热带印度洋秋季偶极子模态与南海夏季风强度变化的关系
RELATIONSHIPS BETWEEN AUTUMN INDIAN OCEAN DIPOLE MODE AND THE STRENGTH OF SOUTH CHINA SEA SUMMER MONSOON
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摘要: 利用多年的Reynolds月平均海表温度资料和NCEP/NCAR全球大气再分析资料,采用经验正交函数(EOF)分析和滑动相关方法,研究了热带印度洋秋季偶极子模态和南海夏季风强度变化的关系。结果表明:(1)热带印度洋秋季海表温度距平(SSTA)的主要模态是全区一致型和偶极子(IOD)型,全区一致型模态主要代表了秋季SSTA全海盆一致的年代际及其以上时间尺度的变化,IOD型模态主要反映热带印度洋秋季SSTA年际时间尺度的变化。(2)当前期秋季热带印度洋存在正(负)IOD模态时,南海的夏季风强度减弱(增强)。二者年际变化的负相关关系在长期趋势的冷位相期不显著,而在暖位相期显著。(3)当南海夏季风强度增强(减弱)时,后期秋季热带印度洋出现正(负)IOD模态。二者年际变化的正相关关系在长期趋势的冷、暖位相期显著,在冷、暖位相转换期前后不显著。Abstract: Based on 1948-2004 monthly Reynolds Sea Surface Temperature(SST)and NCEP/NCAR atmospheric reanalysis data,the relationships between autumn Indian Ocean Dipole Mode(IODM)and the strength of South China Sea(SCS)Summer Monsoon are investigated through EOF and smooth correlation method.The results are as the following.(1)There are two dominant modes of autumn SST anomalies over the tropical Indian Ocean. They are Uniformly Signed Basin-wide Mode(USBM)and Indian Ocean Dipole Mode(IODM),respectively. The SST anomalies associated with USBM are prevailing decadal to interdecadal variability characterized by a unanimous pattern,while the IODM mainly represents interannual variability of SST anomalies.(2)When positive(negative)IODM exists over the tropical Indian Ocean during the preceding fall,the SCS summer monsoon will be weak(strong).The negative correlation between the interannual variability of IODM and that of SCS summer monsoon is significant during the warm phase of long-term trend but insignificant during the cool phase.(3)When the SCS summer monsoon is strong(weak),the IODM will be in its positive(negative)phase during the following fall season.The positive correlation between the interannual variability of SCS summer monsoon and that of IODM is significant during both the warm and cool phase of the long-term trend,but insignificant during the transition between the two phases.
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