亚澳季风区水汽收支时空分布特征

用1980～1989年NCEP/NCAR再分析资料计算了亚澳季风区视水汽汇并分析了其水汽收支时空分布特征。结果表明,该研究范围水汽收支的典型空间分布型为南北型,即南半球澳大利亚季风区与北半球亚洲季风区相反的分布形势,而且这种分布形势有明显的季节变化。冬季北半球亚洲季风区为水汽源,110～135 E之间大陆桥附近、80 E附近及40～50 E之间的三支越赤道水汽输送通道将北半球水汽输送到南半球澳大利亚季风区及南印度洋,成为水汽汇,夏季南半球澳大利亚季风区和南印度洋为水汽源,上述三支越赤道水汽输送通道实现与夏季反向的水汽输送,将水汽由南半球输送到北半球亚洲季风区,此时亚洲季风区为水汽汇。春季和秋季赤道辐合带为主要的水汽汇,亚澳季风区无明显越赤道水汽输送。     

东亚地区秋季水汽输送特征及水汽源地分析

用1980～1997年垂直积分的水汽输送通量资料,分析了秋季东亚地区大尺度水汽输送演变的气候特征以及主要水汽源地,结果表明:秋季各个月东亚大陆的主要水汽来源地并不相同,9月主要来源于孟加拉湾、南海和西太平洋地区;10～11月主要来源于南海、西太平洋地区。从夏季型到冬季型水汽输送的转换特征表现为:来自南半球的越赤道输送的显著减弱、消失直至转向,东亚南支偏西风水汽输送的逐渐建立,赤道太平洋地区的偏东风水汽输送的加强西进。秋季亚洲季风区范围最大的强水汽源地位于南海、西太平洋地区(115～120°E,15～25°N)。     

盛夏东亚季风区水汽源汇的气候特征及山西的水汽输送

本文讨论分析了１９９４年盛夏东亚季风区垂直积分的平均水汽通量及水汽通量散度场，揭示出该时期东亚季风区存在四个强水汽泊；西太平洋、东涨、苏禄海、安达曼海和三个水汽汇：华北、长江中游南岸、南海南部。山西位于华北汇区中，盛夏降水的水汽是由安达曼海和莎经取西南气流，东南气流输送而来。     

夏季东亚地区水汽输送的气候特征

使用 1980—1997年垂直积分的水汽输送通量资料,分析了夏季大尺度水汽输送演变的气候特征及偏南风水汽输送在中国区域内的推进特征。结果表明:夏季各支大尺度水汽输送汇合成一条行星尺度水汽输送大值带,它从南半球出发,经过亚洲季风区,进入北太平洋;东亚夏季偏南风水汽输送所能到达的北界为东北北部50°N附近;西太平洋副高南侧的东南风水汽输送所能到达的西界为甘肃东南部100°E附近。垂直积分的水汽输送通量强辐合区大多位于行星尺度水汽输送大值带中,与降水大值区之间有很好的对应关系。     

青藏高原东部及邻近地区水汽输送的气候特征

利用1980—1997年垂直积分的整层水汽输送通量资料,分析了青藏高原东部及其邻近地区水汽输送的气候特征。结果表明,该区的水汽输送具有明显的季节变化特征:冬、春季的水汽主要来源于中纬度的偏西风水汽输送,夏季(7月)主要来源于孟加拉湾和南海,秋季(10月)主要来源于西太平洋地区。季风携带的南来水汽在高原东侧地区的进退比较缓慢,8月初北扩到40°N附近,10月中旬南退出30°N,其强弱和进退异常能影响极端旱涝事件的发生。来自南海、西太平洋地区的水汽输送对高原东部及其邻近地区的影响值得关注。     

1994年8月亚洲季风区水汽的源汇分布和输送

讨论了水汽气候源汇分布的分析方法,认为只有用季节平均的整层大气水汽通量散度才能准确反映水汽源汇的地理分布。分析了亚洲季风区１９９４年８月水汽源汇分布和输送情况,发现西太平洋１２０－１３３°Ｅ和孟加拉湾地区是水汽气候源区,其中菲律宾东侧、苏绿湾、黄海海域、安达曼海及布拉马普特拉河谷是最主要的５个水汽强源域。南海不是水汽源而是水汽汇。华北降水主要受亚洲两大季风风系和黄海、布拉马普特拉河谷水汽源的影响。     

夏季东亚季风区水汽输送特征及其与南亚季风区水汽输送的差别

利用ECMWF所分析的1980～1989年每日各层的水汽和风场资料分析了东亚季风区夏季风的水汽输送特征,并与印度季风区夏季水汽输送进行比较。分析结果表明了东亚季风区夏季水汽输送特征明显不同于印度季风区夏季水汽输送,东亚季风区夏季水汽输送经向输送要大于纬向输送,而印度季风区夏季水汽输送则以纬向输送为主。分析结果还表明东亚季风区由于夏季水汽分布是南边大、北边小,偏南季风气流所引起的水汽平流是湿平流。因此,水汽的辐合主要由季风气流所引起的水汽平流所造成,而印度季风区季风气流所引起的水汽平流是干平流,它利于水汽输送的辐散,水汽的辐合主要是由于风场的辐合所造成。     

中国东部季风区夏季四类雨型的水汽输送特征及差异

利用1951~2015年NCEP/NCAR再分析逐日资料和中国160站月降水观测资料,及中国东部季风区夏季四类雨型（北方型、中间型、长江型和华南型）的划分结果,分析了东亚水汽输送与中国东部季风区夏季降水的关系,比较了四类雨型的水汽输送、收支特征及其差异,结果表明:（1）夏季影响中国东部季风区的水汽通道主要有以下6条:印度洋通道,表征印度季风区偏南的西风水汽输送;高原南侧通道,表征印度季风区偏北的西风水汽输送;太平洋通道,表征由西太平洋副热带高压（副高）带来的西太平洋的水汽;西风带通道,表征西风带的水汽输送;孟加拉湾通道,表征来自孟加拉湾向北的水汽输送;南海通道,表征来自印度洋和孟加拉湾在中南半岛转向及来自南海的水汽;与中国东部不同地区降水异常相联系的水汽通道存在明显的差异,且同一条水汽通道在夏季不同阶段与降水的关系也不尽相同。（2）四类雨型的水汽输送和收支特征有明显的差异,华北盛夏降水主要受亚洲季风水汽输送的影响,其次是西风带水汽输送,北方型年二者往往偏强,尤其是季风水汽输送增加一倍以上,贡献也明显增加,20世纪70年代中期之后,季风水汽输送显著减弱,西风带水汽输送的重要性相对增大;淮河流域夏季降水异常主要受太平洋通道水汽输送异常的主导,其次是高原南侧通道水汽输送,二者偏强并在淮河流域辐合时,淮河流域降水偏多形成中间型年;长江中下游地区夏季降水主要受太平洋通道水汽输送异常的主导,长江型年,副高西北侧的西南水汽输送异常加强,并与北方冷空气异常在长江中下游地区辐合,区域为正的水汽净收支;华南地区夏季降水则受印度洋通道、太平洋通道及南海通道的共同影响,当三条通道异常偏强,水汽与北方冷空气在华南地区辐合,形成华南型年。本研究所得结论加深了我们对四类雨型形成机理的认识,并为汛期主雨带的预测提供了参考。     

夏季亚洲季风区的水汽输送及其对中国降水的影响

利用1948-2005年NCEP/NCAR逐日及月平均资料,研究了亚洲季风区水汽输送的气候特征及其与中国夏季降水的关系.结果表明:(1)亚洲夏季风区不论在纬向和经向输送上,都表现了其独特性.夏季亚洲季风区为强大的水汽汇,东亚大陆和印度季风区均有较强的水汽辐合中心.(2)大部分水汽集中在对流层中下层,主要来自印度季风区,而对于对流层中上层,则以西太平洋和中纬西风带的输送为主.(3)印度季风在5-7月纬向向东的输送加强,东亚季风在6-7月以经向向北的输送加强为主,7月达最强,8到9月季风减弱直至结束.亚洲季风区青藏高原南侧的南支西风对东亚的水汽输送有重要作用,表现为春季最强,中高纬和热带西风输送变化同步,在盛夏达到最大,7月热带西风输送的水汽占三支水汽总输送的80%左右,来自中高纬地区的水汽约占18%.(4)季风爆发后,大量水汽从南半球输送到亚洲季风区.水汽辐合增加最大在孟加拉湾、中南半岛和南海地区,中国大陆的水汽主要经南海北边界输入.(5)水汽输送的北进与雨带的北推相一致.水汽输送场的时空分析表明,EOF1和EOF2分别代表强弱季风年的水汽输送特征.EOF1反映了东亚季风区一致的异常向北输送,并且在1970年代末发生了明显减弱.它与华北降水相关密切,表明自1980年代以来东亚季风向北水汽输送的减弱是华北干旱的主要原因.EOF2的主要特征是从1980年代之后,来自东北和西南的异常水汽在长江流域辐合,导致长江流域降水增多.相关分析表明,东亚夏季风在年代际尺度上的变化对此起了重要作用.     

亚澳季风各子系统气候学特征的异同研究Ⅱ. 夏季风水汽输送

利用1979～2002年的ERA-40和NCEP/NCAR逐日再分析资料以及CMAP降水资料探讨了亚澳季风各夏季风子系统(南亚夏季风、东亚夏季风、北澳夏季风) 水汽输送的气候学特征及其与夏季降水的关系.分析表明: 各夏季风子系统水汽输送通量主要取决于低层季风气流, 南亚夏季风和北澳夏季风以纬向水汽输送为主, 而东亚夏季风有很强的经向水汽输送.分析也证实, 亚澳季风区的夏季风降水主; 要源于水汽输送的辐合, 而且ERA-40资料对夏季风水汽输送辐合的描述能力强于NCEP/NCAR资料.此外, 受低层季风气流结构的影响, 三夏季风子系统水汽输送辐合的动力机理存在明显差异, 南亚夏季风和北澳夏季风的水汽输送辐合主要由低层西风气流的风场辐合所造成, 而东亚夏季风的水汽输送辐合则由低层南风气流的风场辐合和季风湿平流共同作用造成.因此, 东亚夏季风降水有别于南亚夏季风降水和北澳夏季风降水.     

TBB DATA-REVEALED FEATURES OF ASIAN-AUSTRALIAN MONSOON SEASONAL TRANSITION AND ASIAN SUMMER MONSOOM ESTABLISHMENT

Based on T_BB data from Meteorological Institute Research of Japan, study is carried out of the features of seasonal transition of Asian-Australian monsoons and Asian summer monsoon establishment,indicating that the transition begins as early as in April, followed by abrupt change in May-June; the Asian summer monsoon situation is fully established in June. The winter convective center in Sumatra moved steadily northwestward across the "land bridge" of the maritime continent and the Indo-China Peninsula as time goes from winter to summer, thus giving rise to the change in large scale circulations that is responsible for the summer monsoon establishment over SE Asia and India; the South China Sea to the western Pacific summer monsoon onset bears a close relation to the active convection in the Indo China Peninsula and steady eastward retreat of the subtropical TBB high-value band,corresponding to the western Pacific subtropical high.     

TBB资料揭示的亚澳季风区季节转换及亚洲夏季风建立的特征

发展了一个用于台风路径预报的初始场人造台风方案。该方案除包含对称台风环流外,也考虑了非对称风的作用。使用双向移动套网格模式作的试验预报结果表明,初始场中引入人造台风后能明显提高径预报的水平。     

THE TEMPORAL AND SPATIAL CHARACTERISTICS OF MOISTURE BUDGETS OVER ASIAN AND AUSTRALIAN MONSOON REGIONS

Apparent moisture sink and water vapor transport flux are calculated by using NCAR/NCEP reanalyzed daily data for water vapor and wind fields at various levels from 1980 to 1989.With the aid of EOF analysis method,temporal and spatial characteristics of moisture budgets over Asian and Australian monsoon regions are studied.The results show that there is apparent seasonal transition of moistrue sink and water vapor transport between Asian monsoon region and Australian monsoon region.In winter,the Asian monsoon region is a moisture source,in which three cross-equatorial water vapor transport channels in the “continent bridge“,at 80°E and 40°E～50° transport water vapor to the Australian monsoon region and southern Indian Ocean which are moistrue sinks.In summer,Australian Monsoon region anmd southern Indian Ocean are moistrue sources and by the three cross-equatorial transport channels water vapor is transport to the Asian monsoon region which is a moisture sink.In spring and autumn,ITCZ is the main moisture sink and there is no apparent water vapor transport between Asian monsoon region and Australian monsoon region.     

THE TEMPORAL AND SPATIAL CHARACTERISTICS OF MOISTURE BUDGETS OVER ASIAN AND AUSTRALIAN MONSOON REGIONS

Apparent moisture sink and water vapor transport flux are calculated by using NCAR/NCEP reanalyzed daily data for water vapor and wind fields at various levels from 1980 to 1989. With the aid of EOF analysis method, temporal and spatial characteristics of moisture budgets over Asian and Australian monsoon regions are studied. The results show that there is apparent seasonal transition of moisture sink and water vapor transport between Asian monsoon region and Australian monsoon region. In winter, the Asian monsoon region is a moisture source, in which three cross-equatorial water vapor transport channels in the "continent bridge". at 80°E and 40°E ～ 50°E transport water vapor to the Australian monsoon region and southern Indian Ocean which are moisture sinks. In summer, Australian monsoon region and southern Indian Ocean are moisture sources and by the three cross-equatorial transport channels water vapor is transport to the Asian monsoon region which is a moisture sink. In spring and autumn, ITCZ is the main moisture sink and there is no apparent water vapor transport between Asian monsoon region and Australian monsoon region.     

TBB资料所揭示的亚澳季风之季节循环特征和年际异常

文章利用日本GMS所观测的黑体辐射温度TBB资料研究了亚澳季风的季节循环特征，结果表明:TBB资料在相当大的程度上确能反映低中纬环流系统的变化，它不仅再次证实了已有的关于亚澳季风季节进退的认识，并且揭示了一些新的现象，从而给出了一幅亚澳季风系统季节循环的完整图象。另外，文章还就TBB双赤道低值带的形成，以及由TBB资料所反映的亚澳季风之年际异常特征进行了研究。     

RELATIONSHIP BETWEEN THE SEASONAL TRANSITION OF EAST ASIAN MONSOON CIRCULATION AND ASIAN-PACIFIC THERMAL FIELD AND POSSIBLE MECHANISMS

The NCEP/NCAR reanalysis, CMAP rainfall and Hadley Centre sea surface temperature (SST) datasets are used to investigate the relationship between the seasonal transition of East Asian monsoon and Asian-Pacific thermal contrast, together with the possible causes. Based on the 250 hPa air temperature over two selected key areas, the Asian-Pacific thermal difference (APTD) index is calculated. Results show that the APTD index is highly consistent with the Asian-Pacific Oscillation (APO) index defined by Zhao et al., in terms of different key areas in different seasons. Moreover, the time point of the seasonal transition of the Asian-Pacific thermal contrast can be well determined by the APTD index, indicative of seasonal variation in East Asian atmospheric circulation from winter to summer. The transition characteristic of the circulation can be summarized as follows. The continental cold high at lower tropospheric level moves eastward to the East China Sea and decreases rapidly in intensity, while the low-level northerlies turn to southerlies. At middle tropospheric level, the East Asia major trough is reduced and moves eastward. Furthermore, the subtropical high strengthens and appears near Philippines. The South Asia high shifts from the east of Philippines to the west of Indochina Peninsula, and the prevailing southerlies change into northerlies in upper troposphere. Meanwhile, both the westerly and easterly jets both jump to the north. The seasonal transition of atmospheric circulation is closely related to the thermal contrast, and the possible mechanism can be concluded as follows. Under the background of the APTD seasonal transition, the southerly wind appears firstly at lower troposphere, which triggers the ascending motion via changing vertical shear of meridional winds. The resultant latent heating accelerates the transition of heating pattern from winter to summer. The summer heating pattern can further promote the adjustment of circulation, which favors the formation and strengthening of the low-level southerly and upper-level northerly winds. As a result, the meridional circulation of the East Asian subtropical monsoon is established through a positive feedback between the circulation and thermal fields. Moreover, the time point of this seasonal transition has a significant positive correlation with the SST anomalies over the tropical central-eastern Pacific Ocean, providing a basis for the short-term climate prediction.     

THE CHARACTERISTICS OF SUMMER MONSOON AND TRANSPORT OF MOISTURE IN A HEAVY RAIN OVER SOUTH CHINA IN 1994

The trajectory of atmospheric particles and material lines on an isentropic surface are computed using the Lagrangian method. It is shown that the 1994 heavy rain in South China was closely linked to the summer monsoon, especially the tropical monsoon in East Asia. which plays a decisive role. The method is useful in tracking the source area and evolution of water moisture and analyzing the transporting part of airflow for water moisture.     

2004年南海夏季风活动概述

利用NCEP逐日再分析资料、向外长波辐射（OLR）和卫星降水资料,分析了2004年影响南海夏季风活动的一些特征。结果表明,2004年由于西太平洋副热带高压主体位置比正常偏北、偏西,导致南海夏季风爆发日期比正常偏晚（5月19日）、强度偏大,并主要在南海地区活动。南海季风爆发期间存在明显的季节内振荡,有两个显著振荡周期：一个峰值为20-30天,另一个峰值为40～50天。南海夏季风期间,主要的水汽通量输送集中在南海一西太平洋地区,向北到达华南的水汽输送减少,致使华南地区干旱。     

GENERAL SITUATION ABOUT ACTIVITY OF SUMMER MONSOON OVER SOUTH CHINA SEA IN 2004 ASIAN SUMMER MONSOON INDEX

Based on daily NCEP reanalysis data, OLR and satellite rainfall data, the characteristic of the activities of South China Sea summer monsoon(SCSSM) in 2004 were analyzed. The results showed that the establishment of SCSSM was little later than normal and the intensity was stronger than normal. Influenced by the location of the northwest Pacific subtropical high, which was much northward and westward than normal, SCSSM was active mainly in the South China Sea areas. There existed obvious intraseasonal oscillation and two significant periods of SCSSM, one was about 20-30 days and the other about 40-50 days. The transportation of moisture was concentrated on the South China Sea and the northwest Pacific regions, reducing the northward transportation and resulting in drought in southern China