2013年影响广西热带气旋频数偏多的成因分析

摘要

Based on NOAA OLR,NCEP/NCAR height and wind monthly reanalysis data and CMA tropical cyclone data during 1951-2013,the causes of more tropical cyclones (TCs)that affected Guangxi in 2013 are analyzed.The results show that the West Pacific subtropical high (WPSH)was exceptionally stronger than in other years and its west ridge point abnormally stretched westward and northward from June to September 2013,which is favorable for more TCs to affect Guangxi.At the same time,the condensation latent heat released by rainfall on the south side of WPSH may be in favor of the northward extension of WSPH.Besides,the Somali cross-equatorial flow was stronger than normal,and joined in a southeast air flow on the southwest side of north Pacific anticyclone over South China Sea and Philippines,forming a monsoon trough,which is very conducive to the generation of more TCs in 2013.The results also show that there were much more activities and eastward (westward)propagation of low-frequency convections over India Ocean and west Pacific Ocean,lower SST in the eastern equatorial Pacific,stronger Hadley and Walker circulations and a westward deviation of the ascending branch of Walker circulation,and all of these factors could lead to the occurrence of more TCs in 2013.%提使用1951—2013年NOAA OLR、NCEP／NCAR风场和高度场再分析资料、中国气象局热带气旋资料，分析2013年影响广西热带气旋数量偏多的原因。结果表明：2013年6—9月西太平洋副热带高压明显偏强，西伸脊点明显偏西，脊线略偏北，同时副热带高压南侧对流活跃，降水过程潜热释放有助于副热带高压位置偏北，这种形势非常有利于热带气旋向广西移动。索马里越赤道气流强劲，在南海及菲律宾与北太平洋反气旋西南侧的东南气流相遇，形成季风槽，非常有利于热带气旋生成频数偏多。热带低频强对流带在印度洋和西太平洋活动频繁，并分别向东向西移动；赤道东太平洋海温偏低；哈得来和沃克环流较常年偏强，沃克环流上升支位置偏西，这些也可能是2013年影响广西热带气旋数量偏多的原因之一。