Abstract:

Based on the GRAPES model data, conventional observation meteorological data, and NCEP reanalysis data, mechanisms of the two heavy snow/rain processes on January 3, 2010 (code 0103), and November 3, 2012 (code 1103) in the North China were analyzed. The results indicate that the rain falling areas and relative locations of the surface cyclone are significantly different in these two processes. Precipitation mainly occurs in the east of cyclone for the “0103” process, while it is in the north for the “1103” process. By test, the GRAPE model could simulate well the rain falling areas for the two processes. In terms of the analysis of numerical simulation results, the reasons for the characteristics of precipitation distribution can be explained as follow: From the thermodynamic features, thermodynamic characteristics of cyclone are different for the two processes. It is warm core structure for the "0103" process, while it is cold core structure for the "1103" process. The cold air is continually invaded into the cyclone in the “1103” process and results in its cold core structure. On the other hand, cold air and warm air converge between cyclone and anticyclone for the “0103” process and form the occlusion around the center of the cyclone, while they convege within the cyclone for the “1103” process and front system leans from south to north. Furthermore, entrainment of water vapor by cyclone occurs at the low level for the “1103” process. From the vertical distribution of the wind field, there is surface easternly wind before two processes occur, and the middle and low level flow transits when processes ends up. Wind direction changes from south to north, while the evolution of wind field is obviously different during the process of precipitation.

Key words: Suface cyclone, Heavy snow/rain, Dynamic and thermal structures, Water vapor distribution, Numerical simulation