Hail Size and Dual-Polarization Doppler on Wheels Radar Observations During RELAMPAGO

The RELAMPAGO project took place in north-central Argentina in Fall 2018, aiming to investigate deep convective storms in that region. Previously, satellite observations suggested that some of these storms are among the tallest in the world. Later studies extrapolated these observations to argue that the storms are prolific hail producers. Part of the RELAMPAGO campaign focused on sampling these hailstorms with a suite of instruments, including radiosondes, Doppler polarimetric radars, and a deployable network of hail pads. The hail pads were deployed ahead of the storms in a dense array to sample hail size variability across the hail swath.

Marginally severe to severe hail was observed during several RELAMPAGO IOPs. Time-integrated hail size distributions were estimated from hail pad observations and compared to manual hail size measurements obtained from digital calipers. In one case, an exceptionally large sample size of hailstones (>10000) is obtained from aerial photogrammetry using a drone and agrees well with the hail pad analysis. In most cases, rather narrow hail size distributions are found at any individual hail pad location. These ground-based hail size observations are compared to dual-polarization Doppler on Wheels (DOW) radar data. Signatures of hail growth and fallout regions (including three-body scatter signatures, reduced co-polar correlation coefficient ρ_hv and enhanced linear depolarization ratio LDR aloft, and extremely large specific differential phase K_DP values at low levels) are described and related to hail size at the surface.