Long-Term Impacts of Aerosols on the Cloud, Temperature, and Rainfall Over the North–East Monsoon Region

This study analyses the long-term variation of the aerosol properties at the surface using Moderate Resolution Imaging Spectroradiometer (MODIS) including temperature from radiosonde observations and rainfall during 2001–2018 and within the boundary layer (BL) and free troposphere (FT) using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) during 2007–2018 over Kattankulathur (12.82^oN, 80.04^oE) in the northeast monsoon region. Before estimating the trend using multiple regression analysis, semiannual, annual, and various interannual components are identified using the empirical mode decomposition analysis and removed from the monthly mean data. The relationship between the monthly mean aerosol optical depth (AOD), cloud fraction (CF), cloud top height (CTH), and cloud albedo indicates the dominance of the semi-indirect effect over Kattankulathur. The aerosol-cloud interaction was found to be positive at the liquid water path (LWP) of 40–80 g/m², and 160–200 g/m² while negative at 80–140 g/m². The long-term trend of the AOD and Angstrom exponent is found to increase at a rate of 0.14 ± 0.07 and 0.122 ± 0.04 per decade. Similarly, the cloud parameters CER (CF) are found to be decreasing (increasing) at a rate of − 0.06 ± 0.0013 μm (0.12 ± 0.09 μm) per decade over the period 2001–2018. The long-term increase in the AOD results in a decrease (increase) in BL (FT) temperature indicating the increasing aerosol load causing the surface dimming.