Observational evidence for the radiative impact of Indonesian smoke in modulating the sea surface temperature of the equatorial Indian Ocean

Abstract

The smoke aerosol plume produced by intense forest fires over Indonesia during September–November 1997 provided a unique opportunity to investigate the radiative impact of aerosols on sea surface temperature (SST), primarily due to its episodic nature and occurrence of high aerosol optical depth (>0.8) for ∼2 months over the east equatorial Indian Ocean (EIO). The aerosol radiative effect was well discernible in SST because the month‐to‐month variation in shortwave aerosol direct cooling (ADC) was so large while the corresponding variations in the other governing factors such as surface wind and sea surface upwelling were less significant during this period, when the net cloud radiative forcing had a positive anomaly at the surface. The present study clearly shows that from September to October 1997, ADC at surface has increased by more than −46 Wm −2 over east EIO resulting a decrease in SST by >1°C. This might have provided a positive feedback to the Indian Ocean dipole influencing the meteorology of the south Asian region.