Assimilation of TerraSAR-X data into a snowpack model

This paper presents an approach using data assimilation to take into account X-band Synthetic Aperture Radar (SAR) satellite observations in a detailed snowpack model. The SURFEX/Crocus snow model, developed by MeteoFrance, is used to simulate the detail stratigraphy of multilayer snow-pack from meteorological conditions. The Dense Media Radiative Transfer (DMRT) model allows the simulation of SAR backscattering coefficient using the physical parameters of snowpack (density and optical grain diameter of each layer). The development of an adjoint model of the DMRT and the implementation of three-dimensional variational (3D-Var) data assimilation algorithm enable us to reduce the discrepancy between the backscattering coefficients simulated using DMRT and measured using SAR satellite, through modifying the previously said physical parameters of snowpack. This approach provides the ability to constrain the detailed snowpack model SURFEX/Crocus using SAR observations and allows the retrieval of snowpack properties such as Snow Water Equivalent (SWE). Case study has been carried out using a time series of TerraSAR-X acquisitions on Argentière glacier (Chamonix Mont Blanc, France) in winter 2008-2009.