On the understanding of the trade-wind cumuli daily cycle: the role of convective mixing and mesoscale organization of convection

Oceanic shallow convective clouds, which prevail in the trade-wind regions, have long been of great interest, because they strongly impact climate on a wide range of scales and they are critical in the estimation of the magnitude and pace of global warming. But surprisingly, the most fundamental mode of tropical variability, that is the daily cycle, has received very little attention for this cloud category, so that our knowledge of the diurnal processes in this oceanic shallow cumulus regime and their influence on climate at broader scales remains extremely limited. We recently relaunched the exploration of this topic. New investigating tools have been used, including large-eddy simulations run over large domains in realistic configurations and in-situ observations from the Barbados Cloud Observatory, which have helped study this daily cycle in the North Atlantic trade-wind region with a lot more details than was possible 40 years ago when it was first documented. Important features of this daily cycle have been found, which can have far reaching implications for climate change studies. Our hypothesis is that understanding the processes that control trade-wind cumuli on the diurnal timescale will benefit to our understanding of the mechanisms that are involved in the tropical marine low-level cloud feedbacks. In this regard, the wealth of observational data that will be collected during the EUREC4A campaign is unprecedented and offers a tremendous opportunity to enrich the characterisation and understanding of the mechanisms of the trade-wind daily cycle. Preliminary results will be discussed with a focus on the role of the shallow convective mixing and mesoscale organization in the daily cycle of trade-wind cumuli.