Temporal variations in radar backscatter coefficients of vegetation and snow cover

Microwave remote sensing of vegetation and soil has become an important discipline for the Global Change Research program. Synthetic aperture radar (SAR) technology demonstrated its utility in acquiring biomass data and classification of ecosystems. However single polarization and single frequency radar backscatter coefficients are vulnerable to a number of microphysical parameters. Backscattering coefficients reach saturation limits for biomass levels around 2 kg m/sup -2/ at C-band. The biomass saturation limit increases at lower frequency bands. Detailed field experiment results indicate that for a given biomass. backscatter measurements vary on the order of several dB depending on the changing environmental conditions such as temperature, soil moisture and tree structure. etc.. On the theoretical frontier, microwave canopy scattering models are also incomplete due to their limited potential to handle the realistic canopy and surface structures. This paper presents a temporal and seasonal variations of multi-frequency and multi-polarization backscatter coefficients for birch trees and snow cover. The measurements are collected using a dual-channel and dual-polarization scatterometer system. Frequency of operation for the system is between L- and X-band. Environmental parameters such as temperature, snow cover and visual description of the scene are also documented.<
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