2020年和1998年江淮流域梅雨期降水过程对比分析

Analysis and Comparison of Precipitation Process between 2020 and 1998 Meiyu Periods in the Yangtze-Huaihe River

2020年与1998年均为典型的超强梅雨年,为探讨这两年江淮流域梅雨期降水过程的差异,利用对比分析方法,研究江淮流域2020年与1998年梅雨汛期降水特征的异同点,并对比分析这两年导致降水异常的大气环流特征。结果表明:(1)这两年夏季江淮流域降水量较常年均具有同期偏多,入梅时间早,出梅时间晚,雨季持续时间长,降水范围广,降水强度大的特征,2020年梅雨异常程度总体上强于1998年梅雨期。2020年多雨带覆盖整个江淮流域,最大累计降水量为1623.6 mm,位于安徽黄山附近。1998年多雨带位置较2020年偏南,最大累计降水量为1119.0 mm,位于江西景德镇附近。(2)这两年梅雨期间西太平洋副热带高压均经历了多次阶段性变化过程,副高的北抬和南撤与梅雨的起始和结束、主雨带的位置、降水过程的发生维持都有很好的对应关系。(3)这两年环流特征较相似,南亚高压偏强偏东,副高偏强偏西,中高纬表现为典型的“两脊一槽”型,江淮流域为槽后南下冷空气与副高西南侧北上暖湿气流的水汽辐合区。(4)2020年梅雨期中高纬阻塞高压、东亚沿海低槽、冷空气势力活跃强度较1998年更强,且2020年MJO对流在印度洋的活跃程度强于1998年,更有利于西北太平洋对流层低层产生异常的反气旋环流,因此南下冷空气与北上暖湿气流在江淮流域的辐合更强,具有更有利的水汽条件,导致2020年梅雨期降水强度强于1998年。

In order to explore the difference of the precipitation processes during the extreme Meiyu period in the Yangtze-Huaihe River Basin between the 2020 and 1998,the similarities and differences of the precipitation features in Meiyu periods between the 2020 and 1998 were studied,and the atmospheric circulation characteristics leading to abnormalprecipitation anomalies in these two years are compared and analyzed.The results show that:(1)Thesummer precipitation in the Yangtze-Huaihe River Basin in the two years is more than that in the same period of the normal years,the Meiyu in 2020 and 1998 have the same features of earlier onset,later retreat,longer duration of the rainy season,wider range of precipitation,and higher intensity of precipitation.The abnormal degree of Meiyu period in 2020 is generally stronger than that of 1998.In 2020,the rainfall belt covers the entire Yangtze-Huaihe River Basin,and the maximum accumulative precipitation is 1623.6mm,which is located in Huangshan,Anhui Province.The position of the rainfall belt in 1998 was more southwardthan that in 2020,and the maximum accumulated precipitation is 1119.0mm,which occurred in Jingdezhen,Jiangxi Province.(2)During the Meiyu season in the two years,the western Pacific subtropical high(WPSH)experienced multiple stages of northward migration and southward retreat.The onset and retreat of the Meiyu,the location of the main rainfall belt,and the occurrence and persistence of the rainstorm processes had a good correspondence with the WPSH.(3)The atmospheric circulation during the Meiyu period in 2020 and 1998 has many similar features.The South Asian High is stronger than normal and eastward extending,the WPSH is stronger than normal and westward extending,and the middle and high latitudes show a typical"two ridges and one trough"pattern.The Yangtze-Huaihe River Basin is the water vapor convergence area of the cold air from the South behind the troughs and the warm moisture flow from the southwest of the subtropical high.(4)During the Meiyu period in 2020,the blocking high in the middle and high latitudes,the low trough along the coast of East Asia,the active intensity of cold air force,and the activity of MJO in the Indian Ocean isstronger than those in the two Meiyu periods in 1998,which is more conducive to the abnormal anticyclone circulation in the lower convective layer of the Northwest Pacific.Therefore,the convergence of cold air from the South and warm moisture flow from the Southwest of the subtropical high in the YangtzeHuaihe River Basin is stronger,and has more favorable water vapor conditions,resulting in astronger precipitation intensity duringthe Meiyu period in 2020 than in 1998.