南海夏季风演变的气候学特征

本文总结南海北部地区夏季风演变的气候学特征，发现南海地区５月第３候对流层高层东风和北风爆发，对流层低层西风第１次跃升，东亚经向季风环流圈开始形成，这可以成为南海地区夏季风爆发的标志。对流层低层西风在６月中旬开始的第２次连续跃升对应江淮地区的梅雨爆发期。类似地，中国大陆夏季对流层低层５月初和６月初有两次爆发性增暖过程，第２次比第１次强烈得多。南海北部地区对流层低层纬向风速、比湿盛夏呈双峰型，纬向风速峰值分别出现在６月第５候和８月第４候，比湿峰值分别出现在６月第６候和８月第５候。比湿突升对应纬向风速突升，但略落后于风速峰值出现的时间。南海北部地区季风爆发前，温度是波动式上升的，南海季风爆发后，温度是波动式下降的。中国大陆东部及南海地区夏季对流层低层比湿分布有３次突变，即４月中旬南海北部比湿突增，并开始出现高比湿中心，而南海南部为最大比湿中心；５月中旬最大比湿中心已从南海南部跳到了南海北部－华南并向江淮流域扩展；６月中旬江淮流域比湿突增并一直维持到８月，同时南海南部高比湿带消失。而５月中旬ＯＬＲ有一次突变，ＯＬＲ低值区爆发性向北扩张，这对应于南海地区夏季风的爆发。而孟加拉湾地区夏季风演变的气候学特征与南海地区有较

CLIMATOLOGICAL ASPECTS OF EVOLUTION OF SUMMER MONSOON OVER THE NORTHERN SOUTH CHINA SEA

Using pentad mean ECMWF and OLR data from April to September of seven year mean 1980-1986, some aspects of the climatology of the summer monsoon have been dealt over the South China Sea (SCS). Some interesting evidences were revealed. First, the onset of the northern SCS summer monsoon on the average is marked by the onset of the easterly and northerly at 200hPa, the abrupt enhancement of westerly at 850hPa, and the formation of the meridional monsoon circulation of the East Asia. Another abrupt enhancement of the westerly corresponds to the onset of Meiyu in the Yangtze River valley. Two abrupt increases in the temperatures at 850hPa occur over China continent during early May and early June. Second, at 850hPa, zonal wind and specific humidity appear with two peak pattern, and the abrupt increases of the zonal wind correspond well to the increase of the specific humidity. Before the onset of the summer monsoon, the temperature increases wavily, but drops down wavily after the onset. Last, There exist three abrupt changes in distribution of specific humidity in East Asia separately during middle April with the high humid band appearing over the northern SCS, during middle May with high humid band suddenly jumping from the southern SCS to the northern SCS, and during the period from middle June to August,with the high humid band appearing over the Yangtze River valley and disappearing over the southern SCS. The monsoon evolution characteristics over the northern Bay of Bengal(BOB) much differs from that of the northern SCS, so this means that the SCS and BOB to a certain degree belong to different monsoon system.