Abstract:Based on conventional weather chart, NCEP reanalysis data, microwave radiometer products and Doppler radar observations, the water vapor, thermal and dynamic conditions, temperature and humidity stratification during 7-8 (dry snow) and 18-19 (wet snow) February 2013 are comparatively analyzed. The results show that: (1) The vapor transportation branch in dry snow process is weak southwest air current at 700 hPa, but the vapor transportation branch in wet snow process is the strong southwest air current at 700 hPa and the southeast air current at 850 hPa with sufficient moisture. (2) There is strong cold advection and stable atmospheric layer in dry snow process. However, strong warm advection exits in wet snow process in which cold and warm flow intersection makes atmospheric instability enhanced. (3) The southwest current ascends on the cooling cushion in dry snow process with convergence at middle high levels, and the secondary circulation inhibits ascending motion. In wet snow process, the cold air inserts the bottom of warm flow, making warm flow lifted, and the secondary circulation supplies a continuous and powerful updrafts. (4) The temperature is lower than 0℃ at all levels with cold inversion layer and low vapor density, liquid water content and water vapor content at all levels in dry snow, and the level of -10℃ is found at 925 hPa. On the contrary, warm inversion layer exists in wet snow with high vapor density, liquid water content and water vapor content at all levels, and the level of -10℃ is at 500 hPa. Finally, three dimensional physical model for the formation of dry snow and wet snow is built based on the above researches. The model reflects the main environmental background difference of temperature and humidity air stratification, which has certain reference significance for dry and wet snow forecasting.