绿洲和沙漠下垫面状态对大气边界层特征影响的数值模拟

采用两维高分辩率边界层数值模式,并与一个包括植被和土壤层的生物一大气能量传输模式(BATS)耦合,模拟研究绿洲和沙漠下垫面状态对大气边界层特征的影响。结果表明,沙漠中的绿洲对大气产生"冷湿效应",使之上空形成冷湿气柱;绿洲之间的沙漠对大气呈"暖干效应",使上空形成热干气柱。在水平平流的作用下,在绿洲下游的沙漠边缘形成降水峰值,有利于降水,但沙漠区下游的绿洲则相对于整个绿洲区降水偏少,不利于形成降水。

THE NUMERICAL SIMULATION OF THE FEATURES OF THE PLANERTARY BOUNDARY LAYER OF THE OASIS AND THE GOBI DESERT IN THE ARID REGION

In order simulate and research the influence of the features of the Planetary Boundary Layer (PBL) of the oasis and gobi desert and underlying surface on precipitation etc., two-dimension high resolution PBL model coupling with the BATS scheme has been used in this paper.The underlying surface is desert ,in which there are several hundred km long. Resuls shows that oasis transports little sensible heat to PBL,the peak generally is about 60 w/m²,but latent heat is larger,the peak generally is about 400 w/m². Due to the transportation of the sensible heat and latent heat over the oasis, the cold-wet air column appears in the boundary and lower air. The air column can reach a height of 650 hPa, the ground layer and temperature difference can reach 4 ℃, this case is called "oasis cold-wet effect". In the desert region, due to the latent heat transports little, the peak is about100 w/m², but sensible heat transport is largely about 400 w/m², a hot-dry air column formed, it can reach the height of 600 hPa in the boundary layer and lower air over the desert in between the oasis.The maximum ground layer temperature difference is 5℃, this case is called "desert hot-dry effect".The existernce of oasis in the desert and gobi contributes to the precipitation of oasis and the lowerreaches of the oasis. The cold-wet air transported by advection passes over the desert, it mades layer unstable and precipitation increase over desert contiguous to the fringe of the oasis.