VARIATIONAL DATA ASSIMILATION OF AIRSWOT AND SWOT DATA INTO THE 2D SHALLOW WATER MODEL DASSFLOW. METHOD AND TEST CASE ON GARONNE RIVER (FRANCE)

摘要

For continental water bodies and riverrnhydraulic studies, water level measurements arernfundamental information, yet they are currently mostlyrnprovided by punctual gauging stations located on thernmain river channel. That is why they are sparselyrndistributed in space and can have gaps in their timernseries (e.g. sensors failures). These issues can berncompensated by remote sensing data, which havernconsiderably contributed to improve the observation andrnunderstanding of physical processes in hydrology andrnhydraulics in general. Satellites such as SWOT (SurfacernWater and Ocean Topography) would give spatiallyrndistributed information on water elevations at anrnunprecedented resolution. Gathering pre-mission datarnover specific and varied science targets is the purpose ofrnthe AirSWOT airborne campaign in order to implementrnand test SWOT products retrieval algorithms. A reachrnof the Garonne River, downstream of Toulousern(FRANCE), is a proposed study area for AirSWOTrnflights. This choice is motivated by previous studiesrnalready performed on this section of 100km reach of thernriver. Moreover, on this highly instrumented and studiedrnportion of river many typical free surface flowrnmodelling issue has been encountered, and this riverrnreach represents the limit of SWOT observationrncapability. The 2D hydrodynamic model DassFlowrnespecially designed for variational data assimilation willrnbe used on this portion of the Garonne River withrncartographic sensitivity analysis. An identificationrnstrategy would allow retrieving spatial roughness alongrnthe main channel, variation of the local topographicrnslope or else temporal evolution of the streamflow.rnAddressing such problems and studying horizontal andrnvertical river sinuosity would improve fine scalernhydraulics representation and understanding, whichrncould additionally help to improve global dischargernalgorithms with different scales and complexity levels.