Non-ENSO Tropical SST Influences upon Extratropical Climate

Extratropical anomalies of atmospheric circulation, temperature and surface climate display systematic relationships to spatial anomaly patterns of tropical sea surface temperature (SST).  These connections stem largely from tropical ocean heating of the overlying atmosphere and attendant alteration of midlatitude Rossby-wave patterns. Particularly notable is the influence of high-amplitude eastern Pacific SST anomalies upon winter precipitation patterns over North America during extreme phases of the El Nino-Southern Oscillation (ENSO).  The ENSO influence upon the extratropical Northern Hemisphere is largely limited to the boreal winter season, however, and responses of regional temperatures are generally weak in comparison to those of precipitation. 

A number of studies nonetheless show important extratropical responses to non-ENSO anomaly patterns of tropical SST.  Northern Hemisphere temperatures in boreal summer, for example, show evidence of response to SST anomalies in the western Pacific and broader Indo-Pacific, while tropical Atlantic SSTs are similarly associated with Northern Hemisphere climate anomalies at higher latitudes. 

Here, several methods are used to illustrate connections of tropical Indo-Pacific and Atlantic SSTs upon extratropical anomalies in both hemispheres.  Primary emphasis is placed on extratropical responses at seasonal to interannual time scales; however similar patterns identified on longer time scales suggest that low-frequency (multidecadal to century-scale) extratropical climate anomalies and changes have distinctive atmospheric connections to those observed in the tropics.  These results carry implications for mechanistic interpretation of regional and global climate changes on a range of temporal scales.