The wave forecast system of the “Deutscher Wetterdienst” and the “Bundesamt für Seeschiffahrt und hydrographie”: A verification using ERS-1 altimeter and scatterometer data

Abstract

A new numerical wave forecast system, implemented on the computer of the “Deutscher Wetterdienst” (DWD), has provided operational wave forecasts since June 1992. The system consists of three modules, a deep water wave model for the North Atlantic and two shallow water wave models for the North European shelf area and the Baltic. The North Atlantic wave model is forced by the wind fields of the global atmospheric model T106, while the shallow water wave models are driven by wind forecasts of the “European model” of the DWD. A limited verification of the wave forecasts is based on comparisons with local buoy measurements. A thorough validation of the wave model results follows using “Fast Delivery Products” of the ERS-1 satellite for the one week period from 4th to 10th of January 1993. The ERS-1 products include windspeed and-direction derived by the scatterometer plus windspeed and significant waveheight recorded by the radar altimeter. In general the comparisons show a fairly good agreement between the altimeter waveheights and the wave model results. However, there are considerable deviations between the scatterometer wind directions and those computed by the atmospheric DWD-models in some cases, particularly in rather data sparse regions of the ocean. The measured windspeeds recorded by scatterometer and altimeter are usually smaller than the windspeeds computed by the atmospheric models. In conclusion, the comparisons between satellite and model data demonstrate that the new forecast system works properly and provides reliable data.