no relation between the modulation periods themselves.

  15. Decadal climate variability of precipitation over western North America

    SciTech Connect

    Cayan, D.R.; Graham, N.E.; Diaz, H.F.; Dettinger, M.D.

    1997-11-01

    Data on regionally-coherent interdecadal fluctuations in precipitation patterns over western North America are presented in this paper. Possible links between global circulation patterns and precipitation patterns are examined. Rotated principal components of precipitation show that the spatial scale of interdecadal precipitation anomalies in the West is regional, with several distinct, persistently anomalous wet or dry features. Correlations with decadal filtered sea level pressure anomalies reveal regional to large scale anomaly signatures similar to those involved in producing short period precipitation fluctuations. Inspection of circulation patterns at the monthly level indicates that the decadal precipitation shifts involve changes in the frequency of several primary monthly extratropical North Pacific circulation patterns. The anomalous sea surface temperature is also connected with decadal precipitation fluctuations, and results are consistent with the linkages to the atmospheric circulation. Considering the large scale connections of some of the regional precipitation patterns with circulation and sea surface temperature, it is hypothesized that the climate system contains globally organized precipitation anomalies on scales larger than the subset of western North America studied. For example, the Southwest decadal precipitation rotated principal component is closely aligned, but out of phase with, a global precipitation pattern that includes the Sahel in Africa. 2 refs., 3 figs.

  16. Tropospheric ozone trends at Mauna Loa Observatory tied to decadal climate variability

    NASA Astrophysics Data System (ADS)

    Lin, Meiyun; Horowitz, Larry W.; Oltmans, Samuel J.; Fiore, Arlene M.; Fan, Songmiao

    2014-02-01

    A potent greenhouse gas and biological irritant, tropospheric ozone is also the primary source of atmospheric hydroxyl radicals, which remove numerous hazardous trace gases from the atmosphere. Tropospheric ozone levels have increased in spring at remote sites in the mid-latitudes of the Northern Hemisphere over the past few decades; this increase has been attributed to a growth in Asian precursor emissions. In contrast, 40 years of continuous measurements at Mauna Loa Observatory in Hawaii reveal little change in tropospheric ozone levels during spring (March-April), but a rise in autumn (September-October). Here we examine the contribution of decadal shifts in atmospheric circulation patterns to decadal variability in tropospheric ozone levels at Mauna Loa using a suite of chemistry-climate model simulations. We show that the flow of ozone-rich air from Eurasia towards Hawaii during spring weakened in the 2000s as a result of La-Niña-like decadal cooling in the eastern equatorial Pacific Ocean. During autumn, in contrast, the flow of ozone-rich air from Eurasia to Hawaii strengthened in the mid-1990s onwards, coincident with the positive phase of the Pacific-North American pattern. We suggest that these shifts in atmospheric circulation patterns can reconcile observed trends in tropospheric ozone levels at Mauna Loa and the northern mid-latitudes in recent decades. We conclude that decadal variability in atmospheric circulation patterns needs to be considered when attributing observed changes in tropospheric ozone levels to human-induced trends in precursor emissions.

  17. Heat Recharge of the Equatorial Ocean: from ENSO to Decadal Climate Variability

    NASA Astrophysics Data System (ADS)

    Fedorov, A. V.; Muir, L.; Di Nezio, P. N.

    2012-12-01

    A key element of ENSO dynamics is heat recharge of the equatorial ocean that typically occurs prior to El Niño events. This recharge is evident in the observations and is included into conceptual models of ENSO, such as the recharge oscillator (Jin 1997, Meinen and McPhaden 2000). The focus of the present study is the phase lag between ocean heat recharge (measured as variations in upper ocean heat content along the equator) and variations in the Nino3 SST. First, from a theoretical perspective using the low-frequency approximation (Fedorov 2010), we derive a simple analytical expression for the phase lag that depends on the characteristic frequency of the oscillation, the meridional structure of wind stress anomalies, and oceanic damping. In a realistic parameter range, the phase lag given by the theory approaches 60° for an oscillation with a 4-year period, which on average agrees well with the observations. We next explore the dependence of this phase lag in CMIP5 models. We show that while some of those models do reproduce a reasonable phase lag in the interannual frequency band, many models simulate a lag significantly shorter or longer than observed (±60%). Further, the theory and observations predict a longer phase lag, ~90°, for decadal timescales. Only a few coupled models are able to capture this behavior, whereas other models produce a much shorter phase lag, and some produce a phase lag close to zero. These results suggest several types of dynamical behavior of tropical decadal variability in different models - from a dynamical mode similar to ENSO to purely damped mixed-layer variability. We conclude that differences in the simulated phase lag on timescales from interannual to decadal contribute to the broad diversity of simulated ENSO and decadal variability, as well as different prediction skills of the models.

  18. Inter-decadal variability of summer rainfall in Eastern China detected by the Lepage test

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Huang, Gang; Huang, Ronghui

    2011-12-01

    On the basis of the latest observational datasets, the inter-decadal changes of summer rainfall in East China in the past 50 years are analyzed using the Lepage test. The two traditional methods moving t-test and Mann-Kendall test are also performed on the rainfall data as a comparison. Results indicate four inter-decadal abrupt changes of summer rainfall that occurred near 1979, 1983, 1993, and 1999, and each of them is characterized by remarkable regional features. The abrupt change of summer rainfall around 1979 is accompanied by significant rainfall increase in Yangtze-Huai River Valley and a decrease in its flank. The one near 1983 shows similar structures of the rainfall changes to that near 1979, but with more significant changes in the South China and Northeast China (NEC). The inter-decadal change around 1993 brings a notable increase of summer rainfall to the South China; and the abrupt shift near 1999 exhibits significant decrease in summer rainfall over a large part of North China and NEC. The spatial-temporal features of the inter-decadal changes in summer rainfall are also investigated. Consistent results are observed. Moreover, results indicate that, on the inter-decadal scale, the rainfall variability mode changes from typical tripole to dipole structure since the early 1990s.

  19. Contribution of natural decadal variability to global warming acceleration and hiatus

    NASA Astrophysics Data System (ADS)

    Watanabe, Masahiro; Shiogama, Hideo; Tatebe, Hiroaki; Hayashi, Michiya; Ishii, Masayoshi; Kimoto, Masahide

    2014-10-01

    Reasons for the apparent pause in the rise of global-mean surface air temperature (SAT) after the turn of the century has been a mystery, undermining confidence in climate projections. Recent climate model simulations indicate this warming hiatus originated from eastern equatorial Pacific cooling associated with strengthening of trade winds. Using a climate model that overrides tropical wind stress anomalies with observations for 1958-2012, we show that decadal-mean anomalies of global SAT referenced to the period 1961-1990 are changed by 0.11, 0.13 and -0.11 °C in the 1980s, 1990s and 2000s, respectively, without variation in human-induced radiative forcing. They account for about 47%, 38% and 27% of the respective temperature change. The dominant wind stress variability consistent with this warming/cooling represents the deceleration/acceleration of the Pacific trade winds, which can be robustly reproduced by atmospheric model simulations forced by observed sea surface temperature excluding anthropogenic warming components. Results indicate that inherent decadal climate variability contributes considerably to the observed global-mean SAT time series, but that its influence on decadal-mean SAT has gradually decreased relative to the rising anthropogenic warming signal.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  2. The decadal variability of the heat and freshwater content of the subpolar North Atlantic

    NASA Astrophysics Data System (ADS)

    Boening, Claus W.; Scheinert, Markus; Behrens, Erik; Biastoch, Arne

    2013-04-01

    During the last five decades striking changes occurred in the freshwater and heat content of the subpolar North Atlantic (SNA). The deep and abyssal waters that originate in this region to feed the lower limb of the AMOC experienced a remarkable decrease in salinities after the late 1960s, linked to a progressive dilution of the system of overflows from the Nordic Seas. A rapid reversal of the freshening trend occurred in the mid-1990s, with a pronounced salinification especially in the eastern SNA; at the same time, the freshening of the overflows slowed to a stop. An intriguing feature of the observational record is the tight co-variability of the freshwater and heat content of the SNA: the long-term freshening was accompanied by a progressive decrease in heat content, and both trends reversed simultaneously after 1995. Here we use a sequence of experiments with high-resolution (1/4°, 1/12°, and 1/20°) ocean-sea ice models to identify the dynamical causes of these decadal changes. Hindcast simulations of the oceanic response to the atmospheric variability 1948-2007 (as given by the "CORE" reanalysis) capture the decadal variability in the integral properties of the SNA as reconstructed from historical salinity and temperature data, and reproduce pertinent observational indices of mid-latitude circulation variability. Analysis of the freshwater and heat budgets shows that the largest contribution to the SNA property changes has been due to variations in the inflow of warm, saline water with the subtropical North Atlantic, with only a minor contribution due to variations in the inflow of cold, fresh waters from the northern basins. The subtropical-subpolar flux variability is not directly related to the AMOC; it can conceptually be understood in terms of the "intergyre-gyre" response to the mid-latitude westerlies associated with the NAO.

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

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Dommenget, Dietmar

    2015-12-01

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

  4. Climatological Mean Features and Interannual to Decadal Variability of Ring Formations in the Kuroshio Extension Region

    NASA Astrophysics Data System (ADS)

    Sasaki, Y. N.; Minobe, S.

    2014-12-01

    We examine the climatological mean features of oceanic rings shed from the Kuroshio Extension jet and their interannual to decadal variability using satellite altimeter observations from October 1992 to December 2010. To objectively capture a ring shedding from the Kuroshio Extension jet, a new method that consists of the detection of the jet length changes and the tracking of a ring is proposed. A spatial distribution of the ring formations in the Kuroshio Extension region indicates that cyclonic (cold-core) rings were most frequently formed in the upstream region between 143°-147°E around the steady meander of the Kuroshio Extension jet. In contrast, most of anticyclonic (warm-core) rings formed in the downstream region west of the Shatsky Rise. These pinched-off rings in both the upstream and downstream regions generally propagate westward, but about two-third of the rings is reabsorbed by the jet. Nevertheless, about one-fourth of the meridional eddy heat transport at the latitude of the Kuroshio Extension results from the rings that are not reabsorbed by the jet. The number of ring formations shows substantial interannual to decadal variability. In the upstream and downstream Kuroshio Extension region, decadal and interannual variability is dominant, respectively. These fluctuations of the ring formations are negatively correlated with the strength of the Kuroshio Extension jet. It is also revealed that the ring formation variations play an important role in sea surface temperature changes north of the Kuroshio Extension jet.

  5. 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.

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Liu, Fenfen; Chen, Chuqun; Zhan, Haigang

    2012-11-01

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

  9. 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.

  10. 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.

  11. Greater frequency variability of landfalling tropical cyclones at centennial compared to seasonal and decadal scales

    NASA Astrophysics Data System (ADS)

    Nott, Jonathan; Haig, Jordahna; Neil, Helen; Gillieson, David

    2007-03-01

    Assessing risk from tropical cyclones and predicting the impact of this hazard under a human altered climate is based exclusively upon the behaviour of these events over the past 50-100 yr and often less. Critical to these determinations is an understanding of the full extent of the natural variability of this hazard. The coarse resolution of millennial scale sedimentary records, brevity of the instrumental register, imprecision of longer historical accounts and lack of any long-term, high resolution records has led to the assumption that the total variability of tropical cyclone behaviour is encompassed within the seasonal to multi-decadal oscillations observed to date. We present a near 800 yr long, annual resolution isotope record of tropical cyclones in northeast Australia which displays marked centennial scale regimes. Our record demonstrates that the frequency variability of intense landfalling cyclones is greatest at centennial scale compared to seasonal and decadal oscillations. Switching between centennial scale regimes in this record occurred rapidly (10-20 yr) highlighting the importance of accounting for this phenomenon in coastal planning and risk assessment. Our study highlights the importance of obtaining high resolution multi-century records of tropical cyclone activity in order to more accurately assess future impacts of this hazard to human society.

  12. Variability of oceanic carbon cycle in the North Pacific from seasonal to decadal scales

    NASA Astrophysics Data System (ADS)

    Xiu, Peng; Chai, Fei

    2014-08-01

    Variability of upper-ocean carbon cycle in the North Pacific during 1958-2010 period is investigated using a physical-biogeochemical model. Comparisons with in situ data from five different oceanographic environments in the South China Sea, Monterey Bay, North Pacific gyre, northwestern Pacific, and Gulf of Alaska indicate that the model usually captures observed seasonal and interannual variability in both sea surface pCO2 and sea-air CO2 flux. Seasonal variability of pCO2 and CO2 flux in the North Pacific follows the change in sea surface temperature (SST) closely with high and low values in summer and winter, respectively. Total CO2 modifies pCO2 seasonal pattern in an opposite manner with respect to SST, and surface wind speed modifies the magnitude of CO2 flux variations. On interannual and decadal time scales, sea surface pCO2 is primarily controlled by anthropogenic CO2, followed by modulations by the El Niño-Southern Oscillation and the Pacific Decadal Oscillation (PDO), while sea-air CO2 flux is significantly regulated by the PDO and the North Pacific Gyre Oscillation (NPGO). We show that anthropogenic CO2 tends to amplify the influence on CO2 flux from the PDO but to damp the influence from the NPGO.

  13. IUE observations of cataclysmic variable

    NASA Technical Reports Server (NTRS)

    Szkody, Paula

    1993-01-01

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

  14. Role of ocean-atmosphere interaction in Atlantic Multi-decadal variability

    NASA Astrophysics Data System (ADS)

    Keenlyside, N. S.; Ba, J.; Mecking, J.; Omrani, N.; Shen, M.

    2012-12-01

    The mechanisms for Atlantic Multidecadal Variability (AMV) remain uncertain. In this presentation ocean, atmosphere, and coupled ocean-atmosphere models will be used to investigate one of the key uncertainties: ocean-atmosphere interaction. We first investigate the role of the ocean in setting the timescale. Ocean model experiments with historic and stochastically generated atmospheric forcing are performed; the NEMO ocean model with relatively high resolution (0.5 degree horizontal and 46 vertical levels) is used. Consistent with previous studies, our results show that ocean dynamics dominate decadal SST variations in the subpolar gyre, and decadal shifts in the North Atlantic Oscillation can explain most of the observed changes in this region. In addition, we find no evidence for an ocean-only oscillatory mode to explain AMV, rather a linear response of the ocean is found on multi-decadal and longer timescales and a weak response exists on shorter timescales. Second, we consider the role of active coupling in sustaining AMV. Recent studies suggest that resolving stratosphere troposphere interaction enhances the simulated response of the winter atmosphere to North Atlantic subpolar gyre SST. Here we extend on this work using to investigate the role of better resolving stratospheric processes in simulated AMV. Specifically, we compare twin coupled and uncoupled model experiments that only differ in their representation of the stratosphere. Consistent with our previous results, a warm North Atlantic causes a weakening of the polar vortex and in turn negative North Atlantic Oscillation. This mechanism is missing in the simulation that poorly resolves the stratosphere. How this alters simulated decadal variability, and implications for predictability are discussed.

  15. North Pacific decadal variability in the CMIP5 last millennium simulations

    NASA Astrophysics Data System (ADS)

    Fleming, Laura E.; Anchukaitis, Kevin J.

    2016-02-01

    The Pacific ocean-atmosphere system exerts an important influence on the climate of Asia and North America, but the limited length of the observational record prevents a complete understanding of its bidecadal and multidecadal time scales. Paleoclimate reconstructions provide one source of information on longer time scales, although they differ in their estimation of the behavior of the Pacific decadal oscillation (PDO) prior to the instrumental period. Forced general circulation model simulations offer complementary long-term perspectives on both the history and dynamics of this important mode of variability. Here, we analyze the PDO in the ensemble of CMIP5/PMIP3 last millennium (past1000 + historical) simulations. We evaluate the modeled spatial, temporal, and spectral characteristics of this mode, as well as teleconnections between North Pacific variability and global climate. All models produce a mode of North Pacific variability over the last millennium with spatial patterns and spectral power density similar to observations. CCSM, FGOALS, and IPSL best reproduce observed spatial patterns, spectral characteristics, and teleconnections to terrestrial regions used in paleoclimate proxy reconstructions. In these simulations, the PDO shows no consistent response to solar or volcanic forcing.

  16. Influence of Decadal Variability of Global Oceans on South Asian Monsoon and ENSO-Monsoon Relation

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Lakshmi

    This study has investigated the influence of the decadal variability associated with global oceans on South Asian monsoon and El Nino-Southern Oscillation (ENSO)-monsoon relation. The results are based on observational analysis using long records of monsoon rainfall and circulation and coupled general circulation model experiments using the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM) version 4 model. The multi-channel singular spectrum analysis (MSSA) of the observed rainfall over India yields three decadal modes. The first mode (52 year period) is associated with the Atlantic Multidecadal Oscillation (AMO), the second one (21 year) with the Pacific Decadal Oscillation (PDO) and the third mode (13 year) with the Atlantic tripole. The existence of these decadal modes in the monsoon was also found in the control simulation of NCAR CCSM4. The regionally de-coupled model experiments performed to isolate the influence of North Pacific and North Atlantic also substantiate the above results. The relation between the decadal modes in the monsoon rainfall with the known decadal modes in global SST is examined. The PDO has significant negative correlation with the Indian Monsoon Rainfall (IMR). The mechanism for PDO-monsoon relation is hypothesized through the seasonal footprinting mechanism and further through Walker and Hadley circulations. The model results also confirm the negative correlation between PDO and IMR and the mechanism through which PDO influences monsoon. Both observational and model analysis show that droughts (floods) are more likely over India than floods (droughts) when ENSO and PDO are in their warm (cold) phase. This study emphasizes the importance of carefully distinguishing the different decadal modes in the SST in the North Atlantic Ocean as they have different impacts on the monsoon. The AMO exhibits significant positive correlation with the IMR while the Atlantic tripole has significant negative correlation with the IMR. The AMO influences the Indian monsoon through atmospheric winds related to high summer North Atlantic Oscillation (NAO) mode leading to enhanced moisture flow over the Indian subcontinent. The Atlantic tripole mode affects the rainfall over India by enhancing the moisture flow through the equatorial westerly winds associated with the NAO. The model also simulates the positive and negative relation of AMO and tripole, respectively, with the monsoon rainfall. The model also indicates the enhanced moisture flow over India related to the positive phase of AMO through the equatorial westerly flow. But, for the tripole mode, the model indicates flow of moisture through the Bay of Bengal in contrast to observations where it is through the Arabian Sea. The reason for the absence of decadal mode in IMR inherent to the Indian Ocean is also explored. The SSA on dipole mode index (DMI) index reveals three modes. The first two modes are related to the biennial and canonical ENSO at interannual timescale while the third mode varies on decadal timescale and is related to PDO. The wind regression pattern associated with the PDO-IOD mode shows northeasterly winds enhancing the southeasterly flow from the southeastern Indian Ocean related to the Indian Ocean dipole (IOD) mode. The model also shows the influence of canonical ENSO and PDO influence on IOD, although the variance explained by PDO mode is lower in the model relative to observations.

  17. 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.

  18. Persistent decadal-scale rainfall variability in the tropical South Pacific Convergence Zone through the past six centuries

    NASA Astrophysics Data System (ADS)

    Maupin, C. R.; Partin, J. W.; Shen, C.-C.; Quinn, T. M.; Lin, K.; Taylor, F. W.; Banner, J. L.; Thirumalai, K.; Sinclair, D. J.

    2013-10-01

    Observations and reconstructions of decadal-scale climate variability are necessary to place predictions of future global climate change into temporal context (Goddard et al., 2012). This is especially true for decadal-scale climate variability that originates in the Pacific Ocean (Deser et al., 2004; Dong and Lu, 2013). We focus here on the western tropical Pacific (Solomon Islands; ~ 9.5° S, ~ 160° E), a region directly influenced by: the South Pacific Convergence Zone (SPCZ), the West Pacific Warm Pool (WPWP), the Pacific Walker Circulation (PWC), and the Hadley Circulation. We calibrate δ18O variations in a fast growing stalagmite to local rainfall amount and produce a 600 yr record of rainfall variability from the zonally oriented, tropical portion of the SPCZ. We present evidence for large (~ 1.5 m), persistent and decade(s)-long shifts in total annual rainfall amount in the Solomon Islands since 1416 ± 5 CE. The timing of the decadal changes in rainfall inferred from the 20th century portion of the stalagmite δ18O record coincide with previously identified decadal shifts in Pacific ocean-atmosphere behavior (Clement et al., 2011; Deser et al., 2004). The 600 yr Solomons stalagmite δ18O record indicates that decadal oscillations in rainfall are a robust characteristic of SPCZ-related climate variability, which has important implications to water resource management in this region.

  19. 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.

  20. 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

  1. 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.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  4. 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.

  5. Prioritizing Global Observations Along Essential Climate Variables

    NASA Astrophysics Data System (ADS)

    Bojinski, Stephan; Richter, Carolin

    2010-12-01

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

  6. A Long Term Perspective on Decadal Variability in Climate and Wildfire in the Western United States

    NASA Astrophysics Data System (ADS)

    Westerling, A. L.; Swetnam, T. W.

    2004-12-01

    Despite progress in reconstructing the western United States' paleo- fire and climate regimes, placing recent fire seasons into the context of past variability is difficult. Management practices have altered ecosystems, and modern records and paleo reconstructions of wildfire seldom overlap. Recent work helped to bridge that gap, using statistical models trained on 20th century fire and drought histories (1916 to 1978) to successfully reproduce a reconstruction of annual wildfire extent derived from a fire scar network for the U.S. Southwest for 1701 to 1900. We found that managed wildfire regimes still contained strong climate signals similar to paleofire reconstructions. Moreover, El Nino-Southern Oscillation and Pacific Decadal Oscillation patterns appeared to modulate western U.S. fire activity. Using Cook et al.'s newly available drought reconstructions for North America, this analysis now extends to a minimum of 1000 years the period covered by our statistical reconstruction of western U.S. wildfire. We analyze the decadal variability in reconstructed fire regimes over this longer period, and compare the results to available ENSO and PDO reconstructions. The validation of statistical reconstructions of wildfire area burned against fire scar networks is expanded to include sites in California, the Pacific Northwest, and Rocky Mountains. We extend our statistical reconstruction through 2003 and compare the recent increase in observed annual area burned to the increases in both modeled area burned and the land area protected against wildfires in the western United States since the 1970s. Based on this analysis, we place the recent very active fire seasons experienced in the West into the perspective of the past 1000 years of climate variability, and demonstrate an application of long-term climate-fire relationships to budgeting for fire suppression in the USDA Forest Service.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  8. Multi-decadal variability of the eastern North Atlantic subpolar gyre

    NASA Astrophysics Data System (ADS)

    Cunningham, Stuart; Holliday, N. Penny; Johnson, Clare; Gary, Stefan

    2014-05-01

    The Extended Ellett Line is a hydrographic section sampling the eastern North Atlantic subpolar gyre from Iceland to Scotland. The section samples the main warm-water path of the Atlantic meridional overturning circulation (AMOC) from the subtropics to the Nordic Seas and the cold-water return flow from the Faroe Bank Channel south of Iceland. Here we present property and circulation variability from 18 annual hydrographic sections since 1996. Uncertainties due to aliasing are examined using float-based products, model output and altimetry. Nearest to Scotland in the Rockall Trough we have 65-years of data showing multi-decadal variability of upper ocean heat and salt anomalies feeding into the Nordic Seas. The amplitude of temperature and salinity changes are 0.5°C and 0.08 (salinity), with highs in the mid-2000s. The anomalies are influenced by the strength of the circulation of the subpolar gyre and indicate large-scale changes. The causes of the observed variability of properties and circulation, the relationships between the basins, and the influence of the AMOC and atmosphere are discussed.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. Arctic forcing of decadal variability in the tropical Pacific Ocean in a high-resolution global coupled GCM

    NASA Astrophysics Data System (ADS)

    Karnauskas, Kristopher B.

    2014-06-01

    The hypothesis that northern high-latitude atmospheric variability influences decadal variability in the tropical Pacific Ocean by modulating the wind jet blowing over the Gulf of Tehuantepec (GT) is examined using the high-resolution configuration of the MIROC 3.2 global coupled model. The model is shown to have acceptable skill in replicating the spatial pattern, strength, seasonality, and time scale of observed GT wind events. The decadal variability of the simulated GT winds in a 100-year control integration is driven by the Arctic Oscillation (AO). The regional impacts of the GT winds include strong sea surface cooling, increased salinity, and the generation of westward-propagating anticyclonic eddies, also consistent with observations. However, significant nonlocal effects also emerge in concert with the low-frequency variability of the GT winds, including anomalously low upper ocean heat content (OHC) in the central tropical Pacific Ocean. It is suggested that the mesoscale eddies generated by the wind stress curl signature of the GT winds, which propagate several thousand kilometers toward the central Pacific, contribute to this anomaly by strengthening the meridional overturning associated with the northern subtropical cell. A parallel mechanism for the decadal OHC variability is considered by examining the Ekman and Sverdrup transports inferred from the atmospheric circulation anomalies in the northern midlatitude Pacific directly associated with the AO.

  15. What can we learn from corals about low-frequency (decadal-secular) climate variability?

    NASA Astrophysics Data System (ADS)

    Cole, J. E.; Ault, T. R.; Barnett, H.

    2007-05-01

    Corals offer excellent reconstructions of interannual climate anomalies in the tropical oceans, but many studies have raised questions about their ability to faithfully track decadal variability and long-term trends. Yet resolving such variability in the tropical oceans is crucial for questions of climate dynamics and identification of anthropogenic impacts. Understanding the mechanisms of this low-frequency variability is critical because it provides a basis for prediction, and because such variability may interact with higher-frequency or secular patterns to alter predictability and produce unexpected climate extremes. Long-term climate variations and trends in the tropics have the potential to impact climate globally through altered atmospheric circulation, systems such as ENSO and the monsoons, and teleconnections to extratropical climates. The 20th-century record of instrumental observations is too short to address these issues with confidence. Paleoclimate records from corals can contribute to this effort, if subtle signals of low-frequency change can be disentangled from sources of noise. Here we present several approaches to this issue. First, a synthesis of 23 coral geochemical records suggests that a common pattern of decadal variation can be extracted from these records. This pattern closely resembles a 20th century mode identified from instrumental data, but our analysis indicates that this mode was significantly stronger in the 19th century (explaining nearly half the deseasonalized variance). This mode resembles ENSO in spatial pattern, implicating equatorial dynamics. Second, we explore longer-term modes in individual records and identify an interval in the 17th century during which several global and Pacific-sensitive records appear to follow a bidecadal beat. Finally, we analyze the warming/freshening trends apparent in nearly all coral climate records and assess their correlation to local SST and salinity changes. The amplitude of trends at most sites is near or beyond what can be explained with existing instrumental records, but the lack of local salinity records on reefs, coupled with potential changes in the isotopic content of precipitation, means that these trends cannot yet be dismissed as biological artifacts.

  16. EarthScope's USArray: A Decade of Observations and Results

    NASA Astrophysics Data System (ADS)

    Woodward, R.; Busby, R. W.; Hafner, K.; Gridley, J. M.; Schultz, A.; Frassetto, A.; Simpson, D. W.

    2013-12-01

    EarthScope's USArray observatory provides unprecedented observations of geophysical targets across the contiguous United States through the systematic deployment of seismic, magnetotelluric, and atmospheric instruments. In addition, USArray includes tightly integrated data management and outreach activities. The seismic and atmospheric components of USArray consist of a Transportable Array (TA), Flexible Array (FA), and Reference Network. The TA has now occupied approximately 1700 sites spanning the entire contiguous 48 states, at 70 km inter-station spacing. These stations have provided broadband seismic, barometric pressure and atmospheric infrasound observations. The pool of instruments that comprise the FA have been deployed by numerous individual investigators in dense arrays to investigate local and regional features over time periods ranging from days to years. The Reference Network provides a permanent, stationary foundation for the TA and FA, with approximately 100 broadband stations deployed across the contiguous US at roughly 300 km spacing. The magnetotelluric (MT) component of USArray has provided both fixed and campaign-style long-period magnetotelluric observations at hundreds of locations across the US. Many of the field activities of USArray engaged both students and the public in important ways and this has been a significant component of USArray outreach. The TA alone has engaged well over one hundred students in site reconnaissance activities and placed seismic stations on the property of roughly a thousand different landowners. All data collected by USArray are openly available, most in real time. Many of the observations have also been incorporated into a variety of data products that have been developed to facilitate use of USArray by many different audiences. The scientific community has used USArray data to achieve a wide range of results--some that were anticipated when the facility was proposed and some that were completely unanticipated. Data products such as direct visualizations of seismic wave propagation observed by the TA have been viewed hundreds of thousands of times on the web by the general public. We will provide a brief overview of the deployments and accomplishments of USArray from the past ten years, and an overview of the significant and diverse scientific results that have been achieved. We will touch on some of the technologies and organizational and operational strategies that have enabled the success of USArray. We will conclude with a brief discussion of USArray plans for the next five years.

  17. On the sub-decadal variability of South Atlantic Antarctic Intermediate Water

    NASA Astrophysics Data System (ADS)

    McCarthy, G. D.; King, B. A.; Cipollini, P.; McDonagh, E. L.; Blundell, J. R.; Biastoch, A.

    2012-05-01

    Variability of Antarctic Intermediate Water salinity in the South Atlantic is investigated on interannual and intradecadal timescales. Novel observations of slow, westward propagating salinity anomalies in Argo data are presented. The features have no corresponding signal in temperature and are anomalous in density. Analysis of 40 years of model output supports the existence of these westward propagating salinity anomalies and indicates that they are typical occurrences in time. The features are intensified in a latitude band around 30°S associated with the propagation of Agulhas rings. However, the features are much larger than Agulhas rings and occur on decadal timescales in the model. They propagate westward with speeds of 2.3 cm/s in observations, and 1.7 cm/s in model data. They are more consistent with planetary waves than with the advection of large-scale salinity anomalies. The observation of these features has implications for the interpretation of salinity anomalies, such as the linking of hydrological cycle changes to salinity changes.

  18. The Prominence of Decadal and Multidecadal Variability in North American Precipitation

    NASA Astrophysics Data System (ADS)

    Ault, T. R.; St. George, S.

    2007-12-01

    Recent studies have suggested that the risk of drought over North America changes at timescales of one to several decades, and that these changes are coherent over large areas. We present a complementary perspective that measures the importance of these signals at the local scale. We use singular spectrum analysis to identify regions in North American where decadal to multidecadal (D2M) signals make up a significant fraction of the total variance in annual or seasonal precipitation. In most regions, D2M variability is not significant, as precipitation is dominated by interannual variability and secular trends. Decadal variability is significant at the regional scale in some seasons, most prominently in Minnesota and northern California during winter, and the central Rocky Mountains in autumn. Eastern Quebec is the only region where precipitation exhibits significant variance in the multidecadal band. D2M variability in these four regions is generally not coherent, and does not resemble major modes of climate variability. Decadal signals in the discharge of the Sacramento River and, to a lesser degree, the Colorado River are coherent and in phase with similar signals in regional precipitation. It is possible that D2M signals in other aspects of the climate system or amplification of weak D2M signals in precipitation by landscape response could create large changes in drought severity on decadal or multidecadal timescales. However, our results indicate that changes in precipitation cannot by themselves be the cause of significant D2M variability in drought over most parts of North America.

  19. 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.

  20. Diagnosing the causes of decadal-scale precipitation variability in northeastern sub-Saharan Africa

    NASA Astrophysics Data System (ADS)

    Williams, P.

    2010-12-01

    The northeastern part of sub-Saharan Africa receives maximum rainfall during summer (June-September), as precipitation tracks the migration of the inter-tropical convergence zone (ITCZ) throughout tropical eastern Africa. Importantly, Ethiopia, Sudan, Eritrea, and northern Uganda experienced substantial precipitation declines during the past 50-60 years. These declines have not been spatially uniform. In the southern portion of this region, the decline has been steady and is ongoing with ~15-20% less summer rainfall in recent years than in the 1950s and 1960s. In the northwest, rainfall is much more variable inter-annually and a partial recovery has occurred after declines of ~30% from 1950-1985. In the northeast, declines from 1950-1985 were less extreme and have since completely recovered. What is the reasoning behind the rainfall declines in these regions, and why have they reversed in the north but continued in the south? I use a variety of observational, reanalysis, and modeled climate data to address these questions. The ongoing intensification of drought in the south is mainly attributable to declining moisture transports from the tropical Indian Ocean as a result of increasing subsidence over the eastern Horn of Africa. The increasing subsidence appears to be associated with warming of the tropical warm pool and increasing convection above the warm pool. In northern Sudan and Ethiopia, the drought from 1950-1985 and subsequent recovery appear to be associated with decadal-scale variability in the position and intensity of the ITCZ. This variability may be due to variations in the contrasting temperatures of the northern and southern hemisphere. I will refer to modeled and reconstructed past climate data to address whether increasing global temperatures have impacted these large-scale climate processes impacting summer rainfall in northeastern sub-Saharan Africa.

  1. Top-of-atmosphere radiative contribution to unforced decadal global temperature variability in climate models

    NASA Astrophysics Data System (ADS)

    Brown, Patrick T.; Li, Wenhong; Li, Laifang; Ming, Yi

    2014-07-01

    Much recent work has focused on unforced global mean surface air temperature (T) variability associated with the efficiency of heat transport into the deep ocean. Here the relationship between unforced variability in T and the Earth's top-of-atmosphere (TOA) energy balance is explored in preindustrial control runs of the Coupled Model Intercomparison Project Phase 5 multimodel ensemble. It is found that large decadal scale variations in T tend to be significantly enhanced by the net energy flux at the TOA. This indicates that unforced decadal variability in T is not only caused by a redistribution of heat within the climate system but can also be associated with unforced changes in the total amount of heat in the climate system. It is found that the net TOA radiation imbalances result mostly from changes in albedo associated with the Interdecadal Pacific Oscillation that temporarily counteracts the climate system's outgoing longwave (i.e., Stefan-Boltzmann) response to T change.

  2. Variability and evolution of global land surface phenology over the past three decades (1982-2012).

    PubMed

    Garonna, Irene; de Jong, Rogier; Schaepman, Michael E

    2016-04-01

    Monitoring land surface phenology (LSP) is important for understanding both the responses and feedbacks of ecosystems to the climate system, and for representing these accurately in terrestrial biosphere models. Moreover, by shedding light on phenological trends at a variety of scales, LSP provides the potential to fill the gap between traditional phenological (field) observations and the large-scale view of global models. In this study, we review and evaluate the variability and evolution of satellite-derived growing season length (GSL) globally and over the past three decades. We used the longest continuous record of Normalized Difference Vegetation Index data available to date at global scale to derive LSP metrics consistently over all vegetated land areas and for the period 1982-2012. We tested GSL, start- and end-of-season metrics (SOS and EOS, respectively) for linear trends as well as for significant trend shifts over the study period. We evaluated trends using global environmental stratification information in place of commonly used land cover maps to avoid circular findings. Our results confirmed an average lengthening of the growing season globally during 1982-2012 - averaging 0.22-0.34 days yr(-1) , but with spatially heterogeneous trends. About 13-19% of global land areas displayed significant GSL change, and over 30% of trends occurred in the boreal/alpine biome of the Northern Hemisphere, which showed diverging GSL evolution over the past three decades. Within this biome, the 'Cold and Mesic' environmental zone appeared as an LSP change hotspot. We also examined the relative contribution of SOS and EOS to the overall changes, finding that EOS trends were generally stronger and more prevalent than SOS trends. These findings constitute a step towards the identification of large-scale phenological drivers of vegetated land surfaces, necessary for improving phenological representation in terrestrial biosphere models. PMID:26924776

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  5. Upper ocean heat content and surface current variability associated with the Pacific Decadal Oscillation (PDO)

    NASA Astrophysics Data System (ADS)

    Lagerloef, Gary S. E.; Springer, Scott

    2010-05-01

    Changes in the northeast Pacific Ocean during 1993-2004 are examined as an example of upper ocean heat content variability associated with the Pacific Decadal Oscillation (PDO). The leading empirical orthogonal functions (EOF) of both sea surface temperature (SST) and sea surface height (SSH) in this region are highly correlated with the basin-wide PDO index, which transitioned from the warm to the cold phase in 1999. Sea surface velocities (SSV) constructed from satellite-observed SSH, SST, and vector winds indicate that Ekman and gesotrophic components changed with similar magnitudes but different spatial structures. Combining SSV with the SST field, in situ sub-surface temperature data, and surface heat fluxes from an atmospheric model makes it possible to construct an approximate SST budget. The results demonstrate a principal role for anomalous Ekman advection of the mean temperature gradient and relatively smaller contributions from the other terms, which agrees generally with similar analysis by others using an ocean general circulation model.

  6. 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 East Africa. Finally, to understand the East African regional climate in the context of the broader tropical climate and circulation, zonal momentum balance of the tropical atmospheric circulation during the global monsoon mature months (January and July) are analyzed in three dimensions based on the ERA-Interim Re-Analysis. It is found that the dominant terms in the balance of the atmospheric boundary layer (ABL) in both months are the pressure gradient force, the Coriolis force and friction. The nonlinear advection term plays a significant role only in the Asian summer monsoon regions including off East Africa. In the upper troposphere, the pressure gradient force, the Coriolis force and nonlinear advection are the dominant terms. The transient eddy force and the residual force (which can be explained as convective momentum transfer over open oceans) are secondary yet can not be neglected near the equator. Zonal mean equatorial upper troposphere easterlies are maintained by the absolute angular momentum advection associated with the cross-equatorial Hadley circulation. Equatorial upper troposphere easterlies over the Asian monsoon regions are also controllled by the absolute angular momentum advection but are mainly maintained by the pressure gradient force in January. The equivalent linear Rayleigh friction, which is widely applied in simple tropical models, is calculated and the corresponding spatial distribution of local coefficient and damping time scale are estimated from the linear regression. It is found that the linear momentum model is in general capable of crudely describing the tropical atmospheric circulation dynamics yet the caveat should be kept in mind that the friction coefficient is not uniformly distributed and is even negative in some regions.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  9. 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.

  10. Decadal variability of Russian winter snow accumulation and its associations with Atlantic sea surface temperature anomalies

    NASA Astrophysics Data System (ADS)

    Ye, Hengchun

    2000-11-01

    Russian winter snow depth data over a 48-year period (1936-1983) are analysed to reveal variation characteristics and associations to Atlantic sea surface temperature (SST) anomalies using methods of rotated principal component analysis (RPCA), singular spectrum analysis (SSA), and singular value decomposition (SVD) analysis.The study demonstrates that four time scales (4 years interannual, 11.8 years quasidecadal, 20 years bi-decadal and trend) characterize Russian winter snow depth variations. The decadal and longer time scale variations are found to be significantly associated with Atlantic SST anomalies. The trend, which occurred over much of the study region, is associated with SST trends over the northern north and tropical south Atlantic. Bi-decadal snow depth variation over central Siberia is associated with western tropical north Atlantic SSTs. A quasi-decadal variation over western European Russia is connected to a major Atlantic SST variation pattern of opposite signs over alternative latitudinal belts.This study suggests that the connections between the Atlantic Ocean and regional climate may be better reflected at decadal time scales than interannual and seasonal ones, as the dominant variability over the ocean is at slow modes.

  11. PDO and ENSO modulations intensified decadal sea level variability in the tropical Pacific

    NASA Astrophysics Data System (ADS)

    Moon, Jae-Hong; Song, Y. Tony; Lee, HuiKyo

    2015-12-01

    According to long-term sea level reconstruction and steric sea level data, regional sea levels in the tropical Pacific have oscillated between east and west on a decadal time scale over the past 60 years, but the oscillation has been intensified significantly in the last three decades. Using conditional composite analysis, we show that the recent intensification in sea level variability is caused by modulation between the Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO), i.e., an El Niño in a positive PDO or a La Niña in a negative PDO phase. Our analysis of meteorological fields indicates that atmospheric circulation associated with the changes in ENSO-PDO phase relationship plays a positive role in enhancing the decadal sea level oscillation. The intensified sea level oscillation, when superimposed on the global trend of sea level rise, will have profound implications for coastal communities, therefore, the combined effect of PDO and ENSO should be taken into account in the decadal sea level prediction in the tropical Pacific.

  12. D/H Ratios From Sierra Nevada Varved Lake Sediments Record Decadal Hydroclimate Variability During The Medieval Period

    NASA Astrophysics Data System (ADS)

    Roach, L. D.; Cayan, D. R.; Sessions, A. L.; Charles, C. D.; Anderson, R. S.

    2009-12-01

    Assessment of the risks of persistent drought requires multiple realizations of decadal and centennial scale hydroclimate variability that extend beyond the relatively short period of instrumental record. Much remains to be learned about the so called “mega droughts” in the Sierra Nevada Mountains, where various lines of evidence point toward the occurrence of severe, decades-long droughts during Medieval times, approximately 900-1400 AD. Here we present a continuous, decadal scale record of hydroclimate variability in the Sierra Nevada Mountains that extends through the heart of the purported Medieval mega droughts. Previous work on the stable hydrogen isotope (D/H) ratios of refractory plant lipid compounds stored in lake sediments demonstrated that these compounds reflect the D/H values of lake water and/or shallow ground water--reservoirs both fed by local precipitation. Lake sediment D/H can therefore reflect the processes that determine D/H of precipitation, including temperature, humidity and moisture source. We have measured D/H of aquatic and terrestrial plant fatty acids extracted from a suite of sediment cores collected at Swamp Lake (elevation: 1554m), in Yosemite National Park, along the Sierra Nevada crest. Measurements with biennial resolution were made for two time periods: the 20th century and the 13th-15th centuries. D/H fluctuations in 20th century sediment contain relatively strong decadal structure. Comparison with instrumentally recorded climate variability reveals that lower D/H concentrations are associated with years of higher than normal annual precipitation, cooler than normal wintertime temperatures, and positive April 1 Snow Water Equivalent (SWE) anomalies throughout the Sierra Nevada, (and conversely for elevated D/H concentrations). The range of variability is approximately 50‰. These associations may be driven by the variable mass-balance impact of evaporation on the isotopic composition of lake water and shallow groundwater in the Swamp Lake watershed, depending on the extent to which these reservoirs are replenished seasonally by wintertime precipitation. Throughout the Medieval period, we observe significant (>30‰), reproducible D/H variability that also fluctuates on multi-year to decadal time scales, with mean values falling within the same range as those recorded over the 20th century. Strong covariance among the aquatic and terrestrial plant fatty acids analyzed, along with the mean values, lends confidence that primary isotopic signatures have been retained. These results can therefore be compared directly to other measures of hydroclimate variability throughout the last millennium, offering a unique new perspective on the mega-drought intervals.

  13. Decadal-scale Climate Variability in the Gulf of Mexico During the Past 3000 Years

    NASA Astrophysics Data System (ADS)

    Flower, B. P.; Quinn, T. M.

    2007-12-01

    Understanding 20th century global warming depends in part on documenting natural climate variability beyond the range of instrumental records. However, proxy records of decadal-scale climate variability during the past 3000 years are sparse, especially for low-latitude oceans. Generation of proxy climate records from high accumulation rate sediment cores from the Gulf of Mexico can help evaluate climate variability in the low-latitude North Atlantic region. Here we present paired Mg/Ca and d18O measurements on the planktic foraminifer Globigerinoides ruber (white) from two northern Gulf of Mexico sediment cores that provide decadal-scale records of sea-surface temperature (SST) and d18O of seawater (d18Osw) over the past three thousand years (ka). Mg/Ca SST data exhibit a series of six 0.5 degree C oscillations from ca. 3-1 ka before a 2-3 degree C cooling including the Little Ice Age. These oscillations include warm intervals comparable to mid-20th century levels that may correspond to the Medieval Warm Period ca. 1 ka and the Roman Warm Period ca. 2 ka, but also provide evidence for higher-frequency variability. Time series analysis indicates significant periods in the multi-century band (300-600 years) and the multi-decadal band (60-80 years). Comparison to Sargasso Sea records demonstrates a broadly similar pattern of SST change in the low-latitude North Atlantic Ocean during the past 3 ka. Gulf of Mexico d18Osw, which is at present primarily controlled by Mississippi River input and evaporation- precipitation (E-P), seems to be consistent with some North American continental records. In particular, d18Osw maxima at ca. 2.5, 1.05, and 0.5 ka correlate with previously recognized dry intervals in central North America and the Yucatan peninsula. Gulf of Mexico d18Osw values exhibit significant variability, including strong peaks in the multi-decadal band (60-70 years) that are coherent and in phase with SST, but no change in mean (1.0+/-0.3 per mil) relative to core-top values. Overall, these results support models that suggest the Gulf of Mexico and North America have been strongly influenced by decadal- to century-scale changes in regional atmospheric conditions, including the position and strength of the subtropical high pressure cell.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  15. Southern ocean SST variability and its relationship with ENSO on inter-decadal time scales

    NASA Astrophysics Data System (ADS)

    Yan, Li; Du, Yan; Zhang, Lan

    2013-06-01

    Empirical orthogonal function (EOF) analysis reveals a co-variability of Sea surface temperatures (SSTs) in the Southern Hemisphere (0°-60°S). In the South Indian and Atlantic Oceans, there is a subtropical dipole pattern slanted in the southwest-northeast direction. In the South Pacific Ocean, a meridional tripole structure emerges, whose middle pole co-varies with the dipoles in the South Indian and Atlantic Oceans and is used in this study to track subtropical Pacific variability. The South Indian and Atlantic Ocean dipoles and the subtropical Pacific variability are phase-locked in austral summer. On the inter-decadal time scales, the dipoles in the South Indian and Atlantic Oceans weaken in amplitude after 1979/1980. No such weakening is found in the subtropical South Pacific Ocean. Interestingly, despite the reduced amplitude, the correlation of the Indian Ocean and Atlantic dipoles with El Niño and Southern Oscillation (ENSO) are enhanced after 1979/1980. The same increase in correlation is found for subtropical South Pacific variability after 1979/1980. These inter-decadal modulations imply that the Southern Hemisphere participates in part of the climate shift in the late 1970s. The correlation between Southern Hemisphere SST and ENSO reduces after 2000.

  16. Indian Ocean heat content changes masked by multi-decadal variability: Is the Indian Ocean warming or not?

    NASA Astrophysics Data System (ADS)

    Ummenhofer, Caroline; Biastoch, Arne; Böning, Claus

    2015-04-01

    The Indian Ocean has sustained robust surface warming in recent decades, with warming rates exceeding those of other tropical ocean basins. Significant, non-uniform trends in Indian Ocean sea surface temperatures - both in observations and projections for the 21st Century - have the potential to impact regional climate, through variations in the monsoon circulation, characteristics of Indian Ocean Dipole events, and the associated hydroclimate across the wider Indo-Pacific. However, it remains unclear what role decadal to multi-decadal variability in upper-ocean Indian Ocean thermal characteristics play in these trends. Using high-resolution ocean model hindcasts building on the ocean/sea-ice numerical Nucleus for European Modelling of the Ocean (NEMO) framework forced with atmospheric forcing fields of the Coordinated Ocean Reference Experiments (CORE), the characteristics of Indian Ocean temperature changes are explored. Sensitivity experiments, where interannual atmospheric forcing variability is restricted to thermal or wind-stress forcing only, support the interpretation of forcing mechanisms for the evolution of temperature characteristics across the Indian Ocean, focusing on the top 700m. Simulated temperature changes across the Indian Ocean in the hindcasts are consistent with those recorded in observational products, as well as ocean reanalyses. Assessment of Indian Ocean heat content since the 1950s suggests extensive (subsurface) cooling for much of the tropical Indian Ocean. The presence of substantial multi-decadal variability in its heat content further implies caution in interpreting linear trends in thermal properties, as long-term trends can be masked. The sensitivity experiments reveal that cooling trends in Indian Ocean heat content since the mid-1960s to the late 1990s are largely driven by wind-stress forcing, likely due to remote Pacific wind forcing associated with the Pacific Decadal Oscillation (PDO). As such, multi-decadal wind-forcing has masked increases in Indian Ocean heat content due to thermal forcing since the 1960s. However, wind and thermal forcing both contribute positively to Indian Ocean heat content since 1999 and thus drastic increases in Indian Ocean heat content in coming decades are likely, with implications for regional climate and vulnerable societies in Indian Ocean rim-countries.

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  19. Mesoscale simulations of multi-decadal variability in the wind resource over Korea

    NASA Astrophysics Data System (ADS)

    Kim, Do-Yong; Kim, Jin-Young; Kim, Jae-Jin

    2013-02-01

    This study investigated multi-decadal variability in the wind resource over the Republic of Korea using the Weather Research and Forecasting (WRF) mesoscale meteorological model. Mesoscale simulations were performed for the period from November 1981 to November 2010. The typical wind climatology over the Korean Peninsula, which is influenced by both continental and oceanic features, was represented by the physics-based mesoscale simulations. Winter had windier conditions with northwesterly flows, whereas less windy with southwesterly flows appeared in summer. The annual mean wind speeds over the Republic of Korea were approximately 2 m s-1 with strong wind in mountainous areas, coastal areas, and islands. The multi-decadal variability in wind speed during the study period was characterized by significant increases (positive trend) over many parts of the study area, even though the various local trends appeared depending on the station locations. The longterm trend in the spatially averaged wind speed was approximately 0.002 m s-1 yr-1. The annual frequency of daily mean wind speeds over 5 m s-1 at the turbine hub height also increased during the study period throughout the Republic of Korea. The present study demonstrates that multi-decadal mesoscale simulations can be useful for climatological assessment of wind energy potential.

  20. Observing variable stars. A guide for beginners

    NASA Astrophysics Data System (ADS)

    Levy, David H.

    David Levy's entertaining, well-researched book is aimed at the amateur enthusiast who likes to learn enjoyably. Beginning with advice on binoculars and telescopes, and how to observe the night sky effectively, the author goes on to describe thoroughly the field of variable star observation, a field in which amateurs have made important contributions. He shows how to interpret variations in light output in terms of the life of a star, from birth through to sometimes violent death. All of the major variable stars are described and classified, as well as other variable objects such as active galaxies, asteroids, comets and the sun. The book also contains a guide to the seasonal night sky. Throughout, practical observations serve to complement the text, producing an exciting, very readable introduction to this fascinating subject.

  1. Interannual to decadal summer drought variability over Europe and its relationship with global sea surface temperature

    NASA Astrophysics Data System (ADS)

    Ionita, Monica; Lohmann, Gerrit; Rimbu, Norel; Chelcea, Silvia

    2010-05-01

    Variability and predictability of European summer drought conditions during observational period is investigated. The dominat patterns of European drought and their associated large-scale climatic anomalies are identified through canonical correlation analysis (CCA) of the field of self calibrating Palmer Drought Severity Index (PDSI) and global sea surface temperature (SST) anomalies. At interannual time scales we identified patterns of drought variability which are optimally correlated with SST patterns from previous years. The time lag between drought and SST anomaly patterns can provide valuable skill for the prediction of drought conditions over Europe on interannual time scales. Significant lag-correlation between drought patterns and the North Atlantic Oscillation (NAO) suggests that NAO can be used also as a potential predictor of drought European patterns at interannual time scales. The global trend in temperature, the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO) play a significant role in establishing the drought conditions over Europe at multidecadal time scales. The influences of these climatic patterns on drought conditions at multidecadal time scales were identified also through CCA. The first PDSI pattern (CCA1) shows a dipole-like structure between the central Europe and the northern part of the Scandinavian Peninsula. The corresponding SST pattern is a mixture between the global SST trend and the abrupt shift in the 1970s. Wet (dry) conditions over central Europe (Scandinavia) are associated with a strong positive SST center south of Greenland and a strong negative center over the European coast and the North Sea. The third mode (CCA3) identifies a multidecadal scale variation, strongly related to summer drought conditions over the southern part of the Scandinavian Peninsula, the south-eastern part of Europe and the western part of Russia. The corresponding SST pattern shows SST anomalies in the Atlantic basin similar to those associated with AMO. The AMO index and the canonical time series associated to CCA3 are significantly correlated. Possible drought conditions over Europe in the next decades based on the relationships between large-scale SST patterns and drought conditions over Europe, established in our study, are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  3. Decadal-scale variability in climate proxy records: a search for tidal and solar forcing

    NASA Astrophysics Data System (ADS)

    Berger, W.; Paetzold, J.; Wefer, G.

    2003-04-01

    Decadal-scale climate- and ocean variability is an unsolved problem. The geologic record holds a number of clues as to possible forcing functions; useful proxy series are in ice cores, corals, biogenic deposits in anaerobic basins, marine varves and small turbidites, in the sea and in lakes. Certain decadal-scale cycles seem to occur more commonly than others, and in a number of records with an entirely different pedigree, suggesting effects from outside forcing. If we assume that both solar forcing and tidal forcing play some role (as supported by spectra from corals and varves), we should expect interference between the respective forcing functions. From such interference, we can calculate the most likely periods to be found. Analysis of an 800-y coral record from Bermuda suggests that such interference periods are expressed in this proxy record.

  4. Swithin St. Cleeve: Variable Star Observer

    NASA Astrophysics Data System (ADS)

    Weitzenhoffer, K.

    1986-12-01

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

  5. 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.

  6. 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

  7. Analysis of air quality variability in Shanghai using AOD and API data in the recent decade

    NASA Astrophysics Data System (ADS)

    Zhao, Qing; Gao, Wei; Xiang, Weining; Shi, Runhe; Liu, Chaoshun; Zhai, Tianyong; Huang, Hung-lung Allen; Gumley, Liam E.; Strabala, Kathleen

    2013-06-01

    We use the aerosol optical depth (AOD) measured by the moderate resolution imaging spectrometer (MODIS) onboard the Terra satellite, air pollution index (API) daily data measured by the Shanghai Environmental Monitoring Center (SEMC), and the ensemble empirical mode decomposition (EEMD) method to analyze the air quality variability in Shanghai in the recent decade. The results indicate that a trend with amplitude of 1.0 is a dominant component for the AOD variability in the recent decade. During the World Expo 2010, the average AOD level reduced 30% in comparison to the long-term trend. Two dominant annual components decreased 80% and 100%. This implies that the air quality in Shanghai was remarkably improved, and environmental initiatives and comprehensive actions for reducing air pollution are effective. AOD and API variability analysis results indicate that semi-annual and annual signals are dominant components implying that the monsoon weather is a dominant factor in modulating the AOD and API variability. The variability of AOD and API in selected districts located in both downtown and suburban areas shows similar trends; i.e., in 2000 the AOD began a monotonic increase, reached the maxima around 2006, then monotonically decreased to 2011 and from around 2006 the API started to decrease till 2011. This indicates that the air quality in the entire Shanghai area, whether urban or suburban areas, has remarkably been improved. The AOD improved degrees (IDS) in all the selected districts are (8.6±1.9)%, and API IDS are (9.2±7.1)%, ranging from a minimum value of 1.5% for Putuo District to a maximum value of 22% for Xuhui District.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  10. Interannual to decadal variability in circum-Antarctic sea level and transport

    NASA Astrophysics Data System (ADS)

    Hughes, C. W.; Williams, J.

    2013-12-01

    It is known that intra-annual Antarctic sea level variability is highly coherent and represents a barotropic adjustment process associated with wind-driven fluctuations in circumpolar transport. It is also thought that circumpolar transport adjusts to changes in the oceans to the north on multi-century time scales. However, the Antarctic Circumpolar Current is not barotropic, and questions remain about the nature of the variability on intermediate timescales. Here we use multidecadal runs of two eddy-permitting ocean models, together with 50 years of Antarctic tide gauge data, to show three things. 1) The relationship between transport and averaged southern bottom pressure remains the same at period from days to multidecadal. 2) The sea level signal becomes larger than the bottom pressure signal at periods longer than about 4 years. 3) The variability becomes larger than can be explained by wind-driven fluctuations at periods longer than a decade or two. This suggests that longer period variability is dominated by changes in water mass properties, perhaps due to varying freshwater inputs, although the tide gauge measurements may also be influenced by vertical land movement due to changing ice load nearby.

  11. 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.

  12. 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.

  13. The influence of decadal-scale variability on trends in long European streamflow records

    NASA Astrophysics Data System (ADS)

    Hannaford, J.; Buys, G.; Stahl, K.; Tallaksen, L. M.

    2013-02-01

    This study seeks to provide a long-term context for the growing number of trend analyses which have been applied to river flows in Europe. Most studies apply trend tests to fixed periods, in relatively short (generally 1960s-present) records. This study adopts an alternative "multi-temporal" approach, whereby trends are fitted to every possible combination of start and end years in a record. The method is applied to 132 catchments with long (1932-2004) hydrometric records from northern and central Europe, which were chosen as they are minimally anthropogenically influenced and have good quality data. The catchments are first clustered into five regions, which are broadly homogenous in terms of interdecadal variability of annual mean flow. The multi-temporal trend approach was then applied to regional time series of different hydrological indicators (annual, monthly and high and low flows). The results reveal that the magnitude and even direction of short-term trends are heavily influenced by interdecadal variability. Some short-term trends revealed in previous studies are shown to be unrepresentative of long-term change. For example, previous studies have identified post-1960 river flow decreases in southern and eastern Europe: in parts of eastern Europe, these trends are resilient to study period, extending back to the 1930s; in southern France, longer records show evidence of positive trends which reverse from the 1960s. Recent (post-1960) positive trends in northern Europe are also not present in longer records, due to decadal variations influenced by the North Atlantic Oscillation. The results provide a long-term reference for comparison with published and future studies. The multi-temporal approach advocated here is recommended for use in future trend assessments, to help contextualise short-term trends. Future work should also attempt to explain the decadal-scale variations that drive short-term trends, and thus develop more sophisticated methods for trend detection that take account of interdecadal variability and its drivers.

  14. The influence of decadal-scale variability on trends in long European streamflow records

    NASA Astrophysics Data System (ADS)

    Hannaford, J.; Buys, G.; Stahl, K.; Tallaksen, L. M.

    2013-07-01

    This study seeks to provide a long-term context for the growing number of trend analyses which have been applied to river flows in Europe. Most studies apply trend tests to fixed periods, in relatively short (generally 1960s-present) records. This study adopts an alternative "multi-temporal" approach, whereby trends are fitted to every possible combination of start and end years in a record. The method is applied to 132 catchments with long (1932-2004) hydrometric records from northern and central Europe, which were chosen as they are minimally anthropogenically influenced and have good quality data. The catchments are first clustered into five regions, which are broadly homogenous in terms of interdecadal variability of annual mean flow. The multi-temporal trend approach was then applied to regional time series of different hydrological indicators (annual, monthly and high and low flows). The results reveal that the magnitude and even direction of short-term trends are heavily influenced by interdecadal variability. Some short-term trends revealed in previous studies are shown to be unrepresentative of long-term change. For example, previous studies have identified post-1960 river flow decreases in southern and eastern Europe: in parts of eastern Europe, these trends are resilient to study period, extending back to the 1930s; in southern France, longer records show evidence of positive trends which reverse from the 1960s. Recent (post-1960) positive trends in northern Europe are also not present in longer records, due to decadal variations influenced by the North Atlantic Oscillation. The results provide a long-term reference for comparison with published and future studies. The multi-temporal approach advocated here is recommended for use in future trend assessments, to help contextualise short-term trends. Future work should also attempt to explain the decadal-scale variations that drive short-term trends, and thus develop more sophisticated methods for trend detection that take account of interdecadal variability and its drivers.

  15. Role of Eurasian snow cover in wintertime circulation: Decadal simulations forced with satellite observations

    NASA Astrophysics Data System (ADS)

    Orsolini, Yvan J.; Kvamstø, Nils G.

    2009-10-01

    We investigate the impact of the Eurasian snow cover extent on the Northern Hemisphere winter circulation by performing a suite of ensemble simulations with the Météo-France "Arpege Climat" atmospheric general circulation model, spanning 2 decades (1979-2000). Observed snow cover derived from satellite infrared and visible imagery has been forced weekly into the model. Variability in autumn-early winter snow cover extent over eastern Eurasia is linked to circulation anomalies over the North Pacific that are influencing the North Atlantic sector in late winter through the development of the Aleutian-Icelandic Low Seesaw teleconnection. The forcing of realistic snow cover in the model augments potential predictability over eastern Eurasia and the North Pacific and improves the hindcast skill score of the Aleutian-Icelandic Low Seesaw teleconnection. Enhanced eastern Eurasia snow cover is associated with an anomalous upper-tropospheric wave train across Eurasia, anomalously high upward wave activity flux, and a displaced stratospheric polar vortex.

  16. Decadal variability in the north Atlantic subtropical gyre: Can it explain variability in sea level along the East Coast of the United States?

    NASA Astrophysics Data System (ADS)

    Hong, Byung-Gi

    1998-10-01

    The variation in wind curl over the ocean leads to surprisingly large north-south variability in the computed oceanic response over the subtropical gyre. The peak-to-peak sea level differences are as great as 20 cm and persist for many years. In addition to the open-ocean variability, one of the puzzling features of sea level on the east coast of the United States is a similar, decadal-scale variability; the fluctuations are 10 to 15 cm, peak to peak, at periods longer than a few years. The primary goal of the work described here is to understand the cause(s) of this variability. Furthermore, these large fluctuations at the coast raises the obvious question. Is there similar variability in the slope of sea level across the Gulf Stream and consequently in transport? Using the results of our wind-forced open ocean model, we can determine the ocean variability with a satisfactory degree of accuracy. Once these fluctuations in the thermocline reach the western side of the ocean, the transport is conserved as the signal enters the Gulf Stream. The computed fluctuations at the boundary are compared with observations at tide gauges. Between 80 and 90% of the variance can be explained, depending on the details of the calculation.

  17. Local and remote forcing of decadal sea level and thermocline depth variability in the South Indian Ocean

    NASA Astrophysics Data System (ADS)

    Trenary, Laurie L.; Han, Weiqing

    2013-01-01

    AbstractAnalysis is performed on a set of diagnostic numerical experiments designed to isolate local Indian Ocean forcing versus remote forcing from the Pacific via the Indonesian throughflow on <span class="hlt">decadal</span> <span class="hlt">variability</span> of subsurface temperature, sea level, and thermocline depth of the South Indian Ocean. It is found that the vertical structure of <span class="hlt">decadal</span> temperature <span class="hlt">variability</span> varies from <span class="hlt">decade-to-decade</span>, with maximum variation peaking in the vicinity of the thermocline. The <span class="hlt">decadal</span>-scale temperature variations in the tropical southwestern Indian Ocean between 5°S and 17°S are primarily associated with the vertical displacements of the thermocline. Prior to the early 1990s, <span class="hlt">decadal</span> variations in sea level and thermocline depth can be described in terms of a baroclinic Sverdrup balance, forced by Ekman pumping velocity associated with windstress curl acting on the Indian Ocean. Beginning in the early 1990s, <span class="hlt">decadal</span> <span class="hlt">variability</span> of the equatorial Pacific trades forces thermocline variations that modify the sea level and thermocline depth across the tropical South Indian Ocean basin. Farther south, between 20°S and 30°S, oceanic internal <span class="hlt">variability</span> makes significant contributions to <span class="hlt">decadal</span> <span class="hlt">variability</span> of the thermocline. The anomalies along the western coast of Australia are primarily driven by regional forcing acting on the Indian Ocean prior to the 1990s, and signals originating from the equatorial Pacific make a greater contribution thereafter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H13C1120T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H13C1120T"><span id="translatedtitle"><span class="hlt">Decadal</span> climatic <span class="hlt">variability</span> and regional weather simulation: stochastic nature of forest fuel moisture and climatic forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsinko, Y.; Johnson, E. A.; Martin, Y. E.</p> <p>2014-12-01</p> <p>Natural range of <span class="hlt">variability</span> of forest fire frequency is of great interest due to the current changing climate and seeming increase in the number of fires. The <span class="hlt">variability</span> of the annual area burned in Canada has not been stable in the 20th century. Recently, these changes have been linked to large scale climate cycles, such as Pacific <span class="hlt">Decadal</span> Oscillation (PDO) phases and El Nino Southern Oscillation (ENSO). The positive phase of the PDO was associated with the increased probability of hot dry spells leading to drier fuels and increased area burned. However, so far only one historical timeline was used to assess correlations between the natural climate oscillations and forest fire frequency. To counteract similar problems, weather generators are extensively used in hydrological and agricultural modeling to extend short instrumental record and to synthesize long sequences of daily weather parameters that are different from but statistically similar to historical weather. In the current study synthetic weather models were used to assess effects of alternative weather timelines on fuel moisture in Canada by using Canadian Forest Fire Weather Index moisture codes and potential fire frequency. The <span class="hlt">variability</span> of fuel moisture codes was found to increase with the increased length of simulated series, thus indicating that the natural range of <span class="hlt">variability</span> of forest fire frequency may be larger than that calculated from available short records. It may be viewed as a manifestation of a Hurst effect. Since PDO phases are thought to be caused by diverse mechanisms including overturning oceanic circulation, some of the lower frequency signals may be attributed to the long term memory of the oceanic system. Thus, care must be taken when assessing natural <span class="hlt">variability</span> of climate dependent processes without accounting for potential long-term mechanisms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DSRI...95...85S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DSRI...95...85S"><span id="translatedtitle">Interannual to <span class="hlt">decadal</span> oxygen <span class="hlt">variability</span> in the mid-depth water masses of the eastern North Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stendardo, Ilaria; Kieke, Dagmar; Rhein, Monika; Gruber, Nicolas; Steinfeldt, Reiner</p> <p>2015-01-01</p> <p>The detection of multi-<span class="hlt">decadal</span> 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 <span class="hlt">decadal</span> <span class="hlt">variability</span>, which hitherto is poorly known and characterized. Here we address this gap by studying interannual to <span class="hlt">decadal</span> 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 <span class="hlt">variability</span>, we <span class="hlt">observe</span> 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 <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22711907F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22711907F"><span id="translatedtitle"><span class="hlt">Variability</span> Statistics for Galaxies <span class="hlt">Observed</span> by Kepler</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fanelli, Michael N.; Marcum, Pamela M.; Van Cleve, Jeffrey E.</p> <p>2016-01-01</p> <p>The Kepler / K2 telescope combines high photometric precision with near-continuous <span class="hlt">observing</span> cadence, permitting a unique perspective on the optical / near-IR <span class="hlt">variability</span> of galactic systems. In particular, Kepler / K2 data can be exploited to quantify the amplitude of AGN signals in galaxy cores, to directly address this question - What fraction of galactic nuclei are active at any given time ? Alternatively stated, this question becomes - What is the duty cycle for supermassive black hole accretion of sufficient strength to produce a detectable optical signal ? Additionally, the quasi-continuous cadence provides the capability to detect low-level episodic variations from the central AGN, highly luminous stars and other compact objects.Previously we reported on analysis of a subset of the complete galaxy dataset <span class="hlt">observed</span> during the Kepler prime mission: ~1200 individual light curves of ~150 targeted galaxies <span class="hlt">observed</span> during Quarters 3-10 and ~1000 light curves of galaxies <span class="hlt">observed</span> serendipitously by the exoplanet program from Q2 through Q16. Based on an average of 8 quarters of data for ~300 systems and excluding systems specifically targeted as AGNs, we found that the <span class="hlt">observed</span> occurrence rate of nuclear <span class="hlt">variability</span> in galaxies with amplitude > 1 millimag is ~2-3%, a value which is ~ 2-3 times smaller than previous estimates from ground-based monitoring.Here we provide an update on galactic nuclear <span class="hlt">variability</span> statistics using an expanded dataset from the Kepler Prime mission. We combine the previous data with 1200 light curves for ~200 targeted systems from Q11-16 and ~800 additional light curves found in the exoplanet program. These data are the longest continuous time series for galaxies ever obtained - some systems were <span class="hlt">observed</span> for the entire mission (Q2-16). Our previous result is confirmed using this expanded dataset; only a few percent of galaxies show <span class="hlt">variability</span> above 0.5 millimag. Several systems exhibiting activity in other bands, or via their optical spectra, show no measurable variations in the Kepler band. We also provide some preliminary <span class="hlt">variability</span> estimates from K2 data.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFMPP21A1371V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFMPP21A1371V"><span id="translatedtitle">A Continental Shelf Sediment Transport Proxy Record of <span class="hlt">Decadal</span> Atmospheric and Oceanographic <span class="hlt">Variability</span> in Southern Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vienne, W. F.; Jaeger, J.</p> <p>2004-12-01</p> <p>The Gulf of Alaska (GOA) margin is a prime location to study and quantitatively model glacial climate and continental margin sedimentation. Coupled oceanographic and atmospheric processes control sediment transport and sedimentation patterns on the GOA continental shelf, and consequently contain a proxy record for regional climate <span class="hlt">variability</span>. However, the specifics of this coupled relationship between climate and sediment transport have not been studied. In collaboration with the GOA-NEP GLOBEC program, gravity cores were taken at three sites of high sedimentation rates along the GOA margin in 2001 and 2003 representing proximal and distal shelf depocenters. Chronologies were established using Pb-210 and Cs-137 and sedimentation rates vary from 0.3 to 3 cm/yr, providing near-annual to <span class="hlt">decadal</span>-scale resolution. High-spatial resolution grain-size analyses and multi-sensor core logging of bulk density and magnetic susceptibility were measured to recognize relationships between these three proxies of sediment transport in each core and between sites. The time series of these properties have been compared to oceanographic and atmospheric instrumental records--generally beginning in the early to middle 20th century--such as sea level pressure, temperature, significant wave height, and wind speed. The three measured properties positively correlate within each core and between each core, indicating that these are likely controlled by similar sediment transport processes, such as wave resuspension and bottom-current transport, at all three sites. Strong correlation on a <span class="hlt">decadal</span> scale was found between the physical properties of the cores and the instrumental records of temperature and significant wave height, as well as <span class="hlt">variability</span> in regional precipitation. Also, there is a marked increase in bulk density, magnetic susceptibility, and grain size values from the late 1970's onward, which corresponds to the timing of a shift from a negative to a positive regime in the Pacific <span class="hlt">Decadal</span> Oscillation. These results suggest that temporal <span class="hlt">variability</span> in grain size, bulk density, and magnetic susceptibility on Alaska's continental shelf are, in part, controlled by changes in wind speed, wind direction, and wave height.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H52G..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H52G..07C"><span id="translatedtitle">A Robust Decision-Making Technique for Water Management under <span class="hlt">Decadal</span> Scale Climate <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Callihan, L.; Zagona, E. A.; Rajagopalan, B.</p> <p>2013-12-01</p> <p>Robust decision making, a flexible and dynamic approach to managing water resources in light of deep uncertainties associated with climate <span class="hlt">variability</span> at inter-annual to <span class="hlt">decadal</span> 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 <span class="hlt">decadal</span> scale projections with selection of efficient strategies. Previous approaches to water resources planning under inter-annual climate <span class="hlt">variability</span> combining skillful seasonal flow forecasts with climatology for subsequent years are not skillful for medium term (i.e. <span class="hlt">decadal</span> scale) projections as decision makers are not able to plan adequately to avoid vulnerabilities. We address this need by integrating skillful <span class="hlt">decadal</span> 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 <span class="hlt">decadal</span> 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 <span class="hlt">variability</span>. 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy..tmp..380Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy..tmp..380Z"><span id="translatedtitle">Dynamics and mechanisms of <span class="hlt">decadal</span> <span class="hlt">variability</span> of the Pacific-South America mode over the 20th century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Li; Ma, Hao; Wu, Lixin</p> <p>2015-08-01</p> <p>In this paper, <span class="hlt">decadal</span> <span class="hlt">variability</span> of the Pacific-South America (PSA) mode is examined from year 1871 to 2008 based on the newly developed ocean and atmosphere reanalysis products. The PSA mode, mirroring the Pacific-North America mode in the Northern Hemisphere, emerges as the second EOF mode of 500 mb geopotential height anomalies. The mode displays substantial interannual-<span class="hlt">decadal</span> <span class="hlt">variability</span> with distinct timescales between 3-8 and 10-18 years, respectively. The <span class="hlt">decadal</span> <span class="hlt">variability</span> of the PSA mode is found to be associated with the coupled ocean-atmosphere interaction over the subtropical South and tropical Pacific. The subduction of the subtropical temperature anomalies in the South Pacific in conjunction with the tropical-subtropical atmospheric teleconnection plays important role in the <span class="hlt">decadal</span> <span class="hlt">variability</span> of the PSA mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.7166W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.7166W"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> in seawater pH in the West Pacific: Evidence from coral δ11B records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Gangjian; Wang, Zhibing; Ke, Ting; Liu, Ying; Deng, Wenfeng; Chen, Xuefei; Xu, Jifeng; Zeng, Ti; Xie, Luhua</p> <p>2015-11-01</p> <p>Long-term seawater pH records are essential for evaluating the rates of ocean acidification (OA) driven by anthropogenic emissions. Widespread, natural <span class="hlt">decadal</span> <span class="hlt">variability</span> in seawater pH superimposes on the long-term anthropogenic variations, likely influencing the OA rates estimated from the pH records. Here, we report a record of annual seawater pH estimated using the δ11B proxy over the past 159 years reconstructed from a Porites coral collected to the east of Hainan Island in the northern South China Sea (SCS). By coupling this time series with previously reported long-term seawater pH records in the West Pacific, the <span class="hlt">decadal</span> <span class="hlt">variability</span> in seawater pH records and its possible driving mechanisms were investigated. The results indicate that large <span class="hlt">decadal</span> <span class="hlt">variability</span> in seawater pH has occurred off eastern Hainan Island over the past 159 years, in agreement with previous records. The Qiongdong upwelling system, which controls nutrient supplies, regulates surface water productivity, and is driven by the East Asian summer monsoon, is the primary control of this <span class="hlt">decadal</span> <span class="hlt">variability</span>, while terrestrial inputs appear not influence significantly. Meanwhile the impacts of the Pacific <span class="hlt">Decadal</span> Oscillation (PDO) and the El Nino and Southern Oscillation (ENSO) systems on seawater pH off eastern Hainan Island is likely limited. In contrast, the PDO is the main factor to influence the <span class="hlt">decadal</span> seawater pH <span class="hlt">variability</span> offshore the East Australia, while the mechanism controlling the <span class="hlt">decadal</span> seawater pH <span class="hlt">variability</span> in Guam is not clear yet. Meanwhile, The rate of decrease in seawater pH estimated from coral records are significantly different in different regions and over different time spans, which may reflect a combination of natural <span class="hlt">decadal</span> <span class="hlt">variability</span> in seawater pH and long-term variations. Therefore, understanding the mechanisms driving natural <span class="hlt">variability</span> in seawater pH is important for improving estimates of ocean acidification rates driven by anthropogenic emissions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19820037971&hterms=CVS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DCVS','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19820037971&hterms=CVS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DCVS"><span id="translatedtitle">X-ray <span class="hlt">observations</span> of cataclysmic <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Becker, R. H.</p> <p>1981-01-01</p> <p>Cataclysmic <span class="hlt">variables</span> (CVs) as a class are defined by their optical properties, in particular the amplitudes and frequency of their outbursts. The availability of the Imaging Proportional Counter (IPC) on the Einstein Laboratory has increased significantly the number of CVs which can be studied on the basis of X-ray <span class="hlt">observations</span>. In this connection, Becker and Marshall (1981) and Cordova et al. (1980) have surveyed 20 CVs and detected 70% of them. A description is presented of <span class="hlt">observations</span> of an additional 12 CVs, and the properties of the combined set of 32 CVs are discussed. It is found that the CVs do not have any distinguishing X-ray characteristics. The IPC data alone cannot be used to determine to which category of CVs a particular source belongs, or even to identify an object as a CV. On the other hand, the optical <span class="hlt">observations</span> are essential for estimating the X-ray luminosity from the IPC data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014BGeo...11.5181B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014BGeo...11.5181B"><span id="translatedtitle">Land surface phenological response to <span class="hlt">decadal</span> climate <span class="hlt">variability</span> across Australia using satellite remote sensing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Broich, M.; Huete, A.; Tulbure, M. G.; Ma, X.; Xin, Q.; Paget, M.; Restrepo-Coupe, N.; Davies, K.; Devadas, R.; Held, A.</p> <p>2014-09-01</p> <p>Land surface phenological cycles of vegetation greening and browning are influenced by <span class="hlt">variability</span> in climatic forcing. Quantitative spatial information on phenological cycles and their <span class="hlt">variability</span> is important for agricultural applications, wildfire fuel accumulation, land management, land surface modeling, and climate change studies. Most phenology studies have focused on temperature-driven Northern Hemisphere systems, where phenology shows annually recurring patterns. However, precipitation-driven non-annual phenology of arid and semi-arid systems (i.e., drylands) received much less attention, despite the fact that they cover more than 30% of the global land surface. Here, we focused on Australia, a continent with one of the most <span class="hlt">variable</span> rainfall climates in the world and vast areas of dryland systems, where a detailed phenological investigation and a characterization of the relationship between phenology and climate <span class="hlt">variability</span> are missing. To fill this knowledge gap, we developed an algorithm to characterize phenological cycles, and analyzed geographic and climate-driven <span class="hlt">variability</span> in phenology from 2000 to 2013, which included extreme drought and wet years. We linked derived phenological metrics to rainfall and the Southern Oscillation Index (SOI). We conducted a continent-wide investigation and a more detailed investigation over the Murray-Darling Basin (MDB), the primary agricultural area and largest river catchment of Australia. Results showed high inter- and intra-annual <span class="hlt">variability</span> in phenological cycles across Australia. The peak of phenological cycles occurred not only during the austral summer, but also at any time of the year, and their timing varied by more than a month in the interior of the continent. The magnitude of the phenological cycle peak and the integrated greenness were most significantly correlated with monthly SOI within the preceding 12 months. Correlation patterns occurred primarily over northeastern Australia and within the MDB, 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 <span class="hlt">decadal</span> droughts to flooding caused by La Niña.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.9889S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.9889S"><span id="translatedtitle">Impact of the Atlantic meridional overturning circulation on the <span class="hlt">decadal</span> <span class="hlt">variability</span> of the Gulf Stream path and regional chlorophyll and nutrient concentrations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanchez-Franks, A.; Zhang, R.</p> <p>2015-11-01</p> <p>In this study, we show that the underlying physical driver for the <span class="hlt">decadal</span> <span class="hlt">variability</span> in the Gulf Stream (GS) path and the regional biogeochemical cycling is linked to the low frequency <span class="hlt">variability</span> in the Atlantic meridional overturning circulation (AMOC). There is a significant anticorrelation between AMOC variations and the meridional shifts of the GS path at <span class="hlt">decadal</span> time scale in both <span class="hlt">observations</span> and two Earth system models (ESMs). The chlorophyll and nutrient concentrations in the GS region are found significantly correlated with the AMOC fingerprint and anticorrelated with the GS path at <span class="hlt">decadal</span> time scale through coherent isopycnal changes in the GS front in the ESMs. Our results illustrate how changes in the large-scale ocean circulation, such as AMOC, are teleconnected with regional <span class="hlt">decadal</span> physical and biogeochemical variations near the North American east coast. Such linkages are useful for predicting future physical and biogeochemical variations in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUSM.U41B..02L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUSM.U41B..02L"><span id="translatedtitle">Satellite <span class="hlt">observations</span> of global atmospheric energy budgets: annual means and <span class="hlt">decadal</span> records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, B.; Stackhouse, P.; Minnis, P.; Wielicki, B.; Schlosser, C. A.; Rodell, M.; Hu, Y.; Sun, W.; Fan, T. A.; Hinkelman, L.</p> <p>2008-05-01</p> <p>The global atmospheric energy budget can tell us a lot about the earth's climate system, and is critical for general circulations of the atmosphere. This study uses satellite data sets of the radiation at the top of atmosphere (TOA) and surface from ERBE, CERES and ISCCP and the latent and sensible heat over oceans from SSM/I to assess the global energy budgets. Over land, surface radiation estimates are used to constrain GLDAS model assimilated results and to force the radiation, turbulent heat, and land surface heat storage into balance due to a lack of <span class="hlt">observation</span>-based turbulent heat flux estimations. Because of satellite data availability of broadband <span class="hlt">observations</span> for radiation and microwave measurements for turbulent fluxes, this study considers the atmospheric energy budgets during 1988 and 2005. Global annual means of the TOA net radiation are close to zero. The net radiative energy fluxes into the surface and the surface latent heat transported into the atmosphere are about 113 and 86 W/m2, respectively. The estimated atmospheric and surface heat imbalances are about ­ 8 ~ 9 W/m2, values that are within the uncertainties of surface radiation and sea surface turbulent flux estimates and likely systematic biases in the analyzed <span class="hlt">observations</span>. The potential significant additional absorption of solar radiation within the atmosphere suggested by previous studies does not appear to be required to balance the energy budget: the spurious heat imbalances in the current data are much smaller (about half) than those obtained previously and debated at about a <span class="hlt">decade</span> ago. For long term energy budgets, TOA radiation measurements show a clear relationship with the changes in the ocean heat storage. Although most oceanic latent and sensible heat data sets have significant unrealistic long-term variations, some satellite global <span class="hlt">observations</span> of marine latent heat fluxes from evaporation and precipitation measurements exhibit potential correlations with sea surface temperature records. For satellite surface radiation data, no significant changes during the same time period are found. These differences in the <span class="hlt">variability</span> of radiation and turbulence need to be further investigated. The uncertainties in current satellite data sets may limit our capability of fully closing the atmospheric energy cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JSR....93..118F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JSR....93..118F"><span id="translatedtitle">High marsh foraminiferal assemblages' response to intra-<span class="hlt">decadal</span> and multi-<span class="hlt">decadal</span> precipitation <span class="hlt">variability</span>, between 1934 and 2010 (Minho, NW Portugal)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fatela, Francisco; Moreno, João; Leorri, Eduardo; Corbett, Reide</p> <p>2014-10-01</p> <p>Foraminiferal assemblages of Caminha tidal marshes have been studied since 2002 revealing a peculiar dominance of brackish species, such as Haplophragmoides manilaensis, Haplophragmoides wilberti, Haplophragmoides sp., Pseudothurammina limnetis and Trochamminita salsa/irregularis in the high marshes of the Minho and the Coura lower estuaries. The assemblage composition reflects low salinity conditions, despite the short distance to the estuarine mouth (~ 4 km). However, in May 2010, the presence of salt marsh species Trochammina inflata and Jadammina macrescens became very significant, likely a result of 5 consecutive dry years and a corresponding salinity rise in sediment pore water. Correspondence analysis (CA) groups the surface samples according to their marsh zone, showing a positive correlation with the submersion time of each sampling point. The brackish and normal salinity foraminiferal species appear separated in the CA. This <span class="hlt">observation</span> was applied to the top 10 cm of a high marsh sediment core that corresponds to the period of instrumental record of precipitation and river flow in the Minho region. We found that river flow strongly correlates with precipitation in the Lima and Minho basins. The longer precipitation record was, therefore, used to interpret the foraminiferal assemblages' <span class="hlt">variability</span>. Three main phases were distinguished along ca. 80 years of precipitation data: 1) negative anomalies from 1934 to 1957; 2) positive anomalies from 1958 to 1983; and 3) negative anomalies from 1984 to 2010. This last dryer period exhibits the precipitation maximum and the greatest amplitude of rainfall values. High marsh foraminifera reveals a fast response to these short-term shifts; low salinity species relative abundance increases when precipitation increases over several <span class="hlt">decades</span>, as well as in the same <span class="hlt">decade</span>, in the years of heavy rainfall of dryer periods. High marsh foraminifera records the increase of freshwater flooding and seepage by 1) decreasing abundance and 2) increasing the dominance of low salinity species. On the other hand, low precipitation over ca. 5 years increases the assemblage productivity and the relative abundance of normal salinity species. The positive correlation found between winter precipitation and the NAO winter index indicates that the Minho region is a part of the North Atlantic climate dynamics and demonstrates that the foraminiferal record from Caminha high marsh may be applied in high-resolution studies of SW Europe climate evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014WRR....50.2425G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014WRR....50.2425G"><span id="translatedtitle"><span class="hlt">Decadal</span> surface water quality trends under <span class="hlt">variable</span> climate, land use, and hydrogeochemical setting in Iowa, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Green, Christopher T.; Bekins, Barbara A.; Kalkhoff, Stephen J.; Hirsch, Robert M.; Liao, Lixia; Barnes, Kimberlee K.</p> <p>2014-03-01</p> <p>Understanding how nitrogen fluxes respond to changes in agriculture and climate is important for improving water quality. In the midwestern United States, expansion of corn cropping for ethanol production led to increasing N application rates in the 2000s during a period of extreme <span class="hlt">variability</span> of annual precipitation. To examine the effects of these changes, surface water quality was analyzed in 10 major Iowa Rivers. Several <span class="hlt">decades</span> of concentration and flow data were analyzed with a statistical method that provides internally consistent estimates of the concentration history and reveals flow-normalized trends that are independent of year-to-year streamflow variations. Flow-normalized concentrations of nitrate+nitrite-N decreased from 2000 to 2012 in all basins. To evaluate effects of annual discharge and N loading on these trends, multiple conceptual models were developed and calibrated to flow-weighted annual concentrations. The recent declining concentration trends can be attributed to both very high and very low discharge in the 2000s and to the long (e.g., 8 year) subsurface residence times in some basins. Dilution of N and depletion of stored N occurs in years with high discharge. Reduced N transport and increased N storage occurs in low-discharge years. Central Iowa basins showed the greatest reduction in flow-normalized concentrations, likely because of smaller storage volumes and shorter residence times. Effects of land-use changes on the water quality of major Iowa Rivers may not be noticeable for years or <span class="hlt">decades</span> in peripheral basins of Iowa, and may be obscured in the central basins where extreme flows strongly affect annual concentration trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70100468','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70100468"><span id="translatedtitle"><span class="hlt">Decadal</span> surface water quality trends under <span class="hlt">variable</span> climate, land use, and hydrogeochemical setting in Iowa, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Green, Christopher T.; Bekins, Barbara A.; Kalkhoff, Stephen J.; Hirsch, Robert M.; Liao, Lixia; Barnes, Kimberlee K.</p> <p>2014-01-01</p> <p>Understanding how nitrogen fluxes respond to changes in agriculture and climate is important for improving water quality. In the midwestern United States, expansion of corn cropping for ethanol production led to increasing N application rates in the 2000s during a period of extreme <span class="hlt">variability</span> of annual precipitation. To examine the effects of these changes, surface water quality was analyzed in 10 major Iowa Rivers. Several <span class="hlt">decades</span> of concentration and flow data were analyzed with a statistical method that provides internally consistent estimates of the concentration history and reveals flow-normalized trends that are independent of year-to-year streamflow variations. Flow-normalized concentrations of nitrate+nitrite-N decreased from 2000 to 2012 in all basins. To evaluate effects of annual discharge and N loading on these trends, multiple conceptual models were developed and calibrated to flow-weighted annual concentrations. The recent declining concentration trends can be attributed to both very high and very low discharge in the 2000s and to the long (e.g., 8 year) subsurface residence times in some basins. Dilution of N and depletion of stored N occurs in years with high discharge. Reduced N transport and increased N storage occurs in low-discharge years. Central Iowa basins showed the greatest reduction in flow-normalized concentrations, likely because of smaller storage volumes and shorter residence times. Effects of land-use changes on the water quality of major Iowa Rivers may not be noticeable for years or <span class="hlt">decades</span> in peripheral basins of Iowa, and may be obscured in the central basins where extreme flows strongly affect annual concentration trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......292M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......292M"><span id="translatedtitle">Understanding and predicting temperature <span class="hlt">variability</span> in the <span class="hlt">observational</span> record</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McKinnon, Karen Aline</p> <p></p> <p>Temperature <span class="hlt">variability</span> and change over land and ocean exhibit characteristic spatial and temporal structures. Understanding the physical mechanisms underlying these structures provides information about the movement and storage of heat in the climate system. In this thesis, I first analyze, and present an energy balance model for, seasonal temperature <span class="hlt">variability</span> in the extratropics, which supports the idea that the advection of heat between land and ocean by the mean atmospheric circulation can explain the regional characteristics of seasonal <span class="hlt">variability</span> over both land and ocean. The model is subsequently combined with a large, representative ensemble of Lagrangian atmospheric trajectories to provide a realistic model of the seasonal cycle in the Northern Hemisphere mid-latitudes. Second, based on the Lagrangian trajectories, a new spatially-resolved metric, termed Relative Land Influence, is developed. The metric quantifies the role of land as compared to ocean in influencing the temperature <span class="hlt">variability</span> at a given location. In addition to explaining the majority of the spatial pattern of seasonal <span class="hlt">variability</span>, Relative Land Influence is a significant predictor of the <span class="hlt">observed</span> temperature change over both land and ocean independently since 1950, suggesting that similar physical processes influence temperature <span class="hlt">variability</span> on seasonal and <span class="hlt">decadal</span> timescales. Finally, I explore the tails of temperature distributions in the context of identifying the causes of anomalously hot days in the Eastern United States during peak summer. A coupled ocean-atmosphere mode in the central mid-latitude Pacific is identified, which evolves on a characteristic timescale and ultimately leads to the amplification of a mid-latitude wave train that includes a blocking high over the Eastern United States. The early identification of the sea surface temperature precursors to this mode allows for skillful prediction of heat events at lead times greater than 40 days. The identification of physical processes underlying temperature <span class="hlt">variability</span> on a range of timescales can inform predictions of how temperature <span class="hlt">variability</span> may change in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120..201Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120..201Y"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> of the Pacific Subtropical Cells and its relevance to the sea surface height in the western tropical Pacific during recent <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamanaka, Goro; Tsujino, Hiroyuki; Nakano, Hideyuki; Hirabara, Mikitoshi</p> <p>2015-01-01</p> <p><span class="hlt">variability</span> of the Pacific Subtropical Cells (STCs) and associated sea surface height (SSH) in the western tropical Pacific during recent <span class="hlt">decades</span> are examined by using an historical OGCM simulation. The model represents <span class="hlt">decadal</span> variations of the STCs concurrent with tropical Pacific thermal anomalies: the eastern tropical Pacific is warmer when the STCs are weaker and cooler when they are stronger. The spatial patterns of the SSH in the western tropical Pacific show different features, depending on events associated with <span class="hlt">decadal</span> <span class="hlt">variability</span>. During the warm phase (1977-1987), the SSH anomalies exhibit deviations from a meridionally symmetric distribution, with weakly positive (strongly negative) anomalies in the western tropical North (South) Pacific. Analysis of the heat budget in the upper tropical Pacific indicates that the termination of the warm phase around 1985 results from a poleward heat transport anomaly that is induced by a horizontal gyre associated with the SSH anomalies. During the cold phase (1996-2006), in contrast, the SSH anomalies are nearly meridionally symmetric, with positive anomalies in both hemispheres. Enhanced easterly wind anomalies contribute to the development of the cold phase after the late 1990s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000112946','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000112946"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">Variability</span> and Temperature Trends in the Middle Atmosphere From Historical Rocketsonde Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dunkerton, Timothy J.</p> <p>2000-01-01</p> <p><span class="hlt">Observational</span> studies were performed using historical rocketsonde data to investigate long-term temperature trends, solar-cycle variations, and interactions between tropical and extratropical latitudes in the middle atmosphere. Evidence from tropical, subtropical, and midlatitude North American rocketsonde stations indicated a consistent downward trend over 25 years, with a solar cycle component superposed. The trend is about -1.4 to -2.0 K per <span class="hlt">decade</span> and the amplitude of the <span class="hlt">decadal</span> oscillation is about 1.1 K. Prior to trend derivation it was necessary for us to correct temperatures for aerodynamic heating in the early years. The empirically derived correction profile agrees well with a theoretical profile of Krumins and Lyons. A study was also performed of the correlation between equatorial winds and north polar temperatures in winter, showing that the entire stratospheric wind profile near the equator -- including the quasi-biennial oscillation (QBO) and stratopause semiannual oscillation (SAO) -- is important to the extratropical flow, not merely the QBO component as previously thought. A strong correlation was discovered between winter polar temperatures and equatorial winds in the upper stratosphere during the preceding September, suggesting a role for the second cycle of the SAO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008ACPD....814371F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008ACPD....814371F"><span id="translatedtitle">Interannual-to-<span class="hlt">decadal</span> <span class="hlt">variability</span> of the stratosphere during the 20th century: ensemble simulations with a chemistry-climate model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, A. M.; Schraner, M.; Rozanov, E.; Kenzelmann, P.; Schnadt Poberaj, C.; Brunner, D.; Lustenberger, A.; Luo, B. P.; Bodeker, G. E.; Egorova, T.; Schmutz, W.; Peter, T.; Brönnimann, S.</p> <p>2008-07-01</p> <p>Interannual-to-<span class="hlt">decadal</span> <span class="hlt">variability</span> in stratospheric ozone and climate have a number of common sources, such as variations in solar irradiance, stratospheric aerosol loading due to volcanic eruptions, El Niño Southern Oscillation <span class="hlt">variability</span> and the quasi-biennial oscillation (QBO). Currently available data records as well as model simulations addressing stratospheric chemical climate <span class="hlt">variability</span> mostly cover only the past few <span class="hlt">decades</span>, which is often insufficient to address natural interannual-to-<span class="hlt">decadal</span> <span class="hlt">variability</span>. Here we make use of recently reconstructed and re-evaluated data products to force and validate transient ensemble model simulations (nine members) across the twentieth century computed by means of the chemistry-climate model SOCOL. The forcings included sea surface temperatures, sea ice, solar irradiance, stratospheric aerosols, QBO, changes in land properties, greenhouse gases, ozone depleting substances, and emissions of carbon monoxides, and nitrogen oxides. The transient simulations are in good agreement with <span class="hlt">observations</span>, reconstructions and reanalyses and allow quantification of interannual-to-<span class="hlt">decadal</span> <span class="hlt">variability</span> during the 20th century. All ensemble members are able to capture the low-frequency <span class="hlt">variability</span> in tropical and mid-latitudinal total ozone as well as in the strength of the subtropical jet, suggesting a realistic response to external forcings in this area. The region of the northern polar vortex exhibits a large internal model <span class="hlt">variability</span> that is found in the frequency, seasonality, and strength of major warmings as well as in the strength of the modeled polar vortex. Results from process-oriented analysis, such as correlation between the vertical Eliassen Palm flux (EP flux) component and polar <span class="hlt">variables</span> as well as stratospheric ozone trends, are of comparable magnitude to those <span class="hlt">observed</span> and are consistent in all analysed ensemble members. Yet, trend estimates of the vertical EP flux component vary greatly among ensemble members precluding any robust conclusions. This suggests that internal <span class="hlt">variability</span> in models must be accounted for in order to quantify the atmospheric model response in wave energy upon external forcings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008ACP.....8.7755F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008ACP.....8.7755F"><span id="translatedtitle">Interannual-to-<span class="hlt">decadal</span> <span class="hlt">variability</span> of the stratosphere during the 20th century: ensemble simulations with a chemistry-climate model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, A. M.; Schraner, M.; Rozanov, E.; Kenzelmann, P.; Schnadt Poberaj, C.; Brunner, D.; Lustenberger, A.; Luo, B. P.; Bodeker, G. E.; Egorova, T.; Schmutz, W.; Peter, T.; Brönnimann, S.</p> <p>2008-12-01</p> <p>Interannual-to-<span class="hlt">decadal</span> <span class="hlt">variability</span> in stratospheric ozone and climate have a number of common sources, such as variations in solar irradiance, stratospheric aerosol loading due to volcanic eruptions, El Niño Southern Oscillation <span class="hlt">variability</span> and the quasi-biennial oscillation (QBO). Currently available data records as well as model simulations addressing stratospheric chemical climate <span class="hlt">variability</span> mostly cover only the past few <span class="hlt">decades</span>, which is often insufficient to address natural interannual-to-<span class="hlt">decadal</span> <span class="hlt">variability</span>. Here we make use of recently reconstructed and re-evaluated data products to force and validate transient ensemble model simulations (nine members) across the twentieth century computed by means of the chemistry-climate model SOCOL (SOlar Climate Ozone Links). The forcings include sea surface temperatures, sea ice, solar irradiance, stratospheric aerosols, QBO, changes in land properties, greenhouse gases, ozone depleting substances, and emissions of carbon monoxides, and nitrogen oxides. The transient simulations are in good agreement with <span class="hlt">observations</span>, reconstructions and reanalyses and allow quantification of interannual-to-<span class="hlt">decadal</span> <span class="hlt">variability</span> during the 20th century. All ensemble members are able to capture the low-frequency <span class="hlt">variability</span> in tropical and mid-latitude total ozone as well as in the strength of the subtropical jet, suggesting a realistic response to external forcings in this area. The region of the northern polar vortex exhibits a large internal <span class="hlt">variability</span> that is found in the frequency, seasonality, and strength of major warmings as well as in the strength of the modeled polar vortex. Results from process-oriented analysis, such as correlation between the vertical Eliassen Palm flux (EP flux) component and polar <span class="hlt">variables</span> as well as stratospheric ozone trends, are of comparable magnitude to those <span class="hlt">observed</span> and are consistent in all analysed ensemble members. Yet, trend estimates of the vertical EP flux component vary greatly among ensemble members precluding any robust conclusions. This suggests that internal <span class="hlt">variability</span> in models must be accounted for in order to quantify the atmospheric model response in wave energy upon external forcings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGD....1217643F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGD....1217643F"><span id="translatedtitle">Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: <span class="hlt">variability</span> on seasonal to <span class="hlt">decadal</span> timescales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, G.; Romero, O.; Merkel, U.; Donner, B.; Iversen, M.; Nowald, N.; Ratmeyer, V.; Ruhland, G.; Klann, M.; Wefer, G.</p> <p>2015-11-01</p> <p>A more than two-<span class="hlt">decadal</span> sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analyzed with respect to deep ocean mass fluxes, flux components and their <span class="hlt">variability</span> on seasonal to <span class="hlt">decadal</span> timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on <span class="hlt">decadal</span> timescales possibly linked to the Atlantic Multidedadal Oscillation (AMO). High winter fluxes of biogenic silica (BSi), used as a measure of marine production mostly by diatoms largely correspond to a positive North Atlantic Oscillation (NAO) index during boreal winter (December-March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004-2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter but also in summer/fall enhanced particle sedimentation and carbon export on rather short timescales via the ballasting effect, thus leading to these episodic sedimentation events. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) weakened the relationships between fluxes and larger scale climatic oscillations. As phytoplankton biomass is high throughout the year in our study area, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by being incorporated into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was <span class="hlt">observed</span> for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997-1999 where low fluxes were obtained for almost one year during the warm El Niño and 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 <span class="hlt">observe</span> an increase of any flux component off Cape Blanc during the past two and a half <span class="hlt">decades</span> 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 <span class="hlt">decades</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.S51E2457W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.S51E2457W"><span id="translatedtitle">Linear Ground-Motions in the Wabash Valley, Central United States: Two <span class="hlt">Decades</span> of Unconventional <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woolery, E. W.</p> <p>2012-12-01</p> <p>Since the mid-1980's small and moderate-sized earthquakes in the Ohio and Wabash River valleys of the central United States have been digitally recorded by seismographs, called blast monitors, deployed to monitor vibrations from chemical explosions associated with regional mining and quarrying. Because there were relatively few conventional networked strong-motion and broad-band instruments for this area between 1980 and the early 2000's, the more than 200 <span class="hlt">observations</span> have provided a relatively widespread source of digital earthquake ground motions. Additional deployment of networked instrumentation during the last <span class="hlt">decade</span> and their numerous recordings of the April 2008, Mt. Carmel, Illinois earthquake sequence have provided the first effective means for comparing free-field blast monitor and conventional network ground-motion <span class="hlt">observations</span>. The peak ground-motion characteristics for both data sets relative to a common predictive relationship are similar, suggesting that blast monitor <span class="hlt">observations</span> in the central U.S. compliment conventional network data for moderate-sized (< M5.5) events. Much of the ground motion prediction effort in the central United States has been focused on deep (>> 30 m) alluvial sites, such as those found in the Mississippi embayment. The free-field digital velocity records at blast-monitor sites in the Wabash Valley are more typical of the areas outside the embayment. The ground-motion database is composed of small to moderate size regional earthquakes with a magnitude range between M3 and M5.2; however, the bulk of the <span class="hlt">observations</span> are associated with the 1987 M4.96 and 2008 M5.2 southeastern Illinois earthquakes, and the 2002 M4.5 southwestern Indiana earthquake. The velocity recordings and ancillary site investigations for the 2008 southeastern Illinois earthquake sequence put the findings into context with the previous <span class="hlt">observations</span>, and quantify the reduction in ground-motion <span class="hlt">variability</span> that can be achieved with conventional site-effect characterization techniques. Results show ground-motion characteristics for the 2008 earthquake sequence are consistent with previous <span class="hlt">observations</span> in the area, beginning with the 1987 southwestern Illinois earthquake. In addition, site-effect corrections reduced the range of spectral amplitude for frequencies greater than 2 Hz between 40 and 70 percent, as well as the spectral variation by approximately a factor of 4. The data also show that a peak ground velocity of 1.2 cm/s delineates a clear boundary separating Modified Mercalli intensities IV and V. This <span class="hlt">observation</span> can be useful in scaling ground motions of historical seismicity, as well as predicting the effects of future events. We speculate these quantitative characteristics are likely representative for ground-motions throughout most of the central United States with the exception of those the infrequent thick-sediment-filled areas within major river valleys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.3419B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.3419B"><span id="translatedtitle">Wave power <span class="hlt">variability</span> and trends across the North Atlantic influenced by <span class="hlt">decadal</span> climate patterns</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bromirski, Peter D.; Cayan, Daniel R.</p> <p>2015-05-01</p> <p>Climate variations influence North Atlantic winter storm intensity and resultant variations in wave energy levels. A 60 year hindcast allows investigation of the influence of <span class="hlt">decadal</span> climate <span class="hlt">variability</span> on long-term trends of North Atlantic wave power, PW, spanning the 1948-2008 epoch. PW variations over much of the eastern North Atlantic are strongly influenced by the fluctuating North Atlantic Oscillation (NAO) atmospheric circulation pattern, consistent with previous studies of significant wave height, Hs. Wave activity in the western Atlantic also responds to fluctuations in Pacific climate modes, including the Pacific North American (PNA) pattern and the El Niño/Southern Oscillation. The magnitude of upward long-term trends during winter over the northeast Atlantic is strongly influenced by heightened storm activity under the extreme positive phase of winter NAO in the early 1990s. In contrast, PW along the United States East Coast shows no increasing trend, with wave activity there most closely associated with the PNA. Strong wave power "events" exhibit significant upward trends along the Atlantic coasts of Iceland and Europe during winter months. Importantly, in opposition to the long-term increase of PW, a recent general decrease in PW across the North Atlantic from 2000 to 2008 occurred. The 2000-2008 decrease was associated with a general shift of winter NAO to its negative phase, underscoring the control exerted by fluctuating North Atlantic atmospheric circulation on PW trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CliPa..10.1319M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CliPa..10.1319M"><span id="translatedtitle">Persistent <span class="hlt">decadal</span>-scale rainfall <span class="hlt">variability</span> in the tropical South Pacific Convergence Zone through the past six centuries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maupin, C. R.; Partin, J. W.; Shen, C.-C.; Quinn, T. M.; Lin, K.; Taylor, F. W.; Banner, J. L.; Thirumalai, K.; Sinclair, D. J.</p> <p>2014-07-01</p> <p>Modern Pacific <span class="hlt">decadal</span> <span class="hlt">variability</span> (PDV) has global impacts; hence records of PDV from the pre-instrumental period are needed to better inform models that are used to project future climate <span class="hlt">variability</span>. We focus here on reconstructing rainfall in the western tropical Pacific (Solomon Islands; ~ 9.5° S, ~160° E), a region directly influenced by PDV, using cave deposits (stalagmite). A relationship is developed between δ18O variations in the stalagmite and local rainfall amount to produce a 600 yr record of rainfall <span class="hlt">variability</span> from the South Pacific Convergence Zone (SPCZ). We present evidence for large (~1.5 m), abrupt, and periodic changes in total annual rainfall amount on <span class="hlt">decadal</span> to multidecadal timescales since 1423 ± 5 CE (Common Era) in the Solomon Islands. The timing of the <span class="hlt">decadal</span> changes in rainfall inferred from the 20th century portion of the stalagmite δ18O record coincides with previously identified <span class="hlt">decadal</span> shifts in PDV-related Pacific ocean-atmosphere behavior (Clement et al., 2011; Deser et al., 2004). The Solomons record of PDV is not associated with variations in external forcings, but rather results from internal climate <span class="hlt">variability</span>. The 600 yr Solomon Islands stalagmite δ18O record indicates that <span class="hlt">decadal</span> oscillations in rainfall are a persistent characteristic of SPCZ-related climate <span class="hlt">variability</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6048B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6048B"><span id="translatedtitle"><span class="hlt">Observational</span> constraints on interannual <span class="hlt">variability</span> projections in CMIP5</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borodina, Aleksandra; Fischer, Erich M.; Knutti, Reto</p> <p>2014-05-01</p> <p>Impacts of climate change are sensitive not only to changes in the mean state but also to potential changes in the internal <span class="hlt">variability</span> of the climate system at diurnal to interannual and multi-<span class="hlt">decadal</span> time scales. Internal <span class="hlt">variability</span> arises from nonlinear interactions and complex feedbacks between ocean, sea ice, atmosphere and land surface without any external forcing. However, an external forcing may change both magnitude, spatial patterns and the time scales of these variations. It is crucial to understand whether and on what temporal and spatial scales internal <span class="hlt">variability</span> will undergo changes under anthropogenic radiative forcing and to identify the underlying mechanisms. To address these questions, we here use model simulations of the Coupled Model Intercomparison Project Phase 5 database (CMIP5) with historical (1850-2005) - RCP8.5 (2006-2100) concentration pathway. First, we show over which latitudes CMIP5 models simulate robust changes in <span class="hlt">variability</span>. Second, we explore whether models with low present-day internal <span class="hlt">variability</span> project changes that substantially differ from those models with high present-day internal <span class="hlt">variability</span>. Such an inter-model relationship is found over the high-latitudes of both hemispheres. For the regions and seasons, for which a relationship across the multi-model ensemble exists, we use <span class="hlt">observations</span> and reanalyses, to constrain the model projections. This model constraint is based on the assumption that models with a more realistic representation of present-day <span class="hlt">variability</span> yield more reliable projections. Once a relationship is identified, physical understanding becomes crucial because it must have a strong physical grounding to justify the constraint. We explore mechanisms that explain the inter-model correlation between current <span class="hlt">variability</span> and its future change especially at high latitudes. We use a "joint projection" approach, which is based on the fact that multiple climate <span class="hlt">variables</span> are correlated over different scales in order to understand basic mechanisms and to put forward hypotheses that explain what is <span class="hlt">observed</span> in multi-model projections. Furthermore, the coupling between <span class="hlt">variables</span> allows a more precise quantification of these relationships which ultimately should enable us to reduce the uncertainty associated with their joint projections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAVSO..43Q.109S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAVSO..43Q.109S"><span id="translatedtitle">The Future of Visual <span class="hlt">Observations</span> in <span class="hlt">Variable</span> Star Research: 2015 and Beyond (Abstract)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simonsen, M.</p> <p>2015-06-01</p> <p>(Abstract only) In this paper we examine the strengths and weaknesses of visual <span class="hlt">observations</span> in <span class="hlt">variable</span> star research and outline areas where visual <span class="hlt">observers</span> can still make a contribution to science. We also examine reasons for continuing to support visual <span class="hlt">observers</span> participation in the AAVSO for <span class="hlt">decades</span> to come.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...45.2993F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...45.2993F"><span id="translatedtitle"><span class="hlt">Observed</span> and simulated inter-<span class="hlt">decadal</span> changes in the structure of Southern Hemisphere large-scale circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Freitas, Ana C. V.; Frederiksen, Jorgen S.; Whelan, Jennifer; O'Kane, Terence J.; Ambrizzi, Tércio</p> <p>2015-12-01</p> <p>Several studies have identified that, in the mid-1970s to early 1980s, a major shift occurred in the structure of the large-scale circulation in both hemispheres. This work employs the CSIRO Mk3L general circulation model in ensemble simulations with <span class="hlt">observed</span> sea surface temperatures (SSTs) and historical time-evolving carbon dioxide (CO2) concentrations to investigate the inter-<span class="hlt">decadal</span> changes found <span class="hlt">observationally</span> in the jet streams, temperature, Hadley circulation, mean sea level pressure and precipitation. First, the performance of the model in simulating these changes for the mean July climate fields of 1949-1968 and 1975-1994, in comparison with the corresponding <span class="hlt">observations</span> (NCEP/NCAR Reanalysis I and the Twentieth Century Reanalysis V2), is investigated. We find that the model is quite skilful in reproducing the broad features of the important inter-<span class="hlt">decadal</span> changes that occurred in the mid-1970s. The model simulations and the NCEP/NCAR and twentieth century reanalyses agree in the eastern hemisphere; whereas in the western hemisphere the reanalyses show differences, and the simulations combine aspects of these two datasets. The role of the direct radiative forcing due to CO2 in driving the inter-<span class="hlt">decadal</span> changes is also examined. Results indicate that, in comparison with the indirect effect of CO2 carried by the changing SSTs, there is little additional impact of the direct radiative forcing due to CO2 on the changes in the latter period. However, our simulations with fixed CO2 concentration have shown clearly that the atmospheric simulations with historical time-evolving CO2 concentrations are more skilful in reproducing the inter-<span class="hlt">decadal</span> changes. The sensitivity of the ensemble results to employing the same or different time evolving sea ice boundary conditions in the ensemble members is also studied. The contributions of internal and external <span class="hlt">variability</span> are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.B11G..04P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.B11G..04P"><span id="translatedtitle">Wetland inventory and <span class="hlt">variability</span> over the last two <span class="hlt">decades</span> at a global scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prigent, C.; Papa, F.; Aires, F.; Rossow, W. B.; Matthews, E.</p> <p>2011-12-01</p> <p>Remote sensing techniques employing visible, infrared, and microwave <span class="hlt">observations</span> offer varying success in estimating wetlands and inundation extent and in monitoring their natural and anthropogenic variations. Low spatial resolution (e.g., 30 km) limits detection to large wetlands but has the advantage of frequent coverage. High spatial resolution (e.g., 100 m), while providing more environmental information, suffers from poor temporal resolution, with <span class="hlt">observations</span> for just high/low water or warm/cold seasons. Most existing wetland data sets are limited to a few regions, for specific times in the year. The only global inventories of wetland dynamics over a long period of time is derived from a remote-sensing technique employing a suite of complementary satellite <span class="hlt">observations</span>: it uses passive microwave land-surface microwave emissivities, scatterometer responses, and visible and near infrared reflectances. Combining <span class="hlt">observations</span> from different instruments makes it possible to capitalize on their complementary strengths, and to extract maximum information about inundation characteristics. The technique is globally applicable without any tuning for particular environments. The satellite data are used to calculate monthly-mean inundated fractions of equal-area grid cells (0.25x0.25 at the equator), taking into account the contribution of vegetation to the passive microwave signal (Prigent et al., 2001, 2007). Several adjustments to the initial technique have been applied to account for changes in satellite instruments (Papa et al., 2010). The resulting data set now covers 1993-2008 and has been carefully evaluated. We will present the inter-annual <span class="hlt">variability</span> of the water surface extents under different environments, and relate these variations to other hydrological <span class="hlt">variables</span> such as river height, precipitation, water runoff, or Grace data. Natural wetlands are the world's largest methane source and dominate the inter-annual <span class="hlt">variability</span> of atmospheric methane concentrations, with up to 90% of the global methane flux anomalies related to variations in the wetland extent from some estimation. Our data set quantifying inundation dynamics throughout the world's natural wetlands provides a unique opportunity to reduce uncertainties in the role of natural wetlands in the inter-annual <span class="hlt">variability</span> of the growth rate of atmospheric methane. Papa, F., C. Prigent, C. Jimenez, F. Aires, and W. B. Rossow, Interannual <span class="hlt">variability</span> of surface water extent at global scale, 1993-2004, JGR, 115, D12111, doi:10.1029/2009JD012674, 2010. Prigent, C., F. Papa, F. Aires, W. B. Rossow, and E. Matthews, Global inundation dynamics inferred from multiple satellite <span class="hlt">observations</span>, 1993-2000, JGR, 112, D12107, doi:10.1029/2006JD007847, 2007. Prigent, C., E. Matthews, F. Aires, and W. B. Rossow, Remote sensing of global wetland dynamics with multiple satellite data sets, GRL, 28 , 4631-4634, 2001.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950047289&hterms=global+temperature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dglobal%2Btemperature','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950047289&hterms=global+temperature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dglobal%2Btemperature"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> of the Tropical Atlantic Ocean Surface Temperature in shipboard measurements and in a Global Ocean-Atmosphere model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mehta, Vikram M.; Delworth, Thomas</p> <p>1995-01-01</p> <p>Sea surface temperature (SST) <span class="hlt">variability</span> was investigated in a 200-yr integration of a global model of the coupled oceanic and atmospheric general circulations developed at the Geophysical Fluid Dynamics Laboratory (GFDL). The second 100 yr of SST in the coupled model's tropical Atlantic region were analyzed with a variety of techniques. Analyses of SST time series, averaged over approximately the same subregions as the Global Ocean Surface Temperature Atlas (GOSTA) time series, showed that the GFDL SST anomalies also undergo pronounced quasi-oscillatory <span class="hlt">decadal</span> and multidecadal <span class="hlt">variability</span> but at somewhat shorter timescales than the GOSTA SST anomalies. Further analyses of the horizontal structures of the <span class="hlt">decadal</span> timescale <span class="hlt">variability</span> in the GFDL coupled model showed the existence of two types of <span class="hlt">variability</span> in general agreement with results of the GOSTA SST time series analyses. One type, characterized by timescales between 8 and 11 yr, has high spatial coherence within each hemisphere but not between the two hemispheres of the tropical Atlantic. A second type, characterized by timescales between 12 and 20 yr, has high spatial coherence between the two hemispheres. The second type of <span class="hlt">variability</span> is considerably weaker than the first. As in the GOSTA time series, the multidecadal <span class="hlt">variability</span> in the GFDL SST time series has approximately opposite phases between the tropical North and South Atlantic Oceans. Empirical orthogonal function analyses of the tropical Atlantic SST anomalies revealed a north-south bipolar pattern as the dominant pattern of <span class="hlt">decadal</span> <span class="hlt">variability</span>. It is suggested that the bipolar pattern can be interpreted as <span class="hlt">decadal</span> <span class="hlt">variability</span> of the interhemispheric gradient of SST anomalies. The <span class="hlt">decadal</span> and multidecadal timescale <span class="hlt">variability</span> of the tropical Atlantic SST, both in the actual and in the GFDL model, stands out significantly above the background 'red noise' and is coherent within each of the time series, suggesting that specific sets of processes may be responsible for the choice of the <span class="hlt">decadal</span> and multidecadal timescales. Finally, it must be emphasized that the GFDL coupled ocean-atmosphere model generates the <span class="hlt">decadal</span> and multidecadal timescale <span class="hlt">variability</span> without any externally applied force, solar or lunar, at those timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110023540','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110023540"><span id="translatedtitle">Interannual to <span class="hlt">Decadal</span> <span class="hlt">Variability</span> of Atlantic Water in the Nordic and Adjacent Seas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carton, James A.; Chepurin, Gennady A.; Reagan, James; Haekkinen, Sirpa</p> <p>2011-01-01</p> <p>Warm salty Atlantic Water is the main source water for the Arctic Ocean and thus plays an important role in the mass and heat budget of the Arctic. This study explores interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span> of Atlantic Water properties in the Nordic Seas area where Atlantic Water enters the Arctic, based on a reexamination of the historical hydrographic record for the years 1950-2009, obtained by combining multiple data sets. The analysis shows a succession of four multi-year warm events where temperature anomalies at 100m depth exceed 0.4oC, and three cold events. Three of the four warm events lasted 3-4 years, while the fourth began in 1999 and persists at least through 2009. This most recent warm event is anomalous in other ways as well, being the strongest, having the broadest geographic extent, being surface-intensified, and occurring under exceptional meteorological conditions. Three of the four warm events were accompanied by elevated salinities consistent with enhanced ocean transport into the Nordic Seas, with the exception of the event spanning July 1989-July 1993. Of the three cold events, two lasted for four years, while the third lasted for nearly 14 years. Two of the three cold events are associated with reduced salinities, but the cold event of the 1960s had elevated salinities. The relationship of these events to meteorological conditions is examined. The results show that local surface heat flux variations act in some cases to reinforce the anomalies, but are too weak to be the sole cause.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRD..11620121H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRD..11620121H"><span id="translatedtitle">A dynamical fingerprint of tropical Pacific sea surface temperatures on the <span class="hlt">decadal</span>-scale <span class="hlt">variability</span> of cool-season Arctic precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hegyi, Bradley M.; Deng, Yi</p> <p>2011-10-01</p> <p>The temporal and spatial characteristics of <span class="hlt">decadal</span>-scale <span class="hlt">variability</span> in the Northern Hemisphere (NH) cool-season (October-March) Arctic precipitation are identified from both the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) and the Global Precipitation Climatology Project (GPCP) precipitation data sets. This <span class="hlt">decadal</span> <span class="hlt">variability</span> is shown to be partly connected to the <span class="hlt">decadal</span>-scale variations in tropical central Pacific sea surface temperatures (SSTs) that are primarily associated with a <span class="hlt">decadal</span> modulation of the El Niño-Southern Oscillation (ENSO), i.e., transitions between periods favoring typical eastern Pacific warming (EPW) events and periods favoring central Pacific warming (CPW) events. Regression and composite analyses reveal that increases of central Pacific SSTs drive a stationary Rossby wave train that destructively interferes with the wave number-1 component of the extratropical planetary wave. This destructive interference is opposite to the mean effect of typical EPW on the extratropical planetary wave. It leads to suppressed upward propagation of wave energy into the polar stratosphere, a stronger stratospheric polar vortex, and a tendency toward a positive phase of the Arctic Oscillation (AO). The positive AO tendency is synchronized on the <span class="hlt">decadal</span> scale with a poleward shift of the NH storm tracks, particularly in the North Atlantic. Storm track variations further induce changes in the amount of moisture transported into the Arctic by synoptic eddies. The fluctuations in the eddy moisture transport ultimately contribute to the <span class="hlt">observed</span> <span class="hlt">decadal</span>-scale variations in the total Arctic precipitation in the NH cool season.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A23J..01E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A23J..01E"><span id="translatedtitle">Geostationary atmospheric composition <span class="hlt">observations</span> from the NASA <span class="hlt">Decadal</span> Survey GEO-CAPE mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edwards, D. P.; Jacob, D. J.; Al-Saadi, J. A.; Iraci, L. T.</p> <p>2012-12-01</p> <p>This paper discusses the science definition work that is being performed in preparation for the NASA <span class="hlt">Decadal</span> Survey GEO-CAPE mission. To serve the atmospheric composition community, GEO-CAPE will make a suite of trace gas and aerosol measurements from geostationary orbit concentrating on North America with high spatiotemporal resolution. This will provide unique insights into pollutant sources, transport, chemical transformations and climate impact. In addition to significantly improved understanding of the underlying processes determining atmospheric composition, GEO-CAPE <span class="hlt">observations</span> will also find direct societal application for air quality management and forecasting. The paper will also discuss the potential phased implementation of this mission as a series of hosted payloads, and GEO-CAPE as the U.S. contribution to a constellation of geostationary platforms to achieve continuous coverage at northern mid-latitudes by the turn of the <span class="hlt">decade</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC51E1246R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC51E1246R"><span id="translatedtitle">Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux <span class="hlt">Variability</span> on Daily Through <span class="hlt">Decadal</span> Time Scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Romanski, J.; Romanou, A.; Bauer, M. P.; Tselioudis, G.</p> <p>2012-12-01</p> <p>During the late 1980s and early 1990s, deep water was produced in the Aegean Sea rather than in the Adriatic Sea. The largest production occurred during the winters of 1991/1992 and 1992/1993. This phenomenon, the Eastern Mediterranean Transient (EMT), was due to the confluence of multiple hydrological preconditioning factors and strong atmospheric forcing. This is the only instance of Aegean deep convection which has been <span class="hlt">observed</span>; however it is thought that similar events have occurred in the past, but with unknown frequency. In a recent paper, we showed that a deviation from the usual pattern of cyclones in the central and eastern Mediterranean basins induced atypical heat advection over the Aegean, producing large turbulent heat losses during the winters of 1991/1992 and 1992/1993 (Romanski et al. 2012)]. Here we extend our analysis to the 1958-2001 period, and connect the presence of cyclones in the central and eastern Mediterranean to characteristic patterns of turbulent heat flux in the eastern Mediterranean and Aegean . We show that the relative frequency of storms in each basin determines the heat loss from the Aegean during that winter. We analyze the wintertime cyclone <span class="hlt">variability</span> during 1958-2001, discuss the likelihood of atmospheric conditions conducive to deep convection in the Aegean, and link cyclone <span class="hlt">variability</span>, and Aegean flux <span class="hlt">variability</span>, to changes in large scale circulation as represented by the North Atlantic Oscillation (NAO) and North Caspian Pattern (NCP) teleconnections. We are thus able to identify other possible occurrences of EMT in the 1958-2001 cyclone record.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JAVSO..40..178K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAVSO..40..178K"><span id="translatedtitle">History of Amateur <span class="hlt">Variable</span> Star <span class="hlt">Observations</span> in Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kiyota, S.</p> <p>2012-06-01</p> <p>(Abstract only) Japan has about 100 years of history of <span class="hlt">variable</span> star <span class="hlt">observing</span> since Naozo Ichinohe, professional astronomer in Tokyo Observatory, <span class="hlt">observed</span> d Cep in 1906. The first amateur <span class="hlt">variable</span> star <span class="hlt">observer</span> is Yoshihiko Kasai, who began <span class="hlt">observing</span> <span class="hlt">variable</span> stars in 1918. I introduce a brief history of Japanese amateur <span class="hlt">variable</span> star <span class="hlt">observation</span>, including topics of <span class="hlt">variable</span> star organizations, nova and supernova hunters, collaborations with the AAVSO and the world, PEP and CCD <span class="hlt">observations</span>. I also introduce the most active <span class="hlt">variable</span> star <span class="hlt">observer</span>, Hiroaki Narumi, who made over 260,000 visual estimates since 1975. VSOLJ was established in 1987 in collaborations with the <span class="hlt">variable</span> star sections of Nihon Tenmon Kenkyu-kai (NTK) and the Oriental Astronomical Association (OAA). VSOLJ maintains a database of Japanese <span class="hlt">variable</span> star <span class="hlt">observations</span> (http://vsolj.cetus-net.org) and publishes the <span class="hlt">Variable</span> Star Bulletin in English.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1167250','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1167250"><span id="translatedtitle">A Generalized Stability Analysis of the AMOC in Earth System Models: Implication for <span class="hlt">Decadal</span> <span class="hlt">Variability</span> and Abrupt Climate Change</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fedorov, Alexey V.; Fedorov, Alexey</p> <p>2015-01-14</p> <p>The central goal of this research project was to understand the mechanisms of <span class="hlt">decadal</span> and multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> of the Atlantic Meridional Overturning Circulation (AMOC) as related to climate <span class="hlt">variability</span> and abrupt climate change within a hierarchy of climate models ranging from realistic ocean models to comprehensive Earth system models. Generalized Stability Analysis, a method that quantifies the transient and asymptotic growth of perturbations in the system, is one of the main approaches used throughout this project. The topics we have explored range from physical mechanisms that control AMOC <span class="hlt">variability</span> to the factors that determine AMOC predictability in the Earth system models, to the stability and <span class="hlt">variability</span> of the AMOC in past climates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy..tmp...46Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy..tmp...46Y"><span id="translatedtitle">Space-time <span class="hlt">variability</span> of Indonesian rainfall at inter-annual and multi-<span class="hlt">decadal</span> time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yanto; Rajagopalan, Balaji; Zagona, Edith</p> <p>2016-01-01</p> <p>We investigated the space-time <span class="hlt">variability</span> of wet (Nov-Apr) and dry (May-Oct) season rainfall over Indonesia, using monthly gridded rainfall data from the University of East Angela Climatic Research Unit covering the period 1901-2012. Three complimentary techniques were employed—(1) principal component analysis to identify the dominant modes of <span class="hlt">variability</span>, (2) wavelet spectral analysis to identify the spectral characteristics of the leading modes and their coherence with large scale climate <span class="hlt">variables</span> and (3) Bayesian Dynamical Linear Model (BDLM) to quantify the temporal <span class="hlt">variability</span> of the association between rainfall modes and climate <span class="hlt">variables</span>. In the dry season when the Inter Tropical Convergence Zone (ITCZ) is to the north of the equator the leading two principal components (PCs) explain close to 50 % of the rainfall. In the wet season the ITCZ moves to the south and the leading PCs explain close to 30 % of the variance. El Niño Southern Oscillation (ENSO) is the driver of the leading modes of rainfall <span class="hlt">variability</span> during both seasons. We find asymmetry in the teleconnections of ENSO to high and low rainfall years in the dry season. Furthermore, ENSO and the leading PCs of rainfall have spectral coherence in the inter-annual band (2-8 years) over the entire period of record and in the multi-<span class="hlt">decadal</span> (8-16 years) band in post-1980 years. In addition, during the 1950-1980 period the second mode of <span class="hlt">variability</span> in both seasons has a strong relationship with Pacific <span class="hlt">Decadal</span> Oscillation. The association between ENSO and the leading mode of Indonesian rainfall has strengthened in recent <span class="hlt">decades</span>, more so during dry season. These inter-annual and multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> of Indonesian rainfall modulated by Pacific climate drivers has implications for rainfall and hydrologic predictability important for water resources management.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014QSRv..105...86B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014QSRv..105...86B"><span id="translatedtitle">High resolution sedimentary record of dinoflagellate cysts reflects <span class="hlt">decadal</span> <span class="hlt">variability</span> and 20th century warming in the Santa Barbara Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bringué, Manuel; Pospelova, Vera; Field, David B.</p> <p>2014-12-01</p> <p>We present a continuous record of dinoflagellate cysts from a core of laminated sediments collected in the Santa Barbara Basin (SBB), off Southern California. The core spans the last ∼260 years and is analysed at biennial (two-year) resolution. Variations in dinoflagellate cyst assemblages are compared with 20th century historical changes, and are used to examine changes in primary productivity and species composition, which are bound to the <span class="hlt">variability</span> in upwelling and sea-surface temperature (SST) in the region. Cysts produced by heterotrophic dinoflagellates dominate the assemblages. In particular, Brigantedinium spp. (on average 64.2% of the assemblages) are commonly associated with high levels of primary productivity, typically <span class="hlt">observed</span> under active upwelling conditions, when nutrient supply is higher. Other heterotrophic taxa such as cysts of Protoperidinium americanum, Protoperidinium fukuyoi, Protoperidinium minutum and Archaeperidinium saanichi, all Echinidinium species, Quinquecuspis concreta and Selenopemphix undulata are more abundant in the early part of the record (∼1750s-1870s). These taxa are generally associated with high primary productivity and are <span class="hlt">observed</span> predominantly during intervals marked by relatively <span class="hlt">variable</span> conditions of SST, stratification and nutrient loading. The 20th century is marked by an increase in several species of autotrophic affinity, primarily Lingulodinium machaerophorum and Spiniferites ramosus. In recent surface sediments from the region, these species are more abundant in the Southern California Bight, and they are associated with conditions of relaxed upwelling in the SBB (typically <span class="hlt">observed</span> during summer and fall), when SST is higher and nutrient supply is moderate. Their increasing concentrations since the early 20th century reflect warmer SST and possibly stronger stratification during the warmest season. Taken together, the changes in cyst assemblages provide further evidence that persistently warmer conditions in the SBB began affecting marine populations by the late 1920s. <span class="hlt">Decadal</span>-scale variations in primary productivity are encoded in the heterotrophic dinoflagellate cyst record, with higher (lower) concentrations of heterotrophic taxa occurring during "cool" ("warm") phases of the Pacific <span class="hlt">Decadal</span> Oscillation (PDO) index. Wavelet analysis of heterotrophic taxa concentrations suggests a weaker influence of the PDO on biota of the region during the 19th century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.G21C..02T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.G21C..02T"><span id="translatedtitle">Two <span class="hlt">decades</span> of ice melt reconstruction in Greenland and Antarctica from time-<span class="hlt">variable</span> gravity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Talpe, M.; Nerem, R. S.; Lemoine, F. G.</p> <p>2014-12-01</p> <p>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-<span class="hlt">decade</span> 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-<span class="hlt">variable</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFMPP62A0316M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFMPP62A0316M"><span id="translatedtitle"><span class="hlt">Decadal</span>-Scale Tropical North Atlantic Climate <span class="hlt">Variability</span> Recorded in Slow Growing Cape Verde Corals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moses, C. S.; Swart, P. K.; Dodge, R. E.; Helmle, K. P.; Thorrold, S.</p> <p>2002-12-01</p> <p>The <span class="hlt">decadal</span> to century scale climate <span class="hlt">variability</span> of the tropical North Atlantic has major implications for both neighboring coastal and inland areas. Changes in patterns of sea surface temperature (SST) and SST anomalies (SSTA) in the tropical North Atlantic are known to affect rainfall in Florida, South America, and sub-Saharan Africa, as well as the number of major hurricanes formed in the Atlantic. Because of the significance of these connections, it is important to further increase our predictive capacity for the recognition of trends and cycles in tropical North Atlantic SST and SSTA. Located at 15° N latitude off the west coast of sub-Saharan Africa, the Cape Verde Islands are an ideal geographic location to search for records of the Tropical North Atlantic Index (TNA). Such patterns are present in proxy indicators of climate (O, C, Sr/Ca and Mg/Ca) recorded in the skeletons of slow growing corals, such as Siderastrea radians, found in Cape Verde (growth rate = 1-2 mm/yr). These corals represent an archive for SST and SSTA records that exceed the instrumental period of the eastern tropical North Atlantic. We cored corals from several different locations within the Cape Verde archipelago and analyzed them for stable isotopes (δ13C and δ18O) and minor elements (Sr, Mg, and Ba). The δ18O signal present in these corals shows a distinct relationship to the TNA over the better part of the last 100 years. In addition, the δ18O record in several of these corals also records the onset of the latest Sahel (11°-18° N in Africa) drought which began in 1970. The Sr/Ca and Mg/Ca records of these corals indicate a slight warming of the waters around Cape Verde during the last 100 years, as well as accurately recording the El Niño events of 1982-83 and 1997-98. The correlations present between the records in these corals and the known instrumental record for the eastern tropical North Atlantic suggests that the fluctuations recorded in the proxy indicators may be accurately used as a tool to study both the intensity and duration of SST and SSTA cycles as far back as the 1880's.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013019','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013019"><span id="translatedtitle">North Pacific <span class="hlt">Decadal</span> <span class="hlt">Variability</span> in the GEOS-5 Atmosphere-Ocean Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Achuthavarier, Deepthi; Schubert, Siegfried D.; Vikhliaev, Yury V.</p> <p>2013-01-01</p> <p>This study examines the mechanisms of the Pacific <span class="hlt">decadal</span> oscillation (PDO) in the GEOS-5 general circulation model. The model simulates a realistic PDO pattern that is resolved as the first empirical orthogonal function (EOF) of winter sea surface temperature (SST). The simulated PDO is primarily forced by Aleutian low through Ekman transport and surface fluxes, and shows a red spectrum without any preferred periodicity. This differs from the <span class="hlt">observations</span>, which indicate a greater role of El Nino-Southern Oscillation (ENSO) forcing, and likely reflects the too short time scale of the simulated ENSO. The geostrophic transport in response to the Aleutian low is limited to the Kuroshio-Oyashio Extension, and is unlikely the main controlling factor in this model, although it reinforces the Ekman-induced SST anomalies. The delay between the Aleutian low and the PDO is relatively short (1 year) suggesting that the fast Ekman response (rather than Rossby wave propagation) sets the SST pattern immediately following an Aleutian low fluctuation. The atmospheric feedback (response to the SST) is only about 25 of the forcing and never evolves into an Aleutian low completely, instead projecting onto the North Pacific Oscillation (NPO), a meridional dipole in sea level pressure (SLP). The lack of preferred periodicity and weak atmospheric response bothindicate a coupled oscillation is an unlikely mechanism for the PDO in this model. In agreement with recent studies, the NPO is correlated with the North Pacific Gyre Oscillation (NPGO), which is another leading EOF of the North Pacific SST. A possible connection between the PDO and the NPGO is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C42B..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C42B..08W"><span id="translatedtitle">Spatio-temporal <span class="hlt">Variability</span> of Arctic Sea Ice from Days to <span class="hlt">Decades</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wettlaufer, J. S.; Agarwal, S.</p> <p>2014-12-01</p> <p>We examine the daily satellite retrievals of Arctic sea-ice extent over three <span class="hlt">decades</span>. The Arctic basin is divided into 14 different regions and we study how the Arctic wide <span class="hlt">observations</span> emerge from these regional trends. In order to capture all possible time scales, the temporal dynamics within each spatial region, and in the basin as a whole, are treated as a multifractal. Our approach is Multi-Fractal Temporally Weighted Detrended Fluctuation Analysis (MF-TWDFA), which captures long time scales that are not accessible by standard DFA or MF-DFA and are by definition not part of a procedure that assumes the dynamics are described by an order one auto-regressive process. We examine how the eastern, western, central and the marginal seas control the longest time scales and what processes are responsible for the responses found in the data. Of particular interest is how regions with substantial seasonality contribute to the basin-wide dynamics of the system. The importance of this is intertwined with the general problem of how and when the Arctic may pass on to a state in which the ice cover is seasonal. The transition from a perennial state to a seasonal ice cover is the persistent state of affairs in the marginal regions of the ice cover, which constitute 10 of the 14 subregions, whereas the remaining 4 are in various stages of partial ice cover at various times of the year. In this manner, we use sub-basins as laboratories for the entire basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JSR....86...97T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JSR....86...97T"><span id="translatedtitle">Impact of the river nutrient load <span class="hlt">variability</span> on the North Aegean ecosystem functioning over the last <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsiaras, K. P.; Petihakis, G.; Kourafalou, V. H.; Triantafyllou, G.</p> <p>2014-02-01</p> <p>The impact of river load <span class="hlt">variability</span> on the North Aegean ecosystem functioning over the last <span class="hlt">decades</span> (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 <span class="hlt">observations</span>, 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 <span class="hlt">observed</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B33A0162W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B33A0162W"><span id="translatedtitle"><span class="hlt">Variability</span> of Global Atmospheric CO2 Concentrations over Interannual to Multi-<span class="hlt">Decadal</span> Timescales: A Linear Approximation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, W.; Nemani, R. R.; Hashimoto, H.</p> <p>2014-12-01</p> <p>The Keeling curve, which shows the rapidly increasing atmospheric carbon dioxide concentration since 1958, is one of the most important scientific findings of our time - yet a full and detailed understanding of the curve and its variations is still to be achieved. At year-to-year time scales, for instance, the annual growth rate of the Keeling curve have long been linked to variations of the natural climate-carbon system. But questions remain about what (ocean versus land), where (tropics versus mid-high latitudes) and how (e.g., temperature versus precipitation) different drivers affect the <span class="hlt">observed</span> <span class="hlt">variability</span>. At longer (multidecadal) timescales, on the other hand, the growths of atmospheric CO2 concentration have almost been constantly proportional (by the so-called "airborne fraction") to the corresponding anthropogenic emissions. This study reviews the literature on these questions and presents a box model to describe carbon exchanges between the atmosphere and the surface reservoirs under the disturbances of anthropogenic emissions as well as global climate changes. The results show that the simple linear model can successfully simulate the <span class="hlt">observed</span> changes/variations of the atmospheric CO2 concentration and its growth rate across interannual to multi-<span class="hlt">decadal</span> time scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140011835','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140011835"><span id="translatedtitle">Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux <span class="hlt">Variability</span> on Daily Through <span class="hlt">Decadal</span> Time Scales</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Romanski, Joy; Romanou, Anastasia; Bauer, Michael; Tselioudis, George</p> <p>2013-01-01</p> <p>We analyze daily wintertime cyclone <span class="hlt">variability</span> in the central and eastern Mediterranean during 1958-2001, and identify four distinct cyclone states, corresponding to the presence or absence of cyclones in each basin. Each cyclone state is associated with wind flows that induce characteristic patterns of cooling via turbulent (sensible and latent) heat fluxes in the eastern Mediterranean basin and Aegean Sea. The relative frequency of occurrence of each state determines the heat loss from the Aegean Sea during that winter, with largest heat losses occurring when there is a storm in the eastern but not central Mediterranean (eNOTc), and the smallest occurring when there is a storm in the central but not eastern Mediterranean (cNOTe). Time series of daily cyclone states for each winter allow us to infer Aegean Sea cooling for winters prior to 1985, the earliest year for which we have daily heat flux <span class="hlt">observations</span>. We show that cyclone states conducive to Aegean Sea convection occurred in 1991/1992 and 1992/1993, the winters during which deep water formation was <span class="hlt">observed</span> in the Aegean Sea, and also during the mid-1970s and the winters of 1963/1964 and 1968/1969. We find that the eNOTc cyclone state is anticorrelated with the North Atlantic Oscillation (NAO) prior to 1977/1978. After 1977/1978, the cNOTe state is anticorrelated with both the NAO and the North Caspian Pattern (NCP), showing that the area of influence of large scale atmospheric teleconnections on regional cyclone activity shifted from the eastern to the central Mediterranean during the late 1970s. A trend toward more frequent occurrence of the positive phase of the NAO produced less frequent cNOTe states since the late 1970s, increasing the number of days with strong cooling of the Aegean Sea surface waters.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH33C..07E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH33C..07E"><span id="translatedtitle">Geomagnetic storms during the last <span class="hlt">decade</span>: Cluster and Double Star <span class="hlt">observations</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Escoubet, C.; Taylor, M. G.; Masson, A.; Laakso, H. E.; Liu, Z.; Goldstein, M. L.</p> <p>2013-12-01</p> <p>The launch of the Cluster spacecraft almost coincided with one of the largest geomagnetic storm of the last <span class="hlt">decade</span>, well known as the "Bastille Day" storm, on 14-15 July 2000. Planned on 15 July, the launch was aborted a few minutes before due to a thunderstorm that had hit the Baikonour cosmodrome and made a disruption in the communication lines with the rocket. The launch took place the day after, on 16 July 2000. Our US colleagues had warned us about the storm and recommended not to launch on 15 July. Given the facts that (1) Cluster was built to study the effects of space weather and geomagnetic storms and (2) that the Russian launch authorities were not concerned for the Soyuz rocket, it was decided to go ahead with the launch. The launch was fine and, after a second launch less than a month later, the four Cluster spacecraft were put successfully in their 4x19 RE polar orbit. Since then, Cluster has <span class="hlt">observed</span> many geomagnetic storms and could <span class="hlt">observe</span>, for the first time with a constellation of four spacecraft, the dynamics induced in the magnetosphere by coronal mass ejections or interplanetary shocks coming from the Sun. In this talk we will use storms <span class="hlt">observed</span> by Cluster and Double Star in the last <span class="hlt">decade</span> to illustrate how the magnetosphere was affected. We have <span class="hlt">observed</span> large compressions of the magnetosphere, distortions of the polar cusp, acceleration of particles associated with chorus and ULF waves, intensification of the ring current imaged by energetic neutral atom imagers, oxygen outflow from polar regions, and tail current sheet motions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.6793F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.6793F"><span id="translatedtitle"><span class="hlt">Decadal</span> covariability of Atlantic SSTs and western Amazon dry-season hydroclimate in <span class="hlt">observations</span> and CMIP5 simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernandes, Katia; Giannini, Alessandra; Verchot, Louis; Baethgen, Walter; Pinedo-Vasquez, Miguel</p> <p>2015-08-01</p> <p>The unusual severity and return time of the 2005 and 2010 dry-season droughts in western Amazon is attributed partly to <span class="hlt">decadal</span> climate fluctuations and a modest drying trend. <span class="hlt">Decadal</span> <span class="hlt">variability</span> 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 <span class="hlt">decade</span> when NSG > 0 and 19% when NSG < 0. The western Amazon and NSG <span class="hlt">decadal</span> 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 <span class="hlt">decadal</span> predictability based on GCMs. Persistence of the current NSG positive phase favors above normal frequency of western Amazon dry events in coming <span class="hlt">decades</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=302477','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=302477"><span id="translatedtitle">Intra- to Multi-<span class="hlt">Decadal</span> Temperature <span class="hlt">Variability</span> over the Continental United States: 1896-2012</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-<span class="hlt">decadal</span> (IMD) time windows containing significant ranking sequences in U.S. climate division temperature data. The simplicity of the ORR procedure’s output – a time series’ most significant non-overlapping periods of high o...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DSRII.113....9H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DSRII.113....9H"><span id="translatedtitle">Multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> and trends in the El Niño-Southern Oscillation and tropical Pacific fisheries implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harrison, D. E.; Chiodi, Andrew M.</p> <p>2015-03-01</p> <p>Extremes of the El Niño-Southern Oscillation (ENSO) are known to have various socio-economic impacts, including effects on several Pacific fisheries. The 137-year-long record of Darwin sea-level pressure offers a uniquely long-term perspective on ENSO and provides important insight into various aspects of interannual to century-scale <span class="hlt">variability</span> that affects these fisheries. One particular issue of interest is whether there is a centennial-scale (or longer) trend that can be expected to alter the future distributions of these fisheries. Since most tropical Pacific fishery records are no longer than a few <span class="hlt">decades</span>, another issue is the extent to which trends over these recent <span class="hlt">decades</span> are a good basis for detecting the presence of long-term (e.g., centennial-scale) deterministic changes, and perhaps thereby projecting future conditions. We find that the full 137-yr trend cannot be distinguished from zero with 95% confidence, and also that the ENSO variance in recent <span class="hlt">decades</span> is very similar to that of the early <span class="hlt">decades</span> of the record, suggesting that ENSO has not fundamentally changed over the period of large increase in atmospheric CO2. However, the strong multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> in ENSO is reflected in <span class="hlt">decades</span> with quite different levels of ENSO effects on the ecosystem. Many multi-<span class="hlt">decadal</span> subsets of the full record have statistically significant trends, using standard analysis techniques. These multi-<span class="hlt">decadal</span> trends are not; however, representative of the record-length trend, nor are they a useful basis for projecting conditions in subsequent <span class="hlt">decades</span>. Trend statistical significance is not a robust foundation for speculation about the future. We illustrate how the difficulties involved in determining whether a trend is statistically significant or not mean that, even after careful consideration, an unexpectedly large number of trends may reach standard statistical significance levels over the time spans for which many newer records are available, but still not continue into future <span class="hlt">decades</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000358','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000358"><span id="translatedtitle">Highlights from a <span class="hlt">Decade</span> of OMI-TOMS Total Ozone <span class="hlt">Observations</span> on EOS Aura</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Haffner, David P.; Bhartia, Pawan K.; McPeters, Richard D.; Joiner, Joanna; Ziemke, Jerald R.; Vassilkov, Alexander; Labow, Gordon J.; Chiou, Er-Woon</p> <p>2014-01-01</p> <p>Total ozone measurements from OMI have been instrumental in meeting Aura science objectives. In the last <span class="hlt">decade</span>, OMI has extended the length of the TOMS total ozone record to over 35 years to monitor stratospheric ozone recovery. OMI-TOMS total ozone measurements have also been combined synergistically with measurements from other Aura instruments and MLS in particular, which provides vertically resolved information that complements the total O3 mapping capability of OMI. With this combined approach, the EOS Aura platform has produced more accurate and detailed measurements of tropospheric ozone. This has led in turn to greater understanding of the sources and transport of tropospheric ozone as well as its radiative forcing effect. The combined use of OMI and MLS data was also vital to the analysis of the severe Arctic ozone depletion event of 2011. The quality of OMI-TOMS total O3 data used in these studies is the result of several factors: a mature and well-validated algorithm, the striking stability of the OMI instrument, and OMI's hyperspectral capabilities used to derive cloud pressures. The latter has changed how we think about the effects of clouds on total ozone retrievals. We will discuss the evolution of the operational V8.5 algorithm and provide an overview and motivation for V9. After reviewing results and developments of the past <span class="hlt">decade</span>, we finally highlight how ozone <span class="hlt">observations</span> from EOS Aura are playing an important role in new ozone mapping missions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JCHyd...5..195P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JCHyd...5..195P"><span id="translatedtitle">Field-<span class="hlt">observed</span> ethylene dibromide in an aquifer after two <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pignatello, Joseph J.; Frink, Charles R.; Marin, Paul A.; Droste, Edward X.</p> <p>1990-01-01</p> <p>The fate and transport of the soil fumigant, 1,2-dibromoethane (EDB) was studied at a former tobacco field in Simsbury, Connecticut where it was last used in 1967. The subsurface consists of glacial deposits of stratified sand, gravel, and silt underlain by a fractured sandstone/siltstone bedrock. Contaminant plumes in the bedrock had migrated only slightly from beneath the tobacco field after nearly two <span class="hlt">decades</span>, consistent with calculated flow velocities. Contaminant levels in the overburden aquifer were much lower, which was consistent with higher calculated flow velocities resulting in off-site discharge to a nearby stream, and possibly with faster biodegradation. EDB concentrations in both zones were stable over the study period (1.5-2yr). Earlier demonstration of relatively fast biodegradation of 14C-EDB in aquifer core samples were contradicted by the plume stabilities <span class="hlt">observed</span> here. EDB was found in vadose cores, particularly topsoils, at concentrations up to 32?g kg -1. These residues could not be extracted with water, even after 20 d, and were unavailable for biodegradation. By contrast added 14C-EDBwas mineralized almost completely in 22 d. EDB was also found in overburden aquifer cores, in some cases at concentrations much greater than predicted from equilibrium partition experiments. The results show that kinetically slow, nonequilibrium sorption is a factor in the <span class="hlt">decades</span>-long persistence of this chemical in the topsoil and possibly in the aquifer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP31C1889C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP31C1889C"><span id="translatedtitle"><span class="hlt">Decadal</span> and Centennial <span class="hlt">Variability</span> of Wet and Dry in China since Medieval Warm Period Detected from High Resolution Speleothem Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chu, P. C.; Li, H.</p> <p>2011-12-01</p> <p>High-resolution δ18O data (yearly) since AD 900 from six caves (Dongge, Furong, Heshang, Wanxiang, Buddha, Shihua) in China was analyzed to detect <span class="hlt">decadal</span> and centennial <span class="hlt">variability</span> of wet/dry in the Asian Monsoon region. The empirical mode decomposition method (Huang et al., 1998) was used to obtain trends for the six cave data. The nine-year running average was conducted on the detrened data (Δδ18O, called anomaly) to filter out high-frequency fluctuation such as the interannual <span class="hlt">variability</span>. Mean values of anomaly for each cave were calculated for 5 periods: (1) medieval warm period (MWD, AD 900 -AD 1100), (2) little ice age phase-1 (LIA-1, AD 1250 - AD 1550), (3) little ice age phase-2 (LIA-2, AD 1550 - AD 1850), (4) modern period-1 (MD-1, AD 1850 - AD 1950), and (5) modern period-2 (MD-2, AD 1950-2000). Anomalies in MWP and LIA-2 has opposite signs: negative anomaly (strong monsoon) in MWP and positive anomaly (weak monsoon) in LIA-2 in (Dongge, Wanxiang) cave data otherwise in (Budda, Furong, Heshang, Shihua) cave data. In LIA-1, all the six caves have positive anomalies (weak monsoon). In MD-1 (AD 1850-AD 1950), all the six caves have negative anomalies; and in MD-2 (AD 1950 - AD 2000), all the caves except Buddha have negative anomalies. It implies strong monsoon with global warming trend. Spectral analysis was also conducted on the detrended data of the six caves. The above <span class="hlt">observational</span> studies show the following results: (1) Monsoon strength has spatial variations; (2) Stronger monsoon occurred under both warm and cold climatic conditions. One should not use the relationship of warm condition, i.e., stronger summer monsoon to interpret monsoonal climates in short time scales (less than centennial scale); and (3) Monsoon strengthening continues.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.4220F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.4220F"><span id="translatedtitle"><span class="hlt">Decadal</span> gully development in Northern Ethiopia: Understanding networks, volumes and regional <span class="hlt">variability</span> from remote sensing data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frankl, Amaury; Poesen, Jean; Scholiers, Nelles; Jacob, Miro; Haile, Mitiku; Deckers, Jozef; Nyssen, Jan</p> <p>2013-04-01</p> <p>Understanding historical and present-day gully development is essential when addressing the causes and consequences of land degradation. For Northern Ethiopia, several reports exist on the severity of gully erosion, yet few studies quantified gully development. In this paper, gully network and volume development were quantified over the period 1963-2010 for an area of 123 km², representative for the regional <span class="hlt">variability</span> in environmental characteristics. Gully networks were mapped from small-scale aerial photographs and high-resolution satellite images. As only gully length could be accurately defined from the aerial photographs and satellite images, quantifying gully volume development required to establish relations between gully network volume (V) and length (L) (or catchment area, A). Field <span class="hlt">observations</span> indicated that the lithology and the presence/or absence of check dams or low-active channels were the most important controls of gully cross-sectional shape and size. From the network and volume development over the period 1963-2010, the occurrence of one cut-and-fill cycle is apparent. From a largely low-dynamic gully system in the 1960s, network expansion and increased erosion rates in the 1980s and 1990s caused the drainage density and volume to peak in 1994. The total gully density (Dtotal) was then 2.52 km km-2, coinciding with soil losses of 17.6 ton ha-1 y-1 over the period 1963/1965-1994. By 2010, improved land management and the region-wide implementation of soil and water conservation measures caused 25% the gully network to stabilize, resulting in a recent net infilling of the gully channels. The study validates previous findings that land degradation by gullying was severe in Northern Ethiopia in the second half of the 20th century, but also shows that when proper land management is applied, gullies can be transformed into a linear oasis, which increases the resistance of gullies to further erosion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000707','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000707"><span id="translatedtitle">A <span class="hlt">Decade</span> of Volcanic <span class="hlt">Observations</span> from Aura and the A-Train</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carn, Simon A.; Krotkov, Nickolay Anatoly; Yang, Kai; Krueger, Arlin J.; Hughes, Eric J.; Wang, Jun; Flower, Verity; Telling, Jennifer</p> <p>2014-01-01</p> <p>Aura <span class="hlt">observations</span> have made many seminal contributions to volcanology. Prior to the Aura launch, satellite <span class="hlt">observations</span> of volcanic degassing (e.g., from TOMS) were mostly restricted to large eruptions. However, the vast majority of volcanic gases are released during quiescent 'passive' degassing between eruptions. The improved sensitivity of Aura OMI permitted the first daily, space-borne measurements of passive volcanic SO2 degassing, providing improved constraints on the source locations and magnitude of global SO2 emissions for input to atmospheric chemistry and climate models. As a result of this unique sensitivity to volcanic activity, OMI data were also the first satellite SO2 measurements to be routinely used for volcano monitoring at several volcano observatories worldwide. Furthermore, the Aura OMI SO2 data also offer unprecedented sensitivity to volcanic clouds in the UTLS, elucidating the transport, fate and lifetime of volcanic SO2 and providing critical input to aviation hazard mitigation efforts. Another major advance has been the improved vertical resolution of volcanic clouds made possible by synergy between Aura and other A-Train instruments (e.g., AIRS, CALIPSO, CloudSat), advanced UV SO2 altitude retrievals, and inverse trajectory modeling of detailed SO2 cloud maps. This altitude information is crucial for climate models and aviation hazards. We will review some of the highlights of a <span class="hlt">decade</span> of Aura <span class="hlt">observations</span> of volcanic activity and look ahead to the future of volcanic <span class="hlt">observations</span> from space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1227122','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1227122"><span id="translatedtitle">Collaborative Research. Separating Forced and Unforced <span class="hlt">Decadal</span> Predictability in Models and <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>DelSole, Timothy</p> <p>2015-08-31</p> <p>The purpose of the proposed research was to identify unforced predictable components on <span class="hlt">decadal</span> time scales, distinguish these components from forced predictable components, and to assess the reliability of model predictions of these components. The question of whether anthropogenic forcing changes <span class="hlt">decadal</span> predictability, or gives rise to new forms of <span class="hlt">decadal</span> predictability, also will be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.1739Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.1739Y"><span id="translatedtitle">Climatic controls on the interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span> in Saudi Arabian dust activity: Toward the development of a seasonal dust prediction model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Yan; Notaro, Michael; Liu, Zhengyu; Wang, Fuyao; Alkolibi, Fahad; Fadda, Eyad; Bakhrjy, Fawzieh</p> <p>2015-03-01</p> <p>The <span class="hlt">observed</span> climatic controls on springtime and summertime Saudi Arabian dust activities during 1975-2012 are analyzed, leading to development of a seasonal dust prediction model. According to empirical orthogonal function analysis, dust storm frequency exhibits a dominantly homogeneous pattern across Saudi Arabia, with distinct interannual and <span class="hlt">decadal</span> <span class="hlt">variability</span>. The previously identified positive trend in remotely sensed aerosol optical depth since 2000 is shown to be a segment of the <span class="hlt">decadal</span> oscillation in dust activity, according to long-duration station record. Regression and correlation analyses reveal that the interannual <span class="hlt">variability</span> in Saudi Arabian dust storm frequency is regulated by springtime rainfall across the Arabian Peninsula and summertime Shamal wind intensity. The key drivers of Saudi Arabian dust storm <span class="hlt">variability</span> are identified. Winter-to-spring La Niña enhances subsequent spring dust activity by decreasing rainfall across the country's primary dust source region, the Rub' al Khali Desert. A relatively cool tropical Indian Ocean favors frequent summer dust storms by producing an anomalously anticyclonic circulation over the central Arabian Peninsula, which enhances the Shamal wind. <span class="hlt">Decadal</span> <span class="hlt">variability</span> in Saudi Arabian dust storm frequency is associated with North African rainfall and Sahel vegetation, which regulate African dust emissions and transport to Saudi Arabia. Mediterranean sea surface temperatures (SSTs) also regulate <span class="hlt">decadal</span> dust <span class="hlt">variability</span>, likely through their influence on Sahel rainfall and Shamal intensity. Using antecedent-accumulated rainfall over the Arabian Peninsula and North Africa, and Mediterranean SSTs, as low-frequency predictors, and tropical eastern Pacific and tropical Indian Ocean SSTs as high-frequency predictors, Saudi Arabia's seasonal dust activity is well predicted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.5615M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.5615M"><span id="translatedtitle">Mapping of <span class="hlt">decadal</span> middle Adriatic oceanographic <span class="hlt">variability</span> and its relation to the BiOS regime</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mihanović, Hrvoje; Vilibić, Ivica; Dunić, Natalija; Å epić, Jadranka</p> <p>2015-08-01</p> <p>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 <span class="hlt">decadal</span> 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 <span class="hlt">decadal</span> 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 <span class="hlt">decadal</span> oscillations as seen by ocean climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMGC43D0997K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMGC43D0997K"><span id="translatedtitle"><span class="hlt">Observation</span> of methane in this <span class="hlt">decade</span> by ground-based FTIR Spectrometer over Poker Flat, ALASKA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kasai, Y.; Kagawa, A.; Jones, N. B.; Murayama, Y.</p> <p>2010-12-01</p> <p>Tropospheric CH4 is an important greenhouse gas as second largest radiative forcing in the troposphere with a long lifetime of ~10 years (Rinsland et. al., 2005). Poker Flat is a suitable location to detect CH4 abnormally due to Siberian/Alaskan biomass burning (Kasai et. al., 2005), volcano, and an anthropogenical emissions such as gas leakage from pipe-lines. We have been <span class="hlt">observed</span> troposheric CH4 over 10 years between 2000-2010 by using ground-based spectroscopic infrared solar absorption remote sensing measurement over Poker Flat, ALASKA (65.11N, 147.42W, 0.61km). CH4 vertical profiles were obtained by using SFIT2 ver.3.9 which incorporates Rodgers’ formulation of the Optimal Estimation Method (OEM) with an iterative Newton scheme (Rodgers, 2000). Frequency region of the CH4 is used 2600-2900 cm-1 region with the resolution 0.036cm-1. Seasonal and annual variation of the tropospheric CH4 in this <span class="hlt">decades</span> was obtained. Increasing trend of tropospheric CH4 was <span class="hlt">observed</span>. Several enhancement and depletion events were also <span class="hlt">observed</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25001240','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25001240"><span id="translatedtitle"><span class="hlt">Observed</span> cold season changes in a Fennoscandian fell area over the past three <span class="hlt">decades</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kivinen, Sonja; Rasmus, Sirpa</p> <p>2015-04-01</p> <p>We studied trends and <span class="hlt">variability</span> in snow and climate characteristics in 1978-2012 in the Värriötunturit fell area, northern Finland. Cold season changes were examined using long-term <span class="hlt">observational</span> data on snow depths, meteorological data, large-scale climate indices, and reindeer herders' experiences with difficult snow conditions. Snow depths declined, and temperatures increased significantly over the study period, with the largest changes <span class="hlt">observed</span> in October-December and in April. Snow depths decreased particularly in forests at lower altitudes but not in treeless areas at higher altitudes. Interannual <span class="hlt">variability</span> (but not the trends) in snow depths could be partially linked to large-scale climate indices. A majority of difficult reindeer grazing conditions were related to deep snow in the winter or spring. Our <span class="hlt">observations</span> suggest that shortened duration of snow cover may facilitate reindeer grazing, whereas potentially more frequent formation of ice layers and mold growth on pastures in the future is disadvantageous for reindeer husbandry. PMID:25001240</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.6114Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.6114Y"><span id="translatedtitle">On the mechanisms of <span class="hlt">decadal</span> <span class="hlt">variability</span> of the North Pacific Gyre Oscillation over the 20th century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yi, Daling Li; Zhang, Liping; Wu, Lixin</p> <p>2015-09-01</p> <p>The <span class="hlt">decadal</span> <span class="hlt">variability</span> of the North Pacific gyre oscillation (NPGO) over the 20th century is examined from a long-term integration of the Simple Ocean Data Assimilation (SODA) reanalysis. The NPGO is reflected by the second dominant pattern of sea surface height (SSH) <span class="hlt">variability</span> in SODA, with a north-south dipole structure over the northeast Pacific. SSH anomalies in this region exhibit distinct <span class="hlt">decadal</span> <span class="hlt">variability</span> with a significant spectrum peak at approximately 18 years. The upper-ocean heat budget reveals that this dipole structure associated with the NPGO is predominantly due to the anomalous Ekman pumping and Ekman advection induced by the surface wind. The NPGO mode in SODA reanalysis originates from atmosphere stochastic noise (North Pacific Oscillation) which has a meridional dipole pattern but no preferred time scale. The oceanic planetary wave, particularly the advective baroclinic mode, integration of atmospheric stochastic noise leads to a spatial resonance with preferred <span class="hlt">decadal</span> time scale. The limitation of current study is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014HydJ...22.1825H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014HydJ...22.1825H"><span id="translatedtitle">Watershed-scale response of groundwater recharge to inter-annual and inter-<span class="hlt">decadal</span> <span class="hlt">variability</span> in precipitation (Alberta, Canada)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hayashi, Masaki; Farrow, Christopher R.</p> <p>2014-12-01</p> <p>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 <span class="hlt">variability</span> on recharge, but such data sets are rare. The climate of the Canadian prairies is characterized by large inter-annual and inter-<span class="hlt">decadal</span> <span class="hlt">variability</span> in precipitation, which provides opportunities to examine the response of groundwater recharge to changes in meteorological conditions. A <span class="hlt">decadal</span> 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 <span class="hlt">decadal</span>-scale <span class="hlt">variability</span> of meteorological conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19780051753&hterms=footprint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfootprint','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19780051753&hterms=footprint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfootprint"><span id="translatedtitle"><span class="hlt">Observed</span> <span class="hlt">variability</span> of aircraft noise footprint measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maglieri, D. J.; Henderson, H. R.; Hilton, D. A.</p> <p>1977-01-01</p> <p>A description is presented of some measurements which illustrate the <span class="hlt">variability</span> of the experimentally developed ground noise footprints for a series of landing approach operations of a turbojet aircraft and a turbine powered helicopter. Measurements on the recently developed NASA Remotely Operated Multiple Array Acoustic Range are considered. The information presented is related to a turbojet fighter aircraft and a turbine powered helicopter performing landing approach operations along a 3 deg approach path. Each vehicle was acquired on radar tracking approximately 10 kilometers from the touchdown point and entered the test area at an altitude of about 470 m. The measured variations in meteorological quantities for the two time periods during which these tests were conducted are presented in graphs. Other graphs show the ground noise contour for the turbojet aircraft and the turbine helicopter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ClDy...28..425W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ClDy...28..425W"><span id="translatedtitle">Cycles and shifts: 1,300 years of multi-<span class="hlt">decadal</span> temperature <span class="hlt">variability</span> in the Gulf of Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, Rob; Wiles, Greg; D'Arrigo, Rosanne; Zweck, Chris</p> <p>2007-03-01</p> <p>The Gulf of Alaska (GOA) is highly sensitive to shifts in North Pacific climate <span class="hlt">variability</span>. Here we present an extended tree-ring record of January September GOA coastal surface air temperatures using tree-ring width data from coniferous trees growing in the mountain ranges along the GOA. The reconstruction (1514 1999), based on living trees, explains 44% of the temperature variance, although, as the number of chronologies decreases back in time, this value decreases to, and remains around ˜30% before 1840. Verification of the calibrated models is, however, robust. Utilizing sub-fossil wood, we extend the GOA reconstruction back to the early eighth century. The GOA reconstruction correlates significantly (95% CL) with both the Pacific <span class="hlt">Decadal</span> Oscillation Index (0.53) and North Pacific Index (-0.42) and therefore likely yields important information on past climate <span class="hlt">variability</span> in the North Pacific region. Intervention analysis on the GOA reconstruction identifies the known twentieth century climate shifts around the 1940s and 1970s, although the mid-1920s shift is only weakly expressed. In the context of the full 1,300 years record, the well studied 1976 shift is not unique. Multi-taper method spectral analysis shows that the spectral properties of the living and sub-fossil data are similar, with both records showing significant (95% CL) spectral peaks at ˜9 11, 13 14 and 18 19 years. Singular spectrum analysis identifies (in order of importance) significant oscillatory modes at 18.7, 50.4, 38.0, 91.8, 24.4, 15.3 and 14.1 years. The amplitude of these modes varies through time. It has been suggested (Minobe in Geophys Res Lett 26:855 858, 1999) that the regime shifts during the twentieth century can be explained by the interaction between pentadecadal (50.4 years) and bidecadal (18.7 years) oscillatory modes. Removal of these two modes of variance from our GOA time series does indeed remove the twentieth century shifts, but many are still identified prior to the twentieth century. Our analysis suggests that climate <span class="hlt">variability</span> of the GOA is very complex, and that much more work is required to understand the underlying oscillatory behavior that is <span class="hlt">observed</span> in instrumental and proxy records from the North Pacific region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1558P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1558P"><span id="translatedtitle">Validation of the German Mid-Range Climate Prediction (MiKlip) <span class="hlt">decadal</span> ensemble prediction system using radiosonde <span class="hlt">observations</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pattantys-brahm, Margit; Steinbrecht, Wolfgang</p> <p>2015-04-01</p> <p>We report validation results for three simulations by the Max-Planck-Institute's Earth System Model (MPI-ESM) ensemble prediction system (EPS), which is used for hindcasts and predictions of global-scale <span class="hlt">decadal</span> climate <span class="hlt">variability</span> in the framework of the German MiKlip project. Three experiments were analyzed: Baseline0 simulations with ocean anomaly field initialization, Baseline1 simulations with additional atmospheric full field initialization, and Prototype simulations with full field initialization for both ocean and atmosphere. Our validation compares homogenized radiosonde <span class="hlt">observations</span> to the <span class="hlt">decadal</span> ensemble hindcast projections. So far, we focused on the European region. Comparison of <span class="hlt">observed</span> and simulated European temperature profiles showed noticeable model cold bias, about 1 K near the surface, increasing to about 3 K near the tropopause. This has implications for atmospheric stability, which is underestimated in the simulations compared to the radiosonde profiles. The simulations also tend to overestimate humidity throughout the troposphere. Both biases combine to give, e.g., much larger simulated values for standard severe weather indices, which might be interpreted as higher severe weather probability in the simulations. While Baseline 0 and Baseline 1 simulations showed no dependence of temperature bias on simulation lead years, the temperature bias of Prototype simulations increased systematically with increasing lead years. Apart from bias and probability density functions, the predictive skills of the Ensemble Prediction System were also analyzed with respect to the radiosonde <span class="hlt">observations</span>. Here the Mean Square Error Skill Score (MSESS) and Continuously Ranked Probability Skill Scores (CRPSS) were used. For tropospheric temperatures, the full-field initialized Prototype experiments showed the best skills (MSESS and CRPSS), compared to the Baseline 0 and 1 experiments. In the stratosphere predictive skills were comparable for all experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110012422','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110012422"><span id="translatedtitle">CLARREO Cornerstone of the Earth <span class="hlt">Observing</span> System: Measuring <span class="hlt">Decadal</span> Change Through Accurate Emitted Infrared and Reflected Solar Spectra and Radio Occultation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sandford, Stephen P.</p> <p>2010-01-01</p> <p>The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is one of four Tier 1 missions recommended by the recent NRC <span class="hlt">Decadal</span> Survey report on Earth Science and Applications from Space (NRC, 2007). The CLARREO mission addresses the need to provide accurate, broadly acknowledged climate records that are used to enable validated long-term climate projections that become the foundation for informed decisions on mitigation and adaptation policies that address the effects of climate change on society. The CLARREO mission accomplishes this critical objective through rigorous SI traceable <span class="hlt">decadal</span> change <span class="hlt">observations</span> that are sensitive to many of the key uncertainties in climate radiative forcings, responses, and feedbacks that in turn drive uncertainty in current climate model projections. These same uncertainties also lead to uncertainty in attribution of climate change to anthropogenic forcing. For the first time CLARREO will make highly accurate, global, SI-traceable <span class="hlt">decadal</span> change <span class="hlt">observations</span> sensitive to the most critical, but least understood, climate forcings, responses, and feedbacks. The CLARREO breakthrough is to achieve the required levels of accuracy and traceability to SI standards for a set of <span class="hlt">observations</span> sensitive to a wide range of key <span class="hlt">decadal</span> change <span class="hlt">variables</span>. The required accuracy levels are determined so that climate trend signals can be detected against a background of naturally occurring <span class="hlt">variability</span>. Climate system natural <span class="hlt">variability</span> therefore determines what level of accuracy is overkill, and what level is critical to obtain. In this sense, the CLARREO mission requirements are considered optimal from a science value perspective. The accuracy for <span class="hlt">decadal</span> change traceability to SI standards includes uncertainties associated with instrument calibration, satellite orbit sampling, and analysis methods. Unlike most space missions, the CLARREO requirements are driven not by the instantaneous accuracy of the measurements, but by accuracy in the large time/space scale averages that are key to understanding <span class="hlt">decadal</span> changes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A51A0082S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A51A0082S"><span id="translatedtitle">Atmospheric <span class="hlt">Variability</span> of CO2 impact on space <span class="hlt">observation</span> Requirements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swanson, A. L.; Sen, B.; Newhart, L.; Segal, G.</p> <p>2009-12-01</p> <p>If International governments are to reduce GHG levels by 80% by 2050, as recommended by most scientific bodies concerned with avoiding the most hazardous changes in climate, then massive investments in infrastructure and new technology will be required over the coming <span class="hlt">decades</span>. Such an investment will be a huge commitment by governments and corporations, and while it will offer long-term dividends in lower energy costs, a healthier environment and averted additional global warming, the shear magnitude of upfront costs will drive a call for a monitoring and verification system. Such a system will be required to offer accountability to signatories of governing bodies, as well as, for the global public. Measuring the average global distribution of CO2 is straight forward, as exemplified by the long running station measurements managed by NOAA’s Global Monitoring Division that includes the longterm Keeling record. However, quantifying anthropogenic and natural source/sink distributions and atmospheric mixing have been much more difficult to constrain. And, yet, an accurate accounting of all anthropogenic source strengths is required for Global Treaty verification. The only way to accurately assess Global GHG emissions is to construct an integrated system of ground, air and space based <span class="hlt">observations</span> with extensive chemical modeling capabilities. We look at the measurement requirements for the space based component of the solutions. To determine what space sensor performance requirements for ground resolution, coverage, and revisit, we have analyzed regional CO2 distributions and <span class="hlt">variability</span> using NASA and NOAA aircraft flight campaigns. The results of our analysis are presented as variograms showing average spatial <span class="hlt">variability</span> over several Northern Hemispheric regions. There are distinct regional differences with the starkest contrast between urban versus rural and Coastal Asia versus Coastal US. The results suggest specific consequences on what spatial and temporal requirements might need to be for space based <span class="hlt">observations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H23M1053T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H23M1053T"><span id="translatedtitle">Climate-Informed Multi-Scale Stochastic (CIMSS) Hydrological Modeling: Incorporating <span class="hlt">Decadal</span>-Scale <span class="hlt">Variability</span> Using Paleo Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thyer, M. A.; Henley, B. J.; Kuczera, G. A.</p> <p>2014-12-01</p> <p>Incorporating the influence of climate change and long-term climate <span class="hlt">variability</span> in the estimation of drought risk is a priority for water resource planners. Australia's highly <span class="hlt">variable</span> rainfall regime is influenced by ocean-atmosphere climate mechanisms which induce <span class="hlt">decadal</span>-scale <span class="hlt">variability</span> in hydrological data. This talk will summarize research on the identification of appropriate models for incorporating <span class="hlt">decadal</span> scale <span class="hlt">variability</span> into stochastic hydrological models. These will include autoregressive, hidden Markov models and a Bayesian hierarchical approach which combines paleo information on climate indices and hydrological data into a climate informed multi-time scale stochastic (CIMSS) framework. To characterize long-term <span class="hlt">variability</span> for the first level of the hierarchy, paleoclimate and instrumental data describing the Interdecadal Pacific Oscillation (IPO) and the Pacific <span class="hlt">Decadal</span> Oscillation (PDO) are analyzed. A new paleo IPO-PDO time series dating back 440 yr is produced, combining seven IPO-PDO paleo sources using an objective smoothing procedure to fit low-pass filters to individual records. The paleo data analysis indicates that wet/dry IPO-PDO states have a broad range of run lengths, with 90% between 3 and 33 yr and a mean of 15 yr. Model selection techniques were used to determine a suitable stochastic model to simulate these run lengths. For the second level of the hierarchy, a seasonal rainfall model is conditioned on the simulated IPO-PDO state. Application to two high quality rainfall sites close to water supply reservoirs found that mean seasonal rainfall in the IPO-PDO dry state was 15%-28% lower than the wet state. Furthermore, analysis of the impact of the CIMSS framework on drought risk analysis found that short-term drought risks conditional on IPO/PDO state were far higher than the traditional AR(1) model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2947027','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2947027"><span id="translatedtitle">On the Contextual Independence of Personality: Teachers’ Assessments Predict Directly <span class="hlt">Observed</span> Behavior after Four <span class="hlt">Decades</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Nave, Christopher S.; Sherman, Ryne A.; Funder, David C.; Hampson, Sarah E.; Goldberg, Lewis R.</p> <p>2010-01-01</p> <p>The continuity of personality’s association with directly <span class="hlt">observed</span> behavior is demonstrated across two contexts spanning four <span class="hlt">decades</span>. During the 1960s, elementary school teachers rated personalities of members of the ethnically diverse Hawaii Personality and Health Cohort (Hampson & Goldberg, 2006). The same individuals were interviewed in a medical clinic over 40 years later. Trained coders viewed video recordings of a subset of these interviews (N = 144, 68 F, 76 M) and assessed the behavior they <span class="hlt">observed</span> using the Riverside Behavioral Q-sort Version 3.0 (Funder, Furr & Colvin, 2000; Furr, Wagerman & Funder, 2010). Children rated by their teachers as “verbally fluent” (defined as unrestrained talkativeness) showed dominant and socially adept behavior as middle-aged adults. Early “adaptability” was associated with cheerful and intellectually curious behavior, early “impulsivity” was associated with later talkativeness and loud speech, and early rated tendencies to “self-minimize” were related to adult expressions of insecurity and humility. PMID:20890402</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.2159P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.2159P"><span id="translatedtitle">Shoreline <span class="hlt">variability</span> from days to <span class="hlt">decades</span>: Results of long-term video imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pianca, C.; Holman, R.; Siegle, E.</p> <p>2015-03-01</p> <p>The present work characterizes the time-space scales of <span class="hlt">variability</span> and forcing dependencies of a unique 26 year record of daily to hourly shoreline data from a steep beach at Duck, North Carolina. Shoreline positions over a 1500 m alongshore span were estimated using a new algorithm called ASLIM based on fitting the band of high light intensity in time exposure images to a local Gaussian fit, with a subsequent Kalman filter to reduce noise and uncertainty. Our findings revealed that the shoreline change at long times scales dominates seasonal <span class="hlt">variability</span>, despite that wave forcing had only 2% variance at interannual frequencies. The shoreline response presented 66% of the variance at interannual scales. These results were not expected since from wave forcing it would have been expected that the shoreline response should similarly lack interannual <span class="hlt">variability</span>, but we found it to be dominated by this scale. The alongshore-mean shoreline time series revealed no significant annual cycle. However, there are annual oscillations in the shoreline response that are coherent with wave forcing and deserves further explanations. The pier was found to have a significant influence on shoreline behavior since restricts the seasonal longshore transport between the sides, resulting in a seasonally reversing sediment accumulation. Thus, there is a significant annual peak in shoreline <span class="hlt">variability</span> that is coherent with the annual forcing but becomes insignificant in the longshore-average.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.B52C..03B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.B52C..03B"><span id="translatedtitle">Can we reconcile our understanding of the atmospheric methane budget over the past <span class="hlt">decades</span> with atmospheric <span class="hlt">observations</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bruhwiler, L. M.; Matthews, E.</p> <p>2007-12-01</p> <p>The balance of methane in the atmosphere is determined by surface emission, and losses due to uptake in soils and reaction with the hydroxyl radical. The atmospheric abundance of methane has risen by about a factor of three since pre-industrial times, but the growth rate has decreased substantially since the 1990's. Thus, global atmospheric methane appears to have equilibrated to around 1780 ppb subject to considerable interannual <span class="hlt">variability</span>, the causes of which are not well-understood. Methane emissions are expected to increase in the future due to increases in fossil fuel use and possible changes in wetlands at high-latitudes, and it is therefore important to test our understanding of the methane budget over the last two <span class="hlt">decades</span> against network <span class="hlt">observations</span> of atmospheric methane. Issues of interest are whether we can match the rise in methane over the 1980's, whether we can explain the decrease in growth rate during the 1990's, and whether we are able to simulate the <span class="hlt">observed</span> interannual <span class="hlt">variability</span> in the <span class="hlt">observations</span>. We will show results from a multi-<span class="hlt">decade</span> model simulation using analyzed meteorology from the ERA-40 reanalysis over this period. New times series of methane sources for 1980 through the early 2000's are used in the simulation. Anthropogenic sources include fossil fuels with a total of 7 fuel-process emission combinations associated with mining, processing, transport and distribution of coal, natural gas and oil; ruminant animals and manure based on regionally-representative profiles of bovine populations ; landfills including the impact of on- site methane capture; and irrigated rice cultivation based on seasonal rice-cropping calendars. Natural sources we include are biomass burning from the GFED emission data base, oceans, termites, and natural wetlands using a multiple-regression model derived from a process-based model. If time permits, we will also show preliminary results of a methane data assimilation using the Cooperative Air-Sampling and GMD network <span class="hlt">observations</span>, and our new estimates of methane sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003IAUS..212..208I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003IAUS..212..208I"><span id="translatedtitle">FUSE <span class="hlt">observations</span> of Luminous Blue <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iping, Rosina C.; Sonneborn, George; Massa, Derck L.</p> <p></p> <p>P Cyg, AG Car, HD 5980 and η Car were <span class="hlt">observed</span> with the Far Ultraviolet Spectroscopic Explorer ( FUSE) satellite. FUSE covers the spectral range from 980 Å to 1187 Å at a resolution of 0.05 Å. In this paper we discuss the far-UV properties of these LBVs and explore their similarities and differences. The FUSE <span class="hlt">observations</span> of P Cyg and AG Car, both spectral type B2pe, are very similar. The atmospheres of both η Car and HD 5980 appear to be somewhat hotter and have much higher ionization stages (Si IV, S IV, and P V) in the FUSE spectrum than P Cyg and AG Car. There is a very good agreement between the FUSE spectrum of P Cygni and the model atmosphere computed by John Hillier with his code CMFGEN. The FUSE spectrum of η Car, however, does not agree very well with existing model spectra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1127130','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1127130"><span id="translatedtitle">Collaborative Research: Separating Forced and Unforced <span class="hlt">Decadal</span> Predictability in Models and <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tippett, Michael K.</p> <p>2014-04-09</p> <p>This report is a progress report of the accomplishments of the research grant “Collaborative Research: Separating Forced and Unforced <span class="hlt">Decadal</span> Predictability in Models and Observa- tions” during the period 1 May 2011- 31 August 2013. This project is a collaborative one between Columbia University and George Mason University. George Mason University will submit a final technical report at the conclusion of their no-cost extension. The purpose of the proposed research is to identify unforced predictable components on <span class="hlt">decadal</span> time scales, distinguish these components from forced predictable components, and to assess the reliability of model predictions of these components. Components of unforced <span class="hlt">decadal</span> predictability will be isolated by maximizing the Average Predictability Time (APT) in long, multimodel control runs from state-of-the-art climate models. Components with <span class="hlt">decadal</span> predictability have large APT, so maximizing APT ensures that components with <span class="hlt">decadal</span> predictability will be detected. Optimal fingerprinting techniques, as used in detection and attribution analysis, will be used to separate variations due to natural and anthropogenic forcing from those due to unforced <span class="hlt">decadal</span> predictability. This methodology will be applied to the <span class="hlt">decadal</span> hindcasts generated by the CMIP5 project to assess the reliability of model projections. The question of whether anthropogenic forcing changes <span class="hlt">decadal</span> predictability, or gives rise to new forms of <span class="hlt">decadal</span> predictability, also will be investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.3510C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.3510C"><span id="translatedtitle"><span class="hlt">Observed</span> variations of cloud fraction and types over Russia in last <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chernokulsky, Alexander; Akperov, Mirseid; Bulygina, Olga; Mokhov, Igor; Nikitina, Natalia</p> <p>2013-04-01</p> <p>Cloudiness changes may mitigate or exacerbate global and local warming. Here, we assess changes of total and low cloud fraction and the occurrence of days with different cloud conditions and different cloud types including convective clouds over Russia from 1965 to 2011 years. Our analysis is based on visual daytime routine <span class="hlt">observations</span> from almost 500 Russian meteorological stations for the period 1965-2011 and than 1800 stations for the period 1984-2011. In general, cloud fraction tends to increase during the last years. A major increase of total cloud fraction and a decrease of the number of clear days are revealed in spring and autumn mostly due to an increase of the occurrence of convective and non-precipitating stratiform clouds. In contrast, the occurrence of Nimbostratus clouds tends to decrease, which lead to a general decrease of the occurrence of overcast days. In most regions, the ratio between the occurrence of Cumulonimbus and Nimbostratus clouds has increased in last <span class="hlt">decade</span> compare to previous ones. It worth noting, that for particular stations this redistribution may be associated with <span class="hlt">observers</span> changes. Over some regions (Ural and the Far East), a decrease of total cloud fraction and an increase of the number of clear days are noted. In addition, we assess possible causes of cloudiness variations. In particular, sensitivity of cloudiness changes to temperature changes were evaluated. The relationship of cloud variations with cyclonic/anticyclonic activity including atmospheric centers of action (Azores and Siberian highs, Aleutian and Icelandic lows) were assessed as well. An overall increase of convective clouds occurrence is an additional and independent evidence for the intensification of convective processes in the last <span class="hlt">decades</span> over land in the northern midlatitudes. Alongside with an increase of heavy precipitation events, an increase of occurrence of Cumulonimbus clouds leads to lightning occurrence increase and, in turn, leads to an increase of the risk of forest fire initiation. Together with the projected increase of fire danger indices in southern regions of the European Part and Siberia, it can lead to more fire hazardous regional climate. The work has been supported by the grant of the RF President MK-3259.2012.5 and by the Russian Foundation of Basic Research under grant 12-05-00972.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.U33A0018A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.U33A0018A"><span id="translatedtitle">Global ocean wave intensity changes <span class="hlt">observed</span> across <span class="hlt">decadal</span>-scale time intervals using seismic background noise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aster, R. C.; McNamara, D. E.; Macayeal, D. R.</p> <p>2006-12-01</p> <p>Seismic background energy on Earth between roughly 6 and 25 s period, even in deep continental interiors, is dominated by a persistent "microseism" arising from energy transferred from ocean gravity waves to elastic Rayleigh waves. High-quality continuous digital records from the IRIS/USGS Global Seismographic Network (GSN) and its precursor networks now extend back over 15 years at the longest-operational sites. We examine using the microseism as a proxy for <span class="hlt">decadal</span>-scale changes in storm wave intensity, a topic of considerable interest in the debate about how global change may influence oceanic storm frequency and intensity. Microseism power spectral density (PSD) is dominated by a primary peak centered near ~16 s that is generated by waves breaking on coastlines, and by a (generally much stronger) secondary peak centered near ~8 s that is generated by the half-period periodic variation of sea bottom pressure due to standing wave components of the ocean gravity wave field. We measure microseism intensities on <span class="hlt">decadal</span> intervals, eliminating signals at similar periods arising from earthquakes by evaluating medians of large numbers of 1- hour PSDs over day- to months-long intervals. Integrated PSD median curves over relevant period ranges give representative microseism power levels. Microseism power time series from the GSN show secular changes in the roughness (storm-wave intensity) of Earth's oceans extending back as far as the late 1970's. Resulting time series for northern hemisphere stations clearly show very strong effects from northern Pacific winter storms, where PSD levels can increase by 2 orders of magnitude over summer levels (e.g., as <span class="hlt">observed</span> at Kipapa, Oahu). We also see the effects of southern hemisphere storms during the austral winter and, in Antarctica, seasonal shielding effects that are attributable to the formation/disintegration of sea ice at southern hemisphere stations (e.g., at South Pole). El Nino-induced sea surface roughness changes are also visible at northern hemisphere stations, such as notably increased microseism levels during 1997-1998. These <span class="hlt">observations</span> suggest that the microseism may provide a useful proxy record for evaluating the influence of climate variations on oceanic storminess.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.4956S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.4956S"><span id="translatedtitle"><span class="hlt">Decadal</span> wave power <span class="hlt">variability</span> in the North-East Atlantic and North Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santo, H.; Taylor, P. H.; Woollings, T.; Poulson, S.</p> <p>2015-06-01</p> <p>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 <span class="hlt">variability</span>, which makes wave energy prediction challenging. This <span class="hlt">variability</span> should be considered in any long-term reliability analysis for wave energy devices and in power scheme economics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...46.1517C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...46.1517C"><span id="translatedtitle">Mechanisms of internally generated <span class="hlt">decadal</span>-to-multidecadal <span class="hlt">variability</span> of SST in the Atlantic Ocean in a coupled GCM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Hua; Schneider, Edwin K.; Wu, Zhiwei</p> <p>2016-03-01</p> <p>Mechanisms of the internally generated <span class="hlt">decadal</span>-to-multidecadal <span class="hlt">variability</span> of SST in the Atlantic Ocean are investigated in a long control simulation of the Community Climate System Model version 3 with constant external forcing. The interactive ensemble (IE) coupling strategy, with an ensemble of atmospheric GCMs (AGCM) coupled to an ocean model, a sea-ice model and a land model, is used to diagnose the roles of various processes in the coupled GCM (CGCM). The noise components of heat flux, wind stress and fresh water flux of the control simulation, determined from the CGCM surface fluxes by subtracting the SST-forced surface fluxes, estimated as the ensemble mean of AGCM simulations, are applied at the ocean surface of the IE in different regions and in different combinations. The IE simulations demonstrate that the climate <span class="hlt">variability</span> in the control simulation is predominantly forced by noise. The local noise forcing is found to be responsible for the SST <span class="hlt">variability</span> in the Atlantic Ocean, with noise heat flux and noise wind stress playing a critical role. The control run Atlantic multidecadal <span class="hlt">variability</span> (AMV) index is decomposed into interannual, <span class="hlt">decadal</span> and multidecadal modes based on the ensemble empirical mode decomposition. The AMV multidecadal mode, a combination of 50- and 100-year modes, is examined in detail. The North Atlantic Oscillation (NAO) pattern in the atmosphere, dominated by the noise component, forces the multidecadal mode through noise heat flux and noise wind stress. The noise wind stress forcing on the multidecadal mode is associated with ocean dynamics, including gyre adjustment and the Atlantic Meridional Overturning Circulation (AMOC). The AMV <span class="hlt">decadal</span> mode is also found to be related to noise NAO forcing. The associated ocean dynamics are connected with both noise heat flux and noise wind stress, but the AMOC related to the <span class="hlt">decadal</span> mode is more likely to be forced by noise heat flux. For both multidecadal and <span class="hlt">decadal</span> modes, the atmospheric response to SST, including the SST-forced heat flux and SST-forced wind stress, acts as a damping.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRD..119.5331H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRD..119.5331H"><span id="translatedtitle"><span class="hlt">Decadal</span> change of South China Sea tropical cyclone activity in mid-1990s and its possible linkage with intraseasonal <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ha, Yao; Zhong, Zhong; Sun, Yuan; Lu, Wei</p> <p>2014-05-01</p> <p>This study focuses on the <span class="hlt">decadal</span> <span class="hlt">variability</span> of tropical cyclone (TC) activity over the South China Sea (SCS) since the 1970s and its possible cause behind. It is found that TC activity over the SCS experiences a significant <span class="hlt">decadal</span> change around the mid-1990s. Compared to the period from the 1970s to the early 1990s, the number of TCs formed in the SCS remarkably increases from the mid-1990s through the 2000s. In particular, this change of TC genesis is closely related to a <span class="hlt">decadal</span> shift in atmospheric intraseasonal <span class="hlt">variability</span> (ISV) that occurred in 1994. The ISV on the 30-60 days time scale over the SCS has been increasing since the mid-1990s, and the increased TC frequency after 1994 is attributed primarily to the active convection induced by the enhancement of the SCS ISV. In addition, the TC activities before the mid-1990s are mostly confined within the SCS basin. However, more TCs form over the SCS and move northeastward since the mid-1990s and finally enter the East China Sea and the Philippine Sea. Anomalies of westerly over the northern SCS after 1994 are responsible for the northeastward moving of TCs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.458.2063K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.458.2063K"><span id="translatedtitle">Evolving into a remnant: optical <span class="hlt">observations</span> of SN 1978K at three <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuncarayakti, H.; Maeda, K.; Anderson, J. P.; Hamuy, M.; Nomoto, K.; Galbany, L.; Doi, M.</p> <p>2016-05-01</p> <p>We present new optical <span class="hlt">observations</span> of the supernova SN 1978K, obtained in 2007 and 2014 with the Very Large Telescope. We discover that the supernova has not faded significantly, even more than three <span class="hlt">decades</span> after its explosion. The spectrum exhibits numerous narrow (FWHM ≲600 km s-1) emission lines, indicating that the supernova blastwave is persistently interacting with dense circumstellar material (CSM). Evolution of emission lines indicates that the supernova ejecta is slowly progressing through the reverse shock, and has not expanded past the outer edge of the circumstellar envelope. We demonstrate that the CSM is not likely to be spherically distributed, with mass of ≲1 M⊙. The progenitor mass loss rate is estimated as ≳0.01 M⊙ yr-1. The slowly fading late-time light curve and spectra show striking similarity with SN 1987A, indicating that a rate at which the CSM is being swept-up by the blastwave is gradually decaying and SN 1978K is undergoing similar evolution to become a remnant. Due to its proximity (4 Mpc), SN 1978K serves as the next best example of late-time supernova evolution after SN 1987A.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.tmp..207K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.tmp..207K"><span id="translatedtitle">Evolving into a remnant: optical <span class="hlt">observations</span> of SN 1978K at three <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuncarayakti, H.; Maeda, K.; Anderson, J. P.; Hamuy, M.; Nomoto, K.; Galbany, L.; Doi, M.</p> <p>2016-02-01</p> <p>We present new optical <span class="hlt">observations</span> of the supernova SN 1978K, obtained in 2007 and 2014 with the Very Large Telescope. We discover that the supernova has not faded significantly, even more than three <span class="hlt">decades</span> after its explosion. The spectrum exhibits numerous narrow (FWHM ≲ 600 km s-1) emission lines, indicating that the supernova blastwave is persistently interacting with dense circumstellar material (CSM). Evolution of emission lines indicates that the supernova ejecta is slowly progressing through the reverse shock, and has not expanded past the outer edge of the circumstellar envelope. We demonstrate that the CSM is not likely to be spherically distributed, with mass of ≲ 1 M⊙. The progenitor mass loss rate is estimated as ≳ 0.01 M⊙ yr-1. The slowly fading late-time light curve and spectra show striking similarity with SN 1987A, indicating that a rate at which the CSM is being swept-up by the blastwave is gradually decaying and SN 1978K is undergoing similar evolution to become a remnant. Due to its proximity (4 Mpc), SN 1978K serves as the next best example of late-time supernova evolution after SN 1987A.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.6454T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.6454T"><span id="translatedtitle"><span class="hlt">Decadal</span> hindcasts initialized using <span class="hlt">observed</span> surface wind stress: Evaluation and prediction out to 2024</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thoma, Malte; Greatbatch, Richard J.; Kadow, Christopher; Gerdes, Ruediger</p> <p>2015-08-01</p> <p>We use surface air temperature to evaluate the <span class="hlt">decadal</span> 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 <span class="hlt">observed</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010QSRv...29..324B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010QSRv...29..324B"><span id="translatedtitle">Atmospheric <span class="hlt">decadal</span> <span class="hlt">variability</span> from high-resolution Dome C ice core records of aerosol constituents beyond the Last Interglacial</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bigler, Matthias; Röthlisberger, Regine; Lambert, Fabrice; Wolff, Eric W.; Castellano, Emiliano; Udisti, Roberto; Stocker, Thomas F.; Fischer, Hubertus</p> <p>2010-01-01</p> <p>Along the EPICA Dome C ice core, we measured concentrations of different water-soluble aerosol constituents and deduced total depositional flux records. Here we present high-resolution sodium, calcium, ammonium and nitrate data covering the last 173,000 years. The first three of these species are passive tracers and reveal source and long-range transport changes whereas nitrate is deposited reversibly. However, it can be used to check isotope-derived accumulation rate estimates, a prerequisite to calculate total depositional fluxes. During the last two transitions from glacial to interglacial periods, changes in the total depositional flux differ strongly for different aerosol species. The largest changes are <span class="hlt">observed</span> in the terrestrial aerosol proxy non-sea salt calcium, only moderate changes occur in the marine sea salt indicator sodium, while ammonium, a proxy for marine bioproductivity, remains rather constant. In agreement with previous studies, we find that only considerable glacial-interglacial changes at both, the terrestrial and the marine sea salt aerosol source can explain the <span class="hlt">observed</span> pronounced changes. The unprecedented high-resolution of our data allows for the first time the examination of <span class="hlt">decadal</span> <span class="hlt">variability</span> back to the penultimate glacial period. On the one hand, we find occasional fast shifts occurring within a few years; here we present such an event in the calcium record from the penultimate glacial period. On the other hand, we examine variation coefficients and pairwise correlation coefficients, both determined in 200-year windows. They generally reveal only moderate changes. During glacial periods, slightly lower variation coefficients are found, concurrent with slightly higher correlation coefficients, which points to a more uniform and stronger coupled atmospheric long-range transport of the different aerosol species to the East Antarctic Plateau and less influence of cyclonic activities during cold periods. The opposite is <span class="hlt">observed</span> for interglacial periods with probably even reinforced importance of cyclonic influences during the Last Interglacial period, the Marine Isotope Stage 5.5. This period reveals no evidence for abrupt climatic changes in any of the species, however, the marine sea salt aerosol indicator sodium shows a distinct minimum followed by a pronounced increase. This pattern is explained by significantly reduced sea ice production in the Indian Southern Ocean sector, which is believed to be the dominant source of sodium deposited in Dome C during warm periods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712629H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712629H"><span id="translatedtitle">Modelling the response of cyanobacteria to pH-<span class="hlt">variability</span> on seasonal to <span class="hlt">decadal</span> time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hofmeister, Richard; Hinners, Jana; Hense, Inga</p> <p>2015-04-01</p> <p>Cyanobacteria blooms regularly occurred in the Baltic Sea during the last <span class="hlt">decades</span>. 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.4687S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.4687S"><span id="translatedtitle"><span class="hlt">Decadal</span> changes of water properties in the Aral Sea <span class="hlt">observed</span> by MODIS-Aqua</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shi, Wei; Wang, Menghua</p> <p>2015-07-01</p> <p>Twelve-year satellite <span class="hlt">observations</span> between 2002 and 2013 from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the satellite Aqua are used to quantitatively assess the water property changes in the Aral Sea. The shortwave infrared (SWIR) atmospheric correction algorithm is required and used to derive normalized water-leaving radiance spectra nLw(λ) in the Aral Sea. We used radiance ratio nLw(555)/nLw(443) as a surrogate to characterize the spatial and temporal variations of chlorophyll-a (Chl-a) in the Aral Sea. Both seasonal <span class="hlt">variability</span> and significant interannual changes were <span class="hlt">observed</span> when the Aral Sea desiccated between 2002 and 2013. All three separated regions of the Aral Sea show increased nLw(555)/nLw(443) ratio (a surrogate for Chl-a) and the diffuse attenuation coefficient at the wavelength of 490 nm (Kd(490)) during the fall season. Of the three regions, the North Aral Sea has had the least interannual <span class="hlt">variability</span>, while South-East (SE) Aral Sea experienced drastic changes. Waters in the SE Aral Sea are the most turbid with significantly higher Kd(490) than those in the other two subregions. Kd(490) gradually increased from ˜2 m-1 in 2002 to ˜3.5 m-1 after 2008 in the SE Aral Sea. In comparison, both radiance ratio nLw(555)/nLw(443) and Kd(490) were relatively stable for the North Aral Sea. In the South-West (SW) Aral Sea, however, nLw(555)/nLw(443) values reached peaks in the fall of 2007 and 2010. A possible link between the Aral Sea water property change and the regional climate variation is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013BGD....1015455B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013BGD....1015455B"><span id="translatedtitle">Oxygen minimum zone of the open Arabian Sea: <span class="hlt">variability</span> of oxygen and nitrite from daily to <span class="hlt">decadal</span> time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Banse, K.; Naqvi, S. W. A.; Narvekar, P. V.; Postel, J. R.; Jayakumar, D. A.</p> <p>2013-09-01</p> <p>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 <span class="hlt">decade</span>. 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 μM) 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 μM]). 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 μM a-1; n = 10 and 12, differing at p = 0.01); (2) four <span class="hlt">decades</span> of statistically significant decreases of O2 between 15° and 20° N but a trend to a similar increase near 21° N are <span class="hlt">observed</span>. 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) <span class="hlt">variability</span> 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 <span class="hlt">variable</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMPP23C1506W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMPP23C1506W"><span id="translatedtitle">Tropical Climate <span class="hlt">Variability</span> and the Atlantic Multi-<span class="hlt">decadal</span> Oscillation from the Geochemistry of Corals and Sclerosponges over the last 500 years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waite, A. J.; Swart, P. K.; Dodge, R. E.; Helmle, K. P.; Rosenheim, B. E.</p> <p>2008-12-01</p> <p><span class="hlt">Observational</span> and model data have shown considerable <span class="hlt">variability</span> to exist in North Atlantic sea surface temperatures and climate. In particular, several climate oscillations have been documented, including the North Atlantic Oscillation (NAO) and the Atlantic Multi-<span class="hlt">decadal</span> Oscillation (AMO). While the exact forcing of these modes has yet to be defined, they do appear to produce <span class="hlt">observable</span> climatic <span class="hlt">variability</span> on multi- <span class="hlt">decadal</span> time scales. Recent geochemical analyses on climate proxy archives from the western tropical Atlantic have shown <span class="hlt">variability</span> consistent with that of the AMO. A 300+ year old coral specimen of Montastraea faveolata growing in 6m of water south of Port Everglades, Florida, and a 550+ year old sclerosponge specimen of Ceratoporella nicholsoni collected from 133m of water off of Lee Stocking Island in the Exuma Sound, Bahamas, have been milled at a sub- annual resolution and analyzed for stable C and O isotopes as well as minor element ratios. Salinity calculated from a combination of δ18O and Sr/Ca exhibits similar periodicities to the AMO between ~1700 AD and the present; a rather surprising finding given the significant differences in the local environmental conditions of the two samples. Prior to the 1700s, our sclerosponge record diverges from the AMO record reconstructed from tree rings. Additional analyses from the region will be needed to determine the reasoning for this discrepancy.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JGR...10622401A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JGR...10622401A"><span id="translatedtitle">A <span class="hlt">decade</span> of oceanographic <span class="hlt">variability</span> in summertime near Elephant Island, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amos, Anthony F.</p> <p>2001-10-01</p> <p>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 <span class="hlt">variability</span> 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 <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17333289','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17333289"><span id="translatedtitle">The sensitivity of tree growth to air mass <span class="hlt">variability</span> and the Pacific <span class="hlt">Decadal</span> Oscillation in coastal Alabama.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Senkbeil, Jason C; Rodgers, John C; Sheridan, Scott C</p> <p>2007-08-01</p> <p>This study investigates the relationship between tree growth and air mass type <span class="hlt">variability</span>, using the spatial synoptic classification (SSC) in a bottomland slash pine forest in coastal Alabama (USA). The use of an air mass approach in dendroclimatology is somewhat unconventional and has not been fully explored. However, we believe that it may be useful because the air mass approach represents a holistic and comprehensive measure of surface conditions. Cores from 36 slash pines (Pinus elliotti) were extracted and ring widths were measured to the nearest 0.01 mm. The cores were then cross-dated and a standardized ring index series was established. Relationships were explored between the index series and several climate <span class="hlt">variables</span> and teleconnections. The index series showed significant relationships with SSC air mass types and SSC air mass ratios, but insignificant results with teleconnections. Specifically the Dry Tropical air mass type was negatively correlated with tree growth while Moist Moderate was positively correlated. Concomitantly, Dry Tropical : Moist Moderate, Dry Tropical : Moist Tropical, and Dry Moderate : Moist Moderate air mass ratios also showed negative correlations. Positive Pacific <span class="hlt">Decadal</span> Oscillation (PDO) sea surface temperatures were also associated with significant moisture and air mass <span class="hlt">variability</span> in the region, although the PDO did not have a significant relationship with tree growth. The significance between SSC air mass <span class="hlt">variability</span> and tree growth in the humid subtropical climate of coastal Alabama has favorable implications for dendroclimatological research in drier environments where trees are more sensitive to climatic <span class="hlt">variables</span>. PMID:17333289</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A21E0116R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A21E0116R"><span id="translatedtitle"><span class="hlt">Observing</span> <span class="hlt">Decadal</span> Trends in Atmospheric Feedbacks and Climate Change with Zeus and CLARREO</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Revercomb, H. E.; Best, F. A.; Knuteson, R. O.; Tobin, D. C.; Taylor, J. K.; Gero, P.; Adler, D. P.; Pettersen, C.; Mulligan, M.; Tobin, D. C.</p> <p>2012-12-01</p> <p>New technologies for <span class="hlt">observing</span> <span class="hlt">decadal</span> trends in atmospheric feedbacks and climate change from space have been recently demonstrated via a NASA Instrument Incubator Program (IIP) project of our group and the Anderson Group of Harvard University. Using these new technologies, a mission named Zeus has been proposed to the first NASA Earth Venture Instruments opportunity (EVI-1). Zeus would provide a low cost mechanism to initiate a new era in high spectral resolution IR climate Benchmark and Intercalibration <span class="hlt">observations</span>, the basis for which has been established by definition of the CLARREO mission in the 2007 NRC "<span class="hlt">Decadal</span> Survey" and by the Science Definition Team established by NASA LaRC to further the full blown CLARREO mission. Zeus EVI is a low-cost, low-risk, and high-value EVI mission that will deploy an Absolute Radiance Interferometer (ARI) instrument to measure absolute spectrally resolved infrared radiance over much of the Earth-emitted spectrum with ultra-high accuracy (<0.1 K 3-sigma brightness temperature). Zeus makes use of broad spectral coverage (3.7-50 microns) and high spectral resolution (<1 cm-1) to provide benchmark products for climate trending with much higher information content than traditional spectrally-integrated measurements. While ARI requirements for accuracy and spectral properties are demanding, the overall instrument is relatively simple and low-cost because of the limited requirements on spatial sampling (25-100 km nadir-only footprints spaced at < 250 km) and on noise performance (climate products are created by combining many samples). The orbit chosen for Zeus must provide coverage immune to time-of-day sampling errors. Because of its relatively high rate of precession, an attractive baseline option for Zeus EVI is the 51.6 degrees inclination orbit of the International Space Station (ISS). For Zeus deployment on the ISS, higher latitude climate benchmark information will be obtained from operational sounders intercalibrated by 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611711W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611711W"><span id="translatedtitle">Influence of climate <span class="hlt">variability</span> versus change at multi-<span class="hlt">decadal</span> time scales on hydrological extremes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Willems, Patrick</p> <p>2014-05-01</p> <p>Recent studies have shown that rainfall and hydrological extremes do not randomly occur in time, but are subject to multidecadal oscillations. In addition to these oscillations, there are temporal trends due to climate change. Design statistics, such as intensity-duration-frequency (IDF) for extreme rainfall or flow-duration-frequency (QDF) relationships, are affected by both types of temporal changes (short term and long term). This presentation discusses these changes, how they influence water engineering design and decision making, and how this influence can be assessed and taken into account in practice. The multidecadal oscillations in rainfall and hydrological extremes were studied based on a technique for the identification and analysis of changes in extreme quantiles. The statistical significance of the oscillations was evaluated by means of a non-parametric bootstrapping method. Oscillations in large scale atmospheric circulation were identified as the main drivers for the temporal oscillations in rainfall and hydrological extremes. They also explain why spatial phase shifts (e.g. north-south variations in Europe) exist between the oscillation highs and lows. Next to the multidecadal climate oscillations, several stations show trends during the most recent <span class="hlt">decades</span>, which may be attributed to climate change as a result of anthropogenic global warming. Such attribution to anthropogenic global warming is, however, uncertain. It can be done based on simulation results with climate models, but it is shown that the climate model results are too uncertain to enable a clear attribution. Water engineering design statistics, such as extreme rainfall IDF or peak or low flow QDF statistics, obviously are influenced by these temporal variations (oscillations, trends). It is shown in the paper, based on the Brussels 10-minutes rainfall data, that rainfall design values may be about 20% biased or different when based on short rainfall series of 10 to 15 years length, and 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714427E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714427E"><span id="translatedtitle"><span class="hlt">Decadal</span> slowdown in global air temperature rise triggered by <span class="hlt">variability</span> in the Atlantic Meridional Overturning Circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>England, Matthew H.</p> <p>2015-04-01</p> <p>Various explanations have been proposed for the recent slowdown in global surface air temperature (SAT) rise, either involving enhanced ocean heat uptake or reduced radiation reaching Earth's surface. Among the mechanisms postulated involving enhanced ocean heat uptake, past work has argued for both a Pacific and Atlantic origin, with additional contributions from the Southern Ocean. Here we examine the mechanisms driving 'hiatus' periods originating out of the Atlantic Ocean. We show that while Atlantic-driven hiatuses are entirely plausible and consistent with known climate feedbacks associated with <span class="hlt">variability</span> in the Atlantic Meridional Overturning Circulation (AMOC), the present climate state is configured to enhance global-average SAT, not reduce it. We show that Atlantic hiatuses are instead characterised by anomalously cool fresh oceanic conditions in the North Atlantic, with the atmosphere advecting the cool temperature signature zonally. Compared to the 1980s and 1990s, however, the mean climate since 2001 has been characterised by a warm saline North Atlantic, suggesting the AMOC cannot be implicated as a direct driver of the current hiatus. We further discuss the impacts of a warm tropical Atlantic on the unprecedented trade wind acceleration in the Pacific Ocean, and propose that this is the main way that the Atlantic has contributed to the present "false pause" in global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMGP51A0944W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMGP51A0944W"><span id="translatedtitle">Application of EOF/CEOF methodology to understand correlation between geomagnetic secular variation and <span class="hlt">decadal</span> time-<span class="hlt">variable</span> gravity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Z.; Kuang, W.; Jiang, W.</p> <p>2006-12-01</p> <p>In this presentation we discuss the application of EOF and Complex EOF approaches to examine possible correlation between temporal-spatial distributions of the time <span class="hlt">variable</span> gravity (TVG) and magnetic secular variations (SV) on <span class="hlt">decadal</span> time scales and longer. The advantage of such approaches is to enable us identifying approximately 3 to 4 EOF/CEOF modes that account for the most of the signals. We apply these approaches to examine the gravity and magnetic field data generated by the MoSST numerical core dynamics model and the PREM model. Our results show that the first 3 EOF modes reproduce the most significant features of the spatial distributions, thus sufficient for understanding the correlation between the two potential fields. We are currently working on applying this analysis to the 20-year time <span class="hlt">variable</span> gravity from SLR and satellite measurements, and the surface geomagnetic field from GUFM1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.9857J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.9857J"><span id="translatedtitle">Multi-<span class="hlt">decadal</span>-scale records of North Atlantic climate <span class="hlt">variability</span> during the last and present interglacials and preceding glacial terminations.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jimenez-Amat, Patricia; Zahn, Rainer</p> <p>2013-04-01</p> <p>High-resolution records of natural interglacial climate <span class="hlt">variability</span> can provide knowledge if the currently ongoing climate change and <span class="hlt">variability</span> are part of or are already beyond the natural state. Warmer-than-present climatic conditions, a reduced Greenland Ice Sheet and higher sea level are some of the features the Last Interglacial (LIG, MIS5e; 129-115 kyr) climate has in common with numerous model projections of our future climate (Otto-Bliesner et al., 2006; Koop et al., 2009). Establishing multi-<span class="hlt">decadal</span> resolution records of past North Atlantic climate <span class="hlt">variability</span> hence contributes to a better understanding of the ocean and climate sensitivity of the wider North Atlantic region. We present palaeoceanographic time series of surface ocean climatology from Ocean Drilling Program (ODP) Site 976 in the Alboran Sea, westernmost Mediterranean that span the LIG and Present Interglacial (PIG, Holocene, 11-0 kyr). The site receives North Atlantic climate signals through the atmosphere and with the advection of Atlantic inflow waters which in connection with the high rate of sediment deposition underscores the exceptional quality of the site to monitor North Atlantic climate <span class="hlt">variability</span> at multi-<span class="hlt">decadal</span> resolution (60-90 yrs). Sea surface temperature (SST) time series derived from Mg/Ca ratios and stable isotope records (δ18O, δ13C) of the planktonic foraminifera Globigerina bulloides are presented. Mg/Ca data display similar SST for the climatic optima PIG and LIG. The records compare well with speleothem and ice core palaeoclimatic profiles, confirming that Site 976 palaeo-profiles reflect climate of the North Atlantic region. The close link between SSTMg-Caand the LIG δ18O record from the Antro del Corchia speleothem in northern Italy highlights the strong connection between marine and terrestrial climatology during that time indicating a farfield contribution of atmospheric signals. Comparison with SST and benthic δ13C records at North Atlantic sites instructs on regional climatological offsets and AMOC stability and <span class="hlt">variability</span>. Correlation with atmospheric data (ice core palaeo-CO2, δ13Catm) links the North Atlantic climate <span class="hlt">variability</span> documented in Site 976 with ocean-to-air gas exchanges that were driven by AMOC <span class="hlt">variability</span>. This is a contribution of the European Commission FP7 Collaborative Project "Past4Future".</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.......88V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.......88V"><span id="translatedtitle">Multi-<span class="hlt">decadal</span> <span class="hlt">variability</span> of ice extent in the Barents Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vinje, T.; Colony, R.</p> <p>2003-04-01</p> <p>The European Arctic has been explored and commercially exploited for more than 400 years. In 1596, Willem Barentsz sailed the northern Barents Sea reporting on sea-ice extent and on the large number of whales found along the ice edge. By the early 17th century, an extensive and sophisticated whaling industry had developed in northern Spitzbergen. The whale hunters systematically <span class="hlt">observed</span> and logged sea-ice conditions and ice edge location. These shipboard <span class="hlt">observations</span> provide sea-ice extent information throughout the Nordic Seas and the western Barents for much of the 17th and 18th centuries. In 1850, Norway began extensive whale/seal hunting along the ice edge, stretching from Iceland to Novaya Zemlya. The records of sea-ice conditions and extent were archived by the Norwegian Polar Research Institute and are now placed in the ACSYS Historical Ice Chart Database. The annual April and August latitude of sea-ice extent in the western Barents is constructed for the period 1730-2000. The early part of the record (1730-1790) suggests April and August ice conditions similar to the modern era. However, just at the end of the 18th century, the sea-ice moved 300 km southward of its previous mean position. For the next 200 years (1800-2000), sea ice cover in the western Barents has steadily receded to its present state. Covariance studies offer insight into the processes controlling sea-ice extent and serve to bound the <span class="hlt">observational</span> errors. The instrumental temperature record is mostly limited to the past 150-years. During this period, we estimate the correlation between Northern Hemisphere mean temperature and August sea-ice extent at r = 0.80 (using 7-year running means). Temperature records from central England are available from 1700, as are proxy temperature based data boreholes from the Greenland Ice Sheet Project. Again, significant covariance is found. The most provocative data come from sun spot <span class="hlt">observations</span> and the associated time series of solar total irradiance (1600-2000). Major features of historical sea-ice extent are seen in the Sun’s total irradiance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030102176','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030102176"><span id="translatedtitle">30-Year Satellite Record Reveals Contrasting Arctic and Antarctic <span class="hlt">Decadal</span> Sea Ice <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cavalieri, D. J.; Parkinson, C. L.; Vinnikov, K. Y.</p> <p>2003-01-01</p> <p>A 30-year satellite record of sea ice extents derived mostly from satellite microwave radiometer <span class="hlt">observations</span> reveals that the Arctic sea ice extent decreased by 0.30+0.03 x 10(exp 6) square kilometers per 10 yr from 1972 through 2002, but by 0.36 plus or minus 0.05 x 10(exp 6) square kilometers per 10yr from 1979 through 2002, indicating an acceleration of 20% in the rate of decrease. In contrast, the Antarctic sea ice extent decreased dramatically over the period 1973-1977, then gradually increased. Over the full 30-year period, the Antarctic ice extent decreased by 0.15 plus or minus 0.08 x 10(exp 6) square kilometers per 10 yr. The trend reversal is attributed to a large positive anomaly in Antarctic sea ice extent in the early 1970's, an anomaly that apparently began in the late 1960's, as <span class="hlt">observed</span> in early visible and infrared satellite images.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.132..287S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.132..287S"><span id="translatedtitle">Optimal excitation of AMOC <span class="hlt">decadal</span> <span class="hlt">variability</span>: Links to the subpolar ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sévellec, Florian; Fedorov, Alexey V.</p> <p>2015-03-01</p> <p>This study describes the excitation of <span class="hlt">variability</span> of the Atlantic Meridional Overturning Circulation (AMOC) by optimal perturbations in surface temperature and salinity. Our approach is based on a generalized stability analysis within a realistic ocean general circulation model, which extends the conventional linear stability analysis to transient growth. Unlike methods based on singular value decomposition, our analysis invokes an optimization procedure using Lagrangian multipliers, which is a more general approach allowing us to impose relevant constraints on the perturbations and use linear measures of the AMOC (meridional volume and heat transports). We find that the structure of the optimal perturbations is characterized by anomalies in surface temperature or salinity centered in the subpolar regions of the North Atlantic off the east coasts of Greenland and Canada, south of the Denmark Strait. The maximum impact of such perturbations on the AMOC is reached after 7-9 yr. This is a robust result independent of the perturbations type, the optimization measures, the model surface boundary conditions, or other constraints. The transient growth involves the following mechanism: after the initial (positive) surface density perturbation reaches the deep ocean, it generates a cyclonic geostrophic flow that extracts a zonally-varying temperature anomaly from the mean temperature field in the upper ocean. In turn, the anomalous zonal temperature gradient induces, by thermal wind balance, a northward flow in the upper ocean and a southward flow in the deep ocean, thus strengthening the AMOC. Subsequently, the transient growth gives way to a decaying oscillation corresponding to a damped oceanic eigenmode with a period of about 24 yr. This mode is controlled by westward-propagating large-scale "thermal" Rossby waves, modifying the density field in the North Atlantic and hence the AMOC. Simple estimates show that realistic changes in salinity or temperature in the upper ocean (such as those due to the Great Salinity Anomaly) can induce AMOC variations of several Sverdups via this mechanism, or 10-20% of the mean overturning. An idealized model is formulated to investigate the transient growth and highlight the role of mean convection in communicating surface density anomalies to the deep ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...45..273Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...45..273Q"><span id="translatedtitle">The <span class="hlt">decadal</span> <span class="hlt">variability</span> of the tropical Indian Ocean SST-the South Asian High relation: CMIP5 model study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qu, X.; Huang, G.</p> <p>2015-07-01</p> <p>Based on Coupled Model Intercomparison Project phase 5 (CMIP5) models, present study investigates the <span class="hlt">decadal</span> <span class="hlt">variability</span> 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 <span class="hlt">decadal</span> <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002DSRII..49.5991N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002DSRII..49.5991N"><span id="translatedtitle">Interannual and <span class="hlt">decadal</span> <span class="hlt">variability</span> in zooplankton communities of the southeast Bering Sea shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Napp, Jeffrey M.; Baier, Christine T.; Brodeur, Richard D.; Coyle, Kenneth O.; Shiga, Naonobu; Mier, Kathy</p> <p>2002-12-01</p> <p>The southeastern Bering Sea shelf ecosystem is an important fishing ground for fin- and shellfish, and is the summer foraging grounds for many planktivorous seabirds and marine mammals. In 1997 and 1998, Northern Hemisphere climate anomalies affected the physical and biological environment of the southeastern Bering Sea shelf. The resulting anomalous conditions provided a valuable opportunity to examine how longer-term climate change might affect this productive ecosystem. We compared historical and recent zooplankton biomass and species composition data for the southeastern Bering Sea shelf to examine whether or not there was a response to the atmosphere-ocean-ice anomalies of 1997 and 1998. Summer zooplankton biomass (1954-1994) over the southeastern shelf did not exhibit a decline as previously reported for oceanic stations. In addition, zooplankton biomass in 1997 and 1998 was not appreciably different from other years in the time series. Spring concentrations of numerically abundant copepods ( Acartia spp., Calanus marshallae, and Pseudocalanus spp.), however, were significantly higher during 1994-1998 than 1980-1981; spring concentrations of Metridia pacifica and Neocalanus spp. were not consistently different between the two time periods. Neocalanus spp. was the only taxon to have consistent differences in stage composition between the two time periods—CV copepodites were much more prevalent in May of the 1990s than early 1980s. Since relatively high zooplankton concentrations were <span class="hlt">observed</span> prior to 1997, we do not attribute the high concentrations <span class="hlt">observed</span> in the summers of 1997 and 1998 directly to the acute climate anomalies. With the present data it is not possible to distinguish between increased production (control from below) and decreased predation (control from above) to explain the recent increase in concentrations of the species examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMOS11A1468A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMOS11A1468A"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">Variability</span> in the North Pacific Ocean in a Coupled Physical-Ecosystem Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, M.; Capotondi, A.; Miller, A.; Chai, F.; Brodeur, R.; Deser, C.</p> <p>2006-12-01</p> <p>A basin-wide interdecadal change in both the physical state and the ecology of the North Pacific occurred near the end of 1976. Here we use a physical-ecosystem model to examine whether changes in the physical environment associated with the 1976-77 transition influenced the lower trophic levels of the food web and if so by what means. The physical component is an ocean general circulation model, while the biological component contains 10 compartments: 4 zooplankton, 3 nitrogen, 2 silicate and CO2. The model is forced with <span class="hlt">observed</span> atmospheric fields during 1960-1999. During spring, when the mean plankton biomass peaks in the model, there is a strong (20%) reduction in plankton biomass after the 1976 transition. The epoch difference in plankton appears to be controlled by the mixed layer depth (MLD). The enhancement of Ekman pumping in the latter period caused the halocline to shoal, and thus the MLD could not penetrate as deep in the central Gulf of Alaska during winter. As a result, more phytoplankton remained in the euphotic zone and phytoplankton concentrations began to increase earlier in spring during 1977-88 relative to 1970-76. Zooplankton populations also increased but then grazing pressure lead to a strong decrease in phytoplankton by April followed by a drop off in zooplankton by May. Essentially the mean seasonal cycle of plankton biomass is shifted earlier in the year. Finally, there is a rebound in plankton concentrations leading to an enhancement in zooplankton biomass by mid summer after 1976 but the increase is much smaller than <span class="hlt">observed</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950008093','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950008093"><span id="translatedtitle">FRESIP project <span class="hlt">observations</span> of cataclysmic <span class="hlt">variables</span>: A unique opportunity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Howell, Steve B.</p> <p>1994-01-01</p> <p>FRESIP Project <span class="hlt">observations</span> of cataclysmic <span class="hlt">variables</span> would provide unique data sets. In the study of known cataclysmic <span class="hlt">variables</span> they would provide extended, well sampled temporal photometric information and in addition, they would provide a large area deep survey; obtaining a complete magnitude limited sample of the galaxy in the volume cone defined by the FRESIP field of view.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Almond&pg=5&id=EJ879637','ERIC'); return false;" href="http://eric.ed.gov/?q=Almond&pg=5&id=EJ879637"><span id="translatedtitle">Bayesian Network Models for Local Dependence among <span class="hlt">Observable</span> Outcome <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Almond, Russell G.; Mulder, Joris; Hemat, Lisa A.; Yan, Duanli</p> <p>2009-01-01</p> <p>Bayesian network models offer a large degree of flexibility for modeling dependence among <span class="hlt">observables</span> (item outcome <span class="hlt">variables</span>) from the same task, which may be dependent. This article explores four design patterns for modeling locally dependent <span class="hlt">observations</span>: (a) no context--ignores dependence among <span class="hlt">observables</span>; (b) compensatory context--introduces…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012HESS...16.1389D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012HESS...16.1389D"><span id="translatedtitle">Coupled <span class="hlt">decadal</span> <span class="hlt">variability</span> of the North Atlantic Oscillation, regional rainfall and karst spring discharges in the Campania region (southern Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>De Vita, P.; Allocca, V.; Manna, F.; Fabbrocino, S.</p> <p>2012-05-01</p> <p>Thus far, studies on climate change have focused mainly on the <span class="hlt">variability</span> of the atmospheric and surface components of the hydrologic cycle, investigating the impact of this <span class="hlt">variability</span> 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 <span class="hlt">variability</span> 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 <span class="hlt">variability</span> and its influence on groundwater recharge were analysed by examining <span class="hlt">decadal</span> patterns of precipitation, air temperature and spring discharges in the Campania region (southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, 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 <span class="hlt">decadal</span> <span class="hlt">variability</span> of groundwater flow in Mediterranean karst areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999AtmEn..33.4909D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999AtmEn..33.4909D"><span id="translatedtitle">Comparisons of some parametrizations of wind direction <span class="hlt">variability</span> with <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davies, Belinda M.; Thomson, David J.</p> <p></p> <p>An understanding of wind direction <span class="hlt">variability</span> is important in predicting the dispersion of pollutants in the atmosphere. Parametrizations of wind direction <span class="hlt">variability</span> over different time scales are compared with turbulence <span class="hlt">observations</span> made at the Meteorological Research Unit (MRU) at Cardington. <span class="hlt">Observations</span> of the <span class="hlt">variability</span> averaged over one hour in stable conditions are compared with the parametrizations proposed by Hanna and by Joffre and Laurila for light winds and show broad agreement with these parametrizations. The formula proposed by Hanna, suitably matched to a similarity approach at strong winds, can be recommended for general use. The direction <span class="hlt">variability</span> over longer time periods (up to 12 h) has also been investigated. Results show only a weak dependence on averaging time with the wind direction <span class="hlt">variability</span> roughly proportional to averaging time to the power 1/4.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMGC41B0906C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMGC41B0906C"><span id="translatedtitle">Constraining Model Climate Sensitivity by <span class="hlt">Observations</span> of the <span class="hlt">Decadal</span> Solar Cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Camp, C. D.; Tung, K. K.; Zhou, J.</p> <p>2010-12-01</p> <p>Recent analyses have revealed the global response of the Earth's surface temperature to the <span class="hlt">decadal</span> solar cycle. The strength of this response can be used as a constraint on model climate sensitivity. We shall review evidence supporting the argument that the real climate sensitivity is probably towards the high end in the range of values reported by the coupled atmosphere-ocean general circulation models assessed by the most recent Intergovernmental Panel on Climate Change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060037970&hterms=volcanology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dvolcanology','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060037970&hterms=volcanology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dvolcanology"><span id="translatedtitle">(abstract) Mount Rainier: New Remote Sensing <span class="hlt">Observations</span> of a <span class="hlt">Decade</span> Volcano</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Realmuto, V. J.; Zebker, H. A.; Frank, D.</p> <p>1994-01-01</p> <p>Mount Rainier was selected as a <span class="hlt">Decade</span> Volcano by the International Association of Volcanology and Chemistry of the Earth's Interior. The purpose of this selection is to focus scientific and public attention on Mount Rainier during the current <span class="hlt">decade</span>, the United Nations-designated International <span class="hlt">Decade</span> of Natural Hazard Reduction. The Mount Rainier science plan calls for remote sensing surveys to monitor the volcano. To date, we have conducted airborne surveys with visible and near-infrared, thermal infrared, and interferometric radar instruments. Our preliminary analysis of some night-time time-series thermal infrared survey data sets of the summit suggests that, aside from seasonal variations in snow cover, there have been no qualitative changes in the size or pattern of the summit hot spots. Day-time airborne surveys were done to record the current surface appearance of the volcano and map hydrothermal alteration in the summit region. An interferometric radar survey yielded a high-resolution digital elevation model (DEM) which serves as a base for the registration of the other remote sensing data sets. More importantly, the DEM documents the current topography of glaciers and valleys. Planned biannual radar survey of mount rainier will produce a data set from which seasonal changes in glacier and valley topography can be characterized. Such characterization is essential if we are to recognize geothermally induced changes in snow and ice cover.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcMod..97...65D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcMod..97...65D"><span id="translatedtitle">North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part II: Inter-annual to <span class="hlt">decadal</span> <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Danabasoglu, Gokhan; Yeager, Steve G.; Kim, Who M.; Behrens, Erik; Bentsen, Mats; Bi, Daohua; Biastoch, Arne; Bleck, Rainer; Böning, Claus; Bozec, Alexandra; Canuto, Vittorio M.; Cassou, Christophe; Chassignet, Eric; Coward, Andrew C.; Danilov, Sergey; Diansky, Nikolay; Drange, Helge; Farneti, Riccardo; Fernandez, Elodie; Fogli, Pier Giuseppe; Forget, Gael; Fujii, Yosuke; Griffies, Stephen M.; Gusev, Anatoly; Heimbach, Patrick; Howard, Armando; Ilicak, Mehmet; Jung, Thomas; Karspeck, Alicia R.; Kelley, Maxwell; Large, William G.; Leboissetier, Anthony; Lu, Jianhua; Madec, Gurvan; Marsland, Simon J.; Masina, Simona; Navarra, Antonio; Nurser, A. J. George; Pirani, Anna; Romanou, Anastasia; Salas y Mélia, David; Samuels, Bonita L.; Scheinert, Markus; Sidorenko, Dmitry; Sun, Shan; Treguier, Anne-Marie; Tsujino, Hiroyuki; Uotila, Petteri; Valcke, Sophie; Voldoire, Aurore; Wang, Qiang; Yashayaev, Igor</p> <p>2016-01-01</p> <p>Simulated inter-annual to <span class="hlt">decadal</span> <span class="hlt">variability</span> and trends in the North Atlantic for the 1958-2007 period from twenty global ocean - sea-ice coupled models are presented. These simulations are performed as contributions to the second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II). The study is Part II of our companion paper (Danabasoglu et al., 2014) which documented the mean states in the North Atlantic from the same models. A major focus of the present study is the representation of Atlantic meridional overturning circulation (AMOC) <span class="hlt">variability</span> in the participating models. Relationships between AMOC <span class="hlt">variability</span> and those of some other related <span class="hlt">variables</span>, such as subpolar mixed layer depths, the North Atlantic Oscillation (NAO), and the Labrador Sea upper-ocean hydrographic properties, are also investigated. In general, AMOC <span class="hlt">variability</span> shows three distinct stages. During the first stage that lasts until the mid- to late-1970s, AMOC is relatively steady, remaining lower than its long-term (1958-2007) mean. Thereafter, AMOC intensifies with maximum transports achieved in the mid- to late-1990s. This enhancement is then followed by a weakening trend until the end of our integration period. This sequence of low frequency AMOC <span class="hlt">variability</span> is consistent with previous studies. Regarding strengthening of AMOC between about the mid-1970s and the mid-1990s, our results support a previously identified <span class="hlt">variability</span> mechanism where AMOC intensification is connected to increased deep water formation in the subpolar North Atlantic, driven by NAO-related surface fluxes. The simulations tend to show general agreement in their temporal representations of, for example, AMOC, sea surface temperature (SST), and subpolar mixed layer depth <span class="hlt">variabilities</span>. In particular, the <span class="hlt">observed</span> <span class="hlt">variability</span> of the North Atlantic SSTs is captured well by all models. These findings indicate that simulated <span class="hlt">variability</span> and trends are primarily dictated by the atmospheric datasets which include the influence of ocean dynamics from nature superimposed onto anthropogenic effects. Despite these general agreements, there are many differences among the model solutions, particularly in the spatial structures of <span class="hlt">variability</span> patterns. For example, the location of the maximum AMOC <span class="hlt">variability</span> differs among the models between Northern and Southern Hemispheres.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3834854','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3834854"><span id="translatedtitle">Temporal <span class="hlt">variability</span> and coherence of euphotic zone bacterial communities over a <span class="hlt">decade</span> in the Southern California Bight</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chow, Cheryl-Emiliane T; Sachdeva, Rohan; Cram, Jacob A; Steele, Joshua A; Needham, David M; Patel, Anand; Parada, Alma E; Fuhrman, Jed A</p> <p>2013-01-01</p> <p>Time-series are critical to understanding long-term natural <span class="hlt">variability</span> in the oceans. Bacterial communities in the euphotic zone were investigated for over a <span class="hlt">decade</span> at the San Pedro Ocean Time-series station (SPOT) off southern California. Community composition was assessed by Automated Ribosomal Intergenic Spacer Analysis (ARISA) and coupled with measurements of oceanographic parameters for the surface ocean (0–5 m) and deep chlorophyll maximum (DCM, average depth ∼30 m). SAR11 and cyanobacterial ecotypes comprised typically more than one-third of the measured community; diversity within both was temporally <span class="hlt">variable</span>, although a few operational taxonomic units (OTUs) were consistently more abundant. Persistent OTUs, mostly Alphaproteobacteria (SAR11 clade), Actinobacteria and Flavobacteria, tended to be abundant, in contrast to many rarer yet intermittent and ephemeral OTUs. Association networks revealed potential niches for key OTUs from SAR11, cyanobacteria, SAR86 and other common clades on the basis of robust correlations. Resilience was evident by the average communities drifting only slightly as years passed. Average Bray-Curtis similarity between any pair of dates was ∼40%, with a slight decrease over the <span class="hlt">decade</span> and obvious near-surface seasonality; communities 8–10 years apart were slightly more different than those 1–4 years apart with the highest rate of change at 0–5 m between communities <4 years apart. The surface exhibited more pronounced seasonality than the DCM. Inter-depth Bray-Curtis similarities repeatedly decreased as the water column stratified each summer. Environmental factors were better predictors of shifts in community composition than months or elapsed time alone; yet, the best predictor was community composition at the other depth (that is, 0–5 m versus DCM). PMID:23864126</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1213547S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1213547S"><span id="translatedtitle">The Recognition of Multi-<span class="hlt">Decadal</span> Scale Climate <span class="hlt">Variability</span> in the Paleo-record over the Past 1000 Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swart, Peter; Waite, Amanda; Rosenheim, Brad; Moses, Chris</p> <p>2010-05-01</p> <p>Proxy reconstructions of climate from tree rings, corals, stalagmites, sclerosponges, and deep-sea sediments show multi-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> preserved in records extending back at least 1000 years. Most of these records appear to show a strong correlation with indices such as the North Atlantic Oscillation (NAO) and the Atlantic Multi-<span class="hlt">decadal</span> Oscillation (AMO) over the period of the instrumental record (~1850-present). The repeated recognition of these signals in a number of different archives and geographical locations throughout the Atlantic (Cape Verde Islands, Gulf of Guinea, Puerto Rico, Cariaco Basin , South Florida, and the Bahamas) strongly suggests that these signals are real and have climatic significance. The AMO and NAO climate signals are manifested in these indices through (i) the direct effect of water temperature and salinity on the growth rate of trees and corals and (ii) temperature and salinity influences on the incorporation of geochemical proxies, such as the Mg/Ca, Sr/Ca, and oxygen isotopic ratios, into the skeletons of different carbonate producing organisms. In many areas these relationships are complex and there is often considerable local <span class="hlt">variability</span> in the response of corals and trees, particularly in the growth rate related parameters. Prior to the instrumental period, the tree-ring index compiled by (Gray et al., 2004, GRL,31) has been taken as the principal reconstruction of the AMO. While most of the marine records examined appear to correlate with the tree-ring record during the instrumental period, there are significant discrepancies prior to 1850. This raises many questions about the stationarity and persistence of the AMO and the suitability of individual archives such as tree rings for these modes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014BGeo...11.2237B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014BGeo...11.2237B"><span id="translatedtitle">Oxygen minimum zone of the open Arabian Sea: <span class="hlt">variability</span> of oxygen and nitrite from daily to <span class="hlt">decadal</span> timescales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Banse, K.; Naqvi, S. W. A.; Narvekar, P. V.; Postel, J. R.; Jayakumar, D. A.</p> <p>2014-04-01</p> <p>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 <span class="hlt">decade</span>. 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 μM) 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 μM]). 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 μM a-1; n = 10 and 12, differing at p = 0.01); (2) four <span class="hlt">decades</span> of statistically significant decreases of O2 between 15 and 20° N but an opposing trend toward an increase near 21° N are <span class="hlt">observed</span>. 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 <span class="hlt">variable</span> 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) <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70033816','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70033816"><span id="translatedtitle">An 1800-yr record of <span class="hlt">decadal</span>-scale hydroclimatic <span class="hlt">variability</span> in the upper Arkansas River basin from bristlecone pine</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Woodhouse, C.A.; Pederson, G.T.; Gray, S.T.</p> <p>2011-01-01</p> <p>Bristlecone pine trees are exceptionally long-lived, and with the incorporation of remnant material have been used to construct multi-millennial length ring-width chronologies. These chronologies can provide valuable information about past temperature and moisture <span class="hlt">variability</span>. In this study, we outline a method to build a moisture-sensitive bristlecone chronology and assess the robustness and consistency of this sensitivity over the past 1200. yr using new reconstructions of Arkansas River flow (AD 1275-2002 and 1577-2002) and the summer Palmer Drought Sensitivity Index. The chronology, a composite built from parts of three collections in the central Rocky Mountains, is a proxy for <span class="hlt">decadal</span>-scale moisture <span class="hlt">variability</span> for the past 18 centuries. Since the sample size is small in some portions of the time series, the chronology should be considered preliminary; the timing and duration of drought events are likely the most robust characteristics. This chronology suggests that the region experienced increased aridity during the medieval period, as did much of western North America, but that the timing and duration of drought episodes within this period were somewhat different from those in other western locations, such as the upper Colorado River basin. ?? 2010 University of Washington.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011QuRes..75..483W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011QuRes..75..483W"><span id="translatedtitle">An 1800-yr record of <span class="hlt">decadal</span>-scale hydroclimatic <span class="hlt">variability</span> in the upper Arkansas River basin from bristlecone pine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woodhouse, Connie A.; Pederson, Gregory T.; Gray, Stephen T.</p> <p>2011-05-01</p> <p>Bristlecone pine trees are exceptionally long-lived, and with the incorporation of remnant material have been used to construct multi-millennial length ring-width chronologies. These chronologies can provide valuable information about past temperature and moisture <span class="hlt">variability</span>. In this study, we outline a method to build a moisture-sensitive bristlecone chronology and assess the robustness and consistency of this sensitivity over the past 1200 yr using new reconstructions of Arkansas River flow (AD 1275-2002 and 1577-2002) and the summer Palmer Drought Sensitivity Index. The chronology, a composite built from parts of three collections in the central Rocky Mountains, is a proxy for <span class="hlt">decadal</span>-scale moisture <span class="hlt">variability</span> for the past 18 centuries. Since the sample size is small in some portions of the time series, the chronology should be considered preliminary; the timing and duration of drought events are likely the most robust characteristics. This chronology suggests that the region experienced increased aridity during the medieval period, as did much of western North America, but that the timing and duration of drought episodes within this period were somewhat different from those in other western locations, such as the upper Colorado River basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006cosp...36.2610Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006cosp...36.2610Y"><span id="translatedtitle">Near-infrared <span class="hlt">observations</span> of the <span class="hlt">variable</span> crab nebula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, M.; Mori, K.; Shibata, S.; Tsujimoto, M.; Misawa, T.; Burrows, D.; Kawai, N.</p> <p></p> <p>We present three near-infrared NIR <span class="hlt">observations</span> of the Crab Nebula obtained with CISCO on the Subaru Telescope and Quick Infrared Camera on the University of HAWAII 88 inch Telescope The <span class="hlt">observations</span> were performed on 2004 September 2005 February and 2005 October and were coordinated with X-ray <span class="hlt">observations</span> obtained with the Chandra X-ray observatory within 10 days As shown in previous optical and X-ray monitoring <span class="hlt">observations</span> outward-moving wisps and <span class="hlt">variable</span> knots are detected also in our NIR <span class="hlt">observations</span> The NIR variations are closely correlated with variations in the X-ray <span class="hlt">observations</span> 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 <span class="hlt">variable</span> component</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4058790','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4058790"><span id="translatedtitle">Understanding interannual, <span class="hlt">decadal</span> level <span class="hlt">variability</span> in paralytic shellfish poisoning toxicity in the Gulf of Maine: the HAB Index</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>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.</p> <p>2013-01-01</p> <p>A major goal in harmful algal bloom (HAB) research has been to identify mechanisms underlying interannual <span class="hlt">variability</span> in bloom magnitude and impact. Here the focus is on <span class="hlt">variability</span> in Alexandrium fundyense blooms and paralytic shellfish poisoning (PSP) toxicity in Maine, USA, over 34 years (1978 – 2011). The Maine coastline was divided into two regions -eastern and western Maine, and within those two regions, three measures of PSP toxicity (the percent of stations showing detectable toxicity over the year, the cumulative amount of toxicity per station measured in all shellfish (mussel) samples during that year, and the duration of measurable toxicity) were examined for each year in the time series. These metrics were combined into a simple HAB Index that provides a single measure of annual toxin severity across each region. The three toxin metrics, as well as the HAB Index that integrates them, reveal significant <span class="hlt">variability</span> in overall toxicity between individual years as well as long-term, <span class="hlt">decadal</span> patterns or regimes. Based on different conceptual models of the system, we considered three trend formulations to characterize the long-term patterns in the Index – a three-phase (mean-shift) model, a linear two-phase model, and a pulse-decline model. The first represents a “regime shift” or multiple equilibria formulation as might occur with alternating periods of sustained high and low cyst abundance or favorable and unfavorable growth conditions, the second depicts a scenario of more gradual transitions in cyst abundance or growth conditions of vegetative cells, and the third characterizes a ”sawtooth” pattern in which upward shifts in toxicity are associated with major cyst recruitment events, followed by a gradual but continuous decline until the next pulse. The fitted models were compared using both residual sum of squares and Akaike's Information Criterion. There were some differences between model fits, but none consistently gave a better fit than the 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 <span class="hlt">decadal</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DSRII.103..264A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DSRII.103..264A"><span id="translatedtitle">Understanding interannual, <span class="hlt">decadal</span> level <span class="hlt">variability</span> in paralytic shellfish poisoning toxicity in the Gulf of Maine: The HAB Index</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, Donald M.; Couture, Darcie A.; Kleindinst, Judith L.; Keafer, Bruce A.; McGillicuddy, Dennis J., Jr.; Martin, Jennifer L.; Richlen, Mindy L.; Hickey, J. Michael; Solow, Andrew R.</p> <p>2014-05-01</p> <p>A major goal in harmful algal bloom (HAB) research has been to identify mechanisms underlying interannual <span class="hlt">variability</span> in bloom magnitude and impact. Here the focus is on <span class="hlt">variability</span> in Alexandrium fundyense blooms and paralytic shellfish poisoning (PSP) toxicity in Maine, USA, over 34 years (1978-2011). The Maine coastline was divided into two regions - eastern and western Maine, and within those two regions, three measures of PSP toxicity (the percent of stations showing detectable toxicity over the year, the cumulative amount of toxicity per station measured in all shellfish (mussel) samples during that year, and the duration of measurable toxicity) were examined for each year in the time series. These metrics were combined into a simple HAB Index that provides a single measure of annual toxin severity across each region. The three toxin metrics, as well as the HAB Index that integrates them, reveal significant <span class="hlt">variability</span> in overall toxicity between individual years as well as long-term, <span class="hlt">decadal</span> patterns or regimes. Based on different conceptual models of the system, we considered three trend formulations to characterize the long-term patterns in the Index - a three-phase (mean-shift) model, a linear two-phase model, and a pulse-decline model. The first represents a “regime shift” or multiple equilibria formulation as might occur with alternating periods of sustained high and low cyst abundance or favorable and unfavorable growth conditions, the second depicts a scenario of more gradual transitions in cyst abundance or growth conditions of vegetative cells, and the third characterizes a ”sawtooth” pattern in which upward shifts in toxicity are associated with major cyst recruitment events, followed by a gradual but continuous decline until the next pulse. The fitted models were compared using both residual sum of squares and Akaike's Information Criterion. There were some differences between model fits, but none consistently gave a better fit than the 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 <span class="hlt">decadal</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24948849','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24948849"><span id="translatedtitle">Understanding interannual, <span class="hlt">decadal</span> level <span class="hlt">variability</span> in paralytic shellfish poisoning toxicity in the Gulf of Maine: the HAB Index.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>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</p> <p>2014-05-01</p> <p>A major goal in harmful algal bloom (HAB) research has been to identify mechanisms underlying interannual <span class="hlt">variability</span> in bloom magnitude and impact. Here the focus is on <span class="hlt">variability</span> in Alexandrium fundyense blooms and paralytic shellfish poisoning (PSP) toxicity in Maine, USA, over 34 years (1978 - 2011). The Maine coastline was divided into two regions -eastern and western Maine, and within those two regions, three measures of PSP toxicity (the percent of stations showing detectable toxicity over the year, the cumulative amount of toxicity per station measured in all shellfish (mussel) samples during that year, and the duration of measurable toxicity) were examined for each year in the time series. These metrics were combined into a simple HAB Index that provides a single measure of annual toxin severity across each region. The three toxin metrics, as well as the HAB Index that integrates them, reveal significant <span class="hlt">variability</span> in overall toxicity between individual years as well as long-term, <span class="hlt">decadal</span> patterns or regimes. Based on different conceptual models of the system, we considered three trend formulations to characterize the long-term patterns in the Index - a three-phase (mean-shift) model, a linear two-phase model, and a pulse-decline model. The first represents a "regime shift" or multiple equilibria formulation as might occur with alternating periods of sustained high and low cyst abundance or favorable and unfavorable growth conditions, the second depicts a scenario of more gradual transitions in cyst abundance or growth conditions of vegetative cells, and the third characterizes a "sawtooth" pattern in which upward shifts in toxicity are associated with major cyst recruitment events, followed by a gradual but continuous decline until the next pulse. The fitted models were compared using both residual sum of squares and Akaike's Information Criterion. There were some differences between model fits, but none consistently gave a better fit than the 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 <span class="hlt">decadal</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016QSRv..131..329J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016QSRv..131..329J"><span id="translatedtitle">Comparisons of <span class="hlt">observed</span> and modelled lake δ18O <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, Matthew D.; Cuthbert, Mark O.; Leng, Melanie J.; McGowan, Suzanne; Mariethoz, Gregoire; Arrowsmith, Carol; Sloane, Hilary J.; Humphrey, Kerenza K.; Cross, Iain</p> <p>2016-01-01</p> <p>With the substantial number of lake sediment δ18O records published in recent <span class="hlt">decades</span>, a quantitative, process-based understanding of these systems can increase our understanding of past climate change. We test mass balance models of lake water δ18O <span class="hlt">variability</span> against five years of monthly monitoring data from lakes with different hydrological characteristics, in the East-Midlands region of the UK, and the local isotope composition of precipitation. These mass balance models can explain up to 74% of the measured lake water isotope <span class="hlt">variability</span>. We investigate the sensitivity of the model to differing calculations of evaporation amount, the amount of groundwater, and to different climatic <span class="hlt">variables</span>. We show there is only a small range of values for groundwater exchange flux that can produce suitable lake water isotope compositions and that variations in evaporation and precipitation are both required to produce recorded isotope <span class="hlt">variability</span> in lakes with substantial evaporative water losses. We then discuss the potential for this model to be used in a long-term, palaeo-scenario. This study demonstrates how long term monitoring of a lake system can lead to the development of robust models of lake water isotope compositions. Such systematics-based explanations allow us to move from conceptual, to more quantified reconstructions of past climates and environments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002JCli...15.3170T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002JCli...15.3170T"><span id="translatedtitle">Tropical Atlantic Sea Surface Temperature Forcing of Quasi-<span class="hlt">Decadal</span> Climate <span class="hlt">Variability</span> over the North Atlantic-European Region.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Terray, L.; Cassou, C.</p> <p>2002-11-01</p> <p>Effects of Atlantic sea surface temperature (SST) anomalies on the North Atlantic low-frequency atmospheric <span class="hlt">variability</span> are examined by analyzing two ensembles of integrations of the ARPEGE general circulation model (GCM) forced with differently configured <span class="hlt">observed</span> SSTs and sea ice extents (SIE) over the 1948-98 period. An attempt is made to separate the forced atmospheric response from internal atmospheric <span class="hlt">variability</span> by using a signal-to-noise maximizing empirical orthogonal function (EOF) analysis. This method yields an estimate of the most detectable common forced response given the knowledge of internal <span class="hlt">variability</span> provided by the ensemble. Applying the algorithm to North Atlantic atmospheric model data leads to an atmospheric response associated with a tripole pattern in North Atlantic SSTs. The spatial structure of the forced response, which is most consistent in winter, shows a dipole pattern in mean sea level pressure projecting onto the North Atlantic Oscillation. Examination of other atmospheric <span class="hlt">variables</span> shows a very coherent signal with a quasi-barotropic signature. Additional atmospheric integrations with idealized SST anomaly patterns demonstrate the primary role of the tropical North Atlantic SST anomalies in generating the forced response. The physical mechanism involves related changes in tropical convection, Hadley circulation, and the modulation of the stationary and transient planetary-scale waves by the low-frequency <span class="hlt">variability</span> in subtropical winds induced by the persistent tropical circulation anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998ovsg.book.....L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998ovsg.book.....L"><span id="translatedtitle"><span class="hlt">Observing</span> <span class="hlt">Variable</span> Stars, A Guide for the Beginner</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levy, David H.</p> <p></p> <p>David Levy's entertaining, well-researched book is aimed at the amateur enthusiast who likes to learn enjoyably. Beginning with advice on binoculars and telescopes, and how to <span class="hlt">observe</span> the night sky effectively, the author goes on to describe thoroughly the field of <span class="hlt">variable</span> star <span class="hlt">observation</span>, a field in which amateurs have made important contributions. He shows how to interpret variations in light output in terms of the life of a star, from birth through to sometimes violent death. All of the major <span class="hlt">variable</span> stars are described and classified, as well as other <span class="hlt">variable</span> objects such as active galaxies, asteroids, comets and the sun. The book also contains a guide to the seasonal night sky. Throughout, practical <span class="hlt">observations</span> serve to complement the text, producing an exciting, very readable introduction to this fascinating subject.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011tfa..confE..15W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011tfa..confE..15W"><span id="translatedtitle">More Bang for the Buck: Lessons from a <span class="hlt">Decade</span> of Keck Mainland <span class="hlt">Observing</span> Operations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wirth, Gregory D.; Kibrick, Robert I.; Goodrich, Robert W.; Lyke, James E.; Mader, Jeff A.</p> <p>2011-03-01</p> <p>Most astronomers love <span class="hlt">observing</span> remotely because they can gather their data while avoiding the inconvenience of traveling to the telescope; however, running a true, facility-class remote <span class="hlt">observing</span> system can impose a significant burden on the observatory support staff. Although usage of the remote <span class="hlt">observing</span> capability at Hawaii's W. M. Keck Observatory has risen substantially in the nine years since we began allowing astronomers to <span class="hlt">observe</span> from California and elsewhere, Keck's system has evolved over time to provide better operational performance with less manpower. This talk will describe improvements to our system in several key areas: scheduling remote <span class="hlt">observing</span> requests; maintaining the virtual servers used by remote <span class="hlt">observers</span>; monitoring the health and safety of equipment at remote <span class="hlt">observing</span> stations; and abandoning the distinction between "local" and "remote" <span class="hlt">observing</span>. These measures have substantially lessened the effort required to operate the system, provided new capabilities for training and troubleshooting by the technical staff, and enhanced the convenience and reliability of the system for <span class="hlt">observers</span> and support staff at the remote sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5702487','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5702487"><span id="translatedtitle"><span class="hlt">Observation</span> of possible mode switching in three semiregular <span class="hlt">variable</span> stars</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cadmus, R.R. Jr.; Willson, L.A.; Sneden, C.; Mattei, J.A. Iowa State Univ. of Science and Technology, Ames Texas Univ., Austin American Association of Variable Star Observers, Cambridge, MA )</p> <p>1991-03-01</p> <p>Both the amplitude and period of the light variations of the semiregular long-period <span class="hlt">variables</span> RV And, S Aql, and U Boo dramaticaly decreased, and then suddenly increased, in recent years. These <span class="hlt">observations</span>, in conjunction with spectroscopic data, suggest that these stars may have switched from fundamental to overtone pulsation and back again. Theoretical models are consistent with both the photometric and spectroscopic <span class="hlt">observations</span>. The similarity between the longer-period oscillations of these stars and the behavior of Mira <span class="hlt">variables</span> supports the conclusion that the Miras are fundamental-mode pulsators. 14 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.3444R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.3444R"><span id="translatedtitle">A <span class="hlt">Decade</span> of Global CO2 <span class="hlt">Observations</span> from the Satellite Instrument SCIAMACHY</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reuter, Maximilian; Schneising, Oliver; Hilker, Michael; Buchwitz, Michael; Heymann, Jens; Bovensmann, Heinrich; Burrows, John P.</p> <p>2013-04-01</p> <p>CO2 is the most important anthropogenic greenhouse gas. Its global increasing concentration in the Earth's atmosphere is the main driver for global warming. However, in spite of its importance, there are still large uncertainties on its sources and sinks: What is their global distribution? What is their temporal evolution? How will they behave in a changing climate? Satellite measurements, if accurate and precise enough, have the potential to reduce such surface flux uncertainties. SCIAMACHY started its operation in 2002 with the launch of ENVISAT. Roughly one <span class="hlt">decade</span> later ESA declared end of the mission due to the unexpected loss of ENVISAT. SCIAMACHY was the first and during seven years the only satellite instruments which was able to measure the CO2 mixing ratio (XCO2) with large sensitivity also in the boundary layer. Therefore, SCIAMACHY measurements are essential to create a consistent long term climate data record of XCO2 measurements. We will present two datasets (WFMD and BESD) each of which covering the full SCIAMACHY time series. Analyses of the datasets in respect to land-atmosphere interactions and long term trends will be part of the presentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NHESS..16..469M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NHESS..16..469M"><span id="translatedtitle">Variations in water storage in China over recent <span class="hlt">decades</span> from GRACE <span class="hlt">observations</span> and GLDAS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mo, X.; Wu, J. J.; Wang, Q.; Zhou, H.</p> <p>2016-02-01</p> <p>We applied Gravity Recovery and Climate Experiment (GRACE) Tellus products in combination with Global Land Data Assimilation System (GLDAS) simulations and data from reports, to analyze variations in terrestrial water storage (TWS) in China as a whole and eight of its basins from 2003 to 2013. Amplitudes of TWS were well restored after scaling, and showed good correlations with those estimated from models at the basin scale. TWS generally followed variations in annual precipitation; it decreased linearly in the Huai River basin (-0.56 cm yr-1) and increased with fluctuations in the Changjiang River basin (0.35 cm yr-1), Zhujiang basin (0.55 cm yr-1) and southeast rivers basin (0.70 cm yr-1). In the Hai River basin and Yellow River basin, groundwater exploitation may have altered TWS's response to climate, and TWS kept decreasing until 2012. Changes in soil moisture storage contributed over 50 % of variance in TWS in most basins. Precipitation and runoff showed a large impact on TWS, with more explained TWS in the south than in the north. North China and southwest rivers region exhibited long-term TWS depletions. TWS has increased significantly over recent <span class="hlt">decades</span> in the middle and lower reaches of Changjiang River, southeastern coastal areas, as well as the Hoh Xil, and the headstream region of the Yellow River in the Tibetan Plateau. The findings in this study could be helpful to climate change impact research and disaster mitigation planning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6088S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6088S"><span id="translatedtitle">Trends and <span class="hlt">variability</span> in East African rainfall and temperature <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seregina, Larisa; Ermert, Volker; Fink, Andreas H.; Pinto, Joaquim G.</p> <p>2014-05-01</p> <p>The economy of East Africa is highly dependent on agriculture, leading to a strong vulnerability of local society to fluctuations in seasonal rainfall amounts, including extreme events. Hence, the knowledge about the evolution of seasonal rainfall under future climate conditions is crucial. Rainfall regimes over East Africa are influenced by multiple factors, including two monsoon systems, several convergence zones and the Rift Valley lakes. In addition, local conditions, like topography, modulate the large-scale rainfall pattern. East African rainfall <span class="hlt">variability</span> is also influenced by various teleconnections like the Indian Ocean Zonal Mode and El Niño Southern Oscillation. Regarding future climate projections, regional and global climate models partly disagree on the increase or decrease of East African rainfall. The specific aim of the present study is the acquirement of historic data from weather stations in East Africa (Kenya, Tanzania, Ruanda and Uganda), the use of gridded satellite (rainfall) products (ARC2 and TRMM), and three-dimensional atmospheric reanalysis (e.g., ERA-Interim) to quantify climate <span class="hlt">variability</span> in the recent past and to understand its causes. Climate <span class="hlt">variability</span> and trends, including changes in extreme events, are evaluated using ETCCDI climate change and standardized precipitation indices. These climate indices are determined in order to investigate the <span class="hlt">variability</span> of temperature and rainfall and their trends with the focus on most recent <span class="hlt">decades</span>. In the follow-up, statistical and dynamical analyses are conducted to quantify the local impact of pertinent large-scale modes of climate <span class="hlt">variability</span> (Indian Ocean Zonal Mode, El Niño Southern Oscillation, Sea Surface Temperature of the Indian Ocean).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009848','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009848"><span id="translatedtitle">What We Have Learned About Clusters From a <span class="hlt">Decade</span> of Arcsecond Resolution X-ray <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Markevitch, Maxim</p> <p>2012-01-01</p> <p>This talk will briefly review the main findings from Chandra high angular resolution <span class="hlt">observations</span> of galaxy clusters, emphasizing results on cluster astrophysics. Chandra has discovered shock fronts in merging systems, providing information on the shock Mach number and velocity, and for best-<span class="hlt">observed</span> shocks, constraining the microphysical properties of the intracluster medium (ICM). Cold fronts, a Chandra discovery, are ubiquitous both in merging clusters and in the cool ccres of relaxed systems. They reveal the structure and strength of the intracluster magnetic fields and constrain the ICM viscosity a combined with radio data, these <span class="hlt">observations</span> also shed light on the production of ultra-relativistic particles that are known to coexist with thermal plasma. Finally, in nearly all cool cores, Chandra <span class="hlt">observes</span> cavities in the ICM that are produced by the central AGN. All these phenomena will be extremely interesting for high-resolution SZ studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880023739&hterms=mathematics+books&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmathematics%2Bbooks','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880023739&hterms=mathematics+books&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmathematics%2Bbooks"><span id="translatedtitle">Reconstruction and robust reduced-order <span class="hlt">observation</span> of flexible <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hastings, Gordon G.; Book, Wayne J.</p> <p>1986-01-01</p> <p>This paper discusses reconstruction and estimation of flexible <span class="hlt">variables</span> from multiple strain measurements for use in state feedback control of flexible manipulators. Reconstruction is proposed for obtaining flexible mode amplitudes from the measurements, and estimation for the modal velocities. Design of the <span class="hlt">observer</span> for estimation of the velocities is discussed with regard to robust implementation. The performance of the <span class="hlt">observer</span> is examined experimentally for several specifications of the error dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhDT.........6M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhDT.........6M"><span id="translatedtitle">A <span class="hlt">decade</span> of Rossi X-ray Timing Explorer Seyfert <span class="hlt">observations</span>: An RXTE Seyfert spectral database</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mattson, Barbara Jo</p> <p>2008-10-01</p> <p>With over forty years of X-ray <span class="hlt">observations</span>, 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 <span class="hlt">observations</span> by defining a "typical" AGN geometry, with <span class="hlt">observed</span> 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 <span class="hlt">observed</span> 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 <span class="hlt">observe</span> 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 <span class="hlt">observed</span> spectrum. We <span class="hlt">observe</span> 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 <span class="hlt">observe</span> the previously reported relationship between Gamma and the ratio of L x to the Eddington luminosity.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013HESSD..1013539V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013HESSD..1013539V"><span id="translatedtitle">Links between the Big Dry in Australia and hemispheric multi-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> - implications for water resource management</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Verdon-Kidd, D. C.; Kiem, A. S.; Moran, R.</p> <p>2013-11-01</p> <p>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-<span class="hlt">decadal</span> hydroclimatic <span class="hlt">variability</span>. 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014HESS...18.2235V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014HESS...18.2235V"><span id="translatedtitle">Links between the Big Dry in Australia and hemispheric multi-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> - implications for water resource management</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Verdon-Kidd, D. C.; Kiem, A. S.; Moran, R.</p> <p>2014-06-01</p> <p>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-<span class="hlt">decadal</span> hydroclimatic <span class="hlt">variability</span>. 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990064613&hterms=parkinson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dparkinson','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990064613&hterms=parkinson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dparkinson"><span id="translatedtitle"><span class="hlt">Variability</span> of Arctic Sea Ice as Determined from Satellite <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.</p> <p>1999-01-01</p> <p>The compiled, quality-controlled satellite multichannel passive-microwave record of polar sea ice now spans over 18 years, from November 1978 through December 1996, and is revealing considerable information about the Arctic sea ice cover and its <span class="hlt">variability</span>. The information includes data on ice concentrations (percent areal coverages of ice), ice extents, ice melt, ice velocities, the seasonal cycle of the ice, the interannual <span class="hlt">variability</span> of the ice, the frequency of ice coverage, and the length of the sea ice season. The data reveal marked regional and interannual <span class="hlt">variabilities</span>, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 sq km, while individual regions experienced much greater percent variations, for instance, with the Greenland Sea having a range of 740,000 - 1,110,000 sq km in its yearly maximum ice coverage. In spite of the large variations from year to year and region to region, overall the Arctic ice extents showed a statistically significant, 2.80% / <span class="hlt">decade</span> negative trend over the 18.2-year period. Ice season lengths, which vary from only a few weeks near the ice margins to the full year in the large region of perennial ice coverage, also experienced interannual <span class="hlt">variability</span>, along with spatially coherent overall trends. Linear least squares trends show the sea ice season to have lengthened in much of the Bering Sea, Baffin Bay, the Davis Strait, and the Labrador Sea, but to have shortened over a much larger area, including the Sea of Okhotsk, the Greenland Sea, the Barents Sea, and the southeastern Arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19770053166&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Variable%2Bstars%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19770053166&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Variable%2Bstars%2529"><span id="translatedtitle">Characteristics of IR <span class="hlt">variable</span> stars as <span class="hlt">observed</span> from orbit</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maran, S. P.; Heinsheimer, T. F.; Stocker, T. L.; Chapman, R. D.; Hobbs, R. W.; Michalitsanos, A. G.</p> <p>1976-01-01</p> <p>A selection of infrared <span class="hlt">variable</span> stars was studied at wavelength 2.7 microns during 1971-1975 with data from U.S. Air Force satellites. Stars <span class="hlt">observed</span> in this program are classified as long-period <span class="hlt">variable</span> stars, semiregular <span class="hlt">variables</span>, and irregular <span class="hlt">variables</span> and are among the strongest stellar sources at this wavelength. In addition, a few new, as yet unclassified <span class="hlt">variable</span> stars were identified during the course of the investigation. Time scales of reproducible variations range from a few weeks to a few years, and amplitudes of variation are as large as a factor of three for stars with periods of order one year. The minimum infrared flux density of a long-period star repeats accurately from one cycle to the next, whereas the maximum flux density was found to be unstable. The correlation of 2.7 micron and radio emission line data from one, well-studied long-period <span class="hlt">variable</span> is consistent with the hypothesis that the H2O and OH circumstellar masers are saturated, if pumped by the stellar infrared flux near 2.7 microns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AcAau..57..520S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AcAau..57..520S"><span id="translatedtitle">High resolution earth <span class="hlt">observation</span> satellites and services in the next <span class="hlt">decade</span> a European perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schreier, Gunter; Dech, Stefan</p> <p>2005-07-01</p> <p>Projects to use very high resolution optical satellite sensor data started in the late 90s and are believed to be the major driver for the commercialisation of earth <span class="hlt">observation</span>. The global political security situation and updated legislative frameworks created new opportunities for high resolution, dual use satellite systems. In addition to new optical sensors, very high resolution synthetic aperture radars will become in the next few years an important component in the imaging satellite fleet. The paper will review the development in this domain so far, and give perspectives on future emerging markets and opportunities. With dual-use satellite initiatives and new political frameworks agreed between the European Commission and the European Space Agency (ESA), the European market becomes very attractive for both service suppliers and customers. The political focus on "Global Monitoring for Environment and Security" (GMES) and the "European Defence and Security Policy" drive and amplify this demand which ranges from low resolution climate monitoring to very high resolution reconnaissance tasks. In order to create an operational and sustainable GMES in Europe by 2007, the European infrastructure need to be adapted and extended. This includes the ESA SENTINEL and OXYGEN programmes, aiming for a fleet of earth <span class="hlt">observation</span> satellites and an open and operational earth <span class="hlt">observation</span> ground segment. The harmonisation of national and regional geographic information is driven by the European Commission's INSPIRE programme. The necessary satellite capacity to complement existing systems in the delivery of space based data required for GMES is currently under definition. Embedded in a market with global competition and in the global political framework of a Global Earth <span class="hlt">Observation</span> System of Systems, European companies, agencies and research institutions are now contributing to this joint undertaking. The paper addresses the chances, risks and options for the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011HESSD...811233D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011HESSD...811233D"><span id="translatedtitle">Coupled <span class="hlt">decadal</span> <span class="hlt">variability</span> of the North Atlantic Oscillation, regional rainfall and spring discharges in the Campania region (Southern Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Vita, P.; Allocca, V.; Manna, F.; Fabbrocino, S.</p> <p>2011-12-01</p> <p>Climate change is one of the issues most debated by the scientific community with a special focus to the combined effects of anthropogenic modifications of the atmosphere and the natural climatic cycles. Various scenarios have been formulated in order to forecast the global atmospheric circulation and consequently the <span class="hlt">variability</span> of the global distribution of air temperature and rainfall. The effects of climate change have been analysed with respect to the risks of desertification, droughts and floods, remaining mainly limited to the atmospheric and surface components of the hydrologic cycle. Consequently the impact of the climate change on the recharge of regional aquifers and on the groundwater circulation is still a challenging topic especially in those areas whose aqueduct systems depend basically on springs or wells, such as the Campania region (Southern Italy). In order to analyse the long-term climatic <span class="hlt">variability</span> and its influence on groundwater circulation, we analysed <span class="hlt">decadal</span> patterns of precipitation, air temperature and spring discharges in the Campania region (Southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, in the period from 1921 to 2010, choosing 18 rain gauges and 9 air temperature stations among those with the most continuous functioning as well as arranged in a homogeneous spatial distribution. Moreover, for the same period, we gathered the time series of the winter NAO index (December to March mean) and of the discharges of the Sanità spring, belonging to an extended carbonate aquifer (Cervialto Mount) located in the central-eastern area of the Campania region, as well as of two other shorter time series of spring discharges. The hydrogeological features of this aquifer, its relevance due to the feeding of an important regional aqueduct system, as well as the unique availability of a long-lasting time series of spring discharges, allowed us to consider it as an ideal test site, representative of the other carbonate aquifers in the Campania region. The time series of regional normalised indexes of mean annual precipitation, mean annual air temperature and mean annual effective precipitation, as well as the time series of the normalised annual discharge index were calculated. Different methods were applied to analyse the time series: long-term trend analysis, through smoothing numerical techniques, cross-correlation and Fourier analysis. The investigation of the normalised indexes has highlighted long-term complex periodicities, strongly correlated with the winter NAO index. Moreover, we also found robust correlations among precipitation indexes and the annual discharge index, as well as between the latter and the NAO index itself. Although the effects of the North Atlantic Oscillation had already been proved on long-term precipitation and streamflow patterns of different European countries and Mediterranean areas, the results obtained appear original because they establish a link between a large-scale atmospheric cycle and the groundwater circulation of regional aquifers. Therefore, we demonstrated that the winter NAO index can be considered as an effective proxy to forecast the <span class="hlt">decadal</span> <span class="hlt">variability</span> of groundwater circulation in Mediterranean areas and in estimating critical scenarios for the feeding of aqueduct systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.132..197H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.132..197H"><span id="translatedtitle">North Atlantic atmospheric and ocean inter-annual <span class="hlt">variability</span> over the past fifty years - Dominant patterns and <span class="hlt">decadal</span> shifts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hauser, Tristan; Demirov, Entcho; Zhu, Jieshun; Yashayaev, Igor</p> <p>2015-03-01</p> <p>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 <span class="hlt">variability</span> 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 <span class="hlt">variability</span> 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 <span class="hlt">decadal</span> shift in the atmospheric state between 1970s and 1980s was associated with a change in the dominant interannual patterns towards NAO+ and G- in the late 1980s and early 1990s. The recent warming of the SPNA since the mid-1990s was related to dominance of the G+/G- interannual patterns in the distribution of interannual patterns probability membership. Our analysis suggests that this <span class="hlt">decadal</span> <span class="hlt">variability</span> was associated with long term shifts in atmospheric behavior over the SPNA that can be described by a change in the 1980s of the distribution of membership probabilities for the interannual patterns. Within the interannual pattern phase space, this change is characterized with a shift from the NAO-/G+/G- subspace in the 1950 and 1960s, towards NAO+/G+/G- since the mid 1980s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.G33C..04C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.G33C..04C"><span id="translatedtitle">Inter-annual to <span class="hlt">decadal</span> sea level <span class="hlt">variability</span> along the Norwegian coast and in the Siberian Seas; a link with the Eastern North Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calafat, F. M.; Chambers, D. P.</p> <p>2012-12-01</p> <p>Inter-annual to <span class="hlt">decadal</span> sea level variations from tide gauge records along the Norwegian coast and in the Siberian Seas are examined for the period 1950 to present. A combination of <span class="hlt">observations</span> and theory is used to explore the physical mechanisms responsible for the <span class="hlt">observed</span> sea level <span class="hlt">variability</span>. Tide gauge records are first grouped into 6 geographical regions: the Norwegian Coast, the Barents Sea, the Kara Sea, the Laptev Sea, the East Siberian Sea, and the Chukchi Sea. Then an average of sea level at tide gauges is computed for each region. All regions exhibit large <span class="hlt">decadal</span> sea level variations (up to 20 cm). Sea level corrected for the inverse barometer effect is significantly correlated with the Arctic Oscillation index in all regions except in the East Siberian and Chukchi Seas. There is a coherent sea level signal that affects a region extending from Southwest Norway to the Kara Sea. Previous studies have found that sea level <span class="hlt">variability</span> at the Norwegian coast is related to variations in the Norwegian Atlantic Current (NwAC), which are mainly driven by changes in the wind forcing over the region. Here we show that, apart from the contribution of the NwAC and the local wind, there is an additional contribution to the sea level <span class="hlt">variability</span> at the Norwegian coast resulting from the poleward propagation of wind-driven sea level variations along the continental slope of the Northeast Atlantic. The fact that sea level <span class="hlt">variability</span> in both the Barents and the Kara Seas is highly coherent with that in the Norwegian coast suggests propagation of sea level variations further north into these regions. Eastward of the Kara Sea, where the continental shelf is shallower, sea level variations are much larger than in the other regions and they are highly correlated (~0.75) with the local longshore wind.he average of sea level at 8 tide gauge stations on the Norwegian coast (black line) and a reconstruction of sea level (blue line) using a combination of the tide gauge at Newlyn (on the eastern boundary of the North Atlantic) and the longshore wind over the Faroe-Shetland channel and the Norwegian continental shelf. The grey shaded area represents the uncertainty of the time series. A 2-year running mean has been applied to both time series.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A33I3309K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A33I3309K"><span id="translatedtitle">Changes in SO2 and NO2 Pollution over the Past <span class="hlt">Decade</span> <span class="hlt">Observed</span> by Aura OMI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krotkov, N. A.; Li, C.; Lamsal, L. N.; Celarier, E. A.; Marchenko, S. V.; Swartz, W.; Bucsela, E. J.; Fioletov, V.; McLinden, C. A.; Joiner, J.; Bhartia, P. K.; Duncan, B. N.; Dickerson, R. R.</p> <p>2014-12-01</p> <p>The Ozone Monitoring Instrument (OMI), a NASA partnership with the Netherlands and Finland, flies on the EOS Aura satellite and uses reflected sunlight to measure two critical atmospheric trace gases, nitrogen dioxide (NO2) and sulfur dioxide (SO2), characterizing daily air quality. Both gases and the secondary pollutants they produce (particulate matter, PM2.5, and tropospheric ozone) are among USEPA designated criteria pollutants, posing serious threats to human health and the environment (e.g., acid rain, plant damage, and reduced visibility). A new generation of the OMI standard SO2 and NO2 products (based on critically improved DOAS spectral fitting for NO2 and innovative Principal Component Analysis method for SO2) provides a valuable dataset for studying anthropogenic pollution on local to global scales. Here we highlight some of the OMI <span class="hlt">observed</span> long-term changes in air quality over several regions. Over the US, average NO2 and SO2 pollution levels have decreased dramatically as a result of both technological improvements (e.g., catalytic converters on cars) and stricter regulations of emissions. We see continued decline in NO2 and SO2 pollution over Europe. Over China OMI <span class="hlt">observed</span> a ~ 60% increase in NO2 pollution between 2005 and 2013, despite a temporary reversal of the growing trend due to both 2008 Olympic Games and the economic recession in 2009. Chinese SO2 pollution seems to have stabilized since peaking in 2007, probably due to government efforts to curb SO2 emissions from the power sector. We have also <span class="hlt">observed</span> large increases in both SO2 and NO2 pollution particularly in Eastern India where a number of new large coal power plants have been built in recent years. We expect that further improvements in the OMI NO2 and SO2 products will allow more robust quantification of long-term trends in local to global air quality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC41A0773B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC41A0773B"><span id="translatedtitle">A likelihood-based comparison of CMIP5 <span class="hlt">decadal</span> experiment runs with <span class="hlt">observations</span> from the Atmospheric Infrared Sounder</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braverman, A. J.; Cressie, N.; Teixeira, J.</p> <p>2011-12-01</p> <p>In Braverman, Cressie, and Teixeira (2011) we introduced a new method for assessing the consistency between climate model simulations and <span class="hlt">observational</span> 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 <span class="hlt">observations</span> 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 <span class="hlt">observational</span> statistics are proportional to the likelihoods. These posterior probabilities given an indication of which models are most consistent with the <span class="hlt">observed</span> data record. We have applied this method to CNRM-CM5 and CanCM4 runs from the CMIP5 <span class="hlt">decadal</span> experiment suite using <span class="hlt">observations</span> from NASA's AIRS instrument. In this talk, we report the results of these comparisons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.3407A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.3407A"><span id="translatedtitle">Monitoring multi-<span class="hlt">decadal</span> satellite earth <span class="hlt">observation</span> of soil moisture using era-land global land water resources dataset</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Albergel, Clement; Dorigo, Wouter; Balsamo, Gianpaolo; de Rosnay, Patricia; Muñoz-Sabater, Joaquin; Isaksen, Lars; Brocca, Luca; de Jeu, Richard; Wagner, Wolfgang</p> <p>2014-05-01</p> <p>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 <span class="hlt">variable</span> 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 <span class="hlt">Observation</span> 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 <span class="hlt">observations</span>. 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 <span class="hlt">observations</span> 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 <span class="hlt">observations</span> 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-<span class="hlt">decadal</span> time period (1980-2010).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ysc..conf...53G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ysc..conf...53G"><span id="translatedtitle">X-ray Emission of Cataclysmic <span class="hlt">Variables</span> <span class="hlt">Observed</span> by INTEGRAL</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gális, R.; Eckert, D.; Paltani, S.; Münz, F.; Kocka, M.</p> <p>2009-12-01</p> <p>Magnetic cataclysmic <span class="hlt">variables</span> represent significant fraction of all INTEGRAL detections in hard X-ray/soft γ-ray. Our deep survey of all known intermediate polars revealed 5 new sources, previously undetected by this mission. Our analysis based on all available <span class="hlt">observational</span> data from INTEGRAL/IBIS and INTEGRAL/JEM-X showed that the fluxes of some intermediate polars are long-term <span class="hlt">variable</span>. Moreover this hard X-ray/soft γ-ray <span class="hlt">variability</span> is correlated with the changes in optical spectral band. The broad-band spectra (3-100 keV) of surveyed intermediate polars can be well fitted by a thermal bremsstrahlung model, with reflection from an optically thick cold medium (the surface of the white dwarf) in some cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009BaltA..18..321G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009BaltA..18..321G"><span id="translatedtitle">X-Ray Emission of Cataclysmic <span class="hlt">Variables</span> <span class="hlt">Observed</span> by Integral</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gális, R.; Eckert, D.; Paltani, S.; Münz, F.; Kocka, M.</p> <p></p> <p>Magnetic cataclysmic <span class="hlt">variables</span> represent a significant fraction of all INTEGRAL detections in hard X-rays and soft gamma rays. Our deep survey of all known intermediate polars revealed five new sources, previously undetected by this mission. Our analysis, based on all available <span class="hlt">observational</span> data from the IBIS and JEM-X instruments, has shown that the fluxes of some intermediate polars are long-term <span class="hlt">variable</span>. Moreover, this hard X-ray and soft gamma-ray <span class="hlt">variability</span> is correlated with changes in the optical. The broad-band spectra (3--100 keV) of surveyed intermediate polars can be fitted well by a thermal bremsstrahlung model, in some cases with the reflection from an optically thick cold medium (the surface of the white dwarf).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.2630A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.2630A"><span id="translatedtitle">The IRIS Data Management Center: Enabling Access to <span class="hlt">Observational</span> Time Series Spanning <span class="hlt">Decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahern, T.; Benson, R.; Trabant, C.</p> <p>2009-04-01</p> <p>The Incorporated Research Institutions for Seismology (IRIS) is funded by the National Science Foundation (NSF) to operate the facilities to generate, archive, and distribute seismological data to research communities in the United States and internationally. The IRIS Data Management System (DMS) is responsible for the ingestion, archiving, curation and distribution of these data. The IRIS Data Management Center (DMC) manages data from more than 100 permanent seismic networks, hundreds of temporary seismic deployments as well as data from other geophysical <span class="hlt">observing</span> networks such as magnetotelluric sensors, ocean bottom sensors, superconducting gravimeters, strainmeters, surface meteorological measurements, and in-situ atmospheric pressure measurements. The IRIS DMC has data from more than 20 different types of sensors. The IRIS DMC manages approximately 100 terabytes of primary <span class="hlt">observational</span> data. These data are archived in multiple distributed storage systems that insure data availability independent of any single catastrophic failure. Storage systems include both RAID systems of greater than 100 terabytes as well as robotic tape robots of petabyte capacity. IRIS performs routine transcription of the data to new media and storage systems to insure the long-term viability of the scientific data. IRIS adheres to the OAIS Data Preservation Model in most cases. The IRIS data model requires the availability of metadata describing the characteristics and geographic location of sensors before data can be fully archived. IRIS works with the International Federation of Digital Seismographic Networks (FDSN) in the definition and evolution of the metadata. The metadata insures that the data remain useful to both current and future generations of earth scientists. Curation of the metadata and time series is one of the most important activities at the IRIS DMC. Data analysts and an automated quality assurance system monitor the quality of the incoming data. This insures data 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 <span class="hlt">observations</span> of microbarograph data but that community does not understand the methods of applying instrument corrections to the <span class="hlt">observations</span>. 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.2218T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.2218T"><span id="translatedtitle">A large increase in U.S. methane emissions over the past <span class="hlt">decade</span> inferred from satellite data and surface <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turner, A. J.; Jacob, D. J.; Benmergui, J.; Wofsy, S. C.; Maasakkers, J. D.; Butz, A.; Hasekamp, O.; Biraud, S. C.</p> <p>2016-03-01</p> <p>The global burden of atmospheric methane has been increasing over the past <span class="hlt">decade</span>, but the causes are not well understood. National inventory estimates from the U.S. Environmental Protection Agency indicate no significant trend in U.S. anthropogenic methane emissions from 2002 to present. Here we use satellite retrievals and surface <span class="hlt">observations</span> of atmospheric methane to suggest that U.S. methane emissions have increased by more than 30% over the 2002-2014 period. The trend is largest in the central part of the country, but we cannot readily attribute it to any specific source type. This large increase in U.S. methane emissions could account for 30-60% of the global growth of atmospheric methane seen in the past <span class="hlt">decade</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150023336','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150023336"><span id="translatedtitle">The Earth <span class="hlt">Observing</span> One (EO-1) Satellite Mission: Over a <span class="hlt">Decade</span> in Space</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Middleton, Elizabeth M.; Ungar, Stephen G.; Mandl, Daniel J.; Ong, Lawrence; Frye, Stuart W.; Campbell, Petya E.; Landis, David R.; Pollack, Nathan H.</p> <p>2013-01-01</p> <p>The Earth <span class="hlt">Observing</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20150005603&hterms=climate+change+middle+east&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dclimate%2Bchange%2Bmiddle%2Beast','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20150005603&hterms=climate+change+middle+east&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dclimate%2Bchange%2Bmiddle%2Beast"><span id="translatedtitle">MISR <span class="hlt">Decadal</span> <span class="hlt">Observations</span> of Mineral Dust: Property Characterization and Climate Applications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kalashnikova, Olga V.; Garay, Michael J.; Sokolik, Irina; Kahn, Ralph A.; Lyapustin, A.; Diner, David J.; Lee, Jae N.; Torres, Omar; Leptoukh, Gregory G.; Sabbah, Ismail</p> <p>2012-01-01</p> <p>The Multi-angle Imaging SpectroRadiometer (MISR) provides a unique, independent source of data for studying dust emission and transport. MISR's multiple view angles allow the retrieval of aerosol properties over bright surfaces, and such retrievals have been shown to be sensitive to the non-sphericity of dust aerosols over both land and water. MISR stereographic views of thick aerosol plumes allow height and instantaneous wind derivations at spatial resolutions of better than 1.1 km horizontally and 200m vertically. We will discuss the radiometric and stereo-retrieval capabilities of MISR specifically for dust, and demonstrate the use of MISR data in conjunction with other available satellite <span class="hlt">observations</span> for dust property characterization and climate studies.First, we will discuss MISR non-spherical (dust) fraction product over the global oceans. We will show that over the Atlantic Ocean, changes in the MISR-derived non-spherical AOD fraction illustrate the evolution of dust during transport. Next, we will present a MISR satellite perspective on dust climatology in major dust source regions with a particular emphasis on the West Africa and Middle East and discuss MISR's unique strengths as well as current product biases. Finally, we will discuss MISR dust plume product and climatological applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2911134','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2911134"><span id="translatedtitle">Religious education and midlife <span class="hlt">observance</span> are associated with dementia three <span class="hlt">decades</span> later in Israeli men</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Beeri, Michal Schnaider; Davidson, Michael; Silverman, Jeremy M.; Schmeidler, James; Springer, Ramit Ravona; Noy, Shlomo; Goldbourt, Uri</p> <p>2010-01-01</p> <p>Objective The aim of the study was to examine the association of religious education and <span class="hlt">observance</span> with dementia among participants in the Israeli Ischemic Heart Disease study. Study Design and Setting We assessed dementia in 1,890 participants among 2,604 survivors of 10,059 participants in the Israeli Ischemic Heart Disease study, a longitudinal investigation of the incidence and risk factors for cardiovascular disease among Jewish male civil servants in Israel. Face-to-face interviews were conducted with 651 subjects identified as possibly demented by the Modified Telephone Interview for Cognitive Status. Results Of 1,628 subjects included in this analysis (mean age 82 at assessment), 308 (18.9%) had dementia. The prevalence rates of dementia (and odds ratios (ORs) relative to those with exclusively religious education, adjusted for age, area of birth, and socioeconomic status) were 27.1% for those with exclusively religious education, 12.6% (OR=0.49) for those with mixed education, and 16.1% (OR=0.76) for those with secular education. For religious self-definition and practice, the prevalence rates were 9.7%, 17.7%, 14.1%, 19.3%, and 28.8% for categories from least to most religious (ORs relative to the most religious: 0.43, 0.67, 0.48, 0.55). Conclusions Examining lifestyles associated with religiosity might shed light onto environmental risks for dementia. Mechanisms underlying these associations remain elusive. PMID:18538995</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070038262&hterms=microwaves+works&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmicrowaves%2Bworks','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070038262&hterms=microwaves+works&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmicrowaves%2Bworks"><span id="translatedtitle">Interannual and <span class="hlt">Decadal</span> <span class="hlt">Variability</span> of Ocean Surface Latent Heat Flux as Seen from Passive Microwave Satellite Algorithms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robertson, Franklin R.; Jackson, Darren L.; Wick, Gary A.; Roberts, Brent; Miller, Tim L.</p> <p>2007-01-01</p> <p>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 <span class="hlt">variability</span> 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, <span class="hlt">variability</span> 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 <span class="hlt">decadal</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AAN...471....1W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AAN...471....1W"><span id="translatedtitle">Cataclysmic <span class="hlt">variables</span> to be monitored for HST <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waagen, Elizabeth O.</p> <p>2012-09-01</p> <p>Drs. Boris Gaensicke (Warwick University), Joseph Patterson (Columbia University, Center for Backyard Astrophysics), and Arne Henden (AAVSO), on behalf of a consortium of 16 astronomers, requested the help of AAVSO <span class="hlt">observers</span> in monitoring the ~40 cataclysmic <span class="hlt">variables</span> in support of Hubble Space Telescope <span class="hlt">observations</span> in the coming months. The HST COS (Cosmic Origins Spectrograph) will be carrying out far-ultraviolet spectroscopy of ~40 CVs sequentially, with the aim to measure the temperatures, atmospheric compositions, rotation rates, and eventually masses of their white dwarfs. The primary purpose of the monitoring is to know whether each target is in quiescence immediately prior to the <span class="hlt">observation</span> window; if it is in outburst it will be too bright for the HST instrumentation. Based on the information supplied by the AAVSO, the HST scheduling team will make the decision (usually) the evening before the scheduled <span class="hlt">observing</span> time as to whether to go forward with the HST <span class="hlt">observations</span>. For CCD <span class="hlt">observers</span>, simultaneous photometry [shortly before, during, and after the HST <span class="hlt">observations</span>] would be ideal. B filter would be best for a light curve, although for the magnitude estimates, V would be best. Finder charts may be created using the AAVSO <span class="hlt">Variable</span> Star Plotter (http://www.aavso.org/vsp). <span class="hlt">Observations</span> should be submitted to the AAVSO International Database. If the target is seen in outburst, please contact the AAVSO immediately and post a message to the <span class="hlt">Observations</span> and Campaigns & <span class="hlt">Observations</span> Reports forum (http://www.aavso.org/forum). This campaign will run the better part of a year or longer. See full Alert Notice for more details and list of objects.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.P23A1922P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.P23A1922P"><span id="translatedtitle"><span class="hlt">Observational</span> Evidence for a <span class="hlt">Decade</span>-long climate optimum near the Hesperian/Amazonian Transition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parsons, R.; Moore, J. M.; Howard, A. D.</p> <p>2012-12-01</p> <p>Hesperian to Amazonian-aged valleys (HAVs) are predominantly found in the southern equatorial and mid-latitudes of Mars and form parallel to dendritic networks. These features record a significant warming of the regional/global climate which may have been associated with outflow channel formation and/or a period of alluvial fan deposition in Margaritifer Terra [1]. HAVs are distinct from older valley networks in both their age and morphology and they provide a window into the past climate conditions and potential water sources which formed them. Using quantitative geomorphic analysis we calculate the expected range of timescales, water volumes, precipitation rates and atmospheric conditions which contributed to HAV formation. In Newton crater (40oS, -159oE) we measured valley widths, depths, slopes and alluvial fan volumes. These <span class="hlt">observations</span>, when combined with a set of terrestrial sediment transport prediction functions [2,3,4,5], allow us to calculate an expected duration of fluvial activity ranging from 0.1 to 10 years for water-filled channel depths ranging between 20 and 130 cm, and median sediment grain size ranging from 1 mm to 10 cm. The water volume required to form a single HAV in Newton crater ranges between 1.8 and 5.7~km3 based on the Darcy-Weisbach equation [6] in combination with the aforementioned range in channel depths, grain sizes and formation timescales. These results imply water runoff rates of between 1 to 10~cm/day over a typical, 300~km2, drainage area. Such a high runoff rate and short formation time suggest a brief, dramatic regional to global climate excursion. The source of water which formed these features remains unclear, but it must have been released at the aforementioned rates, and was widely distributed within each drainage catchment, and regionally over Newton crater and the southern highlands. HAV formation was likely a two-step process involving, first, the deposition of a 10s of meters thick regional snowpack along 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GPC...137..131A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GPC...137..131A"><span id="translatedtitle">Lake oxygen isotopes as recorders of North American Rocky Mountain hydroclimate: Holocene patterns and <span class="hlt">variability</span> at multi-<span class="hlt">decadal</span> to millennial time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, Lesleigh; Berkelhammer, Max; Barron, John A.; Steinman, Byron A.; Finney, Bruce P.; Abbott, Mark B.</p> <p>2016-02-01</p> <p>Lake sediment oxygen isotope records (calcium carbonate-δ18O) in the western North American Cordillera developed during the past <span class="hlt">decade</span> provide substantial evidence of Pacific ocean-atmosphere forcing of hydroclimatic <span class="hlt">variability</span> during the Holocene. Here we present an overview of 18 lake sediment δ18O records along with a new compilation of lake water δ18O and δ2H that are used to characterize lake sediment sensitivity to precipitation-δ18O in contrast to fractionation by evaporation. Of the 18 records, 14 have substantial sensitivity to evaporation. Two records reflect precipitation-δ18O since the middle Holocene, Jellybean and Bison Lakes, and are geographically positioned in the northern and southern regions of the study area. Their comparative analysis indicates a sequence of time-varying north-south precipitation-δ18O patterns that is evidence for a highly non-stationary influence by Pacific ocean-atmosphere processes on the hydroclimate of western North America. These <span class="hlt">observations</span> are discussed within the context of previous research on North Pacific precipitation-δ18O based on empirical and modeling methods. The Jellybean and Bison Lake records indicate that a prominent precipitation-δ18O dipole (enriched-north and depleted-south) was sustained between ~ 3.5 and 1.5 ka, which contrasts with earlier Holocene patterns, and appears to indicate the onset of a dominant tropical control on North Pacific ocean-atmosphere dynamics. This remains the state of the system today. Higher frequency reversals of the north-south precipitation-δ18O dipole between ~ 2.5 and 1.5 ka, and during the Medieval Climate Anomaly and the Little Ice Age, also suggest more varieties of Pacific ocean-atmosphere modes than a single Pacific <span class="hlt">Decadal</span> Oscillation (PDO) type analogue. Results indicate that further investigation of precipitation-δ18O patterns on short (<span class="hlt">observational</span>) and long (Holocene) time scales is needed to improve our understanding of the processes that drive regional precipitation-δ18O responses to Pacific ocean-atmosphere <span class="hlt">variability</span>, which in turn, will lead to a better understanding of internal Pacific ocean-atmosphere <span class="hlt">variability</span> and its response to external climate forcing mechanisms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70162171','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70162171"><span id="translatedtitle">Lake oxygen isotopes as recorders of North American Rocky Mountain hydroclimate: Holocene patterns and <span class="hlt">variability</span> at multi-<span class="hlt">decadal</span> to millennial time scales</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Anderson, Lesleigh; Max Berkelhammer; Barron, John A.; Steinman, Byron A.; Finney, Bruce P.; Abbott, Mark B.</p> <p>2016-01-01</p> <p>Lake sediment oxygen isotope records (calcium carbonate-δ18O) in the western North American Cordillera developed during the past <span class="hlt">decade</span> provide substantial evidence of Pacific ocean–atmosphere forcing of hydroclimatic <span class="hlt">variability</span> during the Holocene. Here we present an overview of 18 lake sediment δ18O records along with a new compilation of lake water δ18O and δ2H that are used to characterize lake sediment sensitivity to precipitation-δ18O in contrast to fractionation by evaporation. Of the 18 records, 14 have substantial sensitivity to evaporation. Two records reflect precipitation-δ18O since the middle Holocene, Jellybean and Bison Lakes, and are geographically positioned in the northern and southern regions of the study area. Their comparative analysis indicates a sequence of time-varying north–south precipitation-δ18O patterns that is evidence for a highly non-stationary influence by Pacific ocean–atmosphere processes on the hydroclimate of western North America. These <span class="hlt">observations</span> are discussed within the context of previous research on North Pacific precipitation-δ18O based on empirical and modeling methods. The Jellybean and Bison Lake records indicate that a prominent precipitation-δ18O dipole (enriched-north and depleted-south) was sustained between ~ 3.5 and 1.5 ka, which contrasts with earlier Holocene patterns, and appears to indicate the onset of a dominant tropical control on North Pacific ocean–atmosphere dynamics. This remains the state of the system today. Higher frequency reversals of the north–south precipitation-δ18O dipole between ~ 2.5 and 1.5 ka, and during the Medieval Climate Anomaly and the Little Ice Age, also suggest more varieties of Pacific ocean–atmosphere modes than a single Pacific <span class="hlt">Decadal</span> Oscillation (PDO) type analogue. Results indicate that further investigation of precipitation-δ18O patterns on short (<span class="hlt">observational</span>) and long (Holocene) time scales is needed to improve our understanding of the processes that drive regional precipitation-δ18O responses to Pacific ocean–atmosphere <span class="hlt">variability</span>, which in turn, will lead to a better understanding of internal Pacific ocean–atmosphere <span class="hlt">variability</span> and its response to external climate forcing mechanisms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011CSR....31..951C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011CSR....31..951C"><span id="translatedtitle"><span class="hlt">Variability</span> of water mass properties in the last two <span class="hlt">decades</span> in the South Adriatic Sea with emphasis on the period 2006-2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cardin, Vanessa; Bensi, Manuel; Pacciaroni, Massimo</p> <p>2011-06-01</p> <p>Spatially averaged temperature and salinity profiles from individual cruises between 1990 and 2009 were analysed to outline the temporal evolution of water mass properties in the deep convection site in the South Adriatic Pit (SAP). The long-term <span class="hlt">variability</span> in thermohaline conditions has been explained and related to a close feedback mechanism between the Ionian and the Adriatic Sea. Prominent influences of the Eastern Mediterranean Transient are manifested in changes in the vertical temperature and salinity patterns in the South Adriatic, and the whole studied period was divided into three stages according to the main thermohaline characteristics: 1990-1995, 1995-2004 and the last period from 2005 onwards. Particular attention was given to data collected during 2006-2009, which permitted us to situate the actual thermohaline properties in the context of the <span class="hlt">decadal</span> <span class="hlt">variability</span>. This last period was characterised by a very low production of dense water in the northern basin during 2007, while from winter 2008 high production of North Adriatic Deep Water (NAdDW) and Adriatic Deep Water (AdDW) in the northern and southern basins, respectively, was <span class="hlt">observed</span>. Finally, we used the Optimum Multiparameter Analysis (OMP) to identify the percentages of the different water masses contained in the SAP, and this highlighted some differences between two recent periods studied (2007 and 2008) and the production of dense waters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3827215','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3827215"><span id="translatedtitle">Genetic <span class="hlt">Variability</span> of Microcystin Biosynthesis Genes in Planktothrix as Elucidated from Samples Preserved by Heat Desiccation during Three <span class="hlt">Decades</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ostermaier, Veronika; Christiansen, Guntram; Schanz, Ferdinand; Kurmayer, Rainer</p> <p>2013-01-01</p> <p>Historic samples of phytoplankton can provide information on the abundance of the toxigenic genotypes of cyanobacteria in dependence on increased or decreased eutrophication. The analysis of a time-series from preserved phytoplankton samples by quantitative PCR (qPCR) extends <span class="hlt">observation</span> periods considerably. The analysis of DNA from heat-desiccated samples by qPCR can be aggravated by point substitutions or the fragmentation of DNA introduced by the high temperature. In this study, we analyzed whether the heat desiccation of the cellular material of the cyanobacterium Planktothrix sp. introduced potential errors to the template DNA that is used for qPCR within (i) 16S rDNA and phycocyanin genes and (ii) the mcyA gene indicative of the incorporation of either dehydrobutyrine (Dhb) or N-methyl-dehydroalanine (Mdha) in position 7, and (ii) the mcyB gene, which is indicative of homotyrosine (Hty) in position 2 of the microcystin (MC) molecule. Due to high temperature desiccation, the deterioration of the DNA template quality was rather due to fragmentation than due to nucleotide substitutions. By using the heat-desiccated samples of Lake Zürich, Switzerland the abundance of the Dhb, Mdha and Hty genotypes was determined during three <span class="hlt">decades</span> (1977-2008). Despite major changes in the trophic state of the lake resulting in a major increase of the total Planktothrix population density, the proportion of these genotypes encoding the synthesis of different MC congeners showed high stability. Nevertheless, a decline of the most abundant mcyA genotype indicative of the synthesis of Dhb in position 7 of the MC molecule was <span class="hlt">observed</span>. This decline could be related to the gradual incline in the proportion of a mutant genotype carrying a 1.8kbp deletion of this gene region. The increase of this mcyA (Dhb) gene deletion mutant has been minor so far, however, and likely did not affect the overall toxicity of the population. PMID:24265798</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMPP21D..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMPP21D..07C"><span id="translatedtitle">Mid-Holocene onset of high-amplitude <span class="hlt">decadal</span> to centennial scale <span class="hlt">variability</span> along the Peru Chile Margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chazen, C. R.; Altabet, M.; Herbert, T. D.</p> <p>2008-12-01</p> <p>Understanding the natural climate variations in the eastern tropical Pacific is crucial for predicting the evolution of the El Niño-Southern Oscillation (ENSO) system and for anticipating the ways in which increases in atmospheric CO2 will affect climate. Here we present the first continuous, high-resolution (11-12 yr) climate record across the mid-Holocene transition (10ka-1.4ka) from the Peru-Chile Margin near the epicenter of the modern ENSO system. Although the high productivity of the Peru margin should promote high deposition rates, and the anaerobic bottom water conditions should inhibit sediment mixing by benthic organisms, nearly all sediment cores recovered from this region suffer from major gaps in Holocene sedimentation. Our data comes from a ~5 meter piston core collected from the mid-Peruvian shelf (15° 15"S, 75° 58"W, ~250mwd) in the heart of the oxygen minimum/denitrification zone that provides the first uninterrupted archive of conditions along the Peru-Chile margin. A suite of geochemical proxies allow us to reconstruct sea surface temperature (SST- Uk'37), phytoplankton productivity (C37total and %BSi), and thermocline ventilation (δ15N), <span class="hlt">variables</span> that are tightly correlated to ENSO events today. Despite the <span class="hlt">observation</span> that the mean late Holocene state of all three <span class="hlt">variables</span> did not change over the last 10,000 years, our data reveal a dramatic increase in climate <span class="hlt">variability</span> after the mid Holocene (~5ka); represented by prolonged periods (50-200yrs) of climate extremes, which are absent in the early Holocene. To further investigate these climate extremes we examine benthic foraminiferal assemblages and oxygen isotopes in combination with our other proxy records in selected late Holocene sections. The roughly centennial-scale oscillations do not show typical El Niño-La Niña correlations between proxies. We therefore posit that a significant fraction of super-ENSO variance during the course of the Holocene may originate outside the tropics, through processes that ventilate the subsurface waters of the eastern tropical Pacific and modify its subsurface density structure and nutrient properties. Super-ENSO <span class="hlt">variability</span> in SST may, however, have modulated the frequency of ENSO events over the Holocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910003184','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910003184"><span id="translatedtitle">Long-term Solar Irradiance <span class="hlt">Variability</span>: 1984-1989 <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lee, Robert B., III</p> <p>1990-01-01</p> <p>Long-term <span class="hlt">variability</span> in the total solar irradiance has been <span class="hlt">observed</span> 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 <span class="hlt">variability</span> 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 <span class="hlt">observed</span> irradiance <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3885547','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3885547"><span id="translatedtitle">Coral Luminescence Identifies the Pacific <span class="hlt">Decadal</span> Oscillation as a Primary Driver of River Runoff <span class="hlt">Variability</span> Impacting the Southern Great Barrier Reef</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rodriguez-Ramirez, Alberto; Grove, Craig A.; Zinke, Jens; Pandolfi, John M.; Zhao, Jian-xin</p> <p>2014-01-01</p> <p>The Pacific <span class="hlt">Decadal</span> Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere <span class="hlt">variability</span> on <span class="hlt">decadal</span> time scales. While precipitation and river flow <span class="hlt">variability</span> in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence <span class="hlt">variability</span> (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and <span class="hlt">decadal</span> <span class="hlt">variability</span> of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the <span class="hlt">variability</span> in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate <span class="hlt">variability</span>. PMID:24416214</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24416214','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24416214"><span id="translatedtitle">Coral luminescence identifies the Pacific <span class="hlt">Decadal</span> Oscillation as a primary driver of river runoff <span class="hlt">variability</span> impacting the southern Great Barrier Reef.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rodriguez-Ramirez, Alberto; Grove, Craig A; Zinke, Jens; Pandolfi, John M; Zhao, Jian-xin</p> <p>2014-01-01</p> <p>The Pacific <span class="hlt">Decadal</span> Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere <span class="hlt">variability</span> on <span class="hlt">decadal</span> time scales. While precipitation and river flow <span class="hlt">variability</span> in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence <span class="hlt">variability</span> (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and <span class="hlt">decadal</span> <span class="hlt">variability</span> of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the <span class="hlt">variability</span> in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate <span class="hlt">variability</span>. PMID:24416214</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611025P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611025P"><span id="translatedtitle">The ENSO or there and back again. Trying to understand the connection between its <span class="hlt">decadal</span> <span class="hlt">variability</span> and processes indexed by PDO, NAO and AMO</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Piskozub, Jacek; Gutowska, Dorota</p> <p>2014-05-01</p> <p>Recent research suggests that <span class="hlt">decadal</span> <span class="hlt">variability</span> in ENSO influence not only tropical Pacific SST values but also modulate the rate of change of global temperatures. It may be the main reason for the so called "global warming hiatus" of recent years. This makes it not only an interesting subject of scientific studies but also a subject of interest for general population. Especially predicting average <span class="hlt">decadal</span> ENSO activity would be important, if it would help predict the rate of global warming on <span class="hlt">decadal</span> scales. The only hope for such predictions in foreseeable future would come from understanding the relationship of ENSO <span class="hlt">variability</span> in <span class="hlt">decadal</span> scales to cycles of natural <span class="hlt">variability</span>. Several climate indices have quasi-cyclical components of about 60-70 years. The most obvious example is AMO, a proxy for Atlantic meridional overturning circulation (AMOC) <span class="hlt">variability</span>. However also <span class="hlt">variability</span> of NAO, the index of atmospheric zonal circulation in the North Atlantic sector, has component of similar period significantly correlated with AMO lagged by about 15 years. Even <span class="hlt">variability</span> of PDO the index of multidecadal <span class="hlt">variability</span> in Northern Pacific has a component of similar period and phase as NAO. Then, PDO correlates also with ENSO on <span class="hlt">decadal</span> scales. Correlation does not imply causation. This raises the question whether there are physical mechanisms behind the correlations. Tropical Pacific temperatures have been shown to influence surface pressure in the North Eastern Pacific influencing zonal circulation which may explain the PDO - NAO "teleconnection". Zonal winds influence the rate of deep water production in Labrador and Greenland seas, which may explain its influence on the rate of change in deep water production (the NAO - AMO correlation lagged by cycle). AMO being a proxy of AMOC (heat transport from South to North Hemisphere) obviously influences the inter-hemispherical temperature difference. We have recently showed the statistically significant anticorrelation of this NH-SH temperature difference on ENSO, explaining it by the influence on the position of ITCZ and trade winds. We use statistical analysis of climate indices and discuss the underlying physical processes to argue for existence of causal connection between them. This study tries to create a framework for understanding climate <span class="hlt">variability</span> in Pacific and Atlantic sectors on multidecadal scales as a quasi-cycle of about 65 years involving both ocean and atmospheric circulation involving processes indexed by PDO, NAO, AMO and influencing ENSO <span class="hlt">variability</span> on <span class="hlt">decadal</span> scales. We do not believe this is the final word in this field. Rather a good start.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950053165&hterms=rise&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Drise','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950053165&hterms=rise&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Drise"><span id="translatedtitle"><span class="hlt">Decadal</span>-to-centennial-scale climate <span class="hlt">variability</span>: Insights into the rise and fall of the Great Salt Lake</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mann, Michael E.; Lall, Upmanu; Saltzman, Barry</p> <p>1995-01-01</p> <p>We demonstrate connections between <span class="hlt">decadal</span> and secular global climatic variations, and historical variations in the volume of the Great Salt Lake. The <span class="hlt">decadal</span> variations correspond to a low-frequency shifting of storm tracks which influence winter precipitation and explain nearly 18% of the interannual and longer-term variance in the record of monthly volume change. The secular trend accounts for a more modest approximately 1.5% of the variance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRF..117.2030J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRF..117.2030J"><span id="translatedtitle">Seasonal to <span class="hlt">decadal</span> scale variations in the surface velocity of Jakobshavn Isbrae, Greenland: <span class="hlt">Observation</span> and model-based analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Joughin, Ian; Smith, Ben E.; Howat, Ian M.; Floricioiu, Dana; Alley, Richard B.; Truffer, Martin; Fahnestock, Mark</p> <p>2012-06-01</p> <p>Using new data, we build upon the nearly two-<span class="hlt">decade</span> long record of <span class="hlt">observations</span> from Jakobshavn Isbrae to investigate the processes driving its dynamic evolution. While winter flow speed has not increased substantially over the last three winters, there remains a strong seasonal variation in flow speed that coincides with a cycle of summer thinning and winter thickening. We relate changes in glacier speed to geometry through variations in basal traction and horizontal stresses, using ice-flow models constrained by satellite and airborne <span class="hlt">observations</span>. These results suggest that the bed provides little flow resistance along the main trough within about 20 km of the terminus. While the loss of buttressing from the retreat of grounded and floating ice likely contributed to the initial speedup, other processes are of comparable significance at seasonal to <span class="hlt">decadal</span> time scales. From analysis of the models, we hypothesize that thinning-induced change in basal effective pressure is the dominant process influencing near-terminus behavior, while diffusive processes drive the upstream response. The apparent need for the terminus to thin to near flotation before it can calve may limit the rate at which retreat occurs. Our analysis of the processes controlling the speed suggests little potential for further large acceleration. Thinning and elevated speeds may continue at rates similar to present, however, putting the glacier on course to retreat to the head of its deep trough in about a century, at which point it likely would stabilize with a thinner terminus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006656','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006656"><span id="translatedtitle">Atmospheric CO2 <span class="hlt">Variability</span> <span class="hlt">Observed</span> From ASCENDS Flight Campaigns</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lin, Bing; Browell, Edward; Campbell, Joel; Harrison, F. Wallace; Kooi, Susan; Liu, Zhaoyan; Nehrir, Amin; Obland, Michael; Choi, Yonghoon; Dobler, Jeremy; Fan, Tai-Fang; Meadows, Byron; Plant, James; Yang, Melissa</p> <p>2015-01-01</p> <p>Significant atmospheric CO2 variations on various spatiotemporal scales were <span class="hlt">observed</span> during ASCENDS flight campaigns. For example, around 10-ppm CO2 changes were found within free troposphere in a region of about 200x300 sq km over Iowa during a summer 2014 flight. Even over extended forests, about 2-ppm CO2 column <span class="hlt">variability</span> was measured within about 500-km distance. For winter times, especially over snow covered ground, relatively less horizontal CO2 <span class="hlt">variability</span> was <span class="hlt">observed</span>, likely owing to minimal interactions between the atmosphere and land surface. Inter-annual variations of CO2 drawdown over cornfields in the Mid-West were found to be larger than 5 ppm due to slight differences in the corn growing phase and meteorological conditions even in the same time period of a year. Furthermore, considerable differences in atmospheric CO2 profiles were found during winter and summer campaigns. In the winter CO2 was found to decrease from about 400 ppm in the atmospheric boundary layer (ABL) to about 392 ppm above 10 km, while in the summer CO2 increased from 386 ppm in the ABL to about 396 ppm in free troposphere. These and other CO2 <span class="hlt">observations</span> are discussed in this presentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.9360S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.9360S"><span id="translatedtitle">Sea surface temperature and salinity <span class="hlt">variability</span> in the Levantine Basin during the last <span class="hlt">decade</span>, 1996 to 2006</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Samuel-Rhoads, Y.; Iona, S.; Zodiatis, G.; Hayes, D.; Gertman, I.; Georgiou, G.</p> <p>2009-04-01</p> <p>The reality of global warming since the industrial era is manifested in part by changes in global surface temperatures. Regional temperature increases have also been reported in the Mediterranean Sea, where sea surface temperatures (SSTs) across the Mediterranean as a whole, have been rising about twice as much as those of the global oceans. Here we analyse and compare satellite remote sensing SST data with in-situ data for the period 1996-2006 in the Levantine Basin. Satellite data were collected by the NOAA/NASA Advanced Very High Resolution Radiometers (AVHRR) and processed by the SST Pathfinder program. For our analyses we obtained monthly averaged Level 3, version 5.0, global SST data from the nighttime pass of the satellite at a 4-km resolution and an equal-angle grid of 8192 pixels/360° from January 1996 through December 2006. Monthly quality control flag files for the SST data were also obtained from January 1996 through December 2006 from the same source. Further, 23,000 vertical profiles of temperature and salinity from 160 oceanographic cruises were extracted from the MEDAR/MEDATLAS, WDC-A and the Coriolis databases for the period 1996-2006, in order to study the interannual <span class="hlt">variability</span> in this basin at the surface layer (0-10m). Annual gridded fields were calculated by averaging the top 10m of the in-situ data, and then interpolated horizontally by the Variational Inverse Method (VIM) and a finite element technique using the SeaDataNet Geostatistical Analysis Tool - DIVA. Satellite SST data indicate that over the last 11 years a general warming has occurred over the Levantine Basin, both at interannual and seasonal time scales. This increase in average SSTs is also seen in the seasonal averages, especially during the spring and summer. Moreover, the averages from the top 10m of in-situ SST, using the relevant data from the above oceanographic databases, show a correlation with the satellite SST data particularly at seasonal time scales. Satellite remote sensing data are thus a very good indicator of environmental conditions. We also analyse in-situ sea surface salinity (SSS) data collected over the same period of time to determine any similarities in the patterns of <span class="hlt">variability</span> with SSTs. The pattern of SST <span class="hlt">variability</span> is shared by the patterns of SSS. Therefore, it can be expected that the Levantine Basin has also undergone salinity increases during the last 11 years. Finally, we investigate the <span class="hlt">variability</span> in regional wind speeds and latent heat fluxes as possible driving mechanisms of the changes <span class="hlt">observed</span> in SST and SSS. It will be valuable to investigate future trends in SSTs to determine whether the <span class="hlt">observed</span> patterns of SSTs represent a continued pattern of persistent warming or a new direction for an ever-changing Levantine Basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1311528','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1311528"><span id="translatedtitle"><span class="hlt">Variability</span> of expert <span class="hlt">observers</span> in evaluating the optic disc.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lichter, P R</p> <p>1976-01-01</p> <p>A significant amount of <span class="hlt">variability</span> exists between <span class="hlt">observers</span> in designating cup/diac (C/D) ratios. Further, different methods are used for evaluating the size of the cup. On method uses a combination of contour and color, the other specifically measures contour and pallor separately. This study confirms that these methods yeild different numerical results. Interestingly, the "cupping/pallor" <span class="hlt">observers</span> show no significant difference among one another in C/D determination which may support the notion that cupping <span class="hlt">observations</span> are more consistent than "standard" C/D ratios. Though both groups feel the cup is larger on stereo compared to monocular viewing, the "cupping/pallor" group demonstrated much greater differences in this regard. However, the evaluation of pallor by the latter group corresponded closely to the C/D ratios of the "standard" group both for nonstereo and stereo. An individual <span class="hlt">observer</span> is reasonably consistent on repeat evaluation, but at times, inconsistency is quite substantial. These inconsistencies lead to the conclusion that C/D ratios are an inexact method of recording the status of a disc. Except for considerable changes over time, this numerical method is probably not reliable in checking for small disc changes. However, the disc alone can provide clues as to whether it is physiologic or pathologic. Nevertheless, even with expert <span class="hlt">observers</span>, significant <span class="hlt">variability</span> exists in interpretation of an optic disc in this regard. Individuals who evaluate the disc cup by cupping and pallor tend to call discs more pathologic than other <span class="hlt">observers</span>. The clinical implications of this study suggest that certain <span class="hlt">observers</span> are more accurate than others and certain discs are more easily evaluated than others. Yet, no one method seems foolproof and no specific criteria can as yet distinguish a normal from an abnormal disc. Stereo color transparencies are evaluated more accurately than are nonstereo color prints. Vessel detail and pallor patterns are probably the most useful disc characteristics to <span class="hlt">observe</span>. In this regard, a C/D ratio does nothing to indicate whether a disc is normal or not. A statement as to the <span class="hlt">observer</span>'s opinion should be made for each disc evaluation in addition to recording the appearance of the disc. Images FIGURE 4 1 FIGURE 4 2 FIGURE 4 3 FIGURE 4 4 FIGURE 4 5 FIGURE 4 6 FIGURE 4 7 FIGURE 4 8 FIGURE 4 9 FIGURE 4 10 FIGURE 4 11 FIGURE 4 12 FIGURE 4 13 FIGURE 4 14 FIGURE 4 15 FIGURE 4 16 FIGURE 4 17 FIGURE 4 18 FIGURE 4 19 FIGURE 4 20 PMID:867638</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020080613','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020080613"><span id="translatedtitle">Subtropical Gyre <span class="hlt">Variability</span> <span class="hlt">Observed</span> by Ocean Color Satellites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McClain, Charles R.; Signorini, Sergio R.; Christian, James R.</p> <p>2002-01-01</p> <p>The subtropical gyres of the world are extensive, coherent regions that occupy about 40% of the surface of the earth. Once thought to be homogeneous and static habitats, there is increasing evidence that mid-latitude gyres exhibit substantial physical and biological <span class="hlt">variability</span> on a variety of time scales. While biological productivity within these oligotrophic regions may be relatively small, their immense size makes their total contribution significant. Global distributions of dynamic height derived from satellite altimeter data, and chlorophyll concentration derived from satellite ocean color data, show that the dynamic center of the gyres, the region of maximum dynamic height where the thermocline is deepest, does not coincide with the region of minimum chlorophyll concentration. The physical and biological processes by which this distribution of ocean properties is maintained, and the spatial and temporal scales of <span class="hlt">variability</span> associated with these processes, are analyzed using global surface chlorophyll-a concentrations, sea surface height, sea surface temperature and surface winds from operational satellite and meteorological sources, and hydrographic data from climatologies and individual surveys. Seasonal and interannual <span class="hlt">variability</span> in the areal extent of the subtropical gyres are examined using 8 months (November 1996 - June 1997) of OCTS and nearly 5 years (September 1997 - June 02) of SeaWiFS ocean color data and are interpreted in the context of climate <span class="hlt">variability</span> and measured changes in other ocean properties (i.e., wind forcing, surface currents, Ekman pumping, and vertical mixing). The North Pacific and North Atlantic gyres are <span class="hlt">observed</span> to be shrinking over this period, while the South Pacific, South Atlantic, and South Indian Ocean gyres appear to be expanding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110006887','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110006887"><span id="translatedtitle">Solar Plasma <span class="hlt">Variability</span> <span class="hlt">Observations</span> from the Solar Dynamics Observatory</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chamberlin, Phillip C.</p> <p>2011-01-01</p> <p>The launch of the Solar Dynamics Observatory (SDO) in February 2010 allows for continuous <span class="hlt">observations</span> of the Sun on all times scales from seconds to years. These variations in the solar plasma cause significant deviations in the Earth and space environments on similar time scales, such as affecting the atmospheric densities and composition of particular atoms, molecules, and ions in the atmospheres of the Earth and other planets. Presented and discussed will be examples of initial results using the data from SDO that show how we can trace the origins of solar activity from inside the Sun using different wavelengths, and therefore different temperatures (from 50,OOOK to 20MK+) that cover the atmosphere and plasma temperature range of the solar atmosphere. The presentation will emphasize how the Solar Dynamics Observatory (SDO), the first satellite in NASA's Living with a Star program, is going to improve upon current <span class="hlt">observations</span> and provide further insights into the <span class="hlt">variable</span> Sun and its Heliospheric influence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS53E..05C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS53E..05C"><span id="translatedtitle">Seasonal to <span class="hlt">Decadal</span> <span class="hlt">Variability</span> in the Upper Ocean Scattering Layer in Drake Passage in Relation to Atmospheric and Oceanic Forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chereskin, T. K.; Koenig, Z.</p> <p>2012-12-01</p> <p>The surface shoaling of nutrient-rich waters poleward across the Antarctic Circumpolar Current is responsible for the elevated productivity of the Southern Ocean. Over the last half century, the Southern Ocean has been warming at a faster rate than the global ocean as a whole. In particular, the Antarctic Peninsula region has undergone rapid atmospheric warming, significant glacial retreat and a decrease in seasonal sea ice extent, impacting krill and its predators. Improving knowledge of the Southern Ocean is a high priority for understanding the effects of climate change, but the harsh environment poses substantial <span class="hlt">observational</span> challenges. The U.S. Antarctic Research and Supply Vessel Laurence M. Gould crosses Drake Passage 2-4 times per month in all seasons, collecting underway data on transits between Punta Arenas, Chile and Palmer Station, Antarctica. High-resolution measurements of upper ocean temperature, salinity, velocity and acoustic backscatter, along with concurrent meteorological, surface water CO2 and nutrient measurements have been routinely acquired since the late 1990s. This study makes use of 238 acoustic Doppler current profiler (ADCP) transects collected over a 12-year period to remotely sense the characteristics of the near-surface scattering layer, which at 153.6 kHz is dominated by macrozooplankton. Although the primary use of the shipboard ADCP is to measure ocean currents, the measured acoustic backscatter has provided valuable insights into the depth distributions, vertical migration behaviors and even life cycles of dominant biological scatterers. Diel vertical migration and a well defined annual cycle are <span class="hlt">observed</span>, consistent with krill behavior. Significant geographic variations are present on both seasonal and interannual time scales. Interannual <span class="hlt">variability</span> is linked to two main climate modes, the El Niño-Southern Oscillation and the Southern Annular Mode, as well as to variations in seasonal sea ice extent. Limitations of the present study and proposed sampling to address them will also be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFMPP51E1360K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFMPP51E1360K"><span id="translatedtitle">Solar vs. Tidal Forcing of Centennial to <span class="hlt">Decadal</span> Scale <span class="hlt">Variability</span> in Marine Sedimentary Records from the Western Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirkwood, G.; Domack, E.; Brachfeld, S.</p> <p>2004-12-01</p> <p>Prior studies on Holocene marine sediments from the Antarctic Peninsula, including ODP Site 1098 and USAP N. B. Palmer jumbo piston cores have revealed pronounced multi-century scale variations within a number of paleoenvironmental proxies. In order to fully understand the exact timing of this signal an ultra-high resolution jumbo piston core from the Schollaert Drift was correlated with the well-known Palmer Deep record. A precise and accurate radiocarbon chronology is now available from the former site that utilizes in-situ mollusks, rather than bulk organic matter. The resulting time series spans the last 5000 years over the 20 m length of core NBP99-03 JPC28 and the surface stratigraphy of kasten core NBP01-07 KC8. The corrected and calibrated ages (with an applied reservoir correction of 1170 years) of 10 mollusks dated by the National Ocean Sciences Accelerator Mass Spectrometry Facility and the University of Arizona TAMS facility were used to construct an age-depth profile for JPC28 and KC8. A linear trend (R2 value of 0.993) of the age-depth profile was used to extrapolate the constant time interval between magnetic susceptibility measurements, which were analyzed every 1 cm. Dominant periods in the upper 10 m of the time series were identified using the Arand Spectral Analysis Package (Howell, 2001). This analysis revealed a single pronounced maxima at 160 years, which is inconsistent with the dominant periods found in time series of climate proxies from other sites on the western side of the Antarctic Peninsula. In particular, periods of 200 and 400 years, which are dominant in the Palmer Deep site (Warner and Domack, 2002), are not present in the Schollaert Drift. The spectral peaks derived from the two records are significantly different at the 95% confidence level. The cycles in the Palmer Deep record have been associated with solar <span class="hlt">variability</span>, where as the 160 year cycle in the Schollaert Drift is close to a 180 year cycle in tidal forces (Keeling and Whorf, 2000). We discuss these alternative forcing mechanisms with respect to: contrasts in regional processes of glacial marine sedimentation, the mechanism whereby the tidal or solar signal is transferred to the sediment column and possible cryptic stratigraphy of the Palmer Deep record (ie. missing time, Nederbragt and Thurow, 2002). Resolution of the correct forcing factor is critical to our ability to hind cast the last 100 years of paleoenvironmental data within these cores and hence to our attempts at recognizing an anthropogenic climate signal in the Antarctic Peninsula region. Howell, P. (2001), ARAND time series and spectral analysis package for the Macintosh, Brown University, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2001-044, NOAA/NGDC Paleoclimatology Program, Boulder, Colo. Keeling, Charles D., and Timothy P. Whorf (2000), The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change, Proc. Natl. Acad. Sci., 97 (8), 3814-3819. Nederbragt, A. J., and Thurow, J. (2002) Sediment color variation and annual accumulation rates in laminated Holocene sediments, Site 1098, Palmer Deep. In Barker, P. F., Camerlenghi, A., Acton, G. D., and Ramsay, A.T.S. (eds), Proc. ODP Sci. Results, 178: College Station TX (Ocean Drilling Program). Warner, Nathaniel R., and E. Domack (2002), Millennial-to <span class="hlt">decadal</span>-scale paleoenvironmental change during the Holocene in the Palmer Deep, Antarctica, as recorded by particle size analysis, Paleoceanography, 17 (3), 8004, doi:10.1029/2000PA000602.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMPP43B1671F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMPP43B1671F"><span id="translatedtitle">Interannual and <span class="hlt">decadal</span> <span class="hlt">variability</span> of East Asian Winter Monsoon and ENSO detected in a 120-year coral record from the eastern coast of the Philippines</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fukushima, A.; Kawahata, H.; Suzuki, A.; Kojima, K.; Okai, T.; Ishimura, T.; Siringan, F. P.</p> <p>2010-12-01</p> <p>Coral skeletal climatology has provided increasing knowledge of tropical ocean-atmosphere interaction such as El Niño Southern Oscillation (ENSO). On the other hand, there are only few studies regarding the Asian Monsoon although it also plays an important role in the global climate system. Here we present a 120-year Sr/Ca and δ18O of the coral (δ18Ocoral) record (1883-2002) from the eastern coast of the Philippines. Spectral analyses of both time series showed significant quasi-biennial periodicity, which indicated the Tropospheric Biennial Oscillation (TBO) related to the Monsoon system. The δ18Ocoral time series also identified interannual (3.8 and 8.2 years) and <span class="hlt">decadal</span> (22 years) periodicity. The former indicated ENSO-related frequency. Our reconstruction revealed that winter sea surface temperature (SST) is significantly correlated with East Asian Winter Monsoon Index (WMI) especially within climatic regimes. Then, we showed that the intensity of EAWM had changed on the <span class="hlt">decadal</span> scale using possible regime shift detection method based on the sequential t-test. This transition occurred around regime shift years. It is suggested that winter SST <span class="hlt">variability</span> in this region reflects the change of the wind pattern related to the <span class="hlt">decadal</span> <span class="hlt">variability</span> often found in the mid-latitudes. Our results suggest the potential of Philippines’ coral for monitoring the large-scale climate <span class="hlt">variability</span> on the <span class="hlt">decadal</span> scale.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E2548P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E2548P"><span id="translatedtitle">Ground based <span class="hlt">observations</span> of Io plasma torus <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pinho Magalhes, Fabola; Echer, Ezequiel; Demtrio Gonzalez Alarcon, Walter; Lopes, Rosaly; Morgenthaler, Jeffrey; Echer, Mariza P. S.</p> <p></p> <p>Jupiter is not only the largest planet in the Solar System, it also has the largest magnetosphere. Jupiter's innermost Galilean moon, Io, is the most volcanically active body in the Solar System. This volcanic activity produces tenuous atmosphere which escapes, creating the Io plasma torus, a ring of charged particles encircling Jupiter. The Io plasma torus is composed mainly of sulfur and oxygen ions. It is most dense around Io's orbit (5.6 Rj). It's <span class="hlt">observed</span> in extreme ultraviolet (EUV) emission and in the optical. EUV emission arise from interactions between torus superthermal ("hot") electrons and ions. Optical emission comes from interaction between thermal electrons and sulfur ions. The optical emission trace the densest part of the torus, the EUV trace the hottest part of the torus. In early December, 2013, we <span class="hlt">observed</span> the Io plasma torus at the McMath-Pierce Solar Telescope using a specially designed coronagraph in support of the JAXA EXtrem ultraviolet spectrosCope for ExophEric Dynamics (EXCEED) mission. EXCEED is <span class="hlt">observing</span> the Io plasma torus in the EUV in a manner similar to that of the landmark <span class="hlt">observations</span> made by the Cassini UVIS instrument in 2000. Our ground-based [SII] 6731 angstrom images provide context for the EXCEED <span class="hlt">observations</span>. The analysis of the 2013 [SII] data is important preparation for analysis of a much larger set of <span class="hlt">observations</span> recorded between 1997 and 2008. This large set of over 1000 images were recorded during the Galileo tour, the Cassini flyby, and the Ulysses flyby of Jupiter. The images provide context for in-situ <span class="hlt">observations</span>, EUV images, and several new measurements of the mysterious and <span class="hlt">variable</span> Jovian magnetospheric "system IV" period. In this work, we'll be presenting a comparison between our results and EXCEED's and the methodology which will be used for the 1000 images.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20010015246&hterms=global+warming+temperature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dglobal%2Bwarming%2Btemperature','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010015246&hterms=global+warming+temperature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dglobal%2Bwarming%2Btemperature"><span id="translatedtitle">Satellite <span class="hlt">Observed</span> <span class="hlt">Variability</span> in Antarctic and Arctic Surface Temperatures and Their Correlation to Open Water Areas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, Josefino C.; Zukor, Dorothy (Technical Monitor)</p> <p>2000-01-01</p> <p>Recent studies using meterological station data have indicated that global surface air temperature has been increasing at a rate of 0.05 K/<span class="hlt">decade</span>. Using the same set of data but for stations in the Antarctic and Arctic regions (>50 N) only, the increases in temperature were 0.08, and 0.22 K/<span class="hlt">decade</span>, when record lengths of 100 and 50 years, respectively, were used. To gain insights into the increasing rate of warming, satellite infrared and passive microwave <span class="hlt">observations</span> over the Arctic region during the last 20 years were processed and analyzed. The results show that during this period, the ice extent in the Antarctic has been increasing at the rate of 1.2% per <span class="hlt">decade</span> while the surface temperature has been decreasing at about 0.08 K per <span class="hlt">decade</span>. Conversely, in the Northern Hemisphere, the ice extent has been decreasing at a rate of 2.8% per <span class="hlt">decade</span>, while the surface temperatures have been increasing at the rate of 0.38 K per <span class="hlt">decade</span>. In the Antarctic, it is surprising that there is a short term trend of cooling during a global period of warming. Very large anomalies in open water areas in the Arctic were <span class="hlt">observed</span> especially in the western region, that includes the Beaufort Sea, where the <span class="hlt">observed</span> open water area was about 1x10(exp 6) sq km, about twice the average for the region, during the summer of 1998. In the eastern region, that includes the Laptev Sea, the area of open water was also abnormally large in the summer of 1995. Note that globally, the warmest and second warmest years in this century, were 1998 and 1995, respectively. The data, however, show large spatial <span class="hlt">variability</span> with the open water area distribution showing a cyclic periodicity of about ten years, which is akin to the North Atlantic and Arctic Oscillations. This was <span class="hlt">observed</span> in both western and eastern regions but with the phase of one lagging the other by about two years. This makes it difficult to interpret what the trends really mean. But although the record length of satellite data is still relatively short and the climate trend difficult to establish, the immediate impact of a continued warming trend may be very profound.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000070387&hterms=microwaves+works&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmicrowaves%2Bworks','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000070387&hterms=microwaves+works&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmicrowaves%2Bworks"><span id="translatedtitle"><span class="hlt">Observations</span> of Land Surface <span class="hlt">Variability</span> Using Passive Microwave Sensing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Njoku, Eni G.</p> <p>1999-01-01</p> <p>Understanding the global <span class="hlt">variability</span> of land surface wetness (soil moisture), skin temperature, and related surface fluxes of heat and moisture is key to assessing the importance of the land surface in influencing climate. The feasibility of producing model estimates of these quantities is being studied as part of the International Satellite Land Surface Climatology Project (ISLSCP) Global Soil Wetness Project (GSWP). In the GSWP approach, meteorological <span class="hlt">observations</span> and analyses are used to drive global circulation models. Satellite measurements can provide independent estimates of key land surface parameters that are needed for initializing and validating the climate models and for monitoring long-term change. Satellite <span class="hlt">observations</span> of the land surface can also be assimilated into soil models to estimate moisture in the root zone. In our research, passive microwave satellite data recorded during 1978-1987 from the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) are being used to examine spatial and temporal trends in surface soil moisture, vegetation, and temperature. These data include <span class="hlt">observations</span> at C and X bands (6.6 and 10.7 GHz), which are not available on the current Special Sensor Microwave/Imager (SSM/I) and are precursors to data that will become available from the Advanced Microwave Scanning Radiometer (AMSR) on Advanced Earth <span class="hlt">Observing</span> Satellite (ADEOS-II) and Earth <span class="hlt">Observing</span> System (EOS) PM1 in the year 2000. A chart shows a time-series of SMMR-derived surface temperature, T-e and surface soil moisture M, retrieved on a 0.5 deg x 0.5 deg grid and further averaged over a 4 deg x 10 deg study region in the African Sahel. Also shown are National Center for Environmental Prediction (NCEP) model outputs of surface temperature, T-sfc, and soil wetness, Soil-w. The <span class="hlt">variables</span> have been scaled to have similar dynamic ranges on the plots. The NCEP data from the NCEP Reanalysis Project are monthly averages on a 2.5 deg x 2.5 deg grid averaged over the 4 deg x 10 deg study area. Comparisons of SMMR retrievals with forecast model output show the potential of the satellite data for validating model output and monitoring long-term trends. Continuing work will extend these results to other regions to validate the retrievals more quantitatively. In preparation for the launch of AMSR, field experiments are planned in collaboration with the Global Energy and Water Cycle Experiment (GEWEX) Coordinated Enhanced <span class="hlt">Observing</span> Period (CEOP) experiments to evaluate the satellite-derived soil moisture measurements and to demonstrate their usefulness for land surface hydrology and climate. Additional information is contained in the original.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22714423P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22714423P"><span id="translatedtitle">Analysis of Kepler <span class="hlt">Observations</span> of ASAS <span class="hlt">Variable</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pezzato, Jacklyn M.; Mighell, Kenneth J.</p> <p>2016-01-01</p> <p>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 <span class="hlt">Variable</span> 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 <span class="hlt">observed</span> by the Kepler Mission were selected for analysis, for a total of 599 targets. The <span class="hlt">observations</span> 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 <span class="hlt">observation</span> schedule to that of the ASAS survey, similar issues can be expected with the analysis of LSST data for some types of long period <span class="hlt">variables</span>, 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).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23996901','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23996901"><span id="translatedtitle">Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining <span class="hlt">decadal</span>-scale biological <span class="hlt">variability</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Litzow, Michael A; Mueter, Franz J; Hobday, Alistair J</p> <p>2014-01-01</p> <p>In areas of the North Pacific that are largely free of overfishing, climate regime shifts - abrupt changes in modes of low-frequency climate <span class="hlt">variability</span> - are seen as the dominant drivers of <span class="hlt">decadal</span>-scale ecological <span class="hlt">variability</span>. We assessed the ability of leading modes of climate <span class="hlt">variability</span> [Pacific <span class="hlt">Decadal</span> Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), Arctic Oscillation (AO), Pacific-North American Pattern (PNA), North Pacific Index (NPI), El Niño-Southern Oscillation (ENSO)] to explain <span class="hlt">decadal</span>-scale (1965-2008) patterns of climatic and biological <span class="hlt">variability</span> across two North Pacific ecosystems (Gulf of Alaska and Bering Sea). Our response <span class="hlt">variables</span> were the first principle component (PC1) of four regional climate parameters [sea surface temperature (SST), sea level pressure (SLP), freshwater input, ice cover], and PCs 1-2 of 36 biological time series [production or abundance for populations of salmon (Oncorhynchus spp.), groundfish, herring (Clupea pallasii), shrimp, and jellyfish]. We found that the climate modes alone could not explain ecological <span class="hlt">variability</span> in the study region. Both linear models (for climate PC1) and generalized additive models (for biology PC1-2) invoking only the climate modes produced residuals with significant temporal trends, indicating that the models failed to capture coherent patterns of ecological <span class="hlt">variability</span>. However, when the residual climate trend and a time series of commercial fishery catches were used as additional candidate <span class="hlt">variables</span>, resulting models of biology PC1-2 satisfied assumptions of independent residuals and out-performed models constructed from the climate modes alone in terms of predictive power. As measured by effect size and Akaike weights, the residual climate trend was the most important <span class="hlt">variable</span> for explaining biology PC1 <span class="hlt">variability</span>, and commercial catch the most important <span class="hlt">variable</span> for biology PC2. Patterns of climate sensitivity and exploitation history for taxa strongly associated with biology 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 <span class="hlt">variability</span>, climate regime shift effects can only be understood in the context of other ecosystem perturbations. PMID:23996901</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22127076','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22127076"><span id="translatedtitle"><span class="hlt">OBSERVATIONS</span> OF THERMAL FLARE PLASMA WITH THE EUV <span class="hlt">VARIABILITY</span> EXPERIMENT</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Warren, Harry P.; Doschek, George A.; Mariska, John T.</p> <p>2013-06-20</p> <p>One of the defining characteristics of a solar flare is the impulsive formation of very high temperature plasma. The properties of the thermal emission are not well understood, however, and the analysis of solar flare <span class="hlt">observations</span> is often predicated on the assumption that the flare plasma is isothermal. The EUV <span class="hlt">Variability</span> Experiment (EVE) on the Solar Dynamics Observatory provides spectrally resolved <span class="hlt">observations</span> of emission lines that span a wide range of temperatures (e.g., Fe XV-Fe XXIV) and allow for thermal flare plasma to be studied in detail. In this paper we describe a method for computing the differential emission measure distribution in a flare using EVE <span class="hlt">observations</span> and apply it to several representative events. We find that in all phases of the flare the differential emission measure distribution is broad. Comparisons of EVE spectra with calculations based on parameters derived from the Geostationary Operational Environmental Satellites soft X-ray fluxes indicate that the isothermal approximation is generally a poor representation of the thermal structure of a flare.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850050743&hterms=TELECONNECTION&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DTELECONNECTION','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850050743&hterms=TELECONNECTION&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DTELECONNECTION"><span id="translatedtitle">Climate <span class="hlt">variability</span> and atmospheric teleconnection from satellite <span class="hlt">observed</span> cloud fluctuations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, K. M.; Chan, P. H.</p> <p>1983-01-01</p> <p>To investigate the low-frequency <span class="hlt">variability</span> of the large-scale circulation over the tropics and its relationship with different regions of the globe, statistics of cloud fluctuations, as inferred from outgoing longwave radiation (OLR) are used. The data consists of seven years of global OLR in a 2.5 x 2.5-deg grid derived from NOAA polar orbiting satellite <span class="hlt">observations</span>. The time series of area-averaged monthly deviation from the seven-year mean of OLR over an equatorial Central Pacific region is presented. It is shown that positive and negative deviations reflect local drier and wetter than normal conditions, respectively. Consideration is given to teleconnection based on the Central Pacific variations and to southern oscillation contributions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20080023356&hterms=soil+study+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsoil%2Bstudy%2Bmodel','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20080023356&hterms=soil+study+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsoil%2Bstudy%2Bmodel"><span id="translatedtitle">Field <span class="hlt">Observations</span> of Soil Moisture <span class="hlt">Variability</span> across Scales</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Famiglietti, James S.; Ryu, Dongryeol; Berg, Aaron A.; Rodell, Matthew; Jackson, Thomas J.</p> <p>2008-01-01</p> <p>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 <span class="hlt">variability</span> 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 <span class="hlt">variability</span> 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 <span class="hlt">observed</span> behavior of soil moisture <span class="hlt">variability</span> 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 <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.V13C2137P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.V13C2137P"><span id="translatedtitle">Building on <span class="hlt">Decades</span> of Research on the McMurdo Volcanic Group, Antarctica: A Geologic Field Guide to <span class="hlt">Observation</span> Hill</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pound, K. S.; Panter, K. S.</p> <p>2008-12-01</p> <p>Based on more than four <span class="hlt">decades</span> of research on the rocks of the Erebus Volcanic Province of the McMurdo Volcanic Group, a geologic field guide to the <span class="hlt">Observation</span> 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 <span class="hlt">Observation</span> Hill in exploration literature, there was little in the way of easily-accessible information about the geologic history of Hut Point and <span class="hlt">Observation</span> 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 <span class="hlt">Observation</span> Hill. Questions also focused on smaller scale features of the landscape (e.g. patterned ground) and textures and minerals <span class="hlt">observed</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP51C..02Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP51C..02Y"><span id="translatedtitle"><span class="hlt">Decadal</span>- and Centennial-Scale <span class="hlt">Variability</span> in Sea Surface Temperature in Beppu Bay in Japan During the Last 2900 Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, M.; Kuwae, M.; Abe, M.; Ichikawa, N.</p> <p>2012-12-01</p> <p>We generated 8-year-resolution records of paleotemperatures using UK37‧ and TEX86 and discuss the <span class="hlt">decadal</span> and centennial changes in winter and summer sea surface temperatures (SSTs) in Beppu Bay, Kyushu Island, Japan. Beppu Bay is a silled basin filled with oxygen-deficient bottom water. Because of anoxic environment, organic matter is well preserved in sediments and bioturbation is limited. Fourteen piston and gravity cores were retrieved at the center of the basin. Correlation of cores was conducted using sand and silt seams, and the age-depth model was created by wiggle-matching of forty-two AMS radiocarbon dates from bivalve mollusk shells and excess Pb-210 and Cs-137 concentrations. The sedimentation rates were 230-300 cm/ky. TEX86 and UK37‧ records show different patterns, but both have a similar multi-<span class="hlt">decadal</span> periodicity. The temperature estimated by TEX86 at the core-top sample is lower than mean annual SST, implying that TEX86 reflects the SST weighted in winter. That by UK37‧ corresponds to the SST weighted in summer. UK37‧ shows multi-<span class="hlt">decadal</span> and centennial-scale variation interrupted by frequent short-term cool periods. The periods corresponded to volcanic eruptions recorded in a Greenland ice core. TEX86 shows multi-<span class="hlt">decadal</span> variation that is consistent with a proxy PDO record reconstructed from North American tree-rings. Beppu Bay sediments are a good climate archive to provide high-resolution summer and winter SST records in the northwestern Pacific region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4427210','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4427210"><span id="translatedtitle"><span class="hlt">Variability</span> in the Initial Costs of Care and One-Year Outcomes of <span class="hlt">Observation</span> Services</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Abbass, Ibrahim</p> <p>2015-01-01</p> <p>Introduction The use of <span class="hlt">observation</span> units (OUs) following emergency departments (ED) visits as a model of care has increased exponentially in the last <span class="hlt">decade</span>. About one-third of U.S. hospitals now have OUs within their facilities. While their use is associated with lower costs and comparable level of care compared to inpatient units, there is a wide variation in OUs characteristics and operational procedures. The objective of this research was to explore the <span class="hlt">variability</span> in the initial costs of care of placing patients with non-specific chest pain in <span class="hlt">observation</span> units (OUs) and the one-year outcomes. Methods The author retrospectively investigated medical insurance claims of 22,962 privately insured patients (2009–2011) admitted to 41 OUs. Outcomes included the one-year chest pain/cardiovascular related costs and primary and secondary outcomes. Primary outcomes included myocardial infarction, congestive heart failure, stroke or cardiac arrest, while secondary outcomes included revascularization procedures, ED revisits for angina pectoris or chest pain and hospitalization due to cardiovascular diseases. The author aggregated the adjusted costs and prevalence rates of outcomes for patients over OUs, and computed the weighted coefficients of variation (WCV) to compare variations across OUs. Results There was minimal <span class="hlt">variability</span> in the initial costs of care (WCV=2.2%), while the author noticed greater <span class="hlt">variability</span> in the outcomes. Greater <span class="hlt">variability</span> were associated with the adjusted cardiovascular-related costs of medical services (WCV=17.6%) followed by the adjusted prevalence odds ratio of patients experiencing primary outcomes (WCV=16.3%) and secondary outcomes (WCV=10%). Conclusion Higher <span class="hlt">variability</span> in the outcomes suggests the need for more standardization of the <span class="hlt">observation</span> services for chest pain patients. PMID:25987913</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.1502X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.1502X"><span id="translatedtitle">Interannual to <span class="hlt">decadal</span> climate <span class="hlt">variability</span> of sea salt aerosols in the coupled climate model CESM1.0</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>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.</p> <p>2015-02-01</p> <p>This study examines multiyear climate <span class="hlt">variability</span> associated with sea salt aerosols and their contribution to the <span class="hlt">variability</span> 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 <span class="hlt">variability</span> on longer (interdecadal) timescales is associated with low-frequency <span class="hlt">variability</span> 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 <span class="hlt">variability</span> may contribute to SWCF <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010111482','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010111482"><span id="translatedtitle">Constraints on <span class="hlt">Variability</span> of Brightness and Surface Magnetism on Time Scales of <span class="hlt">Decades</span> to Centuries in the Sun and Sun-Like Stars: A Source of Potential Terrestrial Climate <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baliunas, Sallie L.; Sharber, James (Technical Monitor)</p> <p>2001-01-01</p> <p>These four points summarize our work to date. (1) Conciliation of solar and stellar photometric <span class="hlt">variability</span>. Previous research by us and colleagues suggested that the Sun might at present be showing unusually low photometric <span class="hlt">variability</span> compared to other sun-like stars. Those early results would question the suitability of the technique of using sun-like stars as proxies for solar irradiance change on time scales of <span class="hlt">decades</span> to centuries. However, our results indicate the contrary: the Sun's <span class="hlt">observed</span> short-term (seasonal) and longterm (year-to-year) brightness variations closely agree with <span class="hlt">observed</span> brightness variations in stars of similar mass and age. (2) We have demonstrated an inverse correlation between the global temperature of the terrestrial lower troposphere, inferred from the NASA Microwave Sounding Unit (MSU) radiometers, and the total area of the Sun covered by coronal holes from January 1979 to present (up to May 2000). <span class="hlt">Variable</span> fluxes of either solar charged particles or cosmic rays, or both, may influence the terrestrial tropospheric temperature. The geographical pattern of the correlation is consistent with our interpretation of an extra-terrestrial charged particle forcing. (3) Possible climate mechanism amplifying the impact of solar ultraviolet irradiance variations. The key points of our proposed climate hypersensitivity mechanism are: (a) The Sun is more <span class="hlt">variable</span> in the UV (ultraviolet) than in the visible. However, the increased UV irradiance is mainly absorbed in the lower stratosphere/upper troposphere rather than at the surface. (b) Absorption in the stratosphere raises the temperature moderately around the vicinity of the tropopause, and tends to stabilize the atmosphere against vertical convective/diffusive transport, thus decreasing the flux of heat and moisture carried upward from surface. (c) The decrease in the upward convection of heat and moisture tends to raise the surface temperature because a drier upper atmosphere becomes less cloudy, which in turn allows more solar radiation to reach the Earth's surface. (4) Natural <span class="hlt">variability</span> in an ocean-atmosphere climate model. We use a 14-region, 6-layer, global thermo-hydrodynamic ocean-atmosphere model to study natural climate <span class="hlt">variability</span>. 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 <span class="hlt">observed</span> inter-annual <span class="hlt">variability</span> 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 <span class="hlt">variability</span>, 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 <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC31A1008H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC31A1008H"><span id="translatedtitle"><span class="hlt">Observed</span> and Projected Drought <span class="hlt">Variability</span> over Global Land Areas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, Q. S.; Feng, S.</p> <p>2011-12-01</p> <p>Severe droughts are one of the greatest recurring natural disasters. This study analyzed the <span class="hlt">observations</span> and model simulations for the period 1900-2099, and evaluated the drought <span class="hlt">variability</span> over the global land areas using the Palmer Drought Severity Index and the Standardized Precipitation-Evaporation Index. The model simulations are from 16 fully coupled general circulation models on 3 greenhouse gas emission scenarios from the Intergovernmental Panels on Climate Change (IPCC) Fourth Assessment. These model data were further downscaled, using bias-correction/spatial downscaling method, to a 0.5×0.5 grid. The ensemble of the 16 models can reasonably describe the <span class="hlt">observed</span> drought frequency and intensity during 1950-2000. Future projections made by these models show increasing drought frequency in the middle and low latitudes. Moreover, towards the end of the 21st century, the exceptional droughts occurred during 1950-2000 will become the norm in the middle and low latitudes, especially in arid/semi-arid areas. Drought intensity under higher emission scenario is greater than in low emission scenario. Severe droughts in the future would affect more than 2/3 of the world's population, and likely have severe impacts on food security.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.3332M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.3332M"><span id="translatedtitle"><span class="hlt">Observed</span> and simulated <span class="hlt">variability</span> of the Atlantic meridional overturning circulation and the deep western boundary current</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mielke, Charlotte; Frajka-Williams, Eleanor; Gary, Stefan; Shimizu, Kenji; Toole, John; Baehr, Johanna</p> <p>2014-05-01</p> <p>Despite the importance of Atlantic meridional overturnig circulation (AMOC) for the climate of Africa, America and Europe, continuous AMOC <span class="hlt">observations</span> are at present restricted to two latitudes, and are available for less than ten years. We therefore investigate whether the AMOC's <span class="hlt">variability</span> can be inferred from measurements of the deep western boundary current (DWBC), which are already available at several locations. To that end, we jointly analyze the available 26°N RAPID and the 41°N Argo-based AMOC estimates with RAPID and line W (40°N) DWBC estimates. We also compare them to a 60-year simulation with a high-resolution NCEP-forced ocean model. The DWBC and its layers are defined dynamically in the model based on a comparison of temperature-versus-salinity data in model and <span class="hlt">observations</span> and the time-dependent velocity field. On the timescales where <span class="hlt">observations</span> are available, the model is able to reproduce the <span class="hlt">variability</span> of the DWBC and its individual layers at both locations. Our preliminary analysis of the <span class="hlt">observational</span> data and model results suggests that different mechanisms dominate the DWBC's <span class="hlt">variability</span> at different timescales. On sub-seasonal to seasonal timescales, the DWBC is mostly barotropic, and its <span class="hlt">variability</span> is linked to local processes. Thus, the DWBC has a well-defined seasonal cycle which is opposite to the seasonal cycle of the non-Ekman component of the AMOC seasonal cycle. On interannual timescales, there is no obvious relation between AMOC and DWBC. However, on <span class="hlt">decadal</span> timescales, our analysis indicates covariability between AMOC and DWBC. We conclude that although caution should be exercised on interannual timescales, the DWBC might be used as a proxy for long-term AMOC trends and possibly modulations of the AMOC's seasonal cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27050290','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27050290"><span id="translatedtitle">Characterizing anomalous diffusion in crowded polymer solutions and gels over five <span class="hlt">decades</span> in time with <span class="hlt">variable</span>-lengthscale fluorescence correlation spectroscopy.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Banks, Daniel S; Tressler, Charmaine; Peters, Robert D; Höfling, Felix; Fradin, Cécile</p> <p>2016-05-14</p> <p>The diffusion of macromolecules in cells and in complex fluids is often found to deviate from simple Fickian diffusion. One explanation offered for this behavior is that molecular crowding renders diffusion anomalous, where the mean-squared displacement of the particles scales as 〈r(2)〉∝t(α) with α < 1. Unfortunately, methods such as fluorescence correlation spectroscopy (FCS) or fluorescence recovery after photobleaching (FRAP) probe diffusion only over a narrow range of lengthscales and cannot directly test the dependence of the mean-squared displacement (MSD) on time. Here we show that <span class="hlt">variable</span>-lengthscale FCS (VLS-FCS), where the volume of <span class="hlt">observation</span> is varied over several orders of magnitude, combined with a numerical inversion procedure of the correlation data, allows retrieving the MSD for up to five <span class="hlt">decades</span> in time, bridging the gap between diffusion experiments performed at different lengthscales. In addition, we show that VLS-FCS provides a way to assess whether the propagator associated with the diffusion is Gaussian or non-Gaussian. We used VLS-FCS to investigate two systems where anomalous diffusion had been previously reported. In the case of dense cross-linked agarose gels, the measured MSD confirmed that the diffusion of small beads was anomalous at short lengthscales, with a cross-over to simple diffusion around ≈1 μm, consistent with a caged diffusion process. On the other hand, for solutions crowded with marginally entangled dextran molecules, we uncovered an apparent discrepancy between the MSD, found to be linear, and the propagators at short lengthscales, found to be non-Gaussian. These contradicting features call to mind the "anomalous, yet Brownian" diffusion <span class="hlt">observed</span> in several biological systems, and the recently proposed "diffusing diffusivity" model. PMID:27050290</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6819S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6819S"><span id="translatedtitle"><span class="hlt">Decadal</span> to millennial-scale <span class="hlt">variability</span> in sea ice, primary productivity, and Pacific-Water inflow in the Chukchi/East Siberian Sea area (Arctic Ocean)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stein, Ruediger; Fahl, Kirsten; Matthiessen, Jens; Méheust, Marie; Nam, Seung-il; Niessen, Frank; Schade, Inka; Schreck, Michael; Wassmuth, Saskia; Xiao, Xiaotong</p> <p>2014-05-01</p> <p>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 <span class="hlt">observed</span> in the Arctic Ocean and its marginal seas over the last 30 years. Thus, understanding the processes controlling modern sea-ice <span class="hlt">variability</span> and reconstructing paleo-sea-ice extent and <span class="hlt">variability</span> 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 (<span class="hlt">decadal</span>-, centennial- to millennial-scale) <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...811..127S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...811..127S"><span id="translatedtitle"><span class="hlt">Observed</span> <span class="hlt">Variability</span> of the Solar Mg II h Spectral Line</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmit, D.; Bryans, P.; De Pontieu, B.; McIntosh, S.; Leenaarts, J.; Carlsson, M.</p> <p>2015-10-01</p> <p>The Mg ii h&k doublet are two of the primary spectral lines <span class="hlt">observed</span> by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double-Gaussian model to fit the Mg ii h profile for a full-Sun mosaic data set taken on 2014 August 24. We use the ensemble of high-quality profile fits to conduct a statistical study on the <span class="hlt">variability</span> of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well as h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles that do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared to predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core that is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the <span class="hlt">observed</span> structure and formation of the Mg ii profiles <span class="hlt">observed</span> by IRIS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...44.2703S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...44.2703S"><span id="translatedtitle">Inter-<span class="hlt">decadal</span> transition of the leading mode of inter-annual <span class="hlt">variability</span> of summer rainfall in East China and its associated atmospheric water vapor transport</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Bo; Wang, Huijun</p> <p>2015-05-01</p> <p>This study investigated the inter-<span class="hlt">decadal</span> variations of the leading empirical orthogonal function mode of the inter-annual <span class="hlt">variability</span> of summer precipitation in East China from 1951 to 2012. From the 1950s to the 1980s, the main rain belt in the positive-phase years was centered along the middle and lower Yangtze River Valleys, with negative rainfall anomalies in South China and North China. Since the 1990s, the main rain belt of the positive-phase years has been shifted northward. During the period 2001-2012, the center of the main rain belt in the positive-phase years has shifted to the regions between the Yangtze and Yellow Rivers. This shift could be attributed to the inter-<span class="hlt">decadal</span> variations of the anomalous atmospheric water vapor transport (AWVT) associated with the leading mode, which changed from a previously "anticyclone-cyclone" dipole structure to an anticyclonic monopole structure. The underlying physical mechanisms concerning the exertions from sea surface temperatures (SSTs) have also been preliminarily explored. The results indicate that the significant inter-<span class="hlt">decadal</span> transition in the leading mode of summer precipitation in East China and the causative anomalous AWVT from 2001 to 2012 may be related to an inter-<span class="hlt">decadal</span> change of inter-annual <span class="hlt">variability</span> of the tropical SSTs in both the Indian and Pacific Oceans, which has been below normal from 2001 to 2012. Therefore, the influence of the tropical SSTs on the inter-annual <span class="hlt">variability</span> of the East Asian climate may be diminished from 2001 to 2012, whereby a strongly coupled "anticyclone-cyclone" dipole-structured anomalous AWVT cannot be induced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IzPSE..51..176M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IzPSE..51..176M"><span id="translatedtitle">The free oscillations of the earth excited by three strongest earthquakes of the past <span class="hlt">decade</span> according to deformation <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Milyukov, V. K.; Vinogradov, M. P.; Mironov, A. P.; Myasnikov, A. V.; Perelygin, N. A.</p> <p>2015-03-01</p> <p>Based on the deformation data provided by the Baksan laser interferometer-strainmeter measurements, the free oscillations of the Earth (FOE) excited by the three strongest earthquakes of the past <span class="hlt">decade</span> are analyzed. These seismic events include the Great Sumatra-Andaman earthquake that occurred in 2004 in the Indian Ocean, the Mauli earthquake of 2010 in Chile, and the Great Tohoku earthquake of March 2011 in Japan. The frequency-time structure of the free oscillations is studied, and the pattern of interaction between the modes with close frequencies (cross-coupling effect) is explored. For each earthquake, the correspondence of the <span class="hlt">observed</span> FOE modes to the model predictions by the PREM model is investigated. A reliable consistent shift towards the high frequency of the toroidal modes with angular degree l = 12-19 is revealed. The maximal energy density of the toroidal oscillations is concentrated in the upper mantle of the Earth. Therefore, the established effect corresponds to the higher velocity of the shear waves in the upper mantle than it is predicted by the PREM model.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013029','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013029"><span id="translatedtitle">Multi-<span class="hlt">Decadal</span> Aerosol Variations from 1980 to 2009: A Perspective from <span class="hlt">Observations</span> and a Global Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chin, Mian; Diehl, T.; Tan, Q.; Prospero, J. M.; Kahn, R. A.; Remer, L. A.; Yu, H.; Sayer, A. M.; Bian, H.; Geogdzhayev, I. V.; Holben, B. N.; Howell, S. G.; Huebert, B. J.; Hsu, N. C.; Kim, D.; Kucsera, T. L.; Levy, R. C.; Mishchenko, M. I.; Pan, X.; Quinn, P. K.; Schuster, G. L.; Streets, D. G.; Strode, S. A.; Torres, O.; Zhao, X.-P.</p> <p>2014-01-01</p> <p>Aerosol variations and trends over different land and ocean regions during 1980-2009 are analyzed with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and <span class="hlt">observations</span> from multiple satellite sensors and ground-based networks. Excluding time periods with large volcanic influences, the tendency of aerosol optical depth (AOD) and surface concentration over polluted land regions is consistent with the anthropogenic emission changes.The largest reduction occurs over Europe, and regions in North America and Russia also exhibit reductions. On the other hand, East Asia and South Asia show AOD increases, although relatively large amount of natural aerosols in Asia makes the total changes less directly connected to the pollutant emission trends. Over major dust source regions, model analysis indicates that the dust emissions over the Sahara and Sahel respond mainly to the near-surface wind speed, but over Central Asia they are largely influenced by ground wetness. The decreasing dust trend in the tropical North Atlantic is most closely associated with the decrease of Sahel dust emission and increase of precipitation over the tropical North Atlantic, likely driven by the sea surface temperature increase. Despite significant regional trends, the model-calculated global annual average AOD shows little changes over land and ocean in the past three <span class="hlt">decades</span>, because opposite trends in different regions cancel each other in the global average. This highlights the need for regional-scale aerosol assessment, as the global average value conceals regional changes, and thus is not sufficient for assessing changes in aerosol loading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.T31C0578N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.T31C0578N"><span id="translatedtitle">Spatial and Temporal Distribution of Strain in the Sevier Desert Region from a <span class="hlt">Decade</span> of BARGEN Continuous GPS <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niemi, N. A.; Wernicke, B. P.</p> <p>2007-12-01</p> <p>A transect of four BARGEN GPS sites from 1997-2000 at latitude 39°N revealed a linear increase in velocity from 0 mm/yr on the Colorado Plateau to ~4 mm/yr in east-central Nevada. These geodetic data, when combined with paleoseismic and neotectonic <span class="hlt">observations</span>, were used to argue for present-day strain accumulation on the Sevier Desert detachment, a seismically-imaged, low-angle (12°) normal fault that underlies a significant portion of west central Utah [Niemi et al., 2004]. A new GPS velocity solution [Davis et al., 2006], including 5 additional years of <span class="hlt">observations</span> and a new GPS station in the eastern half of the transect, serves to both clarify and complicate our understanding of the spatial and temporal distribution of strain in this region. Geodetic velocity gradients among the three original eastern sites (from east to west, CAST, SMEL, and FOOT), and including the new site, SPIC, located between CAST and SMEL, continue to suggest a linear strain gradient from the Colorado Plateau to westernmost Utah, on a transect spanning the Wasatch, Sevier Desert, and House Range normal faults. In contrast, the baseline between FOOT and EGAN, which underwent extension from 1997-2000, began to contract in 2000, as site EGAN slowed with respect to the Colorado Plateau. This deviation in velocity continued until 2003, when EGAN began moving westward, and has, as of 2006, returned to near its pre-2000 velocity with respect to the Colorado Plateau. The eastward excursion of GPS site EGAN is not unique, and similar excursions are <span class="hlt">observed</span> in the time series of all BARGEN GPS sites that lie west of ~114.25°W over the time period 2000-2003 [Davis et al., 2006]. The origin of this velocity anomaly is uncertain, but the magnitude and spatial extent of the excursion, as well as the <span class="hlt">observation</span> of a deep earthquake swarm (~30-40 km depth) coincident with dramatic motion of GPS site SLID, near Lake Tahoe, in 2003 [Smith et al., 2004] suggest a deep crustal or mantle influence on the <span class="hlt">observed</span> GPS velocities. Bright, mid-crustal horizontal reflections <span class="hlt">observed</span> in COCORP reflection seismic data west of 114°W have been postulated to represent a detachment that could accommodate shearing along the base of the crust in Nevada [Hauser et al., 1987], a hypothesis broadly consistent with the <span class="hlt">observed</span> GPS velocities, with the crust shearing relatively east over the subcrustal lithosphere. A deep observatory in the Sevier Desert region, transecting the Sevier Desert detachment, would complement existing paleoseismic and neotectonic studies, and the <span class="hlt">decade</span> of BARGEN continuous GPS <span class="hlt">observations</span>, as well as new GPS data from 8 Earthscope Plate Boundary Observatory sites installed along this transect in the past few years. Key questions that could be assessed with a deep observatory are how slip, and strain, at depth on an inclined fault are reflected in geodetic <span class="hlt">observations</span> of strain at the surface; whether the state of stress and strain rate on the Sevier Desert detachment change through time, as suggested by long-term periodicity in strain release as recorded in the geologic record, and what effect long-lived velocity excursions, such as <span class="hlt">observed</span> from 2000-2003, have on the regional stress state, perhaps leading to a clearer understanding of the source of these anomalies, and the aseismic tectonic behavior of the lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP33A2078J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP33A2078J"><span id="translatedtitle">Multi-<span class="hlt">decadal</span>-scale records of North Atlantic climate <span class="hlt">variability</span> during the last and present interglacials: Climate sensitivity and the AMOC</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jimenez-Amat, P.; Zahn, R.; Martrat, B.; Grimalt, J. O.</p> <p>2012-12-01</p> <p>North Atlantic climate sensitivity plays a crucial role in understanding current and future developments of the Atlantic meridional overturning circulation (AMOC). A shifted configuration of Earth's orbital parameters about the Sun caused an approximate 3% higher radiative forcing during the Last Interglacial (LIG, MIS5e; 129-115kyr) and drove climate to measurably warmer conditions than during the Present Interglacial (PIG, Holocene, 11-0Kyr). Paleoceanographic time series of surface ocean climatology from Ocean Drilling Program (ODP) Site 976 in the Alboran Sea, westernmost Mediterranean, reflect the climatic <span class="hlt">variability</span> during the LIG and PIG. The site receives climate signals from the advection of Atlantic inflow waters confirming its quality to monitor North Atlantic climate <span class="hlt">variability</span>. Elevated rates of sedimentation deposition at the site enable resolving <span class="hlt">variability</span> at multi-<span class="hlt">decadal</span> resolution (60-90 yrs). Sea surface temperature (SST) time series were established from element concentrations (Mg/Ca) in the planktonic foraminifera Globigerina bulloides. SST from alkenones were also measured for comparison purposes. Planktonic oxygen isotopes from G. bulloides allow direct comparison with speleothems and ice cores. LIG SST are between 3°- 6°C warmer than PIG SST and multi-<span class="hlt">decadal</span>-scale <span class="hlt">variability</span> by 4°C and more is indicated by highly <span class="hlt">variable</span> Mg/Ca ratios. This <span class="hlt">variability</span> persisted during the LIG climatic optimum, confirming that SST and climatic <span class="hlt">variability</span> were independent of large ice sheets. The high <span class="hlt">variability</span> is contrasted by more stable SST in the Uk37-derived SST record, plausibly alluding to differential SST recording by the molecular biomarker proxy. Correlation with δ18O records from European speleothems suggests the SST pattern reflects climate of the western North Atlantic region. The LIG SST pattern at ODP 976 differs from that at open North Atlantic settings where maximum SST during the LIG climatic optimum remained some 6°C below that at ODP976 while converging with levels at ODP976 in the later stages of the LIG. The ODP976 SST record suggests more <span class="hlt">variable</span> climatic conditions and together with similar <span class="hlt">variability</span> seen in benthic δ13C records at Atlantic sites bears implications for AMOC stability and <span class="hlt">variability</span>. This is a contribution of the European Commission FP7 Collaborative Project "Past4Future".</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSA13B1955B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSA13B1955B"><span id="translatedtitle">Ionospheric <span class="hlt">Variability</span> as <span class="hlt">Observed</span> by the CTECS and CORISS Sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bishop, R. L.; Redding, M.; Straus, P. R.</p> <p>2013-12-01</p> <p>The Compact Total Electron Content Sensor (CTECS) is a GPS radio occultation instrument designed for cubesat platforms that utilizes a COTS receiver, modified firmware, and a custom designed antenna. CTECS was placed on the Pico Satellite Solar Cell Testbed 2 (PSSC2) nanosat that was installed on the Space Shuttle Atlantis (STS-135). PSSC2 was successfully released from the shuttle on 20 July 2011 near 380 km altitude. Because of attitude control and power issues, only 13.5 hours of data was collected during its approximately 5-month mission life. The C/NOFS Occultation Receiver for Ionospheric Sensing and Specification (CORISS) GPS radio occultation sensor on the C/NOFS satellite has collected data nearly continuously from May 2008 to June 2013. Both CTECS and CORISS obtain Total Electron Content and scintillation data. In this presentation the CTECS data is first validated against CORISS and available ground-based <span class="hlt">observations</span>. Then combining the CTECS and CORISS data, low and mid latitude ionospheric <span class="hlt">variability</span> including scintillation events is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7334C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7334C"><span id="translatedtitle">Hydrological <span class="hlt">variability</span> from gauging stations and simulated SWOT data, for major French rivers over the past <span class="hlt">decades</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chevalier, Laetitia; Laignel, Benoit; Turki, Imen; Lyard, Florent; Lion, Christine</p> <p>2014-05-01</p> <p>This study was carried out in the framework of the program Surface Water and Ocean Topography (SWOT) associated to the National Center of Space Studies (CNES). Basing on discharge measurements, and simulated Surface Water and Ocean Topography (SWOT) data, we have investigated the hydrological <span class="hlt">variability</span> of the main French rivers (Seine, Loire, Garonne and Rhône) by the use of a minimum, maximum and mean annual discharge analyses, Loess and wavelet approach (continuous wavelet analyses and wavelet coherence analyses). Results show (i) strong coherence between the four watershed discharges, varying between 73% and 92% and (ii) three different periods for hydrological <span class="hlt">variability</span>: before 1970, between 1970 and 1990, and after 1990. From these results, simulated SWOT data and discharges are compared for these three periods using same analyses. Simulated SWOT data are obtained by re-sampling river discharges from the SWOT crossing time calculated. Simulated SWOT data can reproduce the hydrological <span class="hlt">variability</span> of rivers despite number of SWOT passages (from two to four). These results are validated by coherence wavelet, which underlines coherence higher than 90% between simulated SWOT data and in-situ discharge. However, the results indicate that simulated SWOT data don't reproduce exactly the minimum and maximum annual discharge: (i) maximum annual SWOT data are underestimated and (ii) minimum annual SWOT data are overestimated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A32A..08K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A32A..08K"><span id="translatedtitle">Evaluating carbon dioxide <span class="hlt">variability</span> in the Community Earth System Model against atmospheric <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keppel-Aleks, G.; Randerson, J. T.; Lindsay, K. T.; Stephens, B. B.; Moore, J. K.; Doney, S. C.; Thornton, P. E.; Mahowald, N. M.; Hoffman, F. M.; Sweeney, C.; Tans, P. P.; Wennberg, P. O.; Wofsy, S. C.</p> <p>2012-12-01</p> <p>Changes in atmospheric CO_2 <span class="hlt">variability</span> during the 21st century may provide insight on ecosystem responses to climate change and have implications for the design of carbon monitoring programs. We analyzed results from a fully coupled climate-carbon simulation using the Community Earth System Model (CESM1-BGC). We evaluated CO2 simulated for the historical period against surface, aircraft, and column <span class="hlt">observations</span>. The mean annual cycle in total column atmospheric CO2 was underestimated throughout the northern hemisphere relative to TCCON <span class="hlt">observations</span>, suggesting that the growing season net flux in the land component of CESM was too weak by 50%. Sampling CESM along HIPPO transects confirmed low growing season uptake, but also showed that spring drawdown in the Northern Hemisphere began too early. The vertical gradients in CESM generally agreed with HIPPO data and with NOAA aircraft profiles outside the growing season, but were too weak during the summer. The seasonal bias suggests that vertical transport in CAM4 (the atmospheric component of CESM) was too weak year round. Model evaluation and improvement based on atmospheric <span class="hlt">observations</span> is crucial. The simulation of surface exchange and atmospheric transport of CO2 in coupled models such as CESM may help with the design of optimal detection strategies. For example, in the simulations of the 21st century, CESM predicted increases in the mean annual cycle of atmospheric CO2 and larger horizontal gradients. Both north-south and east-west contrasts in CO2 strengthened due to changing patterns in fossil fuel emissions and terrestrial carbon exchange, and northern hemisphere interannual <span class="hlt">variability</span> increased as well. Our results suggest that using atmospheric <span class="hlt">observations</span> to gain insight about changing terrestrial and ocean processes over the next several <span class="hlt">decades</span> may become more challenging as anthropogenic contributions to <span class="hlt">variability</span> on multiple temporal and spatial scales continue to grow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040111406&hterms=biomass&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dbiomass','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040111406&hterms=biomass&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dbiomass"><span id="translatedtitle">Interannual and Seasonal <span class="hlt">Variability</span> of Biomass Burning Emissions Constrained by Satellite <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Duncan, Bryan N.; Martin, Randall V.; Staudt, Amanda C.; Yevich, Rosemarie; Logan, Jennifer A.</p> <p>2003-01-01</p> <p>We present a methodology for estimating the seasonal and interannual variation of biomass burning designed for use in global chemical transport models. The average seasonal variation is estimated from 4 years of fire-count data from the Along Track Scanning Radiometer (ATSR) and 1-2 years of similar data from the Advanced Very High Resolution Radiometer (AVHRR) World Fire Atlases. We use the Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) data product as a surrogate to estimate interannual <span class="hlt">variability</span> in biomass burning for six regions: Southeast Asia, Indonesia and Malaysia, Brazil, Central America and Mexico, Canada and Alaska, and Asiatic Russia. The AI data set is available from 1979 to the present with an interruption in satellite <span class="hlt">observations</span> from mid-1993 to mid-1996; this data gap is filled where possible with estimates of area burned from the literature for different regions. Between August 1996 and July 2000, the ATSR fire-counts are used to provide specific locations of emissions and a record of interannual <span class="hlt">variability</span> throughout the world. We use our methodology to estimate mean seasonal and interannual variations for emissions of carbon monoxide from biomass burning, and we find that no trend is apparent in these emissions over the last two <span class="hlt">decades</span>, but that there is significant interannual <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JGRD..108.4100D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JGRD..108.4100D"><span id="translatedtitle">Interannual and seasonal <span class="hlt">variability</span> of biomass burning emissions constrained by satellite <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duncan, Bryan N.; Martin, Randall V.; Staudt, Amanda C.; Yevich, Rosemarie; Logan, Jennifer A.</p> <p>2003-01-01</p> <p>We present a methodology for estimating the seasonal and interannual variation of biomass burning designed for use in global chemical transport models. The average seasonal variation is estimated from 4 years of fire-count data from the Along Track Scanning Radiometer (ATSR) and 1-2 years of similar data from the Advanced Very High Resolution Radiometer (AVHRR) World Fire Atlases. We use the Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) data product as a surrogate to estimate interannual <span class="hlt">variability</span> in biomass burning for six regions: Southeast Asia, Indonesia and Malaysia, Brazil, Central America and Mexico, Canada and Alaska, and Asiatic Russia. The AI data set is available from 1979 to the present with an interruption in satellite <span class="hlt">observations</span> from mid-1993 to mid-1996; this data gap is filled where possible with estimates of area burned from the literature for different regions. Between August 1996 and July 2000, the ATSR fire-counts are used to provide specific locations of emissions and a record of interannual <span class="hlt">variability</span> throughout the world. We use our methodology to estimate mean seasonal and interannual variations for emissions of carbon monoxide from biomass burning, and we find that no trend is apparent in these emissions over the last two <span class="hlt">decades</span>, but that there is significant interannual <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JHyd..517..458N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JHyd..517..458N"><span id="translatedtitle">On the use of Standardized Drought Indices under <span class="hlt">decadal</span> climate <span class="hlt">variability</span>: Critical assessment and drought policy implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Núñez, J.; Rivera, D.; Oyarzún, R.; Arumí, J. L.</p> <p>2014-09-01</p> <p>Since the recent High Level Meeting on National Drought Policy held in Geneva in 2013, a greater concern about the creation and adaptation of national drought monitoring systems is expected. Consequently, backed by international recommendations, the use of Standardized Drought Indices (SDI), such as the Standardized Precipitation Index (SPI), as an operational basis of drought monitoring systems has been increasing in many parts of the world. Recommendations for the use of the SPI, and consequently, those indices that share its properties, do not take into account the limitations that this type of index can exhibit under the influence of multidecadal climate <span class="hlt">variability</span>. These limitations are fundamentally related to the lack of consistency among the operational definition expressed by this type of index, the conceptual definition with which it is associated and the political definition it supports. Furthermore, the limitations found are not overcome by the recommendations for their application. This conclusion is supported by the long-term study of the Standardized Streamflow Index (SSI) in the arid north-central region of Chile, under the influence of multidecadal climate <span class="hlt">variability</span>. The implications of the findings of the study are discussed with regard to their link to aspects of drought policy in the cases of Australia, the United States and Chile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Variable+AND+stars&id=EJ200250','ERIC'); return false;" href="http://eric.ed.gov/?q=Variable+AND+stars&id=EJ200250"><span id="translatedtitle"><span class="hlt">Observing</span> Simulated Cepheid <span class="hlt">Variable</span> Stars in an Introductory Astronomy Lab.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Flesch, Terry R.</p> <p>1979-01-01</p> <p>Describes an exercise developed by the author to help college students to become familiar with the technique of photoelectric photometry of <span class="hlt">variable</span> stars and permits each student to work with data he or she has personally obtained. (HM)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JAVSO..24..129W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JAVSO..24..129W"><span id="translatedtitle">Mythological Evidence for Ancient <span class="hlt">Observations</span> of <span class="hlt">Variable</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilk, Stephen R.</p> <p></p> <p>I suggest that the <span class="hlt">variability</span> of Algol was known in pre-classical Greece, and that knowledge of its period is reflected in the myth of Perseus. Moreover, knowledge of the <span class="hlt">variability</span> of Algol, Mira, delta Cephei, and gamma Cassiopeiae accounts for all their parent constellations being associated in the same myth as antagonists of Perseus. Finally, I propose alternative interpretations of the same constellations which show their influence upon classical myth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NPGeo..22..513F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NPGeo..22..513F"><span id="translatedtitle">Systematic attribution of <span class="hlt">observed</span> Southern Hemisphere circulation trends to external forcing and internal <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franzke, C. L. E.; O'Kane, T. J.; Monselesan, D. P.; Risbey, J. S.; Horenko, I.</p> <p>2015-09-01</p> <p>A critical question in the global warming debate concerns the causes of the <span class="hlt">observed</span> trends of the Southern Hemisphere (SH) atmospheric circulation over recent <span class="hlt">decades</span>. Secular trends have been identified in the frequency of occurrence of circulation regimes, namely the positive phase of the Southern Annular Mode (SAM) and the hemispheric wave-3 pattern which is associated with blocking. Previous studies into the causes of these secular trends have either been purely model based, have not included <span class="hlt">observational</span> forcing data or have mixed external forcing with indices of internal climate <span class="hlt">variability</span> impeding a systematic and unbiased attribution of the causes of the secular trends. Most model studies also focused mainly on the austral summer season. However, the changes to the storm tracks have occurred in all seasons and particularly in the austral winter and early spring when midlatitude blocking is most active and stratospheric ozone should not play a role. Here we systematically attribute the secular trends over the recent <span class="hlt">decades</span> using a non-stationary clustering method applied to both reanalysis and <span class="hlt">observational</span> forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing austral summer SH circulation trends, we show <span class="hlt">observational</span> evidence that anthropogenic greenhouse gas concentrations have been the major driver of these secular trends in the SAM and blocking when all seasons are considered. Our results suggest that the recovery of the ozone hole might delay the signal of global warming less strongly than previously thought and that effects from all seasons are likely crucial in understanding the causes of the secular trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NPGD....2..675F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NPGD....2..675F"><span id="translatedtitle">Systematic attribution of <span class="hlt">observed</span> southern hemispheric circulation trends to external forcing and internal <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franzke, C. L. E.; O'Kane, T. J.; Monselesan, D. P.; Risbey, J. S.; Horenko, I.</p> <p>2015-04-01</p> <p>A critical question in the global warming debate concerns the causes of the <span class="hlt">observed</span> trends of the Southern Hemisphere (SH) atmospheric circulation over recent <span class="hlt">decades</span>. Secular trends have been identified in the frequency of occurrence of circulation regimes, namely the positive phase of the Southern Annular Mode (SAM) and the hemispheric wave 3 pattern which is associated with blocking. Previous studies into the causes of these secular trends have either been purely model based, have not included <span class="hlt">observational</span> forcing data or have mixed external forcing with indices of internal climate <span class="hlt">variability</span> impeding a systematic and unbiased attribution of the causes of the secular trends. Most model studies also focused mainly on the austral summer season. However, the changes to the storm tracks have occurred in all seasons and particularly in the austral winter and early spring when mid-latitude blocking is most active and stratospheric ozone should not a play a role. Here we systematically attribute the secular trends over the recent <span class="hlt">decades</span> using a non-stationary clustering method applied to both reanalysis and <span class="hlt">observational</span> forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing austral summer SH circulation trends, we show <span class="hlt">observational</span> evidence that anthropogenic greenhouse gas concentrations have been the major driver of these secular trends in the SAM and blocking when all seasons are considered. Our results suggest that the recovery of the ozone hole might delay the signal of global warming less strongly than previously thought and that effects from all seasons are likely crucial in understanding the causes of the secular trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2614F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2614F"><span id="translatedtitle">Systematic Attribution of <span class="hlt">Observed</span> Southern Hemispheric Circulation Trends to External Forcing and Internal <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franzke, Christian; O'Kane, Terence; Monselesan, Didier; Risbey, James; Horenko, Illia</p> <p>2015-04-01</p> <p>A critical question in the global warming debate concerns the causes of the <span class="hlt">observed</span> trends of the Southern Hemisphere (SH) atmospheric circulation over recent <span class="hlt">decades</span>. Secular trends have been identified in the frequency of occurrence of circulation regimes, namely the positive phase of the Southern Annular Mode (SAM) and the hemispheric wave 3 pattern which is associated with blocking. Previous studies into the causes of these secular trends have either been purely model based, have not included <span class="hlt">observational</span> forcing data or have mixed external forcing with indices of internal climate <span class="hlt">variability</span> impeding a systematic and unbiased attribution of the causes of the secular trends. Most model studies also focused mainly on the austral summer season. However, the changes to the storm tracks have occurred in all seasons and particularly in the winter and early spring when mid-latitude blocking is most active and stratospheric ozone plays no role. Here we systematically attribute the secular trends over the recent <span class="hlt">decades</span> using a non-stationary clustering method applied to both reanalysis and <span class="hlt">observational</span> forcing data from all seasons. While most previous studies emphasized the importance of stratospheric ozone depletion in causing summer SH circulation trends, we show <span class="hlt">observational</span> evidence that anthropogenic greenhouse gas concentrations have been the major driver of these secular trends in the SAM and blocking when all seasons are considered. Our results suggest that the recovery of the ozone hole might delay the signal of global warming less strongly than previously thought and that seasonal effects are likely crucial in understanding the causes of the secular trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JASTP.142...25L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JASTP.142...25L"><span id="translatedtitle"><span class="hlt">Variability</span> of Madden Julian Oscillations (MJO) <span class="hlt">observed</span> over southern India using radiosonde <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leena, P. P.; Ratnam, M. Venkat; Krishna Murthy, B. V.; Bhaskara Rao, S. Vijaya</p> <p>2016-05-01</p> <p>In the present work, characteristics of 30-50 day oscillations (referred to as the MJO) in tropospheric and lower stratospheric wind and temperature have been studied using long-term high resolution radiosonde <span class="hlt">observations</span> at a tropical station, Gadanki (13.5°N, 79.2°E) for the period 2006-2012. Wind and temperature perturbations showed clear features of the MJO with higher amplitudes between 10 and 18 km altitude. Interestingly, the MJO signal is confined vertically to different altitudes in different seasons. <span class="hlt">Variability</span> in the perturbations of wind and temperature similar to that of outgoing long-wave radiation (OLR) with a few cases showing an out of phase relation. The amplitudes of these oscillations are larger in the winter and pre-monsoon seasons than in the monsoon season where the largest amplitudes are confined below the Tropical Easterly Jet (~16 km). There also exists a large inter-annual <span class="hlt">variability</span> in the MJO. Spatio-temporal <span class="hlt">variability</span> of OLR not only showed the features of the MJO but also northward and eastward propagation in the monsoons and winter seasons, respectively, in a few cases. It is found that convection leads the MJO in the zonal wind by 8-12 days in all the seasons except in winter. One intriguing result <span class="hlt">observed</span> is the vitiation of the MJO pattern by the presence of strong wind shears during monsoon season. We expect this study would be helpful in representing the MJO features in the vertical in the general circulation models (GCMs) which is still a major challenge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6738L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6738L"><span id="translatedtitle">Surface Wind <span class="hlt">Observational</span> Database in North Eastern North America: Quality Control Procedure and Climatological <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lucio-Eceiza, Etor E.; Fidel González-Rouco, J.; Navarro, Jorge; Hidalgo, Ángela; Conte, Jorge; Beltrami, Hugo</p> <p>2015-04-01</p> <p>This work summarizes the design and application of a Quality Control (QC) procedure for an <span class="hlt">observational</span> surface wind database located in North Eastern North America. It also presents some insights of the long-term climatological <span class="hlt">variability</span> over the region. The database consists of 527 sites (487 land stations and 40 buoys) with varying resolutions of hourly, 3 hourly and 6 hourly data, compiled from three different source institutions. The records span from 1940 to 2010 and cover an approximate spatial extension of 2.2 × 106 km2. The QC process is composed of different phases focused either on problems related with the providing source institutions or measurement errors. Due to the size of the data set, a great effort has been made on the automation of the procedures. A number of problems are associated with data management and data conventions: unification of measurement units and recording times due to the variety of institutional sources; detection of erroneous data sequence duplications within a station or among different ones; and detection of errors related with physically unrealistic data measurements. From the other hand there is a variety of treated instrumental errors: problems related with low <span class="hlt">variability</span>, placing particular emphasis on the detection of unrealistic low wind speed records with the help of regional references; high <span class="hlt">variability</span> related erroneous records; wind speed biases on week to monthly timescales and homogenization of wind direction records. As a result, around 1.7% of wind speed records and 0.4% of wind direction records have been deleted, making a combined total of 1.9% of removed records. Around 2.4% of wind direction data have been also corrected. The already quality controlled database allows for subsequent climatological analyses. The intra and inter <span class="hlt">decadal</span> <span class="hlt">variability</span> of the monthly surface wind field in such a vast and orographically complex region as the North Eastern North America is explored. Several <span class="hlt">decades</span> of quality <span class="hlt">observations</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H34C..02G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H34C..02G"><span id="translatedtitle">Multi-<span class="hlt">decadal</span> <span class="hlt">Variability</span> of Flood Risk in Southwestern Canadian Prairie Rivers as Characterized by the PDO and ENSO</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gurrapu, S.; St Jacques, J. M.; Sauchyn, D.; Hodder, K. R.</p> <p>2014-12-01</p> <p>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 <span class="hlt">Decadal</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/8057','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/8057"><span id="translatedtitle">Interannual/<span class="hlt">decadal</span> <span class="hlt">variability</span> in MJO activity as diagnosed in the 40-year NCEP/NCAR reanalysis and simulated in an ensemble of GISST integrations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Slingo, J. M.; Rowell, D. P.; Sperber, K. R.; Nortley, F.</p> <p>1999-04-21</p> <p>The Madden-Julian Oscillation (MJO) is the dominant mode of tropical <span class="hlt">variability</span> at intraseasonal timescales. It displays substantial interannual <span class="hlt">variability</span> in intensity which may have important implications for the predictability of the coupled system. The reasons for this interannual <span class="hlt">variability</span> are not understood. The interannual behaviour of the MJO has been diagnosed initially in the 40-year NCEP/NCAR Reanalysis by calculating the variance of the 20-100 day filtered zonal mean zonal wind (10 o N-10 o S averaged) in a 100- day moving window. The results suggest that prior to the mid-1970s the activity of the MJO was consistently lower than during the latter part of the record. This may be related to either inadequacies in the data coverage, particularly over the tropical Indian Ocean prior to the introduction of satellite <span class="hlt">observations</span>, or to the real effects of a <span class="hlt">decadal</span> timescale warming in the tropical SSTs. This interdecadal trend is captured by the dominant EOF (explaining 28% of the variance) of the monthly mean SSTs (after removal of the mean seasonal cycle), as used in the NCEP/NCAR Reanalysis for the region of the tropics where the MJO is convectively active (i.e., 60 o E-180 o E, 20 o S-20 o N). During the latter part of 1970s there was an abrupt change from a predominantly negative PC1 (i.e. colder Indian Ocean) to a positive PC1 (i.e. warmer Indian Ocean), indicative of a general warming of the tropical Indian Ocean by at least 0.5 o K over the last 40 years. However, on interannual timescales, the teleconnection patterns between MJO activity and SST show only a weak, barely significant, influence of El Niño in which the MJO is more active during the cold phase. As well as the NCEP/NCAR Reanalysis, a 4-member ensemble of 45 year integrations with the Hadley Centre climate model (HADAM2a), forced by <span class="hlt">observed</span> SSTs for 1949-93, has been used to investigate the relationship between MJO activity and SST. HADAM2a is known to give a reasonable simulation of the MJO, and the extended record provided by this ensemble of integrations allows a more robust investigation of the predictability of MJO activity than was possible with the 40-year NCEP/NCAR Reanalysis. The results have shown that, for the uncoupled system, with the atmosphere being driven by imposed SSTs, there is no reproducibility of the activity of the MJO from year to year. The interannual behaviour of the MJO is not controlled by the phase of El Niño and would appear to be mainly chaotic in character. However, the model results have confirmed the low frequency, interdecadal timescale <span class="hlt">variability</span> of MJO ac-tivity seen in the NCEP/NCAR Reanalysis. The activity of the MJO is consistently lower in all realisations prior to the mid 1970s, suggesting that the MJO may become more active as tropical SSTs become warmer. This result may have implications for the effects of global warming on the coupled atmosphere-ocean system. The implications of these results for the predictability of the tropical ocean-atmosphere system are im-portant since intraseasonal activity in the atmosphere, associated with MJO's and westerly wind bursts, can have a substantial impact on the Pacific Ocean. As the events in 1997 indicate, MJO activity may have a sig-nificant impact on the magnitude and growth rate of El Niño events. In turn the <span class="hlt">decadal</span> changes in MJO ac-tivity suggest that if tropical SSTs continue to warm, the activity of the MJO may tend to increase which then might have implications for the future behaviour of El Niño. This work is presented in full by Slingo et al. (1999, Quart. J. Roy. Meteorol. Soc., in press).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H11D1181C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H11D1181C"><span id="translatedtitle">New data-based mechanistic methodology to quantify hydrological & biogeochemical recovery following forest disturbance using <span class="hlt">observations</span> monitored from sub-hourly to <span class="hlt">decadal</span> time-scales (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chappell, N. A.; Jones, T.</p> <p>2013-12-01</p> <p>Quantifying recovery in hydrological & biogeochemical processes following forest disturbances is difficult given sensitivities of watershed systems to controlling climate dynamics at sub-daily to <span class="hlt">decadal</span> timescales. Trends associated with forest hydrological & biogeochemical recovery can be difficult to identify where natural climate cycles at seasonal to inter-annual time-scales are present & need to be accounted for. Equally, fundamental relationships between physico-chemical processes within experimental watersheds are often unidentifiable where <span class="hlt">observations</span> are not undertaken at a sufficiently high sampling rate e.g., sub-hourly (Kirchner et al., 2004 Hydrol Process). Consequently, the study of recovery in hydrological & biogeochemical systems requires robust analysis of both short- & long-term dynamic relationships in watersheds. We newly apply two data-based mechanistic (DBM) approaches to characterise change resulting from forest disturbance & recovery in both: (1) longer-term cycles & trends in biogeochemical <span class="hlt">variables</span>; & (2) short-term dynamic relationships between biogeochemical & controlling hydro-climatic <span class="hlt">variables</span>. The Unobserved Components - Dynamic Harmonic Regression (UC-DHR) modeling approach is used to quantify the longer-term trends & cycles (Chappell & Tych, 2012 Hydrol Process), while continuous time transfer function modeling is used to illustrate changes in the short-term (within storm) dynamics over the forest management cycle. The DBM philosophy is appropriate for a new focus on under-studied recovering forests because it first makes no a priori assumptions about processes that need to be described, instead uses information contained in the time-series to derive multiple statistically valid models. In the second stage of the approach only those models that also have robust hydrological &/or geochemical interpretations are accepted for further consideration of the dynamics. This study utilises the longest forest hydrological & associated biogeochemical records available in upland UK, namely those of the Plynlimon & Llyn Brianne experimental catchments, where the authors have recently supplemented these data with continuous 15-minute <span class="hlt">observations</span> from new biogeochemical sensors. The presentation focuses on the dynamics of biogeochemical <span class="hlt">variables</span> of hydrogen ion (H+) concentration & load for three reasons: (1) their critical role in ongoing work on stream acidification; (2) the associated threat to stream biodiversity; & (3) their role in the regulation of carbon & nitrogen release into streams. Both DBM approaches have been able to quantify change in hydrological & biogeochemical characteristics (illustrated with H+ time series) through periods demonstrating significant recovery from forest disturbance. These range from the short-term dynamic response characteristics controlling biogeochemical export during storms to inter-annual characteristics of cycles & trends within time-series. The demonstrated ability to identify changes that are greater than calculated simulation uncertainties has the potential to make a significant contribution to emerging global research on quantifying change within recovering forest systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.7383C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.7383C"><span id="translatedtitle">Are stress drop and rupture velocity of earthquakes independent? Insight from <span class="hlt">observed</span> ground motion <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Causse, Mathieu; Song, Seok Goo</p> <p>2015-09-01</p> <p>We demonstrate that the <span class="hlt">variability</span> of the peak ground acceleration (PGA) generated by earthquakes can be simply related to the <span class="hlt">variability</span> of stress drop (??), rupture velocity (Vr) and their correlation. By compiling recent <span class="hlt">observations</span> of <span class="hlt">variability</span> of ?? and Vr, we show that the hypothesis of independence between ?? and Vr leads to an overestimation of the PGA <span class="hlt">variability</span>. We suggest that ?? and Vr must be anticorrelated so as to match recent <span class="hlt">observations</span> of PGA <span class="hlt">variability</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...44..359G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...44..359G"><span id="translatedtitle"><span class="hlt">Observed</span> and SST-forced multidecadal <span class="hlt">variability</span> in global land surface air temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, L. H.; Yan, Z. W.; Quan, X. W.</p> <p>2015-01-01</p> <p>The characteristics of multidecadal <span class="hlt">variability</span> (MDV) in global land surface air temperature (SAT) are analyzed based on <span class="hlt">observations</span>. The role of sea surface temperature (SST) variations in generating MDV in land SAT is assessed using atmospheric general circulation model simulations forced by <span class="hlt">observed</span> SST. MDV in land SAT exhibits regional differences, with amplitude larger than 0.3 °C mainly over North America, East Asia, Northern Eurasia, Northern Africa and Greenland for the study period of 1902-2004. MDV can account for more than 30 % of long-term temperature variation during the last century in most regions, especially more than 50 % in parts of the above-mentioned regions. The SST-forced simulations reproduce the <span class="hlt">observed</span> feature of zonal mean MDV in land SAT, though with weaker amplitude especially at the northern high-latitudes. Two types of MDV in land SAT, one of 60-year-timescale, mainly <span class="hlt">observed</span> in the northern mid-high-latitude lands, and another of 20-30-year-timescale, mainly <span class="hlt">observed</span> in the low-latitude lands, are also well reproduced. The SST-forced MDV accounts for more than 40 % amplitude of <span class="hlt">observed</span> MDV in most regions. Except for some sporadically distributed regions in central Eurasia, South America and Western Australia, the SST-forced multidecadal variations are well in-phase with <span class="hlt">observations</span>. The Atlantic Multidecadal Oscillation and Pacific <span class="hlt">Decadal</span> Oscillation signals are found dominant in MDV of both the <span class="hlt">observed</span> and SST-forced land SAT, suggesting important roles of these oceanic oscillations in generating MDV in global land SAT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=deficit+AND+attentional+AND+hyperactivity&pg=3&id=EJ836800','ERIC'); return false;" href="http://eric.ed.gov/?q=deficit+AND+attentional+AND+hyperactivity&pg=3&id=EJ836800"><span id="translatedtitle"><span class="hlt">Variability</span> of Attention Processes in ADHD: <span class="hlt">Observations</span> from the Classroom</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Rapport, Mark D.; Kofler, Michael J.; Alderson, R. Matt; Timko, Thomas M., Jr.; DuPaul, George J.</p> <p>2009-01-01</p> <p>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 <span class="hlt">variability</span> in the classroom attentional processing in children with ADHD. Method: High and low attention groups of ADHD children…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14..536P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14..536P"><span id="translatedtitle">Sea state <span class="hlt">variability</span> <span class="hlt">observed</span> by high resolution satellite radar images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pleskachevsky, A.; Lehner, S.</p> <p>2012-04-01</p> <p>The spatial <span class="hlt">variability</span> of the wave parameters is measured and investigated using new TerraSAR-X (TS-X) satellite SAR (Synthetic Aperture Radar) images. Wave groupiness, refraction and breaking of individual wave are studied. Space borne SAR is a unique sensor providing two dimensional information of the ocean surface. Due to its daylight, weather independency and global coverage, the TS-X radar is particularly suitable for many ocean and coastal <span class="hlt">observations</span> and it acquires images of the sea surface with up to 1m resolution; individual ocean waves with wavelength below 30m are detectable. Two-dimensional information of the ocean surface, retrieved using TS-X data, is validated for different oceanographic applications: derivation of the fine resolved wind field (XMOD algorithm) and integrated sea state parameters (XWAVE algorithm). The algorithms are capable to take into account fine-scale effects in the coastal areas. This two-dimensional information can be successfully applied to validate numerical models. For this, wind field and sea state information retrieved from SAR images are given as input for a spectral numerical wave model (wind forcing and boundary condition). The model runs and sensitivity studies are carried out at a fine spatial horizontal resolution of 100m. The model results are compared to buoy time series at one location and with spatially distributed wave parameters obtained from SAR. The comparison shows the sensitivity of waves to local wind variations and the importance of local effects on wave behavior in coastal areas. Examples for the German Bight, North Sea and Rottenest Island, Australia are shown. The wave refraction, rendered by high resolution SAR images, is also studied. The wave ray tracking technique is applied. The wave rays show the propagation of the peak waves in the SAR-scenes and are estimated using image spectral analysis by deriving peak wavelength and direction. The changing of wavelength and direction in the rays allows detecting underwater structures (banks, reefs, shallows) and to obtain bathymetry in case a well-developed swell is imaged. Further, wave energy flux propagation towards the coast and its dissipation are obtained using the wave ray technique: wave height and wavelength are derived from TS-X image spectrum. The height of individual breaking waves is obtained from SAR-image signatures and it is compared to the model results and the buoy measurements. The results show some lower amplitude of the breaking waves, when compared to model results in the shoaling zone. This effect could be explained by an actual stronger dissipation than the one given by the model in the investigated area (coral reefs). Wave groups are detected for a cross sea and in storm condition in the ocean. The parameters of the wave groups are investigated and the conditions, which are responsible for their origin, are studied by numerical simulation using spectral wave model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020045387','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020045387"><span id="translatedtitle">Seasonal to <span class="hlt">Decadal</span>-Scale <span class="hlt">Variability</span> in Satellite Ocean Color and Sea Surface Temperature for the California Current System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mitchell, B. Greg; Kahru, Mati; Marra, John (Technical Monitor)</p> <p>2002-01-01</p> <p>Support for this project was used to develop satellite ocean color and temperature indices (SOCTI) for the California Current System (CCS) using the historic record of CZCS West Coast Time Series (WCTS), OCTS, WiFS and AVHRR SST. The ocean color satellite data have been evaluated in relation to CalCOFI data sets for chlorophyll (CZCS) and ocean spectral reflectance and chlorophyll OCTS and SeaWiFS. New algorithms for the three missions have been implemented based on in-water algorithm data sets, or in the case of CZCS, by comparing retrieved pigments with ship-based <span class="hlt">observations</span>. New algorithms for absorption coefficients, diffuse attenuation coefficients and primary production have also been evaluated. Satellite retrievals are being evaluated based on our large data set of pigments and optics from CalCOFI.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy..tmp..171C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy..tmp..171C"><span id="translatedtitle">Rainfall <span class="hlt">variability</span> and trends of the past six <span class="hlt">decades</span> (1950-2014) in the subtropical NW Argentine Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castino, F.; Bookhagen, B.; Strecker, M. R.</p> <p>2016-04-01</p> <p>The eastern flanks of the Central Andes are characterized by deep convection, exposing them to hydrometeorological extreme events, often resulting in floods and a variety of mass movements. We assessed the spatiotemporal pattern of rainfall trends and the changes in the magnitude and frequency of extreme events (≥95th percentile) along an E-W traverse across the southern Central Andes using rain-gauge and high-resolution gridded datasets (CPC-uni and TRMM 3B42 V7). We generated different climate indices and made three key <span class="hlt">observations</span>: (1) an increase of the annual rainfall has occurred at the transition between low (<0.5 km) and intermediate (0.5-3 km) elevations between 1950 and 2014. Also, rainfall increases during the wet season and, to a lesser degree, decreases during the dry season. Increasing trends in annual total amounts characterize the period 1979-2014 in the arid, high-elevation southern Andean Plateau, whereas trend reversals with decreasing annual total amounts were found at low elevations. (2) For all analyzed periods, we <span class="hlt">observed</span> small or no changes in the median values of the rainfall-frequency distribution, but significant trends with intensification or attenuation in the 95th percentile. (3) In the southern Andean Plateau, extreme rainfall events exhibit trends towards increasing magnitude and, to a lesser degree, frequency during the wet season, at least since 1979. Our analysis revealed that low (<0.5 km), intermediate (0.5-3 km), and high-elevation (>3 km) areas respond differently to changing climate conditions, and the transition zone between low and intermediate elevations is characterized by the most significant changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.8793S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.8793S"><span id="translatedtitle">Interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span> in a control experiment using MIROC4 - a high-resolution AOGCM for the near-term climate prediction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakamoto, Takashi T.; Komuro, Yoshiki; Ishii, Masayoshi; Tatebe, Hiroaki; Hasegawa, Akira; Shiogama, Hideo; Toyoda, Takahiro; Mori, Masato; Kimoto, Masahide</p> <p>2010-05-01</p> <p>Preliminary results, especially mean climate and interannual to <span class="hlt">decadal</span> <span class="hlt">variability</span>, in a general circulation climate model, Model for Interdisciplinary Research on Climate (MIROC) version 4, are presented. The model is developed by the Center for Climate System Research (CCSR), the University of Tokyo; National Institute for Environmental Studies (NIES); and Japan Agency for Marine-Earth Science and Technology (JAMSTEC). MIROC4 is an updated model from the previous version MIROC3_hires, which was used to contribute to the IPCC AR4. Most of the model components are the same as MIROC3_hires, but the atmospheric component is changed to T213 spectrum model from T106 one to inform adaptation policies for near-term climate changes. The ocean component is the same as that used in MIROC3_hires, whose horizontal resolution is 0.28125 zonally and 0.1875 meridionally, while the latitudinal range where the Gent-McWilliams (GM) parameterization is applied is changed in order to improve the climatological distribution of SST. The other components, sea ice, land surface process, and river routing models, are also same as the previous model. To obtain the radiative balance, parameters associated with radiation, clouds, and aerosols are tuned. Using this model, spin-up and control experiments (120 years) under the condition of year 1950 without flux adjustment were conducted. Globally averaged 2-m temperature (T2) and SST are not drifted, and biases in the SST field, typically warm bias in the high-latitudes and cold bias in the low- and mid-latitudes, are reduced in MIROC4, especially in the Northern Hemisphere. Associated with the reduction of the warm SST bias in the high-latitudes, sea ice in the Northern Hemisphere becomes thicker in MIROC4 than MIROC3_hires. The Atlantic meridional overturning circulation (AMOC) is relatively weak in MIROC4, and mean volume transport of the North Atlantic Deep Water (NADW) is 12-13 Sv (Sv?106 m3/s), which is 1-2 Sv weaker than that obtained by MIROC3_hires. However, the 120-year integration is not enough to spin-up AMOC, and the NADW transport will be greater in the end of the control experiment. Simulated ENSO signal in MIROC4 is improved. The standard deviation of the Nio-3 index in MIROC3_hires was 0.33, but that in MIROC4 it is 0.57 (<span class="hlt">observation</span> ~ 0.8). Not only the Nio indices, but also distribution of ENSO related fields, e.g. PNA pattern, are better simulated than MIROC3_hires. The time series of PDO obtained as the EOF1 of low-pass filtered (7 years) SST over the Pacific shows that a 20-year variation is dominant, and explains 37% of the total variance in the MIROC4. Its spatial distribution becomes more realistic than that in MIROC3_hires. Currently, only the spin-up and control experiments are finished using MIROC4. We will conduct near-term climate prediction experiments for the coming <span class="hlt">decades</span> to contribute for CMIP5/IPCC AR5.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhRvE..67e6216Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhRvE..67e6216Z"><span id="translatedtitle">Direct <span class="hlt">observation</span> of homoclinic orbits in human heart rate <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Żebrowski, J. J.; Baranowski, R.</p> <p>2003-05-01</p> <p>Homoclinic trajectories of the interbeat intervals between contractions of ventricles of the human heart are identified. The interbeat intervals are extracted from 24-h Holter ECG recordings. Three such recordings are discussed in detail. Mappings of the measured consecutive interbeat intervals are constructed. In the second and in some cases in the fourth iterate of the map of interbeat intervals homoclinic trajectories associated with a hyperbolic saddle are found. The homoclinic trajectories are often persistent for many interbeat intervals, sometimes spanning many thousands of heartbeats. Several features typical for homoclinic trajectories found in other systems were identified, including a signature of the gluing bifurcation. The homoclinic trajectories are present both in recordings of heart rate <span class="hlt">variability</span> obtained from patients with an increased number of arrhythmias and in cases in which the sinus rhythm is dominant. The results presented are a strong indication of the importance of deterministic nonlinear instabilities in human heart rate <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRC..113.2017A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRC..113.2017A"><span id="translatedtitle"><span class="hlt">Decadal</span> <span class="hlt">variability</span> in the northeast Pacific in a physical-ecosystem model: Role of mixed layer depth and trophic interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, Michael; Capotondi, Antonietta; Miller, Arthur; Chai, Fei; Brodeur, Richard; Deser, Clara</p> <p>2008-02-01</p> <p>A basin-wide interdecadal change in both the physical state and the ecology of the North Pacific occurred near the end of 1976. Here we use a physical-ecosystem model to examine whether changes in the physical environment associated with the 1976-1977 transition influenced the lower trophic levels of the food web and if so by what means. The physical component is an ocean general circulation model, while the biological component contains 10 compartments: two phytoplankton, two zooplankton, two detritus pools, nitrate, ammonium, silicate, and carbon dioxide. The model is forced with <span class="hlt">observed</span> atmospheric fields during 1960-1999. During spring, there is a ˜40% reduction in plankton biomass in all four plankton groups during 1977-1988 relative to 1970-1976 in the central Gulf of Alaska (GOA). The epoch difference in plankton appears to be controlled by the mixed layer depth. Enhanced Ekman pumping after 1976 caused the halocline to shoal, and thus the mixed layer depth, which extends to the top of the halocline in late winter, did not penetrate as deep in the central GOA. As a result, more phytoplankton remained in the euphotic zone, and phytoplankton biomass began to increase earlier in the year after the 1976 transition. Zooplankton biomass also increased, but then grazing pressure led to a strong decrease in phytoplankton by April followed by a drop in zooplankton by May: Essentially, the mean seasonal cycle of plankton biomass was shifted earlier in the year. As the seasonal cycle progressed, the difference in plankton concentrations between epochs reversed sign again, leading to slightly greater zooplankton biomass during summer in the later epoch.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMPP41B1503W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMPP41B1503W"><span id="translatedtitle">A new calibration for the Sr/Ca-temperature relationship in sclerosponges reveals synchronous changes in Caribbean specimens indicative of warming and multi-<span class="hlt">decadal</span> climate <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waite, A. J.; Swart, P. K.; Rosenheim, B. E.</p> <p>2009-12-01</p> <p>Previous work defined the calibration between the skeletal Sr/Ca ratio of the sclerosponge Ceratoporella nicholsoni and the ambient seawater temperature. However, application of this calibration to records throughout the Caribbean reveals a nearly 4°C warming over the last 150 years, in excess of what one might expect from global climate averages. As the original C. nicholsoni Sr/Ca-temperature relationship was calibrated between 26 and 30°C, it is possible that the relationship differed outside of the examined temperature window. This suspicion is confirmed by the measurement of Sr/Ca ratios from additional specimens of the same species. These show a significantly different slope between Sr/Ca and temperature at lower temperatures (21 to 26°C). Using this information, the calibration equation has been refined and the subsequent reconstructions of temperature are much more realistic, indicating a warming of approximately 1°C over the last 150 years. Applying this new calibration to additional published sclerosponge records of Sr/Ca reveals remarkable agreements between records from the Bahamas and Jamaica, both in amplitude of warming and smaller scale <span class="hlt">variability</span>. In addition, the depth versus temperature relationship associated with these specimens is preserved. The refined temperature reconstruction of a 600 year record from Exuma Sound, Bahamas, demonstrates the cyclic nature of its <span class="hlt">variability</span> (~15 and 28 year periodicities). Further use of these data and stable oxygen isotopes to calculate salinity reveals <span class="hlt">variability</span> on multi-<span class="hlt">decadal</span> timescales. This includes an approximately 20 year periodicity between 1400 and 1790. From 1790 to 2000, the dominant mode appears to switch to a roughly 60 year periodicity, consistent with that of the Atlantic Multi-<span class="hlt">decadal</span> Oscillation (AMO).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040081179&hterms=ECC&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DECC','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040081179&hterms=ECC&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DECC"><span id="translatedtitle"><span class="hlt">Variability</span> in Tropical Tropospheric Ozone as <span class="hlt">Observed</span> by SHADOZ</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thompson, Anne M.; Witte, Jacquelyn C.; Coetzee, Geert J. R.; Chatfield, Robert B.; Hudson, Robert D.</p> <p>2004-01-01</p> <p>The SHADOZ (Southern Hemisphere Additional Ozonesondes) ozone sounding network was initiated in 1998 to improve the coverage of tropical in-situ ozone measurements for satellite validation, algorithm development and related process studies. Over 2000 soundings have been archived at the central website, <http://croc.gsfc.nasa.gov/shadoz>, for 12 stations: Ascension Island; Nairobi and Malindi, Kenya; Irene, South Africa; Reunion Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; Natal, Brazil; Paramaribo, Surinam. Some results to date indicate reliability of the measurement and highly <span class="hlt">variable</span> interactions between ozone and tropical meteorology. For example: 1. By using ECC sondes with similar procedures, 5-10% accuracy and precision (1-sigma) of the sonde total ozone measurement was achieved [Thompson et al., 2003al; 2. Week-to-week <span class="hlt">variability</span> in tropospheric ozone is so great that statistics are frequently not Gaussian and most stations vary up to a factor of 3 in column amount over the course of a year [Thompson et al., 2002b]. 3. Longitudinal <span class="hlt">variability</span> in tropospheric ozone profiles is a consistent feature, with a 10- 15 DU column-integrated difference between Atlantic and Pacific sites; this is the cause of the zonal wave-one feature in total ozone [Shiotani, 1992]. The ozone record from Paramaribo, Surinam (6N, 55W) is a marked contrast to southern tropical ozone because Surinam is often north of the Intertropical Convergence Zone. Interpretations of SHADOZ time-series and approaches to classification suggested by SHADOZ data over Africa and the Indian Ocean will be described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.4344V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.4344V"><span id="translatedtitle">A new direction for Antarctic ice cores: reconstructing Pacific <span class="hlt">decadal</span> <span class="hlt">variability</span> and Australian drought history from the Law Dome ice core.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vance, Tessa; Roberts, Jason; Plummer, Chris; Kiem, Anthony; van Ommen, Tas</p> <p>2015-04-01</p> <p><span class="hlt">Decadal</span> scale SST oscillations in the Pacific significantly influence rainfall <span class="hlt">variability</span> and drought risk across and beyond the Pacific region. Understanding long-term <span class="hlt">decadal</span> SST behavior in the Pacific is necessary to assess past and future climate, particularly drought risk. However, short instrumental records through much of the Pacific region, in particular the South Pacific, make such assessments difficult. A new reconstruction of Pacific <span class="hlt">decadal</span> <span class="hlt">variability</span> covering the last millennium has been produced from the Law Dome ice core, a high snow accumulation site in East Antarctica. The Law Dome ice core samples (at sub-annual resolution) a broad mid-latitude swathe of the Indian and South West Pacific region. This region exhibits wind speed and direction anomalies that are coherent with the phase of the Interdecadal Pacific Oscillation (IPO), an index measuring the <span class="hlt">decadal</span>-scale Pacific SST state. This is the first millennial length IPO reconstruction and is based on the annual accumulation (snowfall) and sub-annual sea salt (wind proxy) records from Law Dome. To demonstrate the versatility of this new IPO reconstruction, we used it to explore drought history in eastern Australia, a region where drought risk is elevated during IPO positive phases. To do this, we super-imposed the 1000 year IPO reconstruction on a Law Dome proxy for eastern Australian rainfall (previously shown to represent rainfall with high significance during IPO positive phases (r =0.406-0.677, p <0.0001-0.01). Eight 'mega-droughts' (dry periods >5 years duration) were identified over the last millennium. Six mega-droughts occurred between AD 1000-1320 including one 39 y drought (AD 1174-1212). Water resources and infrastructure planning in Australia has been based on very limited statistical certainty around drought risk due to the short (~100 year) instrumental record and lack of rainfall proxies. This study shows that, similar to SW North America, Australia also experienced mega-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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120013038','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120013038"><span id="translatedtitle">Kepler <span class="hlt">Observations</span> of Rapid Optical <span class="hlt">Variability</span> in Active Galactic Nuclei</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mushotzky, R. F.; Edelson, R.; Baumgartner, W. H.; Gandhi, P.</p> <p>2012-01-01</p> <p>Over three quarters in 2010 - 2011, Kepler monitored optical emission from four active galactic nuclei (AGN) with approx 30 min sampling, > 90% duty cycle and approx < 0.1% repeatability. These data determined the AGN optical fluctuation power spectral density functions (PSDs) over a wide range in temporal frequency. Fits to these PSDs yielded power law slopes of -2.6 to -3.3, much steeper than typically seen in the X-rays. We find evidence that individual AGN exhibit intrinsically different PSD slopes. The steep PSD fits are a challenge to recent AGN <span class="hlt">variability</span> models but seem consistent with first order MRI theoretical calculations of accretion disk fluctuations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730007141','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730007141"><span id="translatedtitle"><span class="hlt">Observations</span> of the sun, an ultraviolet <span class="hlt">variable</span> star</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Heath, D. F.</p> <p>1972-01-01</p> <p>The uncertainty as to whether or not the sun is a <span class="hlt">variable</span> star in that region of the ultraviolet which is absorbed in the mesosphere and stratosphere led to an experiment with acronym MUSE, Monitor of Ultraviolet Solar Energy. The experiment was first flown on an Aerobee rocket in August 1966 and subsequently on Nimbus 3 and 4 in April 1969 and April 1970 respectively. The basic philosophy behind the design of the experiment was to provide an instrument which would not require a solar pointing mechanism and at the same time would be capable of high radiometric accuracy for long periods in space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JHyd..536..426N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JHyd..536..426N"><span id="translatedtitle">Inter-annual to inter-<span class="hlt">decadal</span> streamflow <span class="hlt">variability</span> in Quebec and Ontario in relation to dominant large-scale climate indices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nalley, D.; Adamowski, J.; Khalil, B.; Biswas, A.</p> <p>2016-05-01</p> <p>The impacts of large-scale climate oscillations on hydrological systems and their <span class="hlt">variability</span> have been documented in different parts of the world. Since hydroclimatic data are known to exhibit non-stationary characteristics, spectral analyses such as wavelet transforms are very useful in extracting time-frequency information from such data. As Canadian studies, particularly those of regions east of the Prairies, using wavelet transform-based methods to draw links between relevant climate indices [e.g., the El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the Pacific <span class="hlt">Decadal</span> Oscillation (PDO)] and streamflow <span class="hlt">variability</span> are not common, this study aims to analyze such relationships for the southern regions of Quebec and Ontario. Monthly and annual streamflow data with a record length of 55 years were used to capture streamflow <span class="hlt">variability</span> at intra-annual, inter-annual and inter-<span class="hlt">decadal</span> scales. The continuous wavelet transform spectra of monthly streamflow data revealed consistent significant 6- and 12-month periodicities, which are likely associated with strong seasonality factors. Its annual counterparts showed four different significant periodicities: up to 4 years, 4-6 years, 6-8 years, and greater than 8 years - all of which occurred after the late 1960s/early 1970s. Wavelet coherence analyses show that the influence of ENSO and NAO at the inter-annual scale occurs at 2-6 year periodicities, and the influence of PDO occur at periodicities up to 8 years and exceeding 16 years. Correlations between these climate indices and streamflow were computed to determine the time delay of streamflow response to the influence of ENSO, NAO, and PDO. The lag times ranged from 6-48 months (for monthly data) and 1-4 years (for annual data). This research contributes to our understanding of streamflow <span class="hlt">variability</span> over the southern parts of Quebec and Ontario, and the role of ENSO, NAO, and PDO phenomena on this <span class="hlt">variability</span>. These relationships can be also used to improve hydrological forecasting and water resources management in Ontario and Quebec.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21528851','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21528851"><span id="translatedtitle">Optimization of the transmission of <span class="hlt">observable</span> expectation values and <span class="hlt">observable</span> statistics in continuous-<span class="hlt">variable</span> teleportation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Albano Farias, L.; Stephany, J.</p> <p>2010-12-15</p> <p>We analyze the statistics of <span class="hlt">observables</span> in continuous-<span class="hlt">variable</span> (CV) quantum teleportation in the formalism of the characteristic function. We derive expressions for average values of output-state <span class="hlt">observables</span>, in particular, cumulants which are additive in terms of the input state and the resource of teleportation. Working with a general class of teleportation resources, the squeezed-bell-like states, which may be optimized in a free parameter for better teleportation performance, we discuss the relation between resources optimal for fidelity and those optimal for different <span class="hlt">observable</span> averages. We obtain the values of the free parameter of the squeezed-bell-like states which optimize the central momenta and cumulants up to fourth order. For the cumulants the distortion between in and out states due to teleportation depends only on the resource. We obtain optimal parameters {Delta}{sub (2)}{sup opt} and {Delta}{sub (4)}{sup opt} for the second- and fourth-order cumulants, which do not depend on the squeezing of the resource. The second-order central momenta, which are equal to the second-order cumulants, and the photon number average are also optimized by the resource with {Delta}{sub (2)}{sup opt}. We show that the optimal fidelity resource, which has been found previously to depend on the characteristics of input, approaches for high squeezing to the resource that optimizes the second-order momenta. A similar behavior is obtained for the resource that optimizes the photon statistics, which is treated here using the sum of the squared differences in photon probabilities of input versus output states as the distortion measure. This is interpreted naturally to mean that the distortions associated with second-order momenta dominate the behavior of the output state for large squeezing of the resource. Optimal fidelity resources and optimal photon statistics resources are compared, and it is shown that for mixtures of Fock states both resources are equivalent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JHyd..409..759G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JHyd..409..759G"><span id="translatedtitle">Spatio-temporal <span class="hlt">variability</span> in Ebro river basin (NE Spain): Global SST as potential source of predictability on <span class="hlt">decadal</span> time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gámiz-Fortis, S. R.; Hidalgo-Muñoz, J. M.; Argüeso, D.; Esteban-Parra, M. J.; Castro-Díez, Y.</p> <p>2011-11-01</p> <p>SummaryThis paper investigates the spatial and temporal <span class="hlt">variability</span> of streamflow in the Ebro river basin and its potential predictability. Principal Component Analysis applied to monthly streamflow series from 83 gauging stations distributed through the basin, reveals three homogeneous regions: Basque-Cantabrian, Pyrenees and Southern Mediterranean. Attending to this classification the main characteristic time scales of the maximum monthly streamflows are studied by Singular Spectral Analysis (SSA). <span class="hlt">Decadal</span> variations in streamflow make particularly large contributions to year-to-year streamflow variance in stations placed in the Basque-Cantabrian and Southern Mediterranean regions, while for the Pyrenees flows the interannual contribution is more important. The predictability of the Ebro flow anomalies has been investigated using a combined methodology: at <span class="hlt">decadal</span> time scales SST anomalies from several regions provide a significant source of predictability for the Ebro flow, while at interannual time scales autoregressive-moving-average modelling, applied to the time series previously filtered by SSA, is able to provide potential skill in forecasting. For gauging stations associated to the Basque-Cantabrian region significant correlations between the maximum monthly streamflow anomalies and a tripole-like pattern in the North Atlantic SSTs during the previous spring are found. This association is found maximum and stable for the tropical part of the pattern (approximately 0-20°N). For the gauging stations placed to the southeast of basin some influence from the Pacific <span class="hlt">Decadal</span> Oscillation (PDO) is found. This method allows evaluating, independently, the <span class="hlt">decadal</span> and interannual predictability of the streamflow series. In addition, the combination of both modelling techniques gives as result a methodology that has the capacity to provide basin-specific hydroclimatic predictions which vary (for the 1990-2003 validation period) between 62% for the Basque-Cantabrian region, 76% for the Southern Mediterranean and 81% for the Pyrenees. In summary, this work shows the existence of a valuable <span class="hlt">decadal</span> and interannual predictability of the Ebro streamflow, a result which may be useful to water resources management.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMGC23A0746J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMGC23A0746J"><span id="translatedtitle"><span class="hlt">Variability</span> of Primary Production and Surface Albedo along Desert-steppe Ecotone based on Satellite <span class="hlt">Observation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jia, G.; Wang, H.; Zhou, Y.</p> <p>2009-12-01</p> <p>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 <span class="hlt">variability</span> 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 <span class="hlt">decades</span>, 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 <span class="hlt">decadal</span> trends and extremes of primary production and surface albedo, and identified areas with the greatest <span class="hlt">variability</span> 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 <span class="hlt">observed</span> in some areas over lowlands and edge of sandy desert. There were strong interannual <span class="hlt">variability</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC41C0993D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC41C0993D"><span id="translatedtitle"><span class="hlt">Observed</span> Inter-<span class="hlt">decadal</span> weakening of the Asian summer monsoon and different response of South and East Asian monsoons during a warming climate scenario</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, Y.</p> <p>2012-12-01</p> <p>Based on the <span class="hlt">observed</span> analysis by using 123-yr <span class="hlt">observed</span> data, we have shown the inter-<span class="hlt">decadal</span> weakening of summer monsoon precipitation in East Asia and China, with two major features identified: (1)the rainfall pattern has undergone an obvious southward shift from North China to South China in the mid -and late 1970s. This shift of the precipitation pattern is in good coincidence with a significant abrupt climate change for other <span class="hlt">variables</span>; and (2) occurrence of prolonged droughts in North China and , at the same time, marked flooding in the Yangtze River Valley and South China in the period from the end 1970s to the beginning of the 21st century. On the other hand , it has been found that after the end of the 1970s the Indian summer monsoon has also underwent a weakening processes which is in good agreement with that in East Asia. So, the Asian summer monsoon has holistically become weaker during past 30 years. One key issue is how long this unusual change in the Asian summer monsoon and associated precipitation patterns will continue to occur. By using outputs from climate models of IPCC AR4 we have projected the responses of the South Asian summer monsoon (SASM) and the East Asian summer monsoon (EASM) circulations and precipitation to different warming over land and ocean under a medium warming scenario, SRES A1B. Our results suggest that, at inter-<span class="hlt">decadal</span> and longer time scales, the change in the SASM circulation is consistent with the change in the TP(Tibetan Plateau) -TIO (tropical Indian Ocean) upper-troposphere thermal contrast (i.e. meridional temperature gradient) that is believed to be the main driver for SASM. Conversely, the change in the EASM circulation is consistent with the change in the TP-TPO (tropical Pacific Ocean) lower-troposphere thermal contrast, which will be enhanced due to the decreasing winter snow over TP and SSTA over the tropical Pacific. Further analyses suggest that increases in moisture and change in cloud cover induced by global warming may cause different upper-troposphere warming over the TP and the tropical oceans , respectively. Because the warming over the TIO is stronger than that over the TP, the TP-TIO meridional thermal contrasts will decrease in the future, thus leading to continuous weakening of tropical easterly jet and the monsoon intensity measured with W-Y monsoon index. However, in the lower layer of EA, a larger heating effect in the region of the TP than that over tropical Pacific due to decrease in winter snow can increase the zonal land and sea thermal contrast as well as the EASM intensity. In conclusions, since mid-or late 1970s, the Asian summer monsoon has experienced the inter-<span class="hlt">decadal</span> weakening. However, in this century the South Asian summer monsoon will continue to weaken (mainly for the monsoon circulation) whereas the East Asian summer monsoon will gradually strengthen, especially after 2040's. It should be pointed out that the projection of the summer monsoon change are subject to a large uncertainty which are also discussed in this report, especially for development of convection over tropical oceans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740012549','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740012549"><span id="translatedtitle">Component noise <span class="hlt">variables</span> of a light <span class="hlt">observation</span> helicopter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robinson, F.</p> <p>1973-01-01</p> <p>A test program was conducted to isolate and evaluate the individual noise sources of a light helicopter. To accomplish this, the helicopter was mounted on a special test rig, at a 6-foot skid height, in a simulated hover. The test rig contained by dynamometer for absorbing engine power and an exhaust silencing system for reducing engine noise. This test set-up allowed the various components of the helicopter to be run and listened to individually or in any combination. The sound pressure level was recorded at a point 200 feet from the helicopter as the component parameters were systematically varied. The tests were conducted in an open area, during the middle of the night, with no wind, and with all other known <span class="hlt">variables</span> either eliminated or kept as constant as possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApJ...743L..12M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApJ...743L..12M"><span id="translatedtitle">Kepler <span class="hlt">Observations</span> of Rapid Optical <span class="hlt">Variability</span> in Active Galactic Nuclei</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mushotzky, R. F.; Edelson, R.; Baumgartner, W.; Gandhi, P.</p> <p>2011-12-01</p> <p>Over three quarters in 2010-2011, Kepler monitored optical emission from four active galactic nuclei (AGNs) with ~30 minute sampling, >90% duty cycle, and lsim0.1% repeatability. These data determined the AGN optical fluctuation power spectral density (PSD) functions 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 AGNs exhibit intrinsically different PSD slopes. The steep PSD fits are a challenge to recent AGN <span class="hlt">variability</span> models but seem consistent with first-order magnetorotational instability theoretical calculations of accretion disk fluctuations.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1214798A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1214798A"><span id="translatedtitle">Ozone column content <span class="hlt">variability</span> at the Kishinev site from satellite retrievals and ground <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aculinin, Alexandr; Smicov, Vladimir</p> <p>2010-05-01</p> <p>It is analyzed <span class="hlt">variability</span> of the total ozone content (TOC) in column of atmosphere by using ozone retrievals from satellite platform and from direct ground <span class="hlt">observations</span> at the Kishinev site, Moldova (47.00N; 28.56E). Direct ground <span class="hlt">observations</span> of the TOC are regular carried out by Atmospheric Research Group (ARG), Institute of Applied Physics at the ground-based solar radiation monitoring station, Kishinev site, by using of hand-held ozonemeter MICROTOPS II. TOC measurements started since 2003. Data of ozone <span class="hlt">observations</span> are presented at the research group web-site http://arg.phys.asm.md. Satellite TOC dataset at specific coordinates of Kishinev site was derived by using linear interpolation of the parent gridded databases from TOMS (1979-2004) and OMI (2005-2008) <span class="hlt">observations</span>. It was established that relative difference of TOC between periods from 1979 to 1983 and from 2004 to 2008 was -5.16 %. Data were processed by applying of 5-year averaging "window". For a period from 1979 to 2008 statistical estimation of linear trend of the TOC was -2.08% per <span class="hlt">decade</span>. Climatic norm of TOC for this period was equal to 335 DU. Variation of ozone column content at Kishinev site shows it seasonal character with maximum of the order of ~378 DU (in March and April) and with minimum of the order of ~289 DU (in October). The largest and lowest range of oscillations of monthly means of the TOC retrieved for Kishinev site from TOMS and OMI <span class="hlt">observations</span> in the course of the period from 1979 to 2008 were ~ 102 DU (in February) and ~29 DU (in October). Extremely low and high values of the TOC ever registered for Kishinev site from TOMS and OMI <span class="hlt">observations</span> were ~ 209 DU (on December 1, 1999) and ~ 532 DU (on March 3, 1988). It was shown that ARG ground <span class="hlt">observations</span> give overestimated TOC values in comparison with the TOMS and OMI <span class="hlt">observations</span> from satellite platforms. Relative differences or biases (in %) between satellite and ARG ground <span class="hlt">observations</span> of the TOC at Kishinev site were derived by using of daily means of TOC from the short-long series of simultaneous measurements for respective pairs: TOMS vs ARG (2003-2005) and OMI vs ARG(2004-2008). These differences were -1.85% (or -6 DU) for pair TOMS-ARG and -2.15% (or -7 DU) for pair OMI-ARG <span class="hlt">observations</span>. It should be noted that derived correlation coefficients for sets of TOMS-ARG and OMI-ARG <span class="hlt">observations</span> of daily means of TOC were ~0.981 and ~0.992, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998euve.prop...21G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998euve.prop...21G"><span id="translatedtitle">EUVE Io Plasma Torus <span class="hlt">Observations</span>: Galileo Support and <span class="hlt">Variability</span> Studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gladstone, G. Randall</p> <p></p> <p>We propose a Large <span class="hlt">Observing</span> Program (1000 ksec) to monitor and investigate EUV emissions from the Io plasma torus and Jupiter during the last four Galileo Europa Mission encounters. These encounters all occur in the last half of 1999 (on Aug. 12, Sept. 14, Oct. 11, and Nov. 26), and will provide a perhaps never-to-be-repeated opportunity for acquiring ground truth (i.e., in situ) measurements with which to calibrate remote sensing <span class="hlt">observations</span> of the torus. With these new data, we will 1) monitor the global properties of the torus during the Galileo <span class="hlt">observation</span> epoch, 2) resolve two important but closely spaced torus periodicities, 3) determine the torus stability time constants, 4) search for very faint localized emissions from the Galilean satellites, and 5) continue monitoring the Jovian dayglow. We feel that such a program will make excellent use of EUVEs capabilities, and will allow for a much deeper understanding of the physics of the Jovian system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/534525','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/534525"><span id="translatedtitle">Coupled ocean-atmosphere model system for studies of interannual-to-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> over the North Pacific Basin and precipitation over the Southwestern United States</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lai, Chung-Chieng A.</p> <p>1997-10-01</p> <p>This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The ultimate objective of this research project is to make understanding and predicting regional climate easier. The long-term goals of this project are (1) to construct a coupled ocean-atmosphere model (COAM) system, (2) use it to explore the interannual-to-<span class="hlt">decadal</span> climate <span class="hlt">variability</span> over the North Pacific Basin, and (3) determine climate effects on the precipitation over the Southwestern United States. During this project life, three major tasks were completed: (1) Mesoscale ocean and atmospheric model; (2) global-coupled ocean and atmospheric modeling: completed the coupling of LANL POP global ocean model with NCAR CCM2+ global atmospheric model; and (3) global nested-grid ocean modeling: designed the boundary interface for the nested-grid ocean models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhDT.......150C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhDT.......150C"><span id="translatedtitle">Seasonal and interannual ocean-atmosphere <span class="hlt">variability</span> in the tropical Atlantic: <span class="hlt">Observed</span> structure and model representation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chang, Ching-Yee</p> <p></p> <p>Tropical Atlantic is clamped by the South America (the Amazon) in the west and Africa (the Sahel) in the east. These two regions have been undergoing significant climate/environment changes for <span class="hlt">decades</span>. In order to use climate models to study the impacts of these changes, climate models need to be able to well simulate the seasonal climate of the tropical Atlantic sector. The first part of this dissertation focuses on the representation of the seasonal cycle in the CCSM3 coupled atmosphere-ocean model. CCSM3 SST has a north-south dipole pattern of bias centered at the latitude of the thermal equator, resembling the <span class="hlt">observed</span> pattern of interannual climate <span class="hlt">variability</span> in boreal spring. Along the equator in boreal spring CCSM3 exhibits striking westerly winds at the surface, reminiscent of the pattern of climate <span class="hlt">variability</span> in boreal summer. The westerly winds cause deepening of the eastern thermocline that keeps the east warm despite enhanced coastal upwelling. Next, a comparison is made with a simulation using historical SST to force the atmospheric model (CAM3) in order to deduce information about the origin of bias in CCSM3. The patterns of bias in CAM3 resemble that in CCSM3, indicating that the source of the bias in CCSM3 may be traced to difficulties in the atmospheric model. The next chapter presents a modeling study of the origin of the westerly wind bias CAM3 by using a steady-state linearized atmospheric model. The results indicate that underestimation of rainfall over the eastern Amazon region can lead to the westerly bias in equatorial Atlantic surface winds. They suggest that efforts to reduce coupled model biases, especially seasonal ones, must target continental biases, even in the deep Tropics where ocean-atmosphere interaction generally rules. The fourth chapter investigates the relationship between the two predominate modes of Tropical Atlantic interannual <span class="hlt">variability</span>. The leading modes of Tropical Atlantic SST <span class="hlt">variability</span> in boreal spring and summer are shown to be related, with the spring meridional mode leading into summer equatorial mode. The presence of a meridional mode with warm SST anomalies in the southern tropics in spring leads to a warm phase equatorial mode in summer, and vice-versa. This modal linkage occurs independently of climate <span class="hlt">variability</span> in other ocean basins (e.g., ENSO). Atmospheric diabatic heating associated with a meridional shift of the Inter-Tropical Convergence Zone plays an important role in this relationship. The identification of this relationship enhances the prospects for prediction of boreal summer rainfall over the Guinea Coast of equatorial Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ThApC.119..181Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ThApC.119..181Z"><span id="translatedtitle">Six-<span class="hlt">decade</span> temporal change and seasonal decomposition of climate <span class="hlt">variables</span> in Lake Dianchi watershed (China): stable trend or abrupt shift?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Jing; Liang, Zhongyao; Liu, Yong; Guo, Huaicheng; He, Dan; Zhao, Lei</p> <p>2015-01-01</p> <p>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 <span class="hlt">variables</span> from 1951 to 2009. The <span class="hlt">variables</span> 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 <span class="hlt">decade</span>, respectively; (b) annual precipitation has an insignificant decreasing trend with the decreasing rate of 3.17 mm per <span class="hlt">decade</span>; (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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030067741&hterms=cluster+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcluster%2Bwave','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030067741&hterms=cluster+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcluster%2Bwave"><span id="translatedtitle">Spatiotemporal <span class="hlt">Variability</span> and Propagation of Equatorial Noise <span class="hlt">Observed</span> by Cluster</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Santolik, O.; Pickett, J. S.; Gurnett, D. A.; Maksimovic, M.; Cornilleau-Wehrlin, N.</p> <p>2002-01-01</p> <p>We report a multipoint case study of the electromagnetic equatorial noise <span class="hlt">observed</span> by the Cluster project. High-resolution data were measured in three close points in space located in the morning sector of the outer plasmasphere. We demonstrate a narrow latitudinal extent of the emissions with a typical width of 2 degrees, centered near the minimum-B equator. Power spectra recorded by the different satellites show a complex structure of emission lines whose relative intensities and positions vary at timescales of 1-2 min and/or at spatial scales of tens of wavelengths. These lines do not match harmonics of the local proton cyclotron frequency, as it would be expected if the waves are generated by energetic ions and <span class="hlt">observed</span> near the source region. We bring <span class="hlt">observational</span> evidence that the waves propagate with a significant radial component and thus can propagate from a distant generation region located at different radial distances where ion cyclotron frequencies match the <span class="hlt">observed</span> fine structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5762L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5762L"><span id="translatedtitle">Two <span class="hlt">Decades</span> of Global and Regional Sea Level <span class="hlt">Observations</span> from the ESA Climate Change Initiative Sea Level Project</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Legeais, JeanFrancois; Larnicol, Gilles; Cazenave, Anny; Ablain, Michael; Benveniste, Jrme; Lucas, BrunoManuel; Timms, Gary; Johannessen, Johnny; Knudsen, Per; Cipollini, Paolo; Roca, Monica; Rudenko, Sergei; Fernandes, Joana; Balmaseda, Magdalena; Quartly, Graham; Fenoglio-Marc, Luciana; Scharfennberg, Martin; Meyssignac, Benoit; Guinle, Thierry; Andersen, Ole</p> <p>2015-04-01</p> <p>Sea level is a very sensitive index of climate change and <span class="hlt">variability</span>. Sea level integrates the ocean warming, mountain glaciers and ice sheet melting. Understanding the sea level <span class="hlt">variability</span> and changes implies an accurate monitoring of the sea level <span class="hlt">variable</span> at climate scales, in addition to understanding the ocean <span class="hlt">variability</span> and the exchanges between ocean, land, cryosphere, and atmosphere. That is why Sea Level is one of the Essential Climate <span class="hlt">Variables</span> (ECV) selected in the frame of the ESA Climate Change Initiative (CCI) program. It aims at providing long-term monitoring of the sea level ECV with regular updates, as required for climate studies. After a first phase (2011-2013), the program has started in 2014 a second phase of 3 years. The objectives of this second phase are to involve the climate research community, to refine their needs and collect their feedbacks on product quality, to develop, test and select the best algorithms and standards to generate an updated climate time series and to produce and validate the Sea Level ECV product. This will better answer the climate user needs by improving the quality of the Sea Level products and maintain a sustain service for an up-to-date production. To this extent, the ECV time series has been extended and it now covers the period 1993-2013. We will firstly present the main achievements of the ESA CCI Sea Level Project. On the one hand, the major steps required to produce the 21 years climate time series are briefly described: collect and refine the user requirements, development of adapted algorithms for climate applications and specification of the production system. On the other hand, the product characteristics are described as well as the results from product validation, performed by several groups of the ocean and climate modeling community. At last, the work plan and key challenges of the second phase of the project are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=observation&id=EJ1042328','ERIC'); return false;" href="http://eric.ed.gov/?q=observation&id=EJ1042328"><span id="translatedtitle">A Review of Direct <span class="hlt">Observation</span> Research within the Past <span class="hlt">Decade</span> in the Field of Emotional and Behavioral Disorders</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Adamson, Reesha M.; Wachsmuth, Sean T.</p> <p>2014-01-01</p> <p>This study reviewed prominent journals within the field of emotional and behavioral disorders to identify direct <span class="hlt">observation</span> approaches, reported reliability statistics, and key features of direct <span class="hlt">observation</span>. Selected journals were systematically reviewed for the past 10 years identifying and quantifying specific direct <span class="hlt">observation</span> systems and…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22342105','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22342105"><span id="translatedtitle">Follow up <span class="hlt">observations</span> of SDSS and CRTS candidate cataclysmic <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Szkody, Paula; Vasquez-Soltero, Stephanie; Everett, Mark E.; Silva, David R.; Howell, Steve B.; Landolt, Arlo U.; Bond, Howard E. E-mail: dsilva@noao.edu E-mail: landolt@rouge.phys.lsu.edu</p> <p>2014-10-01</p> <p>We present photometry and spectroscopy of 11 and 35 potential cataclysmic <span class="hlt">variables</span>, respectively, from the Sloan Digital Sky Survey, the Catalina Real-Time Transient Survey, and vsnet alerts. The photometry results include quasi-periodic oscillations during the decline of V1363 Cyg, nightly accretion changes in the likely Polar (AM Herculis binary) SDSS J1344+20, eclipses in SDSS J2141+05 with an orbital period of 76 ± 2 minutes, and possible eclipses in SDSS J2158+09 at an orbital period near 100 minutes. Time-resolved spectra reveal short orbital periods near 80 minutes for SDSS J0206+20, 85 minutes for SDSS J1502+33, and near 100 minutes for CSS J0015+26, RXS J0150+37, SDSS J1132+62, SDSS J2154+15, and SDSS J2158+09. The prominent He II line and velocity amplitude of SDSS J2154+15 are consistent with a Polar nature for this object, while the absence of this line and a low velocity amplitude argue against this classification for RXS J0150+37. Single spectra of 10 objects were obtained near outburst and the rest near quiescence, confirming the dwarf novae nature of these objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.H43J..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.H43J..07S"><span id="translatedtitle">Partitioning of Terrestrial ET <span class="hlt">Variability</span> in the CAM4/CLM4 Climate Model, Contributions to Trends over the Last Two <span class="hlt">Decades</span>, and Sensitivity to Parameterization Changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Y.; Dickinson, R. E.</p> <p>2009-12-01</p> <p>ET is partitioned into canopy evaporation, transpiration, and soil evaporation. For a realistic climate model simulation, it is important that these terms not only add to a realistic total ET but also individually agree with <span class="hlt">observations</span>. In this study, CAM4.0 was run 21 years from 1982 to 2002 with a spatial resolution of 1 by 1 degree, forced by prescribed SST. A global monthly ET dataset was produced and compared with <span class="hlt">observational</span> analyses. The CAM may overestimate the magnitude of global ET flux from too much ground evaporation but its annual cycle was reasonably predicted. Ground evaporation has the highest correlation with total ET variation and is the largest contributor its <span class="hlt">variability</span>. Changes to the current ET parameterizations are suggested that simulate ET <span class="hlt">variability</span> and magnitude in better agreement with <span class="hlt">observations</span> from 64 flux measurement sites over different climate regimes and land covers. Linear trends and their drivers are examined and their change with the suggested parameterizations are analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9638E..0OT','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9638E..0OT"><span id="translatedtitle"><span class="hlt">Observations</span> of SST diurnal <span class="hlt">variability</span> in the South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tu, Qianguang; Pan, Delu; Hao, Zengzhou; Chen, Jianyu</p> <p>2015-10-01</p> <p>In this study, a 3-hourly time resolution gap free sea surface temperature (SST) analysis is generated to resolve the diurnal cycle in the South China Sea (SCS, 0°-25°N, 100°-125°E).It takes advantage of hourly geostationary satellite MTSAT <span class="hlt">observations</span> and combines three infrared and two microwave polar satellite <span class="hlt">observations</span> at different local times. First, all the data are classified into eight SST datasets at 3 hour intervals and then remapped to 0.05°resolution grids. A series of critical quality control is done to remove the outliers.Then bias adjustment is applied to the polar satellite <span class="hlt">observations</span> with reference to the MTSAT data. Finally, the six satellites SST data are blended by using the optimal interpolated algorithm. The 3-hourly blended SST is compared against buoy measurements. It shows a good agreement that the biases do not exceed 0.2 °C and root mean square errors range from 0.5 to 0.65 °C. A typical diurnal cycle similar to sine wave is <span class="hlt">observed</span>. The minimum SST occurs at around 0600h and warming peak occurring between 1300h and 1500h local solar time and then decrease in the late afternoon, tapering off at night on March 13, 2008 for example. The frequency of diurnal warming events derived from four years of the blended SST provides solid statistics to investigate the seasonal and spatial distributions of the diurnal warming in the SCS. The sea surface diurnal warming tends to appear more easily in spring, especially in the coastal regions than other seasons and the central regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010MNRAS.409.1585B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010MNRAS.409.1585B"><span id="translatedtitle">Flavours of <span class="hlt">variability</span>: 29 RR Lyrae stars <span class="hlt">observed</span> with Kepler</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Benkő, J. M.; Kolenberg, K.; Szabó, R.; Kurtz, D. W.; Bryson, S.; Bregman, J.; Still, M.; Smolec, R.; Nuspl, J.; Nemec, J. M.; Moskalik, P.; Kopacki, G.; Kolláth, Z.; Guggenberger, E.; di Criscienzo, M.; Christensen-Dalsgaard, J.; Kjeldsen, H.; Borucki, W. J.; Koch, D.; Jenkins, J. M.; van Cleve, J. E.</p> <p>2010-12-01</p> <p>We present our analysis of Kepler <span class="hlt">observations</span> of 29 RR Lyrae stars, based on 138 d of <span class="hlt">observation</span>. We report precise pulsation periods for all stars. Nine of these stars had incorrect or unknown periods in the literature. 14 of the stars exhibit both amplitude and phase Blazhko modulations, with Blazhko periods ranging from 27.7 to more than 200 d. For V445 Lyr, a longer secondary variation is also <span class="hlt">observed</span> in addition to its 53.2-d Blazhko period. The unprecedented precision of the Kepler photometry has led to the discovery of the the smallest modulations detected so far. Moreover, additional frequencies beyond the well-known harmonics and Blazhko multiplets have been found. These frequencies are located around the half-integer multiples of the main pulsation frequency for at least three stars. In four stars, these frequencies are close to the first and/or second overtone modes. The amplitudes of these periodicities seem to vary over the Blazhko cycle. V350 Lyr, a non-Blazhko star in our sample, is the first example of a double-mode RR Lyrae star that pulsates in its fundamental and second overtone modes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E1910L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E1910L"><span id="translatedtitle">Generic relationships between <span class="hlt">observational</span> parameters defining ionospheric <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lynn, Kenneth; Heitmann, Andrew; Gardener-Garden, Robert</p> <p></p> <p>It has long been known that travelling ionospheric disturbances (TIDs) are seen as a tilted descending variation in isolines of constant electron density derived from ionograms. This is the descending phase front of what is actually an ascending TID, as originally noted by Hines. What is less known is that this descent results in a time delay between the motion of the ionosphere at the greatest <span class="hlt">observed</span> height and the arrival of the disturbance at the base of the layer (typically the F2) which in turn causes a temporary a compression of the layer thickness and a temporary increase in maximum electron density (foF2). The tilt in the descending electron density variation is often used as the identifying mark of a TID. This paper points out that the relationships <span class="hlt">observed</span> between foF2, descending height and layer thickness is not unique to a TID but is a generic relationship <span class="hlt">observed</span> whenever ionization is driven up and down magnetic field lines. Examples of this broader relationship are given for the equatorial post sunset rise and fall in electron density and in equatorial and middle latitude variations in ionospheric diurnal patterns which may repeat over a number of days. Such patterns are definitely not caused by TIDs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A33E3244V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A33E3244V"><span id="translatedtitle">Pacific <span class="hlt">Decadal</span> <span class="hlt">Variability</span> in the Southern Indian Ocean: A 1 ky Interdecadal Pacific Oscillation and Australian Megadrought Reconstruction from Law Dome, East Antarctica.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vance, T.; Roberts, J. L.; Plummer, C. T.; Kiem, A.; van Ommen, T. D.</p> <p>2014-12-01</p> <p>The Interdecadal Pacific Oscillation (IPO) is a multidecadal mode of Pacific basin SST anomalies, and is the basin-wide, bi-hemispheric expression of the Pacific <span class="hlt">Decadal</span> Oscillation (PDO). The two indices are highly correlated, but the extent to which they are merely low frequency ENSO is debated. Nonetheless, the IPO/PDO significantly influences interannual rainfall <span class="hlt">variability</span> and drought risk across and beyond the Pacific region on multi-<span class="hlt">decadal</span> timescales, thus an understanding of long-term IPO/PDO <span class="hlt">variability</span> will help with assessing past and future drought risk. A new and highly accurate 1 ky IPO reconstruction has been produced from the Law Dome ice core (East Antarctica). Law Dome is a high accumulation site on the coast of Antarctica in the Indian Ocean sector of the Southern Ocean, and the Law Dome record is directly related to atmospheric anomalies across a broad mid-latitude swathe of this region. The reconstruction utilizes both the accumulation (snowfall) and sea salt (wind proxy) records to produce a reconstruction that is highly calibrated to the instrumental IPO record from 1870-2009 and shows excellent skill (reduction of error value of 0.86). We then super-imposed the 1 ky IPO on a Law Dome proxy for rainfall in eastern subtropical Australia (previously shown to represent rainfall with high significance during IPO positive phases (r =0.406-0.677, p <0.0001-0.01) to identify eight Australian 'mega-droughts' (dry periods >5 y duration) over the last millennium. Six mega-droughts occur between AD 1000-1320 including one 39 y drought (AD 1174-1212). Water resources and infrastructure planning in Australia has been based on very limited statistical certainty around drought risk due to the short instrumental record and lack of rainfall proxies. A recent drought (the 'Big Dry' ~1995-2009) brought both agricultural and urban water supplies to critically low levels, while the Murray-Darling Basin river system, which provides 65% of the water used for irrigation in Australia, was on the brink of ecosystem collapse. Clearly, <span class="hlt">decadal</span>-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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JASTP.132..124H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JASTP.132..124H"><span id="translatedtitle">The influence of PMCs on water vapor and drivers behind PMC <span class="hlt">variability</span> from SOFIE <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hervig, Mark E.; Siskind, David E.; Bailey, Scott M.; Russell, James M.</p> <p>2015-09-01</p> <p><span class="hlt">Observations</span> from the Solar Occultation For Ice Experiment (SOFIE) are used to quantify relationships between polar mesospheric clouds (PMC) and their environment. Dehydration due to ice growth is found to be greatest ∼1.8 km above the height of peak ice mass density on average, and H2O enhancement due to sublimation is greatest near the bottom of the PMC layer. The dehydration and hydration layers contain a similar amount of H2O, although less than is found in ice layers, a difference that may be due to meridional transport. Because PMCs modify the surrounding water vapor, PMC-H2O relationships can be misleading and recommendations are made for dealing with this issue. The dependence of PMCs on water vapor and temperature was quantified, accounting for the effects of ice on water vapor. The approach examined inter-annual variations and considered the subset of PMCs detected by the Solar Backscatter Ultraviolet (SBUV) instruments, which are less sensitive than SOFIE. Results in the Northern Hemisphere indicate that PMC variations are dominated by temperature, but that a combination of temperature and water vapor provides the best explanation of the <span class="hlt">observations</span>. In the Southern Hemisphere PMC <span class="hlt">variability</span> is attributed primarily to temperature, with water vapor playing a minor role. The subset of SBUV PMCs are found to be one third as sensitive to changing temperature as the entire PMC population <span class="hlt">observed</span> by SOFIE. Finally, an approach is presented which allows temperature and water vapor anomalies to be estimated from various PMC data sets such as SBUV. Using recently reported SBUV PMC trends at 64-74°N latitude with the results of this study indicates a cooling trend of -0.27±0.14 K <span class="hlt">decade</span>-1 and a water vapor increase of +0.66±0.34% <span class="hlt">decade</span>-1 (both at 80-84 km). This cooling trend agrees with reports based on <span class="hlt">observations</span> in the middle atmosphere at similar latitudes. The water vapor increase is lower than expected due to increasing methane, although this difference may be consistent with H2O loss due to photolysis at PMC altitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19760030096&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Variable%2Bstars%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19760030096&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2528Variable%2Bstars%2529"><span id="translatedtitle">Combined optical and X-ray <span class="hlt">observations</span> of <span class="hlt">variable</span> stars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bowyer, C. S.</p> <p>1975-01-01</p> <p>Questions concerning the optical identification of X-ray sources are considered. There are now a total of eight optically identified galactic X-ray sources. Of these eight, five are definitely established as binaries. The nature of the other three sources remains unknown. Studies of U Geminorum conducted on the basis of optical and X-ray <span class="hlt">observations</span> are also discussed. From the upper limit to the accretion rate for U Gem obtained with the aid of soft X-ray data, it is seen that most of the mass flow in U Gem is lost from the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20782889','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20782889"><span id="translatedtitle"><span class="hlt">Observational</span> constraints on a <span class="hlt">variable</span> dark energy model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Movahed, M. Sadegh; Rahvar, Sohrab</p> <p>2006-04-15</p> <p>We study the effect of a phenomenological parameterized quintessence model on low, intermediate and high redshift <span class="hlt">observations</span>. At low and intermediate redshifts, we use the Gold sample of supernova Type Ia (SNIa) data and recently <span class="hlt">observed</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3869725','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3869725"><span id="translatedtitle">Demographic <span class="hlt">Variables</span> for Wild Asian Elephants Using Longitudinal <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>de Silva, Shermin; Webber, C. Elizabeth; Weerathunga, U. S.; Pushpakumara, T. V.; Weerakoon, Devaka K.; Wittemyer, George</p> <p>2013-01-01</p> <p>Detailed demographic data on wild Asian elephants have been difficult to collect due to habitat characteristics of much of the species remaining range. Such data, however, are critical for understanding and modeling population processes in this endangered species. We present data from six years of an ongoing study of Asian elephants (Elephas maximus) in Uda Walawe National Park, Sri Lanka. This relatively undisturbed population numbering over one thousand elephants is individually monitored, providing cohort-based information on mortality and reproduction. Reproduction was seasonal, such that most births occurred during the long inter-monsoon dry season and peaked in May. During the study, the average age at first reproduction was 13.4 years and the 50th percentile inter-birth interval was approximately 6 years. Birth sex ratios did not deviate significantly from parity. Fecundity was relatively stable throughout the <span class="hlt">observed</span> reproductive life of an individual (ages 1160), averaging between 0.130.17 female offspring per individual per year. Mortalities and injuries based on carcasses and disappearances showed that males were significantly more likely than females to be killed or injured through anthropogenic activity. Overall, however, most <span class="hlt">observed</span> injuries did not appear to be fatal. This population exhibits higher fecundity and density relative to published estimates on other Asian elephant populations, possibly enhanced by present range constriction. Understanding the factors responsible for these demographic dynamics can shed insight on the future needs of this elephant population, with probable parallels to other populations in similar settings. PMID:24376581</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130013062','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130013062"><span id="translatedtitle">Interannual <span class="hlt">Variability</span> of OLR as <span class="hlt">Observed</span> by AIRS and CERES</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Susskind, Joel; Molnar, Gyula I.; Iredell, Lena F.; Loeb, Norman G.</p> <p>2012-01-01</p> <p>The paper examines spatial anomaly time series of Outgoing Longwave Radiation (OLR) and Clear Sky OLR (OLR(sub CLR)) as determined using <span class="hlt">observations</span> from CERES Terra and AIRS over the time period September 2002 through June 2011. We find excellent agreement of the two OLR data sets in almost every detail down to the x11deg spatial grid point level. The extremely close agreement of OLR anomaly time series derived from <span class="hlt">observations</span> by two different instruments implies high stability of both sets of results. Anomalies of global mean, and especially tropical mean, OLR are shown to be strongly correlated with an El Nino index. These correlations explain that the recent global and tropical mean decreases in OLR over the time period studied are primarily the result of a transition from an El Nino condition at the beginning of the data record to La Nina conditions toward the end of the data period. We show that the close correlation of mean OLR anomalies with the El Nino Index can be well accounted for by temporal changes of OLR within two spatial regions, one to the east of, and one to the west of, the NOAA Nino-4 region. Anomalies of OLR in these two spatial regions are both strongly correlated with the El Nino Index as a result of the strong anti-correlation of anomalies of cloud cover and mid-tropospheric water vapor in these two regions with the El Nino Index.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120012822','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120012822"><span id="translatedtitle">Interannual <span class="hlt">Variability</span> of OLR as <span class="hlt">Observed</span> by AIRS and CERES</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Susskind, Joel; Molnar, Gyula; Iredell, Lena; Loeb, Norman G.</p> <p>2012-01-01</p> <p>This paper compares spatial anomaly time series of OLR (Outgoing Longwave Radiation) and OLR(sub CLR) (Clear Sky OLR) as determined using <span class="hlt">observations</span> from CERES Terra and AIRS over the time period September 2002 through June 2011. Both AIRS and CERES show a significant decrease in global mean and tropical mean OLR over this time period. We find excellent agreement of the anomaly time-series of the two OLR data sets in almost every detail, down to 1 deg X 1 deg spatial grid point level. The extremely close agreement of OLR anomaly time series derived from <span class="hlt">observations</span> by two different instruments implies that both sets of results must be highly stable. This agreement also validates to some extent the anomaly time series of the AIRS derived products used in the computation of the AIRS OLR product. The paper also examines the correlations of anomaly time series of AIRS and CERES OLR, on different spatial scales, as well as those of other AIRS derived products, with that of the NOAA Sea Surface Temperature (SST) product averaged over the NOAA Nino-4 spatial region. We refer to these SST anomalies as the El Nino Index. Large spatially coherent positive and negative correlations of OLR anomaly time series with that of the El Nino Index are found in different spatial regions. Anomalies of global mean, and especially tropical mean, OLR are highly positively correlated with the El Nino Index. These correlations explain that the recent global and tropical mean decreases in OLR over the period September 2002 through June 2011, as <span class="hlt">observed</span> by both AIRS and CERES, are primarily the result of a transition from an El Nino condition at the beginning of the data record to La Nina conditions toward the end of the data period. We show that the close correlation of global mean, and especially tropical mean, OLR anomalies with the El Nino Index can be well accounted for by temporal changes of OLR within two spatial regions which lie outside the NOAA Nino-4 region, in which anomalies 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.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5354921','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5354921"><span id="translatedtitle">Stable Auroral Red arc occurrences detected by the Pacific Northwest Laboratory photometer network: A <span class="hlt">decade</span> of <span class="hlt">observations</span>, 1978--1988</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Slater, D.W.; Kleckner, E.W.</p> <p>1989-11-01</p> <p>Using data obtained from a network of all-sky scanning photometers designed to operate routinely for long periods of time, a comprehensive inspection of <span class="hlt">observations</span> covering the time period 1978--1988 has revealed features that we interpret to be Stable Auroral Red (SAR) arcs during 250 nighttime <span class="hlt">observing</span> periods. These arcs result from high temperature within the ionospheric electron gas that is maintained by slow leakage of energy from the earth's magnetosphere. A listing of these events, the most complete available for this time interval, is presented for the purpose of complementing <span class="hlt">observations</span> reported for earlier dates. This listing is composed of location of the <span class="hlt">observing</span> photometer, date, time, photometric intensity, and location (as defined by the earth's magnetic coordinate system). The intent is to make these <span class="hlt">observations</span> available to a broad range of researchers and thereby initiate further investigations of these features. 22 refs., 3 figs., 2 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3280757','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3280757"><span id="translatedtitle">Influence of Surface Roughness Spatial <span class="hlt">Variability</span> and Temporal Dynamics on the Retrieval of Soil Moisture from SAR <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Álvarez-Mozos, Jesús; Verhoest, Niko E.C.; Larrañaga, Arantzazu; Casalí, Javier; González-Audícana, María</p> <p>2009-01-01</p> <p>Radar-based surface soil moisture retrieval has been subject of intense research during the last <span class="hlt">decades</span>. However, several difficulties hamper the operational estimation of soil moisture based on currently available spaceborne sensors. The main difficulty experienced so far results from the strong influence of other surface characteristics, mainly roughness, on the backscattering coefficient, which hinders the soil moisture inversion. This is especially true for single configuration <span class="hlt">observations</span> where the solution to the surface backscattering problem is ill-posed. Over agricultural areas cultivated with winter cereal crops, roughness can be assumed to remain constant along the growing cycle allowing the use of simplified approaches that facilitate the estimation of the moisture content of soils. However, the field scale spatial <span class="hlt">variability</span> and temporal variations of roughness can introduce errors in the estimation of soil moisture that are difficult to evaluate. The objective of this study is to assess the impact of roughness spatial <span class="hlt">variability</span> and roughness temporal variations on the retrieval of soil moisture from radar <span class="hlt">observations</span>. A series of laser profilometer measurements were performed over several fields in an experimental watershed from September 2004 to March 2005. The influence of the <span class="hlt">observed</span> roughness <span class="hlt">variability</span> and its temporal variations on the retrieval of soil moisture is studied using simulations performed with the Integral Equation Model, considering different sensor configurations. Results show that both field scale roughness spatial <span class="hlt">variability</span> and its temporal variations are aspects that need to be taken into account, since they can introduce large errors on the retrieved soil moisture values. PMID:22389611</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DPS....4741611K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DPS....4741611K"><span id="translatedtitle">A study of temporal <span class="hlt">variability</span> of clouds in exo-atmospheres using Earth <span class="hlt">observations</span> as a proxy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kopparla, Pushkar; Zhai, Albert; Zhai, Alice; Su, Hui; Jiang, Jonathan H.; Yung, Yuk Ling</p> <p>2015-11-01</p> <p>Clouds are strongly linked to the dynamics of the atmosphere, and have been <span class="hlt">observed</span> to vary over multiple spatial scales and timescales on Earth and the planets: hourly, diurnal, seasonal, interannual and <span class="hlt">decadal</span>. 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 <span class="hlt">observed</span>. However, temporal and spatial variation of cloud fields can have significant implications for the interpreting the <span class="hlt">observed</span> 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 <span class="hlt">observables</span> 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 <span class="hlt">observations</span> on Earth in the past three <span class="hlt">decades</span>, 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)-<span class="hlt">observation</span> based constraints for temporal <span class="hlt">variability</span> of clouds in exo-atmospheres.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7646A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7646A"><span id="translatedtitle">Surface solar radiation <span class="hlt">variability</span> over Eastern Mediterranean: A high spatial resolution view from satellite and ground-based <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexandri, Georgia; Georgoulias, Aristeidis K.; Meleti, Charikleia; Balis, Dimitris</p> <p>2013-04-01</p> <p>Surface Solar Radiation (SSR) has been measured for <span class="hlt">decades</span> from ground-based <span class="hlt">observations</span> for several spots around the planet. On the other hand, during the last <span class="hlt">decades</span>, satellite <span class="hlt">observations</span> made possible the assessment of the spatial <span class="hlt">variability</span> of the SSR at a global as well as regional scale. In this study, a detailed view of the SSR spatiotemporal <span class="hlt">variability</span> is presented at a high spatial resolution, focusing on the region of Eastern Mediterranean. This is a region of particular interest since it is affected by aerosols of various origins (continental, sea, dust and biomass burning particles) and encloses countries with significant socioeconomical changes during the last <span class="hlt">decades</span>. The SSR satellite data used in this study have been obtained from the Satellite Application Facility on Climate Monitoring (CM SAF) (www.cmsaf.eu). The CM SAF SSR dataset is based on reflections in the visible channel of Meteosat First Generation, has a spatial resolution of 0.03ox0.03o and spans from 1983 to 2005. The sate