亚洲热带气候态夏季风涌传播特征及其对中国降水的影响

基于1979—2020年逐日的NOAA向外长波辐射资料、NCEP/NCAR再分析风场资料,以及全球CMAP再分析降水资料,探讨了气候态亚洲热带夏季风涌的传播过程及与我国夏季相应的降水联系。分析结果表明,主汛期亚洲热带气候态夏季风季节内振荡(CISO)活动是亚洲夏季风活动的主要特征,随时间北传的亚洲热带夏季风CISO称为亚洲热带夏季风涌,主要有南亚夏季风涌和南海夏季风涌。亚洲热带夏季风涌的传播可分为四个阶段。在亚洲热带夏季风涌的发展阶段,印度洋区域低频气旋与对流活跃,孟加拉湾和南海热带区域被低频东风控制,我国大部分地区无降水发生,降水中心位于两广地区。当进入亚洲热带夏季风涌活跃阶段,孟加拉湾和南海热带地区低频气旋和对流活跃,东亚低频“PJ”波列显著,我国降水中心北移到长江以南的附近区域。亚洲热带夏季风涌减弱阶段,孟加拉湾与南海低频气旋消亡,对流减弱,低频西风加强,日本南部附近为低频反气旋控制,我国长江中下游低频南风活跃,降水中心也北移到长江中下游地区,而华南地区已基本无降水,此阶段的大气低频环流场与亚洲热带夏季风涌发展阶段基本相反。进入亚洲热带夏季风涌间歇阶段时,孟加拉湾和南海热带地区低频反气旋活跃,对流不显著,日本南部附近的低频反气旋北移减弱,我国东部基本在低频南风的控制下,降水中心也逐步北移到华北-朝鲜半岛一带,此时的大气低频环流场与亚洲季风涌活跃阶段基本相反。      

A DIAGNOSTIC STUDY OF THE TELECONNECTION ASSOCIATED WITH THE WARM POOL OF THE WESTERN PACIFIC AND ASIAN MONSOON DURING EL NINO AND NON-EL NINO YEARS

Based on the monthly mean OLR, geopotential height and wind data from the NCEP/NCAR reanalyzed data sets for 1982-1996, the atmospheric teleconnection associated with the warm pool of the tropical western Pacific and Asian monsoon region during E1 Nino and non-El Niño years are studied diagnostically in this paper. It is found that, the teleconnection pattern caused by the activity of the Asian summer monsoon (ASM) emanates from the Asian monsoon region to the tropical eastern Pacific via the Aleutians in summer of the El Niño years. In the non-El Niño years, however, the ASM-related teleconnection pattern stretches northward and westward from the Asian monsoon region, exerting its influences mainly on the circulation over middle and high latitude rather than that over the tropical eastern Pacific. Evidences also show that the anomalous convection over the tropical western Pacific warm pool leads to the East Asia/Pacific(EAP) teleconnection pattern during the non-El Niño years. It is interesting to note that the teleconnection in the 500 height field associated with the warm pool convection disappears in the El Niño years. The differences of the teleconnection pattern between the El Niño years and the non-El Niño years suggest that the activities of the ASM and the convection over the warm pool of the tropical western Pacific, the most energetic weather events in boreal summer, are intertwined and interactive with other global-scale circulation in different ways under different climate backgrounds.     

东亚夏季风过程大气低频振荡的数值模拟研究

利用区域气候模式RegCM3对东亚夏季风及其中的大气低频振荡(LFO)进行了模拟研究。(1)进行控制试验,借助Lanczos带通滤波等方法分析了实测及模拟结果LFO强度和传播等特征,检验RegCM3对夏季风LFO的模拟能力;(2)通过增、减南海表面海温两个敏感试验探讨海温异常变化对LFO各特征的影响,并探究异常海温下的LFO与季风爆发时间的可能联系。结果表明:季风LFO强值集中在低纬地区,低纬夏季强冬季弱,高纬则相反。季风爆发前后的发生南传向北传的转换。模式RegCM3对季风区LFO基本特征有较好的把握,但高纬地区偏强。南海异常增(减)温有利于季风提前(推迟)爆发,也有利于LFO传向发生转换时间的提前(推迟)。说明季风爆发时间与LFO传向转换存在一定联系。两个试验均有使振荡能量大值区南移的趋势,且通过LFO的变化造成较高纬地区季风后期的气候异常。     

LOW-FREQUENCY OSCILLATION AND MECHANISM OF VERTICAL CIRCULATION OF EASTERN ASIAN MONSOON*

Analysis is performed of low-frequency oscillation (LFO) and its relation to monsoon by means of ECMWF numerical prediction data in the period 1 June to 30 September 1984,indicating that remarkable local LFO exists in the vertical meridional and equatorial zonal circulations.And preliminary discussion is made of the origin of the LFO of the East-Asian summer monsoon meridional circulation in the LFO of the mid and upper troposphere vertical motion around 30°S.The LFOs in the meridional circulations of both hemispheres are linked together by the LFO of the meridional circulation.Finally the possible relation between the tropical monsoon LFO and Meiyu (plum rain).     

东亚梅雨季节内振荡的气候特征

影响中国、日本、朝鲜半岛的东亚梅雨是夏季风向北推进过程中的特有雨季。利用NCEP/NCAR逐日再分析资料、CMAP降水资料,将夏季风影响及夏季风降水的季节转换相结合,定义东亚梅雨的入、出梅指标;进而采用集合经验模态分解信号提取方法对东亚梅雨区降水季节内振荡及其大尺度环流条件的气候特征进行了详细分析;并对东亚梅雨季节内振荡对降水事件的指示作用进行讨论,为东亚梅雨区降水的延伸预报提供依据和参考。研究结果表明:(1)采用标准化候降水量的空间覆盖率,同时兼顾夏季风影响等条件确定的东亚梅雨入、出梅划分指标可较好地反映东亚梅雨的气候特征及东亚梅雨期的大尺度环流形势。(2)东亚梅雨全年降水量存在三峰型分布特征,峰值分别位于第27、36及47候。该三峰型特征主要受10—20及30—60d的低频振荡影响。比较而言,30—60d振荡对梅雨区降水三峰型的贡献较10—20d振荡大。(3)东亚梅雨区峰值降水与热带环流及北方高位涡冷空气输送的低频演变密切关联。在梅雨区北侧,中高纬度里海附近冷空气(高位涡)低频波列的东传及鄂霍次克海高位涡的西南向输送共同影响东亚梅雨区。在梅雨区南侧,通过热带低频异常强对流的激发作用,热带西太平洋至中国东北—鄂霍次克海地区形成沿经向分布的低层气旋-反气旋-气旋-反气旋波列,进而导致梅雨区低层形成低频偏北风和偏南风的辐合;而印度西海岸和阿拉伯海地区异常对流活动产生的波列向东北方向传播,亦对梅雨区低频峰值降水产生影响。对于低频谷值降水的大气低频演变,情况与上述基本相反。(4)东亚梅雨区降水不同位相下出现极端降水事件的概率有明显差异。梅雨区降水低频峰(谷)值位相下出现异常多(少)降水量的概率约为30%。因此,上述梅雨区降水低频振荡演变相关的大气低频振荡特征对梅雨区降水事件的延伸预报具有参考价值。     

1998 SCSMEX期间亚洲30－60天低频振荡特征的分析

对１９９８年 ５－８月南海季风试验（ＳＣＳＭＥＸ）期间东亚地区 ８５０ ｈＰａ中低纬环流指数、东亚季风指数和长江中下游降水进行了Ｍｏｒｌｅｔ 小波分析,结果表明在此期间这些要素均有明显的３０－６０天周期低频振荡。在此基础上对 ５－８月每隔 ５天的 ８５０ ｈＰａ低频流场进行分析,结果表明：（１）１００°－１５０°Ｅ间东亚从中国东中部大陆经南海和西太平洋的南北半球中明显的存在一个以３０－６０天低频荡为特征的东亚季风低频环流系统,东亚季风活动主要受东亚季风系统中低频活动影响;（２）５月第５候南海热带季风爆发、６月中旬长江中下游人梅及产生大暴雨以及７月中旬以后的该地区大暴雨均与低频气旋带在该地区活动有关,而８月长江上游大暴雨则与低频反气旋伸人到大陆有关;（３）ＳＣＳＭＥＸ期间东亚低频振荡系统的源地有二个,即南海赤道和北半球中太平洋中高纬。南海低频系统向北传播,而中高纬低频系统自东北向西南传播为主。长江中下游６、７月二次大暴雨均与上述二个低频气旋系统自热带向北和中高纬向西南传播并于长江中下游汇合有关;（４）５－８月间东亚季风系统中有二次低频气旋带和二次低频反气旋带活动,这些低频环流系统的活动与印度季风低频环流系统活动并无明     

A Study of the Characteristics of the Low-Frequency Circulation over the Tibetan Plateau and its Association with Precipitation in the Yangtze River Valley in 1998

The propagation characteristics of the atmospheric low frequency (LF, 30--60 days) oscillation (LFO) around the Tibetan Plateau from troposphere to stratosphere and its relationship with the floods over the mid-lower reaches of the Yangtze River in the summer of 1998 are studied, based on the GAME dataset from Meteorological Research Institute (MRI)/Japan Meteorological Agency, the TRMM satellite rainfall and the 730-station precipitation over China. The results show that the zonal propagation direction of LFOs in horizontal winds varies with seasons in the troposphere during May to August in 1998. The eastward propagation of LFOs is remarkable before the start of the rainy season in the Tibetan Plateau and the eastern Asian continent, while the westward propagation is significant after the start date. The northward LFOs from the south side of the plateau and the southward LFOs from the north are both significant before and after the start date. The plateau is a LFO sink in the meridional and zonal directions, but the west part of it is an intensifying area for the continual westward LFOs only after the start of the rainy season. Besides, the strongest LFOs occur at the tropopause (100 hPa) and rapidly decay after entering the stratosphere. The rainfall over the mid-low reaches of Yangtze River in the summer of 1998 exhibits two LFO cycles. According to the phases of the two rainfall LFO cycles, the composite analysesof precipitation distribution, LF circulations at 500 and 100 hPa,and LF vertical motion along 30°N are performed. It is the joint effect of the mid-upper tropospheric strong 30--60-day filtered cyclone (anticyclone) over the eastern plateau and the LFO anticyclone (cyclone) over the west subtropical Pacific that induces the whole layer LF descending (ascending) motion over the mid-lower reaches of Yangtze River, which provides the favorable condition for the break (maintenance) of precipitation.     

亚洲热带夏季风的首发地区和机理研究

文中分析了多年逐候平均 85 0hPa风场和黑体辐射温度等物理量的时空演变 ,结果表明 ,90°E以东的孟加拉湾、中南半岛和南海是亚洲热带夏季风首先爆发的地区 ,爆发时间在 2 7～ 2 8候 ,具有突发性和同时性。 90°E以西的印度半岛和阿拉伯海是热带夏季风爆发较晚的地区 ,季风首先在该区 10°N以南爆发 ,时间约在 30～ 31候 ,然后向北推进 ,6月末在全区建立 ,爆发过程具有渐进性。机制分析表明 ,由于 110～ 12 0°E的中高纬东亚大陆在春季和初夏地面感热通量、温度和气压的迅速变化 ,使热带低压带首先在该处冲破高压带 ,生成大陆低压 ,并引导西南气流在 90°E以东地区首先建立。在 90°E以西的印度半岛地区 ,地面感热通量在 4～ 5月间几乎没有明显变化 ,因而印度季风比南海季风晚爆发约 1个月。由此得出 ,90°E是东亚夏季风和南亚夏季风的分界线。此外 ,还着重探讨了南亚高压的季节变化与亚洲热带夏季风爆发的时间联系。发现南亚高压中心位置与亚洲热带夏季风爆发时间有较好的对应关系。南亚高压中心跳过 2 0°N时 ,南海夏季风爆发 ,跳过 2 5°N时 ,印度夏季风在其南部爆发。将用上述方法确定的爆发时间与用其他方法确定的爆发时间相比较 ,发现它们在南海地区有较好的一致性 ,在印度地区略有差异。     

VARIATIONS OF 30—60 DAY OSCILLATION IN ATMOSPHERE BEFORE AND DURING 1982 EL NINO*

By using the upper-wind data from July 1980 to June 1983,the variations of the low-frequency oscillation(LFO) in the atmosphere before and during 1982 El Nino have been investigated.Before the El Nino,the LFO propagates from west to east over the equator of the Eastern Hemisphere and from east to west over 20°N.The eastward propagating LFO over the equator consists of zonal wavenumber 1 propagating eastward and zonal wavenumber 2 with a character of stationary wave.The oscillation of zonal wavenumber 2 can modulate the oscillation strength.After the onset of the El Nino,the propagating directions of the LFO over the equator and 20°N of the Eastern Hemisphere change to be westward and eastward,respectively.The LFO over the western Pacific weakens rapidly and one coming from middle and high latitudes propagates to the equator.From the phase compositions of streamline fields for the zonal wavenumber 1 of equatorial westward propagatirg LFO,it is found that the atmospheric heat source in the equator of the eastern Pacific(EEP)excites a series of the equatorial cyclones and anticyclones which move northward and westward and form the westward propagating LFO over the equator.With the wavelength of 20000km,this kind of equatorial wave is similar to the mixing Rossby-gravity wave.In its westward and northward movement,the circulation in East Asia is modified.This may be the mechanism of the influence of El Nino on the climate of China.     

The Dynamical Influence of Land－Sea Contrast and Sea Surface Temperature on Intraseasonal Oscillation in Tropical Atmosphere

An equatorial β-plane model which includes realistic non-uniform land-sea contrast and the underlying surface temperature distribution is used to simulate the 30-60 day oscillation (LFO) processes in tropical atmosphere, with emphasis on its longitude-dependent evolution and convective seesaw between Indian and the western Pacific oceans.The model simulated the twice-amplification of the disturbances over Indian and the western Pacific oceans while they are travelling eastward. It reproduced the dipole structure caused by the out-of-phase oscillation of the active centres in these two areas and the periodical transition between the phases of LFO. It is suggested that the convective seesaw is the result of interaction of the internal dynamics of tropical atmosphere with the zonally non-uniform thermal forcing from underlying surface. The convective activities are suppressed over Indonesia mari-time continents whilst they are favoured over the Indian Ocean and western Pacific warm waters, so there formed two active oscillation centres. The feedback of convection with large-scale flow slows down the propagation of disturb-ances when they are intensifying over these two areas, therefore they manifest a kind of quasi-stationary component to favor the ‘dipole’ structure. Whereas the disturbances weaken and speed up over the eastern Pacific cold water re-gion due to the interaction of sensible heating and evaporation with perturbational wind. Therefore the two major centers just show out-of-phase oscillation during onecycle around the latitudinal beltBy introducing the SST anomalies in El Ni?o and La Ni?a years into the surface temperature, we also show that they have significant influence on LFO processes. In an anomalously warm year, the LFO disturbances dissipate more slowly over the central-eastern Pacific region and can travel farther eastward; whilst in an anomalously cold year, the opposite is true.     

谱模式SAMIL对南亚季风区大气季节内振荡向北传播的模拟

基于与NCEP资料结果的比较,研究了中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室发展的大气环流模式SAMIL对夏季南亚季风区季节内振荡（ISO）向北传播特征的模拟,并结合目前对ISO北传机制的理解对模拟结果进行了分析讨论。SAMIL在夏季南亚地区模拟出相当强度的季节内振荡的活动,并且模拟的ISO也表现出与NCEP资料相似的从赤道向北传播的特征,但传播的速度要慢于NCEP资料的结果。模拟的北传ISO具有与NCEP资料相似的结构特征,涡度和水汽场明显的呈经向不对称,涡度和水汽的正异常位于ISO对流的北面,最大的上升运动和最强的行星边界层辐合也位于ISO对流的北面。ISO 结构的经向不对称性正是模式模拟的ISO具有向北传播特征的原因;而模式对夏季南亚季风区高低层风场和行星边界层水汽的合理模拟起了关键的作用。同时,根据关于ISO北传机理的已有研究,模式的结果也表明南亚地区夏季风场的垂直结构是那里ISO向北传播的重要机制。     

Interactions between the 30–60 day oscillation,the walker circulation and the convective activities in the tropical western pacific and their relations to the interannual oscillation

In this paper, interactions between the 30-60 day oscillation, the Walker circulation and the convective activities in the tropical western Pacific during the Northern Hemisphere summer are analyzed by using the observed data of wind fields and high-cloud amounts for the period from 1980 to 1989.The analyzed results show that the 30-60 day oscillation (hereafter called LFO) may be largely affected by the convective activities in the tropical western Pacific. The LFO in the tropical western Pacific during the strong convective activities around the Philippines stronger than those during the weak convective activities around the Philippines. Moreover, in the case of strong convective activities around the Philippines, the LFO in the tropical west-ern Pacific and tropical eastern Indian Ocean generally propagates westward, and it is intensified by the LFO with a westward propagating center of maximum oscillation from the east to 140oE. However, in the case of weak convective activities around the Philippines, the LFO gradually becomes stronger with a eastward propagating center of maximum oscillation from the eastern Indian Ocean to the tropical western Pacific.Corresponding to the 30-60 day oscillation, the Walker circulation is also in oscillation over the tropical Pacific and its circulation cell seems to shift gradually westward from the tropical western Pacific to the tropical eastern In-dian Ocean with strong convective activities around the Philippines. This may maintain the intensification of convective activities there. However, during the weak convective activities around the Philippines, the Walker circula-tion gradually moves eastward and an ascending flow may appear in the equatorial central Pacific. This may cause convective activities to be intensified over the equatorial central Pacific.The analyzed results also show that the LFO in the tropical western Pacific and East Asia may be associated with the interannual oscillation of the SST anomaly in the tropical western Pacific.     

东亚夏季风指数的年际变化与东亚大气环流

文中从夏季东亚热带、副热带环流系统特点出发 ,定义了能较好表征东亚夏季风环流年际变化的特征指数 ,并分析了东亚夏季风指数的年际变化与东亚大气环流及夏季中国东部降水的关系。文中定义的东亚夏季风指数既反映了夏季东亚大气环流风场的变化特征 ,也较好地反映了夏季中国东部降水的年际变化特征。此外 ,还探讨了东亚夏季风指数变化的先兆信号     

OLR资料所揭示的热带地区低频振荡的变化特征

本文使用1979年1月至1984年12月射出长波辐射(OLR)资料,对热带地区低频振荡的一些特性进行了研究,认为正常年份30—60天振荡的合成功率谱最强,El Nino年最弱。低频波活动冬夏差异较大,其年际变化大值区冬季在赤道地区,夏季位置偏北,位于印度洋和西太平洋。就六年平均而言,低频波在西太平洋及印度洋地区有明显的经向传播,赤道地区低频波的纬向传播主要集中在北半球夏季。此外,30—60天OLR滤波场的强弱与印度季风的爆发和减弱有较好的对应关系。      

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.     

Boreal summer quasi-monthly oscillation in the global tropics

The boreal summer intraseasonal oscillation (ISO) in the global tropics is documented here using a 7-year suite (1998–2004) of satellite measurements. A composite scenario was made of 28 selected events with reference to the oscillation in the eastern equatorial Indian Ocean (EIO), where the oscillation is most regular and its intensity is indicative of the strength of the subsequent northward propagation. The average oscillation period is about 32 days, and this quasi-monthly oscillation (QMO) is primarily confined to the tropical Indian and Pacific Oceans. Topics that were investigated are the partition of convective versus stratiform clouds, the vertical structure of precipitation rates, and the evolution of cloud types during the initial organization and the development of intraseasonal convective anomalies in the central Indian Ocean. During the initiation of the convective anomalies, the stratiform and convective rains have comparable rates; the prevailing cloud type experiences a trimodal evolution from shallow to deep convection, and finally to anvil and extended stratiform clouds. A major northwest/southeast-slanted rainband forms as the equatorial rainfall anomalies reach Sumatra, and the rainband subsequently propagates northeastward into the west Pacific Ocean. The enhanced precipitation in the west Pacific then rapidly traverses the Pacific along the Intertropical Convergence Zone, meanwhile migrating northward to the Philippine Sea. A seesaw teleconnection in rainfall anomalies is found between the southern Bay of Bengal (5–15°N, 80–100°E) and the eastern Pacific (5–15°N, 85–105°W). Local sea-surface temperature (SST)-rainfall anomalies display a negative simultaneous correlation in the off-equatorial regions but a zero correlation (quadrature phase relationship) near the equator. We propose that atmosphere–ocean interaction and the vertical monsoon easterly shear are important contributors to the northeastward propagation component of the intraseasonal rainband. The observed evidence presented here provides critical information for validating the numerical models, and it supports the self-induction mechanism theory for maintenance of the boreal summer ISO.     

The Earliest Onset Areas and Mechanism of the Tropical Asian Summer Monsoon

The multi-yearly averaged pentad meteorological fields at 850 hPa of the NCEP/NCAR reanalysis dada and the TBB fields of the Japan Meteorological Agency during 1980-1994 are analyzed. It is found that if the pentad is taken as the time unit of the monsoon onset, then the tropical Asian summer monsoon (TASM) onsets earliest, simultaneously and abruptly over the whole area in the Bay of Bengal (BOB), the Indo-China Peninsula (ICP), and the South China Sea (SCS), east of 90°E, in the 27th to 28th pentads of a year (Pentads 3 to 4 in May), while it onsets later in the India Peninsula (IP) and the Arabian Sea (AS), west of 90°E. The TASM bursts first at the south end of the IP in the 30th to 31st pentads near 10°N, and advances gradually northward to the whole area, by the end of June. Analysis of the possible mechanism depicts that the rapid changes of the surface sensible heat flux, air temperature, and pressure in spring and early summer in the middle to high latitudes of the East Asian continent between 100°E and 120癊are crucially responsible for the earliest onset of the TASM in the BOB to the SCS areas. It is their rapid changes that induce a continental depression to form and break through the high system of pressure originally located in the above continental areas. The low depression in turn introduces the southwesterly to come into the BOB to the SCS areas, east of 90°E, and thus makes the SCS summer monsoon (SCSSM) burst out earliest in Asia. In the IP to the AS areas, west of 90°E, the surface sensible heat flux almost does not experience obvious change during April and May, which makes the tropical Indian summer monsoon (TISM) onset later than the SCSSM by about a month. Therefore, it is concluded that the meridian of 90°E is the demarcation line between the South Asian summer monsoon (SASM, i.e., the TISM) and the East Asian summer monsoon (EASM, including the SCSSM). Besides, the temporal relations between the TASM onset and the seasonal variation of the South Asian high (SAH) are discussed, too, and it is found that there are good relations between the monsoon onset time and the SAH center positions. When the SAH center advances to north of 20°N, the SCSSM onsets, and to north of 25°N, the TISM onsets at its south end. Comparison between the onset time such determined and that with other methodologies shows fair consistency in the SCS area and some differences in the IP area.     

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。     

Intensified Eastward and Northward Propagation of Tropical Intraseasonal Oscillation over the Equatorial Indian Ocean in a Global Warming Scenario

Northward propagation in summer and eastward propagation in winter are two distinguished features of tropical intraseasonal oscillation(TISO) over the equatorial Indian Ocean.According to numerical modeling results,under a global warming scenario,both propagations were intensified.The enhanced northward propagation in summer can be attributed to the enhanced atmosphere-ocean interaction and the strengthened mean southerly wind;and the intensified eastward propagation in winter is associated with the enhanced convection-wind coupling process and the strengthened equatorial Kevin wave.Future changes of TISO propagations need to be explored in more climate models.