贵州2010年一次冬季暴雨的诊断

Diagnostic Analysis of a Torrential Rain Occurred in Guizhou in Winter of 2010

利用气象常规观测资料、美国国家环境预报中心NCEP 1°×1°再分析资料,对贵州2010年一次冬季暴雨极端天气的诊断分析发现:这次暴雨天气主要是因南支槽、准静止锋以及850 hPa切变共同影响造成,其形成原因与贵州秋末暴雨非常近似,属于冬行秋令。对比分析本次降水过程中2个重要天气系统之一的南支槽与气候平均态的差异发现:本次过程中南支槽前的强偏南气流提供了有利的暖湿输送,不同于气候平均态的干暖输送;南支槽前偏南气流的水汽辐合、上升运动、低层辐合、高层辐散均明显强于气候平均态。另一个重要天气系统准静止锋具有2个主要特点:(1)锋区温度较高,锋面逆温层温度均高于0℃;(2)锋区表现为等θse密集区,锋区狭窄而陡峭,锋后低空逆温明显。在暴雨发生期间,静止锋是一个加强北抬的过程,在静止锋加强的过程中促使了水汽辐合、上升运动发展以及低层辐合等产生暴雨的有利条件发展。

Based on routine meterological observations and NCEP reanalysis data,a torrential rain occurred in Guizhou in winter of 2010 was analyzed.The results show that the southern branch trough,quasi-stationary front and shear at the level of 850 hPa resulted in this heavy rain process,and which was nearly the same as that of those heavy rain weather events occurred in the end of autumn in Guizhou.During this weather process,the south-west airflow in front of the southern branch trough was warm and moist which was different from climate mean state（dry and warm）,and the moisture convergence,rising motion and the wind convergence at lower layer but divergence at upper layer were stronger than that of the climate mean state.There were two main features of quasi-stationary front in this case： in vertical direction,the frontal inversion layer＇s temperature was above 0 ℃;the front zone presented the dense area of the pseudo-equivalent potential temperature,the frontal structure was narrow and sharp,and behind the frontal zone,the lower level inversion was very significant.The frontogenesis provided favorable large-scale condition for the torrential rain in winter.