Hailstone Size Distributions and Equivalent Radar Reflectivity Factors Computed from Hailstone Momentum Records

Abstract

An electronic hailstone momentum sensor has been developed which records hailstone impacts on magnetic tape. The instrument and the programs for analyzing the recorded data are described. Sensors were operated during six hailstorms in 1969 and recorded 624 hailstone impacts. Derived frequency distributions of hailstone size show the median diameter for all stones recorded to be near 0.9 cm. Significant variations exist among storms. Values of the equivalent radar reflectivity factor Ze have been computed for the hailshafts sampled, for X-hand and S-band radar, and for both wet and dry hailstones. The values range up to 70 dBz (107.0 mm6 m?3) and show good agreement with radar-measured values. The results suggest that dual-wavelength radar systems are not much better than S-band sets alone for estimating hailstone size.