Abstract:Based on the NCEP FNL data, the mesoscale model WRF is used to simulate the process of a cold air snowstorm occurred in Shandong Peninsula during 29-30 December 2010. High spatiotemporal resolution data from model output are adopted to analyze mesoscale and microphysical characteristics of the cold air snowstorm. The results indicate that this snowstorm occurs under the background of significant air sea temperature differences, furthermore heat and moisture are transported from the sea surface of Bohai sea to cold air, which is caused by turbulence. Vapor from the central part of Bohai Sea are transported to the northeast of Shandong Peninsula, where the moisture convergence layer is thin, below 800 hPa. The duration of the maximum value of specific humidity and the saturated layers of relative humidity is corresponding to the heavy snowfall period. The frontogenesis of mesoscale costal front, which shows a strong convergence zone of northerly and westerly winds in the horizontal structure, plays a significant role in the heavy snow process. The ascending motions in the local circumfluence of the costal front directly decide the area and intensity of the snowstorm. In addition, the updraft is the trigger of instable energy and the mechanism of shallow convective snow. The droplets distribute mainly below 600 hPa and their maximum appears in the 850-900 hPa, respectively, which agrees with the structure of the shallow convection. In addition, the contents of droplets are different from each other, among which the contents of snow and graupel are the most.