Hail Particle Size Distributions Parametrization Derived from the T-28 Storm Penetrating Aircraft

Hail and graupel are linked to lightning production, can cause significant damage and are important components of cloud evolution. The accurate prediction of the amount and location of hail and graupel and the effects on other hydrometeor species depends upon the size distribution assumed. Here, we use ~310 km of in-situ observations from flights of the South Dakota School of Mines T-28 storm penetrating aircraft to constrain this representation of the Particle Size Distribution (PSD). Optical probe PSD measurements are normalized using 2 moment normalization relations to obtain an underlying exponential shape. Exponential PSD parameters derived from these observations are typically lower than assumed in models leading to broader size distributions and faster sedimentation rates for the same hail water content than commonly assumed in models. By linking the two normalizing moments through a power-law, a parametrization of the hail PSD is provided based on the hail water content only. The largest hail water content encountered for a 1km sample was ~10 g m^-3.