利用逐月OISST、ERSST及NCEP2表面风场等资料探讨了南印度洋偶极子(Southern Indian Ocean Dipole,SIOD)的结构特征、形成原因及其与ENSO的关系。结果表明:在南印度洋,偶极子形态的年际海表面温度异常在10-12月出现,次年2月达到极值,随后的4-6月消亡。SIOD的形成主要是风场、潜热通量和短波辐射通量起作用,混合层深度异常加厚或变浅有助于SIOD的形成。近30 a资料表明,SIOD的盛期超前ENSO 9~10个月,且具有季节锁相特征。20世纪70年代中期发生年代际气候突变后,SIOD与ENSO的相关关系显著增强。正SIOD事件之后一般都有El Nino事件发生,负SIOD事件之后都有La Nina事件发生。
英文摘要:
Based on OISST,ERSST and NCEP2 monthly surface wind data,the structure characteristics and formation of Southern Indian Ocean Dipole(SIOD) and its correlation with ENSO are investigated.Results show that SIOD develops from October to December,peaks in following February,and decays from April to June.Wind,latent heat flux and shortwave radiation fluxes play an important role in the formation of SIOD.The change of the mixed layer depth also contributes to the formation of SIOD.In recent three decades,SIOD are phase-locked to the austral summer season,preceding the ENSO signal by nine-to-ten months.Furthermore,the relationship between SIOD and ENSO is enhanced after interdecadal abrupt climate change in the mid-1970s.El Nino events usually occur after positive SIOD and La Nina events occur after negative SIOD.