一次东风波演变过程及其对台风“鲇鱼”北翘路径的影响

利用欧洲中期天气预报中心(ECMWF) ERA Interim全球再分析资料(1.5 °×1.5 °)分析了1013号超强台风“鲇鱼”存在期间其东侧东风波的演变、结构以及对台风“鲇鱼”北翘路径的影响。结果显示:在“鲇鱼”存在期间，副热带高压南部、台风“鲇鱼”以东存在明显的中高空东风波。在“鲇鱼”以东和180 °以西存在明显的两脊一槽结构。从250 hPa的位势高度场中心位置来看，其路径经历了西南偏西向西北偏西方向的转变，并最终同“鲇鱼”的高空环流合并。由于东风波槽西移，位于“鲇鱼”南侧的低压环流上空东风迅速增强，垂直切变加大，从而使得此低压环流减弱、消失。低压环流的消失使得“鲇鱼”南侧南风迅速加强。东风波槽的减弱、北抬，其两侧的高压脊区加强、合并。在“鲇鱼”西北侧西风槽发展南落的共同影响下，台风“鲇鱼”路径发生北翘。 

THE EVOLUTION OF EASTERLY WAVE AND ITS INFLUENCE ON THE TRACK OF TYPHOON MEGI

The evolution and structures of easterly wave and its influence on typhoon Megi in 2010 are analyzed using the reanalysis data of ECMWF ERA Interim (1.5 °×1.5 °). The results show that the easterly wave to the east of Megi has a "two-ridge, one-trough" pattern. The geopotential height center of the easterly wave on 250 hPa moved to south-west and turns to north-west after 12 UTC 19, Oct. and merged into the circulation of Megi in the upper level. From 00 UTC 16 to 00 UTC 18 the vertical shear increased and the easterly wind at 200 hPa increased quickly as it traveled westward. The low pressure system to the south of Megi disappeared with the increasing of vertical shear and the southerly wind to the south of Megi increased quickly. With the weakening of the easterly trough, two ridges were merged into a stronger high to the south of Megi. Finally Megi moved northward as it was steered by the trough to the north-west of Megi and the stronger higher.