Microwave radiometry of forests

Microwave remote sensing observations provide all weather, day/night monitoring of the earth's surface and make it possible to probe forest vegetation at various depths by operating at different frequencies. Significant progress in microwave radiometry of land surfaces has been made by using advanced airborne and spaceborne instruments and by developing physical and statistical models needed for interpreting the data. At present, a new multi-frequency scanning radiometer, launched in 2002 is providing global observations of the earth's surface at a relatively high resolution, and collected data are currently under study. This paper provides a review of experimental and theoretical investigations carried out in recent years to study the relationships between microwave emission and forest features at regional and global scale. It is shown that, despite the relatively small amount of experimental data currently available, microwave radiometry has proved to be an efficient technique in monitoring forest environments, and in particular in separating forest types, estimating woody biomass and, in some cases, assessing soil surface properties.