Abstract

Drought often lasts long and is thus closely related to slowly varying external forcing such as sea surface temperature (SST). Here, based on observed precipitation and SST data along with NCEP–DOE reanalysis data, the possible impacts of North Atlantic SST on drought formation in Southwest China are investigated.

Results show that northeast–southwest-orientated dipole SST anomalies in the mid–high latitudes of the North Atlantic are closely related to autumn drought in Southwest China; the linear correlation coefficient between them reaches 0.48 during 1979–2020, significant at the 0.001 level.

The dipole SST anomalies trigger southeastward-propagating Rossby waves and induce barotropic cyclonic circulation anomalies over India and the western Tibetan Plateau. This enhances the upward motion in northern India and the western Tibetan Plateau and causes a compensating downdraft, reduced precipitation, and consequent drought formation in Southwest China.