Estimation of wind speed over lakes in Central Europe using spaceborne C-band SAR

Abstract

The Sentinel-1 satellite mission provides high-resolution, all-weather, day and night Synthetic Aperture Radar images. Studies about wind parameters above the ocean are frequent, inland lakes were seldom investigated. The objective of this article is to investigate the potential of C-band SAR for wind retrieval over lakes for evaluation of representativeness of meteorological station data. A number of lakes from Austria and Hungary (lakes in Salzkammergut, Lake Neusiedl and Lake Balaton), where wind measurements from automatic weather stations are available from the surroundings, has been selected for this study. Functions for speed retrieval are developed from empirical relationships for both available polarizations, VV and VH. Meteorological station data are used for calibration and validation. Best results were obtained for VV although with a dependency on incidence angle. Functions for different incidence angles according to the wind speed were, therefore, determined. There is a good correlation between the measured and the calculated wind speed (R of 0.71–0.91 for calibration sites; average R 0.71 for all sites). Average wind speed patterns for the lakes can be derived, but need to be analyzed separately for descending and ascending acquisitions due to difference in daytime (morning versus late afternoon).