GRAPES模式中地面通量在一次台风数值模拟中的敏感性试验研究

SENSITIVE EXPERIMENTS OF THE SURFACE FLUX ON A SIMULATED TYPHOON IN GRAPES

在中尺度天气数值预报模式(GRAPES)的边界层方案(MRF)中,地面通量的计算与模式分层有直接关系,可能引起计算结果的不准确。在模式中引入Beljaars方案,通过比较分析模拟的台风地表特征量及形势场和风场表明,引入的方案对台风强度和路径的预报效果都起到改善作用。对台风"巨爵"个例的模拟表明,引入Beljaars方案之后,其地表的潜热、感热通量均明显增强,摩擦速度最大值增大,说明地表向上传输的热通量、水汽通量、动量通量均增强,这都有利于台风的发展和加强,因此模拟的台风路径和强度也更接近实况;从台风结构来看,方案二模拟的台风倾斜垂直结构没有方案一的明显,暖心结构有所加强;从风场分析来看,台风眼区的风速低值中心可延伸到500 hPa的高度上,明显高于方案一。

The computation of surface flux in the MRF PBL scheme of GRAPES model is directly associated with the division of model layers, making it inaccurate. A more sophisticated surface flux formulation （the Beljaars scheme） was implemented in GRAPES model. According to the numerical simulation of typhoon Koppu in 2009 with different formulation, the typhoon intensity and track forecast was improved. After introducing the new approach, the surface sensible and latent heat fluxes increased and the maximum of the frictional velocity was larger, which indicates that the surface heat flux, moisture flux and moment flux increased. It should be beneficial to the typhoon development, which makes the forecast typhoon close to reality. As for the typhoon structure, the warm core was stronger and the low-velocity area of the eye extended to the 500 hPa height field. Due to the difference in PBL schemes, the difference in typhoon vertical structure will affect the intensity of typhoon.