Formulation of a dynamic convective adjustment time-scale in the CESM1.2 and its influence on the Indian summer monsoon simulations

This study formulates and implements a dynamic convective adjustment time-scale [Formula: see text]) in the convective parameterization scheme of CESM1.2, replacing the default fixed [Formula: see text]. By allowing [Formula: see text] to vary spatiotemporally with convective cloud depth and updraft velocity, the approach significantly improves Indian summer monsoon simulations. The scheme reduces longstanding precipitation biases, such as excessive precipitation over the Himalayas, Western Ghats, and peninsular India, and underestimations over the eastern equatorial Indian Ocean. The scheme also enhances cloud cover characteristics, particularly the low cloud cover, radiative forcing, and large-scale circulation (subtropical westerly Jet and Somali Jet). Limited improvement in the monsoon quasi-biweekly and intraseasonal mode and precipitation variability, is seen. Despite these improvements, regional biases, extreme event underestimation, intraseasonal oscillations, and ocean-atmosphere coupling limitations persist. These findings underscore the potential of dynamic convective adjustment in reducing key monsoon simulation biases and improving long-term climate projections in global models.