The Numerical Study Of The Effects Of Dust Aerosols As Atmospheric Ice Nuclei On Regional Precipitation

The rainfall from April 8 to 11, 2003 which go with a strong dust storm wassimulated by MM5, and analyzing the precipitation mechanism. Through changingice nuclei concentration of the Reisner 2 explicit cloud scheme, design 5 differentsensitivity experiments to study the effect of increasing atmospheric ice nucleiconcentration on regional precipitation and the redistributing of regional precipitationfrom the thermic and cloud microphysics aspects. The results show that:The process of rain in dust days is fit to "seeding-feeding" mechanism. Thesimulations of the structure of whole cloud system show that there is ununiformitystructure in cloud system. There are different layers in cloud. The simulations of thecloud microphysics process show that the heights of different particles are different:ice is in highest layer, ice-water is in medial layer, liquid water is in lowest layer.This is typical "seeding-feeding" structure.The effects of dust aerosols as atmospheric ice nuclei on precipitation are: theincreasing of pristine ice concentration result in producing many smaller crystals,restrain the procress of snow grow, reduce the amount of snow thaw, then the processof produce rain are restrained, destroy "seeding-feeding" mechanism, result in theamount of precipitation decreasing. When decreasing pristine ice concentration makecrystal may increase bigger, the physics processes of precipitation are opposition theincreasing of pristine ice concentration, enhancing "seeding-feeding" mechanism,result in the amount of precipitation increasing.The effects of dust aerosols as atmospheric ice nuclei on redistributing ofregional precipitation are by changing the distribution of ice concentration in upperair. Dust aerosols may produce more ice in dust days, this damage nicer"seeding-feeding" mechanism which decreasing rain. But in worse "seeding-feeding"cloud increased ice nuclei can ameliorate "seeding-feeding" mechanism, result inprecipitation increase.There are also worse "seeding-feeding" areas in cloud in dust days, if there havegood vapor and supercooled water in these areas, we can do precipitation enhancement experiment, if we add propriety ice in cloud, these ares can enhanceprecipitation.