Limitations of the dense dark vegetation method for aerosol retrieval under Australian conditions

The use of dense dark vegetation (DDV) for atmospheric aerosol correction of Landsat imagery is investigated for Australian conditions. Aerosol optical depth (AOD) measurements from sun photometers are used as a reference data set and compared against estimates of AOD derived from Landsat imagery using the DDV method. The DDV method makes assumptions that the vegetation is sufficiently dark and the ratio between bottom-of-atmosphere reflectances at different wavelengths is constant. These assumptions were tested using Landsat-5 Thematic Mapper (TM) imagery corrected with AOD measured by field-based sun photometers on the AErosol RObotic NETwork (AERONET) network. The assumptions were found to be correct only for one of the three locations studied. In other locations, the spatial and temporal variability of the vegetation and its relative brightness makes the method unsuitable.