关键词: 暴雨, 切变, 流型配置, 辐合, 中尺度

Abstract: The atmospheric circulation pattern, the physical mechanism of four rainstorm events are analyzed over Hetao area of Inner Mongolia by routine observational data, numerical forecast product, satellite cloud images, automatic weather station's data and radar data. These data mentioned above is easy and convenient access in daily forecast business. The purpose of the comparative analysis of the four rainstorm events is to discuss the predictability of the four rainstorm events and improve short-term forecast ability of the rainstorm and early warning capability of short-term strong precipitation. (1) The warm and wet southerly wind from the Bay of Bengal and west side of West Pacific Subtropical High meets with the dry and cold air from higher latitude over 35°-40° N, and the water vapor in the zone has obvious convergence, the premise condition provide a steady stream of water vapor sources and water vapor flux convergence, which is favorable for persistent rainstorm over Hetao area. (2) The exit region of significant streamline and jet stream and shear line of low level is closely related to rainstorm area; Rainstorm always happens to the right of high level jet and to the left of low level jet. (3) The pseudo-equivalent potential temperature usually decreases with the increasing height under 500 hPa before rainstorm; (4) The rainstorm usually appears after warm advection. (5) Ground convergence line is favorable for the upward momentum and triggers the meso-microscale system appearance and development during rainstorm process. (6)The lifting condensation level and the level of the free convection are relatively low, which is favorable for vapor condensation, and equilibrium level is relatively high, which is helpful to the accumulation of energy for convection weather, and these are good denotative signals for convective weather.

Key words: torrential rain, shear line, atmospheric circulation pattern, convergence, meso-scale