夏季亚洲-太平洋涛动与中国近海热带气旋活动的关系

Relation of summer Asia Pacific oscillation to tropi cal cyclone activitiesover the coastal waters of China

中文关键词:  亚洲-太平洋涛动，东亚，热带气旋

英文关键词:Asian Pacific oscillation (APO), East Asia, Tropical cyclone

中文摘要:

      采用联合台风警报中心的台风最佳路径资料和NCEP/NCAR再分析资料，分析了夏季亚洲-太平洋涛动（Asian-Pacific Oscillation,简称APO）与东亚近海西北太平洋大气环流的关系，并进一步探讨了APO与中国近海热带气旋（tropical cyclone,简称TC）活动的关系。研究表明：（1）夏季APO强弱与同期西北太平洋及中国东部近海TC活动存在密切关系，即在APO强（弱）年，西北太平洋TC活动偏西（东）和偏北（南），中国东部近海TC明显增多（ 减少）；（2）当APO偏强（弱）时，中国东部近海大气环流有（不）利于TC的维持和发展，表现为低层存在异常气旋性（反气旋性）环流，对流层高低层纬向风垂直切变减小（增大） ，且对流加强（减弱）；（3）APO强弱也影响着TC引导气流的方向：在APO强（弱）年，西 北太平洋副热带高压（以下简称副高）偏北和偏东（偏南和偏西），副高南侧偏东气流减弱（加强），有利于TC的向西北行或在偏北（南）纬度西行，进入中国东部近海的TC增多（减少）；（4）APO强弱也影响着南海—热带西太平洋TC源地上空的大气环流，在APO强（弱） 年，南海—热带西太平洋季风槽偏北、偏西（偏南、偏东），热带西太平洋TC活动偏北和偏 西（偏南和偏东），有利于进入中国东部近海TC的增多（减少）。

英文摘要:

      Using data from the Joint Typhoon Warning Center (JTWC) optimal typhoon tracks a nd the NCEP NCAR reanalysis, an investigation is made on the summer Asia-Pacif ic Oscillation (APO) in relation to synchronous atmospheric circulation from the coastal waters of East Asia to the western North Pacific (WNP), along with a further exploration on the relationship between the APO and the tropical cyclone (TC) activities over the coastal waters of China. The results show that there exists a close relationship between the APO intensity and the TC activities over the WNP and the coastal waters of eastern China (CWEC) during summer. When the APO is stronger (weaker), the TC activities over the WNP are located in a more west ward (eastward) and northward (southward) position and the TC number over the CW EC greatly increases (decreases). Meanwhile, the atmospheric circulation over th e CWEC is manifested by a low-level anomalous cyclonic (anticyclonic) circulati on, a decreasing (an increasing) vertical shear of zonal wind between the high a nd low levels of the troposphere, and strengthened (weakened) convection. These features are favorable (unfavorable) for the maintenance and development of the TC. The APO also modulates the direction of the steering current that affects th e movement of the TC. Corresponding to a stronger (weaker) APO, the WNP subtropi cal high appears more northward (southward) and eastward (westward), with the we akening (strengthening) of the easterly wind south of the high. This feature fav ors the TC to move northwestwards or westwards at more northern (southern) latit udes, leading to an increase (a decrease) of the numer of the TC that enters int o the CWEC. Moreover, the APO also affects atmospheric circulation over the Sout h China Sea and the tropical WNP from which the TC originates. Corresponding to a stronger (weaker) APO, the monsoon trough over these areas appears northwards (southwards) and westwards (eastwards) and the TC activities are located in a mo re northward (southward) and westward (eastward) position, which favors an incre ase (a decrease) of the TC number over the CWEC.