Wintertime variation of $\mathbf{PM}_{\mathbf{10}},\ \mathbf{PM}_{\mathbf{2}.\mathbf{5}}$, Black Carbon, and Aerosol Optical Depth over Varanasi

Abstract

Black Carbon (BC) and Particulate Matter $(\text{PM}_{10}$ and $\text{PM}_{2.5})$ are measured over Varanasi during the winter season. They are the most crucial atmospheric aerosols that play an important role in Earth's radiation budget by absorbing solar and terrestrial radiation. Aerosol Optical Depth (AOD) is the measure of extinction of incoming solar radiation by air particles distributed in a vertical column of the atmosphere. The influence of the atmospheric boundary layer (ABL) is observed on the diurnal variation of BC, PM10, and $\text{PM}_{2.5}$. The concentration of these parameters was high during morning and evening hours when ABL is lying near the ground. Maximum and minimum concentrations of PM10 and $\text{PM}_{2.5}$ are found to be in November and February. Burning firecrackers during Diwali in November could be the reason for high aerosol loading. Higher BC concentration is measured in January due to increased anthropogenic activities and biomass burning. AOD at 500 nm is found to be higher in December and lower in February. The higher value of AOD at a shorter wavelength suggests the dominance of fine mode particles.