WorldWideScience

Sample records for strong multidecadal variability

  1. Impact of the Atlantic on multidecadal tropical Pacific Variability

    Science.gov (United States)

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

    2017-12-01

    Multidecadal shifts in ENSO variability have been observed, but it is unclear if this variability is just a random variation in the ENSO cycle or whether it is forced by other modes of climate variability. Recent studies have suggested that the observed mean state differences in the tropical Pacific from the first decade and a half of the new millennium were driven by changes in the Atlantic SSTs. Here, we will show that the impact of Atlantic SST forcing on the tropical Pacific mean state are expressed as asymmetric changes to the annual cycle. The asymmetric changes in the tropical Pacific annual cycle creates a distinct signature in the relationship between the ENSO and the tropical Pacific annual cycle that we observe in the multidecadal ENSO variability in reanalysis and proxy records and that this variability follows the Atlantic Multidecadal Variability. We further find that there are concurrent changes in the location of the tropical Pacific ITCZ on multidecadal timescales. The shifts in location of the ITCZ in response to a warmer north Atlantic are consistent with the predictions of an ITCZ shift forced by an enhanced interhemispheric energy gradient. Targeted coupled model experiments are then used to confirm the impact of Atlantic Multidecadal Variability on the tropical Pacific multidecadal variability and explore the impact of SST changes across different regions of the Atlantic.

  2. Western tropical Pacific multidecadal variability forced by the Atlantic multidecadal oscillation

    Science.gov (United States)

    Kucharski, F.; Sun, C.; Li, J.; Jin, F. F.; Kang, I. S.; Ding, R.

    2017-12-01

    Observational analysis suggests that the western tropical Pacific (WTP) sea surface temperature (SST) shows predominant variability over multidecadal time scales, which is unlikely to be explained by the Interdecadal Pacific Oscillation. Here we show that this variability is largely explained by the remote Atlantic multidecadal oscillation (AMO). A suite of Atlantic Pacemaker experiments successfully reproduces the WTP multidecadal variability and the AMO-WTP SST connection. The AMO warm SST anomaly generates an atmospheric teleconnection to the North Pacific, which weakens the Aleutian low and subtropical North Pacific westerlies. The wind changes induce a subtropical North Pacific SST warming through wind-evaporation-SST effect, and in response to this warming, the surface winds converge towards the subtropical North Pacific from the tropics, leading to anomalous cyclonic circulation and low pressure over the WTP region. The warm SST anomaly further develops due to the SST-sea level pressure-cloud-longwave radiation positive feedback. Our findings suggest that the Atlantic Ocean acts as a key pacemaker for the western Pacific decadal climate variability.

  3. Internal modes of multidecadal variability in the Arctic Ocean

    NARCIS (Netherlands)

    Frankcombe, L.M.; Dijkstra, H.A.

    2010-01-01

    Observations of sea ice extent and atmospheric temperature in the Arctic, although sparse, indicate variability on multidecadal time scales. A recent analysis of one of the global climate models [the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (CM2.1)] in the Fourth Assessment

  4. North atlantic multidecadal climate variability: An investigation of dominant time scales and processes

    NARCIS (Netherlands)

    Frankcombe, L.M.|info:eu-repo/dai/nl/304829838; von der Heydt, A.S.|info:eu-repo/dai/nl/245567526; Dijkstra, H.A.|info:eu-repo/dai/nl/073504467

    2010-01-01

    The issue of multidecadal variability in the North Atlantic has been an important topic of late. It is clear that there are multidecadal variations in several climate variables in the North Atlantic, such as sea surface temperature and sea level height. The details of this variability, in particular

  5. Multi-decadal Variability of the Wind Power Output

    Science.gov (United States)

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

    2014-05-01

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

  6. A minimal model of the Atlantic Multidecadal Variability: its genesis and predictability

    Energy Technology Data Exchange (ETDEWEB)

    Ou, Hsien-Wang [Lamont-Doherty Earth Observatory of Columbia University, Department of Earth and Environmental Sciences, Palisades, NY (United States)

    2012-02-15

    Through a box model of the subpolar North Atlantic, we examine the genesis and predictability of the Atlantic Multidecadal Variability (AMV), posited as a linear perturbation sustained by the stochastic atmosphere. Postulating a density-dependent thermohaline circulation (THC), the latter would strongly differentiate the thermal and saline damping, and facilitate a negative feedback between the two fields. This negative feedback preferentially suppresses the low-frequency thermal variance to render a broad multidecadal peak bounded by the thermal and saline damping time. We offer this ''differential variance suppression'' as an alternative paradigm of the AMV in place of the ''damped oscillation'' - the latter generally not allowed by the deterministic dynamics and in any event bears no relation to the thermal peak. With the validated dynamics, we then assess the AMV predictability based on the relative entropy - a difference of the forecast and climatological probability distributions, which decays through both error growth and dynamical damping. Since the stochastic forcing is mainly in the surface heat flux, the thermal noise grows rapidly and together with its climatological variance limited by the THC-aided thermal damping, they strongly curtail the thermal predictability. The latter may be prolonged if the initial thermal and saline anomalies are of the same sign, but even rare events of less than 1% chance of occurrence yield a predictable time that is well short of a decade; we contend therefore that the AMV is in effect unpredictable. (orig.)

  7. Early 20th Century Arctic Warming Intensified by Pacific and Atlantic Multidecadal Variability

    Science.gov (United States)

    Tokinaga, H.; Xie, S. P.; Mukougawa, H.

    2017-12-01

    We investigate the influence of Pacific and Atlantic multidecadal variability on the Arctic temperature, with a particular focus on the early 20th century Arctic warming. Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing than at present. We find that the concurrent phase shift of Pacific and Atlantic multidecadal variability is the major driver for the early 20th century Arctic warming. Atmospheric model simulations reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early Arctic warming is associated with the cold-to-warm phase shifts of Atlantic and Pacific multidecadal variability modes, a SST pattern reminiscent of the positive phase of the Pacific decadal and Atlantic multidecadal oscillations. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. The equatorial Pacific warming deepens the Aleutian low, advecting warm air to the North American Arctic. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, cold-to-warm phase shift of the Pacific and Atlantic multidecadal variability. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region.

  8. North Atlantic warming: patterns of long-term trend and multidecadal variability

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, Igor V.; Alexeev, Vladimir A.; Zhang, Xiangdong [University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, AK (United States); Bhatt, Uma S. [University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK (United States); Polyakova, Evgenia I. [Stanford University, Department of Geological and Environmental Studies, Stanford, CA (United States)

    2010-02-15

    Climate fluctuations in the North Atlantic Ocean have wide-spread implications for Europe, Africa, and the Americas. This study assesses the relative contribution of the long-term trend and variability of North Atlantic warming using EOF analysis of deep-ocean and near-surface observations. Our analysis demonstrates that the recent warming over the North Atlantic is linked to both long-term (including anthropogenic and natural) climate change and multidecadal variability (MDV, {proportional_to}50-80 years). Our results suggest a general warming trend of 0.031 {+-} 0.006 C/decade in the upper 2,000 m North Atlantic over the last 80 years of the twentieth century, although during this time there are periods in which short-term trends were strongly amplified by MDV. For example, MDV accounts for {proportional_to}60% of North Atlantic warming since 1970. The single-sign basin-scale pattern of MDV with prolonged periods of warming (cooling) in the upper ocean layer and opposite tendency in the lower layer is evident from observations. This pattern is associated with a slowdown (enhancement) of the North Atlantic thermohaline overturning circulation during negative (positive) MDV phases. In contrast, the long-term trend exhibits warming in tropical and mid-latitude North Atlantic and a pattern of cooling in regions associated with major northward heat transports, consistent with a slowdown of the North Atlantic circulation as evident from observations and confirmed by selected modeling results. This localized cooling has been masked in recent decades by warming during the positive phase of MDV. Finally, since the North Atlantic Ocean plays a crucial role in establishing and regulating the global thermohaline circulation, the multidecadal fluctuations discussed here should be considered when assessing long-term climate change and variability, both in the North Atlantic and at global scales. (orig.)

  9. Inter-annual to multi-decadal variability in prairie water resources over the past millennium

    International Nuclear Information System (INIS)

    Sauchyn, D.

    2008-01-01

    In the Prairie Provinces, declining levels have been recently recorded for various rivers and lakes, and further reductions are projected. These trends reflect human impact in terms of increasing water consumption and possibly anthropogenic climate change. From the coupling of hydrological models and climate change scenarios, researchers have projected lower future summer flows as global warming brings shorter warmer winters and longer and generally drier summers to western Canada. However, the detection and interpretation of trends from gauge records and model outputs are constrained by the relatively short perspective of decades and the uncertainties associated with projecting climate change and its impacts on hydrological regimes. A longer perspective on inter-annual to multi-decadal variability in water resources is available from moisture-sensitive tree-ring chronologies. We have established a dense network of low elevation chronologies spanning the headwaters of the Saskatchewan, Missouri, Churchill and Mackenzie River basins. Standardized tree-ring width for a large sample of trees and sites is a strong regional signal of annual and seasonal hydroclimate, and an especially good proxy of low water levels. Proxy streamflow records, up to 800 years in length, show quasi-periodic variability at inter-annual to multi-decadal scales that correspond to the tempo of sea-surface temperature anomalies. The industrial sponsors of our research, Manitoba Hydro and EPCOR, anticipate the use of our tree-ring reconstructions for informing forecasts of future water supplies and planning adaptation to climate change. Engineers from these companies, and more than 50 other water managers and planners from the Prairie Provinces, attended a workshop in March 2008 to explore potential applications of paleo-hydrological records to water resource management. (author)

  10. The role of Atlantic-Arctic exchange in North Atlantic multidecadal climate variability

    NARCIS (Netherlands)

    Frankcombe, L.M.; Dijkstra, H.A.

    2011-01-01

    It has recently been suggested that multidecadal variability in North Atlantic sea surface temperature occurs with two dominant periods. In this paper we investigate the origin of these two time scales in a 500 year control run of the GFDL CM2.1 model. We focus on the exchange between the Atlantic

  11. Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework

    Directory of Open Access Journals (Sweden)

    H. K. A. Singh

    2018-02-01

    Full Text Available The Last Millennium Reanalysis (LMR employs a data assimilation approach to reconstruct climate fields from annually resolved proxy data over years 0–2000 CE. We use the LMR to examine Atlantic multidecadal variability (AMV over the last 2 millennia and find several robust thermodynamic features associated with a positive Atlantic Multidecadal Oscillation (AMO index that reveal a dynamically consistent pattern of variability: the Atlantic and most continents warm; sea ice thins over the Arctic and retreats over the Greenland, Iceland, and Norwegian seas; and equatorial precipitation shifts northward. The latter is consistent with anomalous southward energy transport mediated by the atmosphere. Net downward shortwave radiation increases at both the top of the atmosphere and the surface, indicating a decrease in planetary albedo, likely due to a decrease in low clouds. Heat is absorbed by the climate system and the oceans warm. Wavelet analysis of the AMO time series shows a reddening of the frequency spectrum on the 50- to 100-year timescale, but no evidence of a distinct multidecadal or centennial spectral peak. This latter result is insensitive to both the choice of prior model and the calibration dataset used in the data assimilation algorithm, suggesting that the lack of a distinct multidecadal spectral peak is a robust result.

  12. Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework

    Science.gov (United States)

    Singh, Hansi K. A.; Hakim, Gregory J.; Tardif, Robert; Emile-Geay, Julien; Noone, David C.

    2018-02-01

    The Last Millennium Reanalysis (LMR) employs a data assimilation approach to reconstruct climate fields from annually resolved proxy data over years 0-2000 CE. We use the LMR to examine Atlantic multidecadal variability (AMV) over the last 2 millennia and find several robust thermodynamic features associated with a positive Atlantic Multidecadal Oscillation (AMO) index that reveal a dynamically consistent pattern of variability: the Atlantic and most continents warm; sea ice thins over the Arctic and retreats over the Greenland, Iceland, and Norwegian seas; and equatorial precipitation shifts northward. The latter is consistent with anomalous southward energy transport mediated by the atmosphere. Net downward shortwave radiation increases at both the top of the atmosphere and the surface, indicating a decrease in planetary albedo, likely due to a decrease in low clouds. Heat is absorbed by the climate system and the oceans warm. Wavelet analysis of the AMO time series shows a reddening of the frequency spectrum on the 50- to 100-year timescale, but no evidence of a distinct multidecadal or centennial spectral peak. This latter result is insensitive to both the choice of prior model and the calibration dataset used in the data assimilation algorithm, suggesting that the lack of a distinct multidecadal spectral peak is a robust result.

  13. Pronounced differences between observed and CMIP5-simulated multidecadal climate variability in the twentieth century

    Science.gov (United States)

    Kravtsov, Sergey

    2017-06-01

    Identification and dynamical attribution of multidecadal climate undulations to either variations in external forcings or to internal sources is one of the most important topics of modern climate science, especially in conjunction with the issue of human-induced global warming. Here we utilize ensembles of twentieth century climate simulations to isolate the forced signal and residual internal variability in a network of observed and modeled climate indices. The observed internal variability so estimated exhibits a pronounced multidecadal mode with a distinctive spatiotemporal signature, which is altogether absent in model simulations. This single mode explains a major fraction of model-data differences over the entire climate index network considered; it may reflect either biases in the models' forced response or models' lack of requisite internal dynamics, or a combination of both.Plain Language SummaryGlobal and regional warming trends over the course of the twentieth century have been nonuniform, with decadal and longer periods of faster or slower warming, or even cooling. Here we show that state-of-the-art global models used to predict climate fail to adequately reproduce such multidecadal climate variations. In particular, the models underestimate the magnitude of the observed variability and misrepresent its spatial pattern. Therefore, our ability to interpret the observed climate change using these models is limited.

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

    Science.gov (United States)

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

    2006-12-01

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

  15. Role of the Ocean-Atmosphere interactions for the Atlantic Multidecadal Variability in an idealized coupled model

    Science.gov (United States)

    Jamet, Quentin; Huck, Thierry; de Verdière, Alain Colin; Arzel, Olivier; Campin, Jean-Michel

    2015-04-01

    The role of the ocean-atmosphere interactions in the multidecadal variability of the Atlantic Meridional Overturning Circulation (AMOC) is investigated in an idealized coupled configuration of the MIT General Circulation Model. The flat-bottom ocean, composed of an Atlantic-like small basin, a Pacific-like large basin, and an unblocked Antarctic-like circumpolar channel, is coupled to a global atmospheric model (SPEEDY). In order to better represent the atmospheric dynamics and its interactions with the ocean, three set-ups, with horizontal resolution of about 4°, 2° and 1° (at the equator) in both the ocean and atmosphere models, are compared. They show a linearly increasing North Atlantic Oscillation-like variability. At all resolutions, the AMOC undergoes a spontaneous variability on multidecadal time scales between 30-40 yr, with an additional higher frequency in the highest resolution set-up. The AMOC variability responds to temperature anomalies along the western boundary through the thermal wind relationship. These temperature anomalies result from the propagation of large-scale baroclinic Rossby waves across the small basin. The unstable region responsible for the growth of Rossby waves through baroclinic instability, diagnosed using a temperature variance budget, shifts from the eastern boundary at coarse resolution (4°) to the western boundary at higher resolution (2° and 1°). An earlier study, performed with the same coarse resolution set-up (4°), has shown that the AMOC does not participate to the growth of Rossby waves, but passively reacts to these waves. The AMOC being mainly connected to the western boundary dynamics, its role in setting large scale baroclinic Rossby waves might be different between the coarse resolution set-ups (4°) and the higher resolution set-ups (2° and 1°). The ocean-atmosphere interactions are strongly enhanced in the highest resolution set-up (1°), with the development of a significant correlation of about 0

  16. Atlantic Multidecadal Oscillation and Northern Hemisphere's climate variability

    Energy Technology Data Exchange (ETDEWEB)

    Wyatt, Marcia Glaze [University of Colorado-Boulder, Department of Geologic Sciences, CIRES, Benson Earth Sciences Building, Boulder, CO (United States); Kravtsov, Sergey; Tsonis, Anastasios A. [University of Wisconsin-Milwaukee, Department of Mathematical Sciences, Atmospheric Sciences Group, Milwaukee, WI (United States)

    2012-03-15

    Proxy and instrumental records reflect a quasi-cyclic 50-80-year climate signal across the Northern Hemisphere, with particular presence in the North Atlantic. Modeling studies rationalize this variability in terms of intrinsic dynamics of the Atlantic Meridional Overturning Circulation influencing distribution of sea-surface-temperature anomalies in the Atlantic Ocean; hence the name Atlantic Multidecadal Oscillation (AMO). By analyzing a lagged covariance structure of a network of climate indices, this study details the AMO-signal propagation throughout the Northern Hemisphere via a sequence of atmospheric and lagged oceanic teleconnections, which the authors term the ''stadium wave''. Initial changes in the North Atlantic temperature anomaly associated with AMO culminate in an oppositely signed hemispheric signal about 30 years later. Furthermore, shorter-term, interannual-to-interdecadal climate variability alters character according to polarity of the stadium-wave-induced prevailing hemispheric climate regime. Ongoing research suggests mutual interaction between shorter-term variability and the stadium wave, with indication of ensuing modifications of multidecadal variability within the Atlantic sector. Results presented here support the hypothesis that AMO plays a significant role in hemispheric and, by inference, global climate variability, with implications for climate-change attribution and prediction. (orig.)

  17. Multi-decadal 40- to 60-year cycles of precipitation variability in Chile (South America) and their relationship to the AMO and PDO signals

    Science.gov (United States)

    Valdés-Pineda, Rodrigo; Cañón, Julio; Valdés, Juan B.

    2018-01-01

    High-frequency components of precipitation variability have been an important focus of study during the last few decades in Chile. Low-frequency variations, on the other hand, have received less attention, especially in association with multi-decadal cycles that can affect variability trends of precipitation in the long term. This study analyzes these low-frequency patterns of precipitation in Chile (>30 years), and their relationship to global Sea Surface Temperatures (SSTs), with special focus on associations with the Pacific Decadal Oscillation (PDO) and the Atlantic Multi-decadal Oscillation (AMO) indices. Singular Spectrum Analysis (SSA) and its Multi-Channel version (MSSA) techniques were applied to a dataset containing long instrumental records of monthly precipitation aggregated yearly and seasonally. The relationships between the low-frequency variability of precipitation and the PDO are significant to the north of the country, whereas connections with the AMO are significant to the north and also to the south. This is also evident from the global spatial correlation analysis of low-frequency precipitation modes and SSTs, where the southernmost station shows a strong relationship with the Atlantic Ocean. We conclude that a significant multi-decadal precipitation cycle between 40 and 60 years is evident at the rain gauges located in the subtropical and extratropical regions of Chile. This low-frequency variability seems to be largely linked to PDO and AMO modulation.

  18. Strong Decomposition of Random Variables

    DEFF Research Database (Denmark)

    Hoffmann-Jørgensen, Jørgen; Kagan, Abram M.; Pitt, Loren D.

    2007-01-01

    A random variable X is stongly decomposable if X=Y+Z where Y=Φ(X) and Z=X-Φ(X) are independent non-degenerated random variables (called the components). It is shown that at least one of the components is singular, and we derive a necessary and sufficient condition for strong decomposability...

  19. Sahel rainfall and decadal to multi-decadal sea surface temperature variability

    Energy Technology Data Exchange (ETDEWEB)

    Mohino, Elsa [LOCEAN/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Universidad de Sevilla, Seville (Spain); Janicot, Serge [LOCEAN/IPSL, IRD, Universite Pierre et Marie Curie, Paris (France); Bader, Juergen [Bjerknes Centre for Climate Research, Bergen (Norway); Geophysical Institute, University of Bergen, Bergen (Norway)

    2011-08-15

    Decadal Sahelian rainfall variability was mainly driven by sea surface temperatures (SSTs) during the twentieth century. At the same time SSTs showed a marked long-term global warming (GW) trend. Superimposed on this long-term trend decadal and multi-decadal variability patterns are observed like the Atlantic Multidecadal Oscillation (AMO) and the inter-decadal Pacific Oscillation (IPO). Using an atmospheric general circulation model we investigate the relative contribution of each component to the Sahelian precipitation variability. To take into account the uncertainty related to the use of different SST data sets, we perform the experiments using HadISST1 and ERSSTv3 reconstructed sets. The simulations show that all three SST signals have a significant impact over West Africa: the positive phases of the GW and the IPO lead to drought over the Sahel, while a positive AMO enhances Sahel rainfall. The tropical SST warming is the main cause for the GW impact on Sahel rainfall. Regarding the AMO, the pattern of anomalous precipitation is established by the SSTs in the Atlantic and Mediterranean basins. In turn, the tropical SST anomalies control the impact of the IPO component on West Africa. Our results suggest that the low-frequency evolution of Sahel rainfall can be interpreted as the competition of three factors: the effect of the GW, the AMO and the IPO. Following this interpretation, our results show that 50% of the SST-driven Sahel drought in the 1980s is explained by the change to a negative phase of the AMO, and that the GW contribution was 10%. In addition, the partial recovery of Sahel rainfall in recent years was mainly driven by the AMO. (orig.)

  20. CCSM3 simulation of pacific multi-decadal climate variability: the role of subpolar North Pacific Ocean

    International Nuclear Information System (INIS)

    Zhong, Y; Liu, Z

    2008-01-01

    Previous analyses of the CCSM3 standard integration have revealed pronounced multidecadal variability in the Pacific climate system. The purpose of the present work is to investigate the physical mechanism underlying the Pacific multidecadal variability (PMV) using specifically designed sensitivity experiments. A novel mechanism is advanced, characterized by a crucial role of the subpolar North Pacific Ocean. The multidecadal signal in ocean temperature and salinity fields is found to originate from the subsurface of the subpolar North Pacific, as result of the wave adjustment to the preceding basin-scale wind curl forcing. The multidecadal signal then ascends to the surface and is amplified through local temperature/salinity convective feedback. Along the southward Oyashio current, the anomaly travels to the Kuroshio Extension (KOE) region and is further intensified through a similar convective feedback in addition to the wind-evaporation-sea surface temperature feedback. The temperature anomaly in the KOE is able to feed back to the large-scale atmospheric circulation, inducing wind curl anomaly over the subpolar region, which in turn generates anomalous oceanic circulation and causes temperature/salinty variability in the subpolar subsurface. Thereby, a closed loop of PMV is established, in the form of a subpolar delayed oscillator

  1. Synchronous multi-decadal climate variability of the whole Pacific areas revealed in tree rings since 1567

    Science.gov (United States)

    Fang, Keyan; Cook, Edward; Guo, Zhengtang; Chen, Deliang; Ou, Tinghai; Zhao, Yan

    2018-02-01

    Oceanic and atmospheric patterns play a crucial role in modulating climate variability from interannual to multi-decadal timescales by causing large-scale co-varying climate changes. The brevity of the existing instrumental records hinders the ability to recognize climate patterns before the industrial era, which can be alleviated using proxies. Unfortunately, proxy based reconstructions of oceanic and atmospheric modes of the past millennia often have modest agreements with each other before the instrumental period, raising questions about the robustness of the reconstructions. To ensure the stability of climate signals in proxy data through time, we first identified tree-ring datasets from distant regions containing coherent variations in Asia and North America, and then interpreted their climate information. We found that the multi-decadal covarying climate patterns of the middle and high latitudinal regions around the northern Pacific Ocean agreed quite well with the climate reconstructions of the tropical and southern Pacific areas. This indicates a synchronous variability at the multi-decadal timescale of the past 430 years for the entire Pacific Ocean. This pattern is closely linked to the dominant mode of the Pacific sea surface temperature (SST) after removing the warming trend. This Pacific multi-decadal SST variability resembles the Interdecadal Pacific Oscillation.

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

    Science.gov (United States)

    Chen, Hua

    The thesis investigates the physical question of mechanisms of the Atlantic multidecadal variability (AMV) in a new way, using the weather noise forced interactive ensemble. It includes two distinct but closely related components. 1) Verification of the interactive ensemble strategy and justification for the noise forcing. In order to separate the noise from the SST forced response, the SST forced response in the atmospheric GCM (AGCM), forced by the SST from the coupled GCM (CGCM), has to be the same as in the CGCM. To be consistent, the noise should also be the same statistically in the CGCM and AGCM. Comparison of the CGCM and AGCM ensemble shows that these conditions are satisfied. Therefore, the interactive ensemble is an appropriate tool for the investigation, and the "noise" that is diagnosed and used as forcing is appropriate. Our results apply not just to the interactive ensemble, but also have broader implications important for the design of a wide range of climate modeling experiments. 2) Diagnosis of the multidecadal variability in the CGCM simulation. The diagnosis is done using the interactive ensemble CGCM, in which the heat flux, wind stress and fresh water flux weather noise components are applied at the ocean surface in different regions and in different combinations. The interactive ensemble simulations prove that the model's climate variability is predominantly forced by weather noise. The local weather noise forcing is found to be responsible for the SST variability in the Atlantic, with the noise heat flux and noise wind stress playing a critical role, while the noise fresh water flux has negligible impact. The North Atlantic Oscillation (NAO) pattern in the atmosphere, dominated by weather noise, forces the AMV 45-year mode through the noise heat flux and noise wind stress, with the former important in the eastern North Atlantic and the latter along the separated Gulf Stream. The noise wind stress forces the AMV 45-year mode through ocean

  3. Atmospheric response to multidecadal sea surface temperature variability in the Pacific Ocean (IPV) and the North Atlantic Ocean (AMV)

    Science.gov (United States)

    Elsbury, D.; Peings, Y.; Magnusdottir, G.

    2017-12-01

    Multidecadal modes of sea surface temperature (SST) variability in the Pacific and Atlantic Oceans act as forcing fields in a series of atmospheric global climate model (AGCM) simulations. These modes, Interdecadal Pacific Variability (IPV) and Atlantic Multidecadal Variability (AMV), are important regulators of global temperature, precipitation, extreme climate events (droughts and temperature extremes), and have recently been implicated as playing an important role in the global warming hiatus. Despite a growing recognition of the importance of these climate modes, the most fundamental atmospheric and climatic responses to the long-term internal variability and interplay of these two ocean basins is not well understood. In a series of 200-yr experiments using the Whole Atmosphere Community Climate Model (WACCM), the atmosphere is forced by the 9 different combinations of the AMV and IPV states (neutral, positive, negative) using a single polarity from each the IPV and the AMV, and different combinations. The atmospheric response associated with each combination of SST anomalies is investigated, with a focus on modes of variability such as the North Atlantic Oscillation (NAO) and associated temperature/precipitation variability. Of particular interest is the response related to forcing from the tropical Pacific, the stratospheric response and associated stratosphere-troposphere interactions, and the response of extreme weather events in both winter and summer. These results yield a more complete understanding of climate predictability associated with each basin at multidecadal time scales, and how their respective influences interfere with each other.

  4. Positive Low Cloud and Dust Feedbacks Amplify Tropical North Atlantic Multidecadal Variability

    Science.gov (United States)

    Yuan, Tianle; Oraiopoulos, Lazaros; Zelinka, Mark; Yu, Hongbin; Norris, Joel R.; Chin, Mian; Platnick, Steven; Meyer, Kerry

    2016-01-01

    The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropical trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO.

  5. Indo-Pacific variability on seasonal to multidecadal timescales. Part I: Intrinsic SST modes in models and observations

    OpenAIRE

    Slawinska, Joanna; Giannakis, Dimitrios

    2016-01-01

    The variability of Indo-Pacific SST on seasonal to multidecadal timescales is investigated using a recently introduced technique called nonlinear Laplacian spectral analysis (NLSA). Through this technique, drawbacks associated with ad hoc pre-filtering of the input data are avoided, enabling recovery of low-frequency and intermittent modes not previously accessible via classical approaches. Here, a multiscale hierarchy of spatiotemporal modes is identified for Indo-Pacific SST in millennial c...

  6. Variability of fire emissions on interannual to multi-decadal timescales in two Earth System models

    Science.gov (United States)

    Ward, D. S.; Shevliakova, E.; Malyshev, S.; Lamarque, J.-F.; Wittenberg, A. T.

    2016-12-01

    Connections between wildfires and modes of variability in climate are sought as a means for predicting fire activity on interannual to multi-decadal timescales. Several fire drivers, such as temperature and local drought index, have been shown to vary on these timescales, and analysis of tree-ring data suggests covariance between fires and climate oscillation indices in some regions. However, the shortness of the satellite record of global fire events limits investigations on larger spatial scales. Here we explore the interplay between climate variability and wildfire emissions with the preindustrial long control numerical experiments and historical ensembles of CESM1 and the NOAA/GFDL ESM2Mb. We find that interannual variability in fires is underpredicted in both Earth System models (ESMs) compared to present day fire emission inventories. Modeled fire emissions respond to the El Niño/southern oscillation (ENSO) and Pacific decadal oscillation (PDO) with increases in southeast Asia and boreal North America emissions, and decreases in southern North America and Sahel emissions, during the ENSO warm phase in both ESMs, and the PDO warm phase in CESM1. Additionally, CESM1 produces decreases in boreal northern hemisphere fire emissions for the warm phase of the Atlantic Meridional Oscillation. Through analysis of the long control simulations, we show that the 20th century trends in both ESMs are statistically significant, meaning that the signal of anthropogenic activity on fire emissions over this time period is detectable above the annual to decadal timescale noise. However, the trends simulated by the two ESMs are of opposite sign (CESM1 decreasing, ESM2Mb increasing), highlighting the need for improved understanding, proxy observations, and modeling to resolve this discrepancy.

  7. Multidecadal variability of atmospheric methane and the Inter Polar Gradient: 0-1800 C.E

    Science.gov (United States)

    Mitchell, L.; Brook, E.

    2010-12-01

    Atmospheric methane is a potent greenhouse gas that is responsible for ~20% of the total increase in radiative forcing since the industrial revolution. Despite its importance there is a lack of scientific understanding regarding the controls on sources and sinks. Here we present high-precision, high-resolution records of atmospheric methane from the West Antarctic Ice Sheet (WAIS) Divide 05A ice core (WDC05A, 1000-1800 C.E., [Mitchell et al., submitted.]) and preliminary measurements from the WAIS Divide deep ice core (WDC06A, 0-1800 C.E.) and the Greenland ice core (GISP2D, 0-1800 C.E.). These records have decadal scale resolution, analytical precision of period affected methane emissions. Times of war and plague when large population losses could have reduced anthropogenic emissions appear coincident with periods of decreasing global methane concentrations however anthropogenic activity cannot explain all of the observed variability. We conclude that multidecadal variability of methane over the past millennium was not controlled by temperature, precipitation, or anthropogenic activity alone and instead by some combination of these parameters. Methane records from Antarctica and Greenland can be used to reconstruct the methane Inter-Polar Gradient (IPG) which is controlled by the latitudinal distribution of sources and can provide an additional constraint on possible source scenarios. Preliminary measurements reveal that the IPG over 0-1800 C.E. is ~43 ppb and has not changed significantly over this time interval despite an increase of ~40 ppb in global concentrations. This indicates that the latitudinal distribution of methane sources has also not experienced significant changes. Initial efforts to model the IPG will be presented.

  8. Impacts of the Atlantic Multidecadal Variability on the North Pacific Ocean

    Science.gov (United States)

    Ruprich-Robert, Yohan; Msadek, Rym; Castruccio, Frederic; Yeager, Stephen; Delworth, Thomas; Danabasoglu, Gokhan

    2017-04-01

    The Atlantic Multidecadal Variability (AMV) is associated with marked modulations of climate anomalies over many areas of the globe. This includes droughts in Africa and North America, decline in sea ice, changes of tropical cyclone activity in the Atlantic, and changes in the atmospheric large-scale circulation. However, the shortness of the historical observations compared to the AMV period ( 60-80yr) makes it difficult to show that the AMV is a direct driver of these variations. To isolate the AMV climate response, we use a suite of global coupled models from GFDL and NCAR, in which the North Atlantic sea surface temperatures are restored to the observed AMV pattern, while the other ocean basins are left fully coupled. In order to explore and robustly isolate the AMV impacts, we use large ensemble simulations (between 30 and 100 members depending on the model) that are integrated for 10 years. All models show that during boreal summer the AMV alters the Walker Circulation and generates precipitation anomalies over the whole tropical belt. During boreal winter, the AMV warming is associated with large anomalies over the Pacific, with a response that projects onto a negative phase of the Pacific Decadal Oscillation (PDO). In this presentation, we focus on a hierarchy of experiments in which the ocean-atmosphere coupling is globally or regionally precluded to extract the physical mechanisms leading to the Pacific response. We show that the PDO response comes from a lagged adjustment of the tropical Pacific Ocean to the AMV forcing in summer, and it is reinforced by ocean-atmosphere coupling over the extratropical Pacific. It is then show that the PDO response contribute to precipitation and temperature anomalies over North America. Therefore, our study highlights the importance of using a global coupled framework to investigate the climate impacts of the AMV.

  9. Intra- to Multi-Decadal Temperature Variability over the Continental United States: 1896-2012

    Science.gov (United States)

    The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (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...

  10. Groundwater level response in U.S. Principal Aquifers to natural climate variability on interannual to multidecadal timescales

    Science.gov (United States)

    Velasco, E.; Gurdak, J. J.; Dickinson, J.; Hanson, R. T.; Ferré, T. P. A.; Maurer, E. P.

    2014-12-01

    Natural climate variability on interannual to multidecadal timescales are important controls on precipitation, drought, evapotranspiration, streamflow, and groundwater recharge. Climate variability can also augment or diminish human stresses on water resources. Thus, understanding climate variability has particular relevance for groundwater management. Findings will be presented from a national scale study of groundwater level response to natural climate variability in principal aquifers (PAs) of the U.S., including the California Coastal Basin, Rio Grande, Coastal Lowlands, Mississippi Embayment, Floridan, and Glacial aquifer systems. We use the U.S. Geological Survey hydroclimatic analysis toolkit HydroClimATe to perform singular spectrum analysis and identify quasi-periodic signals in precipitation and groundwater time series that are coincident with the Arctic Oscillation (AO) (6-12 mo cycle), Pacific/North American oscillation (PNA) (accounting for more than 90% of the variance in many PAs. The next largest amount of variance in precipitation and groundwater levels was attributed to ENSO, accounting for more than 50% of the variance in many PAs. The AMO was the least frequently detected signal in all time series but accounted for as much as 95% of the variance when detected. Thus, climate variability on interannual to multidecadal timescales has a statistically significant and measurable effect on the lagged responses of precipitation variability and, in turn, groundwater level fluctuations in PAs. Our findings have important implications for the availability and sustainability of groundwater, including management and planning decisions about the locations, cost effectiveness, and optimal time periods for conjunctive use strategies.

  11. Decadal to multi-decadal scale variability of Indian summer monsoon rainfall in the coupled ocean-atmosphere-chemistry climate model SOCOL-MPIOM

    Science.gov (United States)

    Malik, Abdul; Brönnimann, Stefan; Stickler, Alexander; Raible, Christoph C.; Muthers, Stefan; Anet, Julien; Rozanov, Eugene; Schmutz, Werner

    2017-11-01

    The present study is an effort to deepen the understanding of Indian summer monsoon rainfall (ISMR) on decadal to multi-decadal timescales. We use ensemble simulations for the period AD 1600-2000 carried out by the coupled Atmosphere-Ocean-Chemistry-Climate Model (AOCCM) SOCOL-MPIOM. Firstly, the SOCOL-MPIOM is evaluated using observational and reanalyses datasets. The model is able to realistically simulate the ISMR as well as relevant patterns of sea surface temperature and atmospheric circulation. Further, the influence of Atlantic Multi-decadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) variability on ISMR is realistically simulated. Secondly, we investigate the impact of internal climate variability and external climate forcings on ISMR on decadal to multi-decadal timescales over the past 400 years. The results show that AMO, PDO, and Total Solar Irradiance (TSI) play a considerable role in controlling the wet and dry decades of ISMR. Resembling observational findings most of the dry decades of ISMR occur during a negative phase of AMO and a simultaneous positive phase of PDO. The observational and simulated datasets reveal that on decadal to multi-decadal timescales the ISMR has consistent negative correlation with PDO whereas its correlation with AMO and TSI is not stationary over time.

  12. Multidecadal, centennial, and millennial variability in sardine and anchovy abundances in the western North Pacific and climate-fish linkages during the late Holocene

    Science.gov (United States)

    Kuwae, Michinobu; Yamamoto, Masanobu; Sagawa, Takuya; Ikehara, Ken; Irino, Tomohisa; Takemura, Keiji; Takeoka, Hidetaka; Sugimoto, Takashige

    2017-12-01

    Paleorecords of pelagic fish abundance could better define the nature of fishery productivity dynamics and help understand responses of pelagic fish stocks to long-term climate changes. We report a high-resolution record of sardine and anchovy scale deposition rates (SDRs) from Beppu Bay, Southwest Japan, showing multidecadal and centennial variability in the abundance of Japanese sardine and Japanese anchovy during the last 2850 years. Variations in the sardine SDR showed periodicities at ∼50, ∼100, and ∼300 yr, while variations in the anchovy SDR showed periodicities at ∼30 and ∼260 yr. Comparisons between and correlation analyses of the time series of the sardine and anchovy SDRs demonstrate that there is not a consistent out-of-phase relationship during the last 2850 years. This indicates that the multidecadal alternations in the sardine and anchovy populations commonly seen in the 20th century did not necessarily occur during earlier periods. The Japanese sardine SDR record shows a long-term decreasing trend in the amplitudes of the multidecadal to centennial fluctuations. This decreasing trend may have resulted from an increasing trend in the winter sea surface temperature in the western North Pacific. The multicentennial variability in sardine abundance during the last millennium is consistent with the variabilities in the abnormal snow index in East Asia and the American tree ring-based Pacific Decadal Oscillation index, suggesting a basin-wide or regional climate-marine ecosystem linkage.

  13. Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability

    Science.gov (United States)

    Tokinaga, Hiroki; Xie, Shang-Ping; Mukougawa, Hitoshi

    2017-01-01

    With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean–atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region. PMID:28559341

  14. Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability

    Science.gov (United States)

    Tokinaga, Hiroki; Xie, Shang-Ping; Mukougawa, Hitoshi

    2017-06-01

    With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region.

  15. Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability.

    Science.gov (United States)

    Tokinaga, Hiroki; Xie, Shang-Ping; Mukougawa, Hitoshi

    2017-06-13

    With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region.

  16. Multi-decadal modulation of the El Nino-Indian monsoon relationship by Indian Ocean variability

    International Nuclear Information System (INIS)

    Ummenhofer, Caroline C; Sen Gupta, Alexander; Li Yue; Taschetto, Andrea S; England, Matthew H

    2011-01-01

    The role of leading modes of Indo-Pacific climate variability is investigated for modulation of the strength of the Indian summer monsoon during the period 1877-2006. In particular, the effect of Indian Ocean conditions on the relationship between the El Nino-Southern Oscillation (ENSO) and the Indian monsoon is explored. Using an extended classification for ENSO and Indian Ocean dipole (IOD) events for the past 130 years and reanalyses, we have expanded previous interannual work to show that variations in Indian Ocean conditions modulate the ENSO-Indian monsoon relationship also on decadal timescales. El Nino events are frequently accompanied by a significantly reduced Indian monsoon and widespread drought conditions due to anomalous subsidence associated with a shift in the descending branch of the zonal Walker circulation. However, for El Nino events that co-occur with positive IOD (pIOD) events, Indian Ocean conditions act to counter El Nino's drought-inducing subsidence by enhancing moisture convergence over the Indian subcontinent, with an average monsoon season resulting. Decadal modulations of the frequency of independent and combined El Nino and pIOD events are consistent with a strengthened El Nino-Indian monsoon relationship observed at the start of the 20th century and the apparent recent weakening of the El Nino-Indian monsoon relationship.

  17. Imprint of the Atlantic multidecadal oscillation on tree-ring widths in northeastern Asia since 1568.

    Directory of Open Access Journals (Sweden)

    Xiaochun Wang

    Full Text Available We present a new tree-ring reconstruction of the Atlantic Multidecadal Oscillation (AMO spanning 1568-2007 CE from northeast Asia. Comparison of the instrumental AMO index, an existing tree-ring based AMO reconstruction, and this new record show strongly similar annual to multidecadal patterns of variation over the last 440 years. Warm phases of the AMO are related to increases in growth of Scots pine trees and moisture availability in northeast China and central eastern Siberia. Multi-tape method (MTM and cross-wavelet analyses indicate that robust multidecadal (∼64-128 years variability is present throughout the new proxy record. Our results have important implications concerning the influence of North Atlantic sea surface temperatures on East Asian climate, and provide support for the possibility of an AMO signature on global multidecadal climate variability.

  18. The North Atlantic Oscillation as a driver of multidecadal variability of the AMOC, the AMO, and Northern Hemisphere climate

    Science.gov (United States)

    Delworth, T. L.; Zeng, F. J.; Yang, X.; Zhang, L.

    2017-12-01

    We use suites of simulations with coupled ocean-atmosphere models to show that multidecadal changes in the North Atlantic Oscillation (NAO) can drive multidecadal changes in the Atlantic Meridional Overturning Circulation (AMOC) and the Atlantic Multidecadal Oscillation (AMO), with associated hemispheric climatic impacts. These impacts include rapid changes in Arctic sea ice, hemispheric temperature, and modulation of Atlantic hurricane activity. We use models that incorporate either a fully dynamic ocean or a simple slab ocean to explore the role of ocean dynamics and ocean-atmosphere interactions. A positive phase of the NAO is associated with strengthened westerly winds over the North Atlantic. These winds extract more heat than normal from the subpolar ocean, thereby increasing upper ocean density, deepwater formation, and the strength of the AMOC and associated poleward ocean heat transport. This warming leads to a positive phase of the AMO. The enhanced oceanic heat transport extends to the Arctic where it causes a reduction of Arctic sea ice. Large-scale atmospheric warming reduces vertical wind shear in the tropical North Atlantic, creating an environment more favorable for tropical storms. We use models to further show that observed multidecadal variations of the NAO over the 20th and early 21st centuries may have led to multidecadal variations of simulated AMOC and the AMO. Specifically, negative NAO values from the late 1960s through the early 1980s led to a weakened AMOC/cold North Atlantic, whereas increasing NAO values from the late 1980s through the late 1990s increased the model AMOC and led to a positive (warm) phase of the AMO. The warm phase contributed to increases in tropical storm activity and decreases in Arctic sea ice after the mid 1990s. Ocean dynamics are essential for translating the observed NAO variations into ocean heat content variations for the extratropical North Atlantic, but appear less important in the tropical North Atlantic

  19. Spatiotemporal characteristics of seasonal to multidecadal variability of pCO2 and air-sea CO2 fluxes in the equatorial Pacific Ocean

    Science.gov (United States)

    Valsala, Vinu K.; Roxy, Mathew Koll; Ashok, Karumuri; Murtugudde, Raghu

    2014-12-01

    Seasonal, interannual, and multidecadal variability of seawater pCO2 and air-sea CO2 fluxes in the equatorial Pacific Ocean for the past 45 years (1961-2005) are examined using a suite of experiments performed with an offline biogeochemical model driven by reanalysis ocean products. The processes we focus on are: (a) the evolution of seasonal cycle of pCO2 and air-sea CO2 fluxes during the dominant interannual mode in the equatorial Pacific, i.e., the El Niño-Southern Oscillation (ENSO), (b) its spatiotemporal characteristics, (c) the combined and individual effects of wind and ocean dynamics on pCO2 and CO2 flux variability and their relation to canonical (eastern Pacific) and central Pacific (Modoki) ENSOs and (d) the multidecadal variability of carbon dynamics in the equatorial Pacific and its association with the Pacific Decadal Oscillations (PDO). The simulated mean and seasonal cycle of pCO2 and CO2 fluxes are comparable with the observational estimates and with other model results. A new analysis methodology based on the traditional Empirical Orthogonal Functions (EOF) applied over a time-time domain is employed to elucidate the dominant mode of interannual variability of pCO2 and air-sea CO2 fluxes at each longitude in the equatorial Pacific. The results show that the dominant interannual variability of CO2 fluxes in the equatorial Pacific (averaged over 5°N-10°S) coevolves with that of ENSO. Generally a reduced CO2 source in the central-to-eastern equatorial Pacific evident during June-July of the El Niño year (Year:0) peaks through September of Year:0 to February of Year:+1 and recovers to a normal source thereafter. In the region between 160°W and 110°W, the canonical El Niño controls the dominant variability of CO2 fluxes (mean and RMS of anomaly from 1961 to 2005 is 0.43±0.12 PgC yr-1). However, in the western (160°E-160°W) and far eastern (110°W-90°W) equatorial Pacific, CO2 flux variability is dominantly influenced by the El Ni

  20. The dynamics of a low-order model for the Atlantic multidecadal oscillation

    NARCIS (Netherlands)

    Broer, H.; Dijkstra, H.; Simó, C.; Sterk, A.; Vitolo, R.

    Observational and model based studies provide ample evidence for the presence of multidecadal variability in the North Atlantic sea-surface temperature known as the Atlantic Multidecadal Oscillation (AMO). This variability is characterised by a multidecadal time scale, a westward propagation of

  1. Strong Dependence of U.S. Summertime Air Quality on the Decadal Variability of Atlantic Sea Surface Temperatures

    Science.gov (United States)

    Shen, Lu; Mickley, Loretta J.; Leibensperger, Eric M.; Li, Mingwei

    2017-12-01

    We find that summertime air quality in the eastern U.S. displays strong dependence on North Atlantic sea surface temperatures, resulting from large-scale ocean-atmosphere interactions. Using observations, reanalysis data sets, and climate model simulations, we further identify a multidecadal variability in surface air quality driven by the Atlantic Multidecadal Oscillation (AMO). In one-half cycle ( 35 years) of the AMO from cold to warm phase, summertime maximum daily 8 h ozone concentrations increase by 1-4 ppbv and PM2.5 concentrations increase by 0.3-1.0 μg m-3 over much of the east. These air quality changes are related to warmer, drier, and more stagnant weather in the AMO warm phase, together with anomalous circulation patterns at the surface and aloft. If the AMO shifts to the cold phase in future years, it could partly offset the climate penalty on U.S. air quality brought by global warming, an effect which should be considered in long-term air quality planning.

  2. An intercomparison of multidecadal observational and reanalysis data sets for global total ozone trends and variability analysis

    Science.gov (United States)

    Bai, Kaixu; Chang, Ni-Bin; Shi, Runhe; Yu, Huijia; Gao, Wei

    2017-07-01

    A four-step adaptive ozone trend estimation scheme is proposed by integrating multivariate linear regression (MLR) and ensemble empirical mode decomposition (EEMD) to analyze the long-term variability of total column ozone from a set of four observational and reanalysis total ozone data sets, including the rarely explored ERA-Interim total ozone reanalysis, from 1979 to 2009. Consistency among the four data sets was first assessed, indicating a mean relative difference of 1% and root-mean-square error around 2% on average, with respect to collocated ground-based total ozone observations. Nevertheless, large drifts with significant spatiotemporal inhomogeneity were diagnosed in ERA-Interim after 1995. To emphasize long-term trends, natural ozone variations associated with the solar cycle, quasi-biennial oscillation, volcanic aerosols, and El Niño-Southern Oscillation were modeled with MLR and then removed from each total ozone record, respectively, before performing EEMD analyses. The resulting rates of change estimated from the proposed scheme captured the long-term ozone variability well, with an inflection time of 2000 clearly detected. The positive rates of change after 2000 suggest that the ozone layer seems to be on a healing path, but the results are still inadequate to conclude an actual recovery of the ozone layer, and more observational evidence is needed. Further investigations suggest that biases embedded in total ozone records may significantly impact ozone trend estimations by resulting in large uncertainty or even negative rates of change after 2000.

  3. North American Rocky Mountain Hydroclimate: Holocene patterns and variability at multi-decadal to millennial time scales

    Science.gov (United States)

    Finney, B.; Anderson, L.; Berkelhammer, M. B.; Barron, J. A.; Steinman, B. A.; Abbott, M. B.

    2015-12-01

    A network of western North American lake sediment isotope records (calcium carbonate-δ18O) developed during the past decade provides substantial evidence of Pacific ocean-atmosphere forcing of precipitation variability during the Holocene. We present an overview of the eighteen lake carbonate-δ18O records located in the North American Rocky Mountains with a new compilation of modern lake water isotope measurements to characterize their sensitivity to variations in precipitation-δ18O and fractionation effects by evaporation. Comparative analysis of the carbonate-δ18O records that reflect precipitation isotope (δ18O) values (i.e., precipitation "isometers") indicates a sequence of time-varying in-phase and antiphase patterns between northern and southern regions during the Holocene that provide evidence for a highly non-stationary influence of Pacific ocean-atmosphere processes on the hydroclimate of western North America. We identify a prominent precipitation-δ18O dipole, which was sustained for ~2000 years between ~3.5 and 1.5 ka. The dipole contrasts with divergent earlier Holocene patterns and appears to indicate the onset of linkages between northern and tropical Pacific ocean-atmosphere dynamics as we know them today. These observations are informed by previous research on North Pacific precipitation-δ18O. Further investigation of short (observational) and long (Holocene) time scale patterns are needed to improve our understanding of the processes that 1) drive regional precipitation-δ18O responses to Pacific Ocean-atmosphere variability, and 2) cause varying internal ocean-atmosphere responses to external climate forcing.

  4. Pervasive multidecadal variations in productivity within the Peruvian Upwelling System over the last millennium

    Science.gov (United States)

    Fleury, S.; Martinez, P.; Crosta, X.; Charlier, K.; Billy, I.; Hanquiez, V.; Blanz, T.; Schneider, R. R.

    2015-10-01

    There is no agreement on the pluri-decadal expression of El Niño-Southern Oscillation (ENSO) in the Pacific over the last millennium. Marine records from the Peruvian margin indicate humid conditions (El Niño-like mean conditions) over the Little Ice Age, while precipitation records from the eastern equatorial Pacific infer arid conditions (La Niña-like mean conditions) for the same period. We here studied diatom assemblages, nitrogen isotopes, and major and minor elements at the lamination level in three laminated trigger cores located between 11°S and 15°S on the Peruvian shelf within the oxygen minimum zone (OMZ) to reconstruct precipitation and ocean productivity at the multiannual to multidecadal timescales over the last millennium. We respected the sediment structure, thus providing the first records of the mean climatic conditions at the origin of the lamination deposition, which ones represent several years. Light laminations were deposited under productive and dry conditions, indicative of La Niña-like mean conditions in the system, while dark laminations were deposited under non-productive and humid conditions, representative of El Niño-like mean conditions. La Niña-like mean conditions were predominant during the Medieval Warm Period (MWP; 1000-600 years BP) and Current Warm Period (CWP; 150 years BP to present), while El Niño-like mean conditions prevailed over the Little Ice Age (LIA; 600-150 years BP). We provide evidence for persistent multidecadal variations in productivity over the last millennium, which were disconnected from the mean climate state. Multidecadal variability has been stronger over the last 450 years concomitantly to increased variability in the NAO index. Two intervals of strong multidecadal variability were also observed over the MWP, congruent to decreased solar irradiance and increased volcanic activity.

  5. Madagascar corals reveal a multidecadal signature of rainfall and river runoff since 1708

    NARCIS (Netherlands)

    Grove, C.A.; Zinke, J.; Peeters, F.J.C.; Park, W.; Scheufen, T.; Kasper, S.; Randriamanantsoa, B.; McCulloch, M.T.

    2013-01-01

    Pacific Ocean sea surface temperatures (SST) influence rainfall variability on multidecadal and interdecadal timescales in concert with the Pacific Decadal Oscillation (PDO) and Interdecadal Pacific Oscillation (IPO). Rainfall variations in locations such as Australia and North America are therefore

  6. Marine ecosystem response to the Atlantic Multidecadal Oscillation.

    Directory of Open Access Journals (Sweden)

    Martin Edwards

    Full Text Available Against the backdrop of warming of the Northern Hemisphere it has recently been acknowledged that North Atlantic temperature changes undergo considerable variability over multidecadal periods. The leading component of natural low-frequency temperature variability has been termed the Atlantic Multidecadal Oscillation (AMO. Presently, correlative studies on the biological impact of the AMO on marine ecosystems over the duration of a whole AMO cycle (∼60 years is largely unknown due to the rarity of continuously sustained biological observations at the same time period. To test whether there is multidecadal cyclic behaviour in biological time-series in the North Atlantic we used one of the world's longest continuously sustained marine biological time-series in oceanic waters, long-term fisheries data and historical records over the last century and beyond. Our findings suggest that the AMO is far from a trivial presence against the backdrop of continued temperature warming in the North Atlantic and accounts for the second most important macro-trend in North Atlantic plankton records; responsible for habitat switching (abrupt ecosystem/regime shifts over multidecadal scales and influences the fortunes of various fisheries over many centuries.

  7. Multidecadal shoreline changes in Denmark

    DEFF Research Database (Denmark)

    Kabuth, Alina Kristin; Kroon, Aart; Pedersen, Jørn Bjarke Torp

    2014-01-01

    Multidecadal shoreline changes along ca. 7000 km coastline around Denmark were computed for the time interval between 1862 AD and 2005 AD and were connected with a geomorphological coastal classification. The shoreline data set was based on shoreline positions from historical and modern topographic...... shoreline changes around Denmark, the mapping can contribute to enhanced adaptation and mitigation strategies in response to increased risks of erosion and flooding under a changing climate....

  8. Strong Laws of Large Numbers for Arrays of Rowwise NA and LNQD Random Variables

    Directory of Open Access Journals (Sweden)

    Jiangfeng Wang

    2011-01-01

    Full Text Available Some strong laws of large numbers and strong convergence properties for arrays of rowwise negatively associated and linearly negative quadrant dependent random variables are obtained. The results obtained not only generalize the result of Hu and Taylor to negatively associated and linearly negative quadrant dependent random variables, but also improve it.

  9. Sea-ice cover anomalies in the Arctic Basin associated with atmospheric variability from multi-decadal trends to intermittent quasi-biennial oscillations

    Directory of Open Access Journals (Sweden)

    Motoyoshi Ikeda

    2012-06-01

    Full Text Available Arctic Ocean sea ice has been diminishing since 1970, as shown by National Snow and Ice Data Center data. In addition to decadal variability, low ice anomalies in the Pacific–Siberian region have been occurring at shorter timescales. The influence of the widely-known Northern Annular Mode (NAM occurs across all seasons. In this study, empirical orthogonal function (EOF analysis was applied to sea-level pressure in National Centers for Environmental Prediction Reanalysis data for 1960–2007, showing the NAM to be the leading mode of variability and the Arctic Dipole Mode (ADM to be the second leading mode. The ADM changes markedly across seasons. In autumn–winter, it has a pole over Siberia and a pole over Greenland, at opposite signs at a several-year scale, whereas the spring–summer ADM (ADMSS has a pole over Europe and a pole over Canada. In the 1980s, the most influential mode shifted from the NAM to the ADM, when the Pacific sector had low ice cover at a 1-year lag from the positive ADM, which was marked by low pressure over Siberia. In years when the ADMSS was pronounced, it was responsible for distinct ice variability over the East Siberian–Laptev seas. The frequency separation in this study identified the contributions of the ADM and ADMSS. Effects of the latter are difficult to predict since it is intermittent and changes its sign biennially. The ADM and ADMSS should be closely watched in relation to the ongoing ice reduction in the Pacific–Siberian region.

  10. Lake oxygen isotopes as recorders of North American Rocky Mountain hydroclimate: Holocene patterns and variability at multi-decadal to millennial time scales

    Science.gov (United States)

    Anderson, Lesleigh; Berkelhammer, Max; Barron, John A.; Steinman, Byron A.; Finney, Bruce P.; Abbott, Mark B.

    2016-02-01

    Lake sediment oxygen isotope records (calcium carbonate-δ18O) in the western North American Cordillera developed during the past decade provide substantial evidence of Pacific ocean-atmosphere forcing of hydroclimatic variability 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 observations 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 Decadal Oscillation (PDO) type analogue. Results indicate that further investigation of precipitation-δ18O patterns on short (observational) and long (Holocene) time scales is needed to improve our understanding of the processes that drive

  11. Lake oxygen isotopes as recorders of North American Rocky Mountain hydroclimate: Holocene patterns and variability at multi-decadal to millennial time scales

    Science.gov (United States)

    Anderson, Lesleigh; Max Berkelhammer,; Barron, John A.; Steinman, Byron A.; Finney, Bruce P.; Abbott, Mark B.

    2016-01-01

    Lake sediment oxygen isotope records (calcium carbonate-δ18O) in the western North American Cordillera developed during the past decade provide substantial evidence of Pacific ocean–atmosphere forcing of hydroclimatic variability 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 observations 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 Decadal Oscillation (PDO) type analogue. Results indicate that further investigation of precipitation-δ18O patterns on short (observational) and long (Holocene) time scales is needed to improve our understanding of the

  12. Wave energy fluxes and multi-decadal shoreline changes

    DEFF Research Database (Denmark)

    Kabuth, Alina Kristin; Kroon, Aart

    2014-01-01

    Spatial patterns of multidecadal shoreline changes in two microtidal, low-energetic embayments of southern Zealand, Denmark, were investigated by using the directional distribution of wave energy fluxes. The sites include a barrier island system attached to moraine bluffs, and a recurved spit...... variability of directional distributions of wave energy fluxes furthermore outlined potential sediment sources and sinks for the evolution of the barrier island system and for the evolution of the recurved spit....

  13. Predicting the biological variability of environmental rhythms: weak or strong anticipation for sensorimotor synchronization?

    Science.gov (United States)

    Torre, Kjerstin; Varlet, Manuel; Marmelat, Vivien

    2013-12-01

    The internal processes involved in synchronizing our movements with environmental stimuli have traditionally been addressed using regular metronomic sequences. Regarding real-life environments, however, biological rhythms are known to have intrinsic variability, ubiquitously characterized as fractal long-range correlations. In our research we thus investigate to what extent the synchronization processes drawn from regular metronome paradigms can be generalized to other (biologically) variable rhythms. Participants performed synchronized finger tapping under five conditions of long-range and/or short-range correlated, randomly variable, and regular auditory sequences. Combining experimental data analysis and numerical simulation, we found that synchronizing with biologically variable rhythms involves the same internal processes as with other variable rhythms (whether totally random or comprising lawful regularities), but different from those involved with a regular metronome. This challenges both the generalizability of conclusions drawn from regular-metronome paradigms, and recent research assuming that biologically variable rhythms may trigger specific strong anticipatory processes to achieve synchronization. Copyright © 2013 Elsevier Inc. All rights reserved.

  14. Madagascar corals reveal a multidecadal signature of rainfall and river runoff since 1708

    Directory of Open Access Journals (Sweden)

    C. A. Grove

    2013-03-01

    Full Text Available Pacific Ocean sea surface temperatures (SST influence rainfall variability on multidecadal and interdecadal timescales in concert with the Pacific Decadal Oscillation (PDO and Interdecadal Pacific Oscillation (IPO. Rainfall variations in locations such as Australia and North America are therefore linked to phase changes in the PDO. Furthermore, studies have suggested teleconnections exist between the western Indian Ocean and Pacific Decadal Variability (PDV, similar to those observed on interannual timescales related to the El Niño Southern Oscillation (ENSO. However, as instrumental records of rainfall are too short and sparse to confidently assess multidecadal climatic teleconnections, here we present four coral climate archives from Madagascar spanning up to the past 300 yr (1708–2008 to assess such decadal variability. Using spectral luminescence scanning to reconstruct past changes in river runoff, we identify significant multidecadal and interdecadal frequencies in the coral records, which before 1900 are coherent with Asian-based PDO reconstructions. This multidecadal relationship with the Asian-based PDO reconstructions points to an unidentified teleconnection mechanism that affects Madagascar rainfall/runoff, most likely triggered by multidecadal changes in North Pacific SST, influencing the Asian Monsoon circulation. In the 20th century we decouple human deforestation effects from rainfall-induced soil erosion by pairing luminescence with coral geochemistry. Positive PDO phases are associated with increased Indian Ocean temperatures and runoff/rainfall in eastern Madagascar, while precipitation in southern Africa and eastern Australia declines. Consequently, the negative PDO phase that started in 1998 may contribute to reduced rainfall over eastern Madagascar and increased precipitation in southern Africa and eastern Australia. We conclude that multidecadal rainfall variability in Madagascar and the western Indian Ocean needs to be

  15. Application of discrete variable representation to planar H2+ in strong xuv laser fields.

    Science.gov (United States)

    Ning, Qi-Cheng; Peng, Liang-You; Hou, Xue-Feng; Xu, Zhen; Gong, Qihuang

    2012-09-07

    We present an efficient and accurate grid method to study the strong field dynamics of planar H(2)(+) under Born-Oppenheimer approximation. After introducing the elliptical coordinates to the planar H(2)(+), we show that the Coulomb singularities at the nuclei can be successfully overcome so that both bound and continuum states can be accurately calculated by the method of separation of variables. The time-dependent Schrödinger equation (TDSE) can be accurately solved by a two-dimensional discrete variable representation (DVR) method, where the radial coordinate is discretized with the finite-element discrete variable representation for easy parallel computation and the angular coordinate with the trigonometric DVR which can describe the periodicity in this direction. The bound states energies can be accurately calculated by the imaginary time propagation of TDSE, which agree very well with those computed by the separation of variables. We apply the TDSE to study the ionization dynamics of the planar H(2)(+) by short extreme ultra-violet (xuv) pulses, in which case the differential momentum distributions from both the length and the velocity gauge agree very well with those calculated by the lowest order perturbation theory.

  16. Atlantic and Pacific multidecadal oscillations and Northern Hemisphere temperatures

    Science.gov (United States)

    Steinman, Byron A.; Mann, Michael E.; Miller, Sonya K.

    2015-02-01

    The recent slowdown in global warming has brought into question the reliability of climate model projections of future temperature change and has led to a vigorous debate over whether this slowdown is the result of naturally occurring, internal variability or forcing external to Earth’s climate system. To address these issues, we applied a semi-empirical approach that combines climate observations and model simulations to estimate Atlantic- and Pacific-based internal multidecadal variability (termed “AMO” and “PMO,” respectively). Using this method, the AMO and PMO are found to explain a large proportion of internal variability in Northern Hemisphere mean temperatures. Competition between a modest positive peak in the AMO and a substantially negative-trending PMO are seen to produce a slowdown or “false pause” in warming of the past decade.

  17. Atmospheric multidecadal variations in the North Atlantic realm: proxy data, observations, and atmospheric circulation model studies

    Directory of Open Access Journals (Sweden)

    K. Grosfeld

    2007-01-01

    Full Text Available We investigate the spatial and temporal characteristics of multidecadal climate variability in the North Atlantic realm, using observational data, proxy data and model results. The dominant pattern of multidecadal variability of SST depicts a monopolar structure in the North Atlantic during the instrumental period with cold (warm phases during 1900–1925 and 1970–1990 (1870–1890 and 1940–1960. Two atmospheric general circulation models of different complexity forced with global SST over the last century show SLP anomaly patterns from the warm and cold phases of the North Atlantic similar to the corresponding observed patterns. The analysis of a sediment core from Cariaco Basin, a coral record from the northern Red Sea, and a long-term sea level pressure (SLP reconstruction reveals that the multidecadal mode of the atmospheric circulation characterizes climate variability also in the pre-industrial era. The analyses of SLP reconstruction and proxy data depict a persistent atmospheric mode at least over the last 300 years, where SLP shows a dipolar structure in response to monopolar North Atlantic SST, in a similar way as the models' responses do. The combined analysis of observational and proxy data with model experiments provides an understanding of multidecadal climate modes during the late Holocene. The related patterns are useful for the interpretation of proxy data in the North Atlantic realm.

  18. Strong Stability Preserving Explicit Linear Multistep Methods with Variable Step Size

    KAUST Repository

    Hadjimichael, Yiannis

    2016-09-08

    Strong stability preserving (SSP) methods are designed primarily for time integration of nonlinear hyperbolic PDEs, for which the permissible SSP step size varies from one step to the next. We develop the first SSP linear multistep methods (of order two and three) with variable step size, and prove their optimality, stability, and convergence. The choice of step size for multistep SSP methods is an interesting problem because the allowable step size depends on the SSP coefficient, which in turn depends on the chosen step sizes. The description of the methods includes an optimal step-size strategy. We prove sharp upper bounds on the allowable step size for explicit SSP linear multistep methods and show the existence of methods with arbitrarily high order of accuracy. The effectiveness of the methods is demonstrated through numerical examples.

  19. Twentieth-Century Hydrometeorological Reconstructions to Study the Multidecadal Variations of the Water Cycle Over France

    Science.gov (United States)

    Bonnet, R.; Boé, J.; Dayon, G.; Martin, E.

    2017-10-01

    Characterizing and understanding the multidecadal variations of the continental hydrological cycle is a challenging issue given the limitation of observed data sets. In this paper, a new approach to derive twentieth century hydrological reconstructions over France with an hydrological model is presented. The method combines the results of long-term atmospheric reanalyses downscaled with a stochastic statistical method and homogenized station observations to derive the meteorological forcing needed for hydrological modeling. Different methodological choices are tested and evaluated. We show that using homogenized observations to constrain the results of statistical downscaling help to improve the reproduction of precipitation, temperature, and river flows variability. In particular, it corrects some unrealistic long-term trends associated with the atmospheric reanalyses. Observationally constrained reconstructions therefore constitute a valuable data set to study the multidecadal hydrological variations over France. Thanks to these reconstructions, we confirm that the multidecadal variations previously noted in French river flows have mainly a climatic origin. Moreover, we show that multidecadal variations exist in other hydrological variables (evapotranspiration, snow cover, and soil moisture). Depending on the region, the persistence from spring to summer of soil moisture or snow anomalies generated during spring by temperature and precipitation variations may explain river flows variations in summer, when no concomitant climate variations exist.

  20. Fives decades of strong temporal variability in the flow of the Brunt Ice Shelf, Antarctica

    Science.gov (United States)

    De Rydt, Jan; Gudmundsson, Hilmar; Nagler, Thomas

    2017-04-01

    The Brunt Ice Shelf, East Antarctica, is a complex conglomerate of meteoric and marine ice, weakly connected to the much larger and faster-flowing Stancomb Wills Glacier Tongue to the east, and pinned down to the seabed in a small area around the McDonalds Ice Rumples in the north. The ice shelf is home to the UK research station Halley, from which changes to the ice shelf have been monitored closely since the 1960s. A unique 50-year record of the flow speed and an intense surveying programme over the past 10 years, have revealed a strong temporal variability in the flow. In particular, the speed of the ice shelf has increased by 10% each year over the past few years. In order to understand these rapid changes, we use a state-of-the-art flow model in combination with a range of satellite, ground-based and airborne radar data, to accurately simulate the historical flow and recent changes. In particular, we model the effects of a recently formed rift that is propagating at a speed of up to 600m/day and threatens to dislodge the ice shelf from its pinning point at the McDonalds Ice Rumples. We also report on the recent reactivation of a large chasm which has prompted the relocation of the station during the 2016/17 austral summer.

  1. Forcing of the wintertime atmospheric circulation by the multidecadal fluctuations of the North Atlantic ocean

    International Nuclear Information System (INIS)

    Peings, Yannick; Magnusdottir, Gudrun

    2014-01-01

    The North Atlantic sea surface temperature exhibits fluctuations on the multidecadal time scale, a phenomenon known as the Atlantic Multidecadal Oscillation (AMO). This letter demonstrates that the multidecadal fluctuations of the wintertime North Atlantic Oscillation (NAO) are tied to the AMO, with an opposite-signed relationship between the polarities of the AMO and the NAO. Our statistical analyses suggest that the AMO signal precedes the NAO by 10–15 years with an interesting predictability window for decadal forecasting. The AMO footprint is also detected in the multidecadal variability of the intraseasonal weather regimes of the North Atlantic sector. This observational evidence is robust over the entire 20th century and it is supported by numerical experiments with an atmospheric global climate model. The simulations suggest that the AMO-related SST anomalies induce the atmospheric anomalies by shifting the atmospheric baroclinic zone over the North Atlantic basin. As in observations, the positive phase of the AMO results in more frequent negative NAO—and blocking episodes in winter that promote the occurrence of cold extreme temperatures over the eastern United States and Europe. Thus, it is plausible that the AMO plays a role in the recent resurgence of severe winter weather in these regions and that wintertime cold extremes will be promoted as long as the AMO remains positive. (paper)

  2. The Atlantic Multidecadal Oscillation without a role for ocean circulation.

    Science.gov (United States)

    Clement, Amy; Bellomo, Katinka; Murphy, Lisa N; Cane, Mark A; Mauritsen, Thorsten; Rädel, Gaby; Stevens, Bjorn

    2015-10-16

    The Atlantic Multidecadal Oscillation (AMO) is a major mode of climate variability with important societal impacts. Most previous explanations identify the driver of the AMO as the ocean circulation, specifically the Atlantic Meridional Overturning Circulation (AMOC). Here we show that the main features of the observed AMO are reproduced in models where the ocean heat transport is prescribed and thus cannot be the driver. Allowing the ocean circulation to interact with the atmosphere does not significantly alter the characteristics of the AMO in the current generation of climate models. These results suggest that the AMO is the response to stochastic forcing from the mid-latitude atmospheric circulation, with thermal coupling playing a role in the tropics. In this view, the AMOC and other ocean circulation changes would be largely a response to, not a cause of, the AMO. Copyright © 2015, American Association for the Advancement of Science.

  3. Multidecadal climate to within a millikelvin

    Science.gov (United States)

    Pratt, V. R.

    2012-12-01

    We analyze and compare the monthly global land-sea surface temperature datasets HADCRUT3 and HADCRUT4 for 1850-2010 by subtracting two analytically modeled components and demonstrating with a suitable low-pass filter that the residue contains no significant fluctuations with periods longer than the 22-year Hale cycle. It follows that the two components are essentially all there is to recent multidecadal climate thus understood. With either dataset, the model forecasts a 4 C rise for 2100. The first component, AGW, models the impact of increasing CO2 based only on Arrhenius's 1896 logarithmic dependence of surface temperature on CO2, Hofmann's 2009 exponential model of anthropogenic CO2 emissions superimposed on a preindustrial base, and Hansen's 1997 pipeline modeled as a fixed delay between increasing radiative forcing and resulting increasing surface temperature. The delay is the time required to heat the ocean in its role as planetary heatsink; neglecting it creates two problems for our analysis, namely a one-degree-per-doubling difference between theoretically predicted and empirically observed *modern* climate sensitivity, and an apparent absence of parameters leading to anywhere near as good a fit to the data. The best fit is obtained with a pipeline of 14.5 years and a climate sensitivity of 2.8 C/doubling, which would be 1.8 without the pipeline. The second component, SAW, is an inverse sawtooth wave filtered to attenuate and phase-shift its first five harmonics and neglect the rest. The second and third harmonics correlate well with the principal ocean oscillations, e.g. AMO; they are passed through largely unfiltered while the other three are more sharply attenuated. One possible physical origin would be two similarly sized seismic events at the core-mantle boundary in respectively the mid-18th and early 20th centuries. Each event would briefly bring heat from the lower mantle to the crust, felt most strongly in the oceans because the crust there is only

  4. Multi-decadal uptake of carbon dioxide into subtropical mode water of the North Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    N. R. Bates

    2012-07-01

    Full Text Available Natural climate variability impacts the multi-decadal uptake of anthropogenic carbon dioxide (Cant into the North Atlantic Ocean subpolar and subtropical gyres. Previous studies have shown that there is significant uptake of CO2 into subtropical mode water (STMW of the North Atlantic. STMW forms south of the Gulf Stream in winter and constitutes the dominant upper-ocean water mass in the subtropical gyre of the North Atlantic Ocean. Observations at the Bermuda Atlantic Time-series Study (BATS site near Bermuda show an increase in dissolved inorganic carbon (DIC of +1.51 ± 0.08 μmol kg−1 yr−1 between 1988 and 2011, but also an increase in ocean acidification indicators such as pH at rates (−0.0022 ± 0.0002 yr−1 higher than the surface ocean (Bates et al., 2012. It is estimated that the sink of CO2 into STMW was 0.985 ± 0.018 Pg C (Pg = 1015 g C between 1988 and 2011 (70 ± 1.8% of which is due to uptake of Cant. The sink of CO2 into the STMW is 20% of the CO2 uptake in the North Atlantic Ocean between 14°–50° N (Takahashi et al., 2009. However, the STMW sink of CO2 was strongly coupled to the North Atlantic Oscillation (NAO, with large uptake of CO2 into STMW during the 1990s during a predominantly NAO positive phase. In contrast, uptake of CO2 into STMW was much reduced in the 2000s during the NAO neutral/negative phase. Thus, NAO induced variability of the STMW CO2 sink is important when evaluating multi-decadal changes in North Atlantic Ocean CO2 sinks.

  5. Joint spatiotemporal variability of global sea surface temperatures and global Palmer drought severity index values

    Science.gov (United States)

    Apipattanavis, S.; McCabe, G.J.; Rajagopalan, B.; Gangopadhyay, S.

    2009-01-01

    Dominant modes of individual and joint variability in global sea surface temperatures (SST) and global Palmer drought severity index (PDSI) values for the twentieth century are identified through a multivariate frequency domain singular value decomposition. This analysis indicates that a secular trend and variability related to the El Niño–Southern Oscillation (ENSO) are the dominant modes of variance shared among the global datasets. For the SST data the secular trend corresponds to a positive trend in Indian Ocean and South Atlantic SSTs, and a negative trend in North Pacific and North Atlantic SSTs. The ENSO reconstruction shows a strong signal in the tropical Pacific, North Pacific, and Indian Ocean regions. For the PDSI data, the secular trend reconstruction shows high amplitudes over central Africa including the Sahel, whereas the regions with strong ENSO amplitudes in PDSI are the southwestern and northwestern United States, South Africa, northeastern Brazil, central Africa, the Indian subcontinent, and Australia. An additional significant frequency, multidecadal variability, is identified for the Northern Hemisphere. This multidecadal frequency appears to be related to the Atlantic multidecadal oscillation (AMO). The multidecadal frequency is statistically significant in the Northern Hemisphere SST data, but is statistically nonsignificant in the PDSI data.

  6. Amplification of the Atlantic Multidecadal Oscillation associated with the onset of the industrial-era warming

    OpenAIRE

    Moore, G. W. K.; Halfar, J.; Majeed, H.; Adey, W.; Kronz, A.

    2017-01-01

    North Atlantic sea surface temperatures experience variability with a periodicity of 60–80 years that is known as the Atlantic Multidecadal Oscillation (AMO). It has a profound imprint on the global climate system that results in a number of high value societal impacts. However the industrial period, i.e. the middle of the 19th century onwards, contains only two full cycles of the AMO making it difficult to fully characterize this oscillation and its impact on the climate system. ...

  7. Regional influence of decadal to multidecadal Atlantic Oscillations in Morocco during the last 1200 years

    Science.gov (United States)

    Ait Brahim, Y.; Sifeddine, A.; Cheng, H.; Khodri, M.; Cruz, F. W., Sr.; Pérez-Zanón, N.; SHA, L.; Wassenburg, J. A.; Bouchaou, L.

    2016-12-01

    Climate projections predict a substantial increase of extreme heats and drought occurrences during the coming decades in Morocco, while already under severe water stress. It is however not clear what can be attributed to natural climate variability and to anthropogenic forcing, as hydroclimate variations observed in areas such as Morocco are highly influenced by the Atlantic climate modes. Since observational data sets are too short to resolve properly natural modes of variability acting on decadal to multidecadal timescales, high resolution paleoclimate reconstructions are the only alternative to reconstruct climate variability in the remote past. However, the climate processes are still poorly understood in North Africa, which makes the investigation of hydroclimate variations during the last millennium in Morocco highly requested. Here, we present the first well-dated high resolution ( 1.7 years) stable oxygen isotope (δ18O) speleothem record from southwestern Morocco, covering the last 1200 years. Our record reveals substantial decadal to multidecadal swings between dry and humid periods, consistent with regional paleorecords, with prevailing dry conditions during the Medieval Climate Anomaly (MCA), wetter conditions during the Little Ice Age (LIA), and a trend towards dry conditions during the current warm period. These coherent regional climate signals suggest common climate controls. Statistical analyses indicate that the climate of southwestern Morocco remained under the combined influence of both the Atlantic Multidecadal Oscillation (AMO) and the North Atlantic Oscillation (NAO) over the last millennium. Interestingly, the generally warmer MCA and colder LIA at longer multidecadal timescales probably influenced the regional climate in North Africa through the influence on Sahara Low which weakened and strengthened the mean moisture inflow from the Atlantic Ocean during the MCA and LIA respectively.

  8. Strong spatial variability in trace gas dynamics following experimental drought in a humid tropical forest

    Science.gov (United States)

    Tana Wood; W. L. Silver

    2012-01-01

    [1] Soil moisture is a key driver of biogeochemical processes in terrestrial ecosystems, strongly affecting carbon (C) and nutrient availability as well as trace gas production and consumption in soils. Models predict increasing drought frequency in tropical forest ecosystems, which could feed back on future climate change directly via effects on trace gasdynamics and...

  9. Strong but variable associations between social dominance and clutch sex ratio in a colonial corvid

    NARCIS (Netherlands)

    Salomons, H. M.; Dijkstra, C.; Verhulst, S.

    2008-01-01

    We studied primary sex ratio of clutches in relation to social dominance for 6 years in a colony of free-living jackdaws, a small corvid. Social dominance was strongly associated with clutch sex ratio, with the difference in clutch sex ratio between the most and least dominant pairs being 30-40%. To

  10. Amplification of the Atlantic Multidecadal Oscillation associated with the onset of the industrial-era warming

    Science.gov (United States)

    Moore, Kent; Majeed, Haris; Halfar, Jochen; Adey, Walter; Kronz, Andreas

    2017-04-01

    North Atlantic sea surface temperatures experience variability with a periodicity of 60-80 years that is known as the Atlantic Multidecadal Oscillation (AMO). It has a profound imprint on the global climate system that results in a number of high value societal impacts. However the industrial period, i.e. the middle of the 19th century onwards, contains only two full cycles of the AMO making it difficult to fully characterize this oscillation and its impact on the climate system. As a result, there is a clear need to identify paleoclimate records extending into the pre-industrial period that contain an expression of the AMO. This is especially true for extratropical marine paleoclimate proxies where such expressions are currently unavailable. Here we present an annually resolved coralline algal time series from the northwest Atlantic Ocean that exhibits multidecadal variability extending back six centuries. The time series contains a statistically significant trend towards higher values, i.e. warmer conditions, beginning in the 19th century that coincided with an increase in the time series' multidecadal power. We argue that these changes are associated with a regional climate reorganization involving an amplification of the AMO that coincided with onset of the industrial-era warming.

  11. Extension of SMAC scheme for variable density flows under strong temperature gradient

    Science.gov (United States)

    Anwer, S. F.; Khan, H. Naushad; Sanghi, S.; Ahmad, A.; Yahya, S. M.

    2012-06-01

    An extension of SMAC scheme is proposed for variable density flows under low Mach number approximation. The algorithm is based on a predictor-corrector time integration scheme that employs a projection method for the momentum equation. A constant-coefficient Poisson equation is solved for the pressure following both the predictor and corrector steps to satisfy the continuity equation at each time step. Spatial discretization is performed on a collocated grid system that offers computational simplicity and straight forward extension to curvilinear coordinate systems. To avoid the pressure odd-even decoupling that is typically encountered in such grids, a flux interpolation technique is introduced for the equations governing variable density flows. An important characteristic of the proposed algorithm is that it can be applied to flows in both open and closed domains. Its robustness and accuracy are illustrated with a non-isothermal, turbulent channel flow at temperature ratio of 1.01 and 2.

  12. Ionization cross section for a strongly coupled partially ionized hydrogen plasma: variable phase approach

    Energy Technology Data Exchange (ETDEWEB)

    Baimbetov, F B; Kudyshev, Z A [Department of Physics, Al-Farabi Kazakh National University, 050012 Almaty (Kazakhstan)], E-mail: Fazylhan.Baimbetov@kaznu.kz, E-mail: Z.Kudyshev@mail.ru

    2009-05-29

    In the present work an electron impact ionization cross section is considered. The electron impact ionization cross section is calculated with the help of a variable phase approach to potential scattering. The Calogero equation is numerically solved, based on a pseudopotential model of interaction between partially ionized plasma particles, which accounts for correlation effects. As a result, scattering phase shifts are obtained. On the basis of the scattering phase shifts, the ionization cross section is calculated.

  13. Precipitation variability as a strong determinant on tree cover across global tropics

    Science.gov (United States)

    Xu, X.; Medvigy, D.; Guan, K.; Trugman, A. T.; Good, S. P.; Rodriguez-Iturbe, I.

    2017-12-01

    Tropical and subtropical ecosystems support a significant carbon sink and storage and provide various ecosystem services. One challenge for these ecosystems is the changing precipitation variability (PV), which is likely to become more extreme under on-going climate change. However, there is a lack of consensus in the determining role of PV on tropical tree cover, which is a widely-used indicator for ecosystem state and functions in the tropics, as well as the underlying mechanism. Here, we ask whether changes in PV by themselves are likely to lead to changes in tropical tree cover. Using a combination of climate, soil and remotely-sensed tree cover data, we comprehensively assess the effects of PV on tree cover spatial variations at intra-seasonal, seasonal and inter-annual scales. We find that PV contributes 33% -56% to the total explained spatial variation (65% -79%) in tree cover. The contribution of PV depends on mean annual precipitation (MAP) and is highest under intermediate MAP (500 - 1500 mm). In general, tree cover increases with rainy day frequency and wet season length but shows mixed responses to inter-annual precipitation variability. We further use a biophysical model to show that the PV-tree cover relation can be explained by tree-grass water competition. Our results suggest that tropical tree cover can decrease by 3-5% overall and by up to 20% in Amazonia under projected changes in PV at the end of this century.

  14. Age of oil palm plantations causes a strong change in surface biophysical variables

    Science.gov (United States)

    Sabajo, Clifton; le Maire, Guerric; Knohl, Alexander

    2016-04-01

    Over the last decades, Indonesia has experienced dramatic land transformations with an expansion of oil palm plantations at the expense of tropical forests. As vegetation is a modifier of the climate near the ground these large-scale land transformations are expected to have major impacts on the surface biophysical variables i.e. surface temperature, albedo, and vegetation indices, e.g. the NDVI. Remote sensing data are needed to assess such changes at regional scale. We used 2 Landsat images from Jambi Province in Sumatra/Indonesia covering a chronosequence of oil palm plantations to study the 20 - 25 years life cycle of oil palm plantations and its relation with biophysical variables. Our results show large differences between the surface temperature of young oil palm plantations and forest (up to 9.5 ± 1.5 °C) indicating that the surface temperature is raised substantially after the establishment of oil palm plantations following the removal of forests. During the oil palm plantation lifecycle the surface temperature differences gradually decreases and approaches zero around an oil palm plantation age of 10 years. Similarly, NDVI increases and the albedo decreases approaching typical values of forests. Our results show that in order to assess the full climate effects of oil palm expansion biophysical processes play an important role and the full life cycle of oil palm plantations need to be considered.

  15. BONA FIDE, STRONG-VARIABLE GALACTIC LUMINOUS BLUE VARIABLE STARS ARE FAST ROTATORS: DETECTION OF A HIGH ROTATIONAL VELOCITY IN HR CARINAE

    International Nuclear Information System (INIS)

    Groh, J. H.; Damineli, A.; Moises, A. P.; Teodoro, M.; Hillier, D. J.; Barba, R.; Fernandez-Lajus, E.; Gamen, R. C.; Solivella, G.

    2009-01-01

    We report optical observations of the luminous blue variable (LBV) HR Carinae which show that the star has reached a visual minimum phase in 2009. More importantly, we detected absorptions due to Si IV λλ4088-4116. To match their observed line profiles from 2009 May, a high rotational velocity of v rot ≅ 150 ± 20 km s -1 is needed (assuming an inclination angle of 30 deg.), implying that HR Car rotates at ≅0.88 ± 0.2 of its critical velocity for breakup (v crit ). Our results suggest that fast rotation is typical in all strong-variable, bona fide galactic LBVs, which present S-Dor-type variability. Strong-variable LBVs are located in a well-defined region of the HR diagram during visual minimum (the 'LBV minimum instability strip'). We suggest this region corresponds to where v crit is reached. To the left of this strip, a forbidden zone with v rot /v crit >1 is present, explaining why no LBVs are detected in this zone. Since dormant/ex LBVs like P Cygni and HD 168625 have low v rot , we propose that LBVs can be separated into two groups: fast-rotating, strong-variable stars showing S-Dor cycles (such as AG Car and HR Car) and slow-rotating stars with much less variability (such as P Cygni and HD 168625). We speculate that supernova (SN) progenitors which had S-Dor cycles before exploding (such as in SN 2001ig, SN 2003bg, and SN 2005gj) could have been fast rotators. We suggest that the potential difficulty of fast-rotating Galactic LBVs to lose angular momentum is additional evidence that such stars could explode during the LBV phase.

  16. Is there a connection between Earth's core and climate at multidecadal time scales?

    Science.gov (United States)

    Lambert, Sébastien; Marcus, Steven; de Viron, Olivier

    2017-04-01

    The length-of-day (LOD) undergoes multidecadal variations of several milliseconds (ms) attributed to changes in the fluid outer core angular momentum. These variations resemble a quasi-periodic oscillation of duration 60 to 70 years, although the periodicity (and its accurate length) are disputable because of the relatively short observational time span and the lower quality of the observations before the 20th century. Interestingly, similar variations show up in various measured or reconstructed climate indices including the sea surface (SST) and surface air (SAT) temperatures. It has been shown in several studies that LOD variations lead SST and SAT variations by a few years. No clear scenarios have been raised so far to explain the link between external, astronomical forcing (e.g., Solar wind), Earth's rotation (core-driven torsional) oscillations, and Earth's surface processes (climate variations) at these time scales. Accumulating evidence, however, suggests the centrifugal tides generated by multidecadal LOD variations as a 'valve' to control the transfer of thermal energy from the lithosphere to the surface via geothermal fluxes. This hypothesis is supported by recent studies reporting significant correlations between tidal and rotational excitation and seafloor and surface volcanism. In this study, we extend recent works from us and other independent authors by re-assessing the correlations between multidecadal LOD, climate indices, Solar and magnetic activities, as well as gridded data including SST, SAT, and cloud cover. We pay a special attention to the time lags: when a significant correlation is found, the value of the lag may help to discriminate between various possible scenarios. We locate some `hot spots', particularly in the Atlantic ocean and along the trajectory of the upper branch of the Atlantic meridional overturning circulation (AMOC), where the 70-yr oscillation is strongly marked. In addition, we discuss the possibility for centrifugal

  17. Strong inbreeding depression and individually variable mating system in the narrow endemic Erodium cazorlanum (Geraniaceae

    Directory of Open Access Journals (Sweden)

    Alonso, Conchita

    2013-06-01

    Full Text Available Angiosperms evolved different systems to attract effective pollinators while reducing selfing in hermaphroditic flowers. Selfing ability can be advantageous when pollinators and/or mates are scarce, although inbreeding depression may largely reduce those advantages. Recent comparative analyses suggested endemic species tend to evolve self-compatibility but a better understanding of the associated reproductive and genetic tradeoffs is required. Experimental hand-pollinations under greenhouse conditions were conducted to investigate the selfing ability and estimate inbreeding depression up to the offspring’ first reproductive event in Ero dium cazorlanum, a narrow endemic species restricted to dolomite outcrops in SE Spanish mountains. We found autonomous selfing ineffective. Further, when experimentally applied, pollen of the same flower produced significantly fewer fruits and seeds compared to geitonogamous and cross pollinations. The number of seeds per fruit was significantly higher after cross pollinations and strong inbreeding depression accumulated through the life-cycle. Interestingly, individual plants exhibited broad variation in selfing ability with six out of 14 individuals producing no seed after geitonogamy. Understanding the consequences of individual variation in self compatibility deserves further investigation in the field now that we know that strong inbreeding depression may limit recruitment of selfed progeny.Las Angiospermas han desarrollado diversos sistemas para atraer polinizadores eficientes y al mismo tiempo reducir la posibilidad de autopolinización asociada al hermafroditismo. La capacidad de autopolinización puede ser ventajosa en situaciones de escasez de polinizadores y/o individuos reproductores, beneficios que pueden reducirse ampliamente a causa de la depresión por endogamia. Análisis filogenéticos recientes indicaron que las especies endémicas tienden a presentar sistemas de autocompatibilidad, por tanto

  18. What is the variability in US west coast winter precipitation during strong El Niño events?

    Science.gov (United States)

    Kumar, Arun; Chen, Mingyue

    2017-10-01

    Motivated by the fact that the spatial pattern of the observed precipitation anomalies during 2015/16 winter (a year of strong El Niño) over the west coast of the US and that of the El Niño composite precipitation pattern had considerable differences, the variability in the winter precipitation during strong El Niño events is assessed. The analysis is based on a set of hindcasts (1982-2011) and real-time forecasts (2012-2015) from NCEP Climate Forecast System version 2 (CFSv2), and the following aspects for seasonal mean precipitation variability were examined: (1) the mean signal during strong El Niño based on the composite analysis, and further, the variability from the composite on an event-to-event basis; (2) probability of occurrence for precipitation anomalies to be opposite to the signal (inferred as the composite mean); (3) the probability to have precipitation anomaly in different categories varying from wet to dry; and (4) variations in the characteristics of precipitation from OND, NDJ, to DJF (early to late boreal winter). The results show that the model forecasted seasonal mean precipitation composite for strong El Niño was similar to the linear regression signal with the Niño 3.4 index in observations, with negative anomalies over the Pacific Northwest and positive anomalies over California. However, although in response to an El Niño event, the California precipitation PDF was shifted towards positive values relative to the climatological PDF, the overlap between climatological PDF and the PDF for El Niño events was considerable. This is because of the large variability in seasonal mean outcomes of precipitation from one forecast to another, and therefore, chances to have precipitation anomalies with their sign opposite to the composite El Niño signal remain appreciable. In this paradigm, although the seasonal mean precipitation during 2015/16 winter over the west coast of the US differed from the mean signal for a strong El Niño event, the

  19. Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2

    International Nuclear Information System (INIS)

    Williams, Kurtis A.; Winget, D. E.; Montgomery, M. H.; Hermes, J. J.; Falcon, Ross E.; Winget, K. I.; Dufour, Patrick; Kepler, S. O.; Bolte, Michael; Rubin, Kate H. R.; Liebert, James

    2013-01-01

    We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude 0.442% ± 0.024%; no other periodic modulations are observed with amplitudes ≳ 0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: T eff ≈ 15, 500 K, log g ≈ 9, log (C/He) = –1.0, and a mean magnetic field strength of 3.0 ± 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, helium-dominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same.

  20. Multi-decadal Arctic sea ice roughness.

    Science.gov (United States)

    Tsamados, M.; Stroeve, J.; Kharbouche, S.; Muller, J. P., , Prof; Nolin, A. W.; Petty, A.; Haas, C.; Girard-Ardhuin, F.; Landy, J.

    2017-12-01

    The transformation of Arctic sea ice from mainly perennial, multi-year ice to a seasonal, first-year ice is believed to have been accompanied by a reduction of the roughness of the ice cover surface. This smoothening effect has been shown to (i) modify the momentum and heat transfer between the atmosphere and ocean, (ii) to alter the ice thickness distribution which in turn controls the snow and melt pond repartition over the ice cover, and (iii) to bias airborne and satellite remote sensing measurements that depend on the scattering and reflective characteristics over the sea ice surface topography. We will review existing and novel remote sensing methodologies proposed to estimate sea ice roughness, ranging from airborne LIDAR measurement (ie Operation IceBridge), to backscatter coefficients from scatterometers (ASCAT, QUICKSCAT), to multi angle maging spectroradiometer (MISR), and to laser (Icesat) and radar altimeters (Envisat, Cryosat, Altika, Sentinel-3). We will show that by comparing and cross-calibrating these different products we can offer a consistent multi-mission, multi-decadal view of the declining sea ice roughness. Implications for sea ice physics, climate and remote sensing will also be discussed.

  1. FAST VARIABILITY AND MILLIMETER/IR FLARES IN GRMHD MODELS OF Sgr A* FROM STRONG-FIELD GRAVITATIONAL LENSING

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Chi-kwan; Psaltis, Dimitrios; Özel, Feryal; Marrone, Daniel [Steward Observatory and Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Medeiros, Lia [Department of Physics, Broida Hall, University of California, Santa Barbara, Santa Barbara, CA 93106 (United States); Sadowski, Aleksander [MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Narayan, Ramesh, E-mail: chanc@email.arizona.edu [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2015-10-20

    We explore the variability properties of long, high-cadence general relativistic magnetohydrodynamic (GRMHD) simulations across the electromagnetic spectrum using an efficient, GPU-based radiative transfer algorithm. We focus on both standard and normal evolution (SANE) and magnetically arrested disk (MAD) simulations with parameters that successfully reproduce the time-averaged spectral properties of Sgr A* and the size of its image at 1.3 mm. We find that the SANE models produce short-timescale variability with amplitudes and power spectra that closely resemble those inferred observationally. In contrast, MAD models generate only slow variability at lower flux levels. Neither set of models shows any X-ray flares, which most likely indicates that additional physics, such as particle acceleration mechanisms, need to be incorporated into the GRMHD simulations to account for them. The SANE models show strong, short-lived millimeter/infrared (IR) flares, with short (≲1 hr) time lags between the millimeter and IR wavelengths, that arise from the combination of short-lived magnetic flux tubes and strong-field gravitational lensing near the horizon. Such events provide a natural explanation for the observed IR flares with no X-ray counterparts.

  2. Strong-field Breit–Wheeler pair production in two consecutive laser pulses with variable time delay

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, Martin J.A.; Müller, Carsten, E-mail: c.mueller@tp1.uni-duesseldorf.de

    2017-03-10

    Photoproduction of electron–positron pairs by the strong-field Breit–Wheeler process in an intense laser field is studied. The laser field is assumed to consist of two consecutive short pulses, with a variable time delay in between. By numerical calculations within the framework of scalar quantum electrodynamics, we demonstrate that the time delay exerts a strong impact on the pair-creation probability. For the case when both pulses are identical, the effect is traced back to the relative quantum phase of the interfering S-matrix amplitudes and explained within a simplified analytical model. Conversely, when the two laser pulses differ from each other, the pair-creation probability depends not only on the time delay but, in general, also on the temporal order of the pulses.

  3. Tracking the Atlantic Multidecadal Oscillation through the last 8,000 years

    DEFF Research Database (Denmark)

    Knudsen, Mads Faurschou; Seidenkrantz, Marit-Solveig; Jacobsen, B. H.

    2011-01-01

    and reject the hypothesis that this climate oscillation was directly forced by periodic changes in solar activity. We therefore conjecture that a quasi-persistent ~55- to 70-year AMO, linked to internal ocean-atmosphere variability, existed during large parts of the Holocene. Our analyses further suggest......Understanding the internal ocean variability and its influence on climate is imperative for society. A key aspect concerns the enigmatic Atlantic Multidecadal Oscillation (AMO), a feature defined by a 60- to 90-year variability in North Atlantic sea-surface temperatures. The nature and origin...... of the AMO is uncertain, and it remains unknown whether it represents a persistent periodic driver in the climate system, or merely a transient feature. Here, we show that distinct, ~55- to 70-year oscillations characterized the North Atlantic ocean-atmosphere variability over the past 8,000 years. We test...

  4. On the origin of multidecadal to centennial Greenland temperature anomalies over the past 800 yr

    Directory of Open Access Journals (Sweden)

    T. Kobashi

    2013-03-01

    Full Text Available The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies due to its association with sea level rise. However, the causes of multidecadal-to-centennial temperature changes in Greenland temperatures are not well understood, largely owing to short observational records. To examine these, we calculated the Greenland temperature anomalies (GTA[G-NH] over the past 800 yr by subtracting the standardized northern hemispheric (NH temperature from the standardized Greenland temperature. This decomposes the Greenland temperature variation into background climate (NH; polar amplification; and regional variability (GTA[G-NH]. The central Greenland polar amplification factor as expressed by the variance ratio Greenland/NH is 2.6 over the past 161 yr, and 3.3–4.2 over the past 800 yr. The GTA[G-NH] explains 31–35% of the variation of Greenland temperature in the multidecadal-to-centennial time scale over the past 800 yr. We found that the GTA[G-NH] has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO. Climate modeling and proxy temperature records indicate that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC and associated changes in northward oceanic heat transport.

  5. Multi-decadal modulations in the Aleutian-Icelandic Low seesaw and the axial symmetry of the Arctic Oscillation signature, as revealed in the 20th century reanalysis

    Directory of Open Access Journals (Sweden)

    Ning Shi

    2014-08-01

    Full Text Available Seesaw relationship in intensity between the surface Aleutian and Icelandic Lows (AIS is a manifestation of atmospheric teleconnection that bridges the interannual variability over the Pacific and Atlantic in particular winter months. Analysis of the 20th Century Reanalysis data reveals that the strength and timing of AIS have undergone multi-decadal modulations in conjunction with those in structure of the Arctic Oscillation (AO signature, extracted in the leading mode of interannual sea-level pressure (SLP variability over the extratropical Northern Hemisphere. Specifically, events of what may be called ‘pure AO’, in which SLP anomalies exhibit a high degree of axial symmetry in association with in-phase SLP variability between the midlatitude Atlantic and Pacific, tended to occur during multi-decadal periods in which the inter-basin teleconnection through AIS was active under the enhanced interannual variability of the Aleutian Low. In contrast, the axial symmetry of the AO pattern was apparently reduced during a multi-decadal period in which the AIS teleconnection was inactive under the weakened interannual variability of the Aleutian Low. In this period, the leading mode of interannual SLP variability represented a meridional seesaw between the Atlantic and Arctic, which resembles SLP anomaly pattern associated with the cold-ocean/warm-land (COWL temperature pattern. These multi-decadal modulations in interannual AIS signal and the axial symmetry of the interannual AO pattern occurred under multi-decadal changes in the background state that also represented the polarity changes of the COWL-like anomaly pattern.

  6. Multi-decadal oscillations in the hydro-climate of the Okavango River system during the past and under a changing climate

    Science.gov (United States)

    Wolski, P.; Todd, M. C.; Murray-Hudson, M. A.; Tadross, M.

    2012-12-01

    SummaryThe focus of this paper is to understand the multi-decadal oscillatory component of variability in the Okavango River system, in southwestern Africa, and its potential evolution through the 21st century under climate change scenarios. Statistical analyses and hydrological modelling are used to show that the observed multi-decadal wet and dry phases in the Okavango River and Delta result from multi-decadal oscillations in rainfall, which are likely to be related to processes of internal variability in the climate system, rather than external natural or anthropogenic forcing. Analyses of changes in this aspect of variability under projected climate change scenarios are based on data from a multi-model ensemble of 19 General Circulation Models, which are used to drive hydrological models of the Okavango River and Delta. Projections for the 21st century indicate a progressive shift towards drier conditions attributed to the influence of increasing temperatures on water balance. It is, however, highly likely that multi-decadal oscillations, possibly of similar magnitude to that of 20th century, will be superimposed on the overall trend. These may periodically offset or amplify the mean drying trend. This effect should be accounted for in water and catchment management and climate change adaptation strategies.

  7. A conditional stochastic weather generator for seasonal to multi-decadal simulations

    Science.gov (United States)

    Verdin, Andrew; Rajagopalan, Balaji; Kleiber, William; Podestá, Guillermo; Bert, Federico

    2018-01-01

    We present the application of a parametric stochastic weather generator within a nonstationary context, enabling simulations of weather sequences conditioned on interannual and multi-decadal trends. The generalized linear model framework of the weather generator allows any number of covariates to be included, such as large-scale climate indices, local climate information, seasonal precipitation and temperature, among others. Here we focus on the Salado A basin of the Argentine Pampas as a case study, but the methodology is portable to any region. We include domain-averaged (e.g., areal) seasonal total precipitation and mean maximum and minimum temperatures as covariates for conditional simulation. Areal covariates are motivated by a principal component analysis that indicates the seasonal spatial average is the dominant mode of variability across the domain. We find this modification to be effective in capturing the nonstationarity prevalent in interseasonal precipitation and temperature data. We further illustrate the ability of this weather generator to act as a spatiotemporal downscaler of seasonal forecasts and multidecadal projections, both of which are generally of coarse resolution.

  8. Hypoxia in high-resolution sediment records: reconstructing the California Current Oxygen Minimum Zone on multi-decadal timescales

    Science.gov (United States)

    Moffitt, S. E.; Hill, T. M.

    2012-12-01

    The recent deglaciation event is an ideal laboratory to study the rapid expansion of Oxygen Minimum Zones (OMZs) and the ecological ramifications of such events. Santa Barbara Basin (SBB) sediments are high-resolution archives of seafloor ecosystems, recording both global-scale climate and regional-scale hydrographic events. Seafloor hypoxia in the California Current Ecosystem (CCE) is caused by OMZs in intermediate water depths (300-1200 m), and produces striking evidence in SBB sediment archives. We construct a vertical transect of proxies across SBB (34° 15'N, 119° 45'W) using a core from 418 m water depth (MV0811-15JC), and previously investigated cores from 440 m (MD02-2504) and 570 m (MD02-2503) water depths. Benthic foraminiferal assemblages and planktonic δ18O proxies were quantified at all three depths, while benthic invertebrate communities were quantified in the shallowest core at a 1-cm resolution (~10 years). This high-resolution invertebrate record provides a window into rapid, decadal-scale environmental change in continental margin ecosystems. Seafloor biodiversity is highly variable on 10-10^4 year timescales (across Protist, Mollusc, Arthropod and Echinoderm taxonomic groups), and is tightly coupled to both regional-scale environmental change and global-scale climate events. Additionally, we provide evidence that strongly hypoxic waters shoaled to 150 m on multi-decadal timescales. These data confirm that OMZs have rapidly expanded in the CCE during previous events of global-scale warming, and that continental margin seafloor biodiversity is variable on previously undescribed timescales.

  9. Apparent limitations in the ability of CMIP5 climate models to simulate recent multi-decadal change in surface temperature: implications for global temperature projections

    Science.gov (United States)

    Power, Scott; Delage, François; Wang, Guomin; Smith, Ian; Kociuba, Greg

    2017-07-01

    Observed surface temperature trends over the period 1998-2012/2014 have attracted a great deal of interest because of an apparent slowdown in the rate of global warming, and contrasts between climate model simulations and observations of such trends. Many studies have addressed the statistical significance of these relatively short-trends, whether they indicate a possible bias in the model values and the implications for global warming generally. Here we re-examine these issues, but as they relate to changes over much longer-term changes. We find that on multi- decadal time scales there is little evidence for any change in the observed global warming rate, but some evidence for a recent temporary slowdown in the warming rate in the Pacific. This multi-decadal slowdown can be partly explained by a cool phase of the Interdecadal Pacific Oscillation and a short-term excess of La Niña events. We also analyse historical and projected changes in 38 CMIP climate models. All of the model simulations examined simulate multi-decadal warming in the Pacific over the past half-century that exceeds observed values. This difference cannot be fully explained by observed internal multi-decadal climate variability, even if allowance is made for an apparent tendency for models to underestimate internal multi-decadal variability in the Pacific. Models which simulate the greatest global warming over the past half-century also project warming that is among the highest of all models by the end of the twenty-first century, under both low and high greenhouse gas emission scenarios. Given that the same models are poorest in representing observed multi-decadal temperature change, confidence in the highest projections is reduced.

  10. Multidecadal Weakening of Indian Summer Monsoon Circulation Induces an Increasing Northern Indian Ocean Sea Level

    Science.gov (United States)

    Swapna, P.; Jyoti, J.; Krishnan, R.; Sandeep, N.; Griffies, S. M.

    2017-10-01

    North Indian Ocean sea level has shown significant increase during last three to four decades. Analyses of long-term climate data sets and ocean model sensitivity experiments identify a mechanism for multidecadal sea level variability relative to global mean. Our results indicate that North Indian Ocean sea level rise is accompanied by a weakening summer monsoon circulation. Given that Indian Ocean meridional heat transport is primarily regulated by the annual cycle of monsoon winds, weakening of summer monsoon circulation has resulted in reduced upwelling off Arabia and Somalia and decreased southward heat transport, and corresponding increase of heat storage in the North Indian Ocean. These changes in turn lead to increased retention of heat and increased thermosteric sea level rise in the North Indian Ocean, especially in the Arabian Sea. These findings imply that rising North Indian Ocean sea level due to weakening of monsoon circulation demands adaptive strategies to enable a resilient South Asian population.

  11. Internally Generated and Externally Forced Multidecadal Oceanic Modes and their Influence on the Summer Rainfall over East Asia

    Science.gov (United States)

    Si, D.; Hu, A.

    2017-12-01

    The interdecadal oceanic variabilities can be generated from both internal and external processes, and these variabilities can significantly modulate our climate on global and regional scale, such as the warming slowdown in the early 21st century, and the rainfall in East Asia. By analyzing simulations from a unique Community Earth System Model (CESM) Large Ensemble (CESM_LE) project, we show that the Interdecadal Pacific Oscillation (IPO) is primarily an internally generated oceanic variability, while the Atlantic Multidecadal Oscillation (AMO) may be an oceanic variability generated by internal oceanic processes and modulated by external forcings in the 20th century. Although the observed relationship between IPO and the Yangtze-Huaihe River valley (YHRV) summer rainfall in China is well simulated in both the preindustrial control and 20th century ensemble, none of the 20th century ensemble members can reproduce the observed time evolution of both IPO and YHRV due to the unpredictable nature of IPO on multidecade timescale. On the other hand, although CESM_LE cannot reproduce the observed relationship between AMO and Huanghe River valley (HRV) summer rainfall of China in the preindustrial control simulation, this relationship in the 20th century simulations is well reproduced, and the chance to reproduce the observed time evolution of both AMO and HRV rainfall is about 30%, indicating the important role of the interaction between the internal processes and the external forcing to realistically simulate the AMO and HRV rainfall.

  12. Reconciling multidecadal global land-sea warming with rising CO2

    Science.gov (United States)

    Pratt, V. R.

    2013-12-01

    1. AMO as the cause of global warming Global land-sea temperature prior to 1960 exhibits two prominent rises during respectively 1860-1880 and 1910-1940. Since CO2 was changing much more slowly then than recently these rises are likely to be of natural origin. This raises the possibility that the equally prominent rise in 1970-2000 could have the same natural cause instead of rising CO2. The customary counterargument is that the third rise is stronger. We improve on this argument by examing land and sea temperatures separately. Whereas the two earlier rises are much stronger in the sea record than the land, it is the other way round in the recent rise. This difference suggests that the heat flow is upward in the first two rises and downward in the third. Since the greenhouse effect heats from above, the cause of the recent rise is therefore more likely to be increasing greenhouse gases than whatever caused the first two rises. This leaves open the question of what did cause the earlier rises. An intriguing correlation between multidecadal variations in length of day and multidecadal ocean oscillations has been noticed by Goodridge and others. Rotation of the core relative to the crust on a millennial time scale could create temperature fluctuations in the mantle by any of several possible mechanisms. We explore some such and compare each with the detailed behavior of the multidecadal temperature record. 2. The recent pause. Santer et al estimate 17 years as the shortest period over which a meaningful trend in global climate can be observed. We point out that their estimate is based on an implicit assumption of randomness in the noise, and show that this period can be shortened when the noise can be suitably modeled. We use wavelet analysis to identify a strongly periodic 20-year component to the noise that has persisted over the past 150 years and whose removal permits reducing the estimate to about 10 years. Doing so reveals an upward trend in temperature over the

  13. Intra- to multi-decadal terrestrial precipitation regimes at the end of the 20th century

    Energy Technology Data Exchange (ETDEWEB)

    Mauget, S.A. [US Department of Agriculture-Agricultural Research Service, USDA Plant Stress and Water Conservation Laboratory, Lubbock, Texas, 3810 4th Street, Lubbock, TX 79415 (United States)

    2006-10-15

    Intra- to multi-decadal (IMD) variation in terrestrial precipitation during 1901-98 was evaluated here by sampling annual precipitation rankings over 6-30 year moving time windows and converting those rankings to Mann-Whitney U statistics. Those U statistics were then used to identify the most significant concentrations of wet and dry years relative to a null hypothesis that assumes stationary climate variability. This time series analysis approach served as the basis of a climate survey method used to identify IMD precipitation regimes over continental areas, and was also used to evaluate IMD variation in time series of annual precipitation spatially averaged over those areas. These methods showed a highly significant incidence of wet years over North America during 1972-98, with 8 of the 10 wettest years of 1901-98 occurring during that 27-year period. A comparably significant incidence of late century wetness was also found over a northern Europe grid region, with 7 of the 10 wettest years occurring during 1978-98. Although significant wet and dry regimes were also found over other land areas in the last decades of the 20th century, the late century North American and northern European wet periods stood out as the most statistically significant found here during 1901-98. It is suggested that these recent wet periods are actually terrestrial evidence of a single multi-decadal precipitation mode extending across the North Atlantic, and the most observable evidence of an even broader pattern of recent North Atlantic climate change.

  14. Multi-Decadal Oscillations of the Ocean Active Upper-Layer Heat Content

    Science.gov (United States)

    Byshev, Vladimir I.; Neiman, Victor G.; Anisimov, Mikhail V.; Gusev, Anatoly V.; Serykh, Ilya V.; Sidorova, Alexandra N.; Figurkin, Alexander L.; Anisimov, Ivan M.

    2017-07-01

    Spatial patterns in multi-decadal variability in upper ocean heat content for the last 60 years are examined using a numerical model developed at the Institute of Numerical Mathematics of Russia (INM Model) and sea water temperature-salinity data from the World Ocean Database (in: Levitus, NOAA Atlas NESDIS 66, U.S. Wash.: Gov. Printing Office, 2009). Both the model and the observational data show that the heat content of the Active Upper Layer (AUL) in particular regions of the Atlantic, Pacific and Southern oceans have experienced prominent simultaneous variations on multi-decadal (25-35 years) time scales. These variations are compared earlier revealed climatic alternations in the Northern Atlantic region during the last century (Byshev et al. in Doklady Earth Sci 438(2):887-892, 2011). We found that from the middle of 1970s to the end of 1990s the AUL heat content decreased in several oceanic regions, while the mean surface temperature increased on Northern Hemisphere continents according to IPCC (in: Stocker et al. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change, Cambridge University Press, Cambridge, 2013). This means that the climate-forcing effect of the ocean-atmosphere interaction in certain energy-active areas determines not only local climatic processes, but also have an influence on global-scale climate phenomena. Here we show that specific regional features of the AUL thermal structure are in a good agreement with climatic conditions on the adjacent continents. Further, the ocean AUL in the five distinctive regions identified in our study have resumed warming in the first decade of this century. By analogy inference from previous climate scenarios, this may signal the onset of more continental climate over mainlands.

  15. External forcing as a source for the observed multi-decadal relation between AMV and the Indian summer monsoon

    Science.gov (United States)

    Svendsen, Lea; Luo, Feifei; Sankar, Syam; Gao, Yongqi; Keenlyside, Noel; Vareed Joseph, Porathur; Johannessen, Ola

    2016-04-01

    The instrumental records show a significant positive correlation between the Atlantic multi-decadal variability (AMV) and the Indian summer monsoon (ISM) rainfall, where a positive (negative) AMV is associated with more (less) ISM rainfall. We have used both proxy reconstruction and twelve models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to investigate if the observed AMV-ISM relation is a persistent internal climate signal or externally forced. A comparison of several annual resolution proxy records both from the Atlantic and for the ISM show that the multi-decadal variability in both indices is persistent, but the link between them is not. The correlation between the two regions is weak, and even negative in some periods, before the instrumental time period. The analysis of CMIP5 simualtions is consistent with these results. While none of the CMIP5 models investigated simulate the significant AMV-ISM connection in the pre-industrial control simulations with fixed external forcing, three of the models reproduce the relation in the 20th century historical simulations with transient forcing. In these models external forcing is linked to the mid-to-upper tropospheric temperature pattern with a strengthened land-ocean contrast over South Asia, consistent with an enhanced ISM, as well as the evolution of AMV. We conclude that the significant AMV-ISM relation found in the observations after the industrial revolution may be associated with external forcing, rather than being internal climate variability.

  16. Regional influence of decadal to multidecadal Atlantic Oscillations during the last two millennia in Morocco, inferred from two high resolution δ18O speleothem records

    Science.gov (United States)

    Ait Brahim, Yassine; Sifeddine, Abdelfettah; Khodri, Myriam; Bouchaou, Lhoussaine; Cruz, Francisco W.; Pérez-Zanón, Núria; Wassenburg, Jasper A.; Cheng, Hai

    2017-04-01

    Climate projections predict substantial increase of extreme heats and drought occurrences during the coming decades in Morocco. It is however not clear what can be attributed to natural climate variability and to anthropogenic forcing, as hydroclimate variations observed in areas such as Morocco are highly influenced by the Atlantic climate modes. Since observational data sets are too short to resolve properly natural modes of variability acting on decadal to multidecadal timescales, high resolution paleoclimate reconstructions are the only alternative to reconstruct climate variability in the remote past. Herein, we present two high resolution and well dated speleothems oxygen isotope (δ18O) records sampled from Chaara and Ifoulki caves (located in Northeastern and Southwestern Morocco respectively) to investigate hydroclimate variations during the last 2000 years. Our results are supported by a monitoring network of δ18O in precipitation from 17 stations in Morocco. The new paleoclimate records are discussed in the light of existing continental and marine paleoclimate proxies in Morocco to identify significant correlations at various lead times with the main reconstructed oceanic and atmospheric variability modes and possible climate teleconnections that have potentially influenced the climate during the last two millennia in Morocco. The results reveal substantial decadal to multidecadal swings between dry and humid periods, consistent with regional paleorecords. Evidence of dry conditions exist during the Medieval Climate Anomaly (MCA) period and the Climate Warm Period (CWP) and humid conditions during the Little Ice Age (LIA) period. Statistical analyses suggest that the climate of southwestern Morocco remained under the combined influence of both the Atlantic Multidecadal Oscillation (AMO) and the North Atlantic Oscillation (NAO) over the last two millennia. Interestingly, the generally warmer MCA and colder LIA at longer multidecadal timescales probably

  17. Field Observations Of The 29 September Tsunami In American Samoa: Spatial Variability And Indications Of Strong Return Flow

    Science.gov (United States)

    Jaffe, B. E.; Richmond, B. M.; Gelfenbaum, G. R.; Watt, S.; Apotsos, A. A.; Buckley, M. L.; Dudley, W. C.; Peck, B.

    2009-12-01

    The 29 September 2009 tsunami caused 181 fatalities and displaced more than 5000 people on the islands of Samoa, American Samoa, and Tonga. This is the first tsunami to cause significant damage and fatalities on U.S. soil in more than 30 years. Scientists from around the world quickly mobilized to help document the tsunami water levels before this ephemeral data was forever lost as recovery activities and natural processes overtook the effected area. A USGS team collected data in American Samoa from October 6-22 and November 5-12, 2009. The tsunami was large, reaching elevations of greater than 15 m, however wave heights and devastation varied from village to village in American Samoa. Even within villages, some structures were completely destroyed, some flooded and left standing, and others barely touched. Wave heights, flow depths, runup heights, inundation distances, and flow directions were collected for use in ground-truthing inundation models. The team also collected nearshore bathymetry, topography and reef flat elevation, sediment samples, and documented the distribution and characteristics of both sand and boulder deposits. Eyewitness accounts of the tsunami were also videotaped. One striking aspect of this tsunami was the abundance of indicators of strong return flow. For example at Poloa in the northwest of Tutuila, where the runup was greater than 11 m along a 300-m stretch of coast and flow depths exceeded 4 m, the coral reef flat was strewn with debris including chairs, desks, and books from a school. On land, River channels were excavated and new channels formed as return flow scoured sediment and transported it offshore. Possible causes for the strong return flow and the relation between the stength of the return flow, inundation distance, and runup in American Samoa are presented. These relationships and others based on data collected by field survey teams will ultimately reduce loss of life and destruction from tsunamis in the Pacific and

  18. Idiotypes as immunogens: facing the challenge of inducing strong therapeutic immune responses against the variable region of immunoglobulins.

    Directory of Open Access Journals (Sweden)

    Alejandro eLopez-Requena

    2012-11-01

    Full Text Available Idiotype (Id-based immunotherapy has been exploited as cancer treatment option. Conceived as therapy for malignancies bearing idiotypic antigens, it has been also extended to solid tumours because of the capacity of anti-idiotypic antibodies to mimick Id-unrelated antigens. In both these two settings, efforts are being made to overcome the poor immune responsiveness often experienced when using self immunoglobulins as immunogens. Despite bearing a unique gene combination, and thus particular epitopes, it is normally difficult to stimulate the immune response against antibody variable regions. Different strategies are currently used to strengthen Id immunogenicity, such as concomitant use of immune-stimulating molecules, design of Id-containing immunogenic recombinant proteins, specific targeting of relevant immune cells and genetic immunization. This review focuses on the role of anti-Id vaccination in cancer management and on the current developments used to foster anti-idiotypic B- and T-cell responses.

  19. Idiotypes as immunogens: facing the challenge of inducing strong therapeutic immune responses against the variable region of immunoglobulins

    International Nuclear Information System (INIS)

    López-Requena, Alejandro; Burrone, Oscar R.; Cesco-Gaspere, Michela

    2012-01-01

    Idiotype (Id)-based immunotherapy has been exploited as cancer treatment option. Conceived as therapy for malignancies bearing idiotypic antigens, it has been also extended to solid tumors because of the capacity of anti-idiotypic antibodies to mimic Id-unrelated antigens. In both these two settings, efforts are being made to overcome the poor immune responsiveness often experienced when using self immunoglobulins as immunogens. Despite bearing a unique gene combination, and thus particular epitopes, it is normally difficult to stimulate the immune response against antibody variable regions. Different strategies are currently used to strengthen Id immunogenicity, such as concomitant use of immune-stimulating molecules, design of Id-containing immunogenic recombinant proteins, specific targeting of relevant immune cells, and genetic immunization. This review focuses on the role of anti-Id vaccination in cancer management and on the current developments used to foster anti-idiotypic B and T cell responses.

  20. HOW STRONG IS THE RELATIONSHIP BETWEEN RAINFALL VARIABILITY AND CAATINGA PRODUCTIVITY? A CASE STUDY UNDER A CHANGING CLIMATE.

    Science.gov (United States)

    Salimon, Cleber; Anderson, Liana

    2017-05-22

    Despite the knowledge of the influence of rainfall on vegetation dynamics in semiarid tropical Brazil, few studies address and explore quantitatively the various aspects of this relationship. Moreover, Northeast Brazil is expected to have its rainfall reduced by as much as 60% until the end of the 21st Century, under scenario AII of the IPCC Report 2010. We sampled and analyzed satellite-derived monthly rainfall and a vegetation index data for 40 sites with natural vegetation cover in Paraíba State, Brazil from 2001 to 2012. In addition, the anomalies for both variables were calculated. Rainfall variation explained as much as 50% of plant productivity, using the vegetation index as a proxy, and rainfall anomaly explained 80% of the vegetation productivity anomaly. In an extreme dry year (2012), with 65% less rainfall than average for the period 2001-2012, the vegetation index decreased by 25%. If such decrease persists in a long term trend in rainfall reduction, this could lead to a disruption in this ecosystem functioning and the dominant vegetation could become even more xeric or desert-like, bringing serious environmental, social and economical impacts.

  1. The Close AGN Reference Survey (CARS). Mrk 1018 halts dimming and experiences strong short-term variability

    Science.gov (United States)

    Krumpe, M.; Husemann, B.; Tremblay, G. R.; Urrutia, T.; Powell, M.; Davis, T. A.; Scharwächter, J.; Dexter, J.; Busch, G.; Combes, F.; Croom, S. M.; Eckart, A.; McElroy, R. E.; Perez-Torres, M.; Leung, G.

    2017-11-01

    After changing optical AGN type from 1.9 to 1 in 1984, the AGN Mrk 1018 recently reverted back to its type 1.9 state. Our ongoing monitoring now reveals that the AGN has halted its dramatic dimming, reaching a minimum around October 2016. The minimum was followed by an outburst rising with 0.25 U-band mag/month. The rebrightening lasted at least until February 2017, as confirmed by joint Chandra and Hubble observations. Monitoring was resumed in July 2017 after the source emerged from sunblock, at which point the AGN was found only 0.4 mag brighter than its minimum. The intermittent outburst was accompanied by the appearance of a red wing asymmetry in broad-line shape, indicative of an inhomogeneous broad-line region. The current flickering brightness of Mrk 1018 following its rapid fading either suggests that the source has reignited, remains variable at a low level, or may continue dimming over the next few years. Distinguishing between these possibilities requires continuous multiwavelength monitoring. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme(s) 098.B-0672 and 099.B-0159. The scientific results reported in this article are based on observations made by the Chandra X-ray Observatory and the NASA/ESA Hubble Space Telescope.

  2. The mass-metallicity relations for gas and stars in star-forming galaxies: strong outflow versus variable IMF

    Science.gov (United States)

    Lian, Jianhui; Thomas, Daniel; Maraston, Claudia; Goddard, Daniel; Comparat, Johan; Gonzalez-Perez, Violeta; Ventura, Paolo

    2018-02-01

    We investigate the mass-metallicity relations for the gaseous (MZRgas) and stellar components (MZRstar) of local star-forming galaxies based on a representative sample from Sloan Digital Sky Survey Data Release 12. The mass-weighted average stellar metallicities are systematically lower than the gas metallicities. This difference in metallicity increases towards galaxies with lower masses and reaches 0.4-0.8 dex at 109 M⊙ (depending on the gas metallicity calibration). As a result, the MZRstar is much steeper than the MZRgas. The much lower metallicities in stars compared to the gas in low-mass galaxies imply dramatic metallicity evolution with suppressed metal enrichment at early times. The aim of this paper is to explain the observed large difference in gas and stellar metallicity and to infer the origin of the mass-metallicity relations. To this end we develop a galactic chemical evolution model accounting for star formation, gas inflow and outflow. By combining the observed mass-metallicity relation for both gas and stellar components to constrain the models, we find that only two scenarios are able to reproduce the observations. Either strong metal outflow or a steep initial mass function (IMF) slope at early epochs of galaxy evolution is needed. Based on these two scenarios, for the first time we successfully reproduce the observed MZRgas and MZRstar simultaneously, together with other independent observational constraints in the local Universe. Our model also naturally reproduces the flattening of the MZRgas at the high-mass end leaving the MZRstar intact, as seen in observational data.

  3. Modeling brittle fracture, slip weakening, and variable friction in geomaterials with an embedded strong discontinuity finite element.

    Energy Technology Data Exchange (ETDEWEB)

    Regueiro, Richard A. (University of Colorado, Boulder, CO); Borja, R. I. (Stanford University, Stanford, CA); Foster, C. D. (Stanford University, Stanford, CA)

    2006-10-01

    element using a generalized trapezoidal formulation. While the focus is on the constitutive model of interest, the framework is also developed for a general surface response. This report summarizes the major research and development accomplishments for the LDRD project titled 'Cohesive Zone Modeling of Failure in Geomaterials: Formulation and Implementation of a Strong Discontinuity Model Incorporating the Effect of Slip Speed on Frictional Resistance'. This project supported a strategic partnership between Sandia National Laboratories and Stanford University by providing funding for the lead author, Craig Foster, during his doctoral research.

  4. Interannual to multidecadal climate forcings on groundwater resources of the U.S. West Coast

    Science.gov (United States)

    Velasco, Elzie M.; Gurdak, Jason J.; Dickinson, Jesse; Ferré, T.P.A.; Corona, Claudia

    2017-01-01

    Study regionThe U.S. West Coast, including the Pacific Northwest and California Coastal Basins aquifer systems.Study focusGroundwater response to interannual to multidecadal climate variability has important implications for security within the water–energy–food nexus. Here we use Singular Spectrum Analysis to quantify the teleconnections between AMO, PDO, ENSO, and PNA and precipitation and groundwater level fluctuations. The computer program DAMP was used to provide insight on the influence of soil texture, depth to water, and mean and period of a surface infiltration flux on the damping of climate signals in the vadose zone.New hydrological insights for the regionWe find that PDO, ENSO, and PNA have significant influence on precipitation and groundwater fluctuations across a north-south gradient of the West Coast, but the lower frequency climate modes (PDO) have a greater influence on hydrologic patterns than higher frequency climate modes (ENSO and PNA). Low frequency signals tend to be preserved better in groundwater fluctuations than high frequency signals, which is a function of the degree of damping of surface variable fluxes related to soil texture, depth to water, mean and period of the infiltration flux. The teleconnection patterns that exist in surface hydrologic processes are not necessarily the same as those preserved in subsurface processes, which are affected by damping of some climate variability signals within infiltrating water.

  5. Potential and limitations of multidecadal satellite soil moisture observations for selected climate model evaluation studies

    Directory of Open Access Journals (Sweden)

    A. Loew

    2013-09-01

    Full Text Available Soil moisture is an essential climate variable (ECV of major importance for land–atmosphere interactions and global hydrology. An appropriate representation of soil moisture dynamics in global climate models is therefore important. Recently, a first multidecadal, observation-based soil moisture dataset has become available that provides information on soil moisture dynamics from satellite observations (ECVSM, essential climate variable soil moisture. The present study investigates the potential and limitations of this new dataset for several applications in climate model evaluation. We compare soil moisture data from satellite observations, reanalysis and simulations from a state-of-the-art land surface model and analyze relationships between soil moisture and precipitation anomalies in the different dataset. Other potential applications like model parameter optimization or model initialization are not investigated in the present study. In a detailed regional study, we show that ECVSM is capable to capture well the interannual and intraannual soil moisture and precipitation dynamics in the Sahelian region. Current deficits of the new dataset are critically discussed and summarized at the end of the paper to provide guidance for an appropriate usage of the ECVSM dataset for climate studies.

  6. Impact of strong selection for the PrP major gene on genetic variability of four French sheep breeds (Open Access publication

    Directory of Open Access Journals (Sweden)

    Pantano Thais

    2008-11-01

    Full Text Available Abstract Effective selection on the PrP gene has been implemented since October 2001 in all French sheep breeds. After four years, the ARR "resistant" allele frequency increased by about 35% in young males. The aim of this study was to evaluate the impact of this strong selection on genetic variability. It is focussed on four French sheep breeds and based on the comparison of two groups of 94 animals within each breed: the first group of animals was born before the selection began, and the second, 3–4 years later. Genetic variability was assessed using genealogical and molecular data (29 microsatellite markers. The expected loss of genetic variability on the PrP gene was confirmed. Moreover, among the five markers located in the PrP region, only the three closest ones were affected. The evolution of the number of alleles, heterozygote deficiency within population, expected heterozygosity and the Reynolds distances agreed with the criteria from pedigree and pointed out that neutral genetic variability was not much affected. This trend depended on breed, i.e. on their initial states (population size, PrP frequencies and on the selection strategies for improving scrapie resistance while carrying out selection for production traits.

  7. Multi-decadal responses of a cod (Gadus morhua) population to human-induced trophic changes, fishing, and climate

    DEFF Research Database (Denmark)

    Eero, Margit; MacKenzie, Brian; Köster, Fritz

    2011-01-01

    Understanding how human impacts have interacted with natural variability to affect populations and ecosystems is required for sustainable management and conservation. The Baltic Sea is one of the few large marine ecosystems worldwide where the relative contribution of several key forcings...... to changes in fish populations can be analyzed with empirical data. In this study we investigate how climate variability and multiple human impacts (fishing, marine mammal hunting, eutrophication) have affected multi-decadal scale dynamics of cod in the Baltic Sea during the 20th century.We document......-average cod productivity coupled to a temporary reduction in fishing pressure. The Baltic cod example demonstrates how combinations of different forcings can have synergistic effects and consequently dramatic impacts on population dynamics. Our results highlight the potential and limitations of human...

  8. Oxygen Isotope Speleothem record of Decadal and Multidecadal Atlantic Oscillations over the last millennium in Southwestern Morocco

    Science.gov (United States)

    Ait Brahim, Yassine; Sha, LiJuan; Sifeddine, Abdelfettah; Cheng, Hai; Bouchaou, Lhoussaine; Da Cruz Junior, Francisco William; Khodri, Myriam; Peerbocus, Nawaaz; Mariller, Alexandre; Apaestegui, James; Guyot, Jean-Loup; Auler, Augusto; Hassane Beraaouz, El

    2016-04-01

    In this work, we present a stable oxygen isotope (δ18O) speleothem record from Ifoulki cave located South-West of Morocco (N 30°42'29'', W 09°19'39'' and 1267 meters above sea level). The age model, based on eighteen U-Th dates, reveals that the record covers the AD 790-1953 period with a data resolution of ~1.7 years. Stable oxygen isotope variations show substantial decadal to multi-decadal swings between dry and humid periods. The Medieval Climate Anomaly (MCA) is characterized by the longest period with δ18O values above the average, suggestive of pronounced drying possibly as a response to positive North Atlantic Oscillation (NAO) phases and increased volcanic activity during this period. However, at least two short wet phases are recognized during the MCA in Morocco, with peaks centered on the years AD 1040 and AD 1190 and seem to overlap with negative NAO phases as recorded in a recently published NAO reconstruction for the last millennium. During the next centuries, the NAO again depicts predominantly negative values and the δ18O drops below the average during the Little Ice Age (LIA). Furthermore, a striking resemblance is observed between our record and another recently published stalagmite record from the Piste cave in Northeastern Morocco, which is quite remarkable given the different type of tracers (δ18O vs. Mg and Sr) obtained from different environments (Western High Atlas vs. Northeastern Middle Atlas and ~634 km away). Comparison with regional paleorecords from other studies also reveals the replication of many characteristic climate features from the last millennium, first detected in Northern Morocco and the Iberian Peninsula. In particular, the evidence of generally dry conditions during the MCA and wetter conditions in the LIA, which is confirmed by all the paleorecords. These similarities indicate coherent climate variability in Northwest Africa and the Iberian Peninsula and suggest a strong regional control of the NAO during the last

  9. Lake trout otolith chronologies as multidecadal indicators of high-latitude freshwater ecosystems

    Science.gov (United States)

    Black, B.A.; Von Biela, V.R.; Zimmerman, C.E.; Brown, Randy J.

    2013-01-01

    High-latitude ecosystems are among the most vulnerable to long-term climate change, yet continuous, multidecadal indicators by which to gauge effects on biology are scarce, especially in freshwater environments. To address this issue, dendrochronology (tree-ring analysis) techniques were applied to growth-increment widths in otoliths from lake trout (Salvelinus namaycush) from the Chandler Lake system, Alaska (68.23°N, 152.70°W). All otoliths were collected in 1987 and exhibited highly synchronous patterns in growth-increment width. Increments were dated, the widths were measured, and age-related growth declines were removed using standard dendrochronology techniques. The detrended time series were averaged to generate an annually resolved chronology, which continuously spanned 1964–1984. The chronology positively and linearly correlated with August air temperature over the 22-year interval (p otolith chronologies could be used to examine responses between freshwater ecosystems and environmental variability across a range of temporal and spatial scales.

  10. Atlantic Multidecadal Oscillation footprint on global high cloud cover

    Science.gov (United States)

    Vaideanu, Petru; Dima, Mihai; Voiculescu, Mirela

    2017-12-01

    Due to the complexity of the physical processes responsible for cloud formation and to the relatively short satellite database of continuous data records, cloud behavior in a warming climate remains uncertain. Identifying physical links between climate modes and clouds would contribute not only to a better understanding of the physical processes governing their formation and dynamics, but also to an improved representation of the clouds in climate models. Here, we identify the global footprint of the Atlantic Multidecadal Oscillation (AMO) on high cloud cover, with focus on the tropical and North Atlantic, tropical Pacific and on the circum-Antarctic sector. In the tropical band, the sea surface temperature (SST) and high cloud cover (HCC) anomalies are positively correlated, indicating a dominant role played by convection in mediating the influence of the AMO-related SST anomalies on the HCC field. The negative SST-HCC correlation observed in North Atlantic could be explained by the reduced meridional temperature gradient induced by the AMO positive phase, which would be reflected in less storms and negative HCC anomalies. A similar negative SST-HCC correlation is observed around Antarctica. The corresponding negative correlation around Antarctica could be generated dynamically, as a response to the intensified upward motion in the Ferrel cell. Despite the inherent imperfection of the observed and reanalysis data sets, the AMO footprint on HCC is found to be robust to the choice of dataset, statistical method, and specific time period considered.

  11. Multi-decadal Decline of Southeast United States Streamflow

    Science.gov (United States)

    Tootle, G. A.; Lakshmi, V.; Therrell, M.; Huffaker, R.; Elliott, E. A.

    2017-12-01

    Unprecedented population growth combined with environmental and energy demands have led to water conflict in the Southeastern United States. The states of Florida, Georgia and Alabama have recently engaged in litigation on minimum in-stream flows to maintain ecosystems, fisheries and energy demands while satisfying a growing thirst in metropolitan Atlanta. A study of Southeastern United States (Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee) streamflow identified a declining pattern of flow over the past 25 years with increased dry periods being observed in the last decade. When evaluating calendar year streamflow for (56) unimpaired streamflow stations, a robust period of streamflow in the 1970's was followed by a consistent decline in streamflow from 1990 to present. In evaluating 20-year, 10-year and 5-year time periods of annual streamflow volume, the past decade reveals historic lows for each of these periods. When evaluating the influence of high frequency (e.g., El Nino-Southern Oscillation - ENSO) and low frequency (e.g., Atlantic Multi-decadal Oscillation - AMO) climatic phenomenon, the shift of the AMO from a cold phase to a warm phase in the 1990's combined with multiple La Nina events may be associated with the streamflow decline.

  12. Multi-Decadal to Millennial Scale Holocene Hydrologic Variation in the Southern Hemisphere Tropics of South America

    Science.gov (United States)

    Ekdahl, E. J.; Fritz, S. C.; Baker, P. A.; Burns, S. J.; Coley, K.; Rigsby, C. A.

    2005-12-01

    Numerous sites in the Northern Hemisphere show multi-decadal to millennial scale climate variation during the Holocene, many of which have been correlated with changes in atmospheric radiocarbon production or with changes in North Atlantic oceanic circulation. The manifestation of such climate variability in the hydrology of the Southern Hemisphere tropics of South America is unclear, because of the limited number of records at suitably high resolution. In the Lake Titicaca drainage basin of Bolivia and Peru, high-resolution lacustrine records reveal the overall pattern of Holocene lake-level change, the influence of precessional forcing of the South American Summer Monsoon, and the effects of high-frequency climate variability in records of lake productivity and lake ecology. Precessional forcing of regional precipitation is evident in the Lake Titicaca basin as a massive (ca. 85 m) mid-Holocene decline in lake level beginning about 7800 cal yr BP and a subsequent rise in lake level after 4000 cal yr BP. Here we show that multi-decadal to millennial-scale climate variability, superimposed upon the envelope of change at orbital time scales, is similar in timing and pattern to the ice-rafted debris record of Holocene Bond events in the North Atlantic. A high-resolution carbon isotopic record from Lake Titicaca that spans the entire Holocene suggests that cold intervals of Holocene Bond events are periods of increased precipitation, thus indicating an anti-phasing of precipitation variation on the Altiplano relative to the Northern Hemisphere tropics. A similar pattern of variation is also evident in high-resolution (2-30 yr spacing) diatom and geochemical records that span the last 7000 yr from two smaller lakes, Lagos Umayo and Lagunillas, in the Lake Titicaca drainage basin.

  13. Natural variability in the surface ocean carbonate ion concentration

    Directory of Open Access Journals (Sweden)

    N. S. Lovenduski

    2015-11-01

    Full Text Available We investigate variability in the surface ocean carbonate ion concentration ([CO32−] on the basis of a~long control simulation with an Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO32−] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO32−] in the tropical Pacific and at the boundaries between the subtropical and subpolar gyres in the Northern Hemisphere, and relatively low interannual variability in the centers of the subtropical gyres and in the Southern Ocean. Statistical analysis of modeled [CO32−] variance and autocorrelation suggests that significant anthropogenic trends in the saturation state of aragonite (Ωaragonite are already or nearly detectable at the sustained, open-ocean time series sites, whereas several decades of observations are required to detect anthropogenic trends in Ωaragonite in the tropical Pacific, North Pacific, and North Atlantic. The detection timescale for anthropogenic trends in pH is shorter than that for Ωaragonite, due to smaller noise-to-signal ratios and lower autocorrelation in pH. In the tropical Pacific, the leading mode of surface [CO32−] variability is primarily driven by variations in the vertical advection of dissolved inorganic carbon (DIC in association with El Niño–Southern Oscillation. In the North Pacific, surface [CO32−] variability is caused by circulation-driven variations in surface DIC and strongly correlated with the Pacific Decadal Oscillation, with peak spectral power at 20–30-year periods. North Atlantic [CO32−] variability is also driven by variations in surface DIC, and exhibits weak correlations with both the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results

  14. Natural variability in the surface ocean carbonate ion concentration

    Science.gov (United States)

    Lovenduski, N. S.; Long, M. C.; Lindsay, K.

    2015-11-01

    We investigate variability in the surface ocean carbonate ion concentration ([CO32-]) on the basis of a~long control simulation with an Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO32-] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO32-] in the tropical Pacific and at the boundaries between the subtropical and subpolar gyres in the Northern Hemisphere, and relatively low interannual variability in the centers of the subtropical gyres and in the Southern Ocean. Statistical analysis of modeled [CO32-] variance and autocorrelation suggests that significant anthropogenic trends in the saturation state of aragonite (Ωaragonite) are already or nearly detectable at the sustained, open-ocean time series sites, whereas several decades of observations are required to detect anthropogenic trends in Ωaragonite in the tropical Pacific, North Pacific, and North Atlantic. The detection timescale for anthropogenic trends in pH is shorter than that for Ωaragonite, due to smaller noise-to-signal ratios and lower autocorrelation in pH. In the tropical Pacific, the leading mode of surface [CO32-] variability is primarily driven by variations in the vertical advection of dissolved inorganic carbon (DIC) in association with El Niño-Southern Oscillation. In the North Pacific, surface [CO32-] variability is caused by circulation-driven variations in surface DIC and strongly correlated with the Pacific Decadal Oscillation, with peak spectral power at 20-30-year periods. North Atlantic [CO32-] variability is also driven by variations in surface DIC, and exhibits weak correlations with both the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results will aid the interpretation of trends

  15. Internal Climatic Influences From Secular To Multi-decadal Scales: Comparison Of NAO Reconstructions.

    Science.gov (United States)

    Nicolle, M.; Debret, M.; Massei, N.; de Vernal, A.

    2017-12-01

    In the Northern Hemisphere, the North Atlantic Oscillation (NAO) is the major dominant mode of variability in winter atmospheric circulation, with large impacts on temperature, precipitation and storm tracks in the North Atlantic sector. To understand the role of this internal climatic oscillations on the past climate variability, several proxy-based reconstructions of the NAO were published during the last decades. Two of them are available during the past 1,200 years: a first NAO reconstruction published by Trouet et al. (2009) and a second proposed by Ortega et al. (2015). The major discrepancy between the two reconstructions concerns the transition period between the Medieval Climate Anomaly (MCA) and the Little Ice Age. The first NAO reconstruction shows persistent positive phases during the MCA (AD 1000-1300) but this dominant trend is not highlighted in the reconstruction proposed by Ortega et al. (2015), asking the question of the influence of predictors used to reconstruct the NAO signal during the last millennia. In these study, we compare the two NAO reconstructions in order to determine the effect of bi-proxy or multi-proxy approach on the signal reconstructed. Using statistical and wavelet analysis methods, we conclude that the number of predictors used do not have impact on the signal reconstruct. The two reconstructions signals are characterized by similar variabilities expressed from multi-decadal to multi-secular scales. The major trend difference seems to be link to the type of the predictor and particularly the use of Greenland ice cores in the reconstruction proposed in 2015.

  16. STRONG UV AND X-RAY VARIABILITY OF THE NARROW LINE SEYFERT 1 GALAXY WPVS 007-ON THE NATURE OF THE X-RAY LOW STATE

    Energy Technology Data Exchange (ETDEWEB)

    Grupe, Dirk; Barlow, Brad N. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Komossa, S. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Scharwaechter, Julia [Research School of Astronomy and Astrophysics, Australian National University, Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611 (Australia); Dietrich, Matthias [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Leighly, Karen M.; Lucy, Adrian, E-mail: dxg35@psu.edu, E-mail: julia.scharwaechter@obspm.fr, E-mail: leighly@nhn.ou.edu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States)

    2013-10-01

    We report on multi-wavelength observations of the X-ray transient Narrow Line Seyfert 1 (NLS1) galaxy WPVS 007. The galaxy was monitored with Swift between 2005 October and 2013 July, after it had previously undergone a dramatic drop in its X-ray flux. For the first time, we are able to repeatedly detect this NLS1 in X-rays again. This increased number of detections in the last couple of years may suggest that the strong absorber that has been found in this active galactic nucleus (AGN) is starting to become leaky and may eventually disappear. The X-ray spectra obtained for WPVS 007 are all consistent with a partial covering absorber model. A spectrum based on the data during the extreme low X-ray flux states shows that the absorption column density is of the order of 4 Multiplication-Sign 10{sup 23} cm{sup -2} with a covering fraction of 95%. WPVS 007 also displays one of the strongest UV variabilities seen in NLS1s. The UV continuum variability anti-correlates with the optical/UV slope {alpha}{sub UV}, which suggests that the variability may be primarily due to reddening. The UV variability timescales are consistent with moving dust ''clouds'' located beyond the dust sublimation radius of R{sub sub} Almost-Equal-To 20 lt-days. We present for the first time near-infrared JHK data of WPVS 007, which reveal a rich emission-line spectrum. Recent optical spectroscopy does not indicate significant variability in the broad permitted and Fe II emission lines, implying that the ionizing continuum seen by those gas clouds has not significantly changed over the last decades. All X-ray and UV observations are consistent with a scenario in which an evolving broad absorption line (BAL) flow obscures the continuum emission. As such, WPVS 007 is an important target for our understanding of BAL flows in low-mass AGNs.

  17. Multi-decadal responses of a cod (Gadus morhua) population to human-induced trophic changes, fishing, and climate

    DEFF Research Database (Denmark)

    Eero, Margit; MacKenzie, Brian; Köster, Fritz

    2011-01-01

    to changes in fish populations can be analyzed with empirical data. In this study we investigate how climate variability and multiple human impacts (fishing, marine mammal hunting, eutrophication) have affected multi-decadal scale dynamics of cod in the Baltic Sea during the 20th century.We document...... significant climate-driven variations in cod recruitment production at multi-annual timescales, which had major impacts on population dynamics and the yields to commercial fisheries. We also quantify the roles of marine mammal predation, eutrophication, and exploitation on the development of the cod......-average cod productivity coupled to a temporary reduction in fishing pressure. The Baltic cod example demonstrates how combinations of different forcings can have synergistic effects and consequently dramatic impacts on population dynamics. Our results highlight the potential and limitations of human...

  18. Multi-Decadal analysis of Global Trends in Microseism Intensity: A Proxy for Changes in Extremal Storm Activity and Oceanic Wave State

    Science.gov (United States)

    Anthony, R. E.; Aster, R. C.; Rowe, C. A.

    2016-12-01

    The Earth's seismic noise spectrum features two globally ubiquitous peaks near 8 and 16 s periods (secondary and primary bands) that arise when storm-generated ocean gravity waves are converted to seismic energy, predominantly into Rayleigh waves. Because of its regionally integrative nature, microseism intensity and other seismographic data from long running sites can provide useful proxies for wave state. Expanding an earlier study of global microseism trends (Aster et al., 2010), we analyze digitally-archived, up-to-date (through late 2016) multi-decadal seismic data from stations of global seismographic networks to characterize the spatiotemporal evolution of wave climate over the past >20 years. The IRIS Noise Tool Kit (Bahavair et al., 2013) is used to produce ground motion power spectral density (PSD) estimates in 3-hour overlapping time series segments. The result of this effort is a longer duration and more broadly geographically distributed PSD database than attained in previous studies, particularly for the primary microseism band. Integrating power within the primary and secondary microseism bands enables regional characterization of spatially-integrated trends in wave states and storm event statistics of varying thresholds. The results of these analyses are then interpreted within the context of recognized modes of atmospheric variability, including the particularly strong 2015-2016 El Niño. We note a number of statistically significant increasing trends in both raw microseism power and storm activity occurring at multiple stations in the Northwest Atlantic and Southeast Pacific consistent with generally increased wave heights and storminess in these regions. Such trends in wave activity have the potential to significantly influence coastal environments particularly under rising global sea levels.

  19. Global-mean surface temperature variability: space-time perspective from rotated EOFs

    Science.gov (United States)

    Chen, Xianyao; Tung, Ka-Kit

    2017-10-01

    The observed global-mean surface temperature (GST) has been warming in the presence of increasing atmospheric concentration of greenhouse gases, but its rise has not been monotonic. Attention has increasingly been focused on the prominent variations about the linear trend in GST, especially on interdecadal and multidecadal time scales. When the sea-surface temperature (SST) and the land- plus-ocean surface temperature (ST) are averaged globally to yield the global-mean SST (GSST) and the GST, respectively, spatial information is lost. Information on both space and time is needed to properly identify the modes of variability on interannual, decadal, interdecadal and multidecadal time scales contributing to the GSST and GST variability. Empirical Orthogonal Function (EOF) analysis is usually employed to extract the space-time modes of climate variability. Here we use the method of pair-wise rotation of the principal components (PCs) to extract the modes in these time-scale bands and obtain global spatial EOFs that correspond closely with regionally defined climate modes. Global averaging these clearly identified global modes allows us to reconstruct GSST and GST, and in the process identify their components. The results are: Pacific contributes to the global mean variation mostly on the interannual time scale through El Nino-Southern Oscillation (ENSO) and its teleconnections, while the Atlantic contributes strongly to the global mean on the multidecadal time scale through the interhemispheric mode called the Atlantic Multidecadal Oscillation (AMO). The Pacific Decadal Oscillation (PDO) has twice as large a variance as the AMO, but its contribution to GST is only 1/10 that of the AMO because of its compensating patterns of cold and warm SST in northwest and northeast Pacific. Its teleconnection pattern, the Pacific/North America (PNA) pattern over land, is also found to be self-cancelling when globally averaged because of its alternating warm and cold centers. The

  20. Rotationally modulated variability and pulsations of the He-rich star CPD -62°2124 with an extraordinarily strong magnetic field

    Science.gov (United States)

    Hubrig, S.; Mikulášek, Z.; Kholtygin, A. F.; Ilyin, I.; Schöller, M.; Järvinen, S. P.; Scholz, R.-D.; Zejda, M.

    2017-11-01

    A longitudinal magnetic field with a strength of 5.2 kG was recently detected in CPD -62°2124, which has a fractional main-sequence lifetime of about 60 per cent. Strongly magnetic early-B type chemically peculiar stars in an advanced evolutionary state are of special interest to understand the evolution of the angular momentum and spin-down time-scales in the presence of a global magnetic field. We made use of 17 FORS 2 low-resolution spectropolarimetric observations and 844 ASAS3 photometric measurements for the determination of the rotation period, pulsationsand the magnetic field geometry of the star. We calculated periodograms and applied phenomenological models of photometric, spectral and spectropolarimetric variability. We found that all quantities studied, specifically equivalent widths, the mean longitudinal magnetic field 〈Bz〉 and the flux in the V filter, vary with the same period P = 2.628 d, which was identified as the rotation period. The observed variations can be fully explained by a rigidly rotating main-sequence star with an uneven distribution of chemical elements, photometric spots and a stable, nearly dipolar magnetic field with a polar field strength of about 21 kG, frozen into the body of the star. The magnetic field of CPD -62°2124 is tilted to the rotation axis by β = 28° ± 7°, while the inclination of the rotation axis towards the line of sight is only i = 20° ± 5°. In the acquired FORS 2 spectra, we detect short-term line profile variations indicating the presence of β Cephei type pulsations. As of today, no other pulsating star of this type is known to possess such a strong magnetic field.

  1. The multidecadal variations of the interannual relationship between the East Asian summer monsoon and ENSO in a coupled model

    Science.gov (United States)

    Liu, Bo; Huang, Gang; Hu, Kaiming; Wu, Renguang; Gong, Hainan; Wang, Pengfei; Zhao, Guijie

    2017-10-01

    This study investigates the multidecadal variations of the interannual relationship between the East Asian summer monsoon (EASM) and El Niño-Southern Oscillation (ENSO) in 1000-year simulation of a coupled climate model. The interannual relationship between ENSO and EASM has experienced pronounced changes throughout the 1000-year simulation. During the periods with significant ENSO-EASM relationship, the ENSO-related circulation anomalies show a Pacific-Japan (PJ)-like pattern with significant wave-activity flux propagating from the tropics to the north in lower troposphere and from the mid-latitudes to the south in upper troposphere. The resultant ENSO-related precipitation anomalies are more (less) than normal over the East Asia (western North Pacific) in the decaying summers of El Niño events. In contrast, the circulation and precipitation anomalies are weak over East Asia-western North Pacific during the periods with weak ENSO-EASM relationship. Based on the energy conversion analysis, the related anomalies achieve barotropic and baroclinic energy from the mean flow during the periods with strong ENSO-EASM relationship. On the contrary, during the low-correlation periods, the energy conversion is too weak to form the link between the tropics and mid-latitudes. The main reason for the multidecadal variations of ENSO-EASM relationship is the amplitude discrepancy of SST anomalies over the Indo-western Pacific Ocean which, in turn, leads to the intensity difference of the western North Pacific anomalous anticyclone (WPAC) and related climate anomalies.

  2. Why are models unable to reproduce multi-decadal trends in lower tropospheric baseline ozone levels?

    Science.gov (United States)

    Hu, L.; Liu, J.; Mickley, L. J.; Strahan, S. E.; Steenrod, S.

    2017-12-01

    Assessments of tropospheric ozone radiative forcing rely on accurate model simulations. Parrish et al (2014) found that three chemistry-climate models (CCMs) overestimate present-day O3 mixing ratios and capture only 50% of the observed O3 increase over the last five decades at 12 baseline sites in the northern mid-latitudes, indicating large uncertainties in our understanding of the ozone trends and their implications for radiative forcing. Here we present comparisons of outputs from two chemical transport models (CTMs) - GEOS-Chem and the Global Modeling Initiative model - with O3 observations from the same sites and from the global ozonesonde network. Both CTMs are driven by reanalysis meteorological data (MERRA or MERRA2) and thus are expected to be different in atmospheric transport processes relative to those freely running CCMs. We test whether recent model developments leading to more active ozone chemistry affect the computed ozone sensitivity to perturbations in emissions. Preliminary results suggest these CTMs can reproduce present-day ozone levels but fail to capture the multi-decadal trend since 1980. Both models yield widespread overpredictions of free tropospheric ozone in the 1980s. Sensitivity studies in GEOS-Chem suggest that the model estimate of natural background ozone is too high. We discuss factors that contribute to the variability and trends of tropospheric ozone over the last 30 years, with a focus on intermodel differences in spatial resolution and in the representation of stratospheric chemistry, stratosphere-troposphere exchange, halogen chemistry, and biogenic VOC emissions and chemistry. We also discuss uncertainty in the historical emission inventories used in models, and how these affect the simulated ozone trends.

  3. An interaction network perspective on the relation between patterns of sea surface temperature variability and global mean surface temperature

    NARCIS (Netherlands)

    Tantet, A.J.J.; Dijkstra, H.A.

    2014-01-01

    On interannual- to multidecadal timescales variability in sea surface temperature appears to be organized in large-scale spatiotemporal patterns. In this paper, we investigate these patterns by studying the community structure of interaction networks constructed from sea surface temperature

  4. Arctic climate change and decadal variability

    NARCIS (Netherlands)

    Linden, van der Eveline C.

    2016-01-01

    High northern latitudes exhibit enhanced near-surface warming in a climate with increasing greenhouse gases compared to other parts of the globe, indicating an amplified climate response to external forcing. Decadal to multidecadal variability sometimes enhances and at other times reduces the

  5. Arctic climate change and decadal variability

    NARCIS (Netherlands)

    Linden, van der Eveline C.

    2016-01-01

    High northern latitudes exhibit enhanced near-surface warming in a climate with increasing greenhouse gases compared to other parts of the globe, indicating an amplified climate response to external forcing. Decadal to multidecadal variability sometimes enhances and at other times reduces the

  6. Multidecadal response of naturally regenerated southern pine to early competition control and commercial thinning

    Science.gov (United States)

    Andrew S. Nelson; Don C. Bragg

    2016-01-01

    Multidecadal responses to early competition control are poorly documented in naturally regenerated southern pine stands. This study examined the effects of the following early herbicide treatments in thinned southern pine stands through age 31: (1) no control (CK), (2) herbaceous vegetation control only (HC), (3) woody vegetation control only (WC), and (4) total (woody...

  7. Multi-Decadal Averages of Basal Melt for Ross Ice Shelf, Antarctica Using Airborne Observations

    Science.gov (United States)

    Das, I.; Bell, R. E.; Tinto, K. J.; Frearson, N.; Kingslake, J.; Padman, L.; Siddoway, C. S.; Fricker, H. A.

    2017-12-01

    Changes in ice shelf mass balance are key to the long term stability of the Antarctic Ice Sheet. Although the most extensive ice shelf mass loss currently is occurring in the Amundsen Sea sector of West Antarctica, many other ice shelves experience changes in thickness on time scales from annual to ice age cycles. Here, we focus on the Ross Ice Shelf. An 18-year record (1994-2012) of satellite radar altimetry shows substantial variability in Ross Ice Shelf height on interannual time scales, complicating detection of potential long-term climate-change signals in the mass budget of this ice shelf. Variability of radar signal penetration into the ice-shelf surface snow and firn layers further complicates assessment of mass changes. We investigate Ross Ice Shelf mass balance using aerogeophysical data from the ROSETTA-Ice surveys using IcePod. We use two ice-penetrating radars; a 2 GHz unit that images fine-structure in the upper 400 m of the ice surface and a 360 MHz radar to identify the ice shelf base. We have identified internal layers that are continuous along flow from the grounding line to the ice shelf front. Based on layer continuity, we conclude that these layers must be the horizons between the continental ice of the outlet glaciers and snow accumulation once the ice is afloat. We use the Lagrangian change in thickness of these layers, after correcting for strain rates derived using modern day InSAR velocities, to estimate multidecadal averaged basal melt rates. This method provides a novel way to quantify basal melt, avoiding the confounding impacts of spatial and short-timescale variability in surface accumulation and firn densification processes. Our estimates show elevated basal melt rates (> -1m/yr) around Byrd and Mullock glaciers within 100 km from the ice shelf front. We also compare modern InSAR velocity derived strain rates with estimates from the comprehensive ground-based RIGGS observations during 1973-1978 to estimate the potential magnitude of

  8. Northern Hemisphere summer monsoon intensified by mega-El Niño/southern oscillation and Atlantic multidecadal oscillation

    Science.gov (United States)

    Wang, Bin; Liu, Jian; Kim, Hyung-Jin; Webster, Peter J.; Yim, So-Young; Xiang, Baoqiang

    2013-01-01

    Prediction of monsoon changes in the coming decades is important for infrastructure planning and sustainable economic development. The decadal prediction involves both natural decadal variability and anthropogenic forcing. Hitherto, the causes of the decadal variability of Northern Hemisphere summer monsoon (NHSM) are largely unknown because the monsoons over Asia, West Africa, and North America have been studied primarily on a regional basis, which is unable to identify coherent decadal changes and the overriding controls on planetary scales. Here, we show that, during the recent global warming of about 0.4 °C since the late 1970s, a coherent decadal change of precipitation and circulation emerges in the entirety of the NHSM system. Surprisingly, the NHSM as well as the Hadley and Walker circulations have all shown substantial intensification, with a striking increase of NHSM rainfall by 9.5% per degree of global warming. This is unexpected from recent theoretical prediction and model projections of the 21st century. The intensification is primarily attributed to a mega-El Niño/Southern Oscillation (a leading mode of interannual-to-interdecadal variation of global sea surface temperature) and the Atlantic Multidecadal Oscillation, and further influenced by hemispherical asymmetric global warming. These factors driving the present changes of the NHSM system are instrumental for understanding and predicting future decadal changes and determining the proportions of climate change that are attributable to anthropogenic effects and long-term internal variability in the complex climate system. PMID:23509281

  9. Northern Hemisphere summer monsoon intensified by mega-El Nino/southern oscillation and Atlantic multidecadal oscillation.

    Science.gov (United States)

    Wang, Bin; Liu, Jian; Kim, Hyung-Jin; Webster, Peter J; Yim, So-Young; Xiang, Baoqiang

    2013-04-02

    Prediction of monsoon changes in the coming decades is important for infrastructure planning and sustainable economic development. The decadal prediction involves both natural decadal variability and anthropogenic forcing. Hitherto, the causes of the decadal variability of Northern Hemisphere summer monsoon (NHSM) are largely unknown because the monsoons over Asia, West Africa, and North America have been studied primarily on a regional basis, which is unable to identify coherent decadal changes and the overriding controls on planetary scales. Here, we show that, during the recent global warming of about 0.4 °C since the late 1970s, a coherent decadal change of precipitation and circulation emerges in the entirety of the NHSM system. Surprisingly, the NHSM as well as the Hadley and Walker circulations have all shown substantial intensification, with a striking increase of NHSM rainfall by 9.5% per degree of global warming. This is unexpected from recent theoretical prediction and model projections of the 21st century. The intensification is primarily attributed to a mega-El Niño/Southern Oscillation (a leading mode of interannual-to-interdecadal variation of global sea surface temperature) and the Atlantic Multidecadal Oscillation, and further influenced by hemispherical asymmetric global warming. These factors driving the present changes of the NHSM system are instrumental for understanding and predicting future decadal changes and determining the proportions of climate change that are attributable to anthropogenic effects and long-term internal variability in the complex climate system.

  10. Regional amplification of projected changes in extreme temperatures strongly controlled by soil moisture-temperature feedbacks

    Science.gov (United States)

    Vogel, Martha Marie; Orth, René; Cheruy, Frederique; Hagemann, Stefan; Lorenz, Ruth; van den Hurk, Bart; Seneviratne, Sonia Isabelle

    2017-04-01

    Regional hot extremes are projected to increase more strongly than global mean temperature, with substantially larger changes than 2°C even if global warming is limited to this level. We investigate here the role of soil moisture-temperature feedbacks for this response based on multi-model experiments for the 21st century with either interactive or fixed (late 20th century mean seasonal cycle) soil moisture. We analyze changes in the hottest days in each year in both sets of experiments, relate them to the global mean temperature increase, and investigate physical processes leading to these changes. We find that soil moisture-temperature feedbacks significantly contribute to the amplified warming of hottest days compared to that of global mean temperature. This contribution reaches more than 70% in Central Europe and Central North America and between 42%-52% in Amazonia, Northern Australia and Southern Africa. Soil moisture trends (multi-decadal soil moisture variability) are more important for this response than short-term (e.g. seasonal, interannual) soil moisture variability. These results are relevant for reducing uncertainties in regional temperature projections. Vogel, M.M. et al.,2017. Regional amplification of projected changes in extreme temperatures strongly controlled by soil moisture-temperature feedbacks. Geophysical Research Letters, accepted.

  11. A multi-decadal wind-wave hindcast for the North Sea 1949-2014: coastDat2

    Science.gov (United States)

    Groll, Nikolaus; Weisse, Ralf

    2017-12-01

    Long and consistent wave data are important for analysing wave climate variability and change. Moreover, such wave data are also needed in coastal and offshore design and for addressing safety-related issues at sea. Using the third-generation spectral wave model WAM a multi-decadal wind-wave hindcast for the North Sea covering the period 1949-2014 was produced. The hindcast is part of the coastDat database representing a consistent and homogeneous met-ocean data set. It is shown that despite not being perfect, data from the wave hindcast are generally suitable for wave climate analysis. In particular, comparisons of hindcast data with in situ and satellite observations show on average a reasonable agreement, while a tendency towards overestimation of the highest waves could be inferred. Despite these limitations, the wave hindcast still provides useful data for assessing wave climate variability and change as well as for risk analysis, in particular when conservative estimates are needed. Hindcast data are stored at the World Data Center for Climate (WDCC) and can be freely accessed using the doi:10.1594/WDCC/coastDat-2_WAM-North_Sea Groll and Weisse(2016) or via the coastDat web-page http://www.coastdat.de.

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

    Science.gov (United States)

    Vinje, T.; Colony, R.

    2003-04-01

    The European Arctic has been explored and commercially exploited for more than 400 years. In 1596, Willem Barentsz sailed the northern Barents Sea reporting on sea-ice extent and on the large number of whales found along the ice edge. By the early 17th century, an extensive and sophisticated whaling industry had developed in northern Spitzbergen. The whale hunters systematically observed and logged sea-ice conditions and ice edge location. These shipboard observations provide sea-ice extent information throughout the Nordic Seas and the western Barents for much of the 17th and 18th centuries. In 1850, Norway began extensive whale/seal hunting along the ice edge, stretching from Iceland to Novaya Zemlya. The records of sea-ice conditions and extent were archived by the Norwegian Polar Research Institute and are now placed in the ACSYS Historical Ice Chart Database. The annual April and August latitude of sea-ice extent in the western Barents is constructed for the period 1730-2000. The early part of the record (1730-1790) suggests April and August ice conditions similar to the modern era. However, just at the end of the 18th century, the sea-ice moved 300 km southward of its previous mean position. For the next 200 years (1800-2000), sea ice cover in the western Barents has steadily receded to its present state. Covariance studies offer insight into the processes controlling sea-ice extent and serve to bound the observational errors. The instrumental temperature record is mostly limited to the past 150-years. During this period, we estimate the correlation between Northern Hemisphere mean temperature and August sea-ice extent at r = 0.80 (using 7-year running means). Temperature records from central England are available from 1700, as are proxy temperature based data boreholes from the Greenland Ice Sheet Project. Again, significant covariance is found. The most provocative data come from sun spot observations and the associated time series of solar total irradiance (1600-2000). Major features of historical sea-ice extent are seen in the Sun’s total irradiance.

  13. Surface-temperature trends and variability in the low-latitude North Atlantic since 1552

    KAUST Repository

    Saenger, Casey

    2009-06-21

    Sea surface temperature variability in the North Atlantic Ocean recorded since about 1850 has been ascribed to a natural multidecadal oscillation superimposed on a background warming trend1-6. It has been suggested that the multidecadal variability may be a persistent feature6-8, raising the possibility that the associated climate impacts may be predictable7,8. owever, our understanding of the multidecadal ocean variability before the instrumental record is based on interpretations of high-latitude terrestrial proxy records. Here we present an absolutely dated and annually resolved record of sea surface temperature from the Bahamas, based on a 440-year time series of coral growth rates. The reconstruction indicates that temperatures were as warm as today from about 1552 to 1570, then cooled by about 1° C from 1650 to 1730 before warming until the present. Our estimates of background variability suggest that much of the warming since 1900 was driven by anthropogenic forcing. Interdecadal variability with a period of 15-25 years is superimposed on most of the record, but multidecadal variability becomes significant only after 1730. We conclude that the multidecadal variability in sea surface temperatures in the low-latitude western Atlantic Ocean may not be persistent, potentially making accurate decadal climate forecasts more difficult to achieve. © 2009 Macmillan Publishers Limited. All rights reserved.

  14. Phylogenetic assemblage structure of North American trees is more strongly shaped by glacial–interglacial climate variability in gymnosperms than in angiosperms

    DEFF Research Database (Denmark)

    Ma, Ziyu; Sandel, Brody Steven; Svenning, Jens-Christian

    2016-01-01

    to recolonization to quantify glacial-interglacial climate variability. We found: i) Current climate is the dominant factor explaining the overall patterns, with more clustered angiosperm assemblages towards lower temperature, consistent with tropical niche conservatism. ii) Long-term climate stability...... and tropical niche conservatism. However, the role of glacial-interglacial climate variability remains to be determined, and little is known about any of these relationships for gymnosperms. Moreover, phylogenetic edemism, patterns of unique lineages in restricted ranges is also related to glacial......-interglacial climate variability and needs more attention. We used a refined phylogeny of both angiosperms and gymnosperms to map phylogenetic diversity, clustering and endemism of North American trees in 100-km grid cells, and climate change velocity since Last Glacial Maximum together with postglacial accessibility...

  15. Analysis of Historical and CMIP5 Projections of Multi-decadal Climatic Variation and Implications for Ecosystem Management on the Colorado Plateau

    Science.gov (United States)

    Baker, B.; Wang, S. S.; Smith, K.

    2015-12-01

    Increasing pressures on ecosystems of the Colorado Plateau, in particular changes in land use and anthropogenically forced changes in climate, are moving these systems toward "thresholds" that may not be re-traversed once crossed. Recent studies have shown that changes in winter temperature and hydrological fluxes in the western United States are outside the range of natural variability. These observations suggest that the Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) are acting synergistically with underlying climatic trends associated with increased greenhouse gas forcings. Of particular importance for the Colorado Plateau (CP), future warming may alter the position and strength of the North American Monsoon (NAM), which is responsible for a sharp summertime moisture gradient across the region. Natural resource managers are faced with unprecedented challenges if these trends continue. The goal of the project was to describe historical and future projected inter-annual and multi-decadal variability of precipitation in the northern limits of the NAM region, analyze future projected changes on the hydrological regime, and discuss implications for management of these semi-arid ecosystems. Daily climate records were analyzed to quantify the current and historical spatio-temporal pattern of precipitation across the CP using results from ten CMIP5 climate models that best reproduce climate metrics of PDO and ENSO across the study area. Results suggest that a focus on the variability and pattern change in extreme climate anomalies, is vital to inform the management of natural resources. Specifically, inter- and intra-annual variability, seasonality of temperature and precipitation, as well as interactions between multi-decadal cycles trends driven by large-scale climate dynamics, need to be considered. Policies that guide management actions into the future should be based on strategies that cover a wide range of plausible climatic conditions.

  16. Comment on "The Atlantic Multidecadal Oscillation without a role for ocean circulation".

    Science.gov (United States)

    Zhang, Rong; Sutton, Rowan; Danabasoglu, Gokhan; Delworth, Thomas L; Kim, Who M; Robson, Jon; Yeager, Stephen G

    2016-06-24

    Clement et al (Reports, 16 October 2015, p. 320) claim that the Atlantic Multidecadal Oscillation (AMO) is a thermodynamic response of the ocean mixed layer to stochastic atmospheric forcing and that ocean circulation changes have no role in causing the AMO. These claims are not justified. We show that ocean dynamics play a central role in the AMO. Copyright © 2016, American Association for the Advancement of Science.

  17. Phylogenetic assemblage structure of North American trees is more strongly shaped by glacial-interglacial climate variability in gymnosperms than in angiosperms.

    Science.gov (United States)

    Ma, Ziyu; Sandel, Brody; Svenning, Jens-Christian

    2016-05-01

    How fast does biodiversity respond to climate change? The relationship of past and current climate with phylogenetic assemblage structure helps us to understand this question. Studies of angiosperm tree diversity in North America have already suggested effects of current water-energy balance and tropical niche conservatism. However, the role of glacial-interglacial climate variability remains to be determined, and little is known about any of these relationships for gymnosperms. Moreover, phylogenetic endemism, the concentration of unique lineages in restricted ranges, may also be related to glacial-interglacial climate variability and needs more attention. We used a refined phylogeny of both angiosperms and gymnosperms to map phylogenetic diversity, clustering and endemism of North American trees in 100-km grid cells, and climate change velocity since Last Glacial Maximum together with postglacial accessibility to recolonization to quantify glacial-interglacial climate variability. We found: (1) Current climate is the dominant factor explaining the overall patterns, with more clustered angiosperm assemblages toward lower temperature, consistent with tropical niche conservatism. (2) Long-term climate stability is associated with higher angiosperm endemism, while higher postglacial accessibility is linked to to more phylogenetic clustering and endemism in gymnosperms. (3) Factors linked to glacial-interglacial climate change have stronger effects on gymnosperms than on angiosperms. These results suggest that paleoclimate legacies supplement current climate in shaping phylogenetic patterns in North American trees, and especially so for gymnosperms.

  18. The combined influence of Pacific decadal oscillation and Atlantic multidecadal oscillation on central Mexico since the early 1600s

    Science.gov (United States)

    Park, Jungjae; Byrne, Roger; Böhnel, Harald

    2017-04-01

    Periodic droughts have been one of the most serious environmental issues in central Mexico since the earliest times. The impacts of future droughts are likely to become even more severe as the current global warming trend increases potential evaporation and moisture deficits. A full understanding of the mechanism underlying climate variability is imperative to narrow the uncertainty about future droughts and predict water availability. The climatic complexity generated by the combined influence of both Atlantic and Pacific forcings, however, causes considerable difficulty in interpreting central Mexican climate records. Also, the lack of high-resolution information regarding the climate in the recent past makes it difficult to clearly understand current drought mechanisms. Our new high-resolution δ18 O record from Hoya Rincon de Parangueo in central Mexico provides useful information on climate variations since the early 1600s. According to our results, the central Mexican climate has been predominantly controlled by the combined influence of the 20-year Pacific Decadal Oscillation (PDO) and the 70-year Atlantic Multidecadal Oscillation (AMO). However, the AMO probably lost much of its influence in central Mexico in the early 20th century and the PDO has mostly driven climate change since. Marked dryness was mostly associated with co-occurrence of highly positive PDO and negative AMO between ∼1600 and 1900.

  19. Spatial variability of nitrous oxide and methane emissions from an MBT landfill in operation: Strong N{sub 2}O hotspots at the working face

    Energy Technology Data Exchange (ETDEWEB)

    Harborth, Peter, E-mail: p.harborth@tu-bs.de [Department of Waste and Resource Management, Leichtweiß-Institute for Hydraulic Engineering and Water Resources, Technische Universität Braunschweig, Braunschweig (Germany); Fuß, Roland [Institute of Climate-Smart Agriculture, Johann Heinrich von Thünen Institute, Braunschweig (Germany); Münnich, Kai [Department of Waste and Resource Management, Leichtweiß-Institute for Hydraulic Engineering and Water Resources, Technische Universität Braunschweig, Braunschweig (Germany); Flessa, Heinz [Institute of Climate-Smart Agriculture, Johann Heinrich von Thünen Institute, Braunschweig (Germany); Fricke, Klaus [Department of Waste and Resource Management, Leichtweiß-Institute for Hydraulic Engineering and Water Resources, Technische Universität Braunschweig, Braunschweig (Germany)

    2013-10-15

    Highlights: ► First measurements of N{sub 2}O and CH{sub 4} emissions from an MBT landfill. ► High N{sub 2}O emissions from recently deposited material. ► N{sub 2}O emissions associated with aeration and the occurrence of nitrite and nitrate. ► Strong negative correlation between CH{sub 4} and N{sub 2}O production activity. - Abstract: Mechanical biological treatment (MBT) is an effective technique, which removes organic carbon from municipal solid waste (MSW) prior to deposition. Thereby, methane (CH{sub 4}) production in the landfill is strongly mitigated. However, direct measurements of greenhouse gas emissions from full-scale MBT landfills have not been conducted so far. Thus, CH{sub 4} and nitrous oxide (N{sub 2}O) emissions from a German MBT landfill in operation as well as their concentrations in the landfill gas (LFG) were measured. High N{sub 2}O emissions of 20–200 g CO{sub 2} eq. m{sup −2} h{sup −1} magnitude (up to 428 mg N m{sup −2} h{sup −1}) were observed within 20 m of the working face. CH{sub 4} emissions were highest at the landfill zone located at a distance of 30–40 m from the working face, where they reached about 10 g CO{sub 2} eq. m{sup −2} h{sup −1}. The MBT material in this area has been deposited several weeks earlier. Maximum LFG concentration for N{sub 2}O was 24.000 ppmv in material below the emission hotspot. At a depth of 50 cm from the landfill surface a strong negative correlation between N{sub 2}O and CH{sub 4} concentrations was observed. From this and from the distribution pattern of extractable ammonium, nitrite, and nitrate it has been concluded that strong N{sub 2}O production is associated with nitrification activity and the occurrence of nitrite and nitrate, which is initiated by oxygen input during waste deposition. Therefore, CH{sub 4} mitigation measures, which often employ aeration, could result in a net increase of GHG emissions due to increased N{sub 2}O emissions, especially at MBT landfills.

  20. New Tree-Ring Evidence from the Pyrenees Reveals Western Mediterranean Climate Variability since Medieval Times

    Czech Academy of Sciences Publication Activity Database

    Büntgen, Ulf; Krusic, P. J.; Verstege, A.; Sanguesa-Barreda, G.; Wagner, S.; Camarero, J. J.; Ljungqvist, F. C.; Zorita, E.; Oppenheimer, C.; Konter, O.; Tegel, W.; Gärtner, H.; Cherubini, P.; Reinig, F.; Esper, J.

    2017-01-01

    Roč. 30, č. 14 (2017), s. 5295-5318 ISSN 0894-8755 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : Europe * Volcanoes * Climate variability * Interannual variability * Multidecadal variability * Trends Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 4.161, year: 2016

  1. Carbon and nitrogen elemental and isotopic ratios of filter-feeding bivalves along the French coasts: An assessment of specific, geographic, seasonal and multi-decadal variations.

    Science.gov (United States)

    Briant, Nicolas; Savoye, Nicolas; Chouvelon, Tiphaine; David, Valérie; Rodriguez, Samuel; Charlier, Karine; Sonke, Jeroen E; Chiffoleau, Jean François; Brach-Papa, Christophe; Knoery, Joël

    2018-02-01

    Primary consumers play a key role in coastal ecosystems by transferring organic matter from primary producers to predators. Among them, suspension-feeders, like bivalve molluscs are widely used in trophic web studies. The main goal of this study was to investigate variations of C and N elemental and isotopic ratios in common bivalves (M. edulis, M. galloprovincialis, and C. gigas) at large spatial (i.e. among three coastal regions) and different temporal (i.e. from seasonal to multi-decadal) scales in France, in order to identify potential general or specific patterns and speculate on their drivers. The observed spatial variability was related to the trophic status of the coastal regions (oligotrophic Mediterranean Sea versus meso- to eutrophic English Channel and Atlantic ocean), but not to ecosystem typology (estuaries, versus lagoons versus bays versus littoral systems). Furthermore, it highlighted local specificities in terms of the origin of the POM assimilated by bivalves (e.g., mainly continental POM vs. marine phytoplankton vs. microphytobenthic algae). Likewise, seasonal variability was related both to the reproduction cycle for C/N ratios of Mytilus spp. and to changes in trophic resources for δ 13 C of species located close to river mouth. Multi-decadal evolution exhibited shifts and trends for part of the 30-year series with decreases in δ 13 C and δ 15 N. Specifically, shifts appeared in the early 2000's, likely linking bivalve isotopic ratios to a cascade of processes affected by local drivers. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Multi-decadal time series of remotely sensed vegetation improves prediction of soil carbon in a subtropical grassland.

    Science.gov (United States)

    Wilson, Chris H; Caughlin, T Trevor; Rifai, Sami W; Boughton, Elizabeth H; Mack, Michelle C; Flory, S Luke

    2017-07-01

    Soil carbon sequestration in agroecosystems could play a key role in climate change mitigation but will require accurate predictions of soil organic carbon (SOC) stocks over spatial scales relevant to land management. Spatial variation in underlying drivers of SOC, such as plant productivity and soil mineralogy, complicates these predictions. Recent advances in the availability of remotely sensed data make it practical to generate multidecadal time series of vegetation indices with high spatial resolution and coverage. However, the utility of such data largely is unknown, only having been tested with shorter (e.g., 1-2 yr) data summaries. Across a 2,000 ha subtropical grassland, we found that a long time series (28 yr) of a vegetation index (Enhanced Vegetation Index; EVI) derived from the Landsat 5 satellite significantly enhanced prediction of spatially varying SOC pools, while a short summary (2 yr) was an ineffective predictor. EVI was the best predictor for surface SOC (0-5 cm depth) and total measured SOC stocks (0-15 cm). The optimum models for SOC in the upper soil layer combined EVI records with elevation and calcium concentration, while deeper SOC was more strongly associated with calcium availability. We demonstrate how data from the open access Landsat archive can predict SOC stocks, a key ecosystem metric, and illustrate the rich variety of analytical approaches that can be applied to long time series of remotely sensed greenness. Overall, our results showed that SOC pools were closely coupled to EVI in this ecosystem, demonstrating that maintenance of higher average green leaf area is correlated with higher SOC. The strong associations of vegetation greenness and calcium concentration with SOC suggest that the ability to sequester additional SOC likely will rely on strategic management of pasture vegetation and soil fertility. © 2017 by the Ecological Society of America.

  3. Multidecadal shoreline changes of atoll islands in the Marshall Islands

    Science.gov (United States)

    Ford, M.

    2012-12-01

    Atoll islands are considered highly vulnerable to the impacts of continued sea level rise. One of the most commonly predicted outcomes of continued sea level rise is widespread and chronic shoreline erosion. Despite the widespread implications of predicted erosion, the decadal scale changes of atoll island shorelines are poorly resolved. The Marshall Islands is one of only four countries where the majority of inhabited land is comprised of reef and atoll islands. Consisting of 29 atolls and 5 mid-ocean reef islands, the Marshall Islands are considered highly vulnerable to the impacts of sea level rise. A detailed analysis of shoreline change on over 300 islands on 10 atolls was undertaken using historic aerial photos (1945-1978) and modern high resolution satellite imagery (2004-2012). Results highlight the complex and dynamic nature of atoll islands, with significant shifts in shoreline position observed over the period of analysis. Results suggest shoreline accretion is the dominant mode of change on the islands studied, often associated with a net increase in vegetated island area. However, considerable inter- and intra-atoll variability exists with regards to shoreline stability. Findings are discussed with respect to island morphodynamics and potential hazard mitigation and planning responses within atoll settings.

  4. Nitric oxide (NO) emissions from N-saturated subtropical forest soils are strongly affected by spatial and temporal variability in soil moisture

    Science.gov (United States)

    Kang, Ronghua; Dörsch, Peter; Mulder, Jan

    2016-04-01

    Subtropical forests in Southwest China have chronically high nitrogen (N) deposition. This results in high emission rates of N gasses, including N2O, NO and N2. In contrast to N2O, NO emission in subtropical China has received little attention, partly because its quantification is challenging. Here we present NO fluxes in a Masson pine-dominated headwater catchment with acrisols on mesic, well-drained hill slopes at TieShanPing (Chongqing, SW China). Measurements were conducted from July to September in 2015, using a dynamic chamber technique and a portable and highly sensitive chemiluminesence NOx analyzer (LMA-3M, Drummond Technology Inc, Canada). Mean NO fluxes as high as 120 μg N m-2 h-1 (± 56 μg N m-2 h-1) were observed at the foot of the hill slope. Mid-slope positions had intermediate NO emission rates (47 ± 17 μg N m-2 h-1), whereas the top of the hill slope showed the lowest NO fluxes (3 ± 3 μg N m-2 h-1). The magnitude of NO emission seemed to be controlled mainly by site-specific soil moisture, which was on average lower at the foot of the hill slope and in mid-slope positions than at the top of the hill slope. Rainfall episodes caused a pronounced decline in NO emission fluxes in all hill slope positions, whereas the subsequent gradual drying of the soil resulted in an increase. NO fluxes were negatively correlated with soil moisture (r2 = 0.36, p ˂ 0.05). The NO fluxes increased in the early morning, and decreased in the late afternoon, with peak emissions occurring between 2 and 3 pm. The diurnal variation of NO fluxes on mid-slope positions was positively correlated with soil temperature (r2 = 0.9, p ˂ 0.05). Our intensive measurements indicate that NO-N emissions in N-saturated subtropical forests are significant and strongly controlled by local hydrological conditions.

  5. Strong Evidence of Variable Micro-meteor Flux from Apollo 17 Samples Obtained at Shorty Crater and on the Light Mantle Avalanche at Taurus-Littrow

    Science.gov (United States)

    Schmitt, H. H.; Petro, N. E.

    2017-12-01

    , respectively. This difference further supports the hypothesis of a highly variable micro-meteor flux throughout lunar history, with its current flux being significantly higher than for some period both prior to and subsequent to 3.5 Ga.

  6. Response to Comment on "The Atlantic Multidecadal Oscillation without a role for ocean circulation".

    Science.gov (United States)

    Clement, Amy; Cane, Mark A; Murphy, Lisa N; Bellomo, Katinka; Mauritsen, Thorsten; Stevens, Bjorn

    2016-06-24

    Zhang et al interpret the mixed-layer energy budget in models as showing that "ocean dynamics play a central role in the AMO." Here, we show that their diagnostics cannot reveal the causes of the Atlantic Multidecadal Oscillation (AMO) and that their results can be explained with minimal ocean influence. Hence, we reaffirm our findings that the AMO in models can be understood primarily as the upper-ocean thermal response to stochastic atmospheric forcing. Copyright © 2016, American Association for the Advancement of Science.

  7. Natural variability in the surface ocean carbonate ion concentration

    OpenAIRE

    N. S. Lovenduski; M. C. Long; K. Lindsay

    2015-01-01

    We investigate variability in the surface ocean carbonate ion concentration ([CO32−]) on the basis of a long control simulation with a fully-coupled Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO32−] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO32−] in the tropical...

  8. Natural variability in the surface ocean carbonate ion concentration

    OpenAIRE

    Lovenduski, N. S.; Long, M. C.; Lindsay, K.

    2015-01-01

    We investigate variability in the surface ocean carbonate ion concentration ([CO32−]) on the basis of a~long control simulation with an Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO32−] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO32−] in the tropical Pacific and ...

  9. The summer North Atlantic Oscillation (SNAO) variability on decadal to paleoclimate time scales

    Science.gov (United States)

    Linderholm, H. W.; Folland, C. K.; Zhang, P.; Gunnarson, B. E.; Jeong, J. H.; Ren, H.

    2017-12-01

    The summer North Atlantic Oscillation (SNAO), strongly related to the latitude of the North Atlantic and European summer storm tracks, exerts a considerable influence on European summer climate variability and extremes. Here we extend the period covered by the SNAO from July and August to June, July and August (JJA). As well as marked interannual variability, the JJA SNAO has shown a large inter-decadal change since the 1970s. Decadally averaged, there has been a change from a very positive to a rather negative SNAO phase. This change in SNAO phase is opposite in sign from that expected by a number of climate models under enhanced greenhouse forcing by the late twenty first century. It has led to noticeably wetter summers in North West Europe in the last decade. On interannual to multidecadal timescales, SNAO variability is linked to variations in North Atlantic sea surface temperature (SST): observations and models indicate an association between the Atlantic Multi-decadal Oscillation (AMO) where the cold (warm) phase of the AMO corresponds a positive (negative) phase of the SNAO. Observations also indicate a link with SST in the Gulf Stream region of the North Atlantic where, particularly on decadal time scales, SST warming may favour a more positive phase of the SNAO. Influences of Arctic climate change on North Atlantic and European atmospheric circulation may also exist, particularly reduced sea ice coverage, perhaps favouring the negative phase of the SNAO. A new tree-ring data based JJA SNAO reconstruction extending over the last millennium, as well as climate model output for the same period, enables us to examine the influence of North Atlantic SST and Arctic sea-ice coverage, as well as SNAO impacts on European summer climate, in a long-term, pre-industrial context.

  10. A multi-decadal assessment of the performance of gauge- and model-based rainfall products over Saudi Arabia: Climatology, anomalies and trends

    KAUST Repository

    El Kenawy, Ahmed M.

    2015-05-15

    Many arid and semi-arid regions have sparse precipitation observing networks, which limits the capacity for detailed hydrological modelling, water resources management and flood forecasting efforts. The objective of this work is to evaluate the utility of relatively high-spatial resolution rainfall products to reproduce observed multi-decadal rainfall characteristics such as climatologies, anomalies and trends over Saudi Arabia. Our study compares the statistical characteristics of rainfall from 53 observatories over the reference period 1965-2005, with rainfall data from six widely used gauge-based products, including APHRODITE, GPCC, PRINCETON, UDEL, CRU and PREC/L. In addition, the performance of three global climate models (GCMs), including CCSM4, EC-EARTH and MRI-I-CGCM3, integrated as part of the Fifth Coupled Model Intercomparison Project (CMIP5), was also evaluated. Results indicate that the gauge-based products were generally skillful in reproducing rainfall characteristics in Saudi Arabia. In most cases, the gauge-based products were also able to capture the annual cycle, anomalies and climatologies of observed data, although significant inter-product variability was observed, depending on the assessment metric being used. In comparison, the GCM-based products generally exhibited poor performance, with larger biases and very weak correlations, particularly during the summertime. Importantly, all products generally failed to reproduce the observed long-term seasonal and annual trends in the region, particularly during the dry seasons (summer and autumn). Overall, this work suggests that selected gauge-based products with daily (APHRODITE and PRINCETON) and monthly (GPCC and CRU) resolutions show superior performance relative to other products, implying that they may be the most appropriate data source from which multi-decadal variations of rainfall can be investigated at the regional scale over Saudi Arabia. Discriminating these skillful products is

  11. Multidecadal change of winter cyclonic activity in the Mediterranean associated with AMO and PDO

    Directory of Open Access Journals (Sweden)

    Veronika Nikolaevna Maslova

    2017-01-01

    Full Text Available The paper is devoted to analysis of the cold half-year (October to March frequency of cyclones in the Mediterranean-Black Sea region associated with the global processes in the ocean-atmosphere system - the Pacific Decadal Oscillation (PDO and Atlantic Multidecadal Oscillation (AMO. Firstly, climatic conditions in the North Atlantic-European region during positive and negative phases of these global oscillations were shown using NCEP/NCAR reanalysis data for 1948 - 2016 and data of the NASA GISS Atlas of Exratropical Strom Tracks in 1961 - 1998. Mean monthly values / anomalies (composites for equal periods of the negative and positive AMO and PDO phases were calculated and compared. The results of the study support the idea that the Pacific and Atlantic influence on the climatic (multidecadal scale is realized via change of the large-scale fields of the North Atlantic anomalies typical for the interannual scale. Then spatial distribution of the frequency of cyclones in the Mediterranean-Black Sea region was obtained using global NCEP/NCAR reanalysis data sets on 1000 hPa geopotential height in 1948 - 2013. It was shown that during the positive AMO phase, frequency of cyclones in the Mediterranean was higher by absolute values in November to March over the Tyrrhenian and Ionic Seas and lower over the Anatolian peninsula. During the negative PDO phase, frequency of cyclones over the Anatolian peninsula in January to March is significantly higher than in the positive PDO phase.

  12. Multidecadal Scale Detection Time for Potentially Increasing Atlantic Storm Surges in a Warming Climate

    Science.gov (United States)

    Lee, Benjamin Seiyon; Haran, Murali; Keller, Klaus

    2017-10-01

    Storm surges are key drivers of coastal flooding, which generate considerable risks. Strategies to manage these risks can hinge on the ability to (i) project the return periods of extreme storm surges and (ii) detect potential changes in their statistical properties. There are several lines of evidence linking rising global average temperatures and increasingly frequent extreme storm surges. This conclusion is, however, subject to considerable structural uncertainty. This leads to two main questions: What are projections under various plausible statistical models? How long would it take to distinguish among these plausible statistical models? We address these questions by analyzing observed and simulated storm surge data. We find that (1) there is a positive correlation between global mean temperature rise and increasing frequencies of extreme storm surges; (2) there is considerable uncertainty underlying the strength of this relationship; and (3) if the frequency of storm surges is increasing, this increase can be detected within a multidecadal timescale (≈20 years from now).

  13. Multi-decadal dynamic thinning on the northwest margin of the Greenland Ice Sheet

    DEFF Research Database (Denmark)

    Korsgaard, Niels Jákup; Kjær, Kurt H.; Khan, Shfaqat Abbas

    Ice mass changes in the Greenland Ice Sheet have been estimated since the early 1990s from the GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission, of ice sheet thinning from satellite radar altimetry and airborne laser altimetry, and of increased velocities of outlet glaciers...... of increasing dynamic induced ice loss. GRACE data show that this increased mass loss initiated in 2005 ceased in late 2009, thus, defining a dynamic thinning event as seen previous along the coast in southeast Greenland. Here, we present a multi-decadal perspective on ice mass change from northwestern...... records with a 25 m grid resolution and vertical uncertainty of 4.6m. Comparative DEMs were derived from laser altimetry data recorded in 2005 and 2010. Ice loss from the Greenland Ice Sheet (GrIS) can be partitioned into surface mass balance (SMB) processes (runoff and precipitation) and ice dynamics...

  14. Temporal energy partitions of Florida extreme sea level events as a function of Atlantic multidecadal oscillation

    Directory of Open Access Journals (Sweden)

    J. Park

    2010-06-01

    Full Text Available An energy-conservative metric based on the discrete wavelet transform is applied to assess the relative energy distribution of extreme sea level events across different temporal scales. The metric is applied to coastal events at Key West and Pensacola Florida as a function of two Atlantic Multidecadal Oscillation (AMO regimes. Under AMO warm conditions there is a small but significant redistribution of event energy from nearly static into more dynamic (shorter duration timescales at Key West, while at Pensacola the AMO-dependent changes in temporal event behaviour are less pronounced. Extreme events with increased temporal dynamics might be consistent with an increase in total energy of event forcings which may be a reflection of more energetic storm events during AMO warm phases. As dynamical models mature to the point of providing regional climate index predictability, coastal planners may be able to consider such temporal change metrics in planning scenarios.

  15. Historical fire and multidecadal drought as context for piñon - Juniper woodland restoration in western Colorado

    Science.gov (United States)

    Shinneman, Douglas J.; Baker, William L.

    2009-01-01

    Fire is known to structure tree populations, but the role of broad-scale climate variability is less clear. For example, the influence of climatic “teleconnections” (the relationship between oceanic–atmospheric fluctuations and anomalous weather patterns across broad scales) on forest age structure is relatively unexplored. We sampled semiarid piñon–juniper (Pinus edulis–Juniperus osteosperma) woodlands in western Colorado, USA, to test the hypothesis that woodland age structures are shaped by climate, including links to oceanic–atmospheric fluctuations, and by past fires and livestock grazing. Low-severity surface fire was lacking, as fire scars were absent, and did not influence woodland densities, but stand-replacing fires served as long-rotation (>400–600 years), stand-initiating events. Old-growth stands (>300 years old) were found in 75% of plots, consistent with a long fire rotation. Juniper and piñon age structures suggest contrasting responses during the past several centuries to dry and wet episodes linked to the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO). Juniper density increased slightly during periods of drought, positive (warm) AMO (after ∼10-year lag), and negative (cool) PDO. In contrast, piñon populations may still be recovering from a long, drought-filled period (AD 1620–1820), with pulses of recovery favored during cool AMO, warm PDO, and above-average moisture periods. Analysis of 20th-century tree establishment and instrumental climate data corroborate the long-term relationships between age structure and climate. After Euro–American settlement (AD 1881), livestock grazing reduced understory grasses and forbs, reducing competition with tree seedlings and facilitating climate-induced increases in piñons. Thus tree populations in these woodlands are in flux, affected by drought and wet periods linked to oceanic–atmospheric variability, Euro–American livestock grazing, and long

  16. Anoxic sediments off Central Peru record interannual to multidecadal changes of climate and upwelling ecosystem during the last two centuries

    Directory of Open Access Journals (Sweden)

    D. Gutiérrez

    2006-01-01

    Full Text Available High-resolution paleo-environmental and paleo-ecological archives in laminated sequences are present in selected areas from the upper continental Peruvian margin within the oxygen minimum zone. We present initial results of a multidisciplinary study (the PALEOPECES project that aims to reconstruct environmental and ecosystem variability during the past 200 years from high-resolution records. We report chronology development, sediment structure, elemental, organic, and mineralogical compositions of a box core collected at 300 m depth off Pisco, central Peru. An average sedimentation rate of 2.2 mm y-1 was estimated from downcore excess 210Pb activities for the last 100-150 years. Extending this rate further downcore indicates that a slump located at 52 cm depth from the top of the core can be correlated with a large tsunami that struck the coast of central Peru in 1746. X-ray analyses reveal laminated structures composed of couplets of light and dark laminae. Observations under polarized microscope show that light laminae are dominated by more dense, detrital and terrigenous material, while dark laminae are less dense with greater concentrations of amorphous biogenic silica. Downcore variations in dry bulk density and X-ray radioscopy of gray level show similar patterns, including a major shift at 34 cm depth (ca. mid-nineteenth century. A finely laminated sequence, which may include annual varves, is present between 34 cm depth and the slump layer. Sediment characteristics of the sequence suggest increased seasonality of terrigenous versus biogenous sedimentation during the corresponding period. In addition to a mid-nineteenth century change and considerable multidecadal variability in TOC, there is a positive trend in the past 50 years. Mineralogical analyses from a Fourier Transformed Infrared Spectroscopy (FTIR of the upper core covering the last 25 years, indicate higher concentrations of the mineral fraction (quartz, feldspar, kaolinite and

  17. Inter-daily variability of a strong thermally-driven wind system over the Atacama Desert of South America: synoptic forcing and short-term predictability using the GFS global model

    Science.gov (United States)

    Jacques-Coper, Martín; Falvey, Mark; Muñoz, Ricardo C.

    2015-07-01

    Crucial aspects of a strong thermally-driven wind system in the Atacama Desert in northern Chile during the extended austral winter season (May-September) are studied using 2 years of measurement data from the Sierra Gorda 80-m meteorological mast (SGO, 22° 56' 24″ S; 69° 7' 58″ W, 2,069 m above sea level (a.s.l.)). Daily cycles of atmospheric variables reveal a diurnal (nocturnal) regime, with northwesterly (easterly) flow and maximum mean wind speed of 8 m/s (13 m/s) on average. These distinct regimes are caused by pronounced topographic conditions and the diurnal cycle of the local radiative balance. Wind speed extreme events of each regime are negatively correlated at the inter-daily time scale: High diurnal wind speed values are usually observed together with low nocturnal wind speed values and vice versa. The associated synoptic conditions indicate that upper-level troughs at the coastline of southwestern South America reinforce the diurnal northwesterly wind, whereas mean undisturbed upper-level conditions favor the development of the nocturnal easterly flow. We analyze the skill of the numerical weather model Global Forecast System (GFS) in predicting wind speed at SGO. Although forecasted wind speeds at 800 hPa do show the diurnal and nocturnal phases, observations at 80 m are strongly underestimated by the model. This causes a pronounced daily cycle of root-mean-squared error (RMSE) and bias in the forecasts. After applying a simple Model Output Statistics (MOS) post-processing, we achieve a good representation of the wind speed intra-daily and inter-daily variability, a first step toward reducing the uncertainties related to potential wind energy projects in the region.

  18. A Multi-proxy Reconstruction of the Winter Pacific North American Variability over the Past Millennium

    Science.gov (United States)

    Liu, Z.; Tang, Y.; Jian, Z.; Poulsen, C. J.; Bowen, G. J.

    2016-12-01

    The Pacific North American (PNA) pattern is the most prominent mode of atmospheric variability in the North Pacific and North American sectors, strongly influencing temperature, precipitation and storm tracks in North America. The instrumental record indicates a persistent trend toward positive PNA phase in recent decades, which has led to accelerated warming and snowpack decline in northwestern North America. The brevity of the instrumental record, however, limits our understanding of long-term PNA variability and its dynamics. Here we develop a 937-year long reconstruction of the winter PNA based on a network of annually resolved proxy records across the North American continent. We find that the recent persistent positive PNA pattern is unprecedented over the past millennium. The change in PNA may have played a principal role in modulating decadal-to-multidecadal hydroclimate variability over North America, especially in western North America where severe droughts are associated with extreme negative PNA phase. The reconstructed PNA shows a teleconnected response to Pacific sea surface temperature (SST) on interannual and interdecadal timescales. The reconstruction also reveals a positive PNA response to low solar irradiance or strong volcanic eruption during the first post-eruption winter, further corroborating statistical links between the PNA and radiative forcing based on historical and reanalysis data.

  19. Mechanisms of interannual- to decadal-scale winter Labrador Sea ice variability

    Science.gov (United States)

    Close, S.; Herbaut, C.; Houssais, M.-N.; Blaizot, A.-C.

    2017-12-01

    The variability of the winter sea ice cover of the Labrador Sea region and its links to atmospheric and oceanic forcing are investigated using observational data, a coupled ocean-sea ice model and a fully-coupled model simulation drawn from the CMIP5 archive. A consistent series of mechanisms associated with high sea ice cover are found amongst the various data sets. The highest values of sea ice area occur when the northern Labrador Sea is ice covered. This region is found to be primarily thermodynamically forced, contrasting with the dominance of mechanical forcing along the eastern coast of Baffin Island and Labrador, and the growth of sea ice is associated with anomalously fresh local ocean surface conditions. Positive fresh water anomalies are found to propagate to the region from a source area off the southeast Greenland coast with a 1 month transit time. These anomalies are associated with sea ice melt, driven by the enhanced offshore transport of sea ice in the source region, and its subsequent westward transport in the Irminger Current system. By combining sea ice transport through the Denmark Strait in the preceding autumn with the Greenland Blocking Index and the Atlantic Multidecadal Oscillation Index, strong correlation with the Labrador Sea ice area of the following winter is obtained. This relationship represents a dependence on the availability of sea ice to be melted in the source region, the necessary atmospheric forcing to transport this offshore, and a further multidecadal-scale link with the large-scale sea surface temperature conditions.

  20. Multidecadal changes in the Etesians-Indian Summer Monsoon teleconnection along the 20th Century

    Science.gov (United States)

    Gómez-Delgado, F. de Paula; Vega, Inmaculada; Gallego, David; Peña-Ortiz, Cristina; Ribera, Pedro; García-Herrera, Ricardo

    2017-04-01

    In this work we made use of historical winds record taken aboard ships to reconstruct a series of the prevalent summer northerly winds (Etesian winds) over the Eastern Mediterranean for the entire 20th century. Previous studies have shown a significant link between the frequency and strength of these winds and the strength of the Indian Summer Monsoon (ISM), but this relationship had only been studied in detail for the second half of the 20th century due to the absence of long and continous series of observed wind in the Eastern Mediterranean for previous periods. In this work, a new climatic index, the so-called " Etesian Wind Index " (EWI), is defined as the percentage of days with prevalent northerly wind (wind blowing from 305° to 35°) in a fixed region [20E-30E, 32N-37N]. By using historical wind observations, we have been able to compute this index for the summer (JJAS) since 1880 and analyze the long term variability of the Etesians, as well as to research into its relation with the ISM at an unprecedent temporal coverage. A running coverage analysis revealed a strong and significant positive correlation between the EWI and the strength of the ISM for the period 1960-1980, more markedly in July and August. This result is in accordance with other recent studies. However, we have found that the correalation fades out in the first half of the 20th century (1900-1950) and in the period 1980-2012, even showing significant negative values around the subperiod 1920-1950. Similar indices to the EWI were computed using two different 20th century reanalysis datasets (ERA20C and 20CR-V2C). Despite the fact that both indices show some discrepancies with the EWI before 1950, the correlation analysis with the ISM revealed similar results, pointing out a strong loss of the EWI-ISM correlation in the first half of the 20th century and from 1980 onwards, as well as a marked positive correlated period between 1960 and 1980, specially in August. In this study, we show that

  1. An electrical analogy relating the Atlantic multidecadal oscillation to the Atlantic meridional overturning circulation.

    Directory of Open Access Journals (Sweden)

    Bruce E Kurtz

    Full Text Available The Atlantic meridional overturning circulation (AMOC is the northward flow of surface water to subpolar latitudes where deepwater is formed, balanced by southward abyssal flow and upwelling in the vicinity of the Southern Ocean. It is generally accepted that AMOC flow oscillates with a period of 60-80 years, creating a regular variation in North Atlantic sea surface temperature known as the Atlantic multidecadal oscillation (AMO. This article attempts to answer two questions: how is the AMOC driven and why does it oscillate? Using methods commonly employed by chemical engineers for analyzing processes involving flowing liquids, apparently not previously applied to trying to understand the AMOC, an equation is developed for AMOC flow as a function of the meridional density gradient or the corresponding temperature gradient. The equation is based on the similarity between the AMOC and an industrial thermosyphon loop cooler, which circulates a heat transfer liquid without using a mechanical pump. Extending this equation with an analogy between the flow of heat and electricity explains why the AMOC flow oscillates and what determines its period. Calculated values for AMOC flow and AMO oscillation period are in good agreement with measured values.

  2. Multidecadal fCO2 Increase Along the United States Southeast Coastal Margin

    Science.gov (United States)

    Reimer, Janet J.; Wang, Hongjie; Vargas, Rodrigo; Cai, Wei-Jun

    2017-12-01

    Coastal margins could be hotspots for acidification due to terrestrial-influenced CO2 sources. Currently there are no long-term (>20 years) records from biologically important coastal environments that could demonstrate sea surface CO2 fugacity (fCO2) and pH trends. Here, multidecadal fCO2 trends are calculated from underway and moored time series observations along the United States southeast coastal margin, also referred to as the South Atlantic Bight (SAB). fCO2 trends across the SAB, derived from ˜26 years of cruises and ˜9.5 years from a moored time series, range from 3.0 to 4.5 µatm yr-1, and are greater than the open ocean increases. The pH decline related to the fCO2 increases could be as much as -0.004 yr-1; a rate greater than that expected from atmospheric-influenced pH alone. We provide evidence that fCO2 increases and pH decreases on an ocean margin can be faster than those predicted for the open ocean from atmospheric influence alone. We conclude that a substantial fCO2 increase across the marginal SAB is due to both increasing temperature on the middle and outer shelves, but to lateral land-ocean interactions in the coastal zone and on inner shelf.

  3. Sustained production of multi-decadal climate records - Lessons from the NOAA Climate Data Record Program

    Science.gov (United States)

    Bates, J. J.

    2015-12-01

    NOAA's Climate Data Record (CDR) Program was designed to be responsive to the needs of climate monitoring, research, and services with the ultimate aim of serving decision making across a spectrum of users for the long term. It requires the sustained production of high quality, multidecadal time series data describing the global atmosphere, oceans, and land surface that can be used for informed decision making. The challenges of a long-term program of sustaining CDRs, as contrasted with short-term efforts of traditional three-year research programs, are substantial and different. The sustained production of CDRs requires collaboration between experts in the climate community, data management, and software development and maintenance. It is also informed by scientific application and associated user feedback on the accessibility and usability of the produced CDRs. The CDR Program has developed a metric for assessing the maturity of CDRs with respect to data management, software, and user application and applied it to over 28 CDRs. The main/primary lesson learned over the past seven years is that a rigorous, team approach to data management, employing subject matter experts at every step, is critical to open and transparent production. This approach also makes it much easier to support the needs of users who want near-real-time production of "interim" CDRs for monitoring and users who want to use CDRs for tailored authoritative information, such as a drought index. This talk will review of the history of the CDR program, current status, and plans.

  4. Vegetation Interaction Enhances Interdecadal Climate Variability in the Sahel

    Science.gov (United States)

    Zeng, Ning; Neelin, J. David; Lau, William K.-M.

    1999-01-01

    The role of naturally varying vegetation in influencing the climate variability in the Sahel is explored in a coupled atmosphere-land-vegetation model. The Sahel rainfall variability is influenced by sea surface temperature (SST) variations in the oceans. Land-surface feedback is found to increase this variability both on interannual and interdecadal time scales. Interactive vegetation enhances the interdecadal variation significantly, but can reduce year to year variability due to a phase lag introduced by the relatively slow vegetation adjustment time. Variations in vegetation accompany the changes in rainfall, in particular, the multi-decadal drying trend from the 1950s to the 80s.

  5. Changes of extreme precipitation and nonlinear influence of climate variables over monsoon region in China

    KAUST Repository

    Gao, Tao

    2017-07-19

    The El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO) and Pacific decadal oscillation (PDO) are well understood to be major drivers for the variability of precipitation extremes over monsoon regions in China (MRC). However, research on monsoon extremes in China and their associations with climate variables is limited. In this study, we examine the space-time variations of extreme precipitation across the MRC, and assess the time-varying influences of the climate drivers using Bayesian dynamic linear regression and their combined nonlinear effects through fitting generalized additive models. Results suggest that the central-east and south China is dominated by less frequent but more intense precipitation. Extreme rainfalls show significant positive trends, coupled with a significant decline of dry spells, indicating an increasing chance of occurrence of flood-induced disasters in the MRC during 1960–2014. Majority of the regional indices display some abrupt shifts during the 1990s. The influences of climate variables on monsoon extremes exhibit distinct interannual or interdecadal variations. IOD, ENSO and AMO have strong impacts on monsoon and extreme precipitation, especially during the 1990s, which is generally consistent with the abrupt shifts in precipitation regimes around this period. Moreover, ENSO mainly affects moderate rainfalls and dry spells, while IOD has a more significant impact on precipitation extremes. These findings could be helpful for improving the forecasting of monsoon extremes in China and the evaluations of climate models.

  6. Coralline algal barium as indicator for 20th century northwestern North Atlantic surface ocean freshwater variability.

    Science.gov (United States)

    Hetzinger, S; Halfar, J; Zack, T; Mecking, J V; Kunz, B E; Jacob, D E; Adey, W H

    2013-01-01

    During the past decades climate and freshwater dynamics in the northwestern North Atlantic have undergone major changes. Large-scale freshening episodes, related to polar freshwater pulses, have had a strong influence on ocean variability in this climatically important region. However, little is known about variability before 1950, mainly due to the lack of long-term high-resolution marine proxy archives. Here we present the first multidecadal-length records of annually resolved Ba/Ca variations from Northwest Atlantic coralline algae. We observe positive relationships between algal Ba/Ca ratios from two Newfoundland sites and salinity observations back to 1950. Both records capture episodical multi-year freshening events during the 20th century. Variability in algal Ba/Ca is sensitive to freshwater-induced changes in upper ocean stratification, which affect the transport of cold, Ba-enriched deep waters onto the shelf (highly stratified equals less Ba/Ca). Algal Ba/Ca ratios therefore may serve as a new resource for reconstructing past surface ocean freshwater changes.

  7. Changes of extreme precipitation and nonlinear influence of climate variables over monsoon region in China

    Science.gov (United States)

    Gao, Tao; Wang, Huixia Judy; Zhou, Tianjun

    2017-11-01

    The El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO) and Pacific decadal oscillation (PDO) are well understood to be major drivers for the variability of precipitation extremes over monsoon regions in China (MRC). However, research on monsoon extremes in China and their associations with climate variables is limited. In this study, we examine the space-time variations of extreme precipitation across the MRC, and assess the time-varying influences of the climate drivers using Bayesian dynamic linear regression and their combined nonlinear effects through fitting generalized additive models. Results suggest that the central-east and south China is dominated by less frequent but more intense precipitation. Extreme rainfalls show significant positive trends, coupled with a significant decline of dry spells, indicating an increasing chance of occurrence of flood-induced disasters in the MRC during 1960-2014. Majority of the regional indices display some abrupt shifts during the 1990s. The influences of climate variables on monsoon extremes exhibit distinct interannual or interdecadal variations. IOD, ENSO and AMO have strong impacts on monsoon and extreme precipitation, especially during the 1990s, which is generally consistent with the abrupt shifts in precipitation regimes around this period. Moreover, ENSO mainly affects moderate rainfalls and dry spells, while IOD has a more significant impact on precipitation extremes. These findings could be helpful for improving the forecasting of monsoon extremes in China and the evaluations of climate models.

  8. Multi-Decadal Variability in the Bering Sea: A Synthesis of Model Results and Observations from 1948 to the Present

    Science.gov (United States)

    2013-12-01

    bottom mixed layer, sea ice thickness distribution, concentration, deformation, drift and export, fast ice , snow cover, melt ponds and surface albedo ...14. SUBJECT TERMS Oceanography, modeling, regime shifts,Pacific decadal oscillation (PDO), climate change, Bering Sea , ice , Gulf of...3 Figure 2. ICESat measurements of the distribution of winter sea ice thickness over the Arctic Ocean between 2004 and 2008

  9. Multi-decadal scale variability in the eastern Baltic cod fishery 1550-1860 - Evidence and causes

    DEFF Research Database (Denmark)

    MacKenzie, Brian; Bager, M.; Ojaveer, H.

    2007-01-01

    loading and measures to promote recovery of seal and harbour porpoise populations. If these policies are successful, the role of predatory fish in the future Baltic could again be substantial and comparable to that which we show existed 450 years ago. However, such a scenario will also require a major...

  10. Determination of the strong coupling constant αs(MZ2) under regardment of completely resummed leading and next-to-leading logarithms. Analysis of global event variables measured in hadronic Z decays

    International Nuclear Information System (INIS)

    Wehr, A.

    1994-06-01

    The value of the strong coupling constant α s is determined from a combined analysis of the global event shape variables thrust, heavy jet mass and total and wide jet broadening. The extraction of α s includes the full calculation of O(α s 2 ) terms and leading and next-to-leading logarithms resummed to all orders of α s . The analysis is based on data taken with the DELPHI detector at LEP during 1991 and 1992. The dependence of the result on the detailed matching of the resummed and fixed order terms is studied. The result from the combined theory is compared with values coming from a pure NLLA analysis and as pure O(α s 2 ) analysis, respectively. It is found that the inclusion of the resummed logarithms allows the description of the data in the two jet range and reduces the scale dependence of α s (M Z 2 ) compared to pure O(α s 2 ) theory. The value using the combined NLLA+O(α s 2 ) theory at the scale μ 2 =M Z 2 is α S (M Z 2 )=0.118±0.007. The running of α s is measured from the 1991 data in an energy range from 88.5 to 93.7 GeV. The slope of α s obtained at the Z peak is dα s /dQ/ Q=Mz =-(2.9±2.8)x10 -4 GeV -1 . This value is compatible with QCD and exludes an abelian gluon model with more than two standard deviations. (orig.)

  11. Multidecadal stability in tropical rain forest structure and dynamics across an old-growth landscape.

    Science.gov (United States)

    Clark, David B; Clark, Deborah A; Oberbauer, Steven F; Kellner, James R

    2017-01-01

    Have tropical rain forest landscapes changed directionally through recent decades? To answer this question requires tracking forest structure and dynamics through time and across within-forest environmental heterogeneity. While the impacts of major environmental gradients in soil nutrients, climate and topography on lowland tropical rain forest (TRF) structure and function have been extensively analyzed, the effects of the shorter environmental gradients typical of mesoscale TRF landscapes remain poorly understood. To evaluate multi-decadal performance of an old-growth TRF at the La Selva Biological Station, Costa Rica, we established 18 0.5-ha annually-censused forest inventory plots in a stratified-random design across major landscape edaphic gradients. Over the 17-year study period, there were moderate differences in stand dynamics and structure across these gradients but no detectable difference in woody productivity. We found large effects on forest structure and dynamics from the mega-Niño event at the outset of the study, with subdecadal recovery and subsequent stabilization. To extend the timeline to >40 years, we combined our findings with those from earlier studies at this site. While there were annual to multiannual variations in the structure and dynamics, particularly in relation to local disturbances and the mega-Niño event, at the longer temporal scale and broader spatial scale this landscape was remarkably stable. This stability contrasts notably with a current hypothesis of increasing biomass and dynamics of TRF, which we term the Bigger and Faster Hypothesis (B&FHo). We consider possible reasons for the contradiction and conclude that it is currently not possible to independently assess the vast majority of previously published B&FHo evidence due to restricted data access.

  12. Rising climate variability and synchrony in North Pacific ecosystems

    Science.gov (United States)

    Black, Bryan

    2017-04-01

    Rising climate variability and synchrony in North Pacific ecosystems Evidence is growing that climate variability of the northeast Pacific Ocean has increased over the last century, culminating in such events as the record-breaking El Niño years 1983, 1998, and 2016 and the unusually persistent 2014/15 North Pacific Ocean heat wave known as "The Blob." Of particular concern is that rising variability could increase synchrony within and among North Pacific ecosystems, which could reduce the diversity of biological responses to climate (i.e. the "portfolio effect"), diminish resilience, and leave populations more prone to extirpation. To test this phenomenon, we use a network of multidecadal fish otolith growth-increment chronologies that were strongly correlated to records of winter (Jan-Mar) sea level. These biological and physical datasets spanned the California Current through the Gulf of Alaska. Synchrony was quantified as directional changes in running (31-year window) mean pairwise correlation within sea level and then within otolith time series. Synchrony in winter sea level at the nine stations with the longest records has increased by more than 40% over the 1950-2015 interval. Likewise, synchrony among the eight longest otolith chronologies has increased more than 100% over a comparable time period. These directional changes in synchrony are highly unlikely due to chance alone, as confirmed by comparing trends in observed data to those in simulated data (n = 10,000 iterations) with time series of identical number, length, and autocorrelation. Ultimately, this trend in rising synchrony may be linked to increased impacts of the El Niño Southern Oscillation (ENSO) on mid-latitude ecosystems of North America, and may therefore reflect a much broader, global-scale signature.

  13. Multi-decade biomass dynamics in an old-growth hemlock-northern hardwood forest, Michigan, USA

    Directory of Open Access Journals (Sweden)

    Kerry D. Woods

    2014-09-01

    Full Text Available Trends in living aboveground biomass and inputs to the pool of coarse woody debris (CWD in an undisturbed, old-growth hemlock-northern hardwood forest in northern MI were estimated from multi-decade observations of permanent plots. Growth and demographic data from seven plot censuses over 47 years (1962–2009, combined with one-time measurement of CWD pools, help assess biomass/carbon status of this landscape. Are trends consistent with traditional notions of late-successional forests as equilibrial ecosystems? Specifically, do biomass pools and CWD inputs show consistent long-term trends and relationships, and can living and dead biomass pools and trends be related to forest composition and history? Aboveground living biomass densities, estimated using standard allometric relationships, range from 360–450 Mg/ha among sampled stands and types; these values are among the highest recorded for northeastern North American forests. Biomass densities showed significant decade-scale variation, but no consistent trends over the full study period (one stand, originating following an 1830 fire, showed an aggrading trend during the first 25 years of the study. Even though total above-ground biomass pools are neither increasing nor decreasing, they have been increasingly dominated, over the full study period, by very large (>70 cm dbh stems and by the most shade-tolerant species (Acer saccharum and Tsuga canadensis.CWD pools measured in 2007 averaged 151 m3/ha, with highest values in Acer-dominated stands. Snag densities averaged 27/ha, but varied nearly ten-fold with canopy composition (highest in Tsuga-dominated stands, lowest in Acer-dominated; snags constituted 10–50% of CWD biomass. Annualized CWD inputs from tree mortality over the full study period averaged 1.9–3.2 Mg/ha/yr, depending on stand and species composition. CWD input rates tended to increase over the course of the study. Input rates may be expected to increase over longer

  14. Time-Integral Correlations of Multiple Variables With the Relativistic-Electron Flux at Geosynchronous Orbit: The Strong Roles of Substorm-Injected Electrons and the Ion Plasma Sheet

    Science.gov (United States)

    Borovsky, Joseph E.

    2017-12-01

    Time-integral correlations are examined between the geosynchronous relativistic electron flux index Fe1.2 and 31 variables of the solar wind and magnetosphere. An "evolutionary algorithm" is used to maximize correlations. Time integrations (into the past) of the variables are found to be superior to time-lagged variables for maximizing correlations with the radiation belt. Physical arguments are given as to why. Dominant correlations are found for the substorm-injected electron flux at geosynchronous orbit and for the pressure of the ion plasma sheet. Different sets of variables are constructed and correlated with Fe1.2: some sets maximize the correlations, and some sets are based on purely solar wind variables. Examining known physical mechanisms that act on the radiation belt, sets of correlations are constructed (1) using magnetospheric variables that control those physical mechanisms and (2) using the solar wind variables that control those magnetospheric variables. Fe1.2-increasing intervals are correlated separately from Fe1.2-decreasing intervals, and the introduction of autoregression into the time-integral correlations is explored. A great impediment to discerning physical cause and effect from the correlations is the fact that all solar wind variables are intercorrelated and carry much of the same information about the time sequence of the solar wind that drives the time sequence of the magnetosphere.

  15. Evaluation and application of multi-decadal visibility data for trend analysis of atmospheric haze

    Directory of Open Access Journals (Sweden)

    C. Li

    2016-03-01

    Full Text Available There are few multi-decadal observations of atmospheric aerosols worldwide. This study applies global hourly visibility (Vis observations at more than 3000 stations to investigate historical trends in atmospheric haze over 1945–1996 for the US, and over 1973–2013 for Europe and eastern Asia. A comprehensive data screening and processing framework is developed and applied to minimize uncertainties and construct monthly statistics of inverse visibility (1/Vis. This data processing includes removal of relatively clean cases with high uncertainty, and change point detection to identify and separate methodological discontinuities such as the introduction of instrumentation. Although the relation between 1/Vis and atmospheric extinction coefficient (bext varies across different stations, spatially coherent trends of the screened 1/Vis data exhibit consistency with the temporal evolution of collocated aerosol measurements, including the bext trend of −2.4 % yr−1 (95 % CI: −3.7, −1.1 % yr−1 vs. 1/Vis trend of −1.6 % yr−1 (95 % CI: −2.4, −0.8 % yr−1 over the US for 1989–1996, and the fine aerosol mass (PM2.5 trend of −5.8 % yr−1 (95 % CI: −7.8, −4.2 % yr−1 vs. 1/Vis trend of −3.4 % yr−1 (95 % CI: −4.4, −2.4 % yr−1 over Europe for 2006–2013. Regional 1/Vis and Emissions Database for Global Atmospheric Research (EDGAR sulfur dioxide (SO2 emissions are significantly correlated over the eastern US for 1970–1995 (r = 0.73, over Europe for 1973–2008 (r ∼ 0.9 and over China for 1973–2008 (r ∼ 0.9. Consistent "reversal points" from increasing to decreasing in SO2 emission data are also captured by the regional 1/Vis time series (e.g., late 1970s for the eastern US, early 1980s for western Europe, late 1980s for eastern Europe, and mid 2000s for China. The consistency of 1/Vis trends with other in situ measurements and emission data demonstrates promise in applying these quality assured 1/Vis data

  16. Effect of environmental change on the morphology of tidally influenced deltas over multi-decadal timescale

    Science.gov (United States)

    Angamuthu, Balaji; Darby, Stephen; Nicholls, Robert

    2017-04-01

    An understanding of the geomorphological processes affecting deltas is essential to improve our understanding of the risks that deltas face, especially as human impacts are likely to intensify in the future. Unfortunately, there is limited reliable data on river deltas, meaning that the task of demonstrating the links between morphodynamic and environmental change is challenging. This presentation aims to answer the questions of how delta morphology evolves over multi-decadal timescales under multiple drivers, focussing on tidally-influenced deltas, as some of these, such as the Ganges-Brahmaputra-Meghna (GBM) delta are heavily populated. A series of idealised model simulations over 102 years were used to explore the influence of three key drivers on delta morphodynamics, both individually and together: (i) varying combinations of water and sediment discharges from the upstream catchment, (ii) varying rates of relative sea-level rise (RSLR), and (iii) selected human interventions within the delta, such as polders, cross-dams and changing land cover. Model simulations revealed that delta progradation rates are more sensitive to variations in water discharge than variations in fluvial sediment supply. Unlike mere aggradation during RSLR, the delta front experienced aggradational progradation due to tides. As expected, the area of the simulated sub-aerial delta increases with increasing sediment discharge, but decreases with increasing water discharge. But, human modifications are important. For example, the sub-aerial delta shrinks with increasing RSLR, but it does not when the sub-aerial delta is polderised, provided the polders are restricted from erosion. However, the polders are vulnerable to flooding as they lose relative elevation and can make the delta building process unsustainable. Cross-dams built to steer zones of land accretion within the delta accomplish their local goal, but may not result in net land gain at the scale of the delta. Applying these

  17. Hydroclimate variability: comparing dendroclimatic records and future GCM scenarios

    International Nuclear Information System (INIS)

    Lapp, S.

    2008-01-01

    Drought events of the 20th Century in western North America have been linked to teleconnections that influence climate variability on inter-annual and decadal to multi-decadal time scales. These teleconnections represent the changes sea surface temperatures (SSTs) in the tropical and extra-tropical regions of the Pacific Ocean, ENSO (El-Nino Southern Oscillation) and PDO (Pacific Decadal Oscillation), respectively, and the Atlantic Ocean, AMO (Atlantic Multidecadal Oscillation), and also to atmospheric circulation patterns (PNA: Pacific-North American). A network of precipitation sensitive tree-ring chronologies from Montana, Alberta, Saskatchewan and NWT highly correlate to the climate moisture index (CMI) of precipitation potential evapotranspiration (P-PET), thus, capturing the long-term hydroclimatic variability of the region. Reconstructions of annual and seasonal CMI identify drought events in previous centuries that are more extreme in magnitude, frequency and duration than recorded during the instrumental period. Variability in the future climate will include these natural climate cycles as well as modulations of these cycles affected by human induced global warming. The proxy hydroclimate records derived from tree-rings present information on decadal and multi-decadal hydroclimatic variability for the past millennium; therefore, providing a unique opportunity to validate the climate variability simulated by GCMs (Global Climate Models) on longer time scales otherwise constrained by the shorter observation records. Developing scenarios of future variability depends: 1) on our understanding of the interaction of these teleconnection; and, 2) to identify climate models that are able to accurately simulate the hydroclimatic variability as detected in the instrumental and proxy records. (author)

  18. Testing strong interaction theories

    International Nuclear Information System (INIS)

    Ellis, J.

    1979-01-01

    The author discusses possible tests of the current theories of the strong interaction, in particular, quantum chromodynamics. High energy e + e - interactions should provide an excellent means of studying the strong force. (W.D.L.)

  19. Past climate variability between 97 and 7 ka reconstructed from a multi proxy speleothem record from Western Cuba

    Science.gov (United States)

    Winterhalder, Sophie; Scholz, Denis; Mangini, Augusto; Spötl, Christoph; Jochum, Klaus Peter; Pajón, Jesús M.

    2016-04-01

    The tropical hydrological cycle plays a key role in regulating global climate, mainly through the export of heat and moisture to higher latitudes, and is highly sensitive to climate change, for instance due to changes in the position of the Intertropical Convergence Zone (ITCZ). Previous work on Caribbean stalagmites suggests a strong connection of precipitation variability to North Atlantic (NA) sea surface temperatures on multidecadal to millenial timescales (Fensterer et al., 2012; Fensterer et al., 2013; Winter et al., 2011). Cold phases in the NA potentially lead to a southward shift of the ITCZ and thus drier conditions in Cuba. On orbital timescales, Cuban stalagmites suggest a relation of speleothem δ18O values with the δ18O value of Caribbean surface waters (Fensterer et al., 2013). Here we present an expansion of the Cuban speleothem record covering the whole last glacial period from the end of MIS5c (97 ka BP) until 7 ka with hiatuses between 93-80 ka, 37-35 ka and 13-10 ka. Stalagmite Cuba medio (CM) has been precisely dated with 60 230Th/U-ages, mainly performed by the MC-ICPMS technique. The δ18O and δ13C records are completed by a continuous, high resolution LA-ICPMS trace element profile. These data allow for the first time to establish a multi-proxy climate reconstruction for the North Western Caribbean at decadal to centennial resolution for this period. The long-term variability of the δ18O values probably reflects rainfall amount in Cuba. The response to some Dansgaard/Oeschger and Heinrich stadials confirms the previously observed correlation between Caribbean and NA climate variability. However, this connection is not clearly imprinted throughout the record. Furthermore, trace elements, such as Mg, do not proof without ambiguity drier conditions in Cuba during NA cold events, such as the Heinrich stadials. This suggests that climate variability in Cuba was more complex during the last 100ka, and that the NA was not the only driving factor

  20. Variability of the Atlantic meridional overturning circulation in the last millennium and two IPCC scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Pablo; Montoya, Marisa; Gonzalez-Rouco, Fidel [Universidad Complutense de Madrid, Ciudad Universitaria, Dpto. Astrofisica y Ciencias de la Atmosfera/Instituto de Geociencias, Facultad de Ciencias Fisicas, Madrid (Spain); Universidad Complutense de Madrid, Ciudad Universitaria, Instituto de Geociencias (UCM-CSIC), Facultad de Ciencias Fisicas, Madrid (Spain); Mignot, Juliette [IPSL/LOCEAN, UPMC/CNRS/IRD/MNHN, Universite Pierre et Marie Curie, Paris Cedex 05 (France); Legutke, Stephanie [Deutsches Klimarechenzentrum (DKRZ), Hamburg (Germany)

    2012-05-15

    The variability of the Atlantic meridional overturning circulation (AMOC) is investigated in several climate simulations with the ECHO-G atmosphere-ocean general circulation model, including two forced integrations of the last millennium, one millennial-long control run, and two future scenario simulations of the twenty-first century. This constitutes a new framework in which the AMOC response to future climate change conditions is addressed in the context of both its past evolution and its natural variability. The main mechanisms responsible for the AMOC variability at interannual and multidecadal time scales are described. At high frequencies, the AMOC is directly responding to local changes in the Ekman transport, associated with three modes of climate variability: El Nino-Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the East Atlantic (EA) pattern. At low frequencies, the AMOC is largely controlled by convection activity south of Greenland. Again, the atmosphere is found to play a leading role in these variations. Positive anomalies of convection are preceded in 1 year by intensified zonal winds, associated in the forced runs to a positive NAO-like pattern. Finally, the sensitivity of the AMOC to three different forcing factors is investigated. The major impact is associated with increasing greenhouse gases, given their strong and persistent radiative forcing. Starting in the Industrial Era and continuing in the future scenarios, the AMOC experiences a final decrease of up to 40% with respect to the preindustrial average. Also, a weak but significant AMOC strengthening is found in response to the major volcanic eruptions, which produce colder and saltier surface conditions over the main convection regions. In contrast, no meaningful impact of the solar forcing on the AMOC is observed. Indeed, solar irradiance only affects convection in the Nordic Seas, with a marginal contribution to the AMOC variability in the ECHO-G runs. (orig.)

  1. Late Holocene sea level variability and Atlantic Meridional Overturning Circulation

    Science.gov (United States)

    Cronin, Thomas M.; Farmer, Jesse R.; Marzen, R. E.; Thomas, E.; Varekamp, J.C.

    2014-01-01

    Pre-twentieth century sea level (SL) variability remains poorly understood due to limits of tide gauge records, low temporal resolution of tidal marsh records, and regional anomalies caused by dynamic ocean processes, notably multidecadal changes in Atlantic Meridional Overturning Circulation (AMOC). We examined SL and AMOC variability along the eastern United States over the last 2000 years, using a SL curve constructed from proxy sea surface temperature (SST) records from Chesapeake Bay, and twentieth century SL-sea surface temperature (SST) relations derived from tide gauges and instrumental SST. The SL curve shows multidecadal-scale variability (20–30 years) during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), as well as the twentieth century. During these SL oscillations, short-term rates ranged from 2 to 4 mm yr−1, roughly similar to those of the last few decades. These oscillations likely represent internal modes of climate variability related to AMOC variability and originating at high latitudes, although the exact mechanisms remain unclear. Results imply that dynamic ocean changes, in addition to thermosteric, glacio-eustatic, or glacio-isostatic processes are an inherent part of SL variability in coastal regions, even during millennial-scale climate oscillations such as the MCA and LIA and should be factored into efforts that use tide gauges and tidal marsh sediments to understand global sea level rise.

  2. Variable anelastic attenuation and site effect in estimating source parameters of various major earthquakes including M w 7.8 Nepal and M w 7.5 Hindu kush earthquake by using far-field strong-motion data

    Science.gov (United States)

    Kumar, Naresh; Kumar, Parveen; Chauhan, Vishal; Hazarika, Devajit

    2017-10-01

    Strong-motion records of recent Gorkha Nepal earthquake ( M w 7.8), its strong aftershocks and seismic events of Hindu kush region have been analysed for estimation of source parameters. The M w 7.8 Gorkha Nepal earthquake of 25 April 2015 and its six aftershocks of magnitude range 5.3-7.3 are recorded at Multi-Parametric Geophysical Observatory, Ghuttu, Garhwal Himalaya (India) >600 km west from the epicentre of main shock of Gorkha earthquake. The acceleration data of eight earthquakes occurred in the Hindu kush region also recorded at this observatory which is located >1000 km east from the epicentre of M w 7.5 Hindu kush earthquake on 26 October 2015. The shear wave spectra of acceleration record are corrected for the possible effects of anelastic attenuation at both source and recording site as well as for site amplification. The strong-motion data of six local earthquakes are used to estimate the site amplification and the shear wave quality factor ( Q β) at recording site. The frequency-dependent Q β( f) = 124 f 0.98 is computed at Ghuttu station by using inversion technique. The corrected spectrum is compared with theoretical spectrum obtained from Brune's circular model for the horizontal components using grid search algorithm. Computed seismic moment, stress drop and source radius of the earthquakes used in this work range 8.20 × 1016-5.72 × 1020 Nm, 7.1-50.6 bars and 3.55-36.70 km, respectively. The results match with the available values obtained by other agencies.

  3. Trend and variability in western and central Africa streamflow, and their relation to climate variability between 1950 and 2010

    Science.gov (United States)

    Sidibe, Moussa; Dieppois, Bastien; Mahé, Gil; Paturel, Jean-Emmanuel; Rouché, Nathalie; Amoussou, Ernest; Anifowose, Babatunde; Lawler, Damian

    2017-04-01

    Unprecedented drought episodes that struck western and central Africa between the late 1960s and 1980s. This triggered many studies investigating rainfall variability and its impacts on food production systems. However, most studies were focused at the catchment scale. In this study, we examine how rainfall variability has impacted on river flow at the subcontinental scale between 1950 and 2010, as well as the key large-scale controls on this relationship. For the first time, we establish a complete, gap-filled, monthly streamflow data set, which extends from 1950 to 2010, over the western and central African region. To achieve this, we used linear regression modelling across and between 600 flow gauging stations (see initial database information at http://www.hydrosciences.fr/sierem/index_en.htm). Streamflow trend and variability are then seasonally assessed at this subcontinental scale and compared to those observed in three different rainfall data sets (i.e. CRU TS3.24, GPCC V7, IRD-HSM). Long-term trends and variability in streamflow are mainly consistent with trends in rainfall. However, these relationships may have been moderated by: i) changes in land use; and ii) contributions from groundwater resources. In particular, we note that the recent post 1990s partial recovery in Sahel rainfall could have, at least partially, positively impacted river flows (e.g. the Senegal and Niger rivers). Using multi-temporal trend and continuous wavelet analysis, the time-evolution of western and central African river flows are analysed, and are all characterized by very strong decadal fluctuations, which can be interpreted as modulations in the baseflow. These decadal fluctuations, which are also significantly detected in rainfall, are likely related to large-scale sea-surface temperature (SST) anomaly patterns, such as the tropical Atlantic SST variability, the Atlantic Multidecadal Oscillation, the Interdecadal Pacific Oscillation and/or the Pacific Decadal Oscillation

  4. Trend and variability in western and central Africa streamflow, and major drivers of variability between 1950 and 2005

    Science.gov (United States)

    Dieppois, B.; Sidibe, M.; Mahe, G. M.; Paturel, J. E.; Anifowose, B. A.; Lawler, D.; Amoussou, E.

    2017-12-01

    Unprecedented drought episodes that struck western and central Africa between the late 1960s and 1980s, triggered many studies investigating rainfall variability and its impacts on water resources and food production systems. However, most studies were focused at the catchment scale. In this study, we aim at investigating the key large-scale controls determining and modulating climate-river flows relationships at the subcontinental scale between 1950 and 2005. Using the first complete monthly streamflow data set (1950-2005) over western and central Africa, streamflow trend and variability are seasonally assessed at this subcontinental scale and compared to those observed in other hydroclimatic variables (precipitation, temperature and potential evapotranspiration). Long-term trends and variability in streamflow are mainly consistent with trends in rainfall. In particular, the recent post-1990s partial recovery in Sahel rainfall could have, at least partially, positively impacted river flows (e.g. the Senegal and Niger rivers). However, these relationships may have been moderated by: i) changes in land use; and ii) contributions from groundwater resources. In addition, the time-evolution of river flows is shown to be primarily driven by very strong decadal fluctuations, which can be interpreted as modulations in the baseflow, as determined using multi-temporal trend and continuous wavelet analysis. These decadal fluctuations, which are also significantly detected in rainfall, are likely related to large-scale sea-surface temperature (SST) anomaly patterns (such as the tropical Atlantic SST variability, the Atlantic Multidecadal Oscillation, the Interdecadal Pacific Oscillation and the Pacific Decadal Oscillation), which are together modulating the West African monsoon. Furthermore, influences of the catchment properties (e.g. size, vegetation and land use cover, soil properties, direction of stream flow across climate zones) on these decadal fluctuations in river

  5. Abrupt millennial variability and interdecadal-interstadial oscillations in a global coupled model: sensitivity to the background climate state

    Energy Technology Data Exchange (ETDEWEB)

    Arzel, Olivier [The University of New South Wales, Climate Change Research Centre (CCRC), Sydney (Australia); Universite de Bretagne Occidentale, Laboratoire de Physique des Oceans (LPO), Brest (France); England, Matthew H. [The University of New South Wales, Climate Change Research Centre (CCRC), Sydney (Australia); Verdiere, Alain Colin de; Huck, Thierry [Universite de Bretagne Occidentale, Laboratoire de Physique des Oceans (LPO), Brest (France)

    2012-07-15

    The origin and bifurcation structure of abrupt millennial-scale climate transitions under steady external solar forcing and in the absence of atmospheric synoptic variability is studied by means of a global coupled model of intermediate complexity. We show that the origin of Dansgaard-Oeschger type oscillations in the model is caused by the weaker northward oceanic heat transport in the Atlantic basin. This is in agreement with previous studies realized with much simpler models, based on highly idealized geometries and simplified physics. The existence of abrupt millennial-scale climate transitions during glacial times can therefore be interpreted as a consequence of the weakening of the negative temperature-advection feedback. This is confirmed through a series of numerical experiments designed to explore the sensitivity of the bifurcation structure of the Atlantic meridional overturning circulation to increased atmospheric CO{sub 2} levels under glacial boundary conditions. Contrasting with the cold, stadial, phases of millennial oscillations, we also show the emergence of strong interdecadal variability in the North Atlantic sector during warm interstadials. The instability driving these interdecadal-interstadial oscillations is shown to be identical to that found in ocean-only models forced by fixed surface buoyancy fluxes, that is, a large-scale baroclinic instability developing in the vicinity of the western boundary current in the North Atlantic. Comparisons with modern observations further suggest a physical mechanism similar to that driving the 30-40 years time scale associated with the Atlantic multidecadal oscillation. (orig.)

  6. Enhancement of Interdecadal Climate Variability in the Sahel by Vegetation Interaction.

    Science.gov (United States)

    Zeng; Neelin; Lau; Tucker

    1999-11-19

    The role of naturally varying vegetation in influencing the climate variability in the West African Sahel is explored in a coupled atmosphere-land-vegetation model. The Sahel rainfall variability is influenced by sea-surface temperature variations in the oceans. Land-surface feedback is found to increase this variability both on interannual and interdecadal time scales. Interactive vegetation enhances the interdecadal variation substantially but can reduce year-to-year variability because of a phase lag introduced by the relatively slow vegetation adjustment time. Variations in vegetation accompany the changes in rainfall, in particular the multidecadal drying trend from the 1950s to the 1980s.

  7. The forcing of southwestern Asia teleconnections by low-frequency sea surface temperature variability during boreal winter

    Science.gov (United States)

    Hoell, Andrew; Funk, Christopher C.; Mathew Barlow,

    2015-01-01

    Southwestern Asia, defined here as the domain bounded by 20°–40°N and 40°–70°E, which includes the nations of Iraq, Iran, Afghanistan, and Pakistan, is a water-stressed and semiarid region that receives roughly 75% of its annual rainfall during November–April. The November–April climate of southwestern Asia is strongly influenced by tropical Indo-Pacific variability on intraseasonal and interannual time scales, much of which can be attributed to sea surface temperature (SST) variations. The influences of lower-frequency SST variability on southwestern Asia climate during November–April Pacific decadal SST (PDSST) variability and the long-term trend in SST (LTSST) is examined. The U.S. Climate Variability and Predictability Program (CLIVAR) Drought Working Group forced global atmospheric climate models with PDSST and LTSST patterns, identified using empirical orthogonal functions, to show the steady atmospheric response to these modes of decadal to multidecadal SST variability. During November–April, LTSST forces an anticyclone over southwestern Asia, which results in reduced precipitation and increases in surface temperature. The precipitation and tropospheric circulation influences of LTSST are corroborated by independent observed precipitation and circulation datasets during 1901–2004. The decadal variations of southwestern Asia precipitation may be forced by PDSST variability, with two of the three models indicating that the cold phase of PDSST forces an anticyclone and precipitation reductions. However, there are intermodel circulation variations to PDSST that influence subregional precipitation patterns over the Middle East, southwestern Asia, and subtropical Asia. Changes in wintertime temperature and precipitation over southwestern Asia forced by LTSST and PDSST imply important changes to the land surface hydrology during the spring and summer.

  8. Strongly Correlated Topological Insulators

    Science.gov (United States)

    2016-02-03

    Strongly Correlated Topological Insulators In the past year, the grant was used for work in the field of topological phases, with emphasis on finding...surface of topological insulators. In the past 3 years, we have started a new direction, that of fractional topological insulators. These are materials...in which a topologically nontrivial quasi-flat band is fractionally filled and then subject to strong interactions. The views, opinions and/or

  9. Strongly nonlinear oscillators analytical solutions

    CERN Document Server

    Cveticanin, Livija

    2014-01-01

    This book provides the presentation of the motion of pure nonlinear oscillatory systems and various solution procedures which give the approximate solutions of the strong nonlinear oscillator equations. The book presents the original author’s method for the analytical solution procedure of the pure nonlinear oscillator system. After an introduction, the physical explanation of the pure nonlinearity and of the pure nonlinear oscillator is given. The analytical solution for free and forced vibrations of the one-degree-of-freedom strong nonlinear system with constant and time variable parameter is considered. Special attention is given to the one and two mass oscillatory systems with two-degrees-of-freedom. The criteria for the deterministic chaos in ideal and non-ideal pure nonlinear oscillators are derived analytically. The method for suppressing chaos is developed. Important problems are discussed in didactic exercises. The book is self-consistent and suitable as a textbook for students and also for profess...

  10. Strong Cosmic Censorship

    Science.gov (United States)

    Isenberg, James

    2017-01-01

    The Hawking-Penrose theorems tell us that solutions of Einstein's equations are generally singular, in the sense of the incompleteness of causal geodesics (the paths of physical observers). These singularities might be marked by the blowup of curvature and therefore crushing tidal forces, or by the breakdown of physical determinism. Penrose has conjectured (in his `Strong Cosmic Censorship Conjecture`) that it is generically unbounded curvature that causes singularities, rather than causal breakdown. The verification that ``AVTD behavior'' (marked by the domination of time derivatives over space derivatives) is generically present in a family of solutions has proven to be a useful tool for studying model versions of Strong Cosmic Censorship in that family. I discuss some of the history of Strong Cosmic Censorship, and then discuss what is known about AVTD behavior and Strong Cosmic Censorship in families of solutions defined by varying degrees of isometry, and discuss recent results which we believe will extend this knowledge and provide new support for Strong Cosmic Censorship. I also comment on some of the recent work on ``Weak Null Singularities'', and how this relates to Strong Cosmic Censorship.

  11. Last 150-year variability in Japanese anchovy ( Engraulis japonicus) abundance based on the anaerobic sediments of the Yellow Sea Basin in the western North Pacific

    Science.gov (United States)

    Huang, Jiansheng; Sun, Yao; Jia, Haibo; Tang, Qisheng

    2016-02-01

    Relatively short historical catch records show that anchovy populations have exhibited large variability over multi-decadal timescales. In order to understand the driving factors (anthropogenic and/or natural) of such variability, it is essential to develop long-term time series of the population prior to the occurrence of notable anthropogenic impact. Well-preserved fish scales in the sediments are regarded as useful indicators reflecting the fluctuations of fish populations over the last centuries. This study aims to validate the anchovy scale deposition rate as a proxy of local anchovy biomass in the Yellow Sea adjoining the western North Pacific. Our reconstructed results indicated that over the last 150 years, the population size of anchovy in the Yellow Sea has exhibited great fluctuations with periodicity of around 50 years, and the pattern of current recovery and collapse is similar to that of historical records. The pattern of large-scale population synchrony with remote ocean basins provides further evidence proving that fish population dynamics are strongly affected by global and basin-scale oceanic/climatic variability.

  12. Long-term hydroclimatic variability in monsoon shadow zone of western Himalaya, India

    Science.gov (United States)

    Yadav, Ram R.

    2011-04-01

    Tree-ring-width data of Himalayan cedar [ Cedrus deodara (Roxb.) G. Don] from 11 homogeneous moisture stressed sites in the monsoon shadow zone of the western Himalaya were used to develop a mean chronology extending back to ad 1353. The chronology developed using Regional Curve Standardization method is the first from the Himalayan region of India showing centennial-scale variations. The calibration of ring-width chronology with instrumental precipitation data available from stations close to the tree ring sampling sites showed strong, direct relationship with March-April-May-June (MAMJ) precipitation. This strong relationship was used to supplement the instrumental precipitation data back to ad 1410. The precipitation reconstruction showed extended period of drought in fifteenth and sixteenth centuries. Increasingly pluvial conditions were recorded since eighteenth century, with the highest precipitation in the early part of the nineteenth century. The decreasing trend in reconstructed precipitation in the last decade of the twentieth century, consistent with the instrumental records, is associated with the decreasing trend in frequency of western disturbances. MAMJ precipitation over the monsoon shadow zone in the western Himalaya is directly associated with the North Atlantic Oscillation (NAO) and NINO3-SST index of El Nino-Southern Oscillation (ENSO), the leading modes of climate variability influencing climate over large parts of the Northern Hemisphere. However, the relationship between ENSO and MAMJ precipitation collapsed completely during 1930-1960. The breakdown in this relationship is associated with the warm phase of Atlantic Multidecadal Oscillation (AMO). A spectral analysis of reconstructed MAMJ precipitation indicates frequencies in the range of the variability associated with modes of NAO, ENSO and AMO.

  13. Long-term hydroclimatic variability in monsoon shadow zone of western Himalaya, India

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Ram R. [Birbal Sahni Institute of Palaeobotany, Lucknow (India)

    2011-04-15

    Tree-ring-width data of Himalayan cedar [Cedrus deodara (Roxb.) G. Don] from 11 homogeneous moisture stressed sites in the monsoon shadow zone of the western Himalaya were used to develop a mean chronology extending back to ad 1353. The chronology developed using Regional Curve Standardization method is the first from the Himalayan region of India showing centennial-scale variations. The calibration of ring-width chronology with instrumental precipitation data available from stations close to the tree ring sampling sites showed strong, direct relationship with March-April-May-June (MAMJ) precipitation. This strong relationship was used to supplement the instrumental precipitation data back to ad 1410. The precipitation reconstruction showed extended period of drought in fifteenth and sixteenth centuries. Increasingly pluvial conditions were recorded since eighteenth century, with the highest precipitation in the early part of the nineteenth century. The decreasing trend in reconstructed precipitation in the last decade of the twentieth century, consistent with the instrumental records, is associated with the decreasing trend in frequency of western disturbances. MAMJ precipitation over the monsoon shadow zone in the western Himalaya is directly associated with the North Atlantic Oscillation (NAO) and NINO3-SST index of El Nino-Southern Oscillation (ENSO), the leading modes of climate variability influencing climate over large parts of the Northern Hemisphere. However, the relationship between ENSO and MAMJ precipitation collapsed completely during 1930-1960. The breakdown in this relationship is associated with the warm phase of Atlantic Multidecadal Oscillation (AMO). A spectral analysis of reconstructed MAMJ precipitation indicates frequencies in the range of the variability associated with modes of NAO, ENSO and AMO. (orig.)

  14. An analysis of surface air temperature trends and variability along the Andes

    Science.gov (United States)

    Franquist, Eric S.

    Climate change is difficult to study in mountainous regions such as the Andes since steep changes in elevation cannot always be resolved by climate models. However, it is important to examine temperature trends in this region as rises in surface air temperature are leading to the melting of tropical glaciers. Local communities rely on the glacier-fed streamflow to get their water for drinking, irrigation, and livestock. Moreover, communities also rely on the tourism of hikers who come to the region to view the glaciers. As the temperatures increase, these glaciers are no longer in equilibrium with their current climate and are receding rapidly and decreasing the streamflow. This thesis examines surface air temperature from 858 weather stations across Ecuador, Peru, and Chile in order to analyze changes in trends and variability. Three time periods were studied: 1961--1990, 1971--2000, and 1981--2010. The greatest warming occurred during the period of 1971--2000 with 92% of the stations experiencing positive trends with a mean of 0.24°C/decade. There was a clear shift toward cooler temperatures at all latitudes and below elevations of 500 m during the most recent time period studied (1981--2010). Station temperatures were more strongly correlated with the El Nino Southern Oscillation (ENSO), than the Pacific Decadal Oscillation (PDO), and the Southern Annular Mode (SAM). A principal component analysis confirmed ENSO as the main contributor of variability with the most influence in the lower latitudes. There were clear multidecadal changes in correlation strength for the PDO. The PDO contributed the most to the increases in station temperature trends during the 1961--1990 period, consistent with the PDO shift to the positive phase in the middle of this period. There were many strong positive trends at individual stations during the 1971--2000 period; however, these trends could not fully be attributed to ENSO, PDO, or SAM, indicating anthropogenic effects of

  15. Strong Arcwise Connectedness

    OpenAIRE

    Espinoza, Benjamin; Gartside, Paul; Kovan-Bakan, Merve; Mamatelashvili, Ana

    2012-01-01

    A space is `n-strong arc connected' (n-sac) if for any n points in the space there is an arc in the space visiting them in order. A space is omega-strong arc connected (omega-sac) if it is n-sac for all n. We study these properties in finite graphs, regular continua, and rational continua. There are no 4-sac graphs, but there are 3-sac graphs and graphs which are 2-sac but not 3-sac. For every n there is an n-sac regular continuum, but no regular continuum is omega-sac. There is an omega-sac ...

  16. Abortion: Strong's counterexamples fail

    DEFF Research Database (Denmark)

    Di Nucci, Ezio

    2009-01-01

    This paper shows that the counterexamples proposed by Strong in 2008 in the Journal of Medical Ethics to Marquis's argument against abortion fail. Strong's basic idea is that there are cases--for example, terminally ill patients--where killing an adult human being is prima facie seriously morally......'s scenarios have some valuable future or admitted that killing them is not seriously morally wrong. Finally, if "valuable future" is interpreted as referring to objective standards, one ends up with implausible and unpalatable moral claims....

  17. Caribbean Brain coral tracks the Atlantic Multidecadal Oscillation and Past Hurricane Intensity

    NARCIS (Netherlands)

    Hetzinger, S.; Pfeiffer, M.; Dullo, W.-C.; Keenlyside, N.; Latif, M.; Zinke, J.

    2008-01-01

    It is highly debated whether global warming contributed to the strong hurricane activity observed during the last decade. The crux of the recent debate is the limited length of the reliable instrumental record that exacerbates the detection of possible long-term changes in hurricane activity, which

  18. An experimental study of the Atlantic variability on interdecadal timescales

    Directory of Open Access Journals (Sweden)

    M. Vincze

    2012-06-01

    Full Text Available A series of laboratory experiments has been carried out to model the basic dynamics of the multidecadal variability observed in North Atlantic sea surface temperature (SST records. According to the minimal numerical sector model introduced by te Raa and Dijkstra (2002, the three key components to excite such a low-frequency variability are rotation, meridional temperature gradient and additive thermal noise in the surface heat forcing. If these components are present, periodic perturbations of the overturning background flow are excited, leading to thermal Rossby mode like propagation of anomalous patches in the SST field. Our tabletop scale setup was built to capture this phenomenon, and to test whether the aforementioned three components are indeed sufficient to generate a low-frequency variability in the system. The results are compared to those of the numerical models, as well as to oceanic SST reanalysis records. To the best of our knowledge, the experiment described here is the very first to investigate the dynamics of the North Atlantic multidecadal variability in a laboratory-scale setup.

  19. Quantifying the increasing sensitivity of power systems to climate variability

    Science.gov (United States)

    Bloomfield, H. C.; Brayshaw, D. J.; Shaffrey, L. C.; Coker, P. J.; Thornton, H. E.

    2016-12-01

    Large quantities of weather-dependent renewable energy generation are expected in power systems under climate change mitigation policies, yet little attention has been given to the impact of long term climate variability. By combining state-of-the-art multi-decadal meteorological records with a parsimonious representation of a power system, this study characterises the impact of year-to-year climate variability on multiple aspects of the power system of Great Britain (including coal, gas and nuclear generation), demonstrating why multi-decadal approaches are necessary. All aspects of the example system are impacted by inter-annual climate variability, with the impacts being most pronounced for baseload generation. The impacts of inter-annual climate variability increase in a 2025 wind-power scenario, with a 4-fold increase in the inter-annual range of operating hours for baseload such as nuclear. The impacts on peak load and peaking-plant are comparably small. Less than 10 years of power supply and demand data are shown to be insufficient for providing robust power system planning guidance. This suggests renewable integration studies—widely used in policy, investment and system design—should adopt a more robust approach to climate characterisation.

  20. A strong comeback

    International Nuclear Information System (INIS)

    Marier, D.

    1992-01-01

    This article presents the results of a financial rankings survey which show a strong economic activity in the independent energy industry. The topics of the article include advisor turnover, overseas banks, and the increase in public offerings. The article identifies the top project finance investors for new projects and restructurings and rankings for lenders

  1. Decadal variability of the Tropical Atlantic Ocean Surface Temperature in shipboard measurements and in a Global Ocean-Atmosphere model

    Science.gov (United States)

    Mehta, Vikram M.; Delworth, Thomas

    1995-01-01

    Sea surface temperature (SST) variability 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 decadal and multidecadal variability but at somewhat shorter timescales than the GOSTA SST anomalies. Further analyses of the horizontal structures of the decadal timescale variability in the GFDL coupled model showed the existence of two types of variability 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 variability is considerably weaker than the first. As in the GOSTA time series, the multidecadal variability 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 decadal variability. It is suggested that the bipolar pattern can be interpreted as decadal variability of the interhemispheric gradient of SST anomalies. The decadal and multidecadal timescale variability 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

  2. Present and Future Modes of Low Frequency Climate Variability

    Energy Technology Data Exchange (ETDEWEB)

    Cane, Mark A.

    2014-02-20

    This project addressed area (1) of the FOA, “Interaction of Climate Change and Low Frequency Modes of Natural Climate Variability”. Our overarching objective is to detect, describe and understand the changes in low frequency variability between model simulations of the preindustrial climate and simulations of a doubled CO2 climate. The deliverables are a set of papers providing a dynamical characterization of interannual, decadal, and multidecadal variability in coupled models with attention to the changes in this low frequency variability between pre-industrial concentrations of greenhouse gases and a doubling of atmospheric concentrations of CO2. The principle mode of analysis, singular vector decomposition, is designed to advance our physical, mechanistic understanding. This study will include external natural variability due to solar and volcanic aerosol variations as well as variability internal to the climate system. An important byproduct is a set of analysis tools for estimating global singular vector structures from the archived output of model simulations.

  3. Response of Ponderosa Pine to Variable Scale Climate Influences, Salmon River Canyon, Idaho

    Science.gov (United States)

    Wilkins, D. E.; Kaplan, S. W.; Keim, R.; Grissino-Mayer, H.

    2005-12-01

    Growth of trees in sparse stands on low-productivity sites is often strongly controlled by climate variation. We examined tree rings in cores collected from 73 ponderosa pine trees (Pinus ponderosa) at a dry upland site near the confluence of French Creek and the main fork of the Salmon River. Cores were mounted, processed, and visually and statistically cross-dated following standard dendrochronological methods. Ultimately, 41 tree-ring measurement series with a continuous time span of 278 years were used to create ring-width indices of tree growth for the site. These indices were tested against annual and monthly climatic variables. Simultaneous dating of fires scars from trees and snags at the site enabled reconstruction of a 160-year fire history. There were strong (pring width indices and annual Palmer Drought Severity Index (PDSI) and precipitation, indicating trees grew best in wet years. Strongest correlations with monthly climate variables were for prior-year fall and winter temperature and precipitation, as well as November to April snow water equivalent (SWE). The seasonal variable found most strongly correlated with tree growth was September-January total precipitation, most of which falls as snow at this site, which explained 34 percent of the total variance in annual ring widths. The strong relationship with monthly SWE is corollary to the relationship observed in the fall-winter precipitation, but high correlation with SWE in April and May underscores the positive influence of late season snowpack on current year summer growth. The occurrence of fires was greater during years with low precipitation and high PDSI, but growth responses to climate variables were not affected by fires. Although no significant correlation existed between tree growth and Pacific Decadal Oscillation Index, teleconnections with oceanic climatic influences were present in a positive relationship with the Atlantic Multidecadal Oscillation Index. The AMO was also correlated to

  4. Strong Electroweak Symmetry Breaking

    CERN Document Server

    Grinstein, Benjamin

    2011-01-01

    Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor,...

  5. Plasmons in strong superconductors

    International Nuclear Information System (INIS)

    Baldo, M.; Ducoin, C.

    2011-01-01

    We present a study of the possible plasmon excitations that can occur in systems where strong superconductivity is present. In these systems the plasmon energy is comparable to or smaller than the pairing gap. As a prototype of these systems we consider the proton component of Neutron Star matter just below the crust when electron screening is not taken into account. For the realistic case we consider in detail the different aspects of the elementary excitations when the proton, electron components are considered within the Random-Phase Approximation generalized to the superfluid case, while the influence of the neutron component is considered only at qualitative level. Electron screening plays a major role in modifying the proton spectrum and spectral function. At the same time the electron plasmon is strongly modified and damped by the indirect coupling with the superfluid proton component, even at moderately low values of the gap. The excitation spectrum shows the interplay of the different components and their relevance for each excitation modes. The results are relevant for neutrino physics and thermodynamical processes in neutron stars. If electron screening is neglected, the spectral properties of the proton component show some resemblance with the physical situation in high-T c superconductors, and we briefly discuss similarities and differences in this connection. In a general prospect, the results of the study emphasize the role of Coulomb interaction in strong superconductors.

  6. Diverse multi-decadal changes in streamflow within a rapidly urbanizing region

    Science.gov (United States)

    Diem, Jeremy E.; Hill, T. Chee; Milligan, Richard A.

    2018-01-01

    The impact of urbanization on streamflow depends on a variety of factors (e.g., climate, initial land cover, inter-basin transfers, water withdrawals, wastewater effluent, etc.). The purpose of this study is to examine trends in streamflow from 1986 to 2015 in a range of watersheds within the rapidly urbanizing Atlanta, GA metropolitan area. This study compares eight watersheds over three decades, while minimizing the influence of inter-annual precipitation variability. Population and land-cover data were used to analyze changes over approximately twenty years within the watersheds. Precipitation totals for the watersheds were estimated using precipitation totals at nearby weather stations. Multiple streamflow variables, such as annual streamflow, frequencies of high-flow days (HFDs), flashiness, and precipitation-adjusted streamflow, for the eight streams were calculated using daily streamflow data. Variables were tested for significant trends from 1986 to 2015 and significant differences between 1986-2000 and 2001-2015. Flashiness increased for all streams without municipal water withdrawals, and the four watersheds with the largest increase in developed land had significant increases in flashiness. Significant positive trends in precipitation-adjusted mean annual streamflow and HFDs occurred for the two watersheds (Big Creek and Suwanee Creek) that experienced the largest increases in development, and these were the only watersheds that went from majority forest land in 1986 to majority developed land in 2015. With a disproportionate increase in HFD occurrence during summer, Big Creek and Suwannee Creek also had a reduction in intra-annual variability of HFD occurrence. Watersheds that were already substantially developed at the beginning of the period and did not have wastewater discharge had declining streamflow. The most urbanized watershed (Peachtree Creek) had a significant decrease in streamflow, and a possible cause of the decrease was increasing

  7. How does Atlantic Multi-decadal Overturning Circulation modulate Tropical circulation and preciptation responses to global warming ?

    Science.gov (United States)

    Vial, Jessica; Codron, Francis; Cassou, Christophe; Bony, Sandrine

    2017-04-01

    Tropical precipitation response to global warming remains highly uncertain. Most of the uncertainty is attributed to inter-model spread in atmospheric circulation changes. Model diversity in tropical circulation response has been traced further to differences in Tropical surface warming patterns, and in particular to the location of the maximum increase in the Equatorial Pacific. The involved mechanisms point to the importance of ocean-atmosphere interactions assessed through several process metrics. Here, we investigate the role of the Atlantic Multi-decadal Overturning Circulation (AMOC) in the response of the Tropical circulation to increased greenhouse gazes concentration. AMOC has been shown to affect the global Tropics, including the Equatorial surface warming pattern through atmospheric bridges across Central and/or North America. We use two ensembles of the coupled (ocean-atmosphere) CNRM-CM5 climate model that differ from their mean AMOC and apply an abrupt doubling CO2 concentration in both cases. Beyond the modulation role of AMOC in the Tropical circulation and precipitation changes, we show that AMOC has a potential effect on the estimation of the climate sensitivity of the model.

  8. Using the Convergent Cross Mapping method to test causality between Arctic Oscillation / North Atlantic Oscillation and Atlantic Multidecadal Oscillation

    Science.gov (United States)

    Gutowska, Dorota; Piskozub, Jacek

    2017-04-01

    There is a vast literature body on the climate indices and processes they represent. A large part of it deals with "teleconnections" or causal relations between them. However until recently time lagged correlations was the best tool of studying causation. However no correlation (even lagged) proves causation. We use a recently developed method of studying casual relations between short time series, Convergent Cross Mapping (CCM), to search for causation between the atmospheric (AO and NAO) and oceanic (AMO) indices. The version we have chosen (available as an R language package rEDM) allows for comparing time series with time lags. This work builds on previous one, showing with time-lagged correlations that AO/NAO precedes AMO by about 15 years and at the same time is preceded by AMO (but with an inverted sign) also by the same amount of time. This behaviour is identical to the relationship of a sine and cosine with the same period. This may suggest that the multidecadal oscillatory parts of the atmospheric and oceanic indices represent the same global-scale set of processes. In other words they may be symptoms of the same oscillation. The aim of present study is to test this hypothesis with a tool created specially for discovering causal relationships in dynamic systems.

  9. Strong-coupling approximations

    International Nuclear Information System (INIS)

    Abbott, R.B.

    1984-03-01

    Standard path-integral techniques such as instanton calculations give good answers for weak-coupling problems, but become unreliable for strong-coupling. Here we consider a method of replacing the original potential by a suitably chosen harmonic oscillator potential. Physically this is motivated by the fact that potential barriers below the level of the ground-state energy of a quantum-mechanical system have little effect. Numerically, results are good, both for quantum-mechanical problems and for massive phi 4 field theory in 1 + 1 dimensions. 9 references, 6 figures

  10. Strong interaction and QFD

    International Nuclear Information System (INIS)

    Ebata, T.

    1981-01-01

    With an assumed weak multiplet structure for bosonic hadrons, which is consistent with the ΔI = 1/2 rule, it is shown that the strong interaction effective hamiltonian is compatible with the weak SU(2) x U(1) gauge transformation. Especially the rho-meson transforms as a triplet under SU(2)sub(w), and this is the origin of the rho-photon analogy. It is also shown that the existence of the non-vanishing Cabibbo angle is a necessary condition for the absence of the exotic hadrons. (orig.)

  11. Sea surface temperature variability in the North Western Mediterranean Sea (Gulf of Lion) during the Common Era

    Science.gov (United States)

    Sicre, Marie-Alexandrine; Jalali, Bassem; Martrat, Belen; Schmidt, Sabine; Bassetti, Maria-Angela; Kallel, Nejib

    2016-12-01

    This study investigates the multidecadal-scale variability of sea surface temperatures (SSTs) in the convection region of the Gulf of Lion (NW Mediterranean Sea) over the full past 2000 yr (Common Era) using alkenone biomarkers. Our data show colder SSTs by 1.7 °C over most of the first millennium (200-800 AD) and by 1.3 °C during the Little Ice Age (LIA; 1400-1850 AD) than the 20th century mean (17.9 °C). Although on average warmer, those of the Medieval Climate Anomaly (MCA) (1000-1200 AD) were lower by 1 °C. We found a mean SST warming of 2 °C/100 yr over the last century in close agreement with the 0.22 and 0.26 °C/decade values calculated for the western Mediterranean Sea from in situ and satellite data, respectively. Our results also reveal strongly fluctuating SSTs characterized by cold extremes followed by abrupt warming during the LIA. We suggest that the coldest decades of the LIA were likely caused by prevailing negative EA states and associated anticyclone blocking over the North Atlantic resulting in cold continental northeasterly winds to blow over Western Europe and the Mediterranean region.

  12. Strong Coupling Holography

    CERN Document Server

    Dvali, Gia

    2009-01-01

    We show that whenever a 4-dimensional theory with N particle species emerges as a consistent low energy description of a 3-brane embedded in an asymptotically-flat (4+d)-dimensional space, the holographic scale of high-dimensional gravity sets the strong coupling scale of the 4D theory. This connection persists in the limit in which gravity can be consistently decoupled. We demonstrate this effect for orbifold planes, as well as for the solitonic branes and string theoretic D-branes. In all cases the emergence of a 4D strong coupling scale from bulk holography is a persistent phenomenon. The effect turns out to be insensitive even to such extreme deformations of the brane action that seemingly shield 4D theory from the bulk gravity effects. A well understood example of such deformation is given by large 4D Einstein term in the 3-brane action, which is known to suppress the strength of 5D gravity at short distances and change the 5D Newton's law into the four-dimensional one. Nevertheless, we observe that the ...

  13. LIGO: The strong belief

    CERN Multimedia

    Antonella Del Rosso

    2016-01-01

    Twenty years of designing, building and testing a number of innovative technologies, with the strong belief that the endeavour would lead to a historic breakthrough. The Bulletin publishes an abstract of the Courier’s interview with Barry Barish, one of the founding fathers of LIGO.   The plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington. (Image: Caltech/MIT/LIGO Lab) On 11 February, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations published a historic paper in which they showed a gravitational signal emitted by the merger of two black holes. These results come after 20 years of hard work by a large collaboration of scientists operating the two LIGO observatories in the US. Barry Barish, Linde Professor of Physics, Emeritus at the California Institute of Technology and former Director of the Global Design Effort for the Internat...

  14. Multi-decadal storminess fluctuations of Black Sea due to North Atlantic Oscillation

    Science.gov (United States)

    Kuznetsov, Sergey; Saprykina, Yana; Grigorieva, Victoria; Aydoǧan, Berna; Aydoǧan, Burak

    2017-04-01

    Storminess variability is of key importance for many marine applications, naval and coastal engineering. Studying the evolution of this phenomenon along with large scale atmospheric patterns and being able to predict them is crucial for in the context of rising sea level due to climate change what make the low-lying coasts in the Black Sea to become increasingly vulnerable to marine hazards. The aim of this work is to clarify the trends, statistics and reasons of variations of storminess in dependence of such climatic characteristic as NAO (North Atlantic Oscillation Index). The analysis of Black Sea storminess activity was performed on the base of visual wave observations (Voluntary Observing Ship or VOS) for the period 1970-2011. Annual means and maximum heights of wind-driven seas and swell waves averaging over whole Black Sea area were investigated separately. The both wind-driven seas and swell demonstrate the decreasing in heights about 10% the same as their periods for the chosen time frame. Parametric spectral analysis was performed. The periods of wave height fluctuations for wind-driven seas and swell were shown to coincide with each other and with periods of low frequency fluctuation of NOA: 14 and 4 year respectively. Correlation coefficients of wave height and NOA were 0.3 for swell and 0.4 for wind-driven sea. Nonlinear regularities of NAO fluctuations were investigated using wavelet and spavlet (spectra of modules of wavelet coefficients) analyses. Their influence on variability of storminess in Black Sea is discussed. The reported study was funded by RFBR (project No. 16-55-76002 ERA_a) and by TUBITAK (project No. 116M061) in frame of BS STEMA project.

  15. Multi-decadal variation in size of juvenile Summer Flounder (Paralichthys dentatus) in Chesapeake Bay

    Science.gov (United States)

    Nys, Lauren N.; Fabrizio, Mary C.; Tuckey, Troy D.

    2016-01-01

    During the last quarter-century, management of Summer Flounder Paralichthys dentatus along the Atlantic coast resulted in significant increases in abundance such that rebuilding targets were recently achieved. Although spawning stock biomass is high, recruitment of young-of-the-year (YOY) Summer Flounder remains variable. Chesapeake Bay is one of the principal nursery areas for this species, but processes such as growth and survival that affect production of YOY Summer Flounder in this estuary have not been explored. Here, we investigated the relationship between abundance and size of Summer Flounder recruits from the 1988 to 2012 year classes in Chesapeake Bay. We also considered the effects of environmental factors on fish size because conditions in the bay vary spatially during the time that fish occupy nursery areas. To describe variations in Summer Flounder size, we used monthly length observations from 13,018 YOY fish captured by bottom trawl from the lower Chesapeake Bay and the James, York, and Rappahannock river subestuaries where Summer Flounder are commonly observed. We applied a generalized additive model to describe spatial, temporal, and environmental effects on observed fish size; we also considered the density of Summer Flounder and an index of productivity as factors in the model. Summer Flounder in Chesapeake Bay exhibited density-dependent and spatially related variations in mean length: larger fish were found mostly in the Bay and smaller fish in the subestuaries. Additionally, low ( 26 °C) temperatures and low salinities (indicating that individuals found in these environments were typically smaller than conspecifics inhabiting areas of moderate temperatures and higher salinities. Variable nursery habitat conditions in temperate estuaries affect fish size and, subsequently, may influence production of Summer Flounder year classes through effects on maturation and survival. As water temperatures in the mid-Atlantic region continue to increase

  16. Teleconnection stationarity, variability and trends of the Southern Annular Mode (SAM) during the last millennium

    Science.gov (United States)

    Dätwyler, Christoph; Neukom, Raphael; Abram, Nerilie J.; Gallant, Ailie J. E.; Grosjean, Martin; Jacques-Coper, Martín; Karoly, David J.; Villalba, Ricardo

    2017-11-01

    The Southern Annular Mode (SAM) is the leading mode of atmospheric interannual variability in the Southern Hemisphere (SH) extra-tropics. Here, we assess the stationarity of SAM spatial correlations with instrumental and paleoclimate proxy data for the past millennium. The instrumental period shows that temporal non-stationarities in SAM teleconnections are not consistent across the SH land areas. This suggests that the influence of the SAM index is modulated by regional effects. However, within key-regions with good proxy data coverage (South America, Tasmania, New Zealand), teleconnections are mostly stationary over the instrumental period. Using different stationarity criteria for proxy record selection, we provide new austral summer and annual mean SAM index reconstructions over the last millennium. Our summer SAM reconstructions are very robust to changes in proxy record selection and the selection of the calibration period, particularly on the multi-decadal timescale. In contrast, the weaker performance and lower agreement in the annual mean SAM reconstructions point towards changing teleconnection patterns that may be particularly important outside the summer months. Our results clearly portend that the temporal stationarity of the proxy-climate relationships should be taken into account in the design of comprehensive regional and hemispherical climate reconstructions. The summer SAM reconstructions show no significant relationship to solar, greenhouse gas and volcanic forcing, with the exception of an extremely strong negative anomaly following the AD 1257 Samalas eruption. Furthermore, reconstructed pre-industrial summer SAM trends are very similar to trends obtained by model control simulations. We find that recent trends in the summer SAM lie outside the 5-95% range of pre-industrial natural variability.

  17. Twentieth century Sahel rainfall variability as simulated by the ARPEGE AGCM, and future changes

    Energy Technology Data Exchange (ETDEWEB)

    Caminade, C.; Terray, L. [CERFACS, Toulouse-Cedex (France)

    2010-07-15

    The ability of the ARPEGE AGCM in reproducing the twentieth century Sahelian drought when only forced by observed SST time evolution has been characterized. Atmospheric internal variability is shown to have a strong contribution in driving the simulated precipitation variability over the Sahel at decadal to multi-decadal time scales. The simulated drought is associated with a southward shift of the continental rainbelt over central and eastern Sahel, associated with an inter-hemispheric SST mode (the southern hemisphere oceans warming faster than the northern ones after 1970). The analysis of idealized experiments further highlights the importance of the Pacific basin. The related increase of the tropospheric temperature (TT) over the tropics is then suggested to dry the margin of convection zones over Africa, in agreement with the so-called ''upped-ante'' mechanism. A simple metric is then defined to determine the ability of the CMIP3 coupled models in reproducing both the observed Sahel drying and these mechanisms, in order to determine the reliability of the twenty-first century scenarios. Only one model reproduces both the observed drought over the Sahel and consistent SST/TT relationships over the second half of the twentieth century. This model predicts enhanced dry conditions over the Sahel at the end of the twenty-first century. However, as the mechanisms highlighted here for the recent period are not stationary during the twenty-first century when considering the trends, similarities between observed and simulated features of the West African monsoon for the twentieth century are a necessary but insufficient condition for a trustworthy prediction of the future. (orig.)

  18. Towards multi-decadal to multi-millennial ice core records from coastal west Greenland ice caps

    Science.gov (United States)

    Das, Sarah B.; Osman, Matthew B.; Trusel, Luke D.; McConnell, Joseph R.; Smith, Ben E.; Evans, Matthew J.; Frey, Karen E.; Arienzo, Monica; Chellman, Nathan

    2017-04-01

    The Arctic region, and Greenland in particular, is undergoing dramatic change as characterized by atmospheric warming, decreasing sea ice, shifting ocean circulation patterns, and rapid ice sheet mass loss, but longer records are needed to put these changes into context. Ice core records from the Greenland ice sheet have yielded invaluable insight into past climate change both regionally and globally, and provided important constraints on past surface mass balance more directly, but these ice cores are most often from the interior ice sheet accumulation zone, at high altitude and hundreds of kilometers from the coast. Coastal ice caps, situated around the margins of Greenland, have the potential to provide novel high-resolution records of local and regional maritime climate and sea surface conditions, as well as contemporaneous glaciological changes (such as accumulation and surface melt history). But obtaining these records is extremely challenging. Most of these ice caps are unexplored, and thus their thickness, age, stratigraphy, and utility as sites of new and unique paleoclimate records is largely unknown. Access is severely limited due to their high altitude, steep relief, small surface area, and inclement weather. Furthermore, their relatively low elevation and marine moderated climate can contribute to significant surface melting and degradation of the ice stratigraphy. We recently targeted areas near the Disko Bay region of central west Greenland where maritime ice caps are prevalent but unsampled, as potential sites for new multi-decadal to multi-millennial ice core records. In 2014 & 2015 we identified two promising ice caps, one on Disko Island (1250 m. asl) and one on Nuussuaq Peninsula (1980 m. asl) based on airborne and ground-based geophysical observations and physical and glaciochemical stratigraphy from shallow firn cores. In spring 2015 we collected ice cores at both sites using the Badger-Eclipse electromechanical drill, transported by a medley

  19. ENSO and PDO-related climate variability impacts on Midwestern United States crop yields

    Science.gov (United States)

    Henson, Chasity; Market, Patrick; Lupo, Anthony; Guinan, Patrick

    2017-05-01

    An analysis of crop yields for the state of Missouri was completed to determine if an interannual or multidecadal variability existed as a result of the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Corn and soybean yields were recorded in kilograms per hectare for each of the six climate regions of Missouri. An analysis using the Mokhov "method of cycles" demonstrated interannual, interdecadal, and multidecadal variations in crop yields. Cross-spectral analysis was used to determine which region was most impacted by ENSO and PDO influenced seasonal (April-September) temperature and precipitation. Interannual (multidecadal) variations found in the spectral analysis represent a relationship to ENSO (PDO) phase, while interdecadal variations represent a possible interaction between ENSO and PDO. Average crop yields were then calculated for each combination of ENSO and PDO phase, displaying a pronounced increase in corn and soybean yields when ENSO is warm and PDO is positive. Climate regions 1, 2, 4, and 6 displayed significant differences ( p value of 0.10 or less) in yields between El Niño and La Niña years, representing 55-70 % of Missouri soybean and corn productivity, respectively. Final results give the opportunity to produce seasonal predictions of corn and soybean yields, specific to each climate region in Missouri, based on the combination of ENSO and PDO phases.

  20. Climatic drivers for multidecadal shifts in solute transport and methane production zones within a large peat basin

    Science.gov (United States)

    Glaser, Paul H.; Siegel, Donald I.; Chanton, Jeffrey P.; Reeve, Andrew S.; Rosenberry, Donald O.; Corbett, J. Elizabeth; Dasgupta, Soumitri; Levy, Zeno

    2016-01-01

    Northern peatlands are an important source for greenhouse gases, but their capacity to produce methane remains uncertain under changing climatic conditions. We therefore analyzed a 43 year time series of the pore-water chemistry to determine if long-term shifts in precipitation altered the vertical transport of solutes within a large peat basin in northern Minnesota. These data suggest that rates of methane production can be finely tuned to multidecadal shifts in precipitation that drive the vertical penetration of labile carbon substrates within the Glacial Lake Agassiz Peatlands. Tritium and cation profiles demonstrate that only the upper meter of these peat deposits was flushed by downwardly moving recharge from 1965 to 1983 during a Transitional Dry-to-Moist Period. However, a shift to a moister climate after 1984 drove surface waters much deeper, largely flushing the pore waters of all bogs and fens to depths of 2 m. Labile carbon compounds were transported downward from the rhizosphere to the basal peat at this time producing a substantial enrichment of methane in Δ14C with respect to the solid-phase peat from 1991 to 2008. These data indicate that labile carbon substrates can fuel deep production zones of methanogenesis that more than doubled in thickness across this large peat basin after 1984. Moreover, the entire peat profile apparently has the capacity to produce methane from labile carbon substrates depending on climate-driven modes of solute transport. Future changes in precipitation may therefore play a central role in determining the source strength of peatlands in the global methane cycle.

  1. Multi-decadal Records of Ocean Acidification and Toxic Heavy Metal Pollution in Coral Cores from Oahu, Hawaii

    Science.gov (United States)

    Stewart, J.; Tolliver, R.; Field, D. B.; Young, C.; Stafford, G.; Day, R. D.

    2016-12-01

    Monitoring of the physiological/ecological response of marine calcifying organisms to the combination of lower pH and toxic metal pollutants (e.g. Cu and Sn from boat anti-fouling paints) into the oceans requires detailed knowledge of the rates and spatial distribution of ocean acidification (OA) and trace metal composition over time. Yet, measurement of metal concentrations and carbonate system parameters in the modern ocean from seawater bottle data is patchy (e.g. CDIAC/WOCE Carbon Data; http://cdiac.ornl.gov) and there remain few long-term surface water pH monitoring stations; the two longest continuous records of ocean pH extend back less than 30 years (Bermuda - BATS, 31°40'N, 64°10'W; Hawaii - HOTs, 22°45'N, 158°00'W). Much attention has therefore been focused on trace metal and ocean carbonate system proxy development to allow reconstruction of seawater metal content and pH in the past. Of particular promise is the boron isotope (δ11B) pH-proxy measured in marine calcifying organisms such as coral that can be cored enabling multi-decadal, annual-resolution, records of trace element incorporation and seawater pH to be generated. Here we present continuous Cu/Ca and Sn/Ca records in addition to δ11B data from three coral cores of Porites lutea. collected from waters proximal to Oahu, Hawaii. The diagenetic integrity of samples is verified using X-ray diffraction to assess the degree of calcite replacement. These cores reach a maximum depth of 80 cm and represent approximately 80 years of coral growth and seawater chemistry.

  2. John Strong (1941 - 2006)

    CERN Multimedia

    Wickens, F

    Our friend and colleague John Strong was cruelly taken from us by a brain tumour on Monday 31st July, a few days before his 65th birthday John started his career working with a group from Westfield College, under the leadership of Ted Bellamy. He obtained his PhD and spent the early part of his career on experiments at Rutherford Appleton Laboratory (RAL), but after the early 1970s his research was focussed on experiments in CERN. Over the years he made a number of notable contributions to experiments in CERN: The Omega spectrometer adopted a system John had originally developed for experiments at RAL using vidicon cameras to record the sparks in the spark chambers; He contributed to the success of NA1 and NA7, where he became heavily involved in the electronic trigger systems; He was responsible for the second level trigger system for the ALEPH detector and spent five years leading a team that designed and built the system, which ran for twelve years with only minor interventions. Following ALEPH he tur...

  3. Stirring Strongly Coupled Plasma

    CERN Document Server

    Fadafan, Kazem Bitaghsir; Rajagopal, Krishna; Wiedemann, Urs Achim

    2009-01-01

    We determine the energy it takes to move a test quark along a circle of radius L with angular frequency w through the strongly coupled plasma of N=4 supersymmetric Yang-Mills (SYM) theory. We find that for most values of L and w the energy deposited by stirring the plasma in this way is governed either by the drag force acting on a test quark moving through the plasma in a straight line with speed v=Lw or by the energy radiated by a quark in circular motion in the absence of any plasma, whichever is larger. There is a continuous crossover from the drag-dominated regime to the radiation-dominated regime. In the crossover regime we find evidence for significant destructive interference between energy loss due to drag and that due to radiation as if in vacuum. The rotating quark thus serves as a model system in which the relative strength of, and interplay between, two different mechanisms of parton energy loss is accessible via a controlled classical gravity calculation. We close by speculating on the implicati...

  4. Strong-interaction nonuniversality

    International Nuclear Information System (INIS)

    Volkas, R.R.; Foot, R.; He, X.; Joshi, G.C.

    1989-01-01

    The universal QCD color theory is extended to an SU(3) 1 direct product SU(3) 2 direct product SU(3) 3 gauge theory, where quarks of the ith generation transform as triplets under SU(3)/sub i/ and singlets under the other two factors. The usual color group is then identified with the diagonal subgroup, which remains exact after symmetry breaking. The gauge bosons associated with the 16 broken generators then form two massive octets under ordinary color. The interactions between quarks and these heavy gluonlike particles are explicitly nonuniversal and thus an exploration of their physical implications allows us to shed light on the fundamental issue of strong-interaction universality. Nonuniversality and weak flavor mixing are shown to generate heavy-gluon-induced flavor-changing neutral currents. The phenomenology of these processes is studied, as they provide the major experimental constraint on the extended theory. Three symmetry-breaking scenarios are presented. The first has color breaking occurring at the weak scale, while the second and third divorce the two scales. The third model has the interesting feature of radiatively induced off-diagonal Kobayashi-Maskawa matrix elements

  5. Multi-decadal trends in global terrestrial evapotranspiration and its components.

    Science.gov (United States)

    Zhang, Yongqiang; Peña-Arancibia, Jorge L; McVicar, Tim R; Chiew, Francis H S; Vaze, Jai; Liu, Changming; Lu, Xingjie; Zheng, Hongxing; Wang, Yingping; Liu, Yi Y; Miralles, Diego G; Pan, Ming

    2016-01-11

    Evapotranspiration (ET) is the process by which liquid water becomes water vapor and energetically this accounts for much of incoming solar radiation. If this ET did not occur temperatures would be higher, so understanding ET trends is crucial to predict future temperatures. Recent studies have reported prolonged declines in ET in recent decades, although these declines may relate to climate variability. Here, we used a well-validated diagnostic model to estimate daily ET during 1981-2012, and its three components: transpiration from vegetation (Et), direct evaporation from the soil (Es) and vaporization of intercepted rainfall from vegetation (Ei). During this period, ET over land has increased significantly (p trends are primarily driven by increases in vegetation leaf area index, dominated by greening. The overall increase in Et over land is about twofold of the decrease in Es. These opposing trends are not simulated by most Coupled Model Intercomparison Project phase 5 (CMIP5) models, and highlight the importance of realistically representing vegetation changes in earth system models for predicting future changes in the energy and water cycle.

  6. Mechanisms of interdecadal climate variability and the role of ocean-atmosphere coupling

    Energy Technology Data Exchange (ETDEWEB)

    Farneti, Riccardo; Vallis, Geoffrey K. [Princeton University, GFDL/AOS Program, Princeton, NJ (United States)

    2011-01-15

    Climate variability and mid-latitude mechanisms of ocean-atmosphere interactions are investigated with coupled and uncoupled integrations of a three-dimensional ocean-atmosphere-land-ice climate model of intermediate complexity. We focus on the decadal and interdecadal variability of the system and give a statistical and dynamical description of its oceanic and atmospheric signatures. In our coupled control integration, an oceanic oscillation of a period of around 20 years is found to be associated with variability of the meridional overturning circulation and is manifested by surface anomalies of temperature and salinity. On such timescales the oceanic oscillation is able to imprint itself on the atmosphere, which then covaries with the ocean at the oscillation period. The essentially slaved atmospheric pattern helps maintain the oceanic oscillation by providing large-scale anomalous heat fluxes, so catalyzing the oscillation. That is to say, because the atmosphere covaries with the ocean the damping felt by the ocean is less than what would be felt with a fixed atmosphere, so broadening the parameter regime over which such variability occurs. In addition to the presence of an atmosphere, the period and amplitude of the oscillation are found to be influenced both by the oceanic vertical diffusivity {kappa}{sub v}, by geometrical factors, and by the presence of stochastic heat fluxes. In general, oscillations occur most readily for large values of {kappa}{sub v}, when the mean state of the ocean is characterized by a strong meridional overturning circulation. If {kappa}{sub v} is sufficiently strong, the ocean will oscillate even in the absence of a dynamical atmosphere. However, for more realistic values of {kappa}{sub v}, the presence of an interacting atmosphere is required for significant oscillations. If the ocean is forced by imposed stochastic heat fluxes, instead of a fully interacting atmosphere, then decadal-scale oscillations can be produced suggestive

  7. Multi-decadal analysis reveals contrasting patterns of resilience and decline in coral assemblages

    Science.gov (United States)

    Tanner, Jason E.

    2017-12-01

    A 50-yr study of coral dynamics at Heron Island, on Australia's Great Barrier Reef, shows that community change on a single reef is highly variable and that while some areas of the reef are in decline, others are recovering well 40 yr after a major cyclonic disturbance that eliminated all corals in the study plot. At one site, the genus-level composition in 2012 was identical to that before the cyclone, although it took around 30 yr to recover, and there were still differences at the species level. The colony size structure of some species at this site, notably the dominant Acropora digitifera, which had over 40% cover in 2012, also recovered after 30 yr, although sub-dominant species still lacked large colonies even after 40 yr. Given the small scale of the individual study plots (1 m2), this shows an unexpected degree of determinism in assemblage structure. At a second site, however, both composition and size structure changed dramatically over the last 40 yr of the study as both external and internal factors altered local environmental conditions. At both sites, major changes in composition appear to be related to drying out of the reef crest due to changes in flow regimes and/or natural accretion. At the site that has recovered, erosion has reversed this drying out, whereas no such erosion has occurred at the second site. If such erosion occurs, or sea levels increase due to global warming, then the second site may also prove to be resilient over decadal time scales.

  8. Multidecadal Changes in the UTLS Ozone from the MERRA-2 Reanalysis and the GMI Chemistry Model

    Science.gov (United States)

    Wargan, Krzysztof; Orbe, Clara; Pawson, Steven; Ziemke, Jerald R.; Oman, Luke; Olsen, Mark; Coy, Lawrence; Knowland, Emma

    2018-01-01

    Long-term changes of ozone in the UTLS (Upper Troposphere / Lower Stratosphere) reflect the response to decreases in the stratospheric concentrations of ozone-depleting substances as well as changes in the stratospheric circulation induced by climate change. To date, studies of UTLS ozone changes and variability have relied mainly on satellite and in-situ observations as well as chemistry-climate model simulations. By comparison, the potential of reanalysis ozone data remains relatively untapped. This is despite evidence from recent studies, including detailed analyses conducted under SPARC (Scalable Processor Architecture) Reanalysis Intercomparison Project (S-RIP), that demonstrate that stratospheric ozone fields from modern atmospheric reanalyses exhibit good agreement with independent data while delineating issues related to inhomogeneities in the assimilated observations. In this presentation, we will explore the possibility of inferring long-term geographically and vertically resolved behavior of the lower stratospheric (LS) ozone from NASA's MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications -2) reanalysis after accounting for the few known discontinuities and gaps in its assimilated input data. This work builds upon previous studies that have documented excellent agreement between MERRA-2 ozone and ozonesonde observations in the LS. Of particular importance is a relatively good vertical resolution of MERRA-2 allowing precise separation of tropospheric and stratospheric ozone contents. We also compare the MERRA-2 LS ozone results with the recently completed 37-year simulation produced using Goddard Earth Observing System in "replay"� mode coupled with the GMI (Global Modeling Initiative) chemistry mechanism. Replay mode dynamically constrains the model with the MERRA-2 reanalysis winds, temperature, and pressure. We will emphasize the areas of agreement of the reanalysis and replay and interpret differences between them in the context

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

    International Nuclear Information System (INIS)

    Latif, M.; Barnett, T.P.

    1994-01-01

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

  10. Seasonal-to-Interannual Precipitation Variability and Predictability in a Coupled Land-Atmosphere System

    Science.gov (United States)

    Koster, Randal D.; Suarez, M. J.; Heiser, M.

    1998-01-01

    In an earlier GCM study, we showed that interactive land surface processes generally contribute more to continental precipitation variance than do variable sea surface temperatures (SSTs). A new study extends this result through an analysis of 16-member ensembles of multi-decade GCM simulations. We can now show that in many regions, although land processes determine the amplitude of the interannual precipitation anomalies, variable SSTs nevertheless control their timing. The GCM data can be processed into indices that describe geographical variations in (1) the potential for seasonal-to-interannual prediction, and (2) the extent to which the predictability relies on the proper representation of land-atmosphere feedback.

  11. Multi-decadal satellite measurements of passive and eruptive volcanic SO2 emissions

    Science.gov (United States)

    Carn, Simon; Yang, Kai; Krotkov, Nickolay; Prata, Fred; Telling, Jennifer

    2015-04-01

    Periodic injections of sulfur gas species (SO2, H2S) into the stratosphere by volcanic eruptions are among the most important, and yet unpredictable, drivers of natural climate variability. However, passive (lower tropospheric) volcanic degassing is the major component of total volcanic emissions to the atmosphere on a time-averaged basis, but is poorly constrained, impacting estimates of global emissions of other volcanic gases (e.g., CO2). Stratospheric volcanic emissions are very well quantified by satellite remote sensing techniques, and we report ongoing efforts to catalog all significant volcanic SO2 emissions into the stratosphere and troposphere since 1978 using measurements from the ultraviolet (UV) Total Ozone Mapping Spectrometer (TOMS; 1978-2005), Ozone Monitoring Instrument (OMI; 2004 - present) and Ozone Mapping and Profiler Suite (OMPS; 2012 - present) instruments, supplemented by infrared (IR) data from HIRS, MODIS and AIRS. The database, intended for use as a volcanic forcing dataset in climate models, currently includes over 600 eruptions releasing a total of ~100 Tg SO2, with a mean eruption discharge of ~0.2 Tg SO2. Sensitivity to SO2 emissions from smaller eruptions greatly increased following the launch of OMI in 2004, but uncertainties remain on the volcanic flux of other sulfur species other than SO2 (H2S, OCS) due to difficulty of measurement. Although the post-Pinatubo 1991 era is often classified as volcanically quiescent, many smaller eruptions (Volcanic Explosivity Index [VEI] 3-4) since 2000 have injected significant amounts of SO2 into the upper troposphere - lower stratosphere (UTLS), peaking in 2008-2011. We also show how even smaller (VEI 2) tropical eruptions can impact the UTLS and sustain above-background stratospheric aerosol optical depth, thus playing a role in climate forcing on short timescales. To better quantify tropospheric volcanic degassing, we use ~10 years of operational SO2 measurements by OMI to identify the

  12. Continuous non-marine inputs of per- and polyfluoroalkyl substances to the High Arctic: a multi-decadal temporal record

    Directory of Open Access Journals (Sweden)

    H. M. Pickard

    2018-04-01

    Full Text Available Perfluoroalkyl acids (PFAAs are persistent, in some cases, bioaccumulative compounds found ubiquitously within the environment. They can be formed from the atmospheric oxidation of volatile precursor compounds and undergo long-range transport (LRT through the atmosphere and ocean to remote locations. Ice caps preserve a temporal record of PFAA deposition making them useful in studying the atmospheric trends in LRT of PFAAs in polar or mountainous regions, as well as in understanding major pollutant sources and production changes over time. A 15 m ice core representing 38 years of deposition (1977–2015 was collected from the Devon Ice Cap in Nunavut, providing us with the first multi-decadal temporal ice record in PFAA deposition to the Arctic. Ice core samples were concentrated using solid phase extraction and analyzed by liquid and ion chromatography methods. Both perfluoroalkyl carboxylic acids (PFCAs and perfluoroalkyl sulfonic acids (PFSAs were detected in the samples, with fluxes ranging from < LOD to 141 ng m−2 yr−1. Our results demonstrate that the PFCAs and perfluorooctane sulfonate (PFOS have continuous and increasing deposition on the Devon Ice Cap, despite recent North American and international regulations and phase-outs. We propose that this is the result of on-going manufacture, use and emissions of these compounds, their precursors and other newly unidentified compounds in regions outside of North America. By modelling air mass transport densities, and comparing temporal trends in deposition with production changes of possible sources, we find that Eurasian sources, particularly from Continental Asia, are large contributors to the global pollutants impacting the Devon Ice Cap. Comparison of PFAAs to their precursors and correlations of PFCA pairs showed that deposition of PFAAs is dominated by atmospheric formation from volatile precursor sources. Major ion analysis confirmed that marine aerosol inputs are

  13. Thermohaline forcing and interannual variability of northwestern inflows into the northern North Sea

    Science.gov (United States)

    Sheehan, Peter M. F.; Berx, Barbara; Gallego, Alejandro; Hall, Rob A.; Heywood, Karen J.; Hughes, Sarah L.

    2017-04-01

    A long-established, 127 km-long hydrographic section in the northern North Sea at 59.28°N that runs from the eastern coast of Orkney (2.23°W) to the central North Sea (0°) crosses the path of the main inflows of Atlantic water. Data from 122 occupations between 1989 and 2015 are examined to determine the annual cycle and long-term trends of temperature, salinity and depth-varying geostrophic flow across the section. In an average year, the geostrophic flow referenced to the seafloor is at its narrowest (40 km) in winter, during which time it is driven by the strong horizontal salinity gradient; the horizontal temperature gradient is very weak. Velocity exceeds 4 cm s-1, but transport is at a minimum (0.11 Sv). In the deeper water in the east of the section, thermal stratification develops throughout summer and persists until October, whereas the west is tidally mixed all year. The bottom temperature gradient becomes the primary driver of the geostrophic flow, which is fastest (9 cm s-1) in September and broadest (100 km) in October. Maximum transport (0.36 Sv) occurs in October. Throughout the summer, the horizontal salinity gradient weakens, as does its contribution to the flow. However, it nevertheless acts to broaden the flow west of the location of the strongest horizontal temperature gradient. Section-mean de-seasoned temperature is found to be positively correlated to the Atlantic Multidecadal Oscillation and negatively correlated to the North Atlantic Oscillation. These results refine our understanding of the thermohaline forcing of Atlantic inflow into the northern North Sea, particularly in relation to the salinity distribution. Understanding the variability of this inflow is important for understanding the dynamics of the North Sea ecosystem.

  14. Salinity changes relative to the response to anthropogenic forcing and internal variability in the North Atlantic

    Science.gov (United States)

    Vinogradova, Nadya; Buckley, Martha

    2017-04-01

    Over the past few decades, surface waters in the subpolar North Atlantic have experienced substantial fluctuations, including periods of rapid cooling and freshening alternating with the periods of enhanced warming, salinification, and decreased circulation of the gyre. Since these waters feed the North Atlantic thermohaline circulation, such changes have the potential to impact the global ocean circulation and future climate states. A number of potential causes for the observed changes have been suggested, including those related to the strength of the ocean circulation and heat transports, as well as other factors, such as anthropogenic aerosol forcing or changes in surface fluxes. Here we assess how the observed warming/salinification events fit into the long-term picture, focusing on variations in upper-ocean salinity. Salinification of the subpolar North Atlantic may seem counter-intuitive to the reported long-term increase in freshwater supply to the region from river discharge and ice melting, sparking debates about whether the freshening of the subpolar gyre has ceased, and whether the recent salinification, if continued, will be able to forestall the projected slowdown of the overturning circulation. Using a suite of in situ salinity observations spanning the last 60 years, modern satellite salinity observations from Aquarius and SMOS missions, and multi-decadal realizations from global climate models, we estimate the likelihood of such salinity changes in the context of the historical record, contemporary estimates, and future projections. Results are discussed in terms of the probability of occurrence of a decade-long salinification in the presence of the background freshening in response to anthropogenic forcing. In particular, computed probabilities suggest that such "unusual" salinification events are plausible under the strong influence of internal, decadal-to-interdecadal variability.

  15. The impact of monsoon intraseasonal variability on renewable power generation in India

    Science.gov (United States)

    Dunning, C. M.; Turner, A. G.; Brayshaw, D. J.

    2015-06-01

    India is increasingly investing in renewable technology to meet rising energy demands, with hydropower and other renewables comprising one-third of current installed capacity. Installed wind-power is projected to increase 5-fold by 2035 (to nearly 100GW) under the International Energy Agency's New Policies scenario. However, renewable electricity generation is dependent upon the prevailing meteorology, which is strongly influenced by monsoon variability. Prosperity and widespread electrification are increasing the demand for air conditioning, especially during the warm summer. This study uses multi-decadal observations and meteorological reanalysis data to assess the impact of intraseasonal monsoon variability on the balance of electricity supply from wind-power and temperature-related demand in India. Active monsoon phases are characterized by vigorous convection and heavy rainfall over central India. This results in lower temperatures giving lower cooling energy demand, while strong westerly winds yield high wind-power output. In contrast, monsoon breaks are characterized by suppressed precipitation, with higher temperatures and hence greater demand for cooling, and lower wind-power output across much of India. The opposing relationship between wind-power supply and cooling demand during active phases (low demand, high supply) and breaks (high demand, low supply) suggests that monsoon variability will tend to exacerbate fluctuations in the so-called demand-net-wind (i.e., electrical demand that must be supplied from non-wind sources). This study may have important implications for the design of power systems and for investment decisions in conventional schedulable generation facilities (such as coal and gas) that are used to maintain the supply/demand balance. In particular, if it is assumed (as is common) that the generated wind-power operates as a price-taker (i.e., wind farm operators always wish to sell their power, irrespective of price) then investors in

  16. The impact of monsoon intraseasonal variability on renewable power generation in India

    International Nuclear Information System (INIS)

    Dunning, C M; Turner, A G; Brayshaw, D J

    2015-01-01

    India is increasingly investing in renewable technology to meet rising energy demands, with hydropower and other renewables comprising one-third of current installed capacity. Installed wind-power is projected to increase 5-fold by 2035 (to nearly 100GW) under the International Energy Agency's New Policies scenario. However, renewable electricity generation is dependent upon the prevailing meteorology, which is strongly influenced by monsoon variability. Prosperity and widespread electrification are increasing the demand for air conditioning, especially during the warm summer. This study uses multi-decadal observations and meteorological reanalysis data to assess the impact of intraseasonal monsoon variability on the balance of electricity supply from wind-power and temperature-related demand in India. Active monsoon phases are characterized by vigorous convection and heavy rainfall over central India. This results in lower temperatures giving lower cooling energy demand, while strong westerly winds yield high wind-power output. In contrast, monsoon breaks are characterized by suppressed precipitation, with higher temperatures and hence greater demand for cooling, and lower wind-power output across much of India. The opposing relationship between wind-power supply and cooling demand during active phases (low demand, high supply) and breaks (high demand, low supply) suggests that monsoon variability will tend to exacerbate fluctuations in the so-called demand-net-wind (i.e., electrical demand that must be supplied from non-wind sources). This study may have important implications for the design of power systems and for investment decisions in conventional schedulable generation facilities (such as coal and gas) that are used to maintain the supply/demand balance. In particular, if it is assumed (as is common) that the generated wind-power operates as a price-taker (i.e., wind farm operators always wish to sell their power, irrespective of price) then investors

  17. Monitoring variability and changes of the Indonesian Throughflow

    Science.gov (United States)

    Feng, Ming; Wijffels, Susan

    2017-04-01

    The Indonesian Throughflow (ITF) is an important component of the upper cell of the global overturning circulation that provides a low-latitude pathway for warm, fresh waters from the Pacific to enter the Indian Ocean. The IX1 XBT line between the coasts of Australia and Indonesia, initially championed by Gary Meyers, crosses the ITF and has now been in operation for more than 30 years. In this presentation, we review research progresses on the variability and changes of the ITF based on the IX1 XBT data, in memory of Gary's contribution to the Indian Ocean research. The ITF passes across a region that comprises the intersection of two ocean waveguides - those of the equatorial Pacific and equatorial Indian Ocean. The ITF geostrophic transport is stronger during La Niñas and weaker during El Niños. The Indian Ocean wind variability associated with the Indian Ocean Dipole (IOD) in many years offsets the Pacific ENSO influences on the ITF geostrophic transport during the developing and mature phases of El Niño and La Niña, due to the covarying IOD variability with ENSO. The IX1 line reveals the geostrophic ITF decadal and multi-decadal changes: there was a weakening change from the mid-1970s climate regime shift followed by a strengthening trend of about 1 Sv every 10 years over the recent decades. These decadal changes appear mostly due to the ITF responses to decadal variations of the trade winds in the Pacific. Climate models project a weakening trend of the ITF under the global warming, due to the slowdown of the global overturning circulation. The consistent and now multidecadal sampling along IX1 is a precious resource for the climate community and is a testament to the vision and commitment of Gary Meyers to use observations to drive insight into earth's climate variability.

  18. Climate variability during the Medieval Climate Anomaly and Little Ice Age based on ostracod faunas and shell geochemistry from Biscayne Bay, Florida: Chapter 14

    Science.gov (United States)

    Cronin, Thomas M.; Wingard, G. Lynn; Dwyer, Gary S.; Swart, Peter K.; Willard, Debra A.; Albietz, Jessica

    2012-01-01

    An 800-year-long environmental history of Biscayne Bay, Florida, is reconstructed from ostracod faunal and shell geochemical (oxygen, carbon isotopes, Mg/Ca ratios) studies of sediment cores from three mudbanks in the central and southern parts of the bay. Using calibrations derived from analyses of modern Biscayne and Florida Bay ostracods, palaeosalinity oscillations associated with changes in precipitation were identified. These oscillations reflect multidecadal- and centennial-scale climate variability associated with the Atlantic Multidecadal Oscillation during the late Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Evidence suggests wetter regional climate during the MCA and drier conditions during the LIA. In addition, twentieth century anthropogenic modifications to Everglades hydrology influenced bay circulation and/or processes controlling carbon isotopic composition.

  19. Quantum electrodynamics of strong fields

    International Nuclear Information System (INIS)

    Greiner, W.

    1983-01-01

    Quantum Electrodynamics of Strong Fields provides a broad survey of the theoretical and experimental work accomplished, presenting papers by a group of international researchers who have made significant contributions to this developing area. Exploring the quantum theory of strong fields, the volume focuses on the phase transition to a charged vacuum in strong electric fields. The contributors also discuss such related topics as QED at short distances, precision tests of QED, nonperturbative QCD and confinement, pion condensation, and strong gravitational fields In addition, the volume features a historical paper on the roots of quantum field theory in the history of quantum physics by noted researcher Friedrich Hund

  20. Time capsules in natural sediment archives-Tracking phytoplankton population genetic diversity and adaptation over multidecadal timescales in the face of environmental change.

    Science.gov (United States)

    Ellegaard, Marianne; Godhe, Anna; Ribeiro, Sofia

    2018-01-01

    Undisturbed records of resting stages produced in the past and stored in coastal sediments are very valuable to science, because they may provide unique insights into past evolutionary and ecological trajectories. Within marine phytoplankton, multidecadal time series of monoclonal strains germinated from resting stages have been established for diatoms ( Skeletonema marinoi ) and dinoflagellates ( Pentapharsodinium dalei ), spanning ca. a century. Phenotypic and genotypic analyses of these time series have revealed effects of past environmental changes on population genetic structure. Future perspectives include direct comparisons of phenotypes and genotypic data of populations, for example, by genomewide assays that can correlate phenotypic trends with genotypes and allele frequencies in temporally separated strains. Besides their usefulness as historical records, "seed" banks of phytoplankton resting stages also have the potential to provide an inoculum that influences present populations through "dispersal from the past" (the storage effect) and are important for adaptation to future environments through their standing genetic diversity.

  1. Strong WW Interaction at LHC

    Energy Technology Data Exchange (ETDEWEB)

    Pelaez, Jose R

    1998-12-14

    We present a brief pedagogical introduction to the Effective Electroweak Chiral Lagrangians, which provide a model independent description of the WW interactions in the strong regime. When it is complemented with some unitarization or a dispersive approach, this formalism allows the study of the general strong scenario expected at the LHC, including resonances.

  2. Strong-back safety latch

    International Nuclear Information System (INIS)

    DeSantis, G.N.

    1995-01-01

    The calculation decides the integrity of the safety latch that will hold the strong-back to the pump during lifting. The safety latch will be welded to the strong-back and will latch to a 1.5-in. dia cantilever rod welded to the pump baseplate. The static and dynamic analysis shows that the safety latch will hold the strong-back to the pump if the friction clamps fail and the pump become free from the strong-back. Thus, the safety latch will meet the requirements of the Lifting and Rigging Manual for under the hook lifting for static loading; it can withstand shock loads from the strong-back falling 0.25 inch

  3. Strong-back safety latch

    Energy Technology Data Exchange (ETDEWEB)

    DeSantis, G.N.

    1995-03-06

    The calculation decides the integrity of the safety latch that will hold the strong-back to the pump during lifting. The safety latch will be welded to the strong-back and will latch to a 1.5-in. dia cantilever rod welded to the pump baseplate. The static and dynamic analysis shows that the safety latch will hold the strong-back to the pump if the friction clamps fail and the pump become free from the strong-back. Thus, the safety latch will meet the requirements of the Lifting and Rigging Manual for under the hook lifting for static loading; it can withstand shock loads from the strong-back falling 0.25 inch.

  4. Relationship between Climate Variability, Wildfire Risk, and Wildfire Occurrence in Wildland-Urban Interface of the Southwestern United States

    Science.gov (United States)

    Kafatos, M.; Kim, S. H.; Jia, S.; Nghiem, S. V.

    2017-12-01

    As housing units in or near wildlands have grown, the wildland-urban interface (WUI) contain at present approximately one-third of all housing in the contiguous US. Wildfires are a part of the natural cycle in the Southwestern United States (SWUS) but the increasing trend of WUI has made wildfires a serious high-risk hazard. The expansion of WUI has elevated wildfire risks by increasing the chance of human caused ignitions and past fire suppression in the area. Previous studies on climate variability have shown that the SWUS region is prone to frequent droughts and has suffered from severe wildfires in the recent decade. Therefore, assessing the increased vulnerability to the wildfire in WUI is crucial for proactive adaptation under climate change. Our previous study has shown that a strong correlation between North Atlantic Oscillation (NAO) and temperature was found during March-June in the SWUS. The abnormally warm and dry spring conditions, combined with suppression of winter precipitation, can cause an early start of a fire season and high fire risk throughout the summer and fall. Therefore, it is crucial to investigate the connections between climate variability and wildfire danger characteristics. This study aims to identify climate variability using multiple climate indices such as NAO, El Niño-Southern Oscillation and the Pacific Decadal Oscillation closely related with droughts in the SWUS region. Correlation between the variability and fire frequency and severity in WUI were examined. Also, we investigated climate variability and its relationship on local wildfire potential using both Keetch-Byram Drought Index (KBDI) and Fire Weather Index (FWI) which have been used to assessing wildfire potential in the U.S.A and Canada, respectively. We examined the long-term variability of the fire potential indices and relationships between the indices and historical occurrence in WUI using multi-decadal reanalysis data sets. Following our analysis, we investigated

  5. Titanium: light, strong, and white

    Science.gov (United States)

    Woodruff, Laurel; Bedinger, George

    2013-01-01

    Titanium (Ti) is a strong silver-gray metal that is highly resistant to corrosion and is chemically inert. It is as strong as steel but 45 percent lighter, and it is twice as strong as aluminum but only 60 percent heavier. Titanium dioxide (TiO2) has a very high refractive index, which means that it has high light-scattering ability. As a result, TiO2 imparts whiteness, opacity, and brightness to many products. ...Because of the unique physical properties of titanium metal and the whiteness provided by TiO2, titanium is now used widely in modern industrial societies.

  6. Examination of precipitation variability in southern Greenland

    Science.gov (United States)

    Auger, Jeffrey D.; Birkel, Sean D.; Maasch, Kirk A.; Mayewski, Paul A.; Schuenemann, Keah C.

    2017-06-01

    The surface mass balance of the Greenland ice sheet has decreased in recent decades with important implications for global sea level rise. Here a climate reanalysis model is used to examine observed circulation variability and changes in precipitation across southern Greenland to gain insight into the future climate in the region. The influence on precipitation from the North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), Icelandic Low, Azores High, regional blocking patterns, and near-surface temperature and winds are explored. Statistically significant correlations are higher between precipitation and the Icelandic Low and near-surface winds (0.5-0.7; p < 0.05) than correlations between precipitation and either the NAO or AMO climate indices (southwest Greenland: r = 0.12 and 0.28, respectively; and southeast Greenland: r = 0.25 and -0.07, respectively). Moreover, the recent enhanced warming in the Arctic (Arctic amplification) and the increase in the Greenland Blocking Index coincide with increased mean annual precipitation and interannual variability in southwest Greenland.

  7. Interactions of Mineral Dust with Clouds, Sea Surface Temperature, and Climate Modes of Variability

    Science.gov (United States)

    DeFlorio, Michael J.

    boundary layer. We find that ENSO exerts a control on North African dust transport during the summer, and CESM suggests that there is strong multi-decadal variability in the strength of the ENSO-dust relationship. Finally, we compare interactive and prescribed aerosol CESM simulations to demonstrate the importance of dust in increasing tropical Atlantic SST variability, and expose deficiencies in CESM's simulation of the Atlantic Meridional Mode.

  8. Spatial and temporal variability of past rainfall in western Australia inferred from tree rings

    Science.gov (United States)

    O'Donnell, Alison; Cook, Edward; Turney, Chris; Palmer, Jonathan; Skrzypek, Grzegorz; Grierson, Pauline

    2017-04-01

    For much of the Southern Hemisphere, the ability to identify spatial and temporal patterns of past climatic variability is constrained by the short length of instrumental records and the sparse spatial distribution of proxy records. This is particularly true for continental Australia, where instrumental records are generally Australia. These chronologies are currently the only multi-century tree-ring records for mainland Australia. Both chronologies are strongly correlated with hydroclimate and allow robust reconstructions of past hydroclimatic variability over spatially broad areas (i.e., > 3° x 3°) of inland western Australia. These reconstructions represent significant extensions of the instrumental rainfall records and reveal inter-annual to multidecadal-scale variation in past hydroclimate over the last two centuries for northwest Australia and four centuries for southwest Australia. In both the northwest and southwest regions, periods of prolonged drought (typically extending between one and three decades) have been interspersed with shorter periods of above-average rainfall (typically less than a decade). Of particular note our northwest record reveals that the last two decades (1995-2012) have been unusually wet in inland northwest Australia compared to the previous two centuries. This period of unusually high rainfall coincided with both an anomalously high frequency and intensity of tropical cyclones in northwest Australia and the dominance of the positive phase of the Southern Annular Mode, both of which are major mechanisms of rainfall delivery to inland northwest Australia. Our tree-ring records also reveal the occurrence of several prolonged drought periods as well as extreme wet events in the last two centuries that were synchronous between northwest and southwest Australia, suggesting possible teleconnections between the two regions. In addition, there appears to have been a generally anti-phase relationship between the hydroclimate of inland

  9. Electromotive force in strongly compressible magnetohydrodynamic turbulence

    Science.gov (United States)

    Yokoi, N.

    2017-12-01

    Variable density fluid turbulence is ubiquitous in geo-fluids, not to mention in astrophysics. Depending on the source of density variation, variable density fluid turbulence may be divided into two categories: the weak compressible (entropy mode) turbulence for slow flow and the strong compressible (acoustic mode) turbulence for fast flow. In the strong compressible turbulence, the pressure fluctuation induces a strong density fluctuation ρ ', which is represented by the density variance ( denotes the ensemble average). The turbulent effect on the large-scale magnetic-field B induction is represented by the turbulent electromotive force (EMF) (u': velocity fluctuation, b': magnetic-field fluctuation). In the usual treatment in the dynamo theory, the expression for the EMF has been obtained in the framework of incompressible or weak compressible turbulence, where only the variation of the mean density , if any, is taken into account. We see from the equation of the density fluctuation ρ', the density variance is generated by the large mean density variation ∂ coupled with the turbulent mass flux . This means that in the region where the mean density steeply changes, the density variance effect becomes relevant for the magnetic field evolution. This situation is typically the case for phenomena associated with shocks and compositional discontinuities. With the aid of the analytical theory of inhomogeneous compressible magnetohydrodynamic (MHD) turbulence, the expression for the turbulent electromotive force is investigated. It is shown that, among others, an obliqueness (misalignment) between the mean density gradient ∂ and the mean magnetic field B may contribute to the EMF as ≈χ B×∂ with the turbulent transport coefficient χ proportional to the density variance (χ ). This density variance effect is expected to strongly affect the EMF near the interface, and changes the transport properties of turbulence. In the case of an interface under the MHD slow

  10. Assessment of the Interactions Among Tropospheric Aerosol Loading, Radiative Balance and Clouds Through Examination of Their Multi-decadal Trends

    Science.gov (United States)

    While aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, the verification of the spatial and temporal variability of aerosol radiative forcing has remained challenging. Anthropogenic emissions of prima...

  11. Phase diagram of strongly correlated Fermi systems

    International Nuclear Information System (INIS)

    Zverev, M.V.; Khodel', V.A.; Baldo, M.

    2000-01-01

    Phase transitions in uniform Fermi systems with repulsive forces between the particles caused by restructuring of quasiparticle filling n(p) are analyzed. It is found that in terms of variables, i.e. density ρ, nondimensional binding constant η, phase diagram of a strongly correlated Fermi system for rather a wide class of interactions reminds of a puff-pastry pie. Its upper part is filled with fermion condensate, the lower one - with normal Fermi-liquid. They are separated by a narrow interlayer - the Lifshits phase, characterized by the Fermi multibound surface [ru

  12. Amplification of surface temperature trends and variability in thetropical atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Santer, B.D.; Wigley, T.M.L.; Mears, C.; Wentz, F.J.; Klein,S.A.; Seidel, D.J.; Taylor, K.E.; Thorne, P.W.; Wehner, M.F.; Gleckler,P.J.; Boyle, J.S.; Collins, W.D.; Dixon, K.W.; Doutriaux, C.; Free, M.; Fu, Q.; Hansen, J.E.; Jones, G.S.; Ruedy, R.; Karl, T.R.; Lanzante, J.R.; Meehl, G.A.; Ramaswamy, V.; Russell, G.; Schmidt, G.A.

    2005-08-11

    The month-to-month variability of tropical temperatures is larger in the troposphere than at the Earth's surface. This amplification behavior is similar in a range of observations and climate model simulations, and is consistent with basic theory. On multi-decadal timescales, tropospheric amplification of surface warming is a robust feature of model simulations, but occurs in only one observational dataset. Other observations show weak or even negative amplification. These results suggest that either different physical mechanisms control amplification processes on monthly and decadal timescales, and models fail to capture such behavior, or (more plausibly) that residual errors in several observational datasets used here affect their representation of long-term trends.

  13. Isotopic and hydrologic responses of small, closed lakes to climate variability: Hydroclimate reconstructions from lake sediment oxygen isotope records and mass balance models

    Science.gov (United States)

    Steinman, Byron A.; Abbott, Mark B.

    2013-03-01

    Hydroclimate sensitivity simulations were conducted with a lake-catchment hydrologic and isotope mass balance model adapted to two small, closed lakes (Castor and Scanlon) located in the Pacific Northwest. Model simulations were designed to investigate the combined influences of persistent disequilibrium, reddening, and equifinality on lake water and sediment (i.e., biogenic and endogenic carbonate mineral) oxygen isotope (δ18O) values and to provide a basis for quantitative, probabilistic climate reconstructions using lake sediment δ18O records. Simulation results indicate that within closed-basin lakes changes in long-term (i.e., multi-decadal) precipitation amounts produce inconsistent responses in lake water and sediment δ18O values that are strongly influenced by lake basin outseepage and morphometry. Simulations of variable initial conditions in which randomly generated monthly climate data (i.e., precipitation, temperature, and relative humidity) were used to force the model during the equilibration period (which precedes the application of instrumental climate data) demonstrate that Castor Lake and Scanlon Lake have a somewhat limited isotopic 'memory' of ˜10 years. Additional tests conducted using a Monte Carlo ensemble (in which random climate data were used to force the model) combined with δ18O analyses of water samples collected from 2003 to 2011 AD, indicate that within small, closed lakes in the Pacific Northwest November-February precipitation is the strongest seasonal, climatic control on sediment oxygen-isotope values. Further, a Monte Carlo based reconstruction of 20 year average November-February precipitation amounts strongly correlates (R2 = 0.66) to instrumental values from the 20th century (with all observed values falling within modeled 95% prediction limits), indicating that probabilistic, quantitative paleoclimate interpretations of lake sediment δ18O records are attainable.

  14. Sea level trend and variability in the Singapore Strait

    Directory of Open Access Journals (Sweden)

    P. Tkalich

    2013-03-01

    Full Text Available Sea level in the Singapore Strait (SS exhibits response to various scale phenomena, from local to global. Longest tide gauge records in SS are analysed to derive local sea level trend and annual, inter-annual and multi-decadal sea level variability, which then are attributed to regional and global phenomena. Annual data gaps are reconstructed using functions correlating sea level variability with ENSO. At annual scale, sea level anomalies in SS are (quasi-periodic monsoon-driven, of the order of ±20 cm, the highest during northeast monsoon and the lowest during southwest monsoon. Interannual regional sea level drops are associated with El Niño events, while the rises are correlated with La Niña episodes; both variations are in the range of ±5 cm. At multi-decadal scale, annual measured sea levels in SS are varying with global mean sea level, rising at the rate 1.2–1.7 mm yr−1 for 1975–2009, 1.8–2.3 mm yr−1 for 1984–2009 and 1.9–4.6 mm yr−1 for 1993–2009. When SS rates are compared with the global trends (2.0, 2.4 and 2.8 mm yr−1, respectively derived from tide gauge measurements for the same periods, they are smaller in the earlier era and considerably larger in the recent one. Taking into account the first estimate of land subsidence rate, 1–1.5 mm yr−1 in Singapore, the recent trend of absolute sea level rise in SS follows regional tendency.

  15. The SNAP Strong Lens Survey

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, P.

    2005-01-03

    Basic considerations of lens detection and identification indicate that a wide field survey of the types planned for weak lensing and Type Ia SNe with SNAP are close to optimal for the optical detection of strong lenses. Such a ''piggy-back'' survey might be expected even pessimistically to provide a catalogue of a few thousand new strong lenses, with the numbers dominated by systems of faint blue galaxies lensed by foreground ellipticals. After sketching out our strategy for detecting and measuring these galaxy lenses using the SNAP images, we discuss some of the scientific applications of such a large sample of gravitational lenses: in particular we comment on the partition of information between lens structure, the source population properties and cosmology. Understanding this partitioning is key to assessing strong lens cosmography's value as a cosmological probe.

  16. Strong coupling phase in QED

    International Nuclear Information System (INIS)

    Aoki, Ken-ichi

    1988-01-01

    Existence of a strong coupling phase in QED has been suggested in solutions of the Schwinger-Dyson equation and in Monte Carlo simulation of lattice QED. In this article we recapitulate the previous arguments, and formulate the problem in the modern framework of the renormalization theory, Wilsonian renormalization. This scheme of renormalization gives the best understanding of the basic structure of a field theory especially when it has a multi-phase structure. We resolve some misleading arguments in the previous literature. Then we set up a strategy to attack the strong phase, if any. We describe a trial; a coupled Schwinger-Dyson equation. Possible picture of the strong coupling phase QED is presented. (author)

  17. Variability and teleconnections of South and East Asian summer monsoons in present and future projections of CMIP5 climate models

    Science.gov (United States)

    Preethi, Bhaskar; Mujumdar, Milind; Prabhu, Amita; Kripalani, Ramesh

    2017-05-01

    Coupled Model Inter-comparison Project Phase 5 (CMIP5) model outputs of the South and East Asian summer monsoon variability and their tele-connections are investigated using historical simulations (1861-2005) and future projections under the RCP4.5 scenario (2006-2100). Detailed analyses are performed using nine models having better representation of the recent monsoon teleconnections for the interactive Asian monsoon sub-systems. However, these models underestimate rainfall mainly over South Asia and Korea-Japan sector, the regions of heavy rainfall, along with a bias in location of rainfall maxima. Indeed, the simulation biases, underestimations of monsoon variability and teleconnections suggest further improvements for better representation of Asian monsoon in the climate models. Interestingly, the performance of Australian Community Climate and Earth System Simulator version 1.0 (ACCESS1.0) in simulating the annual cycle, spatial pattern of rainfall and multi-decadal variations of summer monsoon rainfall over South and East Asia appears to more realistic. In spite of large spread among the CMIP5 models, historical simulations as well as future projections of summer monsoon rainfall indicate multi-decadal variability. These rainfall variations, displaying certain epochs of more rainfall over South Asia than over East Asia and vice versa, suggest an oscillatory behaviour. Teleconnections between South and East Asian monsoon rainfall also exhibit a multi-decadal variation with alternate epochs of strengthening and weakening relationship. Furthermore, large-scale circulation features such as South Asian monsoon trough and north Pacific subtropical high depict zonal oscillatory behaviour with east-west-east shifts. Periods with eastward or westward extension of the Mascarene High, intensification and expansion of the upper tropospheric South Asian High are also projected by the CMIP5 models.

  18. Variability Bugs:

    DEFF Research Database (Denmark)

    Melo, Jean

    Many modern software systems are highly configurable. They embrace variability to increase adaptability and to lower cost. To implement configurable software, developers often use the C preprocessor (CPP), which is a well-known technique, mainly in industry, to deal with variability in code....... Although many researchers suggest that preprocessor-based variability amplifies maintenance problems, there is little to no hard evidence on how actually variability affects programs and programmers. Specifically, how does variability affect programmers during maintenance tasks (bug finding in particular...... be exploited. Variability bugs are not confined to any particular type of bug, error-prone feature, or location. In addition to introducing an exponential number of program variants, variability increases the complexity of bugs due to unintended feature interactions, hidden features, combinations of layers...

  19. Strong interaction at finite temperature

    Indian Academy of Sciences (India)

    Abstract. We review two methods discussed in the literature to determine the effective parameters of strongly interacting particles as they move through a heat bath. The first one is the general method of chiral perturbation theory, which may be readily applied to this problem. The other is the method of thermal QCD sum rules ...

  20. Strong-strong beam-beam simulation on parallel computer

    Energy Technology Data Exchange (ETDEWEB)

    Qiang, Ji

    2004-08-02

    The beam-beam interaction puts a strong limit on the luminosity of the high energy storage ring colliders. At the interaction points, the electromagnetic fields generated by one beam focus or defocus the opposite beam. This can cause beam blowup and a reduction of luminosity. An accurate simulation of the beam-beam interaction is needed to help optimize the luminosity in high energy colliders.

  1. Strong-strong beam-beam simulation on parallel computer

    International Nuclear Information System (INIS)

    Qiang, Ji

    2004-01-01

    The beam-beam interaction puts a strong limit on the luminosity of the high energy storage ring colliders. At the interaction points, the electromagnetic fields generated by one beam focus or defocus the opposite beam. This can cause beam blowup and a reduction of luminosity. An accurate simulation of the beam-beam interaction is needed to help optimize the luminosity in high energy colliders

  2. PREFACE: Strongly correlated electron systems Strongly correlated electron systems

    Science.gov (United States)

    Saxena, Siddharth S.; Littlewood, P. B.

    2012-07-01

    This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The selected papers derived from invited presentations seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The focus is on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity and metal-insulator transitions. Both experimental and theoretical work is presented. Based on fundamental advances in the understanding of electronic materials, much of 20th century materials physics was driven by miniaturisation and integration in the electronics industry to the current generation of nanometre scale devices. The achievements of this industry have brought unprecedented advances to society and well-being, and no doubt there is much further to go—note that this progress is founded on investments and studies in the fundamentals of condensed matter physics from more than 50 years ago. Nevertheless, the defining challenges for the 21st century will lie in the discovery in science, and deployment through engineering, of technologies that can deliver the scale needed to have an impact on the sustainability agenda. Thus the big developments in nanotechnology may lie not in the pursuit of yet smaller transistors, but in the design of new structures that can revolutionise the performance of solar cells, batteries, fuel cells, light-weight structural materials, refrigeration, water purification, etc. The science presented in the papers of this special section also highlights the underlying interest in energy-dense materials, which

  3. AMOC decadal variability in Earth system models: Mechanisms and climate impacts

    Energy Technology Data Exchange (ETDEWEB)

    Fedorov, Alexey [Yale Univ., New Haven, CT (United States)

    2017-09-06

    This is the final report for the project titled "AMOC decadal variability in Earth system models: Mechanisms and climate impacts". The central goal of this one-year research project was to understand the mechanisms of decadal and multi-decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) within a hierarchy of climate models ranging from realistic ocean GCMs to Earth system models. The AMOC is a key element of ocean circulation responsible for oceanic transport of heat from low to high latitudes and controlling, to a large extent, climate variations in the North Atlantic. The questions of the AMOC stability, variability and predictability, directly relevant to the questions of climate predictability, were at the center of the research work.

  4. Enhanced biennial variability in the Pacific due to Atlantic capacitor effect.

    Science.gov (United States)

    Wang, Lei; Yu, Jin-Yi; Paek, Houk

    2017-03-20

    The El Niño-Southern Oscillation (ENSO) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in ENSO and the PSHs during recent decades. The 'charging' (that is, ENSO imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and 'discharging' (that is, the NTA SST triggering the following ENSO via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global warming trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard events.

  5. Pulsating variables

    International Nuclear Information System (INIS)

    1989-01-01

    The study of stellar pulsations is a major route to the understanding of stellar structure and evolution. At the South African Astronomical Observatory (SAAO) the following stellar pulsation studies were undertaken: rapidly oscillating Ap stars; solar-like oscillations in stars; 8-Scuti type variability in a classical Am star; Beta Cephei variables; a pulsating white dwarf and its companion; RR Lyrae variables and galactic Cepheids. 4 figs

  6. Strongly correlated systems experimental techniques

    CERN Document Server

    Mancini, Ferdinando

    2015-01-01

    The continuous evolution and development of experimental techniques is at the basis of any fundamental achievement in modern physics. Strongly correlated systems (SCS), more than any other, need to be investigated through the greatest variety of experimental techniques in order to unveil and crosscheck the numerous and puzzling anomalous behaviors characterizing them. The study of SCS fostered the improvement of many old experimental techniques, but also the advent of many new ones just invented in order to analyze the complex behaviors of these systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and materials science, belong to this class of systems. The volume presents a representative collection of the modern experimental techniques specifically tailored for the analysis of strongly correlated systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognize...

  7. Strongly Correlated Systems Theoretical Methods

    CERN Document Server

    Avella, Adolfo

    2012-01-01

    The volume presents, for the very first time, an exhaustive collection of those modern theoretical methods specifically tailored for the analysis of Strongly Correlated Systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and materials science, belong to this class of systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognized main contributors. The exposition has a clear pedagogical cut and fully reports on the most relevant case study where the specific technique showed to be very successful in describing and enlightening the puzzling physics of a particular strongly correlated system. The book is intended for advanced graduate students and post-docs in the field as textbook and/or main reference, but also for other researchers in the field who appreciates consulting a single, but comprehensive, source or wishes to get acquainted, in a as painless as po...

  8. Strongly correlated systems numerical methods

    CERN Document Server

    Mancini, Ferdinando

    2013-01-01

    This volume presents, for the very first time, an exhaustive collection of those modern numerical methods specifically tailored for the analysis of Strongly Correlated Systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and material science, belong to this class of systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognized main contributors. The exposition has a clear pedagogical cut and fully reports on the most relevant case study where the specific technique showed to be very successful in describing and enlightening the puzzling physics of a particular strongly correlated system. The book is intended for advanced graduate students and post-docs in the field as textbook and/or main reference, but also for other researchers in the field who appreciate consulting a single, but comprehensive, source or wishes to get acquainted, in a as painless as possi...

  9. Flavour Democracy in Strong Unification

    CERN Document Server

    Abel, S A; Abel, Steven; King, Steven

    1998-01-01

    We show that the fermion mass spectrum may naturally be understood in terms of flavour democratic fixed points in supersymmetric theories which have a large domain of attraction in the presence of "strong unification". Our approach provides an alternative to the approximate Yukawa texture zeroes of the Froggatt-Nielsen mechanism. We discuss a particular model based on a broken gauged $SU(3)_L\\times SU(3)_R$ family symmetry which illustrates our approach.

  10. Factors affecting the inter-annual to centennial timescale variability of Indian summer monsoon rainfall

    Science.gov (United States)

    Malik, Abdul; Brönnimann, Stefan

    2017-09-01

    The Modes of Ocean Variability (MOV) namely Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) can have significant impacts on Indian Summer Monsoon Rainfall (ISMR) on different timescales. The timescales at which these MOV interacts with ISMR and the factors which may perturb their relationship with ISMR need to be investigated. We employ De-trended Cross-Correlation Analysis (DCCA), and De-trended Partial-Cross-Correlation Analysis (DPCCA) to study the timescales of interaction of ISMR with AMO, PDO, and ENSO using observational dataset (AD 1854-1999), and atmosphere-ocean-chemistry climate model simulations with SOCOL-MPIOM (AD 1600-1999). Further, this study uses De-trended Semi-Partial Cross-Correlation Analysis (DSPCCA) to address the relation between solar variability and the ISMR. We find statistically significant evidence of intrinsic correlations of ISMR with AMO, PDO, and ENSO on different timescales, consistent between model simulations and observations. However, the model fails to capture modulation in intrinsic relationship between ISRM and MOV due to external signals. Our analysis indicates that AMO is a potential source of non-stationary relationship between ISMR and ENSO. Furthermore, the pattern of correlation between ISMR and Total Solar Irradiance (TSI) is inconsistent between observations and model simulations. The observational dataset indicates statistically insignificant negative intrinsic correlation between ISMR and TSI on decadal-to-centennial timescales. This statistically insignificant negative intrinsic correlation is transformed to statistically significant positive extrinsic by AMO on 61-86-year timescale. We propose a new mechanism for Sun-monsoon connection which operates through AMO by changes in summer (June-September; JJAS) meridional gradient of tropospheric temperatures (ΔTTJJAS). There is a negative (positive) intrinsic correlation between ΔTTJJAS (AMO) and

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

    Science.gov (United States)

    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

  12. Cognitive Variability

    Science.gov (United States)

    Siegler, Robert S.

    2007-01-01

    Children's thinking is highly variable at every level of analysis, from neural and associative levels to the level of strategies, theories, and other aspects of high-level cognition. This variability exists within people as well as between them; individual children often rely on different strategies or representations on closely related problems…

  13. Detection of Multidecadal Changes in UVB and Total Ozone Concentrations over the Continental US with NASA TOMS Data and USDA Ground-Based Measurements

    Directory of Open Access Journals (Sweden)

    Wei Gao

    2010-01-01

    Full Text Available Thinning of the atmospheric ozone layer leads to elevated levels of Ultraviolet-B (UVB at the Earth's surface, resulting in an increase of health risks to living organisms due to DNA damage. This paper examines the multidecadal changes of total column ozone from 1979 to 2005 with the aid of ground-based UVB stations using the ultraviolet multifilter rotating shadow-band radiometer (UV-MFRSR. For the purpose of demonstration, four USDA ground stations, WA01, CO01, MD01, and AZ01, were selected for detailed comparisons against the satellite data. The major finding of this study is that over the course of the time series, on a monthly scale, the UV index (UVI has increased at the four selected USDA stations while total ozone has decreased in the continental USA over the past three decades and spatial distributions of UVI and total ozone have shown substantial variations from coastal zones to the Midwest Regions of the USA, yet the tendency toward recovery of ozone layer in the continental USA cannot be fully confirmed. This leads to a conclusion that the UVI changes might have been influenced by other factors in addition to the total ozone in the atmospheric environment across at least 76% of the continental USA.

  14. Atoms in strong laser fields

    International Nuclear Information System (INIS)

    L'Huillier, A.

    2002-01-01

    When a high-power laser focuses into a gas of atoms, the electromagnetic field becomes of the same magnitude as the Coulomb field which binds a 1s electron in a hydrogen atom. 3 highly non-linear phenomena can happen: 1) ATI (above threshold ionization): electrons initially in the ground state absorb a large number of photons, many more than the minimum number required for ionization; 2) multiple ionization: many electrons can be emitted one at a time, in a sequential process, or simultaneously in a mechanism called direct or non-sequential; and 3) high order harmonic generation (HHG): efficient photon emission in the extreme ultraviolet range, in the form of high-order harmonics of the fundamental laser field can occur. The theoretical problem consists in solving the time dependent Schroedinger equation (TDSE) that describes the interaction of a many-electron atom with a laser field. A number of methods have been proposed to solve this problem in the case of a hydrogen atom or a single-active electron atom in a strong laser field. A large effort is presently being devoted to go beyond the single-active approximation. The understanding of the physics of the interaction between atoms and strong laser fields has been provided by a very simple model called ''simple man's theory''. A unified view of HHG, ATI, and non-sequential ionization, originating from the simple man's model and the strong field approximation, expressed in terms of electrons trajectories or quantum paths is slowly emerging. (A.C.)

  15. Strongly Interacting Light Dark Matter

    Directory of Open Access Journals (Sweden)

    Sebastian Bruggisser, Francesco Riva, Alfredo Urbano

    2017-09-01

    Full Text Available In the presence of approximate global symmetries that forbid relevant interactions, strongly coupled light Dark Matter (DM can appear weakly coupled at small energy and generate a sizable relic abundance. Fundamental principles like unitarity restrict these symmetries to a small class, where the leading interactions are captured by effective operators up to dimension-8. Chiral symmetry, spontaneously broken global symmetries and non-linearly realized supersymmetry are examples of this. Their DM candidates (composite fermions, pseudo Nambu-Goldstone Bosons and Goldstini are interesting targets for LHC missing-energy searches.

  16. Strongly interacting light dark matter

    International Nuclear Information System (INIS)

    Bruggisser, Sebastian; Riva, Francesco; Urbano, Alfredo

    2016-07-01

    In the presence of approximate global symmetries that forbid relevant interactions, strongly coupled light Dark Matter (DM) can appear weakly coupled at small-energy and generate a sizable relic abundance. Fundamental principles like unitarity restrict these symmetries to a small class, where the leading interactions are captured by effective operators up to dimension-8. Chiral symmetry, spontaneously broken global symmetries and non-linearly realized supersymmetry are examples of this. Their DM candidates (composite fermions, pseudo-Nambu-Goldstone Bosons and Goldstini) are interesting targets for LHC missing-energy searches.

  17. Rydberg atoms in strong fields

    International Nuclear Information System (INIS)

    Kleppner, D.; Tsimmerman, M.

    1985-01-01

    Experimental and theoretical achievements in studying Rydberg atoms in external fields are considered. Only static (or quasistatic) fields and ''one-electron'' atoms, i.e. atoms that are well described by one-electron states, are discussed. Mainly behaviour of alkali metal atoms in electric field is considered. The state of theoretical investigations for hydrogen atom in magnetic field is described, but experimental data for atoms of alkali metals are presented as an illustration. Results of the latest experimental and theoretical investigations into the structure of Rydberg atoms in strong fields are presented

  18. Scalar strong interaction hadron theory

    CERN Document Server

    Hoh, Fang Chao

    2015-01-01

    The scalar strong interaction hadron theory, SSI, is a first principles' and nonlocal theory at quantum mechanical level that provides an alternative to low energy QCD and Higgs related part of the standard model. The quark-quark interaction is scalar rather than color-vectorial. A set of equations of motion for mesons and another set for baryons have been constructed. This book provides an account of the present state of a theory supposedly still at its early stage of development. This work will facilitate researchers interested in entering into this field and serve as a basis for possible future development of this theory.

  19. Strong Plate, Weak Slab Dichotomy

    Science.gov (United States)

    Petersen, R. I.; Stegman, D. R.; Tackley, P.

    2015-12-01

    Models of mantle convection on Earth produce styles of convection that are not observed on Earth.Moreover non-Earth-like modes, such as two-sided downwellings, are the de facto mode of convection in such models.To recreate Earth style subduction, i.e. one-sided asymmetric recycling of the lithosphere, proper treatment of the plates and plate interface are required. Previous work has identified several model features that promote subduction. A free surface or pseudo-free surface and a layer of material with a relatively low strength material (weak crust) allow downgoing plates to bend and slide past overriding without creating undue stress at the plate interface. (Crameri, et al. 2012, GRL)A low viscosity mantle wedge, possibly a result of slab dehydration, decouples the plates in the system. (Gerya et al. 2007, Geo)Plates must be composed of material which, in the case of the overriding plate, are is strong enough to resist bending stresses imposed by the subducting plate and yet, as in the case of the subducting plate, be weak enough to bend and subduct when pulled by the already subducted slab. (Petersen et al. 2015, PEPI) Though strong surface plates are required for subduction such plates may present a problem when they encounter the lower mantle.As the subducting slab approaches the higher viscosity, lower mantle stresses are imposed on the tip.Strong slabs transmit this stress to the surface.There the stress field at the plate interface is modified and potentially modifies the style of convection. In addition to modifying the stress at the plate interface, the strength of the slab affects the morphology of the slab at the base of the upper mantle. (Stegman, et al 2010, Tectonophysics)Slabs that maintain a sufficient portion of their strength after being bent require high stresses to unbend or otherwise change their shape.On the other hand slabs that are weakened though the bending process are more amenable to changes in morphology. We present the results of

  20. Landsat and GRACE observations of arid wetland dynamics in a dryland river system under multi-decadal hydroclimatic extremes

    Science.gov (United States)

    Xie, Zunyi; Huete, Alfredo; Ma, Xuanlong; Restrepo-Coupe, Natalia; Devadas, Rakhesh; Clarke, Kenneth; Lewis, Megan

    2016-12-01

    Arid wetlands are important for biodiversity conservation, but sensitive and vulnerable to climate variability and hydroclimatic events. Amplification of the water cycle, including the increasing frequency and severity of droughts and wet extremes, is expected to alter spatial and temporal hydrological patterns in arid wetlands globally, with potential threats to ecosystem services and their functioning. Despite these pressing challenges, the ecohydrological interactions and resilience of arid wetlands to highly variable water regimes over long time periods remain largely unknown. Recent broad-scale drought and floods over Australia provide unique opportunities to improve our understanding of arid wetland ecosystem responses to hydroclimatic extremes. Here we analysed the ecohydrological dynamics of the Coongie Lakes arid wetland in central Australia, one of the world's largest Ramsar-designated wetlands, using more than two decades (1988-2011) of vegetation and floodwater extent retrievals derived from Landsat satellite observations. To explore the impacts of large-scale hydrological fluctuations on the arid wetland, we further coupled Landsat measurements with Total Water Storage Anomaly (TWSA) data obtained from the Gravity Recovery and Climate Experiment (GRACE) satellites. Pronounced seasonal and inter-annual variabilities of flood and vegetation activities were observed over the wetland, with variations in vegetation growth extent highly correlated with flood extent (r = 0.64, p Drought from 2001 to 2009 resulted in long-term absence of major flood events, which substantially suppressed wetland vegetation growth. However, the 2010-11 La Niña induced flooding events led to an exceptionally large resurgence of vegetation, with a mean vegetation growth extent anomaly exceeding the historical average (1988-2011) by more than 1.5 standard deviations, suggesting a significant resilience of arid wetland ecosystems to climate variability. This study showed the

  1. Low-frequency variability in North Sea and Baltic Sea identified through simulations with the 3-D coupled physical–biogeochemical model ECOSMO

    Directory of Open Access Journals (Sweden)

    U. Daewel

    2017-09-01

    Full Text Available Here we present results from a long-term model simulation of the 3-D coupled ecosystem model ECOSMO II for a North Sea and Baltic Sea set-up. The model allows both multi-decadal hindcast simulation of the marine system and specific process studies under controlled environmental conditions. Model results have been analysed with respect to long-term multi-decadal variability in both physical and biological parameters with the help of empirical orthogonal function (EOF analysis. The analysis of a 61-year (1948–2008 hindcast reveals a quasi-decadal variation in salinity, temperature and current fields in the North Sea in addition to singular events of major changes during restricted time frames. These changes in hydrodynamic variables were found to be associated with changes in ecosystem productivity that are temporally aligned with the timing of reported regime shifts in the areas. Our results clearly indicate that for analysing ecosystem productivity, spatially explicit methods are indispensable. Especially in the North Sea, a correlation analysis between atmospheric forcing and primary production (PP reveals significant correlations between PP and the North Atlantic Oscillation (NAO and wind forcing for the central part of the region, while the Atlantic Multi-decadal Oscillation (AMO and air temperature are correlated to long-term changes in PP in the southern North Sea frontal areas. Since correlations cannot serve to identify causal relationship, we performed scenario model runs perturbing the temporal variability in forcing condition to emphasize specifically the role of solar radiation, wind and eutrophication. The results revealed that, although all parameters are relevant for the magnitude of PP in the North Sea and Baltic Sea, the dominant impact on long-term variability and major shifts in ecosystem productivity was introduced by modulations of the wind fields.

  2. EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems

    Science.gov (United States)

    Ronning, Filip; Batista, Cristian

    2011-03-01

    Strongly correlated electrons is an exciting and diverse field in condensed matter physics. This special issue aims to capture some of that excitement and recent developments in the field. Given that this issue was inspired by the 2010 International Conference on Strongly Correlated Electron Systems (SCES 2010), we briefly give some history in order to place this issue in context. The 2010 International Conference on Strongly Correlated Electron Systems was held in Santa Fe, New Mexico, a reunion of sorts from the 1989 International Conference on the Physics of Highly Correlated Electron Systems that also convened in Santa Fe. SCES 2010—co-chaired by John Sarrao and Joe Thompson—followed the tradition of earlier conferences, in this century, hosted by Buzios (2008), Houston (2007), Vienna (2005), Karlsruhe (2004), Krakow (2002) and Ann Arbor (2001). Every three years since 1997, SCES has joined the International Conference on Magnetism (ICM), held in Recife (2000), Rome (2003), Kyoto (2006) and Karlsruhe (2009). Like its predecessors, SCES 2010 topics included strongly correlated f- and d-electron systems, heavy-fermion behaviors, quantum-phase transitions, non-Fermi liquid phenomena, unconventional superconductivity, and emergent states that arise from electronic correlations. Recent developments from studies of quantum magnetism and cold atoms complemented the traditional subjects and were included in SCES 2010. 2010 celebrated the 400th anniversary of Santa Fe as well as the birth of astronomy. So what's the connection to SCES? The Dutch invention of the first practical telescope and its use by Galileo in 1610 and subsequent years overturned dogma that the sun revolved about the earth. This revolutionary, and at the time heretical, conclusion required innovative combinations of new instrumentation, observation and mathematics. These same combinations are just as important 400 years later and are the foundation of scientific discoveries that were discussed

  3. The Role of Meteorology and Surface Condition to Multi-Decadal Variations of Dust Emission in Sahara and Sahel

    Science.gov (United States)

    Kim, D.; Chin, M.; Diehl, T. L.; Bian, H.; Brown, M. E.; Remer, L. A.; Stockwell, W. R.

    2014-12-01

    North Africa is the world's largest dust source region influencing regional and global climate, human health, and even the local economy. However North Africa as a dust source is not uniform but it consists of the arid region (Sahara) and the semi-arid region (Sahel) with emission rates depending on meteorological and surface conditions. Several recent studies have shown that dust from North Africa seems to have a decreasing trend in the past three decades. The goal of this study is to better understand the controlling factors that determine the change of dust in North Africa using observational data and model simulations. First we analyze surface bareness conditions determined from a long-term satellite observed Normalized Difference Vegetation Index for 1980-2008. Then we examine the key meteorological variables of precipitation and surface winds. Modeling experiments were conducted using the NASA Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, which has been recently updated with a dynamic dust source function. Using the method we separate the dust originating from the Sahel from that of the Sahara desert. We find that the surface wind speed is the most dominant factor affecting Sahelian dust emission while vegetation has a modulating effect. We will show regional differences in meteorological variables, surface conditions, dust emission, and dust distribution and address the relationships among meteorology, surface conditions, and dust emission/loading in the past three decades (1980-2008).

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

    Energy Technology Data Exchange (ETDEWEB)

    Fedorov, Alexey V. [Yale Univ., New Haven, CT (United States)

    2015-01-14

    The central goal of this research project was to understand the mechanisms of decadal and multi-decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) as related to climate variability and abrupt climate change within a hierarchy of climate models ranging from realistic ocean models to comprehensive Earth system models. Generalized Stability Analysis, a method that quantifies the transient and asymptotic growth of perturbations in the system, is one of the main approaches used throughout this project. The topics we have explored range from physical mechanisms that control AMOC variability to the factors that determine AMOC predictability in the Earth system models, to the stability and variability of the AMOC in past climates.

  5. Mismeasurement and the resonance of strong confounders: uncorrelated errors.

    Science.gov (United States)

    Marshall, J R; Hastrup, J L

    1996-05-15

    Greenland first documented (Am J Epidemiol 1980; 112:564-9) that error in the measurement of a confounder could resonate--that it could bias estimates of other study variables, and that the bias could persist even with statistical adjustment for the confounder as measured. An important question is raised by this finding: can such bias be more than trivial within the bounds of realistic data configurations? The authors examine several situations involving dichotomous and continuous data in which a confounder and a null variable are measured with error, and they assess the extent of resultant bias in estimates of the effect of the null variable. They show that, with continuous variables, measurement error amounting to 40% of observed variance in the confounder could cause the observed impact of the null study variable to appear to alter risk by as much as 30%. Similarly, they show, with dichotomous independent variables, that 15% measurement error in the form of misclassification could lead the null study variable to appear to alter risk by as much as 50%. Such bias would result only from strong confounding. Measurement error would obscure the evidence that strong confounding is a likely problem. These results support the need for every epidemiologic inquiry to include evaluations of measurement error in each variable considered.

  6. Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability.

    Science.gov (United States)

    Booth, Ben B B; Dunstone, Nick J; Halloran, Paul R; Andrews, Timothy; Bellouin, Nicolas

    2012-04-04

    Systematic climate shifts have been linked to multidecadal variability in observed sea surface temperatures in the North Atlantic Ocean. These links are extensive, influencing a range of climate processes such as hurricane activity and African Sahel and Amazonian droughts. The variability is distinct from historical global-mean temperature changes and is commonly attributed to natural ocean oscillations. A number of studies have provided evidence that aerosols can influence long-term changes in sea surface temperatures, but climate models have so far failed to reproduce these interactions and the role of aerosols in decadal variability remains unclear. Here we use a state-of-the-art Earth system climate model to show that aerosol emissions and periods of volcanic activity explain 76 per cent of the simulated multidecadal variance in detrended 1860-2005 North Atlantic sea surface temperatures. After 1950, simulated variability is within observational estimates; our estimates for 1910-1940 capture twice the warming of previous generation models but do not explain the entire observed trend. Other processes, such as ocean circulation, may also have contributed to variability in the early twentieth century. Mechanistically, we find that inclusion of aerosol-cloud microphysical effects, which were included in few previous multimodel ensembles, dominates the magnitude (80 per cent) and the spatial pattern of the total surface aerosol forcing in the North Atlantic. Our findings suggest that anthropogenic aerosol emissions influenced a range of societally important historical climate events such as peaks in hurricane activity and Sahel drought. Decadal-scale model predictions of regional Atlantic climate will probably be improved by incorporating aerosol-cloud microphysical interactions and estimates of future concentrations of aerosols, emissions of which are directly addressable by policy actions.

  7. Physics of Strongly Coupled Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kraeft, Wolf-Dietrich [Universitat Rostock (Germany)

    2007-07-15

    Strongly coupled plasmas (or non-ideal plasmas) are multi-component charged many-particle systems, in which the mean value of the potential energy of the system is of the same order as or even higher than the mean value of the kinetic energy. The constituents are electrons, ions, atoms and molecules. Dusty (or complex) plasmas contain still mesoscopic (multiply charged) particles. In such systems, the effects of strong coupling (non-ideality) lead to considerable deviations of physical properties from the corresponding properties of ideal plasmas, i.e., of plasmas in which the mean kinetic energy is essentially larger than the mean potential energy. For instance, bound state energies become density dependent and vanish at higher densities (Mott effect) due to the interaction of the pair with the surrounding particles. Non-ideal plasmas are of interest both for general scientific reasons (including, for example, astrophysical questions), and for technical applications such as inertially confined fusion. In spite of great efforts both experimentally and theoretically, satisfactory information on the physical properties of strongly coupled plasmas is not at hand for any temperature and density. For example, the theoretical description of non-ideal plasmas is possible only at low densities/high temperatures and at extremely high densities (high degeneracy). For intermediate degeneracy, however, numerical experiments have to fill the gap. Experiments are difficult in the region of 'warm dense matter'. The monograph tries to present the state of the art concerning both theoretical and experimental attempts. It mainly includes results of the work performed in famous Russian laboratories in recent decades. After outlining basic concepts (chapter 1), the generation of plasmas is considered (chapter 2, chapter 3). Questions of partial (chapter 4) and full ionization (chapter 5) are discussed including Mott transition and Wigner crystallization. Electrical and

  8. Strongly coupled dust coulomb clusters

    International Nuclear Information System (INIS)

    Juan Wentau; Lai Yingju; Chen Mingheng; I Lin

    1999-01-01

    The structures and motions of quasi-2-dimensional strongly coupled dust Coulomb clusters with particle number N from few to hundreds in a cylindrical rf plasma trap are studied and compared with the results from the molecular dynamic simulation using more ideal models. Shell structures with periodic packing in different shells and intershell rotational motion dominated excitations are observed at small N. As N increases, the boundary has less effect, the system recovers to the triangular lattice with isotropic vortex type cooperative excitations similar to an infinite N system except the outer shell region. The above generic behaviors are mainly determined by the system symmetry and agree with the simulation results. The detailed interaction form causes minor effect such as the fine structure of packing

  9. Probability densities in strong turbulence

    Science.gov (United States)

    Yakhot, Victor

    2006-03-01

    In this work we, using Mellin’s transform combined with the Gaussian large-scale boundary condition, calculate probability densities (PDFs) of velocity increments P(δu,r), velocity derivatives P(u,r) and the PDF of the fluctuating dissipation scales Q(η,Re), where Re is the large-scale Reynolds number. The resulting expressions strongly deviate from the Log-normal PDF P(δu,r) often quoted in the literature. It is shown that the probability density of the small-scale velocity fluctuations includes information about the large (integral) scale dynamics which is responsible for the deviation of P(δu,r) from P(δu,r). An expression for the function D(h) of the multifractal theory, free from spurious logarithms recently discussed in [U. Frisch, M. Martins Afonso, A. Mazzino, V. Yakhot, J. Fluid Mech. 542 (2005) 97] is also obtained.

  10. TEC variability over Havana

    International Nuclear Information System (INIS)

    Lazo, B.; Alazo, K.; Rodriguez, M.; Calzadilla, A.

    2003-01-01

    The variability of total electron content (TEC) measured over Havana using ATS-6, SMS-1 and GOES-3 geosynchronous satellite signals has been investigated for low, middle and high solar activity periods from 1974 to 1982. The obtained results show that standard deviation is smooth during nighttime hours and maximum at noon or postnoon hours. Strong solar activity dependence of standard deviation with a maximum values during HSA has been found. (author)

  11. Ecology and the ratchet of events: climate variability, niche dimensions, and species distributions

    Science.gov (United States)

    Jackson, Stephen T.; Betancourt, Julio L.; Booth, Robert K.; Gray, Stephen T.

    2009-01-01

    Climate change in the coming centuries will be characterized by interannual, decadal, and multidecadal fluctuations superimposed on anthropogenic trends. Predicting ecological and biogeographic responses to these changes constitutes an immense challenge for ecologists. Perspectives from climatic and ecological history indicate that responses will be laden with contingencies, resulting from episodic climatic events interacting with demographic and colonization events. This effect is compounded by the dependency of environmental sensitivity upon life-stage for many species. Climate variables often used in empirical niche models may become decoupled from the proximal variables that directly influence individuals and populations. Greater predictive capacity, and more-fundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics.

  12. Medieval Warm Period, Little Ice Age and 20th century temperature variability from Chesapeake Bay

    Science.gov (United States)

    Cronin, T. M.; Dwyer, G.S.; Kamiya, T.; Schwede, S.; Willard, D.A.

    2003-01-01

    We present paleoclimate evidence for rapid (changes in the strength of North Atlantic thermohaline circulation (THC). Evidence is presented for a long period of sustained regional and North Atlantic-wide warmth with low-amplitude temperature variability between ~450 and 1000 AD. In addition to centennial-scale temperature shifts, the existence of numerous temperature maxima between 2200 and 250 years BP (average ~70 years) suggests that multi-decadal processes typical of the North Atlantic Oscillation (NAO) are an inherent feature of late Holocene climate. However, late 19th and 20th century temperature extremes in Chesapeake Bay associated with NAO climate variability exceeded those of the prior 2000 years, including the interval 450-1000 AD, by 2-3oC, suggesting anomalous recent behavior of the climate system.

  13. Strong Ideal Convergence in Probabilistic Metric Spaces

    Indian Academy of Sciences (India)

    In the present paper we introduce the concepts of strongly ideal convergent sequence and strong ideal Cauchy sequence in a probabilistic metric (PM) space endowed with the strong topology, and establish some basic facts. Next, we define the strong ideal limit points and the strong ideal cluster points of a sequence in this ...

  14. Strong ideal convergence in probabilistic metric spaces

    Indian Academy of Sciences (India)

    In the present paper we introduce the concepts of strongly ideal convergent sequence and strong ideal Cauchy sequence in a probabilistic metric (PM) space endowed with the strong topology, and establish some basic facts. Next, we define the strong ideal limit points and the strong ideal cluster points of a sequence in this ...

  15. Remnants of strong tidal interactions

    International Nuclear Information System (INIS)

    Mcglynn, T.A.

    1990-01-01

    This paper examines the properties of stellar systems that have recently undergone a strong tidal shock, i.e., a shock which removes a significant fraction of the particles in the system, and where the shocked system has a much smaller mass than the producer of the tidal field. N-body calculations of King models shocked in a variety of ways are performed, and the consequences of the shocks are investigated. The results confirm the prediction of Jaffe for shocked systems. Several models are also run where the tidal forces on the system are constant, simulating a circular orbit around a primary, and the development of tidal radii under these static conditions appears to be a mild process which does not dramatically affect material that is not stripped. The tidal radii are about twice as large as classical formulas would predict. Remnant density profiles are compared with a sample of elliptical galaxies, and the implications of the results for the development of stellar populations and galaxies are considered. 38 refs

  16. John Strong - 1941-2006

    CERN Document Server

    2006-01-01

    Our friend and colleague John Strong was cruelly taken from us by a brain tumour on 31 July, a few days before his 65th birthday. John started his career and obtained his PhD in a group from Westfield College, initially working on experiments at Rutherford Appleton Laboratory (RAL). From the early 1970s onwards, however, his research was focused on experiments in CERN, with several particularly notable contributions. The Omega spectrometer adopted a system John had originally developed for experiments at RAL using vidicon cameras (a type of television camera) to record the sparks in the spark chambers. This highly automated system allowed Omega to be used in a similar way to bubble chambers. He contributed to the success of NA1 and NA7, where he became heavily involved in the electronic trigger systems. In these experiments the Westfield group joined forces with Italian colleagues to measure the form factors of the pion and the kaon, and the lifetime of some of the newly discovered charm particles. Such h...

  17. Strong seismic ground motion propagation

    International Nuclear Information System (INIS)

    Seale, S.; Archuleta, R.; Pecker, A.; Bouchon, M.; Mohammadioun, G.; Murphy, A.; Mohammadioun, B.

    1988-10-01

    At the McGee Creek, California, site, 3-component strong-motion accelerometers are located at depths of 166 m, 35 m and 0 m. The surface material is glacial moraine, to a depth of 30.5 m, overlying homfels. Accelerations were recorded from two California earthquakes: Round Valley, M L 5.8, November 23, 1984, 18:08 UTC and Chalfant Valley, M L 6.4, July 21, 1986, 14:42 UTC. By separating out the SH components of acceleration, we were able to determine the orientations of the downhole instruments. By separating out the SV component of acceleration, we were able to determine the approximate angle of incidence of the signal at 166 m. A constant phase velocity Haskell-Thomson model was applied to generate synthetic SH seismograms at the surface using the accelerations recorded at 166 m. In the frequency band 0.0 - 10.0 Hz, we compared the filtered synthetic records to the filtered surface data. The onset of the SH pulse is clearly seen, as are the reflections from the interface at 30.5 m. The synthetic record closely matches the data in amplitude and phase. The fit between the synthetic accelerogram and the data shows that the seismic amplification at the surface is a result of the contrast of the impedances (shear stiffnesses) of the near surface materials

  18. Surfing wave climate variability

    Science.gov (United States)

    Espejo, Antonio; Losada, Iñigo J.; Méndez, Fernando J.

    2014-10-01

    International surfing destinations are highly dependent on specific combinations of wind-wave formation, thermal conditions and local bathymetry. Surf quality depends on a vast number of geophysical variables, and analyses of surf quality require the consideration of the seasonal, interannual and long-term variability of surf conditions on a global scale. A multivariable standardized index based on expert judgment is proposed for this purpose. This index makes it possible to analyze surf conditions objectively over a global domain. A summary of global surf resources based on a new index integrating existing wave, wind, tides and sea surface temperature databases is presented. According to general atmospheric circulation and swell propagation patterns, results show that west-facing low to middle-latitude coasts are more suitable for surfing, especially those in the Southern Hemisphere. Month-to-month analysis reveals strong seasonal variations in the occurrence of surfable events, enhancing the frequency of such events in the North Atlantic and the North Pacific. Interannual variability was investigated by comparing occurrence values with global and regional modes of low-frequency climate variability such as El Niño and the North Atlantic Oscillation, revealing their strong influence at both the global and the regional scale. Results of the long-term trends demonstrate an increase in the probability of surfable events on west-facing coasts around the world in recent years. The resulting maps provide useful information for surfers, the surf tourism industry and surf-related coastal planners and stakeholders.

  19. Complex variables

    CERN Document Server

    Fisher, Stephen D

    1999-01-01

    The most important topics in the theory and application of complex variables receive a thorough, coherent treatment in this introductory text. Intended for undergraduates or graduate students in science, mathematics, and engineering, this volume features hundreds of solved examples, exercises, and applications designed to foster a complete understanding of complex variables as well as an appreciation of their mathematical beauty and elegance. Prerequisites are minimal; a three-semester course in calculus will suffice to prepare students for discussions of these topics: the complex plane, basic

  20. Climate variability in the subarctic area for the last 2 millennia

    Science.gov (United States)

    Nicolle, Marie; Debret, Maxime; Massei, Nicolas; Colin, Christophe; deVernal, Anne; Divine, Dmitry; Werner, Johannes P.; Hormes, Anne; Korhola, Atte; Linderholm, Hans W.

    2018-01-01

    To put recent climate change in perspective, it is necessary to extend the instrumental climate records with proxy data from paleoclimate archives. Arctic climate variability for the last 2 millennia has been investigated using statistical and signal analyses from three regionally averaged records from the North Atlantic, Siberia and Alaska based on many types of proxy data archived in the Arctic 2k database v1.1.1. In the North Atlantic and Alaska, the major climatic trend is characterized by long-term cooling interrupted by recent warming that started at the beginning of the 19th century. This cooling is visible in the Siberian region at two sites, warming at the others. The cooling of the Little Ice Age (LIA) was identified from the individual series, but it is characterized by wide-range spatial and temporal expression of climate variability, in contrary to the Medieval Climate Anomaly. The LIA started at the earliest by around AD 1200 and ended at the latest in the middle of the 20th century. The widespread temporal coverage of the LIA did not show regional consistency or particular spatial distribution and did not show a relationship with archive or proxy type either. A focus on the last 2 centuries shows a recent warming characterized by a well-marked warming trend parallel with increasing greenhouse gas emissions. It also shows a multidecadal variability likely due to natural processes acting on the internal climate system on a regional scale. A ˜ 16-30-year cycle is found in Alaska and seems to be linked to the Pacific Decadal Oscillation, whereas ˜ 20-30- and ˜ 50-90-year periodicities characterize the North Atlantic climate variability, likely in relation with the Atlantic Multidecadal Oscillation. These regional features are probably linked to the sea ice cover fluctuations through ice-temperature positive feedback.

  1. The strong law of large numbers for random quadratic forms

    NARCIS (Netherlands)

    Mikosch, T

    1996-01-01

    The paper establishes strong laws of large numbers for the quadratic forms [GRAPHICS] and the bilinear forms [GRAPHICS] where X = (X(n)) is a sequence of independent random variables and Y = (Y-n) is an independent copy of it. In the case of independent identically distributed symmetric p-stable

  2. On the use of Standardized Drought Indices under decadal climate variability: Critical assessment and drought policy implications

    Science.gov (United States)

    Núñez, J.; Rivera, D.; Oyarzún, R.; Arumí, J. L.

    2014-09-01

    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 variability. 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 variability. 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.

  3. An empirical model of decadal ENSO variability

    Energy Technology Data Exchange (ETDEWEB)

    Kravtsov, S. [University of Wisconsin-Milwaukee, Department of Mathematical Sciences, Atmospheric Sciences Group, P. O. Box 413, Milwaukee, WI (United States)

    2012-11-15

    This paper assesses potential predictability of decadal variations in the El Nino/Southern Oscillation (ENSO) characteristics by constructing and performing simulations using an empirical nonlinear stochastic model of an ENSO index. The model employs decomposition of global sea-surface temperature (SST) anomalies into the modes that maximize the ratio of interdecadal-to-subdecadal SST variance to define low-frequency predictors called the canonical variates (CVs). When the whole available SST time series is so processed, the leading canonical variate (CV-1) is found to be well correlated with the area-averaged SST time series which exhibits a non-uniform warming trend, while the next two (CV-2 and CV-3) describe secular variability arguably associated with a combination of Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) signals. The corresponding ENSO model that uses either all three (CVs 1-3) or only AMO/PDO-related (CVs 2 and 3) predictors captures well the observed autocorrelation function, probability density function, seasonal dependence of ENSO, and, most importantly, the observed interdecadal modulation of ENSO variance. The latter modulation, and its dependence on CVs, is shown to be inconsistent with the null hypothesis of random decadal ENSO variations simulated by multivariate linear inverse models. Cross-validated hindcasts of ENSO variance suggest a potential useful skill at decadal lead times. These findings thus argue that decadal modulations of ENSO variability may be predictable subject to our ability to forecast AMO/PDO-type climate modes; the latter forecasts may need to be based on simulations of dynamical models, rather than on a purely statistical scheme as in the present paper. (orig.)

  4. Strongly interacting photons and atoms

    International Nuclear Information System (INIS)

    Alge, W.

    1999-05-01

    This thesis contains the main results of the research topics I have pursued during the my PhD studies at the University of Innsbruck and partly in collaboration with the Institut d' Optique in Orsay, France. It is divided into three parts. The first and largest part discusses the possibility of using strong standing waves as a tool to cool and trap neutral atoms in optical cavities. This is very important in the field of nonlinear optics where several successful experiments with cold atoms in cavities have been performed recently. A discussion of the optical parametric oscillator in a regime where the nonlinearity dominates the evolution is the topic of the second part. We investigated mainly the statistical properties of the cavity output of the three interactive cavity modes. Very recently a system has been proposed which promises fantastic properties. It should exhibit a giant Kerr nonlinearity with negligible absorption thus leading to a photonic turnstile device based on cold atoms in cavity. We have shown that this model suffers from overly simplistic assumptions and developed several more comprehensive approaches to study the behavior of this system. Apart from the division into three parts of different contents the thesis is divided into publications, supplements and invisible stuff. The intention of the supplements is to reach researchers which work in related areas and provide them with more detailed information about the concepts and the numerical tools we used. It is written especially for diploma and PhD students to give them a chance to use the third part of our work which is actually the largest one. They consist of a large number of computer programs we wrote to investigate the behavior of the systems in parameter regions where no hope exists to solve the equations analytically. (author)

  5. Topics in strong Langmuir turbulence

    International Nuclear Information System (INIS)

    Skoric, M.M.

    1981-01-01

    This thesis discusses certain aspects of the turbulence of a fully ionised non-isothermal plasma dominated by the Langmuir mode. Some of the basic properties of strongly turbulent plasmas are reviewed. In particular, interest is focused on the state of Langmuir turbulence, that is the turbulence of a simple externally unmagnetized plasma. The problem of the existence and dynamics of Langmuir collapse is discussed, often met as a non-linear stage of the modulational instability in the framework of the Zakharov equations (i.e. simple time-averaged dynamical equations). Possible macroscopic consequences of such dynamical turbulent models are investigated. In order to study highly non-linear collapse dynamics in its advanced stage, a set of generalized Zakharov equations are derived. Going beyond the original approximation, the author includes the effects of higher electron non-linearities and a breakdown of slow-timescale quasi-neutrality. He investigates how these corrections may influence the collapse stabilisation. Recently, it has been realised that the modulational instability in a Langmuir plasma will be accompanied by the collisionless-generation of a slow-timescale magnetic field. Accordingly, a novel physical situation has emerged which is investigated in detail. The stability of monochromatic Langmuir waves in a self-magnetized Langmuir plasma, is discussed, and the existence of a novel magneto-modulational instability shown. The wave collapse dynamics is investigated and a physical interpretation of the basic results is given. A problem of the transient analysis of an interaction of time-dependent electromagnetic pulses with linear cold plasma media is investigated. (Auth.)

  6. Promoting Strong Written Communication Skills

    Science.gov (United States)

    Narayanan, M.

    2015-12-01

    The reason that an improvement in the quality of technical writing is still needed in the classroom is due to the fact that universities are facing challenging problems not only on the technological front but also on the socio-economic front. The universities are actively responding to the changes that are taking place in the global consumer marketplace. Obviously, there are numerous benefits of promoting strong written communication skills. They can be summarized into the following six categories. First, and perhaps the most important: The University achieves learner satisfaction. The learner has documented verbally, that the necessary knowledge has been successfully acquired. This results in learner loyalty that in turn will attract more qualified learners.Second, quality communication lowers the cost per pupil, consequently resulting in increased productivity backed by a stronger economic structure and forecast. Third, quality communications help to improve the cash flow and cash reserves of the university. Fourth, having high quality communication enables the university to justify the need for high costs of tuition and fees. Fifth, better quality in written communication skills result in attracting top-quality learners. This will lead to happier and satisfied learners, not to mention greater prosperity for the university as a whole. Sixth, quality written communication skills result in reduced complaints, thus meaning fewer hours spent on answering or correcting the situation. The University faculty and staff are thus able to devote more time on scholarly activities, meaningful research and productive community service. References Boyer, Ernest L. (1990). Scholarship reconsidered: Priorities of the Professorate.Princeton, NJ: Carnegie Foundation for the Advancement of Teaching. Hawkins, P., & Winter, J. (1997). Mastering change: Learning the lessons of the enterprise.London: Department for Education and Employment. Buzzel, Robert D., and Bradley T. Gale. (1987

  7. Spatially Extensive Standardized Surveys Reveal Widespread, Multi-Decadal Increase in East Antarctic Adélie Penguin Populations.

    Science.gov (United States)

    Southwell, Colin; Emmerson, Louise; McKinlay, John; Newbery, Kym; Takahashi, Akinori; Kato, Akiko; Barbraud, Christophe; DeLord, Karine; Weimerskirch, Henri

    2015-01-01

    Seabirds are considered to be useful and practical indicators of the state of marine ecosystems because they integrate across changes in the lower trophic levels and the physical environment. Signals from this key group of species can indicate broad scale impacts or response to environmental change. Recent studies of penguin populations, the most commonly abundant Antarctic seabirds in the west Antarctic Peninsula and western Ross Sea, have demonstrated that physical changes in Antarctic marine environments have profound effects on biota at high trophic levels. Large populations of the circumpolar-breeding Adélie penguin occur in East Antarctica, but direct, standardized population data across much of this vast coastline have been more limited than in other Antarctic regions. We combine extensive new population survey data, new population estimation methods, and re-interpreted historical survey data to assess decadal-scale change in East Antarctic Adélie penguin breeding populations. We show that, in contrast to the west Antarctic Peninsula and western Ross Sea where breeding populations have decreased or shown variable trends over the last 30 years, East Antarctic regional populations have almost doubled in abundance since the 1980's and have been increasing since the earliest counts in the 1960's. The population changes are associated with five-year lagged changes in the physical environment, suggesting that the changing environment impacts primarily on the pre-breeding age classes. East Antarctic marine ecosystems have been subject to a number of changes over the last 50 years which may have influenced Adélie penguin population growth, including decadal-scale climate variation, an inferred mid-20th century sea-ice contraction, and early-to-mid 20th century exploitation of fish and whale populations.

  8. Spatially Extensive Standardized Surveys Reveal Widespread, Multi-Decadal Increase in East Antarctic Adélie Penguin Populations.

    Directory of Open Access Journals (Sweden)

    Colin Southwell

    Full Text Available Seabirds are considered to be useful and practical indicators of the state of marine ecosystems because they integrate across changes in the lower trophic levels and the physical environment. Signals from this key group of species can indicate broad scale impacts or response to environmental change. Recent studies of penguin populations, the most commonly abundant Antarctic seabirds in the west Antarctic Peninsula and western Ross Sea, have demonstrated that physical changes in Antarctic marine environments have profound effects on biota at high trophic levels. Large populations of the circumpolar-breeding Adélie penguin occur in East Antarctica, but direct, standardized population data across much of this vast coastline have been more limited than in other Antarctic regions. We combine extensive new population survey data, new population estimation methods, and re-interpreted historical survey data to assess decadal-scale change in East Antarctic Adélie penguin breeding populations. We show that, in contrast to the west Antarctic Peninsula and western Ross Sea where breeding populations have decreased or shown variable trends over the last 30 years, East Antarctic regional populations have almost doubled in abundance since the 1980's and have been increasing since the earliest counts in the 1960's. The population changes are associated with five-year lagged changes in the physical environment, suggesting that the changing environment impacts primarily on the pre-breeding age classes. East Antarctic marine ecosystems have been subject to a number of changes over the last 50 years which may have influenced Adélie penguin population growth, including decadal-scale climate variation, an inferred mid-20th century sea-ice contraction, and early-to-mid 20th century exploitation of fish and whale populations.

  9. Multi-decadal classification of synoptic weather types, observed trends and links to rainfall characteristics over Saudi Arabia

    KAUST Repository

    El Kenawy, Ahmed M.

    2014-09-15

    An automated version of the Lamb weather type classification scheme was employed to characterize daily circulation conditions in Saudi Arabia from 1960 to 2005. Daily gridded fields of sea level pressure (SLP) from both the NCEP/NCAR and the European Center for Medium-Range Weather Forecast (ECMWF) reanalysis data (ERA40) were used as input data for this classification. The output catalog included 10 basic types, which describe the direction and vorticity of airflow in the region (i.e., cyclonic, anti-cyclonic, and directional). In general, our findings indicate that cyclonic (C) days represent the most frequent type among all days, with 69.2% of the annual count of days from 1960 to 2005, followed by SE directional flows (21%). It was also determined that airflows originating from the Indian Ocean (i.e., S, SE, and E) are more frequent than those from the Mediterranean and Red Seas (i.e., W, NW, and SW). The defined weather types were assessed for the presence of inter-annual and intra-annual trends using the Mann–Kendall tau statistic. The trend analysis suggests statistically significant changes in the frequencies of a majority of the weather types from 1960 to 2005. The relationship between the daily occurrence of rainfall and the frequency of individual weather types was also described using daily rainfall data from a network of 87 weather observatories. Results demonstrate that increasing frequencies of weather types connected to easterly inflows support higher precipitation amounts over the study domain. Characterizing the association between atmospheric circulation patterns and rainfall in Saudi Arabia is important for understanding potential impacts related to climate variability and also for developing circulation-based downscaling methods.

  10. Temporal genetic stability in natural populations of the waterflea Daphnia magna in response to strong selection pressure.

    Science.gov (United States)

    Orsini, Luisa; Marshall, Hollie; Cuenca Cambronero, Maria; Chaturvedi, Anurag; Thomas, Kelley W; Pfrender, Michael E; Spanier, Katina I; De Meester, Luc

    2016-12-01

    Studies monitoring changes in genetic diversity and composition through time allow a unique understanding of evolutionary dynamics and persistence of natural populations. However, such studies are often limited to species with short generation times that can be propagated in the laboratory or few exceptional cases in the wild. Species that produce dormant stages provide powerful models for the reconstruction of evolutionary dynamics in the natural environment. A remaining open question is to what extent dormant egg banks are an unbiased representation of populations and hence of the species' evolutionary potential, especially in the presence of strong environmental selection. We address this key question using the water flea Daphnia magna, which produces dormant stages that accumulate in biological archives over time. We assess temporal genetic stability in three biological archives, previously used in resurrection ecology studies showing adaptive evolutionary responses to rapid environmental change. We show that neutral genetic diversity does not decline with the age of the population and it is maintained in the presence of strong selection. In addition, by comparing temporal genetic stability in hatched and unhatched populations from the same biological archive, we show that dormant egg banks can be consulted to obtain a reliable measure of genetic diversity over time, at least in the multidecadal time frame studied here. The stability of neutral genetic diversity through time is likely mediated by the buffering effect of the resting egg bank. © 2016 John Wiley & Sons Ltd.

  11. Variability and predictability of decadal mean temperature and precipitation over China in the CCSM4 last millennium simulation

    Science.gov (United States)

    Ying, Kairan; Frederiksen, Carsten S.; Zheng, Xiaogu; Lou, Jiale; Zhao, Tianbao

    2018-02-01

    The modes of variability that arise from the slow-decadal (potentially predictable) and intra-decadal (unpredictable) components of decadal mean temperature and precipitation over China are examined, in a 1000 year (850-1850 AD) experiment using the CCSM4 model. Solar variations, volcanic aerosols, orbital forcing, land use, and greenhouse gas concentrations provide the main forcing and boundary conditions. The analysis is done using a decadal variance decomposition method that identifies sources of potential decadal predictability and uncertainty. The average potential decadal predictabilities (ratio of slow-to-total decadal variance) are 0.62 and 0.37 for the temperature and rainfall over China, respectively, indicating that the (multi-)decadal variations of temperature are dominated by slow-decadal variability, while precipitation is dominated by unpredictable decadal noise. Possible sources of decadal predictability for the two leading predictable modes of temperature are the external radiative forcing, and the combined effects of slow-decadal variability of the Arctic oscillation (AO) and the Pacific decadal oscillation (PDO), respectively. Combined AO and PDO slow-decadal variability is associated also with the leading predictable mode of precipitation. External radiative forcing as well as the slow-decadal variability of PDO are associated with the second predictable rainfall mode; the slow-decadal variability of Atlantic multi-decadal oscillation (AMO) is associated with the third predictable precipitation mode. The dominant unpredictable decadal modes are associated with intra-decadal/inter-annual phenomena. In particular, the El Niño-Southern Oscillation and the intra-decadal variability of the AMO, PDO and AO are the most important sources of prediction uncertainty.

  12. Satellite retrieval of actual evapotranspiration in the Tibetan Plateau: Components partitioning, multidecadal trends and dominated factors identifying

    Science.gov (United States)

    Wang, Weiguang; Li, Jinxing; Yu, Zhongbo; Ding, Yimin; Xing, Wanqiu; Lu, Wenjun

    2018-04-01

    . In addition, compared with evaporation-related meteorological variables, precipitation and leaf area index (LAI) provide the more dominated contributions to the changes of ET and Ei in the TP, while LAI is overwhelming contribution factor for Ec changes. As for Es changes, although precipitation play the important role, the effects of other factors are also non-negligible.

  13. Increasing Megadrought Risk at the Intersection of Decadal to Centennial Variability and Climate Change

    Science.gov (United States)

    Overpeck, J. T.; Parsons, L. A.; Loope, G. R.; Ault, T.; Cole, J. E.; Otto-Bliesner, B. L.; Buckle, N.; Stevenson, S.; Fasullo, J.

    2016-12-01

    Even more than the 1930's U.S. Dust Bowl Drought, the 20th century Sahel drought stands out as the most unprecedented drought of the instrumental era, in part because it extended over multiple decades. Paleoclimatic evidence makes it clear that this Sahel drought was nonetheless not really unprecedented - droughts many decades long have occurred in sub-Saharan Africa regularly over the last several thousand years, and these constitute what is now increasingly referred to as "megadrought." Paleoclimatic evidence also makes it clear that all drought-prone semi-arid and arid regions of the globe, including southwestern North America, southeastern Australia, and the Mediterranean/Middle Eastern region likely experienced multiple such multidecadal megadroughts in recent pre-Anthropocene Earth history. In other regions of the globe, including parts of South Asia and Amazonia, short but devastating droughts of the last 50-150 years, were also eclipsed in recent Earth history by much more serious megadrought, although these megadroughts were shorter than the multidecadal droughts of Africa or SW North America. In the past, megadroughts have occurred for reasons that are increasingly well understood in terms of ocean-atmosphere dynamics that led to unusually persistent precipitation deficits. Many of these same dynamics are well simulated in state-of-the-art Earth System Models, and yet comparisons between simulated and observed paleohydroclimatic variability suggests the models generally underestimate the risk of megadrought. Paleohydroclimatic records in some cases overestimate drought persistence, but there appear to be other issues at play that need to be better understood and simulated: positive land-atmosphere feedbacks, overly energetic interannual (i.e., ENSO) modes of variability, and insufficient internal multidecadal to centennial coupled climate system variability. Taking these issues and the impact of anthropogenic climate change into account means that the

  14. Atmospheric forcing of decadal Baltic Sea level variability in the last 200 years. A statistical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Huenicke, B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Kuestenforschung

    2008-11-06

    This study aims at the estimation of the impact of different atmospheric factors on the past sealevel variations (up to 200 years) in the Baltic Sea by statistically analysing the relationship between Baltic Sea level records and observational and proxy-based reconstructed climatic data sets. The focus lies on the identification and possible quantification of the contribution of sealevel pressure (wind), air-temperature and precipitation to the low-frequency (decadal and multi-decadal) variability of Baltic Sea level. It is known that the wind forcing is the main factor explaining average Baltic Sea level variability at inter-annual to decadal timescales, especially in wintertime. In this thesis it is statistically estimated to what extent other regional climate factors contribute to the spatially heterogeneous Baltic Sea level variations around the isostatic trend at multi-decadal timescales. Although the statistical analysis cannot be completely conclusive, as the potential climate drivers are all statistically interrelated to some degree, the results indicate that precipitation should be taken into account as an explanatory variable for sea-level variations. On the one hand it has been detected that the amplitude of the annual cycle of Baltic Sea level has increased throughout the 20th century and precipitation seems to be the only factor among those analysed (wind through SLP field, barometric effect, temperature and precipitation) that can account for this evolution. On the other hand, precipitation increases the ability to hindcast inter-annual variations of sea level in some regions and seasons, especially in the Southern Baltic in summertime. The mechanism by which precipitation exerts its influence on Baltic Sea level is not ascertained in this statistical analysis due to the lack of long salinity time series. This result, however, represents a working hypothesis that can be confirmed or disproved by long simulations of the Baltic Sea system - ocean

  15. Complex variables

    CERN Document Server

    Flanigan, Francis J

    2010-01-01

    A caution to mathematics professors: Complex Variables does not follow conventional outlines of course material. One reviewer noting its originality wrote: ""A standard text is often preferred [to a superior text like this] because the professor knows the order of topics and the problems, and doesn't really have to pay attention to the text. He can go to class without preparation."" Not so here-Dr. Flanigan treats this most important field of contemporary mathematics in a most unusual way. While all the material for an advanced undergraduate or first-year graduate course is covered, discussion

  16. Driven transverse shear waves in a strongly coupled dusty plasma

    International Nuclear Information System (INIS)

    Bandyopadhyay, P.; Prasad, G.; Sen, A.; Kaw, P.K.

    2008-01-01

    The linear dispersion properties of transverse shear waves in a strongly coupled dusty plasma are experimentally studied in a DC discharge device by exciting them in a controlled manner with a variable frequency external source. The dusty plasma is maintained in the strongly coupled fluid regime with (1 c ) where Γ is the Coulomb coupling parameter and Γ c is the crystallization limit. A dispersion relation for the transverse waves is experimentally obtained over a frequency range of 0.1 Hz to 2 Hz and found to show good agreement with viscoelastic theoretical results

  17. Examining spatial variability in relative sea-level in the New York City/New Jersey region during the Common Era

    Science.gov (United States)

    Walker, Jennifer; Clear, Jennifer; Garcia-Artola, Ane; Khan, Nicole; Shaw, Timothy; Corbett, Reide; Kemp, Andrew; Kopp, Robert; Horton, Benjamin

    2017-04-01

    Relative sea-level (RSL) reconstructions extend the 20th century instrumental record (tide gauge and satellite measurements) of spatial and temporal sea-level variability to provide a much longer context for recent trends and projected RSL rise. Common Era (last 2000 years) RSL reconstructions illustrate patterns of natural variability and include natural phases of climate and sea-level which will improve our knowledge basis for sea-level responses to climate changes. The northeast U.S. has exhibited varying rates in relative sea-level rise through the Common Era, primarily due to glacial isostatic adjustment. However, other factors such as ocean/atmosphere dynamics, sediment compaction, and the static equilibrium response to land ice changes, further influence the evolution of relative sea-level. The spatial variability is manifest in the tide gauge records. The tide gauge at the Battery, New York City (1856 to 2015) records a relative sea-level rise of 2.8 mm/yr whereas the tide gauge at Sandy Hook, New Jersey (1932 to 2015), 25 km southeast, records 4.1 mm/yr. Here we present a new reconstruction of RSL in northern New Jersey using geological and tide gauge data. A Common Era sea-level record from northern New Jersey fills in the spatial gap between records completed in southern New Jersey, New York City, and Connecticut. Our field study site is in Cheesequake State Park, where we observed sedimentary sequences dating back 2000 cal. yrs. BP. We use microfossil indicators preserved in salt-marsh sediments as a proxy to reconstruct RSL with decimeter precision. Salt-marsh foraminifera act as reliable RSL indicators because their modern distribution is strongly linked to tidal elevation. The recent application of microfossil-based transfer functions has enabled continuous records of RSL, extending centuries before the modern instrumental period, to be produced with a full consideration of uncertainty. We use a composite chronology of AMS 14C, pollen chrono

  18. Atoms and clusters in strong laser fields

    NARCIS (Netherlands)

    Marchenko, T.

    2008-01-01

    This thesis describes experimental and theoretical studies on the interaction of strong infrared laser fields with atoms and atomic clusters. Part I provides an overview of the main strong-field phenomena in atoms, molecules and clusters and describes the state-of-the-art in strong-field science.

  19. Strong Bisimilarity of Simple Process Algebras

    DEFF Research Database (Denmark)

    Srba, Jirí

    2003-01-01

    We study bisimilarity and regularity problems of simple process algebras. In particular, we show PSPACE-hardness of the following problems: (i) strong bisimilarity of Basic Parallel Processes (BPP), (ii) strong bisimilarity of Basic Process Algebra (BPA), (iii) strong regularity of BPP, and (iv) ...

  20. 78 FR 15710 - Strong Sensitizer Guidance

    Science.gov (United States)

    2013-03-12

    ... definition of ``strong sensitizer'' found at 16 CFR 1500.3(c)(5). The Commission is proposing to revise the supplemental definition of ``strong sensitizer'' due to advancements in the science of sensitization that have... document is intended to clarify the ``strong sensitizer'' definition, assist manufacturers in understanding...

  1. The interannual variability in the tropical Indian Ocean as simulated by a CGCM

    Energy Technology Data Exchange (ETDEWEB)

    Gualdi, S.; Navarra, A.; Masina, S. [INGV, v. Gobetti 101, 40129, Bologna (Italy); Guilyardi, E. [CGAM, Reading (United Kingdom); Delecluse, P. [LODYC, Paris (France)

    2003-04-01

    The interannual variability in the tropical Indian Ocean, and in particular the Indian Ocean dipole mode (IODM), is investigated using both observations and a multi-decadal simulations performed by the coupled atmosphere-ocean general circulation model SINTEX. Overall, the characteristics of the simulated IODM are close to the features of the observed mode. Evidence of significant correlations between sea level pressure anomalies in the southeastern Indian Ocean and sea surface temperature anomalies in the tropical Indian and Pacific Oceans have been found both in observations and a multi-decadal simulation. In particular, a positive SLP anomaly in the southeastern part of the basin seems to produce favorable conditions for the development of an IODM event. The role played by the ocean dynamics both in the developing and closing phases of the IODM events is also investigated. Our results suggest that, during the developing phase, the heat content and SST variability associated with the IODM are influenced by a local response of the ocean to the winds, and a remote response with the excitation of Kelvin and Rossby waves. Ocean wave dynamics appear to be important also during the dying phase of the IODM, when equatorial downwelling Kelvin waves transport positive heat content anomalies from the western to the eastern part of the basin, suppressing the zonal heat content anomaly gradient. The results obtained from the model suggest a mechanism for the IODM. This mechanism is generally consistent with the characteristics of the observed IODM. Furthermore, it might give some clue in understanding the correlation between IODM and ENSO activity found both in the model and in the observations. (orig.)

  2. Towards a large deviation theory for strongly correlated systems

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Guiomar, E-mail: guiomar.ruiz@upm.es [Centro Brasileiro de Pesquisas Fisicas and National Institute of Science and Technology for Complex Systems, Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ (Brazil); Departamento de Matemática Aplicada y Estadística, Universidad Politécnica de Madrid, Pza. Cardenal Cisneros s.n., 28040 Madrid (Spain); Tsallis, Constantino, E-mail: tsallis@cbpf.br [Centro Brasileiro de Pesquisas Fisicas and National Institute of Science and Technology for Complex Systems, Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ (Brazil); Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501 (United States)

    2012-07-23

    A large-deviation connection of statistical mechanics is provided by N independent binary variables, the (N→∞) limit yielding Gaussian distributions. The probability of n≠N/2 out of N throws is governed by e{sup −Nr}, r related to the entropy. Large deviations for a strong correlated model characterized by indices (Q,γ) are studied, the (N→∞) limit yielding Q-Gaussians (Q→1 recovers a Gaussian). Its large deviations are governed by e{sub q}{sup −Nr{sub q}} (∝1/N{sup 1/(q−1)}, q>1), q=(Q−1)/(γ[3−Q])+1. This illustration opens the door towards a large-deviation foundation of nonextensive statistical mechanics. -- Highlights: ► We introduce the formalism of relative entropy for a single random binary variable and its q-generalization. ► We study a model of N strongly correlated binary random variables and their large-deviation probabilities. ► Large-deviation probability of strongly correlated model exhibits a q-exponential decay whose argument is proportional to N, as extensivity requires. ► Our results point to a q-generalized large deviation theory and suggest a large-deviation foundation of nonextensive statistical mechanics.

  3. Application of strong phosphoric acid to radiochemistry

    International Nuclear Information System (INIS)

    Terada, Kikuo

    1977-01-01

    Not only inorganic and organic compounds but also natural substrances, such as accumulations in soil, are completely decomposed and distilled by heating with strong phosphoric acid for 30 to 50 minutes. As applications of strong phosphoric acid to radiochemistry, determination of uranium and boron by use of solubilization effect of this substance, titration of uranyl ion by use of sulfuric iron (II) contained in this substance, application to tracer experiment, and determination of radioactive ruthenium in environmental samples are reviewed. Strong phosphoric acid is also applied to activation analysis, for example, determination of N in pyrographite with iodate potassium-strong phosphoric acid method, separation of Os and Ru with sulfuric cerium (IV) - strong phosphoric acid method or potassium dechromate-strong phosphoric acid method, analysis of Se, As and Sb rocks and accumulations with ammonium bromide, sodium chloride and sodium bromide-strong phosphoric acid method. (Kanao, N.)

  4. Interdecadal variability of the meridional overturning circulation as an ocean internal mode

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiuhua [Universitaet Hamburg, Meteorologisches Institut, Hamburg (Germany); Jungclaus, Johann [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)

    2008-11-15

    The meridional overturning circulation (MOC) in the coupled ECHAM5/MPIOM exhibits variability at periods of near 30 years and near 60 years. The 30-year variability, referred to as interdecadal variability (IDV), exist in an ocean model driven by climatological atmospheric forcing, suggesting that it is maintained by ocean dynamics; the 60-year variability, the multidecadal variability (MDV), is only observed in the fully coupled model and therefore is interpreted as an atmosphere-ocean coupled mode. The coexistence of the 30-year IDV and the 60-year MDV provides a possible explanation for the widespread time scales observed in climate variables. Further analyses of the climatologically forced ocean model shows that, the IDV is related to the interplay between the horizontal temperature-dominated density gradients and the ocean circulation: temperature anomalies move along the cyclonic subpolar gyre leading to fluctuations in horizontal density gradients and the subsequent weakening and strengthening of the MOC. This result is consistent with that from less complex models, indicating the robustness of the IDV. We further show that, along the North Atlantic Current path, the sea surface temperature anomalies are determined by the slow LSW advection at the intermediate depth. (orig.)

  5. Least-rattling feedback from strong time-scale separation

    Science.gov (United States)

    Chvykov, Pavel; England, Jeremy

    2018-03-01

    In most interacting many-body systems associated with some "emergent phenomena," we can identify subgroups of degrees of freedom that relax on dramatically different time scales. Time-scale separation of this kind is particularly helpful in nonequilibrium systems where only the fast variables are subjected to external driving; in such a case, it may be shown through elimination of fast variables that the slow coordinates effectively experience a thermal bath of spatially varying temperature. In this paper, we investigate how such a temperature landscape arises according to how the slow variables affect the character of the driven quasisteady state reached by the fast variables. Brownian motion in the presence of spatial temperature gradients is known to lead to the accumulation of probability density in low-temperature regions. Here, we focus on the implications of attraction to low effective temperature for the long-term evolution of slow variables. After quantitatively deriving the temperature landscape for a general class of overdamped systems using a path-integral technique, we then illustrate in a simple dynamical system how the attraction to low effective temperature has a fine-tuning effect on the slow variable, selecting configurations that bring about exceptionally low force fluctuation in the fast-variable steady state. We furthermore demonstrate that a particularly strong effect of this kind can take place when the slow variable is tuned to bring about orderly, integrable motion in the fast dynamics that avoids thermalizing energy absorbed from the drive. We thus point to a potentially general feedback mechanism in multi-time-scale active systems, that leads to the exploration of slow variable space, as if in search of fine tuning for a "least-rattling" response in the fast coordinates.

  6. Causes of Greenland temperature variability over the past 4000 yr: implications for northern hemispheric temperature changes

    Directory of Open Access Journals (Sweden)

    T. Kobashi

    2013-10-01

    Full Text Available Precise understanding of Greenland temperature variability is important in two ways. First, Greenland ice sheet melting associated with rising temperature is a major global sea level forcing, potentially affecting large populations in coming centuries. Second, Greenland temperatures are highly affected by North Atlantic Oscillation/Arctic Oscillation (NAO/AO and Atlantic multidecadal oscillation (AMO. In our earlier study, we found that Greenland temperature deviated negatively (positively from northern hemispheric (NH temperature trend during stronger (weaker solar activity owing to changes in atmospheric/oceanic changes (e.g. NAO/AO over the past 800 yr (Kobashi et al., 2013. Therefore, a precise Greenland temperature record can provide important constraints on the past atmospheric/oceanic circulation in the region and beyond. Here, we investigated Greenland temperature variability over the past 4000 yr reconstructed from argon and nitrogen isotopes from trapped air in a GISP2 ice core, using a one-dimensional energy balance model with orbital, solar, volcanic, greenhouse gas, and aerosol forcings. The modelled northern Northern Hemisphere (NH temperature exhibits a cooling trend over the past 4000 yr as observed for the reconstructed Greenland temperature through decreasing annual average insolation. With consideration of the negative influence of solar variability, the modelled and observed Greenland temperatures agree with correlation coefficients of r = 0.34–0.36 (p = 0.1–0.04 in 21 yr running means (RMs and r = 0.38–0.45 (p = 0.1–0.05 on a centennial timescale (101 yr RMs. Thus, the model can explain 14 to 20% of variance of the observed Greenland temperature in multidecadal to centennial timescales with a 90–96% confidence interval, suggesting that a weak but persistent negative solar influence on Greenland temperature continued over the past 4000 yr. Then, we estimated the distribution of multidecadal NH and northern high

  7. Impacts of ozone air pollution and temperature extremes on crop yields: Spatial variability, adaptation and implications for future food security

    Science.gov (United States)

    Tai, Amos P. K.; Val Martin, Maria

    2017-11-01

    Ozone air pollution and climate change pose major threats to global crop production, with ramifications for future food security. Previous studies of ozone and warming impacts on crops typically do not account for the strong ozone-temperature correlation when interpreting crop-ozone or crop-temperature relationships, or the spatial variability of crop-to-ozone sensitivity arising from varietal and environmental differences, leading to potential biases in their estimated crop losses. Here we develop an empirical model, called the partial derivative-linear regression (PDLR) model, to estimate the spatial variations in the sensitivities of wheat, maize and soybean yields to ozone exposures and temperature extremes in the US and Europe using a composite of multidecadal datasets, fully correcting for ozone-temperature covariation. We find generally larger and more spatially varying sensitivities of all three crops to ozone exposures than are implied by experimentally derived concentration-response functions used in most previous studies. Stronger ozone tolerance is found in regions with high ozone levels and high consumptive crop water use, reflecting the existence of spatial adaptation and effect of water constraints. The spatially varying sensitivities to temperature extremes also indicate stronger heat tolerance in crops grown in warmer regions. The spatial adaptation of crops to ozone and temperature we find can serve as a surrogate for future adaptation. Using the PDLR-derived sensitivities and 2000-2050 ozone and temperature projections by the Community Earth System Model, we estimate that future warming and unmitigated ozone pollution can combine to cause an average decline in US wheat, maize and soybean production by 13%, 43% and 28%, respectively, and a smaller decline for European crops. Aggressive ozone regulation is shown to offset such decline to various extents, especially for wheat. Our findings demonstrate the importance of considering ozone regulation

  8. Strongly correlating liquids and their isomorphs

    OpenAIRE

    Pedersen, Ulf R.; Gnan, Nicoletta; Bailey, Nicholas P.; Schröder, Thomas B.; Dyre, Jeppe C.

    2010-01-01

    This paper summarizes the properties of strongly correlating liquids, i.e., liquids with strong correlations between virial and potential energy equilibrium fluctuations at constant volume. We proceed to focus on the experimental predictions for strongly correlating glass-forming liquids. These predictions include i) density scaling, ii) isochronal superposition, iii) that there is a single function from which all frequency-dependent viscoelastic response functions may be calculated, iv) that...

  9. Atom collisions in a strong electromagnetic field

    International Nuclear Information System (INIS)

    Smirnov, V.S.; Chaplik, A.V.

    1976-01-01

    It is shown that the long-range part of interatomic interaction is considerably altered in a strong electromagnetic field. Instead of the van der Waals law the potential asymptote can best be described by a dipole-dipole R -3 law. Impact broadening and the line shift in a strong nonresonant field are calculated. The possibility of bound states of two atoms being formed in a strong light field is discussed

  10. Influence of internal variability on population exposure to hydroclimatic changes

    Science.gov (United States)

    Mankin, Justin S.; Viviroli, Daniel; Mekonnen, Mesfin M.; Hoekstra, Arjen Y.; Horton, Radley M.; E Smerdon, Jason; Diffenbaugh, Noah S.

    2017-04-01

    Future freshwater supply, human water demand, and people’s exposure to water stress are subject to multiple sources of uncertainty, including unknown future pathways of fossil fuel and water consumption, and ‘irreducible’ uncertainty arising from internal climate system variability. Such internal variability can conceal forced hydroclimatic changes on multi-decadal timescales and near-continental spatial-scales. Using three projections of population growth, a large ensemble from a single Earth system model, and assuming stationary per capita water consumption, we quantify the likelihoods of future population exposure to increased hydroclimatic deficits, which we define as the average duration and magnitude by which evapotranspiration exceeds precipitation in a basin. We calculate that by 2060, ∽31%-35% of the global population will be exposed to >50% probability of hydroclimatic deficit increases that exceed existing hydrological storage, with up to 9% of people exposed to >90% probability. However, internal variability, which is an irreducible uncertainty in climate model predictions that is under-sampled in water resource projections, creates substantial uncertainty in predicted exposure: ∽86%-91% of people will reside where irreducible uncertainty spans the potential for both increases and decreases in sub-annual water deficits. In one population scenario, changes in exposure to large hydroclimate deficits vary from -3% to +6% of global population, a range arising entirely from internal variability. The uncertainty in risk arising from irreducible uncertainty in the precise pattern of hydroclimatic change, which is typically conflated with other uncertainties in projections, is critical for climate risk management that seeks to optimize adaptations that are robust to the full set of potential real-world outcomes.

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

    Directory of Open Access Journals (Sweden)

    R. Séférian

    2013-04-01

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

  12. Strong ideal convergence in probabilistic metric spaces

    Indian Academy of Sciences (India)

    sequence and strong ideal Cauchy sequence in a probabilistic metric (PM) space endowed with the strong topology, and ... also important applications in nonlinear analysis [2]. The theory was brought to ..... for each t > 0 since each set on the right-hand side of the relation (3.1) belongs to I. Thus, by Definition 2.11 and the ...

  13. Large N baryons, strong coupling theory, quarks

    International Nuclear Information System (INIS)

    Sakita, B.

    1984-01-01

    It is shown that in QCD the large N limit is the same as the static strong coupling limit. By using the static strong coupling techniques some of the results of large N baryons are derived. The results are consistent with the large N SU(6) static quark model. (author)

  14. Optimization of strong and weak coordinates

    NARCIS (Netherlands)

    Swart, M.; Bickelhaupt, F.M.

    2006-01-01

    We present a new scheme for the geometry optimization of equilibrium and transition state structures that can be used for both strong and weak coordinates. We use a screening function that depends on atom-pair distances to differentiate strong coordinates from weak coordinates. This differentiation

  15. Strong decays of nucleon and delta resonances

    International Nuclear Information System (INIS)

    Bijker, R.; Leviatan, A.

    1996-01-01

    We study the strong couplings of the nucleon and delta resonances in a collective model. In the ensuing algebraic treatment we derive closed expressions for decay widths which are used to analyze the experimental data for strong decays into the pion and eta channels. (Author)

  16. Theoretical studies of strongly correlated fermions

    Energy Technology Data Exchange (ETDEWEB)

    Logan, D. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Strongly correlated fermions are investigated. An understanding of strongly correlated fermions underpins a diverse range of phenomena such as metal-insulator transitions, high-temperature superconductivity, magnetic impurity problems and the properties of heavy-fermion systems, in all of which local moments play an important role. (author).

  17. Seismic switch for strong motion measurement

    Science.gov (United States)

    Harben, P.E.; Rodgers, P.W.; Ewert, D.W.

    1995-05-30

    A seismic switching device is described that has an input signal from an existing microseismic station seismometer and a signal from a strong motion measuring instrument. The seismic switch monitors the signal level of the strong motion instrument and passes the seismometer signal to the station data telemetry and recording systems. When the strong motion instrument signal level exceeds a user set threshold level, the seismometer signal is switched out and the strong motion signal is passed to the telemetry system. The amount of time the strong motion signal is passed before switching back to the seismometer signal is user controlled between 1 and 15 seconds. If the threshold level is exceeded during a switch time period, the length of time is extended from that instant by one user set time period. 11 figs.

  18. Zoonoses and climate variability.

    Science.gov (United States)

    Cardenas, Rocio; Sandoval, Claudia M; Rodriguez-Morales, Alfonso J; Vivas, Paul

    2008-12-01

    Leishmaniasis in the Americas is transmitted by Lutzomyia spp., which have many animal reservoirs. Previous studies indicated potential changes in vectors of climate-related distribution, but impact outcomes need to be further studied. We report climatic and El Niño events during 1985-2002 that may have had an impact on leishmaniasis in 11 southern departments of Colombia: Amazonas, Caquetá, Cauca (Ca), Huila, Meta (Mt), Nariño, Putumayo (Py), Tolima, Valle (Va), Vaupes (Vp), and Vichada. Climatic data were obtained by satellite and epidemiologic data were obtained from the Health Ministry. NOAA climatic classification and SOI/ONI indexes were used as indicators of global climate variability. Yearly variation comparisons and median trend deviations were made for disease incidence and climatic variability. During this period there was considerable climatic variability, with a strong El Niño for 6 years and a strong La Niña for 8. During this period, 19,212 cases of leishmaniasis were registered, for a mean of 4756.83 cases/year. Disease in the whole region increased (mean of 4.98%) during the El Niño years in comparison to the La Niña years, but there were differences between departments with increases during El Niño (Mt 6.95%, Vp 4.84%), but the rest showed an increase during La Niña (1.61%-64.41%). Differences were significant in Va (P= 0.0092), Py (P= 0.0001), Ca (P= 0.0313), and for the whole region (P= 0.0023), but not in the rest of the departments. The importance of climate change is shown by shifts in insect and animal distributions. These data reflect the importance of climate on transmission of leishmaniasis and open further investigations related to forecasting and monitoring systems, where understanding the relationship between zoonoses and climate variability could help to improve the management of these emerging and reemerging diseases.

  19. Strong and superstrong pulsed magnetic fields generation

    CERN Document Server

    Shneerson, German A; Krivosheev, Sergey I

    2014-01-01

    Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

  20. Impurity screening in strongly coupled plasma systems

    CERN Document Server

    Kyrkos, S

    2003-01-01

    We present an overview of the problem of screening of an impurity in a strongly coupled one-component plasma within the framework of the linear response (LR) theory. We consider 3D, 2D and quasi-2D layered systems. For a strongly coupled plasma the LR can be determined by way of the known S(k) structure functions. In general, an oscillating screening potential with local overscreening and antiscreening regions emerges. In the case of the bilayer, this phenomenon becomes global, as overscreening develops in the layer of the impurity and antiscreening in the adjacent layer. We comment on the limitations of the LR theory in the strong coupling situation.

  1. The lambda sigma calculus and strong normalization

    DEFF Research Database (Denmark)

    Schack-Nielsen, Anders; Schürmann, Carsten

    Explicit substitution calculi can be classified into several dis- tinct categories depending on whether they are confluent, meta-confluent, strong normalization preserving, strongly normalizing, simulating, fully compositional, and/or local. In this paper we present a variant of the λσ-calculus......, which satisfies all seven conditions. In particular, we show how to circumvent Mellies counter-example to strong normalization by a slight restriction of the congruence rules. The calculus is implemented as the core data structure of the Celf logical framework. All meta-theoretic aspects of this work...

  2. Concurrent variable-interval variable-ratio schedules in a dynamic choice environment.

    Science.gov (United States)

    Bell, Matthew C; Baum, William M

    2017-11-01

    Most studies of operant choice have focused on presenting subjects with a fixed pair of schedules across many experimental sessions. Using these methods, studies of concurrent variable- interval variable-ratio schedules helped to evaluate theories of choice. More recently, a growing literature has focused on dynamic choice behavior. Those dynamic choice studies have analyzed behavior on a number of different time scales using concurrent variable-interval schedules. Following the dynamic choice approach, the present experiment examined performance on concurrent variable-interval variable-ratio schedules in a rapidly changing environment. Our objectives were to compare performance on concurrent variable-interval variable-ratio schedules with extant data on concurrent variable-interval variable-interval schedules using a dynamic choice procedure and to extend earlier work on concurrent variable-interval variable-ratio schedules. We analyzed performances at different time scales, finding strong similarities between concurrent variable-interval variable-interval and concurrent variable-interval variable- ratio performance within dynamic choice procedures. Time-based measures revealed almost identical performance in the two procedures compared with response-based measures, supporting the view that choice is best understood as time allocation. Performance at the smaller time scale of visits accorded with the tendency seen in earlier research toward developing a pattern of strong preference for and long visits to the richer alternative paired with brief "samples" at the leaner alternative ("fix and sample"). © 2017 Society for the Experimental Analysis of Behavior.

  3. Short-timescale variability in cataclysmic binaries

    International Nuclear Information System (INIS)

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

    1982-01-01

    Rapid variability, including flickering and pulsations, has been detected in cataclysmic binaries at optical and x-ray frequencies. In the case of the novalike variable TT Arietis, simultaneous observations reveal that the x-ray and optical flickering activity is strongly correlated, while short period pulsations are observed that occur at the same frequencies in both wavelength bands

  4. Variability of OI 090.4

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... OI 090.4 was monitored on 21 nights from 2006 to 2012 for studying the variability. Strong variations occurred during the past 6 years. The long-term variability amplitude is consistent with previous results. Microvariability was analysed for 43 intra-night light curves. 30 out of 43 light curves showed ...

  5. Strong Coupling Corrections in Quantum Thermodynamics

    Science.gov (United States)

    Perarnau-Llobet, M.; Wilming, H.; Riera, A.; Gallego, R.; Eisert, J.

    2018-03-01

    Quantum systems strongly coupled to many-body systems equilibrate to the reduced state of a global thermal state, deviating from the local thermal state of the system as it occurs in the weak-coupling limit. Taking this insight as a starting point, we study the thermodynamics of systems strongly coupled to thermal baths. First, we provide strong-coupling corrections to the second law applicable to general systems in three of its different readings: As a statement of maximal extractable work, on heat dissipation, and bound to the Carnot efficiency. These corrections become relevant for small quantum systems and vanish in first order in the interaction strength. We then move to the question of power of heat engines, obtaining a bound on the power enhancement due to strong coupling. Our results are exemplified on the paradigmatic non-Markovian quantum Brownian motion.

  6. Finding quantum effects in strong classical potentials

    Science.gov (United States)

    Hegelich, B. Manuel; Labun, Lance; Labun, Ou Z.

    2017-06-01

    The long-standing challenge to describing charged particle dynamics in strong classical electromagnetic fields is how to incorporate classical radiation, classical radiation reaction and quantized photon emission into a consistent unified framework. The current, semiclassical methods to describe the dynamics of quantum particles in strong classical fields also provide the theoretical framework for fundamental questions in gravity and hadron-hadron collisions, including Hawking radiation, cosmological particle production and thermalization of particles created in heavy-ion collisions. However, as we show, these methods break down for highly relativistic particles propagating in strong fields. They must therefore be improved and adapted for the description of laser-plasma experiments that typically involve the acceleration of electrons. Theory developed from quantum electrodynamics, together with dedicated experimental efforts, offer the best controllable context to establish a robust, experimentally validated foundation for the fundamental theory of quantum effects in strong classical potentials.

  7. The Charm and Beauty of Strong Interactions

    Science.gov (United States)

    El-Bennich, Bruno

    2018-01-01

    We briefly review common features and overlapping issues in hadron and flavor physics focussing on continuum QCD approaches to heavy bound states, their mass spectrum and weak decay constants in different strong interaction models.

  8. Atomica ionization by strong coherent radiation

    International Nuclear Information System (INIS)

    Brandi, H.S.; Davidovich, L.

    1979-07-01

    The relation among the three most frequently used non-perturbative methods proposed to study the ionization of atoms by strong electromagnetic fields is established. Their range of validity is also determined. (Author) [pt

  9. Perturbation of an exact strong gravity solution

    International Nuclear Information System (INIS)

    Baran, S.A.

    1982-10-01

    Perturbations of an exact strong gravity solution are investigated. It is shown, by using the new multipole expansions previously presented, that this exact and static spherically symmetric solution is stable under odd parity perturbations. (author)

  10. Strong-force theorists scoop Noble Prize

    CERN Multimedia

    Durrani, Matin

    2004-01-01

    Three US theorists have shared the 2004 Nobel Prize in Physics "for the discovery of asymptotic freedom in the theory of the strong interaction". Their theoretical work explains why quarks behave almost as free particles at high energies (½ page)

  11. Calculating hadronic properties in strong QCD

    International Nuclear Information System (INIS)

    Pennington, M.R.

    1996-01-01

    This talk gives a brief review of the progress that has been made in calculating the properties of hadrons in strong QCD. In keeping with this meeting I will concentrate on those properties that can be studied with electromagnetic probes. Though perturbative QCD is highly successful, it only applies in a limited kinematic regime, where hard scattering occur, and the quarks move in the interaction region as if they are free, pointlike objects. However, the bulk of strong interactions are governed by the long distance regime, where the strong interaction is strong. It is this regime of length scales of the order of a Fermi, that determines the spectrum of light hadrons and their properties. The calculation of these properties requires an understanding of non-perturbative QCD, of confinement and chiral symmetry breaking. (author)

  12. Building strong brands – does it matter?

    OpenAIRE

    Aure, Kristin Gaaseide; Nervik, Kristine Dybvik

    2014-01-01

    Brand equity has proven, through several decades of research, to be a primary source of competitive advantage and future earnings (Yoo & Donthu, 2001). Building strong brands has therefore become a priority for many organizations, with the presumption that building strong brands yields these advantages (Yasin et al., 2007). A quantitative survey was conducted at Sunnmøre in Norway in order to answer the two developed research questions. - Does the brand equity dimensions; brand...

  13. Algebra of strong and electroweak interactions

    International Nuclear Information System (INIS)

    Bolokhov, S.V.; Vladimirov, Yu.S.

    2004-01-01

    The algebraic approach to describing the electroweak and strong interactions is considered within the frames of the binary geometrophysics, based on the principles of the Fokker-Feynman direct interparticle interaction theories of the Kaluza-Klein multidimensional geometrical models and the physical structures theory. It is shown that in this approach the electroweak and strong elementary particles interaction through the intermediate vector bosons, are characterized by the subtypes of the algebraic classification of the complex 3 x 3-matrices [ru

  14. The Variability of Seasonality.

    Science.gov (United States)

    Pezzulli, S.; Stephenson, D. B.; Hannachi, A.

    2005-01-01

    Seasons are the complex nonlinear response of the physical climate system to regular annual solar forcing. There is no a priori reason why they should remain fixed/invariant from year to year, as is often assumed in climate studies when extracting the seasonal component. The widely used econometric variant of Census Method II Seasonal Adjustment Program (X-11), which allows for year-to-year variations in seasonal shape, is shown here to have some advantages for diagnosing climate variability. The X-11 procedure is applied to the monthly mean Niño-3.4 sea surface temperature (SST) index and global gridded NCEP-NCAR reanalyses of 2-m surface air temperature. The resulting seasonal component shows statistically significant interannual variations over many parts of the globe. By taking these variations in seasonality into account, it is shown that one can define less ambiguous ENSO indices. Furthermore, using the X-11 seasonal adjustment approach, it is shown that the three cold ENSO episodes after 1998 are due to an increase in amplitude of seasonality rather than being three distinct La Niña events. Globally, variations in the seasonal component represent a substantial fraction of the year-to-year variability in monthly mean temperatures. In addition, strong teleconnections can be discerned between the magnitude of seasonal variations across the globe. It might be possible to exploit such relationships to improve the skill of seasonal climate forecasts.

  15. Diagnosing a Strong-Fault Model by Conflict and Consistency.

    Science.gov (United States)

    Zhang, Wenfeng; Zhao, Qi; Zhao, Hongbo; Zhou, Gan; Feng, Wenquan

    2018-03-29

    The diagnosis method for a weak-fault model with only normal behaviors of each component has evolved over decades. However, many systems now demand a strong-fault models, the fault modes of which have specific behaviors as well. It is difficult to diagnose a strong-fault model due to its non-monotonicity. Currently, diagnosis methods usually employ conflicts to isolate possible fault and the process can be expedited when some observed output is consistent with the model's prediction where the consistency indicates probably normal components. This paper solves the problem of efficiently diagnosing a strong-fault model by proposing a novel Logic-based Truth Maintenance System (LTMS) with two search approaches based on conflict and consistency. At the beginning, the original a strong-fault model is encoded by Boolean variables and converted into Conjunctive Normal Form (CNF). Then the proposed LTMS is employed to reason over CNF and find multiple minimal conflicts and maximal consistencies when there exists fault. The search approaches offer the best candidate efficiency based on the reasoning result until the diagnosis results are obtained. The completeness, coverage, correctness and complexity of the proposals are analyzed theoretically to show their strength and weakness. Finally, the proposed approaches are demonstrated by applying them to a real-world domain-the heat control unit of a spacecraft-where the proposed methods are significantly better than best first and conflict directly with A* search methods.

  16. Manipulating light with strongly modulated photonic crystals

    International Nuclear Information System (INIS)

    Notomi, Masaya

    2010-01-01

    Recently, strongly modulated photonic crystals, fabricated by the state-of-the-art semiconductor nanofabrication process, have realized various novel optical properties. This paper describes the way in which they differ from other optical media, and clarifies what they can do. In particular, three important issues are considered: light confinement, frequency dispersion and spatial dispersion. First, I describe the latest status and impact of ultra-strong light confinement in a wavelength-cubic volume achieved in photonic crystals. Second, the extreme reduction in the speed of light is reported, which was achieved as a result of frequency dispersion management. Third, strange negative refraction in photonic crystals is introduced, which results from their unique spatial dispersion, and it is clarified how this leads to perfect imaging. The last two sections are devoted to applications of these novel properties. First, I report the fact that strong light confinement and huge light-matter interaction enhancement make strongly modulated photonic crystals promising for on-chip all-optical processing, and present several examples including all-optical switches/memories and optical logics. As a second application, it is shown that the strong light confinement and slow light in strongly modulated photonic crystals enable the adiabatic tuning of light, which leads to various novel ways of controlling light, such as adiabatic frequency conversion, efficient optomechanics systems, photon memories and photons pinning.

  17. Robust signal of Northern Hemisphere summer monsoon variability during recent warming period

    Science.gov (United States)

    Kim, Hyung Jin

    2013-04-01

    Coupled global climate models (CGCMs) predict the overall weakening of tropical circulations in an anthropogenically warmed climate in accordance with a simple thermodynamic theory. However, the actual response of the climate systems, in particular, over the recent decades of unprecedented warming still remains a topic of debate. Here, we show that in a suite of cutting-edge atmospheric GCMs (AGCMs), the simulated Northern Hemisphere summer monsoon (NHSM) variability, measured by vertical wind shear of zonal winds, is in excellent agreement with observations on both interannual and inter-decadal timescales during 1979-2008. Furthermore, the trend of the NHSM variability is nearly unanimously enhanced among the AGCMs. The overriding factors in determining the simulated NHSM variations are El Niño on year-to-year timescale, and Mega-ENSO (defined as a leading mode of internal sea surface temperature variability over the Pacific) and Atlantic Multi-decadal Oscillation on decadal timescale and beyond, which ascertains the findings of a recent observational study. These results suggest that in contrast to the pivotal role of green-house gas forcing in the simulated future warmer climate, the basin-wide natural SST variability has exerted significant impacts on Earth's climate during the recent 30-year period.

  18. Variability of Atlantic Ocean heat transport and its effects on the atmosphere

    Directory of Open Access Journals (Sweden)

    R. T. Sutton

    2003-06-01

    Full Text Available The variability of the Atlantic meridional Ocean Heat Transport (OHT has been diagnosed from a simulation of a coupled ocean-atmosphere general circulation model, and the mechanisms responsible for this variability have been elucidated. It has been demonstrated that the interannual variability in Atlantic OHT is dominated by windstress-driven Ekman fluctuations. In contrast, the decadal and multidecadal variability is associated with the fluctuations of the Thermohaline Circulation (THC, driven by the fluctuations in deep convection over the Greenland-Iceland-Norwegian (GIN Sea. The fluctuations of OHT induce Ocean Heat Content (OHC, and Sea Surface Temperature (SST anomalies over the tropical and subtropical North Atlantic. The SST anomalies, in turn, have an impact on the atmosphere. The lead-lag relationships between the fluctuations of THC-related OHT and those of OHC and SST raise the possibility that a knowledge of OHT fluctuations could be used to predict variations in Atlantic Sea surface temperatures, and perhaps aspects of climate, several years in advance. A comparison of results from a second, independent, coupled model simulation is also presented, and similar conclusions reached.

  19. Comparative Analysis of Upper Ocean Heat Content Variability from Ensemble Operational Ocean Analyses

    Science.gov (United States)

    Xue, Yan; Balmaseda, Magdalena A.; Boyer, Tim; Ferry, Nicolas; Good, Simon; Ishikawa, Ichiro; Rienecker, Michele; Rosati, Tony; Yin, Yonghong; Kumar, Arun

    2012-01-01

    Upper ocean heat content (HC) is one of the key indicators of climate variability on many time-scales extending from seasonal to interannual to long-term climate trends. For example, HC in the tropical Pacific provides information on thermocline anomalies that is critical for the longlead forecast skill of ENSO. Since HC variability is also associated with SST variability, a better understanding and monitoring of HC variability can help us understand and forecast SST variability associated with ENSO and other modes such as Indian Ocean Dipole (IOD), Pacific Decadal Oscillation (PDO), Tropical Atlantic Variability (TAV) and Atlantic Multidecadal Oscillation (AMO). An accurate ocean initialization of HC anomalies in coupled climate models could also contribute to skill in decadal climate prediction. Errors, and/or uncertainties, in the estimation of HC variability can be affected by many factors including uncertainties in surface forcings, ocean model biases, and deficiencies in data assimilation schemes. Changes in observing systems can also leave an imprint on the estimated variability. The availability of multiple operational ocean analyses (ORA) that are routinely produced by operational and research centers around the world provides an opportunity to assess uncertainties in HC analyses, to help identify gaps in observing systems as they impact the quality of ORAs and therefore climate model forecasts. A comparison of ORAs also gives an opportunity to identify deficiencies in data assimilation schemes, and can be used as a basis for development of real-time multi-model ensemble HC monitoring products. The OceanObs09 Conference called for an intercomparison of ORAs and use of ORAs for global ocean monitoring. As a follow up, we intercompared HC variations from ten ORAs -- two objective analyses based on in-situ data only and eight model analyses based on ocean data assimilation systems. The mean, annual cycle, interannual variability and longterm trend of HC have

  20. Indian Summer Monsoon Rainfall: Implications of Contrasting Trends in the Spatial Variability of Means and Extremes.

    Science.gov (United States)

    Ghosh, Subimal; Vittal, H; Sharma, Tarul; Karmakar, Subhankar; Kasiviswanathan, K S; Dhanesh, Y; Sudheer, K P; Gunthe, S S

    2016-01-01

    India's agricultural output, economy, and societal well-being are strappingly dependent on the stability of summer monsoon rainfall, its variability and extremes. Spatial aggregate of intensity and frequency of extreme rainfall events over Central India are significantly increasing, while at local scale they are spatially non-uniform with increasing spatial variability. The reasons behind such increase in spatial variability of extremes are poorly understood and the trends in mean monsoon rainfall have been greatly overlooked. Here, by using multi-decadal gridded daily rainfall data over entire India, we show that the trend in spatial variability of mean monsoon rainfall is decreasing as exactly opposite to that of extremes. The spatial variability of extremes is attributed to the spatial variability of the convective rainfall component. Contrarily, the decrease in spatial variability of the mean rainfall over India poses a pertinent research question on the applicability of large scale inter-basin water transfer by river inter-linking to address the spatial variability of available water in India. We found a significant decrease in the monsoon rainfall over major water surplus river basins in India. Hydrological simulations using a Variable Infiltration Capacity (VIC) model also revealed that the water yield in surplus river basins is decreasing but it is increasing in deficit basins. These findings contradict the traditional notion of dry areas becoming drier and wet areas becoming wetter in response to climate change in India. This result also calls for a re-evaluation of planning for river inter-linking to supply water from surplus to deficit river basins.

  1. Indian Summer Monsoon Rainfall: Implications of Contrasting Trends in the Spatial Variability of Means and Extremes.

    Directory of Open Access Journals (Sweden)

    Subimal Ghosh

    Full Text Available India's agricultural output, economy, and societal well-being are strappingly dependent on the stability of summer monsoon rainfall, its variability and extremes. Spatial aggregate of intensity and frequency of extreme rainfall events over Central India are significantly increasing, while at local scale they are spatially non-uniform with increasing spatial variability. The reasons behind such increase in spatial variability of extremes are poorly understood and the trends in mean monsoon rainfall have been greatly overlooked. Here, by using multi-decadal gridded daily rainfall data over entire India, we show that the trend in spatial variability of mean monsoon rainfall is decreasing as exactly opposite to that of extremes. The spatial variability of extremes is attributed to the spatial variability of the convective rainfall component. Contrarily, the decrease in spatial variability of the mean rainfall over India poses a pertinent research question on the applicability of large scale inter-basin water transfer by river inter-linking to address the spatial variability of available water in India. We found a significant decrease in the monsoon rainfall over major water surplus river basins in India. Hydrological simulations using a Variable Infiltration Capacity (VIC model also revealed that the water yield in surplus river basins is decreasing but it is increasing in deficit basins. These findings contradict the traditional notion of dry areas becoming drier and wet areas becoming wetter in response to climate change in India. This result also calls for a re-evaluation of planning for river inter-linking to supply water from surplus to deficit river basins.

  2. Indian Summer Monsoon Rainfall: Implications of Contrasting Trends in the Spatial Variability of Means and Extremes

    Science.gov (United States)

    Ghosh, Subimal; Vittal, H.; Sharma, Tarul; Karmakar, Subhankar; Kasiviswanathan, K. S.; Dhanesh, Y.; Sudheer, K. P.; Gunthe, S. S.

    2016-01-01

    India’s agricultural output, economy, and societal well-being are strappingly dependent on the stability of summer monsoon rainfall, its variability and extremes. Spatial aggregate of intensity and frequency of extreme rainfall events over Central India are significantly increasing, while at local scale they are spatially non-uniform with increasing spatial variability. The reasons behind such increase in spatial variability of extremes are poorly understood and the trends in mean monsoon rainfall have been greatly overlooked. Here, by using multi-decadal gridded daily rainfall data over entire India, we show that the trend in spatial variability of mean monsoon rainfall is decreasing as exactly opposite to that of extremes. The spatial variability of extremes is attributed to the spatial variability of the convective rainfall component. Contrarily, the decrease in spatial variability of the mean rainfall over India poses a pertinent research question on the applicability of large scale inter-basin water transfer by river inter-linking to address the spatial variability of available water in India. We found a significant decrease in the monsoon rainfall over major water surplus river basins in India. Hydrological simulations using a Variable Infiltration Capacity (VIC) model also revealed that the water yield in surplus river basins is decreasing but it is increasing in deficit basins. These findings contradict the traditional notion of dry areas becoming drier and wet areas becoming wetter in response to climate change in India. This result also calls for a re-evaluation of planning for river inter-linking to supply water from surplus to deficit river basins. PMID:27463092

  3. Strong Motion Earthquake Data Values of Digitized Strong-Motion Accelerograms, 1933-1994

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Strong Motion Earthquake Data Values of Digitized Strong-Motion Accelerograms is a database of over 15,000 digitized and processed accelerograph records from...

  4. Strong matrilineal structure in common pipistrelle bats (Pipistrellus pipistrellus) is associated with variability in echolocation calls

    Czech Academy of Sciences Publication Activity Database

    Fornůsková, Alena; Petit, E.J.; Bartonička, T.; Kaňuch, P.; Butet, A.; Řehák, Z.; Bryja, Josef

    2014-01-01

    Roč. 113, č. 4 (2014), s. 1115-1125 ISSN 0024-4066 R&D Projects: GA ČR GA206/06/0954 Institutional support: RVO:68081766 Keywords : dialects * maternal effects * sex-biased dispersal * philopatry * vocal learning Subject RIV: EG - Zoology Impact factor: 2.264, year: 2014

  5. Strong variability in bacterioplankton abundance and production in central and western Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes; Ramaiah; Paul, J.T.; Sardessai; Jyothibabu; Gauns, M.

    to low or no nutrient injections into the surface, primary production in Bay of Bengal is reportedly low. As a consequence, the Bay of Bengal is considered as a region of low biological productivity. Along with many biological parameters, bacterioplankton...

  6. The extended reciprocity: Strong belief outperforms persistence.

    Science.gov (United States)

    Kurokawa, Shun

    2017-05-21

    The existence of cooperation is a mysterious phenomenon and demands explanation, and direct reciprocity is one key potential explanation for the evolution of cooperation. Direct reciprocity allows cooperation to evolve for cooperators who switch their behavior on the basis of information about the opponent's behavior. Here, relevant to direct reciprocity is information deficiency. When the opponent's last move is unknown, how should players behave? One possibility is to choose cooperation with some default probability without using any further information. In fact, our previous paper (Kurokawa, 2016a) examined this strategy. However, there might be beneficial information other than the opponent's last move. A subsequent study of ours (Kurokawa, 2017) examined the strategy which uses the own last move when the opponent's last move is unknown, and revealed that referring to the own move and trying to imitate it when information is absent is beneficial. Is there any other beneficial information else? How about strong belief (i.e., have infinite memory and believe that the opponent's behavior is unchanged)? Here, we examine the evolution of strategies with strong belief. Analyzing the repeated prisoner's dilemma game and using evolutionarily stable strategy (ESS) analysis against an invasion by unconditional defectors, we find the strategy with strong belief is more likely to evolve than the strategy which does not use information other than the opponent player's last move and more likely to evolve than the strategy which uses not only the opponent player's last move but also the own last move. Strong belief produces the extended reciprocity and facilitates the evolution of cooperation. Additionally, we consider the two strategies game between strategies with strong belief and any strategy, and we consider the four strategies game in which unconditional cooperators, unconditional defectors, pessimistic reciprocators with strong belief, and optimistic reciprocators with

  7. A strongly coupled quark-gluon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Shuryak, Edward [Department of Physics and Astronomy, University at Stony Brook, NY 11794 (United States)

    2004-08-01

    Successful description of robust collective flow phenomena at RHIC by ideal hydrodynamics, recent observations of bound c-barc,q-barq states on the lattice, and other theoretical developments indicate that QGP produced at RHIC, and probably in a wider temperature region T{sub c} < T < 4T{sub c}, is not a weakly coupled quasiparticle gas as believed previously. We discuss how strong the interaction is and why it seems to generate hundreds of binary channels with bound states, surviving well inside the QGP phase. We in particular discuss their effect on pressure and viscosity. We conclude by reviewing the similar phenomena for other 'strongly coupled systems', such as (i) strongly coupled supersymmetric theories studied via Maldacena duality; (ii) trapped ultra-cold atoms with very large scattering length, tuned to Feschbach resonances.

  8. Strong Coupling between Plasmons and Organic Semiconductors

    Directory of Open Access Journals (Sweden)

    Joel Bellessa

    2014-05-01

    Full Text Available In this paper we describe the properties of organic material in strong coupling with plasmon, mainly based on our work in this field of research. The strong coupling modifies the optical transitions of the structure, and occurs when the interaction between molecules and plasmon prevails on the damping of the system. We describe the dispersion relation of different plasmonic systems, delocalized and localized plasmon, coupled to aggregated dyes and the typical properties of these systems in strong coupling. The modification of the dye emission is also studied. In the second part, the effect of the microscopic structure of the organics, which can be seen as a disordered film, is described. As the different molecules couple to the same plasmon mode, an extended coherent state on several microns is observed.

  9. A theory of the strong interactions

    International Nuclear Information System (INIS)

    Gross, D.J.

    1979-01-01

    The most promising candidate for a fundamental microscopic theory of the strong interactions is a gauge theory of colored quarks-Quantum Chromodynamics (QCD). There are many excellent reasons for believing in this theory. It embodies the broken symmetries, SU(3) and chiral SU(3)xSU(3), of the strong interactions and reflects the success of (albeit crude) quark models in explaining the spectrum of the observed hadrons. The hidden quantum number of color, necessary to account for the quantum numbers of the low lying hadrons, plays a fundamental role in this theory as the SU(3) color gauge vector 'gluons' are the mediators of the strong interactions. The absence of physical quark states can be 'explained' by the hypothesis of color confinement i.e. that hadrons are permanently bound in color singlet bound states. Finally this theory is unique in being asymptotically free, thus accounting for the almost free field theory behvior of quarks observed at short distances. (Auth.)

  10. Electromagnetic processes in strong crystalline fields

    CERN Multimedia

    2007-01-01

    We propose a number of new investigations on aspects of radiation from high energy electron and positron beams (10-300 GeV) in single crystals and amorphous targets. The common heading is radiation emission by electrons and positrons in strong electromagnetic fields, but as the setup is quite versatile, other related phenomena in radiation emission can be studied as well. The intent is to clarify the role of a number of important aspects of radiation in strong fields as e.g. observed in crystals. We propose to measure trident 'Klein-like' production in strong crystalline fields, 'crystalline undulator' radiation, 'sandwich' target phenomena, LPM suppression of pair production as well as axial and planar effects in contributions of spin to the radiation.

  11. Patterns of Strong Coupling for LHC Searches

    CERN Document Server

    Liu, Da; Rattazzi, Riccardo; Riva, Francesco

    2016-11-23

    Even though the Standard Model (SM) is weakly coupled at the Fermi scale, a new strong dynamics involving its degrees of freedom may conceivably lurk at slightly higher energies, in the multi TeV range. Approximate symmetries provide a structurally robust context where, within the low energy description, the dimensionless SM couplings are weak, while the new strong dynamics manifests itself exclusively through higher-derivative interactions. We present an exhaustive classification of such scenarios in the form of effective field theories, paying special attention to new classes of models where the strong dynamics involves, along with the Higgs boson, the SM gauge bosons and/or the fermions. The IR softness of the new dynamics suppresses its effects at LEP energies, but deviations are in principle detectable at the LHC, even at energies below the threshold for production of new states. Our construction provides the so far unique structurally robust context where to motivate several searches in Higgs physics, d...

  12. Electronic Structure of Strongly Correlated Materials

    CERN Document Server

    Anisimov, Vladimir

    2010-01-01

    Electronic structure and physical properties of strongly correlated materials containing elements with partially filled 3d, 4d, 4f and 5f electronic shells is analyzed by Dynamical Mean-Field Theory (DMFT). DMFT is the most universal and effective tool used for the theoretical investigation of electronic states with strong correlation effects. In the present book the basics of the method are given and its application to various material classes is shown. The book is aimed at a broad readership: theoretical physicists and experimentalists studying strongly correlated systems. It also serves as a handbook for students and all those who want to be acquainted with fast developing filed of condensed matter physics.

  13. Aperture averaging in strong oceanic turbulence

    Science.gov (United States)

    Gökçe, Muhsin Caner; Baykal, Yahya

    2018-04-01

    Receiver aperture averaging technique is employed in underwater wireless optical communication (UWOC) systems to mitigate the effects of oceanic turbulence, thus to improve the system performance. The irradiance flux variance is a measure of the intensity fluctuations on a lens of the receiver aperture. Using the modified Rytov theory which uses the small-scale and large-scale spatial filters, and our previously presented expression that shows the atmospheric structure constant in terms of oceanic turbulence parameters, we evaluate the irradiance flux variance and the aperture averaging factor of a spherical wave in strong oceanic turbulence. Irradiance flux variance variations are examined versus the oceanic turbulence parameters and the receiver aperture diameter are examined in strong oceanic turbulence. Also, the effect of the receiver aperture diameter on the aperture averaging factor is presented in strong oceanic turbulence.

  14. Electromagnetic Processes in strong Crystalline Fields

    CERN Multimedia

    2007-01-01

    We propose a number of new investigations on aspects of radiation from high energy electron and positron beams (10-300 GeV) in single crystals and amorphous targets. The common heading is radiation emission by electrons and positrons in strong electromagnetic fields, but as the setup is quite versatile, other related phenomena in radiation emission can be studied as well. The intent is to clarify the role of a number of important aspects of radiation in strong fields as e.g. observed in crystals. We propose to measure trident 'Klein-like' production in strong crystalline fields, 'crystalline undulator' radiation, 'sandwich' target phenomena, LPM suppression of pair production as well as axial and planar effects in contributions of spin to the radiation.

  15. Variability of the ocean heat content during the last millennium – an assessment with the ECHO-g Model

    Directory of Open Access Journals (Sweden)

    P. Ortega

    2013-03-01

    Full Text Available Studies addressing climate variability during the last millennium generally focus on variables with a direct influence on climate variability, like the fast thermal response to varying radiative forcing, or the large-scale changes in atmospheric dynamics (e.g. North Atlantic Oscillation. The ocean responds to these variations by slowly integrating in depth the upper heat flux changes, thus producing a delayed influence on ocean heat content (OHC that can later impact low frequency SST (sea surface temperature variability through reemergence processes. In this study, both the externally and internally driven variations of the OHC during the last millennium are investigated using a set of fully coupled simulations with the ECHO-G (coupled climate model ECHAMA4 and ocean model HOPE-G atmosphere–ocean general circulation model (AOGCM. When compared to observations for the last 55 yr, the model tends to overestimate the global trends and underestimate the decadal OHC variability. Extending the analysis back to the last one thousand years, the main impact of the radiative forcing is an OHC increase at high latitudes, explained to some extent by a reduction in cloud cover and the subsequent increase of short-wave radiation at the surface. This OHC response is dominated by the effect of volcanism in the preindustrial era, and by the fast increase of GHGs during the last 150 yr. Likewise, salient impacts from internal climate variability are observed at regional scales. For instance, upper temperature in the equatorial Pacific is controlled by ENSO (El Niño Southern Oscillation variability from interannual to multidecadal timescales. Also, both the Pacific Decadal Oscillation (PDO and the Atlantic Multidecadal Oscillation (AMO modulate intermittently the interdecadal OHC variability in the North Pacific and Mid Atlantic, respectively. The NAO, through its influence on North Atlantic surface heat fluxes and convection, also plays an important role on

  16. Experimental investigation of strong field trident production

    CERN Document Server

    Esberg, J; Knudsen, H; Thomsen, H D; Uggerhøj, E; Uggerhøj, U I; Sona, P; Mangiarotti, A; Ketel, T J; Dizdar, A; Dalton, M M; Ballestrero, S; Connell, S H

    2010-01-01

    We show by experiment that an electron impinging on an electric field that is of critical magnitude in its rest frame, may produce an electron-positron pair. Our measurements address higher-order QED, using the strong electric fields obtainable along particular crystallographic directions in single crystals. For the amorphous material our data are in good agreement with theory, whereas a discrepancy with theory on the magnitude of the trident enhancement is found in the precisely aligned case where the strong electric field acts.

  17. Gluon scattering amplitudes at strong coupling

    Energy Technology Data Exchange (ETDEWEB)

    Alday, Luis F. [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, 3508 TD Utrecht (Netherlands); Maldacena, Juan [School of Natural Sciences, Institute for Advanced Study, Princeton, NJ 08540 (United States)

    2007-06-15

    We describe how to compute planar gluon scattering amplitudes at strong coupling in N = 4 super Yang Mills by using the gauge/string duality. The computation boils down to finding a certain classical string configuration whose boundary conditions are determined by the gluon momenta. The results are infrared divergent. We introduce the gravity version of dimensional regularization to define finite quantities. The leading and subleading IR divergencies are characterized by two functions of the coupling that we compute at strong coupling. We compute also the full finite form for the four point amplitude and we find agreement with a recent ansatz by Bern, Dixon and Smirnov.

  18. Strong boundedness of analytic functions in tubes

    Directory of Open Access Journals (Sweden)

    Richard D. Carmichael

    1979-01-01

    Full Text Available Certain classes of analytic functions in tube domains TC=ℝn+iC in n-dimensional complex space, where C is an open connected cone in ℝn, are studied. We show that the functions have a boundedness property in the strong topology of the space of tempered distributions g′. We further give a direct proof that each analytic function attains the Fourier transform of its spectral function as distributional boundary value in the strong (and weak topology of g′.

  19. Including virtual photons in strong interactions

    International Nuclear Information System (INIS)

    Rusetsky, A.

    2003-01-01

    In the perturbative field-theoretical models we investigate the inclusion of the electromagnetic interactions into the purely strong theory that describes hadronic processes. In particular, we study the convention for splitting electromagnetic and strong interactions and the ambiguity of such a splitting. The issue of the interpretation of the parameters of the low-energy effective field theory in the presence of electromagnetic interactions is addressed, as well as the scale and gauge dependence of the effective theory couplings. We hope, that the results of these studies are relevant for the electromagnetic sector of ChPT. (orig.)

  20. Thermodynamical instabilities under strong magnetic fields

    Science.gov (United States)

    Chen, Y. J.

    2017-03-01

    The thermodynamical instabilities of low densities in the n p matter and n p e matter are studied within several relativistic nuclear models under some values of magnetic fields. The results are compared between each other and the effects of the symmetry energy slope at saturation density on the instability are investigated. The instability regions can exhibit bands due to the presence of Landau levels for very strong magnetic fields of the order of 1017 G, while for weaker magnetic fields, the bands are replaced by many diffused or scattered pieces. It also shows that the proton fraction in the inner crust of neutron stars may be complex under strong magnetic fields.

  1. Universal behavior of strongly correlated Fermi systems

    Energy Technology Data Exchange (ETDEWEB)

    Shaginyan, Vasilii R [B.P. Konstantinov St. Petersburg Institute of Nuclear Physics, Russian Academy of Sciences, Gatchina, Leningrad region, Rusian Federation (Russian Federation); Amusia, M Ya [A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg (Russian Federation); Popov, Konstantin G [Komi Scientific Center, Ural Branch of the Russian Academy of Sciences, Syktyvkar (Russian Federation)

    2007-06-30

    This review discusses the construction of a theory and the analysis of phenomena occurring in strongly correlated Fermi systems such as high-T{sub c} superconductors, heavy-fermion metals, and quasi-two-dimensional Fermi systems. It is shown that the basic properties and the universal behavior of strongly correlated Fermi systems can be described in the framework of the Fermi-condensate quantum phase transition and the well-known Landau paradigm of quasiparticles and the order parameter. The concept of fermion condensation may be fruitful in studying neutron stars, finite Fermi systems, ultra-cold gases in traps, and quark plasma. (reviews of topical problems)

  2. Universal behavior of strongly correlated Fermi systems

    International Nuclear Information System (INIS)

    Shaginyan, Vasilii R; Amusia, M Ya; Popov, Konstantin G

    2007-01-01

    This review discusses the construction of a theory and the analysis of phenomena occurring in strongly correlated Fermi systems such as high-T c superconductors, heavy-fermion metals, and quasi-two-dimensional Fermi systems. It is shown that the basic properties and the universal behavior of strongly correlated Fermi systems can be described in the framework of the Fermi-condensate quantum phase transition and the well-known Landau paradigm of quasiparticles and the order parameter. The concept of fermion condensation may be fruitful in studying neutron stars, finite Fermi systems, ultra-cold gases in traps, and quark plasma. (reviews of topical problems)

  3. Analytical solution of strongly nonlinear Duffing oscillators

    OpenAIRE

    El-Naggar, A.M.; Ismail, G.M.

    2016-01-01

    In this paper, a new perturbation technique is employed to solve strongly nonlinear Duffing oscillators, in which a new parameter α=α(ε)α=α(ε) is defined such that the value of α is always small regardless of the magnitude of the original parameter εε. Therefore, the strongly nonlinear Duffing oscillators with large parameter ε are transformed into a small parameter system with respect to αα. Approximate solution obtained by the present method is compared with the solution of energy balance m...

  4. De Sitter vacua of strongly interacting QFT

    Energy Technology Data Exchange (ETDEWEB)

    Buchel, Alex [Department of Applied Mathematics, University of Western Ontario,London, Ontario N6A 5B7 (Canada); Department of Physics and Astronomy, University of Western Ontario,London, Ontario N6A 5B7 (Canada); Perimeter Institute for Theoretical Physics,Waterloo, Ontario N2J 2W9 (Canada); Karapetyan, Aleksandr [Department of Applied Mathematics, University of Western Ontario,London, Ontario N6A 5B7 (Canada)

    2017-03-22

    We use holographic correspondence to argue that Euclidean (Bunch-Davies) vacuum is a late-time attractor of the dynamical evolution of quantum gauge theories at strong coupling. The Bunch-Davies vacuum is not an adiabatic state, if the gauge theory is non-conformal — the comoving entropy production rate is nonzero. Using the N=2{sup ∗} gauge theory holography, we explore prospects of explaining current accelerated expansion of the Universe as due to the vacuum energy of a strongly coupled QFT.

  5. Variability, trends, and teleconnections of observed precipitation over Pakistan

    Science.gov (United States)

    Iqbal, Muhammad Farooq; Athar, H.

    2017-10-01

    The precipitation variability, trends, and teleconnections are studied over six administrative regions of Pakistan (Gilgit-Baltistan or GB, Azad Jammu and Kashmir or AJK, Khyber Pakhtoonkhawa or KPK, Punjab, Sindh, and Balochistan) on multiple timescales for the period of recent 38 years (1976-2013) using precipitation data of 42 stations and circulation indices datasets (Indian Ocean Dipole [IOD], North Atlantic Oscillation [NAO], Arctic Oscillation [AO], El Niño Southern Oscillation [ENSO], Pacific Decadal Oscillation [PDO], Atlantic Multidecadal Oscillation [AMO], and Quasi-Biennial Oscillation [QBO]). The summer monsoon season received the highest precipitation, amounting to 45%, whereas the winter and pre-monsoon (post-monsoon) seasons contributed 30 and 20% (5%), respectively, of the annual total precipitation. Positive percentile changes were observed in GB, KPK, Punjab, and Balochistan regions during pre-monsoon season and in Balochistan region during post-monsoon season in second half as compared to first half of 38-year period. The Mann-Kendall test revealed increasing trends for the period of 1995-2013 as compared to period of 1976-1994 for entire Pakistan during monsoon season and on annual timescale. A significant influence of ENSO was observed in all the four seasons in Balochistan, KPK, Punjab, and AJK regions during monsoon and post-monsoon seasons. This study not only offers an understanding of precipitation variability linkages with large-scale circulations and trends, but also it contributes as a resource document for policy makers to take measures for adaptation and mitigation of climate change and its impacts with special focus on precipitation over different administrative regions of Pakistan.

  6. Generalized instrumental variable models

    OpenAIRE

    Andrew Chesher; Adam Rosen

    2014-01-01

    This paper develops characterizations of identified sets of structures and structural features for complete and incomplete models involving continuous or discrete variables. Multiple values of unobserved variables can be associated with particular combinations of observed variables. This can arise when there are multiple sources of heterogeneity, censored or discrete endogenous variables, or inequality restrictions on functions of observed and unobserved variables. The models g...

  7. Reaction time variability in ADHD: a review.

    Science.gov (United States)

    Tamm, Leanne; Narad, Megan E; Antonini, Tanya N; O'Brien, Kathleen M; Hawk, Larry W; Epstein, Jeffery N

    2012-07-01

    For the past decade, intra-individual variability in reaction times on computerized tasks has become a central focus of cognitive research on Attention-Deficit/Hyperactivity Disorder (ADHD). Numerous studies document increased reaction time variability among children and adults with ADHD, relative to typically developing controls. However, direct comparisons with other disorders with heightened reaction time variability are virtually nonexistent, despite their potential to inform our understanding of the phenomenon. A growing literature examines the sensitivity of reaction time variability to theoretically and clinically relevant manipulations. There is strong evidence that stimulus treatment reduces reaction time variability during a range of cognitive tasks, but the literature is mixed regarding the impact of motivational incentives and variation in stimulus event rate. Most studies of reaction time variability implicitly assume that heightened reaction time variability reflects occasional lapses in attention, and the dominant neurophysiological interpretation suggests this variability is linked to intrusions of task-negative brain network activity during task performance. Work examining the behavioral and neurophysiological correlates of reaction time variability provides some support for these hypotheses, but considerably more work is needed in this area. Finally, because conclusions from each of domains reviewed are limited by the wide range of measures used to measure reaction time variability, this review highlights the need for increased attention to the cognitive and motivational context in which variability is assessed and recommends that future work always supplement macro-level variability indices with metrics that isolate particular components of reaction time variability.

  8. Earthquake source model using strong motion displacement

    Indian Academy of Sciences (India)

    The strong motion displacement records available during an earthquake can be treated as the response of the earth as the a structural system to unknown forces acting at unknown locations. Thus, if the part of the earth participating in ground motion is modelled as a known finite elastic medium, one can attempt to model the ...

  9. Vector mesons in strongly interacting matter

    Indian Academy of Sciences (India)

    probes like photons, pions or protons or the heated and compressed hadronic matter generated in a heavy-ion collision. Leaving any nuclear medium without strong final-state interactions, dileptons are the optimum decay channel as they avoid any final-state distortion of the 4- momenta of the decay products entering eq.

  10. Vector mesons in strongly interacting matter

    Indian Academy of Sciences (India)

    Properties of hadrons in strongly interacting matter provide a link between quantum chromodynamics in the ... Top: Spectral function of the ρ-meson at normal nuclear matter density as a function of mass and ... directly but folded with the branching ratio ΓV →p1+p2 /Γtot into the specific final channel one is investigating.

  11. Strong industrial base vital for economic revival

    CERN Multimedia

    2001-01-01

    At the inauguration of a 2-day conference on nuclear technology in Islamabad, the chairman of PAEC said that Pakistan needs to develop a strong industrial base and capability to export equipment to improve the economic condition of the country. He descibed how Pakistan has already had a breakthrough with the export of equipment to CERN, Geneva (1 page).

  12. Chaos desynchronization in strongly coupled systems

    International Nuclear Information System (INIS)

    Wu Ye; Liu Weiqing; Xiao, Jinghua; Zhan Meng

    2007-01-01

    The dynamics of chaos desynchronization in strongly coupled oscillator systems is studied. We find a new bifurcation from synchronous chaotic state, chaotic short wave bifurcation, i.e. a chaotic desynchronization attractor is new born in the systems due to chaos desynchronization. In comparison with the usual periodic short wave bifurcation, very rich but distinct phenomena are observed

  13. Strong wind climatic zones in South Africa

    CSIR Research Space (South Africa)

    Kruger, AC

    2010-01-01

    Full Text Available In this paper South Africa is divided into strong wind climate zones, which indicate the main sources of annual maximum wind gusts. By the analysis of wind gust data of 94 weather stations, which had continuous climate time series of 10 years...

  14. Reducing Weak to Strong Bisimilarity in CCP

    Directory of Open Access Journals (Sweden)

    Andrés Aristizábal

    2012-12-01

    Full Text Available Concurrent constraint programming (ccp is a well-established model for concurrency that singles out the fundamental aspects of asynchronous systems whose agents (or processes evolve by posting and querying (partial information in a global medium. Bisimilarity is a standard behavioural equivalence in concurrency theory. However, only recently a well-behaved notion of bisimilarity for ccp, and a ccp partition refinement algorithm for deciding the strong version of this equivalence have been proposed. Weak bisimiliarity is a central behavioural equivalence in process calculi and it is obtained from the strong case by taking into account only the actions that are observable in the system. Typically, the standard partition refinement can also be used for deciding weak bisimilarity simply by using Milner's reduction from weak to strong bisimilarity; a technique referred to as saturation. In this paper we demonstrate that, because of its involved labeled transitions, the above-mentioned saturation technique does not work for ccp. We give an alternative reduction from weak ccp bisimilarity to the strong one that allows us to use the ccp partition refinement algorithm for deciding this equivalence.

  15. Strong motion duration and earthquake magnitude relationships

    International Nuclear Information System (INIS)

    Salmon, M.W.; Short, S.A.; Kennedy, R.P.

    1992-06-01

    Earthquake duration is the total time of ground shaking from the arrival of seismic waves until the return to ambient conditions. Much of this time is at relatively low shaking levels which have little effect on seismic structural response and on earthquake damage potential. As a result, a parameter termed ''strong motion duration'' has been defined by a number of investigators to be used for the purpose of evaluating seismic response and assessing the potential for structural damage due to earthquakes. This report presents methods for determining strong motion duration and a time history envelope function appropriate for various evaluation purposes, for earthquake magnitude and distance, and for site soil properties. There are numerous definitions of strong motion duration. For most of these definitions, empirical studies have been completed which relate duration to earthquake magnitude and distance and to site soil properties. Each of these definitions recognizes that only the portion of an earthquake record which has sufficiently high acceleration amplitude, energy content, or some other parameters significantly affects seismic response. Studies have been performed which indicate that the portion of an earthquake record in which the power (average rate of energy input) is maximum correlates most closely with potential damage to stiff nuclear power plant structures. Hence, this report will concentrate on energy based strong motion duration definitions

  16. Morphological modelling of strongly curved islands

    NARCIS (Netherlands)

    Roelvink, D.; Den Heijer, C.; Van Thiel De Vries, J.S.M.

    2013-01-01

    Land reclamations and island coasts often involve strongly curved shorelines, which are challenging to be properly modeled by numerical morphological models. Evaluation of the long term development of these types of coasts as well as their response to storm conditions requires proper representation

  17. Nonlinear Electron Waves in Strongly Magnetized Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans; Juul Rasmussen, Jens

    1980-01-01

    Weakly nonlinear dispersive electron waves in strongly magnetized plasma are considered. A modified nonlinear Schrodinger equation is derived taking into account the effect of particles resonating with the group velocity of the waves (nonlinear Landau damping). The possibility of including the ion...

  18. Strong and Reversible Monovalent Supramolecular Protein Immobilization

    NARCIS (Netherlands)

    Young, Jacqui F.; Nguyen, Hoang D.; Yang, Lanti; Huskens, Jurriaan; Jonkheijm, Pascal; Brunsveld, Luc

    2010-01-01

    Proteins with an iron clasp: Site-selective incorporation of a ferrocene molecule into a protein allows for easy, strong, and reversible supramolecular protein immobilization through a selective monovalent interaction of the ferrocene with a cucurbit[7]uril immobilized on a gold surface. The

  19. Experimental investigation of strong field trident production

    NARCIS (Netherlands)

    Esberg, J.; Kirsebom, K.; Knudsen, H.; Thomsen, H.D.; Uggerhøj, E.; Uggerhøj, U.I.; Sona, P.; Mangiarotti, A.; Ketel, T.J.; Ditzdar, A.; Dalton, M.M.; Ballestrero, S.; Connell, S.H.

    2010-01-01

    We show by experiment that an electron impinging on an electric field that is of critical magnitude in its rest frame, may produce an electron-positron pair. Our measurements address higher-order QED, using the strong electric fields obtainable along particular crystallographic directions in single

  20. Strong-coupling diffusion in relativistic systems

    Indian Academy of Sciences (India)

    hanced values needed to interpret the data at higher energies point towards the importance of strong-coupling effects. ... when all secondary particles have been created. For short times in the initial phase ... It is decisive for a proper representation of the available data for relativistic heavy-ion collisions at and beyond SPS.

  1. Bottomonia: open bottom strong decays and spectrum

    Directory of Open Access Journals (Sweden)

    Santopinto E.

    2014-05-01

    Full Text Available We present our results for the bottomonium spectrum with self energy corrections. The bare masses used in the calculation are computed within Godfrey and Isgur’s relativized quark model. We also discuss our results for the open bottom strong decay widths of higher bottomonia in the 3P0 pair-creation model.

  2. Strong motion duration and earthquake magnitude relationships

    Energy Technology Data Exchange (ETDEWEB)

    Salmon, M.W.; Short, S.A. [EQE International, Inc., San Francisco, CA (United States); Kennedy, R.P. [RPK Structural Mechanics Consulting, Yorba Linda, CA (United States)

    1992-06-01

    Earthquake duration is the total time of ground shaking from the arrival of seismic waves until the return to ambient conditions. Much of this time is at relatively low shaking levels which have little effect on seismic structural response and on earthquake damage potential. As a result, a parameter termed ``strong motion duration`` has been defined by a number of investigators to be used for the purpose of evaluating seismic response and assessing the potential for structural damage due to earthquakes. This report presents methods for determining strong motion duration and a time history envelope function appropriate for various evaluation purposes, for earthquake magnitude and distance, and for site soil properties. There are numerous definitions of strong motion duration. For most of these definitions, empirical studies have been completed which relate duration to earthquake magnitude and distance and to site soil properties. Each of these definitions recognizes that only the portion of an earthquake record which has sufficiently high acceleration amplitude, energy content, or some other parameters significantly affects seismic response. Studies have been performed which indicate that the portion of an earthquake record in which the power (average rate of energy input) is maximum correlates most closely with potential damage to stiff nuclear power plant structures. Hence, this report will concentrate on energy based strong motion duration definitions.

  3. Controlling Josephson dynamics by strong microwave fields

    NARCIS (Netherlands)

    Chesca, B.; Savel'ev, E.; Rakhmanov, A.L.; Smilde, H.J.H.; Hilgenkamp, Johannes W.M.

    2008-01-01

    We observe several sharp changes in the slope of the current-voltage characteristics (CVCs) of thin-film ramp-edge Josephson junctions between YBa2Cu3O7−delta and Nb when applying strong microwave fields. Such behavior indicates an intriguing Josephson dynamics associated with the switching from a

  4. Strong-coupling diffusion in relativistic systems

    Indian Academy of Sciences (India)

    Different from the early universe, heavy-ion collisions at very high energies do not reach statistical equilibrium, although thermal models explain many of their features. To account for nonequilibrium strong-coupling effects, a Fokker–Planck equation with time-dependent diffusion coefficient is proposed. A schematic model ...

  5. Weak and strong nonlinearities in magnetic bearings

    Czech Academy of Sciences Publication Activity Database

    Půst, Ladislav

    2004-01-01

    Roč. 39, č. 7 (2004), s. 779-795 ISSN 0094-114X R&D Projects: GA ČR GA101/00/1471; GA AV ČR IBS2076301 Institutional research plan: CEZ:AV0Z2076919 Keywords : weak nonlinearitiy * strong nonlinearity * magnetics bearings Subject RIV: BI - Acoustics Impact factor: 0.605, year: 2004

  6. Rotating compressible fluids under strong stratification

    Czech Academy of Sciences Publication Activity Database

    Feireisl, Eduard; Lu, Y.; Novotný, A.

    2014-01-01

    Roč. 19, October (2014), s. 11-18 ISSN 1468-1218 Keywords : rotating fluid * compressible Navier-Stokes * strong stratification Subject RIV: BA - General Mathematics Impact factor: 2.519, year: 2014 http://www.sciencedirect.com/science/article/pii/S1468121814000212#

  7. Super-strong Magnetic Field in Sunspots

    Science.gov (United States)

    Okamoto, Takenori J.; Sakurai, Takashi

    2018-01-01

    Sunspots are the most notable structure on the solar surface with strong magnetic fields. The field is generally strongest in a dark area (umbra), but sometimes stronger fields are found in non-dark regions, such as a penumbra and a light bridge. The formation mechanism of such strong fields outside umbrae is still puzzling. Here we report clear evidence of the magnetic field of 6250 G, which is the strongest field among Stokes I profiles with clear Zeeman splitting ever observed on the Sun. The field was almost parallel to the solar surface and located in a bright region sandwiched by two opposite-polarity umbrae. Using a time series of spectral data sets, we discuss the formation process of the super-strong field and suggest that this strong field region was generated as a result of compression of one umbra pushed by the horizontal flow from the other umbra, such as the subduction of the Earth’s crust in plate tectonics.

  8. Strongly coupled semidirect mediation of supersymmetry breaking

    International Nuclear Information System (INIS)

    Ibe, M.; Izawa, K.-I.; Nakai, Y.

    2009-01-01

    Strongly coupled semidirect gauge mediation models of supersymmetry breaking through massive mediators with standard-model charges are investigated by means of composite degrees of freedom. Sizable mediation is realized to generate the standard-model gaugino masses for a small mediator mass without breaking the standard-model symmetries.

  9. A Note on Strongly Dense Matrices

    Czech Academy of Sciences Publication Activity Database

    Fiedler, Miroslav; Hall, F.J.

    2015-01-01

    Roč. 1, č. 4 (2015), s. 721-730 ISSN 2199-675X Institutional support: RVO:67985807 Keywords : strongly dense matrix * Boolean matrix * nonnegative matrix * idempotent matrix * intrinsic product * generalized complementary basic matrix Subject RIV: BA - General Mathematics

  10. Strongly 2-connected orientations of graphs

    DEFF Research Database (Denmark)

    Thomassen, Carsten

    2014-01-01

    We prove that a graph admits a strongly 2-connected orientation if and only if it is 4-edge-connected, and every vertex-deleted subgraph is 2-edge-connected. In particular, every 4-connected graph has such an orientation while no cubic 3-connected graph has such an orientation....

  11. The Shape of Strongly Disturbed Dayside Magnetopause

    Directory of Open Access Journals (Sweden)

    Alexei V. Dmitriev Alla V. Suvorova

    2013-01-01

    Full Text Available During strong geomagnetic disturbances, the Earth¡¦s magnetosphere exhibits unusual and nonlinear interaction with the incident flow of magnetized solar wind plasma. Global Magneto-hydro-dynamic (MHD modeling of the magnetosphere predicts that the storm-time effects at the magnetopause result from the abnormal plasma transport and/or extremely strong field aligned currents. In-situ observations of the magnetospheric boundary, magnetopause, by Geosynchronous Operational Environmental Satellite (GOES allowed us to find experimentally such effects as a saturation of the dayside reconnection, unusual bluntness and prominent duskward skewing of the nose magnetopause. The saturation and duskward skewing were attributed to the storm-time magnetopause formation under strong southward interplanetary magnetic field (IMF. The unusual bluntness was observed during both high solar wind pressure and strong southward IMF. We suggest that these phenomena are caused by a substantial contribution of the cross-tail current magnetic field and the hot magnetospheric plasma from the asymmetrical ring current into the pressure balance at the dayside magnetopause.

  12. All varieties of encoding variability are not created equal: Separating variable processing from variable tasks

    Science.gov (United States)

    Huff, Mark J.; Bodner, Glen E.

    2014-01-01

    Whether encoding variability facilitates memory is shown to depend on whether item-specific and relational processing are both performed across study blocks, and whether study items are weakly versus strongly related. Variable-processing groups studied a word list once using an item-specific task and once using a relational task. Variable-task groups’ two different study tasks recruited the same type of processing each block. Repeated-task groups performed the same study task each block. Recall and recognition were greatest in the variable-processing group, but only with weakly related lists. A variable-processing benefit was also found when task-based processing and list-type processing were complementary (e.g., item-specific processing of a related list) rather than redundant (e.g., relational processing of a related list). That performing both item-specific and relational processing across trials, or within a trial, yields encoding-variability benefits may help reconcile decades of contradictory findings in this area. PMID:25018583

  13. Interdecadal North-Atlantic meridional overturning circulation variability in EC-EARTH

    International Nuclear Information System (INIS)

    Wouters, Bert; Drijfhout, Sybren; Hazeleger, Wilco

    2012-01-01

    The Atlantic meridional overturning circulation (AMOC) in a 600 years pre-industrial run of the newly developed EC-EARTH model features marked interdecadal variability with a dominant time-scale of 50-60 years. An oscillation of approximately 2 Sverdrup (1 Sv = 10 6 m 3 s -1 ) is identified, which manifests itself as a monopole causing the overturning to simultaneously strengthen (/weaken) and deepen (/shallow) as a whole. Eight years before the AMOC peaks, density in the Labrador-Irminger Sea region reaches a maximum, triggering deep water formation. This density change is caused by a counterclockwise advection of temperature and salinity anomalies at lower latitudes, which we relate to the north-south excursions of the subpolar-subtropical gyre boundary and variations in strength and position of the subpolar gyre and the North Atlantic Current. The AMOC fluctuations are not directly forced by the atmosphere, but occur in a delayed response of the ocean to forcing by the North Atlantic Oscillation, which initiates ''intergyre''-gyre fluctuations. Associated with the AMOC is a 60-year sea surface temperature variability in the Atlantic, with a pattern and timescale showing similarities with the real-world Atlantic Multidecadal Variability. This good agreement with observations lends a certain degree of credibility that the mechanism that is described in this article could be seen as representative of the real climate system. (orig.)

  14. Interdecadal North-Atlantic meridional overturning circulation variability in EC-EARTH

    Energy Technology Data Exchange (ETDEWEB)

    Wouters, Bert; Drijfhout, Sybren; Hazeleger, Wilco

    2012-12-15

    The Atlantic meridional overturning circulation (AMOC) in a 600 years pre-industrial run of the newly developed EC-EARTH model features marked interdecadal variability with a dominant time-scale of 50-60 years. An oscillation of approximately 2 Sverdrup (1 Sv = 10{sup 6} m{sup 3} s{sup -1}) is identified, which manifests itself as a monopole causing the overturning to simultaneously strengthen (/weaken) and deepen (/shallow) as a whole. Eight years before the AMOC peaks, density in the Labrador-Irminger Sea region reaches a maximum, triggering deep water formation. This density change is caused by a counterclockwise advection of temperature and salinity anomalies at lower latitudes, which we relate to the north-south excursions of the subpolar-subtropical gyre boundary and variations in strength and position of the subpolar gyre and the North Atlantic Current. The AMOC fluctuations are not directly forced by the atmosphere, but occur in a delayed response of the ocean to forcing by the North Atlantic Oscillation, which initiates ''intergyre''-gyre fluctuations. Associated with the AMOC is a 60-year sea surface temperature variability in the Atlantic, with a pattern and timescale showing similarities with the real-world Atlantic Multidecadal Variability. This good agreement with observations lends a certain degree of credibility that the mechanism that is described in this article could be seen as representative of the real climate system. (orig.)

  15. Decadal climate variability and the spatial organization of deep hydrological drought

    Science.gov (United States)

    Barros, Ana P.; Hodes, Jared L.; Arulraj, Malarvizhi

    2017-10-01

    Empirical Orthogonal Function (EOF), wavelet, and wavelet coherence analysis of baseflow time-series from 126 streamgauges (record-length > 50 years; small and mid-size watersheds) in the US South Atlantic (USSA) region reveal three principal modes of space-time variability: (1) a region-wide dominant mode tied to annual precipitation that exhibits non-stationary decadal variability after the mid 1990s concurrent with the warming of the AMO (Atlantic Multidecadal Oscillation); (2) two spatial modes, east and west of the Blue Ridge, exhibiting nonstationary seasonal to sub-decadal variability before and after 1990 attributed to complex nonlinear interactions between ENSO and AMO impacting precipitation and recharge; and (3) deep (decadal) and shallow (predictability of hydrological drought in small and mid-size watersheds, where baseflow is a robust indicator of nonstationary yield capacity of the underlying groundwater basins. Predictive associations between climate mode indices and deep baseflow (e.g. persistent decreases of the decadal-scale components of baseflow during the cold phase of the AMO in the USSA) can be instrumental toward improving forecast lead-times and long-range mitigation of severe drought.

  16. Simulating Changes in Tropospheric Aerosol Burden and its Radiative Effects across the Northern Hemisphere: Contrasting Multi-Decadal Trends between Asia and North America

    Science.gov (United States)

    Though aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, the verification of the spatial and temporal variability of the magnitude and directionality of aerosol radiative forcing has remained challeng...

  17. A Strong Kind of Riemann Integrability

    Science.gov (United States)

    Thomson, Brian S.

    2012-01-01

    The usual definition of the Riemann integral as a limit of Riemann sums can be strengthened to demand more of the function to be integrated. This super-Riemann integrability has interesting properties and provides an easy proof of a simple change of variables formula and a novel characterization of derivatives. This theory offers teachers and…

  18. Oscillations and trends of river discharge in the southern Central Andes and linkages with climate variability

    Science.gov (United States)

    Castino, Fabiana; Bookhagen, Bodo; Strecker, Manfred R.

    2017-12-01

    This study analyzes the discharge variability of small to medium drainage basins (102-104 km2) in the southern Central Andes of NW Argentina. The Hilbert-Huang Transform (HHT) was applied to evaluate non-stationary oscillatory modes of variability and trends, based on four time series of monthly-normalized discharge anomaly between 1940 and 2015. Statistically significant trends reveal increasing discharge during the past decades and document an intensification of the hydrological cycle during this period. An Ensemble Empirical Mode Decomposition (EEMD) analysis revealed that discharge variability in this region can be best described by five quasi-periodic statistically significant oscillatory modes, with mean periods varying from 1 to ∼20 y. Moreover, we show that discharge variability is most likely linked to the phases of the Pacific Decadal Oscillation (PDO) at multi-decadal timescales (∼20 y) and, to a lesser degree, to the Tropical South Atlantic SST anomaly (TSA) variability at shorter timescales (∼2-5 y). Previous studies highlighted a rapid increase in discharge in the southern Central Andes during the 1970s, inferred to have been associated with the global 1976-77 climate shift. Our results suggest that the rapid discharge increase in the NW Argentine Andes coincides with the periodic enhancement of discharge, which is mainly linked to a negative to positive transition of the PDO phase and TSA variability associated with a long-term increasing trend. We therefore suggest that variations in discharge in this region are largely driven by both natural variability and the effects of global climate change. We furthermore posit that the links between atmospheric and hydrologic processes result from a combination of forcings that operate on different spatiotemporal scales.

  19. Strong ground motion prediction using virtual earthquakes.

    Science.gov (United States)

    Denolle, M A; Dunham, E M; Prieto, G A; Beroza, G C

    2014-01-24

    Sedimentary basins increase the damaging effects of earthquakes by trapping and amplifying seismic waves. Simulations of seismic wave propagation in sedimentary basins capture this effect; however, there exists no method to validate these results for earthquakes that have not yet occurred. We present a new approach for ground motion prediction that uses the ambient seismic field. We apply our method to a suite of magnitude 7 scenario earthquakes on the southern San Andreas fault and compare our ground motion predictions with simulations. Both methods find strong amplification and coupling of source and structure effects, but they predict substantially different shaking patterns across the Los Angeles Basin. The virtual earthquake approach provides a new approach for predicting long-period strong ground motion.

  20. Strong negative terahertz photoconductivity in photoexcited graphene

    Science.gov (United States)

    Fu, Maixia; Wang, Xinke; Ye, Jiasheng; Feng, Shengfei; Sun, Wenfeng; Han, Peng; Zhang, Yan

    2018-01-01

    Terahertz (THz) response of a chemical vapor deposited graphene on a quartz substrate has been investigated by using an ultrafast optical-pump THz-probe spectroscopy. Without photoexcitation, the frequency-dependence optical conductivity shows a strong carrier response owing to the intrinsically doped graphene. Upon photoexcitation, an enhancement in THz transmission is observed and the transmission increases nonlinearly with the increase of pump power, which is rooted in a reduction of intrinsic conductivity arising from the strong enhancement of carrier scattering rather than THz emission occurrence. The modulation depth of 18.8% was experimentally achieved, which is more than four times greater than that of the previous reported. The photoinduced response here highlights the variety of response possible in graphene depending on the sample quality, carrier mobility and doping level. The graphene provides promising applications in high-performance THz modulators and THz photoelectric devices.

  1. Cosmological applications of strong gravitational lensing

    DEFF Research Database (Denmark)

    Paraficz, Danuta

    value of the energy density of the two above components, together with measuring the Hubble constant that determines the age of the Universe, is a major goal of modern astrophysics. An interesting method for estimating these parameters is strong gravitational lensing of quasars (QSOs). As shown...... by Refsdal (1964), H0, !m and !! can be measured based on the time delay ("t) between multiply lensed images of QSOs, because "t depends on H0 and on the distances to lens and source, hence!m and !!. Determination of cosmological parameters using gravitational lensing suffers from some degeneracies......, but it is based on well understood physics and unlike distance ladder methods there are no calibration issues. Moreover, it has an advantage over some of the leading methods (such as Type Ia SNe) in that it is a purely cosmological approach. In this thesis, the property of strong gravitational lensing - time...

  2. Gallstone ileus resulting in strong intestinal obstruction

    Directory of Open Access Journals (Sweden)

    Israel Szajnbok

    Full Text Available Mechanic intestinal obstruction, caused by the passage of biliary calculus from vesicle to intestine, through fistulization, although not frequent, deserve study due to the morbi-mortality rates. Incidence in elder people explains the association with chronic degenerative diseases, increasing complexity in terms of therapy decision. Literature discusses the need and opportunity for the one or two-phase surgical attack of the cholecystenteric fistule, in front of the resolution on the obstructive urgency and makes reference to Gallstone Ileus as an exception for strong intestinal obstruction. The more frequent intestinal obstruction observed is when it occurs a Gallstone Ileus impacting in terms of ileocecal valve. The authors submit a Gallstone Ileus manifestation as causing strong intestinal obstruction, discussing aspects regarding diagnostic and treatment.

  3. Strong gauge boson scattering at the LHC

    CERN Document Server

    Rindani, S.D.

    2009-01-01

    In the standard model with electroweak symmetry breaking through the Higgs mechanism, electroweak gauge-boson scattering amplitudes are large if the Higgs boson is heavy, and electroweak gauge interactions become strong. In theories with electroweak symmetry breaking through alternative mechanisms, there could be a strongly interacting gauge sector, possibly with resonances in an accessible energy region. In general, the scattering of longitudinally polarized massive gauge bosons can give information on the mechanism of spontaneous symmetry breaking. At energies below the symmetry breaking scale, the equivalence theorem relates the scattering amplitudes to those of the "would-be" Goldstone modes. In the absence of Higgs bosons, unitarity would be restored by some new physics which can be studied through WW scattering. Some representatives models are discussed. Isolating WW scattering at a hadron collider from other contributions involving W emission from parton lines needs a good understanding of the backgrou...

  4. Strong spin-photon coupling in silicon.

    Science.gov (United States)

    Samkharadze, N; Zheng, G; Kalhor, N; Brousse, D; Sammak, A; Mendes, U C; Blais, A; Scappucci, G; Vandersypen, L M K

    2018-03-09

    Long coherence times of single spins in silicon quantum dots make these systems highly attractive for quantum computation, but how to scale up spin qubit systems remains an open question. As a first step to address this issue, we demonstrate the strong coupling of a single electron spin and a single microwave photon. The electron spin is trapped in a silicon double quantum dot, and the microwave photon is stored in an on-chip high-impedance superconducting resonator. The electric field component of the cavity photon couples directly to the charge dipole of the electron in the double dot, and indirectly to the electron spin, through a strong local magnetic field gradient from a nearby micromagnet. Our results provide a route to realizing large networks of quantum dot-based spin qubit registers. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  5. Cosmogenic photons strongly constrain UHECR source models

    Directory of Open Access Journals (Sweden)

    van Vliet Arjen

    2017-01-01

    Full Text Available With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT’s IGRB, as long as their number density is not strongly peaked at recent times.

  6. Waves in strong centrifugal fields: dissipationless gas

    Science.gov (United States)

    Bogovalov, S. V.; Kislov, V. A.; Tronin, I. V.

    2015-04-01

    Linear waves are investigated in a rotating gas under the condition of strong centrifugal acceleration of the order 106 g realized in gas centrifuges for separation of uranium isotopes. Sound waves split into three families of the waves under these conditions. Dispersion equations are obtained. The characteristics of the waves strongly differ from the conventional sound waves on polarization, velocity of propagation and distribution of energy of the waves in space for two families having frequencies above and below the frequency of the conventional sound waves. The energy of these waves is localized in rarefied region of the gas. The waves of the third family were not specified before. They propagate exactly along the rotational axis with the conventional sound velocity. These waves are polarized only along the rotational axis. Radial and azimuthal motions are not excited. Energy of the waves is concentrated near the wall of the rotor where the density of the gas is largest.

  7. Quantum strongly secure ramp secret sharing

    DEFF Research Database (Denmark)

    Zhang, Paul; Matsumoto, Rytaro Yamashita

    2015-01-01

    Quantum secret sharing is a scheme for encoding a quantum state (the secret) into multiple shares and distributing them among several participants. If a sufficient number of shares are put together, then the secret can be fully reconstructed. If an insufficient number of shares are put together...... however, no information about the secret can be revealed. In quantum ramp secret sharing, partial information about the secret is allowed to leak to a set of participants, called an unqualified set, that cannot fully reconstruct the secret. By allowing this, the size of a share can be drastically reduced....... This paper introduces a quantum analog of classical strong security in ramp secret sharing schemes. While the ramp secret sharing scheme still leaks partial information about the secret to unqualified sets of participants, the strong security condition ensures that qudits with critical information can...

  8. Quantum Transport in Strongly Correlated Systems

    DEFF Research Database (Denmark)

    Bohr, Dan

    2007-01-01

    the density matrix renormalization group (DMRG) method. We present two DMRG setups for calculating the linear conductance of strongly correlated nanostructures in the infinitesimal source-drain voltage regime. The first setup describes the leads by modified real-space tight-binding chains, whereas the second...... screening plays a much less significant role than in bulk systems due to the reduced size of the objects, therefore making it necessary to consider the importance of correlations between electrons. The work presented in this thesis deals with quantum transport through strongly correlated systems using....... Thus both coherence and correlation effects are important in this model, and the methods applied should be able to handle both these effects rigorously. We present the DMRG setup for this model and benchmark against existing Greens function results for the model. Then we present initial DMRG results...

  9. Hydrogen atoms in a strong magnetic field

    International Nuclear Information System (INIS)

    Santos, R.R. dos.

    1975-07-01

    The energies and wave functions of the 14 lowest states of a Hydrogen atom in a strong magnetic field are calculated, using a variational scheme. The equivalence between the atomic problem and the problems related with excitons and impurities in semiconductors in the presence of a strong magnetic field are shown. The calculations of the energies and wave functions have been divided in two regions: the first, for the magnetic field ranging between zero and 10 9 G; in the second the magnetic field ranges between 10 9 and 10 11 G. The results have been compared with those obtained by previous authors. The computation time necessary for the calculations is small. Therefore this is a convenient scheme to obtain the energies and wave functions for the problem. Transition probabilities, wavelengths and oscillator strengths for some allowed transitions are also calculated. (Author) [pt

  10. Strong Josephson Coupling in Planar Graphene Junctions

    Science.gov (United States)

    Park, Jinho; Lee, Gil-Ho; Lee, Jae Hyeong; Takane, Yositake; Imura, Ken-Ichiro; Taniguchi, Takashi; Watanabe, Kenji; Lee, Hu-Jong

    A recent breakthrough of processing graphene, employing encapsulation by hexagonal boron nitride layers (BGB structure), allows realizing the ballistic carrier transport in graphene. Thereafter, ballistic Josephson coupling has been studied by closely edge-contacted BGB structure with two superconducting electrodes. Here, we report on the strong Josephson coupling with planar graphene junction in truly short and ballistic regime. Our device showed high transmission probability and the junction critical current (IC) oscillating for sweeping the gate voltage along with the normal conductance oscillation (Fabry-Perot oscillations), providing a direct evidence for the ballistic nature of the junction pair current. We also observed the convex-upward shape of decreasing critical currents with increasing temperature, canonical properties of the short Josephson coupling. By fitting these curves into theoretical models, we demonstrate the strong Josephson coupling in our devices, which is also supported by the exceptionally large value of ICRN ( 2 Δ / e RNis the normal resistance).

  11. Electroweak and Strong Interactions Phenomenology, Concepts, Models

    CERN Document Server

    Scheck, Florian

    2012-01-01

    Electroweak and Strong Interaction: Phenomenology, Concepts, Models, begins with relativistic quantum mechanics and some quantum field theory which lay the foundation for the rest of the text. The phenomenology and the physics of the fundamental interactions are emphasized through a detailed discussion of the empirical fundamentals of unified theories of strong, electromagnetic, and weak interactions. The principles of local gauge theories are described both in a heuristic and a geometric framework. The minimal standard model of the fundamental interactions is developed in detail and characteristic applications are worked out. Possible signals of physics beyond that model, notably in the physics of neutrinos are also discussed. Among the applications scattering on nucleons and on nuclei provide salient examples. Numerous exercises with solutions make the text suitable for advanced courses or individual study. This completely updated revised new edition contains an enlarged chapter on quantum chromodynamics an...

  12. Frictional Coulomb drag in strong magnetic fields

    DEFF Research Database (Denmark)

    Bønsager, Martin Christian; Flensberg, Karsten; Hu, Ben Yu-Kuang

    1997-01-01

    A treatment of frictional Coulomb drag between two two-dimensional electron layers in a strong perpendicular magnetic field, within the independent electron picture, is presented. Assuming fully resolved Landau levels, the linear response theory expression for the transresistivity rho(21) is eval......A treatment of frictional Coulomb drag between two two-dimensional electron layers in a strong perpendicular magnetic field, within the independent electron picture, is presented. Assuming fully resolved Landau levels, the linear response theory expression for the transresistivity rho(21......) is evaluated using diagrammatic techniques. The transresistivity is given by an integral over energy and momentum transfer weighted by the product of the screened interlayer interaction and the phase space for scattering events. We demonstrate, by a numerical analysis of the transresistivity, that for well...

  13. Orbits in weak and strong bars

    CERN Document Server

    Contopoulos, George

    1980-01-01

    The authors study the plane orbits in simple bar models embedded in an axisymmetric background when the bar density is about 1% (weak), 10% (intermediate) or 100% (strong bar) of the axisymmetric density. Most orbits follow the stable periodic orbits. The basic families of periodic orbits are described. In weak bars with two Inner Lindblad Resonances there is a family of stable orbits extending from the center up to the Outer Lindblad Resonance. This family contains the long period orbits near corotation. Other stable families appear between the Inner Lindblad Resonances, outside the Outer Lindblad Resonance, around corotation (short period orbits) and around the center (retrograde). Some families become unstable or disappear in strong bars. A comparison is made with cases having one or no Inner Lindblad Resonance. (12 refs).

  14. Strong sum distance in fuzzy graphs.

    Science.gov (United States)

    Tom, Mini; Sunitha, Muraleedharan Shetty

    2015-01-01

    In this paper the idea of strong sum distance which is a metric, in a fuzzy graph is introduced. Based on this metric the concepts of eccentricity, radius, diameter, center and self centered fuzzy graphs are studied. Some properties of eccentric nodes, peripheral nodes and central nodes are obtained. A characterisation of self centered complete fuzzy graph is obtained and conditions under which a fuzzy cycle is self centered are established. We have proved that based on this metric, an eccentric node of a fuzzy tree G is a fuzzy end node of G and a node is an eccentric node of a fuzzy tree if and only if it is a peripheral node of G and the center of a fuzzy tree consists of either one or two neighboring nodes. The concepts of boundary nodes and interior nodes in a fuzzy graph based on strong sum distance are introduced. Some properties of boundary nodes, interior nodes and complete nodes are studied.

  15. Analytical solution of strongly nonlinear Duffing oscillators

    Directory of Open Access Journals (Sweden)

    A.M. El-Naggar

    2016-06-01

    Full Text Available In this paper, a new perturbation technique is employed to solve strongly nonlinear Duffing oscillators, in which a new parameter α=α(ε is defined such that the value of α is always small regardless of the magnitude of the original parameter ε. Therefore, the strongly nonlinear Duffing oscillators with large parameter ε are transformed into a small parameter system with respect to α. Approximate solution obtained by the present method is compared with the solution of energy balance method, homotopy perturbation method, global error minimization method and lastly numerical solution. We observe from the results that this method is very simple, easy to apply, and gives a very good accuracy not only for small parameter εbut also for large values of ε.

  16. Strong interaction studies with kaonic atoms

    Directory of Open Access Journals (Sweden)

    Marton J.

    2016-01-01

    Full Text Available The strong interaction of antikaons (K− with nucleons and nuclei in the low-energy regime represents an active research field connected intrinsically with few-body physics. There are important open questions like the question of antikaon nuclear bound states - the prototype system being K−pp. A unique and rather direct experimental access to the antikaon-nucleon scattering lengths is provided by precision X-ray spectroscopy of transitions in low-lying states of light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment at the electron-positron collider DAΦNE of LNF-INFN we measured the most precise values of the strong interaction observables, i.e. the strong interaction on the 1s ground state of the electromagnetically bound K−p atom leading to a hadronic shift ϵ1s and a hadronic broadening Γ1s of the 1s state. The SIDDHARTA result triggered new theoretical work which achieved major progress in the understanding of the low-energy strong interaction with strangeness. Antikaon-nucleon scattering lengths have been calculated constrained by the SIDDHARTA data on kaonic hydrogen. For the extraction of the isospin-dependent scattering lengths a measurement of the hadronic shift and width of kaonic deuterium is necessary. Therefore, new X-ray studies with the focus on kaonic deuterium are in preparation (SIDDHARTA2. Many improvements in the experimental setup will allow to measure kaonic deuterium which is challenging due to the anticipated low X-ray yield. Especially important are the data on the X-ray yields of kaonic deuterium extracted from a exploratory experiment within SIDDHARTA.

  17. SUSY strong production (leptonic) with ATLAS

    CERN Document Server

    Saito, Tomoyuki; The ATLAS collaboration

    2017-01-01

    Supersymmetry is one of the most motivated scenarios for physics beyond the Standard Model. This article summarizes recent ATLAS results on searches for supersymmetry in proton-proton collisions at a centre-of-mass energy of 13 TeV at LHC, which target supersymmetric particles produced by strong interaction in events with leptonic fi nal states. No signi ficant excess above the Standard Model expectation is observed and exclusion limits have been set on squark and gluino masses in various scenarios.

  18. Strong coupling QED with two fermionic flavors

    Energy Technology Data Exchange (ETDEWEB)

    Wang, K.C.

    1990-11-01

    We report the recent results of our simulation of strong coupling QED, with non-compact action, on lattices 10{sup 4} and 16{sup 4}. Since we are dealing with two staggered fermionic flavors, we use hybrid algorithm to do the simulation. In addition to the measurement of the chiral order parameter {l angle}{bar {psi}}{psi}{r angle}, we also measure magnetic monopole susceptibility, {chi}, throughout the region of chiral transition. 6 refs., 6 figs.

  19. Magnetic properties of strongly asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Kutschera, M.; Wojcik, W.

    1988-01-01

    We investigate stability of neutron matter containing a small proton admixture with respect to spin fluctuations. We establish conditions under which strongly asymmetric nuclear matter could acquire a permanent magnetization. It is shown that if the protons are localized, the system becomes unstable to spin fluctuations for arbitrarily weak proton-neutron spin interactions. For non-localized protons there exists a threshold value of the spin interaction above which the system can develop a spontaneous polarization. 12 refs., 2 figs. (author)

  20. Strong coupling analogue of the Born series

    International Nuclear Information System (INIS)

    Dolinszky, T.

    1989-10-01

    In a given partial wave, the strength of the centrifugal term to be incorporated into the WKBA solutions in different spatial regions can be adjusted so as to make the first order wave functions everywhere smooth and, in strong coupling, exactly reproduce Quantum Mechanics throughout the space. The relevant higher order approximations supply an absolute convergent series expansion of the exact scattering state. (author) 4 refs.; 2 figs.; 2 tabs

  1. Strong-Q-sequences and small d

    Czech Academy of Sciences Publication Activity Database

    Chodounský, David

    2012-01-01

    Roč. 159, č. 3 (2012), s. 2942-2946 ISSN 0166-8641. [Prague Symposium on General Topology and its Relations to Modern Analysis and Algebra /11./. Prague, 07.08.2011-12.08.2011] Institutional support: RVO:67985840 Keywords : Katowice problem * strong-Q-sequence * dominating number Subject RIV: BA - General Mathematics Impact factor: 0.562, year: 2012 http://www.sciencedirect.com/science/article/pii/S0166864112002222

  2. Superbainite. A novel very strong bainitic microstructure

    International Nuclear Information System (INIS)

    Garcia-Mateo, C.; Caballero, E. G.; Bhadeshia, H. K. D. H.

    2005-01-01

    In this work very recent results are how that reveals the possibility of obtaining bainite by isothermal transformation at very low temperatures, of about 150 degree centigree, in high carbon high silicon steels. The microstructure thus obtained is a mixture of fine plates of bainite ferrite (20-40 nm thickness) and thin films of carbon enriched austenite. These microstructures are very hard (600 HV) and strong (2.5 GPa). (Author) 18 refs

  3. Strong decays of nonstrange q3 baryons

    International Nuclear Information System (INIS)

    Bijker, R.; Iachello, F.; Leviatan, A.

    1997-01-01

    We study strong decays of nonstrange baryons by making use of the algebraic approach to hadron structure. Within this framework we derive closed expressions for decay widths in an elementary-meson emission model and use these to analyze the experimental data for N * →N+π, N * →Δ+π, N * →N+η, Δ * →N+π, Δ * →Δ+π, and Δ * →Δ+η decays. copyright 1997 The American Physical Society

  4. Simulation of turbulent flows containing strong shocks

    Science.gov (United States)

    Fryxell, Bruce; Menon, Suresh

    2008-12-01

    Simulation of turbulent flows with strong shocks is a computationally challenging problem. The requirements for a method to produce accurate results for turbulence are orthogonal to those needed to treat shocks properly. In order to prevent an unphysical rate of decay of turbulent structures, it is necessary to use a method with very low numerical dissipation. Because of this, central difference schemes are widely used. However, computing strong shocks with a central difference scheme can produce unphysical post-shock oscillations that corrupt the entire flow unless additional dissipation is added. This dissipation can be difficult to localize to the area near the shock and can lead to inaccurate treatment of the turbulence. Modern high-resolution shock-capturing methods usually use upwind algorithms to provide the dissipation necessary to stabilize shocks. However, this upwind dissipation can also lead to an unphysical rate of decay of the turbulence. This paper discusses a hybrid method for simulating turbulent flows with strong shocks that couples a high-order central difference scheme with a high-resolution shock-capturing method. The shock-capturing method is used only in the vicinity of discontinuities in the flow, whereas the central difference scheme is used in the remainder of the computational domain. Results of this new method will be shown for a variety of test problems. Preliminary results for a realistic application involving detonation in gas-particle flows will also be presented.

  5. Strong CP, flavor, and twisted split fermions

    International Nuclear Information System (INIS)

    Harnik, Roni; Perez, Gilad; Schwartz, Matthew D.; Shirman, Yuri

    2005-01-01

    We present a natural solution to the strong CP problem in the context of split fermions. By assuming CP is spontaneously broken in the bulk, a weak CKM phase is created in the standard model due to a twisting in flavor space of the bulk fermion wavefunctions. But the strong CP phase remains zero, being essentially protected by parity in the bulk and CP on the branes. As always in models of spontaneous CP breaking, radiative corrections to theta bar from the standard model are tiny, but even higher dimension operators are not that dangerous. The twisting phenomenon was recently shown to be generic, and not to interfere with the way that split fermions naturally weaves small numbers into the standard model. It follows that out approach to strong CP is compatible with flavor, and we sketch a comprehensive model. We also look at deconstructed version of this setup which provides a viable 4D model of spontaneous CP breaking which is not in the Nelson-Barr class. (author)

  6. Transport phenomena in strongly correlated Fermi liquids

    Energy Technology Data Exchange (ETDEWEB)

    Kontani, Hiroshi [Nagoya Univ., Aichi (Japan). Dept. of Physics

    2013-03-01

    Comprehensive overview. Written by an expert of this topic. Provides the reader with current developments in the field. In conventional metals, various transport coefficients are scaled according to the quasiparticle relaxation time, {tau}, which implies that the relaxation time approximation (RTA) holds well. However, such a simple scaling does not hold in many strongly correlated electron systems, reflecting their unique electronic states. The most famous example would be cuprate high-Tc superconductors (HTSCs), where almost all the transport coefficients exhibit a significant deviation from the RTA results. To better understand the origin of this discrepancy, we develop a method for calculating various transport coefficients beyond the RTA by employing field theoretical techniques. Near the magnetic quantum critical point, the current vertex correction (CVC), which describes the electron-electron scattering beyond the relaxation time approximation, gives rise to various anomalous transport phenomena. We explain anomalous transport phenomena in cuprate HTSCs and other metals near their magnetic or orbital quantum critical point using a uniform approach. We also discuss spin related transport phenomena in strongly correlated systems. In many d- and f-electron systems, the spin current induced by the spin Hall effect is considerably greater because of the orbital degrees of freedom. This fact attracts much attention due to its potential application in spintronics. We discuss various novel charge, spin and heat transport phenomena in strongly correlated metals.

  7. Simulation of turbulent flows containing strong shocks

    International Nuclear Information System (INIS)

    Fryxell, Bruce; Menon, Suresh

    2008-01-01

    Simulation of turbulent flows with strong shocks is a computationally challenging problem. The requirements for a method to produce accurate results for turbulence are orthogonal to those needed to treat shocks properly. In order to prevent an unphysical rate of decay of turbulent structures, it is necessary to use a method with very low numerical dissipation. Because of this, central difference schemes are widely used. However, computing strong shocks with a central difference scheme can produce unphysical post-shock oscillations that corrupt the entire flow unless additional dissipation is added. This dissipation can be difficult to localize to the area near the shock and can lead to inaccurate treatment of the turbulence. Modern high-resolution shock-capturing methods usually use upwind algorithms to provide the dissipation necessary to stabilize shocks. However, this upwind dissipation can also lead to an unphysical rate of decay of the turbulence. This paper discusses a hybrid method for simulating turbulent flows with strong shocks that couples a high-order central difference scheme with a high-resolution shock-capturing method. The shock-capturing method is used only in the vicinity of discontinuities in the flow, whereas the central difference scheme is used in the remainder of the computational domain. Results of this new method will be shown for a variety of test problems. Preliminary results for a realistic application involving detonation in gas-particle flows will also be presented.

  8. Climatic Indices and their teleconnections with hydroclimatic variability in the conterminous USA

    Science.gov (United States)

    Betancourt, J. L.; McCabe, G. J.; Pederson, G. T.

    2012-12-01

    Beginning a century ago with the North Atlantic Oscillation (NAO), climate indices derived from synoptic measurements of atmospheric pressure and sea surface temperatures, or their proxies, have been used extensively to investigate ocean/atmosphere teleconnections with hydroclimatological variations and their impacts on land. Here, we address various issues associated with teleconnections between both instrumental and reconstructed climatic indices and USA hydroclimatology, with particular focus on the American West. Modes of ocean variability represented by these indices, and their teleconnections, may or may not operate independently. For example, atmospheric bridging occurs across both the North and tropical Pacific and Atlantic Oceans, and such atmosphere-ocean interactions may amplify and even modulate frequency spectra in interannual modes of variability, including ENSO. The Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO), each defined by basin-wide averages or EOF's, together explain more than half of the decadal-to-multidecadal (D2M) variance in detrended global SST over the 20th century. The Pacific-North American pattern (PNA) and the Northern Annular Mode (NAM)/Arctic Oscillation (AO), particularly dominant in the Northern Hemisphere winter and spring, together explain 30% of all variance in monthly sea level pressure. Independent of global warming, AMO and PDO together explain more than half of the 20th century seasonal temperature and drought variance at D2M timescales in the conterminous USA. PNA and NAM/AO explain much of the variance in winter/spring hydroclimatology, including snowpack, spring onset, and related ecological phenomena. Continental-scale patterns of many of these teleconnections are statistically robust, but regional significance may be limited- e.g., the relationship between combined PDO/ENSO and interannual spring onset variations is truly significant only in the Pacific NW, and then more so for the

  9. The INGV Real Time Strong Motion Database

    Science.gov (United States)

    Massa, Marco; D'Alema, Ezio; Mascandola, Claudia; Lovati, Sara; Scafidi, Davide; Gomez, Antonio; Carannante, Simona; Franceschina, Gianlorenzo; Mirenna, Santi; Augliera, Paolo

    2017-04-01

    The INGV real time strong motion data sharing is assured by the INGV Strong Motion Database. ISMD (http://ismd.mi.ingv.it) was designed in the last months of 2011 in cooperation among different INGV departments, with the aim to organize the distribution of the INGV strong-motion data using standard procedures for data acquisition and processing. The first version of the web portal was published soon after the occurrence of the 2012 Emilia (Northern Italy), Mw 6.1, seismic sequence. At that time ISMD was the first European real time web portal devoted to the engineering seismology community. After four years of successfully operation, the thousands of accelerometric waveforms collected in the archive need necessary a technological improvement of the system in order to better organize the new data archiving and to make more efficient the answer to the user requests. ISMD 2.0 was based on PostgreSQL (www.postgresql.org), an open source object- relational database. The main purpose of the web portal is to distribute few minutes after the origin time the accelerometric waveforms and related metadata of the Italian earthquakes with ML≥3.0. Data are provided both in raw SAC (counts) and automatically corrected ASCII (gal) formats. The web portal also provide, for each event, a detailed description of the ground motion parameters (i.e. Peak Ground Acceleration, Velocity and Displacement, Arias and Housner Intensities) data converted in velocity and displacement, response spectra up to 10.0 s and general maps concerning the recent and the historical seismicity of the area together with information about its seismic hazard. The focal parameters of the events are provided by the INGV National Earthquake Center (CNT, http://cnt.rm.ingv.it). Moreover, the database provides a detailed site characterization section for each strong motion station, based on geological, geomorphological and geophysical information. At present (i.e. January 2017), ISMD includes 987 (121

  10. Engaging Military Fathers in a Reflective Parenting Program: Lessons from Strong Families Strong Forces

    Science.gov (United States)

    DeVoe, Ellen R.; Paris, Ruth

    2015-01-01

    Through Strong Families Strong Forces, a reflective parenting program for military families with young children, we were privileged to work with contemporary military fathers who served in the post-9/11 conflicts in Afghanistan and Iraq. Due to this work, the authors gained valuable insight into the complexity of fathering during wartime, the…

  11. 77 FR 16131 - Establishing a White House Council on Strong Cities, Strong Communities

    Science.gov (United States)

    2012-03-20

    ... Order 13602 of March 15, 2012 Establishing a White House Council on Strong Cities, Strong Communities By... enable them to develop and implement economic strategies to become more competitive, sustainable, and inclusive, it is hereby ordered as follows: Section 1. Policy. Cities, towns, and regions across our Nation...

  12. Variable importance in latent variable regression models

    NARCIS (Netherlands)

    Kvalheim, O.M.; Arneberg, R.; Bleie, O.; Rajalahti, T.; Smilde, A.K.; Westerhuis, J.A.

    2014-01-01

    The quality and practical usefulness of a regression model are a function of both interpretability and prediction performance. This work presents some new graphical tools for improved interpretation of latent variable regression models that can also assist in improved algorithms for variable

  13. Classifying variability modeling techniques

    NARCIS (Netherlands)

    Sinnema, Marco; Deelstra, Sybren

    Variability modeling is important for managing variability in software product families, especially during product derivation. In the past few years, several variability modeling techniques have been developed, each using its own concepts to model the variability provided by a product family. The

  14. Reconstruction of precipitation variability in the Strait of Yucatan associated with latitudinal shifts in the position of the Intertropical Convergence Zone since the Last Glacial Maximum

    Science.gov (United States)

    Staines-Urías, Francisca; Seidenkrantz, Marit-Solveig; Fischel, Andrea; Kuijpers, Antoon

    2017-04-01

    The elemental composition of sediments from gravity core HOLOVAR11-03 provides a ca. 40 ka record of past climate variability in the Strait of Yucatan, between the Caribbean Sea and the Gulf of Mexico, a region where precipitation variability is determined by the seasonal position of the Intertropical Convergence Zone (ITCZ). Within this region, sea level pressure decreases and rainfall increases as the ITCZ moves north of the equator in response to increased solar insolation in the Northern Hemisphere during boreal summer. In contrast, as the ITCZ retracts southward towards the equator during boreal winter, rainfall diminishes and the regional sea level pressure gradient strengthens. On interannual, multidecadal and millennial timescales, fluctuations in the average latitudinal position of the ITCZ in response to insolation forcing modulate the intensity and duration of the seasonal regimens, determining average regional precipitation and, ultimately, the elemental composition of the marine sedimentary record. Regionally, higher titanium and iron content in marine sediments reflect greater terrigenous input from inland runoff, indicating greater precipitation, hence a more northerly position of the ITCZ. Correspondingly, Ti and Fe concentration data were used to reconstruct regional rainfall variability since the Last Glacial Maxima (LGM ˜24 cal ka BP). HOLOVAR11-03 age model (based on 4 AMS 14C dates obtained from multi-specific samples of planktic foraminifera) shows stable sedimentation rates in the area throughout the cored period. Nonetheless, higher terrestrial mineral input is observed since the LGM and all through the last glacial termination (24 to 12 cal ka BP), indicating a period of increased precipitation. In contrast, lower Ti and Fe values are typical for the period between 12 and 8 cal ka BP, indicating reduced precipitation. A positive trend characterizes the following interval, showing a return to wetter conditions lasting until 5 cal ka BP

  15. Renormalization in theories with strong vector forces

    International Nuclear Information System (INIS)

    Kocic, A.

    1991-01-01

    There are not many field theories in four dimensions that have sensible ultraviolet and interesting (non-trivial) infrared behavior. At present, asymptotically free theories seem to have deserved their legitimacy and there is a strong prejudice that they might be the only ones to have such a distinction. This belief stems mostly from the fact that most of the knowledge of field theory in four dimensions comes from perturbation theory. However, nonperturbative studies of the lower dimensional theories reveal a host of interesting phenomena that are perturbative studies of the lower dimensional theories reveal a host of interesting phenomena that perturbatively inaccessible. The lack of asymptotic freedom implies that the coupling constant grows at short distances and perturbation theory breaks down. Thus, in such theories, ultraviolet behavior requires nonperturbative treatment. Recently, the interest in strongly coupled gauge theories has been revived. In particularly, four dimensional quantum electrodynamics has received considerable attention. This was motivated by the discovery of an ultraviolet stable fixed point at strong couplings. If this fixed point would turn out to be non-gaussian, then QED would be the first nontrivial nonasymptotically free theory in four dimensions. The importance of such a result would be twofold. First, the old question of the existence of QED could be settled. Of course, this would be the case provided that the low energy limit of the theory actually describes photons and electrons; apriori, there is no reason to assume this. Second, the discovery of a nontrivial nonasymptotically free theory would be of great paradigmatic value. The theories which quenched QED resembles the most are nonabelian gauge theories with many flavors with beta-function positive or vanishing at weak couplings. These theories are at present considered as viable candidates for technicolor unification schemes

  16. Bound states in a strong magnetic field

    International Nuclear Information System (INIS)

    Machado, C. S.; Navarra, F. S.; Noronha, J.; Oliveira, E. G.; Ferreira Filho, L. G.

    2013-01-01

    We expect a strong magnetic field to be produced in the perpendicular direction to the reaction plane, in a noncentral heavy-ion collision . The strength of the magnetic field is estimated to be eB∼m 2 π ∼ 0.02 GeV 2 at the RHIC and eB∼ 15m 2 π ∼ 0.3 GeV 2 at the LHC. We investigate the effects of the magnetic field on B 0 and D 0 mesons, focusing on the changes of the energy levels and of the mass of the bound states.

  17. Strong signatures of right-handed compositeness

    Energy Technology Data Exchange (ETDEWEB)

    Redi, Michele [INFN, Sesto Fiorentino, Firenze (Italy); Sanz, Veronica [York Univ., Toronto, ON (Canada). Dept. of Physics and Astronomy; Sussex Univ., Brighton (United Kingdom). Dept. of Physics and Astronomy; Vries, Maikel de; Weiler, Andreas [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2013-05-15

    Right-handed light quarks could be significantly composite, yet compatible with experimental searches at the LHC and precision tests on Standard Model couplings. In these scenarios, that are motivated by flavor physics, one expects large cross sections for the production of new resonances coupled to light quarks. We study experimental strong signatures of right-handed compositeness at the LHC, and constrain the parameter space of these models with recent results by ATLAS and CMS. We show that the LHC sensitivity could be significantly improved if dedicated searches were performed, in particular in multi-jet signals.

  18. The Dark Side of Strongly Coupled Theories

    DEFF Research Database (Denmark)

    Kouvaris, Christoforos

    2008-01-01

    We investigate the constraints of dark matter search experiments on the different candidates emerging from the minimal quasi-conformal strong coupling theory with fermions in the adjoint representation. For one candidate, the current limits of CDMS exclude a tiny window of masses around 120 GeV. We...... also investigate under what circumstances the newly proposed candidate composed of a -2 negatively charged particle and a $^4He^{+2}$ can explain the discrepancy between the results of the CDMS and DAMA experiments. We found that this type of dark matter should give negative results in CDMS, while...

  19. Fundamental Structure of Matter and Strong Interaction

    Energy Technology Data Exchange (ETDEWEB)

    Jian-Ping Chen

    2011-11-01

    More than 99% of the visible matter in the universe are the protons and neutrons. Their internal structure is mostly governed by the strong interaction. Understanding their internal structure in terms of fundamental degrees-of-freedom is one of the most important subjects in modern physics. Worldwide efforts in the last few decades have lead to numerous surprises and discoveries, but major challenges still remain. An overview of the progress will be presented with a focus on the recent studies of the proton and neutron's electromagnetic and spin structure. Future perspectives will be discussed.

  20. Strong Interaction Studies with PANDA at FAIR

    International Nuclear Information System (INIS)

    Schönning, Karin

    2016-01-01

    The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of nuclear-, hadron- and atomic physics experiments. The future PANDA experiment at FAIR will offer a broad physics programme with emphasis on different aspects of hadron physics. Understanding the strong interaction in the perturbative regime remains one of the greatest challenges in contemporary physics and hadrons provide several important keys. In these proceedings, PANDA will be presented along with some high-lights of the planned physics programme

  1. Hawking radiation and strong gravity black holes

    International Nuclear Information System (INIS)

    Qadir, A.; Sayed, W.A.

    1979-01-01

    It is shown that the strong gravity theory of Salam et al. places severe restrictions on black hole evaporation. Two major implications are that: mini blck holes (down to masses approximately 10 -16 kg) would be stable in the present epoch; and that some suggested mini black hole mechanisms to explain astrophysical phenomena would not work. The first result implies that f-gravity appears to make black holes much safer by removing the possibility of extremely violent black hole explosions suggested by Hawking. (Auth.)

  2. Wormhole effect in a strong topological insulator

    Science.gov (United States)

    Rosenberg, G.; Guo, H.-M.; Franz, M.

    2010-07-01

    An infinitely thin solenoid carrying magnetic flux Φ (a “Dirac string”) inserted into an ordinary band insulator has no significant effect on the spectrum of electrons. In a strong topological insulator, remarkably, such a solenoid carries protected gapless one-dimensional fermionic modes when Φ=hc/2e . These modes are spin-filtered and represent a distinct bulk manifestation of the topologically nontrivial insulator. We establish this “wormhole” effect by both general qualitative considerations and by numerical calculations within a minimal lattice model. We also discuss the possibility of experimental observation of a closely related effect in artificially engineered nanostructures.

  3. Strong piezoelectricity in bioinspired peptide nanotubes.

    Science.gov (United States)

    Kholkin, Andrei; Amdursky, Nadav; Bdikin, Igor; Gazit, Ehud; Rosenman, Gil

    2010-02-23

    We show anomalously strong shear piezoelectric activity in self-assembled diphenylalanine peptide nanotubes (PNTs), indicating electric polarization directed along the tube axis. Comparison with well-known piezoelectric LiNbO(3) and lateral signal calibration yields sufficiently high effective piezoelectric coefficient values of at least 60 pm/V (shear response for tubes of approximately 200 nm in diameter). PNTs demonstrate linear deformation without irreversible degradation in a broad range of driving voltages. The results open up a wide avenue for developing new generations of "green" piezoelectric materials and piezonanodevices based on bioactive tubular nanostructures potentially compatible with human tissue.

  4. Development of a strong electromagnet wiggler

    International Nuclear Information System (INIS)

    Burns, M.J.; Deis, G.A.; Holmes, R.H.; Van Maren, R.D.; Halbach, K.

    1987-01-01

    The Strong Electromagnet (SEM) wiggler is a permanent magnet-assisted electromagnet under development at the Lawrence Livermore National Laboratory (LLNL) as part of the Induction Linac Free-Electron-Laser (IFEL) program. This concept uses permanent magnets within the wiggler to provide a reverse bias flux in the iron and thus delay the onset of magnetic saturation. The electromagnet coils determine the wiggler field and operate at low current densities by virtue of their placement away from the midplane. We describe here the design approach used and test data from a 7-period wiggler prototype that includes curved pole tips to provide wiggle-plane focusing. 7 refs

  5. Strong Interactions Physics at BaBar

    Energy Technology Data Exchange (ETDEWEB)

    Pioppi, M.

    2005-03-14

    Recent results obtained by BABAR experiment and related to strong interactions physics are presented, with particular attention to the extraction of the first four hadronic-mass moments and the first three lepton-energy moments in semileptonic decays. From a simultaneous fit to the moments, the CKM element |V{sub cb}|, the inclusive B {yields} X{sub c}lv and other heavy quark parameters are derived. The second topic is the ambiguity-free measurement of cos(2{beta}) in B {yields} J/{Psi}K* decays. With approximately 88 million of B{bar B} pairs, negative solutions for cos(2{beta}) are excluded at 89%.

  6. Quantum electrodynamics in strong external fields

    International Nuclear Information System (INIS)

    Mueller, B.; Rafelski, J.; Kirsch, J.

    1981-05-01

    We review the theoretical description of quantum electrodynamics in the presence of strong and supercritical fields. In particular, the process of the spontaneous vacuum decay accompanied by the observable positron emission in heavy ion collisions is described. Emphasis is put on the proper formulation of many-body aspects in the framework of quantum field theory. The extension of the theory to the description of Bose fields and many-body effects is presented, and the Klein paradox is resolved. Some implications of the theoretical methods developed here are presented concerning non-abelian gauge theories and the quark confinement puzzle. (orig.)

  7. Strong Interaction Studies with PANDA at FAIR

    Science.gov (United States)

    Schönning, Karin

    2016-10-01

    The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of nuclear-, hadron- and atomic physics experiments. The future PANDA experiment at FAIR will offer a broad physics programme with emphasis on different aspects of hadron physics. Understanding the strong interaction in the perturbative regime remains one of the greatest challenges in contemporary physics and hadrons provide several important keys. In these proceedings, PANDA will be presented along with some high-lights of the planned physics programme.

  8. Multiscale temporal variability and regional patterns in 555 years of conterminous U.S. streamflow

    Science.gov (United States)

    Ho, Michelle; Lall, Upmanu; Sun, Xun; Cook, Edward R.

    2017-04-01

    The development of paleoclimate streamflow reconstructions in the conterminous United States (CONUS) has provided water resource managers with improved insights into multidecadal and centennial scale variability that cannot be reliably detected using shorter instrumental records. Paleoclimate streamflow reconstructions have largely focused on individual catchments limiting the ability to quantify variability across the CONUS. The Living Blended Drought Atlas (LBDA), a spatially and temporally complete 555 year long paleoclimate record of summer drought across the CONUS, provides an opportunity to reconstruct and characterize streamflow variability at a continental scale. We explore the validity of the first paleoreconstructions of streamflow that span the CONUS informed by the LBDA targeting a set of U.S. Geological Survey streamflow sites. The reconstructions are skillful under cross validation across most of the country, but the variance explained is generally low. Spatial and temporal structures of streamflow variability are analyzed using hierarchical clustering, principal component analysis, and wavelet analyses. Nine spatially coherent clusters are identified. The reconstructions show signals of contemporary droughts such as the Dust Bowl (1930s) and 1950s droughts. Decadal-scale variability was detected in the late 1900s in the western U.S., however, similar modes of temporal variability were rarely present prior to the 1950s. The twentieth century featured longer wet spells and shorter dry spells compared with the preceding 450 years. Streamflows in the Pacific Northwest and Northeast are negatively correlated with the central U.S. suggesting the potential to mitigate some drought impacts by balancing economic activities and insurance pools across these regions during major droughts.

  9. Personality Variables in Alcohol Abuse in College Students.

    Science.gov (United States)

    Brooks, Mark L.; And Others

    1981-01-01

    Studied the relationship between personality variables and alcohol abuse in college students. Results indicated that these personality variables were not strong predictors of alcohol abuse. However, subjects identified as being highly trait anxious or trait angry were more likely to abuse alcohol than subjects low on these variables. (Author)

  10. Cataclysmic variables, Hubble-Sandage variables and eta Carinae

    International Nuclear Information System (INIS)

    Bath, G.T.

    1980-01-01

    The Hubble-Sandage variables are the most luminous stars in external galaxies. They were first investigated by Hubble and Sandage (1953) for use as distance indicators. Their main characteristics are high luminosity, blue colour indices, and irregular variability. Spectroscopically they show hydrogen and helium in emission with occasionally weaker FeII and [FeII], and no Balmer jump (Humphreys 1975, 1978). In this respect they closely resemble cataclysmic variables, particularly dwarf novae. In the quiescent state dwarf novae show broad H and HeI, together with a strong UV continuum. In contrast to the spectroscopic similarities, the luminosities could hardly differ more. Rather than being the brightest stars known, quiescent dwarf novae are as faint or fainter than the sun. It is suggested that the close correspondence between the spectral appearance of the two classes combined with the difference in luminosity is well accounted for by a model of Hubble-Sandage variables in which the same physical processes are occurring, but on a larger scale. (Auth.)

  11. Regionally Strong Feedbacks between the Atmosphere and Terrestrial Biosphere

    Science.gov (United States)

    Green, J. K.; Konings, A. G.; Alemohammad, S. H.; Berry, J. A.; Kolassa, J.; Lee, J. E.; Gentine, P.

    2017-12-01

    Vegetation variability modulates water and energy fluxes to the atmosphere with the potential to impact climate and weather patterns that in turn regulate vegetation dynamics. In this study, we quantify variations in the strength of biosphere-atmosphere feedbacks (influencing the hydrologic cycle) across different biomes and timescales and evaluate the ability of Earth System Models to capture them. We use remote sensing data (using Solar Induced Fluorescence as a proxy for photosynthesis) combined with a statistical Multivariate Granger Causality technique to evaluate the feedback strength and the timescale in which they occur, which is then used as a benchmark for model assessment. Our conclusions have the potential to improve climate and weather predictions and provide insight of ecohydrological processes that have regional scale impact (Green, J.K. et al. 2017). Green, Julia K., et al. Regionally strong feedbacks between the atmosphere and terrestrial biosphere. Nature Geoscience. 10, 410-414 (2017).

  12. A transformation technique to treat strong vibrating absorbers

    International Nuclear Information System (INIS)

    Sahni, D.C.; Garis, N.S.; Pazsit, I.

    1998-06-01

    Calculation of the neutron noise, induced by small amplitude vibrations of a strong absorber, is a difficult task because the traditional linearization technique cannot be applied. Two methods, based on two different representations of the absorber, were developed earlier to solve the problem. In both methods the rod displacements are described by a Taylor expansion, such that the boundary condition needs only to be considered at the surface of a static rod. Only one of the methods is applicable in two dimensions. In this paper an alternative method is developed and used for the solution of the problem. The essence of the method is a variable transformation by which the moving boundary is transformed into a static one without Taylor expansion. The corresponding equations are solved in a linear manner and the solution is transformed back to the original parameter space. The method is equally applicable in one and two dimensions. The solutions are in complete agreement with those of the previous methods

  13. Entanglement via atomic coherence induced by two strong classical fields

    Science.gov (United States)

    Lü, Xin-You; Huang, Pei; Yang, Wen-Xing; Yang, Xiaoxue

    2009-09-01

    Based on the standard criteria [P. van Loock and A. Furusawa, Phys. Rev. A 67, 052315 (2003)], we propose a scheme to achieve the fully tripartite continuous-variable (CV) entanglement in a Y -type atomic system driven by two strong classical fields. By numerically simulating the dynamics of system, we show that the generation of entanglement does not depend intensively on the initial condition of cavity field and the time for which the cavity modes remain entangled can be prolonged via enhancing the intensities of classical fields in our scheme. Moreover, our numerical results also show that a tripartite entanglement amplifier can be realized in the present scheme. The present research provides an efficient approach to achieve fully tripartite CV entangled state even when the three entangled modes have different frequencies and initial states, which may be useful for the progress of quantum information networks with many nodes.

  14. Iterative solutions of nonlinear equations with strongly accretive or strongly pseudocontractive maps

    International Nuclear Information System (INIS)

    Chidume, C.E.

    1994-03-01

    Let E be a real q-uniformly smooth Banach space. Suppose T is a strongly pseudo-contractive map with open domain D(T) in E. Suppose further that T has a fixed point in D(T). Under various continuity assumptions on T it is proved that each of the Mann iteration process or the Ishikawa iteration method converges strongly to the unique fixed point of T. Related results deal with iterative solutions of nonlinear operator equations involving strongly accretive maps. Explicit error estimates are also provided. (author). 38 refs

  15. Towards TDDFT for Strongly Correlated Materials

    Directory of Open Access Journals (Sweden)

    Shree Ram Acharya

    2016-09-01

    Full Text Available We present some details of our recently-proposed Time-Dependent Density-Functional Theory (TDDFT for strongly-correlated materials in which the exchange-correlation (XC kernel is derived from the charge susceptibility obtained using Dynamical Mean-Field Theory (the TDDFT + DMFT approach. We proceed with deriving the expression for the XC kernel for the one-band Hubbard model by solving DMFT equations via two approaches, the Hirsch–Fye Quantum Monte Carlo (HF-QMC and an approximate low-cost perturbation theory approach, and demonstrate that the latter gives results that are comparable to the exact HF-QMC solution. Furthermore, through a variety of applications, we propose a simple analytical formula for the XC kernel. Additionally, we use the exact and approximate kernels to examine the nonhomogeneous ultrafast response of two systems: a one-band Hubbard model and a Mott insulator YTiO3. We show that the frequency dependence of the kernel, i.e., memory effects, is important for dynamics at the femtosecond timescale. We also conclude that strong correlations lead to the presence of beats in the time-dependent electric conductivity in YTiO3, a feature that could be tested experimentally and that could help validate the few approximations used in our formulation. We conclude by proposing an algorithm for the generalization of the theory to non-linear response.

  16. The Athens Acropolis Strong Motion Array

    Science.gov (United States)

    Kalogeras, I. S.; Evangelidis, C. P.; Melis, N. S.; Boukouras, K.

    2012-04-01

    During the last decades, extensive restoration works through a dedicated "Acropolis Restoration Service" (YSMA) take place in the Acropolis, the greatest sanctuary of ancient Athens. Since 2008, a permanent strong motion array was deployed by the Institute of Geodynamics, National Observatory of Athens (NOA-IG) in collaboration with YSMA. Free field installations were decided at sites showing various characteristics, aiming to investigate differences in geotechnical properties as well as the structure response of Parthenon itself. The installation phase is presented, with the techniques used to overcome difficulties (i.e. extreme weather conditions, power and communication limitations, restoration works and visitors) and the special care taken for the specific archaeological site. Furthermore, indicative examples of seismic events recorded by the array are analyzed and the complexity of the hill and the monument is made apparent. Among them, the long distance events of Tohoku, Japan 2010 and Van, Turkey 2011, some regional moderate earthquakes in Greece and some weak earthquakes from the vicinity. Continuous ambient noise monitoring using PQLX software gives some first indicative results, showing a variety of characteristics at installation sites. Finally, further developments and future steps are presented such as: the extension of the array, the integration of seismic data within the GIS platform of YSMA at the site and the use of strong motion records, in conjunction with data from other monitoring systems operating in Acropolis for the study of specific monuments.

  17. Relativistically strong electromagnetic radiation in a plasma

    Science.gov (United States)

    Bulanov, S. V.; Esirkepov, T. Zh.; Kando, M.; Kiriyama, H.; Kondo, K.

    2016-03-01

    Physical processes in a plasma under the action of relativistically strong electromagnetic waves generated by high-power lasers have been briefly reviewed. These processes are of interest in view of the development of new methods for acceleration of charged particles, creation of sources of bright hard electromagnetic radiation, and investigation of macroscopic quantum-electrodynamical processes. Attention is focused on nonlinear waves in a laser plasma for the creation of compact electron accelerators. The acceleration of plasma bunches by the radiation pressure of light is the most efficient regime of ion acceleration. Coherent hard electromagnetic radiation in the relativistic plasma is generated in the form of higher harmonics and/or electromagnetic pulses, which are compressed and intensified after reflection from relativistic mirrors created by nonlinear waves. In the limit of extremely strong electromagnetic waves, radiation friction, which accompanies the conversion of radiation from the optical range to the gamma range, fundamentally changes the behavior of the plasma. This process is accompanied by the production of electron-positron pairs, which is described within quantum electrodynamics theory.

  18. Strong Double Higgs Production at the LHC

    CERN Document Server

    Contino, Roberto; Moretti, Mauro; Piccinini, Fulvio; Rattazzi, Riccardo

    2010-01-01

    The hierarchy problem and the electroweak data, together, provide a plausible motivation for considering a light Higgs emerging as a pseudo-Goldstone boson from a strongly-coupled sector. In that scenario, the rates for Higgs production and decay differ significantly from those in the Standard Model. However, one genuine strong coupling signature is the growth with energy of the scattering amplitudes among the Goldstone bosons, the longitudinally polarized vector bosons as well as the Higgs boson itself. The rate for double Higgs production in vector boson fusion is thus enhanced with respect to its negligible rate in the SM. We study that reaction in pp collisions, where the production of two Higgs bosons at high pT is associated with the emission of two forward jets. We concentrate on the decay mode hh -> WW^(*)WW^(*) and study the semi-leptonic decay chains of the W's with 2, 3 or 4 leptons in the final states. While the 3 lepton final states are the most relevant and can lead to a 3 sigma signal significa...

  19. Finite temperature system of strongly interacting baryons

    Energy Technology Data Exchange (ETDEWEB)

    Bowers, R.L.; Gleeson, A.M.; Pedigo, R.D.; Wheeler, J.W.

    1976-07-01

    A fully relativistic finite temperature many body theory is constructed and used to examine the bulk properties of a system of strongly interacting baryons. The strong interactions are described by a two parameter phenomenological model fit to a simple description of nuclear matter at T = 0. The zero temperature equation of state for such a system which has already been discussed in the literature was developed to give a realistic description of nuclear matter. The model presented here is the exact finite temperature extension of that model. The effect of the inclusion of baryon pairs for T greater than or equal to 2mc/sup 2//k is discussed in detail. The phase transition identified with nuclear matter vanishes for system temperatures in excess of T/sub C/ = 1.034 x 10/sup 11/ /sup 0/K. All values of epsilon (P,T) correspond to systems that are causal in the sense that the locally determined speed of sound never exceeds the speed of light.

  20. Finite temperature system of strongly interacting baryons

    International Nuclear Information System (INIS)

    Bowers, R.L.; Gleeson, A.M.; Pedigo, R.D.; Wheeler, J.W.

    1976-07-01

    A fully relativistic finite temperature many body theory is constructed and used to examine the bulk properties of a system of strongly interacting baryons. The strong interactions are described by a two parameter phenomenological model fit to a simple description of nuclear matter at T = 0. The zero temperature equation of state for such a system which has already been discussed in the literature was developed to give a realistic description of nuclear matter. The model presented here is the exact finite temperature extension of that model. The effect of the inclusion of baryon pairs for T greater than or equal to 2mc 2 /k is discussed in detail. The phase transition identified with nuclear matter vanishes for system temperatures in excess of T/sub C/ = 1.034 x 10 11 0 K. All values of epsilon (P,T) correspond to systems that are causal in the sense that the locally determined speed of sound never exceeds the speed of light

  1. Holographic gauge mediation via strongly coupled messengers

    International Nuclear Information System (INIS)

    McGuirk, Paul; Shiu, Gary; Sumitomo, Yoske

    2010-01-01

    We consider a relative of semidirect gauge mediation where the hidden sector exists at large 't Hooft coupling. Such scenarios can be difficult to describe using perturbative field theory methods but may fall into the class of holographic gauge mediation scenarios, meaning that they are amenable to the techniques of gauge/gravity duality. We use a recently found gravity solution to examine one such case, where the hidden sector is a cascading gauge theory resulting in a confinement scale not much smaller than the messenger mass. In the original construction of holographic gauge mediation, as in other examples of semidirect gauge mediation at strong coupling, the primary contributions to visible sector soft terms come from weakly coupled messenger mesons. In contrast to these examples, we describe the dual of a gauge theory where there are significant contributions from scales in which the strongly coupled messenger quarks are the effective degrees of freedom. In this regime, the visible sector gaugino mass can be calculated entirely from holography.

  2. NMR study of strongly correlated electron systems

    Science.gov (United States)

    Kitaoka, Y.; Tou, H.; Zheng, G.-q.; Ishida, K.; Asayama, K.; Kobayashi, T. C.; Kohda, A.; Takeshita, N.; Amaya, K.; Onuki, Y.; Geibel, G.; Schank, C.; Steglich, F.

    1995-02-01

    Various types of ground states in strongly correlated electron systems have been systematically investigated by means of NMR/NQR at low temperatures under high magnetic field and pressure. We focus on two well-known heavy-electron families, CeCu 2X 2 (X = Si and Ge) (Ce(122)) and UM 2Al 3 (M = Ni and Pd) (U(123)). The Cu NQR experiments on CeCu 2X 2 under high pressure indicate that the physical property of CeCu 2Ge 2 at high pressure, i.e. above the transition at 7.6 GPa from antiferromagnetic (AF) to superconductivity, are clearly related to tha CeCu 2Si 2 at ambient pressure. In addition to the H-T phase diagram established below 7 T, NMR and specific heat experiments on polycrystal CeCu 2.05Si 2 have revealed the presence of a new phase above 7 T. In a high-quality polycrystal of UPd 2Al 3 with a record high- Tc of 2 K at ambient pressure and the narrowest Al NQR line width, the nuclear-spin lattice relaxation rate, 27(1/ T1) measured in zero field has been found to obey the T3 law down to 0.13 K, giving strong evidence that the energy gap vanishes along lines on the Fermi surface. Thus it seems that all heavy-electron superconductors exhibit lines of zero gap, regardless of their different magnetic properties.

  3. Internal variability of the thermohaline ocean circulation

    OpenAIRE

    Raa, Lianke Alinda te

    2003-01-01

    Variations in the ocean circulation can strongly influence climate due to the large heat transport by the ocean currents. Variability of the thermohaline ocean circulation, the part of the ocean circulation driven by density gradients, occurs typically on (inter)decadal and longer time scales and is an important issue in present-day climate research. Although there are many indications from observations and numerical modeling studies that internal variability of the thermohaline circulation m...

  4. Upper-Level Mediterranean Oscillation index and seasonal variability of rainfall and temperature

    Science.gov (United States)

    Redolat, Dario; Monjo, Robert; Lopez-Bustins, Joan A.; Martin-Vide, Javier

    2018-02-01

    The need for early seasonal forecasts stimulates continuous research in climate teleconnections. The large variability of the Mediterranean climate presents a greater difficulty in predicting climate anomalies. This article reviews teleconnection indices commonly used for the Mediterranean basin and explores possible extensions of one of them, the Mediterranean Oscillation index (MOi). In particular, the anomalies of the geopotential height field at 500 hPa are analyzed using segmentation of the Mediterranean basin in seven spatial windows: three at eastern and four at western. That is, different versions of an Upper-Level Mediterranean Oscillation index (ULMOi) were calculated, and monthly and annual variability of precipitation and temperature were analyzed for 53 observatories from 1951 to 2015. Best versions were selected according to the Pearson correlation, its related p value, and two measures of standardized error. The combination of the Balearic Sea and Libya/Egypt windows was the best for precipitation and temperature, respectively. The ULMOi showed the highest predictive ability in combination with the Atlantic Multidecadal Oscillation index (AMOi) for the annual temperature throughout the Mediterranean basin. The best model built from the indices presented a final mean error between 15 and 25% in annual precipitation for most of the studied area.

  5. The recent global warming hiatus: What is the role of Pacific variability?

    Science.gov (United States)

    Douville, H.; Voldoire, A.; Geoffroy, O.

    2015-02-01

    The observed global mean surface air temperature (GMST) has not risen over the last 15 years, spurring outbreaks of skepticism regarding the nature of global warming and challenging the upper range transient response of the current-generation global climate models. Recent numerical studies have, however, tempered the relevance of the observed pause in global warming by highlighting the key role of tropical Pacific internal variability. Here we first show that many climate models overestimate the influence of the El Niño-Southern Oscillation on GMST, thereby shedding doubt on their ability to capture the tropical Pacific contribution to the hiatus. Moreover, we highlight that model results can be quite sensitive to the experimental design. We argue that overriding the surface wind stress is more suitable than nudging the sea surface temperature for controlling the tropical Pacific ocean heat uptake and, thereby, the multidecadal variability of GMST. Using the former technique, our model captures several aspects of the recent climate evolution, including the weaker slowdown of global warming over land and the transition toward a negative phase of the Pacific Decadal Oscillation. Yet the observed global warming is still overestimated not only over the recent 1998-2012 hiatus period but also over former decades, thereby suggesting that the model might be too sensitive to the prescribed radiative forcings.

  6. The continuum of hydroclimate variability in western North America during the last millennium

    Science.gov (United States)

    Ault, Toby R.; Cole, Julia E.; Overpeck, Jonathan T.; Pederson, Gregory T.; St. George, Scott; Otto-Bliesner, Bette; Woodhouse, Connie A.; Deser, Clara

    2013-01-01

    The distribution of climatic variance across the frequency spectrum has substantial importance for anticipating how climate will evolve in the future. Here we estimate power spectra and power laws (ß) from instrumental, proxy, and climate model data to characterize the hydroclimate continuum in western North America (WNA). We test the significance of our estimates of spectral densities and ß against the null hypothesis that they reflect solely the effects of local (non-climate) sources of autocorrelation at the monthly timescale. Although tree-ring based hydroclimate reconstructions are generally consistent with this null hypothesis, values of ß calculated from long-moisture sensitive chronologies (as opposed to reconstructions), and other types of hydroclimate proxies, exceed null expectations. We therefore argue that there is more low-frequency variability in hydroclimate than monthly autocorrelation alone can generate. Coupled model results archived as part of the Climate Model Intercomparison Project 5 (CMIP5) are consistent with the null hypothesis and appear unable to generate variance in hydroclimate commensurate with paleoclimate records. Consequently, at decadal to multidecadal timescales there is more variability in instrumental and proxy data than in the models, suggesting that the risk of prolonged droughts under climate change may be underestimated by CMIP5 simulations of the future.

  7. Mismeasurement and the resonance of strong confounders: correlated errors.

    Science.gov (United States)

    Marshall, J R; Hastrup, J L; Ross, J S

    1999-07-01

    Confounding in epidemiology, and the limits of standard methods of control for an imperfectly measured confounder, have been understood for some time. However, most treatments of this problem are based on the assumption that errors of measurement in confounding and confounded variables are independent. This paper considers the situation in which a strong risk factor (confounder) and an inconsequential but suspected risk factor (confounded) are each measured with errors that are correlated; the situation appears especially likely to occur in the field of nutritional epidemiology. Error correlation appears to add little to measurement error as a source of bias in estimating the impact of a strong risk factor: it can add to, diminish, or reverse the bias induced by measurement error in estimating the impact of the inconsequential risk factor. Correlation of measurement errors can add to the difficulty involved in evaluating structures in which confounding and measurement error are present. In its presence, observed correlations among risk factors can be greater than, less than, or even opposite to the true correlations. Interpretation of multivariate epidemiologic structures in which confounding is likely requires evaluation of measurement error structures, including correlations among measurement errors.

  8. Thermalization and confinement in strongly coupled gauge theories

    Directory of Open Access Journals (Sweden)

    Ishii Takaaki

    2016-01-01

    Full Text Available Quantum field theories of strongly interacting matter sometimes have a useful holographic description in terms of the variables of a gravitational theory in higher dimensions. This duality maps time dependent physics in the gauge theory to time dependent solutions of the Einstein equations in the gravity theory. In order to better understand the process by which “real world” theories such as QCD behave out of thermodynamic equilibrium, we study time dependent perturbations to states in a model of a confining, strongly coupled gauge theory via holography. Operationally, this involves solving a set of non-linear Einstein equations supplemented with specific time dependent boundary conditions. The resulting solutions allow one to comment on the timescale by which the perturbed states thermalize, as well as to quantify the properties of the final state as a function of the perturbation parameters. We comment on the influence of the dual gauge theory’s confinement scale on these results, as well as the appearance of a previously anticipated universal scaling regime in the “abrupt quench” limit.

  9. Research on climate change and variability at the Ab dus Salam International Centre for Theoretical Physics

    International Nuclear Information System (INIS)

    Giorgi, F.; Molteni, F.

    2002-01-01

    The Physics of Weather and Climate Section at the Abdus Salam International Centre for Theoretical Physics, established in 1998, is currently performing research on different aspects of climate variability, dealing with both natural and anthropogenic aspects of climate changes. In addition to performing diagnostic work on multi-decadal observational datasets and climate simulations carried out in major research centres, the PWC section has been developing its own climate modeling capability, which is focused on three main areas: a) modeling of regional climate change; b) seasonal forecasting at global and regional scale; c) development of simplified models of the general circulation. On topic a), research on different aspects of anthropogenic climate change is being carried out using the Regional Climate (RegCM) developed by Giorgi and collaborators at the National Centre for Atmospheric Research. Time-slice experiments with a high-resolution atmospheric GCM, comparing current climate conditions with future climate scenarios in selected decades, are also planned for the near future. On topic b), a strategy based on ensembles of high-resolution simulations with atmospheric GCM's, using sea surface temperature anomalies predicted by lower-resolution coupled models from other institutions, is currently under experimentation. A one-way nesting of RegCM into the GCM simulations will also be tested. On item c), a 5-layer atmospheric GCM with simplified physical parameterizations has been developed. This model has a very small computational cost compared with state-of-the-art GCMs, and is suitable for studies of natural climate variability on inter-decadal and intercentennial time scales. It is planned to couple this model to simplified ocean models of different complexity, from a simple, static mixed layer model, to simplified models of the tropical Pacific circulation suited to the simulation of the El Nino phenomenon. A joint project with the IAEA-MEL Laboratory in

  10. Enhanced thermal photon and dilepton production in strongly coupled = 4 SYM plasma in strong magnetic field

    Science.gov (United States)

    Mamo, Kiminad A.

    2013-08-01

    We calculate the DC conductivity tensor of strongly coupled = 4 super-Yang-Mills (SYM) plasma in a presence of a strong external magnetic field B ≫ T 2 by using its gravity dual and employing both the RG flow approach and membrane paradigm which give the same results. We find that, since the magnetic field B induces anisotropy in the plasma, different components of the DC conductivity tensor have different magnitudes depending on whether its components are in the direction of the magnetic field B. In particular, we find that a component of the DC conductivity tensor in the direction of the magnetic field B increases linearly with B while the other components (which are not in the direction of the magnetic field B) are independent of it. These results are consistent with the lattice computations of the DC conductivity tensor of the QCD plasma in an external magnetic field B. Using the DC conductivity tensor, we calculate the soft or low-frequency thermal photon and dilepton production rates of the strongly coupled = 4 SYM plasma in the presence of the strong external magnetic field B ≫ T 2. We find that the strong magnetic field B enhances both the thermal photon and dilepton production rates of the strongly coupled = 4 SYM plasma in a qualitative agreement with the experimentally observed enhancements at the heavy-ion collision experiments.

  11. Convex Modeling of Interactions with Strong Heredity.

    Science.gov (United States)

    Haris, Asad; Witten, Daniela; Simon, Noah

    2016-01-01

    We consider the task of fitting a regression model involving interactions among a potentially large set of covariates, in which we wish to enforce strong heredity. We propose FAMILY, a very general framework for this task. Our proposal is a generalization of several existing methods, such as VANISH [Radchenko and James, 2010], hierNet [Bien et al., 2013], the all-pairs lasso, and the lasso using only main effects. It can be formulated as the solution to a convex optimization problem, which we solve using an efficient alternating directions method of multipliers (ADMM) algorithm. This algorithm has guaranteed convergence to the global optimum, can be easily specialized to any convex penalty function of interest, and allows for a straightforward extension to the setting of generalized linear models. We derive an unbiased estimator of the degrees of freedom of FAMILY, and explore its performance in a simulation study and on an HIV sequence data set.

  12. Strong Turbulence in Low-beta Plasmas

    DEFF Research Database (Denmark)

    Tchen, C. M.; Pécseli, Hans; Larsen, Søren Ejling

    1980-01-01

    An investigation of the spectral structure of turbulence in a plasma confined by a strong homogeneous magnetic field was made by means of a fluid description. The turbulent spectrum is divided into subranges. Mean gradients of velocity and density excite turbulent motions, and govern the production...... subrange. The spectra of velocity and potential fluctuations interact in the coupling subrange, and the energy is transferred along the spectrum in the inertia subrange. Applying the method of cascade decomposition, the spectral laws k-3, k-3, k-2 are obtained for the velocity fluctuations, and k-3, k-5, k......-3/2 for the potential fluctuations in the production, coupling and inertia subranges, respectively. The coefficient of Bohm diffusion is reproduced, and its role in electrostatic coupling is derived. Comparison is made with measured power laws reported in the literature, from Q-devices, hot...

  13. Strong crystal size effect on deformation twinning

    DEFF Research Database (Denmark)

    Yu, Qian; Shan, Zhi-Wei; Li, Ju

    2010-01-01

    find that the stress required for deformation twinning increases drastically with decreasing sample size of a titanium alloy single crystal7, 8, until the sample size is reduced to one micrometre, below which the deformation twinning is entirely replaced by less correlated, ordinary dislocation...... plasticity. Accompanying the transition in deformation mechanism, the maximum flow stress of the submicrometre-sized pillars was observed to saturate at a value close to titanium’s ideal strength9, 10. We develop a ‘stimulated slip’ model to explain the strong size dependence of deformation twinning....... The sample size in transition is relatively large and easily accessible in experiments, making our understanding of size dependence11, 12, 13, 14, 15, 16, 17 relevant for applications....

  14. Towards Integrated Marmara Strong Motion Network

    Science.gov (United States)

    Durukal, E.; Erdik, M.; Safak, E.; Ansal, A.; Ozel, O.; Alcik, H.; Mert, A.; Kafadar, N.; Korkmaz, A.; Kurtulus, A.

    2009-04-01

    Istanbul has a 65% chance of having a magnitude 7 or above earthquake within the next 30 years. As part of the preparations for the future earthquake, strong motion networks have been installed in and around Istanbul. The Marmara Strong Motion Network, operated by the Department of Earthquake Engineering of Kandilli Observatory and Earthquake Research Institute, encompasses permanent systems outlined below. It is envisaged that the networks will be run by a single entity responsible for technical management and maintanence, as well as for data management, archiving and dissemination through dedicated web-based interfaces. • Istanbul Earthquake Rapid Response and Early Warning System - IERREWS (one hundred 18-bit accelerometers for rapid response; ten 24-bit accelerometers for early warning) • IGDAŞ Gas Shutoff Network (100 accelerometers to be installed in 2010 and integrated with IERREWS) • Structural Monitoring Arrays - Fatih Sultan Mehmet Suspension Bridge (1200m-long suspension bridge across the Bosphorus, five 3-component accelerometers + GPS sensors) - Hagia Sophia Array (1500-year-old historical edifice, 9 accelerometers) - Süleymaniye Mosque Array (450-year-old historical edifice,9 accelerometers) - Fatih Mosque Array (237-year-old historical edifice, 9 accelerometers) - Kanyon Building Array (high-rise office building, 5 accelerometers) - Isbank Tower Array (high-rise office building, 5 accelerometers) - ENRON Array (power generation facility, 4 acelerometers) - Mihrimah Sultan Mosque Array (450-year-old historical edifice,9 accelerometers + tiltmeters, to be installed in 2009) - Sultanahmet Mosque Array, (390-year-old historical edifice, 9 accelerometers + tiltmeters, to be installed in 2009) • Special Arrays - Atakoy Vertical Array (four 3-component accelerometers at 25, 50, 75, and 150 m depths) - Marmara Tube Tunnel (1400 m long submerged tunnel, 128 ch. accelerometric data, 24 ch. strain data, to be installed in 2010) - Air-Force Academy

  15. Strongly coupled band in 140Gd

    International Nuclear Information System (INIS)

    Falla-Sotelo, F.; Oliveira, J.R.B.; Rao, M.N.

    2005-01-01

    Several high-K states are known to exist in the mass 130-140 region. For the N=74 even-even isotopes, Kπ = 8 - isomers, with lifetimes ranging from ns to ms, are known in 128 Xe, 130 Ba, 132 Ce, 134 Nd, 136 Sm, and 138 Gd[. In 140 Gd, we have observed for the first time a band also based on an Iπ = 8 - state. This could be the first case of a Kπ = 8 - state observed in an N=76 even-even isotope. The systematics of the Kπ = 8 - isomeric states in N=74 isotopes has been studied by A.M. Bruce et al. These states decay towards the K = 0 ground state band, and the transitions are K-forbidden. The 140 Gd case presents strong similarities but also some significant differences with relation to the N=74 isotopes. We propose the same configuration but with larger deformation in 140 Gd

  16. Thomson scattering in strong external fields

    Science.gov (United States)

    Varró, S.; Ehlotzky, F.

    1992-09-01

    In the present paper we shall investigate relativistic Thomson scattering in two external fields. A free classical electron will be embedded in a strong, constant and homogeneous magnetic field and in a powerful electromagnetic field. Both fields will be considered in the Redmond configuration, in which case the electromagnetic wave is circularly polarized and propagates in the direction of the homogeneous magnetic field. The electron will be allowed to have arbitrary initial conditions and the electromagnetic wave will be switched on either suddenly or adiabatically. We shall present the exact solution of the Lorentz equation of motion in the above external field configuration and we shall evaluate the spectrum and cross sections of the scattered radiation. In particular, we shall consider scattering close to resonance and we shall compare our results with the findings of earlier work.

  17. Strongly Interacting Matter at High Energy Density

    International Nuclear Information System (INIS)

    McLerran, L.

    2008-01-01

    This lecture concerns the properties of strongly interacting matter (which is described by Quantum Chromodynamics) at very high energy density. I review the properties of matter at high temperature, discussing the deconfinement phase transition. At high baryon density and low temperature, large N c arguments are developed which suggest that high baryonic density matter is a third form of matter, Quarkyonic Matter, that is distinct from confined hadronic matter and deconfined matter. I finally discuss the Color Glass Condensate which controls the high energy limit of QCD, and forms the low x part of a hadron wavefunction. The Glasma is introduced as matter formed by the Color Glass Condensate which eventually thermalizes into a Quark Gluon Plasma

  18. Strong curvature effects in Neumann wave problems

    DEFF Research Database (Denmark)

    Willatzen, Morten; Pors, A.; Gravesen, Jens

    2012-01-01

    Waveguide phenomena play a major role in basic sciences and engineering. The Helmholtz equation is the governing equation for the electric field in electromagnetic wave propagation and the acoustic pressure in the study of pressure dynamics. The Schro¨dinger equation simplifies to the Helmholtz...... equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important...... to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear...

  19. Neutrino oscillations in strong magnetic fields

    International Nuclear Information System (INIS)

    Likhachev, G.G.; Studenikin, A.I.

    1994-07-01

    Neutrino conversion processes between two neutrino species and the corresponding oscillations induced by strong magnetic fields are considered. The value of the critical strength of magnetic field B cr as a function of characteristics of neutrinos in vacuum (Δm 2 ν , mixing angle θ), effective particle density of matter n eff , neutrino (transition) magnetic moment μ-tilde and energy E is introduced. It is shown that the neutrino conversion and oscillations effects induced by magnetic fields B ≥ B cr are important and may result in the depletion of the initial type of ν's in the bunch. A possible increase of these effects in the case when neutrinos pass through a sudden decrease of density of matter (''cross-boundary effect'') and applications to neutrinos from neutron stars and supernova are discussed. (author). 25 refs

  20. Transport phenomena in strongly correlated Fermi liquids

    CERN Document Server

    Kontani, Hiroshi

    2013-01-01

    In conventional metals, various transport coefficients are scaled according to the quasiparticle relaxation time, \\tau, which implies that the relaxation time approximation (RTA) holds well. However, such a simple scaling does not hold in many strongly correlated electron systems, reflecting their unique electronic states. The most famous example would be cuprate high-Tc superconductors (HTSCs), where almost all the transport coefficients exhibit a significant deviation from the RTA results. To better understand the origin of this discrepancy, we develop a method for calculating various transport coefficients beyond the RTA by employing field theoretical techniques. Near the magnetic quantum critical point, the current vertex correction (CVC), which describes the electron-electron scattering beyond the relaxation time approximation, gives rise to various anomalous transport phenomena. We explain anomalous transport phenomena in cuprate HTSCs and other metals near their magnetic or orbital quantum critical poi...