Spatial Organisation Affects the Pathway to Precipitation in Simulated Trade‐Wind Convection.

We investigate whether and how spatial organization affects the pathway to precipitation in large‐domain hectometer simulations of the North Atlantic trades. We decompose the development of surface precipitation (P) in warm shallow trade cumulus into a formation phase, where cloud condensate is converted into rain, and a sedimentation phase, where rain falls toward the ground while some of it evaporates. With strengthened organization, rain forms in weaker updrafts from smaller cloud droplets so that cloud condensate is less efficiently converted into rain. At the same time, organization creates a locally moister environment and modulates the microphysical conversion processes that determine the raindrops' size. This reduces evaporation and more of the formed rain reaches the ground. Organization thus affects how the two phases contribute to P, but only weakly affects the total precipitation efficiency. We conclude that the pathway to precipitation differs with organization and suggest that organization buffers rain development. Plain Language Summary: Clouds in the trade‐wind region organize into a variety of spatial patterns. We investigate how this spatial organization influences rain development in simulations of trade‐wind convection. We divide the formation of surface precipitation into two phases. In the first phase, rain forms from the collision of cloud droplets or the collection of cloud droplets by raindrops. In the second phase, rain falls toward the ground while some of the rain evaporates. Our study shows that as organization strengthens, rain forms less efficiently, but a larger fraction of that rain reaches the ground as evaporation is reduced. Thus, organization in the simulations affects the way surface rain is generated. Our analyses suggest that it does so by modulating the cloud vertical motion in which rain forms, the local moisture environment through which rain falls and the microphysical conversion processes. Key Points: The development of surface precipitation in simulated trade‐wind convection is decomposed into a formation and sedimentation phaseAs organization strengthens, less cloud condensate is converted into rain, but more rain reaches the ground as evaporation is suppressedOrganization affects rain formation by modulating the local moisture environment, cloud vertical motion and microphysical properties [ABSTRACT FROM AUTHOR]