Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 13 2 2009 10.5194/hess-13-115-2009 http://www.hydrol-earth-syst-sci.net/13/115/2009/ http://www.hydrol-earth-syst-sci.net/13/115/2009/hess-13-115-2009.html http://www.hydrol-earth-syst-sci.net/13/115/2009/hess-13-115-2009.pdf 115 124 2009-02-04 An evaluation of ASCAT surface soil moisture products with in-situ observations in Southwestern France C. Albergel C. Rüdiger D. Carrer J.-C. Calvet calvet@meteo.fr N. Fritz V. Naeimi Z. Bartalis S. Hasenauer CNRM/GAME (Météo-France, CNRS), Toulouse, France Institute of Photogrammetry and Remote Sensing, University of Vienna, Vienna, Austria now at: Department of Civil and Environmental Engineering, The University of Melbourne, Melbourne, Australia A long term data acquisition effort of profile soil moisture is currently underway at 13 automatic weather stations located in Southwestern France. In this study, the soil moisture measured in-situ at 5 cm is used to evaluate the normalised surface soil moisture (SSM) estimates derived from coarse-resolution (25 km) active microwave data of the ASCAT scatterometer instrument (onboard METOP), issued by EUMETSAT for a period of 6 months (April–September) in 2007. The seasonal trend is removed from the satellite and in-situ time series by considering scaled anomalies. One station (Mouthoumet) of the ground network, located in a mountainous area, is removed from the analysis as very few ASCAT SSM estimates are available. No correlation is found for the station of Narbonne, which is close to the Mediterranean sea. On the other hand, nine stations present significant correlation levels. For two stations, a significant correlation is obtained when considering only part of the ASCAT data. The soil moisture measured in-situ at those stations, at 30 cm, is used to estimate the characteristic time length (<i>T</i>) of an exponential filter applied to the ASCAT product. The best correlation between a soil water index derived from ASCAT and the in-situ soil moisture observations at 30 cm is obtained with a <i>T</i>-value of 14 days. % vor jede Referenz Albergel, C., Rüdiger, C., Pellarin, T., Calvet, J.-C., Fritz, N., Froissard, F., Suquia, D., Petitpa, A., Piguet, B., and Martin, E.: From near-surface to root-zone soil moisture using an exponential filter: an assessment of the method based on in-situ observations and model simulations, Hydrol. Earth Syst. Sci., 12, 1323–1337, 2008. % vor jede Referenz Bartalis, Z., Wagner, W., Naeimi, V., Hasenauer, S., Scipal, K., Bonekamp, H., Figa, J., and Anderson, C.: Initial soil moisture retrievals from the METOP-A advanced Scatterometer (ASCAT), Geophys. Res. 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