INFLUENCE OF EL NINO ON WEATHER AND CLIMATE IN CHINA

El Nino as well as the Southern Oscillation is one of the strongest signals known so far over climatic noise ininterannual variations of the atmosphere and oceans.A great number of studies have shown definitely relationships be-tween the events and climatic anomalies in China.In this review,observational results obtained in the recent severalyears are first summarized.Then the possible physical mechanisms on the influence of El Nino are presented and,finally,the associated problems are discussed.     

厄尔尼诺/南方涛动与我国秋季气候异常

利用1951—1999年我国秋季(9—11月)降水、温度和南方涛动指数(SOI)1935—2000年资料研究ENS0与我国秋季气候异常的关系，结果表明，秋季降水与ENS0的关系远比夏季降水与ENS0的关系好。E1Nino年我国秋季降水出现南多北少的分布型(S型)的频率增加近20％，而La Nina年出现S型的频率减少20％。反之，当我国秋季降水距平出现大尺度南北降水异常时，往往表示当时有ENS0现象发生。E1 Nino和La Nina年我国秋季降水距平的分布有显著差异，且这种显著差异主要表现在长江南北、西北和河套地区。不同时段SOI对秋季气候异常的影响不同，当年4—10月SOI值与秋季降水EOF分解第二时间系数(反映大尺度南北旱涝异常特征的权重系数)之间为较明显的正相关，其中8月最显著。上一年7—9月和同年1—3月的SOI值同秋季气温EOF分解的第二时间系数的正相关较明显。可根据前期5—8月的月平均SOI值，预报秋季大尺度降水异常，当年5—8月的SOI平均值偏高时，长江以南(北)地区的降水将有减少(增加)的可能，反之亦然。     

El Nino事件与中国东部气温异常

本文进行的多年历史资料的分析表明,中国东部地区的气温异常同El Nino事件有密切的关系 在El Nino年夏季中国东北及附近地区气温多比常年偏低,而在反El Nino年夏季那里气温多出现高温异常。在El Nino年冬季,中国东部广大地区气温比常年偏高:反El Nino年冬季,中国东部广大地区气温比常年编低。中国东部地区的温度异常同El Nino所造成的大气环流异常的关系,本文亦作了分析研究。 中国东部地区冬半年气温的持续编低同El Nino事件的发生有密切关系,表明东亚地区持续的强高空槽活动(寒潮活动)可能是El Nino事件发生的重要触发机制。      

厄尔尼诺与我国汛期降水

本文详细地讨论了厄尔尼诺与我国汛期大尺度降水的关系。指出,厄尔尼诺东部型,北太平洋海温的三个主要正负距平区的结构具有PNA遥相关型;厄尔尼诺中部型,北太平洋海温的三个主要正负距平区分布在赤道东太平洋到千岛群岛一线上。进而指出,厄尔尼诺东部型峰期过后,我国汛期降水的大尺度特征是长江流域降水偏少,江南和华北地区降水偏多。在厄尔尼诺中部型峰期过后则相反,长江流域降水偏多,江南和华北降水偏少。     

厄尼诺与南海的台风活动

本文对厄尼诺年(赤道东太平洋SST有持续正距平)和反厄尼诺年(赤道东太平洋SST有持续负距平)南海的台风(包括进入南海的西太平洋台风和在南海生成的台风)活动进行了统计分析。结果表明,厄尼诺同南海的台风活动有明显关系:厄尼诺年平均台风数偏少,反厄尼诺年平均台风数偏多,其异常主要发生在8—11月份;在两广沿海登陆的平均台风数也是厄尼诺年偏少,反厄尼诺年偏多,其异常以10和11月最显著;在北部湾海域活动的台风多在8—9月份,也是厄尼诺年偏少,反厄尼诺年偏多。文本也对厄尼诺如何影响南海的台风活动提出了初步看法。      

EI Nino类型年对低纬大气环流及我国天气的影响

应用热带格点风及OLR资料,通过统计和物理量诊断,讨论了El Nino不同过程类别的低纬环流的差异和季节性特征以及对我国天气气候的影响。得到如下主要结果:(1)El Nino年的不同类型间存在着差异。它们在常定动能、动量和温度的分布特征等方面都存在着明显的差异。(2)El Nino不同的过程类别对我国降水、气温的影响不同,且表现出明显的季节变化。     

A FURTHER STUDY ON INTERACTION BETWEEN ANOMALOUS WINTER MONSOON IN EAST ASIA AND EL NINO

The interaction between anomalous winter monsoon in East Asia and El Nino is further stud-ied in this paper.The new results still more proved a previous conclusion:there are clear interac-tions between El Nino and winter monsoon in East Asia.The continual westerly burst andstronger cumulus convection over the equatorial central-western Pacific caused by stronger wintermonsoon in East Asia can respectively excite anomalous oceanic Kelvin wave and stronger atmo-spheric intraseasonal oscillation in the tropics,then excite the El Nino event through air-sea inter-action.In El Nino winter,there are warmer and weaker winter monsoons in East Asia.The El Ni-no will still reduce the intensity of intraseasonal oscillation and leads it to be barotropic structure.     

EI Nino类型年对低纬大气环流及我国天气的影响

应用热带格点风及OLR资料,通过统计和物理量诊断,讨论了El Nino不同过程类别的低纬环流的差异和季节性特征以及对我国天气气候的影响。得到如下主要结果:(1)El Nino年的不同类型间存在着差异。它们在常定动能、动量和温度的分布特征等方面都存在着明显的差异。(2)El Nino不同的过程类别对我国降水、气温的影响不同,且表现出明显的季节变化。     

厄尔尼诺年和反厄尔尼诺年热带大气环流及几个主要系统的特征

对近十年出现的3个厄尔尼诺年和2个反厄尔尼诺年中4—10月的夏季热带平均流场及几个主要系统作了定量综合分析和对比,得到:它们的沃克环流和哈得莱环流、对流层低层ITCZ和对流层高层TUTT的位置以及40—50°E、145°155°E处的低层越赤道气流强度均和常年不同,它们各自的年际和月际之间的平均环流和主要系统的特征也有差别。      

北半球500百帕极地环流与厄尔尼诺、南方涛动及我国气温场的遥相关

本文用1951—1984年的资料对500百帕、65°N以北的高度场作自然正交展开,用模糊聚类对典型场归类。指出,极涡月平均场有三种形态,1月份平均场形态较特殊;大尺度距平场也有三种形态,4月份距平场形态较特殊。此外,研究了典型场的时间权重系数与厄尔尼诺、南方涛动的关系。指出,厄尔尼诺现象发生的当年4月、10月极地大尺度距平场有明显的异常特征。这种极地环流异常已明显影响到我国4月份、10月份的气温场。因而,可能是厄尔尼诺年我国气温4月偏低、10月偏高的一个重要原因。     

赤道太平洋降水与厄·尼诺

根据1899年—1982年赤道太平洋降水资料,研究了10月—12月降水量的时空变化。发现中太平洋最主要的特点是赤道地区与20°N以北及10°S以南变化相反。与赤道东太平洋海温变化比较证实,海温高时中太平洋多雨。分析赤道中太平洋多雨及少雨时海平面气压场表明,多雨时赤道低压偏东,南太平洋高压弱,而澳大利亚气压上升。最后指出,1982—1983年的厄·尼诺事件,就其伴随的环流与气候异常来讲,与以前的事件并无本质上的不同,但其强烈程度则是几十年来少见的。     

THE DECADAL CLIMATE VARIABILITY AND THE ANOMALOUS ENSO DEVELOPMENTS IN 1990S

By using the wavelet transform method,the ENSO(2—7 a)signal and the decadal variability(8—20 a)are filtered out from the long-term SST data sets in order to investigate characteristicsof the decadal variability and its impact on the ENSO.It is found that there are two different kindsof decadal SSTA modes-horseshoe and horse saddle patterns in the tropical Pacific.Thehorseshoe pattern represents that the decadal SSTA variability in the central Pacific is in phasewith that in the eastern Pacific.The horse saddle pattern is named that they are out of phase.Theformer constituted the decadal variability before 1990s and the latter mainly prevailed during1990s.As the response of atmosphere to the ocean,two decadal wind patterns appear inassociation with the SST decadal modes.One is characterized by anomalous development of thezonal wind,the other by anomalous development of the meridional wind.These two kinds ofmodes can also be regarded as different phases of the decadal oscillation.Further studies haveshown that the influences of the two kinds of modes on the ENSO are different.The horse saddlemode has a stronger impact on the ENSO than the horseshoe mode.A possible mechanism for the influence of the decadal variability on the ENSO signal ispresented.The central part of the thermocline along the equatorial Pacific moves up or downsimultaneously with its eastern part while the decadal variability bears the horseshoe pattern.Butthe two segments of the thermocline in the central and eastern Pacific act oppositely while thedecadal variability shows the horse saddle pattern.In this case it has an-influence on the individualENSO'events by the superposition of the decadal variability.     

TYPICAL ANOMALOUS WIND STRESS PATTERNS IN TROPICAL PACIFIC ASSOCIATED WITH EL NINO/SOUTHERN OSCILLATION

Based on years of month-to-month observations of sea surface temperature anomaly (SSTA) and wind stress anomaly, typical wind stress patterns in the tropical Pacific associated with ENSO are Studied with the techniques of linear regression and EOF analysis. The anomalous field, which is linearly correlated with ENSO, is found to be varying at low frequencies on the temporal scale and to be in four typical patterns of distribution horizontally.Pattern 1 is of the easterly anomaly and wind stress divergence in the equatorial region east of the date line. Pattern 2 is of the westerly anomaly and wind sttess convergence in the equatorial region east of the date line. Pattern 3 is of the westerly anomaly and wind stress convergence south of the Equator but east of the data line, with the easterly anomaly west of it. Pattern 4 is of the weak easerly anomaly east 160°W and the westerly anomaly west of 160°W. Wind stress fields linearly independent of ENSO are of a high-frequency process with a typical pattern off the Equator that has a large horizontal amplitude. Using an ocean anomaly-forcing model with the regressed wind stress anomaly field that is associated with ENSO, principal signals of ENSO are reproduced. It indicates the fundamental nature of the typical wind field anomaly patterns revealed for the genesis of El Nino.     

El Nino事件当年和次年夏季低纬环流特征的初步分析

分析1950年以来中等强度以上的ElNiño和LaNina当年和次年夏季(7月)低纬度风场和500hPa高度距平场,发现有不同的特征。其中中-西太平洋近赤道地区850、200hPa上风场异常变化十分明显,这种异常变化与南北半球大气相互作用有密切关系。在500hPa高度距平场上,北半球中、高和低纬地区表现出不同的正、负距平分布型式。上述特点对气候短期预测有一定参考意义。     

CHARACTERISTICS OF THE NORTHERN HEMISPHERE 500hPa DIABATIC HEAT FLOW FIELD IN YEARS OF EL NINO AND ANTI-EL NINO

In this paper,by using spectral method,the monthly-and seasonal-scale atmospheric diabatic heat flow(ADHF)departure fields are diagnosed in the period of 1964—1985 with 6 El Nino years and 6 anti-El Nino years over theNorthern hemisphere(NH).The results show that El Nino phenomena have pronounced influence on the ADHF depar-ture fields.The response of atmosphere exhibits a preferred arrangement of organizing positive and negative departurecenters at low,middle and high latitudes.In anti-El Nino years,the response has the same forms as in El Nino years,but departure centers are opposite in phase.Furthermore,ADHF departure shows low-frequency oscillation in El Ninoyears and anti-El Nino years.The center of difference in departure between El Nino and anti-El Nino years displays abi-monthly oscillation.Finally,through air-sea correlation analysis,it is pointed out that the SST anomaly is the most important cause forADHF anomaly.     

中国气候异常变化与ENSO准四年循环的联系分析

从月资料分析入手，分析了中国大陆地区的降水和气温异常与ENSO的联系。首先用REOF方法对降水和气温的变化进行分区分析，并讨论其年际变化特点。然后对降水和海温场、气温和海温场分别进行CSVD分析，讨论了在ENSO准四年循环的不同位相上，气温和降水的异常变化情况。结果表明：（1)在ElNino期间，我国东部地区，尤其是东北、长江中下游的江南地区降水偏多，容易发生洪涝，华北地区、黄河流域尤其是中部降水偏少，可能发生干旱。其中长江中下游的南部降水与赤道中东太平洋海温在准四年变化上关系密切，当中东太平洋海温达到最高值后约3个月，长江中下游的南部降水出现最大正距平。(2)在ElNino期间，东北容易出现低温天气，而其它地区尤其是河套地区及西南南部易出现高温天气。其中东北地区气温变化与赤道中东太平洋海温在准四年变化上关系密切，当中东太平洋海温达到最高值后约2个月，东北气温的负距平出现最低。LaNina阶段，情况与前述相反。     

ANALYSIS OF THE RELATIONSHIP BETWEEN THE CHINA ANOMALOUS CLIMATE VARIATION AND ENSO CYCLE ON THE QUASI-FOUR-YEAR SCALE

1 INTRODUCTION Much work has been done addressing the relationship between anomalous climate changes and ENSO in China and the results vary much. For instance, Li et al. (1987) [1] think that the Mei-yu (sustained rain) starts later, lasts shorter and pre…     

西北太平洋台风路径与厄尼诺关系初步分析

本文分析了近百年西北太平洋台风路径与厄尼诺的关系,得出了在厄尼诺年,西太平洋(120°E以东)转向的台风路径比在反厄尼诺年偏多,而西行路径则偏少。厄尼诺与反厄尼诺年的台风路径差异主要是受副高形势的影响,有明显的月际差异。      

ElNino事件当年和次年夏季低纬环流特征的初步分析

分析１９５０年以来中等强度以上的ＥｌＮｉｎｏ和ＬａＮｉｎａ当年和次年夏季低纬度风场和５００ｈＰａ高度距平场发现有不同特征。其中中－西太平洋近赤道地区８５０、２００ｈＰａ上风场异常变化十分明显,这种异常变化与南北半球大气相互作用有密切关系。     

VARIATIONS IN THE TELECONNECTION INTENSITY INDICES AND THEIR REMOTE RESPONSE TO THE EL NINO EVENTS IN THE NORTHERN HEMISPHERE

In this study,the monthly and seasonal teleconnection intensity indices of the Pacific/North American(PNA),Western Atlantic(WA),Western Pacific(WP),Eastern Atlantic(EA)and Eurasian(EU)patterns for the periodfrom 1951 through 1990 are calculated.On this basis,their climatic variations and the relationship between the fiveteleconnection intensity indices and the El Nino events are examined.It is noted that when El Nino is at its mature stage(winter),the weak WP pattern is mainly characteristic of the circulation and the strong PNA pattern is the next.Insummer when El Nino occurs and develops,the strong EU,weak WP and weak WA patterns are the main characteris-tics without the PNA circulation anomalies.Finally,by the nonlinear mapping method a nonlinear mapping diagram isestablished for diagnosing El Nino using three summer teleeonuection intensity indices and May and August SouthernOscillation Indices(SOIs).Thus,the El Nino phenomenon occurring in 1991 is diagnosed.Besides,the winter atmos-pheric circulation of the 1991/1992 El Nino is found to be the weak WP pattern and the PNA pattern is also weak.