本文运用PSU/NCAR中尺度模式第四改进型(MM₄), 对"81.7"四川暴雨期西南涡的演变^[1]进行了一系列96和72小时数值模拟; 其目的在于研究模式物理过程和空间分辨率以及行星边界层(PBL)参数化对西南涡生成和发展模拟的影响。96小时的控制试验(方案Ⅰ)结果表明: 水平分辨率160km和总体PBL的10层MM₄对西南涡发展模拟得较好, 但对其生成只有初步模拟的能力; 各种物理过程主要影响西南涡演变的强度, 而对其位置影响较小; 去掉潜热释放会显著影响西南涡在后期的发展; 没有地面通量将使西南涡的生成和发展强度明显减弱; 于试验不能模拟出西南涡在整个暴雨期的发展, 且使其移速略快, 无摩擦试验指出, 地面摩擦对西南涡的生成是不重要的。提高模式空间分辨率和采用高分辨PBL模式, 能使西南涡生成和发展位置的模拟有明显改进, 但其强度一般偏强于实况。事实表明, 进一步完善模式物理过程、改进PBL参数化和提高模式空间分辨率将是十分必要的。

A series of 96-and 72-h numerical experiments were carried out to simulate the evolution of the SW vortex during the period of 11-15 July 1981 through the use of the fourth generation version of PSU/NCAR mesoscale model(MM⁴). Aim at investigating the influence of the physical Processes and spatial resolution of MM 4 along with PBL parameterization on mesoscale simulation of the formation and development of the SW vortex. The result of 96-h Control Experiment (Scheme I) showed that a version of MM 4 with 10-layer, a horizontal resolution of 160 km and bulk PBL, is capable of simulating better for the development of the SW vortex, however, this version has only the capability of preliminary simulating for the formation of the SW vortex. The physical processes effect mainly on the intensity and less on the location for the evolution of the SW vortex. The removal of latent heat release from Control has a substantial impact on the development of the SW vortex at the later stage. The intensity of the evolution of the SW vortex in the NO Flux Experiment is notable weaker than that in the Control.The Dry Experiment fails to develop the SW vortex during the period of heavy rainfall, and the vortex has slightly faster movement than that in the Control. The NO Friction Experiment showed that the surface friction is not important for the formation of the SW vortex. The enhancement of spatial resolution of MM₄ and the adoption of high-resolution PBL model are able to improve substantially simulated location of the formation and development of the SW vortex, however, in which case the evolutive intensity of the SW vortex is more intensive than that realistic analysis. The fact showed that it is necessary to perfect further the physical processes of MM₄, to improve PBL parameterization and to enhance spatial resolution of MM₄.