A model of wind transformation over water-land surfaces

A simple physical model of the wind transformation on abrupt changes in surface roughness and temperature across a coastal line is suggested. The model is based on a concept of the internal boundary layer (IBL) growth with the fetch. It consistently describes both small scale (order of 1km) and mesoscale (order of 10-100 km) evolution of the IBL. The planetary boundary layer (PBL) problem is solved using the similarity approach, which is applied for the IBL confined to the surface boundary layer. The description of the Ekman part of the PBL is based on the analytical solution of the momentum and heat balance equations. A 3-layer eddy-viscosity model of the PBL is introduced for the description of the mesoscale evolution of the IBL. The PBL model takes into account the baroclinicity effects due to the temperature gradient across a coastal line. The model is verified against existing data of the wind transformation across the Dutch coast of the North Sea and a reasonable agreement with observations is obtained. The model can be used as a module in multi-component coupled models describing dynamical processes in the ocean and the atmosphere and is viewed as a tool for engineering applications in the coastal zone.