低空越赤道气流准双周振荡与西北太平洋台风路径的关系

The relationship between the low level quasi-biweekly oscillation of cross-equatorial flow and typhoon tracks over the Western North Pacific

基于1979～2010年的NCEP/NCAR再分析风场资料和美国联合台风预警中心（JTWC）热带气旋资料，文章通过研究越赤道气流准双周振荡对东风波、赤道辐合带等的影响进而揭示低空越赤道气流准双周振荡与西北太平洋台风路径的关系。传统意义上，西北太平洋台风路径可划分为：西行路径、西北行路径、转向路径和异常路径，文章的主要研究对象为西行路径和西北行路径。首先利用风场资料对低空（925hPa）经向风进行低频（10～20天）滤波并对滤波后低频经向风场进行 EOF 分解，分析表明低空越赤道气流及与其相联系的经向风存在明显的准双周（10～20天）振荡现象。研究表明，越赤道气流对西北太平洋台风路径预报有一定的指示作用，较大的低频越赤道气流经向分量使得季风槽位置北抬，从而影响台风移动路径偏北，相反，较小的低频越赤道气流经向分量或负的分量不易使台风转向。

Based on 1979 to 2010, reanalysis wind data by NCEP/NCAR and Tropical cyclones （TC） data from the American joint typhoon warning center （JTWC）. This paper studies the cross-equatorial airflow quasi-biweekly oscillation’s influence on the easterly waves and the equatorial convergence zone, and then reveals the relationship between the low-level cross-equatorial flow quasi-biweekly oscillation and the tracks of Northwest Pacific typhoon. Traditionally, the Northwest Pacific typhoon path can be divided as follows： straight west-moving, northwest-moving, typhoons with recurvature track and typhoons with unusual track, the main object of study is west line path and northwest line path. First use the wind data filtered radial wind at low altitude （925hPa） low frequency （10 ~ 20 days）.and then EOF analysis the filtered low-frequency radial wind. The results show that the radial wind and cross-equatorial flow in 925hPa have the characteristics of periodic oscillations of 10 to 20 days. Studies have shown that cross-equatorial flow has prediction instructions on the western North Pacific typhoon track, larger low-frequency cross-equatorial flow makes the ITCZ position northward, thus affecting the typhoon moving path more north. On the contrary, smaller or the negative low-frequency cross-equatorial flow is not easy to make the track of typhoon steering.