Evidence of a topographic signal in surface soil moisture derived from ENVISAT ASAR wide swath data

(2016) Evidence of a topographic signal in surface soil moisture derived from ENVISAT ASAR wide swath data. It is advisable to refer to the publisher's version if you intend to cite from the work. All outputs in CentAUR are protected by Intellectual Property Rights law, including copyright law. Copyright and IPR is retained by the creators or other copyright holders. Terms and conditions for use of this material are defined in the End User Agreement. Abstract 10 11 The susceptibility of a catchment to flooding is affected by its soil moisture prior to an extreme 12 rainfall event. While soil moisture is routinely observed by satellite instruments, results from 13 previous work on the assimilation of remotely sensed soil moisture into hydrologic models have 14 been mixed. This may have been due in part to the low spatial resolution of the observations 15 used. In this study, the remote sensing aspects of a project attempting to improve flow 16 predictions from a distributed hydrologic model by assimilating soil moisture measurements are 17 described. Advanced Synthetic Aperture Radar (ASAR) Wide Swath data were used to measure 18 soil moisture as, unlike low resolution microwave data, they have sufficient resolution to allow 19 soil moisture variations due to local topography to be detected, which may help to take into 20 account the spatial heterogeneity of hydrological processes. Surface soil moisture content 21 (SSMC) was measured over the catchments of the Severn and Avon rivers in the South West 22 UK. To reduce the influence of vegetation, measurements were made only over homogeneous 23 2 pixels of improved grassland determined from a land cover map. Radar backscatter was 1 corrected for terrain variations and normalised to a common incidence angle. SSMC was 2 calculated using change detection.