Hailstone Shapes
Hailstone Shapes
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冰雹形状
DOI：
10.1175/jas-d-20-0250.1
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发表时间：
2021
影响因子：
3.1
通讯作者：
Maiden, B. Ross
中科院分区：
文献类型：
--
作者：
Shedd, Laura;Kumjian, Matthew R.;Giammanco, Ian;Brown-Giammanco, Tanya;Maiden, B. Ross
冰雹的生长导致冰雹形状的变化。这些形状的冰雹过程，冰雹下降的行为，包括下降速度和冰雹的遥感签名的建模的影响。这项研究是一个深入的分析自然冰雹的形状，使用一个大的数据集，在现场收集的冰雹超过6年的时间。这些数据来自数字卡尺和三维红外激光扫描的手动测量。冰雹往往具有椭圆形的几何形状，短轴与长轴之比在0.4至0.8之间，中轴与长轴之比在0.8至1.0之间。这表明冰雹更好地表示为三轴椭球体，而不是球体或椭球体，这是通常假设的。激光扫描首次实现了精确的球度测量。冰雹随着最大尺寸的增加而变得越来越非球形，典型的球形度值范围为0.57至0.99。这些球度值用于估计阻力系数，发现其具有0.5至超过0.9的典型范围。冰雹的最大尺度往往比等效体积球径大20%-50%。作为理解和量化冰雹形状的一步，这项研究可能有助于更好地参数化冰雹模型和遥感冰雹检测和大小的算法。
Hailstone growth results in a variety of hailstone shapes. These shapes hold implications for modeling of hail processes, hailstone fall behaviors including fall speeds, and remote sensing signatures of hail. This study is an in-depth analysis of natural hailstone shapes, using a large dataset of hailstones collected in the field over a 6-yr period. These data come from manual measurements with digital calipers and three-dimensional infrared laser scans. Hailstones tend to have an ellipsoidal geometry with minor-to-major axis ratios ranging from 0.4 to 0.8, and intermediate-to-major axis ratios between 0.8 and 1.0. These suggest hailstones are better represented as triaxial ellipsoids as opposed to spheres or spheroids, which is commonly assumed. The laser scans allow for precise sphericity measurements, for the first time. Hailstones become increasingly nonspherical with increasing maximum dimension, with a typical range of sphericity values of 0.57 to 0.99. These sphericity values were used to estimate the drag coefficient, which was found to have a typical range of 0.5 to over 0.9. Hailstone maximum dimension tends to be 20%–50% larger than the equivalent-volume spherical diameter. As a step toward understanding and quantifying hailstone shapes, this study may aid in better parameterizations of hail in models and remote sensing hail detection and sizing algorithms.