Advances in Geosciences www.adv-geosci.net 1680-7340 1680-7359 26 11th EGU Plinius Conference on Mediterranean Storms (2009) 2010 10.5194/adgeo-26-77-2010 http://www.adv-geosci.net/26/77/2010/ http://www.adv-geosci.net/26/77/2010/adgeo-26-77-2010.html http://www.adv-geosci.net/26/77/2010/adgeo-26-77-2010.pdf 77 82 2010-07-22 The use of products from ground-based GNSS observations in meteorological nowcasting E. Terradellas eterradellasj@aemet.es B. Téllez Agencia Estatal de Meteorología, Barcelona, Spain Convective rainfall is often focalized in areas of moisture convergence. A close relationship between precipitation and fast variations of vertically-integrated water vapour (IWV) has been found in numerous cases. Therefore, continuous monitoring of atmospheric humidity and its spatial distribution is crucial to the operational forecaster for a proper nowcasting of heavy rainfall events. <br><br> The microwave signals continuously broadcasted by the Global Navigation Satellite Systems (GNSS) satellites are influenced by the water vapour as they travel through the atmosphere. Estimates of IWV retrieved from ground-based GNSS observations may, then, constitute a source of information on the horizontal distribution and the time evolution of atmospheric humidity. At the Spanish Meteorological Agency (AEMET), a near-real-time map of IWV estimates retrieved from ground GNSS measurements in the Iberian Peninsula and West Mediterranean region is operationally built and presented to the forecaster. The maps are generated every 15 minutes following a one-dimensional variational assimilation scheme with the previous map as the background state. <br><br> A case study is presented in order to illustrate some strengths and weaknesses of the product, to assess the potential benefit of using GNSS products in nowcasting and to define the steps to be done in order to make use of the full potential of the method. % vor jede Referenz Bevis, M., Businger, S., Herring, T. A., Rocken, C., Anthes, R. A., and Ware, R. H.: G.P.S. meteorology: remote sensing of atmospheric water vapour using the Global Positioning System, J. Geophys. Res., 97, 15787–15801, 1992. Bevis, M., Businger, S., Chiswell, S., Herirng, T. A., Anthes, R. A., Rockmen, C., and Ware, R. H.: GPS meteorology: Mapping zenith wet delays onto perceptible water, J. Appl. Meteor., 33, 379–386, 1994. Brunner, F. K. and Gu, M.: An improved model for the dual frequency ionospheric correction of GPS observations, Manusc. 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