Using remotely sensed solar radiation data for reference evapotranspiration estimation at a daily time step

International audienceSolar radiation is an important climatic variable for assessing reference evapotranspiration (E0), but it is seldom available in weather station records. Meteosat satellite images processed with the Heliosat-2 method provide the HelioClim-1 database, which displays spatialized solar radiation data at a daily time step for Europe and Africa. The aim of the present work was to investigate the interest of satellite-sensed solar radiation for E0 calculation, where air temperature is the sole local weather data available. There were two study areas in Southern France. One (Southwest, SW) is characterized by Oceanic climate and the other (Southeast, SE) by Mediterranean climate. A data set of daily values for 19 weather stations spanning five years (2000–2004) was used. First, a sensitivity analysis of the Penman–Monteith formula to climate input variables was performed, using the Sobol' method. It shows that E0 is mainly governed by solar radiation during summer, and by wind speed during winter. Uncertainties of HelioClim-1 solar radiation data and their repercussions on E0 formulae were evaluated, using the FAO-56 Penman–Monteith formulae (PM) and radiation-based methods (Turc, TU; Priestley–Taylor, PT and Hargreaves-Radiation, HR). It was shown that HelioClim-1 data slightly underestimate solar radiation and provide relative RMSE (root mean square error) of 20% of the mean annual value for SW and 14% for SE. The propagation of HelioClim-1 data uncertainties is small in PM but considerable in radiation methods. Four estimation methods were then compared to PM data: the 1985 Hargreaves formula (HT) based on air temperature only; TU, PT and HR, based on air temperature and satellite-sensed solar radiation. Radiation methods were more precise and more accurate than HT, with RMSE ranging from 0.52 mm to 0.86 mm against 0.67–0.96 mm. These results suggest that using satellite-sensed solar radiation may improve E0 estimates for areas where air temperature is the only available record at ground level

Distinct and combined impacts of climate and land use scenarios on water availability and sediment loads for a water supply reservoir in northern Morocco

The objective of this study was to examine the impacts of climate and land use changes on water availability and sediment loads for a water supply reservoir in northern Morocco using data-intensive simulation models in a data-scarce region. Impacts were assessed by comparing the simulated water and sediment entering the reservoir between the future period 2031e2050 and the 1983e2010 reference period. Three scenarios of land use change and two scenarios of climate change were developed in the Tleta watershed. Simulations under current and future conditions were performed using the Soil and Water Assessment Tool (SWAT) model. The simulations showed that climate change will lead to a significant decrease in the annual water supply to the reservoir ( 16.9% and 27.5%) and in the annual volume of sediment entering the reservoir ( 7.4% and 12.6%), depending on the climate change scenarios tested. The three scenarios of land use change will lead to a moderate change in annual water inflow into the reservoir (between 6.7% and þ6.2%), while causing a significant decrease in sediment entering the reservoir ( 37% to 24%). The combined impacts of climate and land use changes will cause a reduction in annual water availability ( 9.9% to 33.3%) and sediment supplies ( 28.7% to 45.8%). As a result, the lifetime of the reservoir will be extended, but at the same time, the risk of water shortages will increase, especially from July to March. Therefore, alternative water resources must be considered.info:eu-repo/semantics/publishedVersio

IV Grid Plugtests: composing dedicated tools to run an application efficiently on Grid'5000

Exploiting efficiently the resources of whole Grid'5000 with the same application requires to solve several issues: 1) resources reservation; 2) application's processes deployment; 3) application's tasks scheduling. For the IV Grid Plugtests, we used a dedicated tool for each issue to solve. The N-Queens contest rules imposed ProActive for the resources reservations (issue 1). Issue 2 was solved using TakTuk which allows to deploy a large set of remote nodes. Deployed nodes take part in the deployment using an adaptive algorithm that makes it very efficient. For the 3rd issue, we wrote our application with Athapascan API whose model is based on the concepts of tasks and shared data. The application is described as a data-flow graph using the Shared and Fork keywords. This high level abstraction of hardware gives us an efficient execution with the Kaapi runtime engine using a work-stealing scheduling algorithm to balance the workload between all the distributed processes

Spatialisation fine des projections climatiques dans le bassin versant du Tleta, Nord Maroc

Local studies of climate change impact require high spatial resolution of climate predictions. Within ALMIRA research project, agronomists and hydrologists wish to integrate climate predictions into their models in order to characterize the behavior of Tleta watershed by 2050. Global and regional climate models can only apprehend it through one or fewer pixels at best. It is also essential to use a statistical downscaling method, which allows for improving spatial resolution. Based on climate predictions from the French ALADIN-Climate model and available climatic series, a processing sequence has been developed to provide spatialized fields of climatic variables over the period 2021-2060 at 1 km² resolution. Keywords: Climate predictions, Spatialization, Nakhla Watershed, Rif, MoroccoLes études locales de l’impact du changement climatique nécessitent des projections climatiques à haute résolution spatiale. Dans le cadre du projet de recherche ALMIRA, les agronomes et hydrologues souhaitent intégrer à leurs modèles des projections climatiques afin de caractériser le fonctionnement du bassin versant du Tleta à l’horizon des années 2050. Les modèles climatiques globaux et régionaux ne peuvent l’appréhender qu’à travers un, voire quelques pixels au mieux. Aussi, il est indispensable de pratiquer une descente d’échelle statistique qui permette d’affiner la résolution spatiale. En s’appuyant sur les projections climatiques issues du modèle français ALADIN-Climat et des sériesclimatiques disponibles, une chaîne de traitements a été développée afin de fournir des champs spatialisés de variables climatiques sur la période 2021-2060 à une maille de 1 km². Mots clés : Projections climatiques, Spatialisation, Bassin versant Nakhla, Rif, Maro

Microclimate beneath pine plantation, semi-mature pine plantation and mixed broadleaved-pine forest

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Direct and Indirect Analysis of the Elevational Shift of Larch Budmoth Outbreaks Along an Elevation Gradient

International audienceLarch budmoth (LBM) periodically defoliates alpine stands of European larch during vast outbreaks occurring generally at 8-10 year intervals. LBM outbreaks recently declined and the ongoing global warming has been pointed out as a possible cause of this decline. In this article, we reconstructed the recent history of LBM outbreaks at different elevations along a larch elevational gradient in the French Alps using direct and indirect observations based on tree-ring width and density analysis, and compared it with local climatic data. We found that LBM outbreaks time-series were better reconstructed with latewood density than with ring width. We also found that there was a recent but limited elevational shift of LBM outbreaks from medium toward higher elevations. We suggest that this elevational shift is a consequence of the variable effect of the global warming at the different elevations. Winter warming is expected to affect differently the timing of LBM egg hatch as well as that of larch bud flush, larvae being at present susceptible to emerge whereas no needles are available as food at the former optimal elevation. A better synchronization between larch and LBM may exist at higher elevations

An overview of the consequences of the 2003 summer for agriculture in France

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An overview of the consequences of the 2003 summer for agriculture in France

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Spatial daily rainfall descriptors to reproduce sub-daily dynamics in the analog method for temporal disaggregation

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