Impact of precipitation and land biophysical variables on the simulated discharge of European and Mediterranean rivers
Abstract. This study investigates the use of the ERA-Interim 3-hourly atmospheric reanalysis over Europe and the Mediterranean basin, to drive the ISBA-TRIP continental hydrological system, at a spatial resolution of 0.5°, over the 1991–2008 period. Several versions of the representation of evapotranspiration in the ISBA land surface model are used to simulate the runoff which is converted into river discharge by the TRIP river routing model. In particular, the impact of using contrasting representations of the vegetation variables is investigated: ISBA is used together with its upgraded carbon flux version (ISBA-A-gs). The latter is either driven by a satellite-derived climatology of the Leaf Area Index (LAI) or performs prognostic LAI simulations. As ERA-Interim tends to underestimate precipitation, a number of precipitation corrections are proposed. In particular, the monthly GPCC precipitation product is used to un-bias the 3-hourly ERA-Interim estimates. This correction markedly improves the match between the ISBA-TRIP simulations and the river discharge observations of the Global Runoff Data Centre (GRDC), at 150 gauging stations. The interactive LAI version of ISBA-A-gs does not perform as well as the original ISBA model at springtime. On the other hand, the use of the ISBA-A-gs model allows a better representation of river discharge at low water levels. Constraining the ISBA-A-gs LAI with satellite-derived LAI data improves the simulations at springtime.