Sensitivity of Cloud Invigoration and Suppression Effects to Major Aerosol species During the Indian Summer Monsoon in a Global Climate Model

Tropical deep convective clouds (DCCs) play a pivotal role in Earth's hydrological cycle, with their dynamics strongly influenced by aerosols. Depending on their properties, aerosols can either invigorate or suppress cloud formation and development. Previous observational studies and cloud-resolving model simulations have shown that aerosols such as black carbon (BC) and sulfates modify cloud microphysics, affecting droplet size distribution, latent heat release, and precipitation patterns. However, the use of global climate models (GCMs) to study these aerosol-cloud interactions remain limited, despite their ability to capture large-scale circulation patterns and associated non-linear feedback. This study investigates the sensitivity of aerosol-induced cloud invigoration and suppression (AIVe) to major aerosol species during the Indian summer monsoon (ISM) season using the Community Earth System Model, specifically its atmospheric component, the Community Atmosphere Model version 5 (CESM-CAM5). The analysis focuses on DCCs over central India during the monsoon months of June–September (JJAS) for the period 2005–2008. Aerosol and cloud parameters from CESM-CAM5 simulations, conducted at 0.5-degree horizontal resolution, are compared with satellite observations. Five Atmospheric Model Intercomparison Project (AMIP)-style simulations were performed: one with aerosols at pre-industrial level (PI) levels, another at present-day (PD) levels, and three additional simulations perturbing specific aerosol species (dust, BC, and sulfate) under PD conditions to isolate their individual effects on AIVe. The findings highlight that aerosol physico-chemical properties critically influence DCC behavior. Black carbon near the boundary layer increases cloud condensation nuclei (CCN) concentrations, delaying precipitation, enhancing warm-phase invigoration, and strengthening updrafts. In the upper troposphere, BC absorbs solar radiation, causing atmospheric warming that promotes cloud deepening and cold-phase processes. Additionally, BC intensifies both shortwave and longwave heating, prolonging cloud lifetimes and supporting deeper convection. Sulfate aerosols primarily enhance warm-phase invigoration through increased CCN concentrations at lower altitudes. However, their weaker vertical transport limits their impact on cold phase processes and deep convection compared to BC and dust. Dust aerosols with high concentrations in the mid-troposphere, act as efficient ice-nucleating particles (INPs), enhancing cold phase invigoration. However, suppressed updrafts in the upper troposphere reduce their overall effect on deep convective systems, emphasizing the importance of aerosol size, number concentration, and properties in shaping AIVe. This study underscores the complex interplay between aerosol characteristics and their vertical distribution in influencing cloud dynamics during the ISM. Detailed results and further implications will be presented.