WorldWideScience

Sample records for atlantic oscillation index

  1. Climate Prediction Center (CPC) Monthly North Atlantic Oscillation (NAO) teleconnection index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Monthly tabulated index of the North Atlantic Oscillation (NAO) teleconnection pattern. The data spans the period 1950 to present. The index is derived from a...

  2. Modulation of extreme temperatures in Europe under extreme values of the North Atlantic Oscillation Index.

    Science.gov (United States)

    Beniston, Martin

    2018-03-10

    This paper reports on the influence that extreme values in the tails of the North Atlantic Oscillation (NAO) Index probability density function (PDF) can exert on temperatures in Europe. When the NAO Index enters into its lowest (10% quantile or less) and highest (90% quantile or higher) modes, European temperatures often exhibit large negative or positive departures from their mean values, respectively. Analyses of the joint quantiles of the Index and temperatures (i.e., the simultaneous exceedance of particular quantile thresholds by the two variables) show that temperatures enter into the upper or lower tails of their PDF when the NAO Index also enters into its extreme tails, more often that could be expected from random statistics. Studies of this nature help further our understanding of the manner by which mechanisms of decadal-scale climate variability can influence extremes of temperature-and thus perhaps improve the forecasting of extreme temperatures in weather and climate models. © 2018 New York Academy of Sciences.

  3. Challenging a 15-year-old claim: The North Atlantic Oscillation index as a predictor of spring migration phenology of birds.

    Science.gov (United States)

    Haest, Birgen; Hüppop, Ommo; Bairlein, Franz

    2018-04-01

    Many migrant bird species that breed in the Northern Hemisphere show advancement in spring arrival dates. The North Atlantic Oscillation (NAO) index is one of the climatic variables that have been most often investigated and shown to be correlated with these changes in spring arrival. Although the NAO is often claimed to be a good predictor or even to have a marked effect on interannual changes in spring migration phenology of Northern Hemisphere breeding birds, the results on relations between spring migration phenology and NAO show a large variety, ranging from no, over weak, to a strong association. Several factors, such as geographic location, migration phase, and the NAO index time window, have been suggested to partly explain these observed differences in association. A combination of a literature meta-analysis, and a meta-analysis and sliding time window analysis of a dataset of 23 short- and long-distance migrants from the constant-effort trapping garden at Helgoland, Germany, however, paints a completely different picture. We found a statistically significant overall effect size of the NAO on spring migration phenology (coefficient = -0.14, SE = 0.054), but this on average only explains 0%-6% of the variance in spring migration phenology across all species. As such, the value and biological meaning of the NAO as a general predictor or explanatory variable for climate change effects on migration phenology of birds, seems highly questionable. We found little to no definite support for previously suggested factors, such as geographic location, migration phenology phase, or the NAO time window, to explain the heterogeneity in correlation differences. We, however, did find compelling evidence that the lack of accounting for trends in both time series has led to strongly inflated (spurious) correlations in many studies (coefficient = -0.13, SE = 0.019). © 2017 John Wiley & Sons Ltd.

  4. Seasonal predictability of the North Atlantic Oscillation

    Science.gov (United States)

    Vellinga, Michael; Scaife, Adam

    2015-04-01

    Until recently, long-range forecast systems showed only modest levels of skill in predicting surface winter climate around the Atlantic Basin and associated fluctuations in the North Atlantic Oscillation at seasonal lead times. Here we use a new forecast system to assess seasonal predictability of winter North Atlantic climate. We demonstrate that key aspects of European and North American winter climate and the surface North Atlantic Oscillation are highly predictable months ahead. We demonstrate high levels of prediction skill in retrospective forecasts of the surface North Atlantic Oscillation, winter storminess, near-surface temperature, and wind speed, all of which have high value for planning and adaptation to extreme winter conditions. Analysis of forecast ensembles suggests that while useful levels of seasonal forecast skill have now been achieved, key sources of predictability are still only partially represented and there is further untapped predictability. This work is distributed under the Creative Commons Attribution 3.0 Unported License together with an author copyright. This license does not conflict with the regulations of the Crown Copyright.

  5. The North Atlantic Oscillation: variability and interactions with the North Atlantic ocean and Artic sea ice

    Energy Technology Data Exchange (ETDEWEB)

    Jung, T

    2000-07-01

    The North Atlantic oscillation (NAO) represents the dominant mode of atmospheric variability in the North Atlantic region and describes the strengthening and weakening of the midlatitude westerlies. In this study, variability of the NAO during wintertime and its relationship to the North Atlantic ocean and Arctic sea ice is investigated. For this purpose, observational data are analyzed along with integrations of models for the Atlantic ocean, Arctic sea ice, and the coupled global climate system. From a statistical point of view, the observed NAO index shows unusually high variance on interdecadal time scales during the 20th century. Variability on other time scales is consistent with realizations of random processes (''white noise''). Recurrence of wintertime NAO anomalies from winter-to-winter with missing signals during the inbetween nonwinter seasons is primarily associated with interdecadal variability of the NAO. This recurrence indicates that low-frequency changes of the NAO during the 20th century were in part externally forced. (orig.)

  6. Evaluation of the Atlantic Multidecadal Oscillation Impact on Large-Scale Atmospheric Circulation in the Atlantic Region in Summer

    Science.gov (United States)

    Semenov, V. A.; Cherenkova, E. A.

    2018-02-01

    The influence of the Atlantic Multidecadal Oscillation (AMO) on large-scale atmospheric circulation in the Atlantic region in summer for the period of 1950-2015 is investigated. It is shown that the intensification of the summer North Atlantic Oscillation (NAO) with significant changes in sea level pressure anomalies in the main centers of action (over Greenland and the British Isles) occurred while the North Atlantic was cooler. Sea surface temperature anomalies, which are linked to the AMO in the summer season, affect both the NAO index and fluctuations of the Eastern Atlantic/Western Russia (EAWR) centers of action. The positive (negative) phase of the AMO is characterized by a combination of negative (positive) values of the NAO and EAWR indices. The dominance of the opposite phases of the teleconnection indices in summer during the warm North Atlantic and in its colder period resulted in differences in the regional climate in Europe.

  7. The Global Land-Ocean Temperature Index in Relation to Sunspot Number, the Atlantic Multidecadal Oscillation Index, the Mauna Loa Atmospheric Concentration of CO2, and Anthropogenic Carbon Emissions

    Science.gov (United States)

    Wilson, Robert M.

    2013-01-01

    Global warming/climate change has been a subject of scientific interest since the early 19th century. In particular, increases in the atmospheric concentration of carbon dioxide (CO2) have long been thought to account for Earth's increased warming, although the lack of a dependable set of observational data was apparent as late as the mid 1950s. However, beginning in the late 1950s, being associated with the International Geophysical Year, the opportunity arose to begin accurate continuous monitoring of the Earth's atmospheric concentration of CO2. Consequently, it is now well established that the atmospheric concentration of CO2, while varying seasonally within any particular year, has steadily increased over time. Associated with this rising trend in the atmospheric concentration of CO2 is a rising trend in the surface-air and sea-surface temperatures (SSTs). This Technical Publication (TP) examines the statistical relationships between 10-year moving averages (10-yma) of the Global Land-Ocean Temperature Index (GLOTI), sunspot number (SSN), the Atlantic Multidecadal Oscillation (AMO) index, and the Mauna Loa CO2 (MLCO2) index for the common interval 1964-2006, where the 10-yma values are used to indicate trends in the data. Scatter plots using the 10-yma values between GLOTI and each of the other parameters are determined, both as single-variate and multivariate fits. Scatter plots are also determined for MLCO2 using single-variate and bivariate (BV) fits, based on the GLOTI alone and the GLOTI in combination with the AMO index. On the basis of the inferred preferential fits for MLCO2, estimates for MLCO2 are determined for the interval 1885-1964, thereby yielding an estimate of the preindustrial level of atmospheric concentration of CO2. Lastly, 10-yma values of MLCO2 are compared against 10-yma estimates of the total carbon emissions (TCE) to determine the likelihood that manmade sources of carbon emissions are indeed responsible for the recent warming now

  8. The North Atlantic Oscillation: variability and interactions with the North Atlantic ocean and Artic sea ice

    Energy Technology Data Exchange (ETDEWEB)

    Jung, T.

    2000-07-01

    The North Atlantic oscillation (NAO) represents the dominant mode of atmospheric variability in the North Atlantic region and describes the strengthening and weakening of the midlatitude westerlies. In this study, variability of the NAO during wintertime and its relationship to the North Atlantic ocean and Arctic sea ice is investigated. For this purpose, observational data are analyzed along with integrations of models for the Atlantic ocean, Arctic sea ice, and the coupled global climate system. From a statistical point of view, the observed NAO index shows unusually high variance on interdecadal time scales during the 20th century. Variability on other time scales is consistent with realizations of random processes (''white noise''). Recurrence of wintertime NAO anomalies from winter-to-winter with missing signals during the inbetween nonwinter seasons is primarily associated with interdecadal variability of the NAO. This recurrence indicates that low-frequency changes of the NAO during the 20th century were in part externally forced. (orig.)

  9. Climate Prediction Center Southern Oscillation Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is one of the CPC?s Monthly Atmospheric and Sea Surface Temperature (SST)Indices. It contains Southern Oscillation Index which is standardized sea level...

  10. The subpolar North Atlantic - Response to North Atlantic oscillation like forcing and Influence on the Atlantic meridional overturning circulation

    Science.gov (United States)

    Lohmann, Katja; Drange, Helge; Jungclaus, Johann

    2010-05-01

    The extent and strength of the North Atlantic subpolar gyre (SPG) changed rapidly in the mid-1990s, going from large and strong in 1995 to substantially weakened in the following years. The abrupt change in the intensity of the SPG is commonly linked to the reversal of the North Atlantic Oscillation (NAO) index, changing from strong positive to negative values, in the winter 1995/96. In this study we investigate the impact of the initial SPG state on its subsequent behavior by means of an ocean general circulation model driven by NCEP-NCAR reanalysis fields. Our sensitivity integrations suggest that the weakening of the SPG cannot be explained by the change in the atmospheric forcing alone. Rather, for the time period around 1995, the SPG was about to weaken, irrespective of the actual atmospheric forcing, due to the ocean state governed by the persistently strong positive NAO during the preceding seven years (1989 to 1995). Our analysis indicates that it was this preconditioning of the ocean, in combination with the sudden drop in the NAO in 1995/96, that lead to the strong and rapid weakening of the SPG in the second half of the 1990s. In the second part, the sensitivity of the low-frequency variability of the Atlantic meridional overturning circulation to changes in the subpolar North Atlantic is investigated using a 2000 year long control integration as well as sensitivity experiments with the MPI-M Earth System Model. Two 1000 year long sensitivity experiments will be performed, in which the low-frequency variability in the overflow transports from the Nordic Seas and in the subpolar deep water formation rates is suppressed respectively. This is achieved by nudging temperature and salinity in the GIN Sea or in the subpolar North Atlantic (up to about 1500m depth) towards a monthly climatology obtained from the last 1000 years of the control integration.

  11. Effects of the North Atlantic Oscillation on Spanish catches of albacore, Thunnus alalunga, and yellowfin tuna, Thunnus albacares, in the North–east Atlantic Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Rubio, C.J.; MacIas, D.; Camiñas, J.A.; Fernandez, I.L.; Baez, J.C.

    2016-07-01

    Tuna are highly migratory pelagic species (HMPS) with great importance in commercial fishing. Several authors have highlighted the effect of climatic oscillations such as the NAO (North Atlantic Oscillation) on HMPS. This paper analyzes the effects of the NAO on two HMPS: albacore, Thunnus alalunga, and yellowfin tuna, Thunnus albacares. Fishing data from the Spanish fleet operating in the North Atlantic area were obtained from the International Commission for the Conservation of Atlantic Tunas (ICCAT) database. The results show a positive correlation between the NAO index and the Catch per Unit Effort (CPUE) for both albacore and yellowfin tuna, depicting a potential effect on their capturability. (Author)

  12. Auto-indexing of oscillation images

    International Nuclear Information System (INIS)

    Higashi, Tsuneyuki

    1990-01-01

    A method is presented which indexes spots recorded on single oscillation images without any a priori knowledge of cell parameters. The strategy is similar to that used in four-circle diffractometry and the method works in a fully automatic manner. It is applicable to multiple oscillation images or multiple stills. A complementary method is also described to obtain orientation angles for the case where cell parameters have already been determined. (orig.)

  13. Intraseasonal interaction between the Madden-Julian Oscillation and the North Atlantic Oscillation.

    Science.gov (United States)

    Cassou, Christophe

    2008-09-25

    Bridging the traditional gap between the spatio-temporal scales of weather and climate is a significant challenge facing the atmospheric community. In particular, progress in both medium-range and seasonal-to-interannual climate prediction relies on our understanding of recurrent weather patterns and the identification of specific causes responsible for their favoured occurrence, persistence or transition. Within this framework, I here present evidence that the main climate intra-seasonal oscillation in the tropics-the Madden-Julian Oscillation (MJO)-controls part of the distribution and sequences of the four daily weather regimes defined over the North Atlantic-European region in winter. North Atlantic Oscillation (NAO) regimes are the most affected, allowing for medium-range predictability of their phase far exceeding the limit of around one week that is usually quoted. The tropical-extratropical lagged relationship is asymmetrical. Positive NAO events mostly respond to a mid-latitude low-frequency wave train initiated by the MJO in the western-central tropical Pacific and propagating eastwards. Precursors for negative NAO events are found in the eastern tropical Pacific-western Atlantic, leading to changes along the North Atlantic storm track. Wave-breaking diagnostics tend to support the MJO preconditioning and the role of transient eddies in setting the phase of the NAO. I present a simple statistical model to quantitatively assess the potential predictability of the daily NAO index or the sign of the NAO regimes when they occur. Forecasts are successful in approximately 70 per cent of the cases based on the knowledge of the previous approximately 12-day MJO phase used as a predictor. This promising skill could be of importance considering the tight link between weather regimes and both mean conditions and the chances of extreme events occurring over Europe. These findings are useful for further stressing the need to better simulate and forecast the tropical

  14. Are the North Atlantic oscillation and the southern oscillation related in any time-scale?

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, R.; Ribera, P.; Hernandez, E. [Universidad Complutense de Madrid (Spain). Facultad de Ciencias Fisicas; Gimenoo, L. [Fac. Ciencias, Univ. Vigo, Ourense (Spain)

    2000-02-01

    The north Atlantic oscillation (NAO) and the southern oscillation (SO) are compared from the standpoint of a possible common temporal scale of oscillation. To do this a cross-spectrum of the temporal series of NAO and SO indices was determined, finding a significant common oscillation of 6-8 years. To assure this finding, both series were decomposed in their main oscillations using singular spectrum analysis (SSA). Resulting reconstructed series of 6-8 years' oscillation were then cross-correlated without and with pre-whitened, the latter being significant. The main conclusion is a possible relationship between a common oscillation of 6-8 years that represents about 20% of the SO variance and about 25% of the NAO variance. (orig.)

  15. Atmospheric circulation in northern hemisphere and north atlantic oscillation

    Directory of Open Access Journals (Sweden)

    Александр Вадимович Холопцев

    2015-08-01

    Full Text Available Conditions under which statistical connections of interannual changes of repitition duration periods in Northern hemisphere of elementary circulation mechanisms associated to meridional northern and meridional southern groups with variations of North Atlantic oscillation are significant were revealed. It is shown, that the characteristics changes of these connections taking place in modern period can be caused by distribution changes of distribution of sea surface temperatures

  16. 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.

  17. 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.

  18. Climate Prediction Center (CPC) East Atlantic Teleconnection Pattern Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Monthly tabulated index of the East Atlantic Teleconnection pattern. The data spans the period 1950 to present. The index is derived from a rotated principal...

  19. Differential response of continental stock complexes of Atlantic salmon (Salmo salar) to the Atlantic Multidecadal Oscillation

    Science.gov (United States)

    Friedland, Kevin D.; Shank, Burton V.; Todd, Christopher D.; McGinnity, Philip; Nye, Janet A.

    2014-05-01

    Atlantic salmon, Salmo salar, in the North Atlantic are managed as a set of population complexes distributed in North America and Europe. In recent years, these complexes have experienced reduced marine survival and many populations within the complexes are at risk, especially those at the southern ends of the species amphi-Atlantic range. Atlantic salmon is an anadromous fish dividing its life history between residence in freshwater and the marine environment. The freshwater portion of the life history includes spawning and the rearing of juveniles where in-river production has tended to be relatively stable, whereas the first year at sea, termed the post-smolt year, is characterized by more variable rates of mortality. Although their habitats are widely separated geographically along the North Atlantic seaboards, strong recruitment coherence exists between North American and European stock complexes. This recruitment coherence is correlated with ocean temperature variation associated with the Atlantic Multidecadal Oscillation (AMO). The North Atlantic Oscillation (NAO) appears to be relatively unimportant as a driver of salmon abundance. The mechanism determining the link between AMO-related thermal variation and abundance appears to differ fundamentally for the two continental stock groupings. Whereas ocean climate variability during the first springtime months of juvenile salmon migration to sea appears to be important to the survival of North American stocks, summer climate variation appears to be central to adult recruitment variation for European stocks. This contrast in seasonal effects appears to be related to the varying roles of predation pressure and size-related mortality on the continental stock complexes. The anticipated warming due to global climate change will impose thermal conditions on salmon populations outside historical context and challenge the ability of many populations to persist.

  20. Forest productivity in southwestern Europe is controlled by coupled North Atlantic and Atlantic Multidecadal Oscillations

    OpenAIRE

    Madrigal Gonzalez, Jaime; Ballesteros Canovas, Juan Antonio; Herrero, Asier; Ruiz-Benito, Paloma; Stoffel, Markus; Lucas-Borja, Manuel E.; Andivia, Enrique; Sancho-García, Cesar; Zavala, Miguel A.

    2017-01-01

    The North Atlantic Oscillation (NAO) depicts annual and decadal oscillatory modes of variability responsible for dry spells over the European continent. The NAO therefore holds a great potential to evaluate the role, as carbon sinks, of water-limited forests under climate change. However, uncertainties related to inconsistent responses of long-term forest productivity to NAO have so far hampered firm conclusions on its impacts. We hypothesize that, in part, such inconsistencies might have the...

  1. Variability of North Sea pH and CO2 in response to North Atlantic Oscillation forcing

    DEFF Research Database (Denmark)

    Salt, Lesley A.; Thomas, Helmuth; Prowe, Friederike

    2013-01-01

    [1] High biological activity causes a distinct seasonality of surface water pH in the North Sea, which is a strong sink for atmospheric CO2 via an effective shelf pump. The intimate connection between the North Sea and the North Atlantic Ocean suggests that the variability of the CO2 system...... of the North Atlantic Ocean may, in part, be responsible for the observed variability of pH and CO2 in the North Sea. In this work, we demonstrate the role of the North Atlantic Oscillation (NAO), the dominant climate mode for the North Atlantic, in governing this variability. Based on three extensive...... observational records covering the relevant levels of the NAO index, we provide evidence that the North Sea pH and CO2 system strongly responds to external and internal expressions of the NAO. Under positive NAO, the higher rates of inflow of water from the North Atlantic Ocean and the Baltic outflow lead...

  2. 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.

  3. Modulation of Atlantic Aerosols by the Madden-Julian Oscillation

    Science.gov (United States)

    Tian, B.; Waliser, D. E.; Kahn, Ralph A.; Wong, S.

    2010-01-01

    Much like the better-known EI Nino-Southern Oscillation, the Madden-Julian Oscillation (MJO) is a global-scale atmospheric phenomenon. The MJO involves periodic, systematic changes in the distribution of clouds and precipitation over the western Pacific and Indian oceans, along with differences in wind intensity over even more extensive areas, including the north and subtropical Atlantic Ocean. The lead authors of this paper developed a sophisticated mathematical technique for mapping the spatial and temporal behavior of changes in the atmosphere produced by the MJO. In a previous paper, we applied this technique to search for modulation of airborne particle amount in the eastern hemisphere associated with the "wet" (cloudy) vs. "dry" phases of the MJO. The study used primarily AVHRR, MODIS, and TOMS satellite-retrieved aerosol amount, but concluded that other factors, such as cloud contamination of the satellite signals, probably dominated the observed variations. The current paper looks at MJO modulation of desert dust transport eastward across the Atlantic from northern Africa, a region much less subject to systematic cloud contamination than the eastern hemisphere areas studied previously. In this case, a distinct aerosol signal appears, showing that dust is transported westward much more effectively during the MJO phase that favors westward-flowing wind, and such transport is suppressed when the MJO reduces these winds. Aside form the significant achievement in identifying such an effect, the result implies that an important component of global dust transport can be predicted based on the phase of the MJO. As a consequence, the impact of airborne dust on storm development in the Atlantic, and on dust deposition downwind of the desert sources, can also be predicted and more accurately modeled.

  4. 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.

  5. Forest productivity in southwestern Europe is controlled by coupled North Atlantic and Atlantic Multidecadal Oscillations.

    Science.gov (United States)

    Madrigal-González, Jaime; Ballesteros-Cánovas, Juan A; Herrero, Asier; Ruiz-Benito, Paloma; Stoffel, Markus; Lucas-Borja, Manuel E; Andivia, Enrique; Sancho-García, Cesar; Zavala, Miguel A

    2017-12-20

    The North Atlantic Oscillation (NAO) depicts annual and decadal oscillatory modes of variability responsible for dry spells over the European continent. The NAO therefore holds a great potential to evaluate the role, as carbon sinks, of water-limited forests under climate change. However, uncertainties related to inconsistent responses of long-term forest productivity to NAO have so far hampered firm conclusions on its impacts. We hypothesize that, in part, such inconsistencies might have their origin in periodical sea surface temperature anomalies in the Atlantic Ocean (i.e., Atlantic Multidecadal Oscillation, AMO). Here we show strong empirical evidence in support of this hypothesis using 120 years of periodical inventory data from Iberian pine forests. Our results point to AMO + NAO + and AMO - NAO - phases as being critical for forest productivity, likely due to decreased winter water balance and abnormally low winter temperatures, respectively. Our findings could be essential for the evaluation of ecosystem functioning vulnerabilities associated with increased climatic anomalies under unprecedented warming conditions in the Mediterranean.

  6. The impact of Arctic and North Atlantic oscillation on temperature and precipitation anomalies in Serbia

    Directory of Open Access Journals (Sweden)

    Pavlović-Berdon Nada

    2012-01-01

    Full Text Available The impact of the Arctic Oscillations (AO and the North Atlantic Oscillations (NAO is considered as the most prominent of atmospheric oscillations in the area of the northern hemisphere from the United States to Siberia and from the Arctic to the subtropical Atlantic. The aim of this study was to determine how these fluctuations affect the temperature and precipitation in Serbia. This paper explores the impact for the period of 50 years (1958-2007 by months and in 20 synoptic stations. The influence of the AO on temperature anomalies in Serbia can be seen by the correlation coefficient, the largest in the month of January, while its impact on precipitation is the largest in the month of February. After the test of linear correlation between the NAO index and temperature anomalies for the base period 1971-2000 for 20 synoptic stations in Serbia, it has been found that the highest correlation is in the month of January. The correlation between the NAO and the precipitation anomalies for the stations mentioned above is the highest in the month of February. Spatial patterns of the AO and the NAO influence on temperature in January and on precipitation in February were obtained by applying principal component analysis.

  7. The Energy Cascade Associated with the North Atlantic Oscillation

    Science.gov (United States)

    Castanheira, J. M.; Marques, C. A. F.

    2017-12-01

    The North Atlantic Oscillation or Arctic Oscillation (NAO/AO), in a more hemispheric expression, is the dominant mode of variability of the extratropical atmospheric circulation. In the literature which analyses the association of low frequency variability of the NAO/AO with other climate variables, it is very common to find the idea of circulation and climate impacts of the NAO/AO. It is usually suggested that the NAO influences the position of North Atlantic storm tracks and the related transport of heat and moisture. However, in spite of the long time since the NAO variability mode was uncovered (Walker and Bliss, 1932), its underlying dynamical mechanisms are not well understood yet. In fact, it is not yet consensual that the NAO influences the position of the storm tracks, being possible that the relationship is in the opposite way with the storm track activity influencing de NAO. In this communication we will present an analysis of anomalies of the energy cascade associated with the NAO. A detailed version of the Lorenz energy cycle, which decomposes the energy flows into baroclinic and barotropic terms and into zonal mean and eddy components, was applied to the 6-hourly ERA-I reanalysis for the period of 1979 to 2016. The obtained results show that the positive NAO phase is preceded by an significant increase of synoptic baroclinic eddy activity. The eddy available potential energy is converted into kinetic energy and transferred to barotropic synoptic eddies. Then, the kinetic energy is transferred upscale into the barotropic planetary waves, which reproduce the NAO pattern. Therefore, we conclude that the synoptic baroclinic eddy activity forces the NAO variability. No clear signal was found for a modulating role of the NAO in the baroclinic eddy activity.

  8. Contrasting spatial structures of Atlantic Multidecadal Oscillation between observations and slab ocean model simulations

    Science.gov (United States)

    Sun, Cheng; Li, Jianping; Kucharski, Fred; Xue, Jiaqing; Li, Xiang

    2018-04-01

    The spatial structure of Atlantic multidecadal oscillation (AMO) is analyzed and compared between the observations and simulations from slab ocean models (SOMs) and fully coupled models. The observed sea surface temperature (SST) pattern of AMO is characterized by a basin-wide monopole structure, and there is a significantly high degree of spatial coherence of decadal SST variations across the entire North Atlantic basin. The observed SST anomalies share a common decadal-scale signal, corresponding to the basin-wide average (i. e., the AMO). In contrast, the simulated AMO in SOMs (AMOs) exhibits a tripole-like structure, with the mid-latitude North Atlantic SST showing an inverse relationship with other parts of the basin, and the SOMs fail to reproduce the observed strong spatial coherence of decadal SST variations associated with the AMO. The observed spatial coherence of AMO SST anomalies is identified as a key feature that can be used to distinguish the AMO mechanism. The tripole-like SST pattern of AMOs in SOMs can be largely explained by the atmosphere-forced thermodynamics mechanism due to the surface heat flux changes associated with the North Atlantic Oscillation (NAO). The thermodynamic forcing of AMOs by the NAO gives rise to a simultaneous inverse NAO-AMOs relationship at both interannual and decadal timescales and a seasonal phase locking of the AMOs variability to the cold season. However, the NAO-forced thermodynamics mechanism cannot explain the observed NAO-AMO relationship and the seasonal phase locking of observed AMO variability to the warm season. At decadal timescales, a strong lagged relationship between NAO and AMO is observed, with the NAO leading by up to two decades, while the simultaneous correlation of NAO with AMO is weak. This lagged relationship and the spatial coherence of AMO can be well understood from the view point of ocean dynamics. A time-integrated NAO index, which reflects the variations in Atlantic meridional overturning

  9. The Influence of the North Atlantic Oscillation on Tropospheric Distributions of Ozone and Carbon Monoxide.

    Science.gov (United States)

    Knowland, K. E.; Doherty, R. M.; Hodges, K.

    2015-12-01

    The influence of the North Atlantic Oscillation (NAO) on the tropospheric distributions of ozone (O3) and carbon monoxide (CO) has been quantified. The Monitoring Atmospheric Composition and Climate (MACC) Reanalysis, a combined meteorology and composition dataset for the period 2003-2012 (Innes et al., 2013), is used to investigate the composition of the troposphere and lower stratosphere in relation to the location of the storm track as well as other meteorological parameters over the North Atlantic associated with the different NAO phases. Cyclone tracks in the MACC Reanalysis compare well to the cyclone tracks in the widely-used ERA-Interim Reanalysis for the same 10-year period (cyclone tracking performed using the tracking algorithm of Hodges (1995, 1999)), as both are based on the European Centre for Medium-Range Weather Forecasts' (ECMWF) Integrated Forecast System (IFS). A seasonal analysis is performed whereby the MACC reanalysis meteorological fields, O3 and CO mixing ratios are weighted by the monthly NAO index values. The location of the main storm track, which tilts towards high latitudes (toward the Arctic) during positive NAO phases to a more zonal location in the mid-latitudes (toward Europe) during negative NAO phases, impacts the location of both horizontal and vertical transport across the North Atlantic and into the Arctic. During positive NAO seasons, the persistence of cyclones over the North Atlantic coupled with a stronger Azores High promotes strong horizontal transport across the North Atlantic throughout the troposphere. In all seasons, significantly more intense cyclones occur at higher latitudes (north of ~50°C) during the positive phase of the NAO and in the southern mid-latitudes during the negative NAO phase. This impacts the location of stratospheric intrusions within the descending dry airstream behind the associated cold front of the extratropical cyclone and the venting of low-level pollution up into the free troposphere within

  10. Climate Prediction Center (CPC) Madden-Julian Oscillation (MJO) Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Climate Prediction Center (CPC) Madden Julian Oscillation index (MJO) is a dataset that allows evaluation of the strength and phase of the MJO during the dataset...

  11. Impacts of radiation management techniques on the North Atlantic Oscillation

    Science.gov (United States)

    Adakudlu, Muralidhar; Helge Otterå, Odd; Tjiputra, Jerry; Muri, Helene; Grini, Alf; Schulz, Michael

    2017-04-01

    The effectiveness of various climate engineering techniques in limiting the global warming signal to reasonable levels has been the topic of state-of-the-art research on climate change. Using an Earth system model, we show that these techniques have the potential to bring down the high CO2 concentration climate in RCP8.5 to a moderate climate similar to RCP4.5 in terms of global temperature. Nevertheless, their influence on the regional aspects of atmospheric circulation is not clear. The regional circulation patterns in the atmosphere are largely characterized by the natural variability modes, such as the North Atlantic Oscillation (NAO). In this study, we assess the impacts of three radiation managment techniques, namely, Stratospheric Aerosol Injection (SAI), Marine Sky Brightening (MSB) and Cirrus Cloud Thinning (CCT), on the structure and features of the NAO. The results indicate an east-northeastward shift as well as intensification of the NAO spatial pattern in the global warming scenarios of RCP4.5 and RCP8.5, with the signal being most intense in the latter. The climate engineering forcings when applied to the RCP8.5 case tend to reduce the strength of the NAO with little impact on its position. The CCT case appears to have the maximum effect on the NAO signal. The patterns of cloud radiative forcing, expressed as the difference between net radiative forcing at TOA under average conditions and clear sky conditions, reveal a northeastward shift of the radiative heating in the north Atlantic region. This implies a possible link between the changes in the NAO signal and the cloud radiative forcing.

  12. 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.

  13. The North Atlantic Oscillation and sea surface temperature affect loggerhead abundance around the Strait of Gibraltar

    Directory of Open Access Journals (Sweden)

    José C. Báez

    2011-04-01

    Full Text Available The aim of this study was to explore the possible link between variations in the North Atlantic Oscillation (NAO and sea surface temperature (SST and the abundance of loggerhead turtles around the Strait of Gibraltar, using stranding data for the Andalusian coastal area as a proxy for abundance. The annual average SST (from November to October in the Gulf of Cadiz was negatively associated with the total number of loggerhead strandings each year from November 1997 to October 2006 in the Gulf of Cadiz and the Alboran Sea. The average NAO index was positively associated with the number of strandings in the Gulf of Cadiz in the following year. Prevailing westerly winds during positive NAO phases and the subsequent delayed decrease in SST may lead to turtles from the west Atlantic accumulating in the Gulf of Cadiz and unsuccessfully attempting to return. Secondary causes, such as buoyancy, cold stunning, longline fisheries, net fisheries, debilitated turtle syndrome, and trauma may also increase the number of turtle strandings.

  14. 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

    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...... 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...

  15. 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.

  16. Internal variability in a 1000-yr control simulation with the coupled climate model ECHO-G - II. El Nino Southern Oscillation and North Atlantic Oscillation

    Energy Technology Data Exchange (ETDEWEB)

    Min, Seung-Ki; Hense, Andreas [Univ. of Bonn (Germany). Meteorological Inst.; Legutke, Stephanie [Max Planck Inst. for Meteorology, Hamburg (Germany); Kwon, Won-Tae [Meteorological Research Inst., Seoul (Korea, Republic of)

    2005-08-01

    A 1000-yr control simulation (CTL) performed with the atmosphere-ocean global climate model ECHO-G is analysed with regard to the El Nino Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), the two major natural climatic variabilities, in comparison with observations and other model simulations. The ENSO-related sea surface temperature climate and its seasonal cycle in the tropical Pacific and a single Intertropical Convergence Zone in the eastern tropical Pacific are simulated reasonably, and the ENSO phase-locking to the annual cycle and the subsurface ocean behaviour related to equatorial wave dynamics are also reproduced well. The simulated amplitude of the ENSO signal is however too large and its occurrence is too regular and frequent. Also, the observed westward propagation of zonal wind stress over the equatorial Pacific is not captured by the model. Nevertheless, the ENSO-related teleconnection patterns of near-surface temperature (T2m), precipitation (PCP) and mean sea level pressure (MSLP) are reproduced realistically. The NAO index, defined as the MSLP difference between Gibraltar and Iceland, has a 'white' noise spectrum similar to that of the detrended index obtained from observed data. The correlation and regression patterns of T2m, PCP and MSLP with the NAO index are also successfully simulated. However, the model overestimates the warming over the North Pacific in the high index phase of the NAO, a feature it shares with other coupled models. This might be associated with an enhanced Atlantic/Pacific teleconnection, which is hardly seen in the observations. A detection analysis of the NAO index shows that the observed recent 4060 yr trend cannot be explained by the model's internal variability while the recent 2030 yr trend occurs with a more than 1% chance in ECHO-G CTL.

  17. North Atlantic Oscillation dynamics recorded in shells of a long-lived bivalve mollusk

    Science.gov (United States)

    Schöne, Bernd R.; Oschmann, Wolfgang; Rössler, Jochen; Freyre Castro, Antuané D.; Houk, Stephen D.; Kröncke, Ingrid; Dreyer, Wolfgang; Janssen, Ronald; Rumohr, Heye; Dunca, Elena

    2003-12-01

    Existing reconstructions of the winter North Atlantic Oscillation (WNAO) are based on terrestrial proxies and historical documents. No direct high-resolution, long-term rec ords from marine settings are available for this major climate-dictating phenomenon, which severely affects a variety of economic aspects of our society. Here we present a 245 yr proxy WNAO index based on shells of the long-lived marine bivalve mollusk Arctica islandica. Variations in annual rates of shell growth are positively correlated with WNAO-related changes in the food supply. Maximum amplitudes in frequency bands of 7 9 and 5 7 yr fall exactly within the range of instrumental and other proxy WNAO indices. These estimates were obtained for specimens collected live, 2000 km apart, in the central North Sea and on the Norwegian Shelf. Hence, the WNAO influences hydrographic regimes of large regions of the ocean. Our study demonstrates that A. islandica can reliably reconstruct WNAO dynamics for time intervals and regions without instrumental records. Our new tool functions as a proxy for the WNAO index prior to the twentieth-century greenhouse forcing and has the potential to further validate other proxy-based WNAO records.

  18. Effects of the North Atlantic Oscillation and wind waves on salt marsh dynamics in the Danish Wadden Sea

    DEFF Research Database (Denmark)

    Kim, Daehyun; Grant, William E.; Cairns, David M.

    2013-01-01

    Long-term eustatic sea-level variation has been recognized as a primary factor affecting the hydrological and geomorphic dynamics of salt marshes. However, recent studies suggest that wind waves influenced by atmospheric oscillations also may play an important role in many coastal areas. Although...... this notion has been conceptually introduced for the Wadden Sea, no modeling attempts have been made yet. As a proof of concept, this study developed a simulation model using the commercially available STELLAA (R) software, based on long-term data on water level and sedimentation collected at a back......-barrier marsh on the Skallingen peninsula in Denmark. In the model, the frequency (number year(-1)) of wind-driven extreme high water level (HWL) events (> 130 cm Danish Ordnance Zero) was simulated in terms of the North Atlantic Oscillation (NAO) index. Then, surface accretion (cm year(-1)) and submergence...

  19. Greenland ice core evidence for spatial and temporal variability of the Atlantic Multidecadal Oscillation

    NARCIS (Netherlands)

    Chylek, P.; Folland, C.K.; Frankcombe, L.M.; Dijkstra, H.A.; Lesins, G.; Dubey, M.

    2012-01-01

    [1] The Greenland δ18O ice core record is used as a proxy for Greenland surface air temperatures and to interpret Atlantic Multidecadal Oscillation (AMO) variability. An analysis of annual δ18O data from six Arctic ice cores (five from Greenland and one from Canada's Ellesmere Island) suggests a

  20. Decadal summer drought frequency in China: the increasing influence of the Atlantic Multi-decadal Oscillation

    International Nuclear Information System (INIS)

    Qian, Chengcheng; Yu, Jin-Yi; Chen, Ge

    2014-01-01

    Decadal variations in summer drought events during 1956–2005 are examined over Eastern China to identify their leading variability modes and their linkages to the Pacific Decadal Oscillation (PDO), Atlantic Multi-decadal Oscillation (AMO), and global warming. The PDO influence is found to dominate China drought frequency from the 1960s to early 1990s via modulating the Western Pacific Subtropical High and the Mongolian High. The four-pole drought pattern produced by the PDO diminished after the early 1990s, being replaced by a dipolar drought pattern that is produced by the AMO via a Eurasian wave train emanating from North Atlantic to China. The increasing influence of the AMO on China drought since the early 1990s is further shown to be a consequence of global warming. This study indicates that the early 1990s is a time when the Atlantic began to exert a stronger influence on climate over China and even larger part of Asia. (letter)

  1. Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age.

    Science.gov (United States)

    Knudsen, Mads Faurschou; Jacobsen, Bo Holm; Seidenkrantz, Marit-Solveig; Olsen, Jesper

    2014-02-25

    The Atlantic Multidecadal Oscillation (AMO) represents a significant driver of Northern Hemisphere climate, but the forcing mechanisms pacing the AMO remain poorly understood. Here we use the available proxy records to investigate the influence of solar and volcanic forcing on the AMO over the last ~450 years. The evidence suggests that external forcing played a dominant role in pacing the AMO after termination of the Little Ice Age (LIA; ca. 1400-1800), with an instantaneous impact on mid-latitude sea-surface temperatures that spread across the North Atlantic over the ensuing ~5 years. In contrast, the role of external forcing was more ambiguous during the LIA. Our study further suggests that the Atlantic Meridional Overturning Circulation is important for linking external forcing with North Atlantic sea-surface temperatures, a conjecture that reconciles two opposing theories concerning the origin of the AMO.

  2. 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.

  3. Long term changes in flooding and heavy rainfall associated with North Atlantic tropical cyclones: Roles of the North Atlantic Oscillation and El Niño-Southern Oscillation

    Science.gov (United States)

    Aryal, Yog N.; Villarini, Gabriele; Zhang, Wei; Vecchi, Gabriel A.

    2018-04-01

    The aim of this study is to examine the contribution of North Atlantic tropical cyclones (TCs) to flooding and heavy rainfall across the continental United States. Analyses highlight the spatial variability in these hazards, their temporal changes in terms of frequency and magnitude, and their connection to large-scale climate, in particular to the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO). We use long-term stream and rain gage measurements, and our analyses are based on annual maxima (AMs) and peaks-over-threshold (POTs). TCs contribute to ∼20-30% of AMs and POTs over Florida and coastal areas of the eastern United States, and the contribution decreases as we move inland. We do not detect statistically significant trends in the magnitude or frequency of TC floods. Regarding the role of climate, NAO and ENSO do not play a large role in controlling the frequency and magnitude of TC flooding. The connection between heavy rainfall and TCs is comparable to what observed in terms of flooding. Unlike flooding, NAO plays a significant role in TC-related extreme rainfall along the U.S. East Coast, while ENSO is most strongly linked to the TC precipitation in Texas.

  4. Climate Prediction Center (CPC) East Atlantic/ Western Russia Teleconnection Pattern Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Monthly tabulated index of the East Atlantic/ Western Russia teleconnection pattern. The data spans the period 1950 to present. The index is derived from a rotated...

  5. Interaction between Tropical Atlantic Variability and El Niño-Southern Oscillation.

    Science.gov (United States)

    Saravanan, R.; Chang, Ping

    2000-07-01

    The interaction between tropical Atlantic variability and El Niño-Southern Oscillation (ENSO) is investigated using three ensembles of atmospheric general circulation model integrations. The integrations are forced by specifying observed sea surface temperature (SST) variability over a forcing domain. The forcing domain is the global ocean for the first ensemble, limited to the tropical ocean for the second ensemble, and further limited to the tropical Atlantic region for the third ensemble. The ensemble integrations show that extratropical SST anomalies have little impact on tropical variability, but the effect of ENSO is pervasive in the Tropics. Consistent with previous studies, the most significant influence of ENSO is found during the boreal spring season and is associated with an anomalous Walker circulation. Two important aspects of ENSO's influence on tropical Atlantic variability are noted. First, the ENSO signal contributes significantly to the `dipole' correlation structure between tropical Atlantic SST and rainfall in the Nordeste Brazil region. In the absence of the ENSO signal, the correlations are dominated by SST variability in the southern tropical Atlantic, resulting in less of a dipole structure. Second, the remote influence of ENSO also contributes to positive correlations between SST anomalies and downward surface heat flux in the tropical Atlantic during the boreal spring season. However, even when ENSO forcing is absent, the model integrations provide evidence for a positive surface heat flux feedback in the deep Tropics, which is analyzed in a companion study by Chang et al. The analysis of model simulations shows that interannual atmospheric variability in the tropical Pacific-Atlantic system is dominated by the interaction between two distinct sources of tropical heating: (i) an equatorial heat source in the eastern Pacific associated with ENSO and (ii) an off-equatorial heat source associated with SST anomalies near the Caribbean

  6. 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.

  7. Shallow and deep landslides induced by rainfall in the Lisbon region (Portugal: assessment of relationships with the North Atlantic Oscillation

    Directory of Open Access Journals (Sweden)

    J. L. Zêzere

    2005-01-01

    Full Text Available The aim of this study is to assess the impact of the North Atlantic Oscillation (NAO on both the winter precipitation and the temporal occurrence of different landslide types in Portugal. The analysis is applied to five sample areas located just north of Lisbon, the capital of Portugal. These sites are particularly relevant because actual dates of most of the recent landslide events are known but also because the landslides occurred in a suburban area with growing urbanization pressure. Results show that the large inter-annual variability of winter precipitation observed in western Iberia, i.e. Portugal and parts of Spain, is largely modulated by the NAO mode. In particular, precipitation falling in Portugal between November and March presents a correlation coefficient of R=–0.66 with the NAO index. Precipitation distribution for the reference rain gauge in the study area reveals that the probability of a wet month to occur is much higher for low NAO index composites than for the corresponding high NAO index composite. It is shown that this control, exerted by NAO on the precipitation regime, is related to corresponding changes in the associated activity of North-Atlantic storm tracks that affect the western Iberia. Landslide activity in the study area is related to both intense, short duration precipitation events (1–15 days and long-lasting rainfall episodes (1–3 months. The former events trigger shallow translational slides while the later episodes are usually associated with deeper and larger slope movements. This second group of landslides is shown to be statistically associated with the 3-month average of the NAO index.

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

    Directory of Open Access Journals (Sweden)

    P. De Vita

    2012-05-01

    Full Text Available Thus far, studies on climate change have focused mainly on the variability of the atmospheric and surface components of the hydrologic cycle, investigating the impact of this variability on the environment, especially with respect to the risks of desertification, droughts and floods. Conversely, the impacts of climate change on the recharge of aquifers and on the variability of groundwater flow have been less investigated, especially in Mediterranean karst areas whose water supply systems depend heavily upon groundwater exploitation.

    In this paper, long-term climatic variability and its influence on groundwater recharge were analysed by examining decadal patterns of precipitation, air temperature and spring discharges in the Campania region (southern Italy, coupled with the North Atlantic Oscillation (NAO.

    The time series of precipitation and air temperature were gathered over 90 yr, from 1921 to 2010, using 18 rain gauges and 9 air temperature stations with the most continuous functioning. The time series of the winter NAO index and of the discharges of 3 karst springs, selected from those feeding the major aqueducts systems, were collected for the same period.

    Regional normalised indexes of the precipitation, air temperature and karst spring discharges were calculated, and different methods were applied to analyse the related time series, including long-term trend analysis using smoothing numerical techniques, cross-correlation and Fourier analysis.

    The investigation of the normalised indexes highlighted the existence of long-term complex periodicities, from 2 to more than 30 yr, with differences in average values of up to approximately ±30% for precipitation and karst spring discharges, which were both strongly correlated with the winter NAO index.

    Although the effects of the North Atlantic Oscillation (NAO had already been demonstrated in the long-term precipitation and streamflow patterns of

  9. Reconstructing the history of the Atlantic Multidecadal Oscillation using high-resolution Mg/Ca paleothermometry from a Cariaco Basin core

    Science.gov (United States)

    Wurtzel, J. B.; Black, D. E.; Rahman, S.; Thunell, R.; Peterson, L. C.; Tappa, E.

    2010-12-01

    Instrumental and proxy-reconstructions show the existence of an approximately 70-year periodicity in Atlantic sea surface temperature (SST), known as the Atlantic Multidecadal Oscillation (AMO). The AMO is correlated with circum-tropical Atlantic climate phenomena such as Sahel and Nordeste rainfall, and Atlantic hurricane patterns. Though it has been suggested that the AMO is controlled by thermohaline circulation, much debate exists as to whether the SST fluctuations are a result of anthropogenic forcing or a natural climate mode, or even if the AMO is a true oscillation at all. Our ability to address this issue has been limited by instrumental SST records that rarely extend back more than 50-100 years and proxy reconstructions that are mostly terrestrial-based. Additionally, the modern instrumental variability likely contains an anthropogenic component that is not easily distinguished from the natural background of the system. From a marine sediment core taken in the Cariaco Basin, we have developed a high-resolution SST reconstruction for the past ca. 1500 years using Mg/Ca paleothermometry on seasonally-representative foraminifera, with the most recent data calibrated to the instrumental record. Previous studies have shown Cariaco Basin Mg/Ca-SSTs to be well-correlated to the Caribbean Sea and much of the western tropical Atlantic, which allows us to create a record that can be used to determine pre-anthropogenic rates and ranges of SST variability and observe how they change over time. Averaging the seasonal temperatures derived from the two foraminiferal species over the instrumental period yields a strong correlation to the AMO index from A. D. 1880 through 1970 (r = 0.44, p<0.0001). Wavelet analysis of the proxy average annual SST data indicates that modern AMO variability is not a consistent feature through time, and may be a function of warm-period climate.

  10. Influence of the North Atlantic Oscillation on European tropospheric composition: an observational and modelling study

    Science.gov (United States)

    Pope, R.; Chipperfield, M.

    2017-12-01

    The North Atlantic Oscillation (NAO) has a strong influence on winter-time North Atlantic and European circulation patterns. Under the positive phase of the NAO (NAO+), intensification of the climatological Icelandic low and Azores high pressure systems results in strong westerly flow across the Atlantic into Europe. Under the NAO negative phase (NAO-), there is a weakening of this meridional pressure gradient resulting in a southerly shift in the westerlies flow towards the sub-tropical Atlantic. Therefore, NAO+ and NAO- introduce unstable stormy and drier stable conditions into Europe, respectively. Under NAO+ conditions, the strong westerlies tend to enhance transport of European pollution (e.g. nitrogen oxides) away from anthropogenic source regions. While during NAO-, the more stable conditions lead to a build up of pollutants. However, secondary pollutants (i.e. tropospheric ozone) show the opposite signal where NAO+, while transporting primary pollutants away, introduces Atlantic ozone enriched air into Europe. Here ozone can form downwind of pollution from continental North America and be transported into Europe via the westerly flow. Under NAO-, this westerly ozone transport is reduced yielding lower European ozone concentrations also depleted further by ozone loss through the reaction with NOx, which has accumulated over the continent. Peroxyacetyl nitrate (PAN), observed in the upper troposphere - lower stratosphere (UTLS) by satellite, peaks over Iceland/Southern Greenland in NAO-, between 200-100 hPa, consistent with trapping by an anticyclone at this altitude. During NAO+, PAN is enhanced over the sub-tropical Atlantic and Arctic. Model simulations show that enhanced PAN over Iceland/Southern Greenland in NAO- is associated with vertical transport from the troposphere into the UTLS, while peak Arctic PAN in NAO+ is its accumulation given the strong northerly meridional transport in the UTLS. UTLS ozone spatial anomalies, relative to the winter

  11. Impact of the North Atlantic Oscillation on the trans-Atlantic migrations of the European eel (Anguilla anguilla)

    Science.gov (United States)

    Kettle, A. James; Bakker, Dorothee C. E.; Haines, Keith

    2008-09-01

    Glass eel catches and FAO (Food and Agricultural Organization) landings of the European freshwater eel (Anguilla anguilla) show a decrease over the past 20 years. The long-term trends in the time series mask an interannual fluctuation, which becomes apparent on the application of a high-pass filter and autocorrelation analysis. Both the FAO landings and the glass eel catches show interannual fluctuations with a repeat period of 6-8 years, similar to the period of the North Atlantic Oscillation (NAO). Most glass eel catch monitoring stations are in phase. The glass eel catches show a significant negative correlation with the NAO lagged by 0-2 years, consistent with the hypothesis that the positive NAO phase has an adverse impact on the larval survival in and migration from the Sargasso Sea spawning location, one year prior to the arrival of the glass eels in Europe and North Africa. The FAO landings can be divided into two groups of different phase that have an approximate correspondence to the NAO dipole in winter rainfall in Europe and North Africa. One group (P) comprises Denmark, Ireland, Morocco, Netherlands, Norway, Sweden, Tunisia, and the United Kingdom, and the other group (N) comprises France, Germany, Italy, Poland, Portugal, Spain, and Turkey. At least for the interannual fluctuations, the success of the glass eel fishery (and eel recruitment) may be coupled with the number of migrating silver eels from the N group of countries and uncoupled with the P group of countries.

  12. Climate Prediction Center(CPC)Daily Arctic Oscillation Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Arctic Oscillation (AO) is a leading teleconnection pattern in the Northern Hemisphere circulation. It is calculated as the first Empirical Orthogonal Function...

  13. Climate Prediction Center Monthly(CPC)Arctic Oscillation Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Arctic Oscillation (AO) is a leading teleconnection pattern in the Northern Hemisphere circulation. It is calculated as the first Empirical Orthogonal Function...

  14. Climate Prediction Center (CPC) Daily Antarctic Oscillation Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Antarctic Oscillation (AAO) is a leading teleconnection pattern in the Southern Hemisphere circulation. It is calculated as the first Empirical Orthogonal...

  15. Climate Prediction Center(CPC)Monthly Antarctic Oscillation Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Antarctic Oscillation (AAO) is a leading teleconnection pattern in the Southern Hemisphere circulation. It is calculated as the first Empirical Orthogonal...

  16. The impact of global warming on the Southern Oscillation Index

    Energy Technology Data Exchange (ETDEWEB)

    Power, Scott B.; Kociuba, Greg [Bureau of Meteorology, Centre for Australian Weather and Climate Research, Melbourne (Australia)

    2011-11-15

    The Southern Oscillation Index (SOI) - a measure of air pressure difference across the Pacific Ocean, from Tahiti in the south-east to Darwin in the west - is one of the world's most important climatic indices. The SOI is used to track and predict changes in both the El Nino-Southern Oscillation phenomenon, and the Walker Circulation (WC). During El Nino, for example, the WC weakens and the SOI tends to be negative. Climatic variations linked to changes in the WC have a profound influence on climate, ecosystems, agriculture, and societies in many parts of the world. Previous research has shown that (1) the WC and the SOI weakened in recent decades and that (2) the WC in climate models tends to weaken in response to elevated atmospheric greenhouse gas concentrations. Here we examine changes in the SOI and air pressure across the Pacific in the observations and in numerous WCRP/CMIP3 climate model integrations for both the 20th and 21st centuries. The difference in mean-sea level air pressure (MSLP) between the eastern and western equatorial Pacific tends to weaken during the 21st century, consistent with previous research. Here we show that this primarily arises because of an increase in MSLP in the west Pacific and not a decline in the east. We also show, in stark contrast to expectations, that the SOI actually tends to increase during the 21st century, not decrease. Under global warming MSLP tends to increase at both Darwin and Tahiti, but tends to rise more at Tahiti than at Darwin. Tahiti lies in an extensive region where MSLP tends to rise in response to global warming. So while the SOI is an excellent indicator of interannual variability in both the equatorial MSLP gradient and the WC, it is a highly misleading indicator of long-term equatorial changes linked to global warming. Our results also indicate that the observed decline in the SOI in recent decades has been driven by natural, internally generated variability. The externally forced signal in the

  17. Understanding the North Atlantic Oscillation and Its Effects in the Mediterranean

    Science.gov (United States)

    Trigo, Ricardo M.; Serrano, Sergio M. Vicente

    2010-11-01

    ESF-MedCLIVAR Workshop on Hydrological, Socioeconomic and Ecological Impacts of the North Atlantic Oscillation in the Mediterranean; Zaragoza, Spain, 24-27 May 2010; According to the latest Intergovernmental Panel on Climate Change report, the Mediterranean basin represents one of the most important hot spots of climate change in the world, with recent trends toward a hotter and drier climate being related to changes in atmospheric circulation patterns. Among these patterns the North Atlantic Oscillation (NAO) is the most important one and the only one that exerts a clear influence throughout the year, although with stronger intensity and extension during winter. In the framework of the European Science Foundation's Mediterranean Climate Variability and Predictability (MedCLIVAR) program (http://www.medclivar.eu/), a thematic workshop devoted to the hydrological, socioeconomic, and ecological impacts of the NAO in the Mediterranean area was held in Spain. The main objective of this 3-day workshop was to foster interaction in this increasingly interdisciplinary topic, in particular, among climatologists, hydrologists, geographers, agronomists, biologists, and other scientists. The workshop was attended by 62 participants from 15 different countries and included a mix of senior scientists and graduate students. The workshop was divided into five sessions focusing on (1) natural hazards, including droughts, severe precipitations, floods, heat waves, and cold spells; (2) vegetation activity and agriculture production; (3) natural ecosystems and environment, including forest dynamics, fisheries, dynamics of animal populations, and air quality; (4) geomorphology, including landslides and debris flows, erosivity mechanisms, and surface erosion processes; and (5) renewable energies production, including hydraulic, eolic, and solar.

  18. Land surface anomalies preceding the 2010 Russian heat wave and a link to the North Atlantic oscillation

    International Nuclear Information System (INIS)

    Wright, Christopher K; Henebry, Geoffrey M; De Beurs, Kirsten M

    2014-01-01

    The Eurasian wheat belt (EWB) spans a region across Eastern Ukraine, Southern Russia, and Northern Kazakhstan; accounting for nearly 15% of global wheat production. We assessed land surface conditions across the EWB during the early growing season (April–May–June; AMJ) leading up to the 2010 Russian heat wave, and over a longer-term period from 2000 to 2010. A substantial reduction in early season values of the normalized difference vegetation index occurred prior to the Russian heat wave, continuing a decadal decline in early season primary production in the region. In 2010, an anomalously cold winter followed by an abrupt shift to a warmer-than-normal early growing season was consistent with a persistently negative phase of the North Atlantic oscillation (NAO). Regression analyses showed that early season vegetation productivity in the EWB is a function of both the winter (December–January–February; DJF) and AMJ phases of the NAO. Land surface anomalies preceding the heat wave were thus consistent with highly negative values of both the DJF NAO and AMJ NAO in 2010. (letter)

  19. North Atlantic Oscillation and moisture transport towards the Iberian Peninsula during winter

    Science.gov (United States)

    Ordóñez, Paulina; Liberato, Margarida L. R.; Gouveia, Célia; Trigo, Ricardo M.

    2013-04-01

    The North Atlantic Oscillation (NAO) is the major source of interannual variability in winter precipitation over the Iberian Peninsula (IP). Recent works have identified the most important sources of moisture that supply the IP during different seasons of the year, including the nearby western Mediterranean and the tropical-subtropical North Atlantic corridor that extends from the Gulf of Mexico to the IP, and the IP itself (Gimeno et al., 2010). However, although rainfall is directly related to the moisture supply, the relationship between the water vapor transported towards IP and the NAO phase remains unclear. In this work the moisture transport towards IP was analyzed using a Lagrangian diagnosis method, which relies on the Lagrangian particle dispersion model FLEXPART. This methodology computes budgets of evaporation minus precipitation (E-P) by evaluating changes in the specific humidity along back-trajectories. Here we have computed (for each day) the evolution of moisture of the particles bound for Iberia up to 10 days prior to their arrival. The analysis was constrained to the winter (DJF) season, responsible for the largest fraction of precipitation, for the 20 years of ECMWF Reanalyses ERA40 dataset from 1980 to 2000. The contribution of the NAO phase on the water budgets is examined using composites of the obtained (E - P) fields for the 5 most extreme positive and negative NAO years of the study period. Results confirm that the IP is dominated by positive (negative) E-P anomalies during positive (negative) NAO phase. Additionally an anomalous water vapor sink (source) region located approximately over the Gulf Stream is found during positive (negative) NAO phase. Gimeno L., Nieto R., Trigo R.M. , Vicente-Serrano S.M, Lopes-Moreno J.I., (2010) "Where does the Iberian Peninsula moisture come from? An answer based on a Lagrangian approach". J. Hydrometeorology, 11, 421-436 DOI: 10.1175/2009JHM1182.1.

  20. Decadal modulation of the ENSO-East Asian winter monsoon relationship by the Atlantic Multidecadal Oscillation

    Science.gov (United States)

    Geng, Xin; Zhang, Wenjun; Stuecker, Malte F.; Liu, Peng; Jin, Fei-Fei; Tan, Guirong

    2017-10-01

    This work investigates the decadal modulation of the El Niño-Southern Oscillation (ENSO)-East Asian winter monsoon (EAWM) relationship by the Atlantic Multidecadal Oscillation (AMO). A stable ENSO-EAWM relationship is found during the positive AMO phase but not during the negative phase. While the impact of El Niño events on the EAWM does not depend on the AMO phase, a different picture is observed for La Niña events. The La Niña boreal winter season coincides with a strengthened EAWM during a positive AMO phase and a weakened EAWM during a negative AMO phase. We suggest that the AMO's modulating effect mainly comprises two pathways that influence ENSO's impact on the EAWM. On one hand, when La Niña coincides with a positive AMO, the warm SST anomalies over the western North Pacific (WNP) are amplified both in intensity and spatial extent, which favors strengthened WNP cyclonic anomalies and an enhanced EAWM. During La Niña with a negative AMO, only very weak SST anomalies occur over the WNP with reduced WNP cyclonic anomalies that are confined to the tropics, thus having little effect on the EAWM. On the other hand, an eastward-propagating Rossby wavetrain across the mid-high latitudes of Eurasia during a warm AMO phase strengthens the Siberian high and thus leads to a strengthened EAWM, while during a cold AMO phase the Siberian high is weakened, leading to a reduced EAWM. In contrast, El Niño and its associated atmospheric responses are relatively strong and stable, independent of the AMO phase. These results carry important implications to the seasonal-to-interannual predictability associated with ENSO.

  1. Winter North Atlantic Oscillation impact on European precipitation and drought under climate change

    Science.gov (United States)

    Tsanis, I.; Tapoglou, E.

    2018-01-01

    The North Atlantic Oscillation (NAO) is responsible for the climatic variability in the Northern Hemisphere, in particular, in Europe and is related to extreme events, such as droughts. The purpose of this paper is to study the correlation between precipitation and winter (December-January-February-March (DJFM)) NAO both for the historical period (1951-2000) and two future periods (2001-2050 and 2051-2100). NAO is calculated for these three periods by using sea level pressure, while precipitation data from seven climate models following the representative concentration pathway (RCP) 8.5 are also used in this study. An increasing trend in years with positive DJFM NAO values in the future is defined by this data, along with higher average DJFM NAO values. The correlation between precipitation and DJFM NAO is high, especially in the Northern (high positive) and Southern Europe (high negative). Therefore, higher precipitation in Northern Europe and lower precipitation in Southern Europe are expected in the future. Cross-spectral analysis between precipitation and DJFM NAO time series in three different locations in Europe revealed the best coherence in a dominant cycle between 3 and 4 years. Finally, the maximum drought period in terms of consecutive months with drought is examined in these three locations. The results can be used for strategic planning in a sustainable water resources management plan, since there is a link between drought events and NAO.

  2. Spatial patterns of North Atlantic Oscillation influence on mass balance variability of European glaciers

    Directory of Open Access Journals (Sweden)

    B. Marzeion

    2012-06-01

    Full Text Available We present and validate a set of minimal models of glacier mass balance variability. The most skillful model is then applied to reconstruct 7735 individual time series of mass balance variability for all glaciers in the European Alps and Scandinavia. Subsequently, we investigate the influence of atmospheric variability associated with the North Atlantic Oscillation (NAO on the glaciers' mass balances.

    We find a spatial coherence in the glaciers' sensitivity to NAO forcing which is caused by regionally similar mechanisms relating the NAO forcing to the mass balance: in southwestern Scandinavia, winter precipitation causes a correlation of mass balances with the NAO. In northern Scandinavia, temperature anomalies outside the core winter season cause an anti-correlation between NAO and mass balances. In the western Alps, both temperature and winter precipitation anomalies lead to a weak anti-correlation of mass balances with the NAO, while in the eastern Alps, the influences of winter precipitation and temperature anomalies tend to cancel each other, and only on the southern side a slight anti-correlation of mass balances with the NAO prevails.

  3. Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics

    Science.gov (United States)

    Zipkin, Elise F.; Gardner, Beth; Gilbert, Andrew T.; O'Connell, Allan F.; Royle, J. Andrew; Silverman, Emily D.

    2010-01-01

    Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species-habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate

  4. Life history tactics shape amphibians' demographic responses to the North Atlantic Oscillation.

    Science.gov (United States)

    Cayuela, Hugo; Joly, Pierre; Schmidt, Benedikt R; Pichenot, Julian; Bonnaire, Eric; Priol, Pauline; Peyronel, Olivier; Laville, Mathias; Besnard, Aurélien

    2017-11-01

    Over the last three decades, climate abnormalities have been reported to be involved in biodiversity decline by affecting population dynamics. A growing number of studies have shown that the North Atlantic Oscillation (NAO) influences the demographic parameters of a wide range of plant and animal taxa in different ways. Life history theory could help to understand these different demographic responses to the NAO. Indeed, theory states that the impact of weather variation on a species' demographic traits should depend on its position along the fast-slow continuum. In particular, it is expected that NAO would have a higher impact on recruitment than on adult survival in slow species, while the opposite pattern is expected occur in fast species. To test these predictions, we used long-term capture-recapture datasets (more than 15,000 individuals marked from 1965 to 2015) on different surveyed populations of three amphibian species in Western Europe: Triturus cristatus, Bombina variegata, and Salamandra salamandra. Despite substantial intraspecific variation, our study revealed that these three species differ in their position on a slow-fast gradient of pace of life. Our results also suggest that the differences in life history tactics influence amphibian responses to NAO fluctuations: Adult survival was most affected by the NAO in the species with the fastest pace of life (T. cristatus), whereas recruitment was most impacted in species with a slower pace of life (B. variegata and S. salamandra). In the context of climate change, our findings suggest that the capacity of organisms to deal with future changes in NAO values could be closely linked to their position on the fast-slow continuum. © 2017 John Wiley & Sons Ltd.

  5. The Spatial and Temporal Variability of the North Atlantic Oscillation Recorded in Ice Core Major Ion Time Series

    Science.gov (United States)

    Wawrzeniak, T. L.; Wake, C. P.; Fischer, H.; Fisher, D. A.; Schwikowski, M.

    2006-05-01

    The North Atlantic Oscillation represents a significant mode of atmospheric variability for the Arctic and sub- Artic climate system. Developing a longer-term record of the spatial and temporal variability of the NAO could improve our understanding of natural climate variability in the region. Previous work has shown a significant relationship between Greenland ice core records and the NAO. Here, we have compared sea-salt and dust records from nine ice cores around the Arctic region to sea level pressure and NAO indices to evaluate the extent to which these ice cores can be used to reconstruct the NAO.

  6. Beta, but not gamma, band oscillations index visual form-motion integration.

    Directory of Open Access Journals (Sweden)

    Charles Aissani

    Full Text Available Electrophysiological oscillations in different frequency bands co-occur with perceptual, motor and cognitive processes but their function and respective contributions to these processes need further investigations. Here, we recorded MEG signals and seek for percept related modulations of alpha, beta and gamma band activity during a perceptual form/motion integration task. Participants reported their bound or unbound perception of ambiguously moving displays that could either be seen as a whole square-like shape moving along a Lissajou's figure (bound percept or as pairs of bars oscillating independently along cardinal axes (unbound percept. We found that beta (15-25 Hz, but not gamma (55-85 Hz oscillations, index perceptual states at the individual and group level. The gamma band activity found in the occipital lobe, although significantly higher during visual stimulation than during base line, is similar in all perceptual states. Similarly, decreased alpha activity during visual stimulation is not different for the different percepts. Trial-by-trial classification of perceptual reports based on beta band oscillations was significant in most observers, further supporting the view that modulation of beta power reliably index perceptual integration of form/motion stimuli, even at the individual level.

  7. Delta, theta, beta, and gamma brain oscillations index levels of auditory sentence processing.

    Science.gov (United States)

    Mai, Guangting; Minett, James W; Wang, William S-Y

    2016-06-01

    A growing number of studies indicate that multiple ranges of brain oscillations, especially the delta (δ, processing. It is not clear, however, how these oscillations relate to functional processing at different linguistic hierarchical levels. Using scalp electroencephalography (EEG), the current study tested the hypothesis that phonological and the higher-level linguistic (semantic/syntactic) organizations during auditory sentence processing are indexed by distinct EEG signatures derived from the δ, θ, β, and γ oscillations. We analyzed specific EEG signatures while subjects listened to Mandarin speech stimuli in three different conditions in order to dissociate phonological and semantic/syntactic processing: (1) sentences comprising valid disyllabic words assembled in a valid syntactic structure (real-word condition); (2) utterances with morphologically valid syllables, but not constituting valid disyllabic words (pseudo-word condition); and (3) backward versions of the real-word and pseudo-word conditions. We tested four signatures: band power, EEG-acoustic entrainment (EAE), cross-frequency coupling (CFC), and inter-electrode renormalized partial directed coherence (rPDC). The results show significant effects of band power and EAE of δ and θ oscillations for phonological, rather than semantic/syntactic processing, indicating the importance of tracking δ- and θ-rate phonetic patterns during phonological analysis. We also found significant β-related effects, suggesting tracking of EEG to the acoustic stimulus (high-β EAE), memory processing (θ-low-β CFC), and auditory-motor interactions (20-Hz rPDC) during phonological analysis. For semantic/syntactic processing, we obtained a significant effect of γ power, suggesting lexical memory retrieval or processing grammatical word categories. Based on these findings, we confirm that scalp EEG signatures relevant to δ, θ, β, and γ oscillations can index phonological and semantic/syntactic organizations

  8. Evidence for the role of the Atlantic multidecadal oscillation and the ocean heat uptake in hiatus prediction

    Science.gov (United States)

    Pasini, Antonello; Triacca, Umberto; Attanasio, Alessandro

    2017-08-01

    The recent hiatus in global temperature at the surface has been analysed by several studies, mainly using global climate models. The common accepted picture is that since the late 1990s, the increase in anthropogenic radiative forcings has been counterbalanced by other factors, e.g., a decrease in natural forcings, augmented ocean heat storage and negative phases of ocean-atmosphere-coupled oscillation patterns. Here, simple vector autoregressive models are used for forecasting the temperature hiatus in the period 2001-2014. This gives new insight into the problem of understanding the ocean contribution (in terms of heat uptake and atmosphere-ocean-coupled oscillations) to the appearance of this recent hiatus. In particular, considering data about the ocean heat content until a depth of 700 m and the Atlantic multidecadal oscillation is necessary for correctly forecasting the hiatus, so catching both trend and interannual variability. Our models also show that the ocean heat uptake is substantially driven by the natural component of the total radiative forcing at a decadal time scale, confining the importance of the anthropogenic influences to a longer range warming of the ocean.

  9. Quality Index Method (QIM) scheme developed for farmed Atlantic salmon ( Salmo salar )

    DEFF Research Database (Denmark)

    Sveinsdóttir, K.; Hyldig, Grethe; Martinsdóttir, E.

    2003-01-01

    The aim of the study was to develop 'Quality Index Method (QIM) scheme for raw, farmed Atlantic salmon (Salmo salar) and to evaluate the scheme. in a shelf life study. QIM is based on the evaluation of key parameters in the deterioration of seafood's. Demerit points are assigned to selected...... parameters according to their importance and a Quality Index (QI) is established by cumulating the resulting scores. The maximum storage time in ice was determined with Quantitative Descriptive Analysis (QDA) of the salmon after cooking and found to be 20-21 days. This was used as a reference to enable...... prediction of the remaining storage time of raw salmon in ice with QIM. The calculated QI evolved linearly with storage time in ice (QI=0.82x (days in ice)+0.18, R-2=0.97). Individual salmon varied in QI within each storage day. However, the multivariate analysis (PLS1) demonstrated that storage time could...

  10. Geochemistry of Slow-Growing Corals: Reconstructing Sea Surface Temperature, Salinity and the North Atlantic Oscillation

    Science.gov (United States)

    2007-06-01

    Number 8, October 1989) The island of Bermuda (64°W, 32°N) (Fig. 1.3) located in the western sub- tropical Atlantic is an excellent location for examining...lobata at Clipperton Atoll, Coral Reefv, 18, 13-27, 1999. Lough, J. M., A strategy to improve the contribution of coral data to high-resolution...to evaluate winter Sr/Ca. The island of Bermuda (64°W, 32°N) is located in the Sargasso Sea in the sub-tropical North Atlantic. This site is

  11. Orbital forcing of the late Pleistocene boreal summer monsoon: Links to North Atlantic cold events and El Nino; Southern Oscillation. Geologica Ultraiectina (313)

    NARCIS (Netherlands)

    Ziegler, M.

    2009-01-01

    This thesis revolves about the timing of precession-related variations in the boreal summer monsoon and the impact of North Atlantic cold events and the El Nino Southern Oscillation on this timing. Transient climate modelling experiments indicate that the intensity of the Northern Hemisphere summer

  12. A switch in the Atlantic Oscillation correlates with inter-annual changes in foraging location and food habits of Macaronesian shearwaters (Puffinus baroli) nesting on two islands of the sub-tropical Atlantic Ocean

    Science.gov (United States)

    Ramos, Jaime A.; Isabel Fagundes, Ana; Xavier, José C.; Fidalgo, Vera; Ceia, Filipe R.; Medeiros, Renata; Paiva, Vitor H.

    2015-10-01

    Changes in oceanographic conditions, shaped by changes in large-scale atmospheric phenomena such as the North Atlantic Oscillation (NAO), alters the structure and functioning of marine ecosystems. Such signals are readily captured by marine top predators, given that their use of foraging habitats and diets change when the NAO changes. In this study we assessed sexual, seasonal and annual (2010/11-2012/13) differences in diet, trophic and isotopic niche (using δ15N and δ13C values of whole blood, 1st primary, 8th secondary and breast feathers), foraging locations and oceanographic variation within foraging areas for Macaronesian shearwaters' (Puffinus baroli) during two years of contrasting NAO values, and between two sub-tropical islands 330 km apart in the North Atlantic Ocean, Cima Islet and Selvagem Grande. These two locations provide contrasting oceanographic foraging regimes for the birds, because the second colony is much closer to the African coast (375 vs 650 km), and, therefore, to the upwelling area of the Canary Current. There was a marked environmental perturbation in 2010/2011, related with a negative NAO Index and lower marine productivity (lower concentration of Chlorophyll a). This event corresponded to the Macaronesian shearwaters feeding farther north and west, which was readily seen in change of both δ15N and δ13C values, and in a higher intake of cephalopods. Diet and stable isotopes did not differ between sexes. Regurgitation analysis indicate a dominance of cephalopods in both islands, but prey fish were important for Selvagem Grande in 2012 and cephalopods for Cima Islet in 2011. Both δ15N and δ13C values were significantly higher for Cima Islet than for Selvagem Grande, irrespective of year, season and tissue sampled. SIBER analysis showed smaller isotopic niches for the breeding period. Our study suggests that during years of poor environmental conditions Macaronesian shearwaters shift their foraging location to more pelagic waters

  13. Observed linkages between the northern annular mode/North Atlantic Oscillation, cloud incidence, and cloud radiative forcing

    Science.gov (United States)

    Li, Ying; Thompson, David W. J.; Huang, Yi; Zhang, Minghong

    2014-03-01

    The signature of the northern annular mode/North Atlantic Oscillation (NAM/NAO) in the vertical and horizontal distribution of tropospheric cloudiness is investigated in CloudSat and CALIPSO data from June 2006 to April 2011. During the Northern Hemisphere winter, the positive polarity of the NAM/NAO is marked by increases in zonally averaged cloud incidence north of ~60°N, decreases between ~25 and 50°N, and increases in the subtropics. The tripolar-like anomalies in cloud incidence associated with the NAM/NAO are largest over the North Atlantic Ocean basin/Middle East and are physically consistent with the NAM/NAO-related anomalies in vertical motion. Importantly, the NAM/NAO-related anomalies in tropospheric cloud incidence lead to significant top of atmosphere cloud radiative forcing anomalies that are comparable in amplitude to those associated with the NAM/NAO-related temperature anomalies. The results provide observational evidence that the most prominent pattern of Northern Hemisphere climate variability is significantly linked to variations in cloud radiative forcing. Implications for two-way feedback between extratropical dynamics and cloud radiative forcing are discussed.

  14. The impact of the winter North Atlantic Oscillation on the frequency of spring dust storms over Tarim Basin in northwest China in the past half-century

    International Nuclear Information System (INIS)

    Zhao Yong; Huang Anning; Zhou Yang; Huang Ying; Zhu Xinsheng

    2013-01-01

    The relationship between the frequency of spring dust storms over Tarim Basin in northwest China and the winter North Atlantic Oscillation (NAO) is investigated by using the observed dust storm frequency (DSF) and the 10 m wind velocity at 36 stations in Tarim Basin and the National Centers for Environment Prediction/National Center for Atmospheric Research reanalysis data for the period 1961–2007. The spring DSF (winter NAO) index shows a clear decreasing (increasing) linear trend over 1961–2007. The winter NAO correlates well with the subsequent spring DSF over Tarim Basin on both interannual and interdecadal time scales and its interannual to interdecadal variation plays an important role in the spring DSF. Two possible physical mechanisms are identified. One is related to the large scale anomalous circulations in spring in the middle to high troposphere modulated by the winter NAO, providing the background of dynamical conditions for the dust storm occurrences. The other is related to the shifts in the local horizontal sea level pressure (SLP) gradients and 10 m wind speed, corresponding to changes in the large scale circulations in spring. The decrease in the local 10 m wind speed due to the reduced horizontal SLP gradients over Tarim Basin during the strong winter NAO years contributes to the decline of the DSF in the subsequent spring. (letter)

  15. Oscillation of tissue oxygen index in non-exercising muscle during exercise.

    Science.gov (United States)

    Yano, T; Afroundeh, R; Shirakawa, K; Lian, C-S; Shibata, K; Xiao, Z; Yunoki, T

    2015-09-01

    The purpose of the present study was to examine how oscillation of tissue oxygen index (TOI) in non-exercising exercise is affected during high-intensity and low-intensity exercises. Three exercises were performed with exercise intensities of 30% and 70% peak oxygen uptake (Vo(2)peak) for 12 min and with exercise intensity of 70% Vo(2)peak for 30 s. TOI in non-exercising muscle (biceps brachii) during the exercises for 12 min was determined by nearinfrared spectroscopy. TOI in the non-exercising muscle during the exercises was analyzed by fast Fourier transform (FFT) to obtain power spectra density (PSD). The frequency at which maximal PSD appeared (Fmax) during the exercise with 70% Vo(2)peak for 12 min (0.00477 ± 0.00172 Hz) was significantly lower than that during the exercise with 30% Vo2peak for 12 min (0.00781 ± 0.00338 Hz). There were significant differences in blood pH and blood lactate between the exercise with 70% Vo(2)peak and the exercise with 30% Vo(2)peak. It is concluded that TOI in nonexercising muscle oscillates during low-intensity exercise as well as during high-intensity exercise and that the difference in Fmax between the two exercises is associated with the difference in increase in blood lactate derived from the exercise.

  16. The influence of sea surface temperature anomalies on low-frequency variability of the North Atlantic Oscillation

    Energy Technology Data Exchange (ETDEWEB)

    Manganello, Julia V. [Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States)

    2008-05-15

    The influence of sea surface temperature anomalies (SSTA) on multi-year persistence of the North Atlantic Oscillation (NAO) during the second half of the twentieth century is investigated using the Center for Ocean-Land-Atmosphere Studies (COLA) Atmospheric GCM (AGCM) with an emphasis on isolating the geographic location of the SSTA that produce this influence. The present study focuses on calculating the atmospheric response to the SSTA averaged over 1988-1995 (1961-1968) corresponding to the observed period of strong persistence of the positive (negative) phase of the decadal NAO. The model response to the global 1988-1995 average SSTA shows a statistically significant large-scale pattern characteristic of the positive phase of the NAO. Forcing with the global 1961-1968 average SSTA generates a NAO of the opposite polarity compared to observations. However, all large-scale features both in the model and observations during this period are weaker in magnitude and less significant compared to 1988-1995. Additional idealized experiments show that over the northern center of the NAO the non-linear component of the forced response appears to be quite important and acts to enhance the positive NAO signal. On the other hand, over the southern center where the model response is the strongest, it is also essentially linear. The 1988-1995 average SSTA restricted to the western tropical Pacific region produce a positive NAO remarkably similar in structure but stronger in magnitude than the model response to the global and tropical Indo-Pacific 1988-1995 forcing. A 200-hPa geopotential height response in these experiments shows a positive anomaly over the southern center of the NAO embedded in the Rossby wave trains propagating from the western tropical Pacific. Indian Ocean SSTA lead to much weaker positive NAO primarily through the effect on its northern center. SST forcing confined to the North Atlantic north of equator does not produce a response statistically different

  17. Trends of precipitation characteristics in the Czech Republic over 1961–2012, their spatial patterns and links to temperature and the North Atlantic Oscillation

    Czech Academy of Sciences Publication Activity Database

    Beranová, Romana; Kyselý, Jan

    (2017) ISSN 0899-8418 R&D Projects: GA ČR(CZ) GA16-04676S Institutional support: RVO:68378289 Keywords : precipitation * trend analysis * spatial pattern * temperature * the North Atlantic Oscillation * the Czech Republic Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 3.760, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/joc.5392/full

  18. Development of the Wintertime Sr/Ca-SST Record from Red Sea Corals as a Proxy for the North Atlantic Oscillation

    Science.gov (United States)

    Bernstein, W. N.; Hughen, K. A.

    2009-12-01

    -weekly temporal resolution for downcore SST reconstructions over the past 140 years, which will be used to evaluate the ability of the coral proxies to capture instrumental NAO variability. We expect that this winter Sr/Ca record will exhibit coherence with the NAO similar to that evident between Red Sea instrumental SST and the NAO index. Future work will involve construction of an NAO record back ~400 years, using the multi-core Sr/Ca-SST calibration applied to a combination of new records from modern and fossil coral material. This record will be examined to identify changes in NAO behavior as a function of frequency, and to compare frequency-dependent NAO variability between periods of relatively warm and cold hemispheric climate. This analysis will allow us to test the hypothesized link between NAO behavior and mean climate conditions, and if confirmed, improve predictions regarding the role of the NAO in impending climate change. References Hurrell, J. et al., 2003, in The North Atlantic Oscillation: Climatic Significance and Environmental Impact, 1-36 (A.G.U., Washington, D.C.). Visbeck, M. et al., 2001, Proc. Nat. Acad. Sci. 98, 12876-12877.

  19. Variability of the North Atlantic Oscillation over the past 5,200 years

    DEFF Research Database (Denmark)

    Olsen, Jesper; Anderson, N. John; Knudsen, Mads Faurschou

    2012-01-01

    the index is positive, Europe and the eastern US are mild and wet, whereas Greenland and northern Canada are cold and dry. A negative index is associated with the reverse pattern. Reconstructions of the NAO have so far been limited to the past 900 years(3). Here we analyse a 5,200-year-long, high......-resolution lake sediment record from southwestern Greenland to reconstruct lake hypolimnic anoxia, and link the results to an existing reconstruction of the NAO index from tree rings and speleothems(3). Using the relationship between the two records, we find that around 4,500 and 650 years ago-around the end....... However, the onset of the Medieval Climate Anomaly was not associated with any notable changes in the NAO....

  20. Influences of North Atlantic Oscillation (NAO) on warm season temperature and crop yields in the southwestern US

    Science.gov (United States)

    Myoung, B.; Kim, S.; Kim, J.; Kafatos, M.

    2013-12-01

    Despite advancements in agricultural technology, agricultural productivity remains vulnerable to extreme meteorological conditions. This study has found significant impacts of North Atlantic Oscillation (NAO) on extreme temperatures and in turn on crop yields in the Southwestern United States (SW US) region. Analyses of multi-year data of observed temperatures and simulated maize yields reveal that NAO affects positively the daily temperature maxima and minima in the green-up periods (March-June) and that the response of maize yields to NAO varies according to the climatological mean temperatures. In warmer regions, a combination of above-normal NAO in the planting periods and below-normal NAO in the growing periods is favorable for high maize yields by reducing extremely cold days during the planting periods and extremely hot days in the later periods, respectively. In colder regions, continuously above-normal NAO conditions favor higher yields via above normal thermal conditions. Results in this study suggest that NAO predictions can benefit agricultural planning in SW US.

  1. The Mediterranean Oscillation Teleconnection Index: Station-Based versus Principal Component Paradigms

    Directory of Open Access Journals (Sweden)

    Francisco Criado-Aldeanueva

    2013-01-01

    Full Text Available Two different paradigms of the Mediterranean Oscillation (MO teleconnection index have been compared in this work: station-based definitions obtained by the difference of some climate variable between two selected points in the eastern and western basins (i.e., Algiers and Cairo, Gibraltar and Israel, Marseille and Jerusalem, or south France and Levantine basin and the principal component (PC approach in which the index is obtained as the time series of the first mode of normalised sea level pressure anomalies across the extended Mediterranean region. Interannual to interdecadal precipitation (P, evaporation (E, E-P, and net heat flux have been correlated with the different MO indices to compare their relative importance in the long-term variability of heat and freshwater budgets over the Mediterranean Sea. On an annual basis, the PC paradigm is the most effective tool to assess the effect of the large-scale atmospheric forcing in the Mediterranean Sea because the station-based indices exhibit a very poor correlation with all climatic variables and only influence a reduced fraction of the basin. In winter, the station-based indices highly improve their ability to represent the atmospheric forcing and results are fairly independent of the paradigm used.

  2. Observations of inertial oscillations affected by mesoscale activity in the Northeast Atlantic Ocean

    Science.gov (United States)

    Aguiar-González, B.; Hormazábal, S.; Rodríguez-Santana, A.; Cisneros-Aguirre, J.; Martínez-Marrero, A.

    2012-04-01

    Observations of surface drifters launched over the continental slope of Portugal (Bay of Setúbal) are analyzed with the Rotary Wavelet Spectrum Method to study the contribution of mesoscale activity to near-inertial variability. Drifter data used here are part of the MREA04 (Maritime Rapid Environmental Assessment 2004) sea trial carried out by the NATO Undersea Research Centre (NURC) off the west coast of Portugal. Altimetry data from AVISO on a 1/3° Mercator grid are used to compute vertical relative vorticity (ζ) maps and track near-inertial variability along the drifter records. Subsequently, the local Coriolis (f) and effective Coriolis (feff = f + 1/2ζ) frequencies are estimated for every drifter position. In this work we take a special interest in the area of Cape St. Vicent where a remarkable blue shift of near-inertial oscillations is observed in association with a cyclonic eddy migrating northward along the Portuguese coast. Results of the Rotary Wavelet Method highlight the consistency of near-inertial variability observed in the drifter records with the subinertial geostrophic activity computed with altimetry data.

  3. Summer monsoon rainfall variability over North East regions of India and its association with Eurasian snow, Atlantic Sea Surface temperature and Arctic Oscillation

    Science.gov (United States)

    Prabhu, Amita; Oh, Jaiho; Kim, In-won; Kripalani, R. H.; Mitra, A. K.; Pandithurai, G.

    2017-10-01

    This observational study during the 29-year period from 1979 to 2007 evaluates the potential role of Eurasian snow in modulating the North East-Indian Summer Monsoon Rainfall with a lead time of almost 6 months. This link is manifested by the changes in high-latitude atmospheric winter snow variability over Eurasia associated with Arctic Oscillation (AO). Excessive wintertime Eurasian snow leads to an anomalous cooling of the overlying atmosphere and is associated with the negative mode of AO, inducing a meridional wave-train descending over the tropical north Atlantic and is associated with cooling of this region. Once the cold anomalies are established over the tropical Atlantic, it persists up to the following summer leading to an anomalous zonal wave-train further inducing a descending branch over NE-India resulting in weak summer monsoon rainfall.

  4. 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

  5. Alpha and theta brain oscillations index dissociable processes in spoken word recognition.

    Science.gov (United States)

    Strauß, Antje; Kotz, Sonja A; Scharinger, Mathias; Obleser, Jonas

    2014-08-15

    Slow neural oscillations (~1-15 Hz) are thought to orchestrate the neural processes of spoken language comprehension. However, functional subdivisions within this broad range of frequencies are disputed, with most studies hypothesizing only about single frequency bands. The present study utilizes an established paradigm of spoken word recognition (lexical decision) to test the hypothesis that within the slow neural oscillatory frequency range, distinct functional signatures and cortical networks can be identified at least for theta- (~3-7 Hz) and alpha-frequencies (~8-12 Hz). Listeners performed an auditory lexical decision task on a set of items that formed a word-pseudoword continuum: ranging from (1) real words over (2) ambiguous pseudowords (deviating from real words only in one vowel; comparable to natural mispronunciations in speech) to (3) pseudowords (clearly deviating from real words by randomized syllables). By means of time-frequency analysis and spatial filtering, we observed a dissociation into distinct but simultaneous patterns of alpha power suppression and theta power enhancement. Alpha exhibited a parametric suppression as items increasingly matched real words, in line with lowered functional inhibition in a left-dominant lexical processing network for more word-like input. Simultaneously, theta power in a bilateral fronto-temporal network was selectively enhanced for ambiguous pseudowords only. Thus, enhanced alpha power can neurally 'gate' lexical integration, while enhanced theta power might index functionally more specific ambiguity-resolution processes. To this end, a joint analysis of both frequency bands provides neural evidence for parallel processes in achieving spoken word recognition. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. 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

  7. Brain Oscillations Elicited by the Cold Pressor Test: A Putative Index of Untreated Essential Hypertension

    Directory of Open Access Journals (Sweden)

    Christos Papageorgiou

    2017-01-01

    Full Text Available Objective. Essential hypertension is associated with reduced pain sensitivity of unclear aetiology. This study explores this issue using the Cold Pressor Test (CPT, a reliable pain/stress model, comparing CPT-related EEG activity in first episode hypertensives and controls. Method. 22 untreated hypertensives and 18 matched normotensives underwent 24-hour ambulatory blood pressure monitoring (ABPM. EEG recordings were taken before, during, and after CPT exposure. Results. Significant group differences in CPT-induced EEG oscillations were covaried with the most robust cardiovascular differentiators by means of a Canonical Analysis. Positive correlations were noted between ABPM variables and Delta (1–4 Hz oscillations during the tolerance phase; in high-alpha (10–12 Hz oscillations during the stress unit and posttest phase; and in low-alpha (8–10 Hz oscillations during CPT phases overall. Negative correlations were found between ABPM variables and Beta2 oscillations (16.5–20 Hz during the posttest phase and Gamma (28.5–45 Hz oscillations during the CPT phases overall. These relationships were localised at several sites across the cerebral hemispheres with predominance in the right hemisphere and left frontal lobe. Conclusions. These findings provide a starting point for increasing our understanding of the complex relationships between cerebral activation and cardiovascular functioning involved in regulating blood pressure changes.

  8. Brain Oscillations Elicited by the Cold Pressor Test: A Putative Index of Untreated Essential Hypertension.

    Science.gov (United States)

    Papageorgiou, Christos; Manios, Efstathios; Tsaltas, Eleftheria; Koroboki, Eleni; Alevizaki, Maria; Angelopoulos, Elias; Dimopoulos, Meletios-Athanasios; Papageorgiou, Charalabos; Zakopoulos, Nikolaos

    2017-01-01

    Essential hypertension is associated with reduced pain sensitivity of unclear aetiology. This study explores this issue using the Cold Pressor Test (CPT), a reliable pain/stress model, comparing CPT-related EEG activity in first episode hypertensives and controls. 22 untreated hypertensives and 18 matched normotensives underwent 24-hour ambulatory blood pressure monitoring (ABPM). EEG recordings were taken before, during, and after CPT exposure. Significant group differences in CPT-induced EEG oscillations were covaried with the most robust cardiovascular differentiators by means of a Canonical Analysis. Positive correlations were noted between ABPM variables and Delta (1-4 Hz) oscillations during the tolerance phase; in high-alpha (10-12 Hz) oscillations during the stress unit and posttest phase; and in low-alpha (8-10 Hz) oscillations during CPT phases overall. Negative correlations were found between ABPM variables and Beta2 oscillations (16.5-20 Hz) during the posttest phase and Gamma (28.5-45 Hz) oscillations during the CPT phases overall. These relationships were localised at several sites across the cerebral hemispheres with predominance in the right hemisphere and left frontal lobe. These findings provide a starting point for increasing our understanding of the complex relationships between cerebral activation and cardiovascular functioning involved in regulating blood pressure changes.

  9. Multi-scale approach to Euro-Atlantic climatic cycles based on phenological time series, air temperatures and circulation indexes.

    Science.gov (United States)

    Mariani, Luigi; Zavatti, Franco

    2017-09-01

    The spectral periods in North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO) and El Nino Southern Oscillation (ENSO) were analyzed and has been verified how they imprint a time series of European temperature anomalies (ETA), two European temperature time series and some phenological series (dates of cherry flowering and grapevine harvest). Such work had as reference scenario the linear causal chain MCTP (Macroscale Circulation→Temperature→Phenology of crops) that links oceanic and atmospheric circulation to surface air temperature which in its turn determines the earliness of appearance of phenological phases of plants. Results show that in the three segments of the MCTP causal chain are present cycles with the following central period in years (the % of the 12 analyzed time series interested by these cycles are in brackets): 65 (58%), 24 (58%), 20.5 (58%), 13.5 (50%), 11.5 (58%), 7.7 (75%), 5.5 (58%), 4.1 (58%), 3 (50%), 2.4 (67%). A comparison with short term spectral peaks of the four El Niño regions (nino1+2, nino3, nino3.4 and nino4) show that 10 of the 12 series are imprinted by periods around 2.3-2.4yr while 50-58% of the series are imprinted by El Niño periods of 4-4.2, 3.8-3.9, 3-3.1years. The analysis highlights the links among physical and biological variables of the climate system at scales that range from macro to microscale whose knowledge is crucial to reach a suitable understanding of the ecosystem behavior. The spectral analysis was also applied to a time series of spring - summer precipitation in order to evaluate the presence of peaks common with other 12 selected series with result substantially negative which brings us to rule out the existence of a linear causal chain MCPP (Macroscale Circulation→Precipitation→Phenology). Copyright © 2017 Elsevier B.V. All rights reserved.

  10. The changing relationship between the December North Atlantic Oscillation and the following February East Asian trough before and after the late 1980s

    Science.gov (United States)

    Feng, Guolin; Zou, Meng; Qiao, Shaobo; Zhi, Rong; Gong, Zhiqiang

    2018-03-01

    This study investigates the changing relationship between the December North Atlantic Oscillation (NAO) and the following February East Asian trough (EAT) throughout the past 60 years. We found that the relationship between the December NAO and the following February EAT is significantly enhanced after the late 1980s compared with the period before the late 1980s. The changing relationship mainly results from the enhanced relationship between the December NAO and the following February North Atlantic mid-latitudes' sea surface temperature (SST) anomalies (NAMA) during the same period. During the period after the late 1980s, the persistent positive (negative) NAO pattern from December to the following January contributes to a positive (negative) NAMA, which reaches its maximum magnitude in the following February and excites an anomalous wave train along the North Atlantic and northern Eurasia, and significantly impacts the EAT. During the period before the late 1980s, the positive (negative) NAO pattern during December cannot persist into the following January, and the related positive (negative) NAMA is insignificant during the following February, causing the response of the simultaneous EAT to be insignificant as well. Moreover, there exists a significant impact of the December NAO on the December-January NAMA after the late 1980s, while the December-January NAMA is relatively less affected by the December NAO before the late 1980s. As a result, the simultaneous response of the atmospheric circulation anomalies to the December-January NAMA are evident before the late 1980s, and the positive (negative) NAMA can excite an anomalous wave train along the North Atlantic and northern Eurasia and significantly deepen (shallow) the downstream EAT. By contrast, after involving a feature of atmosphere forcing of SST, the simultaneous feedback of the December-January NAMA on EAT is significantly decreased after the 1980s.

  11. El Niño-Southern Oscillation-based index insurance for floods: Statistical risk analyses and application to Peru

    Science.gov (United States)

    Khalil, Abedalrazq F.; Kwon, Hyun-Han; Lall, Upmanu; Miranda, Mario J.; Skees, Jerry

    2007-10-01

    Index insurance has recently been advocated as a useful risk transfer tool for disaster management situations where rapid fiscal relief is desirable and where estimating insured losses may be difficult, time consuming, or subject to manipulation and falsification. For climate-related hazards, a rainfall or temperature index may be proposed. However, rainfall may be highly spatially variable relative to the gauge network, and in many locations, data are inadequate to develop an index because of short time series and the spatial dispersion of stations. In such cases, it may be helpful to consider a climate proxy index as a regional rainfall index. This is particularly useful if a long record is available for the climate index through an independent source and it is well correlated with the regional rainfall hazard. Here El Niño-Southern Oscillation (ENSO) related climate indices are explored for use as a proxy to extreme rainfall in one of the districts of Peru, Piura. The ENSO index insurance product may be purchased by banks or microfinance institutions to aid agricultural damage relief in Peru. Crop losses in the region are highly correlated with floods but are difficult to assess directly. Beyond agriculture, many other sectors suffer as well. Basic infrastructure is destroyed during the most severe events. This disrupts trade for many microenterprises. The reliability and quality of the local rainfall data are variable. Averaging the financial risk across the region is desirable. Some issues with the implementation of the proxy ENSO index are identified and discussed. Specifically, we explore (1) the reliability of the index at different levels of probability of exceedance of maximum seasonal rainfall, (2) the effect of sampling uncertainties and the strength of the proxy's association to local outcome, (3) the potential for clustering of payoffs, (4) the potential that the index could be predicted with some lead time prior to the flood season, and (5) evidence

  12. The El Niño Southern Oscillation index and wildfire prediction in British Columbia

    NARCIS (Netherlands)

    Xu, Zhen; Kooten, van G.C.

    2014-01-01

    This study investigates the potential to predict monthly wildfires and area burned in British Columbia's interior using El Niño Southern Oscillation (ENSO). The zero-inflated negative binomial (ZINB) and the generalized Pareto (GP) distributions are used, respectively, to account for uncertainty in

  13. Analysis of monthly, winter, and annual temperatures in Zagreb, Croatia, from 1864 to 2010: the 7.7-year cycle and the North Atlantic Oscillation

    Science.gov (United States)

    Sen, Asok K.; Ogrin, Darko

    2016-02-01

    Long instrumental records of meteorological variables such as temperature and precipitation are very useful for studying regional climate in the past, present, and future. They can also be useful for understanding the influence of large-scale atmospheric circulation processes on the regional climate. This paper investigates the monthly, winter, and annual temperature time series obtained from the instrumental records in Zagreb, Croatia, for the period 1864-2010. Using wavelet analysis, the dominant modes of variability in these temperature series are identified, and the time intervals over which these modes may persist are delineated. The results reveal that all three temperature records exhibit low-frequency variability with a dominant periodicity at around 7.7 years. The 7.7-year cycle has also been observed in the temperature data recorded at several other stations in Europe, especially in Northern and Western Europe, and may be linked to the North Atlantic Oscillation (NAO) and/or solar/geomagnetic activity.

  14. Two sides of the same coin: extinctions and originations across the Atlantic/Indian Ocean boundary as consequences of the same climate oscillation

    Directory of Open Access Journals (Sweden)

    Peter R. Teske

    2013-04-01

    Full Text Available Global climate change is correlated not only with variation in extinction rates, but also with speciation rates. However, few mechanisms have been proposed to explain how climate change may have driven the emergence of new evolutionary lineages that eventually became distinct species. Here, we discuss a model of range extension followed by divergence, in which the same climate oscillations that resulted in the extinction of coastal species across the Atlantic/Indian Ocean boundary in southwestern Africa also sowed the seeds of new biodiversity. We present evidence for range extensions and evolutionary divergence from both fossil and genetic data, but also point out the many challenges to the model that need to be addressed before its validity can be accepted.

  15. Inter-Relationship Between Subtropical Pacific Sea Surface Temperature, Arctic Sea Ice Concentration, and the North Atlantic Oscillation in Recent Summers and Winters

    Science.gov (United States)

    Lim, Young-Kwon; Cullather, Richard I.; Nowicki, Sophie M.; Kim, Kyu-Myong

    2017-01-01

    The inter-relationship between subtropical western-central Pacific sea surface temperatures (STWCPSST), sea ice concentration in the Beaufort Sea (SICBS), and the North Atlantic Oscillation (NAO) are investigated for the last 37 summers and winters (1980-2016). Lag-correlation of the STWCPSST×(-1) in spring with the NAO phase and SICBS in summer increases over the last two decades, reaching r = 0.4-0.5 with significance at 5 percent, while winter has strong correlations in approximately 1985-2005. Observational analysis and the atmospheric general circulation model experiments both suggest that STWCPSST warming acts to increase the Arctic geopotential height and temperature in the following season. This atmospheric response extends to Greenland, providing favorable conditions for developing the negative phase of the NAO. SIC and surface albedo tend to decrease over the Beaufort Sea in summer, linked to the positive surface net shortwave flux. Energy balance considering radiative and turbulent fluxes reveal that available energy that can heat surface is larger over the Arctic and Greenland and smaller over the south of Greenland, in response to the STWCPSST warming in spring. XXXX Arctic & Atlantic: Positive upper-level height/T anomaly over the Arctic and Greenland, and a negative anomaly over the central-eastern Atlantic, resembling the (-) phase of the NAO. Pacific: The negative height/T anomaly over the mid-latitudes, along with the positive anomaly over the STWCP, where 1degC warming above climatology is prescribed. Discussion: It is likely that the Arctic gets warm and the NAO is in the negative phase in response to the STWCP warming. But, there are other factors (e.g., internal variability) that contribute to determination of the NAO phase: not always the negative phase of the NAO in the event of STWCP warming (e.g.: recent winters and near neutral NAO in 2017 summer).

  16. Monitoring Drought along the Gulf of Mexico and the Southeastern Atlantic Ocean Using the Coastal Salinity Index

    Science.gov (United States)

    Conrads, P. A.; Rouen, L.; Lackstrom, K.; McCloskey, B.

    2017-12-01

    Coastal droughts have a different dynamic than upland droughts, which are typically characterized by agricultural, hydrologic, meteorological, and (or) socio-economic impacts. Drought uniquely affects coastal ecosystems due to changes in salinity conditions of estuarine creeks and rivers. The location of the freshwater-saltwater interface in surface-water bodies is an important factor in the ecological and socio-economic dynamics of coastal communities. The location of the interface determines the freshwater and saltwater aquatic communities, fisheries spawning habitat, and the freshwater availability for municipal and industrial water intakes. The severity of coastal drought may explain changes in Vibrio bacteria impacts on shellfish harvesting and occurrence of wound infection, fish kills, harmful algal blooms, hypoxia, and beach closures. To address the data and information gap for characterizing coastal drought, a coastal salinity index (CSI) was developed using salinity data. The CSI uses a computational approach similar to the Standardized Precipitation Index (SPI). The CSI is computed for unique time intervals (for example 1-, 6-, 12-, and 24-month) that can characterize the onset and recovery of short- and long-term drought. Evaluation of the CSI indicates that the index can be used for different estuary types (for example: brackish, oligohaline, or mesohaline), for regional comparison between estuaries, and as an index of wet conditions (high freshwater inflow) in addition to drought (saline) conditions. In 2017, three activities in 2017 will be presented that enhance the use and application of the CSI. One, a software package was developed for the consistent computation of the CSI that includes preprocessing of salinity data, filling missing data, computing the CSI, post-processing, and generating the supporting metadata. Two, the CSI has been computed at sites along the Gulf of Mexico (Texas to Florida) and the Southeastern Atlantic Ocean (Florida to

  17. Analysis of South Atlantic Anomaly perturbations on Sentinel-3A Ultra Stable Oscillator. Impact on DORIS phase measurement and DORIS station positioning

    Science.gov (United States)

    Jalabert, Eva; Mercier, Flavien

    2018-07-01

    DORIS measurements rely on the precise knowledge of the embedded oscillator which is called the Ultra Stable Oscillator (DORIS USO). The important radiations in the South Atlantic Anomaly (SAA) perturb the USO behavior by causing rapid frequency variations when the satellite is flying through the SAA. These variations are not taken into account in standard DORIS processing, since the USO is modelled as a third degree polynomial over 7-10 days. Therefore, there are systematic measurements errors when the satellite passes through SAA. In standard GNSS processing, the clock is directly estimated at each epoch. On Sentinel-3A, the GPS receiver and the DORIS receiver use the same USO. It is thus possible to estimate the behavior of the USO using GPS measurements. This estimated USO behavior can be used in the DORIS processing, instead of the third degree polynomial, hence allowing an estimation of the orbit sensitivity to these USO anomalies. This study shows two main results. First, the SAA effect on the DORIS USO is observed well using GPS measurements. Second, the USO behavior observed with GPS can be used to mitigate the SAA effect. Indeed, when used in Sentinel-3A processing, the resulting DORIS orbit shows improved phase measurements and station positioning for stations inside the SAA (Arequipa and Cachoeira). The phase measurements residuals are improved by up to 10 cm, and station vertical positioning (i.e. on the estimated Up component in the North-East-Up station frame) is improved by up to a few centimeters. However, the orbit itself is not sensitive to the correction because only two stations (out of almost 60) are SAA-sensitive on Sentinel-3A.

  18. Impact of ice sheet induced North Atlantic oscillation on East Asian summer monsoon during an interglacial 500,000 years ago

    Energy Technology Data Exchange (ETDEWEB)

    Sundaram, S.; Yin, Q.Z.; Berger, A.; Muri, H. [Universite Catholique de Louvain, Earth and Life Institute (ELI), Georges Lemaitre Centre for Earth and Climate Research (TECLIM), Louvain la Neuve (Belgium)

    2012-09-15

    Marine Isotope Stage (MIS) 13, an interglacial about 500,000 years ago, is unique due to an exceptionally strong East Asia summer monsoon (EASM) occurring in a relatively cool climate with low greenhouse gas concentrations (GHG). This paper attempts to find one of the possible mechanisms for this seeming paradox. Simulations with an Earth System model LOVECLIM show that the presence of ice sheets over North America and Eurasia during MIS-13 induces a positive phase of the winter North Atlantic Oscillation (NAO) like feature. The ocean having a longer memory than the atmosphere, the oceanic anomalies associated with NAO persists until summer. The signals of summer NAO are transmitted to East Asia to reinforce the monsoon there through the stationary waves excited at the Asian Jet entrance. The geopotential height shows clearly a mid-latitude wave train with positive anomalies over the eastern Mediterranean/Caspian Sea and the Okhotsk Sea and a negative anomaly over Lake Baikal. This reinforces the effect of the high-latitude wave train induced independently by the Eurasian ice sheet topography as shown in previous study. These features reinforce the Meiyu front and enhance the precipitation over East Asia. The results obtained from LOVECLIM are further confirmed by an atmospheric general circulation model, ARPEGE. (orig.)

  19. The Role of the North Atlantic Oscillation (NAO) on Recent Greenland Surface Mass Loss and Mass Partitioning

    Science.gov (United States)

    Tedesco, M.; Alexander, P.; Porter, D. F.; Fettweis, X.; Luthcke, S. B.; Mote, T. L.; Rennermalm, A.; Hanna, E.

    2017-12-01

    Despite recent changes in Greenland surface mass losses and atmospheric circulation over the Arctic, little attention has been given to the potential role of large-scale atmospheric processes on the spatial and temporal variability of mass loss and partitioning of the GrIS mass loss. Using a combination of satellite gravimetry measurements, outputs of the MAR regional climate model and reanalysis data, we show that changes in atmospheric patterns since 2013 over the North Atlantic region of the Arctic (NAA) modulate total mass loss trends over Greenland together with the spatial and temporal distribution of mass loss partitioning. For example, during the 2002 - 2012 period, melting persistently increased, especially along the west coast, as a consequence of increased insulation and negative NAO conditions characterizing that period. Starting in 2013, runoff along the west coast decreased while snowfall increased substantially, when NAO turned to a more neutral/positive state. Modeled surface mass balance terms since 1950 indicate that part of the GRACE-period, specifically the period between 2002 and 2012, was exceptional in terms of snowfall over the east and northeast regions. During that period snowfall trend decreased to almost 0 Gt/yr from a long-term increasing trend, which presumed again in 2013. To identify the potential impact of atmospheric patterns on mass balance and its partitioning, we studied the spatial and temporal correlations between NAO and snowfall/runoff. Our results indicate that the correlation between summer snowfall and NAO is not stable during the 1950 - 2015 period. We further looked at changes in patterns of circulation using self organizing maps (SOMs) to identify the atmospheric patterns characterizing snowfall during different periods. We discuss potential implications for past changes and future GCM and RCM simulations.

  20. Cave Conservation Priority Index to Adopt a Rapid Protection Strategy: A Case Study in Brazilian Atlantic Rain Forest

    Science.gov (United States)

    Souza Silva, Marconi; Martins, Rogério Parentoni; Ferreira, Rodrigo Lopes

    2015-02-01

    Cave environments are characterized by possessing specialized fauna living in high environmental stability with limited food conditions. These fauna are highly vulnerable to impacts, because this condition can frequently be easily altered. Moreover, environmental determinants of the biodiversity patterns of caves remain poorly understood and protected. Therefore, the main goal of this work is to propose a cave conservation priority index (CCPi) for a rapid assessment for troglobiotic and troglophile protection. Furthermore, the troglobiotic diversity, distribution and threats have been mapped in the Brazilian Atlantic forest. To propose the CCPi, the human impacts and richness of troglobiotic and troglophile species of 100 caves were associated. Data related to troglomorphic/troglobiotic fauna from another 200 caves were used to map the troglobiotic diversity and distribution. The CCPi reveals extremely high conservation priority for 15 % of the caves, high for 36 % and average for 46 % of the caves. Fourteen caves with extremely high priorities should have urgent conservation and management actions. The geographical distribution of the 221 known troglobiotic/troglomorphic species allowed us to select 19 karst areas that need conservation actions. Seven areas were considered to have urgent priority for conservation actions. The two richest areas correspond to the "iron quadrangle" with iron ore caves (67 spp.) and the "Açungui limestone group" (56 spp.). Both areas have several caves and are important aquifers. The use of the CCPi can prevent future losses because it helps assessors to select caves with priorities for conservation which should receive emergency attention in relation to protection, management and conservation actions.

  1. Variability of the Tropical Ocean Surface Temperatures at Decadal-Multidecadal Timescales. Part I: The Atlantic Ocean.

    Science.gov (United States)

    Mehta, Vikram M.

    1998-09-01

    Gridded time series from the Global Ocean Surface Temperature Atlas were analyzed with a variety of techniques to identify spatial structures and oscillation periods of the tropical Atlantic sea surface temperature (SST) variations at decadal timescales, and to develop physical interpretations of statistical patterns of decadal SST variations. Each time series was 110 yr (1882-1991) long. The tropical Atlantic SST variations were compared with decadal variations in a 74-yr-long (1912-85) north Nordeste Brazil rainfall time series and a 106-yr-long (1886-1991) tropical Atlantic cyclone activity index time series. The tropical Atlantic SST variations were also compared with decadal variations in the extratropical Atlantic SST.Multiyear to multidecadal variations in the cross-equatorial dipole pattern identified as a dominant empirical pattern of the tropical Atlantic SST variations in earlier and present studies are shown to be variations in the approximately north-south gradient of SST anomalies. It is also shown that there was no dynamical-thermodynamical, dipole mode of SST variations during the analysis period. There was a distinct decadal timescale (12-13 yr) of SST variations in the tropical South Atlantic, whereas no distinct decadal timescale was found in the tropical North Atlantic SST variations. Approximately 80% of the coherent decadal variance in the cross-equatorial SST gradient was `explained' by coherent decadal oscillations in the tropical South Atlantic SSTs. There were three, possibly physical, modes of decadal variations in the tropical Atlantic SSTs during the analysis period. In the more energetic mode of the North Atlantic decadal SST variations, anomalies traveled into the tropical North Atlantic from the extratropical North Atlantic along the eastern boundary of the basin. The anomalies strengthened and resided in the tropical North Atlantic for several years, then frequently traveled northward into the mid-high-latitude North Atlantic along

  2. Refractive index effects on the oscillator strength and radiative decay rate of 2,3-diazabicyclo[2.2.2]oct-2-ene.

    Science.gov (United States)

    Mohanty, Jyotirmayee; Nau, Werner M

    2004-01-01

    The photophysical properties of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) were determined in 15 solvents, two supramolecular hosts (cucurbit[7]uril and beta-cyclodextrin) as well as in the gas phase. The oscillator strength and radiative decay rate of DBO as a function of refractive index i.e. polarizability have been analyzed. The oscillator strength increases by a factor of 10 upon going from the gas phase to the most polarizable carbon disulfide, while the corresponding radiative decay rates increase by a factor of 40. There is a good empirical correlation between the oscillator strength of the weakly allowed n,pi* transition of DBO and the reciprocal bulk polarizability, which can be employed to assess the polarizability of unknown microheterogeneous environments. A satisfactory correlation between the radiative decay rate and the square of the refractive index is also found, as previously documented for chromophores with allowed transitions. However, the correlation improves significantly when the oscillator strength is included in the correlation, which demonstrates the importance of this factor in the Strickler-Berg equation for chromophores with forbidden or weakly allowed transitions, for which the oscillator strength may be strongly solvent dependent. The radiative decay rate of DBO in two supramolecular assemblies has been determined, confirming the very low polarizability inside the cucurbituril cavity, in between perfluorohexane and the gas phase. The fluorescence quantum yield of DBO in the gas phase has been remeasured (5.1 +/- 0.5%) and was found to fall one full order of magnitude below a previously reported value.

  3. DEVELOPMENT OF A STREAM BENTHIC MACROINVERTEBRATE INTEGRITY INDEX (SBMII) FOR WADEABLE STREAMS IN THE MID-ATLANTIC HIGHLANDS REGION

    Science.gov (United States)

    The Stream Benthic Macroinvertebrate Integrity Index (SBMII), a multimetric biotic index for assessing biological conditions of wadeable streams, was developed using seven macroinvertebrate metrics (Ephemeroptera richness, Plecoptera richness, Trichoptera richness, Collector-Filt...

  4. Identification of Holocene millennial-scale forcing in the North Atlantic area: Ocean/atmosphere contribution

    Science.gov (United States)

    Debret, M.; Masson-Delmotte, V.; Christophe, C.; de Vernal, A.; Massei, N.; Eynaud, F.; Nicolle, M.; Frank, N.; Mary, Y.; Magny, M.

    2017-12-01

    Millennial (1500-year) cycles were evidenced decades ago from the advance and retreat of glaciers but many subsequent studies failed to demonstrate the unequivocal character of such oscillation from paleoclimate time series. Hence, the identification of a persistent 1500 year periodicity remains controversial both for the last glacial episode and the Holocene. Applying wavelet analysis to Holocene climate records, we have identified synchronous millennial-scale oscillations which permit to establish a North Atlantic millennial variability index (NAV-Index), maximum at 5330 ± 245, 3560 ± 190, 1810 ± 160 cal years BP and minimum at 4430 ± 250, 2640 ± 225 and 970 ± 200 years before present. This NAV-index was compared with the millennial variability of cosmogenic 10Be isotope, a proxy of solar activity. Differences between the two sets of records suggest that an internal mechanism (Ocean/atmosphere) must be at the origin of the North Atlantic millennial scale variability. Our data document an increased coherence and magnitude of the North Atlantic millennial variability since 6000 cal. years BP, with a frequency of 1780 ± 240 years. During the early Holocene, deglacial meltwater fluxes had strong regional impact and the coupling between subpolar gyre migration and Atlantic meridional oceanic circulation observed since afterward seems to be related to the end of the Laurentide and Inuitian ice sheet meltwater discharge. Hence, we may conclude that the evolution of this millennial oscillation in the future will depend upon the Greenland stability or melting.

  5. Indexed

    CERN Document Server

    Hagy, Jessica

    2008-01-01

    Jessica Hagy is a different kind of thinker. She has an astonishing talent for visualizing relationships, capturing in pictures what is difficult for most of us to express in words. At indexed.blogspot.com, she posts charts, graphs, and Venn diagrams drawn on index cards that reveal in a simple and intuitive way the large and small truths of modern life. Praised throughout the blogosphere as “brilliant,” “incredibly creative,” and “comic genius,” Jessica turns her incisive, deadpan sense of humor on everything from office politics to relationships to religion. With new material along with some of Jessica’s greatest hits, this utterly unique book will thrill readers who demand humor that makes them both laugh and think.

  6. Impact of the Winter North Pacific Oscillation on the Surface Air Temperature over Eurasia and North America: Sensitivity to the Index Definition

    Science.gov (United States)

    Chen, Shangfeng; Song, Linye

    2018-06-01

    This study analyzes the impact of the winter North Pacific Oscillation (NPO) on the surface air temperature (SAT) variations over Eurasia and North America based on six different NPO indices. Results show that the influences of the winter NPO on the SAT over Eurasia and North America are sensitive to the definition of the NPO index. The impact of the winter NPO on the SAT variations over Eurasia (North America) is significant (insignificant) when the anticyclonic anomaly associated with the NPO index over the North Pacific midlatitudes shifts westward and pronounced northerly wind anomalies appear around Lake Baikal. By contrast, the impact of the winter NPO on the SAT variations over Eurasia (North America) is insignificant (significant) when the anticyclonic anomaly over the North Pacific related to the NPO index shifts eastward and the associated northerly wind anomalies to its eastern flank extend to North America. The present study suggests that the NPO definition should be taken into account when analyzing the impact of the winter NPO on Eurasian and North American SAT variations.

  7. The Use of Pre-Storm Boundary-Layer Baroclinicity in Determining and Operationally Implementing the Atlantic Surface Cyclone Intensification Index

    Science.gov (United States)

    Cione, Joseph; Pietrafes, Leonard J.

    The lateral motion of the Gulf Stream off the eastern seaboard of the United States during the winter season can act to dramatically enhance the low-level baroclinicity within the coastal zone during periods of offshore cold advection. The ralative close proximity of the Gulf Stream current off the mid-Atlantic coast can result in the rapid and intense destabilization of the marine atmospheric boundary layer directly above and shoreward of the Gulf Stream within this region. This airmass modification period often precedes either wintertime coastal cyclogenesis or the cyclonic re-development of existing mid-latitude cyclones. A climatological study investigating the relationship between the severity of the pre-storm, cold advection period and subsequent cyclogenic intensification was undertaken by Cione et al. in 1993. Findings from this study illustrate that the thermal structure of the continental airmass as well as the position of the Gulf Stream front relative to land during the pre-storm period (i.e., 24-48 h prior to the initial cyclonic intensification) are linked to the observed rate of surface cyclonic deepening for storms that either advected into or initially developed within the Carolina-southeast Virginia offshore coastal zone. It is a major objective of this research to test the potential operational utility of this pre-storm low level baroclinic linkage to subsequent cyclogenesis in an actual National Weather Service (NWS) coastal winter storm forecast setting.The ability to produce coastal surface cyclone intensity forecasts recently became available to North Carolina State University researchers and NWS forecasters. This statistical forecast guidance utilizes regression relationships derived from a nine-season (January 1982-April 1990), 116-storm study conducted previously. During the period between February 1994 and February 1996, the Atlantic Surface Cyclone Intensification Index (ASCII) was successfully implemented in an operational setting by

  8. Application of Quality Index Method (QIM) scheme in shelf-life study of farmed Atlantic salmon ( Salmo salar )

    DEFF Research Database (Denmark)

    Sveinsdóttir, K.; Martinsdóttir, E.; Hyldig, Grethe

    2002-01-01

    measurements (compression test). Maximum storage time in ice was determined with QDA and fat content by Soxhlet extraction. A high correlation between QIM and storage time in ice was found. Storage time could be predicted with +/- 2 d. TVC increased exponentially with storage and was dominated by H2S......Salmon (Salmo salar) was stored in ice up to 24 d, and changes during storage were observed with sensory evaluation using the Quality Index Method (QIM), and Quantitative Descriptive Analysis (QDA), total viable counts (TVC), hydrogen sulfide (H2S)-producing bacteria, and instrumental texture......-producing bacteria after 20 d in ice, which was the maximum storage time. Texture measurements indicated softening of salmon flesh with storage...

  9. Detecting quasi-oscillations in the monthly precipitation regimes of the Iberian Peninsula

    Directory of Open Access Journals (Sweden)

    L. Morala

    2003-03-01

    Full Text Available A spectral analysis of the time series corresponding to the main monthly precipitation regimes of the Iberian Peninsula was performed using two methods, the Multi-Taper Method and Monte Carlo Singular Spectrum Analysis. The Multi-Taper Method gave a preliminary view of the presence of signals in some of the time series. Monte Carlo Singular Spectrum Analysis discriminated between potential oscillations and noise. From the results of the two methods it is concluded that there exist three significant quasi-oscillations at the 95% level of confidence: a 5.0 year quasi-oscillation and a long-term trend in the Atlantic pattern of March, a 3.2 year quasi-oscillation in the Cantabrian pattern of January, and a 4.0 year quasi-oscillation in the Catalonian pattern of February. These quasi-oscillations might be related to climatic variations with similar periodicities over the North Atlantic Ocean. The possible simultaneity of high values of precipitation generated by the significant quasi-oscillations and high sea–level pressures was studied by means of composite maps. It was found that high values of precipitation generated by the oscillations of the Atlantic patterns of January and March exist simultaneously with a specific high pressure structure over the North Atlantic Ocean, that allow cyclonic perturbations to cross the Iberian Peninsula. During the non-wet years, this high pressure structure moves northwards, keeping the track of the low pressure centers to the north, far from the Iberian Peninsula. On the other hand, high values of precipitation generated by the oscillation of the Cantabrian pattern of January exist simultaneously with a high pressure structure over the Galicia region and the Cantabrian Sea, that allow a northerly flow over the region. Also, a positive trend in the NAO index for March has been found, starting in the sixties, which is not evident for other winter months. This trend agrees with the decreasing trend found in the

  10. Thermal Habitat Index of Many Northwest Atlantic Temperate Species Stays Neutral under Warming Projected for 2030 but Changes Radically by 2060

    Czech Academy of Sciences Publication Activity Database

    Shackell, N.L.; Ricard, Daniel; Stortini, C.

    2014-01-01

    Roč. 9, č. 3 (2014), e90662 E-ISSN 1932-6203 Institutional support: RVO:60077344 Keywords : climate change * environmental parameters * Atlantic Ocean * greenhouse effect Subject RIV: EH - Ecology, Behaviour Impact factor: 3.234, year: 2014

  11. A boundary-value inverse model and its application to the calculation of tidal oscillation systems in the Western South Atlantic Ocean

    International Nuclear Information System (INIS)

    Miranda-Alonso, S.

    1991-01-01

    A Cauchy-Riemann problem is solved for the case of the linearized equations for long waves. The initial-values are amplitudes and phases measured at the coast. No boundary values are made use of. This inverse-problem is solved by starting the calculations at the coast and continuing outwards to the open ocean in a rectangular areas with one side at the coast and the other three at the open ocean. The initial values were expanded into the complex plane to get a platform to perform with the calculations. This non-well-posed problem was solved by means of two different mathematical techniques for comparison. The results produced with the inverse model were compared with those produced with a 'classical' model initialized at the three open boundaries with the results of the inverse model. The oscillating systems produced by both models were quite similar, giving validity to this invese modeling approach which should be a useful technique to solve problems when only initial values are known. (orig.)

  12. Atlantic Region

    NARCIS (Netherlands)

    Elands, B.H.M.; Bell, S.; Blok, J.

    2010-01-01

    Chapter 2 explores recreation and tourism practices in forest areas in the Atlantic region, which refers to the geographical area close to the North Sea and the Atlantic Ocean. The Atlantic countries described in this section are Belgium (Flanders and Wallonia), Denmark, Iceland, Ireland, the

  13. The relationship between the Southern Oscillation Index, rainfall and the occurrence of canine tick paralysis, feline tick paralysis and canine parvovirus in Australia.

    Science.gov (United States)

    Rika-Heke, Tamara; Kelman, Mark; Ward, Michael P

    2015-07-01

    The aim of this study was to describe the association between climate, weather and the occurrence of canine tick paralysis, feline tick paralysis and canine parvovirus in Australia. The Southern Oscillation Index (SOI) and monthly average rainfall (mm) data were used as indices for climate and weather, respectively. Case data were extracted from a voluntary national companion animal disease surveillance resource. Climate and weather data were obtained from the Australian Government Bureau of Meteorology. During the 4-year study period (January 2010-December 2013), a total of 4742 canine parvovirus cases and 8417 tick paralysis cases were reported. No significant (P ≥ 0.05) correlations were found between the SOI and parvovirus, canine tick paralysis or feline tick paralysis. A significant (P parvovirus occurrence and rainfall in the same month (0.28), and significant negative cross-correlations (-0.26 to -0.36) between parvovirus occurrence and rainfall 4-6 months previously. Significant (P canine tick paralysis occurrence and rainfall 1-3 months previously, and significant positive cross-correlations (0.29-0.47) between canine tick paralysis occurrence and rainfall 7-10 months previously. Significant positive cross-correlations (0.37-0.68) were found between cases of feline tick paralysis and rainfall 6-10 months previously. These findings may offer a useful tool for the management and prevention of tick paralysis and canine parvovirus, by providing an evidence base supporting the recommendations of veterinarians to clients thus reducing the impact of these diseases. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Marine proxy evidence linking decadal North Pacific and Atlantic climate

    Energy Technology Data Exchange (ETDEWEB)

    Hetzinger, S. [University of Toronto Mississauga, CPS-Department, Mississauga, ON (Canada); Leibniz Institute of Marine Sciences, IFM-GEOMAR, Kiel (Germany); Halfar, J. [University of Toronto Mississauga, CPS-Department, Mississauga, ON (Canada); Mecking, J.V.; Keenlyside, N.S. [Leibniz Institute of Marine Sciences, IFM-GEOMAR, Kiel (Germany); University of Bergen, Geophysical Institute and Bjerknes Centre for Climate Research, Bergen (Norway); Kronz, A. [University of Goettingen, Geowissenschaftliches Zentrum, Goettingen (Germany); Steneck, R.S. [University of Maine, Darling Marine Center, Walpole, ME (United States); Adey, W.H. [Smithsonian Institution, Department of Botany, Washington, DC (United States); Lebednik, P.A. [ARCADIS U.S. Inc., Walnut Creek, CA (United States)

    2012-09-15

    Decadal- to multidecadal variability in the extra-tropical North Pacific is evident in 20th century instrumental records and has significant impacts on Northern Hemisphere climate and marine ecosystems. Several studies have discussed a potential linkage between North Pacific and Atlantic climate on various time scales. On decadal time scales no relationship could be confirmed, potentially due to sparse instrumental observations before 1950. Proxy data are limited and no multi-centennial high-resolution marine geochemical proxy records are available from the subarctic North Pacific. Here we present an annually-resolved record (1818-1967) of Mg/Ca variations from a North Pacific/Bering Sea coralline alga that extends our knowledge in this region beyond available data. It shows for the first time a statistically significant link between decadal fluctuations in sea-level pressure in the North Pacific and North Atlantic. The record is a lagged proxy for decadal-scale variations of the Aleutian Low. It is significantly related to regional sea surface temperature and the North Atlantic Oscillation (NAO) index in late boreal winter on these time scales. Our data show that on decadal time scales a weaker Aleutian Low precedes a negative NAO by several years. This atmospheric link can explain the coherence of decadal North Pacific and Atlantic Multidecadal Variability, as suggested by earlier studies using climate models and limited instrumental data. (orig.)

  15. Impacts of SST anomalies on the North Atlantic atmospheric circulation: a case study for the northern winter 1995/1996

    Energy Technology Data Exchange (ETDEWEB)

    Losada, T.; Rodriguez-Fonseca, B. [Universidad Complutense de Madrid, Departmento de Geofisica y Meteorologia, Madrid (Spain); Mechoso, C.R.; Ma, H.Y. [University of California Los Angeles, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States)

    2007-12-15

    The present paper selects the northern winter of December 1995-February 1996 for a case study on the impact of sea surface temperature (SST) anomalies on the atmospheric circulation over the North Atlantic and Western Europe. In the Atlantic, the selected winter was characterized by positive SST anomalies over the northern subtropics and east of Newfoundland, and negative anomalies along the US coast. A weak La Nina event developed in the Pacific. The North Atlantic Oscillation (NAO) index was low, precipitation over the Iberian Peninsula and northern Africa was anomalously high, and precipitation over northern Europe was anomalously low. The method of study consists of assessing the sensitivity of ensemble simulations by the UCLA atmospheric general circulation model (UCLA AGCM) to SST anomalies from the observation, which are prescribed either in the World Oceans, the Atlantic Ocean only, or the subtropical North Atlantic only. The results obtained are compared with a control run that uses global, time-varying climatological SST. The ensemble simulations with global and Atlantic-only SST anomalies both produce results that resemble the observations over the North Atlantic and Western Europe. It is suggested that the anomalous behavior of the atmosphere in the selected winter over those regions, therefore, was primarily determined by conditions within the Atlantic basin. The simulated fields in the tropical North Atlantic show anomalous upward motion and lower (upper) level convergence (divergence) in the atmosphere overlying the positive SST anomalies. Consistently, the subtropical jet intensifies and its core moves equatorward, and precipitation increases over northern Africa and southern Europe. The results also suggest that the SST anomalies in the tropical North Atlantic only do not suffice to produce the atmospheric anomalies observed in the basin during the selected winter. The extratropical SST anomalies would provide a key contribution through increased

  16. Connecting Atlantic temperature variability and biological cycling in two earth system models

    Science.gov (United States)

    Gnanadesikan, Anand; Dunne, John P.; Msadek, Rym

    2014-05-01

    Connections between the interdecadal variability in North Atlantic temperatures and biological cycling have been widely hypothesized. However, it is unclear whether such connections are due to small changes in basin-averaged temperatures indicated by the Atlantic Multidecadal Oscillation (AMO) Index, or whether both biological cycling and the AMO index are causally linked to changes in the Atlantic Meridional Overturning Circulation (AMOC). We examine interdecadal variability in the annual and month-by-month diatom biomass in two Earth System Models with the same formulations of atmospheric, land, sea ice and ocean biogeochemical dynamics but different formulations of ocean physics and thus different AMOC structures and variability. In the isopycnal-layered ESM2G, strong interdecadal changes in surface salinity associated with changes in AMOC produce spatially heterogeneous variability in convection, nutrient supply and thus diatom biomass. These changes also produce changes in ice cover, shortwave absorption and temperature and hence the AMO Index. Off West Greenland, these changes are consistent with observed changes in fisheries and support climate as a causal driver. In the level-coordinate ESM2M, nutrient supply is much higher and interdecadal changes in diatom biomass are much smaller in amplitude and not strongly linked to the AMO index.

  17. Geomagnetic activity and the North Atlantic Oscillation

    Czech Academy of Sciences Publication Activity Database

    Bucha, Václav

    2014-01-01

    Roč. 58, č. 3 (2014), s. 461-472 ISSN 0039-3169 Institutional support: RVO:67985530 Keywords : geomagnetic activity * solar wind * polar vortex intensification * downward winds Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.806, year: 2014

  18. Oscillator monitor

    International Nuclear Information System (INIS)

    McNeill, G.A.

    1981-01-01

    Present high-speed data acquisition systems in nuclear diagnostics use high-frequency oscillators to provide timing references for signals recorded on fast, traveling-wave oscilloscopes. An oscillator's sinusoidal wave shape is superimposed on the recorded signal with each cycle representing a fixed time increment. During data analysis the sinusoid is stripped from the signal, leaving a clean signal shape with known timing. Since all signal/time relationships are totally dependant upon working oscillators, these critical devices must have remote verification of proper operation. This manual presents the newly-developed oscillator monitor which will provide the required verification

  19. Are North Atlantic Multidecadal SST Anomalies Westward Propagating?

    NARCIS (Netherlands)

    Feng, Qingyi; Dijkstra, Hendrik

    2014-01-01

    The westward propagation of sea surface temperature (SST) anomalies is one of the main characteristics of one of the theories of the Atlantic Multidecadal Oscillation. Here we use techniques from complex network modeling to investigate the existence of the westward propagation in the North Atlantic

  20. Construction of prediction intervals for Palmer Drought Severity Index using bootstrap

    Science.gov (United States)

    Beyaztas, Ufuk; Bickici Arikan, Bugrayhan; Beyaztas, Beste Hamiye; Kahya, Ercan

    2018-04-01

    In this study, we propose an approach based on the residual-based bootstrap method to obtain valid prediction intervals using monthly, short-term (three-months) and mid-term (six-months) drought observations. The effects of North Atlantic and Arctic Oscillation indexes on the constructed prediction intervals are also examined. Performance of the proposed approach is evaluated for the Palmer Drought Severity Index (PDSI) obtained from Konya closed basin located in Central Anatolia, Turkey. The finite sample properties of the proposed method are further illustrated by an extensive simulation study. Our results revealed that the proposed approach is capable of producing valid prediction intervals for future PDSI values.

  1. Chromospheric oscillations

    NARCIS (Netherlands)

    Lites, B.W.; Rutten, R.J.; Thomas, J.H.

    1995-01-01

    We show results from SO/Sacramento Peak data to discuss three issues: (i)--the spatial occurrence of chromospheric 3--min oscillations; (ii)--the validity of Ca II H&K line-center Doppler Shift measurements; (iii)--the signi ?cance of oscillation power and phase at frequencies above 10 mHz.

  2. Inverted oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Yuce, C [Physics Department, Anadolu University, Eskisehir (Turkey); Kilic, A [Physics Department, Anadolu University, Eskisehir (Turkey); Coruh, A [Physics Department, Sakarya University, Sakarya (Turkey)

    2006-07-15

    The inverted harmonic oscillator problem is investigated quantum mechanically. The exact wavefunction for the confined inverted oscillator is obtained and it is shown that the associated energy eigenvalues are discrete, and the energy is given as a linear function of the quantum number n.

  3. Pacific and Atlantic influences on Mesoamerican climate over the past millennium

    Energy Technology Data Exchange (ETDEWEB)

    Stahle, D.W.; Burnette, D.J.; Fye, F.K.; Cleaveland, M.K. [University of Arkansas, Department of Geosciences, Fayetteville, AR (United States); Diaz, J.V.; Paredes, J.C. [Instituto Nacional de Investigaciones Forestales, Agricolas, y Pecuarias, Laboratorio de Dendrocronologia, Gomez Palacio, Durango (Mexico); Heim, R.R. [NOAA, National Climatic Data Center, Asheville, NC (United States); Soto, R.A. [UNAM, Departamento Microbiologia y Parastologia, Mexico, D.F. (Mexico)

    2012-09-15

    A new tree-ring reconstruction of the Palmer Drought Severity Index (PDSI) for Mesoamerica from AD 771 to 2008 identifies megadroughts more severe and sustained than any witnessed during the twentieth century. Correlation analyses indicate strong forcing of instrumental and reconstructed June PDSI over Mesoamerica from the El Nino/Southern Oscillation (ENSO). Spectral analyses of the 1,238-year reconstruction indicate significant concentrations of variance at ENSO, sub-decadal, bi-decadal, and multidecadal timescales. Instrumental and model-based analyses indicate that the Atlantic Multidecadal Oscillation is important to warm season climate variability over Mexico. Ocean-atmospheric variability in the Atlantic is not strongly correlated with the June PDSI reconstruction during the instrumental era, but may be responsible for the strong multidecadal variance detected in the reconstruction episodically over the past millennium. June drought indices in Mesoamerica are negatively correlated with gridded June PDSI over the United States from 1950 to 2005, based on both instrumental and reconstructed data. Interannual variability in this latitudinal moisture gradient is due in part to ENSO forcing, where warm events favor wet June PDSI conditions over the southern US and northern Mexico, but dryness over central and southern Mexico (Mesoamerica). Strong anti-phasing between multidecadal regimes of tree-ring reconstructed June PDSI over Mesoamerica and reconstructed summer (JJA) PDSI over the Southwest has also been detected episodically over the past millennium, including the 1950-1960s when La Nina and warm Atlantic SSTs prevailed, and the 1980-1990s when El Nino and cold Atlantic SSTs prevailed. Several Mesoamerican megadroughts are reconstructed when wetness prevailed over the Southwest, including the early tenth century Terminal Classic Drought, implicating El Nino and Atlantic SSTs in this intense and widespread drought that may have contributed to social changes

  4. IN SITU AND MODIS MOD15A2 LEAF AREA INDEX MEASUREMENTS OF A MID-ATLANTIC DECIDOUS FOREST SITE: PERSPECTIVES FROM FOUR-YEARS OF FIELD STUDIES

    Science.gov (United States)

    The U.S. Environmental Protection Agency is interested in leaf area index as it pertains to biogenic emissions, atmospheric pollutant deposition, ecological indicators, vegetation phenology, and land cover mapping.

  5. Chemical Oscillations

    Indian Academy of Sciences (India)

    IMTECH),. Chandigarh. Praveen Kumar is pursuing his PhD in chemical dynamics at. Panjab University,. Chandigarh. Keywords. Chemical oscillations, autoca-. talYSis, Lotka-Volterra model, bistability, hysteresis, Briggs-. Rauscher reaction.

  6. Chemical Oscillations

    Indian Academy of Sciences (India)

    the law of mass-action that every simple reaction approaches ... from thermodynamic equilibrium. Such oscillating systems cor- respond to thermodynamically open systems. .... experimentally observable, and the third is always unstable.

  7. Evidences linking ENSO and coral growth in the Southwestern-South Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Evangelista, H. [LARAMG, Laboratorio de Radioecologia e Mudancas Globais/DBB/UERJ. Pav. HLC, Subsolo, Maracana, RJ (Brazil); Godiva, D. [LARAMG, Laboratorio de Radioecologia e Mudancas Globais/DBB/UERJ. Pav. HLC, Subsolo, Maracana, RJ (Brazil); Universidade Federal Fluminense, Outeiro Sao Joao Batista, s/n, Centro, Departamento de Geoquimica Ambiental, Niteroi, RJ (Brazil); Sifeddine, A. [IRD, Institut de Recherche Pour le Developpement, UR055 Paleotropique, Bondy (France); Universidade Federal Fluminense, Outeiro Sao Joao Batista, s/n, Centro, Departamento de Geoquimica Ambiental, Niteroi, RJ (Brazil); Leao, Z.M.A.N.; Kikuchi, R.K.P. [UFBA/Instituto de Geociencias. Rua Barao de Geremoabo, s/n, Federacao, Salvador, BA (Brazil); Rigozo, N.R. [LARAMG, Laboratorio de Radioecologia e Mudancas Globais/DBB/UERJ. Pav. HLC, Subsolo, Maracana, RJ (Brazil); FAETEC, Faculdade de Educacao e Tecnologia Thereza Porto Marques, Jacarei, SP (Brazil); Segal, B. [UFRJ/Museu Nacional/Setor de Celenterologia/Departamento de Invertebrados, Quinta da Boa Vista s/n, Sao Cristovao, RJ (Brazil); Ambrizzi, T. [USP/Department of Atmospheric Sciences, Sao Paulo, SP (Brazil); Kampel, M. [INPE/Divisao de Sensoriamento Remoto, Sao Paulo, SP (Brazil); Cornec, F. le [Universidade Federal Fluminense, Outeiro Sao Joao Batista, s/n, Centro, Departamento de Geoquimica Ambiental, Niteroi, RJ (Brazil)

    2007-12-15

    Physical and biological changes in the marine environment, induced by oceanic-atmospheric processes, can be imprinted in massive coral skeletons. Herein, we present an evidence of potential El Nino impacts at the Southwestern South Atlantic Ocean (SWSA) inferred from the sclerochronology of the reef coral Favia leptophylla. The application of spectral analysis (wavelet decomposition and the iterative regression) to coral growth length and to meteorological-oceanographic parameters (air temperature, sea surface temperature and precipitation) as well as to Southern Oscillation Index (SOI) and solar irradiation indicated a major significant inverse relationship between SOI and coral growth length at the 4-8 years frequency band. We propose here that coral growth length from the SWSA could be affected by El Nino Southern Oscillation (ENSO) events through an ''atmospheric bridge'', in contrast to its direct effect at the Pacific Ocean, related to the increase in sea surface temperature. (orig.)

  8. Response of benthic opportunistic polychaetes and amphipods index to different perturbations in coastal oligotrophic areas (Canary archipelago, North East Atlantic Ocean)

    OpenAIRE

    Riera, Rodrigo; de-la-Ossa-Carretero, Jose Antonio

    2014-01-01

    Oligotrophic areas harbour low macrofaunal abundance and patchy distribution. In these areas it is necessary to test the reliability of biological indicators, especially those based on taxonomic sufficiency where the level of identification is balanced against the need for ecological information and could affect the efficiency of bioindicators. The BOPA (benthic opportunistic polychaetes and amphipods) index was applied in five coastal areas subjected to different perturbations (aquaculture, ...

  9. Nonlinear oscillations

    CERN Document Server

    Nayfeh, Ali Hasan

    1995-01-01

    Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim

  10. Modes of winter precipitation variability in the North Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Zorita, E. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Hydrophysik; Saenz, J.; Fernandez, J.; Zubillaga, J. [Bilbao Univ. (Spain)

    2001-07-01

    The modes of variability of winter precipitation in the North Atlantic sector are identified by Empirical Orthogonal Functions Analysis in the NCEP/NCAR global reanalysis data sets. These modes are also present in a gridded precipitation data set over the Western Europe. The large-scale fields of atmospheric seasonal mean circulation, baroclinic activity, evaporation and humidity transport that are connected to the rainfall modes have been also analyzed in order to investigate the physical mechanisms that are causally linked to the rainfall modes. The results indicate that the leading rainfall mode is associated to the North Atlantic oscillation and represents a meridional redistribution of precipitation in the North Atlantic through displacements of the storm tracks. The second mode is related to evaporation anomalies in the Eastern Atlantic that precipitate almost entirely in the Western Atlantic. The third mode seems to be associated to meridional transport of water vapor from the Tropical Atlantic. (orig.)

  11. North Atlantic teleconnection patterns signature on sea level from satellite altimetry

    Science.gov (United States)

    Iglesias, Isabel; Lázaro, Clara; Joana Fernandes, M.; Bastos, Luísa

    2015-04-01

    Porto (Fernandes et al., 2010; Fernandes et al., 2013). Regular 0.25°x0.25° latitude-longitude grids were generated at a 10-day interval for the NA Ocean (60°W-5°W, 5°N-60°N) using optimal interpolation with a realistic space-time correlation function (Lázaro et al., 2013). These grids are used to inspect the response of sea level anomalies to several teleconnection patterns as well as the NA variability on annual and longer timescales. The teleconnection patterns selected are the ones that have influence on the NA basin: North Atlantic Oscillation, East Atlantic pattern, East Atlantic/Western Russia pattern, Scandinavia pattern, Western Mediterranean Oscillation index, El Niño Southern Oscillation, Tropical North Atlantic Index, and Atlantic Multidecadal Oscillation. Acknowledgments: RAIA tec (0688-RAIATEC-1-P) project. The RAIA Coastal Observatory has been funded by the Programa Operativo de Cooperación Transfronteriza España-Portugal (POCTEP 2007-2013). References: Fernandes M.J., C. Lázaro, A.L. Nunes, N. Pires, L. Bastos, V.B. Mendes (2010). GNSS-derived Path Delay: an approach to compute the wet tropospheric correction for coastal altimetry. IEEE Geosci. Rem. Sens Lett., Vol. 7, NO. 3, 596 - 600, doi: 10.1109/LGRS.2010.2042425. Lázaro, C., M. J. Juliano, M. J. Fernandes (2013): Semi-automatic determination of the Azores Current axis using satellite altimetry: application to the study of the current variability during 1995-2006. Advances in Space Research, Vol. 51(11), pp. 2155-2170, doi:10.1016/j.asr.2012.12.021. Fernandes, M. J., A.L. Nunes, C. Lázaro (2013). Analysis and Inter-Calibration of Wet Path Delay Datasets to Compute the Wet Tropospheric Correction for CryoSat-2 over Ocean. Remote Sensing, 5, 4977-5005.

  12. Effects of Atlantic warm pool variability over climate of South America tropical transition zone

    Science.gov (United States)

    Ricaurte Villota, Constanza; Romero-Rodríguez, Deisy; Andrés Ordoñez-Zuñiga, Silvio; Murcia-Riaño, Magnolia; Coca-Domínguez, Oswaldo

    2016-04-01

    Colombia is located in the northwestern corner of South America in a climatically complex region due to the influence processes modulators of climate both the Pacific and Atlantic region, becoming in a transition zone between phenomena of northern and southern hemisphere. Variations in the climatic conditions of this region, especially rainfall, have been attributed to the influence of the El Nino Southern Oscillation (ENSO), but little is known about the interaction within Atlantic Ocean and specifically Caribbean Sea with the environmental conditions of this region. In this work We studied the influence of the Atlantic Warm Pool (AWP) on the Colombian Caribbean (CC) climate using data of Sea Surface Temperature (SST) between 1900 - 2014 from ERSST V4, compared with in situ data SIMAC (National System for Coral Reef Monitoring in Colombia - INVEMAR), rainfall between 1953-2013 of meteorological stations located at main airports in the Colombian Caribbean zone, administered by IDEAM, and winds data between 2003 - 2014 from WindSat sensor. The parameters analyzed showed spatial differences throughout the study area. SST anomalies, representing the variability of the AWP, showed to be associated with Multidecadal Atlantic Oscillation (AMO) and with the index of sea surface temperature of the North-tropical Atlantic (NTA), the variations was on 3 to 5 years on the ENSO scale and of approximately 11 years possibly related to solar cycles. Rainfall anomalies in the central and northern CC respond to changes in SST, while in the south zone these are not fully engage and show a high relationship with the ENSO. Finally, the winds also respond to changes in SST and showed a signal approximately 90 days possibly related to the Madden-Julian Oscillation, whose intensity depends on the CC region being analyzed. The results confirm that region is a transition zone in which operate several forcing, the variability of climate conditions is difficult to attribute only one, as ENSO

  13. An Atlantic influence on Amazon rainfall

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jin-Ho [University of Maryland, Department of Atmospheric and Oceanic Science, College Park, MD (United States); Zeng, Ning [University of Maryland, Earth System Science Interdisciplinary Center, College Park, MD (United States); University of Maryland, Department of Atmospheric and Oceanic Science, College Park, MD (United States)

    2010-02-15

    Rainfall variability over the Amazon basin has often been linked to variations in Pacific sea surface temperature (SST), and in particular, to the El Nino/Southern Oscillation (ENSO). However, only a fraction of Amazon rainfall variability can be explained by ENSO. Building upon the recent work of Zeng (Environ Res Lett 3:014002, 2008), here we provide further evidence for an influence on Amazon rainfall from the tropical Atlantic Ocean. The strength of the North Atlantic influence is found to be comparable to the better-known Pacific ENSO connection. The tropical South Atlantic Ocean also shows some influence during the wet-to-dry season transition period. The Atlantic influence is through changes in the north-south divergent circulation and the movement of the ITCZ following warm SST. Therefore, it is strongest in the southern part of the Amazon basin during the Amazon's dry season (July-October). In contrast, the ENSO related teleconnection is through anomalous east-west Walker circulation with largely concentrated in the eastern (lower) Amazon. This ENSO connection is seasonally locked to boreal winter. A complication due to the influence of ENSO on Atlantic SST causes an apparent North Atlantic SST lag of Amazon rainfall. Removing ENSO from North Atlantic SST via linear regression resolves this causality problem in that the residual Atlantic variability correlates well and is in phase with the Amazon rainfall. A strong Atlantic influence during boreal summer and autumn is particularly significant in terms of the impact on the hydro-ecosystem which is most vulnerable during the dry season, as highlighted by the severe 2005 Amazon drought. Such findings have implications for both seasonal-interannual climate prediction and understanding the longer-term changes of the Amazon rainforest. (orig.)

  14. Seasonal influence of ENSO on the Atlantic ITCZ and equatorial South America

    Science.gov (United States)

    Münnich, M.; Neelin, J. D.

    2005-11-01

    In late boreal spring, especially May, a strong relationship exists in observations among precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ), and eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA). A chain of correlations of equatorial Pacific SSTA, western equatorial Atlantic wind stress (WEA), equatorial Atlantic SSTA, sea surface height, and precipitation supports a causal chain in which El Niño/Southern Oscillation (ENSO) induces WEA stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain. This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic. The equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.

  15. Oscillator circuits

    CERN Document Server

    Graf, Rudolf F

    1996-01-01

    This series of circuits provides designers with a quick source for oscillator circuits. Why waste time paging through huge encyclopedias when you can choose the topic you need and select any of the specialized circuits sorted by application?This book in the series has 250-300 practical, ready-to-use circuit designs, with schematics and brief explanations of circuit operation. The original source for each circuit is listed in an appendix, making it easy to obtain additional information.Ready-to-use circuits.Grouped by application for easy look-up.Circuit source listing

  16. 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.

  17. 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.

  18. 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.

  19. Episodes of aeolian sand movement on a large spit system (Skagen Odde, Denmark) and North Atlantic storminess during the Little Ice Age

    DEFF Research Database (Denmark)

    Clemmensen, Lars B.; Glad, Aslaug C.; Hansen, Kristian W. T.

    2015-01-01

    . A change in the atmospheric circulation, so that both the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO) were negative, apparently led to an increased number of intense cyclones causing inland sand movement and dune building. The second and third phase of aeolian sand...

  20. Simple climatic indices for the tropical Atlantic Ocean and some applications

    Science.gov (United States)

    Servain, Jacques

    1991-08-01

    Two indices related to the sea surface temperature (SST) variability in the tropical Atlantic are proposed. One index describes the SST averaged over the whole basin (30°N to 20°S, 60°W to 15°E), and the other illustrates a meridional dipole between the northern and southern hemispheres. The computational method for obtaining these indices is intentionally kept simple, the objective being to reproduce the signature of the main results previously provided from more complicated statistical analyses. Monthly time series for both indices are produced from 1964 up to the present time. The whole basin index exhibits principally a sustained warming which has intensified since about 1975, and it has a significant periodicity close to that of the quasi-biennial oscillation. The dipole index exhibits a decadal-scale variation, and its building up seems to be related to other worldwide climatic changes, as for instance El Niño / Southern Oscillation extreme episodes, rainfall variabilities over the Brazilian Nordeste and African Sahel.

  1. One dimension harmonic oscillator

    International Nuclear Information System (INIS)

    Cohen-Tannoudji, Claude; Diu, Bernard; Laloe, Franck.

    1977-01-01

    The importance of harmonic oscillator in classical and quantum physics, eigenvalues and eigenstates of hamiltonian operator are discussed. In complement are presented: study of some physical examples of harmonic oscillators; study of stationnary states in the /x> representation; Hermite polynomials; resolution of eigenvalue equation of harmonic oscillator by polynomial method; isotope harmonic oscillator with three dimensions; charged harmonic oscillator in uniform electric field; quasi classical coherent states of harmonic oscillator; eigenmodes of vibration of two coupled harmonic oscillators; vibration modus of a continuous physical system (application to radiation: photons); vibration modus of indefinite linear chain of coupled harmonic oscillators (phonons); one-dimensional harmonic oscillator in thermodynamic equilibrium at temperature T [fr

  2. Power oscillation damping controller

    DEFF Research Database (Denmark)

    2012-01-01

    A power oscillation damping controller is provided for a power generation device such as a wind turbine device. The power oscillation damping controller receives an oscillation indicating signal indicative of a power oscillation in an electricity network and provides an oscillation damping control...

  3. Oscillations of void lattices

    International Nuclear Information System (INIS)

    Akhiezer, A.I.; Davydov, L.N.; Spol'nik, Z.A.

    1976-01-01

    Oscillations of a nonideal crystal are studied, in which macroscopic defects (pores) form a hyperlattice. It is shown that alongside with acoustic and optical phonons (relative to the hyperlattice), in such a crystal oscillations of the third type are possible which are a hydridization of sound oscillations of atoms and surface oscillations of a pore. Oscillation spectra of all three types were obtained

  4. A 65--70 year oscillation in observed surface temperatures

    International Nuclear Information System (INIS)

    Schlesinger, M.E.; Ramankutty, N.

    1994-01-01

    There are three possible sources for the 65--70-year ''global'' oscillation: (1) random forcing of the ocean by the atmosphere, such as by white noise; (2) external oscillatory forcing of the climate system, such as by a variation in the solar irradiance; and (3) an internal oscillation of the atmosphere-ocean system. It is unlikely that putative variations in solar irradiance are the source of the oscillation because solar forcing should generate a global response, but the oscillation is not global. It is also unlikely that white-noise forcing is the source of the oscillation because such forcing should generate an oceanwide response, but the oscillation is not panoceanic. Consequently, the most probable cause of the oscillation is an internal oscillation of the atmosphere-ocean system. This conclusion is supported by a growing body of observational evidence and coupled atmosphere/ocean general circulation model simulation results. Comparison of the regional and global-mean temperature changes caused by the oscillation with those induced by GHG + ASA forcing shows that the rapid rise in global-mean temperature between about 1908 and 1946, and the subsequent reversal of this warming until about 1965 were the result of the oscillation. In the North Atlantic and North American regions, the domination of the GHG + ASA-induced warming by the oscillation has obscured and confounded detection of this warming

  5. Oscillators - a simple introduction

    DEFF Research Database (Denmark)

    Lindberg, Erik

    2013-01-01

    Oscillators are kernel components of electrical and electronic circuits. Discussion of history, mechanisms and design based on Barkhausens observation. Discussion of a Wien Bridge oscillator based on the question: Why does this circuit oscillate ?......Oscillators are kernel components of electrical and electronic circuits. Discussion of history, mechanisms and design based on Barkhausens observation. Discussion of a Wien Bridge oscillator based on the question: Why does this circuit oscillate ?...

  6. Oscillators and Eigenvalues

    DEFF Research Database (Denmark)

    Lindberg, Erik

    1997-01-01

    In order to obtain insight in the nature of nonlinear oscillators the eigenvalues of the linearized Jacobian of the differential equations describing the oscillator are found and displayed as functions of time. A number of oscillators are studied including Dewey's oscillator (piecewise linear wit...... with negative resistance), Kennedy's Colpitts-oscillator (with and without chaos) and a new 4'th order oscillator with hyper-chaos....

  7. 2005 Atlantic Hurricanes Poster

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 2005 Atlantic Hurricanes poster features high quality satellite images of 15 hurricanes which formed in the Atlantic Basin (includes Gulf of Mexico and Caribbean...

  8. Northeast Atlantic blue whiting

    OpenAIRE

    Heino, Mikko

    2010-01-01

    Heino, M. 2010. Northeast Atlantic blue whiting. In Life cycle spatial patterns of small pelagic fish in the Northeast Atlantic, pp. 59-64. Ed by P. Petitgas. ICES Cooperative Research Report 306. ICES, Copenhagen.

  9. Ecological regime shift drives declining growth rates of sea turtles throughout the West Atlantic

    Science.gov (United States)

    Bjorndal, Karen A.; Bolten, Alan B.; Chaloupka, Milani; Saba, Vincent S.; Bellini, Cláudio; Marcovaldi, Maria A.G.; Santos, Armando J.B.; Bortolon, Luis Felipe Wurdig; Meylan, Anne B.; Meylan, Peter A.; Gray, Jennifer; Hardy, Robert; Brost, Beth; Bresette, Michael; Gorham, Jonathan C.; Connett, Stephen; Crouchley, Barbara Van Sciver; Dawson, Mike; Hayes, Deborah; Diez, Carlos E.; van Dam, Robert P.; Willis, Sue; Nava, Mabel; Hart, Kristen M.; Cherkiss, Michael S.; Crowder, Andrew; Pollock, Clayton; Hillis-Starr, Zandy; Muñoz Tenería, Fernando A.; Herrera-Pavón, Roberto; Labrada-Martagón, Vanessa; Lorences, Armando; Negrete-Philippe, Ana; Lamont, Margaret M.; Foley, Allen M.; Bailey, Rhonda; Carthy, Raymond R.; Scarpino, Russell; McMichael, Erin; Provancha, Jane A.; Brooks, Annabelle; Jardim, Adriana; López-Mendilaharsu, Milagros; González-Paredes, Daniel; Estrades, Andrés; Fallabrino, Alejandro; Martínez-Souza, Gustavo; Vélez-Rubio, Gabriela M.; Boulon, Ralf H.; Collazo, Jaime; Wershoven, Robert; Hernández, Vicente Guzmán; Stringell, Thomas B.; Sanghera, Amdeep; Richardson, Peter B.; Broderick, Annette C.; Phillips, Quinton; Calosso, Marta C.; Claydon, John A.B.; Metz, Tasha L.; Gordon, Amanda L.; Landry, Andre M.; Shaver, Donna J.; Blumenthal, Janice; Collyer, Lucy; Godley, Brendan J.; McGowan, Andrew; Witt, Matthew J.; Campbell, Cathi L.; Lagueux, Cynthia J.; Bethel, Thomas L.; Kenyon, Lory

    2017-01-01

    Somatic growth is an integrated, individual-based response to environmental conditions, especially in ectotherms. Growth dynamics of large, mobile animals are particularly useful as bio-indicators of environmental change at regional scales. We assembled growth rate data from throughout the West Atlantic for green turtles, Chelonia mydas, which are long-lived, highly migratory, primarily herbivorous mega-consumers that may migrate over hundreds to thousands of kilometers. Our dataset, the largest ever compiled for sea turtles, has 9690 growth increments from 30 sites from Bermuda to Uruguay from 1973 to 2015. Using generalized additive mixed models, we evaluated covariates that could affect growth rates; body size, diet, and year have significant effects on growth. Growth increases in early years until 1999, then declines by 26% to 2015. The temporal (year) effect is of particular interest because two carnivorous species of sea turtles – hawksbills, Eretmochelys imbricata, and loggerheads, Caretta caretta – exhibited similar significant declines in growth rates starting in 1997 in the West Atlantic, based on previous studies. These synchronous declines in productivity among three sea turtle species across a trophic spectrum provide strong evidence that an ecological regime shift (ERS) in the Atlantic is driving growth dynamics. The ERS resulted from a synergy of the 1997/1998 El Niño Southern Oscillation (ENSO) – the strongest on record – combined with an unprecedented warming rate over the last two to three decades. Further support is provided by the strong correlations between annualized mean growth rates of green turtles and both sea surface temperatures (SST) in the West Atlantic for years of declining growth rates (r = -0.94) and the Multivariate ENSO Index (MEI) for all years (r = 0.74). Granger-causality analysis also supports the latter finding. We discuss multiple stressors that could reinforce and prolong the effect of the ERS. This study

  10. Warm and Saline Events Embedded in the Meridional Circulation of the Northern North Atlantic

    Science.gov (United States)

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

    2011-01-01

    Ocean state estimates from 1958 to 2005 from the Simple Ocean Assimilation System (SODA) system are analyzed to understand circulation between subtropical and subpolar Atlantic and their connection with atmospheric forcing. This analysis shows three periods (1960s, around 1980, and 2000s) with enhanced warm, saline waters reaching high latitudes, alternating with freshwater events originating at high latitudes. It complements surface drifter and altimetry data showing the subtropical -subpolar exchange leading to a significant temperature and salinity increase in the northeast Atlantic after 2001. The warm water limb of the Atlantic meridional overturning cell represented by SODA expanded in density/salinity space during these warm events. Tracer simulations using SODA velocities also show decadal variation of the Gulf Stream waters reaching the subpolar gyre and Nordic seas. The negative phase of the North Atlantic Oscillation index, usually invoked in such variability, fails to predict the warming and salinization in the early 2000s, with salinities not seen since the 1960s. Wind stress curl variability provided a linkage to this subtropical/subpolar gyre exchange as illustrated using an idealized two ]layer circulation model. The ocean response to the modulation of the climatological wind stress curl pattern was found to be such that the northward penetration of subtropical tracers is enhanced when amplitude of the wind stress curl is weaker than normal. In this case both the subtropical and subpolar gyres weaken and the subpolar density surfaces relax; hence, the polar front moves westward, opening an enhanced northward access of the subtropical waters in the eastern boundary current.

  11. Ecological regime shift drives declining growth rates of sea turtles throughout the West Atlantic.

    Science.gov (United States)

    Bjorndal, Karen A; Bolten, Alan B; Chaloupka, Milani; Saba, Vincent S; Bellini, Cláudio; Marcovaldi, Maria A G; Santos, Armando J B; Bortolon, Luis Felipe Wurdig; Meylan, Anne B; Meylan, Peter A; Gray, Jennifer; Hardy, Robert; Brost, Beth; Bresette, Michael; Gorham, Jonathan C; Connett, Stephen; Crouchley, Barbara Van Sciver; Dawson, Mike; Hayes, Deborah; Diez, Carlos E; van Dam, Robert P; Willis, Sue; Nava, Mabel; Hart, Kristen M; Cherkiss, Michael S; Crowder, Andrew G; Pollock, Clayton; Hillis-Starr, Zandy; Muñoz Tenería, Fernando A; Herrera-Pavón, Roberto; Labrada-Martagón, Vanessa; Lorences, Armando; Negrete-Philippe, Ana; Lamont, Margaret M; Foley, Allen M; Bailey, Rhonda; Carthy, Raymond R; Scarpino, Russell; McMichael, Erin; Provancha, Jane A; Brooks, Annabelle; Jardim, Adriana; López-Mendilaharsu, Milagros; González-Paredes, Daniel; Estrades, Andrés; Fallabrino, Alejandro; Martínez-Souza, Gustavo; Vélez-Rubio, Gabriela M; Boulon, Ralf H; Collazo, Jaime A; Wershoven, Robert; Guzmán Hernández, Vicente; Stringell, Thomas B; Sanghera, Amdeep; Richardson, Peter B; Broderick, Annette C; Phillips, Quinton; Calosso, Marta; Claydon, John A B; Metz, Tasha L; Gordon, Amanda L; Landry, Andre M; Shaver, Donna J; Blumenthal, Janice; Collyer, Lucy; Godley, Brendan J; McGowan, Andrew; Witt, Matthew J; Campbell, Cathi L; Lagueux, Cynthia J; Bethel, Thomas L; Kenyon, Lory

    2017-11-01

    Somatic growth is an integrated, individual-based response to environmental conditions, especially in ectotherms. Growth dynamics of large, mobile animals are particularly useful as bio-indicators of environmental change at regional scales. We assembled growth rate data from throughout the West Atlantic for green turtles, Chelonia mydas, which are long-lived, highly migratory, primarily herbivorous mega-consumers that may migrate over hundreds to thousands of kilometers. Our dataset, the largest ever compiled for sea turtles, has 9690 growth increments from 30 sites from Bermuda to Uruguay from 1973 to 2015. Using generalized additive mixed models, we evaluated covariates that could affect growth rates; body size, diet, and year have significant effects on growth. Growth increases in early years until 1999, then declines by 26% to 2015. The temporal (year) effect is of particular interest because two carnivorous species of sea turtles-hawksbills, Eretmochelys imbricata, and loggerheads, Caretta caretta-exhibited similar significant declines in growth rates starting in 1997 in the West Atlantic, based on previous studies. These synchronous declines in productivity among three sea turtle species across a trophic spectrum provide strong evidence that an ecological regime shift (ERS) in the Atlantic is driving growth dynamics. The ERS resulted from a synergy of the 1997/1998 El Niño Southern Oscillation (ENSO)-the strongest on record-combined with an unprecedented warming rate over the last two to three decades. Further support is provided by the strong correlations between annualized mean growth rates of green turtles and both sea surface temperatures (SST) in the West Atlantic for years of declining growth rates (r = -.94) and the Multivariate ENSO Index (MEI) for all years (r = .74). Granger-causality analysis also supports the latter finding. We discuss multiple stressors that could reinforce and prolong the effect of the ERS. This study demonstrates the

  12. Automatic oscillator frequency control system

    Science.gov (United States)

    Smith, S. F. (Inventor)

    1985-01-01

    A frequency control system makes an initial correction of the frequency of its own timing circuit after comparison against a frequency of known accuracy and then sequentially checks and corrects the frequencies of several voltage controlled local oscillator circuits. The timing circuit initiates the machine cycles of a central processing unit which applies a frequency index to an input register in a modulo-sum frequency divider stage and enables a multiplexer to clock an accumulator register in the divider stage with a cyclical signal derived from the oscillator circuit being checked. Upon expiration of the interval, the processing unit compares the remainder held as the contents of the accumulator against a stored zero error constant and applies an appropriate correction word to a correction stage to shift the frequency of the oscillator being checked. A signal from the accumulator register may be used to drive a phase plane ROM and, with periodic shifts in the applied frequency index, to provide frequency shift keying of the resultant output signal. Interposition of a phase adder between the accumulator register and phase plane ROM permits phase shift keying of the output signal by periodic variation in the value of a phase index applied to one input of the phase adder.

  13. Visual record of intertidal disturbance caused by drift ice in the spring on the Atlantic coast of Nova Scotia [v1; ref status: indexed, http://f1000r.es/3fb

    Directory of Open Access Journals (Sweden)

    Willy Petzold

    2014-05-01

    Full Text Available In the early spring of 2014, an unusually large amount of sea ice drifted from the Gulf of St. Lawrence, where it had been produced, towards the open Atlantic Ocean through the Cabot Strait, between Nova Scotia and Newfoundland, Canada. In early April, significant amounts of drift ice reached the Atlantic coast of mainland Nova Scotia. The ice floes persisted in those coastal waters for up to 16 days, depending on the location. During that time, the ice fragments caused extensive physical disturbance in rocky intertidal communities, removing high quantities of seaweeds and invertebrates. For example, at a location where the ice stayed for 9 days, the loss of macroalgal and invertebrate biomass was almost total. At a location where the ice stayed for 4 days, losses were lower, albeit still high overall. Such a magnitude of disturbance is not common on this coast, as sea ice had not reached the surveyed locations in the previous 4–5 years. We suggest that the frequency of ice scour events may help to predict intertidal community structure. This notion could be tested through multiannual surveys of ice conditions and biological communities along the Atlantic coast of Nova Scotia.

  14. INDEXING AND INDEX FUNDS

    Directory of Open Access Journals (Sweden)

    HAKAN SARITAŞ

    2013-06-01

    Full Text Available Proponents of the efficient market hypothesis believe that active portfolio management is largely wasted effort and unlikely to justify the expenses incurred. Therefore, they advocate a passive investment strategy that makes no attempt to outsmart the market. One common strategy for passive management is indexing where a fund is designed to replicate the performance of a broad-based index of stocks and bonds. Traditionally, indexing was used by institutional investors, but today, the use of index funds proliferated among individual investors. Over the years, both international and domestic index funds have disproportionately outperformed the market more than the actively managed funds have.

  15. Discrete wavelet transform-based investigation into the variability of standardized precipitation index in Northwest China during 1960-2014

    Science.gov (United States)

    Yang, Peng; Xia, Jun; Zhan, Chesheng; Zhang, Yongyong; Hu, Sheng

    2018-04-01

    In this study, the temporal variations of the standard precipitation index (SPI) were analyzed at different scales in Northwest China (NWC). Discrete wavelet transform (DWT) was used in conjunction with the Mann-Kendall (MK) test in this study. This study also investigated the relationships between original precipitation and different periodic components of SPI series with datasets spanning 55 years (1960-2014). The results showed that with the exception of the annual and summer SPI in the Inner Mongolia Inland Rivers Basin (IMIRB), spring SPI in the Qinghai Lake Rivers Basin (QLRB), and spring SPI in the Central Asia Rivers Basin (CARB), it had an increasing trend in other regions for other time series. In the spring, summer, and autumn series, though the MK trends test in most areas was at the insignificant level, they showed an increasing trend in precipitation. Meanwhile, the SPI series in most subbasins of NWC displayed a turning point in 1980-1990, with the significant increasing levels after 2000. Additionally, there was a significant difference between the trend of the original SPI series and the largest approximations. The annual and seasonal SPI series were composed of the short periodicities, which were less than a decade. The MK value would increase by adding the multiple D components (and approximations), and the MK value of the combined series was in harmony with that of the original series. Additionally, the major trend of the annual SPI in NWC was based on the four kinds of climate indices (e.g., Atlantic Oscillation [AO], North Atlantic Oscillation [NAO], Pacific Decadal Oscillation [PDO], and El Nino-Southern Oscillation index [ENSO/NINO]), especially the ENSO.

  16. Oscillating heat pipes

    CERN Document Server

    Ma, Hongbin

    2015-01-01

    This book presents the fundamental fluid flow and heat transfer principles occurring in oscillating heat pipes and also provides updated developments and recent innovations in research and applications of heat pipes. Starting with fundamental presentation of heat pipes, the focus is on oscillating motions and its heat transfer enhancement in a two-phase heat transfer system. The book covers thermodynamic analysis, interfacial phenomenon, thin film evaporation,  theoretical models of oscillating motion and heat transfer of single phase and two-phase flows, primary  factors affecting oscillating motions and heat transfer,  neutron imaging study of oscillating motions in an oscillating heat pipes, and nanofluid’s effect on the heat transfer performance in oscillating heat pipes.  The importance of thermally-excited oscillating motion combined with phase change heat transfer to a wide variety of applications is emphasized. This book is an essential resource and learning tool for senior undergraduate, gradua...

  17. Automatic Oscillating Turret.

    Science.gov (United States)

    1981-03-01

    Final Report: February 1978 ZAUTOMATIC OSCILLATING TURRET SYSTEM September 1980 * 6. PERFORMING 01G. REPORT NUMBER .J7. AUTHOR(S) S. CONTRACT OR GRANT...o....e.... *24 APPENDIX P-4 OSCILLATING BUMPER TURRET ...................... 25 A. DESCRIPTION 1. Turret Controls ...Other criteria requirements were: 1. Turret controls inside cab. 2. Automatic oscillation with fixed elevation to range from 20* below the horizontal to

  18. Neutrino oscillations in matter

    International Nuclear Information System (INIS)

    Mikheyev, S.P.; Smirnov, A.Yu.

    1986-01-01

    In this paper we describe united formalism of ν-oscillations for different regimes, which is immediate generalization of vacuum oscillations theory. Adequate graphical representation of this formalism is given. We summarize main properties of ν-oscillations for different density distributions. (orig./BBOE)

  19. The colpitts oscillator family

    DEFF Research Database (Denmark)

    Lindberg, Erik; Murali, K.; Tamasevicius, A.

    A tutorial study of the Colpitts oscillator family defined as all oscillators based on a nonlinear amplifier and a three- terminal linear resonance circuit with one coil and two capacitors. The original patents are investigated. The eigenvalues of the linearized Jacobian for oscillators based...

  20. Patterns of variations in large pelagic fish: A comparative approach between the Indian and the Atlantic Oceans

    Science.gov (United States)

    Corbineau, A.; Rouyer, T.; Fromentin, J.-M.; Cazelles, B.; Fonteneau, A.; Ménard, F.

    2010-07-01

    Catch data of large pelagic fish such as tuna, swordfish and billfish are highly variable ranging from short to long term. Based on fisheries data, these time series are noisy and reflect mixed information on exploitation (targeting, strategy, fishing power), population dynamics (recruitment, growth, mortality, migration, etc.), and environmental forcing (local conditions or dominant climate patterns). In this work, we investigated patterns of variation of large pelagic fish (i.e. yellowfin tuna, bigeye tuna, swordfish and blue marlin) in Japanese longliners catch data from 1960 to 2004. We performed wavelet analyses on the yearly time series of each fish species in each biogeographic province of the tropical Indian and Atlantic Oceans. In addition, we carried out cross-wavelet analyses between these biological time series and a large-scale climatic index, i.e. the Southern Oscillation Index (SOI). Results showed that the biogeographic province was the most important factor structuring the patterns of variability of Japanese catch time series. Relationships between the SOI and the fish catches in the Indian and Atlantic Oceans also pointed out the role of climatic variability for structuring patterns of variation of catch time series. This work finally confirmed that Japanese longline CPUE data poorly reflect the underlying population dynamics of tunas.

  1. Atlantic Warm Pool Trigger for the Younger Dryas Climate Event

    Science.gov (United States)

    Abdul, N. A.; Mortlock, R. A.; Wright, J. D.; Fairbanks, R. G.; Teneva, L. T.

    2011-12-01

    There is growing evidence that variability in the size and heat content of the tropical Atlantic Warm Pool impacts circum-North Atlantic climate via the Atlantic Multi-decadal Oscillation mode (Wang et al., 2008). The Atlantic Warm Pool spans the Gulf of Mexico, Caribbean Sea and the western tropical North Atlantic. Barbados is located near the center of the tropical Atlantic Warm Pool and coupled ocean models suggest that Barbados remains near the center of the tropical Atlantic Warm Pool under varying wind stress simulations. Measurements of the oxygen isotope paleothermometer in Acropora palmata coral species recovered from cores offshore Barbados, show a 3oC monotonic decrease in sea surface temperature from 13106 ± 83 to 12744 ± 61 years before present (errors given as 2 sigma). This interval corresponds to a sea level rise from 71.4 meters to 67.1 meters below present levels at Barbados. The 3oC temperature decrease is captured in eight A. palmata specimens that are in stratigraphic sequence, 230Th/234U dated, and analyzed for oxygen isotopes. All measurements are replicated. We are confident that this is the warm pool equivalent of the Younger Dryas climate event. The initiation of this temperature drop in the Atlantic Warm Pool predates the Younger Dryas start in Greenland ice cores, reported to start at 12896 ± 138 years (relative to AD 2000) (Rasmussen et al., 2006), while few other Younger Dryas climate records are dated with similar accuracy to make the comparison. Rasmussen, S.O., Andersen, K.K., Svensson, A.M., Steffensen, J.P., Vinther, B.M., Clausen, H.B., Siggaard-Andersen, M.L., Johnsen, S.J., Larsen, L.B., Dahl-Jensen, D., Bigler, M., Röthlisberger, R., Fischer, H., Goto-Azuma, K., Hansson, M.E., and Ruth, U., 2006, A new Greenland ice core chronology for the last glacial termination: J. Geophys. Res., v. 111, p. D06102. Wang, C., Lee, S.-K., and Enfield, D.B., 2008, Atlantic Warm Pool acting as a link between Atlantic Multidecadal

  2. Nature's Autonomous Oscillators

    Science.gov (United States)

    Mayr, H. G.; Yee, J.-H.; Mayr, M.; Schnetzler, R.

    2012-01-01

    Nonlinearity is required to produce autonomous oscillations without external time dependent source, and an example is the pendulum clock. The escapement mechanism of the clock imparts an impulse for each swing direction, which keeps the pendulum oscillating at the resonance frequency. Among nature's observed autonomous oscillators, examples are the quasi-biennial oscillation and bimonthly oscillation of the Earth atmosphere, and the 22-year solar oscillation. The oscillations have been simulated in numerical models without external time dependent source, and in Section 2 we summarize the results. Specifically, we shall discuss the nonlinearities that are involved in generating the oscillations, and the processes that produce the periodicities. In biology, insects have flight muscles, which function autonomously with wing frequencies that far exceed the animals' neural capacity; Stretch-activation of muscle contraction is the mechanism that produces the high frequency oscillation of insect flight, discussed in Section 3. The same mechanism is also invoked to explain the functioning of the cardiac muscle. In Section 4, we present a tutorial review of the cardio-vascular system, heart anatomy, and muscle cell physiology, leading up to Starling's Law of the Heart, which supports our notion that the human heart is also a nonlinear oscillator. In Section 5, we offer a broad perspective of the tenuous links between the fluid dynamical oscillators and the human heart physiology.

  3. Northward advection of Atlantic water in the eastern Nordic Seas over the last 3000 yr

    Directory of Open Access Journals (Sweden)

    C. V. Dylmer

    2013-07-01

    Full Text Available Three marine sediment cores distributed along the Norwegian (MD95-2011, Barents Sea (JM09-KA11-GC, and Svalbard (HH11-134-BC continental margins have been investigated in order to reconstruct changes in the poleward flow of Atlantic waters (AW and in the nature of upper surface water masses within the eastern Nordic Seas over the last 3000 yr. These reconstructions are based on a limited set of coccolith proxies: the abundance ratio between Emiliania huxleyi and Coccolithus pelagicus, an index of Atlantic vs. Polar/Arctic surface water masses; and Gephyrocapsa muellerae, a drifted coccolith species from the temperate North Atlantic, whose abundance changes are related to variations in the strength of the North Atlantic Current. The entire investigated area, from 66 to 77° N, was affected by an overall increase in AW flow from 3000 cal yr BP (before present to the present. The long-term modulation of westerlies' strength and location, which are essentially driven by the dominant mode of the North Atlantic Oscillation (NAO, is thought to explain the observed dynamics of poleward AW flow. The same mechanism also reconciles the recorded opposite zonal shifts in the location of the Arctic front between the area off western Norway and the western Barents Sea–eastern Fram Strait region. The Little Ice Age (LIA was governed by deteriorating conditions, with Arctic/Polar waters dominating in the surface off western Svalbard and western Barents Sea, possibly associated with both severe sea ice conditions and a strongly reduced AW strength. A sudden short pulse of resumed high WSC (West Spitsbergen Current flow interrupted this cold spell in eastern Fram Strait from 330 to 410 cal yr BP. Our dataset not only confirms the high amplitude warming of surface waters at the turn of the 19th century off western Svalbard, it also shows that such a warming was primarily induced by an excess flow of AW which stands as unprecedented over the last 3000 yr.

  4. The Response of African Land Surface Phenology to Large Scale Climate Oscillations

    Science.gov (United States)

    Brown, Molly E.; de Beurs, Kirsten; Vrieling, Anton

    2010-01-01

    Variations in agricultural production due to rainfall and temperature fluctuations are a primary cause of food insecurity on the African continent. Analysis of changes in phenology can provide quantitative information on the effect of climate variability on growing seasons in agricultural regions. Using a robust statistical methodology, we describe the relationship between phenology metrics derived from the 26 year AVHRR NDVI record and the North Atlantic Oscillation index (NAO), the Indian Ocean Dipole (IOD), the Pacific Decadal Oscillation (PDO), and the Multivariate ENSO Index (MEI). We map the most significant positive and negative correlation for the four climate indices in Eastern, Western and Southern Africa between two phenological metrics and the climate indices. Our objective is to provide evidence of whether climate variability captured in the four indices has had a significant impact on the vegetative productivity of Africa during the past quarter century. We found that the start of season and cumulative NDVI were significantly affected by large scale variations in climate. The particular climate index and the timing showing highest correlation depended heavily on the region examined. In Western Africa the cumulative NDVI correlates with PDO in September-November. In Eastern Africa the start of the June-October season strongly correlates with PDO in March-May, while the PDO in December-February correlates with the start of the February-June season. The cumulative NDVI over this last season relates to the MEI of March-May. For Southern Africa, high correlations exist between SOS and NAO of September-November, and cumulative NDVI and MEI of March-May. The research shows that climate indices can be used to anticipate late start and variable vigor in the growing season of sensitive agricultural regions in Africa.

  5. The North Atlantic Oscillation system and plant phenology

    Czech Academy of Sciences Publication Activity Database

    Hubálek, Zdeněk

    2016-01-01

    Roč. 60, č. 5 (2016), s. 749-756 ISSN 0020-7128 Institutional support: RVO:68081766 Keywords : NAO * atmospheric circulation * weather * temperature * flowering timing * Czech Republic Subject RIV: EH - Ecology, Behaviour Impact factor: 2.204, year: 2016

  6. A memristor-based third-order oscillator: beyond oscillation

    KAUST Repository

    Talukdar, Abdul Hafiz Ibne

    2012-10-06

    This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.

  7. A memristor-based third-order oscillator: beyond oscillation

    KAUST Repository

    Talukdar, Abdul Hafiz Ibne; Radwan, Ahmed G.; Salama, Khaled N.

    2012-01-01

    This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.

  8. Oscillations of disks

    CERN Document Server

    Kato, Shoji

    2016-01-01

    This book presents the current state of research on disk oscillation theory, focusing on relativistic disks and tidally deformed disks. Since the launch of the Rossi X-ray Timing Explorer (RXTE) in 1996, many high-frequency quasiperiodic oscillations (HFQPOs) have been observed in X-ray binaries. Subsequently, similar quasi-periodic oscillations have been found in such relativistic objects as microquasars, ultra-luminous X-ray sources, and galactic nuclei. One of the most promising explanations of their origin is based on oscillations in relativistic disks, and a new field called discoseismology is currently developing. After reviewing observational aspects, the book presents the basic characteristics of disk oscillations, especially focusing on those in relativistic disks. Relativistic disks are essentially different from Newtonian disks in terms of several basic characteristics of their disk oscillations, including the radial distributions of epicyclic frequencies. In order to understand the basic processes...

  9. Oscillations in stellar atmospheres

    International Nuclear Information System (INIS)

    Costa, A.; Ringuelet, A.E.; Fontenla, J.M.

    1989-01-01

    Atmospheric excitation and propagation of oscillations are analyzed for typical pulsating stars. The linear, plane-parallel approach for the pulsating atmosphere gives a local description of the phenomenon. From the local analysis of oscillations, the minimum frequencies are obtained for radially propagating waves. The comparison of the minimum frequencies obtained for a variety of stellar types is in good agreement with the observed periods of the oscillations. The role of the atmosphere in the globar stellar pulsations is thus emphasized. 7 refs

  10. Atlantic Salmon Telemetry Monitoring

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Annual telemetry data are collected as part of specific projects (assessments within watersheds) or as opportunistic efforts to characterize Atlantic salmon smolt...

  11. GARP Atlantic Tropical Experiment

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The GARP Atlantic Tropical Experiment (GATE) was the first major international experiment of the Global Atmospheric Research Program (GARP). It was conducted over...

  12. The Recent Atlantic Cold Anomaly: Causes, Consequences, and Related Phenomena

    Science.gov (United States)

    Josey, Simon A.; Hirschi, Joel J.-M.; Sinha, Bablu; Duchez, Aurélie; Grist, Jeremy P.; Marsh, Robert

    2018-01-01

    Cold ocean temperature anomalies have been observed in the mid- to high-latitude North Atlantic on interannual to centennial timescales. Most notably, a large region of persistently low surface temperatures accompanied by a sharp reduction in ocean heat content was evident in the subpolar gyre from the winter of 2013-2014 to 2016, and the presence of this feature at a time of pervasive warming elsewhere has stimulated considerable debate. Here, we review the role of air-sea interaction and ocean processes in generating this cold anomaly and place it in a longer-term context. We also discuss the potential impacts of surface temperature anomalies for the atmosphere, including the North Atlantic Oscillation and European heat waves; contrast the behavior of the Atlantic with the extreme warm surface event that occurred in the North Pacific over a similar timescale; and consider the possibility that these events represent a response to a change in atmospheric planetary wave forcing.

  13. Influence of North Atlantic modes on European climate extremes

    Science.gov (United States)

    Proemmel, K.; Cubasch, U.

    2017-12-01

    It is well known that the North Atlantic strongly influences European climate. Only few studies exist that focus on its impact on climate extremes. We are interested in these extremes and the processes and mechanisms behind it. For the analysis of the North Atlantic Oscillation (NAO) we use simulations performed with the Max Planck Institute for Meteorology Earth System Model (MPI-ESM). The NAO has a strong impact especially on European winter and the changes in minimum temperature are even larger than in maximum temperature. The impact of the Atlantic Multi-decadal Variability (AMV) on climate extremes is analyzed in ECHAM6 simulations forced with AMV warm and AMV cold sea surface temperature patterns. We analyze different extreme indices and try to understand the processes.

  14. The Oscillator Principle of Nature

    DEFF Research Database (Denmark)

    Lindberg, Erik

    2012-01-01

    Oscillators are found on all levels in Nature. The general oscillator concept is defined and investigated. Oscillators may synchronize into fractal patterns. Apparently oscillators are the basic principle in Nature. The concepts of zero and infinite are discussed. Electronic manmade oscillators...

  15. Longevity of Atlantic Sharpnose Sharks Rhizoprionodon terraenovae and Blacknose Sharks Carcharhinus acronotus in the western North Atlantic Ocean based on tag-recapture data and direct age estimates [v2; ref status: indexed, http://f1000r.es/4fj

    Directory of Open Access Journals (Sweden)

    Bryan S. Frazier

    2015-01-01

    Full Text Available Longevity of Rhizoprionodon terraenovae and Carcharhinus acronotus in the western North Atlantic Ocean was examined using direct age estimates from vertebral sections and tag-recapture data. Time-at-liberty ranged from 7.7-14.0 years (mean =10.1 for R. terraenovae and 10.9-12.8 years (mean =11.9 for C. acronotus. Maximum estimated longevity was determined to be 19.8 years through tag-recapture data and 18.5 years from direct age estimates for R. terraenovae and 22.8 years through tag-recapture data and 20.5 years through direct age estimates for C. acronotus. These longevity estimates represent a large increase over previous estimates and may have significant effects on analyses that depend on longevity including lifetime fecundity, mortality rates, demographic analyses and stock assessments.

  16. On the Dirac oscillator

    International Nuclear Information System (INIS)

    Rodrigues, R. de Lima

    2007-01-01

    In the present work we obtain a new representation for the Dirac oscillator based on the Clifford algebra C 7. The symmetry breaking and the energy eigenvalues for our model of the Dirac oscillator are studied in the non-relativistic limit. (author)

  17. A Conspiracy of Oscillators

    DEFF Research Database (Denmark)

    Hjorth, Poul G.

    2008-01-01

    We discuss nonlinear mechanical systems containing several oscillators whose frequecies are all much higher than frequencies associated with the remaining degrees of freedom. In this situation a near constant of the motion, an adiabatic invariant, exists which is the sum of all the oscillator...... actions. The phenomenon is illustrated, and calculations of the small change of the adiabatic invariant is outlined....

  18. Synchronization of hyperchaotic oscillators

    DEFF Research Database (Denmark)

    Tamasevicius, A.; Cenys, A.; Mykolaitis, G.

    1997-01-01

    Synchronization of chaotic oscillators is believed to have promising applications in secure communications. Hyperchaotic systems with multiple positive Lyapunov exponents (LEs) have an advantage over common chaotic systems with only one positive LE. Three different types of hyperchaotic electronic...... oscillators are investigated demonstrating synchronization by means of only one properly selected variable....

  19. ATLANTIC-DIP: raised maternal body mass index (BMI) adversely affects maternal and foetal outcomes in glucose tolerant women classified using International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria

    LENUS (Irish Health Repository)

    Dennedy, MC

    2011-09-15

    Background and aims: Raised maternal body mass index (BMI), in association with hyperglycaemia is associated with adverse pregnancy outcome. Whether BMI has an independent effect on adverse pregnancy outcome is not clear. We aimed to investigate the effects of raised maternal BMI on pregnancy outcome in glucose tolerant women, classified using the IADPSG criteria.\\r\

  20. Atlantic menhaden adult tagging study

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Atlantic menhaden are a schooling forage fish species, which are subject to a large commercial purse seine fishery. Atlantic menhaden are harvested for reduction...

  1. Somatic growth dynamics of West Atlantic hawksbill sea turtles: a spatio-temporal perspective

    Science.gov (United States)

    Bjorndal, Karen A.; Chaloupka, Milani; Saba, Vincent S.; Diez, Carlos E.; van Dam, Robert P.; Krueger, Barry H.; Horrocks, Julia A.; Santos, Armando J.B.; Bellini, Cláudio; Marcovaldi, Maria A.G.; Nava, Mabel; Willis, Sue; Godley, Brendan J.; Gore, Shannon; Hawkes, Lucy A.; McGowan, Andrew; Witt, Matthew J.; Stringell, Thomas B.; Sanghera, Amdeep; Richardson, Peter B.; Broderick, Annette C.; Phillips, Quinton; Calosso, Marta C.; Claydon, John A.B.; Blumenthal, Janice; Moncada, Felix; Nodarse, Gonzalo; Medina, Yosvani; Dunbar, Stephen G.; Wood, Lawrence D.; Lagueux, Cynthia J.; Campbell, Cathi L.; Meylan, Anne B.; Meylan, Peter A.; Burns Perez, Virginia R.; Coleman, Robin A.; Strindberg, Samantha; Guzmán-H, Vicente; Hart, Kristen M.; Cherkiss, Michael S.; Hillis-Starr, Zandy; Lundgren, Ian; Boulon, Ralf H.; Connett, Stephen; Outerbridge, Mark E.; Bolten, Alan B.

    2016-01-01

    Somatic growth dynamics are an integrated response to environmental conditions. Hawksbill sea turtles (Eretmochelys imbricata) are long-lived, major consumers in coral reef habitats that move over broad geographic areas (hundreds to thousands of kilometers). We evaluated spatio-temporal effects on hawksbill growth dynamics over a 33-yr period and 24 study sites throughout the West Atlantic and explored relationships between growth dynamics and climate indices. We compiled the largest ever data set on somatic growth rates for hawksbills – 3541 growth increments from 1980 to 2013. Using generalized additive mixed model analyses, we evaluated 10 covariates, including spatial and temporal variation, that could affect growth rates. Growth rates throughout the region responded similarly over space and time. The lack of a spatial effect or spatio-temporal interaction and the very strong temporal effect reveal that growth rates in West Atlantic hawksbills are likely driven by region-wide forces. Between 1997 and 2013, mean growth rates declined significantly and steadily by 18%. Regional climate indices have significant relationships with annual growth rates with 0- or 1-yr lags: positive with the Multivariate El Niño Southern Oscillation Index (correlation = 0.99) and negative with Caribbean sea surface temperature (correlation = −0.85). Declines in growth rates between 1997 and 2013 throughout the West Atlantic most likely resulted from warming waters through indirect negative effects on foraging resources of hawksbills. These climatic influences are complex. With increasing temperatures, trajectories of decline of coral cover and availability in reef habitats of major prey species of hawksbills are not parallel. Knowledge of how choice of foraging habitats, prey selection, and prey abundance are affected by warming water temperatures is needed to understand how climate change will affect productivity of consumers that live in association with coral reefs. Main

  2. Variability of tropical cyclone rapid intensification in the North Atlantic and its relationship with climate variations

    Science.gov (United States)

    Wang, Chunzai; Wang, Xidong; Weisberg, Robert H.; Black, Michael L.

    2017-12-01

    The paper uses observational data from 1950 to 2014 to investigate rapid intensification (RI) variability of tropical cyclones (TCs) in the North Atlantic and its relationships with large-scale climate variations. RI is defined as a TC intensity increase of at least 15.4 m/s (30 knots) in 24 h. The seasonal RI distribution follows the seasonal TC distribution, with the highest number in September. Although an RI event can occur anywhere over the tropical North Atlantic (TNA), there are three regions of maximum RI occurrence: (1) the western TNA of 12°N-18°N and 60°W-45°W, (2) the Gulf of Mexico and the western Caribbean Sea, and (3) the open ocean southeast and east of Florida. RI events also show a minimum value in the eastern Caribbean Sea north of South America—a place called a hurricane graveyard due to atmospheric divergence and subsidence. On longer time scales, RI displays both interannual and multidecadal variability, but RI does not show a long-term trend due to global warming. The top three climate indices showing high correlations with RI are the June-November ENSO and Atlantic warm pool indices, and the January-March North Atlantic oscillation index. It is found that variabilities of vertical wind shear and TC heat potential are important for TC RI in the hurricane main development region, whereas relative humidity at 500 hPa is the main factor responsible for TC RI in the eastern TNA. However, the large-scale oceanic and atmospheric variables analyzed in this study do not show an important role in TC RI in the Gulf of Mexico and the open ocean southeast and east of Florida. This suggests that other factors such as small-scale changes of oceanic and atmospheric variables or TC internal processes may be responsible for TC RI in these two regions. Additionally, the analyses indicate that large-scale atmospheric and oceanic variables are not critical to TC genesis and formation; however, once a tropical depression forms, large-scale climate

  3. Coccolithophore surface distributions in the North Atlantic and their modulation of the air-sea flux of CO2 from 10 years of satellite Earth observation data

    Directory of Open Access Journals (Sweden)

    J. D. Shutler

    2013-04-01

    Full Text Available Coccolithophores are the primary oceanic phytoplankton responsible for the production of calcium carbonate (CaCO3. These climatically important plankton play a key role in the oceanic carbon cycle as a major contributor of carbon to the open ocean carbonate pump (~50% and their calcification can affect the atmosphere-to-ocean (air-sea uptake of carbon dioxide (CO2 through increasing the seawater partial pressure of CO2 (pCO2. Here we document variations in the areal extent of surface blooms of the globally important coccolithophore, Emiliania huxleyi, in the North Atlantic over a 10-year period (1998–2007, using Earth observation data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS. We calculate the annual mean sea surface areal coverage of E. huxleyi in the North Atlantic to be 474 000 ± 104 000 km2, which results in a net CaCO3 carbon (CaCO3-C production of 0.14–1.71 Tg CaCO3-C per year. However, this surface coverage (and, thus, net production can fluctuate inter-annually by −54/+8% about the mean value and is strongly correlated with the El Niño/Southern Oscillation (ENSO climate oscillation index (r=0.75, pE. huxleyi blooms in the North Atlantic can increase the pCO2 and, thus, decrease the localised air-sea flux of atmospheric CO2. In regions where the blooms are prevalent, the average reduction in the monthly air-sea CO2 flux can reach 55%. The maximum reduction of the monthly air-sea CO2 flux in the time series is 155%. This work suggests that the high variability, frequency and distribution of these calcifying plankton and their impact on pCO2 should be considered if we are to fully understand the variability of the North Atlantic air-to-sea flux of CO2. We estimate that these blooms can reduce the annual N. Atlantic net sink atmospheric CO2 by between 3–28%.

  4. Discover the Atlantic Ocean: An Exciting Coloring Book of Fish and Shellfish.

    Science.gov (United States)

    Flick, George J.

    This coloring book contains pictures of more than 79 fish and shellfish found on the Atlantic Coast. Captions give information on habitats, behavior, or commercial uses of the species pictured. Indexes of both common and scientific names are given. (BB)

  5. Observation of Quasichanneling Oscillations

    International Nuclear Information System (INIS)

    Wistisen, T. N.; Mikkelsen, R. E.; Uggerhoj, University I.; Wienands, University; Markiewicz, T. W.

    2017-01-01

    Here, we report on the first experimental observations of quasichanneling oscillations, recently seen in simulations and described theoretically. Although above-barrier particles penetrating a single crystal are generally seen as behaving almost as in an amorphous substance, distinct oscillation peaks nevertheless appear for particles in that category. The quasichanneling oscillations were observed at SLAC National Accelerator Laboratory by aiming 20.35 GeV positrons and electrons at a thin silicon crystal bent to a radius of R = 0.15 m, exploiting the quasimosaic effect. For electrons, two relatively faint quasichanneling peaks were observed, while for positrons, seven quasichanneling peaks were clearly identified.

  6. LSND neutrino oscillation results

    International Nuclear Information System (INIS)

    Louis, W.C.

    1996-01-01

    In the past several years, a number of experiments have searched for neutrino oscillations, where a neutrino of one type (say bar ν μ ) spontaneously transforms into a neutrino of another type (say bar ν e ). For this phenomenon to occur, neutrinos must be massive and the apparent conservation law of lepton families must be violated. In 1995 the LSND experiment published data showing candidate events that are consistent with bar ν μ oscillations. Additional data are reported here which provide stronger evidence for neutrino oscillations

  7. Neutrino Oscillation Physics

    International Nuclear Information System (INIS)

    Kayser, Boris

    2014-01-01

    To complement the neutrino-physics lectures given at the 2011 International School on Astro Particle Physics devoted to Neutrino Physics and Astrophysics (ISAPP 2011; Varenna, Italy), at the 2011 European School of High Energy Physics (ESHEP 2011; Cheila Gradistei, Romania), and, in modified form, at other summer schools, we present here a written description of the physics of neutrino oscillation. This description is centered on a new way of deriving the oscillation probability. We also provide a brief guide to references relevant to topics other than neutrino oscillation that were covered in the lectures

  8. Neutrino Oscillation Physics

    Energy Technology Data Exchange (ETDEWEB)

    Kayser, Boris [Fermilab (United States)

    2014-07-01

    To complement the neutrino-physics lectures given at the 2011 International School on Astro Particle Physics devoted to Neutrino Physics and Astrophysics (ISAPP 2011; Varenna, Italy), at the 2011 European School of High Energy Physics (ESHEP 2011; Cheila Gradistei, Romania), and, in modified form, at other summer schools, we present here a written description of the physics of neutrino oscillation. This description is centered on a new way of deriving the oscillation probability. We also provide a brief guide to references relevant to topics other than neutrino oscillation that were covered in the lectures.

  9. Oscillator, neutron modulator

    International Nuclear Information System (INIS)

    Agaisse, R.; Leguen, R.; Ombredane, D.

    1960-01-01

    The authors present a mechanical device and an electronic control circuit which have been designed to sinusoidally modulate the reactivity of the Proserpine atomic pile. The mechanical device comprises an oscillator and a mechanism assembly. The oscillator is made of cadmium blades which generate the reactivity oscillation. The mechanism assembly comprises a pulse generator for cycle splitting, a gearbox and an engine. The electronic device comprises or performs pulse detection, an on-off device, cycle pulse shaping, phase separation, a dephasing amplifier, electronic switches, counting scales, and control devices. All these elements are briefly presented

  10. Subject Index

    Indian Academy of Sciences (India)

    Seismic Study of Magnetic Field in the Solar Interior (H. M. Antia), 85 ... Hα Intensity Oscillations in Large Flares (Ram Ajor Maurya & Ashok Ambastha), 249 .... Utilization of GPS Satellites for Precise Irradiation Measurement and Monitoring.

  11. OSCILLATING FILAMENTS. I. OSCILLATION AND GEOMETRICAL FRAGMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    Gritschneder, Matthias; Heigl, Stefan; Burkert, Andreas, E-mail: gritschm@usm.uni-muenchen.de [University Observatory Munich, LMU Munich, Scheinerstrasse 1, D-81679 Munich (Germany)

    2017-01-10

    We study the stability of filaments in equilibrium between gravity and internal as well as external pressure using the grid-based AMR code RAMSES. A homogeneous, straight cylinder below a critical line mass is marginally stable. However, if the cylinder is bent, such as with a slight sinusoidal perturbation, an otherwise stable configuration starts to oscillate, is triggered into fragmentation, and collapses. This previously unstudied behavior allows a filament to fragment at any given scale, as long as it has slight bends. We call this process “geometrical fragmentation.” In our realization, the spacing between the cores matches the wavelength of the sinusoidal perturbation, whereas up to now, filaments were thought to be only fragmenting on the characteristic scale set by the mass-to-line ratio. Using first principles, we derive the oscillation period as well as the collapse timescale analytically. To enable a direct comparison with observations, we study the line-of-sight velocity for different inclinations. We show that the overall oscillation pattern can hide the infall signature of cores.

  12. Weakening and strengthening of the Indian monsoon during Heinrich events and Dansgaard-Oeschger oscillations

    NARCIS (Netherlands)

    Deplazes, G.; Lückge, A.; Stuut, J.-B.; Pätzold, J.; Kuhlmann, H.; Husson, D.; Fant, M.; Haug, G.H.

    2014-01-01

    The Dansgaard-Oeschger oscillations and Heinrich events described in North Atlantic sediments and Greenland ice are expressed in the climate of the tropics, for example, as documented in Arabian Sea sediments. Given the strength of this teleconnection, we seek to reconstruct its range of

  13. Again on neutrino oscillations

    International Nuclear Information System (INIS)

    Bilenky, S.M.; Pontecorvo, B.

    1976-01-01

    The general case is treated of a weak interaction theory in which a term violating lepton charges is present. In such a scheme the particles with definite masses are Majorana neutrinos (2N if in the weak interaction participate N four-component neutrinos). Neutrino oscillations are discussed and it is shown that the minimum average intensity at the earth of solar neutrinos is 1/2N of the intensity expected when oscillations are absent

  14. Density-wave oscillations

    International Nuclear Information System (INIS)

    Belblidia, L.A.; Bratianu, C.

    1979-01-01

    Boiling flow in a steam generator, a water-cooled reactor, and other multiphase processes can be subject to instabilities. It appears that the most predominant instabilities are the so-called density-wave oscillations. They can cause difficulties for three main reasons; they may induce burnout; they may cause mechanical vibrations of components; and they create system control problems. A comprehensive review is presented of experimental and theoretical studies concerning density-wave oscillations. (author)

  15. Oscillators and operational amplifiers

    OpenAIRE

    Lindberg, Erik

    2005-01-01

    A generalized approach to the design of oscillators using operational amplifiers as active elements is presented. A piecewise-linear model of the amplifier is used so that it make sense to investigate the eigenvalues of the Jacobian of the differential equations. The characteristic equation of the general circuit is derived. The dynamic nonlinear transfer characteristic of the amplifier is investigated. Examples of negative resistance oscillators are discussed.

  16. Chaotic solar oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Blacher, S; Perdang, J [Institut d' Astrophysique, B-4200 Cointe-Ougree (Belgium)

    1981-09-01

    A numerical experiment on Hamiltonian oscillations demonstrates the existence of chaotic motions which satisfy the property of phase coherence. It is observed that the low-frequency end of the power spectrum of such motions is remarkably similar in structure to the low-frequency SCLERA spectra. Since the smallness of the observed solar amplitudes is not a sufficient mathematical ground for inefficiency of non-linear effects the possibility of chaos among solar oscillations cannot be discarded a priori.

  17. NOAA predicts near-normal or below-normal 2014 Atlantic hurricane season

    Science.gov (United States)

    Related link: Atlantic Basin Hurricane Season Outlook Discussion El Niño/Southern Oscillation (ENSO ) Diagnostic Discussion National Hurricane Preparedness Week FEMA Media Contact Maureen O'Leary 301-427-9000 tips, along with video and audio public service announcements in both English and Spanish, featuring

  18. Decadal variability of drought conditions over the southern part of Europe based on Principal Oscillation Pattern Analysis

    Science.gov (United States)

    Ionita-Scholz, Monica; Tallaksen, Lena M.; Scholz, Patrick

    2017-04-01

    This study introduces a novel method of estimating the decay time, mean period and forcing statistics of drought conditions over large spatial domains, demonstrated here for southern part of Europe (10°E - 40°E, 35°N - 50°N). It uses a two-dimensional stochastically forced damped linear oscillator model with the model parameters estimated from a Principal Oscillation Pattern (POP) analysis and associated observed power spectra. POP is a diagnostic technique that aims to derive the space-time characteristics of a data set objectively. This analysis is performed on an extended observational time series of 114 years (1902 - 2015) of the Standardized Precipitation Evapotranspiration Index for an accumulation period of 12 months (SPEI12), based on the Climate Research Unit (CRU TS v. 3.24) data set. The POP analysis reveals four exceptionally stable modes of variability, which together explain more than 62% of the total explained variance. The most stable POP mode, which explains 16.3% of the total explained variance, is characterized by a period of oscillation of 14 years and a decay time of 31 years. The real part of POP1 is characterized by a monopole-like structure with the highest loadings over Portugal, western part of Spain and Turkey. The second stable mode, which explains 15.9% of the total explained variance, is characterized by a period of oscillation of 20 years and a decay time of 26.4 years. The spatial structure of the real part of POP2 has a dipole-like structure with the highest positive loadings over France, southern Germany and Romania and negative loadings over southern part of Spain. The third POP mode, in terms of stability, explains 14.0% of the total variance and is characterized by a period of oscillation of 33 years and a decay time of 43.5 years. The real part of POP3 is characterized by negative loadings over the eastern part of Europe and positive loadings over Turkey. The fourth stable POP mode, explaining 15.5% of the total variance

  19. Case for neutrino oscillations

    International Nuclear Information System (INIS)

    Ramond, P.

    1982-01-01

    The building of a machine capable of producing an intense, well-calibrated beam of muon neutrinos is regarded by particle physicists with keen interest because of its ability of studying neutrino oscillations. The possibility of neutrino oscillations has long been recognized, but it was not made necessary on theoretical or experimental grounds; one knew that oscillations could be avoided if neutrinos were massless, and this was easily done by the conservation of lepton number. The idea of grand unification has led physicists to question the existence (at higher energies) of global conservation laws. The prime examples are baryon-number conservation, which prevents proton decay, and lepton-number conservation, which keeps neutrinos massless, and therefore free of oscillations. The detection of proton decay and neutrino oscillations would therefore be an indirect indication of the idea of Grand Unification, and therefore of paramount importance. Neutrino oscillations occur when neutrinos acquire mass in such a way that the neutrino mass eigenstates do not match the (neutrino) eigenstates produced by the weak interactions. We shall study the ways in which neutrinos can get mass, first at the level of the standard SU 2 x U 1 model, then at the level of its Grand Unification Generalizations

  20. Atlantic multidecadal oceanic variability and its influence on the atmosphere in a climate model

    Energy Technology Data Exchange (ETDEWEB)

    Msadek, Rym; Frankignoul, Claude [Universite Pierre et Marie Curie, Paris 6, LOCEAN/IPSL, Paris (France)

    2009-07-15

    The mechanisms controlling the decadal to multidecadal variability of the Atlantic Meridional Overturning Circulation (MOC) and its influence on the atmosphere are investigated using a control simulation with the IPSL-CM4 climate model. The multidecadal fluctuations of the MOC are mostly driven by deep convection in the subpolar gyre, which occurs south of Iceland in the model. The latter is primarily influenced by the anomalous advection of salinity due to changes in the East Atlantic Pattern (EAP), which is the second mode of atmospheric variability in the North Atlantic region. The North Atlantic Oscillation is the dominant mode, but it plays a secondary role in the MOC fluctuations. During summer, the MOC variability is shown to have a significant impact on the atmosphere in the North Atlantic-European sector. The MOC influence is due to an interhemispheric sea surface temperature (SST) anomaly with opposite signs in the two hemispheres but largest amplitude in the northern one. The SST pattern driven by the MOC mostly resembles the model Atlantic Multidecadal Oscillation (AMO) and bears some similarity with the observed one. It is shown that the AMO reflects both the MOC influence and the local atmospheric forcing. Hence, the MOC influence on climate is best detected using lagged relations between climatic fields. The atmospheric response resembles the EAP, in a phase that might induce a weak positive feedback on the MOC. (orig.)

  1. Multidecadal oscillations in rainfall and hydrological extremes

    Science.gov (United States)

    Willems, Patrick

    2013-04-01

    Many studies have anticipated a worldwide increase in the frequency and intensity of precipitation extremes and floods since the last decade(s). Natural variability by climate oscillations partly determines the observed evolution of precipitation extremes. Based on a technique for the identification and analysis of changes in extreme quantiles, it is shown that hydrological extremes have oscillatory behaviour at multidecadal time scales. Results are based on nearly independent extremes extracted from long-term historical time series of precipitation intensities and river flows. Study regions include Belgium - The Netherlands (Meuse basin), Ethiopia (Blue Nile basin) and Ecuador (Paute basin). For Belgium - The Netherlands, the past 100 years showed larger and more hydrological extremes around the 1910s, 1950-1960s, and more recently during the 1990-2000s. Interestingly, the oscillations for southwestern Europe are anti-correlated with these of northwestern Europe, thus with oscillation highs in the 1930-1940s and 1970s. The precipitation oscillation peaks are explained by persistence in atmospheric circulation patterns over the North Atlantic during periods of 10 to 15 years. References: Ntegeka V., Willems P. (2008), 'Trends and multidecadal oscillations in rainfall extremes, based on a more than 100 years time series of 10 minutes rainfall intensities at Uccle, Belgium', Water Resources Research, 44, W07402, doi:10.1029/2007WR006471 Mora, D., Willems, P. (2012), 'Decadal oscillations in rainfall and air temperature in the Paute River Basin - Southern Andes of Ecuador', Theoretical and Applied Climatology, 108(1), 267-282, doi:0.1007/s00704-011-0527-4 Taye, M.T., Willems, P. (2011). 'Influence of climate variability on representative QDF predictions of the upper Blue Nile Basin', Journal of Hydrology, 411, 355-365, doi:10.1016/j.jhydrol.2011.10.019 Taye, M.T., Willems, P. (2012). 'Temporal variability of hydro-climatic extremes in the Blue Nile basin', Water

  2. Climate and changing winter distribution of alcids in the Northwest Atlantic

    Directory of Open Access Journals (Sweden)

    Richard R. Veit

    2015-04-01

    Full Text Available Population level impacts upon seabirds from changing climate are increasingly evident, and include effects on phenology, migration, dispersal, annual survivorship and reproduction. Most population data on seabirds derive from nesting colonies; documented climate impacts on winter ecology are scarce. We studied interannual variability in winter abundance of six species of alcids (Charadriiformes, Alcidae from a 58-year time series of data collected in Massachusetts 1954-2011. We used counts of birds taken during fall and winter from coastal vantage points. Counts were made by amateur birders, but coverage was consistent in timing and location. We found significant association between winter abundance of all six species of alcids and climate, indexed by North Atlantic Oscillation (NAO, at two temporal scales: 1. Significant linear trends at the 58-year scale of the time series; and 2. Shorter term fluctuations corresponding to the 5-8 year periodicity of NAO. Thus, variation in winter abundance of all six species of alcids was significantly related to the combined short-term and longer-term components of variation in NAO. Two low-Arctic species (Atlantic Puffin and Black Guillemot peaked during NAO positive years, while two high Arctic species (Dovekie and Thick-billed Murre peaked during NAO negative years. For Common Murres and Razorbills, southward shifts in winter distribution have been accompanied by southward expansion of breeding range, and increase within the core of the range. The proximate mechanism governing these changes is unclear, but, as for most other species of seabirds whose distributions have changed with climate, seems likely to be through their prey.

  3. 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.)

  4. ECMWF Extreme Forecast Index for water vapor transport: A forecast tool for atmospheric rivers and extreme precipitation

    Science.gov (United States)

    Lavers, David A.; Pappenberger, Florian; Richardson, David S.; Zsoter, Ervin

    2016-11-01

    In winter, heavy precipitation and floods along the west coasts of midlatitude continents are largely caused by intense water vapor transport (integrated vapor transport (IVT)) within the atmospheric river of extratropical cyclones. This study builds on previous findings that showed that forecasts of IVT have higher predictability than precipitation, by applying and evaluating the European Centre for Medium-Range Weather Forecasts Extreme Forecast Index (EFI) for IVT in ensemble forecasts during three winters across Europe. We show that the IVT EFI is more able (than the precipitation EFI) to capture extreme precipitation in forecast week 2 during forecasts initialized in a positive North Atlantic Oscillation (NAO) phase; conversely, the precipitation EFI is better during the negative NAO phase and at shorter leads. An IVT EFI example for storm Desmond in December 2015 highlights its potential to identify upcoming hydrometeorological extremes, which may prove useful to the user and forecasting communities.

  5. Harvesting Atlantic Cod under Climate Variability

    Science.gov (United States)

    Oremus, K. L.

    2016-12-01

    Previous literature links the growth of a fishery to climate variability. This study uses an age-structured bioeconomic model to compare optimal harvest in the Gulf of Maine Atlantic cod fishery under a variable climate versus a static climate. The optimal harvest path depends on the relationship between fishery growth and the interest rate, with higher interest rates dictating greater harvests now at the cost of long-term stock sustainability. Given the time horizon of a single generation of fishermen under assumptions of a static climate, the model finds that the economically optimal management strategy is to harvest the entire stock in the short term and allow the fishery to collapse. However, if the biological growth of the fishery is assumed to vary with climate conditions, such as the North Atlantic Oscillation, there will always be pulses of high growth in the stock. During some of these high-growth years, the growth of the stock and its economic yield can exceed the growth rate of the economy even under high interest rates. This implies that it is not economically optimal to exhaust the New England cod fishery if NAO is included in the biological growth function. This finding may have theoretical implications for the management of other renewable yet exhaustible resources whose growth rates are subject to climate variability.

  6. Do muons oscillate?

    International Nuclear Information System (INIS)

    Dolgov, A.D.; Morozov, A.Yu.; Okun, L.B.; Schepkin, M.G.

    1997-01-01

    We develop a theory of the EPR-like effects due to neutrino oscillations in the π→μν decays. Its experimental implications are space-time correlations of the neutrino and muon when they are both detected, while the pion decay point is not fixed. However, the more radical possibility of μ-oscillations in experiments where only muons are detected (as suggested in hep-ph/9509261), is ruled out. We start by discussing decays of monochromatic pions, and point out a few ''paradoxes''. Then we consider pion wave packets, solve the ''paradoxes'', and show that the formulas for μν correlations can be transformed into the usual expressions, describing neutrino oscillations, as soon as the pion decay point is fixed. (orig.)

  7. Oscillations in neutron stars

    International Nuclear Information System (INIS)

    Hoeye, Gudrun Kristine

    1999-01-01

    We have studied radial and nonradial oscillations in neutron stars, both in a general relativistic and non-relativistic frame, for several different equilibrium models. Different equations of state were combined, and our results show that it is possible to distinguish between the models based on their oscillation periods. We have particularly focused on the p-, f-, and g-modes. We find oscillation periods of II approx. 0.1 ms for the p-modes, II approx. 0.1 - 0.8 ms for the f-modes and II approx. 10 - 400 ms for the g-modes. For high-order (l → 4) f-modes we were also able to derive a formula that determines II l+1 from II l and II l-1 to an accuracy of 0.1%. Further, for the radial f-mode we find that the oscillation period goes to infinity as the maximum mass of the star is approached. Both p-, f-, and g-modes are sensitive to changes in the central baryon number density n c , while the g-modes are also sensitive to variations in the surface temperature. The g-modes are concentrated in the surface layer, while p- and f-modes can be found in all parts of the star. The effects of general relativity were studied, and we find that these are important at high central baryon number densities, especially for the p- and f-modes. General relativistic effects can therefore not be neglected when studying oscillations in neutron stars. We have further developed an improved Cowling approximation in the non-relativistic frame, which eliminates about half of the gap in the oscillation periods that results from use of the ordinary Cowling approximation. We suggest to develop an improved Cowling approximation also in the general relativistic frame. (Author)

  8. Oscillations in neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Hoeye, Gudrun Kristine

    1999-07-01

    We have studied radial and nonradial oscillations in neutron stars, both in a general relativistic and non-relativistic frame, for several different equilibrium models. Different equations of state were combined, and our results show that it is possible to distinguish between the models based on their oscillation periods. We have particularly focused on the p-, f-, and g-modes. We find oscillation periods of II approx. 0.1 ms for the p-modes, II approx. 0.1 - 0.8 ms for the f-modes and II approx. 10 - 400 ms for the g-modes. For high-order (l (>{sub )} 4) f-modes we were also able to derive a formula that determines II{sub l+1} from II{sub l} and II{sub l-1} to an accuracy of 0.1%. Further, for the radial f-mode we find that the oscillation period goes to infinity as the maximum mass of the star is approached. Both p-, f-, and g-modes are sensitive to changes in the central baryon number density n{sub c}, while the g-modes are also sensitive to variations in the surface temperature. The g-modes are concentrated in the surface layer, while p- and f-modes can be found in all parts of the star. The effects of general relativity were studied, and we find that these are important at high central baryon number densities, especially for the p- and f-modes. General relativistic effects can therefore not be neglected when studying oscillations in neutron stars. We have further developed an improved Cowling approximation in the non-relativistic frame, which eliminates about half of the gap in the oscillation periods that results from use of the ordinary Cowling approximation. We suggest to develop an improved Cowling approximation also in the general relativistic frame. (Author)

  9. The impact of gyre dynamics on the mid-depth salinity signature of the eastern North Atlantic

    Science.gov (United States)

    Burkholder, K. C.; Lozier, M. S.

    2009-04-01

    The Mediterranean Overflow Water (MOW) is widely recognized for its role in establishing the mid-depth salinity signature of the subtropical North Atlantic. However, recent work has revealed an intermittent impact of MOW on the salinity signature of the eastern subpolar basin. This impact results from a temporally variable penetration of the northward flowing branch of the MOW past Porcupine Bank into the eastern subpolar basin. It has been shown that the salinity signature of the eastern subpolar basin, in particular the Rockall Trough, varies with the state of the North Atlantic Oscillation (NAO): during persistent periods of strong winds (high NAO index), when the subpolar front moves eastward, waters in the subpolar gyre block the northward flowing MOW, preventing its entry into the subpolar gyre. Conversely, during persistent periods of weak winds (low NAO index), the front moves westward, allowing MOW to penetrate north of Porcupine Bank and into the subpolar gyre. Here, we investigate the manner in which the spatial and temporal variability in the northward penetration of the MOW and the position of the eastern limb of the subpolar front affect the mid-depth property fields not only in the subpolar gyre, but in the subtropical gyre as well. Using approximately 55 years of historical hydrographic data and output from the 1/12° FLAME model, we analyze the temporal variability of salinity along the eastern boundary and compare this variability to the position of the subpolar front in both the observational record and the FLAME model. We conclude that when the zonal position of the subpolar front moves relatively far offshore and the MOW is able to penetrate to the north, high salinity anomalies are observed at high latitudes and low salinity anomalies are observed at low latitudes. Conversely, when the frontal position shifts to the east, the MOW (and thus, the high salinity signature) is blocked, resulting in a drop in salinity anomalies at high latitudes

  10. Oscillating acoustic streaming jet

    International Nuclear Information System (INIS)

    Moudjed, Brahim; Botton, Valery; Henry, Daniel; Millet, Severine; Ben Hadid, Hamda; Garandet, Jean-Paul

    2014-01-01

    The present paper provides the first experimental investigation of an oscillating acoustic streaming jet. The observations are performed in the far field of a 2 MHz circular plane ultrasound transducer introduced in a rectangular cavity filled with water. Measurements are made by Particle Image Velocimetry (PIV) in horizontal and vertical planes near the end of the cavity. Oscillations of the jet appear in this zone, for a sufficiently high Reynolds number, as an intermittent phenomenon on an otherwise straight jet fluctuating in intensity. The observed perturbation pattern is similar to that of former theoretical studies. This intermittently oscillatory behavior is the first step to the transition to turbulence. (authors)

  11. Oscillating Finite Sums

    KAUST Repository

    Alabdulmohsin, Ibrahim M.

    2018-03-07

    In this chapter, we use the theory of summability of divergent series, presented earlier in Chap. 4, to derive the analogs of the Euler-Maclaurin summation formula for oscillating sums. These formulas will, in turn, be used to perform many remarkable deeds with ease. For instance, they can be used to derive analytic expressions for summable divergent series, obtain asymptotic expressions of oscillating series, and even accelerate the convergence of series by several orders of magnitude. Moreover, we will prove the notable fact that, as far as the foundational rules of summability calculus are concerned, summable divergent series behave exactly as if they were convergent.

  12. Brownian parametric oscillators

    Science.gov (United States)

    Zerbe, Christine; Jung, Peter; Hänggi, Peter

    1994-05-01

    We discuss the stochastic dynamics of dissipative, white-noise-driven Floquet oscillators, characterized by a time-periodic stiffness. Thus far, little attention has been paid to these exactly solvable nonstationary systems, although they carry a rich potential for several experimental applications. Here, we calculate and discuss the mean values and variances, as well as the correlation functions and the Floquet spectrum. As one main result, we find for certain parameter values that the fluctuations of the position coordinate are suppressed as compared to the equilibrium value of a harmonic oscillator (parametric squeezing).

  13. Friedel oscillations in graphene

    DEFF Research Database (Denmark)

    Lawlor, J. A.; Power, S. R.; Ferreira, M.S.

    2013-01-01

    Symmetry breaking perturbations in an electronically conducting medium are known to produce Friedel oscillations in various physical quantities of an otherwise pristine material. Here we show in a mathematically transparent fashion that Friedel oscillations in graphene have a strong sublattice...... asymmetry. As a result, the presence of impurities and/or defects may impact the distinct graphene sublattices very differently. Furthermore, such an asymmetry can be used to explain the recent observations that nitrogen atoms and dimers are not randomly distributed in graphene but prefer to occupy one...

  14. Proprioceptive evoked gamma oscillations

    DEFF Research Database (Denmark)

    Arnfred, S.M.; Hansen, Lars Kai; Parnas, J.

    2007-01-01

    A proprioceptive stimulus consisting of a weight change of a handheld load has recently been shown to elicit an evoked potential. Previously, somatosensory gamma oscillations have only been evoked by electrical stimuli. We conjectured that a natural proprioceptive stimulus also would be able...... to evoke gamma oscillations. EEG was recorded using 64 channels in 14 healthy subjects. In each of three runs a stimulus of 100 g load increment in each hand was presented in 120 trials. Data were wavelet transformed and runs collapsed. Inter-trial phase coherence (ITPC) was computed as the best measure...

  15. Oscillating Finite Sums

    KAUST Repository

    Alabdulmohsin, Ibrahim M.

    2018-01-01

    In this chapter, we use the theory of summability of divergent series, presented earlier in Chap. 4, to derive the analogs of the Euler-Maclaurin summation formula for oscillating sums. These formulas will, in turn, be used to perform many remarkable deeds with ease. For instance, they can be used to derive analytic expressions for summable divergent series, obtain asymptotic expressions of oscillating series, and even accelerate the convergence of series by several orders of magnitude. Moreover, we will prove the notable fact that, as far as the foundational rules of summability calculus are concerned, summable divergent series behave exactly as if they were convergent.

  16. Oscillators from nonlinear realizations

    Science.gov (United States)

    Kozyrev, N.; Krivonos, S.

    2018-02-01

    We construct the systems of the harmonic and Pais-Uhlenbeck oscillators, which are invariant with respect to arbitrary noncompact Lie algebras. The equations of motion of these systems can be obtained with the help of the formalism of nonlinear realizations. We prove that it is always possible to choose time and the fields within this formalism in such a way that the equations of motion become linear and, therefore, reduce to ones of ordinary harmonic and Pais-Uhlenbeck oscillators. The first-order actions, that produce these equations, can also be provided. As particular examples of this construction, we discuss the so(2, 3) and G 2(2) algebras.

  17. Oscillation Baselining and Analysis Tool

    Energy Technology Data Exchange (ETDEWEB)

    2017-03-27

    PNNL developed a new tool for oscillation analysis and baselining. This tool has been developed under a new DOE Grid Modernization Laboratory Consortium (GMLC) Project (GM0072 - “Suite of open-source applications and models for advanced synchrophasor analysis”) and it is based on the open platform for PMU analysis. The Oscillation Baselining and Analysis Tool (OBAT) performs the oscillation analysis and identifies modes of oscillations (frequency, damping, energy, and shape). The tool also does oscillation event baselining (fining correlation between oscillations characteristics and system operating conditions).

  18. The East Atlantic - West Russia Teleconnection in the North Atlantic: Climate Impact and Relation to Rossby Wave Propagation

    Science.gov (United States)

    Lim, Young-Kwon

    2014-01-01

    Large-scale winter teleconnection of the East Atlantic - West Russia (EA-WR) over the Atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence. A rotated empirical orthogonal function (REOF) analysis of the upper-tropospheric monthly height field captures successfully the EA-WR pattern and its interannual variation, with the North Atlantic Oscillation as the first mode. EA-WRs climate impact extends from eastern North America to Eurasia. The positive (negative) EA-WR produces positive (negative) temperature anomalies over the eastern US, western Europe and Russia east of Caspian Sea, with negative (positive) anomalies over eastern Canada, eastern Europe including Ural Mountains and the Middle East. These anomalies are largely explained by lower-tropospheric temperature advections. Positive (negative) precipitation anomalies are found over the mid-latitude Atlantic and central Russia around 60E, where lower-level cyclonic (anticyclonic) circulation anomaly is dominant. The eastern Canada and the western Europe are characterized by negative (positive) precipitation anomalies.The EA-WR is found to be closely associated with Rossby wave propagation. Wave activity fluxes show that it is strongly tied to large-scale stationary waves. Furthermore, a stationary wave model (SWM) forced with vorticity transients in the mid-latitude Atlantic (approximately 40N) or diabatic heat source over the subtropical Atlantic near the Caribbean Sea produces well-organized EA-WR-like wave patterns, respectively. Sensitivity tests with the SWM indicate improvement in the simulation of the EA-WR when the mean state is modified to have a positive NAO component that enhances upper-level westerlies between 40-60N.

  19. Atlantic Basin refining profitability

    International Nuclear Information System (INIS)

    Jones, R.J.

    1998-01-01

    A review of the profitability margins of oil refining in the Atlantic Basin was presented. Petroleum refiners face the continuous challenge of balancing supply with demand. It would appear that the profitability margins in the Atlantic Basin will increase significantly in the near future because of shrinking supply surpluses. Refinery capacity utilization has reached higher levels than ever before. The American Petroleum Institute reported that in August 1997, U.S. refineries used 99 per cent of their capacity for several weeks in a row. U.S. gasoline inventories have also declined as the industry has focused on reducing capital costs. This is further evidence that supply and demand are tightly balanced. Some of the reasons for tightening supplies were reviewed. It was predicted that U.S. gasoline demand will continue to grow in the near future. Gasoline demand has not declined as expected because new vehicles are not any more fuel efficient today than they were a decade ago. Although federally-mandated fuel efficiency standards were designed to lower gasoline consumption, they may actually have prevented consumption from falling. Atlantic margins were predicted to continue moving up because of the supply and demand evidence: high capacity utilization rates, low operating inventories, limited capacity addition resulting from lower capital spending, continued U.S. gasoline demand growth, and steady total oil demand growth. 11 figs

  20. North Atlantic observations sharpen meridional overturning projections

    Science.gov (United States)

    Olson, R.; An, S.-I.; Fan, Y.; Evans, J. P.; Caesar, L.

    2018-06-01

    Atlantic Meridional Overturning Circulation (AMOC) projections are uncertain due to both model errors, as well as internal climate variability. An AMOC slowdown projected by many climate models is likely to have considerable effects on many aspects of global and North Atlantic climate. Previous studies to make probabilistic AMOC projections have broken new ground. However, they do not drift-correct or cross-validate the projections, and do not fully account for internal variability. Furthermore, they consider a limited subset of models, and ignore the skill of models at representing the temporal North Atlantic dynamics. We improve on previous work by applying Bayesian Model Averaging to weight 13 Coupled Model Intercomparison Project phase 5 models by their skill at modeling the AMOC strength, and its temporal dynamics, as approximated by the northern North-Atlantic temperature-based AMOC Index. We make drift-corrected projections accounting for structural model errors, and for the internal variability. Cross-validation experiments give approximately correct empirical coverage probabilities, which validates our method. Our results present more evidence that AMOC likely already started slowing down. While weighting considerably moderates and sharpens our projections, our results are at low end of previously published estimates. We project mean AMOC changes between periods 1960-1999 and 2060-2099 of -4.0 Sv and -6.8 Sv for RCP4.5 and RCP8.5 emissions scenarios respectively. The corresponding average 90% credible intervals for our weighted experiments are [-7.2, -1.2] and [-10.5, -3.7] Sv respectively for the two scenarios.

  1. Solar wind: A possible factor driving the interannual sea surface temperature tripolar mode over North Atlantic

    Science.gov (United States)

    Xiao, Ziniu; Li, Delin

    2016-06-01

    The effect of solar wind (SW) on the North Atlantic sea surface temperature (SST) in boreal winter is examined through an analysis of observational data during 1964-2013. The North Atlantic SSTs show a pronounced meridional tripolar pattern in response to solar wind speed (SWS) variations. This pattern is broadly similar to the leading empirical orthogonal function (EOF) mode of interannual variations in the wintertime SSTs over North Atlantic. The time series of this leading EOF mode of SST shows a significant interannual period, which is the same as that of wintertime SWS. This response also appears as a compact north-south seesaw of sea level pressure and a vertical tripolar structure of zonal wind, which simultaneously resembles the North Atlantic Oscillation (NAO) in the overlying atmosphere. As compared with the typical low SWS winters, during the typical high SWS winters, the stratospheric polar night jet (PNJ) is evidently enhanced and extends from the stratosphere to the troposphere, even down to the North Atlantic Ocean surface. Notably, the North Atlantic Ocean is an exclusive region in which the SW signal spreads downward from the stratosphere to the troposphere. Thus, it seems that the SW is a possible factor for this North Atlantic SST tripolar mode. The dynamical process of stratosphere-troposphere coupling, together with the global atmospheric electric circuit-cloud microphysical process, probably accounts for the particular downward propagation of the SW signal.

  2. Atlantic Oceanographic and Meteorological Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Atlantic Oceanographic and Meteorological Laboratory conducts research to understand the physical, chemical, and biological characteristics and processes of the...

  3. Drought in West Africa: How CHIRPS and Reference Evapotranspiration can be used for Index Insurance in a Non-Stationary Setting

    Science.gov (United States)

    Blakeley, S. L.; Husak, G. J.; Harrison, L.; Funk, C. C.; Osgood, D. E.; Peterson, P.

    2017-12-01

    Index insurance is increasingly used as a safety net and productivity tool in order to improve the resilience of small-holder farmers in developing countries. In West Africa, there are already index insurance projects in many countries, and various non-governmental organizations are eager to expand implementation of this risk management tool. Often, index insurance payouts rely on rainfall to determine drought years, but designation of years based on precipitation variations is particularly complex in places like West Africa where precipitation is subject to much natural variability across timescales [Giannini 2003, among others]. Furthermore, farmers must also rely on other weather factors for good crop yields, such as the availability of moisture for their plants to absorb and maximum daily temperatures staying within an acceptable range for the crops. In this presentation, the payouts of an index based on rainfall (as measured by the Climate Hazards Group Infrared Precipitation with Stations {CHIRPS} dataset) is compared to the payouts of an index using reference evapotranspiration data (using the ASCE's Penmen-Monteith formula and MERRA-2 drivers). The West African rainfall index exhibits a fair amount of long-term variability, reflective of the Atlantic Multidecadal Oscillation, but the reference evapotranspiration index shows different variability, through changes in radiative forcing and temperatures. Therefore, the use of rainfall for an index is appropriate for capturing rainfall deficits, but reference evapotranspiration may also be an appropriate addition to an index or as a stand-alone index for capturing crop stress. In summary, the results point to farmer input as an invaluable source of knowledge in determining the most appropriate dataset as an index for crop insurance. Alessandra Giannini, R Saravanan, and P Chang. Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales. Science, 302(5647):1027-1030, 2003.

  4. From excitability to oscillations

    DEFF Research Database (Denmark)

    Postnov, D. E.; Neganova, A. Y.; Jacobsen, J. C. B.

    2013-01-01

    One consequence of cell-to-cell communication is the appearance of synchronized behavior, where many cells cooperate to generate new dynamical patterns. We present a simple functional model of vasomotion based on the concept of a two-mode oscillator with dual interactions: via relatively slow dif...

  5. Neutrino oscillation experiments

    International Nuclear Information System (INIS)

    Camilleri, L.

    1996-01-01

    Neutrino oscillation experiments (ν μ →ν e and ν μ →ν τ ) currently being performed at accelerators are reviewed. Future plans for short and long base-line experiments are summarized. (author) 10 figs., 2 tabs., 29 refs

  6. A simple violin oscillator

    Science.gov (United States)

    Jones, R. T.

    1976-01-01

    For acoustic tests the violin is driven laterally at the bridge by a small speaker of the type commonly found in pocket transistor radios. An audio oscillator excites the tone which is picked up by a sound level meter. Gross patterns of vibration modes are obtained by the Chladni method.

  7. Nonlinearity in oscillating bridges

    Directory of Open Access Journals (Sweden)

    Filippo Gazzola

    2013-09-01

    Full Text Available We first recall several historical oscillating bridges that, in some cases, led to collapses. Some of them are quite recent and show that, nowadays, oscillations in suspension bridges are not yet well understood. Next, we survey some attempts to model bridges with differential equations. Although these equations arise from quite different scientific communities, they display some common features. One of them, which we believe to be incorrect, is the acceptance of the linear Hooke law in elasticity. This law should be used only in presence of small deviations from equilibrium, a situation which does not occur in widely oscillating bridges. Then we discuss a couple of recent models whose solutions exhibit self-excited oscillations, the phenomenon visible in real bridges. This suggests a different point of view in modeling equations and gives a strong hint how to modify the existing models in order to obtain a reliable theory. The purpose of this paper is precisely to highlight the necessity of revisiting the classical models, to introduce reliable models, and to indicate the steps we believe necessary to reach this target.

  8. Integrated optoelectronic oscillator.

    Science.gov (United States)

    Tang, Jian; Hao, Tengfei; Li, Wei; Domenech, David; Baños, Rocio; Muñoz, Pascual; Zhu, Ninghua; Capmany, José; Li, Ming

    2018-04-30

    With the rapid development of the modern communication systems, radar and wireless services, microwave signal with high-frequency, high-spectral-purity and frequency tunability as well as microwave generator with light weight, compact size, power-efficient and low cost are increasingly demanded. Integrated microwave photonics (IMWP) is regarded as a prospective way to meet these demands by hybridizing the microwave circuits and the photonics circuits on chip. In this article, we propose and experimentally demonstrate an integrated optoelectronic oscillator (IOEO). All of the devices needed in the optoelectronic oscillation loop circuit are monolithically integrated on chip within size of 5×6cm 2 . By tuning the injection current to 44 mA, the output frequency of the proposed IOEO is located at 7.30 GHz with phase noise value of -91 dBc/Hz@1MHz. When the injection current is increased to 65 mA, the output frequency can be changed to 8.87 GHz with phase noise value of -92 dBc/Hz@1MHz. Both of the oscillation frequency can be slightly tuned within 20 MHz around the center oscillation frequency by tuning the injection current. The method about improving the performance of IOEO is carefully discussed at the end of in this article.

  9. The variational spiked oscillator

    International Nuclear Information System (INIS)

    Aguilera-Navarro, V.C.; Ullah, N.

    1992-08-01

    A variational analysis of the spiked harmonic oscillator Hamiltonian -d 2 / d x 2 + x 2 + δ/ x 5/2 , δ > 0, is reported in this work. A trial function satisfying Dirichlet boundary conditions is suggested. The results are excellent for a large range of values of the coupling parameter. (author)

  10. Neutrino oscillation experiments

    Energy Technology Data Exchange (ETDEWEB)

    Camilleri, L [European Organization for Nuclear Research, Geneva (Switzerland)

    1996-11-01

    Neutrino oscillation experiments ({nu}{sub {mu}}{yields}{nu}{sub e} and {nu}{sub {mu}}{yields}{nu}{sub {tau}}) currently being performed at accelerators are reviewed. Future plans for short and long base-line experiments are summarized. (author) 10 figs., 2 tabs., 29 refs.

  11. Genetic diversity of Bromeliaceae species from the Atlantic Forest.

    Science.gov (United States)

    Sheu, Y; Cunha-Machado, A S; Gontijo, A B P L; Favoreto, F C; Soares, T B C; Miranda, F D

    2017-04-20

    The Bromeliaceae family includes a range of species used for many purposes, including ornamental use and use as food, medicine, feed, and fiber. The state of Espírito Santo, Brazil is a center of diversity for this family in the Atlantic Forest. We evaluated the genetic diversity of five populations of the Bromeliaceae family, including specimens of the genera Aechmea, Billbergia (subfamily Bromelioideae), and Pitcairnia (subfamily Pitcairnioidea), all found in the Atlantic Forest and distributed in the state of Espírito Santo. The number of alleles per locus in populations ranged from two to six and the fixation index (F), estimated for some simple sequence repeats in bromeliad populations, was less than zero in all populations. All markers in the Pitcairnia flammea population were in Hardy-Weinberg equilibrium (P Atlantic Forest remnants in the south of Espírito Santo state.

  12. Anharmonic oscillator and Bogoliubov transformation

    International Nuclear Information System (INIS)

    Pattnayak, G.C.; Torasia, S.; Rath, B.

    1990-01-01

    The anharmonic oscillator occupies a cornerstone in many problems in physics. It was observed that none of the authors have tested Bogoliubov transformation to study anharmonic oscillator. The groundstate energy of the anharmonic oscillator is studied using Bogoliubov transformation and the results presented. (author)

  13. Bimodal oscillations in nephron autoregulation

    DEFF Research Database (Denmark)

    Sosnovtseva, Olga; Pavlov, A.N.; Mosekilde, Erik

    2002-01-01

    The individual functional unit of the kidney (the nephron) displays oscillations in its pressure and flow regulation at two different time scales: fast oscillations associated with a myogenic dynamics of the afferent arteriole, and slower oscillations arising from a delay in the tubuloglomerular ...

  14. Salinity Trends within the Upper Layers of the Subpolar North Atlantic

    Science.gov (United States)

    Tesdal, J. E.; Abernathey, R.; Goes, J. I.; Gordon, A. L.; Haine, T. W. N.

    2017-12-01

    Examination of a range of salinity products collectively suggest widespread freshening of the North Atlantic from the mid-2000 to the present. Monthly salinity fields reveal negative trends that differ in magnitude and significance between western and eastern regions of the North Atlantic. These differences can be attributed to the large negative interannual excursions in salinity in the western subpolar gyre and the Labrador Sea, which are not apparent in the central or eastern subpolar gyre. This study demonstrates that temporal trends in salinity in the northwest (including the Labrador Sea) are subject to mechanisms that are distinct from those responsible for the salinity trends in central and eastern North Atlantic. In the western subpolar gyre a negative correlation between near surface salinity and the circulation strength of the subpolar gyre suggests that negative salinity anomalies are connected to an intensification of the subpolar gyre, which is causing increased flux of freshwater from the East Greenland Current and subsequent transport into the Labrador Sea during the melting season. Analyses of sea surface wind fields suggest that the strength of the subpolar gyre is linked to the North Atlantic Oscillation and Arctic Oscillation-driven changes in wind stress curl in the eastern subpolar gyre. If this trend of decreasing salinity continues, it has the potential to enhance water column stratification, reduce vertical fluxes of nutrients and cause a decline in biological production and carbon export in the North Atlantic Ocean.

  15. 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.)

  16. 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)

  17. Changing characteristics of streamflow in the Midwest and its relation to oceanic-atmospheric oscillations

    Science.gov (United States)

    Thakur, B.; Pathak, P.; Kalra, A.; Ahmad, S.

    2016-12-01

    The identification of primary drivers of streamflow may prove beneficial in forecasting streamflow in the Midwestern U.S. In the past researches, streamflow in the region have been strongly correlated with El Niño-Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO). The present study takes in to account the pre-defined Pacific and Atlantic Ocean regions (e.g., ENSO, PDO, AMO) along with new regions with an intent to identify new significantly correlated regions. This study assesses the interrelationship between sea surface temperatures (SST) anomalies in the Pacific and Atlantic Ocean and seasonal streamflow in the Midwestern U.S. Average Pacific and Atlantic Ocean SST anomalies, were calculated for 2 different 3 month series: September-November and December-February so as to create a lead time varying from 3 to 9 months. Streamflow were averaged for three seasons: spring (April-June), spring-summer (April-August) and summer (June-August). The correlation between streamflow and SST is analyzed using singular value decomposition for a period of 1960-2013. The result of the study showed several regions-other than the known Pacific and Atlantic Ocean regions- that were significantly correlated with streamflow stations. Higher correlation between the climate indices and streamflow were observed as the lead time decreased. The identification of the associations between SST and streamflow and significant SST regions in the Pacific and Atlantic Ocean may enhance the skill of streamflow predictability and water management in the region.

  18. Observation and analysis of oscillations in linear accelerators

    International Nuclear Information System (INIS)

    Seeman, J.T.

    1991-11-01

    This report discusses the following on oscillation in linear accelerators: Betatron Oscillations; Betatron Oscillations at High Currents; Transverse Profile Oscillations; Transverse Profile Oscillations at High Currents.; Oscillation and Profile Transient Jitter; and Feedback on Transverse Oscillations

  19. Reactor oscillator - Proposal of the organisation for oscillator operation; Reaktorski oscilator - Predlog organizacije rada na oscilatoru

    Energy Technology Data Exchange (ETDEWEB)

    Lolic, B; Loloc, B [Institute of Nuclear Sciences Boris Kidric, Laboratorija za fiziku reaktora, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    The organizational structure for operating the reactor with the reactor oscillator describes the duties of the reactor operators; staff responsible for operating the oscillator who are responsible for measurements, preparation of the samples and further treatment of the obtained results.

  20. Quenching oscillating behaviors in fractional coupled Stuart-Landau oscillators

    Science.gov (United States)

    Sun, Zhongkui; Xiao, Rui; Yang, Xiaoli; Xu, Wei

    2018-03-01

    Oscillation quenching has been widely studied during the past several decades in fields ranging from natural sciences to engineering, but investigations have so far been restricted to oscillators with an integer-order derivative. Here, we report the first study of amplitude death (AD) in fractional coupled Stuart-Landau oscillators with partial and/or complete conjugate couplings to explore oscillation quenching patterns and dynamics. It has been found that the fractional-order derivative impacts the AD state crucially. The area of the AD state increases along with the decrease of the fractional-order derivative. Furthermore, by introducing and adjusting a limiting feedback factor in coupling links, the AD state can be well tamed in fractional coupled oscillators. Hence, it provides one an effective approach to analyze and control the oscillating behaviors in fractional coupled oscillators.

  1. Walkability Index

    Science.gov (United States)

    The Walkability Index dataset characterizes every Census 2010 block group in the U.S. based on its relative walkability. Walkability depends upon characteristics of the built environment that influence the likelihood of walking being used as a mode of travel. The Walkability Index is based on the EPA's previous data product, the Smart Location Database (SLD). Block group data from the SLD was the only input into the Walkability Index, and consisted of four variables from the SLD weighted in a formula to create the new Walkability Index. This dataset shares the SLD's block group boundary definitions from Census 2010. The methodology describing the process of creating the Walkability Index can be found in the documents located at ftp://newftp.epa.gov/EPADataCommons/OP/WalkabilityIndex.zip. You can also learn more about the Smart Location Database at https://edg.epa.gov/data/Public/OP/Smart_Location_DB_v02b.zip.

  2. Pattern formation in arrays of chemical oscillators

    Indian Academy of Sciences (India)

    Chemical oscillators; phase flip; oscillation death. PACS No. 05.45 .... array oscillate (with varying amplitudes and frequencies), while the others experience oscillation death .... Barring the boundary cells, one observes near phase flip and near ...

  3. Restoration practicesin Brazil's Atlantic rainforest.

    Science.gov (United States)

    Jorge Correa de Lima Palidon; Maisa dos Santos Guapyassu

    2005-01-01

    The atlantic Rain Forst (Mata Atlantica) extends along the southern coast of Brazil and inland into Argentina and Paraguay. Originally covering 15% of the land area of Brazil, it was a region of an estimated 1.3 million km2 (MMA 2000). Today, remnants of the Atlantic Forest represents about 8% of the original area, or some 94,000 km2...

  4. Mechanisms of the atmospheric response to North Atlantic multidecadal variability: a model study

    Energy Technology Data Exchange (ETDEWEB)

    Msadek, Rym [Universite Pierre et Marie Curie-Paris 6, LOCEAN/IPSL, Paris Cedex 05 (France); Princeton University, GFDL/NOAA, AOS Program, Princeton, NJ (United States); Frankignoul, Claude [Universite Pierre et Marie Curie-Paris 6, LOCEAN/IPSL, Paris Cedex 05 (France); Li, Laurent Z.X. [Universite Pierre et Marie Curie-Paris 6, LMD/IPSL, Paris Cedex 05 (France)

    2011-04-15

    The atmospheric circulation response to decadal fluctuations of the Atlantic meridional overturning circulation (MOC) in the IPSL climate model is investigated using the associated sea surface temperature signature. A SST anomaly is prescribed in sensitivity experiments with the atmospheric component of the IPSL model coupled to a slab ocean. The prescribed SST anomaly in the North Atlantic is the surface signature of the MOC influence on the atmosphere detected in the coupled simulation. It follows a maximum of the MOC by a few years and resembles the model Atlantic multidecadal oscillation. It is mainly characterized by a warming of the North Atlantic south of Iceland, and a cooling of the Nordic Seas. There are substantial seasonal variations in the geopotential height response to the prescribed SST anomaly, with an East Atlantic Pattern-like response in summer and a North Atlantic oscillation-like signal in winter. In summer, the response of the atmosphere is global in scale, resembling the climatic impact detected in the coupled simulation, albeit with a weaker amplitude. The zonally asymmetric or eddy part of the response is characterized by a trough over warm SST associated with changes in the stationary waves. A diagnostic analysis with daily data emphasizes the role of transient-eddy forcing in shaping and maintaining the equilibrium response. We show that in response to an intensified MOC, the North Atlantic storm tracks are enhanced and shifted northward during summer, consistent with a strengthening of the westerlies. However the anomalous response is weak, which suggests a statistically significant but rather modest influence of the extratropical SST on the atmosphere. The winter response to the MOC-induced North Atlantic warming is an intensification of the subtropical jet and a southward shift of the Atlantic storm track activity, resulting in an equatorward shift of the polar jet. Although the SST anomaly is only prescribed in the Atlantic ocean

  5. Entanglement in neutrino oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Blasone, M.; Dell' Anno, F.; De Siena, S.; Illuminati, F. [Universita degli Studi di Salerno Via Ponte don Melillon, Dipt. di Matematica e Informatica, Fisciano SA (Italy); INFN Sezione di Napoli, Gruppo collegato di Salerno - Baronissi SA (Italy); Dell' Anno, F.; De Siena, S.; Illuminati, F. [CNR-INFM Coherentia - Napoli (Italy); Blasone, M. [ISI Foundation for Scientific Interchange, Torino (Italy)

    2009-03-15

    Flavor oscillations in elementary particle physics are related to multimode entanglement of single-particle states. We show that mode entanglement can be expressed in terms of flavor transition probabilities, and therefore that single-particle entangled states acquire a precise operational characterization in the context of particle mixing. We treat in detail the physically relevant cases of two- and three-flavor neutrino oscillations, including the effective measure of CP violation. We discuss experimental schemes for the transfer of the quantum information encoded in single-neutrino states to spatially delocalized two-flavor charged-lepton states, thus showing, at least in principle, that single-particle entangled states of neutrino mixing are legitimate physical resources for quantum information tasks. (authors)

  6. Nonlinear (Anharmonic Casimir Oscillator

    Directory of Open Access Journals (Sweden)

    Habibollah Razmi

    2011-01-01

    Full Text Available We want to study the dynamics of a simple linear harmonic micro spring which is under the influence of the quantum Casimir force/pressure and thus behaves as a (an nonlinear (anharmonic Casimir oscillator. Generally, the equation of motion of this nonlinear micromechanical Casimir oscillator has no exact solvable (analytical solution and the turning point(s of the system has (have no fixed position(s; however, for particular values of the stiffness of the micro spring and at appropriately well-chosen distance scales and conditions, there is (are approximately sinusoidal solution(s for the problem (the variable turning points are collected in a very small interval of positions. This, as a simple and elementary plan, may be useful in controlling the Casimir stiction problem in micromechanical devices.

  7. Entanglement in neutrino oscillations

    International Nuclear Information System (INIS)

    Blasone, M.; Dell'Anno, F.; De Siena, S.; Illuminati, F.; Dell'Anno, F.; De Siena, S.; Illuminati, F.; Blasone, M.

    2009-01-01

    Flavor oscillations in elementary particle physics are related to multimode entanglement of single-particle states. We show that mode entanglement can be expressed in terms of flavor transition probabilities, and therefore that single-particle entangled states acquire a precise operational characterization in the context of particle mixing. We treat in detail the physically relevant cases of two- and three-flavor neutrino oscillations, including the effective measure of CP violation. We discuss experimental schemes for the transfer of the quantum information encoded in single-neutrino states to spatially delocalized two-flavor charged-lepton states, thus showing, at least in principle, that single-particle entangled states of neutrino mixing are legitimate physical resources for quantum information tasks. (authors)

  8. Acoustics waves and oscillations

    CERN Document Server

    Sen, S.N.

    2013-01-01

    Parameters of acoustics presented in a logical and lucid style Physical principles discussed with mathematical formulations Importance of ultrasonic waves highlighted Dispersion of ultrasonic waves in viscous liquids explained This book presents the theory of waves and oscillations and various applications of acoustics in a logical and simple form. The physical principles have been explained with necessary mathematical formulation and supported by experimental layout wherever possible. Incorporating the classical view point all aspects of acoustic waves and oscillations have been discussed together with detailed elaboration of modern technological applications of sound. A separate chapter on ultrasonics emphasizes the importance of this branch of science in fundamental and applied research. In this edition a new chapter ''Hypersonic Velocity in Viscous Liquids as revealed from Brillouin Spectra'' has been added. The book is expected to present to its readers a comprehensive presentation of the subject matter...

  9. Discrete repulsive oscillator wavefunctions

    International Nuclear Information System (INIS)

    Munoz, Carlos A; Rueda-Paz, Juvenal; Wolf, Kurt Bernardo

    2009-01-01

    For the study of infinite discrete systems on phase space, the three-dimensional Lorentz algebra and group, so(2,1) and SO(2,1), provide a discrete model of the repulsive oscillator. Its eigenfunctions are found in the principal irreducible representation series, where the compact generator-that we identify with the position operator-has the infinite discrete spectrum of the integers Z, while the spectrum of energies is a double continuum. The right- and left-moving wavefunctions are given by hypergeometric functions that form a Dirac basis for l 2 (Z). Under contraction, the discrete system limits to the well-known quantum repulsive oscillator. Numerical computations of finite approximations raise further questions on the use of Dirac bases for infinite discrete systems.

  10. Neutrino Masses and Oscillations

    CERN Multimedia

    CERN. Geneva. Audiovisual Unit; Treille, Daniel

    2002-01-01

    This course will not cover its subject in the customary way. The emphasis will be on the simple theoretical concepts (helicity, handedness, chirality, Majorana masses) which are obscure in most of the literature, and on the quantum mechanics of oscillations, that ALL books get wrong. Which, hopefully, will not deter me from discussing some of the most interesting results from the labs and from the cosmos.

  11. Oscillations in quasineutral plasmas

    International Nuclear Information System (INIS)

    Grenier, E.

    1996-01-01

    The purpose of this article is to describe the limit, as the vacuum electric permittivity goes to zero, of a plasma physics system, deduced from the Vlasov-Poisson system for special initial data (distribution functions which are analytic in the space variable, with compact support in velocity), a limit also called open-quotes quasineutral regimeclose quotes of the plasma, and the related oscillations of the electric field, with high frequency in time. 20 refs

  12. Density oscillations within hadrons

    International Nuclear Information System (INIS)

    Arnold, R.; Barshay, S.

    1976-01-01

    In models of extended hadrons, in which small bits of matter carrying charge and effective mass exist confined within a medium, oscillations in the matter density may occur. A way of investigating this possibility experimentally in high-energy hadron-hadron elastic diffraction scattering is suggested, and the effect is illustrated by examining some existing data which might be relevant to the question [fr

  13. Variations of Sea Surface Temperature, Wind Stress, and Rainfall over the Tropical Atlantic and South America.

    Science.gov (United States)

    Nobre, Paulo; Srukla, J.

    1996-10-01

    Empirical orthogonal functions (E0Fs) and composite analyses are used to investigate the development of sea surface temperature (SST) anomaly patterns over the tropical Atlantic. The evolution of large-scale rainfall anomaly patterns over the equatorial Atlantic and South America are also investigated. 71e EOF analyses revealed that a pattern of anomalous SST and wind stress asymmetric relative to the equator is the dominant mode of interannual and longer variability over the tropical Atlantic. The most important findings of this study are as follows.Atmospheric circulation anomalies precede the development of basinwide anomalous SST patterns over the tropical Atlantic. Anomalous SST originate off the African coast simultaneously with atmospheric circulation anomalies and expand westward afterward. The time lag between wind stress relaxation (strengthening) and maximum SST warming (cooling) is about two months.Anomalous atmospheric circulation patterns over northern tropical Atlantic are phase locked to the seasonal cycle. Composite fields of SLP and wind stress over northern tropical Atlantic can be distinguished from random only within a few months preceding the March-May (MAM) season. Observational evidence is presented to show that the El Niño-Southern Oscillation phenomenon in the Pacific influences atmospheric circulation and SST anomalies over northern tropical Atlantic through atmospheric teleconnection patterns into higher latitudes of the Northern Hemisphere.The well-known droughts over northeastern Brazil (Nordeste) are a local manifestation of a much larger-scale rainfall anomaly pattern encompassing the whole equatorial Atlantic and Amazon region. Negative rainfall anomalies to the south of the equator during MAM, which is the rainy season for the Nordeste region, are related to an early withdrawal of the intertropical convergence zone toward the warm SST anomalies over the northern tropical Atlantic. Also, it is shown that precipitation anomalies

  14. Neutrino Oscillations Physics

    Science.gov (United States)

    Fogli, Gianluigi

    2005-06-01

    We review the status of the neutrino oscillations physics, with a particular emphasis on the present knowledge of the neutrino mass-mixing parameters. We consider first the νμ → ντ flavor transitions of atmospheric neutrinos. It is found that standard oscillations provide the best description of the SK+K2K data, and that the associated mass-mixing parameters are determined at ±1σ (and NDF = 1) as: Δm2 = (2.6 ± 0.4) × 10-3 eV2 and sin 2 2θ = 1.00{ - 0.05}{ + 0.00} . Such indications, presently dominated by SK, could be strengthened by further K2K data. Then we point out that the recent data from the Sudbury Neutrino Observatory, together with other relevant measurements from solar and reactor neutrino experiments, in particular the KamLAND data, convincingly show that the flavor transitions of solar neutrinos are affected by Mikheyev-Smirnov-Wolfenstein (MSW) effects. Finally, we perform an updated analysis of two-family active oscillations of solar and reactor neutrinos in the standard MSW case.

  15. Inter-annual variability of aerosol optical depth over the tropical Atlantic Ocean based on MODIS-Aqua observations over the period 2002-2012

    Science.gov (United States)

    Gkikas, Antonis; Hatzianastassiou, Nikolaos

    2013-04-01

    The tropical Atlantic Ocean is affected by dust and biomass burning aerosol loads transported from the western parts of the Saharan desert and the sub-Sahel regions, respectively. The spatial and temporal patterns of this transport are determined by the aerosol emission rates, their deposition (wet and dry), by the latitudinal shift of the Intertropical Convergence Zone (ITCZ) and the prevailing wind fields. More specifically, in summer, Saharan dust aerosols are transported towards the Atlantic Ocean, even reaching the Gulf of Mexico, while in winter the Atlantic Ocean transport takes place in more southern latitudes, near the equator, sometimes reaching the northern parts of South America. In the later case, dust is mixed with biomass burning aerosols originating from agricultural activities in the sub-Sahel, associated with prevailing north-easterly airflow (Harmattan winds). Satellite observations are the appropriate tool for describing this African aerosol export, which is important to atmospheric, oceanic and climate processes, offering the advantage of complete spatial coverage. In the present study, we use satellite measurements of aerosol optical depth at 550nm (AOD550nm), on a daily and monthly basis, derived from MODIS-Aqua platform, at 1ox1o spatial resolution (Level 3), for the period 2002-2012. The primary objective is to determine the pixel-level and regional mean anomalies of AOD550nm over the entire study period. The regime of the anomalies of African export is interpreted in relation to the aerosol source areas, precipitation, wind patterns and temporal variability of the North Atlantic Oscillation Index (NAOI). In order to ensure availability of AOD over the Sahara desert, MODIS-Aqua Deep Blue products are also used. As for precipitation, Global Precipitation Climatology Project (GPCP) data at 2.5ox2.5o are used. The wind fields are taken from the National Center for Environmental Prediction (NCEP). Apart from the regime of African aerosol export

  16. AP Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Planetary Amplitude index - Bartels 1951. The a-index ranges from 0 to 400 and represents a K-value converted to a linear scale in gammas (nanoTeslas)--a scale that...

  17. Post-1980 shifts in the sensitivity of boreal tree growth to North Atlantic Ocean dynamics and seasonal climate. Tree growth responses to North Atlantic Ocean dynamics

    Science.gov (United States)

    Ols, Clémentine; Trouet, Valerie; Girardin, Martin P.; Hofgaard, Annika; Bergeron, Yves; Drobyshev, Igor

    2018-06-01

    The mid-20th century changes in North Atlantic Ocean dynamics, e.g. slow-down of the Atlantic meridional overturning thermohaline circulation (AMOC), have been considered as early signs of tipping points in the Earth climate system. We hypothesized that these changes have significantly altered boreal forest growth dynamics in northeastern North America (NA) and northern Europe (NE), two areas geographically adjacent to the North Atlantic Ocean. To test our hypothesis, we investigated tree growth responses to seasonal large-scale oceanic and atmospheric indices (the AMOC, North Atlantic Oscillation (NAO), and Arctic Oscillation (AO)) and climate (temperature and precipitation) from 1950 onwards, both at the regional and local levels. We developed a network of 6876 black spruce (NA) and 14437 Norway spruce (NE) tree-ring width series, extracted from forest inventory databases. Analyses revealed post-1980 shifts from insignificant to significant tree growth responses to summer oceanic and atmospheric dynamics both in NA (negative responses to NAO and AO indices) and NE (positive response to NAO and AMOC indices). The strength and sign of these responses varied, however, through space with stronger responses in western and central boreal Quebec and in central and northern boreal Sweden, and across scales with stronger responses at the regional level than at the local level. Emerging post-1980 associations with North Atlantic Ocean dynamics synchronized with stronger tree growth responses to local seasonal climate, particularly to winter temperatures. Our results suggest that ongoing and future anomalies in oceanic and atmospheric dynamics may impact forest growth and carbon sequestration to a greater extent than previously thought. Cross-scale differences in responses to North Atlantic Ocean dynamics highlight complex interplays in the effects of local climate and ocean-atmosphere dynamics on tree growth processes and advocate for the use of different spatial scales in

  18. Heartbeat of the Southern Oscillation explains ENSO climatic resonances

    Science.gov (United States)

    Bruun, John T.; Allen, J. Icarus; Smyth, Timothy J.

    2017-08-01

    The El Niño-Southern Oscillation (ENSO) nonlinear oscillator phenomenon has a far reaching influence on the climate and human activities. The up to 10 year quasi-period cycle of the El Niño and subsequent La Niña is known to be dominated in the tropics by nonlinear physical interaction of wind with the equatorial waveguide in the Pacific. Long-term cyclic phenomena do not feature in the current theory of the ENSO process. We update the theory by assessing low (>10 years) and high (features. The observational data sets of the Southern Oscillation Index (SOI), North Pacific Index Anomaly, and ENSO Sea Surface Temperature Anomaly, as well as a theoretical model all confirm the existence of long-term and short-term climatic cycles of the ENSO process with resonance frequencies of {2.5, 3.8, 5, 12-14, 61-75, 180} years. This fundamental result shows long-term and short-term signal coupling with mode locking across the dominant ENSO dynamics. These dominant oscillation frequency dynamics, defined as ENSO frequency states, contain a stable attractor with three frequencies in resonance allowing us to coin the term Heartbeat of the Southern Oscillation due to its characteristic shape. We predict future ENSO states based on a stable hysteresis scenario of short-term and long-term ENSO oscillations over the next century.Plain Language SummaryThe Pacific El Niño-Southern Oscillation (ENSO) nonlinear oscillator phenomenon has a far reaching influence on the climate and our human activities. This work can help predict both long-term and short-term future ENSO events and to assess the risk of future climate hysteresis changes: is the elastic band that regulates the ENSO climate breaking? We update the current theory of the ENSO process with a sophisticated analysis approach (Dominant Frequency State Analysis) to include long-term oscillations (up to 200 years) as well as tropical and extratropical interaction dynamics. The analysis uses instrumental and paleoproxy data

  19. Direction of coupling from phases of interacting oscillators: An information-theoretic approach

    Science.gov (United States)

    Paluš, Milan; Stefanovska, Aneta

    2003-05-01

    A directionality index based on conditional mutual information is proposed for application to the instantaneous phases of weakly coupled oscillators. Its abilities to distinguish unidirectional from bidirectional coupling, as well as to reveal and quantify asymmetry in bidirectional coupling, are demonstrated using numerical examples of quasiperiodic, chaotic, and noisy oscillators, as well as real human cardiorespiratory data.

  20. Climate Prediction Center (CPC)Oceanic Nino Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Oceanic Nino Index (ONI) is one of the primary indices used to monitor the El Nino-Southern Oscillation (ENSO). The ONI is calculated by averaging sea surface...

  1. Regional seesaw between the North Atlantic and Nordic Seas during the last glacial abrupt climate events

    Directory of Open Access Journals (Sweden)

    M. Wary

    2017-06-01

    Full Text Available Dansgaard–Oeschger oscillations constitute one of the most enigmatic features of the last glacial cycle. Their cold atmospheric phases have been commonly associated with cold sea-surface temperatures and expansion of sea ice in the North Atlantic and adjacent seas. Here, based on dinocyst analyses from the 48–30 ka interval of four sediment cores from the northern Northeast Atlantic and southern Norwegian Sea, we provide direct and quantitative evidence of a regional paradoxical seesaw pattern: cold Greenland and North Atlantic phases coincide with warmer sea-surface conditions and shorter seasonal sea-ice cover durations in the Norwegian Sea as compared to warm phases. Combined with additional palaeorecords and multi-model hosing simulations, our results suggest that during cold Greenland phases, reduced Atlantic meridional overturning circulation and cold North Atlantic sea-surface conditions were accompanied by the subsurface propagation of warm Atlantic waters that re-emerged in the Nordic Seas and provided moisture towards Greenland summit.

  2. A Review of ENSO Influence on the North Atlantic. A Non-Stationary Signal

    Directory of Open Access Journals (Sweden)

    Belén Rodríguez-Fonseca

    2016-06-01

    Full Text Available The atmospheric seasonal cycle of the North Atlantic region is dominated by meridional movements of the circulation systems: from the tropics, where the West African Monsoon and extreme tropical weather events take place, to the extratropics, where the circulation is dominated by seasonal changes in the jetstream and extratropical cyclones. Climate variability over the North Atlantic is controlled by various mechanisms. Atmospheric internal variability plays a crucial role in the mid-latitudes. However, El Niño-Southern Oscillation (ENSO is still the main source of predictability in this region situated far away from the Pacific. Although the ENSO influence over tropical and extra-tropical areas is related to different physical mechanisms, in both regions this teleconnection seems to be non-stationary in time and modulated by multidecadal changes of the mean flow. Nowadays, long observational records (greater than 100 years and modeling projects (e.g., CMIP permit detecting non-stationarities in the influence of ENSO over the Atlantic basin, and further analyzing its potential mechanisms. The present article reviews the ENSO influence over the Atlantic region, paying special attention to the stability of this teleconnection over time and the possible modulators. Evidence is given that the ENSO–Atlantic teleconnection is weak over the North Atlantic. In this regard, the multidecadal ocean variability seems to modulate the presence of teleconnections, which can lead to important impacts of ENSO and to open windows of opportunity for seasonal predictability.

  3. Quasioptical Josephson oscillator

    International Nuclear Information System (INIS)

    Wengler, M.J.; Pance, A.; Liu, B.

    1991-01-01

    This paper discusses the authors' work with large 2-dimensional arrays of Josephson junctions for submillimeter power generation. The basic design of the Quasioptical Josephson Oscillator (QJO) is presented. The reasons for each design decision are discussed. Superconducting devices have not yet been fabricated, but scale models and computer simulations have been done. A method for characterizing array rf coupling structures is described, and initial results with this method are presented. Microwave scale models of the radiation structure are built and a series of measurements are made with a network analyzer

  4. Modeling microtubule oscillations

    DEFF Research Database (Denmark)

    Jobs, E.; Wolf, D.E.; Flyvbjerg, H.

    1997-01-01

    Synchronization of molecular reactions in a macroscopic volume may cause the volume's physical properties to change dynamically and thus reveal much about the reactions. As an example, experimental time series for so-called microtubule oscillations are analyzed in terms of a minimal model...... for this complex polymerization-depolymerization cycle. The model reproduces well the qualitatively different time series that result from different experimental conditions, and illuminates the role and importance of individual processes in the cycle. Simple experiments are suggested that can further test...... and define the model and the polymer's reaction cycle....

  5. Oscillations in nonlinear systems

    CERN Document Server

    Hale, Jack K

    2015-01-01

    By focusing on ordinary differential equations that contain a small parameter, this concise graduate-level introduction to the theory of nonlinear oscillations provides a unified approach to obtaining periodic solutions to nonautonomous and autonomous differential equations. It also indicates key relationships with other related procedures and probes the consequences of the methods of averaging and integral manifolds.Part I of the text features introductory material, including discussions of matrices, linear systems of differential equations, and stability of solutions of nonlinear systems. Pa

  6. Neutrino oscillations at LAMPF

    International Nuclear Information System (INIS)

    Carlini, R.; Choi, C.; Donohue, J.

    1985-01-01

    Work at Argonne continues on the construction of the neutrino oscillation experiment (E645). Construction of detector supports and active shield components were completed at the Provo plant of the principal contractor for the project (the Pittsburgh-Des Moines Corporation). Erection of the major experimental components was completed at the LAMPF experimental site in mid-March 1985. Work continues on the tunnel which will house the detector. Construction of detector components (scintillators and proportional drift tubes) is proceeding at Ohio State University and Louisiana State University. Consolidation of these components into the 20-ton neutrino detector is beginning at LAMPF

  7. Theory of oscillators

    CERN Document Server

    Andronov, Aleksandr Aleksandrovich; Vitt, Aleksandr Adolfovich

    1966-01-01

    Theory of Oscillators presents the applications and exposition of the qualitative theory of differential equations. This book discusses the idea of a discontinuous transition in a dynamic process. Organized into 11 chapters, this book begins with an overview of the simplest type of oscillatory system in which the motion is described by a linear differential equation. This text then examines the character of the motion of the representative point along the hyperbola. Other chapters consider examples of two basic types of non-linear non-conservative systems, namely, dissipative systems and self-

  8. Solar and stellar oscillations

    International Nuclear Information System (INIS)

    Fossat, E.

    1981-01-01

    We try to explain in simple words what a stellar oscillation is, what kind of restoring forces and excitation mechanisms can be responsible for its occurence, what kind of questions the theoretician asks to the observer and what kind of tools the latter is using to look for the answers. A selected review of the most striking results obtained in the last few years in solar seismology and the present status of their consequences on solar models is presented. A brief discussion on the expected extension towards stellar seismology will end the paper. A selected bibliography on theory as well as observations and recent papers is also included. (orig.)

  9. Coupled nonlinear oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, J; Scott, A C

    1983-01-01

    Topics discussed include transitions in weakly coupled nonlinear oscillators, singularly perturbed delay-differential equations, and chaos in simple laser systems. Papers are presented on truncated Navier-Stokes equations in a two-dimensional torus, on frequency locking in Josephson point contacts, and on soliton excitations in Josephson tunnel junctions. Attention is also given to the nonlinear coupling of radiation pulses to absorbing anharmonic molecular media, to aspects of interrupted coarse-graining in stimulated excitation, and to a statistical analysis of long-term dynamic irregularity in an exactly soluble quantum mechanical model.

  10. AA Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The geomagnetic aa index provides a long climatology of global geomagnetic activity using 2 antipodal observatories at Greenwich and Melbourne- IAGA Bulletin 37,...

  11. Walkability Index

    Data.gov (United States)

    U.S. Environmental Protection Agency — The Walkability Index dataset characterizes every Census 2010 block group in the U.S. based on its relative walkability. Walkability depends upon characteristics of...

  12. Diversity Index

    Data.gov (United States)

    Town of Chapel Hill, North Carolina — This map service summarizes racial and ethnic diversity in the United States in 2012.The Diversity Index shows the likelihood that two persons chosen at random from...

  13. AUTHOR INDEX

    Indian Academy of Sciences (India)

    a granitic terrain of southern India using factor analysis and GIS. 1059. Radhakrishna M see Dev Sheena V .... Landslide susceptibility analysis using Probabilistic. Certainty Factor ... index via entropy-difference analysis. 687. Yidana Sandow ...

  14. Relationships between the Antarctic oscillation, the Madden-Julian oscillation, and ENSO, and consequences for rainfall analysis

    CSIR Research Space (South Africa)

    Pohl, B

    2010-01-01

    Full Text Available range, it is not unambiguously related to the global-scale Madden–Julian oscillation (MJO) activity, with in particular no coherent phase relationship with the MJO index. Moreover, in the high southern latitudes, the MJO-associated anomaly fields do...

  15. Breeding biology of a winter-breeding procellariiform in the North Atlantic, the Macaronesian shearwater Puffinus lherminieri baroli.

    Science.gov (United States)

    Fagundes, Ana Isabel; Ramos, Jaime A; Ramos, Urtelinda; Medeiros, Renata; Paiva, Vitor H

    2016-10-01

    The breeding success of burrow-nesting seabirds may be influenced by both nest site characteristics and oceanographic conditions influencing food availability at sea. In this study we describe the breeding biology of the winter-breeding Macaronesian shearwater (Puffinus lherminieri baroli), including nest site characteristics and interspecific competition. We also evaluate the possible effects of changing oceanographic conditions on breeding phenology and breeding success. The study was carried out over two breeding seasons on two islands in the North Atlantic Ocean, Cima Islet and Selvagem Grande. Oceanographic characteristics differed between years. On a regional scale, the North Atlantic Oscillation (NAO) index was low and negative in 2011, and on a local scale, birds used areas with significantly lower values of chlorophyll a concentration and significantly higher values of sea surface temperature anomalies. Hatching success was higher in 2012 than in 2011. At both colonies, egg cracking was the main cause of hatching failure, but in 2011 several eggs on Selvagem Grande were deserted. In 2012 birds laid earlier and chicks had longer wings and were heavier. At both colonies, nests that were deeper, were sheltered from prevailing winds and had small chambers and a soil substrate had a higher probability of being used successfully by the birds. Nests occupied solely by Macaronesian shearwaters were much deeper and had less volume than nests shared with other species. Our study suggests that the breeding success of Macaronesian shearwaters is strongly related to nest site characteristics and that at-sea environmental conditions exert a strong influence on reproductive parameters, with birds breeding in a poor year (evaluated in terms of lower marine productivity) laying much later and their chicks growing at a slower rate than in a good year. The influence of nest site characteristics and environmental conditions may be very important for understanding the breeding

  16. Intelligent indexing

    International Nuclear Information System (INIS)

    Farkas, J.

    1992-01-01

    In this paper we discuss the relevance of artificial intelligence to the automatic indexing of natural language text. We describe the use of domain-specific semantically-based thesauruses and address the problem of creating adequate knowledge bases for intelligent indexing systems. We also discuss the relevance of the Hilbert space ι 2 to the compact representation of documents and to the definition of the similarity of natural language texts. (author). 17 refs., 2 figs

  17. Intelligent indexing

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, J

    1993-12-31

    In this paper we discuss the relevance of artificial intelligence to the automatic indexing of natural language text. We describe the use of domain-specific semantically-based thesauruses and address the problem of creating adequate knowledge bases for intelligent indexing systems. We also discuss the relevance of the Hilbert space {iota}{sup 2} to the compact representation of documents and to the definition of the similarity of natural language texts. (author). 17 refs., 2 figs.

  18. Brain Oscillations, Hypnosis, and Hypnotizability.

    Science.gov (United States)

    Jensen, Mark P; Adachi, Tomonori; Hakimian, Shahin

    2015-01-01

    This article summarizes the state-of-science knowledge regarding the associations between hypnosis and brain oscillations. Brain oscillations represent the combined electrical activity of neuronal assemblies, usually measured as specific frequencies representing slower (delta, theta, alpha) and faster (beta, gamma) oscillations. Hypnosis has been most closely linked to power in the theta band and changes in gamma activity. These oscillations are thought to play a critical role in both the recording and recall of declarative memory and emotional limbic circuits. The authors propose that this role may be the mechanistic link between theta (and perhaps gamma) oscillations and hypnosis, specifically, that the increases in theta oscillations and changes in gamma activity observed with hypnosis may underlie some hypnotic responses. If these hypotheses are supported, they have important implications for both understanding the effects of hypnosis and for enhancing response to hypnotic treatments.

  19. Bounded-oscillation Pushdown Automata

    Directory of Open Access Journals (Sweden)

    Pierre Ganty

    2016-09-01

    Full Text Available We present an underapproximation for context-free languages by filtering out runs of the underlying pushdown automaton depending on how the stack height evolves over time. In particular, we assign to each run a number quantifying the oscillating behavior of the stack along the run. We study languages accepted by pushdown automata restricted to k-oscillating runs. We relate oscillation on pushdown automata with a counterpart restriction on context-free grammars. We also provide a way to filter all but the k-oscillating runs from a given PDA by annotating stack symbols with information about the oscillation. Finally, we study closure properties of the defined class of languages and the complexity of the k-emptiness problem asking, given a pushdown automaton P and k >= 0, whether P has a k-oscillating run. We show that, when k is not part of the input, the k-emptiness problem is NLOGSPACE-complete.

  20. Rethinking Atlantic History

    Directory of Open Access Journals (Sweden)

    James Walvin

    2009-12-01

    Full Text Available [First paragraph] Shaping the Stuart World 1603-1714: The Atlantic Connection. Allan I. Macinnes & Arthur H. Williamson (eds.. Leiden: Brill Academic Publishers, 2006. xiv + 389 pp. (Cloth US$ 135.00 Slavery and the British Empire: From Africa to America. Kenneth Morgan. New York: Oxford University Press, 2007. x + 221 pp. (Paper US$ 32.00 Although an important debate continues about the concept itself, the use of “the Atlantic” has embedded itself in scholarly vernacular. The scholarly output directly spawned by an engagement with the concept continues apace. That ocean, and the peoples who lived and traded along its edges, and who finally moved across it, have provided an important geographical focus for some major reconsiderations of modern history. Prompted by the Macinnes/Williamson volume, I returned to my own undergraduate and graduate notes and essays from courses on Stuart Britain: the Atlantic was totally absent – not even present as a distant speck on our intellectual map. We studied, and debated, the formal histories of migrations to the Americas (i.e. European migrations but there was no mention of Africa or Africans. And no sense was conveyed that the European engagement with the Americas (in their totality – as opposed to North America was a two-way, mutual force: that the European world was influenced, indeed shaped in many critical regards, by the Americas: by the land, the products, the peoples, and by the markets of that hemisphere. At its most obvious in the ebb and flow of peoples, even that eluded the historians I encountered as a student. It was as if we were talking about a different cosmos; few moved beyond the conventions of European migrations westwards and little attention was paid to that most dominant of migrations – the enforced African migrations to the Americas.

  1. Single ICCII Sinusoidal Oscillators Employing Grounded Capacitors

    Directory of Open Access Journals (Sweden)

    J. W. Horng

    2011-09-01

    Full Text Available Two inverting second-generation current conveyors (ICCII based sinusoidal oscillators are presented. The first sinusoidal oscillator is composed of one ICCII, two grounded capacitors and two resistors. The oscillation condition and oscillation frequency can be orthogonally controllable. The second sinusoidal oscillator is composed of one ICCII, two grounded capacitors and three resistors. The oscillation condition and oscillation frequency can be independently controllable through different resistors.

  2. Stable And Oscillating Acoustic Levitation

    Science.gov (United States)

    Barmatz, Martin B.; Garrett, Steven L.

    1988-01-01

    Sample stability or instability determined by levitating frequency. Degree of oscillation of acoustically levitated object along axis of levitation chamber controlled by varying frequency of acoustic driver for axis above or below frequency of corresponding chamber resonance. Stabilization/oscillation technique applied in normal Earth gravity, or in absence of gravity to bring object quickly to rest at nominal levitation position or make object oscillate in desired range about that position.

  3. Isotropic oscillator: spheroidal wave functions

    International Nuclear Information System (INIS)

    Mardoyan, L.G.; Pogosyan, G.S.; Ter-Antonyan, V.M.; Sisakyan, A.N.

    1985-01-01

    Solutions of the Schroedinger equation are found for an isotropic oscillator (10) in prolate and oblate spheroidal coordinates. It is shown that the obtained solutions turn into spherical and cylindrical bases of the isotropic oscillator at R→0 and R→ infinity (R is the dimensional parameter entering into the definition of prolate and oblate spheroidal coordinates). The explicit form is given for both prolate and oblate basis of the isotropic oscillator for the lowest quantum states

  4. Neutrino oscillations. Theory and experiment

    International Nuclear Information System (INIS)

    Beshtoev, Kh.M.

    2001-01-01

    Theoretical schemes on neutrino oscillations are considered. The experimental data on neutrino oscillations obtained in the Super-Kamiokande (Japan) and SNO (Canada) experiments are given. Comparison of these data with the predictions obtained in the theoretical schemes is done. Conclusion is made that the experimental data confirm only the scheme with transitions (oscillations) between aromatic ν e -, ν μ -, ν τ - neutrinos with maximal angle mixings. (author)

  5. Chemotaxis and Actin Oscillations

    Science.gov (United States)

    Bodenschatz, Eberhard; Hsu, Hsin-Fang; Negrete, Jose; Beta, Carsten; Pumir, Alain; Gholami, Azam; Tarantola, Marco; Westendorf, Christian; Zykov, Vladimir

    Recently, self-oscillations of the cytoskeletal actin have been observed in Dictyostelium, a model system for studying chemotaxis. Here we report experimental results on the self-oscillation mechanism and the role of regulatory proteins and myosin II. We stimulate cells rapidly and periodically by using photo un-caging of the chemoattractant in a micro-fluidic device and measured the cellular responses. We found that the response amplitude grows with stimulation strength only in a very narrow region of stimulation, after which the response amplitude reaches a plateau. Moreover, the frequency-response is not constant but rather varies with the strength of external stimuli. To understand the underlying mechanism, we analyzed the polymerization and de-polymerization time in the single cell level. Despite of the large cell-to-cell variability, we found that the polymerization time is independent of external stimuli and the de-polymerization time is prolonged as the stimulation strength increases. Our conclusions will be summarized and the role of noise in the signaling network will be discussed. German Science Foundation CRC 937.

  6. The Wien Bridge Oscillator Family

    DEFF Research Database (Denmark)

    Lindberg, Erik

    2006-01-01

    A tutorial in which the Wien bridge family of oscillators is defined and investigated. Oscillators which do not fit into the Barkhausen criterion topology may be designed. A design procedure based on initial complex pole quality factor is reported. The dynamic transfer characteristic of the ampli......A tutorial in which the Wien bridge family of oscillators is defined and investigated. Oscillators which do not fit into the Barkhausen criterion topology may be designed. A design procedure based on initial complex pole quality factor is reported. The dynamic transfer characteristic...

  7. Unstable oscillators based hyperchaotic circuit

    DEFF Research Database (Denmark)

    Murali, K.; Tamasevicius, A.; G. Mykolaitis, A.

    1999-01-01

    A simple 4th order hyperchaotic circuit with unstable oscillators is described. The circuit contains two negative impedance converters, two inductors, two capacitors, a linear resistor and a diode. The Lyapunov exponents are presented to confirm hyperchaotic nature of the oscillations in the circ...... in the circuit. The performance of the circuit is investigated by means of numerical integration of appropriate differential equations, PSPICE simulations, and hardware experiment.......A simple 4th order hyperchaotic circuit with unstable oscillators is described. The circuit contains two negative impedance converters, two inductors, two capacitors, a linear resistor and a diode. The Lyapunov exponents are presented to confirm hyperchaotic nature of the oscillations...

  8. Heat exchanger with oscillating flow

    Science.gov (United States)

    Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)

    1993-01-01

    Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.

  9. Virginia Atlantic Coast Recreational Use

    Data.gov (United States)

    Virginia Department of Environmental Quality — As a member of the Mid-Atlantic Regional Council on the Ocean (MARCO), Virginia, through its Coastal Zone Management (CZM) Program, collected information on how the...

  10. VA Atlantic Coast Recreational Use

    Data.gov (United States)

    Virginia Department of Environmental Quality — As a member of the Mid-Atlantic Regional Council on the Ocean (MARCO), Virginia, through its Coastal Zone Management (CZM) Program, collected information on how the...

  11. The relationship between the Asian dust and Arctic Oscillation: An observational investigation

    Science.gov (United States)

    Lee, Y.; Kim, J.; Cho, H.

    2009-12-01

    The Arctic Oscillation (AO) represents the leading empirical orthogonal function of winter sea level pressure (SLP) fields, which resembles North Atlantic Oscillation, but has a more zonally symmetric structure (Thompson and Wallace, 1998; Wallace, 2000; Wu and Wang, 2002). This primary mode of the internal dynamics in the atmosphere predominates the Extratropical Northern Hemisphere circulation from surface to the lower stratosphere showing an equivalent barotropic structure during cold season(November-April) (Thompson and Wallace, 2000). Also, the Asian dust storms show strong interannual variation (Sun et al., 2001; Yoshino, 2002; Zhao et al., 2006; Hara et al., 2006), which are suggested to be associated with climate indices. Therefore, the purpose of this study is to identify the possible connection for the AO and the Asian dust emission during periods from late winter to spring, based on the observational investigations. In order to examine these complex associations closely, the Aerosol Index (AI) from Total Ozone Mapping Spectrometer (TOMS) are used starting from November 1978 to December 1999, except for data pause from May 1993 to August 1996. SLP and geopotential height at 500hPa (Z500) monthly fields are derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalyses (1958-2001). Also, source regions of Asian dust are mainly focused on three source areas, including the Taklimakan Desert (R1), Badain Jaran Desert (R2), and Mongolia (R3) in this study. In composite study during different phases of AO, the AO exhibits a “negative phase” with relatively high pressure over the polar region and low pressure at mid-latitudes (about 45 degrees North). In strong “negative phase” of AO, decrease of AO is found to be associated with decreases of local tropospheric temperature, U-wind, and geopotential height and strong north-south gradients over the source regions of Asian dust. Therefore, we also notice that a negative index phase

  12. Fuzzy modelling of Atlantic salmon physical habitat

    Science.gov (United States)

    St-Hilaire, André; Mocq, Julien; Cunjak, Richard

    2015-04-01

    Fish habitat models typically attempt to quantify the amount of available river habitat for a given fish species for various flow and hydraulic conditions. To achieve this, information on the preferred range of values of key physical habitat variables (e.g. water level, velocity, substrate diameter) for the targeted fishs pecies need to be modelled. In this context, we developed several habitat suitability indices sets for three Atlantic salmon life stages (young-of-the-year (YOY), parr, spawning adults) with the help of fuzzy logic modeling. Using the knowledge of twenty-seven experts, from both sides of the Atlantic Ocean, we defined fuzzy sets of four variables (depth, substrate size, velocity and Habitat Suitability Index, or HSI) and associated fuzzy rules. When applied to the Romaine River (Canada), median curves of standardized Weighted Usable Area (WUA) were calculated and a confidence interval was obtained by bootstrap resampling. Despite the large range of WUA covered by the expert WUA curves, confidence intervals were relatively narrow: an average width of 0.095 (on a scale of 0 to 1) for spawning habitat, 0.155 for parr rearing habitat and 0.160 for YOY rearing habitat. When considering an environmental flow value corresponding to 90% of the maximum reached by WUA curve, results seem acceptable for the Romaine River. Generally, this proposed fuzzy logic method seems suitable to model habitat availability for the three life stages, while also providing an estimate of uncertainty in salmon preferences.

  13. A Reassessment of the Integrated Impact of Tropical Cyclones on Surface Chlorophyll in the Western Subtropical North Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Foltz, Gregory R.; Balaguru, Karthik; Leung, Lai-Yung R.

    2015-02-28

    The impact of tropical cyclones on surface chlorophyll concentration is assessed in the western subtropical North Atlantic Ocean during 1998–2011. Previous studies in this area focused on individual cyclones and gave mixed results regarding the importance of tropical cyclone-induced mixing for changes in surface chlorophyll. Using a more integrated and comprehensive approach that includes quantification of cyclone-induced changes in mixed layer depth, here it is shown that accumulated cyclone energy explains 22% of the interannual variability in seasonally-averaged (June–November) chlorophyll concentration in the western subtropical North Atlantic, after removing the influence of the North Atlantic Oscillation (NAO). The variance explained by tropical cyclones is thus about 70% of that explained by the NAO, which has well-known impacts in this region. It is therefore likely that tropical cyclones contribute significantly to interannual variations of primary productivity in the western subtropical North Atlantic during the hurricane season.

  14. Virginia ESI: INDEX (Index Polygons)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains vector polygons representing the boundaries of all hardcopy cartographic products produced as part of the Environmental Sensitivity Index...

  15. U.S. Hail Frequency and the Global Wind Oscillation

    Science.gov (United States)

    Gensini, Vittorio A.; Allen, John T.

    2018-02-01

    Changes in Earth relative atmospheric angular momentum can be described by an index known as the Global Wind Oscillation. This global index accounts for changes in Earth's atmospheric budget of relative angular momentum through interactions of tropical convection anomalies, extratropical dynamics, and engagement of surface torques (e.g., friction and mountain). It is shown herein that U.S. hail events are more (less) likely to occur in low (high) atmospheric angular momentum base states when excluding weak Global Wind Oscillation days, with the strongest relationships found in the boreal spring and fall. Severe, significant severe, and giant hail events are more likely to occur during Global Wind Oscillation phases 8, 1, 2, and 3 during the peak of U.S. severe weather season. Lower frequencies of hail events are generally found in Global Wind Oscillation phases 4-7 but vary based on Global Wind Oscillation amplitude and month. In addition, probabilistic anomalies of atmospheric ingredients supportive of hail producing supercell thunderstorms closely mimic locations of reported hail frequency, helping to corroborate report results.

  16. Maximum covariance analysis to identify intraseasonal oscillations over tropical Brazil

    Science.gov (United States)

    Barreto, Naurinete J. C.; Mesquita, Michel d. S.; Mendes, David; Spyrides, Maria H. C.; Pedra, George U.; Lucio, Paulo S.

    2017-09-01

    A reliable prognosis of extreme precipitation events in the tropics is arguably challenging to obtain due to the interaction of meteorological systems at various time scales. A pivotal component of the global climate variability is the so-called intraseasonal oscillations, phenomena that occur between 20 and 100 days. The Madden-Julian Oscillation (MJO), which is directly related to the modulation of convective precipitation in the equatorial belt, is considered the primary oscillation in the tropical region. The aim of this study is to diagnose the connection between the MJO signal and the regional intraseasonal rainfall variability over tropical Brazil. This is achieved through the development of an index called Multivariate Intraseasonal Index for Tropical Brazil (MITB). This index is based on Maximum Covariance Analysis (MCA) applied to the filtered daily anomalies of rainfall data over tropical Brazil against a group of covariates consisting of: outgoing longwave radiation and the zonal component u of the wind at 850 and 200 hPa. The first two MCA modes, which were used to create the { MITB}_1 and { MITB}_2 indices, represent 65 and 16 % of the explained variance, respectively. The combined multivariate index was able to satisfactorily represent the pattern of intraseasonal variability over tropical Brazil, showing that there are periods of activation and inhibition of precipitation connected with the pattern of MJO propagation. The MITB index could potentially be used as a diagnostic tool for intraseasonal forecasting.

  17. Role of Frontal Alpha Oscillations in Creativity

    Science.gov (United States)

    Lustenberger, Caroline; Boyle, Michael R.; Foulser, A. Alban; Mellin, Juliann M.; Fröhlich, Flavio

    2015-01-01

    Creativity, the ability to produce innovative ideas, is a key higher-order cognitive function that is poorly understood. At the level of macroscopic cortical network dynamics, recent EEG data suggests that cortical oscillations in the alpha frequency band (8 – 12 Hz) are correlated with creative thinking. However, whether alpha oscillations play a fundamental role in creativity has remained unknown. Here we show that creativity is increased by enhancing alpha power using 10 Hz transcranial alternating current stimulation (10Hz-tACS) of the frontal cortex. In a study of 20 healthy participants with a randomized, balanced cross-over design, we found a significant improvement of 7.4% in the Creativity Index measured by the Torrance Test of Creative Thinking, a comprehensive and most frequently used assay of creative potential and strengths. In a second similar study with 20 subjects, 40Hz-tACS was used in instead of 10Hz-tACS to rule out a general “electrical stimulation” effect. No significant change in the Creativity Index was found for such frontal gamma stimulation. Our results suggest that alpha activity in frontal brain areas is selectively involved in creativity; this enhancement represents the first demonstration of specific neuronal dynamics that drive creativity and can be modulated by non-invasive brain stimulation. Our findings agree with the model that alpha recruitment increases with internal processing demands and is involved in inhibitory top-down control, which is an important requirement for creative ideation. PMID:25913062

  18. Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice.

    Science.gov (United States)

    Li, Xichen; Holland, David M; Gerber, Edwin P; Yoo, Changhyun

    2014-01-23

    In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming of any region on the planet, causing rapid changes in land ice. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution. Antarctic climate is influenced by, among other factors, changes in radiative forcing and remote Pacific climate variability, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen-Bellingshausen-Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation and sea-level change.

  19. Two millennia of Mesoamerican monsoon variability driven by Pacific and Atlantic synergistic forcing

    Science.gov (United States)

    Lachniet, Matthew S.; Asmerom, Yemane; Polyak, Victor; Bernal, Juan Pablo

    2017-01-01

    The drivers of Mesoamerican monsoon variability over the last two millennia remain poorly known because of a lack of precisely-dated and climate-calibrated proxy records. Here, we present a new high resolution (∼2 yrs) and precisely-dated (± 4 yr) wet season hydroclimate reconstruction for the Mesoamerican sector of the North American Monsoon over the past 2250 years based on two aragonite stalagmites from southwestern Mexico which replicate oxygen isotope variations over the 950-1950 CE interval. The reconstruction is quantitatively calibrated to instrumental rainfall variations in the Basin of Mexico. Comparisons to proxy indices of ocean-atmosphere circulation show a synergistic forcing by the North Atlantic and El Niño/Southern Oscillations, whereby monsoon strengthening coincided with a La Niña-like mode and a negative North Atlantic Oscillation, and vice versa for droughts. Our data suggest that weak monsoon intervals are associated with a strong North Atlantic subtropical high pressure system and a weak Intertropical convergence zone in the eastern Pacific Ocean. Population expansions at three major highland Mexico civilization of Teotihuacan, Tula, and Aztec Tenochtitlan were all associated with drought to pluvial transitions, suggesting that urban population growth was favored by increasing freshwater availability in the semi-arid Mexican highlands, and that this hydroclimatic change was controlled by Pacific and Atlantic Ocean forcing.

  20. Reactor oscillator - I - III, Part I

    International Nuclear Information System (INIS)

    Lolic, B.

    1961-12-01

    Project 'Reactor oscillator' covers the following activities: designing reactor oscillators for reactors RA and RB with detailed engineering drawings; constructing and mounting of the oscillator; designing and constructing the appropriate electronic equipment for the oscillator; measurements at the RA and RB reactors needed for completing the oscillator construction

  1. Atlantic and Pacific Ocean synergistic forcing of the Mesomerican monsoon over the last two millennia

    Science.gov (United States)

    Lachniet, M. S.; Asmerom, Y.; Polyak, V. J.; Bernal, J. P.

    2015-12-01

    We present a new replicated, high resolution (~2 yrs) and precisely-dated (± 4 yr) wet season hydroclimate reconstruction for the Mesoamerican sector of the North American Monsoon over the past 2250 years. Our new reconstruction is based on two aragonite stalagmites from southwestern Mexico which replicate oxygen isotope variations over the 950-1950 CE interval, and are calibrated to instrumental rainfall variations in the Basin of Mexico. Such data complement existing dendroclimatic reconstructions of early wet season and winter drought severity. Comparisons to indices of ocean-atmosphere circulation show a combined forcing by the North Atlantic Oscillation and the El Niño/Southern Oscillation. Monsoon strengthening coincided with synergistic forcing of a La Niña-like mode and a negative North Atlantic Oscillation, and vice versa for droughts. Although drought is commonly invoked as an stressor leading to societal change, the role of intensified monsoon onto cultural development is rarely explored. We observe that prominent transitions from drought to pluvial conditions are associated with population increases in three of the major highland Mexico civilizations of Teotihuacan, Tula Grande, and the Aztecs. These data suggest a role for ocean-atmosphere dynamics arising from the Atlantic and Pacific Oceans on Mesoamerican monsoon strength.

  2. Increasing magnitude of Hurricane Rapid Intensification in the central-eastern Atlantic over the past 30 years

    Science.gov (United States)

    Leung, L. R.; Balaguru, K.; Foltz, G. R.

    2017-12-01

    During the 2017 Atlantic hurricane season, several hurricanes underwent rapid intensification (RI) in the central-eastern Atlantic. This motivates an analysis of trends in the strength of hurricane RI during the 30-year post-satellite period of 1986-2015. Our results show that in the eastern tropical Atlantic, to the east of 60W, the mean RI magnitude averaged during 2001-2015 was 3.8 kt per 24 hr higher than during 1986-2000. However, in the western tropical Atlantic, to the west of 60W, changes in RI magnitude over the same period were not statistically significant. We examined the large-scale environment to understand the causes behind these changes in RI magnitude and found that various oceanic and atmospheric parameters that play an important role in RI changed favorably in the eastern tropical Atlantic. More specifically, changes in SST, Potential Intensity, upper-ocean heat content, wind shear, relative humidity and upper-level divergence enhanced the ability for hurricanes to undergo RI in the eastern tropical Atlantic. In contrast, changes in the same factors are inconsistent in the western tropical Atlantic. While changes in SST and Potential Intensity were positive, changes in upper-ocean heat content, wind shear and upper-level divergence were either insignificant or unfavorable for RI. Finally, we examined the potential role of various climate phenomena, which are well-known to impact Atlantic hurricane activity, in causing the changes in the large-scale environment. Our analysis reveals that changes in the Atlantic Multidecadal Oscillation over the 30-year period are predominantly responsible. These results provide important aspects of the large-scale context to understand the Atlantic hurricane season of 2017.

  3. Time domain oscillating poles: Stability redefined in Memristor based Wien-oscillators

    KAUST Repository

    Talukdar, Abdul Hafiz Ibne; Radwan, Ahmed G.; Salama, Khaled N.

    2012-01-01

    poles. The idea is verified using a Memristor based Wien oscillator. Sustained oscillations are observed without having the poles of the system fixed on the imaginary axis and the oscillating behavior of the system poles is reported. The oscillating

  4. Indexing mechanisms

    International Nuclear Information System (INIS)

    Wood, A.G.; Parker, G.E.; Berry, R.

    1976-01-01

    It is stated that the indexing mechanism described can be used in a nuclear reactor fuel element inspection rig. It comprises a tubular body adapted to house a canister containing a number of fuel elements located longtitudinally, and has two chucks spaced apart for displacing the fuel elements longitudinally in a stepwise manner, together with a plunger mechanism for displacing them successively into the chucks. A measuring unit is located between the chucks for measuring the diameter of the fuel elements at intervals about their circumferences, and a secondary indexing mechanism is provided for rotating the measuring unit in a stepwise manner. (U.K.)

  5. Damping of Coherent oscillations

    CERN Document Server

    Vos, L

    1996-01-01

    Damping of coherent oscillations by feedback is straightforward in principle. It has been a vital ingredient for the safe operation of accelerators since a long time. The increasing dimensions and beam intensities of the new generation of hadron colliders impose unprecedented demands on the performance of future systems. The arguments leading to the specification of a transverse feedback system for the CERN SPS in its role as LHC injector and the LHC collider itself are developped to illustrate this. The preservation of the transverse emittance is the guiding principle during this exercise keeping in mind the hostile environment which comprises: transverse impedance bent on developping coupled bunch instabilities, injection errors, unwanted transverse excitation, unavoidable tune spreads and noise in the damping loop.

  6. Convection and stellar oscillations

    DEFF Research Database (Denmark)

    Aarslev, Magnus Johan

    2017-01-01

    for asteroseismology, because of the challenges inherent in modelling turbulent convection in 1D stellar models. As a result of oversimplifying the physics near the surface, theoretical calculations systematically overestimate the oscillation frequencies. This has become known as the asteroseismic surface effect. Due...... to lacking better options, this frequency difference is typically corrected for with ad-hoc formulae. The topic of this thesis is the improvement of 1D stellar convection models and the effects this has on asteroseismic properties. The source of improvements is 3D simulations of radiation...... atmospheres to replace the outer layers of stellar models. The additional turbulent pressure and asymmetrical opacity effects in the atmosphere model, compared to convection in stellar evolution models, serve to expand the atmosphere. The enlarged acoustic cavity lowers the pulsation frequencies bringing them...

  7. Photospheric oscillations. Pt. 1

    International Nuclear Information System (INIS)

    Fossat, E.; Ricort, G.

    1975-01-01

    Intensity fluctuations in the wings of the Fraunhofer line Na D 1 5896 have been recorded for about two hundred hours at the focus of the Nice coude refractor, using a sodium optical resonance device. Because of the large beam aperture available, records have been made on circular apertures from 22'' up to 32' diameter (the whole sun). The principal results from the analysis of these date are: As shown by White and Cha, the five-minute oscillation has a gaussian random character with a mean lifetime of about 20 min. Its two-dimensional spatial power spectrum is roughly gaussian for every temporal frequency between 2 and 6 MHz. The width of this gaussian spectrum is near 5 x 10 -5 km -1 (i.e. π = 20,000 km). (orig./BJ) [de

  8. Coronal Waves and Oscillations

    Directory of Open Access Journals (Sweden)

    Nakariakov Valery M.

    2005-07-01

    Full Text Available Wave and oscillatory activity of the solar corona is confidently observed with modern imaging and spectral instruments in the visible light, EUV, X-ray and radio bands, and interpreted in terms of magnetohydrodynamic (MHD wave theory. The review reflects the current trends in the observational study of coronal waves and oscillations (standing kink, sausage and longitudinal modes, propagating slow waves and fast wave trains, the search for torsional waves, theoretical modelling of interaction of MHD waves with plasma structures, and implementation of the theoretical results for the mode identification. Also the use of MHD waves for remote diagnostics of coronal plasma - MHD coronal seismology - is discussed and the applicability of this method for the estimation of coronal magnetic field, transport coefficients, fine structuring and heating function is demonstrated.

  9. Oscillator strengths for neutral technetium

    International Nuclear Information System (INIS)

    Garstang, R.H.

    1981-01-01

    Oscillator strengths have been calculated for most of the spectral lines of TcI which are of interest in the study of stars of spectral type S. Oscillator strengths have been computed for the corresponding transitions in MnI as a partial check of the technetium calculations

  10. Hyperchaos in coupled Colpitts oscillators

    DEFF Research Database (Denmark)

    Cenys, Antanas; Tamasevicius, Arunas; Baziliauskas, Antanas

    2003-01-01

    The paper suggests a simple solution of building a hyperchaotic oscillator. Two chaotic Colpitts oscillators, either identical or non-identical ones are coupled by means of two linear resistors R-k. The hyperchaotic output signal v(t) is a linear combination, specifically the mean of the individual...

  11. Stochastic and Chaotic Relaxation Oscillations

    NARCIS (Netherlands)

    Grasman, J.; Roerdink, J.B.T.M.

    1988-01-01

    For relaxation oscillators stochastic and chaotic dynamics are investigated. The effect of random perturbations upon the period is computed. For an extended system with additional state variables chaotic behavior can be expected. As an example, the Van der Pol oscillator is changed into a

  12. Oscillating solitons in nonlinear optics

    Indian Academy of Sciences (India)

    ... are derived, and the relevant properties and features of oscillating solitons are illustrated. Oscillating solitons are controlled by the reciprocal of the group velocity and Kerr nonlinearity. Results of this paper will be valuable to the study of dispersion-managed optical communication system and mode-locked fibre lasers.

  13. Augmenting cognition by neuronal oscillations

    NARCIS (Netherlands)

    Horschig, J.M.; Zumer, J.; Bahramisharif, A.

    2014-01-01

    Cortical oscillations have been shown to represent fundamental functions of a working brain, e.g., communication, stimulus binding, error monitoring, and inhibition, and are directly linked to behavior. Recent studies intervening with these oscillations have demonstrated effective modulation of both

  14. Predicting chaos in memristive oscillator via harmonic balance method.

    Science.gov (United States)

    Wang, Xin; Li, Chuandong; Huang, Tingwen; Duan, Shukai

    2012-12-01

    This paper studies the possible chaotic behaviors in a memristive oscillator with cubic nonlinearities via harmonic balance method which is also called the method of describing function. This method was proposed to detect chaos in classical Chua's circuit. We first transform the considered memristive oscillator system into Lur'e model and present the prediction of the existence of chaotic behaviors. To ensure the prediction result is correct, the distortion index is also measured. Numerical simulations are presented to show the effectiveness of theoretical results.

  15. Tropical Atlantic-Korea teleconnection pattern during boreal summer season

    Science.gov (United States)

    Ham, Yoo-Geun; Chikamoto, Yoshimitsu; Kug, Jong-Seong; Kimoto, Masahide; Mochizuki, Takashi

    2017-10-01

    The remote impact of tropical Atlantic sea surface temperature (SST) variability on Korean summer precipitation is examined based on observational data analysis along with the idealized and hindcast model experiments. Observations show a significant correlation (i.e. 0.64) between Korean precipitation anomalies (averaged over 120-130°E, 35-40°N) and the tropical Atlantic SST index (averaged over 60°W-20°E, 30°S-30°N) during the June-July-August (JJA) season for the 1979-2010 period. Our observational analysis and partial-data assimilation experiments using the coupled general circulation model demonstrate that tropical Atlantic SST warming induces the equatorial low-level easterly over the western Pacific through a reorganization of the global Walker Circulation, causing a decreased precipitation over the off-equatorial western Pacific. As a Gill-type response to this diabatic forcing, an anomalous low-level anticyclonic circulation appears over the Philippine Sea, which transports wet air from the tropics to East Asia through low-level southerly, resulting an enhanced precipitation in the Korean peninsula. Multi-model hindcast experiments also show that predictive skills of Korean summer precipitation are improved by utilizing predictions of tropical Atlantic SST anomalies as a predictor for Korean precipitation anomalies.

  16. Oscillating universe with quintom matter

    International Nuclear Information System (INIS)

    Xiong Huahui; Cai Yifu; Qiu Taotao; Piao Yunsong; Zhang Xinmin

    2008-01-01

    In this Letter, we study the possibility of building a model of the oscillating universe with quintom matter in the framework of 4-dimensional Friedmann-Robertson-Walker background. Taking the two-scalar-field quintom model as an example, we find in the model parameter space there are five different types of solutions which correspond to: (I) a cyclic universe with the minimal and maximal values of the scale factor remaining the same in every cycle, (II) an oscillating universe with its minimal and maximal values of the scale factor increasing cycle by cycle, (III) an oscillating universe with its scale factor always increasing, (IV) an oscillating universe with its minimal and maximal values of the scale factor decreasing cycle by cycle, and (V) an oscillating universe with its scale factor always decreasing

  17. Author Index

    Indian Academy of Sciences (India)

    user1

    Astr. (2012) 33, 419–420. Author Index. 419. AGGARWAL SUNNY. Photoionization Cross-Section of Chlorine-like Iron, 291. AMBASTHA ASHOK see Das, A. C., 1. ARAKIDA HIDEYOSHI. Effect of Inhomogeneity of the Universe on a Gravitationally. Bound Local System: A No-Go Result for Explaining the Secular Increase in.

  18. AUTHOR INDEX

    Indian Academy of Sciences (India)

    automorphic solutions to fractional order abstract integro-differential equations. 323. Afrouzi G A see Ala Samira ... 521. Agarwal Praveen. Certain fractional integral operators and the generalized multi-index Mittag- ... of positive solutions for sys- tems of second order multi-point bound- ary value problems on time scales 353.

  19. North Atlantic Energy Structures

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, S. [North Atlantic Energy Structures Inc., St. John' s, NL (Canada); Derradji, A. [National Research Council of Canada, St. John' s, NL (Canada). Inst. for Ocean Technology

    2005-07-01

    North Atlantic Energy Structures Inc. is in the process of designing a tidal fence for a site near the Straits of Belle Isle. This presentation provided details of both the design and the location in which the wave energy plant will be installed. Design constraints included a short seasonal work window, and a harsh but pristine environment. Design specifications of the paddlewheels and caissons were presented. The paddlewheel is iceberg and slab ice resistant, and has portals below the wheel axis, a water-free upper chamber, and bi-directional power generation. The planned installation sequence was presented, as well as details of a hydrodynamic simulation examining torque on the turbines in the tidal energy chamber. Results of the study indicated that 20 paddlewheels per caisson provided the equivalent of 12 MW of energy. A tidal fence of 70 to 80 caissons provided the equivalent of 1.2 GW of energy. A slab ice simulation study was outlined, and details of the pumping station, inlet and hydro-generation station were provided. A map of the proposed siting of the tidal fence was presented. It was concluded that financing for the pilot project has been granted. However, further financing for research and development is required. refs., tabs., figs.

  20. Free oscillation of the Earth

    Directory of Open Access Journals (Sweden)

    Y. Abedini

    2000-06-01

    Full Text Available   This work is a study of the Earths free oscillations considering a merge of solid and liquid model. At the turn of 19th century Geophysicists presented the theory of the free oscillations for a self-gravitating, isotropic and compressible sphere. Assuming a steel structure for an Earth size sphere, they predicted a period of oscillation of about 1 hour. About 50 years later, the free oscillations of stars was studied by Cowling and others. They classified the oscillation modes of the stars into acoustic and gravity modes on the basis of their driving forces. These are pressure and buoyancy forces respectively. The earliest measurements for the period of the free oscillations of the Earth was made by Benyove from a study of Kamchathca earthquake. Since then, the Geophysicists have been trying to provide a theoretical basis for these measurements. Recently, the theory concerning oscillations of celestial fluids is extended by Sobouti to include the possible oscillations of the Earthlike bodies. Using the same technique, we study the free oscillations of a spherically symmetric, non-rotating and elastic model for the Earth.   We used the actual data of the Earths interior structure in our numerical calculations. Numerical results show that there exist three distinct oscillation modes namely acoustic, gravity and toroidal modes. These modes are driven by pressure, buoyancy and shear forces respectively. The shear force is due to the elastic properties of the solid part of the Earth. Our numerical results are consistent with the seismic data recorded from earthquake measurements.

  1. ProAtlantic - The Atlantic Checkpoint - Data Availability and Adequacy in the Atlantic Basin

    Science.gov (United States)

    McGrath, F.

    2017-12-01

    DG MAREs Atlantic Checkpoint is a basin scale wide monitoring system assessment activity based upon targeted end-user applications. It is designed to be a benchmark for the assessment of hydrographic, geological, habitat, climate and fisheries data existence and availability in the Atlantic basin. DG MAREs Atlantic Checkpoint service will be delivered by the ProAtlantic project. The objective of this project is to investigate, through appropriate methodologies in the framework of 11 key marine challenges, how current international and national data providers - e.g. EMODNet, Copernicus - meet the requirements of the stakeholders and deliver fit for purpose data. By so doing, the main thematic and geographic gaps will be readily identified in the Atlantic basin for future consideration by DG MARE. For each challenge, specific web products in the form of maps, metadata, spreadsheets and reports will be delivered. These products are not an end by themselves but rather a means of showing whether data were available, let alone accessible. For example, the Fisheries Impact Challenge outputs include data grids (VMS/Seabed) and data adequacy reports. Production of gridded data layers in order to show the extent of fisheries impact on the seafloor involved the identification, acquisition and collation of data sources for the required data types (VMS/Seabed/Habitats Data) in the Atlantic basin. The resulting spatial coverage of these grids indicates the relatively low level of data availability and adequacy across the Atlantic basin. Aside from the data delivered by programmes such as EMODNet and Copernicus, there are a lot of initiatives by regional bodies such as OSPAR and ICES that consist of assembling and disseminating data to address specific issues. Several international projects have delivered research, data collection, and networking around several of the Atlantic Checkpoint challenge topics, namely MPAs, renewable energy assessment, seabed mapping, oil spill

  2. Non-stationary influence of El Niño-Southern Oscillation and winter temperature on oak latewood growth in NW Iberian Peninsula.

    Science.gov (United States)

    Rozas, Vicente; García-González, Ignacio

    2012-09-01

    The properties of El Niño-Southern Oscillation (ENSO), such as period, amplitude, and teleconnection strength to extratropical regions, have changed since the mid-1970s. ENSO affects the regional climatic regime in SW Europe, thus tree performance in the Iberian Peninsula could be affected by recent ENSO dynamics. We established four Quercus robur chronologies of earlywood and latewood widths in the NW Iberian Peninsula. The relationship between tree growth and the Southern Oscillation Index (SOI), the atmospheric expression of ENSO, showed that only latewood growth was correlated negatively with the SOI of the previous summer-autumn-winter. This relationship was non-stationary, with significant correlations only during the period 1952-1980; and also non-linear, with enhanced latewood growth only in La Niña years, i.e. years with a negative SOI index for the previous autumn. Non-linear relationship between latewood and SOI indicates an asymmetric influence of ENSO on tree performance, biassed towards negative SOI phases. During La Niña years, climate in the study area was warmer and wetter than during positive years, but only for 1952-1980. Winter temperatures became the most limiting factor for latewood growth since 1980, when mean regional temperatures increased by 1°C in comparison to previous periods. As a result, higher winter respiration rates, and the extension of the growing season, would probably cause an additional consumption of stored carbohydrates. The influence of ENSO and winter temperatures proved to be of great importance for tree growth, even at lower altitudes and under mild Atlantic climate in the NW Iberian Peninsula.

  3. 75 FR 30483 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures; Amendment 3

    Science.gov (United States)

    2010-06-01

    ... and 635 Atlantic Highly Migratory Species; Atlantic Shark Management Measures; Amendment 3; Final Rule... and 635 [Docket No. 080519678-0217-02] RIN 0648-AW65 Atlantic Highly Migratory Species; Atlantic Shark... available to rebuild blacknose sharks and end overfishing of blacknose and shortfin mako sharks, consistent...

  4. 77 FR 61562 - Atlantic Highly Migratory Species; 2013 Atlantic Shark Commercial Fishing Season

    Science.gov (United States)

    2012-10-10

    .... 120706221-2481-01] RIN 0648-XC106 Atlantic Highly Migratory Species; 2013 Atlantic Shark Commercial Fishing... establish opening dates and adjust quotas for the 2013 fishing season for the Atlantic commercial shark... the 2011 and 2012 Atlantic commercial shark fishing seasons. We propose to keep the porbeagle shark...

  5. 78 FR 59878 - Atlantic Highly Migratory Species; Commercial Atlantic Aggregated Large Coastal Shark (LCS...

    Science.gov (United States)

    2013-09-30

    ... Coastal Shark (LCS), Atlantic Hammerhead Shark, Atlantic Blacknose Shark, and Atlantic Non-Blacknose Small Coastal Shark (SCS) Management Groups AGENCY: National Marine Fisheries Service (NMFS), National Oceanic... closing the commercial management groups for aggregated LCS and hammerhead sharks in the Atlantic region...

  6. 76 FR 72383 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures

    Science.gov (United States)

    2011-11-23

    ...-BA17 Atlantic Highly Migratory Species; Atlantic Shark Management Measures AGENCY: National Marine... plan (FMP) amendment that would consider catch shares for the Atlantic shark fisheries. The comment... potential catch shares programs in the Atlantic shark fisheries. Additionally, NMFS is extending the comment...

  7. 78 FR 54195 - Atlantic Highly Migratory Species; Atlantic Commercial Shark Fisheries

    Science.gov (United States)

    2013-09-03

    .... 110831548-3536-02] RIN 0648-XC836 Atlantic Highly Migratory Species; Atlantic Commercial Shark Fisheries...) dressed weight (dw) of non-blacknose small coastal shark (SCS) quota from the Atlantic region to the Gulf... Atlantic shark permitted vessels. DATES: The quota transfer is effective from September 2, 2013 until...

  8. 76 FR 67121 - Atlantic Highly Migratory Species; 2012 Atlantic Shark Commercial Fishing Season

    Science.gov (United States)

    2011-10-31

    .... 110913585-1625-01] RIN 0648-BB36 Atlantic Highly Migratory Species; 2012 Atlantic Shark Commercial Fishing... establish opening dates and adjust quotas for the 2012 fishing season for the Atlantic commercial shark... 2011 Atlantic commercial shark fishing seasons. In addition, NMFS proposes season openings based on...

  9. Atlantic menhaden processing plant test tagging data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Atlantic menhaden are a schooling forage fish species, which are subject to a large commercial purse seine fishery. Atlantic menhaden are harvested for reduction...

  10. Afghanistan Index

    DEFF Research Database (Denmark)

    Linnet, Poul Martin

    2007-01-01

    basis. The data are divided into different indicators such as security, polls, drug, social, economic, refugees etc. This represents a practical division and does not indicate that a picture as to for instance security can be obtained by solely looking at the data under security. In order to obtain...... a more valid picture on security this must incorporate an integrated look on all data meaning that for instance the economic data provides an element as to the whole picture of security.......The Afghanistan index is a compilation of quantitative and qualitative data on the reconstruction and security effort in Afghanistan. The index aims at providing data for benchmarking of the international performance and thus provides the reader with a quick possibility to retrieve valid...

  11. A theory of generalized Bloch oscillations

    International Nuclear Information System (INIS)

    Duggen, Lars; Lassen, Benny; Lew Yan Voon, L C; Willatzen, Morten

    2016-01-01

    Bloch oscillations of electrons are shown to occur for cases when the energy spectrum does not consist of the traditional evenly-spaced ladders and the potential gradient does not result from an external electric field. A theory of such generalized Bloch oscillations is presented and an exact calculation is given to confirm this phenomenon. Our results allow for a greater freedom of design for experimentally observing Bloch oscillations. For strongly coupled oscillator systems displaying Bloch oscillations, it is further demonstrated that reordering of oscillators leads to destruction of Bloch oscillations. We stipulate that the presented theory of generalized Bloch oscillations can be extended to other systems such as acoustics and photonics. (paper)

  12. Cold-season atmospheric response to the natural variability of the Atlantic meridional overturning circulation

    Energy Technology Data Exchange (ETDEWEB)

    Gastineau, Guillaume; Frankignoul, Claude [LOCEAN/IPSL, Universite Pierre et Marie Curie, 4 place Jussieu, BP100, Paris Cedex 05 (France)

    2012-07-15

    The influence of the natural variability of the Atlantic meridional overturning circulation (AMOC) on the atmosphere is studied in multi-centennial simulations of six global climate models, using Maximum Covariance Analysis (MCA). In all models, a significant but weak influence of the AMOC changes is found during the Northern Hemisphere cold-season, when the ocean leads the atmosphere by a few years. Although the oceanic pattern slightly varies, an intensification of the AMOC is followed in all models by a weak sea level pressure response that resembles a negative phase of the North Atlantic Oscillation (NAO). The signal amplitude is typically 0.5 hPa and explains about 10% of the yearly variability of the NAO in all models. The atmospheric response seems to be due primarily due to an increase of the heat loss along the North Atlantic Current and the subpolar gyre, associated with an AMOC-driven warming. Sea-ice changes appear to be less important. The stronger heating is associated to a southward shift of the lower-tropospheric baroclinicity and a decrease of the eddy activity in the North Atlantic storm track, which is consistent with the equivalent barotropic perturbation resembling the negative phase of the NAO. This study thus provides some evidence of an atmospheric signature of the AMOC in the cold-season, which may have some implications for the decadal predictability of climate in the North Atlantic region. (orig.)

  13. Atlantic Seaduck Project

    Science.gov (United States)

    Perry, M.C.; Hanson, Alan; Kerekes, Joseph; Paquet, Julie

    2006-01-01

    Atlantic Seaduck Project is being conducted to learn more about the breeding and moulting areas of seaducks in northern Canada and more about their feeding ecology on wintering areas, especially Chesapeake Bay. Satellite telemetry is being used to track surf scoters wintering in Chesapeake Bay, Maryland and black scoters on migrational staging areas in New Brunswick, Canada to breeding and moulting areas in northern Canada. Various techniques used to capture the scoters included mist netting, night-lighting, and net capture guns. All captured ducks were transported to a veterinary hospital where surgery was conducted following general anaesthesia procedures. A PTT100 transmitter (39 g) manufactured by Microwave, Inc., Columbia, Maryland was implanted into the duck?s abdominal cavity with an external (percutaneous) antenna. Eight of the surf scoters from Chesapeake Bay successfully migrated to possible breeding areas in Canada and all 13 of the black scoters migrated to suspected breeding areas. Ten of the 11 black scoter males migrated to James Bay presumably for moulting. Updated information from the ARGOS Systems aboard the NOAA satellites on scoter movements was made accessible on the Patuxent Website. Habitat cover types of locations using GIS (Geographical Information Systems) and aerial photographs (in conjunction with remote sensing software) are currently being analyzed to build thematic maps with varying cosmetic layer applications. Many factors related to human population increases have been implicated in causing changes in the distribution and abundance of wintering seaducks. Analyses of the gullet (oesophagus and proventriculus) and the gizzard of seaducks are currently being conducted to determine if changes from historical data have occurred. Scoters in the Bay feed predominantly on the hooked mussel and several species of clams. The long-tailed duck appears to select the gem clam in greater amounts than other seaducks, but exhibits a diverse diet of

  14. Neutrino oscillation: status and outlooks

    International Nuclear Information System (INIS)

    Nedelec, P.

    1994-01-01

    Whether the neutrinos are massive or not is one of the most puzzling question of physics today. If they are massive, they can contribute significantly to the Dark Matter of the Universe. An other consequence of a non-zero mass of neutrinos is that they might oscillate from one flavor to another. This oscillation process is by now the only way to detect a neutrino with a mass in the few eV range. Several neutrino experiments are currently looking for such an oscillation, in different modes, using different techniques. An overview of the experimental situation for neutrino experiments at accelerators is given. (author). 9 refs., 5 figs., 5 tabs

  15. Synchronous Oscillations in Microtubule Polymerization

    Science.gov (United States)

    Carlier, M. F.; Melki, R.; Pantaloni, D.; Hill, T. L.; Chen, Y.

    1987-08-01

    Under conditions where microtubule nucleation and growth are fast (i.e., high magnesium ion and tubulin concentrations and absence of glycerol), microtubule assembly in vitro exhibits an oscillatory regime preceding the establishment of steady state. The amplitude of the oscillations can represent >50% of the maximum turbidity change and oscillations persist for up to 20 periods of 80 s each. Oscillations are accompanied by extensive length redistribution of microtubules. Preliminary work suggests that the oscillatory kinetics can be simulated using a model in which many microtubules undergo synchronous transitions between growing and rapidly depolymerizing phases, complicated by the kinetically limiting rate of nucleotide exchange on free tubulin.

  16. Atlantic CFC data in CARINA

    Directory of Open Access Journals (Sweden)

    R. Steinfeldt

    2010-01-01

    Full Text Available Water column data of carbon and carbon-relevant parameters have been collected and merged into a new database called CARINA (CARbon IN the Atlantic. In order to provide a consistent data set, all data have been examined for systematic biases and adjusted if necessary (secondary quality control (QC. The CARINA data set is divided into three regions: the Arctic/Nordic Seas, the Atlantic region and the Southern Ocean. Here we present the CFC data for the Atlantic region, including the chlorofluorocarbons CFC-11, CFC-12 and CFC-113 as well as carbon tetrachloride (CCl4. The methods applied for the secondary quality control, a crossover analyses, the investigation of CFC ratios in the ocean and the CFC surface saturation are presented. Based on the results, the CFC data of some cruises are adjusted by a certain factor or given a "poor'' quality flag.

  17. North Atlantic explosive cyclones and large scale atmospheric variability modes

    Science.gov (United States)

    Liberato, Margarida L. R.

    2015-04-01

    Extreme windstorms are one of the major natural catastrophes in the extratropics, one of the most costly natural hazards in Europe and are responsible for substantial economic damages and even fatalities. During the last decades Europe witnessed major damage from winter storms such as Lothar (December 1999), Kyrill (January 2007), Klaus (January 2009), Xynthia (February 2010), Gong (January 2013) and Stephanie (February 2014) which exhibited uncommon characteristics. In fact, most of these storms crossed the Atlantic in direction of Europe experiencing an explosive development at unusual lower latitudes along the edge of the dominant North Atlantic storm track and reaching Iberia with an uncommon intensity (Liberato et al., 2011; 2013; Liberato 2014). Results show that the explosive cyclogenesis process of most of these storms at such low latitudes is driven by: (i) the southerly displacement of a very strong polar jet stream; and (ii) the presence of an atmospheric river (AR), that is, by a (sub)tropical moisture export over the western and central (sub)tropical Atlantic which converges into the cyclogenesis region and then moves along with the storm towards Iberia. Previous studies have pointed to a link between the North Atlantic Oscillation (NAO) and intense European windstorms. On the other hand, the NAO exerts a decisive control on the average latitudinal location of the jet stream over the North Atlantic basin (Woollings et al. 2010). In this work the link between North Atlantic explosive cyclogenesis, atmospheric rivers and large scale atmospheric variability modes is reviewed and discussed. Liberato MLR (2014) The 19 January 2013 windstorm over the north Atlantic: Large-scale dynamics and impacts on Iberia. Weather and Climate Extremes, 5-6, 16-28. doi: 10.1016/j.wace.2014.06.002 Liberato MRL, Pinto JG, Trigo IF, Trigo RM. (2011) Klaus - an exceptional winter storm over Northern Iberia and Southern France. Weather 66:330-334. doi:10.1002/wea.755 Liberato

  18. Rabi oscillation between states of a coupled harmonic oscillator

    International Nuclear Information System (INIS)

    Park, Tae Jun

    2003-01-01

    Rabi oscillation between bound states of a single potential is well known. However the corresponding formula between the states of two different potentials has not been obtained yet. In this work, we derive Rabi formula between the states of a coupled harmonic oscillator which may be used as a simple model for the electron transfer. The expression is similar to typical Rabi formula for a single potential. This result may be used to describe transitions between coupled diabatic potential curves

  19. Oscillations in Mathematical Biology

    CERN Document Server

    1983-01-01

    The papers in this volume are based on talks given at a one day conference held on the campus of Adelphi University in April 1982. The conference was organized with the title "Oscillations in Mathematical Biology;" however the speakers were allowed considerable latitutde in their choice of topics. In the event, the talks all concerned the dynamics of non-linear systems arising in biology so that the conference achieved a good measure of cohesion. Some of the speakers cho~e not to submit a manuscript for these proceedings, feeling that their material was too conjectural to be committed to print. Also the paper of Rinzel and Troy is a distillation of the two separate talks that the authors gave. Otherwise the material reproduces the conference proceedings. The conference was made possible by the generous support of the Office of the Dean of the College of Arts and Sciences at Adelphi. The bulk of the organization of the conference was carried out by Dr. Ronald Grisell whose energy was in large measure responsib...

  20. Principal oscillation patterns

    International Nuclear Information System (INIS)

    Storch, H. von; Buerger, G.; Storch, J.S. von

    1993-01-01

    The Principal Oscillation Pattern (POP) analysis is a technique which is used to simultaneously infer the characteristic patterns and time scales of a vector time series. The POPs may be seen as the normal modes of a linearized system whose system matrix is estimated from data. The concept of POP analysis is reviewed. Examples are used to illustrate the potential of the POP technique. The best defined POPs of tropospheric day-to-day variability coincide with the most unstable modes derived from linearized theory. POPs can be derived even from a space-time subset of data. POPs are successful in identifying two independent modes with similar time scales in the same data set. The POP method can also produce forecasts which may potentially be used as a reference for other forecast models. The conventional POP analysis technique has been generalized in various ways. In the cyclostationary POP analysis, the estimated system matrix is allowed to vary deterministically with an externally forced cycle. In the complex POP analysis not only the state of the system but also its ''momentum'' is modeled. Associated correlation patterns are a useful tool to describe the appearance of a signal previously identified by a POP analysis in other parameters. (orig.)

  1. A Tropical View of Atlantic Multidecadal SST Variability over the Last Two Millennia

    Science.gov (United States)

    Wurtzel, J. B.; Black, D. E.; Thunell, R.; Peterson, L. C.; Tappa, E. J.; Rahman, S.

    2011-12-01

    Instrumental and proxy-reconstructions show the existence of a 60-80 year periodicity in Atlantic sea surface temperature (SST), known as the Atlantic Multidecadal Oscillation (AMO). The AMO is correlated with circum-tropical Atlantic climate phenomena such as Sahel and Nordeste rainfall, as well as Atlantic hurricane patterns. Though it has been suggested that the AMO is controlled by thermohaline circulation, much debate exists as to whether the SST fluctuations are a result of anthropogenic forcing or natural climate variability. Our ability to address this issue has been limited by instrumental SST records that rarely extend back more than 50-100 years and proxy reconstructions that are largely terrestrial-based. Here we present a high-resolution marine sediment-derived reconstruction of seasonal tropical Atlantic SSTs from the Cariaco Basin spanning the past two millennia that is correlated with instrumental SSTs and the AMO for the period of overlap. The full record demonstrates that seasonality is largely controlled by variations in winter/spring SST. Wavelet analysis of the proxy data suggest that variability in the 60-80 year band evolved 250 years ago, while 40-60 year periodicities dominate earlier parts of the record. At least over the last millennia, multidecadal- and centennial- scale SST variability in the tropical Atlantic appears related to Atlantic meridional overturning circulation (AMOC) fluctuations and its associated northward heat transport that in turn may be driven by solar variability. An inverse correlation between the tropical proxy annual average SST record and Δ14C indicates that the tropics experienced positive SST anomalies during times of reduced solar activity, possibly as a result of decreased AMOC strength (Figure 1).

  2. Fast reconnaissance of carbonate dissolution based on the size distribution of calcareous ooze on Walvis Ridge, SE Atlantic Ocean.

    NARCIS (Netherlands)

    Stuut, J.-B. W.; Prins, M.A.; Jansen, J.H.F.

    2002-01-01

    We present a new index of carbonate fragmentation based on the size distribution of bulk sediments in core MD962094 from Walvis Ridge (SE Atlantic Ocean). The carbonate fragmentation index is constructed by taking a ratio of the two coarsest fractions in the grain size distributions of the bulk

  3. Modulation of extremes in the Atlantic region by modes of climate variability/change: A mechanistic coupled regional model study

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, Ramalingam [Texas A & M Univ., College Station, TX (United States)

    2015-01-09

    During the course of this project, we have accomplished the following: 1) Explored the parameter space of component models to minimize regional model bias 2) Assessed the impact of air-sea interaction on hurricanes, focusing in particular on the role of the oceanic barrier layer 3) Contributed to the activities of the U.S. CLIVAR Hurricane Working Group 4) Assessed the impact of lateral and lower boundary conditions on extreme flooding events in the U.S. Midwest in regional model simulations 5) Analyzed the concurrent impact of El Niño-Southern Oscillation and Atlantic Meridional Mode on Atlantic Hurricane activity using observations and regional model simulations

  4. How do the multiple large-scale climate oscillations trigger extreme precipitation?

    Science.gov (United States)

    Shi, Pengfei; Yang, Tao; Xu, Chong-Yu; Yong, Bin; Shao, Quanxi; Li, Zhenya; Wang, Xiaoyan; Zhou, Xudong; Li, Shu

    2017-10-01

    Identifying the links between variations in large-scale climate patterns and precipitation is of tremendous assistance in characterizing surplus or deficit of precipitation, which is especially important for evaluation of local water resources and ecosystems in semi-humid and semi-arid regions. Restricted by current limited knowledge on underlying mechanisms, statistical correlation methods are often used rather than physical based model to characterize the connections. Nevertheless, available correlation methods are generally unable to reveal the interactions among a wide range of climate oscillations and associated effects on precipitation, especially on extreme precipitation. In this work, a probabilistic analysis approach by means of a state-of-the-art Copula-based joint probability distribution is developed to characterize the aggregated behaviors for large-scale climate patterns and their connections to precipitation. This method is employed to identify the complex connections between climate patterns (Atlantic Multidecadal Oscillation (AMO), El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)) and seasonal precipitation over a typical semi-humid and semi-arid region, the Haihe River Basin in China. Results show that the interactions among multiple climate oscillations are non-uniform in most seasons and phases. Certain joint extreme phases can significantly trigger extreme precipitation (flood and drought) owing to the amplification effect among climate oscillations.

  5. The Duffing oscillator with damping

    DEFF Research Database (Denmark)

    Johannessen, Kim

    2015-01-01

    An analytical solution to the differential equation describing the Duffing oscillator with damping is presented. The damping term of the differential equation and the initial conditions satisfy an algebraic equation, and thus the solution is specific for this type of damping. The nonlinear term...... of the differential equation is allowed to be considerable compared to the linear term. The solution is expressed in terms of the Jacobi elliptic functions by including a parameter-dependent elliptic modulus. The analytical solution is compared to the numerical solution, and the agreement is found to be very good....... It is established that the period of oscillation is shorter compared to that of a linearized model but increasing with time and asymptotically approaching the period of oscillation of the linear damped model. An explicit expression for the period of oscillation has been derived, and it is found to be very accurate....

  6. Electronically tunable RC sinusoidal oscillators

    International Nuclear Information System (INIS)

    Florescu, Valeriu

    2008-01-01

    This paper presents two types of active configurations for realizing electronically tunable RC sinusoidal oscillators. The type-1 network employs two grounded scaled resistances KR 1 and KR 2 , where K is scaling factor. The frequency of oscillation W 0 is controlled conveniently by adjusting K, since W 0 appears in the form W 0 =1/K √ R 1 C 1 R 2 C 2 . For realizing the scaled resistances, an active configuration is proposed, which realizes KR 1 =R 1 /(1+f(V B )), where f(V B ) denotes a function of a controlling voltage V B . Thus the frequency tuning can be effected by controlling a voltage V B . The type-2 oscillator uses two periodically switched conductances. It is shown that the tuning of oscillation frequency can be done by varying the pulse width-to-period ratio (t/T) of the periodically switched conductances. (author)

  7. Thermoelastic Loss in Microscale Oscillators

    National Research Council Canada - National Science Library

    Houston, B. H; Photiadis, D. M; Marcus, M. H; Bucaro, J. A; Liu, Xiao; Vignola, J. F

    2001-01-01

    ...) and nanoelectromechanical (NEMS) oscillators. The theory defines a flexural modal participation factor, the fraction of potential energy stored in flexure, and approximates the internal friction by assuming the energy loss to occur solely via...

  8. Oscillating nonlinear acoustic shock waves

    DEFF Research Database (Denmark)

    Gaididei, Yuri; Rasmussen, Anders Rønne; Christiansen, Peter Leth

    2016-01-01

    We investigate oscillating shock waves in a tube using a higher order weakly nonlinear acoustic model. The model includes thermoviscous effects and is non isentropic. The oscillating shock waves are generated at one end of the tube by a sinusoidal driver. Numerical simulations show that at resona......We investigate oscillating shock waves in a tube using a higher order weakly nonlinear acoustic model. The model includes thermoviscous effects and is non isentropic. The oscillating shock waves are generated at one end of the tube by a sinusoidal driver. Numerical simulations show...... polynomial in the space and time variables, we find analytical approximations to the observed single shock waves in an infinitely long tube. Using perturbation theory for the driven acoustic system approximative analytical solutions for the off resonant case are determined....

  9. Transient voltage oscillations in coils

    International Nuclear Information System (INIS)

    Chowdhuri, P.

    1985-01-01

    Magnet coils may be excited into internal voltage oscillations by transient voltages. Such oscillations may electrically stress the magnet's dielectric components to many times its normal stress. This may precipitate a dielectric failure, and the attendant prolonged loss of service and costly repair work. Therefore, it is important to know the natural frequencies of oscillations of a magnet during the design stage, and to determine whether the expected switching transient voltages can excite the magnet into high-voltage internal oscillations. The series capacitance of a winding significantly affects its natural frequencies. However, the series capacitance is difficult to calculate, because it may comprise complex capacitance network, consisting of intra- and inter-coil turn-to-turn capacitances of the coil sections. A method of calculating the series capacitance of a winding is proposed. This method is rigorous but simple to execute. The time-varying transient voltages along the winding are also calculated

  10. Phylobetadiversity among forest types in the Brazilian Atlantic Forest complex.

    Science.gov (United States)

    Duarte, Leandro Da Silva; Bergamin, Rodrigo Scarton; Marcilio-Silva, Vinícius; Seger, Guilherme Dubal Dos Santos; Marques, Márcia Cristina Mendes

    2014-01-01

    Phylobetadiversity is defined as the phylogenetic resemblance between communities or biomes. Analyzing phylobetadiversity patterns among different vegetation physiognomies within a single biome is crucial to understand the historical affinities between them. Based on the widely accepted idea that different forest physiognomies within the Southern Brazilian Atlantic Forest constitute different facies of a single biome, we hypothesize that more recent phylogenetic nodes should drive phylobetadiversity gradients between the different forest types within the Atlantic Forest, as the phylogenetic divergence among those forest types is biogeographically recent. We compiled information from 206 checklists describing the occurrence of shrub/tree species across three different forest physiognomies within the Southern Brazilian Atlantic Forest (Dense, Mixed and Seasonal forests). We analyzed intra-site phylogenetic structure (phylogenetic diversity, net relatedness index and nearest taxon index) and phylobetadiversity between plots located at different forest types, using five different methods differing in sensitivity to either basal or terminal nodes (phylogenetic fuzzy weighting, COMDIST, COMDISTNT, UniFrac and Rao's H). Mixed forests showed higher phylogenetic diversity and overdispersion than the other forest types. Furthermore, all forest types differed from each other in relation phylobetadiversity patterns, particularly when phylobetadiversity methods more sensitive to terminal nodes were employed. Mixed forests tended to show higher phylogenetic differentiation to Dense and Seasonal forests than these latter from each other. The higher phylogenetic diversity and phylobetadiversity levels found in Mixed forests when compared to the others likely result from the biogeographical origin of several taxa occurring in these forests. On one hand, Mixed forests shelter several temperate taxa, like the conifers Araucaria and Podocarpus. On the other hand, tropical groups, like

  11. Modelling solar-like oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Eggenberger, P; Miglio, A [Institut d' Astrophysique et de Geophysique de l' Universite de Liege, 17 Allee du 6 Aout, B-4000 Liege (Belgium); Carrier, F [Institute of Astronomy, University of Leuven, Celestijnenlaan 200 D, B-3001 Leuven (Belgium); Mathis, S [CEA/DSM/DAPNIA/Service d' Astrophysique, CEA/Saclay, AIM-Unite Mixte de Recherche CEA-CNRS-Universite Paris VII, UMR 7158, 91191 Gif-sur-Yvette Cedex (France)], E-mail: eggenberger@Qastro.ulg.ac.be

    2008-10-15

    The computation of models of stars for which solar-like oscillations have been observed is discussed. After a brief intoduction on the observations of solar-like oscillations, the modelling of isolated stars and of stars belonging to a binary system is presented with specific examples of recent theoretical calibrations. Finally the input physics introduced in stellar evolution codes for the computation of solar-type stars is discussed with a peculiar emphasis on the modelling of rotation for these stars.

  12. Statistical Relationship between Sawtooth Oscillations and Geomagnetic Storms

    Directory of Open Access Journals (Sweden)

    Jae-Hun Kim

    2008-06-01

    Full Text Available We have investigated a statistical relationship between sawtooth oscillations and geomagnetic storms during 2000-2004. First of all we selected a total of 154 geomagnetic storms based on the Dst index, and distinguished between different drivers such as Coronal Mass Ejection (CME and Co-rotating Interaction Region (CIR. Also, we identified a total of 48 sawtooth oscillation events based on geosynchronous energetic particle data for the same 2000-2004 period. We found that out of the 154 storms identified, 47 storms indicated the presence of sawtooth oscillations. Also, all but one sawtooth event identified occurred during a geomagnetic storm interval. It was also found that sawtooth oscillation events occur more frequently for storms driven by CME (˜62% than for storms driven by CIR (˜30%. In addition, sawtooth oscillations occurred mainly (˜82% in the main phase of storms for CME-driven storms while they occurred mostly (˜78% during the storm recovery phase for CIR-driven storms. Next we have examined the average characteristics of the Bz component of IMF, and solar wind speed, which were the main components for driving geomagnetic storm. We found that for most of the sawtooth events, the IMF Bz corresponds to --15 to 0 nT and the solar wind speed was in the range of 400˜700 km/s. We found that there was a weak tendency that the number of teeth for a given sawtooth event interval was proportional to the southward IMF Bz magnitude.

  13. Atlantic Environmental Resource Directory, 1989: A directory of non-profit environmental and development organizations in Atlantic Canada

    Energy Technology Data Exchange (ETDEWEB)

    Cuthbertson, L.L.

    1989-01-01

    This directory lists 161 non-profit groups in the Atlantic region, along with contacts for the environmental networks across the country and in New England and appropriate federal and provincial offices in Atlantic Canada. The directory was compiled from questionnaires sent out to a list of contacts that were on an original mailing list of groups known to have taken stands on environmental issues in the past. Follow-up mailouts and phone calls were also made. As well, some contacts were discovered through word-of-mouth. Groups are listed alphabetically by province and are classified by subjects. Information includes address and phone number, contact, date formed, number of members, scope, language and objectives. Groups and resources are indexed by subject area and groups are listed by resources available, environmental networks, Eastern states-United States citizen groups, labour unions, federal and provincial government.

  14. Interannual-to-decadal air-sea interactions in the tropical Atlantic region

    Science.gov (United States)

    Ruiz-Barradas, Alfredo

    2001-09-01

    Atlantic but winds and heating of the midlatitude North Atlantic have little impact on the deep tropics. The remote influence of El Niño-Southern Oscillation in the tropical Atlantic, similar to the Interhemispheric mode, is the result of two mechanisms triggered by anomalous warming in the central and eastern tropical Pacific: enhancement of the Atlantic Walker circulation, and coupled intrusion of negative 200 mb geopotential height anomalies and negative sea level pressure anomalies that induce southwesterly surface wind anomalies in the northern tropical Atlantic.

  15. Modeling nonlinearities in MEMS oscillators.

    Science.gov (United States)

    Agrawal, Deepak K; Woodhouse, Jim; Seshia, Ashwin A

    2013-08-01

    We present a mathematical model of a microelectromechanical system (MEMS) oscillator that integrates the nonlinearities of the MEMS resonator and the oscillator circuitry in a single numerical modeling environment. This is achieved by transforming the conventional nonlinear mechanical model into the electrical domain while simultaneously considering the prominent nonlinearities of the resonator. The proposed nonlinear electrical model is validated by comparing the simulated amplitude-frequency response with measurements on an open-loop electrically addressed flexural silicon MEMS resonator driven to large motional amplitudes. Next, the essential nonlinearities in the oscillator circuit are investigated and a mathematical model of a MEMS oscillator is proposed that integrates the nonlinearities of the resonator. The concept is illustrated for MEMS transimpedance-amplifier- based square-wave and sine-wave oscillators. Closed-form expressions of steady-state output power and output frequency are derived for both oscillator models and compared with experimental and simulation results, with a good match in the predicted trends in all three cases.

  16. Use of variability modes to evaluate AR4 climate models over the Euro-Atlantic region

    Energy Technology Data Exchange (ETDEWEB)

    Casado, M.J.; Pastor, M.A. [Agencia Estatal de Meteorologia (AEMET), Madrid (Spain)

    2012-01-15

    This paper analyzes the ability of the multi-model simulations from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) to simulate the main leading modes of variability over the Euro-Atlantic region in winter: the North-Atlantic Oscillation (NAO), the Scandinavian mode (SCAND), the East/Atlantic Oscillation (EA) and the East Atlantic/Western Russia mode (EA/WR). These modes of variability have been evaluated both spatially, by analyzing the intensity and location of their anomaly centres, as well as temporally, by focusing on the probability density functions and e-folding time scales. The choice of variability modes as a tool for climate model assessment can be justified by the fact that modes of variability determine local climatic conditions and their likely change may have important implications for future climate changes. It is found that all the models considered are able to simulate reasonably well these four variability modes, the SCAND being the mode which is best spatially simulated. From a temporal point of view the NAO and SCAND modes are the best simulated. UKMO-HadGEM1 and CGCM3.1(T63) are the models best at reproducing spatial characteristics, whereas CCSM3 and CGCM3.1(T63) are the best ones with regard to the temporal features. GISS-AOM is the model showing the worst performance, in terms of both spatial and temporal features. These results may bring new insight into the selection and use of specific models to simulate Euro-Atlantic climate, with some models being clearly more successful in simulating patterns of temporal and spatial variability than others. (orig.)

  17. On the nonlinear modeling of ring oscillators

    KAUST Repository

    Elwakil, Ahmed S.

    2009-06-01

    We develop higher-order nonlinear models of three-stage and five-stage ring oscillators based on a novel inverter model. The oscillation condition and oscillation frequency are derived and compared to classical linear model analysis. Two important special cases for five-stage ring oscillators are also studied. Numerical simulations are shown. © 2009 World Scientific Publishing Company.

  18. Some comparison of two fractional oscillators

    International Nuclear Information System (INIS)

    Kang Yonggang; Zhang Xiu'e

    2010-01-01

    The other form of fractional oscillator equation comparing to the widely discussed one is ushered in. The properties of vibration of two fractional oscillators are discussed under the influence of different initial conditions. The interpretation of the characteristics of the fractional oscillators using different method is illustrated. Based on two fractional oscillator equations, two linked bodies and the continuous system are studied.

  19. Magnetically Coupled Magnet-Spring Oscillators

    Science.gov (United States)

    Donoso, G.; Ladera, C. L.; Martin, P.

    2010-01-01

    A system of two magnets hung from two vertical springs and oscillating in the hollows of a pair of coils connected in series is a new, interesting and useful example of coupled oscillators. The electromagnetically coupled oscillations of these oscillators are experimentally and theoretically studied. Its coupling is electromagnetic instead of…

  20. On the nonlinear modeling of ring oscillators

    KAUST Repository

    Elwakil, Ahmed S.; Salama, Khaled N.

    2009-01-01

    We develop higher-order nonlinear models of three-stage and five-stage ring oscillators based on a novel inverter model. The oscillation condition and oscillation frequency are derived and compared to classical linear model analysis. Two important special cases for five-stage ring oscillators are also studied. Numerical simulations are shown. © 2009 World Scientific Publishing Company.

  1. Enhanced aridity and atmospheric high-pressure stability over the western Mediterranean during the North Atlantic cold events of the past 50 k.y.

    Science.gov (United States)

    Combourieu Nebout, N.; Turon, J. L.; Zahn, R.; Capotondi, L.; Londeix, L.; Pahnke, K.

    2002-10-01

    Multiproxy paleoenvironmental records (pollen and planktonic isotope) from Ocean Drilling Program Site 976 (Alboran Sea) document rapid ocean and climate variations during the last glacial that follow the Dansgaard-Oeschger climate oscillations seen in the Greenland ice core records, thus suggesting a close link of the Mediterranean climate swings with North Atlantic climates. Continental conditions rapidly oscillated through cold-arid and warm-wet conditions in the course of stadial-interstadial climate jumps. At the time of Heinrich events, i.e., maximum meltwater flux to the North Atlantic, western Mediterranean marine microflora and microfauna show rapid cooling correlated with increasing continental dryness. Enhanced aridity conceivably points to prolonged wintertime stability of atmospheric high-pressure systems over the southwestern Mediterranean in conjunction with cooling of the North Atlantic.

  2. Standing Wave Field Distribution in Graded-Index Antireflection Coatings

    Directory of Open Access Journals (Sweden)

    Hongxiang Deng

    2018-01-01

    Full Text Available Standing wave field distributions in three classic types of graded-index antireflection coatings are studied. These graded-index antireflection coatings are designed at wavelengths from 200 nm to 1200 nm, which is the working wavelength range of high energy laser system for inertial-fusion research. The standing wave field distributions in these coatings are obtained by the numerical calculation of electromagnetic wave equation. We find that standing wave field distributions in these three graded-index anti-reflection coatings are quite different. For the coating with linear index distribution, intensity of standing wave field decreases periodically from surface to substrate with narrow oscillation range and the period is proportional to the incident wavelength. For the coating with exponential index distribution, intensity of standing wave field decreases periodically from surface to substrate with large oscillation range and the period is also proportional to the incident wavelength. Finally, for the coating with polynomial index, intensity of standing wave field is quickly falling down from surface to substrate without an obvious oscillation. We find that the intensity of standing wave field in the interface between coating and substrate for linear index, exponential index and polynomial index are about 0.7, 0.9 and 0.7, respectively. Our results indicate that the distributions of standing wave field in linear index coating and polynomial index coating are better than that in exponential index coating for the application in high energy laser system. Moreover, we find that the transmittance of linear index coating and polynomial index coating are also better than exponential index coating at the designed wavelength range. Present simulation results are useful for the design and application of graded-index antireflection coating in high energy laser system.

  3. On the mechanism of oscillations in neutrophils

    DEFF Research Database (Denmark)

    Brasen, Jens Christian; Barington, Torben; Olsen, Lars Folke

    2010-01-01

    We have investigated the regulation of the oscillatory generation of H(2)O(2) and oscillations in shape and size in neutrophils in suspension. The oscillations are independent of cell density and hence do not represent a collective phenomena. Furthermore, the oscillations are independent...... of the external glucose concentration and the oscillations in H(2)O(2) production are 180 degrees out of phase with the oscillations in NAD(P)H. Cytochalasin B blocked the oscillations in shape and size whereas it increased the period of the oscillations in H(2)O(2) production. 1- and 2-butanol also blocked...... the oscillations in shape and size, but only 1-butanol inhibited the oscillations in H(2)O(2) production. We conjecture that the oscillations are likely to be due to feedback regulations in the signal transduction cascade involving phosphoinositide 3-kinases (PI3K). We have tested this using a simple mathematical...

  4. Reactor oscillator - I - III, Part I; Reaktorski oscilator - I-III, I Deo

    Energy Technology Data Exchange (ETDEWEB)

    Lolic, B [Institute of Nuclear Sciences Boris Kidric, Laboratorija za fiziku reaktora, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    Project 'Reactor oscillator' covers the following activities: designing reactor oscillators for reactors RA and RB with detailed engineering drawings; constructing and mounting of the oscillator; designing and constructing the appropriate electronic equipment for the oscillator; measurements at the RA and RB reactors needed for completing the oscillator construction.

  5. A New Method for Suppressing Periodic Narrowband Interference Based on the Chaotic van der Pol Oscillator

    Science.gov (United States)

    Lu, Jia; Zhang, Xiaoxing; Xiong, Hao

    The chaotic van der Pol oscillator is a powerful tool for detecting defects in electric systems by using online partial discharge (PD) monitoring. This paper focuses on realizing weak PD signal detection in the strong periodic narrowband interference by using high sensitivity to the periodic narrowband interference signals and immunity to white noise and PD signals of chaotic systems. A new approach to removing the periodic narrowband interference by using a van der Pol chaotic oscillator is described by analyzing the motion characteristic of the chaotic oscillator on the basis of the van der Pol equation. Furthermore, the Floquet index for measuring the amplitude of periodic narrowband signals is redefined. The denoising signal processed by the chaotic van der Pol oscillators is further processed by wavelet analysis. Finally, the denoising results verify that the periodic narrowband and white noise interference can be removed efficiently by combining the theory of the chaotic van der Pol oscillator and wavelet analysis.

  6. 76 FR 13583 - Atlantic Highly Migratory Species; Atlantic Bluefin Tuna Quotas and Atlantic Tuna Fisheries...

    Science.gov (United States)

    2011-03-14

    ... address concerns raised in a recent decision by a NOAA Administrative Law Judge (see Atlantic Tunas Transfer at Sea section for case reference). NMFS has prepared a draft Environmental Assessment (EA... subtraction of these allocations directly from the TAC, the recommendation allocates the remainder to the UK...

  7. Variability of the North Atlantic summer storm track: mechanisms and impacts on European climate

    International Nuclear Information System (INIS)

    Dong, Buwen; Sutton, Rowan T; Woollings, Tim; Hodges, Kevin

    2013-01-01

    The summertime variability of the extratropical storm track over the Atlantic sector and its links to European climate have been analysed for the period 1948–2011 using observations and reanalyses. The main results are as follows. (1) The dominant mode of the summer storm track density variability is characterized by a meridional shift of the storm track between two distinct paths and is related to a bimodal distribution in the climatology for this region. It is also closely related to the Summer North Atlantic Oscillation (SNAO). (2) A southward shift is associated with a downstream extension of the storm track and a decrease in blocking frequency over the UK and northwestern Europe. (3) The southward shift is associated with enhanced precipitation over the UK and northwestern Europe and decreased precipitation over southern Europe (contrary to the behaviour in winter). (4) There are strong ocean–atmosphere interactions related to the dominant mode of storm track variability. The atmosphere forces the ocean through anomalous surface fluxes and Ekman currents, but there is also some evidence consistent with an ocean influence on the atmosphere, and that coupled ocean–atmosphere feedbacks might play a role. The ocean influence on the atmosphere may be particularly important on decadal timescales, related to the Atlantic Multidecadal Oscillation (AMO). (letter)

  8. Flashing oscillation in pool water

    International Nuclear Information System (INIS)

    Takamasa, Tomoji; Kondo, Koichi; Hazuku, Tatsuya

    1996-01-01

    This paper presents an experimental study of high-pressure saturated water discharging into the pool water. The purpose of the experiment is to clarify the phenomena that occur in blow-down of high-pressure saturated water from the pressure vessel into the water-filled containment in the case of a wall-crack accident or a LOCA in an advanced reactor. The results revealed that a flashing oscillation (FO) occurs when high-pressure saturated water discharges into the pool water, under specified experimental settings. The range of the flashing oscillates between a point very close to and some distance from the vent hole. The pressures in the vent tube and pool water vary according to the flashing oscillation. The pressure oscillation and frequency of flashing position might be caused by the balancing action between the supply of saturated water, flashing at the control volume and its condensation on the steam-water interface. A linear analysis was conducted using a spherical flashing bubble model. The period of the flashing oscillation in the experiments can be explained by theoretical analysis

  9. Neutrino oscillations at proton accelerators

    International Nuclear Information System (INIS)

    Michael, Douglas

    2002-01-01

    Data from many different experiments have started to build a first glimpse of the phenomenology associated with neutrino oscillations. Results on atmospheric and solar neutrinos are particularly clear while a third result from LSND suggests a possibly very complex oscillation phenomenology. As impressive as the results from current experiments are, it is clear that we are just getting started on a long-term experimental program to understand neutrino masses, mixings and the physics which produce them. A number of exciting fundamental physics possibilities exist, including that neutrino oscillations could demonstrate CP or CPT violation and could be tied to exotic high-energy phenomena including strings and extra dimensions. A complete exploration of oscillation phenomena demands many experiments, including those possible using neutrino beams produced at high energy proton accelerators. Most existing neutrino experiments are statistics limited even though they use gigantic detectors. High intensity proton beams are essential for producing the intense neutrino beams which we need for next generation neutrino oscillation experiments

  10. Neutrino Oscillations at Proton Accelerators

    Science.gov (United States)

    Michael, Douglas

    2002-12-01

    Data from many different experiments have started to build a first glimpse of the phenomenology associated with neutrino oscillations. Results on atmospheric and solar neutrinos are particularly clear while a third result from LSND suggests a possibly very complex oscillation phenomenology. As impressive as the results from current experiments are, it is clear that we are just getting started on a long-term experimental program to understand neutrino masses, mixings and the physics which produce them. A number of exciting fundamental physics possibilities exist, including that neutrino oscillations could demonstrate CP or CPT violation and could be tied to exotic high-energy phenomena including strings and extra dimensions. A complete exploration of oscillation phenomena demands many experiments, including those possible using neutrino beams produced at high energy proton accelerators. Most existing neutrino experiments are statistics limited even though they use gigantic detectors. High intensity proton beams are essential for producing the intense neutrino beams which we need for next generation neutrino oscillation experiments.

  11. Investigation of switching frequency variations in self-oscillating class D amplifiers

    OpenAIRE

    Nielsen, Dennis; Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael A. E.

    2009-01-01

    Class D audio amplifiers have gained significant influence in sound reproduction due to their high efficiency. One of the most commonly used control methods in class D amplifiers is known as self-oscillation. An parameter of key interest in self-oscillating class D amplifiers is the switching frequency, which can be directly related to the performance of the amplifier. This paper will clearify the myth of the switching frequency through investigation of its dependency on modulation index and ...

  12. North Atlantic Origin of Interdecadal variability of Siberian High

    Science.gov (United States)

    Kim, Seon-Hwa; Sung, Mi-Kyung; Kim, Baek-Min

    2017-04-01

    We suggest that the changes in the mean atmospheric circulation structure in the North Atlantic Ocean upstream region of Eurasian continent play an important role in the interdecadal variability of Siberian High (SH) through the modulation of Ural blocking frequency. Previous studies suggested that the interdecadal variability of SH is partly explained by the Arctic Oscillation. However, in this study, we emphasize the role of 'Warm Arctic and Cold Eurasia (WACE)', which is the second mode of winter surface air temperature variability over Eurasia. We show that the correlation between SH and WACE is high in general compared to that between SH and AO. However, the correlation between SH and WACE does not always exhibit high constant value. It shows a distinctive interdecadal fluctuation in the correlation. We found that this fluctuation in the correlation is due to the interdecadal fluctuation of the continental trough over the North Atlantic and the resultant strengthening of in-situ atmospheric baroclinicity. This accompanies changes in the transient vorticity flux divergence which leads to the downstream wave development and anomalous anticyclonic flow near Ural region. Obviously, the existence of anticyclonic flow over Ural region helps more frequent occurrence of Ural blocking and it is shown that this condition favors positive WACE event, which links to an intensified SH.

  13. Late Holocene Radiocarbon Variability in Northwest Atlantic Slope Waters

    Energy Technology Data Exchange (ETDEWEB)

    Sherwood, O; Edinger, E; Guilderson, T P; Ghaleb, B; Risk, M J; Scott, D B

    2008-08-15

    Deep-sea gorgonian corals secrete a 2-part skeleton of calcite, derived from dissolved inorganic carbon at depth, and gorgonin, derived from recently fixed and exported particulate organic matter. Radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters, respectively. Using specimens collected from Northwest Atlantic slope waters, we generated radiocarbon records for surface and upper intermediate water layers spanning the pre- and post bomb-{sup 14}C eras. In Labrador Slope Water (LSW), convective mixing homogenizes the pre-bomb {Delta}{sup 14}C signature (-67 {+-} 4{per_thousand}) to at least 1000 m depth. Surface water bomb-{sup 14}C signals were lagged and damped (peaking at {approx} +45{per_thousand} in the early 1980s) relative to other regions of the northwest Atlantic, and intermediate water signals were damped further. Off southwest Nova Scotia, the vertical gradient in {Delta}{sup 14}C is much stronger. In surface water, pre-bomb {Delta}{sup 14}C averaged -75 {+-} 5{per_thousand}. At 250-475 m depth, prebomb {Delta}{sup 14}C oscillated quasi-decadally between -80 and -100{per_thousand}, likely reflecting interannual variability in the presence of Labrador Slope Water vs. Warm Slope Water (WSW). Finally, subfossil corals reveal no systematic changes in vertical {Delta}{sup 14}C gradients over the last 1200 years.

  14. Restoration of oscillation in network of oscillators in presence of direct and indirect interactions

    Energy Technology Data Exchange (ETDEWEB)

    Majhi, Soumen; Bera, Bidesh K. [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India); Bhowmick, Sourav K. [Department of Electronics, Asutosh College, Kolkata-700026 (India); Ghosh, Dibakar, E-mail: diba.ghosh@gmail.com [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India)

    2016-10-23

    The suppression of oscillations in coupled systems may lead to several unwanted situations, which requires a suitable treatment to overcome the suppression. In this paper, we show that the environmental coupling in the presence of direct interaction, which can suppress oscillation even in a network of identical oscillators, can be modified by introducing a feedback factor in the coupling scheme in order to restore the oscillation. We inspect how the introduction of the feedback factor helps to resurrect oscillation from various kinds of death states. We numerically verify the resurrection of oscillations for two paradigmatic limit cycle systems, namely Landau–Stuart and Van der Pol oscillators and also in generic chaotic Lorenz oscillator. We also study the effect of parameter mismatch in the process of restoring oscillation for coupled oscillators. - Highlights: • Amplitude death is observed using direct and indirect coupling. • Revival of oscillation using feedback parameter is discussed. • Restoration of oscillation is observed in limit cycle and chaotic systems.

  15. Recent intensified impact of December Arctic Oscillation on subsequent January temperature in Eurasia and North Africa

    Science.gov (United States)

    He, Shengping; Wang, Huijun; Gao, Yongqi; Li, Fei

    2018-03-01

    This study reveals an intensified influence of December Arctic Oscillation (AO) on the subsequent January surface air temperature (SAT) over Eurasia and North Africa in recent decades. The connection is statistically insignificant during 1957/58-1979/80 (P1), which becomes statistically significant during 1989/90-2011/12 (P2). The possible causes are further investigated. Associated with positive December AO during P2, significant anomalous anticyclone emerges over the central North Atlantic, which is accompanied with significant westerly and easterly anomalies along 45°-65°N and 20°-40°N, respectively. This favors the significant influence of December AO on the subsequent January SAT and atmospheric circulation over Eurasia and North Africa via triggering the North Atlantic tripole sea surface temperature (SST) anomaly that persists into the subsequent January. By contrast, the December AO-related anomalous anticyclone during P1 is weak and is characterized by two separate centers located in the eastern and western North Atlantic. Correspondingly, the westerly and easterly anomalies over the North Atlantic Ocean are weak and the-related tripole SST anomaly is not well formed, unfavorable for the persistent impact of the December AO into the subsequent January. Further analyses indicate that the different anomalous anticyclone associated with the December AO over the North Atlantic may be induced by the strengthened synoptic-scale eddy feedbacks over the North Atlantic, which may be related to the interdecadal intensification of the storm track activity. Additionally, the planetary stationary wave related to the December AO propagates from surface into upper stratosphere at mid-latitudes during P2, which further propagates downward to the troposphere and causes anomalous atmospheric circulation in the subsequent January.

  16. Reconstruction of the North Atlantic tropical cyclones in Azores for the last 800 years.

    Science.gov (United States)

    Rubio-Ingles, Maria Jesus; Sánchez, Guiomar; Trigo, Ricardo; Francus, Pierre; Gonçalves, Vitor; Raposeiro, Pedro; Freitas, Conceiçao; Borges, Paolo; Hernández, Armand; Bao, Roberto; Vázquez-Loureiro, David; Andrade, Cesar; Sáez, Alberto; Giralt, Santiago

    2014-05-01

    The variability of North Atlantic tropical storms has been the focus of several studies. Duration and seasonality has been attributed to a number of climate patterns and processes such as El Niño-Southern Oscillation, Atlantic Meridional Mode, African easterly waves, and atmospheric Rossby waves, but their tracks have been widely related to the North Atlantic Oscillation. Several authors have pointed out an increase and track shifting of North Atlantic tropical cyclones since 1995 with increased probability of these turning north far away from the North American continent. However, this cannot be regarded as an infrequent phenomenon as most proxy records from the Atlantic North have shown the existence of similar patterns in the past. Sao Miguel Island (Azores archipelago, Portugal) is settled in the middle of the Atlantic Ocean. This location makes this island an excellent natural laboratory to record shifts on North Atlantic tropical storms tracks that can reach the archipelago as low intensity hurricanes (e.g. Nadine in 2012) or downgraded to tropical storm (e.g. Grace in 2009). In the present work, lake sediment records have been used as a proxy sensor of tropical storms. Lagoa Azul is located inside Sete Cidades volcanic caldera and its catchment is characterized by stepped and forested caldera walls. Tropical storms and heavy rainfalls produce a flashy and substantial enhancement in the erosion of the catchment, increasing the sediments reaching the lake by rockfalls deposits (in littoral zones) and flood events deposits (in offshore zones). These flood events can be recognized in the sedimentary record as lobe deposits dominated by terrestrial components. It can be found in the sedimentary record and the bathymetry. Instrumental meteorological data and historical records have been compiled to reconstruct the most recent history of the North Atlantic tropical storms that have landed or affected the Sao Miguel Island (Andrade et al., 2008). In addition, a 1

  17. Nonstationary oscillations in gyrotrons revisited

    International Nuclear Information System (INIS)

    Dumbrajs, O.; Kalis, H.

    2015-01-01

    Development of gyrotrons requires careful understanding of different regimes of gyrotron oscillations. It is known that in the planes of the generalized gyrotron variables: cyclotron resonance mismatch and dimensionless current or cyclotron resonance mismatch and dimensionless interaction length complicated alternating sequences of regions of stationary, periodic, automodulation, and chaotic oscillations exist. In the past, these regions were investigated on the supposition that the transit time of electrons through the interaction space is much shorter than the cavity decay time. This assumption is valid for short and/or high diffraction quality resonators. However, in the case of long and/or low diffraction quality resonators, which are often utilized, this assumption is no longer valid. In such a case, a different mathematical formalism has to be used for studying nonstationary oscillations. One example of such a formalism is described in the present paper

  18. Prediction of pilot induced oscillations

    Directory of Open Access Journals (Sweden)

    Valentin PANĂ

    2011-03-01

    Full Text Available An important problem in the design of flight-control systems for aircraft under pilotedcontrol is the determination of handling qualities and pilot-induced oscillations (PIO tendencieswhen significant nonlinearities exist in the vehicle description. The paper presents a method to detectpossible pilot-induced oscillations of Category II (with rate and position limiting, a phenomenonusually due to a misadaptation between the pilot and the aircraft response during some tasks in whichtight closed loop control of the aircraft is required from the pilot. For the analysis of Pilot in the LoopOscillations an approach, based on robust stability analysis of a system subject to uncertainparameters, is proposed. In this analysis the nonlinear elements are substituted by linear uncertainparameters. This approach assumes that PIO are characterized by a limit cycle behavior.

  19. Magnetically insulated transmission line oscillator

    Science.gov (United States)

    Bacon, L.D.; Ballard, W.P.; Clark, M.C.; Marder, B.M.

    1987-05-19

    A magnetically insulated transmission line oscillator employs self-generated magnetic fields to generate microwave energy. An anode of the oscillator includes slow-wave structures which are formed of a plurality of thin conductive vanes defining cavities therebetween, and a gap is formed between the anode and a cathode of the oscillator. In response to a pulsed voltage applied to the anode and cathode, self-generated magnetic fields are produced in a cross-field orientation with respect to the orientation of the electric field between the anode and the cathode. The cross-field magnetic fields insulate the flow of electrons in the gap and confine the flow of electrons within the gap. 11 figs.

  20. The impact of the subtropical South Atlantic SST on South American precipitation

    Directory of Open Access Journals (Sweden)

    A. S. Taschetto

    2008-11-01

    Full Text Available The Community Climate Model (CCM3 from the National Center for Atmospheric Research (NCAR is used to investigate the effect of the South Atlantic sea surface temperature (SST anomalies on interannual to decadal variability of South American precipitation. Two ensembles composed of multidecadal simulations forced with monthly SST data from the Hadley Centre for the period 1949 to 2001 are analysed.

    A statistical treatment based on signal-to-noise ratio and Empirical Orthogonal Functions (EOF is applied to the ensembles in order to reduce the internal variability among the integrations. The ensemble treatment shows a spatial and temporal dependence of reproducibility. High degree of reproducibility is found in the tropics while the extratropics is apparently less reproducible. Austral autumn (MAM and spring (SON precipitation appears to be more reproducible over the South America-South Atlantic region than the summer (DJF and winter (JJA rainfall. While the Inter-tropical Convergence Zone (ITCZ region is dominated by external variance, the South Atlantic Convergence Zone (SACZ over South America is predominantly determined by internal variance, which makes it a difficult phenomenon to predict. Alternatively, the SACZ over western South Atlantic appears to be more sensitive to the subtropical SST anomalies than over the continent.

    An attempt is made to separate the atmospheric response forced by the South Atlantic SST anomalies from that associated with the El Niño – Southern Oscillation (ENSO. Results show that both the South Atlantic and Pacific SSTs modulate the intensity and position of the SACZ during DJF. Particularly, the subtropical South Atlantic SSTs are more important than ENSO in determining the position of the SACZ over the southeast Brazilian coast during DJF. On the other hand, the ENSO signal seems to influence the intensity of the SACZ not only in DJF but especially its oceanic branch during MAM. Both local and

  1. Rotational atmospheric circulation during North Atlantic-European winter: the influence of ENSO

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Serrano, J. [UCM, Departamento de Geofisica y Meteorologia, Madrid (Spain); Institut Catala de Ciencies del Clima (IC3), Barcelona (Spain); Rodriguez-Fonseca, B.; Zurita-Gotor, P.; Camara, A. de la [UCM, Departamento de Geofisica y Meteorologia, Madrid (Spain); Blade, I. [UB, Departament d' Astronomia i Meteorologia, Barcelona (Spain)

    2011-11-15

    The dominant variability modes of the North Atlantic-European rotational flow are examined by applying a principal component analysis (PCA/EOF) to the 200 hPa streamfunction mid-winter anomalies (Jan-Feb monthly means). The results reveal that, when this norm is used, the leading mode (EOF1) does not correspond to the traditional North Atlantic Oscillation (NAO, which appears in our analysis as the second leading mode, EOF2) but is the local manifestation of the leading hemispheric streamfunction EOF. The regression of this regional mode onto the global SST field exhibits a clear El Nino signature, with no signal over the Atlantic, while the associated upper height anomalies resemble the Tropical/Northern Hemisphere (TNH) pattern. East of North America, this TNH-like wavetrain produces a meridional dipole-like pattern at lower levels. Although in some ways this pattern resembles the NAO (EOF2), the dynamics of these two modes are very different in that only EOF2 is associated with a latitudinal shift of the North Atlantic stormtrack. Thus, the choice of the streamfunction norm in the EOF analysis allows the separation of two different phenomena that can produce similar dipolar surface pressure anomalies over the North Atlantic but that have different impact on European climate. These two modes also differ on their contribution to variability at lower levels: while NAO-EOF2 is mostly confined to the North Atlantic, TNH-EOF1 has a more annular, global character. At upper levels NAO-EOF2 also produces a global pattern but with no annular structure, reminiscent of the ''circumglobal'' teleconnection. (orig.)

  2. The impact of North Atlantic wind and cyclone trends on European precipitation and significant wave height in the Atlantic.

    Science.gov (United States)

    Trigo, Ricardo M; Valente, Maria A; Trigo, Isabel F; Miranda, Pedro M A; Ramos, Alexandre M; Paredes, Daniel; García-Herrera, Ricardo

    2008-12-01

    An analysis of the frequency of cyclones and surface wind velocity for the Euro-Atlantic sector is performed by means of an objective methodology. Monthly and seasonal trends of cyclones and wind speed magnitude are computed and trends between 1960 and 2000 evaluated. Results reveal a significant frequency decrease (increase) in the western Mediterranean (Greenland and Scandinavia), particularly in December, February, and March. Seasonal and monthly analysis of wind magnitude trends shows similar spatial patterns. We show that these changes in the frequency of low-pressure centers and the associated wind patterns are partially responsible for trends in the significant height of waves. Throughout the extended winter months (October-March), regions with positive (negative) wind magnitude trends, of up to 5 cm/s/year, often correspond to regions of positive (negative) significant wave height trends. The cyclone and wind speed trends computed for January-March are well matched by the corresponding trends in significant wave height, with February being the month with the highest trends (negative south of lat 50 degrees N up to -3 cm/year, and positive up to 5 cm/year just north of Scotland). Trends in European precipitation are assessed using the Climatic Research Unit data set. The results of the assessment emphasize the link with the corresponding tendencies of cyclone frequencies. Finally, it is shown that these changes are associated, to a large extent, with the preferred phases of major large-scale atmospheric circulation modes, particularly with the North Atlantic Oscillation, the eastern Atlantic pattern, and the Scandinavian pattern.

  3. Simulated variability of the Atlantic meridional overturning circulation

    Science.gov (United States)

    Bentsen, M.; Drange, H.; Furevik, T.; Zhou, T.

    yields a NAO-like pattern with intensified Icelandic low and Azores high, and a warming of 0.25-0.5 °C of the central North Atlantic sea-surface temperature (SST). The reanalysis forced simulations indicate a coupling between the Labrador Sea Water production rate and an equatorial Atlantic SST index in accordance with observations. This coupling is not identified in the coupled simulation.

  4. 75 FR 33531 - Atlantic Highly Migratory Species; Atlantic Bluefin Tuna Fisheries

    Science.gov (United States)

    2010-06-14

    ... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 635 RIN 0648-XW79 Atlantic Highly Migratory Species; Atlantic Bluefin Tuna Fisheries AGENCY: National Marine..., recent Large Pelagics Survey estimates indicate that charter/headboat BFT landings constitute...

  5. Spontaneous oscillations in microfluidic networks

    Science.gov (United States)

    Case, Daniel; Angilella, Jean-Regis; Motter, Adilson

    2017-11-01

    Precisely controlling flows within microfluidic systems is often difficult which typically results in systems being heavily reliant on numerous external pumps and computers. Here, I present a simple microfluidic network that exhibits flow rate switching, bistablity, and spontaneous oscillations controlled by a single pressure. That is, by solely changing the driving pressure, it is possible to switch between an oscillating and steady flow state. Such functionality does not rely on external hardware and may even serve as an on-chip memory or timing mechanism. I use an analytic model and rigorous fluid dynamics simulations to show these results.

  6. Oscillating liquid flow ICF Reactor

    International Nuclear Information System (INIS)

    Petzoldt, R.W.

    1990-01-01

    Oscillating liquid flow in a falling molten salt inertial confinement fusion reactor is predicted to rapidly clear driver beam paths of residual liquid droplets. Oscillating flow will also provide adequate neutron and x-ray protection for the reactor structure with a short (2-m) fall distance permitting an 8 Hz repetition rate. A reactor chamber configuration is presented with specific features to clear the entire heavy-ion beam path of splashed molten salt. The structural components, including the structure between beam ports, are shielded. 3 refs., 12 figs

  7. Neutrino oscillation measurements with reactors

    Energy Technology Data Exchange (ETDEWEB)

    McKeown, R.D. [W. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States)

    2010-11-01

    Since the first direct observations of antineutrino events by Reines and Cowan in the 1950's, nuclear reactors have been an important tool in the study of neutrino properties. More recently, the study of neutrino oscillations has been a very active area of research. The pioneering observation of oscillations by the KamLAND experiment has provided important information on the neutrino masses and the neutrino mixing matrix. New experiments to study the remaining unknown mixing angle are currently under development. These recent studies and potential future developments will be discussed.

  8. ALG-2 oscillates in subcellular localization, unitemporally with calcium oscillations

    DEFF Research Database (Denmark)

    la Cour, Jonas Marstrand; Mollerup, Jens; Berchtold, Martin Werner

    2007-01-01

    discovered that the subcellular distribution of a tagged version of ALG-2 could be directed by physiological external stimuli (including ATP, EGF, prostaglandin, histamine), which provoke intracellular Ca2+ oscillations. Cellular stimulation led to a redistribution of ALG-2 from the cytosol to a punctate...

  9. Phytoplankton bloom and subpolar gyre induced dynamics in the North Atlantic

    DEFF Research Database (Denmark)

    Ferreira, Ana Sofia; Hátún, H.; Counillon, F.

    Several hypotheses have been promoted for phytoplankton bloom onset in the North Atlantic. First we show that the bloom dynamics in the northeastern corner stand out from the rest of the subpolar Atlantic, and thus warrants focused attention. We hypothesized that, for this region, late and weak...... blooms are expected in years of a strong subpolar gyre, i.e. strong atmospheric forcing, and cold and low saline conditions. We apply novel phenology algorithms to satellite ocean colour data, and analyse the outcome together with the subpolar gyre index. We find that the relationship between the bloom...

  10. TOWARDS THRESHOLD FREQUENCY IN CHAOTIC COLPITTS OSCILLATOR

    DEFF Research Database (Denmark)

    Lindberg, Erik; Tamasevicius, Arunas; Mykolaitis, Gytis

    2007-01-01

    A novel version of chaotic Colpitts oscillator is described. Instead of a linear loss resistor, it includes an extra inductor and diode in the collector circuit of the transistor. The modified circuit in comparison with the common Colpitts oscillator may generate chaotic oscillations at the funda......A novel version of chaotic Colpitts oscillator is described. Instead of a linear loss resistor, it includes an extra inductor and diode in the collector circuit of the transistor. The modified circuit in comparison with the common Colpitts oscillator may generate chaotic oscillations...

  11. The influence of climate modes on streamflow in the Mid-Atlantic region of the United States

    Directory of Open Access Journals (Sweden)

    Justin A. Schulte

    2016-03-01

    Full Text Available Study region: The Mid-Atlantic region of the United States. Study focus: An understanding of past streamflow variability is necessary for developing future management practices that will help mitigate the impacts of extreme events such as drought or floods on agriculture and other human activities. To better understand mechanisms driving streamflow variability at all timescales, annual to multi-decadal streamflow variability of three major rivers in the Mid-Atlantic region of the United States (the Susquehanna, Delaware, and Hudson Rivers was studied in the context of climate modes using correlation and wavelet analyses. New hydrological insights for the region: Results from the correlation analysis detected statistically significant relationships between climate indices and streamflow that were similar for the three rivers. The results from the wavelet analysis showed that 18- and 26-year periodicities were embedded in the streamflow time series. Decadal variability of streamflow was coherent with the El-Niño Southern Oscillation (SO and the Pacific Decadal Oscillation (PDO. The time series for the PDO and SO indices and precipitation were found to be synchronized to the decadal variability of a global circulation pattern consisting of a Rossby wave train emanating from the North Pacific. The SO explained 37–54% of the 1960s drought, 33–49% of the 1970s pluvial, and 19–50% of the 2000s pluvial in the three river basins. Keywords: Streamflow, Climate, Climate variability, Wavelet analysis, El-Niño-Southern Oscillation, Mid-Atlantic region

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

    Energy Technology Data Exchange (ETDEWEB)

    Medhaug, I.; Eldevik, T.; Furevik, T. [University of Bergen, Geophysical Institute, Bergen (Norway); Bjerknes Centre for Climate Research, Bergen (Norway); Langehaug, H.R. [Nansen Environmental and Remote Sensing Center, Bergen (Norway); Bjerknes Centre for Climate Research, Bergen (Norway); Bentsen, M. [Uni Bjerknes Centre, Uni Research, Bergen (Norway); Bjerknes Centre for Climate Research, Bergen (Norway)

    2012-07-15

    Variability in the Atlantic Meridional Overturning Circulation (AMOC) has been analysed using a 600-year pre-industrial control simulation with the Bergen Climate Model. The typical AMOC variability has amplitudes of 1 Sverdrup (1 Sv = 10{sup 6} m{sup 3} s{sup -1}) and time scales of 40-70 years. The model is reproducing the observed dense water formation regions and has very realistic ocean transports and water mass distributions. The dense water produced in the Labrador Sea (1/3) and in the Nordic Seas, including the water entrained into the dense overflows across the Greenland-Scotland Ridge (GSR; 2/3), are the sources of North Atlantic Deep Water (NADW) forming the lower limb of the AMOC's northern overturning. The variability in the Labrador Sea and the Nordic Seas convection is driven by decadal scale air-sea fluxes in the convective region that can be related to opposite phases of the North Atlantic Oscillation. The Labrador Sea convection is directly linked to the variability in AMOC. Linkages between convection and water mass transformation in the Nordic Seas are more indirect. The Scandinavian Pattern, the third mode of atmospheric variability in the North Atlantic, is a driver of the ocean's poleward heat transport (PHT), the overall constraint on northern water mass transformation. Increased PHT is both associated with an increased water mass exchange across the GSR, and a stronger AMOC. (orig.)

  13. Convective Lofting Links Indian Ocean Air Pollution to Recurrent South Atlantic Ozone Maxima

    Science.gov (United States)

    Chatfield, R. B.; Guan, H.; Thompson, A. M.; Witte, J.

    2003-12-01

    We extend on our analysis of equatorial tropospheric ozone to illustrate the contributions of South Asian pollution export in forming episodes of high O3 over the Atlantic Ocean. We amplify on an earlier description of a broad resolution of the "Atlantic Paradox," for the Jan-Feb-March period, which included initial indications of a very long-distance contribution from South Asia. The approach has been to describe typical periods of significant maximum and minimum tropospheric ozone for early 1999, exploiting TOMS tropospheric ozone estimates jointly with characteristic features of the SHADOZ (Southern Hemisphere Additional Ozonesondes) ozone soundings. Further investigation of the Total Tropospheric Ozone (TTO) record for all of 1999 suggests that there are repeated periods of very long-distance Asian influence crossing Africa, with an apparent effect on those portions of the Atlantic Equatorial troposphere which are downwind. Trajectory analyses suggest that the pattern over the Indian Ocean is complex: a sequence invoving multiple or mixed combustion sources, low level transport, cumulonimbus venting, and high-level transport to the west seem to be indicated by the TTO record. Biomass burning, fossil and biofuel combustion, and lighting seem to all contribute. For the Atlantic, burning and lighting on adjacent continents as well as episodes of this cross-Africa long-distance transport are all linked in a coordinated seasonal march: all are related by movement of the sun. However, interseasonal tropical variability related to the Madden-Julian oscillation allows intermittent ozone buildups that depart from the seasonal norm.

  14. 77 FR 25144 - Fisheries of the South Atlantic; South Atlantic Fishery Management Council; Public Meetings

    Science.gov (United States)

    2012-04-27

    .... The Council will consider input from the workgroup and workshops during its June meeting in Orlando... Atlantic; South Atlantic Fishery Management Council; Public Meetings AGENCY: National Marine Fisheries... public meeting and public workshop. SUMMARY: The South Atlantic Fishery Management Council (Council) will...

  15. 78 FR 52487 - Atlantic Highly Migratory Species; 2014 Atlantic Shark Commercial Fishing Season

    Science.gov (United States)

    2013-08-23

    .... 130402317-3707-01] RIN 0648-XC611 Atlantic Highly Migratory Species; 2014 Atlantic Shark Commercial Fishing... establish opening dates and adjust quotas for the 2014 fishing season for the Atlantic commercial shark... management measures to provide, to the extent practicable, fishing opportunities for commercial shark...

  16. 75 FR 44938 - Atlantic Coastal Fisheries Cooperative Management Act Provisions; Atlantic Coastal Shark Fishery

    Science.gov (United States)

    2010-07-30

    ... Coastal Fisheries Cooperative Management Act Provisions; Atlantic Coastal Shark Fishery AGENCY: National... moratorium on fishing for Atlantic coastal sharks in the State waters of New Jersey. NMFS canceled the... Fisheries Commission's (Commission) Interstate Fishery Management Plan for Atlantic Coastal Sharks (Coastal...

  17. 75 FR 57235 - Atlantic Highly Migratory Species; Atlantic Shark Management Measures

    Science.gov (United States)

    2010-09-20

    .... 100825390-0431-01] RIN 0648-BA17 Atlantic Highly Migratory Species; Atlantic Shark Management Measures... on potential adjustments to the regulations governing the U.S. Atlantic shark fishery to address several specific issues currently affecting management of the shark fishery and to identify specific goals...

  18. 75 FR 54597 - Fisheries of the South Atlantic; Southeast Data, Assessment, and Review (SEDAR); South Atlantic...

    Science.gov (United States)

    2010-09-08

    ... Atlantic, and Caribbean Fishery Management Councils, in conjunction with NOAA Fisheries and the Atlantic... are appointed by the Gulf of Mexico, South Atlantic, and Caribbean Fishery Management Councils; the..., environmentalists, and NGO's; International experts; and staff of Councils, Commissions, and state and federal...

  19. 78 FR 65974 - Atlantic Highly Migratory Species; Advisory Panel for Atlantic Highly Migratory Species Southeast...

    Science.gov (United States)

    2013-11-04

    ... Management Councils, the 18 states in the Atlantic and Gulf of Mexico, both the U.S. Virgin Islands and... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration RIN 0648-XC935 Atlantic Highly Migratory Species; Advisory Panel for Atlantic Highly Migratory Species Southeast Data, Assessment...

  20. 76 FR 65700 - Atlantic Highly Migratory Species; Advisory Panel for Atlantic Highly Migratory Species Southeast...

    Science.gov (United States)

    2011-10-24

    .... Virgin Islands and Puerto Rico, and each of the constituent interstate commissions: the Atlantic States... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration RIN 0648-XA776 Atlantic Highly Migratory Species; Advisory Panel for Atlantic Highly Migratory Species Southeast Data, Assessment...

  1. 78 FR 26523 - Fisheries of the Northeastern United States; Atlantic Bluefish Fishery; 2013 and 2014 Atlantic...

    Science.gov (United States)

    2013-05-07

    .... 130104009-3416-02] RIN 0648-XC432 Fisheries of the Northeastern United States; Atlantic Bluefish Fishery; 2013 and 2014 Atlantic Bluefish Specifications AGENCY: National Marine Fisheries Service (NMFS... final specifications for the 2013 and 2014 Atlantic bluefish fishery, including annual catch limits...

  2. 77 FR 25100 - Fisheries of the Northeastern United States; Atlantic Bluefish Fishery; 2012 Atlantic Bluefish...

    Science.gov (United States)

    2012-04-27

    .... 120201086-2418-02] RIN 0648-XA904 Fisheries of the Northeastern United States; Atlantic Bluefish Fishery; 2012 Atlantic Bluefish Specifications AGENCY: National Marine Fisheries Service (NMFS), National... specifications for the 2012 Atlantic bluefish fishery, including an annual catch limit, total allowable landings...

  3. 77 FR 8776 - Fisheries of the Northeastern United States; Atlantic Bluefish Fishery; 2012 Atlantic Bluefish...

    Science.gov (United States)

    2012-02-15

    .... 120201086-2085-01] RIN 0648-XA904 Fisheries of the Northeastern United States; Atlantic Bluefish Fishery; 2012 Atlantic Bluefish Specifications AGENCY: National Marine Fisheries Service (NMFS), National... comments. SUMMARY: NMFS proposes specifications for the 2012 Atlantic bluefish fishery, including an annual...

  4. 78 FR 11809 - Fisheries of the Northeastern United States; Atlantic Bluefish Fishery; 2013-2014 Atlantic...

    Science.gov (United States)

    2013-02-20

    .... 130104009-3099-01] RIN 0648-XC432 Fisheries of the Northeastern United States; Atlantic Bluefish Fishery; 2013-2014 Atlantic Bluefish Specifications AGENCY: National Marine Fisheries Service (NMFS), National... comments. SUMMARY: NMFS proposes specifications for the 2013 and 2014 Atlantic bluefish fishery, including...

  5. 76 FR 14378 - Fisheries of the South Atlantic; South Atlantic Fishery Management Council; Public Meeting

    Science.gov (United States)

    2011-03-16

    ... the South Atlantic; South Atlantic Fishery Management Council; Public Meeting AGENCY: National Marine... the Coastal Migratory Pelagics Fishery Management Plan (FMP) for the South Atlantic and Gulf of Mexico... AP will also review Amendment 19 to the Coastal Migratory Pelagics FMP regarding alternatives for bag...

  6. The Teleconnection of the Tropical Atlantic to Indo-Pacific Sea Surface Temperatures on Inter-Annual to Centennial Time Scales: A Review of Recent Findings

    Directory of Open Access Journals (Sweden)

    Fred Kucharski

    2016-02-01

    Full Text Available In this paper, the teleconnections from the tropical Atlantic to the Indo-Pacific region from inter-annual to centennial time scales will be reviewed. Identified teleconnections and hypotheses on mechanisms at work are reviewed and further explored in a century-long pacemaker coupled ocean-atmosphere simulation ensemble. There is a substantial impact of the tropical Atlantic on the Pacific region at inter-annual time scales. An Atlantic Niño (Niña event leads to rising (sinking motion in the Atlantic region, which is compensated by sinking (rising motion in the central-western Pacific. The sinking (rising motion in the central-western Pacific induces easterly (westerly surface wind anomalies just to the west, which alter the thermocline. These perturbations propagate eastward as upwelling (downwelling Kelvin-waves, where they increase the probability for a La Niña (El Niño event. Moreover, tropical North Atlantic sea surface temperature anomalies are also able to lead La Niña/El Niño development. At multidecadal time scales, a positive (negative Atlantic Multidecadal Oscillation leads to a cooling (warming of the eastern Pacific and a warming (cooling of the western Pacific and Indian Ocean regions. The physical mechanism for this impact is similar to that at inter-annual time scales. At centennial time scales, the Atlantic warming induces a substantial reduction of the eastern Pacific warming even under CO2 increase and to a strong subsurface cooling.

  7. Neutrino masses and neutrino oscillations

    CERN Document Server

    Di Lella, L

    2000-01-01

    These lectures review direct measurements of neutrino masses and the status of neutrino oscillation searches using both natural neutrino sources (the Sun and cosmic rays interacting in the Earth atmosphere) and artificial neutrinos (produced by nuclear reactors and accelerators). Finally, future experiments and plans are presented. (68 refs).

  8. Harmonic oscillator in Snyder space

    Indian Academy of Sciences (India)

    The harmonic oscillator in Snyder space is investigated in its classical and quantum versions. The classical trajectory is obtained and the semiclassical quantization from the phase space trajectories is discussed. An effective cut-off to high frequencies is found. The quantum version is developed and an equivalent usual ...

  9. Compressible flow in fluidic oscillators

    Science.gov (United States)

    Graff, Emilio; Hirsch, Damian; Gharib, Mory

    2013-11-01

    We present qualitative observations on the internal flow characteristics of fluidic oscillator geometries commonly referred to as sweeping jets in active flow control applications. We also discuss the effect of the geometry on the output jet in conditions from startup to supersonic exit velocity. Supported by the Boeing Company.

  10. Ellipsoidal basis for isotropic oscillator

    International Nuclear Information System (INIS)

    Kallies, W.; Lukac, I.; Pogosyan, G.S.; Sisakyan, A.N.

    1994-01-01

    The solutions of the Schroedinger equation are derived for the isotropic oscillator potential in the ellipsoidal coordinate system. The explicit expression is obtained for the ellipsoidal integrals of motion through the components of the orbital moment and Demkov's tensor. The explicit form of the ellipsoidal basis is given for the lowest quantum numbers. 10 refs.; 1 tab. (author)

  11. The relativistic harmonic oscillator reconsidered

    International Nuclear Information System (INIS)

    Hofsaess, T.

    1978-01-01

    The bound states of scalar quarks interacting through a scalar harmonic oscillator are investigated. In the presence of this interaction the dressed quark propagator differs substantially from the free one. This leads to a Bethe Salpeter equation which does not allow for any stable bound states of positive mass. (orig.) [de

  12. Inverse problem of solar oscillations

    International Nuclear Information System (INIS)

    Sekii, T.; Shibahashi, H.

    1987-01-01

    The authors present some preliminary results of numerical simulation to infer the sound velocity distribution in the solar interior from the oscillation data of the Sun as the inverse problem. They analyze the acoustic potential itself by taking account of some factors other than the sound velocity, and infer the sound velocity distribution in the deep interior of the Sun

  13. Sum rules for neutrino oscillations

    International Nuclear Information System (INIS)

    Kobzarev, I.Yu.; Martemyanov, B.V.; Okun, L.B.; Schepkin, M.G.

    1981-01-01

    Sum rules for neutrino oscillations are obtained. The derivation of the general form of the s matrix for two stage process lsub(i)sup(-)→ν→lsub(k)sup(+-) (where lsub(i)sup(-)e, μ, tau, ... are initial leptons with flavor i and lsub(k)sup(+-) is final lepton) is presented. The consideration of two stage process lsub(i)sup(-)→ν→lsub(k)sup(+-) gives the possibility to take into account neutrino masses and to obtain the expressions for the oscillating cross sections. In the case of Dirac and left-handed Majorana neutrino is obtained the sum rule for the quantities 1/Vsub(K)σ(lsub(i)sup(-)→lsub(K)sup(+-)), (where Vsub(K) is a velocity of lsub(K)). In the left-handed Majorana neutrino case there is an additional antineutrino admixture leading to lsub(i)sup(-)→lsub(K)sup(+) process. Both components (neutrino and antineutrino) oscillate independently. The sums Σsub(K)1/Vsub(k)σ(lsub(i)sup(-) - lsub(K)sup(+-) then oscillate due to the presence of left-handed antineutrinos and right-handed neutrinos which do not take part in weak interactions. If right-handed currents are added sum rules analogous to considered above may be obtained. All conclusions are valid in the general case when CP is not conserved [ru

  14. Oscillating solitons in nonlinear optics

    Indian Academy of Sciences (India)

    The study of solitons in those physical systems reveals some exciting .... With the following power series expansions for g(z,t) and f(z,t): g(z,t) = εg1(z,t) + ... If nonlinearity γ (z) is also taken as a function in figure 1b, the periodic and oscillation.

  15. Low-Vibration Oscillating Compressor

    Science.gov (United States)

    Studer, P. A.

    1984-01-01

    Oscillating compressor momentum compensated: produces little vibration in its supporting structure. Compressure requires no lubrication and virtually free of wear. Compresses working fluids such as helium, nitrogen or chlorfluorocarbons for Stirling-cycle refrigeration or other purposes. Compressor includes two mutually opposed ferromagnetic pistons of same shape and mass. Electromagnetic flux links both pistons, causing magnetic attraction between them.

  16. Matter effects in neutrino oscillations

    International Nuclear Information System (INIS)

    Dass, G.V.

    1989-01-01

    After a review of the relevant aspects of neutrino oscillations for propagation in vacuum and in material media, this paper discuss the Mikheyev-Smirnov-Wolfenstein mechanism and its application to a solution of the solar neutrino puzzle. The elementary level of the talk is suitable to people not working in neutrino physics

  17. Mesino oscillation in MFV SUSY

    Energy Technology Data Exchange (ETDEWEB)

    Berger, Joshua [Cornell University, Department of Physics, LEPP, Ithaca, NY (United States); SLAC National Accelerator Laboratory, Menlo Park, CA (United States); Csaki, Csaba; Grossman, Yuval; Heidenreich, Ben [Cornell University, Department of Physics, LEPP, Ithaca, NY (United States)

    2013-04-15

    R-parity violating supersymmetry in a Minimal Flavor Violation paradigm can produce same-sign dilepton signals via direct sbottom-LSP pair production. Such signals arise when the sbottom hadronizes and the resulting mesino oscillates into an antimesino. The first bounds on the sbottom mass are placed in this scenario using current LHC results. (orig.)

  18. Chimera States in Neural Oscillators

    Science.gov (United States)

    Bahar, Sonya; Glaze, Tera

    2014-03-01

    Chimera states have recently been explored both theoretically and experimentally, in various coupled nonlinear oscillators, ranging from phase-oscillator models to coupled chemical reactions. In a chimera state, both coherent and incoherent (or synchronized and desynchronized) states occur simultaneously in populations of identical oscillators. We investigate chimera behavior in a population of neural oscillators using the Huber-Braun model, a Hodgkin-Huxley-like model originally developed to characterize the temperature-dependent bursting behavior of mammalian cold receptors. One population of neurons is allowed to synchronize, with each neuron receiving input from all the others in its group (global within-group coupling). Subsequently, a second population of identical neurons is placed under an identical global within-group coupling, and the two populations are also coupled to each other (between-group coupling). For certain values of the coupling constants, the neurons in the two populations exhibit radically different synchronization behavior. We will discuss the range of chimera activity in the model, and discuss its implications for actual neural activity, such as unihemispheric sleep.

  19. Multidecadal increase in North Atlantic coccolithophores and the potential role of rising CO₂.

    Science.gov (United States)

    Rivero-Calle, Sara; Gnanadesikan, Anand; Del Castillo, Carlos E; Balch, William M; Guikema, Seth D

    2015-12-18

    As anthropogenic carbon dioxide (CO2) emissions acidify the oceans, calcifiers generally are expected to be negatively affected. However, using data from the Continuous Plankton Recorder, we show that coccolithophore occurrence in the North Atlantic increased from ~2 to more than 20% from 1965 through 2010. We used random forest models to examine more than 20 possible environmental drivers of this change, finding that CO2 and the Atlantic Multidecadal Oscillation were the best predictors, leading us to hypothesize that higher CO2 levels might be encouraging growth. A compilation of 41 independent laboratory studies supports our hypothesis. Our study shows a long-term basin-scale increase in coccolithophores and suggests that increasing CO2 and temperature have accelerated the growth of a phytoplankton group that is important for carbon cycling. Copyright © 2015, American Association for the Advancement of Science.

  20. Multidecadal Increase in North Atlantic Coccolithophores and Potential Role of Increasing CO2

    Science.gov (United States)

    Rivero-Calle, S.; Gnanadesikan, A.; del Castillo, C. E.; Balch, W. M.; Guikema, S.

    2016-02-01

    As anthropogenic CO2 emissions acidify the oceans, calcifiers are expected to be negatively impacted. Using data from the Continuous Plankton Recorder, we show that coccolithophore occurrence in the North Atlantic has increased from 2 to over 20% from 1965 through 2010. We used Random Forest models to examine more than 20 possible environmental drivers of this change. CO2 and the Atlantic Multidecadal Oscillation were the best predictors. Since coccolithophore photosynthesis is strongly carbon-limited, we hypothesize that higher CO2 levels might be encouraging growth. A compilation of 41 independent laboratory studies supports our hypothesis. Our study shows a long-term basin-scale increase in coccolithophores and suggests that increasing pCO2 and temperature accelerated the growth rate of a key phytoplankton group for carbon cycling.

  1. Multidecadal increase in North Atlantic coccolithophores and the potential role of rising CO2

    Science.gov (United States)

    Rivero-Calle, Sara; Gnanadesikan, Anand; Del Castillo, Carlos E.; Balch, William M.; Guikema, Seth D.

    2015-12-01

    As anthropogenic carbon dioxide (CO2) emissions acidify the oceans, calcifiers generally are expected to be negatively affected. However, using data from the Continuous Plankton Recorder, we show that coccolithophore occurrence in the North Atlantic increased from ~2 to more than 20% from 1965 through 2010. We used random forest models to examine more than 20 possible environmental drivers of this change, finding that CO2 and the Atlantic Multidecadal Oscillation were the best predictors, leading us to hypothesize that higher CO2 levels might be encouraging growth. A compilation of 41 independent laboratory studies supports our hypothesis. Our study shows a long-term basin-scale increase in coccolithophores and suggests that increasing CO2 and temperature have accelerated the growth of a phytoplankton group that is important for carbon cycling.

  2. Scales of North Atlantic wind stress curl determined from the comprehensive ocean-atmosphere data set

    Science.gov (United States)

    Ehret, Laura L.; O'Brien, James J.

    1989-01-01

    Nineteen years of wind data over the North Atlantic are used to calculate a field of wind stress curl. An empirical orthogonal function (EOF) analysis is performed on this field, resulting in spatial patterns of wind stress curl and associated time series. A Monte Carlo technique is used to establish the statistical significance of each spatial pattern, and the associated time series are spectrally analyzed. The first four statistically significant EOF modes represent more than 50 percent of the curl variance, and the spatial patterns of curl associated with these modes exhibit the major elements of North Atlantic climatology. Most of the time series spectral variance is contained in annual and semiannual frequencies. The features observed include the individual annual variation of the subtropical high and the subpolar low, the annual oscillation of intensity between pressure centers, the influence of localized strong SST gradients and associated cyclogenesis regions, and the constant nature of the trades.

  3. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    Science.gov (United States)

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. Copyright © 2016, American Association for the Advancement of Science.

  4. Generalized oscillator systems and their parabosonic interpretation

    Energy Technology Data Exchange (ETDEWEB)

    Macfarlane, A J [Cambridge Univ. (United Kingdom). Dept. of Applied Mathematics and Theoretical Physics

    1994-12-31

    The Fock space description of various bosonic oscillator systems are carried out. All descriptions are based on a single creation - annihilation pair. Special attention is paid to the q-deformed Calogero-Vasiliev oscillator. 23 refs.

  5. Analytic Neutrino Oscillation Probabilities in Matter: Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Parke, Stephen J. [Fermilab; Denton, Peter B. [Copenhagen U.; Minakata, Hisakazu [Madrid, IFT

    2018-01-02

    We summarize our recent paper on neutrino oscillation probabilities in matter, explaining the importance, relevance and need for simple, highly accurate approximations to the neutrino oscillation probabilities in matter.

  6. Characterizing brain oscillations in cognition and disease

    NARCIS (Netherlands)

    Jiang, H.

    2016-01-01

    It has been suggested that neuronal oscillations play a fundamental role for shaping the functional architecture of the working brain. This thesis investigates brain oscillations in rat, human healthy population and major depressive disorder (MDD) patients. A novel measurement termed

  7. The Caspian Sea Catchment influenced by Atlantic Teleconnections in CESM1.2.2 and Observations

    Science.gov (United States)

    Nandini, S. D.; Prange, M.; Schulz, M.

    2017-12-01

    The Caspian Sea (CS) is the world's largest inland sea and located within a closed (endorheic) drainage basin [ 37°-47N, 47°-54°E]. It has undergone dynamic variations (>3 m) during the past century with huge impacts on the economy, ecosystem and livelihood of coastal people. The origin of these variations as well as future changes are disputable. Here, we examine the impact of the major seasonal North Atlantic teleconnection patterns, the North Atlantic Oscillation (NAO) and the East Atlantic pattern (EA) on Caspian hydroclimate variability from 1850-2100 CE. Five Numerical experiments at different atmospheric grid resolutions (2° and 1°) and atmospheric model versions (CAM4 and CAM5) are carried out with the coupled Community Earth System Model (CESM1.2.2). Results reveal the 1° CESM1.2.2 CAM5 captures DJF NAO (46.5%) and EA (13.4%), agreeing well with observational data (1850-2000). The DJF NAO has a strong influence on the DJF temperature, rainfall and evaporation minus precipitation (E-P) over the Caspian sub-basins (Volga, Ural, Terek and Kura). Furthermore, 1° model climate projections (2020-2100 CE) are performed with different Representative Concentration Pathways (RCP4.5 and RCP8.5) to examine likely changes in the NAO and EA and their influence on the Caspian catchment. The NAO under the RCP4.5 and RCP8.5 scenarios remains the leading mode with the highest variance and influences E-P with increased precipitation over the Volga basin and increased evaporation over the Caspian Sea. The above canceling effects act on the hydroclimate variability in the Caspian sub-basins. Moreover, it is indicated that no substantial change is predicted in the CSL by the year 2100. Keywords: North Atlantic Oscillation (NAO), CESM1.2.2 resolutions, Evaporation minus Precipitation (E-P), RCP4.5, RCP8.5

  8. Two particle states, lepton mixing and oscillations

    CERN Document Server

    Kachelriess, M; Schönert, S

    2000-01-01

    Discussions of lepton mixing and oscillations consider generally only flavor oscillations of neutrinos and neglect the accompanying charged leptons. In cases of experimental interest like pion or nuclear beta decay an oscillation pattern is expected indeed only for neutrinos if only one of the two produced particles is observed. We argue that flavor oscillations of neutrinos without detecting the accompanying lepton is a peculiarity of the two-particle states $|l\

  9. A theory of generalized Bloch oscillations

    DEFF Research Database (Denmark)

    Duggen, Lars; Lew Yan Voon, L. C.; Lassen, Benny

    2016-01-01

    Bloch oscillations of electrons are shown to occur for cases when the energy spectrum does not consist of the traditional evenly-spaced ladders and the potential gradient does not result from an external electric field. A theory of such generalized Bloch oscillations is presented and an exact...... oscillations. We stipulate that the presented theory of generalized Bloch oscillations can be extended to other systems such as acoustics and photonics....

  10. Pile oscillator ROB-1, cooperation NPY

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, M; Markovic, V; Obradovic, D; Kocic, A; Velickovic, LJ; Jovanovic, S [Boris Kidric Institute of nuclear sciences Vinca, Belgrade (Yugoslavia)

    1965-11-15

    The present paper explains the purpose of the work on reactor kinetics and separately deals with the region for which the ROB-1 reactor oscillator is constructed. The theoretical part concerns the basic principles on which the oscillator operates. the paper also discusses the details of the oscillator, the procedure for preparation and measurement, and analyzes the source of errors. In addition several examples of the use of oscillator are given. (author)

  11. Nonlinear analysis of ring oscillator circuits

    KAUST Repository

    Ge, Xiaoqing

    2010-06-01

    Using nonlinear systems techniques, we analyze the stability properties and synchronization conditions for ring oscillator circuits, which are essential building blocks in digital systems. By making use of its cyclic structure, we investigate local and global stability properties of an n-stage ring oscillator. We present a sufficient condition for global asymptotic stability of the origin and obtain necessity if the ring oscillator consists of identical inverter elements. We then give a synchronization condition for identical interconnected ring oscillators.

  12. Comparison of Methods for Oscillation Detection

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Trangbæk, Klaus

    2006-01-01

    This paper compares a selection of methods for detecting oscillations in control loops. The methods are tested on measurement data from a coal-fired power plant, where some oscillations are occurring. Emphasis is put on being able to detect oscillations without having a system model and without...... using process knowledge. The tested methods show potential for detecting the oscillations, however, transient components in the signals cause false detections as well, motivating usage of models in order to remove the expected signals behavior....

  13. Pile oscillator ROB-1, cooperation NPY

    International Nuclear Information System (INIS)

    Petrovic, M.; Markovic, V.; Obradovic, D.; Kocic, A.; Velickovic, LJ.; Jovanovic, S.

    1965-11-01

    The present paper explains the purpose of the work on reactor kinetics and separately deals with the region for which the ROB-1 reactor oscillator is constructed. The theoretical part concerns the basic principles on which the oscillator operates. the paper also discusses the details of the oscillator, the procedure for preparation and measurement, and analyzes the source of errors. In addition several examples of the use of oscillator are given. (author)

  14. Nonlinear analysis of ring oscillator circuits

    KAUST Repository

    Ge, Xiaoqing; Arcak, Murat; Salama, Khaled N.

    2010-01-01

    Using nonlinear systems techniques, we analyze the stability properties and synchronization conditions for ring oscillator circuits, which are essential building blocks in digital systems. By making use of its cyclic structure, we investigate local and global stability properties of an n-stage ring oscillator. We present a sufficient condition for global asymptotic stability of the origin and obtain necessity if the ring oscillator consists of identical inverter elements. We then give a synchronization condition for identical interconnected ring oscillators.

  15. Sea level anomaly in the North Atlantic and seas around Europe: Long-term variability and response to North Atlantic teleconnection patterns.

    Science.gov (United States)

    Iglesias, Isabel; Lorenzo, M Nieves; Lázaro, Clara; Fernandes, M Joana; Bastos, Luísa

    2017-12-31

    Sea level anomaly (SLA), provided globally by satellite altimetry, is considered a valuable proxy for detecting long-term changes of the global ocean, as well as short-term and annual variations. In this manuscript, monthly sea level anomaly grids for the period 1993-2013 are used to characterise the North Atlantic Ocean variability at inter-annual timescales and its response to the North Atlantic main patterns of atmospheric circulation variability (North Atlantic Oscillation, Eastern Atlantic, Eastern Atlantic/Western Russia, Scandinavian and Polar/Eurasia) and main driven factors as sea level pressure, sea surface temperature and wind fields. SLA variability and long-term trends are analysed for the North Atlantic Ocean and several sub-regions (North, Baltic and Mediterranean and Black seas, Bay of Biscay extended to the west coast of the Iberian Peninsula, and the northern North Atlantic Ocean), depicting the SLA fluctuations at basin and sub-basin scales, aiming at representing the regions of maximum sea level variability. A significant correlation between SLA and the different phases of the teleconnection patterns due to the generated winds, sea level pressure and sea surface temperature anomalies, with a strong variability on temporal and spatial scales, has been identified. Long-term analysis reveals the existence of non-stationary inter-annual SLA fluctuations in terms of the temporal scale. Spectral density analysis has shown the existence of long-period signals in the SLA inter-annual component, with periods of ~10, 5, 4 and 2years, depending on the analysed sub-region. Also, a non-uniform increase in sea level since 1993 is identified for all sub-regions, with trend values between 2.05mm/year, for the Bay of Biscay region, and 3.98mm/year for the Baltic Sea (no GIA correction considered). The obtained results demonstrated a strong link between the atmospheric patterns and SLA, as well as strong long-period fluctuations of this variable in spatial and

  16. NOx Emission Reduction by Oscillating Combustion

    Energy Technology Data Exchange (ETDEWEB)

    None

    2005-09-01

    This project focuses on a new technology that reduces NOx emissions while increasing furnace efficiency for both air- and oxygen-fired furnaces. Oscillating combustion is a retrofit technology that involves the forced oscillation of the fuel flow rate to a furnace. These oscillations create successive, fuel-rich and fuel-lean zones within the furnace.

  17. Neutrino oscillations: present status and outlook

    International Nuclear Information System (INIS)

    Schwetz, T.

    2005-01-01

    In this talk the present status of neutrino oscillations is reviewed, based on a global analysis of world neutrino oscillation data from solar, atmospheric, reactor, and accelerator neutrino experiments. Furthermore, I discuss the expected improvements in the determination of neutrino parameters by future oscillation experiments within a timescale of 10 years. (author)

  18. Neutrino oscillations in the early universe

    International Nuclear Information System (INIS)

    Enqvist, K.

    1990-01-01

    The oscillations of electron neutrinos into inert neutrinos may have resonant behaviour in the heat bath of the early Universe. It is shown that any initial neutrino asymmetry will be washed away by the oscillations. Neutrino oscillations would affect also primordial helium production, which implies stringent limits on the neutrino mixing parameters. (orig.)

  19. The supersymmetric Pegg-Barnett oscillator

    International Nuclear Information System (INIS)

    Shen, Jian Qi

    2005-01-01

    The su(n) Lie algebraic structure of the Pegg-Barnett oscillator that possesses a finite-dimensional number-state space is demonstrated. The supersymmetric generalization of the Pegg-Barnett oscillator is suggested. it is shown that such a supersymmetric Pegg-Barnett oscillator may have some potential applications, e.g., the mass spectrum of the charged leptons

  20. Three flavour oscillation interpretation of neutrino data

    Indian Academy of Sciences (India)

    To explain the atmospheric neutrino problem in terms of neutrino oscillations, ЖС¾ of about 10-¿. eV. ¾. [8] is needed whereas the neutrino oscil- lation solution to the solar neutrino problem requires ЖС¾ ~10- eV. ¾ . Hence both solar and atmospheric neutrino problems cannot be explained in terms of e ° μ oscillations.

  1. Slow oscillations orchestrating fast oscillations and memory consolidation.

    Science.gov (United States)

    Mölle, Matthias; Born, Jan

    2011-01-01

    Slow-wave sleep (SWS) facilitates the consolidation of hippocampus-dependent declarative memory. Based on the standard two-stage memory model, we propose that memory consolidation during SWS represents a process of system consolidation which is orchestrated by the neocortical memory. The slow oscillations temporally group neuronal activity into up-states of strongly enhanced neuronal activity and down-states of neuronal silence. In a feed-forward efferent action, this grouping is induced not only in the neocortex but also in other structures relevant to consolidation, namely the thalamus generating 10-15Hz spindles, and the hippocampus generating sharp wave-ripples, with the latter well known to accompany a replay of newly encoded memories taking place in hippocampal circuitries. The feed-forward synchronizing effect of the slow oscillation enables the formation of spindle-ripple events where ripples and accompanying reactivated hippocampal memory information become nested into the single troughs of spindles. Spindle-ripple events thus enable reactivated memory-related hippocampal information to be fed back to neocortical networks in the excitable slow oscillation up-state where they can induce enduring plastic synaptic changes underlying the effective formation of long-term memories. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Mid-depth South Atlantic Ocean circulation and chemical stratification during MIS-10 to 12: implications for atmospheric CO2

    Directory of Open Access Journals (Sweden)

    M. A. Maslin

    2008-12-01

    Full Text Available A detailed record of benthic foraminifera carbon isotopes from the intermediate-depth South East Atlantic margin shows little glacial-interglacial variability between MIS-12 to MIS-10, suggesting that Northern Atlantic deepwaters consistently penetrated to at least 30° S. Millennial-scale increases in either the mass or flux of northern-sourced deepwaters over the core site occurred alongside reductions in Lower North Atlantic Deep Water recorded in North Atlantic sediment cores and show that the lower and intermediate limb of the Atlantic deepwater convective cell oscillated in anti-phase during previous glacial periods. In addition, a 500 yr resolution record of the Cape Basin intermediate-deep δ13C gradient shows that a reduction in deep Southern Ocean ventilation at the end of MIS-11 was consistent with a modelled CO2 drawdown of ~21–30 ppm. Further increases in the Southern Ocean chemical divide during the transition into MIS-10 were completed before minimum CO2 levels were reached, suggesting that other mechanisms such as alkalinity changes were responsible for the remaining ~45 ppm drawdown.

  3. Measuring neutrino oscillation parameters using $\

    Energy Technology Data Exchange (ETDEWEB)

    Backhouse, Christopher James [Oriel College, Oxford (United Kingdom)

    2011-01-01

    MINOS is a long-baseline neutrino oscillation experiment. It consists of two large steel-scintillator tracking calorimeters. The near detector is situated at Fermilab, close to the production point of the NuMI muon-neutrino beam. The far detector is 735 km away, 716m underground in the Soudan mine, Northern Minnesota. The primary purpose of the MINOS experiment is to make precise measurements of the 'atmospheric' neutrino oscillation parameters (Δmatm2 and sin2atm). The oscillation signal consists of an energy-dependent deficit of vμ interactions in the far detector. The near detector is used to characterize the properties of the beam before oscillations develop. The two-detector design allows many potential sources of systematic error in the far detector to be mitigated by the near detector observations. This thesis describes the details of the vμ-disappearance analysis, and presents a new technique to estimate the hadronic energy of neutrino interactions. This estimator achieves a significant improvement in the energy resolution of the neutrino spectrum, and in the sensitivity of the neutrino oscillation fit. The systematic uncertainty on the hadronic energy scale was re-evaluated and found to be comparable to that of the energy estimator previously in use. The best-fit oscillation parameters of the vμ-disappearance analysis, incorporating this new estimator were: Δm2 = 2.32-0.08+0.12 x 10-3 eV2, sin 2 2θ > 0.90 (90% C.L.). A similar analysis, using data from a period of running where the NuMI beam was operated in a configuration producing a predominantly $\\bar{v}$μ beam, yielded somewhat different best-fit parameters Δ$\\bar{m}${sup 2} = (3.36-0.40+0.46(stat.) ± 0.06(syst.)) x 10-3eV2, sin2 2$\\bar{θ}$ = 0.86-0.12_0

  4. Time domain oscillating poles: Stability redefined in Memristor based Wien-oscillators

    KAUST Repository

    Talukdar, Abdul Hafiz Ibne

    2012-07-28

    Traditionally, the necessary and sufficient condition for any system to be oscillating is that its poles are located on the imaginary (jω) axis. In this paper, for the first time, we have shown that systems can oscillate with time-domain oscillating poles. The idea is verified using a Memristor based Wien oscillator. Sustained oscillations are observed without having the poles of the system fixed on the imaginary axis and the oscillating behavior of the system poles is reported. The oscillating resistance and triangular shape of FFT are also demonstrated with mathematical reasoning and simulation results to support the unusual and surprising characteristics. © 2009 IEEE.

  5. The Red Atlantic: Transoceanic Cultural Exchanges

    Science.gov (United States)

    Weaver, Jace

    2011-01-01

    The development of David Armitage's "white Atlantic" history parallels the Cold War origins of American studies with its mission to define and promote "American culture" or "American civilization." British scholar Paul Gilroy's "The Black Atlantic" served as a necessary corrective. Armitage's statement leads…

  6. Identifying the Climatic Conditions in Iraq by Tracking Down Cooling Events in the North Atlantic Ocean in the Period 3000–0 BC

    Directory of Open Access Journals (Sweden)

    Muslih Khamis D.

    2014-09-01

    Full Text Available North Atlantic Oscillation (NAO, monthly averages of precipitation in the Baghdad station, and petrologic tracer proxy data for ocean properties in the North Atlantic (NA have been used in an attempt to identify climatic conditions in Iraq during the study period. The study showed that contemporary changes in precipitation in Iraq are associated with NAO, as a negative relationship is found between them. Moreover, the study found that there is a strong negative correlation between NAOI and SST in NA, where drift ice indices explain between 33–36% of the NAOI variability.

  7. Accelerator studies of neutrino oscillations

    CERN Document Server

    Ereditato, A

    2000-01-01

    The question of whether the neutrino has a non-vanishing mass plays acrucial role in particle physics. A massive neutrino would unambiguously reveal the existence of new physics beyond the Standard Model. In addition, it could have profound implications on astrophysics and cosmology, with effects on the evolution of the Universe. Experiments aiming at direct neutrino-mass measurements based on kinematics have not been able, so far, to measure the very small neutrino mass. Indirect measurements can be performed by exploiting reactions which may only occur for massive neutrinos. Neutrino oscillation is one of those processes. The mass difference between neutrino mass-eigenstates can be inferred from a phase measurement. This feature allows for high sensitivity experiments. Neutrinos from different sources can be used to search for oscillations: solar neutrinos, neutrinos produced in the interaction of cosmic rays with the atmosphere and artificially produced neutrinos from nuclear reactors and particle accelera...

  8. Oscillators that sync and swarm.

    Science.gov (United States)

    O'Keeffe, Kevin P; Hong, Hyunsuk; Strogatz, Steven H

    2017-11-15

    Synchronization occurs in many natural and technological systems, from cardiac pacemaker cells to coupled lasers. In the synchronized state, the individual cells or lasers coordinate the timing of their oscillations, but they do not move through space. A complementary form of self-organization occurs among swarming insects, flocking birds, or schooling fish; now the individuals move through space, but without conspicuously altering their internal states. Here we explore systems in which both synchronization and swarming occur together. Specifically, we consider oscillators whose phase dynamics and spatial dynamics are coupled. We call them swarmalators, to highlight their dual character. A case study of a generalized Kuramoto model predicts five collective states as possible long-term modes of organization. These states may be observable in groups of sperm, Japanese tree frogs, colloidal suspensions of magnetic particles, and other biological and physical systems in which self-assembly and synchronization interact.

  9. Experimental studies of neutrino oscillations

    CERN Document Server

    Kajita, Takaaki

    2016-01-01

    The 2015 Nobel Prize in physics has been awarded to Takaaki Kajita and Arthur McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass". Takaaki Kajita of Tokyo University is a Japanese physicist, known for neutrino experiments at the Kamiokande and its successor, Super-Kamiokande. This volume of collected works of Kajita on neutrino oscillations provides a good glimpse into as well as a record of the rise and the role of Asian research in the frontiers of neutrino physics. Japan is now a major force in the study of the 3 families of neutrinos. Much remains to be done to clarify the Dirac vs. Majorana nature of the neutrino, and the cosmological implications of the neutrino. The collected works of Kajita and his Super-Kamiokande group will leave an indelible foot-print in the history of big and better science.

  10. Torsional oscillations of the sun

    International Nuclear Information System (INIS)

    Snodgrass, H.B.; Howard, R.; National Solar Observatory, Tucson, AZ)

    1985-01-01

    The sun's differential rotation has a cyclic pattern of change that is tightly correlated with the sunspot, or magnetic activity, cycle. This pattern can be described as a torsional oscillation, in which the solar rotation is periodically sped up or slowed down in certain zones of latitude while elsewhere the rotation remains essentially steady. The zones of anomalous rotation move on the sun in wavelike fashion, keeping pace with and flanking the zones of magnetic activity. It is uncertain whether this torsional oscillation is a globally coherent ringing of the sun or whether it is a local pattern caused by and causing local changes in the magnetic fields. In either case, it may be an important link in the connection between the rotation and the cycle that is widely believed to exist but is not yet understood. 46 references

  11. Cubication of conservative nonlinear oscillators

    International Nuclear Information System (INIS)

    Belendez, Augusto; Alvarez, Mariela L; Fernandez, Elena; Pascual, Inmaculada

    2009-01-01

    A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme.

  12. Coding of Information in Limit Cycle Oscillators

    Science.gov (United States)

    Schleimer, Jan-Hendrik; Stemmler, Martin

    2009-12-01

    Starting from a general description of noisy limit cycle oscillators, we derive from the Fokker-Planck equations the linear response of the instantaneous oscillator frequency to a time-varying external force. We consider the time series of zero crossings of the oscillator’s phase and compute the mutual information between it and the driving force. A direct link is established between the phase response curve summarizing the oscillator dynamics and the ability of a limit cycle oscillator, such as a heart cell or neuron, to encode information in the timing of peaks in the oscillation.

  13. Quantum oscillations of conductivity in bismuth wires

    International Nuclear Information System (INIS)

    Condrea, Elena

    2011-01-01

    Measurements of the resistance of bismuth nanowires with several diameters and different quality reveal oscillations on the dependence of resistance under uniaxial strain at T = 4.2 K. Amplitude of oscillations is significant (38 %) at helium temperature and becomes smearing at T = 77 K. Observed oscillations originate from quantum size effect. A simple evaluation of period of oscillations allows us to identify the groups of carriers involved in transport. Calculated periods of 42.2 and 25.9 nm satisfy approximately the ratio 2:1 for two experimentally observed sets of oscillations from light and heavy electrons.

  14. Memristor-based reactance-less oscillator

    KAUST Repository

    Zidan, Mohammed A.

    2012-10-02

    The first reactance-less oscillator is introduced. By using a memristor, the oscillator can be fully implemented on-chip without the need for any capacitors or inductors, which results in an area-efficient fully integrated solution. The concept of operation of the proposed oscillator is explained and detailed mathematical analysis is introduced. Closed-form expressions for the oscillation frequency and oscillation conditions are derived. Finally, the derived equations are verified with circuit simulations showing excellent agreement. © 2011 The Institution of Engineering and Technology.

  15. Low-frequency oscillations in Hall thrusters

    International Nuclear Information System (INIS)

    Wei Li-Qiu; Han Liang; Yu Da-Ren; Guo Ning

    2015-01-01

    In this paper, we summarize the research development of low-frequency oscillations in the last few decades. The findings of physical mechanism, characteristics and stabilizing methods of low-frequency oscillations are discussed. It shows that it is unreasonable and incomplete to model an ionization region separately to analyze the physical mechanism of low-frequency oscillations. Electro-dynamics as well as the formation conditions of ionization distribution play an important role in characteristics and stabilizing of low-frequency oscillations. Understanding the physical mechanism and characteristics of low- frequency oscillations thoroughly and developing a feasible method stabilizing this instability are still important research subjects. (review)

  16. Memristor-based reactance-less oscillator

    KAUST Repository

    Zidan, Mohammed A.; Omran, Hesham; Radwan, Ahmed G.; Salama, Khaled N.

    2012-01-01

    The first reactance-less oscillator is introduced. By using a memristor, the oscillator can be fully implemented on-chip without the need for any capacitors or inductors, which results in an area-efficient fully integrated solution. The concept of operation of the proposed oscillator is explained and detailed mathematical analysis is introduced. Closed-form expressions for the oscillation frequency and oscillation conditions are derived. Finally, the derived equations are verified with circuit simulations showing excellent agreement. © 2011 The Institution of Engineering and Technology.

  17. Variability in the supply, distribution and transport of the transient tracer 99Tc in the NE Atlantic

    Science.gov (United States)

    Kershaw, Peter John; Heldal, Hilde Elise; Mork, Kjell Arne; Rudjord, Anne Liv

    2004-01-01

    In April 1994, a new waste treatment plant, the Enhanced Actinide Removal Plant (EARP), began operation at the nuclear reprocessing facilities at Sellafield in Cumbria, UK. EARP was introduced primarily to reduce the discharges of plutonium and americium, and does not remove technetium-99 ( 99Tc) from the effluents. An increased waste throughput from Sellafield since 1994 has resulted in increased discharges of 99Tc into the Irish Sea. Studies of the propagation of 99Tc from the Irish Sea into the North Sea post-EARP showed much more rapid transport than reported for other radionuclides prior to EARP. The purpose of the present study was fourfold: to extend the geographical range of sampling to allow the continuing spread of EARP-related 99Tc to be followed; to place the results in an appropriate oceanographic setting; to test whether the apparent initial rapid transport had been maintained; and to provide a dataset which could be used for model development and validation. Our results confirm that the EARP-related 99Tc contamination had reached Arctic waters by 2000. The 99Tc concentration was an order of magnitude higher than background levels in the Norwegian Coastal Current (NwCC) outside Tromsø in June/July 1999, and ˜6 times higher than background levels in the West Spitsbergen Current (WSC) in May/June 2000. Our results suggest that, following the initial rapid transport of 99Tc from the Irish Sea into the North Sea in 1994-1995, the transport rate from the North Sea and northwards with the NwCC and WSC slowed markedly, in apparent correspondence with variations in the North Atlantic Oscillation (NAO) winter index.

  18. Harmonic oscillator on a lattice

    International Nuclear Information System (INIS)

    Ader, J.P.; Bonnier, B.; Hontebeyrie, M.; Meyers, C.

    1983-01-01

    The continuum limit of the ground state energy for the harmonic oscillator with discrete time is derived for all possible choices of the lattice derivative. The occurrence of unphysical values is shown to arise whenever the lattice laplacian is not strictly positive on its Brillouin zone. These undesirable limits can either be finite and arbitrary (multiple spectrum) or infinite (overlapping sublattices with multiple spectrum). (orig.)

  19. Multipartite entanglement in neutrino oscillations

    International Nuclear Information System (INIS)

    Blasone, Massimo; Dell'Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio

    2009-01-01

    Particle mixing is related to multi-mode entanglement of single-particle states The occupation number of both flavor eigenstates and mass eigenstates can be used to define a multiqubit space. In such a framework, flavor neutrino states can be interpreted as multipartite mode-entangled states. By using two different entanglement measures, we analyze the behavior of multipartite entanglement in the phenomenon of neutrino oscillations.

  20. Multipartite entanglement in neutrino oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Blasone, Massimo; Dell' Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio, E-mail: blasone@sa.infn.i [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)

    2009-06-01

    Particle mixing is related to multi-mode entanglement of single-particle states The occupation number of both flavor eigenstates and mass eigenstates can be used to define a multiqubit space. In such a framework, flavor neutrino states can be interpreted as multipartite mode-entangled states. By using two different entanglement measures, we analyze the behavior of multipartite entanglement in the phenomenon of neutrino oscillations.

  1. Invariants of collective neutrino oscillations

    International Nuclear Information System (INIS)

    Pehlivan, Y.; Balantekin, A. B.; Kajino, Toshitaka; Yoshida, Takashi

    2011-01-01

    We consider the flavor evolution of a dense neutrino gas by taking into account both vacuum oscillations and self-interactions of neutrinos. We examine the system from a many-body perspective as well as from the point of view of an effective one-body description formulated in terms of the neutrino polarization vectors. We show that, in the single angle approximation, both the many-body picture and the effective one-particle picture possess several constants of motion. We write down these constants of motion explicitly in terms of the neutrino isospin operators for the many-body case and in terms of the polarization vectors for the effective one-body case. The existence of these constants of motion is a direct consequence of the fact that the collective neutrino oscillation Hamiltonian belongs to the class of Gaudin Hamiltonians. This class of Hamiltonians also includes the (reduced) BCS pairing Hamiltonian describing superconductivity. We point out the similarity between the collective neutrino oscillation Hamiltonian and the BCS pairing Hamiltonian. The constants of motion manifest the exact solvability of the system. Borrowing the well established techniques of calculating the exact BCS spectrum, we present exact eigenstates and eigenvalues of both the many-body and the effective one-particle Hamiltonians describing the collective neutrino oscillations. For the effective one-body case, we show that spectral splits of neutrinos can be understood in terms of the adiabatic evolution of some quasiparticle degrees of freedom from a high-density region where they coincide with flavor eigenstates to the vacuum where they coincide with mass eigenstates. We write down the most general consistency equations which should be satisfied by the effective one-body eigenstates and show that they reduce to the spectral split consistency equations for the appropriate initial conditions.

  2. Oscillations and Waves in Sunspots

    Directory of Open Access Journals (Sweden)

    Elena Khomenko

    2015-11-01

    Full Text Available A magnetic field modifies the properties of waves in a complex way. Significant advances have been made recently in our understanding of the physics of sunspot waves with the help of high-resolution observations, analytical theories, as well as numerical simulations. We review the current ideas in the field, providing the most coherent picture of sunspot oscillations as by present understanding.

  3. Micro-machined resonator oscillator

    Science.gov (United States)

    Koehler, Dale R.; Sniegowski, Jeffry J.; Bivens, Hugh M.; Wessendorf, Kurt O.

    1994-01-01

    A micro-miniature resonator-oscillator is disclosed. Due to the miniaturization of the resonator-oscillator, oscillation frequencies of one MHz and higher are utilized. A thickness-mode quartz resonator housed in a micro-machined silicon package and operated as a "telemetered sensor beacon" that is, a digital, self-powered, remote, parameter measuring-transmitter in the FM-band. The resonator design uses trapped energy principles and temperature dependence methodology through crystal orientation control, with operation in the 20-100 MHz range. High volume batch-processing manufacturing is utilized, with package and resonator assembly at the wafer level. Unique design features include squeeze-film damping for robust vibration and shock performance, capacitive coupling through micro-machined diaphragms allowing resonator excitation at the package exterior, circuit integration and extremely small (0.1 in. square) dimensioning. A family of micro-miniature sensor beacons is also disclosed with widespread applications as bio-medical sensors, vehicle status monitors and high-volume animal identification and health sensors. The sensor family allows measurement of temperatures, chemicals, acceleration and pressure. A microphone and clock realization is also available.

  4. Drifting oscillations in axion monodromy

    Energy Technology Data Exchange (ETDEWEB)

    Flauger, Raphael [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); McAllister, Liam [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Silverstein, Eva [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94305 (United States); Westphal, Alexander, E-mail: flauger@physics.ucsd.edu, E-mail: mcallister@cornell.edu, E-mail: evas@stanford.edu, E-mail: alexander.westphal@desy.de [Theory Group, Deutsches Elektronen-Synchrotron DESY, D-22603 Hamburg (Germany)

    2017-10-01

    We study the pattern of oscillations in the primordial power spectrum in axion monodromy inflation, accounting for drifts in the oscillation period that can be important for comparing to cosmological data. In these models the potential energy has a monomial form over a super-Planckian field range, with superimposed modulations whose size is model-dependent. The amplitude and frequency of the modulations are set by the expectation values of moduli fields. We show that during the course of inflation, the diminishing energy density can induce slow adjustments of the moduli, changing the modulations. We provide templates capturing the effects of drifting moduli, as well as drifts arising in effective field theory models based on softly broken discrete shift symmetries, and we estimate the precision required to detect a drifting period. A non-drifting template suffices over a wide range of parameters, but for the highest frequencies of interest, or for sufficiently strong drift, it is necessary to include parameters characterizing the change in frequency over the e-folds visible in the CMB. We use these templates to perform a preliminary search for drifting oscillations in a part of the parameter space in the Planck nominal mission data.

  5. Neutrino Oscillation Experiment at JHF

    CERN Multimedia

    2002-01-01

    T2K is a long baseline neutrino experiment designed to investigate how neutrinos change from one flavor to another as they travel (neutrino oscillations). An intense beam of muon neutrinos is generated at the J-PARC nuclear physics site on the East coast of Japan and directed across the country to the Super-Kamiokande neutrino detector in the mountains of western Japan. The beam is measured once before it leaves the J-PARC site, using the near detector ND280, and again at Super-K, 295 km away: the change in the measured intensity and composition of the beam is used to provide information on the properties of neutrinos. The high intensity neutrino beam is produced in an off-axis configuration. The peak neutrino energy is tuned to the oscillation maximum of ∼ 0.6 GeV to maximize the sensitivity to neutrino oscillations. The science goals of T2K can be summarized as follows: •\tsearch for CP violation in the neutrino sector •\tdiscovery of νμ → νe ( i.e. the confirmation that θ13 > 0 ) •\tprecision ...

  6. Superconducting low-noise oscillator

    International Nuclear Information System (INIS)

    Riebman, L.

    1992-01-01

    This patent describes a cryogenic oscillator having low phase noise and low noise. It comprises resonant circuit means formed of superconducting material for generating a signal at a desired frequency; linear amplifier means electrically connected to the resonant circuit means at first and second locations thereon; limiter means electrically connected to the resonant circuit means at a third location thereon; and buffer amplifier means for applying the signal generated by the resonant circuit means to a load and electrically connected to the resonant circuit means at a fourth location thereon. This patent also describes a method of minimizing phase noise and 1/f noise in an oscillator circuit of the type having a resonant circuit driving a load and at least a linear amplifier connected to the resonant circuit defining a closed loop having a loop gain greater than unity, and having a limiter for stabilizing the oscillator. It comprises connecting between the resonant circuit and the load a buffer amplifier and connecting the linear amplifier and the buffer amplifier to the resonant circuit

  7. Boltzmann map for quantum oscillators

    International Nuclear Information System (INIS)

    Streater, R.F.

    1987-01-01

    The authors define a map tau on the space of quasifree states of the CCR or CAR of more than one harmonic oscillator which increases entropy except at fixed points of tau. The map tau is the composition of a double stochastic map T*, and the quasifree reduction Q. Under mixing conditions on T, iterates of tau take any initial state to the Gibbs states, provided that the oscillator frequencies are mutually rational. They give an example of a system with three degrees of freedom with energies omega 1 , omega 2 , and omega 3 mutually irrational, but obeying a relation n 1 omega 1 + n 2 omega 2 = n 3 omega 3 , n/sub i/epsilon Z. The iterated Boltzmann map converges from an initial state rho to independent Gibbs states of the three oscillators at betas (inverse temperatures) β 1 , β 2 , β 3 obeying the equation n 1 omega 1 β 1 + n 2 omega 3 β 1 number. The equilibrium state can be rewritten as a grand canonical state. They show that for two, three, or four fermions we can get the usual rate equations as a special case

  8. Neutrino Oscillations:. a Phenomenological Approach

    Science.gov (United States)

    Fogli, G. L.; Lisi, E.; Marrone, A.; Palazzo, A.; Rotunno, A. M.; Montanino, D.

    We review the status of the neutrino oscillations physics, with a particular emphasis on the present knowledge of the neutrino mass-mixing parameters. We consider first the νμ → ντ flavor transitions of atmospheric neutrinos. It is found that standard oscillations provide the best description of the SK+K2K data, and that the associated mass-mixing parameters are determined at ±1σ (and NDF = 1) as: Δm2 = (2.6 ± 0.4) × 10-3 eV2 and sin 2 2θ = 1.00{ - 0.05}{ + 0.00} . Such indications, presently dominated by SK, could be strengthened by further K2K data. Then we point out that the recent data from the Sudbury Neutrino Observatory, together with other relevant measurements from solar and reactor neutrino experiments, in particular the KamLAND data, convincingly show that the flavor transitions of solar neutrinos are affected by Mikheyev-Smirnov-Wolfenstein (MSW) effects. Finally, we perform an updated analysis of two-family active oscillations of solar and reactor neutrinos in the standard MSW case.

  9. Drifting oscillations in axion monodromy

    International Nuclear Information System (INIS)

    Flauger, Raphael; Westphal, Alexander

    2014-12-01

    We study the pattern of oscillations in the primordial power spectrum in axion monodromy inflation, accounting for drifts in the oscillation period that can be important for comparing to cosmological data. In these models the potential energy has a monomial form over a super-Planckian field range, with superimposed modulations whose size is model-dependent. The amplitude and frequency of the modulations are set by the expectation values of moduli fields. We show that during the course of inflation, the diminishing energy density can induce slow adjustments of the moduli, changing the modulations. We provide templates capturing the effects of drifting moduli, as well as drifts arising in effective field theory models based on softly broken discrete shift symmetries, and we estimate the precision required to detect a drifting period. A non-drifting template suffices over a wide range of parameters, but for the highest frequencies of interest, or for sufficiently strong drift, it is necessary to include parameters characterizing the change in frequency over the e-folds visible in the CMB. We use these templates to perform a preliminary search for drifting oscillations in a part of the parameter space in the Planck nominal mission data.

  10. Nonlinearity induced synchronization enhancement in mechanical oscillators

    Science.gov (United States)

    Czaplewski, David A.; Lopez, Omar; Guest, Jeffrey R.; Antonio, Dario; Arroyo, Sebastian I.; Zanette, Damian H.

    2018-05-08

    An autonomous oscillator synchronizes to an external harmonic force only when the forcing frequency lies within a certain interval, known as the synchronization range, around the oscillator's natural frequency. Under ordinary conditions, the width of the synchronization range decreases when the oscillation amplitude grows, which constrains synchronized motion of micro- and nano-mechanical resonators to narrow frequency and amplitude bounds. The present invention shows that nonlinearity in the oscillator can be exploited to manifest a regime where the synchronization range increases with an increasing oscillation amplitude. The present invention shows that nonlinearities in specific configurations of oscillator systems, as described herein, are the key determinants of the effect. The present invention presents a new configuration and operation regime that enhances the synchronization of micro- and nano-mechanical oscillators by capitalizing on their intrinsic nonlinear dynamics.

  11. Nonlocal synchronization in nearest neighbour coupled oscillators

    International Nuclear Information System (INIS)

    El-Nashar, H.F.; Elgazzar, A.S.; Cerdeira, H.A.

    2002-02-01

    We investigate a system of nearest neighbour coupled oscillators. We show that the nonlocal frequency synchronization, that might appear in such a system, occurs as a consequence of the nearest neighbour coupling. The power spectra of nonadjacent oscillators shows that there is no complete coincidence between all frequency peaks of the oscillators in the nonlocal cluster, while the peaks for neighbouring oscillators approximately coincide even if they are not yet in a cluster. It is shown that nonadjacent oscillators closer in frequencies, share slow modes with their adjacent oscillators which are neighbours in space. It is also shown that when a direct coupling between non-neighbours oscillators is introduced explicitly, the peaks of the spectra of the frequencies of those non-neighbours coincide. (author)

  12. Daily rhythmicity of clock gene transcripts in atlantic cod fast skeletal muscle.

    Directory of Open Access Journals (Sweden)

    Carlo C Lazado

    Full Text Available The classical notion of a centralized clock that governs circadian rhythmicity has been challenged with the discovery of peripheral oscillators that enable organisms to cope with daily changes in their environment. The present study aimed to identify the molecular clock components in Atlantic cod (Gadus morhua and to investigate their daily gene expression in fast skeletal muscle. Atlantic cod clock genes were closely related to their orthologs in teleosts and tetrapods. Synteny was conserved to varying degrees in the majority of the 18 clock genes examined. In particular, aryl hydrocarbon receptor nuclear translocator-like 2 (arntl2, RAR-related orphan receptor A (rora and timeless (tim displayed high degrees of conservation. Expression profiling during the early ontogenesis revealed that some transcripts were maternally transferred, namely arntl2, cryptochrome 1b and 2 (cry1b and cry2, and period 2a and 2b (per2a and per2b. Most clock genes were ubiquitously expressed in various tissues, suggesting the possible existence of multiple peripheral clock systems in Atlantic cod. In particular, they were all detected in fast skeletal muscle, with the exception of neuronal PAS (Per-Arnt-Single-minded domain-containing protein (npas1 and rora. Rhythmicity analysis revealed 8 clock genes with daily rhythmic expression, namely arntl2, circadian locomotor output cycles kaput (clock, npas2, cry2, cry3 per2a, nuclear receptor subfamily 1, group D, member 1 (nr1d1, and nr1d2a. Transcript levels of the myogenic genes myogenic factor 5 (myf5 and muscleblind-like 1 (mbnl1 strongly correlated with clock gene expression. This is the first study to unravel the molecular components of peripheral clocks in Atlantic cod. Taken together, our data suggest that the putative clock system in fast skeletal muscle of Atlantic cod has regulatory implications on muscle physiology, particularly in the expression of genes related to myogenesis.

  13. The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

    Energy Technology Data Exchange (ETDEWEB)

    Frankignoul, Claude [Universite Pierre et Marie Curie, Paris 6, LOCEAN/IPSL, Paris Cedex 05 (France); Deshayes, Julie; Curry, Ruth [Woods Hole Oceanographic Institution, Woods Hole, MA (United States)

    2009-11-15

    An OGCM hindcast is used to investigate the linkages between North Atlantic Ocean salinity and circulation changes during 1963-2003. The focus is on the eastern subpolar region consisting of the Irminger Sea and the eastern North Atlantic where a careful assessment shows that the simulated interannual to decadal salinity changes in the upper 1,500 m reproduce well those derived from the available record of hydrographic measurements. In the model, the variability of the Atlantic meridional overturning circulation (MOC) is primarily driven by changes in deep water formation taking place in the Irminger Sea and, to a lesser extent, the Labrador Sea. Both are strongly influenced by the North Atlantic Oscillation (NAO). The modeled interannual to decadal salinity changes in the subpolar basins are mostly controlled by circulation-driven anomalies of freshwater flux convergence, although surface salinity restoring to climatology and other boundary fluxes each account for approximately 25% of the variance. The NAO plays an important role: a positive NAO phase is associated with increased precipitation, reduced northward salt transport by the wind-driven intergyre gyre, and increased southward flows of freshwater across the Greenland-Scotland ridge. Since the NAO largely controlled deep convection in the subpolar gyre, fresher waters are found near the sinking region during convective events. This markedly differs from the active influence on the MOC that salinity exerts at decadal and longer timescales in most coupled models. The intensification of the MOC that follows a positive NAO phase by about 2 years does not lead to an increase in the northward salt transport into the subpolar domain at low frequencies because it is cancelled by the concomitant intensification of the subpolar gyre which shifts the subpolar front eastward and reduces the northward salt transport by the North Atlantic Current waters. This differs again from most coupled models, where the gyre

  14. Application of the Lyapunov exponent to detect noise-induced chaos in oscillating microbial cultures

    International Nuclear Information System (INIS)

    Patnaik, P.R.

    2005-01-01

    Oscillating microbial processes can, under certain conditions, gravitate into chaotic behavior induced by external noise. Detection and control of chaos are important for the survival of the microorganisms and to operate a process usefully. In this study the largest Lyapunov exponent is recommended as a convenient and reliable index of chaos in continuous oscillating cultures. For the growth of Saccharomyces cerevisiae as a model system, the exponents increase with the oxygen mass transfer coefficient and decrease as the dilution rate increases. By comparing with the corresponding time-domain oscillations determined earlier, it is inferred that weakly oscillating cultures are less likely to be driven to chaotic behavior. The main carbon source, glucose, is quite robust to chaotic destabilization, thus enhancing its suitability as a manipulated variable for bioreactor control

  15. Dysrhythmias of the respiratory oscillator

    Science.gov (United States)

    Paydarfar, David; Buerkel, Daniel M.

    1995-03-01

    Breathing is regulated by a central neural oscillator that produces rhythmic output to the respiratory muscles. Pathological disturbances in rhythm (dysrhythmias) are observed in the breathing pattern of children and adults with neurological and cardiopulmonary diseases. The mechanisms responsible for genesis of respiratory dysrhythmias are poorly understood. The present studies take a novel approach to this problem. The basic postulate is that the rhythm of the respiratory oscillator can be altered by a variety of stimuli. When the oscillator recovers its rhythm after such perturbations, its phase may be reset relative to the original rhythm. The amount of phase resetting is dependent upon stimulus parameters and the level of respiratory drive. The long-range hypothesis is that respiratory dysrhythmias can be induced by stimuli that impinge upon or arise within the respiratory oscillator with certain combinations of strength and timing relative to the respiratory cycle. Animal studies were performed in anesthetized or decerebrate preparations. Neural respiratory rhythmicity is represented by phrenic nerve activity, allowing use of open-loop experimental conditions which avoid negative chemical feedback associated with changes in ventilation. In animal experiments, respiratory dysrhythmias can be induced by stimuli having specific combinations of strength and timing. Newborn animals readily exhibit spontaneous dysrhythmias which become more prominent at lower respiratory drives. In human subjects, swallowing was studied as a physiological perturbation of respiratory rhythm, causing a pattern of phase resetting that is characterized topologically as type 0. Computational studies of the Bonhoeffer-van der Pol (BvP) equations, whose qualitative behavior is representative of many excitable systems, supports a unified interpretation of these experimental findings. Rhythmicity is observed when the BvP model exhibits recurrent periods of excitation alternating with

  16. Millennial-scale northern Hemisphere Atlantic-Pacific climate teleconnections in the earliest Middle Pleistocene.

    Science.gov (United States)

    Hyodo, Masayuki; Bradák, Balázs; Okada, Makoto; Katoh, Shigehiro; Kitaba, Ikuko; Dettman, David L; Hayashi, Hiroki; Kumazawa, Koyo; Hirose, Kotaro; Kazaoka, Osamu; Shikoku, Kizuku; Kitamura, Akihisa

    2017-08-30

    Suborbital-scale climate variations, possibly caused by solar activity, are observed in the Holocene and last-glacial climates. Recently published bicentennial-resolution paleoceanic environmental records reveal millennial-scale high-amplitude oscillations postdating the last geomagnetic reversal in the Marine Isotope Stage (MIS) 19 interglacial. These oscillations, together with decoupling of post-reversal warming from maximum sea-level highstand in mid-latitudes, are key features for understanding the climate system of MIS 19 and the following Middle Pleistocene. It is unclear whether the oscillations are synchronous, or have the same driver as Holocene cycles. Here we present a high resolution record of western North Pacific submarine anoxia and sea surface bioproductivity from the Chiba Section, central Japan. The record reveals many oxic events in MIS 19, coincident with cold intervals, or with combined cold and sea-level fall events. This allows detailed correlations with paleoceanic records from the mid-latitude North Atlantic and Osaka Bay, southwest Japan. We find that the millennial-scale oscillations are synchronous between East and West hemispheres. In addition, during the two warmest intervals, bioproductivity follows the same pattern of change modulated by bicentennial cycles that are possibly related to solar activity.

  17. Retrospective analysis of seasonal ocean growth rates of two sea winter Atlantic Salmon in eastern Maine using historic scales

    Science.gov (United States)

    Izzo, Lisa K.; Zydlewski, Joseph D.

    2017-01-01

    Substantial declines of anadromous Atlantic Salmon Salmo salar have occurred throughout its range, with many populations at the southern extent of the distribution currently extirpated or endangered. While both one sea winter (1SW) and two sea winter (2SW) spawner numbers for the North American stocks have declined since the 1950s, the decline has been most severe in 2SW spawners. The first months at sea are considered a period of high mortality. However, early ocean mortality alone cannot explain the more pronounced decline of 2SW spawners, suggesting that the second year at sea may be more critical than previously thought. Atlantic Salmon scales collected by anglers and the state agency from 1946 to 2013 from five rivers in eastern Maine were used to estimate smolt age and ocean age of returning adults. Additionally, seasonal growth rates of maiden 2SW spawners were estimated using intercirculi measurements and linear back-calculation methods. Generalized linear mixed models (Gaussian family, log link function) were used to investigate the influence of average sea surface temperature, accumulated thermal units, the Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation indices, smolt age, smolt length, postsmolt growth, and river of origin on growth rate during the oceanic migration of North American Atlantic Salmon. Results suggest that different factors influence salmon growth throughout their oceanic migration, and previous growth can be a strong predictor of future size. Growth was negatively impacted by the phase of the AMO, which has been linked to salmon abundance trends, in early spring following the postsmolt period. This is likely when the 1SW and 2SW stock components separate, and our results suggest that this period may be of interest in future work examining the disproportionate decline in 2SW spawners.

  18. EJSCREEN Indexes 2015 Public

    Data.gov (United States)

    U.S. Environmental Protection Agency — There is an EJ Index for each environmental indicator. There are eight EJ Indexes in EJSCREEN reflecting the 8 environmental indicators. The EJ Index names are:...

  19. EJSCREEN Indexes 2016 Public

    Data.gov (United States)

    U.S. Environmental Protection Agency — There is an EJ Index for each environmental indicator. There are eleven EJ Indexes in EJSCREEN reflecting the 11 environmental indicators. The EJ Index names are:...

  20. Dual annual spawning races in Atlantic sturgeon.

    Directory of Open Access Journals (Sweden)

    Matthew T Balazik

    Full Text Available Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus, Acipenseridae populations in the United States were listed as either endangered or threatened under the Endangered Species Act in 2012. Because of the endangered/threatened status, a better understanding of Atlantic sturgeon life-history behavior and habitat use is important for effective management. It has been widely documented that Atlantic sturgeon reproduction occurs from late winter to early summer, varying clinally with latitude. However, recent data show Atlantic sturgeon also spawn later in the year. The group that spawns later in the year seems to be completely separate from the spring spawning run. Recognition of the later spawning season has drastically modified estimates of the population status of Atlantic sturgeon in Virginia. With the combination of new telemetry data and historical documentation we describe a dual spawning strategy that likely occurs in various degrees along most, if not all, of the Atlantic sturgeon's range. Using new data combined with historical sources, a new spawning strategy emerges which managers and researchers should note when determining the status of Atlantic sturgeon populations and implementing conservation measures.

  1. Separation control with fluidic oscillators in water

    Science.gov (United States)

    Schmidt, H.-J.; Woszidlo, R.; Nayeri, C. N.; Paschereit, C. O.

    2017-08-01

    The present study assesses the applicability of fluidic oscillators for separation control in water. The first part of this work evaluates the properties of the fluidic oscillators including frequency, cavitation effects, and exerted thrust. Derived from the governing internal dynamics, the oscillation frequency is found to scale directly with the jet's exit velocity and the size of the fluidic oscillator independent of the working fluid. Frequency data from various experiments collapse onto a single curve. The occurrence of cavitation is examined by visual inspection and hydrophone measurements. The oscillation frequency is not affected by cavitation because it does not occur inside the oscillators. The spectral information obtained with the hydrophone provide a reliable indicator for the onset of cavitation at the exit. The performance of the fluidic oscillators for separation control on a bluff body does not seem to be affected by the presence of cavitation. The thrust exerted by an array of fluidic oscillators with water as the working fluid is measured to be even larger than theoretically estimated values. The second part of the presented work compares the performance of fluidic oscillators for separation control in water with previous results in air. The array of fluidic oscillators is installed into the rear end of a bluff body model. The drag improvements based on force balance measurements agree well with previous wind tunnel experiments on the same model. The flow field is examined by pressure measurements and with particle image velocimetry. Similar performance and flow field characteristics are observed in both water and air.

  2. North Atlantic weather oscillation and human infectious diseases in the Czech Republic, 1951-2003

    Czech Academy of Sciences Publication Activity Database

    Hubálek, Zdeněk

    2005-01-01

    Roč. 20, č. 3 (2005), s. 263-270 ISSN 0393-2990 R&D Projects: GA ČR(CZ) GA206/03/0726 Institutional research plan: CEZ:AV0Z60930519 Keywords : climate change * cluster analysis * human infectious diseases Subject RIV: FN - Epidemiology, Contagious Diseases ; Clinical Immunology Impact factor: 1.361, year: 2005

  3. Regional climatic and North Atlantic Oscillation signatures in West Virginia red cedar over the past millennium

    Science.gov (United States)

    D'Arrigo, Rosanne; Anchukaitis, Kevin J.; Buckley, Brendan; Cook, Ed; Wilson, Rob

    2012-03-01

    We describe a millennial length (~ 1500-yr) tree-ring chronology developed from West Virginia (WVA), USA red cedar (Juniperus virginiana) ring widths that is significantly correlated with local to regional temperature and precipitation for the region. Using ensemble methods of tree-ring standardization, above average ring widths are indicated for the period between ~ 1000 and 1300 CE, the approximate time of the Medieval Climate Anomaly (MCA), the most recent major warm episode prior to the modern era. The chronology then transitions to more negative overall growth persisting through much of the subsequent period known as the Little Ice Age (LIA). While WVA cedar growth levels during the MCA are broadly similar to the 20th century mean, the most positive values during the MCA are associated with RCS-standardized chronologies, which pseudoproxy tests reveal are likely biased artificially positive, warranting further investigation. This cedar record is significantly correlated with the NAO, due to the tendency for warmer, wetter conditions to occur in the eastern-central USA during the NAO's positive phase. These types of conditions are inferred for this cedar chronology during the MCA period, during which NAO reconstructions suggest a persistently-positive NAO state.

  4. The North Atlantic Oscillation Influence on the Wave Regime in Portugal: An Extreme Wave Event Analysis

    Science.gov (United States)

    2005-03-01

    picture at 22/00Z.............50 x Figure 24. Case 5 – wave parameters........................51 Figure 25. Evolution of energy density (arrow...equation or energy balance equation: . in nl ds F v F S S S S t ∂ + ∇ = ≡ + + ∂ r (1) where ( , ; , )F f x tθ r is the two dimensional...collected from an offshore directional Seawatch buoy, in the vicinity of Cape Silleiro, Rayo Silleiro 19 (“E1”), (Figure 3), was provided by the

  5. 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

  6. Changes in Greenland’s peripheral glaciers linked to the North Atlantic Oscillation

    DEFF Research Database (Denmark)

    Bjørk, A. A.; Aagaard, S.; Lütt, A.

    2018-01-01

    Glaciers and ice caps peripheral to the main Greenland Ice Sheet contribute markedly to sea-level rise1,2,3. Their changes and variability, however, have been difficult to quantify on multi-decadal timescales due to an absence of long-term data4. Here, using historical aerial surveys, expedition...

  7. An exactly solvable model of an oscillator with nonlinear coupling and zeros of Bessel functions

    Science.gov (United States)

    Dodonov, V. V.; Klimov, A. B.

    1993-01-01

    We consider an oscillator model with nonpolynomial interaction. The model admits exact solutions for two situations: for energy eigenvalues in terms of zeros of Bessel functions, that were considered as functions of the continuous index; and for the corresponding eigenstates in terms of Lommel polynomials.

  8. Northern tropical Atlantic climate since late Medieval times from Northern Caribbean coral geochemistry

    Science.gov (United States)

    Kilbourne, K. H.; Xu, Y.

    2015-12-01

    Paleoclimate reconstructions of different global climate modes over the last 1000 years provide the basis for testing the relative roles of forced and unforced variability climate system, which can help us improve projections of future climate change. The Medieval Climate Anomaly (MCA) has been characterized by a combination of persistent La Niña-like conditions, a positive North Atlantic Oscillation (+NAO), and increased Atlantic Meridional Overturning Circulation (AMOC). The northern tropical Atlantic is sensitive to each of these climate patterns, but not all of them have the same regional fingerprint in the modern northern tropical Atlantic. The relative influence of different processes related to these climate patterns can help us better understand regional responses to climate change. The regional response of the northern tropical Atlantic is important because the tropical Atlantic Ocean is a large source of heat and moisture to the global climate system that can feedback onto global climate patterns. This study presents new coral Sr/Ca and δ18O data from the northern tropical Atlantic (Anegada, British Virgin Islands). Comparison of the sub-fossil corals that grew during the 13th and 14th Centuries with modern coral geochemical data from this site indicates relatively cooler mean conditions with a decrease in the oxygen isotopic composition of the water consistent with lower salinities. Similar average annual cycles between modern and sub-fossil Sr/Ca indicate no change in seasonal temperature range, but a difference in the relative phasing of the δ18O seasonal cycles indicates that the fresher mean conditions may be due to a more northerly position of the regional salinity front. This localized response is consistent with some, but not all of the expected regional responses to a La Niña-like state, a +NAO state, and increased AMOC. Understanding these differences can provide insight into the relative importance of advection versus surface fluxes for

  9. Clusters in nonsmooth oscillator networks

    Science.gov (United States)

    Nicks, Rachel; Chambon, Lucie; Coombes, Stephen

    2018-03-01

    For coupled oscillator networks with Laplacian coupling, the master stability function (MSF) has proven a particularly powerful tool for assessing the stability of the synchronous state. Using tools from group theory, this approach has recently been extended to treat more general cluster states. However, the MSF and its generalizations require the determination of a set of Floquet multipliers from variational equations obtained by linearization around a periodic orbit. Since closed form solutions for periodic orbits are invariably hard to come by, the framework is often explored using numerical techniques. Here, we show that further insight into network dynamics can be obtained by focusing on piecewise linear (PWL) oscillator models. Not only do these allow for the explicit construction of periodic orbits, their variational analysis can also be explicitly performed. The price for adopting such nonsmooth systems is that many of the notions from smooth dynamical systems, and in particular linear stability, need to be modified to take into account possible jumps in the components of Jacobians. This is naturally accommodated with the use of saltation matrices. By augmenting the variational approach for studying smooth dynamical systems with such matrices we show that, for a wide variety of networks that have been used as models of biological systems, cluster states can be explicitly investigated. By way of illustration, we analyze an integrate-and-fire network model with event-driven synaptic coupling as well as a diffusively coupled network built from planar PWL nodes, including a reduction of the popular Morris-Lecar neuron model. We use these examples to emphasize that the stability of network cluster states can depend as much on the choice of single node dynamics as it does on the form of network structural connectivity. Importantly, the procedure that we present here, for understanding cluster synchronization in networks, is valid for a wide variety of systems in

  10. Power oscillations in BWR reactors

    International Nuclear Information System (INIS)

    Espinosa P, G.

    2002-01-01

    One of the main problems in the operation of BWR type reactors is the instability in power that these could present. One type of oscillations and that is the objective of this work is the named density wave, which is attributed to the thermohydraulic processes that take place in the reactor core. From the beginnings of the development of BWR reactors, the stability of these has been an important aspect in their design, due to its possible consequences on the fuel integrity. The reactor core operates in two phase flow conditions and it is observed that under certain power and flow conditions, power instabilities appear. Studying this type of phenomena is complex, due to that a reactor core is constituted approximately by 27,000 fuel bars with different distributions of power and flow. The phenomena that cause the instability in BWR reactors continue being matter of scientific study. In the literature mainly in nuclear subject, it can be observed that exist different methods and approximations for studying this type of phenomena, nevertheless, their results are focused to establish safety limits in the reactor operation, instead of studying in depth of the knowledge about. Also in this line sense of the reactor data analysis, the oscillations characteristic frequencies are obtained for trying to establish if the power is growing or decreasing. In addition to that before mentioned in this paper it is presented a rigorous study applying the volumetric average method, for obtaining the vacuum waves propagation velocities and its possible connection with the power oscillations. (Author)

  11. Modeling of Coupled Chaotic Oscillators

    International Nuclear Information System (INIS)

    Lai, Y.; Grebogi, C.

    1999-01-01

    Chaotic dynamics may impose severe limits to deterministic modeling by dynamical equations of natural systems. We give theoretical argument that severe modeling difficulties may occur for high-dimensional chaotic systems in the sense that no model is able to produce reasonably long solutions that are realized by nature. We make these ideas concrete by investigating systems of coupled chaotic oscillators. They arise in many situations of physical and biological interests, and they also arise from discretization of nonlinear partial differential equations. copyright 1999 The American Physical Society

  12. Magnus approximation in neutrino oscillations

    International Nuclear Information System (INIS)

    Acero, Mario A; Aguilar-Arevalo, Alexis A; D'Olivo, J C

    2011-01-01

    Oscillations between active and sterile neutrinos remain as an open possibility to explain some anomalous experimental observations. In a four-neutrino (three active plus one sterile) mixing scheme, we use the Magnus expansion of the evolution operator to study the evolution of neutrino flavor amplitudes within the Earth. We apply this formalism to calculate the transition probabilities from active to sterile neutrinos with energies of the order of a few GeV, taking into account the matter effect for a varying terrestrial density.

  13. Waves and Oscillations in Plasmas

    CERN Document Server

    Pecseli, Hans L

    2012-01-01

    The result of more than 15 years of lectures in plasma sciences presented at universities in Denmark, Norway, and the United States, Waves and Oscillations in Plasmas addresses central issues in modern plasma sciences. The book covers fluid models as well as kinetic plasma models, including a detailed discussion of, for instance, collisionless Landau damping. Offering a clear separation of linear and nonlinear models, the book can be tailored for readers of varying levels of expertise.Designed to provide basic training in linear as well as nonlinear plasma dynamics, and practical in areas as d

  14. Pair creation and plasma oscillations

    International Nuclear Information System (INIS)

    Prozorkevich, A. V.; Vinnik, D. V.; Schmidt, S. M.; Hecht, M. B.; Roberts, C. D.

    2000-01-01

    We describe aspects of particle creation in strong fields using a quantum kinetic equation with a relaxation-time approximation to the collision term. The strong electric background field is determined by solving Maxwell's equation in tandem with the Vlasov equation. Plasma oscillations appear as a result of feedback between the background field and the field generated by the particles produced. The plasma frequency depends on the strength of the initial background fields and the collision frequency, and is sensitive to the necessary momentum-dependence of dressed-parton masses

  15. Wave Physics Oscillations - Solitons - Chaos

    CERN Document Server

    Nettel, Stephen

    2009-01-01

    This textbook is intended for those second year undergraduates in science and engineering who will later need an understanding of electromagnetic theory and quantum mechanics. The classical physics of oscillations and waves is developed at a more advanced level than has been customary for the second year, providing a basis for the quantum mechanics that follows. In this new edition the Green's function is explained, reinforcing the integration of quantum mechanics with classical physics. The text may also form the basis of an "introduction to theoretical physics" for physics majors. The concluding chapters give special attention to topics in current wave physics: nonlinear waves, solitons, and chaotic behavior.

  16. Abiotic factors drives floristic variations of fern’s metacommunity in an Atlantic Forest remnant

    OpenAIRE

    L. E. N. Costa; R. P. Farias; A. C. P. Santiago; I. A. A. Silva; I. C. L. Barros

    2018-01-01

    Abstract We analyzed floristic variations in fern’s metacommunity at the local scale and their relationship with abiotic factors in an Atlantic Forest remnant of northeastern Brazil. Floristic and environmental variations were accessed on ten plots of 10 × 20 m. We performed cluster analyses, based on Bray-Curtis dissimilarity index to establish the floristic relationship. The influence of abiotic factors: luminosity, temperature, relative air humidity and relative soil moisture was evaluated...

  17. Role of interannual Kelvin wave propagations in the equatorial Atlantic on the Angola Benguela Current system

    Science.gov (United States)

    Imbol Koungue, Rodrigue Anicet; Illig, Serena; Rouault, Mathieu

    2017-06-01

    The link between equatorial Atlantic Ocean variability and the coastal region of Angola-Namibia is investigated at interannual time scales from 1998 to 2012. An index of equatorial Kelvin wave activity is defined based on Prediction and Research Moored Array in the Tropical Atlantic (PIRATA). Along the equator, results show a significant correlation between interannual PIRATA monthly dynamic height anomalies, altimetric monthly Sea Surface Height Anomalies (SSHA), and SSHA calculated with an Ocean Linear Model. This allows us to interpret PIRATA records in terms of equatorial Kelvin waves. Estimated phase speed of eastward propagations from PIRATA equatorial mooring remains in agreement with the linear theory, emphasizing the dominance of the second baroclinic mode. Systematic analysis of all strong interannual equatorial SSHA shows that they precede by 1-2 months extreme interannual Sea Surface Temperature Anomalies along the African coast, which confirms the hypothesis that major warm and cold events in the Angola-Benguela current system are remotely forced by ocean atmosphere interactions in the equatorial Atlantic. Equatorial wave dynamics is at the origin of their developments. Wind anomalies in the Western Equatorial Atlantic force equatorial downwelling and upwelling Kelvin waves that propagate eastward along the equator and then poleward along the African coast triggering extreme warm and cold events, respectively. A proxy index based on linear ocean dynamics appears to be significantly more correlated with coastal variability than an index based on wind variability. Results show a seasonal phasing, with significantly higher correlations between our equatorial index and coastal SSTA in October-April season.

  18. Browse Title Index

    African Journals Online (AJOL)

    Items 651 - 700 of 763 ... Vol 4, No 1 (2010), Spatial and temporal distribution of North Atlantic tropical .... Vol 5, No 2 (2011), Sustainable development in Cameroon's forestry sector: Progress, ... The current pollution status of the new Calabar river in the Niger ... Vol 11, No 1 (2017), The earthquake/seismic risk, vulnerability ...

  19. Browse Title Index

    African Journals Online (AJOL)

    Items 151 - 200 of 260 ... Vol 40 (2000), Plastic mulch and 4-chloro-phenoxyacetic acid (CPA) interaction on growth and yield of eggplant (Solanum aethiopicum L.) Abstract. GO Nkansah ... Vol 30, No 1-2 (1990): Volume 29-30; 1989-1990, Potassiium-Argon radiometric dates of the Mid-Atlantic ocean floor, Abstract. EK Agyei.

  20. Browse Title Index

    African Journals Online (AJOL)

    Items 301 - 350 of 503 ... Vol 25, No 2 (2005), Modelling of hydropower systems of Ghana at low level conditions of Akosombo dam, Abstract PDF. DM Obeng, YAK Fiagbe. Vol 27, No 2 (2007), Molecular responce of Atlantic cod's (Gadus morhua L.) cypia, prolactin and Zona radiata genes upon exposure to polychlorinated ...