Half hourly wind data from satellite derived water vapour measurements

Abstract

Vector fields derived from successive METEOSAT water vapour (WV) images (5.7 – 7.1 μm) have been produced operationally at ESOC (European Space Operations Centre) four times per day since autumn 1993. The development of a fast Transputer Augmented Workstation (TAW) has enabled a real time derivation of these vector fields on a half hourly basis. The WV vector fields describe accurately the large scale high level atmospheric motion, but the existence of some bad vectors reduce the overall quality of the fields. In order to identify these odd winds, an automatic quality control, which assigns a quality indicator to each vector, is performed. These indicators can then be utilised in e.g. Numerical Weather Prediction (NWP) models during data assimilation. The development of the NWP assimilation schemes have now enabled the usage of data at the frequency produced by the TAW and the TAW WV vector fields provide an excellent opportunity to validate the new assimilation schemes. Simultaneously performance of the TAW quality control can be assessed. The TAW is also producing information related to the Upper Tropospheric Humidity (UTH) and Total Column Water (TCW). In conjunction with the WV vector fields the complicated interaction between atmospheric humidity and dynamics can be better understood. In order to address these question a Water Vapour Wind Vector (WVWV) validation campaign was performed was performed during August and September 1994. After a brief introduction to the TAW and the quality of the WVWV fields, this paper will present the first results derived with the TAW, the critical aspects addressed during the WVWV campaign as well as outlining the main areas of future development and research.