Wave-dependence of friction velocity,roughness length,and drag coefficient over coastal and open water surfaces by using three databases

The parameterization of friction velocity, roughness length, and the drag coefficient over coastalzones and open water surfaces enables us to better understand the physical processes of air-water interaction.In context of measurements from the Humidity Exchange over the Sea Main Experiment (HEXMAX), we recently proposedwave-parameter dependent approaches to sea surface friction velocity and the aerodynamic roughness by using thedimensional analysis method. To extend the application of these approaches to a range of natural surface conditions,the present study is to assess this approach by using both coastal shallow (RASEX) and open water surface measurements(Lake Ontario and Grand Banks ERS-1 SAR) where wind speeds were greater than 6.44 m s^-1. Friction velocities,the surface aerodynamic roughness, and the neutral drag coefficient estimated by these approaches under moderate windconditions were compared with the measurements mentioned above. Results showed that the coefficients in these approachesfor coastal shallow water surface differ from those for open water surfaces, and that the aerodynamic roughness lengthin terms of wave age or significant wave height should be treated differently for coastal shallow and open water surfaces.