Towards an approved model set-up for HARMONIE Contribution to WP 1 of the SBW-HB Wind modeling.

For the derivation of the Hydraulic Boundary Conditions (HBCs), information on extreme winds over open-water areas is required. To this end, a new method is developed that will answer the need for a description of both the strength and the space- and time-characteristics of extreme storms. The method relies on using high-resolution atmospheric model simulations rather than on using spatial interpolation of sparse point measurements of wind speed. The HARMONIE model, which has a grid spacing of 2.5 km, has been selected to perform the simulations. This report documents the configuration of HARMONIE that will be used in the project. The quality of the high-resolution model results depends on the settings of the model.
We have tested various domain settings, forcing strategies and model options. On the basis of the results, we selected a standard model set-up. This set-up was used in simulations of 14 storms that are contained in the storm test set recommended by Groen and Caires (2011).
As a first evaluation of the standard model set-up, we compared the maximum attained wind speed in the model with the observations for each storm. Over sea the agreement between the model results and the observations is good. Over land the modelled wind extremes are slightly lower than observed. To establish the value of the high-resolution model for the determination of the HBCs, a comprehensive evaluation of the spatial and temporal characteristics of the selected storms is needed. In accordance with the Adjusted SBW Wind Modelling project, this work is anticipated for 2013.