The impact of small-scale coastal phenomena such as sea-breeze circulations and low-level jets have been well-studied with atmospheric meso-scale modeling with horizontal grid resolutions on the order of a few kilometers. Equally it has been shown that there is a need for high numerical resolution in wave models to resolve coastal zones and ice-edges in a realistic way. A compromise is often done in the resolution of the atmospheric forcing in coupled model systems but it has not been well-investigated how large impact this compromise can have for significant wave height and other parameters crucial for a number of applications including wave energy installations, routing of ships and off-shore safety.
This project will use high-resolution atmospheric forcing for the Baltic Sea on 1 km resolution from the Weather Research and Forecasting (WRF) model as input for high-resolution wave modeling using the WAM model at 1 km resolution for 1 year of simulations. This allows for both a study on the seasonal response to air-sea coupling effects and simulation of frequently occurring small-scale coastal phenomena. For selected shorter time periods we will also study the details of the coupling effects using coupled model systems on a range of resolutions which will characterize the uncertainties associated with common practical approximations when long time series of statistics are generated by running models at low resolution. Lower resolution that can be expected to have trouble resolving several important coastal processes.
The applicant PI has previous experience of performing numerical studies of air-sea coupling effects on scales ranging from a couple of meters, using Large-Eddy Simulation (LES) to resolve turbulent processes in PhD work (SNIC project, s00109-22: Impact of waves on turbulence, on UPPMAX clusters Isis and Tintin) as well as more recent wave climate studies (SNIC project, 2016/5-60: Modelling Baltic Sea wave climate). The proposal is a complementary project to investigate additional aspects of wave impact and wave-atmosphere coupling related to a project funded by the Swedish Energy Agency to investigate the wave energy potential of the Baltic Sea area. The present project would allow us to study the underlying processes at a greater detail than previously possible and allow us to form estimates of uncertainty. This is of potential great impact in numerical weather prediction and climate modeling. It is also very important to be able to make a good and unique assessement of the wave energy potential in the Baltic Sea and its related uncertainties.