一次暴雨过程大气边界层结构的数值分析

NUMERICAL ANALYSIS OF THE PBL STRUCTURE FOR A RAINSTORM CASE

1979年7月28日河北唐山地区的强暴雨,10小时总降水量达430mm,降水强度大,从时间和空间上都非常集中。这次太平洋副热带高压北侧暖区发生的强暴雨引起国内气象界的普遍重视。游景炎,陆一强等对这次暴雨过程的大尺度环境、中尺度结构进行了详细分析并分别讨论了边界层急流、强对流性云团以及地形等的作用。游景炎根据地面天气图的分析,发现明显的雷暴高压和中尺度低压。这种中尺度系统在大气边界层内如何表现呢?这次暴雨系统延伸多高呢?

In the paper, the planetary boundary layer (PBL) structure for the 28 July 1979 Tangshan rainstorm on the north edge of the subtropical high is diagnosed by use of the of the 9-level unequal-interval PBL model. The synoptic scale variables are interpolated to the upper boundary of the model and the observed wind data at the 1500, 900, 600, 300m levels and the surface are utilized. The effects of thermal stratification and baroclinicity on wind distribution in the PBL are taken into account. The dynamic adjustment scheme is applied to get the wind fields at the model levels. The computed wind fields show that there are a clear convergence zone and cyclonic circulation in the lower layer of the PBL. The vertical fluxes of momentum, heat and moisture at the surface as well as the fields of vertical motion, vorticity and divergence at all levels are calculated by using the model. It is clear that the results give full details of the thin structure of the PBL and show the effects of topography forcing. And the quality and ability of the used PBL model are further checked.