北部湾海面夏季一次持续性西南大风的成因分析

根据近45 a涠洲岛气象站近地面测风资料统计北部湾海面夏季西南大风的气候特征,并用NCEP/NCAR再分析资料对2015年7月下旬出现的一次持续性西南大风进行成因分析。研究结果表明:(1)北部湾海面西南大风是一种低压(或低涡)大风,造成此次持续性西南大风产生的根本原因是中南半岛-南海西南季风持续增强;(2)西南季风增强起源于南半球澳大利亚北岸冷空气活动;与90°～110°E越赤道气流、南亚高压的加强东扩和西太平洋副热带高压的加强西伸有密切关系;(3)北部湾海面不断有南海热带低压、西南低涡和北部湾低涡等低值系统生成发展或移近或移入。

Cause analysis of a sustained southwest gale over the Beibu Gulf Sea in summer

This study analyzes observed land surface wind of Weizhou island meteorological station for nearly 45 years to reveal the climatic characteristics of southwest gale over the Beibu Gulf Sea in summer,and investigates the causes of a sustained southwest gale in late July 2015 using NCEP/NCAR reanalysis data.It is shown that the southwest gale in the Beibu Gulf is caused by low pressure or vortex.The continually intensified southwest monsoon from the Indo-China Peninsula to the South China Sea is the main reason for the generation of such a sustained southwest gale.The intensified southwest monsoon originate from the cold air system over the northern coast of Australia in the Southern Hemisphere,which closely relates to the eastward expansion of cross-equatorial flow between 90°E and 110°E and the South Asia high and to the westward expansion of subtropical high over the western Pacific Ocean.We also demonstrate that low pressure systems,including tropical depression in the South China Sea and vortex in the southwest China and Beibu Gulf,generates,approaches or moves into the Beibu Gulf area.