Reflectance Properties of Snow and Forest Canopy: Impact on Snow Retrieval Algorithms

Field spectroscopy is an effective means to determine the reflectance of different terrain surfaces for the development and validation of monitoring systems using Earth Observation data. The objective of this investigation is to examine the variability of snow and forest canopy reflectance in the boreal forest area in order to improve the existing snow mapping algorithms, such as the reflectance model-based snow covered area (SCA) SCAmod snow mapping method by the Finnish Environment Institute (SYKE). The field experiments were conducted by using two identical spectroradiometers. One instrument was in portable use and the other was installed to a 30-meter mast in order to obtain the forest canopy reflectances. We present here the obtained reflectance variability for dry snow and the simulated results for scene reflectance above the tree cover obtained by the comparison of mast-based spectrometer measurements with linear spectral mixing of ground-based reflectances. The results show that the field spectrometer observations are feasible for the assessment of the variability of reflectance and validation of satellite based mapping.