| 一次大冰雹形成机制的数值模拟 |
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| 引用本文： | 郭欣,郭学良,陈宝君,何晖,马新成,田平,张邢.一次大冰雹形成机制的数值模拟[J].应用气象学报,2019,30(6):651-664. |
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| 作者姓名： | 郭欣 郭学良 陈宝君 何晖 马新成 田平 张邢 |
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| 作者单位： | 1.南京大学大气科学学院, 南京 210023 |
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| 摘 要： | 利用可模拟冰雹尺度的三维冰雹分档对流云模式，研究了2014年7月16日北京一次大冰雹的形成过程。此次冰雹天气过程的地面降雹最大尺度为7 cm，对流有效位能为1785.3 J·kg-1，具有上干下湿的大气层结条件。数值模拟的冰雹云顶高度达13 km，与雷达观测比较一致，模拟的最大上升气流达30 m·s-1。由于风切变较大，冰雹云出现明显倾斜垂直结构，使冰雹云持续时间较长。此次大冰雹形成的微物理过程具有明显特点，冰雹云中-35~-10℃层存在含量达12~16 g·kg-1的高过冷雨水累积区，冰雹胚胎主要通过受到冰晶接触扰动的过冷雨滴冻结产生，其产生率量级达10-2 g·kg-1·s-1，冰雹增长过程主要依靠雹胚撞冻过冷云水，其增长率的量级与冰雹胚胎产生率的量级一致。
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| 关 键 词： | 过冷雨滴 累积带 大冰雹形成 冰雹分档数值模拟 北京 |
| 收稿时间： | 2019-07-15 |
Numerical Simulation on the Formation of Large-size Hailstones |
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| Affiliation: | 1.College of Atmospheric Science, Nanjing University, Nanjing 2100232.Beijing Weather Modification Office, Beijing 1000893.Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 1000294.Chinese Academy of Meteorological Sciences, Beijing 100081 |
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| Abstract: | Although large-size hailstones may cause damages to agriculture, human life and properties, the formation mechanism of large-size hailstones has not been completely understood. In order to further understand the formation of large-size hailstones, the three-dimensional compressible non-hydrostatic hailstorm model with hail-bin microphysics that can simulate different sizes of hailstones developed by Institute of Atmospheric Physics, Chinese Academy of Sciences, is used to investigate the formation process of a heavy hailstorm in Beijing on 16 July 2014. The observed maximum diameter of hailstones on the ground is up to 7 cm. The convection effective potential energy is 1785.3 J·kg-1 and the moisture content is high in the lower layer and low in the upper layer, indicating that the atmosphere is strongly instable and is conducive to the formation of strong convection. The simulated hail cloud-top height is about 13 km, which is consistent with that observed by the S-band radar in Beijing. The simulated maximum updraft is up to 30 m·s-1, indicating that the hailstorm is strong and severe. Moreover, the storm has an obvious tilting dynamic structure due to the strong wind shear at middle and upper levels, which makes the separation of falling path of hailstones and raindrops from the main updraft and causes the long duration of hailstorm. The simulated microphysical process of the hailstorm has some obvious characteristics, one of the most prominent properties is that there is an accumulation zone of high supercooled rain water with 12-16 g·kg-1 located between -35℃—-10℃. The main process of embryos production for hailstones is the collision between cloud ice and supercooled raindrops, and the production rate may be up to 10-2 g·kg-1·s-1. And the hailstone growth process strongly depends on the accretion of supercooled cloud water by hailstones, and the growth rate is the same as that of production rate of embryos of hailstones. This research shows that the supercooled rainwater accumulation zone may exist in the formation process of large hailstones in Beijing. However, the model is not able to simulate the size of hailstones up to 7 cm, the simulated maximum sizes of hailstones are usually about 2-3 cm. Causes are not clear, one important cause might be related with the melting process of hailstones in the model, and the initial atmospheric field used in the model. The issue needs to be further clarified and the microphysical processes relevant to hailstones need to be improved in the future study. |
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