hide
Free keywords:
-
Abstract:
This study addresses the role of the ocean small scale in the north-west tropical Atlantic air-sea interactions using satellite observations, ERA5, a set of regional WRF simulations and in-situ data.
First, we focus on the coupling between SST and the atmospheric boundary layer, evaluating latent heat flux (LHF) sensitivity to SST. When smaller scales are considered, U10m-SST are positively correlated and the q2m-SST regression significantly differs from the Clausius-Clapeyron scaling. This is interpreted in terms of an active ocean modifying the near-surface atmospheric state. The small-scale coupling information is used to develop a downscaling method aiming to include the impact of these fine-scale SST features into an available low-resolution LHF data set. The results show that they induce a significant increase of LHF (30% - 40% per °C of SST), partitioned between a dynamic (~28%) and a thermodynamic (~5%) mode. To validate our results, the downscaling is applied to a set of high-resolution simulations, reducing by a factor of 2 our LHF estimate biases.
The north-west tropical Atlantic is also subject to the Amazon water discharge. This generates large salinity contrasts and affects LHF, which is significantly reduced over the freshwater plume (20% – 30% less than in saltier waters). To elucidate the causes of this behaviour, we use several in-situ datasets collected during the EUREC4A-OA/ATOMIC campaigns. The high spatio-temporal resolution of these data sources, is likely to provide better estimates of the air-sea interface processes involved and their connections with the upper ocean heat budget and/or the concomitant atmospheric conditions.
