Study On The Linkage Of The Southern Hemisphere Extratropical Climate Variability To Two Types Of ENSO And The Relationship Between ENSO And SAM

This study uses the Climate Forecast System Reanalysis(CFSR)of America National Center for Environmental Prediction(NCEP)from 1979 to 2010 to investigate the responses of the Southern Hemisphere(SH)extratropical climate to two types of El Ni?o-Southern Oscillation(ENSO)--the eastern Pacific(EP)type and the central Pacific(CP)type in different seasons.Variable response fields are denoted by the anomalies of climate variables associated with one-standard-deviation increase in the Ni?o3 or Ni?o4 index.The results show that for all seasons,the strength of the climate ENSO related anomalies(ERAs)depends on if there are close relationship between ENSO and the major climate modes of the SH extratropics.For the ocean variables,the ERA patterns are generally controlled by sea level pressure and surface wind anomalies and mirrored by the surface heat flux anomalies and mixed layer temperature anomalies.The mixed layer depth anomalies are primarily modulated by surface heat flux anomalies and occasionally by anomalous wind.There is no evidence that the SH extratropical climate variability anomalous induced by Ni?o3 variations are stronger in the EP ENSO(1979-1998)dominant period,and that variability anomalous induced by Ni?o4 variations are stronger in the CP ENSO(1999-2010)dominant period.In addition,we study the relationship between ENSO and major extratropical climate models in the SH in spring and summer.The results show that in the spring of the SH,the anomalous field of sea level pressure during EP ENSO dominant period is mainly affected by the correlation between ENSO and PSA 2,which disappears during the CP ENSO dominant period.The interdecadal variations of the correlation between ENSO and PSA2 further affect the anomalous fields of sea surface wind,sea surface temperature and sea mixing layer temperature through sea-level pressure field,which eventually leads to significant differences in sea ice concentration anomalies in the Southern Ocean.There was no correlation between SAM and ENSO in autumn and winter.In summer,1979-1998,SAM was significantly correlated with CP ENSO,and the correlation disappeared in 1999-2010.In spring,1979-1998,there was no significant correlation between SAM and EP ENSO or CP ENSO,but in 1999-2010,there was a significant correlation between SAM and EP ENSO or CP ENSO.Moreover,in the EP ENSO dominant period,ENSO stimulates SAM through tropospheric path mechanism;in the CP ENSO dominant period,ENSO stimulates SAM through stratospheric path mechanism.