Impact of Indonesian forest fires during the 1997 El Nino on the aerosol distribution over the Indian Ocean

The El Nino event of 1997–1998 followed by the La Nina in 1998–1999 was the strongest of its kind encountered in the 20th century. Associated with this event Indonesia experienced severe drought leading to large-scale forest fires. Large aerosol plumes from these fires advected over the equatorial Indian Ocean region. Development and decay of this plume and its regional transport are studied using the aerosol optical depth derived from the NOAA14-AVHRR data along with the tropospheric circulation and meteorological conditions derived from NCEP/NCAR reanalysis. The study shows that associated with the large-scale fires in the Indonesian region, a substantially large aerosol plume formed over the equatorial Indian Ocean in the latitude range of 5°N to 10°S, during September–November period of 1997. This plume was confined to the eastern equatorial Indian Ocean in September, and reached up to about 60°E by October. The westward transport of this aerosol plume was driven by the anomalous easterly winds over the tropical Indian Ocean during the El Nino period. A close association is observed between the aerosol optical depth over equatorial Indian Ocean and the fire counts over Southeast Asia derived from Along Track Scanning Radiometer data.