Comparison of Simultaneous Airborne and Radiometric Measurements of Supercooled Liquid Water

Abstract

Simultaneous measurements of supercooled liquid water by an instrumented aircraft and a dual-frequency microwave radiometer were made at Lake Ontario, New York, during wintertime. The geographic location and typical meteorological conditions for making the measurements were specifically selected to facilitate the comparisons. Flight paths from below cloud base to above cloud tops were made over the radiometer site. Seven flights were made; supercooled liquid water was measured by a calibrated Rosemount icing meter. The primary finding is that when the temperature of the atmosphere in the viewing path of the radiometer is below the melting point of ice, the airborne liquid-water measurements are in general agreement with the radiometric measurements. When an inversion with the temperature above the melting point is present, the radiometric readings of liquid water are much larger than the values found from the aircraft. Also, the, possibility is raised that in very heavy snowfall with large ice particles the amount of supercooled liquid water will appear too large according to the radiometer.