Environmental Control of Wind Response to Sea Surface Temperature Patterns From Remote Sensing Data

Sea surface temperature (SST) gradients modulate surface wind variability at the mesoscale O(100 km), with relevant impacts on surface fluxes, rainfall, cloudiness and storms. The dependence of the SST-wind coupling mechanisms on environmental conditions has been proven using global ERA5 reanalysis data. However, recent literature calls for the need of an observational confirmation to overcome the limitations of numerical models in representing such turbulent processes. Here, we employ O(10 km) MetOp A observations of surface wind and SST to verify the dependence of the downward momentum mixing (DMM) mechanism on large-scale wind U and atmospheric stability. We propose a simple empirical model describing the scaling of the coupling intensity on U, accounting for the role of the characteristic SST length scale LSST and the boundary layer height h in determining the decoupling of the atmospheric response from the SST forcing due to advection. Fitting such a model to the observations we retrieve a scaling with U that depends on the atmospheric stability, in agreement with the literature. The physical interpretation from ERA5 is confirmed, albeit relevant discrepancies emerge in stable regimes and specific regional contexts. This suggests that global numerical models are not able to properly reproduce the coupling in certain conditions, which might have important implication on air-sea fluxes.