Abstract: The paper studied a heavy hail disaster occurring on the northeastern edge of Qinghai-Tibetan Plateau on 10th May 2012 based on an analysis to planet boundary layer and land surface process by using WRF V3.4 model. The results indicated that the hail disaster was caused by a secondary circulation because of the prior energy accumulating. The hail disaster was a extraordinarily serious calamitic event with the characteristics of a short-duration, high intensity, breaking out suddenly and multi-disasters accompanied with the synoptic-scale systems. At the time, the maximum height of convective boundary layer (CBL) in the early stage became thicker as a result of the energy accumulating, although the height was greatly lower than the average one. All of this demonstrated that the thermal convection environment of boundary layer maybe was the important energy source for the convection of weather development. Judging from the distribution of convective available potential energy (CAPE), the energy gradient was pretty and the thermodynamic system was extremely in homogenous. The latent heat flux and sensible heat flux value exceeded the average before the disaster. The height of absolute stable stratification, above the conditional unstable stratification in the near surface, was decreased gradually. The lapse rate of potential pseudo-equivalent temperature in conditional unstable layer had the tendency of increasing first and then decreasing, and its peak was 0.88 K·(100m)^-1 at 13:00. In the meanwhile, the horizontal gradient of potential temperature was maximum. The friction velocity exhibited a significant increase before and after this process probably because of the abnormal transfer of turbulent momentum and meso-scale momentum flux.

Key words: hail, WRF model, dynamic effect, thermodynamic effect, stratification stability, Qinghai-Tibetan Plateau