Published in:
Ocean Science, 14 (2018) 6, Seite 1503-1521
Language:
English
DOI:
10.5194/os-14-1503-2018
ISSN:
1812-0792
Origination:
Footnote:
Description:
Abstract. In this study, the quality of wave data provided by thenew Sentinel-3A satellite is evaluated and the sensitivity of the wave modelto wind forcing is tested. We focus on coastal areas, where altimeter dataare of lower quality and wave modelling is more complex than for the openocean. In the first part of the study, the sensitivity of the wave model towind forcing is evaluated using data with different temporal and spatialresolution, such as ERA-Interim and ERA5 reanalyses, the European Centre forMedium-Range Weather Forecasts (ECMWF) operational analysis and short-rangeforecasts, German Weather Service (DWD) forecasts and regional atmosphericmodel simulations (coastDat). Numerical simulations show thatthe wave model forced using the ERA5 reanalyses and that forced using theECMWF operational analysis/forecast demonstrate the best capability over thewhole study period, as well as during extreme events. To further estimate thevariance of the significant wave height of ensemble members for differentwind forcings, especially during extreme events, an empirical orthogonalfunction (EOF) analysis is performed. In the second part of the study, thesatellite data of Sentinel-3A, Jason-2 and CryoSat-2 are assessed incomparison with in situ measurements and spectral wave model (WAM)simulations. Intercomparisons between remote sensing and in situ observationsdemonstrate that the overall quality of the former is good over the North Seaand Baltic Sea throughout the study period, although the significant waveheights estimated based on satellite data tend to be greater than the in situmeasurements by 7 to 26 cm. The quality of all satellite data nearthe coastal area decreases; however, within 10 km off the coast,Sentinel-3A performs better than the other two satellites. Analyses in whichdata from satellite tracks are separated in terms of onshore and offshoreflights have been carried out. No substantial differences are found whencomparing the statistics for onshore and offshore flights. Moreover, nosubstantial differences are found between satellite tracks under variousmetocean conditions. Furthermore, the satellite data quality does not dependon the wind direction relative to the flight direction. Thus, the quality ofthe data obtained by the new Sentinel-3A satellite over coastal areasis improved compared to that of older satellites.