中纬度夏季一次深厚对流过程的数值模拟研究:高空热力层结和风切变影响

针对一次发生在中纬度夏季的深厚对流过程进行的数值模拟研究的结果,引入一个较详细描述深厚对流状态下云微物理过程的参数化方案,对一个有限差分三维非静力弹性大气数值模式进行了改进.数值模拟得到了与天气雷达观测一致的结果.结果还显示,对于这次穿透高度超过了对流层顶的深厚对流过程,与高空斜压扰动有关的上对流层弱稳定热力层结对系统的维持起到了重要的作用.另外,还发现强烈的对流发展到对流层顶的高度时,受上曳体的驱动,在对流层顶附近的稳定层结中产生浮力性的扰动;它们与风切变相结合,进而对系统的水平移动产生控制作用.

A Numerical Study of a Mid-Latitude Deep Convection Case:Influence of the Upper Tropospheric Stratification and Wind Shear

The results of a numerical simulation study based on a mid-latitude deep convection case are presented in this paper. A 3-dimensional finite-difference non-hydrostatic compressible atmospheric model integrated with the semi-Lagrangian semi-implicit scheme and in eluding a detailed cloud-microphysics scheme was utilized to implement the simulations. The simulated storm fitted the weather radar detection. Further investigation of the model output revealed that the baroclinic disturbances in the upper troposphere played an essential role in the development of a mid-latitude deep convection. For example, the cold advection in the upper troposphere resulted in a layer with much weaker static stability, i.e., the lapse rate was -8 K km-1 in the range from 12 km to 14 km. Further, this stratification maintained the convection developed from below, and resulted in a upper tropospheric convection. It was also revealed that the shear status in the range from the upper troposphere to above the tropopause, and the buoyancy forcing associated to the tropopause penetration of the upwelling above the storm navigated the horizontal movement of the deep convection.