Direct Observations of the Momentum Flux in the Surfzone

Abstract

<p>The accuracy of weather and climate models depends on reliable quantification of air-sea momentum transfer. While decades of research has led to significant improvements to momentum flux parameterization, even the most robust models are developed from open-ocean measurements where conditions are spatially uniform and similarity theory generally applies. Nearshore, wave shoaling and breaking, varying wind-swell incidence angles, complex currents patterns, rapid bathymetric changes, and shore-side topographic features all contrast open-ocean homogeneity meaning flux parameterizations are less effective. Therefore, there is a critical need<em> </em>to identify and systematically quantify the impact of coastal processes and features on the momentum flux. To this end, we deployed a suite of sonic anemometers outside the surfzone and onshore at the Army Corp Field Research Facility (FRF) in Duck, North Carolina, USA. Complimented by FRF’s extensive metocean observational network, we used our data to study the horizontal and vertical momentum flux variability with to understanding how transient nearshore processes and flux footprints alter the flux. This presentation will focus on the surfzone momentum flux as observed during a strong storm and compare it to the flux collect further offshore.</p>