| Human beings can affect the weather and climate through conscious and unconscious behavior.In this paper,a mesoscale model WRF with partial two parametric microphysical scheme is used to simulate a winter orographic cloud precipitation process in Tianshan,Xinjiang.The sensitivity tests of cloud structure evolution and precipitation process to the changes of atmospheric aerosol concentration and the seeding of silver iodide particles in ground-based generators are carried out.The test setup and main conclusions are as follows:In this orographic cloud process,the ground precipitation is mainly snow.Sublimation is the main microphysical process of snow particle growth.As cloud condensation nuclei(CCN)and ice nuclei(IN),the change of aerosol concentration mainly affects the surface precipitation by affecting the content of snow below 2km height in the cloud.For the research area selected in this paper,which is obviously affected by aerosols,when CCN concentration increases,cloud water increases and particle size decreases,which promotes cloud water evaporation and Bergeron process.Under the condition of moderate pollution(three times the background CCN concentration),the promotion of Bergeron process is less than that of snow sublimation,after that,the snow sublimation and deposition rate decreases,but the snow deposition rate decreases more,which leads to the reduction of the mixing ratio of snow below 2km and the reduction of ground snowfall.Under the condition of severe pollution(10times the background CCN concentration),the increase of CCN concentration has an obvious promoting effect on the snow deposition process,and also has an inhibitory effect on the snow sublimation process,resulting in the increase of the mixing ratio of snow below 2km and the increase of ground snowfall.With the increase of IN,the particle size of cloud droplets decreases,and the evaporation rate of cloud water below 2km height accelerates,which promotes the Bergeron process in the cloud,and the growth rate of snow deposition increases,which increases the mixing ratio of snow below 2km height,and finally leads to the increase of ground snowfall.In the seeding experiment,according to the actual position of the ground-based generators in the Tianshan area of Xinjiang,the position of the ground-based generator array of Baiyanggou Mushi station is selected as the position of the ground-based generator in the model.The ground-based generator catalytic simulation of the winter orographic cloud process is carried out from 18:00 to 19:00 on the 22 nd.The main conclusions are as follows:The silver iodide particles released from the ground-based generator diffuse to the wind and cloud area under the action of airflow and terrain,nucleate and generate ice crystals through freezing and condensation,and consume cloud water.The consumption of cloud water and the formation of ice crystals are mainly concentrated over the hillside in the West and south of the ground-based generator.The activation process of silver iodide particles is mainly concentrated from 18:00 to 20:00.The activation process promotes the transformation of cloud droplets below 3km to ice crystals and the transformation of ice crystals to snow in this period time,which increases the content of snow below 3km,resulting in the enhancement of ground snowfall intensity at 18:00 to 20:00 and the increase of cumulative ground snowfall.The catalytic test of different doses shows that for this orographic cloud,seeding catalysis is carried out in the ground-based generator array of Baiyanggou Mushi station from 18:00 to19:00,and when the total amount of Ag I is within 480 g,the snow enhancement efficiency increases with the raise of the total amount of Ag I.The total amount of Ag I is between 480 g and 4800 g,and there is a total amount value with the maximum snow enhancement efficiency.For the six generators in the ground-based generator array,the more ground-based generator start-up,the greater the snow enhancement efficiency. |
PDF Full Text Request