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1.
Current Progresses in Study of Impacts of the Tibetan Plateau on Asian Summer Climate 总被引：2，自引：1，他引：2 
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下载免费PDF全文 The current progresses in the study of impacts of the Tibetan Plateau on Asian summer climate in the last decade are reviewed. By analyzing evolution of the transitional zone between westerly to the north and easterly to the south (WEB), it is shown that due to the strong heating over the Tibetan Plateau in spring, the overturning in the prevailing wind direction from easterly in winter to westerly in summer occurs firstly over the eastern Bay of Bengal (BOB), accompanied with vigorous convective precipitation to its east. The area between eastern BOB and western Indo-China Peninsula thus becomes the area with the earliest onset of Asian monsoon, which may be referred as BOB monsoon in short. It is shown that the summertime circulations triggered by the thermal forcing of the Iranian Plateau and the Tibetan Plateau are embedded in phase with the continental-scale circulation forced by the diabatic heating over the Eurasian Continent. As a result, the East Asian summer monsoon is intensified and the drought climate over the western and central Asian areas is enhanced. Together with perturbations triggered by the Tibetan Plateau, the above scenarios and the associated heating have important influences on the climate patterns over Asia. Furthermore, the characteristics of the Tibetan mode of the summertime South Asian high are compared with those of Iranian mode. Results demonstrate that corresponding to each of the bimodality of the South Asian high, the rainfall anomaly distributions over Asia exhibit different patterns. 相似文献
2.
青藏高原影响亚洲夏季气候研究的最新进展 总被引：40，自引：6，他引：40
文中回顾了近 10a来吴国雄等在青藏高原影响亚洲夏季气候研究方面的最新进展。通过分析东西风交界面的演变证明 ,由于青藏高原的春季加热 ,亚洲季风区对流层低层冬季盛行偏东风转变为夏季偏西南风最早发生在孟加拉湾东部 ,与其相伴随的激烈对流降水出现在其东面。因此孟加拉湾东部至中印半岛西部是亚洲季风最早爆发的地区。同时也指出盛夏伊朗高原和青藏高原加热所激发的同相环流嵌套在欧亚大陆尺度的热力环流中 ,从而加强了东亚的夏季风 ,加剧了中西亚的干旱 ;并通过其所激发的波动对夏季东亚的气候格局产生重要影响。文中还比较了夏季南亚高压的伊朗模态和青藏模态性质的异同及其对亚洲夏季降水异常分布的不同影响。 相似文献
3.
青藏高原冬春积雪和地表热源影响亚洲夏季风的研究进展 总被引：2，自引：0，他引：2
青藏高原冬春积雪和地表热源的气候效应是青藏高原气候动力学的两个重要内容。大量资料分析和数值试验研究均表明这两个因子对亚洲季风有一定的预测意义,本文对此做了比较系统的回顾和总结,并进一步比较了青藏高原积雪和地表热源影响东亚和南亚夏季降水的异同。结果表明,东亚夏季降水在年际和年代际尺度上均存在"三极型"和"南北反相"型的空间分布特征,高原春季地表热源在年代际和年际尺度上主要影响东亚夏季降水"三极型"模态;在年代际尺度上它是中国东部出现"南涝北旱"格局的重要原因,而高原冬季积雪的作用相反。另一方面,高原冬季积雪在年际和年代际尺度上对印度夏季风降水的预测效果均要优于高原地表热源。无论是空间分布还是时间演变特征,高原冬季积雪与春季地表热源整体上均无统计意义上的显著联系。不断完善高原地面观测网和改进模式在高原地区的模拟性能,将是进一步深入理解高原积雪和地表热源影响亚洲季风物理过程和机制的关键所在。 相似文献
4.
资料分析显示,与850 hPa风场相比,地面风的变化能更好地表征亚洲各季风系统的特征。基于地面风的季节性反转和降水的显著变化所构建的亚洲夏季风(ASM)爆发指数和等时线图表明:亚洲热带夏季风(TASM)在5月初首先在孟加拉湾(BOB)东南部爆发后不是向西传播,而是向东经中印半岛向东推进,于5月中到达中国南海(SCS),6月初到达热带西北太平洋。印度夏季风的表面低压系统源于近赤道阿拉伯海地区,于6月初到达印度西南部喀拉拉邦,印度夏季风随之爆发。亚洲副热带夏季风(STASM)5月初在西北太平洋日本本州东南的海区发生后向西南伸展,于6月初与南海季风降水区连接,形成东北—西南向雨带,夏季风在中国东南沿海登陆,日本的“梅雨”(Baiu)开始。6月中该雨带向北到达长江流域和韩国,江淮梅雨和韩国的“梅雨”(Changma) 开始。本文还回顾了亚洲热带夏季风爆发的动力学研究的若干近期进展。春季青藏高原和南亚海陆分布的联合强迫作用使海表温度(SST)在BOB中东部形成短暂但强盛的暖池,在高层南亚高压的抽吸作用下,常伴有季风爆发涡旋(MOV)发展,使冬季连续带状的副高脊线在孟加拉湾东部断裂,导致亚洲热带季风首先在BOB爆发。BOB东/西部有东/西风型垂直切变,利于激发/抑制对流活动,并增加/减少海洋向大气的表面感热加热,从而使得亚洲夏季风爆发的向西传播在BOB西海岸遇到屏障。季风爆发逐渐向东伸展引发南海和热带西太平洋夏季风相继爆发。季风降水释放的强大潜热使南亚高压发展西伸,纬向非对称位涡强迫显著增强;在阿拉伯半岛强烈的表面感热加热所诱发的中层阿拉伯反气旋的共同作用下,位于阿拉伯海近赤道的低压系统北移发展成为季风爆发涡旋,导致印度季风爆发。由此可见,历时约一个月的亚洲热带夏季风爆发的三个阶段(孟加拉湾、南海和印度季风爆发)是发生在特定的地理环境下受特定的动力—热力学规律驱动的接续过程。 相似文献
5.
通过对青藏高原多、少雪年的合成分析及数值试验，研究了青藏高原积雪对亚洲 夏季风和我国东部气候异常的影响。结果表明:青藏高原积雪造成亚洲大气环流较大的年际变化。高原积雪改变了高原陆面春、夏季的热状况，使亚洲夏季风爆发推迟20天左右。高原积雪通过以下物理过程影响亚洲夏季风和我国东部气候:高原积雪多(少)→高原春、夏季的感热弱(强)→感热加热引起的上升运动弱(强)，高原强(弱)环境风场→不利(有利)于高原感热通量向上输送→高原上空对流层加热弱(强)→高原对流层温度低(高)→高原南侧温度对比弱(强)→造成亚洲夏季风弱(强)→我国长江流域易涝(旱)。 相似文献
6.
青藏高原积雪与亚洲季风环流年代际变化的关系 总被引：12，自引：1，他引：12
利用高原测站的月平均雪深资料和NCEP／NCAR再分析资料，分析了20世纪70年代末以来，青藏高原积雪的显著增多与亚洲季风环流转变的联系。研究表明，高原南侧冬春季西风的增强及西风扰动的活跃是造成青藏高原冬春积雪显著增多的主要原因，高原积雪的增多与亚洲夏季风的减弱均是亚洲季风环流转变的结果；20世纪70年代末以来，夏季华东降水的增多、华南降水的减少及华北的干旱化与青藏高原冬春积雪增多及东亚夏季风的减弱是基本同步的，高原冬春积雪与华东夏季降水的正相关、与华北及华南夏季降水的负相关主要是建立在年代际时间尺度上，因此，高原积雪与我国夏季降水关系的研究应以亚洲季风环流的年代际变化为背景。 相似文献
7.
青藏高原的热力和动力作用对亚洲季风区环流的影响 总被引：22，自引：1，他引：21
利用NCEP/NCAR再分析资料,研究了青藏高原热状况的季节变化、动力和热力作用对周围环流,特别是对亚洲热带季风环流的影响。高原对西风带的机械作用在冬季最强,春季次之。冬季的机械作用形成以高原为主,南侧气旋性、北侧反气旋性的"偶极子"偏差环流,它比传统认识的爬坡、绕流的影响范围大得多,遍及东亚的高、低纬度。随着西风带的北移和高原总加热在4月由负变正,南侧气旋性偏差环流增强并逐渐北移,6月形成气旋盘踞整个高原的夏季型。在高原南侧,高原冬季偶极型、夏季加热的作用导致孟加拉湾地区常年存在印缅槽,使得印度半岛的感热加热始终强于中南半岛,而中南半岛上空的潜热加热大于印度半岛。印缅槽的演变存在明显的半年周期,证明2月初和8月初的较强低压槽分别对应冬季高原最强的动力强迫和夏季高原最强的热力强迫。对低纬经向风场的分析还表明,季风爆发前高原的热力作用尤为重要,是导致江南春雨的形成,亚洲季风最早在孟加拉湾东部爆发,最后在印度半岛爆发的原因。 相似文献
8.
青藏高原大气热源和冬春积雪与中国东部降水的年代际变化关系 总被引：25，自引：0，他引：25
利用NCEP 1950—2004年逐日再分析资料,采用倒算法,对青藏高原大气热源的长期变化进行了计算,结果发现,青藏高原及附近地区上空大气春夏季热源在过去50年里,尤其是最近20年,表现为持续减弱的趋势。而1960—2004年青藏高原50站的冬春雪深却出现了增加,尤其是春季雪深在1977年出现了由少到多的突变。用SVD方法对高原积雪和高原大气热源关系的分析表明,二者存在非常显著的反相关关系,即高原冬春积雪偏多,高原大气春夏季热源偏弱。高原大气春夏季热源和中国160站降水的SVD分析表明,高原大气春夏季热源和夏季长江中下游降水呈反相关,与华南和华北降水呈正相关;而高原冬春积雪和中国160站降水的SVD分析显示,高原冬春积雪和夏季长江流域降水呈显著正相关,与华南和华北降水呈反相关。在年代际尺度上,青藏高原大气热源和冬春积雪与中国东部降水型的年代际变化(南涝北旱)有很好的相关。最后讨论了青藏高原大气热源影响中国东部降水的机制。青藏高原春夏季热源减弱,使得海陆热力差异减小,致使东亚夏季风强度减弱,输送到华北的水汽减少,而到达长江流域的水汽却增加;同时,高原热源减弱,使得副热带高压偏西,夏季雨带在长江流域维持更长时间。导致近20年来长江流域降水偏多,华北偏少,形成"南涝北旱"雨型。高原冬春积雪的增加,降低了地表温度,减弱了地面热源,并进而使得青藏高原及附近地区大气热源减弱。 相似文献
9.
The evident effects of the thermal anomalies over the Tibetan Plateau (TP) and its vicinities are summarized and discussed in this paper. By the singular value decomposition (SVD) technique and numerical simulations of the effect of the snow depth anomaly over the TP, it is shown that the snow depth anomaly, especially in winter, is one of the factors influencing precipitation in China, and the winter snow anomaly is more important than the spring one. The relations between the sensible heat anomaly over the TP and the intensity of the South China Sea summer monsoon (SCSSM) are studied, too, and two key areas of the sensible heat anomaly over the TP are found. The relationships between the South Asia High (SAH). and the precipitation in the years with typical droughts or floods in the mid to lower valleys of the Yangtze River (MLVYR) and North China are investigated in some detail. It is found that not only the intensity of the SAH over the TP, but also the 100-hPa height in a large area influences the precipitation in the above two regions. The effects of the SAH on the onsets of the tropical Asian summer monsoon (TASM) including the SCSSM and the tropical Indian summer monsoon (TISM) are studied as well. It is found that the onset times of both the SCSSM and the TISM are highly dependent upon the latitudinal position of the SAH center. 相似文献
10.
青藏高原冬春季积雪异常对中国春夏季降水的影响 总被引：27，自引：3，他引：27
利用1956年12月～1998年12月共42a，青藏高原及其附近地区78个积雪观测站的雪深和我国160站月降水的距平资料，分析了其气候特征，并用SVD方法分析了冬春季积雪异常与春夏季我国降水异常的关系。用区域气候模式RegCM2模拟了青藏高原积雪异常的气候效应并检验了诊断分析的结果。分析表明，雪深异常，尤其是冬季雪深异常是影响中国降水的一个因子。研究证明，高原冬季雪深异常对后期中国区域降水的影响比春季雪深异常的影响更为重要。数值模拟的结果表明，高原雪深和雪盖的正异常推迟了东亚夏季风的爆发日期，减弱了季风强度，造成华南和华北降水减少，而长江和淮河流域降水增加。冬季雪深异常比冬季雪盖异常和春季雪深异常对降水的影响更为显著。机理分析指出，高原及其邻近地区的积雪异常首先通过融雪改变土壤湿度和地表温度，从而改变了地面到大气的热量、水汽和辐射通量。由此所引起的大气环流变化又反过来影响下垫面的特征和通量输送。在湿土壤和大气之间，这样一种长时间的相互作用是造成后期气候变化的关键过程。与干土壤和大气的相互作用过程有本质差别。 相似文献
11.
Factors favorable to frequent extreme precipitation in the upper Yangtze River Valley 总被引：1，自引：0，他引：1
Extreme precipitation events in the upper Yangtze River Valley (YRV) have recently become an increasingly important focus in China because they often cause droughts and floods. Unfortunately, little is known about the climate processes responsible for these events. This paper investigates factors favorable to frequent extreme precipitation events in the upper YRV. Our results reveal that a weakened South China Sea summer monsoon trough, intensified Eurasian-Pacific blocking highs, an intensified South Asian High, a southward subtropical westerly jet and an intensified Western North Pacific Subtropical High (WNPSH) increase atmospheric instability and enhance the convergence of moisture over the upper YRV, which result in more extreme precipitation events. The snow depth over the eastern Tibetan Plateau (TP) in winter and sea surface temperature anomalies (SSTAs) over three key regions in summer are important external forcing factors in the atmospheric circulation anomalies. Deep snow on the Tibetan Plateau in winter can weaken the subsequent East Asian summer monsoon circulation above by increasing the soil moisture content in summer and weakening the land–sea thermal contrast over East Asia. The positive SSTA in the western North Pacific may affect southwestward extension of the WNPSH and the blocking high over northeastern Asia by arousing the East Asian-Pacific pattern. The positive SSTA in the North Atlantic can affect extreme precipitation event frequency in the upper YRV via a wave train pattern along the westerly jet between the North Atlantic and East Asia. A tripolar pattern from west to east over the Indian Ocean can strengthen moisture transport by enhancing Somali cross-equatorial flow. 相似文献
12.
Interannual variability in the onset of the summer monsoon over the Eastern Bay of Bengal 总被引：3，自引：0，他引：3
Summary Climatological characteristics associated with summer monsoon onset over the eastern Bay of Bengal (BOB) are examined in terms
of the westerly-easterly boundary surface (WEB). The vertical tilt of the WEB depends on the horizontal meridional temperature
gradient (MTG) near the WEB, under the constraint of the thermal wind balance. The switch in the WEB tilt firstly occurs between
90 and 100°E during the first pentad of May. At this time the 850 hPa ridgeline splits over the BOB and heavy rainfall commences
over the eastern BOB, indicating the onset of the BOB summer monsoon (BOBSM). The area-averaged MTG (200–500 hPa) is proposed
as an index to define the BOBSM onset. A comparison of the onset determined by the MTG, 850 hPa zonal wind, and outgoing longwave
radiation (OLR) shows that the MTG index is the most effective in characterizing the interannual variability of the BOBSM
onset.
Strong precursor signals are found prior to an anomalous BOBSM onset. Composite results show that early (late) BOBSM onset
follows excessive (deficient) rainfall over the western Pacific and anomalous lower tropospheric cyclonic circulation which
extends zonally from the northern Indian Ocean into the western Pacific, and strong (weak) equatorial westerly anomalies in
the preceding winter and spring. Prior to an early (late) BOBSM onset, significant positive (negative) thickness anomalies
exist around the Tibetan Plateau, accompanied by anomalous upper tropospheric anticyclonic (cyclonic) circulation. The interannual
variations of the BOBSM onset are significantly correlated with anomalous sea surface temperature related to ENSO. These occurs
through changes in the Walker circulation and local Hadley circulation, leading to middle and upper tropospheric temperature
anomalies over the Asian sector. The strong precursor signals around the Tibetan Plateau may be partly caused by local snow
cover anomalies, and an early (late) BOBSM onset is preceded by less (more) snow accumulation over the Tibetan Plateau during
the preceding winter. 相似文献
13.
In spring over the southern Bay of Bengal (BOB), a vortex commonly develops, followed by the Asian summer monsoon onset. An analysis of relevant data and a case study reveals that the BOB monsoon onset vortex is formed as a consequence of air–sea interaction over BOB, which is modulated by Tibetan Plateau forcing and the land–sea thermal contrast over the South Asian area during the spring season. Tibetan Plateau forcing in spring generates a prevailing cold northwesterly over India in the lower troposphere. Strong surface sensible heating is then released, forming a prominent surface cyclone with a strong southwesterly along the coastal ocean in northwestern BOB. This southwesterly induces a local offshore current and upwelling, resulting in cold sea surface temperatures (SSTs). The southwesterly, together with the near-equatorial westerly, also results in a surface anticyclone with descending air over most of BOB and a cyclone with ascending air over the southern part of BOB. In the eastern part of central BOB, where sky is clear, surface wind is weak, and ocean mixed layer is shallow, intense solar radiation and low energy loss due to weak surface latent and sensible heat fluxes act onto a thin ocean layer, resulting in the development of a unique BOB warm pool in spring. Near the surface, water vapor is transferred from northern BOB and other regions to southeastern BOB, where surface sensible heating is relatively high. The atmospheric available potential energy is generated and converted to kinetic energy, thereby resulting in vortex formation. The vortex then intensifies and moves northward, where SST is higher and surface sensible heating is stronger. Meanwhile, the zonal-mean kinetic energy is converted to eddy kinetic energy in the area east of the vortex, and the vortex turns eastward. Eventually, southwesterly sweeps over eastern BOB and merges with the subtropical westerly, leading to the onset of the Asian summer monsoon. 相似文献
14.
Xingwen Jiang Yueqing Li Song Yang Guangbi He 《Theoretical and Applied Climatology》2014,117(3-4):565-577
The variability of climate in the lee side of the Tibetan Plateau (TP) often exhibits unique features. In this study, the authors investigate the variations of early autumn rainfall in the lee side of the TP (LSTP). The rainfall amount and number of rain days in LSTP increase from August to September. The center of heavy and torrential rains during September is located in LSTP as well. These unique features are attributed to later withdrawal of the East Asian summer monsoon in the middle and higher troposphere compared to the lower troposphere and stronger South Asian summer monsoon and thermal forcing of the TP. The September rainfall in LSTP experienced strong interdecadal fluctuation, with overall below normal rainfall from mid-1980s to late 2000s, while there was no apparent long-term trend in the August and October rainfall amount. The above normal September rainfall is associated with an anomalous anticyclone over the western North Pacific, a weaker-than-normal ridge around the Lake Baikal, a stronger-than-normal East Asian jet stream, and warmer air over the southeastern TP. The interdecadal decrease in rainfall in September may be caused by the central equatorial Pacific warming, which induces an anomalous cyclone over the western North Pacific. The September anomalous cyclone is stronger and more westward compared to that in August and October, and thus favors the below normal rainfall in LSTP. 相似文献
15.
A Possible Impact of Cooling over the Tibetan Plateau on the Mid-Holocene East Asian Monsoon Climate 总被引：5，自引：3，他引：5
By using a 9-level global atmospheric general circulation model developed at the Institute of Atmospheric Physics (IAP9L-AGCM) under the Chinese Academy of Sciences, the authors investigated the response of the East Asian monsoon climate to changes both in orbital forcing and the snow and glaciers over the Tibetan Plateau at the mid-Holocene, about 6000 calendar years before the present (6 kyr BP). With the Earth’s orbital parameters appropriate for the mid-Holocene, the IAP9L-AGCM computed warmer and wetter conditions in boreal summer than for the present day. Under the precondition of continental snow and glacier cover existing over part of the Tibetan Plateau at the mid-Holocene, the authors examined the regional climate response to the Tibetan Plateau cooling. The simulations indicated that climate changes in South Asia and parts of central Asia as well as in East Asia are sensitive to the Tibetan Plateau cooling at the mid-Holocene, showing a significant decrease in precipitation in northern India, northern China and southern Mongolia and an increase in Southeast Asia during boreal summer. The latter seems to correspond to the weakening, southeastward shift of the Asian summer monsoon system resulting from reduced heat contrast between the Eurasian continent and the Pacific and Indian Oceans when a cooling over the Tibetan Plateau was imposed. The simulation results suggest that the snow and glacier environment over the Tibetan Plateau is an important factor for mid-Holocene climate change in the areas highly influenced by the Asian monsoon. 相似文献
16.
青藏高原的热力和机械强迫作用以及亚洲季风的爆发I. 爆发地点 总被引：68，自引：8，他引：60
使用欧洲中期天气预报中心（ECMWF）的客观分析资料、ECMWF/TOGA补充数据集,美国NMC气候分析中心的向外长波辐射（OLR）资料以及国家气候中心存档的中国336个测站的降水资料,研究了1989年春天青藏高原和邻近地区的热力特征和环流特征,及其对亚洲季风区季节转换的影响。文中集中分析了表面感热和潜热通量的时空分布特征。结果表明:1989年亚洲季风的爆发由三个接续的阶段组成。第一阶段是5月上旬在孟加拉湾东岸,称为孟加拉（BOB）季风爆发阶段。第二阶段是5月20日左右开始的中国南海（SCS）季风爆发阶段。第三阶段是6月10日左右开始的印度上空的南亚季风（或称印度季风）的爆发阶段。分析表明,正是由于青藏高原的热力和机械强迫作用才使亚洲季风首先在孟加拉湾地区出现。BOB季风环流提供了有利的背景条件,使SCS季风接着爆发。最后随着亚洲热带流型的西移,印度季风爆发才发生。 相似文献
17.
Decadal Relationship Between Atmospheric Heat Source and Winter-Spring Snow Cover over the Tibetan Plateau and Rainfall in East China 下载免费PDF全文
下载免费PDF全文 By using a reverse computation method and the NCEP/NCAR daily reanalysis data from 1960 to 2004, the atmospheric heat source （AHS） was calculated and analyzed. The results show that AHS over the Tibetan Plateau （TP） and its neighboring areas takes on a persistent downtrend in spring and summer during the foregone 50 years, especially the latest 20 years. Snow depth at 50 stations over the TP in winter and spring presents an increase, especially the spring snow depth exhibits a sharp increase in the late 1970s. A close negative correlation exists between snow cover and AHS over the TP and its neighboring areas, as revealed by an SVD analysis, namely if there is more snow over the TP in winter and spring, then the weaker AHS would appear over the TP in spring and summer. The SVD analysis between AHS over the TP in spring and summer and rainfall at 160 stations indicates that the former has a negative correlation with summer precipitation in the middle and lower reaches of the Yangtze River, and a positive correlation with that in South China and North China. The SVD analysis of both snow cover over the TP in winter and spring and rainfall at the same 160 stations indicates that the former has a marked positive correlation with precipitation in the middle and lower reaches of the Yangtze River, and a reversed correlation in South China and North China. On the decadal scale, the AHS and winter and spring snow cover over the TP have a close correlation with the decadal precipitation pattern shift （southern flood and northern drought） in East China. The mechanism on how the AHS over the TP influences rainfall in East China is discussed. The weakening of AHS over the TP in spring and summer reduces the thermodynamic difference between ocean and continent, leading to a weaker East Asian summer monsoon, which brings more water vapor to the Yangtze River Valley and less water vapor to North China. Meanwhile, the weakening of AHS over the TP renders the position of the subtropical high further westward and the r 相似文献
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19.
Using idealized snow forcing to test teleconnections with the Indian summer monsoon in the Hadley Centre GCM 总被引：2，自引：1，他引：1
Anomalous heavy snow during winter or spring has long been regarded as a possible precursor of deficient Indian monsoon rainfall during the subsequent summer. However previous work in this field is inconclusive, in terms of the mechanism that communicates snow anomalies to the monsoon summer, and even the region from which snow has the most impact. In this study we explore these issues in coupled and atmosphere-only versions of the Hadley Centre model. A 1050-year control integration of the HadCM3 coupled model, which well represents the seasonal cycle of snow cover over the Eurasian continent, is analysed and shows evidence for weakened monsoons being preceded by strong snow forcing (in the absence of ENSO) over either the Himalaya/Tibetan Plateau or north/west Eurasia regions. However, empirical orthogonal function (EOF) analysis of springtime interannual variability in snow depth shows the leading mode to have opposite signs between these two regions, suggesting that competing mechanisms may be possible. To determine the dominant region, ensemble integrations are carried out using HadAM3, the atmospheric component of HadCM3, and a variety of anomalous snow forcing initial conditions obtained from the control integration of the coupled model. Forcings are applied during spring in separate experiments over the Himalaya/Tibetan Plateau and north/west Eurasia regions, in conjunction with climatological SSTs in order to avoid the direct effects of ENSO. With the aid of idealized forcing conditions in sensitivity tests, we demonstrate that forcing from the Himalaya region is dominant in this model via a Blanford-type mechanism involving reduced surface sensible heat and longwave fluxes, reduced heating of the troposphere over the Tibetan Plateau and consequently a reduced meridional tropospheric temperature gradient which weakens the monsoon during early summer. Snow albedo is shown to be key to the mechanism, explaining around 50% of the perturbation in sensible heating over the Tibetan Plateau, and accounting for the majority of cooling through the troposphere. 相似文献
20.
通过数值模拟,研究了青藏高原位于不同经度位置时,亚洲夏季风的爆发和演变情况,从动力和热力学角度分析了青藏高原大地形对亚洲夏季风爆发位置的影响。结果表明,青藏高原的“热力滑轮”作用引起:高原东南面热带陆地上空的偏南气流加强,降水增加,凝结潜热加强;高原西南面热带陆地上空出现偏北气流,降水减弱,陆面的感热加热加强。青藏高原对于亚洲夏季风的爆发地点有锚定的作用,在热带海陆分布的背景下,使亚洲夏季风首先在高原东南面的海洋东岸—陆地西岸爆发,并使亚洲季风降水重新分布。 相似文献