鄂东暖区暴雨个例的高分辨率模拟对边界层方案的敏感性  

Sensitivity of High-Resolution Simulations of the Warm-Sector Rainstorm in Eastern Hubei to Planetary Boundary Layer Schemes

作　　者：许建玉[1] XU Jianyu(Hubei Key Laboratory for Heavy Rain Monitoring and Warning Research,Institute of Heavy Rain China Meteorological Administration,Wuhan 430205,Hubei,China)

机构地区：[1]中国气象局武汉暴雨研究所暴雨监测预警湖北省重点实验室,湖北武汉430205

出　　处：《高原气象》2018年第5期1313-1324,共12页Plateau Meteorology

基　　金：国家自然科学基金项目(41620104009);中国气象局预报关键技术发展专项[YBGJXM(2017)1A];2017年度湖北省气象局自筹经费项目(2017C01)

摘　　要：2016年7月5-6日,鄂东发生了一次典型的副热带高压边缘型暖区暴雨。本研究使用WRF模式对该过程进行积云可分辨模拟,重点关注不同边界层方案下(ACM2、YSU、MYJ)短时强降水的差异及其可能原因。结果表明:相比ACM2,YSU和MYJ方案的短时强降水呈现先强后弱的特点;究其原因,与后两种方案下强对流的提前触发和消散有关。具体地,在对流触发前,YSU和MYJ方案模拟的涡流扩散性系数较ACM2偏小,边界层V风倾向偏弱,从而低层南风减速不明显,使得南风辐合偏强并提前触发强对流;而在消亡阶段,YSU和MYJ方案下强对流很快消散,但ACM2方案模拟的低层切变线上不断有对流新生;进一步,通过关闭微物理潜热加热的敏感试验,证实了低层切变线的产生与前期强降水潜热释放对中尺度环境场的改变有关,边界层过程的作用相对较小。另一方面,使用高分辨率模式结果对不同边界层方案下云微物理特征的分析表明,短时强降水的形成与霰的融化主导冷云降水过程有关,相比ACM2,YSU和MYJ方案下短时强降水的先强后弱对应于霰含量的先多后少。A typical warm-sector rainstorm occurred in eastern Hubei during 5-6 July 2016,causing severe flooding and damage.This heavy rainfall event,associated with an unusual environment to trigger convection,happened on the edge of subtropical high.The Weather Research and Forecast（WRF） model is used to simulate this event in cloud-resolving resolution（3km）.Experiments are conducted to examine the sensitivity of the simulation to the use of three different planetary boundary layer schemes, including the asymmetric convective models like version 2（ACM2）,Yonsei University（YSU）,and Mellor-Yamada-Janjic（MYJ） schemes.Numerical results showa significant sensitivity of the short-time heavy rainfall to planetary boundary layer schemes,with the YSU and MYJ schemes produce stronger rainstorm in the development stage of precipitation and weaker rainstorm in the extinction stage compared to the ACM2 scheme,which is mainly due to the earlier triggering and earlier extinction of the strong convection in the simulations with the YSU and MYJ schemes.Specifically,before convection triggering,the eddy diffusivity coefficients simulated by the YSU and MYJ schemes are much less than the ACM2 scheme,and the meridional wind tendencies due to planetary boundary layer processes are much weaker,so the deceleration of the low-level south wind is less,leading to the enhanced convergence of south wind and the earlier triggering of strong convection.While in the extinction stage of precipitation,convections simulated by the YSU and MYJ schemes disappear quickly,comparing with the newconvections initiated continuously on the lowlevel shear line which is more obvious in the simulation with the ACM2 scheme.Furthermore,a sensitivity test is carried out with the latent heating from the microphysical processes turned off during the extinction stage of precipitation,which shows that the generation of the lowlevel shear line is mainly due to the regulation of the mesoscale environment by the latent heat release from precipitation in the

关 键 词：暖区暴雨 高分辨率模拟 边界层方案 

分 类 号：P457.6[天文地球—大气科学及气象学]