Improvement of the performance of the SAFRAN-ISBA-MODCOU model for hydrological applications on the Mediterranean region of France.
The SIM suite is composed of the SAFRAN meteorological analysis, the surface scheme ISBA and the distributed hydrological model MODCOU. This model is being used over France for both research and operational applications.
In this work, some modifications to the physics and the parameters have been applied to the ISBA model aiming to improve its hydrological performance in the Mediterranean region of France, as the model will be used for further studies in this region under the framework of the CYPRIM project.
Soil hydrological transfers have been modified introducing an exponential profile of hydraulic conductivity at saturation in the three layered version of ISBA. It is, in fact, the parameterisation developed and implemented at the regional and local scales by Decharme et al (2006). Two new parameters are introduced, representing the sub-grid hydrological transfers: near the surface the hydraulic conductivity is increased, and decreases in the deeper layer. Sensibility tests have bee done with different values of these parameters. The impact over water and energy fluxes, and over the river discharges have been evaluated. After calibration, the river discharges are improved. This improvement is mainly due to a better reactivity of the runoff and a better low flow due to a slower drainage.
Sensibility tests of the depth of the root soil layer of Mediterranean vegetation types have shown that higher values of this depth were also important to better reproduce the observed discharges.
HyMeX – Hydrological cycle in the Mediterranean Experiment 2010-2020