MONITORING LOCAL ENVIRONMENTAL-CONDITIONS WITH SIR-C X-SAR/

This article examines temporal changes in the Spaceborne Imaging Radar -C (SIR-C) C- and L-band radar backscatter over an agricultural test s ite centred on Altona, Manitoba, Canada in relation to changing enviro nmental conditions during April and October 1994. The results indicate that environmental events such as frost and rain can be monitored. Ho wever, care must be taken as some soil targets at high moisture conten ts may behave as specular reflectors at longer wavelengths, such as L- band at large incidence angles, thus masking soil moisture effects. Th e strongest correlation between radar backscatter and soil moisture (r =0.84) was obtained for the 0-2.5 cm soil profile at HH polarizations. The strength of the correlation was approximately the same at C- and L-band. All polarizations displayed a decrease in soil moisture correl ation with increasing soil profile depth. It was observed that soil te xture effects on the estimation of soil moisture from radar backscatte r were relatively small and consequently can be neglected. Although th e sensitivity to surface roughness is greater at HV and VV than at HH polarization, results indicate that roughness could be neglected when measuring soil moisture over relatively short periods of time at a giv en site, without significantly reducing the sensitivity of the relatio nship between radar backscatter and soil moisture. (C)Government of Ca nada, 1997.