A High-precision and Fast Solution Method of Gamma Raindrop Size Distribution based on 0-Moment and 3-Moment in South China
A High-precision and Fast Solution Method of Gamma Raindrop Size Distribution based on 0-Moment and 3-Moment in South China
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DOI：
10.1175/jamc-d-21-0043.1
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发表时间：
2021-08
影响因子：
3
通讯作者：
Xiantong Liu;Huiqi Li;Sheng Hu;Q. Wan;Hui Xiao;Tengfei Zheng;Minghua Li;Langming Ye;
中科院分区：
文献类型：
--
作者：
Xiantong Liu;Huiqi Li;Sheng Hu;Q. Wan;Hui Xiao;Tengfei Zheng;Minghua Li;Langming Ye;
根据我国南方地区多台二维视频距离仪（2DVD）观测到的高精度线性形状-斜率（μ-Λ）关系，提出了一种基于γ（r）雨滴谱分布（RSD）零阶矩（M0）和三阶矩（M3）的高精度快速求解RSD函数的方法。RSD的0阶矩（M0）和3阶矩（M3）可分别由两阶矩（2 M）微物理方案模拟的雨质量混合比（Qr）和总粒子数浓度（Ntr）计算得到。选取2019年华南地区3次典型强降水过程和观测到的全部RSD样本，验证方法的准确性。与目前广泛使用的2 M微物理方案中形状参数固定为零的指数RSD相比，使用线性约束伽玛（C-G）方法的Γ RSD函数与2DVD观测的Γ拟合RSD更吻合。特征降水参数（例如，降水率M_2、M_6和M_9）与用2DVD观测资料的Γ拟合RSD计算的参数基本一致。该方法有效地解决了2 M微物理方案中形状参数设置为常数的问题，使计算得到的Γ RSD函数更接近观测值，误差明显减小。该方法具有很好的应用潜力，可应用于2 M微物理方案中，以提高华南强降水的模拟效果，同时也为雷达资料在数值天气预报模式中的深入应用铺平了道路。
According to the high accuracy linear shape-slope (μ-Λ) relationship observed by several 2-Dimensional-Video-Distrometers (2DVD) in South China, a high-precision and fast solution method of gamma (Γ) raindrop size distribution (RSD) function based on the zeroth order moment (M0) and the third order moment (M3) of RSD has been proposed. The 0-moment (M0) and 3-moment (M3) of RSD can be easily calculated from rain mass mixing ratio (Qr) and total number concentration (Ntr) simulated by the two-moment (2M) microphysical scheme, respectively. Three typical heavy rainfall processes and all RSD samples observed during 2019 in South China were selected to verify the accuracy of the method. Compared to the current widely used exponential RSD with a fixed shape parameter of zero in 2M microphysical scheme, the Γ RSD function using the linear constrained gamma (C-G) method agreed better with the Γ fit RSD from 2DVD observations. The characteristic precipitation parameters (e.g., rain rate, M2, M6 and M9) obtained by the proposed method are generally consistent with the parameters calculated by Γ fit RSD from 2DVD observations. The proposed method has effectively solved the problem that the shape parameter in the 2M microphysical scheme set to a constant, so that the Γ RSD functions are closer to the observations and have obviously smaller errors. This method has a good potential to be applied to the 2M microphysical schemes to improve the simulation of heavy precipitation in South China, but also paves the way for in-depth applications of radar data in numerical weather prediction models.