近海海温对再入海台风数值模拟影响的研究

Near-shore SST’s impact on typhoon return to the sea in numerical simulation

以WRF(weather research forecasting)模式模拟了登陆后再入海0713号台风韦帕,同时考虑了中纬度过程不变与过程时变的各类SST海温场对模拟效果的作用。试验中重点分析热力影响因子[即模式的两种微物理方案LIN(Purdue Lin scheme)、WSM6(WRF single-moment 6-class scheme)]以及动力影响因子(即模式的台风BOGUS模型)对各类SST海温场的反应。分别并综合研究了热力、动力、及海温因子对再入海台风的路径及强度模拟所产生的影响。多项成组试验显示,台风过程时变的SST场的使用能够更好地诊断和模拟台风区海气相互作用并改善对再入海台风路径与强度的预测。对0713号台风模拟而言,微物理过程WSM6方案给出的结果(包括路径、气压、风力、以及感热和潜热等要素)比LIN方案更好。采用BOGUS模型对再入海台风的路径模拟有较明显改善。在台风再入海阶段,模拟的海气界面感热通量与潜热通量分布显示,正的感热通量高值区为台风生存提供能量,并对台风移动有较好的指示性;台风潜热通量高值区位于台风风力辐合增强区,此处潜热高值区与台风结构配合,对入海台风活动的持续有正贡献。而过程时变的SST场的使用对台风预测是有利的,其中6h时变的SST较日平均SST效果更显著。

We simulate the return to the sea of Typhoon Wipha （No.0713） using the weather research forecasting （WRF） model, by considering influences of different sea surface temperature （SST） fields that change or unchange with time during typhoon lifetime. We emphasize the responses to the SST fields, of thermodynamic factors, which are two microphysics schemes of LIN （Purdue Lin scheme） and WSM6 （WRF single-moment 6-class scheme） in the model, and of dynamic factor, which is Typhoon BOGUS scheme in the model. Furthermore, we investigate the impacts from thermodynamic factors, dynamic factors, and SST fields respectively and the combined impacts of the factors on the simulated typhoon track and intensity. The results from a set of experiments show that when SST changes with time we can obtain better diagnosis and simulation of air-sea interaction in typhoon area, and improve the prediction of typhoon＇s track and intensity. For the simulation of Typhoon Wipha, the WSM6 scheme is more suitable than the LIN scheme, according to a number of model output variables, including typhoon track, central air pressure, the biggest wind speed, sensible heat flux and latent heat flux, at the stages of landfall and return to the sea. The Typhoon BOGUS scheme gives an obvious improvement on typhoon track simulation. During the stage of typhoon return to the sea, the simulated sensible heat flux and latent heat flux distributions show that the positive high value areas of sensible heat flux provide energy to typhoon and indicate its future track in advance. The high value area of latent heat flux is located at the typhoon wind convergence and strengthening area. The high latent heat flux in the typhoon system structure contributes to maintain the typhoon activity of return to the sea. To use the SST field that changes with time in the typhoon simulation is of benefit to the improvement of prediction, and the 6h SST gives a better result than daily averaged SST.