Downscaling and hydrological uncertainties in 20th century hydrometeorological reconstructions over France
Incertitudes de descente d'échelle et hydrologique dans les reconstructions hydrométéorologiques sur le XXe siècle sur la France
Vidal, J.P. ; Caillouet, L. ; Dayon, G. ; Boe, J. ; Sauquet, E. ; Thirel, G. ; Graff, B.
Type de document
Affiliation de l'auteur
IRSTEA LYON UR HHLY FRA ; IRSTEA LYON UR HHLY FRA ; URA 1875 CNRS CERFACS TOULOUSE FRA ; URA 1875 CNRS CERFACS TOULOUSE FRA ; IRSTEA LYON UR HHLY FRA ; IRSTEA ANTONY UR HBAN FRA ; CNR LYON FRA
Résumé / Abstract
The record length of streamflow observations is generally limited to the last 50 years, which is not enough to properly explore the natural hydrometeorological variability, a key to better understand the effects of anthropogenic climate change. This work proposes a comparison of different hydrometeorological reconstruction datasets over France built on the downscaling of the NOAA 20th century global extended reanalysis (20CR, Compo et al., 2011). It aims at assessing the uncertainties related to these reconstructions and improving our knowledge of the multi-decadal hydrometeorological variability over the 20th century. High-resolution daily meteorological reconstructions over the period 1871-2012 are obtained with two statistical downscaling methods based on the analogue approach: the deterministic ANALOG method (Dayon et al., 2015) and the probabilistic SCOPE method (Caillouet et al., 2016). These reconstructions are then used as forcings for the GR6J lumped conceptual rainfall-runoff model and the SIM physically-based distributed hydrological model, in order to derive daily streamflow reconstructions over a set of around 70 reference near-natural catchments. Results show a large multi-decadal streamflow variability over the last 140 years, which is however relatively consistent over France. Empirical estimates of three types of uncertainty – structure of the downscaling method, small-scale internal variability, and hydrological model structure – show roughly equal contributions to the streamflow uncertainty at the annual time scale, with values as high as 20% of the interannual mean.
EGU General Assembly 2017, 23/04/2017 - 28/04/2017, Vienne, AUT