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 PM_2.5 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 PM_2.5 exhibit similar seasonal variability with maximum concentration in winter and minimum in monsoon seasons. The PM₁₀ concentration is mainly attributed to PM_2.5 with minimal contribution from PM_10-2.5. The long term monthly mean PM₁₀ and PM_2.5 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 PM_2.5 gradually increased from 2007 to 2010 and decreased thereafter. An overall slow decreasing trend in PM₁₀ and PM_2.5 concentrations together with black carbon (BC) concentrations has been observed. The examination of microphysical and optical properties also reveals the dominance of PM_2.5 aerosols. Higher percentage contributions of BC to both PM₁₀ and PM_2.5 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.