bin和bulk微物理方案在我国飑线模拟中的敏感性研究

分别利用weather research and forecasting(WRF)中尺度模式中的bulk和bin微物理参数化方案,对2014年7月12日发生在华东地区的一次飑线过程进行了数值模拟。结果表明:bulk方案基本模拟出了飑线初生、发展、成熟和消亡的生命史,但与实况存在1~2 h的延迟,且强度偏弱;而bin方案模拟的雷达回波结构松散,组织化程度较低,更类似于现状对流。从模拟的地面降水看,bin方案模拟的雨带偏窄,且强降水区偏北;而bulk方案则基本模拟出了强降水区的位置。在此基础上进一步分析了两种方案模拟的各水凝物的垂直分布,结果表明bulk方案在高层产生了大量云冰,而bin方案中雪和霰粒子数量较多。

Sensitivity study of bulk and bin microphysical scheme to a simulated squall line in east China

A squall line occurred in east China during 12 July 2014 was simulated with the Weather Research and Forecasting (WRF) model using spectral bin and two-moment bulk microphysical parameterization scheme respectively. By comparison with the observed radar reflectivity, the bulk scheme has basically reproduced the initiation, developing, maturing and dissipating processes of squall line although it occurred two hours later than observation. While the bin scheme simulated a less-organized radar structure with relatively isolated convective cells in the leading edge. As for the surface rainfall, the strong rainfall areas were better simulated by bulk scheme despite it underestimated the precipitation in southwestern part of the rain band. By comparison the bin scheme produced a thinner rain band. The statistics of hydrometeor mixing ratio revealed a large amount of ice particles were produced in bulk scheme, while snow particles dominated at upper levels in bin scheme. In summary, the traditional bulk scheme seems to have a better performance than newly-incorporated bin scheme in WRF model in our case study. But detailed analysis and sensitivity tests are needed in future to further investigate the possible mechanisms that responsible for the distinctive results.