Henan Province, Autumn And Winter Stratiform Precipitation Characteristics And Physical Mechanisms

Combining observational data analysis with numerical simulation, synoptic methods with cloud physical methods, mesoscale model with microscale cloud model, the evolvement, macroscopic and microscopic structures and precipitation mechanism of the stratiform cloud precipitation and snowfall process that occurred in Henan area during 17-19 October and 20-22 December 2002, have been studied in this paper.In the case of precipitation in Autumn, situ data analysis and numerical simulation results show that, raindrop, rainfall intensity, water content and number concentration are small; the aera of saturation and ice-water change was located in the level of 500-400hPa; the aera of unstable energy was located in the level of 500-700hPa; the frontal system took on clear layered structure. Ice particles were formed in the high level, the number concentration of which was several per cube decimeter. Ice water and supercooled water exist in mid level. Liquid water locates in the low level. The cloud frame of "seeder-feeder" was distinct. The height and temperature of "seeder" cloud were between 200hPa and 500hPa, -10C and -40C, respectively. The "feeder" cloud located at about 0C level, between -10C and 5C, 500hPa and 900hPa, respectively. Simulation of different part of the frontal have shown that pre-frontal cloud precipitation was generated by warm-cloud process as well as ice-phase process and "seeder-feeder" michanism was distinct while the result was contrast in the frontal cloud and post-frontal cloud.Winter snowfall process was stable and extensive. The microphysical characteristics were smaller than that of Autumn. There were ice, snow and supercooled water in cloud, the number concentration of which was more than several per cube decimeter. The cloud frame of "seeder-feeder" was distinct. The height and temperature of "seeder" cloud were between 300hPa and 500hPa, -20C and -40C, respectively. The "feeder" cloud located above 0C level. Simulation of different part of the frontal have shown that frontal cloud and pre-frontal cloud precipitation was mainly generated by ice-phase process and "seeder-feeder" michanism was not distinct. In the post-frontal cloud there was only iceand snow so there is no "seeder-feeder" mechanism, while vapor deposition was verystrong.