Complementarity of ERS-1 wind scatterometer and GVI data forregional vegetation monitoring

摘要

The ERS-1 wind scatterometer provides measurements of the radarnbackscattering coefficient σ° along different azimuthalndirections, from which parameters can be retrieved. However, the lownspatial resolution (about 50 km.), its high temporal repetitivity (thensame point can be seen every 4 days with an incidence angle ranging fromn18° to 59° ), and above all a frequency (5.3 GHz, VVnpolarisation) sensitive to land surface parameters such as vegetationncover and soil surface moisture content make this instrument well suitednfor terrestrial vegetation studies. At present, two years of fullyncalibrated data acquired by the ERS-1 scatterometer over the whole landnsurfaces offer a unique opportunity to assess the contribution of lownresolution active microwave systems to global monitoring of terrestrialnsurfaces. On the other hand, several studies with NOAA/AVHRR GVI datan(available since 1981) have shown how these data can be related tonvegetation phenology and vegetation dynamics. Their rather coarsenspatial resolution (about 10 km. At the equator) justifies thencomparison with scatterometer data. In this paper, multitemporalnprofiles of both data sets acquired over representative vegetation typesnthroughout the world for a 2-year period are shown. The complementaritynof these two sources of satellite data are then examined. Results shownthat ERS-1 scatterometer data are sensitive to different land parametersnaccording to their incidence angle. In particular, a good correlationnbetween GVI data and scatterometer data acquired around 45° ofnincidence angle is observed