太平洋-印度洋海温异常模态及其指数定义的初步研究

通过对太平洋地区海温场的经验正交函数分解,分析其第一特征向量场发现,春夏秋冬四季在印度洋中西部大范围地区、赤道中东太平洋的大范围地区的海面温度西太平洋地区的相反,这一特征向量在四个季节的方差贡献率均大于33%,说明这一海温场的空间分布结构是稳定的,我们称之为太平洋-印度洋海温异常模态.并对这种模态经过认真分析比较和研究后定义了该模态的指数.     

印度洋地区异常海温的偶极振荡与中国降水及温度的关系

利用1951-1997年近47年的印度洋海温距平场资料以及相应中国160站降水资料，通过相关普查得出，印度洋地区东西海温的偶极振荡与中国6-8月汛期的降水有较好的相关关系，特别是前期3-5月份的印度洋地区东西海温的偶极指数与中国6-8月降水的相关较好。分析1958-1995年NCEP 500hPa北半球高度场资料发现，印度洋偶极指数与欧亚中高纬度地区的高度场异常有密切的联系，其中印度洋偶极指数IODI负位相年有明显的PJ波列存在，印度洋偶极海湿异常很可能是通过PJ波列来影响中国的降水。同时，对印度洋地区海温偶极指数和中国地区温度的相关分析表明，印度洋地区海温偶极指数与冬季中国南部地区的温度也有较好的相关关系。     

印尼贯穿流对热带太平洋-印度洋海温异常综合模影响的初步模拟研究

印尼海域是联系热带太平洋和印度洋的纽带,为了讨论印度尼西亚贯穿流对热带太平洋-印度洋海温异常综合模的影响,利用一个准全球海洋环流模式,设计了打开、关闭印度尼西亚通道的数值试验对该问题进行初步探讨。试验结果表明,印尼贯穿流对热带太平洋、印度洋海温和海流的模拟有重要影响。在海洋表层,印尼贯穿流对热带太平洋-印度洋海温异常综合模所起作用不大,这时海洋的外强迫(大气风场、太阳辐射等)起主要作用;而在次表层,印尼贯穿流对热带太平洋-印度洋海温异常综合模起着重要的作用。     

INDIAN OCEAN DIPOLE AND ITS RELATIONSHIP WITH ENSO MODE

Near 100-year observed data sets are analyzed, and the results show that the variation of seasurface temperature(SST)in the equatorial Indian Ocean has a feature as a dipole oscillation.Thesituation of the dipole oscillation mainly shows the positive phase pattern(higher SST in the westand lower SST in the east than normal)and the negative phase pattern(higher SST in the east andlower SST in the west).The amplitude of the positive phase is larger than that of the negativephase.The dipole is stronger in September—November and weaker in January—April than inother months.It principally shows obviously inter-annual(4—5 year period)and inter-decadalvariation(25—30 year period).Although the Indian Ocean dipole in the individual year seems tobe independent of ENSO in the equatorial Pacific Ocean,in general,the Indian Ocean dipole hasobviously negative correlation with the Pacific Ocean “dipole”(similar to the inverse phase ofENSO).The atmospheric zonal(Walker) circulation is fundamental for relating the two dipoles toeach other.     

NUMERICAL SIMULATION OF INFLUENCE OF INDIAN OCEAN SSTA ON WEATHER AND CLIMATE IN ASIAN MONSOON REGION

Sea surface temperature anomaly (SSTA) exerts great influence on the generation of global weather and climate. Much progress has been made with respect to SSTA in the Pacific Ocean region in contrast to the Indian Ocean. The IAP9L model, which is developed at the Institute of Atmospheric Physics of the Chinese Academy of Science, is used to simulate the influence of the Indian Ocean SSTA on the general circulation and weather/climate anomalies in the monsoon region of Asia. It is found that the warm (cool) SSTA in the equatorial low latitudes of the Indian Ocean triggers winter (summer) teleconnection patterns in middle and higher latitudes of the Northern Hemisphere that are similar to PNA or EAP. They play a very important role in the anomaly of circulation or weather and climate in the middle and lower latitudes of the Asian summer monsoon region. With the warm (cool) SSTA forcing in the Indian Ocean, the Asian summer monsoon sets up at a late (early) date and withdraws at a early (late) date, lasting for a short (long) duration at a weak (strong) intensity. The Indian Ocean SSTA is shown to be an indicator for precipitation variation in China.     

降水对热带西南太平洋海温异常响应的数值试验

本文应用IAP9-AGCMⅡ九层大气环流数值模式，通过数值试验，研究了降水对热带西南太平洋SSTA(海温异常)的响应。结果表明：海温正异常下，夏季北半球热带中太平洋降水明显偏多；我国东部地区降水正常或偏多。海温负异常下，夏季赤道中太平洋降水偏少，我国大部地区降水正常或略偏少。当该区域SST异常时，从总体看降水对该异常响应最敏感的地区为北半球热带中太平洋、我国华中和西南、孟加拉湾和中南半岛。     

RELATIONSHIPS BETWEEN AUTUMN INDIAN OCEAN DIPOLE MODE AND THE STRENGTH OF SCS SUMMER MONSOON

Based on 1948 - 2004 monthly Reynolds Sea Surface Temperature (SST) and NCEP/NCAR atmospheric reanalysis data, the relationships between autumn Indian Ocean Dipole Mode (IODM) and the strength of South China Sea (SCS) Summer Monsoon are investigated through the EOF and smooth correlation methods. The results are as the following. (1) There are two dominant modes of autumn SSTA over the tropical Indian Ocean. They are the uniformly signed basin-wide mode (USBM) and Indian Ocean dipole mode (IODM), respectively. The SSTA associated with USBM are prevailing decadal to interdecadal variability characterized by a unanimous pattern, while the IODM mainly represents interannual variability of SSTA. (2) When positive (negative) IODM exists over the tropical Indian Ocean during the preceding fall, the SCS summer monsoon will be weak (strong). The negative correlation between the interannual variability of IODM and that of SCS summer monsoon is significant during the warm phase of long-term trend but insignificant during the cool phase. (3) When the SCS summer monsoon is strong (weak), the IODM will be in its positive (negative) phase during the following fall season. The positive correlation between the interannual variability of SCS summer monsoon and that of IODM is significant during both the warm and cool phase of the long-term trend, but insignificant during the transition between the two phases.     

印度洋海表温度主模态及其与亚洲夏季季风的关系

分析了印度洋SST主模态的时空特征,并探讨其对亚洲夏季季风的影响,结果表明:印度洋SST主模态的主要特征为整个海盆一致的增温趋势,主要具有准3a和准11a周期,在1976/1977年和1997/1998年分别具有两次年代际显著增温.印度洋SST主模态与中国雨区夏季降水有很好的关系,其增温趋势与华北、东北南部、华南东部和西南西部降水减少,长江中下游地区、东北北部和西北地区降水增多具有很好的关系,并与长江中下游梅雨雨量具有较好的正相关关系;其变化趋势对亚洲夏季季风系统具有显著影响,在高空,使南亚高压、高原南侧的高空东风以及从南海、东南亚至西南印度洋的高空越赤道气流减弱,但增强10°-20°N、40°-110°E的北风;在中层,使西北太平洋副热带高压强度偏强,面积偏大;在低层,增强索马里越赤道气流,但却削弱印度夏季季风低层环流,并且在加强东亚地区的低层南风在中国长江中下游地区及其以南地区的同时减弱华北地区的低层西南风;地面,使亚洲大陆的气压升高;与对流层整层垂直积分水汽输送通量的相关分布与低层环流的相似.因此,印度洋SST主模态的上升趋势是亚洲夏季季风趋于减弱和中国雨带南移的一个原因.     

东亚南亚夏季降水对海温异常响应的数值模拟

利用IAP AGCM-Ⅱ大气环流模式，模拟了赤道中太平洋地区海温异常对东亚和南亚夏季（6～8月）降水的影响。结果表明：当1～4月该海温呈正异常时，中南半岛和我国东部降水将明显偏多，孟加拉湾附近降水偏少；而该海温呈负异常时，则我国华中和孟加拉湾附近降水偏多；对以上海温异常最敏感处为中南半岛和孟加拉湾附近地区，其中前者降水与该海温异常呈正相关，后者则呈负相关；该海温异常还会在中高纬地区激发出强迫波列。     

热带印度洋秋季偶极子模态与南海夏季风强度变化的关系

利用多年的Reynolds月平均海表温度资料和NCEP／NCAR全球大气再分析资料,采用经验正交函数（EOF）分析和滑动相关方法,研究了热带印度洋秋季偶极子模态和南海夏季风强度变化的关系。结果表明：（1）热带印度洋秋季海表温度距平（SSTA）的主要模态是全区一致型和偶极子（IOD）型,全区一致型模态主要代表了秋季SSTA全海盆一致的年代际及其以上时间尺度的变化,IOD型模态主要反映热带印度洋秋季SSTA年际时间尺度的变化。（2）当前期秋季热带印度洋存在正（负）IOD模态时,南海的夏季风强度减弱（增强）。二者年际变化的负相关关系在长期趋势的冷位相期不显著,而在暖位相期显著。（3）当南海夏季风强度增强（减弱）时,后期秋季热带印度洋出现正（负）IOD模态。二者年际变化的正相关关系在长期趋势的冷、暖位相期显著,在冷、暖位相转换期前后不显著。     

印度洋海温异常对亚洲季风区天气气候影响的数值模拟研究

利用中国科学院大气物理研究所ＩＡＰ９Ｌ大气环流模式，模拟研究了印度洋ＳＳＴＡ对亚洲季风区大气环流和天气气候异常的影响。结果表明，印度洋赤道低纬地区的暖（冷）ＳＳＴＡ，可以在北半球中高纬度地区激发产生与ＰＮＡ和ＥＡＰ类似的冬季型或夏季遥相关型波列，对亚洲季风区中低纬度地区的环流异常或天气气候异常有重要作用。当印度洋暖（冷）ＳＳＴＡ强迫时，亚洲夏季风建立较正常偏晚（偏早），撤退较早（较晚），季风季节长     

INDIAN OCEAN DIPOLE AND ITS RELATIONSHIP WITH ENSO MODE*

Near 100-year observed data sets are analyzed, and the results show that the variation of sea surface temperature(SST)in the equatorial Indian Ocean has a feature as a dipole oscillation.The situation of the dipole oscillation mainly shows the positive phase pattern(higher SST in the west and lower SST in the east than normal)and the negative phase pattern(higher SST in the east and lower SST in the west).The amplitude of the positive phase is larger than that of the negative phase.The dipole is stronger in September—November and weaker in January—April than in other months.It principally shows obviously inter-annual(4—5 year period)and inter-decadal variation(25—30 year period).Although the Indian Ocean dipole in the individual year seems to be independent of ENSO in the equatorial Pacific Ocean,in general,the Indian Ocean dipole has obviously negative correlation with the Pacific Ocean "dipole"(similar to the inverse phase of ENSO).The atmospheric zonal(Walker) circulation is fundamental for relating the two dipoles to each other.     

热带印度洋-太平洋热力异常联合模对我国夏季降水的影响

基于我国160个台站的降水资料和西太平洋副热带高压指数,利用典型相关分析和合成分析等方法,研究了热带印度洋-太平洋热力异常联合模对我国夏季降水的影响,并探讨了该联合模与西太平洋副热带高压的关系。结果表明,该联合模对我国夏季降水有一年到半年的超前影响,且以冬季联合模对次年夏季降水的影响最显著。当冬季联合模出现正异常时,次年夏季我国四川地区、长江流域、华北南部降水偏多,而华北北部和江南大部分地区降水偏少;反之亦然。进一步分析表明,冬季热带印度洋-太平洋热力异常联合模对我国夏季降水的影响可能是通过夏季西太平洋副热带高压的变动来实现的。     

EFFECTS OF INDIAN OCEAN SSTA WITH ENSO ON WINTER RAINFALL IN CHINA

Based on Hadley Center monthly global SST, 1960-2009 NCEP/NCAR reanalysis data and observation rainfall data over 160 stations across China, the combined effect of Indian Ocean Dipole （IOD） and Pacific SSTA （ENSO） on winter rainfall in China and their different roles are investigated in the work. The study focuses on the differences among the winter precipitation pattern during the years with Indian Ocean Dipole （IOD） only, ENSO only, and IOD and ENSO concurrence. It is shown that although the occurrences of the sea surface temperature anomalies of IOD and ENSO are of a high degree of synergy, their impacts on the winter precipitation are not the same. In the year with positive phase of IOD, the winter rainfall will be more than normal in Southwest China （except western Yunnan）, North China and Northeast China while it will be less in Yangtze River and Huaihe River Basins. The result is contrary during the year with negative phase of IOD. However, the impact of IOD positive phase on winter precipitation is more significant than that of the negative phase. When the IOD appears along with ENSO, the ENSO signal will enhance the influence of IOD on winter precipitation of Southwest China （except western Yunnan）, Inner Mongolia and Northeast China. In addition, this paper makes a preliminary analysis of the circulation causes of the relationship between IOD and the winter rainfall in China.     

RELATIONSHIP BETWEEN DIPOLE OSCILLATION OF SSTA OF AND TEMPERATURE IN CHINA

The work is a general survey SSTA data of the Indian Ocean and of precipitation at 160 Chinese weather stations over 1951～1997(47years).It reveals that the dipole oscillation of SST,especially the dipole index of March～May,in the eastern and western parts of the ocean correlates well with the precipitation during the June～August raining season in China.As shown in analysis of 500-hPa Northern Hemisphere geopotential height height by NCEP for 1958-1995,the Indian Ocean dipole index(IODI) is closely related with geopotential height anomalies in the middle-and higher-latitudes in the Eurasian region.As a negative phase year of IODI corresponds to significant Pacific-Japan(PJ) wavetrain,it is highly likely that the SST for the dipole may affect the precipitation in China through the wavetrain.Additionally,correlation analysis of links between SST dipole index of the Indian Ocean region and air temperature in China also shows good correlation between the former and wintertime temperature in southern China.     

ENSO循环的两个不同位相期印度海洋表温度异常的特征分析

通过对ENSO循环的两个不同位相中印度洋地区海表温度变化特征的分析，指出印度洋地区的海温变化与赤道东太平洋地区的海温变化有较好 的相关关系，是ENSO循环的重要组成部分，对应于赤道东太平洋暖位相期，印度洋地区的海温分布为东冷西暖，与此相反，在赤道东太平洋冷位相，印度洋地区的温分布为东暖西冷，进一步的分析还发现，印度洋东，西部地区海温变化纬向差异最明显的区域位于印度洋赤道以南0－25℃附近，且这种差异具有明显的年季变化特征，在整个夏季风期间差异较大，而冬季风期间较小，其中冷位相期间的纬向差异比暖位相期间的纬向差异大，代表印度洋纬向差异的IDM（偶极指数）变化与赤道东太平洋地区的海温变化有很好的正相关关系。     

中国夏季降水与太平洋SSTA年代际变化关系的初步研究

利用1951-2001年逐月NCEP再分析高度场、风场资料，COADS海表温度资料及中国147个台站逐月降水资料，运用SVD分析、SVD与回归分析相结合等方法，研究了太平洋SSTA与中国夏季降水年代际变化的相互关系，发现热带西太平洋是影响中国华南降水年代际变化的关键区，1950年代-1970年代后期，该海域SSTA为正，对应中国长江以南地区的夏季降水偏多，而长江以北则偏少；1970年代以后反之；影响中国长江中下游地区及其两侧降水年代际变化的关键区在中纬中部北太平洋，1970年代后期-1990年代前期，该海域SSTA为负，对应长江中下游夏季降水偏多，其两侧降水偏少；影响中国东北降水年代际变化的关键区是低纬中太平洋，1970年代-1980年代前期，低纬中太平洋SSTA为负，与之对应，中国东北夏季降水偏少；1950年代～1960年代中期、1990年代前、中期则反之。进一步对太平洋SSTA年代际变化影响中国夏季降水年代际变化的可能机制作了初步的研究。     

NUMERICAL SIMULATION OF THE INFLUENCE OF INDIAN OCEAN DIPOLE ON CLIMATIC VARIATIONS OVER EAST ASIAN MONSOON REGION DURING EQUATORIAL EAST PACIFIC OCEAN SSTA

1 INTRODUCTION In the recent years, more and more researches have shown that the effect of Tropical Ocean is very evident in the process of ocean-air interaction; Sea-Surface Temperature Anomaly (SSTA) takes on global configuration and SSTA in different areas are interrelated and also have their respective characteristics. The SSTA over Indian Ocean and Pacific Ocean are interrelated. WU et al.[1] and MENG et al.[2] indicated that the evident positive correlation of inter-annual…     

ROLE OF EQUATORIAL PACIFIC OCEAN SUBSURFACE OCEANIC TEMPERATURE MODE IN ENSO CYCLE

Based on the simple ocean data assimilation (SODA) reanalysis dataset from the University of Maryland and the method of Empirical Orthogonal Functions (EOF), the characteristics of interannual and interdecadal variabilities of the equatorial Pacific subsurface oceanic temperature anomaly (SOTA) are captured. The first and second modes of the equatorial Pacific SOTA in the interannual and interdecadal variations are found respectively and the effect of the second mode on the ENSO cycle is discussed. Results show that the first mode of SOTA’s interannual and interdecadal variabilities exhibit a dipole pattern, indicating that the warm and cold temperature anomalies appear simultaneously in the equatorial subsurface Pacific. The second mode shows coherent large-scale temperature anomalies in the equatorial subsurface Pacific, which is a dominant mode in the evolution of ENSO cycle. The temporal series of the second mode has a significant lead correlation with the Ni?o-3.4 index, which can make a precursory prediction signal for ENSO. The function of this prediction factor in SOTA is verified by composite and case analyses.     

热带太平洋次表层海温异常年代际变率及其对中国气候异常的影响

利用近50年月平均的SODA海洋同化资料和NCEP大气再分析资料,研究了热带太平洋次表层海温异常(SOTA)年代际变率主要分布型以及与之相关的亚洲-北太平洋-北美地区上空异常大气环流场,并揭示了类ENSO模态与中国气候异常之间的联系.得到主要结果:(1)热带太平洋SOTA年代际变率有两种类ENSO模态.第一模为类ENSO事件成熟期热带太平洋年代际SOTA状态；第二模为类ENSO过渡期热带太平洋年代际SOTA状态.二者组合构成类ENSO事件40年左右及其背景下13年左右的周期振荡.(2)类ENSO事件对亚洲-北太平洋-北美上空中高纬和副热带大气系统年代际变化具有重要影响.类El Ni(n)o成熟期间冬季,中高纬地区大气环流经向型发展,贝加尔湖高压脊加强,西太平洋副高偏强、位置偏西,蒙古高原为较强的异常反气旋环流.类El Ni(n)o衰退期(类La Ni(n)a发展期)夏季,贝加尔湖低压槽加深,乌拉尔山高压脊加强,西太平洋副高偏弱,新疆-河套地区为较强的异常反气旋环流距平.类La Ni(n)a事件时相反.(3)热带太平洋类ENSO事件通过影响中高纬和副热带大气系统,造成中国北部地区上空南风距平的年代际变化,进而导致东亚季风和中国气候异常.类El Ni(n)o事件成熟期,中国北部地区上空多异常偏北风,东亚季风弱,华北少雨,长江中、下游多雨；类El Ni(n)o衰退(类La Ni(n)a发展)期,中国北部地区上空亦为异常偏北气流,东亚季风较弱,华北少雨.中国气候异常型主要取决于类ENSO第一模态,而第二模态主要视位相异同来加强或减弱第一模态.两个类ENSO模态的共同作用导致1978年前后中国气候跃变和华北地区持续20余年的干旱.近期类ENSO模的振荡从1998年左右开始转为类La Ni(n)a模态,大致在2018年左右结束.在此期间,华北降水有望增加,长江中、下游降水可能减少.