Impacts Of Two Types Of ENSO On Extratropical Climate Of Southern Hemisphere

As one of the most important air-sea interaction phenomenon in the earth system,ENSO(El Ni?o-Southern Oscillation)has always been an important climate model affecting global climate change.Although the ENSO phenomenon itself is confined to the tropical Pacific,it can affect the global atmospheric circulation in the form of teleconnection,thus affects the global climate.Research ENSO and its impact on the climate have great significant for understanding ENSO,forecasting ENSO,and understanding its global climate impact.Although the research theory on ENSO is becoming more and more mature,many scholars have done a lot of research on the impact of ENSO on the global climate in recent years,but there are relatively few studies have distinguished the two types of ENSO in previous studies.For studies that distinguish different ENSO forms,are less related to seasonal changes,and the variables examined are also limited to a few climate variables such as sea surface temperature and heat flux,lack of holistic and systematic understanding of atmospheric processes,ocean and sea ice processes.This article focuses on the effects of two different forms of ENSO on the extratropical climate in the Southern Hemisphere during 1979-2012,considering that the ENSO form has undergone major changes around 1999,we divide the research period into 1979-1998 and 1999-2012.This paper also pays attention to the interdecadal variations of the extratropical climate in the Southern Hemisphere during the two periods and the interaction between climate variables.Research shows,from the correlation analysis between the main component time series of multiple variables and the Ni?o index and the regression response field of the variable to ENSO variation,we can see that,the response of the eastern-Pacific type ENSO to the extratropical climate variation in the Southern Hemisphere in 79-98 period is stronger than that of the central-Pacific type ENSO,indicating that the eastern-Pacific type ENSO has the dominant influence on the extratropical climate in the Southern Hemisphere at this time,which is in good agreement with the previous research.The influence of central-Pacific type ENSO on the multiple variables in the Southern Hemisphere after 1999 is stronger than before,however,it has not been seen that the changes in the atmosphere/ocean/sea ice variables are stronger than the eastern-Pacific type ENSO,and in some seasons or even weaker than the latter,which may be the result of the seasonal differences in the impact of ENSO on the climate.Before 1999,the regression field of variables in the Southern Hemisphere,especially in the austral winter,showed a more obvious PSA(Pacific-South America mode)structure.After 1999,the regression field had very obvious seasonal differences: strong SAM(Southern Annular Mode)signal was shown in austral summer,strong PSA2 signal in austral autumn and strong PSA1 signal in austral winter and austral spring.Compared with other atmospheric variables,sea surface temperature changes are strongly influenced by ocean changes.The response field of mixed layer temperature is greatly influenced by the variation of sea surface temperature in austral summer and austral autumn,and is more influenced by the variation of mixed layer in austral winter and austral spring.The response field of sea ice is stronger in the ice freezing season,it is mainly affected by the sea surface temperature,besides the influence of the sea surface wind field.