1976/1977年前后热带印度洋海表温度年际异常的变化

Interannual Variation of the Tropical Indian Ocean Sea Surface Temperature Pre-and Post-1976/1977

基于1948～2005年NCEP/NCAR（美国大气研究中心/环境预测中心）再分析资料,讨论了1976/1977年前后的年代际气候变化对热带印度洋海表温度（SST）年际变率特征的影响,结果表明：在气候变化前后,EN-SO都能导致热带印度洋SSTA（海表面温度异常）出现全海盆同号的变化,这种模态在冬季最强;气候变化前与变化后相比,该模态对该地区海温年际变率的方差贡献大22.1%,达到最强的时间早2个月。气候变化前,秋季热带印度洋SSTA的主导年际变率模态表现为全海盆同号,变化后则表现为“偶极子模态”（IODM）。导致上述SSTA特征变化的重要原因,是气候变化前后印度洋风场对ENSO的响应不同。在气候变化前,与ENSO相关联的热带印度洋东风异常首先在夏季出现,而变化后则首先在春季出现,并且有一反气旋性环流异常维持在热带东南印度洋。

Based on 58-year（1948-2005） NCEP/NCAR reanalysis data,interannual variation of the tropical Indian Ocean sea surface temperature pre-and post-1976/1977 is studied.The original data are filtered to retain the variation with periods from 13 months to 8 years.The results show that ENSO could cause a basin-wide warming/cooling mode with the strongest phase in winter in the tropical Indian Ocean which lags ENSO 2-6 months both pre-and post-1977.But the mode pre-1977 is stronger than that post-1977.The former leads the latter two months in phase.Prior to 1977,the dominant mode of the tropical Indian Ocean SSTA（SST anomaly） in autumn appeared as a basin-wide uniform pattern.After 1977,however,the dominant mode appeared as a dipole or zonal gradient pattern.Changes in the response of the Indian Ocean surface wind to ENSO pre-and post-1977 account for the shift of dominant mode.Prior to 1977,the ENSO-related anomalous tropical Indian Ocean surface easterly firstly appeared in summer.After 1977,however,it appeared firstly in spring and a strong anticyclone dominated the southern tropical Indian Ocean throughout the season.