Understanding the role of mesoscale organization in air-sea interactions

The population of clouds over the subtropical oceans is dominated by trade wind cumulus which often organize in a variety of mesoscale shapes and sizes. The subtropical ocean, too, exhibits much fine-scale variability, in the form of sea surface temperature (SST) anomalies and ocean mesoscale eddies. Because observed patches of aggregated shallow cumulus, SST variations, ocean eddies, and associated mesoscale circulations exist in the “grey zone” for current global models, our ability to model these phenomena and understand their relevance to the climate system is crude. Here we propose a process modeling study to investigate the role of mesoscale spatial organization in air-sea interactions. Our main objectives are:
(i) to assess how mesoscale spatial organization of shallow cumulus may affect atmosphere-ocean coupling by modulating wind speeds and cloudiness, and
(ii) to investigate how mesoscale organization of shallow clouds and the circulations in which they are embedded are affected by transient SST perturbations driven by surface fluxes and persistent SST structures maintained by oceanic mesoscale eddies.
We will address these questions with large eddy simulations (LES) with resolutions fine enough to resolve cloud-scale circulations but large enough to admit the organizing mesoscale circulations. We will diagnose how mesoscale organization affects the net surface energy budget and how SST perturbations in turn affect mesoscale organization. By using LES to interpolate the data from ATOMIC/EUREC4A-OA, our primary focus is to examine how mesoscale structures in the lower atmosphere and the upper ocean might interact and regulate air-sea coupling.
This goal is directly aligned with this CVP target competition aim of better understanding air-sea interactions within the ATOMIC/EUREC4A-OA field campaigns region, with focus on lower atmospheric boundary layer processes and their influence on the ocean. This knowledge will then be used to inform physical parametrizations, and ultimately, to improve climate predictions. Therefore, the proposal also contributes to NOAA’s goal of providing high quality environmental information.