Circling in on Convective Self-Aggregation.

In radiative-convective equilibrium simulations, convective self-aggregation (CSA) is the spontaneous organization into segregated cloudy and cloud-free regions. Evidence exists for how CSA is stabilized, but how it arises favorably on large domains is not settled. Using large-eddy simulations, we link the spatial organization emerging from the interaction of cold pools (CPs) to CSA. We systematically weaken simulated rain evaporation to reduce maximal CP radii, R max , and find reducing R max causes CSA to occur earlier. We further identify a typical rain cell generation time and a minimum radius, R min , around a given rain cell, within which the formation of subsequent rain cells is suppressed. Incorporating R min and R max , we propose a toy model that captures how CSA arises earlier on large domains: when two CPs of radii r i , r j ∈ [ R min , R max ] collide, they form a new convective event. These findings imply that interactions between CPs may explain the initial stages of CSA.