Interdecadal Change Of Tropical Indian-pacific Ocean Joint Mode And Its Impact On Climate Over China

The interannual variability of the sea surface temperature anomalies(SSTA)in the tropical Indian-Pacific Ocean has been discussed from different perspectives in previous studies,but the cause of the its interdecadal change and its influence on climate over China have not been discussed.Based on the monthly mean Had ISST data from 1870 to 2016,the subsurface sea temperature data from 1945 to 2012,the monthly mean wind and the surface air temperature data from NOAA-CIRES Twentieth Century Reanalysis,and the Global Precipitation Climatology Centre(GPCC)monthly precipitation data,using the methods of Seasonal Empirical Orthogonal Function(S-EOF)and sliding correlation,the spatial-temporal variabilities of the dominant modes of the tropical Indian-Pacific SSTA and sub-surface(0-400m)mean temperature anomalies are analyzed,the interdecadal change characteristics and its cause of the joint mode are discussed in detail,and the interdecadal difference of its influence on climate over China are studied in this paper.The results showed as followed.Firstly,the joint modes defined by two angles have similar seasonal evolution of spatial distribution and interannual variability,which can represent the basic information of Indian Ocean Dipole(IOD)and ENSO events well,and both reflect a consistent distinct interdecadal change: the oscillation intensity and the correlation with IOD were weak before 1970,then significantly enhanced.Secondly,the interdecadal change of the joint mode is actually a direct expression of the interdecadal change of the interaction between IOD and ENSO.Before 1970,the interaction between IOD and ENSO was weak,so the joint mode signal was weak.But since 1970,they were closely linked and the joint mode signal was enhanced.Furthermore,it is found that the change is caused by the coupling of zonal vertical circulation anomalies circles over the two basins.Finally,after 1970,when the joint mode was in positive(negative)phase,the regions of positive(negative)anomalies of precipitation increase obviously,and the regions of positive(negative)anomalies of temperature decreases obviously over China,especially in winter and spring.This may due to the different effects of the joint mode on the meridional circulation over middle-high levels in the middle-high latitude regions,the middle-low levels circulation in the subtropical and tropical regions,and the sea-level pressure in different ages.