7 research outputs found
Simulation hydrologique en région méditerranéenne avec SAFRAN-ISBA-MODCOU : amélioration de la physique et évaluation des risques dans le cadre du changement climatique
Le modĂšle SAFRAN-ISBA-MODCOU est Ă©valuĂ© et sa physique amĂ©liorĂ©e. L'analyse mĂ©tĂ©orologique SAFRAN est tout d'abord validĂ©e en dĂ©tail. Le modĂšle de surface ISBA est ensuite modifiĂ© pour mieux dĂ©crire la conductivitĂ© hydraulique dans le sol. Une stratĂ©gie de calibration est dĂ©finie et appliquĂ©e Ă l'Ă©chelle de la France. Le modĂšle amĂ©liorĂ© est finalement utilisĂ© pour Ă©valuer les impacts du changement climatique en rĂ©gion mĂ©diterranĂ©enne. Un scĂ©nario d'un modĂšle de climat rĂ©gional est dĂ©sagrĂ©gĂ© en utilisant deux mĂ©thodes diffĂ©rentes. L'Ă©tude montre que les incertitudes liĂ©es Ă la dĂ©sagrĂ©gation sont importantes. L'incertitude au modĂšle d'impact est moindre, mais doit ĂȘtre prise en compte pour les extrĂȘmes. Dans cette rĂ©gion les dĂ©bits extrĂȘmes et, parfois, moyens, augmenteront pendant la premiĂšre moitiĂ© du XXIe siĂšcle. A la fin du siĂšcle le scĂ©nario indique une baisse des dĂ©bits moyens dĂ©croisent et une stabilitĂ© des dĂ©bits extrĂȘmes, ce qui conduit Ă une augmentation de la variabilitĂ©.The SAFRAN-ISBA-MODCOU model is assessed and its physics are improved. The SAFRAN meteorological analysis is first validated in detail. The surface model ISBA is then modified to better describe the hydraulic conductivity in the soil. A strategy of calibration is defined and applied at the scale of France. The improved model is then used to assess the impacts of climate change in the Mediterranean region. A regional climate model is downscaled by two different methods. The study shows that the uncertainties related to the downscaling are important. Uncertainty related to the impact model is smaller, but must be taken into account for the extremes. In this region, the extremes of riverflows, and sometimes the means, will increase during the first half of the twenty-first century. At the end of the century, the scenario indicates a decline of the average of riverflows and the extremes will remain stable, leading to increased variability
Scaling precipitation extremes with temperature in the Mediterranean: past climate assessment and projection in anthropogenic scenarios
Simulation hydrologique en région méditerranéenne avec SAFRAN-ISBA-MODCOU (amélioration de la physique et évaluation des risques dans le cadre du changement climatique)
TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF
Irrigation Mapping Using Sentinel-1 Time Series at Field Scale
The recently launched Sentinel-1 satellite with a Synthetic Aperture Radar (SAR) sensor onboard offers a powerful tool for irrigation monitoring under various weather conditions, with high spatial and temporal resolution. This research discusses the potential of different metrics calculated from the Sentinel-1 time series for mapping irrigated fields. A methodology for irrigation mapping using SAR data is proposed. The study is performed using VV (vertical–vertical) and VH (vertical–horizontal) polarizations over an agricultural site in Urgell, Catalunya (Spain). With field segmentation information from SIGPAC (the Geographic Information System for Agricultural Parcels), the backscatter intensities are averaged within each field. From the Sentinel-1 time series for each field, the statistics and metrics, including the mean value, the variance of the signal, the correlation length, and the fractal dimension, are analyzed. With the Support Vector Machine (SVM), the classification of irrigated crops, irrigated trees, and non-irrigated fields is performed with the metrics vector. The results derived from the SVM are validated with ground truthing from SIGPAC over the whole study area, with a good overall accuracy of 81.08%. Random Forest (RF) machine classification is also tested in this study, which gives an accuracy of around 82.2% when setting the tree depth at three. The methodology is based only on SAR data, which makes it applicable to all areas, even with frequent cloud cover, but this method may be less robust when irrigation is less dominated to soil moisture change
Scaling precipitation extremes with temperature in the Mediterranean: past climate assessment and projection in anthropogenic scenarios
International audienceIn this study we investigate the scaling of precipitation extremes with temperature in the Mediterranean region by assessing against observations the present day and future regional climate simulations performed in the frame of the HyMeX and MED-CORDEX programs. Over the 1979â2008 period, despite differences in quantitative precipitation simulation across the various models, the change in precipitation extremes with respect to temperature is robust and consistent. The spatial variability of the temperatureâprecipitation extremes relationship displays a hook shape across the Mediterranean, with negative slope at high temperatures and a slope following ClausiusâClapeyron (CC)-scaling at low temperatures. The temperature at which the slope of the temperatureâprecipitation extreme relation sharply changes (or temperature break), ranges from about 20 °C in the western Mediterranean to <10 °C in Greece. In addition, this slope is always negative in the arid regions of the Mediterranean. The scaling of the simulated precipitation extremes is insensitive to oceanâatmosphere coupling, while it depends very weakly on the resolution at high temperatures for short precipitation accumulation times. In future climate scenario simulations covering the 2070â2100 period, the temperature break shifts to higher temperatures by a value which is on average the mean regional temperature change due to global warming. The slope of the simulated future temperatureâprecipitation extremes relationship is close to CC-scaling at temperatures below the temperature break, while at high temperatures, the negative slope is close, but somewhat flatter or steeper, than in the current climate depending on the model. Overall, models predict more intense precipitation extremes in the future. Adjusting the temperatureâprecipitation extremes relationship in the present climate using the CC law and the temperature shift in the future allows the recovery of the temperatureâprecipitation extremes relationship in the future climate. This implies negligible regional changes of relative humidity in the future despite the large warming and drying over the Mediterranean. This suggests that the Mediterranean Sea is the primary source of moisture which counteracts the drying and warming impacts on relative humidity in parts of the Mediterranean region
Scaling precipitation extremes with temperature in the Mediterranean: past climate assessment and projection in anthropogenic scenarios
International audienceFuture climate change projections indicate that many temperature and precipitation extremes become more frequent and intense in a warmer climate on a global scale, and concomitantly the risks of severe impacts to society will increase, calling for proactive adaptation measures. In order to support the adaptation decision making process, information on climate extremes is especially needed on a regional to local scale including time scales from sub-seasons to decades