WMS Numerical sea gang forecasts for the German coasts (CWAM)

The basis of the numerical seagoing prediction system in the German Weather Service (DWD) is a spectral seagoing model of the 3 rd generation (3G-WAveModel). Spectral models describe the state of the seagoing over the so-called frequency-directional seagoing spectrum — this is the 2-dimensional distribution of wave energy by wave frequency (or wave period or wave number) and direction of propagation. In the current version, a resolution of 36 directions and 30 frequencies (wave periods between 1.5 and 24 seconds) is used. In the numerical model, the temporal evolution of the seagoing spectrum is calculated at a variety of points of a lattice stretched over the sea surface. The wave energy changes through the following physical processes: • Wave growth due to the downward impulse flow from the wind field • Wave kinematics (advection, reflection) • redistribution of energy between wave numbers through nonlinear interactions • Dissipation (internal friction and breakage) Similar to the chain of atmospheric models (ICON, ICON-EU and ICON-D2), the sea gait prediction system is divided into different predictive areas: The global model GWAM, the European model EWAM and the high-resolution coastal model CWAM. The model sea walk is driven by analysed and predicted 10 m winds of the atmospheric models.