Identification and observation of desertification processes with the aid of measurements from space: Results from the European Field Experiment in Desertification-threatened Areas (EFEDA)
- 85 Downloads
The ECHIVAL Field Experiment in Desertification-threatened Areas (EFEDA) addresses the question of desertification from the viewpoint of changing interactions between the land surface and the atmosphere under varying climatic conditions. The basic tool to improve our understandin of these processes are Soil-Vegetation-Atmosphere-Transfer (SVAT) and climate models. In testing techniques for deriving the needed input data from observations from space, EFEDA requires high-precision data sets that can be used to aggregate desertification-related land-surface characteristics into the scale up to the grid width of global climate models (104−105 km2). In this context schemes have been developed to infer from satellite measurements fluxes at the surface. To validate the information inferred from observations in space, ground measurements have been performed on 2500 km2 of Castilla-La Mancha, Spain, during the drying periods of the summers of 1991 and 1994. Ultimately EFEDA aims to determine cumulative fluxes over longer periods to allow discrimination between natural variability and trends over large areas, such as the land around the Mediterranean. To recalibrate and adjust the algorithms used to infer information about the land surfaces from satellite measurements, “anchor stations” are proposed for critical areas to provide collateral information and continuous quality control of inferred information.
KeywordsLand Surface Natural Variability Measurement Flux Global Climate Model Collateral Information
Unable to display preview. Download preview PDF.
- Bastiaanssen, W.G.M., D.H. Hoekman and R.A. Roebeling. 1994. A methodology for the assessment of surface resistance and soil water storage variability at mesoscale based on remote sensing measurements, IAHS Special Publication No. 2. International Association of Hydrological Sciences Press, Wallingford.Google Scholar
- Bastiaanssen, W.G.M. and R.A. Roebeling. 1993. Analysis of land surface exchange processes in two agricultural regions in Spain using Thematic Mapper Simulator data, in H.J. Bolle, R.A. Feddes, and J.D. Kalma (Eds.), Exchange processes at the land surface for a range of space and time scales, IAHS Publication No. 212. International Association of Hydrological Sciences Press, Wallingford, pp. 407–416.Google Scholar
- Bolle, H.J. et al. 1993. EFEDA: European field experiments in a desertification threatened area. Annales Geophysicae 11: 173–189.Google Scholar
- Dedieu, G., P.Y. Deschamps and Y.H. Kerr. 1987. Satellite estimation of solar irradiance at the surface of the Earth and of surface albedo using a physical model applied to METEOSAT data. Journal of Climate and Applied Meteorology 26: 79–87.Google Scholar
- Nerry, F. 1993. Longwave infrared measurements. In EFEDA: Final report. EFEDA-Project Office, Berlin, pp. 312–319.Google Scholar
- Nerry, F., J. Label and M.P. Stoll. 1988. Emissivity signatures in the thermal IR band for remote sensing: Calibration procedure and method of measurement. Applied Optics 27: 758–764.Google Scholar
- van de Griend, A.A. 1993. On the relationship between thermal emissivity and the normalized difference vegetation index for natural surfaces. International Journal of Remote Sensing 14(6): 119–1131.2Google Scholar