晴天及阴天条件下WRF模式中几种边界层参数化方案的对比分析研究

Comparison and analysis of several planetary boundary layer schemes in WRF model between clear and overcast days

利用WRF模式中5种常用边界层参数化方案(ACM2、YSU、BouLac、MYJ和MYNN2.5)及美国能源部大气辐射观测试验(ARM)寿县综合观测数据(2008年8—12月),对比分析了晴天及阴天条件下,不同参数化方案对典型农田下垫面气象要素及边界层结构的模拟效果,结果表明:(1)模式对于云层状况的模拟,非局地方案ACM2和YSU方案优于局地方案.(2)对于近地层气象要素,晴天和阴天条件下均是ACM2方案对于2 m温度和比湿的模拟效果最好,MYJ方案对于风向风速的模拟效果最好.(3)对于位温及比湿垂直廓线的模拟,晴天和阴天条件下均是非局地方案(ACM2和YSU)对白天的模拟效果优于局地方案;ACM2方案对夜间弱稳定层结和逆湿结构的模拟最优;(4)对于风速垂直廓线的模拟,白天不稳定条件下,晴天条件MYJ方案最优,阴天MYNN2.5方案的模拟效果最好;夜间弱稳定条件下,晴天条件ACM2方案与观测值之间的偏差最小,阴天YSU方案模拟效果最好;(5)总体而言,在对典型农田下垫面进行模拟时,晴天和阴天条件下均是ACM2方案更具优势.

In the present study, several most commonly used planetary boundary layer （PBL） parameterization schemes in the WRF model are utilized together with the observed data at Shouxian （from August to December, 2008）. The present work is a part of Atmospheric Radiation Measurement （ARM） facility supported by the U. S. Department of Energy installed at Shouxian in China. In this study, we compared the simulation effect of meteorological elements and the structure of PBL over typical farmlands underlying from different parameterization schemes between clear and overcast days. The observed results revealed that for the simulation of cloud status, non-local schemes such as the ACM2 and YSU are superior to the local schemes.Further, the ACM2 scheme is better in simulating temperature and specific humidity at a height of 2 m from the surface, and the MYJ scheme has an advantage over other schemes when simulating the wind direction or its velocity. Also, for the simulation of potential temperature and specific humidity profile, non-local schemes （ACM2 and YSU） are superior to the local schemes both during clear and overcast days. It is depicted that the ACM2 scheme has better advantages when simulating under weak stable conditions and moisture inversion structure during nighttime. Moreover, for the simulation of wind velocity profile, the MYJ and MYNN2.5 schemes are the best respectively during the clear and overcast days under unstable daytime condition. However, when considering weak stable condition, ACM2 scheme has minimum deviation on clear days and YSU scheme is the best choice on overcast days. From the overall results, ACM2 scheme is superior both on clear and overcast days, when simulation is based on typical farmland underlying.