Brief review of wind and drag transformations in WBI2017

To determine the hydraulic boundary conditions for the design of coastal defence structures, hydraulic (wave, water level) models are forced by observation-based winds. Winds observed at land stations are first transformed to open-water winds and then into stress to drive the respective model. The translation to stress is done using a drag coefficient that is parametrised as a function of wind speed. At first sight all production runs have to be repeated if new research suggests a new drag parameterization to be used. A recent memorandum describes a method to avoid repeating these runs. We here evaluate that method, and at the same time assess the method to translate the land wind to open-water wind.