西北太平洋台风频数异常及其与海气通量的关系

利用1984-2002年联合台风预警中心(JTWC)最佳路径台风资料、全球海洋客观分析海气通量(OAFluxes)资料和NCAR/NCEP-2再分析资料,使用SVD等统计方法,对西北太平洋台风频数与低层大气环流及海气通量异常之间的关系进行了研究,结果发现150°E以东的低纬海区是台风频数年际异常变化最显著的区域,台风频数与低层大气环流异常、潜热通量和短波辐射通量变化有着密切的联系:当副热带高压强度减弱(增强)、脊线偏北(南)、主体东移(西伸)时,季风槽加深东进至160°E(西退至140°E),低纬的纬向西风加强(减弱),海洋输送给大气较多(少)潜热通量,盛行的纬向西风携带着季风槽南侧的暖湿水汽与副热带高压南缘偏东气流的水汽输送在150°E以东(以西)的低纬海区辐合,150°E以东辐合上升的暖湿气团吸收的短波辐射偏多(少),有利于(不利于)形成高温高湿的不稳定结构,台风能量不断(不易)积累,在低层强(弱)辐合、高层强(弱)辐散的环境场作用下,有利于(不利于)台风在150°E以东的低纬海区的生成。

Characteristics of typhoon frequency in the western North Pacific and it relation to the air-sea fluxes

Relying on the investigation and study, it is verified that the most abnormal places of western North Pacific typhoon frequency is the east part of 150°E in low latitude region. Whats more, having been testified, typhoon frequency is closely related to the 850 hPa atmospheric circulation, latent heat flux and short-wave radiation flux. It is found that when western Pacific subtropical high becomes weaker (stronger) and moves eastward (westward), the westerly in the low latitude region will be strengthened (weakened). Along with the monsoon troughs east movement to 160°E (west movement to 140°E), more (less) latent heat flux will be transmitted from the ocean to the air. A strong (weak) vapor source can be found in the southern of monsoon trough, which is brought by the prevailing (un-prevailing) westerly and then convergences the vapor of the south subtropical high that is embedded in the easterly vapor stream. Meanwhile, the converging upward warm wet vapor cloud clusters absorb plenty (lack) of short-wave radiation flux so (not) as to form a deep-thick high temperature and high humidity unstable structure. Finally, the accumulation of the typhoon energy, together with the strong (weak) lower convergence, and the increase (decrease) of the upper divergence, is beneficial (unbeneficial) to the typhoon generation in the east part of 150°E in the low latitude region.