A study of vegetation cover effects on ERS scatterometer data

The scatterometer flown onboard the European remote-sensing satellites ERS- 1 and ERS-2 is a vertically polarized radar operating at 5.3 GHz (C-band) a nd has a spatial resolution of 50 km. In a number of studies, the sensitivi ty of the ERS scatterometer to vegetation has been demonstrated, but it is not yet clear which vegetation parameters are of primary importance to expl ain the ERS scatterometer signal. In this paper, the effects of land cover and seasonal vegetation development are investigated bg comparing ERS scatt erometer data with land cover information, normalized difference vegetation index (NDVI) data sets, and meteorological observations, As a study area, the Iberian Peninsula was chosen. The Iberian Peninsula is characterized by the Mediterranean climate that has a wet winter and a dry summer. This all ows us to better differentiate the effects of the annual vegetation and pre cipitation cycle on the temporal evolution of the backscattering coefficien t sigma(0), It is shown that the ERS scatterometer has only limited capabil ities for monitoring the vegetation development within a given Scar because most of the temporal variability of sigma(0) is due to soil moisture chang es. On the other hand, it might be of merit for vegetation discrimination o n large scales (regional to global) because the percentage al ea of forests , hushes, and shrubs within one ERS scatterometer pixel is found to explain a significant part of the spatial variability of the signal.