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1.
In the summers of 1998 and 2010, severe floods occurred in the middle and lower reaches of the Yangtze River. Although an El Niño event took place preceding each of the summer floods, significant differences between the two summer floods and the two El Niño events were identified. The 1997/98 El Niño is a conventional one with strongest warming in the central-eastern Pacific, whereas the 2009/10 event is an El Niño Modoki with strongest warming in the central Pacific. In this study, summer rainfall anomalies (SRA) in the two years were first compared based on the rainfall data at 160 stations in mainland China, and a significant difference in SRA was found. To understand the underlying mechanism for the difference, the atmospheric circulation systems, particularly the western North Pacific anticyclone (WNPAC), the western Pacific subtropical high (WPSH), and the low-level air flows, were compared in the two years by using the NCEP/NCAR reanalysis data. The results display that the WNPAC was stronger in 2010 than in 1998, along with a northwestward shift, causing weakened southwesterly from the Bay of Bengal to the South China Sea but intensified southerly in eastern China. This resulted in less water vapor transport from the tropical Indian Ocean and the South China Sea but more from the subtropical western Pacific to East Asia. Subsequently, the rainband in 2010 shifted northward. The difference in the WNPAC was caused by the anomalous ascending motion associated with the warming location in the two El Niño events. Furthermore, the role of tropical sea surface temperature (SST) in modulating these differences was investigated by conducting sensitivity experiments using GFDL AM2.1 (Geophysical Fluid Dynamics Laboratory Atmospheric Model). Two experiments were performed, one with the observed monthly SST and the other with June SST persisting through the whole summer. The results suggest that the model well reproduced the primary differences in the atmospheric circulation systems in the two years. It is found that the difference in El Niño events has shaped the rainfall patterns in the two years of 1998 and 2010. At last, the case of 2010 was compared with the composite of historical El Niño Modoki events, and the results indicate that the impact of El Niño Modoki varies from case to case and is more complicated than previously revealed.  相似文献   

2.
王钦  李双林  付建建  李国平 《气象学报》2012,70(6):1207-1222
1998和2010年夏季长江流域均发生了明显的洪涝灾害,且都是厄尔尼诺事件的次年(衰亡位相).不同的是:1997/1998年冬季的厄尔尼诺事件是传统东部型,而2009/2010年冬季的厄尔尼诺事件是中部型(EL Ni(n)o Modoki).首先利用中国160个台站月降水观测资料,对比了1998和2010年降水异常情况,结果显示除长江流域多降水这一共同特征外,1998和2010年降水分布还存在一定差异.利用NCEP/NCAR再分析资料,对比了大气环流异常特征.结果表明:与1998年相比,2010年西北太平洋对流层低层异常反气旋中心位置偏北偏西,西太平洋副热带高压偏强、脊线偏北,使得南海孟加拉湾西南风减弱而东亚南风加强,导致自印度洋、南海向内陆的水汽输送减少,而自西太平洋的水汽输送增加并输送到偏北的位置,雨带比1998年偏北,中国西南地区降水比1998年偏少.进一步分析厄尔尼诺的影响,揭示环流形势的变化与中部型厄尔尼诺年赤道太平洋异常上升气流比传统厄尔尼诺年偏西、西太平洋异常下沉气流随之变化有关.利用GFDL大气环流模式AM2.1,进行了给定1998和2010年实际观测海温强迫的试验,显示海温差异能够部分解释观测到的环流异常.最后,将这两个个例与历史合成进行了比较,发现2010年与历史合成的中部型厄尔尼诺存在较大差异,表明中部型厄尔尼诺对中国夏季降水的影响比以前所认识的要复杂.  相似文献   

3.
利用1979—2007年NOAA重建海温逐月资料和中国160站夏季降水资料,使用扩展奇异值分解(extended singular value decomposition,ESVD)方法,研究了冬季热带太平洋海温异常与次年夏季中国降水异常季节内演变型之间的关系,指出前冬El Nino事件是与次年夏季中国降水季节内变化相联系的最重要的热带太平洋海温异常模态。相应的降水异常季节内变化情况为:6月在长江以南为正异常,江淮流域有负异常;7月在华南沿海有负降水异常,而正异常北进到长江流域,华北地区也出现正降水异常;8月在长江南北分别为少雨和多雨。进一步研究前冬El Nino事件与次年春夏印度洋、太平洋海温异常、对流层低层风场异常以及副热带高压等的联系,结果表明:El Nio事件发生的次年春夏,热带西太平洋周边存在东负西正的海温异常分布;西太平洋反气旋异常较强;副高在6月、7月偏西偏北,但在8月迅速南退。虽然与El Nino事件相联系的6月与7月、8月的降水型不同,但是西太平洋反气旋异常带来的充沛水汽造成7月长江流域雨季多雨,8月副高迅速南退带来的又一次长江流域降水,造成了El Nino事件发生次年夏季长江流域涝而华南沿海旱的夏季平均降水异常型。  相似文献   

4.
利用季节平均Had ISST海温、CMAP降水及NCEP风场数据,分析了2015/2016超级厄尔尼诺衰减期的特征及其对应的西北太平洋大气环流异常。结果表明:2015/2016厄尔尼诺事件除了成熟位相冬季强度大以外,还具有在随后春季衰减快,到夏季就消亡的特征。伴随着厄尔尼诺的迅速衰减,西北太平洋有较强的反气旋环流异常维持。厄尔尼诺衰减位相与西太反气旋异常存在相互作用。一方面,由于此次厄尔尼诺事件强度强,衰减期热带印度洋有显著的暖海温异常从冬季一直维持到夏季,有利于西太反气旋的增强和维持。另一方面,西太反气旋环流异常的维持及其南侧东风异常的发展使得中东太平洋正海温异常减弱,令厄尔尼诺事件快速衰退。此外,通过与1982/1983和1997/1998年比较发现,这三次超强厄尔尼诺事件虽强度相当,但衰减位相及与之相联系的西太反气旋异常都不尽相同。1982/1983事件衰减慢,维持时间长,对应的西太反气旋强度弱。而1997/1998事件衰减快,维持时间短,对应的西太反气旋强度在春季和夏季都强盛维持。2015/2016事件的衰减速度明显快于1982/1983事件,对应的西太反气旋也强于1982/1983事件,由于2015/2016事件增暖中心偏向于中东太平洋,而这里是厄尔尼诺衰减过程中负海温异常最先出现的区域,因此尽管2015/2016事件中西太反气旋异常的强度弱于1997/1998事件,但衰减速度及衰减位相维持时间与1997/1998相当。本文研究结果表明厄尔尼诺衰减与西太反气旋异常之间的关系较为复杂,需进一步研究。  相似文献   

5.
利用观测诊断和数值模拟相结合的方法,研究了2020年江淮流域6~7月超强梅雨年际异常的环流特征和驱动因子。结果表明:(1)2020年梅雨期长度和江淮流域总降水量均为1961年以来第一位,超强梅雨主要与西北太平洋异常反气旋(WNPAC)的异常偏强和异常西伸有关,WNPAC为江淮流域梅雨期持续的强降水提供了充沛的水汽来源;(2)2019年11月至2020年3月,赤道中东太平洋发生一次弱的中部型El Ni?o事件,本次事件持续时间短、强度偏弱,不足以激发和维持2020年梅雨期异常偏强的WNPAC,而春、夏季热带印度洋和热带北大西洋海温异常持续偏暖是WNPAC异常偏强和西伸的主要驱动因子;(3)热带印度洋暖海温在其东部的西太平洋激发出大气Kelvin波响应,造成了纬向风变化的不均匀分布,通过埃克曼抽吸,抑制了局地对流活动,驱动了WNPAC的生成;而热带北大西洋暖海温则引起局地对流活动增强,导致热带北大西洋上空上升运动和热带中部太平洋下沉运动增强,在西北太平洋上空激发异常的低空反气旋;热带印度洋和热带北大西洋暖海温对2020年6~7月WNPAC异常偏强均有显著的正贡献。  相似文献   

6.
2020年梅汛期长江流域强降雨范围超越1998年,且雨量中心偏北,这与两年的异常大气环流和海表温度强迫差异有密切联系。与1998年相比,2020年西北太平洋异常反气旋(WNPAC)偏北偏强,中心偏东,东亚双阻形势偏弱,使得副高北抬加强,北侧的西南气流亦偏北偏强,中高纬反气旋和气旋对的存在使得30°N以北为异常东北风控制,冷空气偏强,长江流域上空的水汽含量亦偏多,这些环流差异直接导致2020年降水较1998年偏多且中心偏北。这两年在对流层中层都存在大西洋—西太平洋的波列,但2020年波列偏南,有利于东亚反气旋和气旋对的维持以及WNPAC和副高的北抬加强,而1998年波列偏北且偏强,有利于双阻形势的稳定。2019/2020年(1997/1998年)冬季发生中部型(东部型)El Ni?o事件,前者强迫的6—7月WNPAC北界位置较后者偏北;同时2019/2020年印度洋—太平洋中部一致增暖,使得WNPAC加强,中心东移。2020年(1998年)同期处在北大西洋强(弱)负三极子模态,可能是两年中高纬度环流形势差异的主要原因之一。2020年(1998年)南太平洋中部暖海温异常(冷异常)能加强(减弱)越赤道气流,有利于WNPAC偏东偏北(偏西偏南)和水汽输送加强(减弱)。综上,2020年与1998年梅汛期降水差异可能由多洋盆海温强迫协同作用所致。  相似文献   

7.
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.  相似文献   

8.
Record-breaking heavy and persistent precipitation occurred over the Yangtze River Valley (YRV) in June-July (JJ) 2020. An observational data analysis has indicated that the strong and persistent rainfall arose from the confluence of southerly wind anomalies to the south associated with an extremely strong anomalous anticyclone over the western North Pacific (WNPAC) and northeasterly anomalies to the north associated with a high-pressure anomaly over Northeast Asia. A further observational and modeling study has shown that the extremely strong WNPAC was caused by both La Ni?a-like SST anomaly (SSTA) forcing in the equatorial Pacific and warm SSTA forcing in the tropical Indian Ocean (IO). Different from conventional central Pacific (CP) El Ni?os that decay slowly, a CP El Ni?o in early 2020 decayed quickly and became a La Ni?a by early summer. This quick transition had a critical impact on the WNPAC. Meanwhile, an unusually large area of SST warming occurred in the tropical IO because a moderate interannual SSTA over the IO associated with the CP El Ni?o was superposed by an interdecadal/long-term trend component. Numerical sensitivity experiments have demonstrated that both the heating anomaly in the IO and the heating anomaly in the tropical Pacific contributed to the formation and maintenance of the WNPAC. The persistent high-pressure anomaly in Northeast Asia was part of a stationary Rossby wave train in the midlatitudes, driven by combined heating anomalies over India, the tropical eastern Pacific, and the tropical Atlantic.  相似文献   

9.
El Nio Modoki,similar to but different from canonical El Nio,has been observed since the late1970s.In this paper,using HadISST and NCEP/NCAR wind data,we analyze the relationship between El Nio Modoki and Sea Surface Temperature(SST)in the offshore area of China and its adjacent waters for different seasons.Our results show a significant negative correlation between El Nio Modoki in summer and SST in autumn in the offshore area of China and its adjacent waters,particularly for regions located in the east of the Kuroshio.It is also found that during El Nio Modoki period,anomalous northerlies prevail over the regions from the northern part of the Philippines to the offshore area of China,indicating that the northerlies are unfavorable for the transport of warm water from the western tropical Pacific to the mid-latitude area.Consequently,El Nio Modoki in summer may play a substantial role in cold SST anomalies in the offshore area of China and its adjacent waters in autumn through the influence of the Kuroshio,with a lagged response of the ocean to the atmospheric wind field.  相似文献   

10.
E1 Nino Modoki, similar to but different from canonical E1 Nino, has been observed since the late 1970s. In this paper, using HadlSST and NCEP/NCAR wind data, we analyze the relationship between E1 Nifio Modoki and Sea Surface Temperature (SST) in the offshore area of China and its adjacent waters for different seasons. Our results show a significant negative correlation between E1 Nifio Modoki in summer and SST in autumn in the offshore area of China and its adjacent waters, particularly for regions located in the east of the Kuroshio. It is also found that during E1 Nifio Modoki period, anomalous northerlies prevail over the regions from the northern part of the Philippines to the offshore area of China, indicating that the northerlies are unfavorable for the transport of warm water from the western tropical Pacific to the mid-latitude area. Consequently, E1 Nifio Modoki in summer may play a substantial role in cold SST anomalies in the offshore area of China and its adjacent waters in autumn through the influence of the Kuroshio, with a lagged response of the ocean to the atmospheric wind field.  相似文献   

11.
Present work uses 1979–2005 monthly observational data to study the impacts of El Niño Modoki on dry/wet conditions in the Pacific rim during boreal summer. The El Niño Modoki phenomenon is characterized by the anomalously warm central equatorial Pacific flanked by anomalously cool regions in both west and east. Such zonal SST gradients result in anomalous two-cell Walker Circulation over the tropical Pacific, with a wet region in the central Pacific. There are two mid-tropospheric wave trains passing over the extratropical and subtropical North Pacific. They contain a positive phase of a Pacific-Japan pattern in the northwestern Pacific, and a positive phase of a summertime Pacific-North American pattern in the northeastern Pacific/North America region. The western North Pacific summer monsoon is enhanced, while the East Asian summer monsoon is weakened. In the South Pacific, there is a basin-wide low in the mid-latitude with enhanced Australian high and the eastern South Pacific subtropical high. Such an atmospheric circulation pattern favors a dry rim surrounding the wet central tropical Pacific. The El Niño Modoki and its climate impacts are very different from those of El Niño. Possible geographical regions for dry/wet conditions influenced by El Niño Modoki and El Niño are compared. The two phenomena also have very different temporal features. El Niño Modoki has a large decadal background while El Niño is predominated by interannual variability. Mixing-up the two different phenomena may increase the difficulty in understanding their mechanisms, climate impacts, and uncertainty in their predictions.  相似文献   

12.
El Nio可通过海—气相互作用遥相关型影响东亚季风,进而影响中国气候,是中国短期气候最重要的预测指标之一。典型的El Nio事件通常在春、夏季开始,在秋、冬季成熟,在下一年的春、夏季消退,考虑到海—气作用的滞后效应,El Nio事件甚至可以在消退时期对东亚大气环流系统造成影响。因此,利用中国160站的逐月降水资料、NCEP/NCAR再分析资料以及美国NOAA提供的全球海温数据,对比分析了2015/2016年和1997/1998年典型El Nio衰减年我国夏季降水和东亚环流特征的差异,并讨论了造成差异的可能原因。结果表明:1)2016年和2008年夏季降水都大范围偏多,2016年夏季降水异常更为集中,但降水强度不及1998年。2)2016年降水的季节推进特征不明显。1998年6—8月的降水逐渐从南向北推进,与传统的季风降水演变进程较为一致。3)2016年和2008年我国夏季降水的差异与副热带高压的变化有直接的关系。1998年6—7月副热带高压较2016年同期偏西偏南,而2016年8月副热带高压更为偏西并明显比气候平均偏北。4)1997/1998年El Nio事件中的赤道西太平洋异常冷海温比较强盛,而2015/2016年基本表现为偏暖,可能是造成1998年6—7月副热带高压较2016年同期偏西偏南的原因。  相似文献   

13.
Xin Wang  Chunzai Wang 《Climate Dynamics》2014,42(3-4):991-1005
Our early work (Wang and Wang in J Clim 26:1322–1338, 2013) separates El Niño Modoki events into El Niño Modoki I and II because they show different impacts on rainfall in southern China and typhoon landfall activity. The warm SST anomalies originate in the equatorial central Pacific and subtropical northeastern Pacific for El Niño Modoki I and II, respectively. El Niño Modoki I features a symmetric SST anomaly distribution about the equator with the maximum warming in the equatorial central Pacific, whereas El Niño Modoki II shows an asymmetric distribution with the warm SST anomalies extending from the northeastern Pacific to the equatorial central Pacific. The present paper investigates the influence of the various groups of El Niño events on the Indian Ocean Dipole (IOD). Similar to canonical El Niño, El Niño Modoki I is associated with a weakening of the Walker circulation in the Indo-Pacific region which decreases precipitation in the eastern tropical Indian Ocean and maritime continent and thus results in the surface easterly wind anomalies off Java-Sumatra. Under the Bjerknes feedback, the easterly wind anomalies induce cold SST anomalies off Java- Sumatra, and thus a positive IOD tends to occur in the Indian Ocean during canonical El Niño and El Niño Modoki I. However, El Niño Modoki II has an opposite impact on the Walker circulation, resulting in more precipitation and surface westerly wind anomalies off Java-Sumatra. Thus, El Niño Modoki II is favorable for the onset and development of a negative IOD on the frame of the Bjerknes feedback.  相似文献   

14.
In recent decades, the typical El Nio events with the warmest SSTs in the tropical eastern Pacific have become less common, and a different of El Nio with the warmest SSTs in the central Pacific, which is flanked on the east and west by cooler SSTs, has become more fre-quent. The more recent type of El Nio was referred to as central Pacific El Nio, warm pool El Nio, or dateline El Nio, or the El Nio Modoki. Central Pacific El Nio links to a different tropical-to-extratropical teleconnection and exerts different impacts on climate, and several classification approaches have been proposed. In this study, a new classification approach is proposed, which is based on the linear combination (sum or difference) of the two leading Empirical Orthogonal Functions (EOFs) of tropical Pacific Ocean sea surface temperature anomaly (SSTA), and the typical El Ni o index (TENI) and the central El Nio index (CENI) are able to be derived by projecting the observed SSTA onto these combinations. This classification not only reflects the characteristics of non-orthogonality between the two types of events but also yields one period peaking at approximate two to seven years. In particular, this classification can distin-guish the different impacts of the two types of events on rainfall in the following summer in East China. The typical El Nio events tend to induce intensified rainfall in the Yangtze River valley, whereas the central Pacific El Nio tends to induce intensified rainfall in the Huaihe River valley. Thus, the present approach may be appropriate for studying the impact of different types of El Nio on the East Asian climate.  相似文献   

15.
利用NOAA逐月海表温度(SST)资料,NCEP/NCAR风场、高度场和比湿再分析资料和国家信息中心提供的753站逐日降水资料,对比分析了1997/1998年和2015/2016年两次强厄尔尼诺事件的海温异常分布特征、次年中国东部夏季降水以及环流异常特征,结果表明:1)2015/2016的厄尔尼诺事件是自1950年以来持续时间最长,强度最强的一次事件,日界线附近的海温较1997/1998年的偏高。2)1997/1998年厄尔尼诺事件次年华南西部、江南北部到长江流域、黄淮北部到华北南部以及我国东北地区降水较常年偏多。而2015/2016年厄尔尼诺事件次年降水范围和强度相对较小,强雨带主要分布在长江流域一带、黄淮地区和华北一带及河套北部。3)1997/1998年事件次年夏季西北太平洋副热带高压强盛,位置偏西,脊线偏南,向上垂直质量输送异常偏强、高低层水平风场配合以及水汽通量异常辐合偏强均有利于长江流域一带以及我国东北地区降水产生,而2015/2016年事件次年的副高相对偏弱,且脊线位置偏北、偏东,水平、垂直异常环流和水汽偏弱,因此降水范围和程度较1997/1998年的偏弱。从海温分布型和次年对我国东部夏季降水造成的影响上看,2015/2016年的超强厄尔尼诺事件有别于传统东部型事件。  相似文献   

16.
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   总被引:12,自引:1,他引:12  
袁媛  杨辉  李崇银 《气象学报》2012,70(3):467-478
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。  相似文献   

17.
周群  陈文 《大气科学》2012,36(4):851-862
本文利用美国NCEP/NCAR再分析资料、海温、降水和反映太阳活动强弱的太阳10.7 cm射电流量资料,研究了1952~2010年太阳活动11年周期对ENSO年海温异常演变以及与之相联系的东亚降水的影响,在此基础上着重分析了ENSO发展期秋季东亚地区降水异常对太阳射电流量高(HS)/低(LS)的不同响应以及相关的物理过...  相似文献   

18.
Indices of El Nino and El Nino Modoki: An Improved El Nino Modoki Index   总被引:2,自引:0,他引:2  
In recent years, El Nino Modoki (pseudo-El Nino) has been distinguished as a unique large-scale ocean warming phenomenon happening in the central tropical Pacific that is quite different from the traditional El Nino. Empirical Orthogonal Function (EOF) analysis is used to successfully separate El Nino and El Nino Modoki. The abilities of the NINO3 index, NINO3.4 index, NINO1+2 index and NINO4 index in characterizing the El Nino are explored in detail. It is suggested that the NINO3 index is comparatively optimal to monitor the El Nino among the four NINO indices, since other NINO indices either cannot well distinguish El Nino and El Nino Modoki signals or are easily disturbed by El Nino Modoki signals. Further, an improved El Nino Modoki index (IEMI) is introduced to better represent the El Nino Modoki that is captured by the second leading EOF mode of monthly tropical Pacific sea surface temperature anomalies (SSTA). The IEMI is an improvement of the El Nino Modoki index (EMI) through adjusting the inappropriate weight coefficients of the three boxes of EMI, and it effectively overcomes the lack of EMI in monitoring the two historical El Nino Modoki events and also avoids the possible risk of EMI in excluding the interference of El Nino signal, indicating the realistic and potential advantages.  相似文献   

19.
The present study reveals cross-season connections of rainfall variability in the South China Sea (SCS) region between winter and summer. Rainfall anomalies over northern South China Sea in boreal summer tend to be preceded by the same sign rainfall anomalies over southern South China Sea in boreal winter (denoted as in-phase relation) and succeeded by opposite sign rainfall anomalies over southern South China Sea in the following winter (denoted as out-of-phase relation). Analysis shows that the in-phase relation from winter to summer occurs more often in El Niño/La Niña decaying years and the out-of-phase relation from summer to winter appears more frequently in El Niño/La Niña developing years. In the summer during the El Niño/La Niña decaying years, cold/warm and warm/cold sea surface temperature (SST) anomalies develop in tropical central North Pacific and the North Indian Ocean, respectively, forming an east–west contrast pattern. The in-phase relation is associated with the influence of anomalous heating/cooling over the equatorial central Pacific during the mature phase of El Niño/La Niña events that suppresses/enhances precipitation over southern South China Sea and the impact of the above east–west SST anomaly pattern that reduces/increases precipitation over northern South China Sea during the following summer. The impact of the east–west contrast SST anomaly pattern is confirmed by numerical experiments with specified SST anomalies. In the El Niño/La Niña developing years, regional air-sea interactions induce cold/warm SST anomalies in the equatorial western North Pacific. The out-of-phase relation is associated with a Rossby wave type response to anomalous heating/cooling over the equatorial central Pacific during summer and the combined effect of warm/cold SST anomalies in the equatorial central Pacific and cold/warm SST anomalies in the western North Pacific during the mature phase of El Niño/La Niña events.  相似文献   

20.
基于1901-2000年多种海-气资料,分析了厄尔尼诺成熟年冬季-初夏西北太平洋异常反气旋(WNPAC)的年际变化特征及其对东亚气候的影响。结果表明,无论是厄尔尼诺事件成熟期的冬季还是次年的春季和初夏,WNPAC的年际变化主要存在两个空间变化型,即反映其强度变化的经验正交函数分解第1模态和反映其位置变化的第2模态。厄尔尼诺成熟年冬季WNPAC强度不仅与赤道中东太平洋海温异常有关,而且与太平洋西部(WP)型遥相关的强度有关,而其位置的变化则主要与西北太平洋局地海温异常以及北极涛动(AO)有关;次年春季,WNPAC的强度除了与赤道中东太平洋海温异常和太平洋西部型遥相关存在显著相关外,还与赤道大西洋海温异常有关,而其位置的变化则主要与西北太平洋局地海温异常和太平洋西部型遥相关有关;次年初夏,WNPAC强度主要与西北印度洋和西南印度洋的海温异常以及东亚-太平洋(EAP)型遥相关的强度有关。进一步分析表明,成熟年冬季-初夏WNPAC的强度和位置的变化均可对东亚地区降水异常分布产生影响,这对预测厄尔尼诺事件发生后冬季及后期春、夏季节东亚地区降水异常分布具有一定的指示意义。此外,次年初夏,WNPAC强度变化与西北太平洋台风发生频数存在显著负相关,即WNPAC越强,台风发生的频数越少,反之亦然。  相似文献   

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