Microwave/optical Studies of Saline Ice, Snow, Melt Ponds and Refrozen Melt Pond Ice

Abstract

Optical and microwave measurements of a variety of ice and snow targets were obtained in a large indoor cold room at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, N.H. Bistatic measurements performed in the plane of incidence were obtained at 632.8 nm and backscatter measurements as a function of incidence angle were obtained at 13.6 GHz. The 632.8 instrument that was used is a portable version of the UTA Automated Bidirectional Reflectance Acquisition Measurement System (ABRAMS) and the University of Kansas 13 GHz instrument is a step frequency radar that is based around the HP8753 network analyzer. In this report we will consider the scattering behavior of thermally modified saline ice, snow, melt ponds and refrozen melt pond ice. Preliminary results indicate that air bubbles in saline ice and melt pond ice are important sources of scattering at optical wavelengths. Microwave frequencies, on the other hand, are sensitive to brine inclusions in the ice and to liquid water at the ice surface; microwave measurements showed a dramatic (8 dB) decrease in nadir backscattering as a quiescent melt pond refroze. Other topics that will be included in this report deal with system calibration, and the use of polarization in the plane of incidence to distinguish between volume and surface scattering.