Interdecadal change of the boreal summer circumglobal teleconnection (1958–2010)

Abstract

The tropical‐extratropical teleconnection during boreal summer is characterized by a circumglobal teleconnection (CGT) pattern in the northern hemisphere (NH). Around the late 1970s, there was an abrupt change in the coupled atmosphere‐ocean system over the NH and global tropics. This study found that the CGT has experienced a significant change since late 1970s. During the recent epoch (1979‐2010), the major CGT centers weakened with pronounced changes over the North Atlantic and Europe. Partial correlation analysis of 200‐hPa geopotential height and the NH summer monsoon heat sources indicates that the change of Indian summer monsoon (ISM) rainfall has a global impact on the CGT, whereas other NH summer monsoons (West African, western North Pacific, and North American) have only a regional modification to the CGT. The weakening of the CGT pattern in the recent epoch is a consequence of weakened coupling between ISM rainfall and midlatitude circulation, which results from the reduced interannual variability of ISM rainfall due to changes in El Niño‐Southern Oscillation properties. The large change of the CGT over the North Atlantic and Europe is attributed to a southward shift of upper‐level westerlies and enhanced coupling to West African monsoon rainfall.