Snow Retrieval by Airborne Radar

Airborne radar has shown promise in accurately inferring microphysical properties of snow if the measurements are made at more than one wavelengths. Previous study has revealed that the median volume diameter of snow can be reasonably well derived from a dual-wavelength airborne radar operating at 10 and 35 GHz. Its retrieval results are nearly independent of the snow density assumed in the retrieval. Estimates of the snow number concentration, however, are sensitive to the snow density. This may lead to an uncertainty in the retrieval of the number concentration unless the snow density is known. Recent field experiments, such as AMSR-Wakasa Bay Field Experiment and CRYSTAL-FACE, present an excellent opportunity to study the radar techniques for the retrieval of snow parameters. In the first part of our study, a dual-wavelength algorithm that uses measurements of radar reflectivity factors at 10 and 94 GHz is analyzed for the retrieval of snow, based on the measurements of EDOP (10 GHz) and CRS (94 GHz) radars that both were mounted on the NASA ER-2 aircraft during CRYSTAL-FACE. With the Doppler capabilities of EDOP and CRS radars, the measured mean Doppler velocities at two wavelengths can be used to aid in validation of the dual-wavelength algorithm. In the second part of the paper, the combined measurements of snow from the APR-2 dual-wavelength (14 and 35 GHz) and ACR (94 GHz) radars carried on the NASA P3 aircraft during AMSR-Wakasa Bay Field Experiment will be used to test the radar algorithms and check whether some of the uncertainties using the dual-wavelength radar can be resolved if three-wavelength radar measurements are employed.