Structure of an Evolving Hailstorm Part IV: Internal Structure from Penetrating Aircraft

Abstract

Precipitation particle sizes were measured using a continuous hydrometeor sampler (foil impactor) during penetrations of hailstorms with an armored T-28 aircraft. Data have been analyzed from three penetrations of a storm near Raymer, Colorado, on 9 July 1973 at altitudes between 5.5 and 7.2 km MSL, which correspond to temperatures between about ?2°C and ?12°C. Other results pertinent to the Raymer storm are discussed in Parts I,II,III and elsewhere in this issue. Most of the particles were identified as ice particles or ones containing both ice and water; however, significant amounts of liquid particles were found in the updrafts of developing cells at temperatures as cold as ?12°C. Particles larger than 5 mm in diameter were typically found along the edges of the updrafts, with the precipitation concentrations being strongly dependent on these larger particles. The downdrafts were composed of ice particles. Several particle size distributions from one of the penetrations were examined. The distributions are roughly exponential, or bi-exponential when large particles are present.