Abstract
Abstract. In the framework of the international CORDEX program, new regional climate model (RCM) simulations at high spatial resolutions are becoming available for the Mediterranean region (Med-CORDEX initiative). This study provides the first evaluation for hydrological impact studies of one of these high-resolution simulations in a 1800 km2 catchment located in North Morocco. Different approaches are compared to analyze the climate change impacts on the hydrology of this catchment using a high-resolution RCM (ALADIN-Climate) from the Med-CORDEX initiative at two different spatial resolutions (50 and 12 km) and for two different Radiative Concentration Pathway scenarios (RCP4.5 and RCP8.5). The main issues addressed in the present study are: (i) what is the impact of increased RCM resolution on present-climate hydrological simulations and on future projections? (ii) Are the bias-correction of the RCM model and the parameters of the hydrological model stationary and transferable to different climatic conditions? (iii) What is the climate and hydrological change signal based on the new Radiative Concentration Pathways scenarios (RCP4.5 and RCP8.5)? Results indicate that high resolution simulations at 12 km better reproduce the seasonal patterns, the seasonal distributions and the extreme events of precipitation. The parameters of the hydrological model, calibrated to reproduce runoff at the monthly time step over the 1984–2010 period, do not show a strong variability between dry and wet calibration periods in a differential split-sample test. However the bias correction of precipitation by quantile-matching does not give satisfactory results in validation using the same differential split-sample testing method. Therefore a quantile-perturbation method that does not rely on any stationarity assumption and produces ensembles of perturbed series of precipitation was introduced. The climate change signal under scenarios 4.5 and 8.5 indicates a decrease of respectively −30 to −57% in surface runoff for the mid-term (2041–2062), when for the same period the projections for precipitation are ranging between −15 and −19% and for temperature between +1.3 and +1.9 °C.
Highlights
The most common approach for hydrological impact studies of climate change is to run hydrological models with climate scenarios, usually provided by the outputs of precipitation and temperature from climate models downscaled or corrected to the catchment of interest (Etchevers et al, 2002; Fowler et al, 2007; Chiew et al, 2009; Senatore et al, 2011; Ruelland et al, 2012)
The new generation of regional climate model simulations dedicated to the Mediterranean area such as those provided by the Med-CORDEX initiative in the line with the CMIP5 and CORDEX programs aims at increasing the reliability of past and future regional climate information and understanding the processes that are responsible for the Mediterranean climate variability and trends
This study provides the first evaluation for hydrological impact studies of one of the high-resolution regional climate model (RCM) simulations available in framework of the Med-CORDEX initiative: the new version of the ALADIN-Climate model at two resolutions, 12 and 50 km, with the lateral boundary conditions provided by ERA-Interim and the CNRM-CM5 global climate models (GCM) for the historical period and the scenarios RCP4.5 and 8.5
Summary
The most common approach for hydrological impact studies of climate change is to run hydrological models with climate scenarios, usually provided by the outputs of precipitation and temperature from climate models downscaled or corrected to the catchment of interest (Etchevers et al, 2002; Fowler et al, 2007; Chiew et al, 2009; Senatore et al, 2011; Ruelland et al, 2012). The Mediterranean region is a transition zone between arid and temperate climates with several mountainous areas, a complex climate system affected by the interactions between midlatitude and sub-tropical processes. The new generation of regional climate model simulations dedicated to the Mediterranean area such as those provided by the Med-CORDEX initiative (www.medcordex.eu, Ruti et al, 2013; Herrmann et al, 2011) in the line with the CMIP5 and CORDEX programs aims at increasing the reliability of past and future regional climate information and understanding the processes that are responsible for the Mediterranean climate variability and trends
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