THE IMPORTANCE OF L-FREQUENCY SAR VOLUME SCATTERING ON LOWLAND TUNDRA IN PERIGLACIAL AND PERMAFROST TERRAINS

Geodetic methods to measure centimeter to millimeter-scale changes using aircraft- and spacecraft deployed Synthetic Aperture RADAR cannot ignore volume scattering. Backscatter and coherence at L-frequency and others possess both surface and volumetric scattering. On lowland tundra underlain by permafrost volume scattering dominants the RADAR backscatter coherence. Measurement of the L-frequency penetration depth for evaluation of mass change (loss and transport) through permafrost thaw-degradation with erosion is necessary. Data from the NASA Ice, Cloud, and land Elevation Satellite Geoscience Laser Altimeter System (ICESat GLAS), JAXA Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture RADAR (ALOS PALSAR), aircraft-deployed NASA L-band UAVSAR, the Polar Geospatial Center Arctic DEM, the USGS IfSAR DEM and in-situ measurements with observations are employed. Collocation of ICESat GLAS exact-repeat profiles for elevation change (surface scattering) indicates PALSAR InSAR Line-Of-Sight changes are due to volume scattering. UAVSAR L-frequency Full Polarimetry Cross-Pole HHVV (polarization rotation) confirms the dominance of volume scattering on lowland tundra (RADAR-soft target) whereas surface scattering (HHHH or VVVV, no rotation) dominates on river channel deposits, rock outcrops and metal objects (RADAR-hard targets). Quantifying polarization rotation and the L-frequency penetration depth on lowland tundra are challenges for a new field validation experiment.