Triple-dip La Niña contributes to Pakistan flooding and southern China drought in summer 2022

In the summer of 2022, a long-lasting La Niña entered its third year. In
Asia, southern China was in the grip of a historic drought while heavy
rainfall ravaged Pakistan. Using a climate model forced by observed sea
surface temperatures (SST) over the equatorial Pacific, we show that the
back-to-back La Niña events from 2020 to 2022 are a key contributor to the
global SST pattern in 2022 including the negative phase of Pacific decadal
oscillation and exceptionally strong negative Indian Ocean dipole. The
model reproduces the observed precipitation pattern over South and East
Asia, including enhanced rainfall over Pakistan–northwest India and
reduced rainfall over southern China. Additional model simulations
indicate that the negative Indian Ocean dipole combined with La Niña can
decrease southern China rainfall by causing anomalous subsidence and
anticyclonic flows. These results highlight the dominant role of
long-lasting La Niña in modulating rainfall over heavily populated monsoon
Asia.