Recent changes in dust and its impact on aerosol trends over the Indo-Gangetic Plain (IGP)

Abstract

A synergistic use of satellite and ground based remote sensing data has been utilized to analyze recent changes in the aerosol column loading over the Indo Gangetic Plain (IGP). Despite an overall statistically significant increase in the trend of annual mean aerosol optical depth (AOD) over the past decade, a prominent difference within seasons was observed. Summer and monsoon seasons have a slight decreasing trend, while post monsoon and winter have significant increasing trend. The optically equivalent composition inferred from ground based long term measurements of aerosol size and absorption characteristics reveals that summer and monsoon season are mostly dust dominated. Whereas, post monsoon and winter seasons are dominated by black carbon (BC) and/or other absorbing aerosols. We find that the observed decrease in AOD is associated with decrease in dust loading in the atmosphere with a large spatial extent covering the whole of North-Western part of India and IGP. Similar changes are associated with absorbing carbonaceous aerosol species during the periods showing an increasing trend. The decreasing dust loading over Indian region during summer along with increase in absorbing black carbon aerosols during the pre-monsoon and the monsoon period may have significant impact on aerosol radiative forcing and hence Indian summer monsoon rainfall.