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南大洋淡水强迫对南半球环状模的影响分析 总被引：1，自引：0，他引：1
南半球环状模是南半球热带外大气环流变异的主导模态,对南半球海洋—大气—海冰耦合系统有重要的影响。冰川融化激发的淡水强迫是南大洋的一种重要外强迫。在历史气候记录中,南大洋淡水通量异常曾引发数次全球性气候异常事件。基于海—气完全耦合模式FOAM,在60°S以南的海洋中施加强度为1.0 Sv的理想化淡水通量异常,分析南半球环状模的响应。结果表明：南大洋淡水通量异常可使局地西风增强,且西风的增强在垂向各个层次上均有体现。西风强度的变化导致对流层中大气斜压性增强,平流层中大气斜压性减弱。此外,淡水强迫使环状模的年际变率振幅显著减弱,而年代际变率开始增强,谱能量的变化具有垂向一致性。海温和海冰等外强迫因子的变化对环状模年代际振幅的增强具有重要意义。 相似文献
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There is little doubt that between now and 2050 Earth faces global warming and other changes in climate unprecedented in magnitude since the end of the last glaciation some 10 000 years ago. Predicting the exact nature of that change is, however, difficult. Arguments from palaeoclimatic analogues, comparisons of recent warm versus cool years, physical reasoning and computer simulations are all subject to error and uncertainty. This is more so in the relatively less well understood climate system of the Southern Hemisphere, and at the local and regional scale, than in the Northern Hemisphere and at a zonally averaged scale. Nevertheless some broad features can be described with some confidence, and we can at least identify some of the major uncertainties and processes which we need to understand better.Increased poleward penetration of the subtropical monsoonal regimes is likely, and tropical cyclones may also occur at higher latitudes than at present. The role of the oceans, especially at high southern latitudes and in the tropics, and effects which may change with time as greenhouse gas concentrations gradually increase (transient effects) are particularly important and uncertain in the Southern Hemisphere.We know enough to declare the urgency of slowing down and eventually limiting the greenhouse effect. However, more research is needed to guide decision makers and planners at the local and regional level as they try to cope with those climatic changes which are unavoidable. Regional cooperation is essential to make the best use of the research and planning facilities available. 相似文献
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利用探空、NCEP/NCAR 1°×1°再分析资料、地面气象站观测资料,对新疆塔里木盆地2014年10月28—29日的沙尘暴天气过程前、中、后大气稳定度、混合层厚度、风、温、湿廓线等边界层特征量进行分析。结果表明:此次天气过程为欧洲脊东移,推动西西伯利亚低槽快速进入北疆地区,随后东移翻越东天山进入南疆,造成"东灌"沙尘暴天气;沙尘暴造成边界层特征量表现为K指数减小,沙氏指数增大,理查逊数减小,混合层厚度降低等特征;风向由偏西风转为偏东风,风速则在静风转为30 m/s的偏东急流;温度为沙尘暴之前为贴地逆温,之后大气混合比较均匀,相对湿度为先增加后减小,沙尘暴天气是一个降温增湿的过程,边界层风、温、湿廓线都打破了原有分布规律;沙尘暴过程是大气不稳定层结变为稳定层结的过程。 相似文献
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南支槽影响下西藏高原南部3次暴雪天气特征分析 总被引：2，自引：1，他引：1
利用NCEP/NCAR再分析资料和常规观测资料,对2013年1-2月西藏高原南部3次暴雪天气的环流形势、动力、水汽条件等进行诊断对比分析。结果表明:3次暴雪天气中高纬度均以经向型环流形势为主,从长波槽脊配置可分为长波槽型和横槽型两大类;西太平洋副热带高压偏西偏强、伊朗高压东北发展对南支槽加深和缓慢东移起到关键作用。南支槽区560 dagpm线在30°N以南,并东移至70°E附近或以东时西藏高原南部开始出现暴雪天气;暴雪区附近涡度场变化反映了南支槽强度特征,中高层强辐散对南支槽发展起到重要作用;水汽主要源于阿拉伯海,孟加拉湾水汽对东部降雪起到补充作用,南支槽前高空西南急流对水汽输送起关键作用,同时喜马拉雅山脉的大地形抬升,有利于上升运动和水汽凝结成云;水汽通量、水汽通量散度等变化及中心的移动方向,对降雪的强度、落区和时段具有较好的预报指示意义。 相似文献
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Graeme D. La Cock 《Climatic change》1986,8(2):173-184
Mass mortalities and breeding failures of seabirds in the Pacific Ocean have been directly or indirectly linked to local manifestations of the Southern Oscillation. Similar seabird mortalities have been reported in the Benguela upwelling system along the southern African coast. A Boolean factor analysis of binary data (occurrence vs. non-occurrence) showed that certain worldwide and southern African anomalous climatic events tended to co-occur in the same year, and that seabird mortalities and scarcities of small fish along the southern African coast occurred in either the same year, or the year before, the anomalous climatic events. The environmental conditions leading up to warm-water events in southern Africa appear as detrimental to seabird populations as the warm-water events themselves. 相似文献
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本文基于44年ERA40再分析月平均土壤湿度资料和大气环流变量场资料,去除ENSO遥相关以及趋势影响后,利用滞后最大协方差方法分析非洲南部地区土壤湿度分布与南半球大气环流异常之间的线性耦合。第一最大协方差模态的结果表明:在南半球冬季（Jun-Jul-Aug,6～8月）和夏季（Jan-Feb-Mar,1～3月）,大气中类似南极涛动（Antarctic Oscillation,简称AAO）正位相的环流型与超前月份（最长时间达到5个月）的非洲南部地区土壤湿度的异常分布显著相关。基于土壤湿度变率中心的线性回归分析方法证实非洲南部地区其北部土壤湿度正异常、中南部土壤湿度负异常的空间分布对后期夏季和冬季的大气有显著的反馈作用。诊断结果显示由于夏秋季节和春季初夏非洲南部地区土壤湿度异常均有显著的持续性,同时对后期AAO产生持续增强作用,所以滞后最大协方差方法可以检测出它们对后期AAO的显著影响。以上非洲南部地区土壤湿度异常超前于南极涛动的信号,将有助于加强对土壤湿度反馈机制及其对南半球大尺度环流变率影响的认识。 相似文献
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E.K. Bigg 《Atmospheric Research》1990,25(6)
In a first attempt to assess a proposed climatic change feedback process involving cloud condensation nuclei (CCN) and cloud albedo, CCN concentrations N as a function of supersaturation S were measured on a voyage from latitude 43 to 65°S in October–November 1988. The usual relationship N=CSk, with k=0.5 and C a constant was a fair apprraximation for S in the range 0.3–0.7% implying that CCN concentrations should largely determine cloud drop concentrations and hence albedo for clouds with S in that range. South of latitude 50°S and at smaller S,k was 1 or larger on average, which would lead to reduced dependence of albedo on CCN for the relevant clouds. N varied very widely for separations of the order of 100 km or 6 hours in time, particularly when the sea was partly ice-covered, suggesting strong local influences. During a large increase in N 60°S, unaccompanied by an increase in condensation nuclei (CN), cloud drops grew more rapidly than usual. In a subsidiary experiment particles were collected and examined by transmission electron microscopy. For particles less than 0.2 μm diameter, 80–90% appeared to consist of ammonium sulfate, the remainder being sea salt or an unknown substance which was more liquid and heat-resistant. Dialysis showed that the sulfate particles contained a few percent of insoluble material. Particles which formed cloud drops in vapours other water, were also studied. Comparison of these and water CCN and the rates of droplet suggested that the water insoluble portion of the particles was ethanol-soluble and surface-active. CN concentrations decreased by a factor of about 2 between 43 and 65°S, a change closely paralleled by ethanol CCN concentrations. 相似文献
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A climatology of Southern Hemisphere anticyclones 总被引：1，自引：0，他引：1
A climatology of anticyclones generated by an objective automatic scheme applied to 15 years of once-daily Australian Bureau of Meteorology hemispheric analyses is presented. Contour maps of the anticyclone system density, positions of formation and dissipation together with other statistics are shown. The distribution of anticyclones through the hemisphere was found to be dominated by a mid latitude belt of high density, located in the band 25–42°S, typically 24° south of the time-mean subtropical ridge. Within this band the anticyclone density displays considerable structure with greater system numbers over the eastern parts of the three subtropical ocean basins in the vicinity of the three subtropical ocean time-mean anticyclones. During winter the system density displays a bifurcation in the New Zealand sector, with the highest density along the 30 and 45°S latitude bands. The movement of systems in the subtropical ocean basins was found to be in a general easterly direction with a weak equatorwards component, the transport of systems closely following the orientation of the belt of highest system density. In the vicinity of the African and South American continents, movement was more complex with east-south-east motion upstream, and east-north-east movement downstream, the net transport being such as to encourage a general steering of systems around the continental land masses more particularly during the warmer seasons. To highlight the dynamic role played by these systems and their cyclonic counterparts, we present a limited investigation of the response of Southern Hemisphere synoptic systems to variations of the broader atmospheric system and compare these findings to those obtained by more traditional analysis techniques. 相似文献
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Weather patterns in Southern West Pakistan 总被引：1，自引：0，他引：1
Prof. Rodman E. Snead 《Theoretical and Applied Climatology》1968,16(4):316-346
Summary Southern West Pakistan is an area of transition between the Indian summer monsoon system to the east and the winter cyclonic system of southwest Asia to the west. As a transition area, it receives scanty, unreliable rainfall averaging less than 10 in. (254 mm) per year from several storm types. Six main weather patterns cross the region: the large subtropical anticylonic high pressure cell which predominates most of the year; western depressions originating over the Mediterranean Sea; Arabian Sea cyclones; local thunderstorms and dust storms; a modified monsoon pattern; and eastern depressions originating over the Bay of Bengal or central India. A discussion of the physical and synoptic characteristics for each weather pattern and storm type is presented and summary charts of the weather patterns are included.
With 7 Figures 相似文献
Zusammenfassung Das südliche Westpakistan ist ein Übergangsgebiet zwischen dem indischen Sommermonsunsystem gegen Osten und dem winterlichen Zyklonalsystem von Südwestasien gegen Westen. Als Übergangsgebiet erhält es von einzelnen Stürmen nur geringen und unregelmäßigen Regen, der in der Jahressumme durchschnittlich weniger als 10 inches (254 mm) beträgt. Sechs verschiedene Wettersituationen durchqueren die Gegend: die ausgedehnte subtropische antizyklonale Hochdruckzelle, die während des größten Teils des Jahres vorherrscht; westliche Depressionen aus dem Mittelmeerraum; Zyklonen aus dem Arabischen Meer; lokale Gewitter und Staubstürme; eine modifizierte Monsunlage; sowie östliche Depressionen, die aus dem Golf von Bengalen oder aus Zentralindien stammen. Für jede dieser Wetterlagen und Sturmtypen werden die physikalischen und synoptischen Züge diskutiert und durch summarische Karten der Wettertypen dargestellt.
Résumé Le sud du Pakistan occidental est une région de transition entre le système indou de la mousson d'été à l'est d'une part et le système des cyclones d'hiver de l'asie du sud-ouest à l'ouest d'autre part. Comme zone de transition, cette contrée ne reçoit que des précipitations faibles et irrégulières provenant de quelques ouragans, précipitations qui n'atteignent pas 10 pouces (254 mm) en moyenne annuelle. On distingue six types de temps dans cette région: La cellule anticyclonique subtropicale qui domine durant la plus grande partie de l'année; des dépressions venues de l'ouest, c'est à dire du bassin méditerranéen; des cyclones de la Mer d'Arabie; des orages locaux et des tempêtes de sable; uen situation de mousson modifiée; des dépressions venues de l'est, c'est à dire du Golfe du Bengale ou de l'Inde centrale. On discute pour chacune de ces situations les traits caractéristiques des points de vue physique et synoptique. On les représente en outre au moyen de cartes générales.
With 7 Figures 相似文献
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A climatology of Southern Hemisphere extratropical cyclones 总被引：4，自引：0，他引：4
A climatology of extratropical cyclones determined by an objective automatic scheme applied to 15 years (1975–89) of once-daily Australian Bureau of Meteorology hemispheric analyses is presented. Contour maps of the positions of formation (cyclogenesis), dissipation (cyclolysis) together with other cyclone statistics are presented. The distribution of cyclones through the hemisphere was found to be dominated by a permanent high latitude core coincident with the circumpolar trough. During the winter and intermediate seasons, two mid latitude branches are evident in the cyclone density originating in the Tasman Sea and South American sectors, both spiraling poleward and merging with the circumpolar core in the Southern Oceans. Systems were observed to move in an castsouth-east direction, away from their location of formation, exhibiting peak speeds of migration in the mid latitudes. Little seasonality was evident in the densitiy distribution of cyclones through the Southern Oceans, but a considerable amount was found in their central pressure.
Correspondence to: I Simmonds 相似文献
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我国中部和南部地区降水再循环率评估 总被引：3，自引：1，他引：2
利用1976～1995 年20 年NCEP 再分析资料,对我国中、南部地区降水再循环率进行了评估,发现长江上游总的降雨有20%来自我国中、南部地区水汽蒸发,长江中下游总的降雨则有40%来自这一地区. 降水再循环率有很强的季节变化规律,8、9、10三个月的降水再循环率最高,达四成左右,而5、6、7三个月的降水再循环率不到四分之一.蒸发率和降水再循环率在20年中均有增加的趋势,这可能与气候变暖有关. 相似文献
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A. Downey J. D. Jasper J. J. Gras S. Whittlestone 《Journal of Atmospheric Chemistry》1990,11(1-2):43-68
Radon and particle concentrations obtained at Macquarie Island, halfway between Australia and Antarctica, and on Tasmania's north-west coast at Cape Grim during 1987 are examined. Four-day trajectories based on 12 hourly analyses over the Australian region are used to explore the transport of continental material across the Southern Ocean. This study suggests that at least 25% of the variance of radon concentration at Macquarie Island can be accounted for by transport from the Australian continent. Trajectories at intervals of one hour are used to demonstrate the agreement between episodes of trajectories passing over land and episodes of elevated radon and particle concentration. Wind roses of percentage probability of various levels of radon and particle concentration are compared with back trajectories for their accuracy in depicting episodes of continental air incursion. 相似文献
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1857—1987年南方涛动指数 总被引：12，自引：1，他引：12
本文利用塔希提和达尔文的气压差将美国气候分析中心的SOI序列从1935年向前接补到1857年,并用SOI周期及其与SST的关系进行了检验,证明可以将两段SOI接续起来。 相似文献