A Comprehensive Observational Study of Graupel and Hail Terminal Velocity, Mass Flux, and Kinetic Energy
A Comprehensive Observational Study of Graupel and Hail Terminal Velocity, Mass Flux, and Kinetic Energy
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DOI：
10.1175/jas-d-18-0035.1
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发表时间：
2018-10
影响因子：
3.1
通讯作者：
A. Heymsfield;M. Szakáll;Alexander Jost;I. Giammanco;R. Wright
中科院分区：
文献类型：
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作者：
A. Heymsfield;M. Szakáll;Alexander Jost;I. Giammanco;R. Wright
这项研究使用新的方法来估计冰雹的下落特征，覆盖范围从0.5到7厘米，以及块状和圆锥状重力的阻力系数。在德国美因茨的垂直风洞中，用丙烯腈-丁二烯-苯乙烯(ABS)塑料打印了大小2.5~6.7 cm的60个冰雹的三维体积扫描图像，并测量了它们的终端速度。为了模拟块状风暴，对40个冰雹进行了最大尺寸分别为0.2、0.3和0.5 cm的打印，并测量了它们的末端速度。圆锥形颗粒，其三维(最大尺寸0.1-1厘米)由解析表示法估计并打印出来，并在隧道中测量了七组颗粒的终端速度。从这些实验中，打印出的颗粒密度从0.2g cm−3，结合以前的观测，得出了在大气中广泛的颗粒尺寸和高度(压力)下，阻力系数与雷诺数以及雷诺数与最佳数之间的关系。这一信息与2800多块冰雹的质量和横截面积的总和一起被用来建立实际冰雹的终端速度、质量通量和动能的尺寸依赖关系。
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 analytical representation and printed, and the terminal velocities of seven groups of particles were measured in the tunnel. From these experiments, with printed particle densities from 0.2 to 0.9 g cm−3, together with earlier observations, relationships between the drag coefficient and the Reynolds number and between the Reynolds number and the Best number were derived for a wide range of particle sizes and heights (pressures) in the atmosphere. This information, together with the combined total of more than 2800 hailstones for which the mass and the cross-sectional area were measured, has been used to develop size-dependent relationships for the terminal velocity, the mass flux, and the kinetic energy of realistic hailstones.