Mesoscale Organized Trade Wind Cumulus Clouds are Dynamically More Efficient

Boundary layer clouds can organize into mesoscale (O~100 km) patterns of clustered cloud structures. Mesoscale organization influences low cloud radiative properties globally, through modulating both cloud amount and opacity, and contributes to the tropical hydrologic cycle, through its role in convective energy discharge-recharge cycles. Trade-wind cumuli occur with varying degrees of organization and are a large source of uncertainty in global climate models. The linkage between trade cumuli development and dynamics is especially difficult to capture in climate models, impacting low cloud feedback estimates. In this study, we utilize in situ observations of the wintertime trades, especially from a ship-based Doppler wind-lidar, to investigate the relationship between mesoscale organization and cumuli updraft dynamics. We contrast two periods with similar cloud structure sizes but different degrees of clustering and find that cumuli structures are dynamically more efficient when they are more organized: for a given core size, more organized clouds have stronger cloud base updrafts that import more moisture into the cloud layer. Updrafts in more organized clouds are also stronger throughout the sub-cloud layer as well as at cloud base. More organized clouds tend to be associated with wider plumes. However, clear-sky plumes are similar in both organization regimes. This suggests that there may be a mechanism, such as mesoscale circulations, that reinforces the updrafts of more organized clouds and their overall dynamic efficiency, supporting their continued development. These differences in cloud development dynamics across mesoscale organizational states has important implications for understanding and simulating cloud behavior under future climates.