越赤道气流ISO特征在台风季节预报中的可行性研究

The study on practicability of the intra-seasonal oscillation feature of the cross-equatorial flow in the typhoon seasonal forecasting

越赤道气流作为南北半球物质、能量和水汽的输送通道,它的季节内变化引起台风水汽源变化,影响台风的生成频数和路径。该文研究了越赤道气流ISO特征在台风季节预报中的可行性。台风路径在传统的分类基础上细分为7种,对不同路径的台风所对应的低频流场进行超前和滞后合成,发现不同台风路径对应着不同的低频越赤道气流通道,低层20°N附近的低频气旋外围气流总是预示着台风路径未来的走向。低层低频流场的演变表明,越赤道气流的振荡周期为准40 d,它的ISO特征影响低纬地区的低频气旋的位置和强度,进而影响台风路径。高层低频流场刚好与低层反向,越赤道气流不再是以通道出现而是呈现区域特征。越赤道气流ISO特征可以作为台风季节预报的参考量之一。

The cross-equatorial flows are the main passages for exchanges of material and energy between northern and southern hemisphere.And its intra-seasonal oscillations（ISO） have very influences on typhoon,typhoon intensity and the typhoon tracks.The modulation of the cross-equatorial flow in the ISO on the typhoon tracks over the Western North Pacific is studied by observation data analysis.The authors divide the main classes tracks of typhoon into seven types based on the traditional methods.The results show that the cross-equatorial flow in the ISO may affect the tracks of typhoon.The low-frequency cross-equatorial flow influences the position or strength of the low-frequency cyclone,low-frequency anticyclone and then influences the typhoon tracks.Preliminary view is that different types typhoon track have different low-frequency cross-equatorial flow channels,the low-frequency flows to the north of the low-frequency cyclone around 20°N lead the approaching typhoon track.Further more,the cycle of cross-equatorial flow in the ISO is quasi-40 day.As a whole,the cross-equatorial flow in the ISO can be used as a basis for the typhoon seasonal forecasting.