共查询到20条相似文献，搜索用时 46 毫秒
1.
A Madden-Julian Oscillation (MJO) is a massive weather event consisting of deep convection coupled with atmospheric circulation, moving slowly eastward over the Indian and Pacific Oceans. Despite its enormous influence on many weather and climate systems worldwide, it has proven very difficult to simulate an MJO because of assumptions about cumulus clouds in global meteorological models. Using a model that allows direct coupling of the atmospheric circulation and clouds, we successfully simulated the slow eastward migration of an MJO event. Topography, the zonal sea surface temperature gradient, and interplay between eastward- and westward-propagating signals controlled the timing of the eastward transition of the convective center. Our results demonstrate the potential making of month-long MJO predictions when global cloud-resolving models with realistic initial conditions are used. 相似文献
2.
Using the new Argo array of profiling floats that gives unprecedented space-time coverage of the upper 2000 meters of the global ocean, we present definitive evidence of a deep tropical ocean component of the Madden-Julian Oscillation (MJO). The surface wind stress anomalies associated with the MJO force eastward-propagating oceanic equatorial Kelvin waves that extend downward to 1500 meters. The amplitude of the deep ocean anomalies is up to six times the amplitude of the observed annual cycle. This deep ocean sink of energy input from the wind is potentially important for understanding phenomena such as El Ni?o-Southern Oscillation and for interpreting deep ocean measurements made from ships. 相似文献
3.
Brasefield CJ 《Science (New York, N.Y.)》1963,142(3594):952-953
The gamma ray activity of particulate matter filtered from air samples of northerly winds and of southerly winds has been studied during the period October 1961 to May 1963 with a scintillation spectrometer. It was found that the gamma activity at 0.75, 0.49, and 0.145 Mev was greater when the wind was southerly than when the wind was northerly during the months December through May; the opposite was true from June through September. The gamma ray activity was least during the summer of 1962, the decrease being more pronounced for southerly winds than for northerly winds. These results can be accounted for by modifying the Brewer-Dobson theory of stratospheric circulation so that during most of the year stratospheric debris first reaches the ground south of latitude 40 degrees N. No diurnal effect on the gamma ray activity of the samples could be detected. 相似文献
4.
The recent trend of declining winter and spring snow cover over Eurasia is causing a land-ocean thermal gradient that is particularly favorable to stronger southwest (summer) monsoon winds. Since 1997, sea surface winds have been strengthening over the western Arabian Sea. This escalation in the intensity of summer monsoon winds, accompanied by enhanced upwelling and an increase of more than 350% in average summertime phytoplankton biomass along the coast and over 300% offshore, raises the possibility that the current warming trend of the Eurasian landmass is making the Arabian Sea more productive. 相似文献
5.
Ingersoll AP 《Science (New York, N.Y.)》1990,248(4953):308-315
Despite major differences in the solar and internal energy inputs, the atmospheres of the four Jovian planets all exhibit latitudinal banding and high-speed jet streams. Neptune and Saturn are the windiest planets, Jupiter is the most active, and Uranus is a tipped-over version of the others. Large oval storm systems exhibit complicated time-dependent behavior that can be simulated in numerical models and laboratory experiments. The largest storm system, the Great Red Spot of Jupiter, has survived for more than 300 years in a chaotic shear zone where smaller structures appear and dissipate every few days. Future space missions will add to our understanding of small-scale processes, chemical composition, and vertical structure. Theoretical hypotheses about the interiors provide input for fluid dynamical models that reproduce many observed features of the winds, temperatures, and cloud patterns. In one set of models the winds are confined to the thin layer where clouds form. In other models, the winds extend deep into the planetary fluid interiors. Hypotheses will be tested further as observations and theories become more exact and detailed comparisons are made. 相似文献
6.
温度、湿度、光照、大风等气象要素直接影响着沾化冬枣的生长发育。枣树开花期对气候条件最为敏感,当花期出现低温连阴雨气时,就会出现大量的落花;当枣花授粉时遇有大风、沙尘天气时,枣花不能正常授粉,坐果受到影响;当出现干旱少雨的天气时,因气湿度较小,会出现焦花现象,枣花的授粉受到限制,坐果率明显下降。 相似文献
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Greeley R Squyres SW Arvidson RE Bartlett P Bell JF Blaney D Cabrol NA Farmer J Farrand B Golombek MP Gorevan SP Grant JA Haldemann AF Herkenhoff KE Johnson J Landis G Madsen MB McLennan SM Moersch J Rice JW Richter L Ruff S Sullivan RJ Thompson SD Wang A Weitz CM Whelley P 《Science (New York, N.Y.)》2004,305(5685):810-813
Wind-abraded rocks, ripples, drifts, and other deposits of windblown sediments are seen at the Columbia Memorial Station where the Spirit rover landed. Orientations of these features suggest formative winds from the north-northwest, consistent with predictions from atmospheric models of afternoon winds in Gusev Crater. Cuttings from the rover Rock Abrasion Tool are asymmetrically distributed toward the south-southeast, suggesting active winds from the north-northwest at the time (midday) of the abrasion operations. Characteristics of some rocks, such as a two-toned appearance, suggest that they were possibly buried and exhumed on the order of 5 to 60 centimeters by wind deflation, depending on location. 相似文献
9.
A simulation with a coupled atmosphere-ocean general circulation model configured for the Last Glacial Maximum delivered a tropical climate that is much cooler than that produced by atmosphere-only models. The main reason is a decrease in tropical sea surface temperatures, up to 6 degrees C in the western tropical Pacific, which occurs because of two processes. The trade winds induce equatorial upwelling and zonal advection of cold water that further intensify the trade winds, and an exchange of water occurs between the tropical and extratropical Pacific in which the poleward surface flow is balanced by equatorward flow of cold water in the thermocline. Simulated tropical temperature depressions are of the same magnitude as those that have been proposed from recent proxy data. 相似文献
10.
The appearance of sustained equatorial surface westerlies during the 1982 pacific warm event 总被引：1，自引：0，他引：1
Harrison DE 《Science (New York, N.Y.)》1984,224(4653):1099-1102
In June 1982 a band of anomalous southerly surface wind, extending from the equator as far south as the Tasman Sea, formed east of Australia (150 degrees E to 160 degrees E). This flow crossed the equator just before the appearance of sustained westerly winds on the equator somewhat west of the date line. Because these westerly winds induced the initial strong equatorial warming of the ocean east of the date line during the 1982 El Ni?o-Southern Oscillation (ENSO) event, the southerly jet appears to be an important atmospheric component leading to the onset of the vigorous phase of this event. Some historical evidence suggests that anomalous southerly winds in the same region occurred prior to the appearance of sustained equatorial westerly winds in the major ENSO events of 1957, 1965, and 1972. 相似文献
11.
Stappers BW Gaensler BM Kaspi VM van der Klis M Lewin WH 《Science (New York, N.Y.)》2003,299(5611):1372-1374
We have detected an x-ray nebula around the binary millisecond pulsar B1957+20. A narrow tail, corresponding to the shocked pulsar wind, is seen interior to the known Halpha bow shock and proves the long-held assumption that the rotational energy of millisecond pulsars is dissipated through relativistic winds. Unresolved x-ray emission likely represents the shock where the winds of the pulsar and its companion collide. This emission indicates that the efficiency with which relativistic particles are accelerated in the postshock flow is similar to that for young pulsars, despite the shock proximity and much weaker surface magnetic field of this millisecond pulsar. 相似文献
12.
Great quantities of African dust are carried over large areas of the Atlantic and to the Caribbean during much of the year. Measurements made from 1965 to 1998 in Barbados trade winds show large interannual changes that are highly anticorrelated with rainfall in the Soudano-Sahel, a region that has suffered varying degrees of drought since 1970. Regression estimates based on long-term rainfall data suggest that dust concentrations were sharply lower during much of the 20th century before 1970, when rainfall was more normal. Because of the great sensitivity of dust emissions to climate, future changes in climate could result in large changes in emissions from African and other arid regions that, in turn, could lead to impacts on climate over large areas. 相似文献
13.
Hot massive stars represent only a small fraction of the stellar population of the galaxy, but their enormous luminosities make them visible over large distances. Therefore, they are ideal standard candles, used to determine distances of near galaxies. Their mass loss due to supersonic winds driven by radiation pressure contributes significantly to the interstellar medium and thus to the chemical evolution of galaxies. All hot stars are soft x-ray sources; in contrast to the sun with its highly variable x-ray flux, long time scale x-ray variability is not common among hot stars. An analysis is presented here of an unusual increase in x-ray flux observed with the roentgen observatory satellite during a period of 2 days for the hot supergiant zeta Orionis, the only episode of x-ray variability that has been found in a hot star. These observations provide the most direct evidence so far for the scenario of shock-heated gas in the winds of hot stars. 相似文献
14.
褐飞虱在中国东部秋季回迁的雷达观察 总被引：14，自引：0，他引：14
１９８８和１９９０年秋季，在南京市郊江浦县用超高频雷达、气球拖带空中捕虫网及田间笼罩，对褐飞虱秋季回迁进行了研究。江浦县位于中国东部江淮稻区，以种植单季中、晚稻为主（中稻占７０％），随着水稻的灌浆，成熟，褐飞虱长翅型成虫迁出从８月末到９月末逐渐增多。９月中旬，季风转为东北风占优势时，正待迁飞的虫群数量达到高峰，东北风被台风加强时，回迁尤为加快。９月间季风风向的这一转变，对褐飞虱后代的存续是重要的，它保证了迁飞虫群大部分被带到适宜冬春季繁衍的地方。 相似文献
15.
The ocean currents connecting the western tropical Pacific Ocean with the eastern tropical Pacific Ocean are driven by surface winds. The surface winds are in turn driven by the sea-surface temperature (SST) differences between these two regions. This dynamic coupling between the atmosphere and ocean may limit the SST in the tropical Pacific Ocean to below 305 kelvin even in the absence of cloud feedbacks. 相似文献
16.
贾杰 《浙江农林大学学报》2014,31(4):604-610
风倒是形成林隙的主要原因, 是发生频率较高、波及范围较广、造成损失较严重的一种自然灾害。因此, 研究风倒具有重要的理论和实践意义。针对相关理论模型的不足, 利用动力学理论建立了林木风倒的非线性动态模型, 分别从稳定风速作用和阵风作用2个方面对林木的风倒机理进行了研究, 通过严格的数学推导获得了林木发生风倒的判断条件。结果表明:稳定风速和阵风作用下林木发生风倒的条件不同, 且互为补充。基于理论分析, 以西加云杉Picea sitchensis为例进行数值计算, 得到了风倒的标准风速值, 研究结果可以应用到其他树种的风倒问题中。同时, 稳定风速和阵风交错作用下发生风倒的标准风速值与还与风荷载的作用时间有关。研究结果为后续的理论研究和工程应用提供了指导。 相似文献
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Wilkerson JC Brown RA Cardone VJ Coons RE Loomis AA Overland JE Peteherych S Pierson WJ Woiceshyn PM Wurtele MG 《Science (New York, N.Y.)》1979,204(4400):1408-1410
The surface observations used in the initial assessment of Seasat are discussed with emphasis on their ability to describe the synoptic-scale winds over the ocean. 相似文献
19.
Gnanadesikan A 《Science (New York, N.Y.)》1999,283(5410):2077-2079
A simple theory for the large-scale oceanic circulation is developed, relating pycnocline depth, Northern Hemisphere sinking, and low-latitude upwelling to pycnocline diffusivity and Southern Ocean winds and eddies. The results show that Southern Ocean processes help maintain the global ocean structure and that pycnocline diffusion controls low-latitude upwelling. 相似文献
20.
Neptune receives only 1/900th of the earth's solar energy, but has wind speeds of nearly 600 meters per second. How the near-supersonic winds can be maintained has been a puzzle. A plausible mechanism, based on principles of angular momentum and energy conservation in conjunction with deep convection, leads to a regime of uniform angular momentum at low latitudes. In this model, the rapid retrograde winds observed are a manifestation of deep convection, and the high efficiency of the planet's heat engine is intrinsic from the room allowed at low latitudes for reversible processes, the high temperatures at which heat is added to the atmosphere, and the low temperatures at which heat is extracted. 相似文献