Shift in the Relationship Between Summer Extreme Humid-Heat Events in Eastern China and Tropical Sea Surface Temperature in the Mid-1990s

Abstract

The social losses associated with extreme humid-heat events (EHHE) increased sharply in recent decades. This study has explored the changing relationship between EHHE in eastern China and tropical sea surface temperature (SST) anomalies. Results show that the monopolar mode of EHHE is significantly associated with spring SST anomalies in Northwest Pacific (NWP) before the mid-1990s, which can impact humid-heat conditions in eastern China through an atmospheric meridional overturning circulation extending from NWP to eastern China. Then, the associated eastward shift of convection center after the mid-1990s weakens connection between NWP SST anomalies and the monopolar mode. Further analysis reveals that the weakened Kelvin waves, induced by persistent SST anomalies from spring in tropical Indian Ocean after the mid-1990s, cause the westward-shifted anomalous convection in western Pacific, and then reinforce formation of the dipolar mode via exciting zonal wave trains. Numerical simulations via linear baroclinic model further validate atmospheric response to displacement of diabatic forcings.