首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 440 毫秒
1.
王娜  顾伟宗  邱粲  孟祥新  周放 《高原气象》2021,40(1):159-168
利用山东省气象站的降水量资料和JRA-55、NCEP/NCAR再分析资料,分析了1962-2016年山东夏季整层大气可降水量、降水转化率、水汽通量及输送路径的分布特征和变化规律,探讨了夏季降水与水汽通量及其散度的相关性和多雨年的水汽来源。结果表明:从常年值来看,山东平均夏季降水量为401.2 mm,大气可降水量为3478.8 mm,降水转化率为11.5%。降水转化率和降水量的时空演变特征更加一致,经向水汽输送和局地水汽通量散度与地面有效降水的关系更加密切,当大气可降水量充沛、外部水汽输送充足并出现局地水汽辐合时,更加有利于山东南部地区降水的发生发展,从而形成夏季降水量和降水转化率气候特征表现出东南地区大于西北地区的空间分布型态。西北太平洋、南海、孟加拉湾和鄂霍茨克海至日本海是造成山东夏季降水异常偏多的重要水汽源地,巴尔喀什湖至贝加尔湖地区是重要的冷空气输送区域;当山东上游盛行偏西风时,自新疆和青藏高原至内蒙古的狭长带出现异常水汽扰动并发展,是由水汽异常引起的水汽通量异常对山东局地降水异常贡献的主要条件。  相似文献   

2.
The regions where the divergence of vertically integrated water vapor flux, averaged over a season or a year, is positive (negative) are sources (sinks) of moisture for the atmosphere. An aerial river is defined as a stream of strong water vapor flux connecting a source and a sink. Moisture flux, its divergence, and sources and sinks over the tropics of South and Central America and the adjoining Atlantic Ocean are obtained for dry years and for wet years in the Amazon Basin. Results show that the Amazon Basin is a sink region for atmospheric moisture in all seasons and that there are two source regions for the moisture in the basin, one situated in the South Atlantic and the other in the North Atlantic, both located equator-ward of the respective subtropical high-pressure centers. The convergence of moisture increases over the Amazon Basin in austral summer, and at the same time it decreases in the Pacific and Atlantic ITCZs. Box model calculations reveal that the wet years, on the average, present about 55 % more moisture convergence than the dry years in the Amazon Basin. A reduction in the moisture inflow across the eastern and northern boundaries of the basin (at 45°W and at the Equator, respectively) and an increase in the outflow across the southern boundary (at 15°S) lead to dry conditions. The annual mean contribution of moisture convergence to the precipitation over the Amazon Basin is estimated to be 70 %. In the dry years, it lowers to around 50 %. The net convergence of water vapor flux over the basin is a good indicator of the wet or dry condition.  相似文献   

3.
This paper examines moisture transport on intraseasonal timescales over the continent and over the South Atlantic convergence zone (SACZ) during the South America (SA) summer monsoon. Combined Empirical Orthogonal Function analysis (EOFc) of Global Precipitation Climatology Project pentad precipitation, specific humidity, air temperature, zonal and meridional winds at 850?hPa (NCEP/NCAR reanalysis) are performed to identify the large-scale variability of the South America monsoon system and the SACZ. The first EOFc was used as a large-scale index for the South American monsoon (LISAM), whereas the second EOFc characterized the SACZ. LISAM (SACZ) index showed spectral variance on 30?C90 (15?C20) days and were both band filtered (10?C100?days). Intraseasonal wet anomalies were defined when LISAM and SACZ anomalies were above the 75th percentile of their respective distribution. LISAM and SACZ wet events were examined independently of each other and when they occur simultaneously. LISAM wet events were observed with the amplification of wave activity in the Northern Hemisphere and the enhancement of northwesterly cross-equatorial moisture transport over tropical continental SA. Enhanced SACZ was observed with moisture transport from the extratropics of the Southern Hemisphere. Simultaneous LISAM and SACZ wet events are associated with cross-equatorial moisture transport along with moisture transport from Subtropical Southwestern Atlantic.  相似文献   

4.
Apparent moisture sink and water vapor transport flux are calculated by using NCAR/NCEP reanalyzed daily data for water vapor and wind fields at various levels from 1980 to 1989. With the aid of EOF analysis method, temporal and spatial characteristics of moisture budgets over Asian and Australian monsoon regions are studied. The results show that there is apparent seasonal transition of moisture sink and water vapor transport between Asian monsoon region and Australian monsoon region. In winter, the Asian monsoon region is a moisture source, in which three cross-equatorial water vapor transport channels in the "continent bridge". at 80°E and 40°E ～ 50°E transport water vapor to the Australian monsoon region and southern Indian Ocean which are moisture sinks. In summer, Australian monsoon region and southern Indian Ocean are moisture sources and by the three cross-equatorial transport channels water vapor is transport to the Asian monsoon region which is a moisture sink. In spring and autumn, ITCZ is the main moisture sink and there is no apparent water vapor transport between Asian monsoon region and Australian monsoon region.  相似文献   

5.
利用NCEP/NCAR再分析资料和中科院大气物理研究所PIAP3大气环流模式,分析了印度洋偶极子对夏季中国南海西南季风水汽输送的影响。结果表明,印度洋偶极子正位相期间夏季中国南海西南水汽输送较强,负位相期间则较弱。原因可归结为以下:正位相期间,MJO（Madden-Julian Oscillation）多活动于热带西印度洋,其向东传播受到阻碍,但经向传播明显,通常可传播至孟加拉湾地区,同时PIAP3显示印度洋季风槽位置偏北,且印尼以西过赤道气流较强,从而使得这一地区气旋性环流得到建立与加强。孟加拉湾地区对应着较强的对流活动以及深厚积云对流加热,从而通过对流加热的二级热力响应使西太平洋副热带高压位置向北推进,进而使得南海地区西南季风水汽输送得到建立与加强。在此期间孟加拉湾、中南半岛至南海地区对流活动较强,而苏门答腊沿岸对流活动受到抑制,由此增强了Reverse-Hadley环流,使低层经向风较强,进而增强了南海西南季风的水汽输送,PIAP3大气环流模式证实了Reverse-Hadley环流的增强。负位相期间,MJO多活动于热带东印度洋,在东传过程中受到Walker环流配置影响,在140°E赤道附近形成东西向非对称积云对流加热热源,其东侧Kelvin波响应加强了东风异常并配合副热带高压南缘东风压制了中国南海的西南季风水汽输送。在此期间,MJO在南海地区的经向传播较强,但经向传播常止步于南海地区15°N附近,虽携带大量水汽,但深厚积云对流强烈地消耗水汽使大气中水汽含量降低,PIAP3大气环流模式证实负位相期间深厚积云对流对水汽消耗加大,从而使得负位相期间南海地区水汽含量与正位相期间大体相近,但由于经向风不足使水汽向北输送较弱。  相似文献   

6.
程智  高辉  曹勇 《大气科学》2018,42(6):1363-1377
基于1961~2016年淮河流域172个测站逐日降水资料,分析了淮河夏季降水的多时间尺度变率,发现其具有显著的准两年周期,1990年代以来亦呈现出明显的年代际变化。EOF分析结果显示,淮河夏季降水的异常主要表现为全流域一致偏多或偏少型（第一模态）,其方差贡献高达37%。相比于长江中下游地区,淮河夏季降水与东亚500 hPa位势高度场上的EAP遥相关型关系很弱,但和对流层低层西南水汽输送有更好的对应关系,表现为从索马里半岛至淮河流域的多个正负交替的相关波列。这一波列表明当索马里越赤道气流加强时,通过热带印度洋西风的纽带作用加强了进入淮河流域的西南暖湿气流,并在淮河上空低层形成水汽辐合,造成淮河多雨,反之当索马里越赤道气流强度弱时,淮河夏季降水偏少。索马里越赤道气流和中国台站降水的空间相关同样显示出最显著的相关区位于淮河流域。进一步的分析发现,研究时段内二者关系并非稳定维持,而是表现出显著的年代际变化,近二十年来索马里越赤道气流对淮河流域夏季降水的影响明显增强,且在季节预测上的指示意义也在增强。这一增强的可能原因是索马里越赤道气流与流域南侧的经向水汽输送和西侧的纬向水汽输送的关系均发生了年代际反转,并且这两条水汽输送带对流域夏季降水的影响发生了年代际增强。  相似文献   

7.
The goal of this study is to assess the ability of a set of global climate models (GCMs) to represent the main regional spatial patterns of austral summer moisture transport in South America in order to evaluate if one of the possible causes of GCMs misestimating summer precipitation in this region could be associated with an erroneous representation of these patterns. For this purpose, NCEP/NCAR reanalysis and 20 GCMs from the WCRP/CMIP3 multi-model dataset for the period 1960–1999 were considered. Extreme cases of moisture transport patterns were selected to assess their association with rainfall anomalies. Results obtained indicate that only some aspects of water vapor transport and convergence in South America as well as the associated precipitation anomalies can be reproduced adequately by GCMs. Finally, a case study is presented showing that one of the moisture transport patterns identified was observed during December 2008–February 2009.  相似文献   

8.
The South American Summer Monsoon (SASM) is a prominent feature of summertime climate over South America and has been identified in a number of paleoclimatic records from across the continent, including records based on stable isotopes. The relationship between the stable isotopic composition of precipitation and interannual variations in monsoon strength, however, has received little attention so far. Here we investigate how variations in the intensity of the SASM influence δ18O in precipitation based on both observational data and Atmospheric General Circulation Model (AGCM) simulations. An index of vertical wind shear over the SASM entrance (low level) and exit (upper level) region over the western equatorial Atlantic is used to define interannual variations in summer monsoon strength. This index is closely correlated with variations in deep convection over tropical and subtropical South America during the mature stage of the SASM. Observational data from the International Atomic Energy Agency-Global Network of Isotopes in Precipitation (IAEA-GNIP) and from tropical ice cores show a significant negative association between δ18O and SASM strength over the Amazon basin, SE South America and the central Andes. The more depleted stable isotopic values during intense monsoon seasons are consistent with the so-called ’‘amount effect‘’, often observed in tropical regions. In many locations, however, our results indicate that the moisture transport history and the degree of rainout upstream may be more important factors explaining interannual variations in δ18O. In many locations the stable isotopic composition is closely related to El Niño-Southern Oscillation (ENSO), even though the moisture source is located over the tropical Atlantic and precipitation is the result of the southward expansion and intensification of the SASM during austral summer. ENSO induces significant atmospheric circulation anomalies over tropical South America, which affect both SASM precipitation and δ18O variability. Therefore many regions show a weakened relationship between SASM and δ18O, once the SASM signal is decomposed into its ENSO-, and non-ENSO-related variance.  相似文献   

9.
南半球中纬度偶极模态与亚洲—非洲夏季降水   总被引：1，自引：1，他引：0  
南半球大气环流第一模态为南极涛动, 它表现出较好的纬向对称结构。本工作利用经验正交分解方法研究发现, 在南半球的东半球, 夏季(6~9月)大气环流还存在一个重要的模态。不同于南极涛动, 该模态表现为显著的纬向偶极分布, 本文定义其为偶极模态。在海平面气压场上, 该模态的解释方差可以达到20%以上, 表现出显著的年际变化特征。进一步的研究发现, 该偶极模态与亚非夏季降水存在密切联系, 尤其与我国华南、南亚以及热带非洲东部地区的夏季降水存在显著的正相关关系。机制分析表明, 南半球这一偶极模态的异常会影响东半球越赤道气流的变化, 从而造成向上述三个地区的水汽输送的多寡, 并最终导致这三个地区夏季降水发生变化。本工作揭示的偶极模态变化独立于南极涛动, 研究结果不但可以深化对南半球环流系统变化特征及影响的认识, 而且对亚非夏季降水的变化特征和机制研究也具有重要意义。  相似文献   

10.
We summarize the recent progress in regional climate modeling in South America with the Rossby Centre regional atmospheric climate model (RCA3-E), with emphasis on soil moisture processes. A series of climatological integrations using a continental scale domain nested in reanalysis data were carried out for the initial and mature stages of the South American Monsoon System (SAMS) of 1993–92 and were analyzed on seasonal and monthly timescales. The role of including a spatially varying soil depth, which extends to 8 m in tropical forest, was evaluated against the standard constant soil depth of the model of about 2 m, through two five member ensemble simulations. The influence of the soil depth was relatively weak, with both beneficial and detrimental effects on the simulation of the seasonal mean rainfall. Secondly, two ensembles that differ in their initial state of soil moisture were prepared to study the influence of anomalously dry and wet soil moisture initial conditions on the intraseasonal development of the SAMS. In these simulations the austral winter soil moisture initial condition has a strong influence on wet season rainfall over feed back upon the monsoon, not only over the Amazon region but in subtropical South America as well. Finally, we calculated the soil moisture–precipitation coupling strength through comparing a ten member ensemble forced by the same space–time series of soil moisture fields with an ensemble with interactive soil moisture. Coupling strength is defined as the degree to which the prescribed boundary conditions affect some atmospheric quantity in a climate model, in this context a quantification of the fraction of atmospheric variability that can be ascribed to soil moisture anomalies. La Plata Basin appears as a region where the precipitation is partly controlled by soil moisture, especially in November and January. The continental convective monsoon regions and subtropical South America appears as a region with relatively high coupling strength during the mature phase of monsoon development.  相似文献   

11.
To enable downscaling of seasonal prediction and climate change scenarios, long-term baseline regional climatologies which employ global model forcing are needed for South America. As a first step in this process, this work examines climatological integrations with a regional climate model using a continental scale domain nested in both reanalysis data and multiple realizations of an atmospheric general circulation model (GCM). The analysis presents an evaluation of the nested model simulated large scale circulation, mean annual cycle and interannual variability which is compared against observational estimates and also with the driving GCM for the Northeast, Amazon, Monsoon and Southeast regions of South America. Results indicate that the regional climate model simulates the annual cycle of precipitation well in the Northeast region and Monsoon regions; it exhibits a dry bias during winter (July–September) in the Southeast, and simulates a semi-annual cycle with a dry bias in summer (December–February) in the Amazon region. There is little difference in the annual cycle between the GCM and renalyses driven simulations, however, substantial differences are seen in the interannual variability. Despite the biases in the annual cycle, the regional model captures much of the interannual variability observed in the Northeast, Southeast and Amazon regions. In the Monsoon region, where remote influences are weak, the regional model improves upon the GCM, though neither show substantial predictability. We conclude that in regions where remote influences are strong and the global model performs well it is difficult for the regional model to improve the large scale climatological features, indeed the regional model may degrade the simulation. Where remote forcing is weak and local processes dominate, there is some potential for the regional model to add value. This, however, will require improvments in physical parameterizations for high resolution tropical simulations.  相似文献   

12.
江淮区域持续性暴雨过程的水汽源地和输送特征   总被引：5，自引：0，他引：5  
采用HYSPLIT模式和NCEP/NCAR再分析资料,对中国江淮流域持续性暴雨过程（PHREs）的江南型和江北型过程的水汽源地、输送路径以及干空气路径进行分析。主要结果如下:江南型PHREs的干空气主要通过2条路径进入江淮地区,即源自地中海-欧洲平原的西北路径和来自蒙古高原的东北路径,而江北型PHREs干空气主要有1条路径,即西北路径。干空气是通过对流层中高层的槽脊活动和急流输送至江淮区域。江南型水汽主要由源自印度半岛以南的热带印度洋的西南路径和来自印度尼西亚与中国南海的偏南路径这2条路径输送到江淮流域。江北型的水汽路径有3条,前2条路径与江南型类似,且为主要水汽来源,还有来自西太平洋的东南路径水汽输送。江淮流域的持续性降雨过程中,来自南方的水汽输送主要受索马里越赤道急流、孟加拉湾南部和印度尼西亚群岛附近越赤道气流,以及受西太平洋副热带高压这些系统的影响。   相似文献   

13.
To examine the ability of the Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT) model to detect the origins and paths of moisture supplied to Southeast China, trajectories of air particles released over Southeast China were traced backward during 1 April 2012 to 31 March 2013 and three typical regional persistent heavy rainfall events. The HYSPLIT model provides more insightful information than water vapor flux. Analysis of the specific humidity along the trajectories revealed the origins of moisture and their contributions to the moisture supply in Southeast China. In the boreal summer half year, four key moisture transport paths from the eastern Indian Ocean, central Indian Ocean, South China Sea(SCS), and western North Pacific(WNP) contribute 10%, 20%, 31%, and 16% of the moisture to Southeast China,respectively. In the winter half year, the contributions of the paths from the WNP and North China double. Examination of heavy rainfall events showed that under tropical storm conditions, all moisture transport routines are rotated cyclonically before reaching Southeast China. The invasion of cold air can trigger heavy rainfall in both the summer and winter half years but plays different roles: it does not contribute to the moisture supply but plays a key role in converging and uplifting the moisture in the summer half year, while it supplies a great amount of moisture in the winter half year as it absorbs abundant moisture in crossing the WNP.  相似文献   

14.
定常波和瞬变波在亚洲季风区大气水分循环中的作用   总被引：12，自引：0，他引：12  
伊兰  陶诗言 《气象学报》1997,55(5):532-544
利用欧洲中心ＥＣＭＷＦ１０ａ逐日资料，对定常波和瞬变波在亚洲季风区大气水分循环中的作用进行了计算分析。结果表明，瞬变涡动总把水汽从高水汽含量区送到低水汽含量区，实现与平均环流相反的输送，维持了热带地区和中高纬地区水汽的平衡。夏季定常涡动输送的经向分量是将水汽从热带向副热带输送的主要机制，而瞬变涡动输送的经向分量则是把水汽从副热带输送到中高纬的主要机制。由于季风经圈环流的存在，使得亚洲季风区的热带地区为重要的水汽源区，而其副热带和中纬度地区是水汽汇区，这与同纬度其它地区相反。  相似文献   

15.
利用1979~2015年NCEP/NCAR发布的月平均全球再分析资料,分析了热带印度洋-西太平洋水汽输送异常对中国东部夏季降水的影响及其形成机理。研究结果表明:热带印度洋-西太平洋地区（10°S~30°N,60°~140°E）夏季异常水汽输送主要包括两个模态,他们可以解释总的水汽输送异常34%的方差。其中,第一模态（EOF1）表现为异常水汽沿反气旋从热带西太平洋经过南海及孟加拉湾输送到中国东部上空,对应南海、孟加拉湾水汽路径输送均偏多,此时西太平洋副热带高压显著偏强,异常水汽在长江中下游地区辐合并伴随显著上升运动,有利于长江中下游降水偏多;第二模态（EOF2）表现为异常水汽从热带印度洋沿阿拉伯海、印度半岛、中南半岛等呈反气旋式输送,华南上空相应出现气旋式水汽输送异常,并对应异常水汽辐合和上升运动,有利于华南降水偏多。就可能的外部成因而言,EOF1与ENSO关系密切,表现为前冬热带中东太平洋显著偏暖,夏季同期热带北印度洋、南海上空显著偏暖,造成西太平洋副热带高压显著偏强,异常水汽主要来源于热带西太平洋和南海;EOF2与同期热带印度洋偶极子（TIOD）异常有关,TIOD为正位相时热带印度洋上空出现异常东风,华南上空出现异常气旋并伴随水汽异常辐合,异常水汽主要来源于热带南印度洋。  相似文献   

16.
The objective of this study is to assess the climate projections over South America using the Eta-CPTEC regional model driven by four members of an ensemble of the Met Office Hadley Centre Global Coupled climate model HadCM3. The global model ensemble was run over the twenty-first century according to the SRES A1B emissions scenario, but with each member having a different climate sensitivity. The four members selected to drive the Eta-CPTEC model span the sensitivity range in the global model ensemble. The Eta-CPTEC model nested in these lateral boundary conditions was configured with a 40-km grid size and was run over 1961–1990 to represent baseline climate, and 2011–2100 to simulate possible future changes. Results presented here focus on austral summer and winter climate of 2011–2040, 2041–2070 and 2071–2100 periods, for South America and for three major river basins in Brazil. Projections of changes in upper and low-level circulation and the mean sea level pressure (SLP) fields simulate a pattern of weakening of the tropical circulation and strengthening of the subtropical circulation, marked by intensification at the surface of the Chaco Low and the subtropical highs. Strong warming (4–6°C) of continental South America increases the temperature gradient between continental South America and the South Atlantic. This leads to stronger SLP gradients between continent and oceans, and to changes in moisture transport and rainfall. Large rainfall reductions are simulated in Amazonia and Northeast Brazil (reaching up to 40%), and rainfall increases around the northern coast of Peru and Ecuador and in southeastern South America, reaching up to 30% in northern Argentina. All changes are more intense after 2040. The Precipitation–Evaporation (P–E) difference in the A1B downscaled scenario suggest water deficits and river runoff reductions in the eastern Amazon and S?o Francisco Basin, making these regions susceptible to drier conditions and droughts in the future.  相似文献   

17.
The present study demonstrates that (1) the simulation of the South American warm season (December?CFebruary) climate by an atmospheric general circulation model (AGCM) is sensitive to the representation of land surface processes, (2) the sensitivity is not confined to the ??hot spot?? in Amazonia, and (3) upgrading the representation of those processes can produce a significant improvement in AGCM performance. The reasons for sensitivity and higher success are investigated based on comparisons between observational datasets and simulations by the AGCM coupled to either a simple land scheme that specifies soil moisture availability or to the Simplified Simple Biosphere Model (SSiB) that allows for consideration of soil and vegetation biophysical process. The context for the study is the UCLA AGCM. The most notable simulation improvements are along the lee of the Andes in the lower troposphere, where poleward flow transports abundant moisture from the Amazon basin to high latitudes, and in the monsoon region where the intensity and pattern of precipitation and upper level ice water content are more realistic. It is argued that a better depiction of the Chaco Low, which is controlled by local effects of land surface processes, decisively contributes to the superior model performance with low-level flows in central South America. The better representation of the atmospheric column static stability and large-scale moisture convergence in tropical South America contribute to more realistic precipitation over the monsoon region. The overall simulation improvement is, therefore, due to a combination of different regional processes. This finding is supported by idealized AGCM experiments.  相似文献   

18.
谢坤  任雪娟  张耀存  姚素香 《气象学报》2009,67(6):1002-1012
将区域海气耦合模式RegCM3-POM和区域气候模式RegCM3 40年(1963-2002年)的模拟结果与NCEP/NCAR再分析资料进行对比,检验区域海气耦合模式对中国华北地区夏季大气水汽含量和水汽输送特征的模拟能力,比较耦合模式与单独区域气候模式的差异.结果表明,区域海气耦合模式RegCM3-POM的模拟性能相对于单独区域气候模式RegCM3,大气水汽输送特征的模拟能力有了较大的改进.分析显示两种模式都能够较好地再现东哑地区气候平均夏季大气水汽储量浅红和水汽输送的空间分布特征,而耦合模式对大气水汽输送的模拟更为合理.在对流层中低层更接近观测;耦合模式对中国华北地区夏季平均大气水汽输送通量在垂直方向卜的分布型及水平4个边界水汽输送收支的模拟,相对于单独大气模式有了一定的改进;耦合模式对伴随华北地区夏季早涝的大气水汽异常输送也具有较好的模拟能力,其模拟的水汽输送异常的来源与观测基本一致,尤其是在20°N以北地区,耦合模式结果相对于单独区域气候模式有了很大的改进.但同时耦合模式在低纬度海洋上对气候平均夏季大气水汽含量模拟的偏差比区域气候模式显著;与观测相比,耦合模式对来自孟加拉湾地区的大气水汽输送模拟偏弱,而对西太平洋副热带高压西侧水汽输送模拟偏强,与华北夏季旱涝相联系的水汽输送异常的模拟在低纬度海洋上也存在明显偏差.  相似文献   

19.
Atmospheric moisture transport from the Atlantic to the Pacific basin plays an important role in regulating North Atlantic salinity and thus the strength of the thermohaline circulation. Potential changes in the strength of this moisture transport are investigated for two different climate-change scenarios: North Atlantic cooling representative of Heinrich events, and increased greenhouse gas (GHG) forcing. The effect of North Atlantic cooling is studied using a coupled regional model with comparatively high resolution that successfully simulates Central American gap winds and other important aspects of the region. Cooler North Atlantic sea surface temperature (SST) in this model leads to a regional decrease of atmospheric moisture but also to an increase in wind speed across Central America via an anomalous pressure gradient. The latter effect dominates, resulting in a 0.13 Sv (1 Sv = 106 m3 s?1) increase in overall moisture transport to the Pacific basin. In fresh water forcing simulations with four different general circulation models, the wind speed effect is also present but not strong enough to completely offset the effect of moisture decrease except in one model. The influence of GHG forcing is studied using simulations from the Intergovernmental Panel on Climate Change archive. In these simulations atmospheric moisture increases globally, resulting in an increase of moisture transport by 0.25 Sv from the Atlantic to Pacific. Thus, in both scenarios, moisture transport changes act to stabilize the thermohaline circulation. The notion that the Andes effectively block moisture transport from the Atlantic to the Pacific basin is not supported by the simulations and atmospheric reanalyses examined here. This indicates that such a blocking effect does not exist or else that higher resolution is needed to adequately represent the steep orography of the Andes.  相似文献   

20.
With the objective of providing a relatively accurate and complete diagram,the global scale interbasin transport of atmospheric moisture on the basis of the NCEP/NCAR reanalysis data for the period 1980 to 1994 is evaluated.The results show that the net zonal vapor flux for the Pacific,the Atlantic and the Indian Oceans is 0.25 Sv,-0.68 Sv and-0.29 Sv respectively.The marking differences in the zonal moisture budget among individual basins are speculated as the reason that dominates the differences in the salinity between the Pacific and the Atlantic Oceans.Though current evaluation on the net zonal moisture flux for the Atlantic basin is generally in qualitative agreement with the previous estimate,quantitative discrepancy is found to exist.According to current statistics,the tropical easterlies carry water vapor of 0.43 Sv from the Atlantic basin across Central America into the Pacific,and the northern westerliesal low water vapor of 0.25 Sv to escape from the Pacific.Quantitative analyses also reveal that the seasonal variation of net zonal vapor flux for the Pacific and the Indian Oceans is stronger than that for the Atlantic,which may be favorable for the maintenance of high salinity feature of the Atlantic Ocean.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号