A Hail Growth Trajectory Model for Exploring the Environmental Controls on Hail Size: Model Physics and Idealized Tests
A Hail Growth Trajectory Model for Exploring the Environmental Controls on Hail Size: Model Physics and Idealized Tests
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DOI：
10.1175/jas-d-20-0016.1
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发表时间：
2020-07
影响因子：
3.1
通讯作者：
M. Kumjian;K. Lombardo
中科院分区：
文献类型：
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作者：
M. Kumjian;K. Lombardo
发展了一个详细的冰雹增长微物理模式，并将其应用于深对流风暴的理想化数值模拟。不同大小和密度的冰雹胚胎可能会在模拟的对流风暴上升气流中及其周围初始化，然后随着它们被平流输送并通过各种微物理过程生长而被跟踪。应用到一个理想化的飑线和超级单体风暴的结果在一个合理的现实分布的最大冰雹大小为每个。通过理想化的超级单体风暴模拟冰雹增长轨迹表现出许多与以前的冰雹轨迹工作，使用观测到的风暴。不确定的模型参数和参数化进行了系统的测试，结果突出了冰雹大小分布的敏感性，这些变化。一组理想化的模拟进行了不同的垂直风切变的环境中的超级单体，以扩展和澄清我们以前的工作。轨迹计算表明，随着纬向深层切变的增加，更广泛的上升气流导致停留时间增加，从而更大的最大冰雹尺寸。在纬向低空切变增加的情况下，上升气流的宽度也增加，但冰雹的尺寸较小。这是由于上升气流中的停留时间减少，由于上升气流中更快的向北流动，使冰雹更快地平流通过生长区。结果表明，环境导致削弱超级单体上升气流内的水平流动可能会导致更大的最大冰雹尺寸。
A detailed microphysical model of hail growth is developed and applied to idealized numerical simulations of deep convective storms. Hailstone embryos of various sizes and densities may be initialized in and around the simulated convective storm updraft, and then are tracked as they are advected and grow through various microphysical processes. Application to an idealized squall line and supercell storm results in a plausibly realistic distribution of maximum hailstone sizes for each. Simulated hail growth trajectories through idealized supercell storms exhibit many consistencies with previous hail trajectory work that used observed storms. Systematic tests of uncertain model parameters and parameterizations are performed, with results highlighting the sensitivity of hail size distributions to these changes. A set of idealized simulations is performed for supercells in environments with varying vertical wind shear to extend and clarify our prior work. The trajectory calculations reveal that, with increased zonal deep-layer shear, broader updrafts lead to increased residence time and thus larger maximum hail sizes. For cases with increased meridional low-level shear, updraft width is also increased, but hailstone sizes are smaller. This is a result of decreased residence time in the updraft, owing to faster northward flow within the updraft that advects hailstones through the growth region more rapidly. The results suggest that environments leading to weakened horizontal flow within supercell updrafts may lead to larger maximum hailstone sizes.