Shallow convection modulation of wind stress patterns in marine atmospheric boundary layer

Shallow convection and precipitation in the marine atmospheric boundary layer can modulate near-surface winds on scales from 100 m - 100 km. This may substantially influence the exchange of heat and momentum across the air-sea interface and turbulent mixing on either side of the interface. Here we analyze spatial patterns of near-surface wind and momentum flux down to a 100 m scale as a function of Richardson number and as a function of the development in moist precipitating convection in many large-domain large eddy simulations (DALES) as part of the BOTANY ensemble. To assess the modulation effect that convection has on surface momentum fluxes, we decompose the LES wind stress across the simulations into contributions from different scales and processes, and answer how these dependencies change as simulations develop deeper moist convection and consequently precipitation. At the ocean surface, DALES currently uses a rough-wall boundary condition with a bulk flux formulation that relates surface fluxes to resolved-scale variables at the first grid level, consistent with Monin-Obukhov similarity theory. Knowing that the representation of wind stress in LES is likely flawed, we reflect on the largest uncertainties given the model assumptions and how observations from space and from the recent ORCESTRA/BOWTIE campaigns can help validate and improve the formulation of wind stress.