Abstract

A regularly spaced 3.8 km2 mesh hailpad network covers 800 km2 in the Grossversuch IV Experiment in Switzerland and allows the recording of distinct hailpatterns and the calculation of their kinetic energy. With natural hailfall data over four years (1975–78), we show that annual kinetic energy means are different from one year to another and that the multi-annual distribution is lognormal with a probability density function: f(logEG) = 0.392 exp − [(logEG − 1.58)/1.44]2. We establish several close relationships between hailpattern global kinetic energy (EG), hailed surface (SG), maximum diameter (Dm), maximum point number (NTm), and point kinetic energy of hailstones (ETm) in particular with EG = 0.0043SG0.56Dm1.2NTm0.85 (r = 0.995). These relations have been established over four years with dependent data and have been positively tested with independent data (1979).

In analyzing the distribution of the decreasing values of point kinetic energy related to cumulated values of area S inside a hailpattern, we obtain an exponential distribution that we fit by the equation ET = ET0 exp(−μES) and we show that the energy gradient μE decreases as hailfall surface (SG) increases.

These kinetic energy characteristics seem to indicate a uniform hail phenomenon with a continuous parameter evolution from small to large hailfalls. Some of these properties would help identify physical effects in storm modification experiments.

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