NUMERICAL SIMULATION OF SSTA IMPACTS UPON THE INTERDECADAL VARIATION OF THE CROSS-EQUATOR FLOWS IN EASTERN HEMISPHERE

Impacts of regional sea surface temperature anomaly(SSTA) on the interdecadal variation of the cross-equator flows(CEF) in eastern hemisphere are studied using numerical simulations with a global atmospheric circulation model(NCAR CAM3) driven with 1950—2000 monthly SSTs in different sea areas(global,extratropical,tropical,tropical Indian Ocean-Pacific,and tropical Pacific) and ERA-40 reanalysis data.Results show that all simulations except one driven with extratropical SSTs can simulate the interdecadal scale strengthening of CEFs around Somali,120 ?E,and 150 oE occurred in mid-late 1970s.Among those simulated CEFs,the interdecadal variability of simulated CEF in Somali and its interdecadeal relationship with East Asian summer monsoon are in better agreement with observations,suggesting that changes in SSTs of tropical oceans,especially the tropical Pacific plays a crucial role in the interdecadal variability of CEF in Somali.The interdacadal changes of CEF in Somali is highly associated with the interdecadal variation of tropical Pacific SST.As the interdecadal warmer(colder) SST happens in the tropical Pacific,a sandwich type SSTA pattern +、-、+(-、+、-) will occur in the eastern tropical Pacific from north to south with a pair of anomaly anticyclone(cyclone) at the lower troposphere;the anticyclone(cyclone) pair links to another pair cyclone(anticyclone) in tropical Indian Ocean through atmosphere bridge,and thus strengthen(weaken) CEF in Somali.