Unveiling the effects of post-monsoon agricultural biomass burning on aerosols, clouds, and radiation in Northwest India

Abstract The post-monsoon agricultural biomass burning activities in Northwest India have been recognized as a significant socio-environmental problem in recent years, primarily due to their severe impacts on air quality degradation across a wide area, including the capital New Delhi. Although these biomass burning activities have been extensively studied from an air quality perspective, their potential impacts on the climate system, particularly through their influences on cloud and radiation fields, have been largely overlooked. In this study, we aim to address this research gap by analyzing fire, meteorological parameters, aerosol, cloud, and radiation data spanning nearly two decades (2002–2021), obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite, Modern-Era Retrospective Analysis Research and Applications, Version 2 (MERRA-2), and the Fifth Generation of European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5). Our analysis reveals a notable increase in agricultural biomass burning intensity in Northwest India over the past two decades, contributing significantly to air quality degradation. Our analysis further indicates a delay in peak burning time (day of the year) and a shortening of the period of intense burning, reflecting changes in farming practices and agricultural biomass burning in Northwest India over the past two decades. These agricultural biomass burning activities substantially elevate total and light-absorbing aerosols, thereby affecting cloud properties and altering the radiation budget. The intensification of these burning activities can cause an increase in cloud droplet size and a decrease in cloud optical thickness, suggesting an enhancement of the cloud droplet collision-coalescence process during the period of intense burning. Similarly, the intensification of burning activities leads to increased cooling effects at the surface and top-of-the-atmosphere across shortwave and longwave spectral ranges, while inducing a heating effect within the atmosphere. These findings highlight the potential impacts of agricultural biomass burning activities on the regional climate system and hydrological cycle, emphasizing the need for more detailed studies in the future.