Investigation of PM_2.5 mass concentration over India using a regional climate model

Seasonal variation of PM_2.5 (Particulate Matter <2.5 μm) mass concentration simulated from WRF-Chem (Weather Research and Forecasting coupled with Chemistry) over Indian sub-continent are studied. The simulated PM_2.5 are also compared with the observations during winter, pre-monsoon, monsoon and post-monsoon seasons of 2008. Higher value of simulated PM_2.5 is observed during winter followed by post-monsoon, while lower values are found during monsoon. Indo-Gangetic Basin (IGB) exhibits high amount of PM_2.5 (60- 200 μg m^-3) throughout the year. The percentage differences between model simulated and observed PM_2.5 are found higher (40- 60%) during winter, while lower (< 30%) during pre-monsoon and monsoon over most of the study locations. The weighted correlation coefficient between model simulated and observed PM_2.5 is 0.81 at the significance of 98%. Associated RMSE (Root Mean Square Error) is 0.91 μg m^-3. Large variability in vertically distributed PM_2.5 are also found during pre-monsoon and monsoon. The study reveals that, model is able to capture the variabilities in spatial, seasonal and vertical distributions of PM_2.5 over Indian region, however significant bias is observed in the model. PM_2.5 mass concentrations are highest over West Bengal (82± 33 μg m^-3) and the lowest in Jammu & Kashmir (14± 11 μg m^-3). Annual mean of simulated PM_2.5 mass over the Indian region is found to be 35± 9 μg m^-3. Higher values of PM_2.5 are found over the states, where the reported respiratory disorders are high. WRF-Chem simulated PM_2.5 mass concentration gives a clear perspective of seasonal and spatial distribution of fine aerosols over the Indian region. The outcomes of the study have significant impacts on environment, human health and climate.