Numerical Simulations of Cloud Structure and Seedability of a Precipitating Stratiform Case in North China

A case of westerly trough precipitating stratiform cloud on Sep 21, 2012 is simulated using the mesoscale model WRF coupled with CAMS microphysical scheme. The simulated rain band, cloud top temperature and hydrometeors are basically consistent with observations. Meso- and micro- structures of this precipitation are analyzed using simulations and observations of satellite, radar and aircraft. The large-scale weather systems of the precipitation are westerly trough at 500hPa and shear line at 700hPa. There is no obviously cold front at low levels. The cloud structures are different at different area of the cloud system. In the forepart, the cloud system composes of only supercooled cloud water and ice particles. There is a little cold cloud precipitation. The cloud top temperature is -35℃. Near the line of westerly trough, the cloud is mixed phase with more ice, snow, graupel and more supercooled cloud water in cold area and more cloud water and rain water in warm area. The cloud top temperature is -20℃.In the rearpart, the cloud system composes of mostly warm cloud water. The cloud top temperature is -5℃. There is a little warm cloud precipitation. The production of cloud water needs updraft and high saturation and is proportional to them. The seeding areas are distinguished by supercooled water, updraft, number concentration of ice, temperature and precipitation intensity. It is strongly seedable near the trough line due to the much more supercooled water. The seeding height is 3.8-6.5km. These areas have good potential of artificial precipitation enhancement.