Long term climatology of particulate matter and associated microphysical and optical properties over Dibrugarh, North-East India and inter-comparison with SPRINTARS simulations

The long term climatology of PM10 and PM2.5 concentrations for the five year period from June 2007–March 2012 is studied using measurements made with a Quartz Crystal Microbalance Impactor over Dibrugarh, North-East India. The PM10 and PM2.5 exhibit similar seasonal variability with maximum concentration in winter and minimum in monsoon seasons. The PM10 concentration is mainly attributed to PM2.5 with minimal contribution from PM10–2.5. The long term monthly mean PM10 and PM2.5 concentrations shows maximum value in late winter and early pre-monsoon. This temporal variability is positively correlated with the MODIS retrieved fire counts associated mostly with the biomass burning activities and negatively correlated with rainfall. PM10 and PM2.5 gradually increased from 2007 to 2010 and decreased thereafter. An overall slow decreasing trend in PM10 and PM2.5 concentrations together with black carbon (BC) concentrations has been observed. The examination of microphysical and optical properties also reveals the dominance of PM2.5 aerosols. Higher percentage contributions of BC to both PM10 and PM2.5 are observed in post-monsoon season followed by winter. The inter-comparison of measured PM and BC concentrations with SPRINTARS simulation reveals that model underestimates the measurements except in pre-monsoon. The discrepancy might have arisen due to the topography of the location and inadequate emission inventory for the climate zone.