Hybridation de réanalyses météorologiques de surface pour les zones de montagne : exemple du produit DuO sur le bassin de la Durance

Abstract : ABSTRACT.-In mountainous regions, near-surface meteorological reanalyses can carry significant uncertainties due to the complex topography and the scarcity of observations. Combining different reanalyses has proved to be efficient in reducing these uncertainties. This technique is applied over a French mountainous basin in the southern Alps, the Durance basin, where two reanalyses exist : SAFRAN and SPAZM. The comparison of the features of these two rea-nalyses shows that they are complementary. The precipitations provided by SPAZM are at a finer spatial resolution than SAFRAN and are based on more observations at high altitudes. However, on the contrary to SAFRAN, SPAZM does not provide the full set of atmospheric variables required by hydrological models based on water and energy balance. SPAZM and SAFRAN were thus combined. Precipitation and temperature from SAFRAN are corrected by monthly temperature and precipitation from SPAZM, and the other variables from SAFRAN are then corrected accordingly. As a result, the meteorological product called DuO was obtained, providing eight atmospheric variables (temperature at 2 m, rainfall, snowfall, incoming solar and infrared radiation, air humidity, wind speed and potential evapotranspiration), at the hourly timescale and at the 1-km 2 resolution. The strong topographical heterogeneity is thus better represented in the upstream part of the Durance catchment. DuO is tested for hydrological modelling, using the Catchment Land Surface Model (CLSM), a land surface model distributed over sub-catchments. The analysis of various output variables (stream-flow, snowpack and evapotranspiration) shows that the hybridization of the two reanalyses benefits from their respective qualities and yields a more realistic representation of the hydrological processes in the CLSM model.
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Claire Magand, Agnès Ducharne, François Tilmant, Nicolas Le Moine, Eric Sauquet, et al.. Hybridation de réanalyses météorologiques de surface pour les zones de montagne : exemple du produit DuO sur le bassin de la Durance. La Houille Blanche - Revue internationale de l'eau, EDP Sciences, 2018, 3 (3), pp.77 - 85. ⟨10.1051/lhb/2018035⟩. ⟨hal-01899583⟩

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