Donald J. Cavalieri

Multi-Frequency, Multi-Polarization SAR And Radiometer Sea Ice Classification

Microwave remotely sensed data were acquired simultaneously in March 1988 over Beaufort, Chukchi, and Bering Sea ice using the JPL multifrequency, polarimetric synthetic aperture radar (SAR), and multifrequency dual-polarization GSFC radiometer. The experiment was conducted as a series of coordinated underflights of the DMSP SSM/I satellite radiometer to validate ice products derived from its radiance values. Concurrent flights by an NRL P-3 aircraft enabled overlapping high-resolution, single-frequency images to be acquired over the same surfaces using a Ka-band scanning microwave radiometer. Precise coregistration to an accuracy of 100 m, +/- 25 m enables comparison of temporally and spatially coincident active and passive microwave datasets. Three-channel polarimetric SAR data are compared with dual-polarized radiometer data at several SSM/I frequencies, showing backscatter signatures to be highly correlated with radiometric temperatures. Further comparisons are used to evaluate ice concentration retrievals and to show how multiparameter datasets can be used to resolve ambiguities present in identifying certain sea ice forms with a single microwave instrument.

Conjunctive Radar and Laser Altimetry Data Processing to Measure Snow Thickness

Sea ice is generally covered with snow. Information about snow thickness is essential to estimate sea-ice thickness from freeboard measurements and to model ocean-ice-atmosphere interactions. This paper discusses an algorithm to measure snow thickness by processing of coincident radar and the laser altimetry data. Radar return is dominated by the reflected signal from the snow-ice interface whereas laser return by the snow-air interface. Radar data are processed to obtain an accurate estimate of range to the snow-ice interface using aircraft trajectory derived from differential Global Positioning system (GPS) and Inertial Navigation System (INS). Laser data are processed to obtain range to the snow-air interface. The snow cover thickness is estimated from the difference in the radar and laser range estimates. The snow-thickness estimates obtained from radar and laser altimeter are comparing with the in situ snow thickness data collected over the Chukchi and Beufort lines.