TY - JOUR TI - Assimilation of radar altimeter data in numerical wave models: An impact study in two different wave climate regions AU - Emmanouil, G. AU - Galanis, G. AU - Kallos, G. AU - Breivik, L.A. AU - Heiberg, H. AU - Reistad, M. JO - Annales geophysicae PY - 2007 VL - 25 TODO - 3 SP - 581-595 PB - European Geosciences Union (EGU) SN - 0755-0685 TODO - 10.5194/angeo-25-581-2007 TODO - air-sea interaction; data assimilation; forecasting method; numerical model; radar altimetry; satellite data; wave climate; wave height, Indian Ocean; Mediterranean Sea TODO - An operational assimilation system incorporating significant wave height observations in high resolution numerical wave models is studied and evaluated. In particular, altimeter satellite data provided by the European Space Agency (ESA-ENVISAT) are assimilated in the wave model WAM which operates in two different wave climate areas: the Mediterranean Sea and the Indian Ocean. The first is a wind-sea dominated area while in the second, swell is the principal part of the sea state, a fact that seriously affects the performance of the assimilation scheme. A detailed study of the different impact is presented and the resulting forecasts are evaluated against available buoy and satellite observations. The corresponding results show a considerable improvement in wave forecasting for the Indian Ocean while in the Mediterranean Sea the assimilation impact is restricted to isolated areas. ER -