南极海冰涛动对北半球夏季大气环流的影响

南极海冰首要模态呈现偶极子型异常,正负异常中心分别位于别林斯高晋海/阿蒙森海和威德尔海。过去研究表明冬春季节南极海冰涛动异常对后期南极涛动（Antarctic Oscillation,AAO）型大气环流有显著影响,而AAO可以通过经向遥相关等机制影响北半球大气环流和东亚气候。本文中我们利用观测分析发现南极海冰涛动从5～7月（May–July,MJJ）到8～10月（August–October, ASO）有很好的持续性,并进一步分析其对北半球夏季大气环流的可能影响及其物理过程。结果表明,MJJ南极海冰涛动首先通过冰气相互作用在南半球激发持续性的AAO型大气环流异常,使得南半球中纬度和极地及热带之间的气压梯度加大,在MJJ至JAS,纬向平均纬向风呈现显著的正负相间的从南极到北极的经向遥相关型分布。对流层中层位势高度场上,在澳大利亚北部到海洋性大陆区域,出现显著的负异常,在东亚沿岸从低纬到高纬呈现南北走向的“? + ?”太平洋—日本（Pacific–Japan,PJ）遥相关波列,其对应赤道中部太平洋及赤道印度洋存在显著的降水和海温负异常,西北太平洋至我国东部沿海地区存在显著降水正异常和温度负异常;低纬度北美洲到大西洋一带存在的负位势高度异常和北大西洋附近存在的正位势高度异常中心,构成一个类似于西大西洋型遥相关（Western Atlantic,WA）的结构,对应赤道南大西洋降水增加和南撒哈拉地区降水减少。从物理过程来看,南极海冰涛动首先通过局地效应影响Ferrel环流,进而通过经圈环流调整使得海洋性大陆区域和热带大西洋上方的Hadley环流上升支得到增强,海洋性大陆区域特别是菲律宾附近的热带对流活动偏强,激发类似于负位相的PJ波列,影响东亚北太平洋地区的大气环流,而热带大西洋对流增强和北传特征,则通过激发WA遥相关影响大西洋和欧洲地区的大气环流。以上两种通道将持续性MJJ至ASO南极海冰涛动强迫的大气环流信号从南半球中高纬度经热带地区传递到北半球中高纬地区,从而对热带和北半球夏季大气环流产生显著影响。     

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 period from 1951 through 1990 are calculated.On this basis,their climatic variations and the relationship between the five teleconnection 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.In summer when El Nino occurs and develops,the strong EU,weak WP and weak WA patterns are the main characteristics without the PNA circulation anomalies.Finally,by the nonlinear mapping method a nonlinear mapping diagram is established for diagnosing El Nino using three summer teleeonuection intensity indices and May and August Southern Oscillation Indices(SOIs).Thus,the El Nino phenomenon occurring in 1991 is diagnosed.Besides,the winter atmospheric circulation of the 1991/1992 El Nino is found to be the weak WP pattern and the PNA pattern is also weak.     

Evolution of intraseasonal oscillation over the tropical western pacific / south china sea and its effect to the summer precipitation in southern china{1{

In this paper, the evolution of intraseasonal oscillation over the South China Sea and tropical western Pacific area and its effect to the summer rainfall in the southern China are studied based on the ECMWF data and TBB data) analyses. A very low-frequency waves exist in the tropics and play an important role in dominating intraseasonal oscillation and lead to special seasonal variation of intraseasonal oscillation over the South China Sea / tropical western Pacific area. The intraseasonal oscillation (convection) over the South China Sea and tropical western Pacific area is closely related to the summer rainfall (convection) in the southern China. Their relationship seems to be a seesaw feature, and this relationship resulting from the different pattern of convection in those two re-gions is caused by the different type of local meridional circulation     

Evolution of Intraseasonal Oscillation over the Tropica lWestern Pacific/South China Sea and Its Effect to the Summer Precipitation in Southern China

ＥｖｏｌｕｔｉｏｎｏｆＩｎｔｒａｓｅａｓｏｎａｌＯｓｃｉｌａｔｉｏｎｏｖｅｒｔｈｅＴｒｏｐｉｃａｌＷｅｓｔｅｒｎＰａｃｉｆｉｃ／ＳｏｕｔｈＣｈｉｎａＳｅａａｎｄＩｔｓＥｆｅｃｔｔｏｔｈｅＳｕｍｍｅｒＰｒｅｃｉｐｉｔａｔｉｏｎｉｎＳｏｕｔｈｅｒｎＣｈｉ...     

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.     

华北春季沙尘暴频次与环流年际变率的相关分析

分析了近40年来华北春季沙尘暴频次与前秋、前冬和当年春季大尺度大气环流因子的关系,重点是检查年际尺度上的相关。结果表明,年际尺度上与沙尘暴频次有密切关系的环流因子包括:春季太平洋/北美遥相关型(PNA)、春季北太平洋指数(NP)、冬季亚洲区极涡面积。前者为正相关,后二者为负相关。这与用包含低频变率的原始序列进行分析的结果有很大的不同。原始序列分析的结果表明,与华北沙尘暴频次有关的环流因子主要是春季太平洋准10年振荡(PDO,为负相关),春季北半球极涡面积和亚洲区极涡面积(正相关)、前冬西大西洋型(WA,为正相关),以及前秋亚洲区极涡面积(正相关)。说明在不同时间尺度上,大气环流因子有不同的作用。此外,除了PNA、NP和亚洲区极涡面积外,年际尺度上ENSO及WA也可能对沙尘暴频次存在适度的影响。年际尺度上春季12个环流因子对春季沙尘暴频次的方差贡献率为65.3%。     

2014年夏季浙江低温多雨的大尺度环流特征及与海温异常关系

利用NECP/NCAR再分析资料、国家气候中心和NOAA相关资料,研究了与2014年浙江夏季低温多雨事件相关的大尺度环流特征和海温因子。结果表明:中纬度我国东部到日本南部气旋性环流异常的存在有利于浙江夏季出现低温多雨,异常偏强偏南的西太平洋副热带高压（简称副高）是8月罕见低温多雨的直接原因;东亚-太平洋型遥相关（EAP）和欧亚型遥相关（EU）是影响浙江夏季低温阴雨的主要遥相关型,当EAP负位相和EU正位相时,冷空气容易堆积和南下,与暖湿气流交汇,有利于降水降温,8月罕见低温阴雨是EAP负位相和EU正位相协同作用的结果。进一步的分析表明ENSO暖位相激发了西太平洋上空强烈的异常下沉气流和反气旋,使得副高偏南偏强,东亚地区呈EAP波列型响应;热带印度洋海温全区一致模态（IOBW）暖位相的维持进一步减弱了8月海洋性大陆地区的对流活动;北大西洋中部海温季内的变化或许与EU位相的转变有联系。     

Studies on the northern early summer teleconnection patterns,their interannual variations and relation to drought/flood in China

By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the Eastern Atlantic (EA), the Eurasian (EU), the Bengal / Northern Pacific (BNP), the Western Pacific (WP), the East Asian / Pacific (EAP), and the Huanghe / East Asian (HEA) patterns. Their centers are determined and their yearly intensity indices (1951-1990) are calculated. On this basis the relationship between their interannual variations and the drought / flood in China is examined. It is noted that the EU, HEA and EAP wave trains are closely related to the drought/ flood in China. The HEA and EAP patterns strongly influence the precipitation in eastern China. For ex-ample, the fierce floods experienced in 1991 early summer over China are related to the weak EAP and strong HEA patterns.     

Seasonal prediction of tropical cyclone genesis frequency over the western North Pacific using teleconnection patterns

This study has developed a multiple linear regression model for the seasonal prediction of the summer tropical cyclone genesis frequency (TCGF) in the western North Pacific using the three teleconnection patterns. These patterns are representative of the Siberian High Oscillation (SHO) in the East Asian continent, the North Pacific Oscillation in the North Pacific, and Antarctic Oscillation (AAO) near the Australia during the boreal spring (April–May). This statistical model is verified through the two analyses: (a) statistical method of cross validation and (b) differences between the high TCGF years and low TCGF years that is hindcasted by the statistical model. The high TCGF years are characterized by the following anomalous features: Three anomalous teleconnection patterns such as anticyclonic circulation (positive SHO phase) in the East Asian continent, pressure pattern like “north-high and south-low” in the North Pacific, and cyclonic circulation (negative AAO phase) near the Australia were strengthened during the period from boreal spring to boreal summer. Thus, anomalous trade winds in the tropical western Pacific (TWP) were weakened by anomalous cyclonic circulations that located in the subtropical western Pacific (SWP) in both hemispheres. In consequence, this spatial distribution of anomalous pressure pattern suppressed convection in the TWP but strengthened convection in the SWP.     

北半球夏季500hPa候平均高度场的遥相关和环流特征

本文用10年(1980—1989)夏季北半球500hPa候平均高度场资料进行遥相关分析,得到东亚太平洋型(EAP)和西欧型(WE)两种遥相关型及西亚-太平洋-大西洋振荡,并对高度场进行主成分分析(PCA),讨论了环流的时空分布特征.     

Teleconnections associated with Northern Hemisphere summer monsoon intraseasonal oscillation

The boreal summer intraseasonal oscillation (BSISO) has strong convective activity centers in Indian (I), Western North Pacific (WNP), and North American (NA) summer monsoon (SM) regions. The present study attempts to reveal BSISO teleconnection patterns associated with these dominant intraseasonal variability centers. During the active phase of ISM, a zonally elongated band of enhanced convection extends from India via the Bay of Bengal and Philippine Sea to tropical central Pacific with suppressed convection over the eastern Pacific near Mexico. The corresponding extratropical circulation anomalies occur along the waveguides generated by the North African-Asian jet and North Atlantic-North European jet. When the tropical convection strengthens over the WNPSM sector, a distinct great circle-like Rossby wave train emanates from the WNP to the western coast of United States (US) with an eastward shift of enhanced meridional circulation. In the active phase of NASM, large anticyclonic anomalies anchor over the western coast of US and eastern Canada and the global teleconnection pattern is similar to that during a break phase of the ISM. Examination of the evolution of the BSISO teleconnection reveals quasi-stationary patterns with preferred centers of teleconnection located at Europe, Russia, central Asia, East Asia, western US, and eastern US and Canada, respectively. Most centers are embedded in the waveguide along the westerly jet stream, but the centers at Europe and Russia occur to the north of the jet-induced waveguide. Eastward propagation of the ISO teleconnection is evident over the Pacific-North America sector. The rainfall anomalies over the elongated band near the monsoon domain over the Indo-western Pacific sector have an opposite tendency with that over the central and southern China, Mexico and southern US, providing a source of intraseasonal predictability to extratropical regions. The BSISO teleconnection along and to the north of the subtropical jet provides a good indication of the surface sir temperature anomalies in the NH extratropics.     

冬季积雪的异常分布型及其与冬、夏大气环流的耦合关系

采用 ECMWF1 979～ 1 993年 2 .5°× 2 .5°的网格点积雪深度资料 ,研究了较为细致的积雪异常的空间分布特征 ,揭示了欧亚大陆冬季积雪的异常空间分布型 ;并采用 SVD方法研究了冬季积雪的异常分布型与冬、夏大气环流的耦合关系。结果表明 :欧亚大陆冬季积雪深度存在典型的异常空间分布型 ;积雪的异常分布型与冬、夏大气环流之间均存在一定的耦合关系。冬季积雪的异常分布型与大气 EU遥相关型存在明显的同时性相互作用 ,大气 EU遥相关型有利于冬季积雪异常分布型的出现和维持 ,而积雪异常分布型对大气 EU遥相关型的发生起一定的作用 ,进而对冬季风活动产生影响。冬季积雪的这种异常分布型与夏季大气环流 ,尤其是东亚地区的夏季大气环流 ,也存在一定的联系。积雪异常分布型可以通过影响副热带高压的南北进退 ,对东亚季风及中国夏季雨带产生影响。     

多因子协同作用对1992年和1998年黄淮地区夏季降水异常的影响

1991年5月和1997年4月赤道中东太平洋均发生了El Ni?o事件,但是1992年夏季黄淮地区降水异常偏少,而1998年夏季却异常偏多。分析结果显示,1992年夏季西北太平洋副热带高压（以下简称副高）偏东,中高纬阻塞高压偏弱,黄淮地区降水异常偏少;而1998年夏季,副高偏西,中高纬阻塞高压活动频繁,黄淮地区降水异常偏多。对海温外强迫信号的诊断和数值模式试验显示:当西太平洋对流活动偏弱时,有利于副高西伸;鄂霍茨克海及以东海温偏高时,其上空的阻塞高压增强;北大西洋中纬度地区海温偏高时,有利于后期乌拉尔山高压脊明显增强。即在赤道中东太平洋发生El Ni?o事件的背景下,西太平洋对流、鄂霍茨克海附近亲潮区域和北大西洋中纬度区域海温异常可能是导致黄淮区域1992年夏季和1998年夏季降水差异大的主要原因。该工作显示仅根据El Ni?o事件的发生时间和强度无法完全预测黄淮地区夏季降水变化,需要综合考虑西太平洋对流、鄂霍茨克海附近海域和北大西洋中纬度区域海温异常对季风环流的影响,从多因子协同作用的角度诊断和预测黄淮地区夏季降水异常趋势,提高预测能力。     

冬季中高纬500hPa高度和海表温度异常特征及其相关分析

用旋转主分量（ＲＰＣ）方法，分析１９４８年到１９８８年４０个冬季的中高纬５００ｈＰａ高度场以及全球海表温度异常（ＳＳＴＡ）场的最主要的时空分布特征。然后通过交叉相关来讨论海气的同期相关特征。结果显示，冬季中高纬５００ｈＰａ高度场最明显的异常型分别是太平洋北美型（ＰＮＡ），西太平洋型（ＷＰ），西大西洋型（ＷＡ）以及东大西洋欧亚型（ＥＡＥＵ）。冬季ＳＳＴＡ最明显的区域是赤道东太平洋（ＥＥＰ）和赤道大西洋（ＥＡＬ）。其次是中纬度东北太平洋（ＮＥＰ）及两大洋西部（ＮＷＰ和ＮＷＡ）。中高纬度海气之间有很好的相关。与中高纬度５００ｈＰａ高度场ＰＮＡ型明显相关的是中高纬度东北太平洋（ＮＥＰ）和赤道东太平洋（ＥＥＰ）的ＳＳＴＡ。前者的强相关中心在中高纬；后者的强相关中心在中低纬。而与ＷＡ型明显相关的是中高纬度北大西洋的ＳＳＴＡ。中高纬度海气之间最强的相关在海气异常对应的空间位置上。而且这种区域性或邻域性的海气相关呈正相关，暖ＳＳＴＡ对应于正高度异常，冷ＳＳＴＡ对应于负高度异常     

The impact of global warming on Kuroshio Extension and its southern recirculation using CMIP5 experiments with a high-resolution climate model MIROC4h

The impacts of four teleconnection patterns on atmospheric circulation components over Eurasia and the Pacific region, from low to high latitudes in the Northern Hemisphere (NH), were investigated comprehensively in this study. The patterns, as identified by the Climate Prediction Center (USA), were the East Atlantic (EA), East Atlantic/Western Russia (EAWR), Polar/Eurasia (POLEUR), and Scandinavian (SCAND) teleconnections. Results indicate that the EA pattern is closely related to the intensity of the subtropical high over different sectors of the NH in all seasons, especially boreal winter. The wave train associated with this pattern serves as an atmospheric bridge that transfers Atlantic influence into the low-latitude region of the Pacific. In addition, the amplitudes of the EAWR, SCAND, and POLEUR patterns were found to have considerable control on the “Vangengeim–Girs” circulation that forms over the Atlantic–Eurasian region in winter or spring. The EA and EAWR mainly affect the westerlies in winter and spring and the POLEUR and SCAND, respectively, in summer and winter. Strong westerlies confine the extension of the North Polar vortex, which generally results in a small weak vortex and a shallow East Asian trough located in a position further east than normal. Furthermore, the North Polar vortex presents significant connections with the patterns during winter and summer. Analyses in this work suggest that the teleconnection patterns in summer could be driven, at least partly, by the Atlantic Multidecadal Oscillation, which to some degree might transmit the influence of the Atlantic Ocean to Eurasia and the Pacific region.     

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。     

Anomalies in the tropics associated with the heavy rainfall in east asia during the summer of 1998

1.IntroductionInthesummerof1998,theYangtzeRiverbasin,includingNenjiangRiverValleyinNortheastChinasufferedaseverelarge--scalefloodonlynexttothatinthesummerof1954inthiscentury.Thefloodcausedapproximatelythedeathof3000individualsandthedirecteconomicdamageof250billionRMByuans(Yan,1998).Thisextremedisasterpromptedaseriesofimmediatestudiesonit(e.g.,Iluangetal.,1998;Taoetal.,1998).TheevolutionoftheEastAsiansupsmermonsoonshowsagreatvariabilityfromyeartoOThisstudywassupportedbytheNationalNatura…     

北半球冬半年遥相关型强度指数的年际变化特征及其与厄尔尼诺的遥响应

计算了1951—1990年冬半年逐月以及冬季的PNA、WA、WP、EA、EU型的遥相关强度指数。在此基础上,研究了它们的气候变化特征以及这5个遥相关型强度指数与厄尔尼诺的关系。指出,厄尔尼诺发展的盛期(冬季),以北半球西太平洋型(WP)明显偏弱为主要特征,其次才是太平洋北美型(PNA)偏强。1991年发生的一次厄尔尼诺,在盛期是弱PNA型,弱WP型。此外,还研究了遥相关强度指数用于天气预报的问题。     

西太平洋副热带高压异常进退的对比分析

对1980年7月29日—8月16日西太平洋副高位置持续偏南和1983年7月16日—8月12日西太平洋副高位置持续偏北的两次季节内副高中期进退过程的环流特征和加热差异作了对比分析,讨论了东亚季风与对流活动、副高进退之间的关系.      

Teleconnected influence of North Atlantic sea surface temperature on the El Ni?o onset

Influence of North Atlantic sea surface temperature (SST) anomalies on tropical Pacific SST anomalies is examined. Both summer and winter North Atlantic SST anomalies are negatively related to central-eastern tropical Pacific SST anomalies in the subsequent months varying from 5 to 13?months. In particular, when the North Atlantic is colder than normal in the summer, an El Ni?o event is likely to be initiated in the subsequent spring in the tropical Pacific. Associated with summer cold North Atlantic SST anomalies is an anomalous cyclonic circulation at low-level over the North Atlantic from subsequent October to April. Corresponded to this local response, an SST-induced heating over the North Atlantic produces a teleconnected pattern, similar to the East Atlantic/West Russia teleconnection. The pattern features two anticyclonic circulations near England and Lake Baikal, and two cyclonic circulations over the North Atlantic and near the Caspian Sea. The anticyclonic circulation near Lake Baikal enhances the continent northerlies, and strengthens the East-Asian winter monsoon. These are also associated with an off-equatorial cyclonic circulation in the western Pacific during the subsequent winter and spring, which produces equatorial westerly wind anomalies in the western Pacific. The equatorial westerly wind anomalies in the winter and spring can help initiate a Pacific El Ni?o event following a cold North Atlantic in the summer.