Influence of Black Carbon Aerosol on the Atmospheric Instability

To date, influence of aerosols on the atmospheric stability and hence on the convection/precipitation is not well understood. From the detailed analysis carried out using high-accuracy radiosonde and Aethalometer measurements, a significant decrease in the convective available potential energy has been noticed in association with the increase in surface concentration of black carbon (BC) for a restricted range of precipitable water vapor and under similar environmental background (wind speed, direction, and cloud cover) over Gadanki (13.5 degrees N, 79.2 degrees E), a tropical rural site in southern peninsular India. A number of case studies along with statistical analysis indicate a notable perturbation in the temperature profile associated with high-surface BC concentration conditions compared to the regional mean concentration of the same. A discernible fall in the temperature lapse rate within and above the local boundary layer in association with the higher BC concentration has been observed, which in turn reduces the available potential energy for convection decreasing the positive buoyancy required for a rising moist air parcel. This observation has been noticed over a nonurban location, but the phenomenon is not location dependent and is more applicable to the urban regions where BC concentration is likely to be much higher. Plain Language Summary Our daily needs of energy lead us to massive usage of fuel burning. These burnings release huge amount of tiny particles into the atmosphere, which significantly influence our environment. Black carbon (BC) is such a man-made health hazardous pollutant aerosol particle which warms up our environment by absorbing solar radiation. Generally, the temperature of our surroundings decreases with height in a certain rate. Due to this nature of temperature in our atmosphere, the warm moist air from the ground can move upward and is cooled down. The upward movement of moist air eventually causes rainfall mostly during summer in tropical areas. But our present observation shows that higher amount of BC in our environment can disturb the normal upward movement of moist air by heating up the atmosphere. Thus, the increase in the amount of this man-made pollutant particle affects not only human health but also the normality of our atmosphere disturbing its balance. Our study provides some important evidences on how BC particles can disturb the balance of our atmosphere. This observation has been done over a rural location, but the phenomenon should be more prominent over urban environment where BC is likely to be more in amount.