河套地区一次短时强降水过程诊断分析

Diagnostic Analysis of a Short-Time Heavy Rainfall Process in Hetao Area

本文利用自动站实况降水观测资料、风云2号卫星资料及美国气象环境预报中心(NCEP)提供的FNL再分析资料,对2013年7月7日河套地区短时强降水的形成、发展过程进行了分析,结果表明:此次过程中,环流形势场上,本次过程是西风带槽脊与副热带系统相互作用导致。副高偏北,贝加尔湖南部至河套南部为宽广槽区,南部阶梯槽为前倾结构,低层存在风场切变线,且700 hPa上的西南低空急流为降水区输送大量的暖湿气流。副高西伸北抬,南北方形成阶梯槽,配合弱冷空气南下,低层风场出现辐合,是造成本次强对流过程的主要影响系统。水汽通量输送中心和水汽通量散度辐合中心几乎叠置,动量下传促使低空急流形成,显著的差动平流,不稳定能量的大量积聚、地形和地面中尺度辐合线对能量的出发作用为本次短时强降水过程提供了水汽、动力、热力和不稳定条件。

In this paper, the formation and development process of the short-term strong precipitation in Hetao region on 7th July, 2013 are analyzed by using the real-time precipitation observation data of the automatic station, the Fengyun 2 satellite data and the FNL reanalysis data provided by the United States Meteorological Environment Prediction Center (NCEP). The results show that: in this process, in the circulation situation field, this process is caused by the interaction between the trough ridge of the westerlies and the subtropical system. The subtropical high is to the north, the southern part of Baikal to the southern part of Hetao is a wide trough area, the southern step trough is a forward-dipping structure, there is a wind field shear line at the lower level, and the southwest low-level jet at 700 hPa delivers a large amount of warm and humid air for the precipitation area. The subtropical high extends to the west and lifts to the north, forms a stepped trough in the south and the north, cooperates with the weak cold air to the south, and the low-level wind field converges, which is the main influence system of this strong convection process. The water vapor flux transfer center and the water vapor flux divergence convergence center are almost superimposed. The momentum downward transfer promotes the formation of the low-level jet, the significant differential advection, the massive accumulation of unstable energy, and the starting effect of the terrain and the surface mesoscale convergence line on the energy provide the water vapor, power, heat and unstable conditions for this short-term strong precipitation process.