近46年江淮下游梅雨期的划分和演变特征

THE DELIMITATION OF MEIYU PERIOD IN THE LOWER REACHES OF YANGTZE-HUAIHE RIVER AND THEIR EVOLVING CHARACTERISTICS FOR 46 RECENT YEARS

应用近46年江苏省中、南部各五站逐日雨量和西太平洋副高逐候脊线纬度资料分别划分出苏南和江淮两区梅雨期。部分梅雨期内含2段甚至3段梅雨集中期，因此也存在间歇期；出梅并不等同于入（盛）夏，少数年虽出梅却无（盛）夏。在所揭示的一系列区域气候特点中，最值得注意的是首次划分出的江淮梅雨期，它与苏南梅雨期并不尽同，有二成年份出梅期延迟至8月。两区梅雨期都具有很大的年际变化，尤其是苏南梅雨量的年际变化一直处于上升趋势且在近十年达到极大。

The Meiyu (plum rain) periods of South Jiangsu and Jianghuai region (mid-dle part of Jiangsu province) have been delimited by using data of daily rainfall of 5 stationsfor each region with the consideration of pentad latitude of central ridge line of West PacificHigh at 500hPa level for 46 recent years (1951-1996). The results show that part of Meiyuperiods including 2 or even 3 sections of concentrating rainy days with intermission spell between them- The end of Meiyu period does not identify the coming of high summer-there isno high summer in a few years after the end of Meiyu period. In a series of regional c1imatecharacteristics disclosed,meiyu hlriod of Jianghuai region is noticeable,which is first delimit-ed in present work with lots of differences comparing to that of South Jiangsu,the endingdates of former in 20% years may delay to August. Large interannual oscillations existed inMeiyu periods of above 2 regions,especially in the case of South Jiangsu,which has still arising trend reaching a maximum during 10 recent years.There exist different points and methods in delimitating Meiyu period,but present workstresses that the delimitation of Meiyu period should consider not only the coupling betweenregional persistent raining and short-medium processes of subtropical circulation in East Asi-a,but also the turning change of natural season in above regions.