Synergistic Approach for the Aerosol Monitoring and Identification of Types over Indo-Gangetic Basin in Pre-Monsoon Season

Abstract

Aerosol optical and microphysical properties were studied at two major industrial cities (Delhi and Kanpur) of the Indo-Gangetic Basin (IGB) during three (2007–2009) consecutive pre-monsoon (PrM: March–May) seasons, using synergetic analyses of CALIOP, MODIS, AERONET and PARASOL observations. CALIOP-derived aerosol properties show vertically elevated aerosol profiles (up to 4 km altitude), majorly consisting of dust particles during all three PrM seasons with maximum loading in May, 2008. The above inference is well corroborated with columnar aerosol properties from MODIS and AERONET observations. The results also show higher aerosol optical depth (AOD) over Delhi as compared to Kanpur. The high aerosol loading found during the late PrM season at both locations can be attributed to the fact that dust/burning activities are at their peak in May during the PrM season over the IGB. The analyses of optical and microphysical parameters coupled with backward trajectory analyses indicate the presence of three different aerosol types (Type I, Type II and Type III) over both cities during PrM 2009. Type I is characterized as dust-dominated aerosols coming via long-range transportation from major dust sources (desert of Sahara, Iran, Afghanistan and western India), whereas a mixture of absorbing aerosols and dust coming from the Arabian Peninsula and the Thar Desert is characterized as Type II aerosols. The presence of highly absorbing, fine mode dominated Type III aerosols are categorized as urban-industrial/biomass burning aerosols, mainly locally originated and/or influenced by agriculture fires in the Himalayan foothills. A combination of CALIOP and PARASOL observations with ground-based measurements also highlights the dominance of biomass burning smoke (mixed with polluted continental) over the IGB during the middle of May in 2009. The variability in aerosol types found during the PrM season indicates the significant effect of natural/human activities, associated with different meteorological conditions, on aerosol behavior over the region.