THE VARIATION OF THE SPRING PRECIPITATION IN GUANGZHOU AND ITS PRECURSORY SIGNALS

Guangzhou spring rainfall mainly exhibits interannual variation of Quasi-biannual and interdecadal variation of 30 yrs, and is in the period of weak rainfall at interdecadal time scale. SST anomalies (SSTA) of Nino3 are the strongest precursor of Guangzhou spring rainfall. They have significant positive correlation from previous November and persist stably to April. Nino3 SSTA in the previous winter affects Guangzhou spring rainfall through North Pacific subtropical high and low wind in spring. When Nino3 SSTA is positive in the previous winter, spring subtropical high is intense and westward, South China is located in the area of ascending airflow at the edge of the subtropical high, and water vapor transporting to South China is intensified by anticyclone circulation to the east of the Philippines. So Guangzhou spring rainfall is heavy. When Nino3 SSTA is negative, the subtropical high is weak and eastward, South China is far away from the subtropical high and is located in the area of descending airflow, and water vapor transporting to South China is weak because low-level cyclonic circulation controls areas to the east of the Philippines and north wind prevails in South China. So Guangzhou spring rainfall is weak and spring drought is resulted.     

RELATIONSHIPS BETWEEN SPRING KUROSHIO SSTA AND SUMMER RAINFALL IN CHINA

Based on the data of SST and NCEP/NCAR reanalysis data, the relationship is analyzed of spring SSTA in the Kuroshio region with summer precipitation in China, summer 500 hPa field and water vapor transport, using the methods of Morlet wave, correlation and composite analysis. The results show that annual and interdecadal change of spring SST in the Kuroshio region is distinct. Spring SST displays a significantly increasing trend and there exist different periodic oscillations in the Kuroshio region, with the 23-year periodic oscillation being the most obvious. Troughs and ridges in the mid- and higher- latitudes turn deeper in high Kuroshio SSTA years. At the same time, the western Pacific subtropical high strengthens and stretches westwards. As a result, the warm / wet air from the west of the subtropical high locates in the mid- and lower- reaches of the Yangtze River and south China and summer rainfall in the above regions increases accordingly. Composite anomalous water vapor flux fields indicate that the vapor transport from the South China Sea and western Pacific and the vapor from the north converge over the mid- and lower- reaches of the Yangtze River and south China, which results in the increase of the summer rainfall in the mid- and lower- reaches of the Yangtze River and south China. On the contrary, the summer rainfall in the mid- and lower- reaches of the Yangtze River and south China decreases correspondingly in low Kuroshio SSTA years.     

Persistent Heavy Rainfall over South China During May-August：Subseasonal Anomalies of Circulation and Sea Surface Temperature

This study investigates the relationship between subseasonal variations of the circulation and sea surface temperature（SST） over the South China–East Asian coastal region（EACR） in association with the persistent heavy rainfall（PHR） events over South China during May–August through statistical analysis. Based on the intensity threshold and duration criterion of the daily rainfall, a total of 63 May–June（MJ） and 59July–August（JA） PHR events are selected over South China from 1979 to 2011. The lower-level circulation anomalies on subseasonal timescale exhibit an anomalous cyclone over South China and an anomalous anticyclone shaped like a tongue over the South China Sea（SCS） during the PHR events for MJ group.The anomalous cyclone over South China in MJ originates from low-value systems in the mid-high latitudes before the rainfall. The anomalous anticyclone over the SCS is due to the westward extension of the western Pacific subtropical high（WPSH） and the southeastward propagation of the anomalous anticyclone from South China before the rainfall. For JA group, the lower-level anomalous circulation pattern is similar to that for MJ over the South China–EACR, but with di？erent features of propagation. The subseasonal anomalous anticyclone is also related to the westward stretch of the WPSH, while the anomalous cyclone is traced back to the weak anomalous cyclone over the Philippine Sea several days before the rainfall events.Positive SST anomaly（SSTA） is observed over the SCS and the Philippine Sea during the MJ PHR events on the subseasonal timescale. It is closely linked with the variation of local anomalous anticyclone. In contrast, negative SSTA occupies the South China coastal region for the JA PHR events, and it is driven by the anomalous cyclone which propagates northwestward from the Philippine Sea. The subseasonal positive（negative） SSTAs are generated via the local processes of above（below）-normal incident solar radiation and below（above）-normal latent heat fluxes. The possible role of the subseasonal SSTA in the local convective instability is also analyzed in this study.     

Different Summer Rainfall Anomaly Patterns in Northeast China Associated with Two Kinds of El Niño Events

The relationship between summer rainfall anomalies in northeast China and two types of El Ni?o events is investigated by using observation data and an AGCM. It is shown that, for different types of El Ni?o events, there is different rainfall anomaly pattern in the following summer. In the following year of a typical El Ni?o event, there are remarkable positive rainfall anomalies in the central-western region of northeast China, whereas the pattern of more rainfall in the south end and less rainfall in the north end of northeast China easily appears in an El Ni?o Modoki event. The reason for the distinct differences is that, associated with the different sea surface temperature anomalies (SSTA) along the equatorial Pacific, the large-scale circulation anomalies along east coast of East Asia shift northward in the following summer of El Ni?o Modoki events. Influenced by the anomalous anticyclone in Philippine Sea, southwesterly anomalies over eastern China strengthens summer monsoon and bring more water vapor to Northeast China. Meanwhile, convergence and updraft is strengthened by the anomalous cyclone right in Northeast China in typical El Ni?o events. These moisture and atmospheric circulation conditions are favorable for enhanced precipitation. However, because of the northward shift, the anomalous anticyclone which is in Philippine Sea in typical El Ni?o cases shifts to the south of Japan in Modoki years, and the anomalous cyclone which is in the Northeast China in typical El Ni?o cases shifts to the north of Northeast China, leading to the “dipole pattern” of rainfall anomalies. According to the results of numerical experiments, we further conform that the tropical SSTA in different types of El Ni?o event can give rise to observed rainfall anomaly patterns in Northeast China.     

华南4—5月持续性干旱及其环流背景

用测站降水量资料和NCEP-DOEⅡ再分析资料等,统计分析了华南春季各月降水量逐年变化的相互关系以及华南4—5月持续性干旱对应的大气环流异常特征,初步探讨了与华南4—5月持续性干旱有关的海温异常及其可能的影响机理。华南春季降水量主要变异型为全区一致型,近30年来华南春季降水量在减少,华南4、5月降水量的逐年变化有显著的同相特征。华南春旱主要是由4—5月的降水持续偏少造成的。在华南4—5月持续干旱年,华南附近高低空都存在一个异常的反气旋,并在华南上空造成异常下沉运动;东亚大槽南支偏弱,不利于中高纬度冷空气南下,因而不利于华南降水。在华南4—5月持续干旱年,热带中太平洋的海温正距平可从前一年12月一直持续到当年5月,其影响华南春旱的机制是:由于赤道中太平洋地区海温正距平,导致该区域的异常辐合上升运动,同时通过罗斯贝波的响应在其西侧即西太平洋赤道南、北两侧低空强迫形成气旋性环流异常,在菲律宾东侧的热带西太平洋上空强迫出异常的上升运动,进而使南海北部和华南地区出现异常的下沉运动,导致干旱;在南海及热带西太平洋上空大气低层出现的偏北风异常也使得来源于南海—西太平洋的水汽输送减弱,不利于华南降水。在华南4—5月持续干旱年,4、5月欧亚大陆中高纬度地区也存在一个持续性的西北—东南向的异常环流波列,其对华南干旱的发生也具有显著的影响作用。     

春季热带大西洋北部海温异常与我国盛夏降水异常的联系

利用Hadley中心的海表温度资料、全国160站降水资料以及NCEP-DOE AMIP-Ⅱ再分析等资料,运用多种统计分析方法,分析了春季（3—5月）热带大西洋北部海温异常变化特征及其对我国盛夏（7、8月）降水异常的影响。结果表明:春季热带大西洋北部模态是热带大西洋海温异常REOF分解的第一模态,方差贡献率为34.5%。热带大西洋北部海温异常年际变率具有明显的季节差异,其中春季最为显著。春季热带大西洋北部海温异常与我国盛夏华中地区降水异常有显著的正相关关系。进一步分析表明,春季热带大西洋北部的海温正异常可以激发出Rossby波,在热带大西洋西北部和热带东太平洋北部产生异常的气旋式环流,引起上述区域的对流层低层（上层）大气出现异常辐合（辐散）,并通过热带大西洋北部地区和太平洋之间的垂直环流异常,在中太平洋地区对流层低层大气出现异常辐散,有利于西北太平洋地区产生异常反气旋式环流,异常反气旋西北侧的西南气流有利于水汽输送至我国华中地区,使该地区降水偏多。且这种影响可以通过热带大西洋北部海温异常的持续性,从春季一直持续到盛夏。      

亚洲夏季风30～60天季节内振荡对中国东部地区持续性极端降水的影响

本文基于1979～2015年中国台站观测的格点化高分辨率降水和NCEP II大气再分析逐日资料,探讨了亚洲季风区夏季30～60天大气季节内振荡（ISO）与长江中下游地区持续性降水异常的关系,重点揭示了南亚和东亚子季风区ISO的相互作用及二者协同引起长江中下游持续性极端降水的物理机制。合成分析表明,南亚和东亚ISO是通过高层辐散环流发生相互作用。在ISO位相1～3（5～7）,异常活跃（抑制）对流从赤道印度洋北传至孟加拉湾—印度次大陆区域,其伴随的高层异常辐散（辐合）环流通过补偿效应,引起南海—热带西北太平洋的异常高层辐合（辐散）,加强了局地的异常下沉（上升）运动,有利于南海—西北太平洋的异常抑制（活跃）对流发展并维持。南海—西北太平洋的异常抑制（活跃）对流伴随着显著的斜压散度,并进一步激发出一个连接南海和长江中下游的经向垂直环流圈,引起长江中下游强烈的异常上升（下沉）运动和低层水汽辐合（辐散）,使得降水持续性偏多（少）,极端降水的发生概率持续地偏高（低）,有利于（不利于）形成持续性极端降水事件。研究还表明,亚洲季风区ISO的强度存在显著的年际变化,并对长江中下游持续性极端降水的发生频次和持续时间具有调制作用。在ISO偏强（弱）年,长江中下游持续性极端降水的发生频次较高（低）,且持续时间较长（短）。     

不同分布型厄尔尼诺事件及对中国次年夏季降水的可能影响

利用1951—2009年线性最优插值全球海温资料,NCEP/NCAR再分析大气资料,以及中国160个站的降水资料等,重点分析了不同分布型厄尔尼诺事件的海温演变特征及对应的热带大气的响应情况,并进一步探讨了不同分布型厄尔尼诺事件对次年夏季中国降水的可能影响。根据厄尔尼诺事件发展达到盛期时海温距平的分布特点,将1950年以来的厄尔尼诺事件分为东部型、中部型和混合型。不同分布型厄尔尼诺事件的海温演变及后期的发展都表现出较为明显的差异,对应的热带太平洋上空向外长波辐射距平分布及热带印度洋-太平洋上空的沃克环流异常也表现出明显的不同。在厄尔尼诺的次年夏季,通过影响850hPa风场、水汽输送及500hPa西太平洋副热带高压系统,东部型、中部型及混合型厄尔尼诺事件可能分别导致中国雨带呈现南方型(III类)、中间型(II类)和北方型(I类)的分布特点。     

Indo-Pacific remote forcing in summer rainfall variability over the South China Sea

This study investigates summer rainfall variability in the South China Sea (SCS) region and the roles of remote sea surface temperature (SST) forcing in the tropical Indian and Pacific Ocean regions. The SCS summer rainfall displays a positive and negative relationship with simultaneous SST in the equatorial central Pacific (ECP) and the North Indian Ocean (NIO), respectively. Positive ECP SST anomalies induce an anomalous low-level cyclone over the SCS-western North Pacific as a Rossby-wave type response, leading to above-normal precipitation over northern SCS. Negative NIO SST anomalies contribute to anomalous cyclonic winds over the western North Pacific by an anomalous east–west vertical circulation north of the equator, favoring more rainfall over northern SCS. These NIO SST anomalies are closely related to preceding La Niña and El Niño events through the “atmospheric bridge”. Thus, the NIO SST anomalies serve as a medium for an indirect impact of preceding ECP SST anomalies on the SCS summer rainfall variability. The ECP SST influence is identified to be dominant after 1990 and the NIO SST impact is relatively more important during 1980s. These Indo-Pacific SST effects are further investigated by conducting numerical experiments with an atmospheric general circulation model. The consistency between the numerical experiments and the observations enhances the credibility of the Indo-Pacific SST influence on the SCS summer rainfall variability.     

山西省夏季年际气候异常研究1.山西省一致多雨或少雨型

利用美国国家环境预报中心(NCEP)再分析资料以及山西64个测站的月降水量等资料,采用EOF分解和合成分析方法研究了1960-2003年山西夏季降水的年际变化异常以及时空特征.利用EOF方法分析山西夏季降水,第一类雨型是山西省夏季一致多雨型,并给出此类异常雨型的时空分布和相应的典型年份.山西省夏季降水趋势分析表明,自1960年以来山西省夏季降水趋于减少.从500hPa位势高度场、纬向风、850hPa风场、700hPa水汽场、海温场等物理量场分析表明,山西夏季一致多雨年对应偏强的东亚夏季风,一般出现在La Nina事件(冷水事件)发生的当年和El Nino事件(暖水事件)发生的来年,中高纬度地区易出现纬向排列的 - -环流异常纬向分布型,大陆地区为一个异常槽和两个异常脊,乌拉尔山以东地区和鄂霍次克海是异常高压脊,而贝加尔湖地区是一个异常低压槽.山西省夏季一致少雨年对应偏弱的东亚夏季风,一般出现在El Nino事件(暖水事件)发生的当年和La Nina事件(冷水事件)发生的来年,与一致多雨年相反,中高纬度地区通常呈现纬向排列的- - 环流异常纬向分布型,大陆地区出现两个异常槽和一个异常脊.山西省夏季第一类雨型的发生与中高纬度地区纬向排列的环流异常分布和赤道太平洋海温异常有关系.     

冬季热带太平洋和印度洋SSTA对大气协同作用的数值试验

通过比较热带太平洋和印度洋典型分布的海表温度距平（ＳＳＴＡ）场以及热带西太平洋孤立海域ＳＳＴＡ对大气环流影响的数值试验结果，发现两者存在明显的差异，前者与观测事实一致，由此说明大气环流异常是热带太平洋和印度洋ＳＳＴＡ协同作用的结果。     

西太平洋副热带高压异常及其与1998年长江流域洪涝过程关系的研究

文中结合 1 998年长江流域的洪涝过程研究了太平洋的活动特征 ,探讨了副热带高压活动与海温的关系 ,以及视热源、水汽汇的特征与副高活动的关系等。首先描述了 1 998年太平洋副热带高压的基本特征 ,给出了它异常的季节位置、强度和形态 ,及其与长江流域降水异常的关系。SVD分析表明 ,1 997至 1 998年的 El Nino过程的演变特征所对应的太平洋副热带高压的最佳耦合模态是 :主体强而位置偏南 ,特别是其西部。赤道辐合带也偏弱 ;1 998年夏季副热带高压的基本特征正符合该模态的特征。热带地区东西向的垂直环流明显地出现东太平洋的异常上升气流与西太平洋的下沉距平气流。视热源、水汽汇的分布能很好地描写副热带高压区的季节位置和强度。副热带高压区为明显的 Q1<0的辐射冷却区和 Q2 <0的变干区。这种特征也有助于副热带高压区的维持。同样 ,视热源、水汽汇的分布也能很好地解释副热带高压区的季节内异常活动。在长江流域持续暴雨期和间隙期 ,Q1,Q2 所指示的副热带高压与雨带的相对位置有很大的差异。不同的热力结构能较好地解释副热带高压区的迅速南落 ,由此造成长江流域的二度梅     

AIR-SEA COUPLING FEATURES FROM THE WARM PHASE TO THE COLD PHASE OF ENSO CYCLES IN THE SEVENTIES TO THE EIGHTIES*

Using the sea surface temperature and wind anomalies(SSTA and SSWA for short) of the tropical Pacific from January 1970 to December 1989,main spatial patterns of tropical Pacific SSTA and SSWA coupling features in the transform course from the warm phase to the cold phase of El Nino-southern Oscillation(ENSO) cycles are discussed.The main conclusions are as follows:(1)air-sea coupling patterns at the mature stage of El Nino(La Nina) are main spatial ones of tropical Pacific SSWA and SSTA coupling:(2)at the mature stage of El Nino,the interaction of the anticyclonic anomaly wind,generated by the forcing of distinct meridional SSTA gradient in the Northern Hemisphere tropical central Pacific.with the California cold current and SSTA is mainly responsible for weakening of El Nino;(3)the second sea temperature increase along the South American coast in the decaying course of El Nino results from the eastward movement of the weakened positive SSTA in the tropical central-eastern Pacific forced by anomalous west wind stress:(4)La Nina results from the joint effect of Walker circulation,Ekman drift and negative SSTA in the tropical central-eastern Pacific.     

Spatial and interannual variations of spring rainfall over eastern China in association with PDO–ENSO events

The spatio-temporal variations of eastern China spring rainfall are identified via empirical orthogonal function (EOF) analysis of rain-gauge (gridded) precipitation datasets for the period 1958–2013 (1920–2013). The interannual variations of the first two leading EOF modes are linked with the El Niño–Southern Oscillation (ENSO), with this linkage being modulated by the Pacific Decadal Oscillation (PDO). The EOF1 mode, characterized by predominant rainfall anomalies from the Yangtze River to North China (YNC), is more likely associated with out-of-phase PDO–ENSO events [i.e., El Niño during cold PDO (EN_CPDO) and La Niña during warm PDO (LN_WPDO)]. The sea surface temperature anomaly (SSTA) distributions of EN_CPDO (LN_WPDO) events induce a significant anomalous anticyclone (cyclone) over the western North Pacific stretching northward to the Korean Peninsula and southern Japan, resulting in anomalous southwesterlies (northeasterlies) prevailing over eastern China and above-normal (below-normal) rainfall over YNC. In contrast, EOF2 exhibits a dipole pattern with predominantly positive rainfall anomalies over southern China along with negative anomalies over YNC, which is more likely connected to in-phase PDO–ENSO events [i.e., El Niño during warm PDO (EN_WPDO) and La Niña during cold PDO (LN_CPDO)]. EN_WPDO (LN_CPDO) events force a southwest–northeast oriented dipole-like circulation pattern leading to significant anomalous southwesterlies (northeasterlies) and above-normal (below-normal) rainfall over southern China. Numerical experiments with the CAM5 model forced by the SSTA patterns of EN_WPDO and EN_CPDO events reproduce reasonably well the corresponding anomalous atmospheric circulation patterns and spring rainfall modes over eastern China, validating the related mechanisms.     

AIR-SEA COUPLING FEATURES FROM THE WARM PHASE TO THE COLD PHASE OF ENSO CYCLES IN THE SEVENTIES TO THE EIGHTIES

Using the sea surface temperature and wind anomalies(SSTA and SSWA for short)of thetropical Pacific from January 1970 to December 1989,main spatial patterns of tropical PacificSSTA and SSWA coupling features in the transform course from the warm phase to the cold phaseof El Nino-southern Oscillation(ENSO)cycles are discussed.The main conclusions are as follows:(1)air-sea coupling patterns at the mature stage of ElNino(La Nina)are main spatial ones of tropical Pacific SSWA and SSTA coupling:(2)at themature stage of El Nino,the interaction of the anticyclonic anomaly wind,generated by the forcingof distinct meridional SSTA gradient in the Northern Hemisphere tropical central Pacific.with theCalifornia cold current and SSTA is mainly responsible for weakening of El Nino;(3)the secondsea temperature increase along the South American coast in the decaying course of El Nino resultsfrom the eastward movement of the weakened positive SSTA in the tropical central-eastern Pacificforced by anomalous west wind stress:(4)La Nina results from the joint effect of Walkercirculation,Ekman drift and negative SSTA in the tropical central-eastern Pacific.     

季节背景对ENSO循环过程中SSTA增/减幅作用的数值试验研究

利用热带太平洋地区 2层区域海洋模式和再分析资料探讨了大气 /海洋的季节背景对ENSO时间尺度上海温异常的增幅或减幅作用。结果表明 :不论什么季节背景下 ,就海洋变化而言 ,El Nino/La Nina事件均可存在 ,说明 El Nino/La Nina事件的存在和维持并没有季节性选择 ;模式海洋的西太平洋赤道地区次表层海水温度异常变化位相明显超前于东太平洋SSTA且在空间上自西向东传播 ,同时有位相超前的量还包括模式第 1层厚度异常及热容量异常 ,这些对 ENSO的预测和机制研究具有重要意义。 SSTA的振幅在不同的季节背景下可受到不同的调节。以春季为背景 ,同样的异常风应力作用于海洋 ,可使 NINO3区 SSTA较正常季节背景下该区的 SSTA振幅明显增大 ;而在冬季背景下可使 SSTA受到一定程度的减幅 ,这说明 El Nino/L a Nina现象的发生和消亡有季节选择倾向。与春季背景下 NINO 3区SSTA的增幅倾向相反 ,模式第 1层厚度异常的振幅则受到削弱。而西太平洋赤道地区 ,模式海洋混合层的厚度异常则有所增强。这种与 SSTA增 /减幅反相关的现象需要进一步研究     

500hPa全球动能年际变率及1983和1987年两个厄尼诺年动能距平的差异

利用１９８０—１９８８年９年期间ＥＣＭＷＦ５００ｈＰａ全球风场资料，计算７个“纬度带”上三种基本动能模态，研究这些动能模态的各年异常情况。结果表明，１９８３年是这９年内动能唯一的正值异常年，而１９８７年和１９８５年动能基本上属于正常年，只有个别动能模态有异常。这说明，１９８０年代两个厄尼诺年的异常情况有很大的差异。动能模态与赤道东太平洋海温距平（ＳＳＴＡ）的后延相关表明，１９８３年事件的影响可以波及范围相当广泛甚至波及全球大气，而１９８７年事件所能影响的范围远比１９８３年事件要小。此外，还表明北半球副热带急流轴附近是对ＳＳＴＡ响应的敏感地区。     

山西省夏季年际气候异常研究2．北少（多）南多（少）雨型

采用EOF分解和合成分析方法研究了1960-2003年山西夏季降水异常之北少(多)南多(少)型(第二类雨型)和山西省气温的变化异常.结果表明,两者具有较好的对应关系.分析了第二类异常雨型的时空分布,并给出相应的典型年份.EOF时间系数变化特征揭示了山西夏季降水第二类雨型有显著的年际振荡.利用合成分析,从500hPa位势高度场、纬向风、850hPa风场、700hPa水汽场和水汽输送场等物理量场研究了山西夏季第二类雨型的环流异常特征.结果表明,第二类雨型与弱的东亚夏季风相关联,北多南少和北少南多是弱夏季风的不同表现.山西省夏季降水北多南少年副高呈带状分布,位置偏北,强度较强;中高纬度地区异常波列呈大圆路径分布,在高纬度地区存在纬向排列的- -波列,同时在东亚大陆沿岸存在经向排列的- -波列.并且华北北部有西风异常,北支锋区偏北,由西南向东北水汽输送较强.北少南多年与之相反.海温场分析表明,第二类雨型与中北太平洋海温异常紧密相关.     

华南夏季12-30 d持续性强降水的低频特征分析

利用1982-2011年夏季（5-8月）中国气象观测站点逐日降水资料、NCEP/NCAR逐日再分析资料、NOAA逐日向外长波辐射和海表温度资料集,通过选取低频降水事件的方法,分析了华南夏季12-30 d持续性强降水事件的基本特征,然后利用位相合成法对持续性强降水期间伴随的低频大气环流型以及低频信号的来源和传播情况进行研究,同时也分析了低频海-气耦合过程对持续性强降水的影响。结果表明：（1）华南夏季降水具有显著的12-30 d低频振荡特征,持续性强降水事件在6月发生次数最多,低频降水期间的雨带自东南向西北传播。（2）在持续性强降水发生期间,华南及邻近海域低层受强大的低频气旋式环流控制,低频上升运动显著,而中国南海-菲律宾海一带则是强的低频反气旋式环流,其西侧向北的低频水汽输送不断将中国南海的水汽送至华南及邻近海域进行辐合上升。低层的低频信号来源于热带西太平洋和中国南海-菲律宾海一带低频振荡的西北向传播,同时伴随着西太平洋副热带高压明显的西伸东退过程。（3）在高层,华南北侧（22°-45°N,95°-130°E）区域强大的低频气旋式环流和孟加拉湾-中国南海一带的低频反气旋式环流相互配合,使华南高层处于强大的辐散环境中,从而加强了华南低层的辐合与低频上升运动,造成持续性强降水的增强。高层的低频信号来源于低频罗斯贝波列的东南向传播。（4）低频大气环流异常通过云辐射和热通量过程改变低频海表温度异常,而由大气强迫的低频海表温度异常通过影响低层大气的稳定性来对大气施加明显的反馈作用,该海-气耦合过程有利于大气低层低频信号向华南地区传播,从而影响了华南持续性强降水的发生、发展与结束。     

NUMERICAL STUDY OF INFLUENCE OF THE SSTA IN WESTERN PACIFIC WARM POOL ON RAINFALL IN THE FIRST FLOOD PERIOD IN SOUTH CHINA

1 INTRODUCTION The flood period in South China (SC) lasts long and rains heavily. Its relationship with the SST in the near sea has been studied by Chinese meteorologists early. Liang[1] found that the rainfall of Guangdong in warm water years of South China Sea (SCS) is more than in cold water years. Xie et al[2]. analyzed the relations between the rainfall in Guangdong flood period (from April to September) and SST in northwest Pacific, and built prognostic equations for monthl…