摘要
利用快速同化系统LAPS资料,结合卫星、雷达、GPS和地面逐小时加密观测资料,对比分析了2012年7月12—13日鄂东北地区连续两次大暴雨过程的中尺度对流系统特征。结果表明:鄂东北地区两次大暴雨过程发生的强迫机制明显不同,分别为热力因子主导的暖平流强迫和动力因子主导的锋生强迫。在两种不同动力机制条件下,第一次大暴雨过程对流云团呈不对称分布,强回波伸展高度较高,强降水主要位于黑体亮温(Temperature of Black Body,TBB)梯度大值区,产生的降水强度较大,并伴有强雷电活动;第二次大暴雨过程对流云团呈对称分布,强回波伸展高度较低,强降水主要位于TBB大值中心,表现为明显的暖云降水。但在两种动力机制下,两次大暴雨过程均形成了长时间的降水,一方面由于边界层冷池的冷出流与南风入流在对流系统后侧交汇,形成后向传播,强降水单体传播和移动相互抵消,从而使对流系统稳定维持;另一方面由于对流系统移动方向与引导气流方向一致,强降水单体依次经过同一地点,产生较大的累积降水。
Based on data from the Local Analysis and Prediction System（ LAPS）, as well as observations from sat- ellite, radar, GPS, and automatic meteorological stations, characteristics of a mesoscale convective system （ MCS ） were comparatively analyzed during two heavy rainstorms in the northeast region of Hubei province on July 12-13, 2012. The results indicate that forcing mechanisms of the two heavy rainstorms are distinctly different. One is forced by warm advection due to thermodynamic factors and the other is forced by the front due to dynamic fac- tors. For the first heavy rainstorm, convective cloud has an asymmetric structure. Intensive echoes extend to the high altitudes. Its strong precipitation mainly locates in the areas with great gradients of TBB （Temperature of Black Body）accompanying with thunder and lightning. While for the second one, convective cloud has a symmet- ric structure. Intensive echoes only reach the lower altitudes. Its heavy precipitation mainly occurs in the center with a large-TBB value, indicating warm cloud precipitation. Two heavy rainstorms last for a long period of time. One reason is that the cold outflows from cool pool in the boundary layer converge with the southerly inflows in the rear of convective system and form a backward propagation that offsets the movement of heavy rain cells, which favors the maintenance of convective systems. The other one is that the convection system moves to the same direc- tion with the steering flows. Heavy rain cells pass the same place successively, resulting in a strong cumulative pre- cipitation.
出处
《气象与环境学报》
2016年第4期1-11,共11页
Journal of Meteorology and Environment
基金
中国气象局预报员专项"2012年特殊地形下致洪暴雨过程对比分析"(CMAYBY2013-044)
中国气象局小型基建项目"中尺度天气分析业务建设"共同资助
关键词
大暴雨
中尺度对流系统
强迫机制
动力因子
热力因子
Heavy rainstorm
Mesoscale convective system
Forcing mechanism
Dynamic factors
Thermodynamicfactors
