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1.
The 1999 East Asian summer monsoon was very unusual for its weak northward advance and remarkably anomalous climate conditions. The monsoonal southwesterly airflow and related rain belt in East Asia were blocked south of the Yangtze River Valley. The monsoonal airflow and major moisture transport conduct shifted eastward and turned northward to Japan from the tropical western Pacific rather than to East China from the South China Sea （SCS） as in normal years. Severe and prolonged drought occurred over extensive areas of North China and heavy precipitation in South China and Japan. The investigation on the possible intrinsic mechanisms related to such an anomalous monsoon year has shown that the unique behavior of intraseasonal oscillation may play an essential role during this process. During this year, the northward propagation of 30-60-day anomalous low-level cyclone/anticyclone collapsed in the region around 20°N and did not extend beyond the latitudes of the Yangtze River basin due to the barrier of strong cold air intrusion from the mid-latitudes. The southwesterly moisture flux on the northwestern flank of the anticyclonic moisture transport system in the western North Pacific, which was regulated by the northward shift of 30-60-day cyclonic/anticyclonic moisture transport, also did not reach the region north of 30°N as well. Under this circumstance, the weak northward advance of the monsoon westerlies and associated northward moisture transport could not arrive in North China and led to the severe droughts there in 1999. The SCS and South China were mostly affected by the airflow in the southern and northern flanks of the same 30-60-day cyclones or anticyclones, respectively, and thus controlled by the nearly reverse zonal wind and moisture convergent/divergent conditions. The rainfall in the SCS and South China showed out-of-phase oscillation through the transient local Hadley circulation, with the rainfall maximum occurring in the SCS （South China） when the 30-60-day anticyclone （cyclone） r  相似文献   

2.
The interannual variability of autumn precipitation over South China and its relationship with atmospheric circulation and SST anomalies are examined using the autumn precipitation data of 160 stations in China and the NCEP-NCAR reanalysis dataset from 1951 to 2004. Results indicate a strong interannual variability of autumn precipitation over South China and its positive correlation with the autumn western Pacific subtropical high （WPSH）. In the flood years, the WPSH ridge line lies over the south of South China and the strengthened ridge over North Asia triggers cold air to move southward. Furthermore, there exists a significantly anomalous updraft and cyclone with the northward stream strengthened at 850 hPa and a positive anomaly center of meridional moisture transport strengthening the northward warm and humid water transport over South China. These display the reverse feature in drought years. The autumn precipitation interannual variability over South China correlates positively with SST in the western Pacific and North Pacific, whereas a negative correlation occurs in the South Indian Ocean in July. The time of the strongest lag-correlation coefficients between SST and autumn precipitation over South China is about two months, implying that the SST of the three ocean areas in July might be one of the predictors for autumn precipitation interannual variability over South China. Discussion about the linkage among July SSTs in the western Pacific, the autumn WPSH and autumn precipitation over South China suggests that SST anomalies might contribute to autumn precipitation through its close relation to the autumn WPSH.  相似文献   

3.
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   

4.
近50年来中国夏季降水及水汽输送特征研究   总被引：15，自引：3，他引：12  
利用1951-2006年中国448站夏季降水资料、NCEP/NCAR VersionⅠ的再分析资料,研究了近50年来中国夏季降水年代际变化特征及其分区,并从季风性水汽输送的变化角度出发,讨论了影响中国一些主要地区降水变化的可能机制.研究发现:(1)从总体上来说,自1951年至今,中国夏季降水存在3个突变时段,即1956-1960年,1980年前后以及1993年以后.且90°E以东突变后的主要变化特征都是多雨区由北向南传播,而90°E以西则是多雨区由南向北传播;2)近56年来就110°E以东的中国东部夏季降水而言,1980年以后多雨区由华北南移到长江中下游,又于1993年以后由长江中下游继续南移至华南;3)中国东部各地区降水和850 hpa风场、整层水汽输送场的相关分布一致表明,中国110°E以东各降水区以南为来自偏东偏南的季风性异常水汽输送,而以北为来自偏北风和相应的异常水汽输送,两者在降水区汇合造成风和水汽输送异常辐合.因而,西太平洋副热带高压南侧的东南季风及其异常水汽输送、北方冷槽的偏北风及其异常水汽输送是中国东部夏季降水异常的主要成员,这和一般认为的这些地区降水异常来自孟加拉湾的季风性异常水汽输送的观点不同,需要作进一步研究.总之,对于中国东部旱涝的形成,应该重点注意来自西北太平洋副热带高压西侧的直接或间接经南海到达的异常四南季风性水汽输送.  相似文献   

5.
孙畅  王子谦  杨崧 《大气科学》2019,43(2):350-360
基于全球降水气候中心（GPCC）和全球降水气候计划（GPCP）的降水数据及ERA-interim再分析资料,分析了1979~2012年冬季青藏高原（简称高原）西侧地区降水的基本特征及影响其年际变率的潜在因子。结果表明高原冬季降水主要发生在其西侧地区且为全区变化一致型,降水所需的水汽主要来自上游地区,从该区域的西边界输入。然而,高原西侧地区冬季降水的年际变率主要由水汽输送的动力过程所决定,表现为高原西侧的西南风异常。此外,高原西侧冬季降水的年际变率与其上游典型的大气内部变率北大西洋涛动和北极涛动相关性不强,而与赤道西印度洋和热带中东太平洋的海温显著相关。热带中东太平洋海温异常通过影响大气环流变化,在印度洋北部激发一个反气旋式的环流异常,使得高原西侧地区出现异常西南风,从而加强了水汽通量输送的动力作用。同时在赤道异常东风的作用下,暖水也向印度洋西部输送堆积。赤道中东太平洋海温的异常可进一步导致西风急流发生南北移动,从而也在一定程度上影响了高原西侧冬季水汽输送以及降水的年际变率。  相似文献   

6.
In this study, the Weather Research and Forecasting (WRF) model and meteorological observation data were used to research the long-distance moisture transport supply source of the extreme rainfall event that occurred on July 21, 2012 in Beijing. Recording a maximum rainfall amount of 460 mm in 24 h, this rainstorm event had two dominant moisture transport channels. In the early stage of the rainstorm, the first channel comprised southwesterly monsoonal moisture from the Bay of Bengal (BOB) that was directly transported to north China along the eastern edge of Tibetan Plateau (TP) by orographic uplift. During the rainstorm, the southwesterly moisture transport was weakened by the transfer of Typhoon Vicente. Moreover, the southeasterly moisture transport between the typhoon and western Pacific subtropical high (WPSH) became another dominant moisture transport channel. The moisture in the lower troposphere was mainly associated with the southeasterly moisture transport from the South China Sea and the East China Sea, and the moisture in the middle troposphere was mainly transported from the BOB and Indian Ocean. The control experiment well reproduced the distribution and intensity of rainfall and moisture transport. By comparing the control and three sensitivity experiments, we found that the moisture transported from Typhoon Vicente and a tropical cyclone in the BOB both significantly affected this extreme rainfall event. After Typhoon Vicente was removed in a sensitivity experiment, the maximum 24-h accumulated rainfall in north China was reduced by approximately 50% compared with that of the control experiment, while the rainfall after removing the tropical cyclone was reduced by 30%. When both the typhoon and tropical cyclone were removed, the southwesterly moisture transport was enhanced. Moreover, the sensitivity experiment of removing Typhoon Vicente also weakened the tropical cyclone in the BOB. Thus, the moisture pump driven by Typhoon Vicente played an important role in maintaining and strengthening the tropical cyclone in the BOB through its westerly airflow. Typhoon Vicente was not only the moisture transfer source for the southwesterly monsoonal moisture but also affected the tropical cyclone in the BOB, which was a key supply source of long-distance moisture transport for the extreme rainfall event on July 21, 2012 in Beijing.  相似文献   

7.
本文利用观测和再分析资料,通过奇异值分解(Singular Value Decomposition, SVD)分析,发现北极涛动(Arctic Oscillation, AO)是显著影响中国夏季降水年际异常的前冬中高纬大气环流变异的主模态。AO在冬季发展成熟,在春季衰亡,在夏季发生位相反转。AO会导致华北、东北、长江中下游和华南夏季降水异常呈现三极型分布。伴随正位相的AO,在黄海至日本海上空的异常低压伴随的东北风异常引起华北和东北水汽通量异常辐散及降水减少,而西北太平洋的异常高压不仅增强其北侧的西南风水汽输送,和北部异常低压共同作用导致长江中下游水汽通量异常辐合及降水增加,而且使得华南水汽通量异常辐散,降水减少。因此,本文发现的前冬AO模态与我国夏季三极型异常降水分布的关系可为我国夏季旱涝预测提供一个重要的中高纬前期因子。  相似文献   

8.
Based on observational precipitation at 63 stations in South China and NCEP NCAR reanalysis data during 1951 2010,a cluster analysis is performed to classify large-scale circulation patterns responsible for persistent precipitation extremes(PPEs) that are independent of the influence of tropical cyclones(TCs).Conceptual schematics depicting configurations among planetary-scale systems at different levels are established for each type.The PPEs free from TCs account for 38.6%of total events,and they tend to occur during April August and October,with the highest frequency observed in June.Corresponding circulation patterns during June August can be mainly categorized into two types,i.e.,summer-Ⅰ type and summer-Ⅱtype.In summer-Ⅰ type,the South Asian high takes the form of a zonal-belt type.The axis of upstream westerly jets is northwest-oriented.At the middle level,the westerly jets at midlatitudes extend zonally.Along the southern edge of the westerly jet,synoptic eddies steer cold air to penetrate southward;the Bay of Bengal(BOB) trough is located to the north;a shallow trough resides over coastal areas of western South China;and an intensified western Pacific subtropical high(WPSH) extends westward.The anomalous moisture is mainly contributed by horizontal advection via southwesterlies around 20°N and southeasterlies from the southern flange of the WPSH.Moisture convergence maximizes in coastal regions of eastern South China,which is the very place recording extreme precipitation.In summer-Ⅱ type,the South Asian high behaves as a western-center type.The BOB trough is much deeper,accompanied by a cyclone to its north;and a lower-level trough appears in northwestern parts of South China.Different to summer-Ⅰ type,moisture transport via southwesterlies is mostly responsible for the anomalous moisture in this type.The moisture convergence zones cover Guangdong,Guangxi,and Hainan,matching well with the areas of flooding.It is these set combinations among different systems at different levels that trigger PPEs in South China.  相似文献   

9.
South China(SC) experienced persistent heavy rain in June 2010.The climatic anomalies and related mechanism are analyzed in this study.Results show that the large-scale circulation pattern favorable for precipitation was maintained.In the upper level,the South Asian High and westerly jet stream provided a divergent circulation over SC.In the middle and low levels,an anomalous strong subtropical high(STH) extended to the South China Sea.The southwesterly monsoon flow along the northwest flank of the STH transported abundant water vapor from the western North Pacific,the Bay of Bengal,and the South China Sea to SC.The precipitation can be classified into two types:the West Siberia low(WSL)-induced low-level cyclone mode,and the STH-induced low-level jet mode.STH and WSL indices are defined to estimate the influence of these two systems,respectively.Analysis shows that both are critical for precipitation,but their respective contributions differ from year to year.In 2010,both were important factors for the heavy rainfall in June.  相似文献   

10.
Using the regional climate model RegCM4.4.5, coupled with the land model CLM4.5, we investigated the effects of springtime soil moisture in the Indochina Peninsula on summer precipitation over the South China Sea and its surrounding areas in 1999. Results have indicated that there exists positive correlation between soil moisture and summer precipitation over the western Pacific Ocean and negative correlation between soil moisture and summer precipitation over the eastern Indian Ocean. Summer precipitation in the South China Sea and its surrounding areas responds to springtime soil moisture in the Indochina Peninsula (the northwest region is critical) because general atmospheric circulation is sensitive to the near-surface thermodynamic state. Increased (decreased) soil moisture would result in decreased (increased) local surface temperatures. Latitudinal, small-scale land–sea thermal differences would then result in northeasterly wind (southwesterly wind) anomalies in the upper layer and southwesterly wind (northeasterly wind) anomalies in the lower layer, which strengthen (weaken) monsoon development. As a result, precipitation would enter the Western Pacific region earlier (later), and water vapor over the eastern Indian Ocean would enter the South China Sea earlier (later), causing a precipitation reduction (increase) in the eastern Indian Ocean and increase (reduction) in the Western Pacific.  相似文献   

11.
利用1951～2005年华南4、5月份降水资料、NOAA海温资料以及NCEP再分析资料,对华南4、5月份降水年代际变化的特征、及其所对应的大尺度环流以及与中西太平洋海温的关系作了分析。结果表明,华南4、5月份降水均在1970年代初期发生显著的年代际转变,从之前的降水偏少转变为降水偏多。华南4月份降水与前一年7～11月份的中西太平洋海温、华南5月份降水与当年2～5月份的中西太平洋海温有显著的负相关。在4、5月份年代际降水偏少(多)时期,前期中西太平洋海温偏暖(冷);同期亚洲大陆南部及非洲大陆的海平面气压显著偏低(高),北太平洋海区海平面气压偏高(低);我国华南上空存在反气旋性(气旋性)环流异常,我国华南地区北边界存在显著的南(北)风异常,造成华南地区北边界异常水汽输出增强(减弱)。同时,我国大陆对流层中上层大气显著偏暖(冷),东亚高空急流显著偏北(南),副热带高压偏弱(强)偏东(西),向华南地区输送的水汽减少(增加),从而在华南地区形成异常的水汽辐散(辐合),最终导致华南地区4、5月份降水的减少(增加)。  相似文献   

12.
春季中国南方雨带年际变动与大气环流异常   总被引：1，自引：1，他引：0  
蒋品平  赵平 《气象学报》2012,70(4):681-689
利用1960—2008年中国693个站逐日降水资料和NCEP/NCAR日平均再分析资料,采用统计分析方法,分析了中国南方春季降水强度和位置的年际变率及其与大气环流的关系。结果表明:在年代际尺度上,江南春季降水在20世纪60年代中、后期偏少,70年代中期到80年代初偏多,90年代初开始减少;在年际尺度上,当春季西太平洋副热带高压和青藏高原东侧的低层低压系统加强,并且异常中心分别位于20°N以南和30°N以南时,异常西南风主要位于长江以南地区,在异常西南风逐渐减弱区出现明显的辐合,伴随着该地区低层空气质量辐合、对流层上升运动和水汽辐合加强,造成江南地区降水偏多,此时来自西太平洋的异常水汽到达南海后,没有在南海聚集,而是转向北输送到江南;当春季西太平洋副热带高压以及青藏高原东侧低压系统加强且异常中心位于30°N以北时,异常西南风盛行在中国东部大部分地区,此时低层异常空气质量辐合、对流层异常上升运动以及异常水汽通量辐合区都向北移到江淮地区,使江淮地区降水增加,而华南地区为异常空气质量辐散、异常下沉运动以及异常水汽通量辐散,伴随着降水减少,这时异常水汽主要来自西太平洋副热带地区。由于上述观测结果与通过改变东亚和周边海域海-陆热力差异的数值试验结果有很好的一致性,因此,这里观测到的降水和大气环流异常可以被东亚区域热力差异异常激发出来。  相似文献   

13.
Using the 5-day averaged data from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, and precipitation from rain gauge stations in China for the period 1981–2000, we investigated seasonal variations and associated atmospheric circulation and precipitation of the southwesterly wind over eastern China. The southwesterly wind over eastern China begins earliest over southeastern China and strengthens gradually from spring to the early summer, as it extends northward. The strengthening of the spring southwesterly wind, the tropospheric upward motion, and the convergence of low-level water vapor over southeastern China results in the beginning of the local rainy season. The beginning of the Mei-yu (Plum rainfall) is connected with the northward march of the southwesterly wind. The southwesterly wind reaches the valley of the Yangtze River in the early summer and northern China in the middle summer. This signifies an onset of the large-scale southwesterly wind over eastern China. Accordingly, the rain belt over southeastern China moves to the valley of the Yangtze River in the early summer and to northern China in the middle summer. Moreover, the southerly wind extends southward to the South China Sea from the spring to summer, though it does not stretch from the South China Sea to southeastern China at those times. The strengthening of the southerly wind over southeastern China is associated with a weakening/strengthening of the eastward/westward subtropical tropospheric temperature gradient between southwestern China and the western North Pacific. The developments of a low-pressure system over southwestern China and the subtropical high-pressure system over the western North Pacific may contribute to the strengthening of the southwesterly wind. A northward advance of the high-pressure system favors the southwesterly wind stretching from southeastern China to northern China. The onset of the Indian summer monsoon also strengthens the summer southwesterly wind over eastern China.  相似文献   

14.
影响华北汛期降水的水汽输送过程   总被引：9，自引：3，他引：6  
利用1951～2005年NCEP再分析资料和中国160站月降水资料,分析了华北汛期水汽输送的时空特征及其与降水的关系,发现不同水汽通道对华北降水的影响区域不同。华北的水汽输送也具有明显的年际变化,华北多雨年和少雨年的水汽通量分布有明显差异。EOF分析表明,在华北汛期多雨年,上述水汽通道有向华北地区的正异常水汽输送。华北汛期水汽主要来自亚洲季风水汽输送,其次是西风带的水汽输送,它们与降水具有相似的年代际变化。1970年代中期以后,季风的水汽输送显著减弱,西风带水汽输送的重要性相对增大,华北降水在1980年代初的突变与季风水汽输送1970年代中期的突变密切相关。  相似文献   

15.
Winter-spring precipitation in southern China tends to be higher (lower) than normal in El Niño (La Niña) years during 1953–1973. The relationship between the southern China winter-spring precipitation and El Niño-Southern Oscillation (ENSO) is weakened during 1974–1994. During 1953–1973, above-normal southern China rainfall corresponds to warmer sea surface temperature (SST) in the equatorial central Pacific. There are two anomalous vertical circulations with ascent over the equatorial central Pacific and ascent over southern China and a common branch of descent over the western North Pacific that is accompanied by an anomalous lower-level anticyclone. During 1974–1994, above-normal southern China rainfall corresponds to warmer SST in eastern South Indian Ocean and cooler SST in western South Indian Ocean. Two anomalous vertical circulations act to link southern China rainfall and eastern South Indian Ocean SST anomalies, with ascent over eastern South Indian Ocean and southern China and a common branch of descent over the western North Pacific. Present analysis shows that South Indian Ocean SST anomalies can contribute to southern China winter-spring precipitation variability independently. The observed change in the relationship between southern China winter-spring rainfall and ENSO is likely related to the increased SST variability in eastern South Indian Ocean and the modulation of the Pacific decadal oscillation.  相似文献   

16.
基于1961-2016年中国地面台站降水观测资料和多种再分析资料,分析了东部型和中部型两类厄尔尼诺事件对中国夏季水汽输送和降水的不同影响。结果表明：（1）厄尔尼诺事件对中国夏季降水的影响在发生当年和次年有明显的不同,主要影响是在其发生的次年,中国大部分地区的夏季降水明显偏多。（2）东部型厄尔尼诺事件当年夏季,西北太平洋副热带高压（副高）偏东偏弱,水汽输送条件较弱,不利于中国大范围降水的发生;中部型事件当年夏季,低纬度印度洋和西太平洋蒸发异常偏强,来自阿拉伯海、孟加拉湾和西北太平洋向华南地区的水汽输送和净水汽收支增加,有利于华南地区降水的异常增多。（3）东部型厄尔尼诺事件次年夏季,副热带太平洋蒸发异常偏强,副高西伸,由于东亚-太平洋（EAP）遥相关型的建立,副高西侧的强西南气流将来自太平洋蒸发的大量水汽持续输送至中国中东部地区。此外,在东亚-太平洋遥相关型影响下中高纬度地区建立了亚洲双阻型环流,其间的低槽冷涡与上游阻高之间的强偏北气流有利于北冰洋的水汽持续输送到西北和华北北部地区,中国大部分地区净水汽收支均增加,中国北方和南方地区的降水均产生了明显的同步性增多响应,形成了南北两条异常雨带。中部型厄尔尼诺事件次年夏季,副高较常年偏西且偏北,来自太平洋蒸发的大量水汽输送到江淮地区,使其净水汽收支增加和降水偏多。因此,厄尔尼诺事件的发生不仅对长江流域和淮河流域等南方地区的降水有重要影响,对华北、东北和西北地区的降水异常也有相当的作用。  相似文献   

17.
利用1957~2011年我国502个测站逐日降水资料,定义区域平均降水量连续5 d超过1个标准差为1次区域性持续强降水,分析了我国东部(105°E以东)长江流域、华北和东北地区夏季(6~8月)的强降水,共得到74个个例,并探讨了造成长江流域和华北地区持续性强降水的主要环流与水汽输送模态。结果表明,中高纬出现阻塞形势是造成我国东部夏季区域性持续强降水的主要环流型,占比86%。其中影响长江流域强降水的主要阻塞形势为中阻型(贝加尔湖为高压脊)和双阻型(乌拉尔山和鄂霍次克海同时出现高压脊);影响华北地区强降水的主要阻塞形势为中阻型。同时,必须建立一条自热带海洋至降雨区的水汽通道,长江流域强降水的水汽通道为印度洋—孟加拉湾—南海;对于华北地区,除此水汽通道外,西北太平洋水汽输送也是一个重要水汽来源。长江流域强降水的异常水汽输送在菲律宾北部出现反气旋中心,导致从南海有异常水汽输送并在长江流域辐合,这一反气旋中心对应500 h Pa上西太平洋副热带高压的加强;华北地区强降水的异常水汽输送在渤海—朝鲜半岛出现反气旋中心,异常水汽来自南海和西北太平洋。渤海—朝鲜半岛在500 h Pa出现正高度异常对维持华北地区持续降水有重要作用。深厚的上升运动或低层辐合高层辐散是华北与长江流域持续强降水发生的共同特点。中阻型和双阻型的长江流域强降水在水汽输送上没有明显差异,而是动力上升条件的分布差异决定了雨带主要位置的不同。  相似文献   

18.
朱玮  刘芸芸  何金海 《气象科学》2007,27(2):155-161
利用NCEP／NCAR1957-2001年45a逐日的再分析资料，从地面开始积分计算整层的水汽输送通量，减去平均场的水汽的输送量，从而得到扰动水汽输送量，初步讨论了我国江淮地区水汽输送场的季节变化特征，并分析了我国江淮梅雨期旱、涝年平均场水汽输送与扰动场水汽输送的差异。分析发现：扰动场水汽输送与平均场水汽输送差别较大，源自孟加拉湾的平均水汽输送对我国东部地区的降水影响较大，但该地区的扰动水汽输送却主要是影响印度北部地区。而影响我国江淮地区的扰动场水汽输送主要来自于南海地区。源自西太平洋和我国北方的偏强的水汽输送是造成江淮梅雨期降水偏多的主要因子，扰动场水汽输送在我国江淮地区梅雨期降水异常时期与平均场水汽输送基本呈反方向输送，其差值散度场与平均场水汽输送差值散度则为反位相分布，因此说扰动场的水汽输送对平均场的水汽输送起削弱作用。  相似文献   

19.
Based on the ERA-40 and NCEP/NCAR reanalysis data,the NOAA Climate Prediction Center’s merged analysis of precipitation(CMAP),and the fifth-generation PSU/NCAR Mesoscale Model version 3(MM5v3),we defined a monsoon intensity index over the East Asian tropical region and analyzed the impacts of summer(June-July) South China Sea(SCS) monsoon anomaly on monsoon precipitation over the middle-lower reaches of the Yangtze River(MLRYR) using both observational data analysis and numerical simulation methods.The results from the data analysis show that the interannual variations of the tropical monsoon over the SCS are negatively correlated with the southwesterly winds and precipitation over the MLRYR during June-July.Corresponding to stronger(weaker) tropical monsoon and precipitation,the southwesterly winds are weaker(stronger) over the MLRYR,with less(more) local precipitation.The simulation results further exhibit that when changing the SCS monsoon intensity,there are significant variations of monsoon and precipitation over the MLRYR.The simulated anomalies generally consist with the observations,which verifies the impact of the tropical monsoon on the monsoon precipitation over the MLRYR.This impact might be supported by certain physical processes.Moreover,when the tropical summer monsoon is stronger,the tropical anomalous westerly winds and positive precipitation anomalies usually maintain in the tropics and do not move northward into the MLRYR,hence the transport of water vapor toward southern China is weakened and the southwest flow and precipitation over southern China are also attenuated.On the other hand,the strengthened tropical monsoon may result in the weakening and southward shift of the western Pacific subtropical high through self-adjustment of the atmospheric circulation,leading to the weakening of the monsoon flows and precipitation over the MLRYR.  相似文献   

20.
中国东部季风区夏季四类雨型的水汽输送特征及差异   总被引：2，自引：1，他引：1  
利用1951~2015年NCEP/NCAR再分析逐日资料和中国160站月降水观测资料,及中国东部季风区夏季四类雨型（北方型、中间型、长江型和华南型）的划分结果,分析了东亚水汽输送与中国东部季风区夏季降水的关系,比较了四类雨型的水汽输送、收支特征及其差异,结果表明:（1）夏季影响中国东部季风区的水汽通道主要有以下6条:印度洋通道,表征印度季风区偏南的西风水汽输送;高原南侧通道,表征印度季风区偏北的西风水汽输送;太平洋通道,表征由西太平洋副热带高压（副高）带来的西太平洋的水汽;西风带通道,表征西风带的水汽输送;孟加拉湾通道,表征来自孟加拉湾向北的水汽输送;南海通道,表征来自印度洋和孟加拉湾在中南半岛转向及来自南海的水汽;与中国东部不同地区降水异常相联系的水汽通道存在明显的差异,且同一条水汽通道在夏季不同阶段与降水的关系也不尽相同。（2）四类雨型的水汽输送和收支特征有明显的差异,华北盛夏降水主要受亚洲季风水汽输送的影响,其次是西风带水汽输送,北方型年二者往往偏强,尤其是季风水汽输送增加一倍以上,贡献也明显增加,20世纪70年代中期之后,季风水汽输送显著减弱,西风带水汽输送的重要性相对增大;淮河流域夏季降水异常主要受太平洋通道水汽输送异常的主导,其次是高原南侧通道水汽输送,二者偏强并在淮河流域辐合时,淮河流域降水偏多形成中间型年;长江中下游地区夏季降水主要受太平洋通道水汽输送异常的主导,长江型年,副高西北侧的西南水汽输送异常加强,并与北方冷空气异常在长江中下游地区辐合,区域为正的水汽净收支;华南地区夏季降水则受印度洋通道、太平洋通道及南海通道的共同影响,当三条通道异常偏强,水汽与北方冷空气在华南地区辐合,形成华南型年。本研究所得结论加深了我们对四类雨型形成机理的认识,并为汛期主雨带的预测提供了参考。  相似文献   

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