Observations and Simulation of Multifrequency SAR Data Over a Snow-Covered Boreal Forest

A significant part of the Earth affected by seasonal snow is covered by forest. Moreover, the presence of forest modifies the snow accumulation and its metamorphism during the winter season. Recent studies, which were carried out within the framework of ESA's CoReH<inf>2</inf>O Phase-A mission, demonstrate that multifrequency SAR data are able to quantify the amount of snow mass on land surfaces and or glaciers. On the other hand, the presence of forest has a significant impact on the propagation of the radar signal, depending on its structure, biomass, water content, and cover fraction. In particular, for dense forest scattering of vegetation strongly hides the signal from snow, and consequently, compromises the sensitivity to snow parameters. Within the development of the mission's snow water equivalent (SWE) retrieval algorithm, a method to compensate the vegetation effect, and then to retrieve snow in sparse forested areas, was implemented. The method is based on the development of an e.m. model for simulating the backscattering of a snow-covered vegetated terrain and the availability of some ancillary data about forest characteristics. Model description and validation using real airborne and space-borne SAR data collected over a boreal test site in Finland are presented here. The use of the developed model in the SWE retrieval algorithm is also presented.