海温异常对东亚夏季风及长江流域降水影响的分析及数值试验  

Analysis and Numerical Experiment on the Relationship between the 1998 Summer Monsoon Activities and SSTA in Tropical Regions

作　　者：孙淑清[1] 马淑杰[1] 

机构地区：[1]中国科学院大气物理研究所,北京100029

出　　处：《大气科学》2003年第1期36-52,共17页Chinese Journal of Atmospheric Sciences

基　　金：国家重点基础研究发展规划项目G1 9980 4 0 90 0第一部分资助

摘　　要：对夏季的向外长波辐射 (OLR)场及前期热带海温之间的奇异值分解 (SVD)分析表明 ,当自前冬开始的热带海温呈LaNi a型异常分布 ,相应的对流的最佳耦合模态将是 :从印度半岛经孟加拉湾直至南海以及西太平洋暖池都为强对流活动区 ,而在中国江淮流域地区则为弱区。当海温呈ElNi o分布时 ,则相反。数值试验的结果是 :在 1 998年实际海温强迫下 ,模式十分成功地模拟了该年夏季流场的基本特征 ,南海季风爆发的日期及强度皆与实际十分符合 ,印度季风也偏弱。特别是模式成功地模拟出了 1 998年长江流域 6～ 7月的强降水 ,距平百分率达到 1 0 0 %以上。改变热带海温 ,分别用气候海温代替赤道东太平洋和西印度洋实际海温。结果发现 ,在用赤道东太平洋气候海温取代实际海温时 ,与 1 998年实况相比 ,印度季风与南海季风明显加强 ,长江流域降水趋于正常值。即如果 1 998年不出现ElNi o现象 ,或者海温异常的强度减弱 ,则长江流域降水就会大大减弱。 1 998年热带西印度洋海温异常对东亚季风的影响与热带东太平洋十分相像。暖洋面将有利于长江流域的强降水 ,而不利于南海季风的加强。Using SVD analysis between OLR in summer and SST in the pre-winter and spring, the coupled modes are obtained to describe the relationship of the two fields. When SST in winter and spring presents a La Nia-like pattern, the corresponding anomalous OLR in the later summer will have a distribution with the positive areas over the Yangtze River valley and the tropical eastern Pacific (indicating a weaker convection), and a negative belt from the Indian Peninsula to the South China Sea and the western Pacific (indicating a stronger convection). However, for the El Nio pattern, it will be opposite. Taking the 1998 summer monsoon as a typical case, a numerical experiment has been done by using the T42L9 global spectral model developed by the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS) for investigating the influence of SSTA of that year on the severe flooding in the Yangtze River valley and the South China Sea Summer Monsoon (SCSM). The model has successfully simulated SCSM including its onset date and strength. Meanwhile, the features of tropical current, subtropical high in the western Pacific, Qinghai-Xizang high in the upper troposphere and the westerlies are all well simulated. More important is that the model gives a heavy rainfall around the Yangtze River valley in June and July. The percentage departure of rainfall reaches above 100%. Moreover, the situation is just opposite in the South China Sea region, where the summer rainfall is weak in 1998. All these are in good agreement to the observed results. Sensitivity experiments show that SSTA in the central and eastern Pacific plays a main role in the variation of the onset and strength of SCSM and the precipitation in the eastern China. Replacing the SST of 1998 in the tropical eastern Pacific region by the climate mean, we may find that SCSM becomes stronger than the observed, and the precipitation in the Yangtze River valley turns to be normal, hence, severe flooding would no longer appear. The relationship between SST of

关 键 词：海温异常 东亚 夏季风 长江流域 降水 数值试验 

分 类 号：P732.6[天文地球—海洋科学] P461.2