台风数值模拟中边界层方案的敏感性试验I.对台风结构的影响

通过比较不同边界层方案下中尺度数值模式模拟的台风地表特征量以及形势场和风场, 表明台风边界层通过摩擦混合和辐射等作用与地表产生水汽、热量和动量的交换, 并通过湍流效应和积云的夹卷作用将边界层的影响扩展至整个自由大气.对台风Dan的模拟个例表明, 由于边界层过程的差异导致台风尺度大小不同, 风场、形势场的水平和垂直分布结构都有所差异.不同边界层方案模拟的台风结构的差异必然导致强度的差异, 与此相对应, 在不同边界层方案下, Eta方案模拟的台风强度偏大; 而Burk-Thompson和Blackadar方案略次之,在没有边界层方案的情况下模拟的强度非常弱,体现了边界层过程对台风发生发展的巨大影响.

The Experiments of the Boundary Layer Schemes on Simulated Typhoon Part I. The Effect on the Structure of Typhoon

Based on the numerical simulation of typhoon Dan in 1999 with different Planetary Boundary Layer (PBL) schemes, it can be found that there exists the exchange of heat flux, vapor flux and momentum flux through friction mixing and radiation between PBL and the surface layer, and the fluxes can diffuse to the free atmosphere through the effect of entrainment and vertical diffusion in cumulus process. Due to the difference in PBL processes, the scale of typhoon, the horizontal and vertical structure of simulated typhoon are different. The difference of structure will affect the intensity of typhoon, therefore, it shows that the Burk\|Thompson scheme and Blackadar scheme produce weaker surface momentum than that of the Eta scheme, while the model will produce a very weak cyclone without PBL process.