四川盆地一次污染过程的WRF模式参数化方案最优配置

精准的气象场是空气质量模型的基础,本文对中尺度气象模式WRF(The Weather Research and Forecasting)中微物理过程方案、陆面过程方案、行星边界层方案以及积云参数化方案进行组合,设计了24组参数化方案,对2014年5月初四川盆地内一次空气重污染过程中的气象场进行了模拟,将模拟输出的10 m风速、2 m温度、2 m相对湿度、水汽混合比廓线及位温廓线与研究区内14个气象站及1个探空站的实测数据进行对比.结果表明,Mellor-Yamada-Janjic(MYJ)边界层方案能更好的模拟出盆地内风速的变化趋势,而Yonsei University(YSU)边界层方案模拟的2 m相对湿度效果更优.第16组参数化方案(由WRF Single-Moment 3-class(WSM3)方案,热扩散(SLAB)方案、Mellor-Yamada-Janjic(MYJ)方案及Grell-Devenyi(GD)方案组合)能够较好地模拟盆地近地面风场的水平分布及风速的日变化规律,模拟的温度日变化规律更贴合实际情况,同时能够模拟出边界层内水汽混合比及位温的垂直分布特征,对边界层内逆温层和混合层的模拟也更加贴近实际,尽管该方案对2m相对湿度的模拟并不是最好,但基本能够模拟出四川盆地气象要素的变化特征,因此认为第16组参数化方案(WSM3,SLAB,MYJ及GD)适用于模拟此次重污染过程的气象场.

Optimal configuration of parameterized schemes in WRF model during a pollution episode in Sichuan Basin

Accurate depiction of meteorological conditions is the basis of air quality modeling. In this study, the Weather Research and Forecast(WRF) model was used to conduct 24 experiments with different parameterization configurations (Microphysics, Land Surface, Planetary Boundary layer and Cumulus Parameterization), and meteorological conditions were simulated during a severe regional air pollution episode in Sichuan Basin early May 2014. Five factors, including 10 m wind, 2 m temperature, 2 m relative humidity, vertical profiles of vapor mixing ratio and potential temperature, were output from the simulation and compared with those observed at 14 meteorological stations and 1 sounding station. The results indicated that the Mellor-Yamada-Janjic (MYJ) scheme and the Yonsei University (YSU) scheme was the optimal choice for simulating the variation of wind velocity and 2 m relative humidity simulation, respectively. The No.16 group of parameterized schemes (including WRF Single-Moment 3-class (WSM3) scheme, Thermal Diffusion (SLAB) scheme, Mellor-Yamada-Janjic (MYJ)scheme and Grell-Devenyi (GD) ensemble scheme) gave the best simulation results of wind and temperature field at the surface layer. This scheme could also successfully simulate the vertical distribution of vapor mixing ratio and potential temperature. Overall, it was concluded that the No.16 group of parameterized schemes(WSM3, SLAB, MYJ and GD)can simulate the variations of meteorological conditions in Sichuan Basin, and is the most suitable parameterized scheme for this air pollution episode.