Synergetic Use of Radar and Optical Satellite Images to Support Severe Storm Prediction for Offshore Wind Farming

Abstract

In this paper we show how satellite images taken by space-borne radar sensors can be used to determine mesoscale high resolution wind fields in synergy with optical data. The aim of this study is to analyse severe weather systems, in particular to describe the spatial evolution of the atmospheric boundary layer processes involved in cold air outbreaks. A severe weather event happened in early November 2006 over the North Sea and damaged the research platform FiNO 1. This case of a particularly intense cold air outbreak over the North Sea is investigated using satellite data. Atmospheric boundary layer rolls and open cell convection were observed by the Advanced Synthetic Aperture Radar (ASAR) and the Medium Resolution Imaging Spectrometer (MERIS) instrument, sensors on board the ENVISAT satellite. Cloud patterns parallel as well as perpendicular to the mean wind direction showing a cell structure of about 15 km diameter. Similar patterns were observed in SAR images. These are believed to be surface effects of gust fronts induced by the mesoscale cellular convection and enhanced by the overall northwesterly flow. The phenomenon is explained by downward transport of higher momentum in convective clouds. The satellite data are used to validate numerical model results (LM, HIRLAM). The focus of this paper is on the impact of high variability in wind speed of mesoscale convective cloud patterns, which are not well captured by these numerical models.