华南前汛期印度洋海温异常与海南岛降水的关系

摘要

利用1969-2013年海南岛7个基本气象观测站前汛期(4-6 月)的月降水观测资料、NCEP/NCAR再分析资料和HadISST海温资料,分析了华南前汛期印度洋海温异常与海南岛降水的联系,并利用ECHAM5对印度洋海温与海南岛降水的关系进行了敏感性实验.结果表明:1969-2013年海南岛前汛期降水时段主要集中在5-6月,降水极大值分布在海南岛东部及北部地区.华南前汛期印度洋海温与海南岛降水存在显著的负相关关系,印度洋海温异常增暖,对应较弱的印度季风和赤道太平洋地区较强的东风异常,导致西北太平洋及南海北部存在异常的反气旋环流,不利于海南岛对流发展,同时反气旋南侧的异常东风不利于孟加拉湾水汽的输送,使海南岛降水偏少,反之亦然.数值模拟实验表明,印度洋海温异常增暖有利于西北太平洋低层反气旋的维持和发展,导致海南岛在华南前汛期降水偏少.%Based on monthly precipitation data obtained from seven meteorological stations on Hainan Island in the pre-flood season (April-June) from 1969 to 2013,the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data and the HadISST (Hadley Centre sea-Ice and Sea Surface Temperature) dataset,the relationship between sea surface temperature (SST) anomaly over the Indian Ocean and precipitation in Hainan Island was investigated,and a sensitivity experiment was conducted by using the ECHAM5 model.The results show that precipitation in the pre-flood season in Hainan Island mainly occurs in May and June,and the maximum rainfall occurs in the eastern and northern regions of Hainan Island.There is a significantly negative correlation between SST over the Indian Ocean and precipitation in Hainan Island during the pre-flood season.The SST over the Indian Ocean increases anomalously,corresponding to the weak Indian monsoon and strong anomalous easterlies in the equatorial region over the Pacific Ocean.It causes anomalous anticyclones over the northwest Pacific Ocean and the northern South China Sea,which suppresses the convective development over the Hainan Island.Moreover,the anomalous easterlies in the southern edge of anticyclone hinder the transport of water vapor in the Bay of Bengal,resulting in the decreasing precipitation over Hainan Island,and vice versa.The results from numerical experiments indicate that the warmer SST over the Indian Ocean favors the maintenance and development of anticyclones at lower levels over the northwest Pacific Ocean and leads to less precipitation in Hainan Island during the pre-flood season of South China.