不同边界层方案对一次西南涡暴雨过程模拟的对比试验

利用WRF中尺度预报模式（V3.7.1版本）采用6种边界层参数化方案（YSU、MYJ、ACM2、MYNN2.5、BouLac、QNSE），对2015年8月16日~19日一次西南低涡强降水过程进行数值试验，对比分析了不同边界层方案对西南涡特征、降水及边界层物理量场等模拟的影响。结果表明：6种边界层方案对西南涡路径、强度及降水的模拟具有明显的影响，其中ACM2方案对低涡移动路径和降水的模拟效果最好。不同边界层方案模拟的位势高度和风场、相对涡度、垂直速度和相当位温的分布具有显著的差异，YSU和QNSE方案模拟的西南低涡中心的正涡度柱可从对流层低层伸展到200 hPa，ACM2方案模拟的相对涡度与实况最接近。6种方案均较好地模拟出了边界层高度、地表感热和潜热通量的日变化特征，其中QNSE方案模拟的边界层高度和地表热通量的值最大，而ACM2模拟的值较小，这可能与QNSE方案考虑了湍流与波的共同作用等更为细致的物理过程有关。可见，不同边界层方案对西南涡暴雨过程中不同物理量场的模拟有着较大的影响，选择合适的边界层方案能提高对西南涡天气过程的预报准确率。 关键词： 参数化方案；西南低涡；降水；边界层结构；数值模拟

Comparative Experiments on a Southwest Vortex Rainstorm Process with Different Boundary Layer Parameterization Schemes

Based on Weather Research and Forecast system mesoscale model (WRF V3.7.1 version), a case of Southwest vortex (SWV ) rainstorm process during August 16-19, 2015 was simulated with six different Planetary Boundary Layer (PBL ) parameterization schemes (YSU, MYJ, ACM2, MYNN2.5, BouLac, QNSE), and the effects of different PBL schemes on the characteristics of southwest vortex, precipitation and boundary layer physical field are analyzed and compared. The results showed that six PBL schemes have obvious influence on simulating precipitation, moving path and intensity of SWV. The ACM2 can preferably reflect the change of track of SWV and the center position, intensity, and dispersibility of the precipitation. Different PBL schemes made significant differences in simulating geopotential height and wind, relative vorticity, vertical velocity and equivalent potential temperature field. Compared with other schemes, the positive vorticity of SWV simulated by YSU and QNSE can extend from the lower troposphere to 200 hPa, and the result of ACM2 was closer to the facts than others. Six PBL schemes performed better in the PBL height, surface sensible heat and latent heat fluxes, which the diurnal change is evident. Among these schemes, the QNSE simulated larger PBL height and surface heat flux, which was probably caused by more detailed physical processes such as the interaction between internal wave and turbulence, while the ACM2 made ones smaller. It can be seen that different PBL schemes in WRF model have great influence on the simulation of different physical quantity field of the SWV rainstorm process, choosing the appropriate PBL scheme can improve the forecasting accuracy of the SWV weather process.