0000000000563709
AUTHOR
Alexander Jost
A Comprehensive Observational Study of Graupel and Hail Terminal Velocity, Mass Flux, and Kinetic Energy
Abstract This study uses novel approaches to estimate the fall characteristics of hail, covering a size range from about 0.5 to 7 cm, and the drag coefficients of lump and conical graupel. Three-dimensional (3D) volume scans of 60 hailstones of sizes from 2.5 to 6.7 cm were printed in three dimensions using acrylonitrile butadiene styrene (ABS) plastic, and their terminal velocities were measured in the Mainz, Germany, vertical wind tunnel. To simulate lump graupel, 40 of the hailstones were printed with maximum dimensions of about 0.2, 0.3, and 0.5 cm, and their terminal velocities were measured. Conical graupel, whose three dimensions (maximum dimension 0.1–1 cm) were estimated from an an…
The Effect of Turbulence on the Accretional Growth of Graupel
Abstract Wind tunnel experiments were carried out to investigate the influence of turbulence on the collection kernel of graupel. The collection kernel defines the growth rate of a graupel accreting supercooled droplets as it falls through a cloud. The ambient conditions were similar to those occurring typically in the mixed-phase zone of convective clouds, that is, at temperatures between −7° and −16°C and with liquid water contents from 0.5 to 1.3 g m−3. Tethered spherical collectors with radii between 220 and 340 μm were exposed in a flow carrying supercooled droplets with a mean volume radius of 10 μm. The vertical root-mean-square fluctuation velocity, the dissipation rate, and the Tay…