Assimilation de débits observés pour des prévisions hydrologiques probabilistes sur la France
Thirel, G.
Observed discharge assimilation for probabilistic hydrological forecasts over France
A 10-day hydrological ensemble prediction system is running on France at Météo-France since 2004. This system uses the SAFRAN-ISBA-MODCOU chain as well as the meteorological ensemble predictions from the ECMWF. In order to be closer to discharge observations and thus respond to end-users requests, a past discharge assimilation system has been studied with the use of an improvement of the physics of ISBA. The discharge assimilation is described in this article ; it aims at getting closer to the observed discharges, the streamflows simulated by the chain (SIM-analyse) initializing the ensemble streamflow forecasts, by adjusting the ISBA soil moisture. The impact of the discharge assimilation, as well on SIM-analyse as on the ensemble streamflow forecasts, has been quantified. The improvement of the statistical scores is real, even for 10-day lead-time forecasts.
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