Spatio-Temporal Variability of Atmospheric Aerosols Affecting Cloud Properties around Mangaluru along the Southwest Coast of India

Abstract

Abstract The study analyzed the effect of aerosols on cloud properties in the summer monsoon-dominated region around Mangaluru along the southwest coast of India from 2001 to 2020. AOD (aerosol optical depth) and Angstrom Exponent (AE) datasets were used to examine aerosols' spatial and temporal distribution over the study area and the adjacent Arabian Sea. The back trajectories of the airmass computed from the hybrid single-particle lagrangian integrated trajectory (HYSPLIT) model indicate that this region is highly influenced by the marine airmass of the Arabian Sea, which is considerably contaminated by those emitted over the landmass, particularly from the anthropocentric region, throughout the year. Seasonally, the coarse particles especially dominate during the summer and, to some extent, during the spring, whereas the fine-mode aerosols especially dominate during the winter and autumn seasons. The latter types of aerosols gradually increased from 2001 to 2018, but a sudden decrease in the level was noticed in 2019–20 due to the COVID-19 lockdown. The correlation between AOD and cloud characteristics, i.e., cloud fraction (CF), cloud top pressure (CTP), cloud top temperature (CTT), and water vapor (WV), indicates that the positive correlation of AOD with CF and WV suggests that aerosols responsible for AOD are also responsible for cloud formation, especially in areas with high levels of industrial activity. In contrast, negative correlations with CTT and CTP suggest the dominance of sea salt and dust aerosols, which can scatter sunlight back into space and cool the atmosphere by lowering CTT and CTP, during monsoon season.