Methods of Detection of change and feedback in semi-arid regions (North Africa and Sahel) Chehbouni A. Ghani ; L. Jarlan and E. Mougin Center of Space Study of the Biosphere: CESBIO 18, avenue Edouard Belin, Toulouse Cedex 9 France.CESBIO (CNES-CNRS-UPS-IRD), Toulouse, France Presentation outline INTRODUCTION Integrated Modelling and Remote Sensing approach for Sustainable management of water resources a semi-arid basin in Morocco : The SUDMED (SALSA-MED) Program GENERAL OBJECTIVE 2 2 * * * 2 Euro- Mediterranean network Geo-Information for sustainable management of Land and Water ressources in the MEDiterranean region Changes in Urban zone since 1975 Changes in Irrigated area since 1975 Changes in water table level from 1986 to 2002 MONTHLY VARIATION OF SNOW COVER INDEX OVER THE ATLAS MONTAIN SPOT4/VEGETATION 1999 Runoff simulation Snow depth simulation The right answer for the wrong reasons PhD : Chaponniere 2005 Spatial representativeness of flux measurements LAS 1 R 10m tower LAS 1 T 10m tower LAS 2 R 5m tower LAS 2 T 5m tower EC 5m tower EC ( Hydra ) EC AMMA EXPERIMENT 2006: Wankama Basin, Niger Dominant wind direction AMMA SITE, WANKAMA Basin NIGER 2006 Spatially integrated Sensible and Latent Heat fluxes Clear modeling evidences (using coupled land surface and dynamic ecosystem models) of the role of vegetation, jointly with Sea Surface Temperatures (SST), in shaping Sahelian rainfall variability at decadal to interannual time- scales (Eltahir 2000a, 2000b). The links between the mean annual integrated NPP and the mean annual rainfall amounts are particularly strong and linear over the semi-arid regions of West Africa where less than 1000mm are recorded (Soil Limited Evaporation) NDVI data appear to be an attractive proxy of rainfall on small spatial scales Sahel region Vegetation time response to rainfall varies between 3 to 6 weeks from the wettest to the driest environments (Shinoda 1995) On an interannual time-scale, the strong year to year changes observed in rainfall seasonal cycle and amplitude lead to marked changes in NDVI seasonal cycle and amplitude. Some discrepancies appear between the rainfall and NDVI patterns due to soil characteristics or recovery effects Sahel region The Sahel region faces greater vulnerability to both human and natural perturbation Anomalies Precip in the Sahel Increase in water demands Climate Variability Human pressure Vegetation in Sahel ( Anomalies semi-arid conditions Impact Feedback Impact Feedback ERS1/2 WINDSCAT Innovative approach Schematic description of the assimilation scheme based on the evolution strategies algorithm. Concluding remarks The recent availability of corrected and inter-calibrated long- term time-series of NDVI on the 10-day time-scale offers a unique opportunity to explore the West African vegetation in terms of its interannual and intraseasonal variability Some discrepancies appear between the rainfall and NDVI patterns due to soil characteristics or recovery effects Need to explore other type of satellite data or a combination of them (OLR, Ts, Soil Moisture) Coupling between process models, satellite data and assimilation scheme appears to be the most promising approach For realistic Climate scenarios, models need to incorporate changes in Land-use Thank You