Temporal trends of microwave emission from forest areas observed from satellite

In this paper, temporal trends of brightness temperature and related microwave indexes from AMSR-E and SMOS satellites were analyzed. Datasets were collected on three forest areas characterized by different climatic conditions and tree species. The test plots are: a deciduous forest of Larix in China; an evergreen Spruce forest in Russia; the mixed "Foreste Casentinesi" in Central Italy. The availability of different frequencies allowed us to investigate various canopy and soil effects. At the higher frequencies, the frequency index is sensitive to the snow cycle, and the polarization index is sensitive to the leaf cycle. At L band, a clear decrease of emissivity, at both polarizations, is associated to the snow melting process.