湖南两次暴雪过程的双偏振雷达云相态垂直特征观测分析OA北大核心CSTPCD

According to the two extensive snowfall events in Hunan in 2021 and 2022,by utilizing ERA5 global reanalysis data along with detection data from Changsha radiosonda radar and Changsha S-band polarimetric radar,the environmental conditions leading to these events are investigated.The analysis reveals that the thickness of the positive vorticity region extends to 450 hPa,strong vertical motion exists in the mid-high levels,and south-west airflow transports abundant water vapor,providing favorable dynamic,thermal,and moisture conditions for heavy snowfall.Cold-season snowfall exhibits elevated convective characteristics,and the presence of low-level clouds near 850 hPa is a crucial indicator for snowfall.The cloud top of these layer clouds serves as the thermal ini-tiation point for the snowfall.Furthermore,utilizing data from Changsha polarimetric radar,we analyze the micro-physical characteristics of the two snowfalls.The results indicate:①There are significant differences in the basic reflectivity and polarization texture features between heavy snowfall and snow pellets,enabling effective identifica-tion of the two precipitation particles.②Vertical profiles of phase indicate a phase transition corresponding to low-level cloudiness during snowfall.The vertical velocity profiles show a characteristic of higher velocities aloft reach-ing-20 m/s,while near-surface snowfall echo vertical velocities range between 1-5 m/s,significantly slower than the falling speed of rain in layer clouds.③Vertical profiles of radar polarization parameters reveal that active supercooling processes further increase the ice-water content and non-uniformity of particle morphology in snow particles.This leads to a significant feature of high differential reflectivity(ZDR),high differential phase shift(KDP),and low correlation coefficient(CC)corresponding to the active layer of ice crystal attachment.The vertical structure of radar echoes exhibits a time-series skewed distribution.In conclusion,the study confirms that polari-metric radar can capture the fine structural evolution of snow cloud clusters,providing a scientific basis for short-term forecasting of heavy snowfall.