2010b: Dynamical analysis of the boundary layer and surface wind responses tomesoscale SST perturbations

The dynamical response of the marine atmospheric boundary layer (MABL) to mesoscale sea surface temperature (SST) perturbations is investigated over the Agulhas Return Current during winter from a 1-month, high-resolution, three-dimensional simulation using the Weather Research and Forecasting (WRF) mesoscale model. A steady lower boundary condition for July 2002 is obtained using SST measurements from the Advanced Microwave Scanning Radiometer on the Earth Observing System (EOS)–Aqua satellite (AMSR-E). The WRF models ’ ability to accurately simulate the SST-induced surface wind response is demonstrated from a comparison with satellite surface wind observations from the SeaWinds scatterometer on the Quick Scatterometer (QuikSCAT) satellite. Relevant features of this simulation include a quasi-periodic distribution of mesoscale SST perturbations with spatial scales;200 km and strong winds that lead to a large surface sensible heat flux response, whose broad range of 80–100 W m22 between warm and cool SST perturbations is much larger than seen in most previous simulations of mesoscale wind–SST coupling. This simulation provides the first realistic example of vertical turbulent redistribution of momentum driven by the SST-induced surface heating perturbations acting in concert with the SST-induced pressure gradients to accelerate near-surface flow toward warm water and decelerate near-surface flow toward cool water. Thi