摘要:利用欧洲中心ERA-Interim再分析资料，对"05·6"华南持续性暴雨发生前上对流层及平流层信号进行分析。分析结果表明，暴雨发生前一周，暴雨区域上空对流层顶高度出现先降低后升高再降低的变化，这种变化与日本南部的位涡异常存在较好的对应关系，即我国中纬度沿海一带至日本的高位涡带向华南延伸，使得华南地区上空的位涡升高，对流层顶下降。在环流场中，本次暴雨发生前低纬地区上对流层下平流层（UTLS）区域的东风与1991~2010年平均值相比偏强偏北，华南地区上空平流层东风场也偏强，平流层低层东风在暴雨发生前第9天提早向下传播；位势高度场中，"05·6"华南暴雨发生前中低纬度100 hPa上的南亚高压中心位置偏东偏南；华南地区UTLS区域有较强的位势高度场正异常，在暴雨发生前随时间出现两次明显的加强，但在暴雨发生后减弱。南亚高压中心位置的偏移、东风信号的提早下传、高位涡空气入侵华南均有利于降水的发生。
关键词:华南暴雨/
上对流层/
平流层
Abstract:Using the ERA-Interim reanalysis data, the upper tropospheric and stratospheric signals before the "05·6" heavy rainfall event in South China are analyzed. The results show that before the heavy rain, the tropopause over the rainfall region exhibited a lower-lift-lower trend that was consistent with the evolution of potential vorticity (PV) anomalies over southern Japan. Specifically, a relatively high PV belt over Japan extended southward and led to higher PV (lower tropopause) over southern China. Compared with the mean values between 1991 and 2010, easterly winds in the upper troposphere and lower stratosphere (UTLS) over the subtropical region were stronger and located more northward before the heavy rain. There also existed positive easterly wind anomalies over South China, which propagated downward on the 9th day before the heavy rain. The center of the South Asian High was located more eastward and southward than its mean position before the heavy rainfall. The relatively high geopotential height that enhanced twice with time could be found in the upper troposphere and lower stratosphere over South China. The shift of the center of the South Asia high, the early downward propagation of lower stratospheric easterly winds and the airmass of high PV all were favorable for the onset of the heavy precipitation.
Key words:Heavy rainfall in South China/
Upper troposphere/
Stratosphere
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