西太平洋副热带高压异常及其与1998年长江流域洪涝过程关系的研究  

A STUDY ON THE RELATIONSHIP BETWEEN THE ANOMALY OF SUBTROPICAL HIGH OVER THE WESTERN PACIFIC AND THE HEAVY FLOODING IN YANGTZE RIVER VALLEY IN 1998

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：《气象学报》2001年第6期719-729,共11页Acta Meteorologica Sinica

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;中国科学院知识创新项目 ( ZKCX2 -SW-2 1 0 )

摘　　要：文中结合 1 998年长江流域的洪涝过程研究了太平洋的活动特征 ,探讨了副热带高压活动与海温的关系 ,以及视热源、水汽汇的特征与副高活动的关系等。首先描述了 1 998年太平洋副热带高压的基本特征 ,给出了它异常的季节位置、强度和形态 ,及其与长江流域降水异常的关系。SVD分析表明 ,1 997至 1 998年的 El Nino过程的演变特征所对应的太平洋副热带高压的最佳耦合模态是 :主体强而位置偏南 ,特别是其西部。赤道辐合带也偏弱 ;1 998年夏季副热带高压的基本特征正符合该模态的特征。热带地区东西向的垂直环流明显地出现东太平洋的异常上升气流与西太平洋的下沉距平气流。视热源、水汽汇的分布能很好地描写副热带高压区的季节位置和强度。副热带高压区为明显的 Q1<0的辐射冷却区和 Q2 <0的变干区。这种特征也有助于副热带高压区的维持。同样 ,视热源、水汽汇的分布也能很好地解释副热带高压区的季节内异常活动。在长江流域持续暴雨期和间隙期 ,Q1,Q2 所指示的副热带高压与雨带的相对位置有很大的差异。不同的热力结构能较好地解释副热带高压区的迅速南落 。The anomalous activity of subtropical high over the western Pacific is studied during the summer of 1998, when the heavy flooding occurred in the Yangtze River region. The paper presents the influence of El Nio event in that period on the subtropical high anomaly and the relationship between the distributions of apparent heat source Q 1 and moist sink Q 2 and the anomalous subtropical high. The main characteristics of subtropical high in that summer are given including its seasonal position, strength and the relation to the precipitation in the Yangtze River Valley.The main coupled mode between SST and subtropical current revealed by SVD analysis shows that if the distribution of SSTA presents an El Nio pattern and its strength decays from preceding winter to summer, the strength of subtropical high in the western Pacific in the summer would be stronger and located at the lower latitudes, especially at its western part. The ITCZ at the southern side would be comparatively weaker. The 1997-1998 El Nio event was decaying from winter to summer, and the features of circulation around the subtropical high are similar to that mode. Therefore the influence of 1997-1998 El Nio on the anomalous subtropical high is very clear. The vertical circulations have shown an anomalous upward flow over the eastern equatorial Pacific, and a downward current over the western Pacific. The distribution of Q 1 and Q 2 may well describe the position and intraseasonal variation of the subtropical high,therefore explain the second period of Meiyu in the end of July in 1998.

关 键 词：1998年 长江流域 洪涝过程 副热带高压 海温异常 大气热状态 

分 类 号：P426.615[天文地球—大气科学及气象学]