Abstract: In this paper, the synoptic situation, dry intrusion, vorticity budget, apparent heat source and apparent moisture sink of a rainstorm occurred in Dunhuang during June 15-16, 2011 were analyzed using the sounding and surface meteorological data, satellite cloud images and reanalyzed data of NCEP 1°×1°. The results show that the rainstorm was caused by an interaction of the mid-high-latitude weather system and a low-latitude weather system. During the genesis of vortex, dry intrusion occurred in upper troposphere on the south side of the vortex. During the rapid development of the vortex, the dry intrusion was the strongest. During the maturity of the vortex, dry intrusion began to wane. During the rapid development of the vortex, the contribution of horizontal divergence term was the highest for the vertical vorticity in low troposphere, however, horizontal advection term and vertical transmission term played a main role in middle troposphere. During the maturity of the vortex, effect of horizontal divergence term in low troposphere and vertical transmission term in middle troposphere were enhanced, however, the effect of horizontal advection term in middle troposphere was weakened. The negative center of vertical velocity corresponded to the heating center of apparent heat source and apparent moisture sink. These indicated that atmospheric heating and ascending motion were closely coupled, and the condensed latent heat release was the main heat source.

Key words: rainstorm, plateau vortex, dry intrusion, troposphere, vorticity budget, diabatic heating, Dunhuang