Abstract:Using conventional sounding data, surface observation data, NCEP 1.0×1.0 reanalysis data and Doppler radar data, three times of rain and snow processes in Hunan in early February 2014 are analyzed. The results show that (1) the first process is a freezing rain process in southern Hunan, which is characterized by obvious inversion layer between 700 hPa and 850 hPa. The temperature at 700 hPa is above 0℃, but at 850 hPa and 925 hPa it is below -4℃ while the ground temperature is below 0℃. From the perspective of main system configuration, strong southwest jet at 700 hPa plays an important role in water vapor transmission and the formation of melting layer. A stationary front and deep cold pad which is comprised of the cold air blocked by Nanling Mountains, are the causes for the long lasting southern Hunan freezing rain. (2) The second and third processes are snow based processes with surface temperature around 0℃, and the temperature above surface is lower than 0℃. (3) The third process of rain/snow is the heaviest. Warm moist air rises along the front, and low level cold air results in this severe rain and snow process. Radar echo of this process has the characteristics of mixed echo of cumulus and stratus as well as low centroid high efficient precipitation feature.