Mesoscale Numerical Simulation of the Influence of PBL Parameterization and Moist Process on Development of a Shear-line Vortex
边界层参数化和湿过程对切变线低涡发展影响的中尺度模拟

During the period of 14-22 August 1981 , a persistent heavy rainfall event occurred over adjoining region of Shanxi, Gansu and Sichuan provinces which are located on the eastern side of the Tibetan Plateau. The vorticity diagnosis of the main heavy rainfall event showed that the shear-line vortex originated in lower level of the eastern side of the Tibetan Plateau . Following that event, not only vorticity centers superimposed and conpled at the upperand lower-level , but also an intensive process took place rapidly in the PBL. This process was accompanying by persistent development of the shear line vortex.A series of 48 hr and 72 hr mesoscale numerical simulations reveal that only the high resolution PBL parameterization with moist process can well simulate the rapidly intensive process in the PBL, vorticity evolution and vertical structure of the shear-line vortex . The bulk PBL parameterization can not simulate this rapidly intensive process of the shear-line vortex although its vorticity evolution and vertical structure can beroughly simulated . The simulative result of the bulk PBL parameterization with dry process indicates that this scheme is worse than the two schemes with moist processes as mentioned above , especially , the intension of simulated shear-line vortex was significantly weaken and the location deviated.The comparisons of the simulations , diagnoses and observations reveal that only by improving PBL parameterization and moist physical processes as careful as possible can we improve the simulations of the formation and development of this kind of mesoscale systems.