江淮流域持续性暴雨过程前期环流特征

Preceding Atmospheric Circulation Characteristics of Persistent Heavy Rainfall in Yangtze and Huaihe River Basin

利用NCEP逐日再分析资料,通过合成分析以及滑动平均的低通滤波效果分析在江淮地区持续性暴雨过程发生前的环流场特征。研究认为持续性暴雨过程前期环流特征主要有以下几点:澳大利亚高压强度变化幅度小,马斯克林高压强度变化幅度大,两者之间呈现此消彼长的关系;副热带高压明显比常年偏强,脊线平均位置偏南,西脊点平均位置偏西;南亚高压属于西部型,强度偏弱,东伸脊点偏东;南亚高压的东伸脊点与副高的西伸脊点具有明显的相向而行,相背而去的活动特征;副高脊线比南亚高压脊线偏南4～6个纬距,并且两者具有步调一致的南北移动,但是南亚高压脊线移动时间比副高脊线提前1天左右。

The persistent heavy rainfall is a kind of extreme precipitation events that have a long duration, extensive coverage, and relatively stable heavy precipitation areas. Based on the daily averaged data derived from the NCEP/NCAR reanalysis dataset, the preceding signals in atmospheric circulation of persistent heavy rainfall events happened in the Yangtze and Huaihe River Basin in June are revealed by using the moving average analysis and composite methods. The results suggest that Australia high and the Mascarene high has a relation of ＂seesaw＂; the subtropical high is obviously stronger than usual; the average position of the ridge line is farther south, and the average position of the west ridge point is farther west ; the South Asia high, belonging to the west-type high, is weaker, and the eastward-stretch ridge point is farther east; the eastward-stretch ridge point of the South Asia high and the westward-stretch ridge point obviously come toward each other and goes away from each other; the ridge line of the subtropical high is 4 to 6 latitude distances farther south that that of the South Asia high, and they have concerted north-south movement, but the movement of the ridge line of the South Asia high is about one day later than that of the ridge line of the subtropical high.