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Filahi S.,Direction de la Meteorologie Nationale | Filahi S.,Hassan II University | Tanarhte M.,Max Planck Institute for Chemistry | Tanarhte M.,Hassan II University | And 3 more authors.
Theoretical and Applied Climatology | Year: 2015

The purpose of this paper is to provide a summary of Morocco’s climate extreme trends during the last four decades. Indices were computed based on a daily temperature and precipitation using a consistent approach recommended by the ETCCDI. Trends in these indices were calculated at 20 stations from 1970 to 2012. Twelve indices were considered to detect trends in temperature. A large number of stations have significant trends and confirm an increase in temperature, showing increased warming during spring and summer seasons. The results also show a decrease in the number of cold days and nights and an increase in the number of warm days and nights. Increasing trends have also been found in the absolute warmest and coldest temperatures of the year. A clear increase is detected for warm nights and diurnal temperature range. Eight indices for precipitation were also analyzed, but the trends for these precipitation indices are much less significant than for temperature indices and show more mixed spatial patterns of change. Heavy precipitation events do not exhibit significant trends except at a few locations, in the north and central parts of Morocco, with a general tendency towards drier conditions. The correlation between these climate indices and the large-scale atmospheric circulations indices such as the NAO, MO, and WEMO were also analyzed. Results show a stronger relationship with these climatic indices for the precipitation indices compared to the temperature indices. The correlations are more significant in the Atlantic regions, but they remain moderate at the whole country scale. © 2015 Springer-Verlag Wien

Hublart P.,CNRS HydroSciences Montpellier Laboratory | Ruelland D.,French National Center for Scientific Research | Garcla De Cortazar Atauri I.,French National Institute for Agricultural Research | Ibacache A.,Institute Investigaciones Agropecuarias
IAHS-AISH Proceedings and Reports | Year: 2015

This paper explores the reliability of low-flow simulations by conceptual models in a semi-arid, Andean catchment (30° S) facing climate variability and water-use changes. Depending on water availability, a significant part of surface water resources are diverted to meet irrigation requirements. In return, these water withdrawals are likely to influence the hydrological behavior of the catchment. The value of model-based analyses thus relies on our ability to adequately represent the complex interactions between climate variability, human-induced flow perturbations and crop water use. In this study, a parsimonious hydrological model (GR4J) including a snow routine was combined with a model of irrigation water-use (IWU) to provide a new, 6-parameter model of the catchment behavior (called GR4J/IWU). The original, 4-parameter GR4J model and the 6-parameter GR6J model were also used as benchmarks to evaluate the usefulness of explicitly accounting for water abstractions. Calibration and validation of these three models were performed successively over two different 5-year periods representing contrasted water-use and climate conditions. Overall, the GR4J/IWU model provided better simulations than the GR4J and GR6J models over both periods. Further research is required to quantify the predictive uncertainty associated with model structures, parameters and inputs.

Ducrocq V.,Meteo - France | Braud I.,IRSTEA | Davolio S.,CNR Institute of Neuroscience | Ferretti R.,University of LAquila | And 46 more authors.
Bulletin of the American Meteorological Society | Year: 2014

The establishment of a cold pool can maintain intense convective systems far upstream from the mountain barrier. For instance, the unusual location of the HPE over the Gard plain in September 2002 was explained by the presence of a low-level cold pool induced by the convective system itself. These lifting mechanisms were further studied by examining how characteristics of a conditionally unstable flow impinging upon the coastal complex terrain of the northwestern Mediterranean influence the location and intensity of quasi-stationary MCSs. A dedicated field campaign was thus designed to improve the present state of knowledge of Mediterranean HPEs and flash-flooding events and to improve numerical models. The Hpiconet rain supersite, located in the eastern extremity of the northern east west transect, aimed at characterizing the very finescale variability of the surface rainfall with one rain gauge or disdrometer per 4 km2.

Neppel L.,CNRS HydroSciences Montpellier Laboratory | Arnaud P.,IRSTEA | Borchi F.,CNRS HydroSciences Montpellier Laboratory | Carreau J.,CNRS HydroSciences Montpellier Laboratory | And 6 more authors.
Houille Blanche | Year: 2014

This paper focuses on a comparison of 3 families of extreme rainfall frequency analysis methods: 1) purely local approaches which consist in fitting a probability distribution function (pdf) to a sample of observed daily rainfall, 2) local-regional approaches where the sample of annual maxima daily rainfall at the target site is enlarged by rainfall observations in a surrounding homogeneous neighbourhood and 3) purely regional approaches for estimating the extreme rainfall pdf at an ungaged site. For 2) and 3) the extreme rainfall pdf can be estimated either by frequency analysis based on the extreme value theory or from the simulations of the French stochastical rainfall model named SHYREG. The comparison relies on a dataset of 1568 daily rainfall gages belonging to the French Weather Service (Météo-France) or the French Electricity Company (EDF) in the southern half of France. A comparison methodology and several comparison criteria have been defined to evaluate the bias and variances of the quantiles and the confidence intervals. The main results are: 1) At the local scale, the General Pareto Distribution fitted on a peak over threshold sample performs better that the Generalized Extreme Value pdf fitted on max annual sample, 2) the exponential pdf is clearly unsuitable in Mediterranean area, 3 the local approaches perform poorly compared to the local-regional and purely regional frequency analyses except for the MEWP weather pattern frequency analysis which is comparable to the local regional frequency analysis for non-Mediterranean climate and when the calibration sample size exceeds 10 years, 4) the local regional frequency analysis and the SHYREG method performances are comparable, and 5) there is only a weak decrease in performances when using a purely regional frequency analysis instead of a local-regional frequency analysis. © 2014 Société Hydrotechnique de France.

Fabre J.,French National Center for Scientific Research | Collet L.,CNRS HydroSciences Montpellier Laboratory | Milano M.,CNRS HydroSciences Montpellier Laboratory | Ruelland D.,French National Center for Scientific Research | And 3 more authors.
IAHS-AISH Proceedings and Reports | Year: 2014

This study aims at defining the main stakes in the development of a generic, multidisciplinary approach to evaluate water supply capacity and its spatial and temporal variability over long time periods. A common modelling framework was applied over two Mediterranean basins with different physical and anthropogenic characteristics: the Ebro (85 000 km2, Spain) and the Herault (2500 km2, France) catchments. Runoff and river flow regulations were simulated using conceptual hydrological models and reservoir management models, respectively. Water demand was estimated from population and unit water consumption data for the domestic sector, and from irrigated area, crop, soil and climatic data for the agricultural sector. A ratio comparing water resource availability to water demand was computed on each catchment. Working on two catchments with different geographical scales and water management issues underlines the challenges in the development of a reliable and generic water allocation assessment method. © Copyright 2014 IAHS Press.

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