广东省开汛期一次连续强对流过程动力热力条件分析

Dynamical and Thermal Conditions for a Continuing Severe Convective Weather Event during Onset Period of Rain Season in Guangdong

2014年3月底广东省开汛期间,出现了大范围的多灾种连续强对流天气。利用区域加密地面自动站资料、风廓线雷达资料、常规观测和NCEP再分析资料,分析了此次连续强对流发生期间大尺度环流背景条件和动力热力条件,重点讨论了大气层结不稳定维持的原因。动力分析发现,强对流天气出现在低空急流的中尺度大风速中心前方强烈的辐合区和上升气流中,垂直风切变在强对流天气发生前迅速增大,具有一定的预报指示意义。中尺度低压和地面辐合线在对流落区预报中具有较好的指示性;热力分析和热流量方程诊断表明,低空西南急流由北部湾附近暖区沿温度梯度方向不断向广东输送强暖平流,使得不稳定能量得到补充,是导致广东大气层结不稳定维持的根本原因;对于广东开汛期间的强对流天气,业务预报中需要特别关注低空急流的演变及其与温度场的配置。

Based on the intensive regional automatic meteorological station data, wind profiler data, routine observations, and NCEP reanalysis data, the circulation background, dynamical, and thermal conditions, especially the atmospheric stratification, are analyzed for the continuing severe convective weather during the onset period of 2014 rain season in Guangdong province. The results show that the severe convective weather appeared in the severe convergent area and updrafts in front of the maximum wind speed of a low-level jet, and the vertical wind shear increased rapidly before the severe convective weather happening, which has indicative significance for prediction. The mesoscale depression and ground convergence line are indicative of the convection location. Thermodynamic analyses show that the lasting warm advection by low-level jet along the temperature gradient from the warm area of Beibu Gulf is the fundamental cause of the maintenance of the instable stratification in Guangdong Province. Therefore, the variation of low-level jet and temperature field should be paid more attention for the severe convective weather during the onset period of the rain season in Guangdong Province in forecasting.