The possible impact of sand-dust particles to cloud and recipitation in the Northwest China----a simulation study

It has been revealed that one of the main sources of sand-dust aerosol in the troposphere is from the arid and semi-arid area in the Northwestern China, which is important to the global climate. With the typical distributions of the local sand-dust particles, recapitulated from published research results, the impact of different sand-dust aerosol particles atmospheric backgrounds to mix cloud and its precipitation is analyzed using the numerical simulation method. Using the factorial experiment method, the sand-dust aerosol particles and the local air humidity, which one is more important to local precipitation and hail fall is analyzed too. The results show that the increase of sand-dust aerosol particles leads to the precipitation decrease, the hail fall depression and the cloud lifetime elongation, subsequently the changed cloud space structure and microphysical structure will change the original atmospheric radiation balance. The factorial experiment reveals that on the arid and semi-arid background the accumulated precipitation amount from mix cloud is more sensitivity to the variation of the distribution of the local sand-dust particles than the variation of the atmospheric circumstance humidity, the increase of sand-dust aerosol particles will decrease the accumulated precipitation amount, in opposition to the atmospheric circumstance humidity. The conclusion can be used to explain the observation facts in climatically, such as the total sun radiation on the land surface decrease over the arid and semi-arid area and the hail fall day number decrease during arid period.