关键词: 甘肃中部, 高架雷暴, 冷锋, 逆温

Abstract: Based on the conventional meteorological observation data, ECMWF reanalysis data and reflectivity factor data of Doppler radar, the circulation situations, weather systems configuration, dynamic and thermal conditions of an elevated thunderstorm weather process behind cold front in the central of Gansu Province from October 8 to 9, 2017 were diagnosed synthetically. The results show that the weather systems affecting the occurrence and development of the elevated thunderstorm weather were mainly cold front, 700 hPa shear line, southwestern jet and 500 hPa upper-level trough. The cold air moving southward formed a cold pad near the ground, and the warm and humid airflow climbed along cold front, which triggered the elevated thunderstorm weather at the inversion layer top near 620 hPa. The inversion layer of the elevated thunderstorm weather was deep, and there were three 0 ℃ layers in vertical direction. Under the influence of rainfall before the occurrence of the elevated thunderstorm process and southwest warm and moist airflow, the atmosphere was dry in upper layer and humid in lower layer, and it was cold in upper and lower layers and warm in middle layer, which indicated the atmospheric stratification was instability. The vertical wind shear in middle and lower levels of troposphere, convergence in lower level and divergence in upper level prompted the uplift of warm and humid air. The high energy tongue and BCAPE in middle and lower levels could reflect unstable energy conditions well during the process. During the elevated thunderstorms process, the rainfall (snowfall) and hail weather accompanying wide-range and northeast-southwest thunder and lightning appeared over Lanzhou and its surrounding. The strong echo height of radar reflectivity factor exceeded 8 km, and the echo characteristic of hail was typical.

Key words: central Gansu, elevated thunderstorm, cold front, inversion