Sensitivity of storm wave modeling to wind stress evaluation methods

The application of the wave boundary layer model (WBLM) for wind stress evaluation to storm wave modeling is studied using Hurricane Katrina (2005) as an example, which is chosen due to its great intensity and good availability of field data. The WBLM is based on the momentum and energy conservation equations and takes into account the physical details of air-sea interaction processes as well as energy dissipation due to the presence of sea spray. Four widely-used bulk-type formulas are also used for comparison. Simulated significant wave heights with WBLM are shown to agree well with the observed data over deep water. The WBLM yields a smaller wind stress coefficient on the left hand side of the hurricane track, which is reasonable considering the effect of the sea state on momentum transfer. Quantitative results show that large differences of the significant wave height are observed in the hurricane core among five wind stress evaluation methods and the differences are up to 12 m, which is in agreement with the general knowlege that the ocean dynamic processes under storm conditions are very sensitive to the amount of momentum exchange at the air-sea interface. However, it is the depth-induced energy dissipation, rather than the wind energy input, that dominates the wave height in the shallow water region. A larger value of depth-induced breaking parameter in the wave model results in better agreement with the measurements over shallow water.