SAR Derived Wind Fields of Mesoscale Cyclones

In this study we show how satellite images taken by space-borne radar sensors can be used to determine mesoscale high resolution wind fields in synergy with cloud parameters from optical data. The aim of this study is to use Synthetic Aperture Radar (SAR) and Medium Resolution Imaging Spectrometer (MERIS) onboard the ENVIronmental SATellite (ENVISAT) in synergy to analyse severe weather systems. We investigated the fine scale structure of a severe weather case on Nov 1, 2006 over the North Sea using satellite data. The satellite data are compared with numerical model results of the German Weather Service "Lokal Modell", LM and the High Resolution Limited Area Model, HIRLAM. LM and HIRLAM show differences in mesoscale turbulent behaviour. Maximum wind speeds of up to 25 m/s are measured by SAR and are confirmed by the models. Significant differences are observed in the location of the maxima. Due to the high resolution ENVISAT ASAR measurements provide very detailed information on small scale atmospheric features, which seem to be not well captured by the analyzed numerical models in particular in coastal areas..