热带印度洋海温的年际变化与ENSO

文中讨论了热带印度洋海表温度距平空间分布的年际变化与赤道中东太平洋海温的关系。EOF分析的结果表明 ,印度洋海温的变化主要存在全区符号一致的单极型和西部与东南部符号相反的偶极型 ,它们具有显著的年际变化。小波凝聚谱揭示了单极、偶极的变化与Nino3区海表温度距平存在密切关系 ,印度洋海温距平从偶极到单极的变化对应着ElNi no事件从发展到衰减的过程。平均而言 ,印度洋偶极超前Nino3区海温距平约 4个月 ,单极滞后约 6个月。整个热带印度洋 -太平洋地区海气耦合特征的演变表明 ,与ElNino从发展到衰减相联系的热带西太平洋海气耦合相互作用在印度洋海温距平从偶极到单极的演变过程中起着非常重要的作用。

RELATIONSHIP OF THE INTERANNUAL VARIATIONS OF SEA SURFACE TEMPERATURE IN TROPICAL INDIAN OCEAN TO ENSO

By using long rangesea surface temperature,850hPa wind and out going long-wave radiation data,the relat ionship of the interannual variation of sea surface temperature anomalies (SSTA) between the tropical Indian ocean (TIO) and equatorial mideastern Pacific ocean has been investigated.The empirical orthogonal function (EOF) analyses of SSTA show that the dominant modes in the TIO are the monopole mode with same SST Asign in basin scale and the dipole mode with a reversal in sign across the basin,respectively.The dominant pattern in the tropical Pacific ocean is the El Niño mode.All monopole,dipole and El Niño modes display noticeable interannual variations.The wavelet squared coherency analyses show that in the interannual time scale,the SSTA in NinO₃ region (5°S-5°N,150-90°W) are closely related to the monopole and dipole modes in the TIO,i.e.,the El Niño from its developing phase to the decaying phase corresponds to SSTA in the TIO varying from the dipole mode to the monopole mode.In average,the El Niño lags behind the dipole mode 4 months and precedes the monopole 6 months.It is revealed by the evolution of the air-sea coupled charact eristics in the TIO and Pacific ocean that the interactions in the western Pacific ocean associated with the El Niño shifting from the developing episode to the decaying play an import ant role on the transformation of SSTA in the TIO from the dipole to the monopole.The variations of the zonal wind anomalies over both TIO and Pacific ocean are affected greatly by the convections over the area in the eastern TIO and western tropical Pacific.The variations of the convection accom panied with the evolution of El Niño alter the zonal winds and hence associate oceanic processes,which are responsible for SSTA in the TIO changing from the dipole to monopole mode.