Numerical Simulation on Macrophysics and Microphysics Structure of the Orographic Cloud and Precipitation in Summer of the Qilian Mountains

A case of heavy rainfall in the Qilian Mountains on 19 July 2007 was simulated using the mesoscale numerical model ARPS(Advanced regional prediction system).The simulated rain band was basically consistent with the observations.The macrophysics and microphysics structure characteristics of the cloud and precipitation of the heavy precipitation process were mainly discussed.Results show that under the influence of the Qilian Moutains,the horizontal distribution features of the hydrometeor in the cloud system were as follows: in the early stage,the content of all hydrometeor was little and homogeneous,and in the initial stage of development,due to the intrusion of lower cold air in northwest,the content of cloud water,cloud ice,snow,graupel(hail) and rain water began to increase and became less homogeneous;in the development and prosperity period,along with the emergence of the lower shear line and vortex center on the north side of the Qilian Mountains,the content of all hydromeror in horizontal direction increased significantly and vertical thickness extended obviously;with a gradual eastward shift of cloud system,the scope of the hydrometeor became narrow and its content decreased.The vertical distribution features of the hydrometeor in the orographic cloud were as follows: in the early stage,cloud water mainly distributed in the lower layer and graupel mainly in the freezing level,ice water mainly in the middle and upper level,rain water mainly in the warm zone of lower part close to the ground in the cloud;in the initial stage of development,as a result of enhanced vertical motion,the content of the different hydrometeor increased;in the heavy rainfall period,from the ground to the top level,the content of cloud water,ice,snow and graupel(hail) had the highest value;in the weakened period,the content of all hydrometeor decreased significantly and even disappear.