Evaluating the potential of ENVISAT/ASAR data in monitoring the Poyang lake wetland

In order to evaluate the potential of ENVISAT/ASAR (ENVIronment SATellite /Advanced Synthetic Aperture Radar) imagery with multi-incidence angle and multi-polarization for Poyang lake wetland study, a microwave canopy backscatter model for herbaceous vegetation was used to simulate the ASAR backscatter from wetland vegetation at two different growing status. Field measurements from areas covered with Miscanthus floridulus acquired in middle April and in May, 2005 were averaged respectively as model inputs to simulate ASAR backscatter from different vegetation components with seven incidence angles (15 degrees to 45 degrees). In April, 2005, Miscanthus floridulus still has not spread adequately, HV polarization is more sensitive to vegetation canopy parameters than HH and VV; HH is more suitable for retrieving surface moisture content and roughness; and VV cannot differentiate the influence of vegetation from surface effects. Inundation results in significant increment in HV backscatter; for HH, it depends on vegetation growing status, for instance, a reduction in areas of low vegetation and an increase in areas of high vegetation; for VV polarization, enhancement in total backscatter is insufficient to be used in flood detection. However, as the height of Miscanthus floridulus is more than I meter in late May, the simulated ASAR backscatter is not sensitive to the variations of vegetation parameters, surface parameters, or even inundation.