快速西行进入南海台风的统计特征

通过对快速西行进入南海的 1 3个台风快速西行期间西风带环流系统、副热带高压活动和台风环境流场的特征以及这些台风进一步的移向、移速进行统计分析 ,结果表明 ,台风快速西行进南海期间西风带的特点是中纬从中亚到东亚有高压脊或以纬向环流为主 ,西风槽偏北 ;西北太平洋副热带高压一直强大且呈带状分布或不断加强与西伸 ,造成副热带高压南侧与台风之间梯度加大 ,使偏东引导气流加强。研究还发现 ,如果台风南北两侧均为偏东环境流场 ,将使台风西行更快。

Statistical Characteristics of Tracking Westward Typhoons at High Speed into the South China Sea

Thirteen tropical cyclones tracking westward at high speed into the South China Sea are analyzed. It shows that the major characteristics of the westerlies is that from Middle Asia to East Asia was covered by a ridge or zonal circulation and westerly troughs were at higher latitudes. The results also show that a constantly intense zonal spreading subtropical high dominated from the west North Pacific to central and southern China or a continually strengthening subtropical ridge that extending westward gradually built up the gradient between the ridge and tropical cyclone and strengthened the easterly steering flows. Moreover, the easterly environmental flows prevailing in both of the southern and northern sides of tropical cyclone would drive it to travel more quickly.