西行穿越南海台风的特征及机制研究

Study on the Typhoons With Westward Tracks Crossing the South China Sea

基于日本气象厅1982-2018年台风最佳路径数据集,选取生成于西北太平洋后西行穿越南海的台风个例,通过对比分析探讨研究了该类台风的轨迹、强度、运动速度和生命周期等特征。研究发现,西行穿越南海的台风最早出现于6月,10月份最为活跃。该类台风的最大强度和平均强度分别比西北太平洋台风的平均水平强5~10 m/s和1~4 m/s(随月份变化)。此类台风在9-11月的平均生命周期可达7.0~7.5 d。进一步分析发现,生成于135°E东西两侧台风也存在明显差异。135°E东侧生成的台风期间,副热带高压和垂直风切变较弱、海表温度较高,导致台风强度更强,一般在菲律宾以东海区达到最大强度;135°E西侧生成的台风期间,副热带高压和垂直风切变较强、海表温度偏低,导致台风强度较弱,一般在南海中西部达到最大强度,但进入南海后在暖海表温度驱动下有二次增强现象。

Basing on the typhoon best track data provided by Japan Meteorological Agency,typhoons that are generated over the western North Pacific Ocean(WNP)and passed through the South China Sea(SCS)with westward moving tracks from 1982 to 2018 are selected for analysis of their tracks,intensity,translation speed and duration.Analysis shows that the typhoons crossing the SCS with westward tracks appeared in June,and were most active in October.Their maximum and average intensity were 5~10 m/s and 1~4 m/s stronger than those of the other typhoons,and mean duration were 7.0~7.5 days from September to November.Further analysis shows that distinct differences exist between the typhoons generated to the east and west of 135°E.Typhoons generated to the east of 135°E were more intense due to the influence by weak WNP subtropical high,weak wind vertical shear and high sea surface temperature,and reached their lifetime maximum intensity to the east of Philippines Islands,while those generated to the west of 135°E reached their maximum intensity in the central-western part of the SCS.