Ground-based GPS water vapour estimation: potential for meteorological forecasting

In order to assess the impact of ground-based GPS water vapour estimates in meteorological forecasting applications, estimates must be available within near real time and must be produced with an accuracy comparable with that of existing meteorological measurement techniques. Before the potential benefit of GPS-integrated water vapour (IWV) estimates in numerical weather prediction (NWP) models could be determined, extensive tests were performed to examine the effect of various process error models, constraints and estimation techniques involved within GPS processing procedures in order to devise a recommended processing strategy. Ten months of GPS data from a selection of stations, which are co-located with radiosonde launch sites, within the UK permanent GPS network, have been processed to validate these findings. Near real-time estimation issues have subsequently been examined, primarily using a sliding-window processing approach to demonstrate the feasibility of producing accurate GPS IWV estimates within the required time frame. Additionally, preliminary simulation work has been performed to assimilate GPS IWV into the UK Meteorological Office (UKMO) numerical weather prediction models, in preparation for impact assessments on the quality of mesoscale weather forecasts. Crown Copyright (C) 2001 Published by Elsevier Science Ltd. All rights reserved.