A comparison of Baltic Sea wave properties simulated using two modelled wind data sets

Abstract

We calculated two sets of idealised ice-free wave hindcast data on a high-resolution, three-layer nested grid covering the Baltic Sea, using two different wind datasets (ERA5 and BaltAn65+), to evaluate the performance of the model in the open and sheltered parts of the sea. The highest resolution of the grids is 260 m. The outcome of simulations is compared against the available in-situ measurements. The main statistical properties of the Baltic Sea wave climate as well as the timing and maximum values of extreme significant wave heights are well replicated in the Baltic proper using the 3 nautical mile (nmi) grid. Simulations using BaltAn65+ have a better match with recorded average wave properties while the ERA5 forcing better replicates wave extremes. The largest differences between the two simulations occur in the Sea of Bothnia, Bay of Bothnia and to the east of large islands. Wave climate in the Gulf of Finland is replicated with a resolution of 1 nmi in the open part of the gulf a down to a resolution of 260 m in selected coastal areas. The wave intensity is the largest in the central part of the gulf and decreases towards the coast and from the West to the East. The use of ERA5 winds yields higher wave heights at the entrance of the gulf and in the central part of the gulf along its axis. Simulations using BaltAn65+ winds show higher waves in the nearshore regions.