海温异常影响江淮流域入梅的数值模拟

利用CCM3模式模拟了海温异常对江淮流域人梅的影响。结果表明,西风带的槽脊活动对西太平洋副高的北跳有较大影响,孟加拉湾、菲律宾、四川北部、江淮流域及其北部的潜热释放对副高也有较大影响。当马斯克林高压附近的区域为负海温异常时,江淮流域入梅偏早,正海温异常时入梅偏晚。当南大西洋区域的海温为正或负异常时,江淮流域的入梅均偏早。台湾以东区域的海温为正或负异常时,江淮流域的入梅均偏晚。这些结果表明,影响入梅早晚的主要因子可能是大气环流背景异常,而不是同期海温异常。     

长江中下游入梅指数及早晚梅年的海气背景特征

利用1957～2001年全国160站逐月降水资料和116站入梅日期资料,定义了一个长江中下游入梅指数,以定量描述长江中下游地区平均入梅的早晚,再结合ERA－40高分辨率再分析资料和ERSST海温资料,利用相关分析和合成分析, 分别研究了早、晚梅年同期（6～7月份）和前期（前一年12月份至当年5月份）的大尺度大气环流及海温的异常特征。结果表明:早梅年同期,200 hPa南亚高压偏北,印度北部、孟加拉湾－印度尼西亚－副热带太平洋地区上空的对流偏强,西太平洋副热带高压和赤道辐合带位置偏北,东亚副热带夏季风偏强,晚梅年则相反。前期1月份北太平洋涛动及4月份西太平洋暖池附近的对流与当年入梅早晚存在显著的相关关系:早梅年,1月份北太平洋涛动偏弱,4月份西太平洋暖池附近的对流活跃;晚梅年,1月份北太平洋涛动偏强,4月份西太平洋暖池附近的对流偏弱。此外, 从前期海温场来看,早梅年,1～4月份北大西洋中高纬地区海温偏低,低纬地区海温偏高,呈南北偶极子分布状态,2月份西太平洋暖池附近海域及北半球冬、春季环澳大利亚海域海温明显偏高,晚梅年情况正好相反。以上这些前期信号为长江中下游地区入梅的短期气候预测提供了参考依据。     

江淮入梅异常的强信号及其对入梅的影响

江淮入梅具有显著的年际变化特征.利用NCEP/NCAR再分析数据集以及NOAA提供的全球射出长波辐射(OLR)和扩展重建海温(ERSST)等资料,采用相关分析和合成分析等方法研究了江淮入梅异常的前兆强信号,并初步分析了其影响入梅的可能机制.结果表明,ENSO事件是影响江淮入梅早晚较强的前兆信号.前期冬春季出现ENSO暖位相时有利于入梅开始偏晚,ENSO冷位相出现时入梅往往偏早.前期冬季2月和春季Nino 4区的海温异常能较好地预测入梅早晚,具有短期气候预测的指示意义和实用性.ENSO暖位相年,亚澳"大陆桥"、菲律宾、西太平洋暖池以及印度半岛附近对流偏弱,不利于西太平洋副热带高压北跳和印度夏季风爆发,东亚地区大气环流季节转换偏晚,入梅因而偏晚;ENSO冷位相年情况则相反.     

东亚高空急流异常与江淮入梅的关系

使用NCEP/NCAR再分析资料分析了东亚高空急流异常与江淮入梅的关系,得出:东亚高空急流对江淮入梅早、晚有一定的短期预测指示意义。当东亚高空急流偏北时,江淮入梅偏早;反之,当东亚高空急流偏南时,江淮入梅偏晚。东亚高空急流偏北年,西北太平洋海区异常冷,亚欧大陆异常暖,东亚大陆和西太平洋的纬向海陆热力差异由冬到夏的季节转变异常偏早,导致东亚地区大气环流发生季节性转变也偏早;同时,中东太平洋地区ITCZ异常活跃,夏季风系统的推进和副热带高压以及南亚高压的北跳都异常偏早,这种环流有利于江淮梅雨季节开始偏早;高空急流偏南年情况正好相反。     

2005年江淮流域入梅偏晚的成因分析

2005年是江淮流域入梅偏晚年。利用NCEP／NCAR再分析资料、OLR资料和江苏省气象台提供的2005年逐日降水资料，对2005年江淮流域入梅前的异常环流形势进行分析，探讨了西太平洋副热带高压和低层中高纬冷空气的活动异常与东亚大槽、中西太平洋ITCZ以及东亚副热带高空西风急流等活动异常的关系。结果表明，入梅前，东亚大槽发展强盛，ITCZ偏弱以及东亚副热带高空西风急流强劲少动导致西太平洋副热带高压北抬偏晚。同时，东亚副热带高空西风急流的强劲少动也使南下冷空气势力强劲，中低层副热带锋区偏南，抑制了暖湿的东亚夏季风向江淮流域推进。东亚副热带高空西风急流和西太平洋副热带高压向北突跳偏晚是江淮流域2005年入梅偏晚的主要原因。     

赤道东太平洋海温与我国江淮流域夏季旱涝的成因分析

对赤道东太平洋和西太平洋暖池海温与江淮流域夏季降水的关系作功率谱分析和相关分析.指出秋冬季增暖的厄尔尼诺事件对应江淮流域夏季降水偏多, 春夏季开始发展的ENSO事件江淮流域夏季降水偏少.对两种在不同季节增暖的ENSO事件对应的异常流场特征及其对江淮流域降水的影响用1991年和1994年实例作对比分析.不同季节增暖的ENSO事件在太平洋热带地区环流调整的不同阶段可能是影响夏季风活动和东亚夏季天气气候异常的主要原因.     

江淮流域梅雨期降水的空间非均匀分布与前期海温的关系

利用中国气象局提供的1978-2007年全国753站逐日降水资料、NECP/NCAR提供的逐日再分析资料和NOAA提供的第2套扩展重建海温资料,从区域整体角度确定了近30 a（1978-2007年）江淮流域梅雨期.采用EOF（empirical orthogonal function,经验正交函数）分析,讨论了江淮流域梅雨期降水空间非均匀分布特征,着重研究了影响江淮梅雨空间非均匀分布的前期海温关键区及关键时段.结果表明：全区一致梅雨旱涝与前期冬季北太平洋鄂霍次克海附近的海温异常有密切的联系.当前期冬季该海域海温偏高时,冬季风偏弱,对应后期梅雨一致偏涝,反之则偏旱.5月南海至台湾和菲律宾以东附近海温偏低,江淮流域梅雨量偏多,反之则偏少.梅雨的南北反相分布与前期秋冬季中印度洋的海温有非常密切的关系,当前一年10月至当年1月中印度洋海温偏高时,梅雨期850 hPa江淮之间易形成切变线,有利于梅雨区“南旱北涝”,反之则“南涝北旱”.梅雨的东西反相分布与前期秋、冬季热带中东太平洋的海温关系密切,ENSO事件有可能通过影响西太平洋副热带高压的东西位置,从而引起东亚大气环流异常,导致梅雨东西分布反相.前期秋季和冬季热带中东太平洋海温偏高年（对应ENSO暖事件）,西太副高位置偏西,有利于梅雨区“东旱西涝”,反之则“东涝西旱”.     

江淮梅雨与冬季西太平洋海温的SVD分析

利用江淮流域1954—2001年48年梅雨量资料和美国NCEP/NCAR1953—2001全球逐月海温再分析格点资料,网格距为2°×2°,采用EOF、合成分析和SVD分解等方法讨论了江淮梅雨与西太平洋海温的关系。结果表明:影响江淮梅雨的海温关键区是西太平洋暖池区,关键影响时段是前1年的12月至当年的2月(以下简称冬季);当年冬季西太平洋暖池区海温异常偏高,同年江淮大部地区梅雨量异常偏多,反之亦然。SVD分解结果与合成分析的结果相吻合,通过信度0.05的Monte-Carlo显著性检验。     

江淮地区夏季降水与西北太平洋海温关系的诊断分析和数值试验

运用NCEP/NCAR再分析资料、英国气象局的海温资料和国家气候中心整编的160站月降水量资料,对江淮夏季降水及其前期冬季环流和海温场进行分析,并利用NCAR CCM3模式进行海温的敏感性试验。结果表明：前期环流在亚洲中高纬地区有明显的异常,这种环流异常与北太平洋西北部的海温异常有关,西北太平洋海温异常偏高（低）是江淮夏季降水偏多（少）的重要原因之一,即当前期西北太平洋海温异常偏高时,后期夏季从乌拉尔山到鄂霍次克海附近为高度正距平,亚洲中纬度为弱的负距平,这时亚洲中高纬度多阻塞高压活动,中纬度多低槽活动,有利于冷暖空气在江淮地区交汇,江淮流域降水偏多;反之,江淮流域降水偏少。     

江淮入梅的年际变化及其与北大西洋涛动和海温异常的联系

文中首先采用简单相关和合成分析的方法研究了江淮入梅的年际变化与前期冬季环流和前期冬、春全球海温的关系。研究结果表明江淮入梅的早晚与前期冬季北半球大型环流存在显著的相关 :入梅早的年份 ,其前期冬季北大西洋涛动强 ,北半球只有一个强的极涡并位于格陵兰上空 ,东亚大槽弱 ;入梅晚的年份 ,则其前期冬季环流表现为 ,北大西洋涛动弱 ,北半球存在两个极涡 ,其中一个仍然位于格陵兰上空 ,而另一个则位于西伯利亚上空 ,东亚大槽较常年强。江淮入梅的年际变化与前期冬春北大西洋海温的相关分析表明 :入梅早的年份 ,北大西洋海温较常年偏暖 ;入梅晚的年份 ,前期冬春北大西洋海温较常年偏冷。文中还用 CCM3模拟了冬、春季北大西洋海温增暖对后期江淮入梅和梅雨期降水的影响 ,并探讨了其影响的物理机制     

Climate responses in the tropical pacific associated with atlantic warming in recent decades

In this study, we investigated the impact of the Atlantic decadal-scale sea surface temperature (SST) variation on the tropical Pacific climate using a Atmospheric General Circulation Model (AGCM). During the recent decade from 2000 to 2010 when the Atlantic SST has sharply increased, observations have shown that the strong easterly and increased precipitation anomalies appeared over the western-central Pacific. It is different from the conventional Gilltype response in which the easterly due to heating in the Atlantic is expected to be extended to the Indian Ocean. We have found that the warm pool over the western Pacific plays an important role in enhancing the atmospheric response to the Atlantic SST forcing in the Pacific basin. Simplified Aqua planet GCM experiments showed that the central location of the anomalous easterly over the Pacific produced by the Atlantic SST forcing highly depends on the location of the idealized warm pool. The reason for this is because the moisture feedback is strongest over the warm pool region, which leads to additional local anomalous convergence, and therefore the easterly produced by the Atlantic SST forcing is enhanced only over the east of the warm pool region.     

Delayed Impacts of the E1 Nino Episodes in the Central Pacific on the Summertime Climate Anomalies of Eastern China in 2003 and 2007

In the summers of 2003 and 2007, eastern China suffered similar climate disasters with severe flooding in the Huaihe River valley and heat waves in the southern Yangtze River delta and South China. Using SST data and outgoing longwave radiation (OLR) data from NOAA along with reanalysis data from NCEP/NCAR, the 2002/03 and 2006/07 El Ni(n)o episodes in the central Pacific and their delayed impacts on the following early summertime climate anomalies of eastern China were analyzed. The possible physical progresses behaved as follows: Both of the moderate E1 Ni(n)o episodes matured in the central equatorial Pacific during the early winter. The zonal wind anomalies near the sea surface of the west-central equatorial Pacific excited equatorial Kelvin waves propagating eastward and affected the evolution of the E1 Ni(n)o episodes. From spring to early summer, the concurring anomalous easterly winds in the central equatorial Pacific and the end of upwelling Kelvin waves propagating eastward in the western equatorial Pacific, favored the equatorial warm water both of the SST and the subsurface temperature in the western Pacific. These conditions favored the warm state of the western equatorial Pacific in the early summer for both cases of 2003 and 2007. Due to the active convection in the western equatorial Pacific in the early summer and the weak warm SST anomalies in the tropical western Pacific from spring to early summer, the convective activities in the western Pacific warm pool showed the pattern in which the anomalous strong convection only appeared over the southern regions of the tropical western Pacific warm pool, which effects the meridional shift of the western Pacific subtropical high in the summer. The physical progress of the delayed impacts of the E1 Nifio episodes in the central equatorial Pacific and their decaying evolution on the climate anomalies in eastern China were interpreted through the key role of special pattern for the heat convection in the tropical western Pacific warm pool and the response of the western North Pacific anomalous anticyclone.     

Delayed impacts of the El Niño episodes in the central Pacific on the summertime climate anomalies of eastern China in 2003 and 2007

In the summers of 2003 and 2007, eastern China suffered similar climate disasters with severe flooding in the Huaihe River valley and heat waves in the southern Yangtze River delta and South China. Using SST data and outgoing longwave radiation (OLR) data from NOAA along with reanalysis data from NCEP/NCAR, the 2002/03 and 2006/07 El Nino episodes in the central Pacific and their delayed impacts on the following early summertime climate anomalies of eastern China were analyzed. The possible physical progresses behaved as follows: Both of the moderate El Nino episodes matured in the central equatorial Pacific during the early winter. The zonal wind anomalies near the sea surface of the west-central equatorial Pacific excited equatorial Kelvin waves propagating eastward and affected the evolution of the El Ni\~no episodes. From spring to early summer, the concurring anomalous easterly winds in the central equatorial Pacific and the end of upwelling Kelvin waves propagating eastward in the western equatorial Pacific, favored the equatorial warm water both of the SST and the subsurface temperature in the western Pacific. These conditions favored the warm state of the western equatorial Pacific in the early summer for both cases of 2003 and 2007. Due to the active convection in the western equatorial Pacific in the early summer and the weak warm SST anomalies in the tropical western Pacific from spring to early summer, the convective activities in the western Pacific warm pool showed the pattern in which the anomalous strong convection only appeared over the southern regions of the tropical western Pacific warm pool, which effects the meridional shift of the western Pacific subtropical high in the summer. The physical progress of the delayed impacts of the El Ni\~no episodes in the central equatorial Pacific and their decaying evolution on the climate anomalies in eastern China were interpreted through the key role of special pattern for the heat convection in the tropical western Pacific warm pool and the response of the western North Pacific anomalous anticyclone.     

CLIMATIC FEATURES OF SEA TEMPERATURE OF WARM POOL AND RELATIONSHIP WITH SST OF ITS ADJACENT REGIONS*

In this paper,climatic features of sea temperature of western Pacific warm pool and the relationship with sea surface temperature (SST) of its adjacent regions are analyzed based on the observed sea temperature on vertical cross section along 137°E in western Pacific,the monthly mean SST of Xisha Station in South China Sea and the global monthly mean SST with resolution of 1°×1° (U.K./GISST2.2).The results indicate that (1) in a sense of correlation.SST of western Pacific warm pool can represent its sea subsurface temperature from surface to 200 m-depth level in winter,and it can only represent sea temperature from surface to 70 m depth in summer.The sea subsurface temperature anomaly of warm pool may be more suitable for representing thermal regime of western Pacific warm pool.The sea subsurface temperature of warm pool has a characteristic of quasi-biennial oscillation.(2)Warm pool and Kuroshio current are subject to different ocean current systems (3)Furthermore,the relationship between SST of Xisha Station and SST of warm pool has a characteristic of negative correlation in winter and positive correlation in summer,and a better lag negative correlation of SST of Xisha Station with sea subsurface temperature of warm pool exists.(4)Additionally,oscillation structure of sea temperature like "a seesaw" exists in between warm pool and Regions Nino3 and Nino4.January (June) maximum (minimum) sea subsurface temperature anomaly of warm pool may serve as a strong signal that indicates maturity phase (development phase) of La Nina (El Nino) event,it also acts as a strong signal which reveals variations of SST of Regions Nino3 and Nino4.     

西太平洋暖池对流三类显著月际变化及其成因

基于1979～2018年观测的向外长波辐射（outgoing longwave radiation, OLR）资料和其他多种再分析资料,发现西太平洋暖池对流存在3类显著的月际变化。第一类为OLR在6月和8月为负异常而7月为正异常;第二类与第一类完全相反;第三类为OLR在6～7月为正异常,8月为负异常。3类月际变化与ENSO循环的背景有关,前两类发生在较弱的La Ni?a年和El Ni?o发展年,与春季暖池海温异常有关。当前一个月海温偏高时,后一个月对流偏强,造成局地海温降低,偏低的海温又反过来抑制了后一个月的对流发展,因此暖池地区局地海气相互作用在这两类月际变化中起到关键作用。与前两类不同的是,第三类月际变化发生在El Ni?o衰减年,与春季热带印度洋海温偏高有关。热带印度洋海温偏高造成印度附近对流在6～7月间增强,通过东传Kelvin波抑制了暖池对流发展。同时,印度附近对流偏强造成8月印度洋海温降低和对流减弱,对暖池对流的影响因而减弱。另一方面,6～7月暖池对流偏弱造成8月暖池海温升高,结果造成暖池对流增强。因此,第三类月际变化受到热带印度洋强迫以及暖池地区局地海气相互作用的共同影响。     

江淮入梅的年际变化与前冬环流的联系及其可能成因

采用简单相关和合成分析的方法研究了江淮入梅的年际变化与前期冬季环流和前期冬、春全球海温的关系。研究结果表明江淮入梅的早晚与前期冬季北半球大型环流存在显著的相关：入梅早的年份,其前期冬季北太西洋涛动强,北半球只有一个强的极涡并位于格陵兰上空,相应东亚大槽弱;入梅晚的年份,则其前冬环流表现为,北大西洋涛动弱,北半球存在两个极涡,其中一个仍然位于格陵兰上空,而另一个则位于西伯利亚上空,相应东亚大槽较常年     

南海夏季风爆发与热带海洋海温和大气环流异常变化关系的研究

用合成和相关分析方法及SVD技术研究了南海夏季风爆发早、晚年份4～6月季风建立时期季风环流的异常及其与热带太平洋-印度洋海温的关系。结果表明,南海夏季风爆发与热带大气环流和海温变异密切相关。（1）当热带中、东太平洋—印度洋（主要在西南部）及南海海温低（高）,西太平洋—澳洲邻近海域海温高（低）时,南海夏季风爆发早（晚）。不同区域海温对季风的影响有明显的季节差异,印度洋主要为晚春至初夏（4～6月）,南海为5～6月,而热带太平洋从前冬一直持续到夏季。（2）不同的海温异常产生不同的季风环流型,南海夏季风爆发早、晚年大气环流的异常变化基本相反。南海夏季风的活动主要受印度季风环流变化的影响,与前期冬春季西太副高的强弱及位置变化密切相关。西太副高弱时,南海夏季风爆发早;反之,爆发晚。（3）热带太平洋—印度洋海温异常引起季风环流和Walker环流的异常变化可能是影响南海夏季风爆发早、晚的物理过程。     

夏季逐月东亚高空西风急流经向偏移与热带中、东太平洋海温的关联

Previous studies have shown that meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) dominates interannual variability of the EAJS in the summer months. This study investigates the tropical Pacific sea surface temperature (SST) anomalies associated with meridional displacement of the monthly EAJS during the summer. The meridional displacement of the EAJS in June is significantly associated with the tropical central Pacific SST anomaly in the winter of previous years, while displacements in July and August are related to tropical eastern Pacific SST anomalies in the late spring and concurrent summer. The EAJS tends to shift southward in the following June (July and August) corresponding to a warm SST anomaly in the central (eastern) Pacific in the winter (late spring-summer). The westerly anomaly south of the Asian jet stream is a result of tropical central Pacific warm SST anomaly-related warming in the tropical troposphere, which is proposed as a possible reason for southward displacement of the EAJS in June. The late spring-summer warm SST anomaly in the tropical eastern Pacific, however, may be linked to southward displacement of the EAJS in July and August through a meridional teleconnection over the western North Pacific (WNP) and East Asia.