大连地区暖锋暴雨个例成因与雷达回波特征

Forming reason of a warm front rainstorm case and its radar echo characters in Dalian area

利用常规观测资料、自动站资料和多普勒雷达资料等,对2009年7月14日大连暴雨过程进行分析。结果表明:这是一次暖锋大暴雨过程,高空河套槽北抬与北支槽尾段相叠加,中低层在渤海北部到大连地区形成涡旋环流,700 hPa气旋式较大曲率出现在地面暖锋上空,大连地区位于地面气旋顶部即暖锋顶部,造成强降水的产生。强湿区配合暖锋前低层辐合中心、高层辐散中心,为暖锋大暴雨天气提供了水汽和动力条件。从雷达回波分析可以看出,暖锋前部45 dBz的β中尺度反射率及速度场上"单牛眼"特征,是造成暴雨过程的直接原因。VWP资料分析表明,低层东南急流与高层西南急流形成切变层的高度以及两支急流的强度变化,与暖锋相对应并决定降水强弱。

Based on the conventionally observational data, meteorological data from automatic weather stations and Doppler radar data and so on, a rainstorm event on July 14,2009 in Dalian area was analyzed. The results show that it is a warm front rainstorm process. The upper-level trough located in Hetao area moves northward and over- lays with the tail of the north branch trough. In the middle and low levels, a vortex circulation forms from the northern Bohai Sea to Dalian area. The region of high cyclonic curvature at 700 hPa is located above surface warm front. The top of surface cyclone, i. e. the top of warm front is just in Dalian area. This weather pattern results in the occurrence of heavy precipitation. High humidity area together with low-level convergence centre in front of the warm front and upper-level divergence centre provides favorable moisture and dynamic conditions for the heavy rainstorm event. Radar echo analysis shows the fl-middle scale reflectivity area with 45 dBz in front of the warm front and the ＂single oxeye＂ characteristics in radial velocity field directly contribute to this rainstorm and short- time strong precipitation. The analysis of VWP data shows the height of shear layer formed by low-level southeast- erly jet and upper-level southwesterly jet and the intensity variation of the two jets correspond to warm front and determine the rainfall intensity.