20世纪90年代以来东北暴雨过程特征分析

使用1990～2005年全国730站日降水资料和NCEP格点分析资料对1990～2005年东北地区大暴雨过程进行了分类研究,探讨21世纪前后夏季东北暴雨的主要特征.按照东北地区日降雨量大于50 mm的站点数不少于5个的标准,统计出1990～2005年东北地区的69个暴雨个例(共90天).在统计的基础上,进一步对造成大范围暴雨过程的天气形势进行分类研究.考虑阻塞高压、热带、副热带系统和西风带之间的相互关系,将暴雨过程的主要影响系统大致分为6类:(1)台风与西风带系统(西风槽、东北低涡)的远距离相互作用(20个,28.9%);(2)登陆台风(或南来低涡)北上与西风带系统(西风槽、东北低涡)相互作用(16个,23.2%);(3)台风直接暴雨(1个,1.5%);(4)低槽冷锋暴雨(16个,23.2%);(5)低空切变型暴雨(2个,2.9%);(6)东北低涡暴雨(14个,20.3%).在所有个例中与台风有关的共有37个,超过一半,占总数53.6%.台风的远距离水汽输送或登陆台风北上与西风带系统相互作用是东北地区产生大暴雨或持续性大暴雨的重要环流条件.此外,东北低涡和西风槽前系统造成暴雨个例也比较多,也是东北地区大范围暴雨的重要影响系统,低槽冷锋暴雨和东北低涡暴雨也各分为4小类.低空切变暴雨的切变线一般在低层较为明显.上述分析表明,夏季东北地区暴雨过程种类繁多,情况较为复杂,且进入新世纪以来该区降雨过程较为活跃,值得深入研究.

Characteristics of Heavy Rainfall in Northeast China since the 1990s

The heavy rainfall cases in Northeast China between 1990 and 2005 are classified by utilizing the daily precipitation data at 730 stations in China and NCEP grid reanalysis data from 1990 to 2005.According to the crite-ria that in Northeast China there are more than five stations with daily precipitation amount more than 50 mm in 24 hours, 69 heavy rainfall cases (totally 90 days) in Northeast China are selected between 1990 and 2005. Based on the statistics, the synoptic systems and large-scale circulation related with the heavy rainfall cases are studied fur-ther.Considering the interaction among blocking high, tropical and subtropical systems, and westerlies, the main impact systems for the heavy rainfall cases are approximately classified into six types : (1) The remote interaction between typhoon and westerly systems (westerlies troughs, vortexes in Northeast China) (20 cases, 28.9%) ; (2) the direct interaction between the northward landing typhoons ( northward propagating vortexes) and westerlies sys-tems (westerlies troughs, vortexes in Northeast China) (16 cases, 23.2%); (3) the heavy rainfall caused directly by the typhoon (one case, 1.5%); (4) the heavy rainfall associated with low tough and cold front (16 cases, 23.2%) ; (5) the heavy rainfall caused by the low level shear line (two cases, 2.9%) ; (6) the heavy rainfall caused by vortexes in Northeast China (14 cases, 20.3%).37 cases, more than half of the heavy rainfall cases, are associ-ated with typhoon The typhoon's long distance moisture transportation or the interaction between northward mov-ing typhoons after landing and westerlies systems are still important circulation conditions for the occurrence or per-sistence of the heavy rainfall in Northeast China. Furthermore, there are also plenty of heavy rainfall cases caused by vortexes in Northeast China and westerlies trough, both of which could be classified into four sul:rtypes.The shear line of the heavy rainfall with low-level warm shear line is usually obvious in the lower troposphere The analyses a-bove indicate that there are various kinds of heavy rainfall in Northeast China in summer and the circs are complicated Fur-thermore, the rainfall in this region has been active since the new century and worthy of further research