SAR SATELLITE IMAGE DERIVED WIND SPEED MAPS VALIDATED WITH IN-SITU METEOROLOGICAL OBSERVATIONS AND FOOTPRINT THEORY FOR OFFSHORE WIND RESOURCE MAPPING

摘要

Synthetic Aperture Radar (SAR) satellite images from the European satellite ERS-2 are used for deriving wind speeds and wind directions offshore for 16 cases in the North Sea. The area investigated is the Horns Rev site 15 km west of the Jutland coast in Denmark. It is investigated how well satellite SAR wind speed maps correspond to in-situ mast observations. The SAR satellite wind speed mapping is performed with an empirical algorithm (CMOD-IFR2). The physical principle is based on the near-instantaneous wind interaction at the sea surface generating capillary and short gravity waves. The pattern of these waves is related to the radar backscatter signals received by the satellite. The resolution of the maps is 400 by 400 m covering 100 by 100 km as snapshots (within a few seconds) around every third day. A simple footprint method is used as a tool to compare spatial (SAR) and temporal (meteorological) data. The footprint theory takes into account the relative influence of the upwind conditions to the observed wind speed as a function of measurement height and stability. The results are promising with high correlation between in-situ and SAR wind speed and SAR wind direction.