2006年超级台风“桑美”强度与结构变化的数值模拟研究

A numerical simulation study of super Typhoon Saomei(2006) intensity and structure changes

使用一个高分辨率、非静力数值模式WRF模式对2006年超级台风Saomei强度和结构进行了数值模拟研究。首先,评估了Makin的粗糙度长度公式对台风Saomei强度和结构变化的影响,结果表明,采用新参数后,使得模拟的台风强度变化与实况最佳路径资料的强度变化更一致,对超级台风Saomei强度预报有改进;但对台风路径的影响不大。通过QuikSCAT、雷达和TRMM非常规资料的验证,进一步表明模拟的台风Saomei的结构与实况很接近,可以再现台风内核区域的部分"双眼墙"和"Annular"结构。其次,通过对台风Saomei边界层过程模拟的改进,表明在平均风速大于40m/s时边界层各物理量明显改善,使得模式最大强度比传统的简单外推插值方案有显著改进,特别是在台风最强阶段,当台风Saomei眼墙区域的海表面拖曳系数C_d的相对变小,使得其眼墙区域的平均切向风速、径向风速、垂直风速、温度距平、涡旋动能和绝对角动量等物理量均有增强。表明台风Saomei眼墙区域(20—40 km)各物理量的贡献对其强度和结构变化的影响十分重要。最后,在此基础上进一步分析模式海温和大尺度环境垂直风切变对台风Saomei强度和结构变化的可能影响,讨论了台风Saomei在其增强和消弱阶段中,大尺度环境垂直风切变对其强度变化的负反馈作用。

A high resolution and nonhydrostatic WRF （weather research and forecasting） mo del were used to study the intensity and structure changes of super Typhoon Saom ei （2006）. Firstly, the effect on the intensity and structure changes of Typhoon Saomei （2006） by adopting the parameterization scheme of roughness length of Makin. The result shows that the intensity change tendency of the simulated TC is more agreed with the intensity variation of the best track data than that of con trol experiment, when the new scheme is applied. It also indicates that the inte nsity prediction of Typhoon Saomei （2006） has been improved, but there is no any effect on its forecasting of track. The simulated TC structure is more coincide d with the real structure of Typhoon Saomei （2006） by verifying the nonconvent ional data from QuikScat, TRMM, and radar data, with reproducing its “Double ey ewall＂ and “Annular＂ structure in the inner core region. Secondly, the final in tensity of the model storm is significantly increased by using of the new parame terization for Typhoon Saomei （2006） boundary layer processes, compared with the traditional extrapolation, while the physical factors in its boundary layer have dramatically changes above 40 m/s, in particular, during the period o f the strongest intensity of TC, the averaged tangential, radial, and vertical wind, temperature anormaly, eddy kinetic energy, and absolute angular momentum i n its inner core region are increasing with the decrease of the sea surface drag coefficient, C d, in TC eyewall. Distributions of all the physical element s around 20-40 km of in the eyewall regions of Typhoon Saomei （2006） affect on its intensity and structure changes. Furthermore, the possible effect of large sc ale environmental vertical wind shear and SST in model on Typhoon Saomei （2006） intensity and structure changes was finally analyzed. And the negative effect of large scale environmental vertical wind shear on the TC intensity changes is is sued when Typhoon Saomei （2006） suffering intensification and weakening.