Convective Self-Aggregation Occurs Without Radiative Feedbacks in Warm Climates

Previous research showed that radiative feedbacks are essential to the spontaneous development of convective aggregation (CSA) in idealized atmosphere models. We find that the contribution of radiative feedbacks decreases with warming and that, in warm climates, CSA occurs without radiative feedbacks. We perform 2D simulations in different climates using a cloud-resolving model and use a layerwise moist static energy (LMSE) framework to quantify the contribution of radiative feedbacks to the increase of LMSE variance, which characterizes the development of CSA. The result shows that positive radiative contribution dominates the LMSE variance production when SST is below 300 K; when SST exceeds 300 K, adiabatic contribution shifts from negative to positive and dominates the variance production. Then we turn off radiative feedbacks by horizontally homogenizing radiative heating rates at all model levels. CSA still occurs in warmer climates (310–320 K). This result agrees with the LMSE diagnosis and additional 3D simulations.