Institute of Atmosphere Physics,Chinese Academy Sciences
In this study, by taking account of the complex topographic effect in Xinjiang and the condensation latent heat heating of the moist atmosphere near frontal rainstorm area, 1) we derive the thermodynamic frontogenesis functions under terrain-following coordinates based on the potential temperature, equivalent potential temperature and generalized potential temperature, and a dynamic frontogenesis function driven by the deformation field. The advantages of frontogenesis functions in terrain-following coordinate in studying frontal processes in in complex topographical region are expounded; 2)We discuss the advantages and disadvantages of the four frontogenesis from the perspective of the temperature and humidity gradient increase, which is the more essential process during a frontogenesis process, and find that the generalized potential temperature and deformation frontogenesis have a better correspondence with the precipitation process; 3) We perform numerical simulation of a frontal precipitation event by utilizing of WRF model, which propagate from north to south of Tianshan in Xinjiang, and carry out the analysis of the main forcing of the thermodynamic and dynamic frontogenesis functions, as well as their effect during the rainfall. The results suggest that dynamic frontogenesis plays an important role in precipitation triggering and weakening stage and is caused by energy conversion between vorticity, divergence and deformation. Thermodynamic frontogenesis mainly acts on precipitation development stage, and latent heating is the main forcing. In practical applications, the overlapping region of two frontogenesis functions in the near-surface layer and mid-lower troposphere could indicate the direction of future precipitation propagation.