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Prediction of extreme convective rainfall intensities using a free-running 3-D sub-km-scale cloud model initialized from WRF km-scale NWP forecasts
Journal of Atmospheric and Solar-Terrestrial Physics ( IF 1.9 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.jastp.2020.105401
Vlado Spiridonov , Julian Baez , Bosko Telenta , Boro Jakimovski

Abstract Most of the heavy rainfall comes from the severe convective storms. Convective scale numerical weather prediction with grid-lengths of a few km or less, is capable for a more successful representation of convective scale processes and explicitly representing different types of convective storms. However, despite these high-non-hydrostatic models, in some specific atmospheric cases associated with very intense convection, the present mesoscale models show some uncertainties and limitations in more accurate quantitative estimation of the intensity of heavy convective rainfall. In a way to overcome this problem we propose a novel forecasting system, that employs three-dimensional (3-D) cloud resolving model at Large Eddy Simulations (LES) type with greatly refined resolution of 100-m over a small sub-domain with the initial representative averaged vertical profiles derived from WRF-NMM 1-km forecasts. LES model is configured to explicitly simulate small-scale, high-intensity convective rainfall at that time and location where convective criteria and threshold values defined in the system interface are previously met. The cloud-model then evolves independently, with open lateral boundary conditions. A set of numerical experiments have been conducted and the method has been extensively tested on both tropical and mid-latitude convective cases. Results show some potential benefits in simulation of convective elements, cell structure and intensity. In this preliminary study, we show that the proposed method gives quantitatively more accurate forecast of high-intensity convective precipitation in most of the eight case-studies presented, when compared to the WRF-NMM 1-km scale forecasts. The improved skill of the forecasts using this forecast system will probably provide useful value to forecasters, so that they would be able to enhance their operational flood prediction capabilities and warnings of severe convective weather risk.

中文翻译:

使用从 WRF 公里尺度 NWP 预测初始化的自由运行 3-D 亚公里尺度云模型预测极端对流降雨强度

摘要 大部分强降雨来自强对流风暴。网格长度为几公里或更短的对流尺度数值天气预报能够更成功地表示对流尺度过程并明确表示不同类型的对流风暴。然而,尽管有这些高非静水力模型,但在一些与非常强烈对流相关的特定大气情况下,目前的中尺度模型在更准确地定量估计强对流降雨强度方面表现出一些不确定性和局限性。为了克服这个问题,我们提出了一种新颖的预测系统,它采用大涡模拟 (LES) 类型的三维 (3-D) 云解析模型,在一个小子域上具有 100 米的极大改进分辨率,初始代表性平均垂直剖面来自 WRF-NMM 1 公里预测。LES 模型被配置为显式模拟小规模、高强度对流降雨,在之前满足系统接口中定义的对流标准和阈值的时间和位置。然后,云模型独立发展,具有开放的横向边界条件。已经进行了一组数值实验,并且该方法已经在热带和中纬度对流情况下进行了广泛的测试。结果显示在对流元素、单元结构和强度的模拟中具有一些潜在优势。在这项初步研究中,我们表明,与 WRF-NMM 1 公里尺度预测相比,所提出的方法在所提出的八个案例研究中的大多数案例中对高强度对流降水进行了定量更准确的预测。使用该预报系统提高预报技能可能会为预报员提供有用的价值,使他们能够提高他们的业务洪水预报能力和强对流天气风险预警。
更新日期:2020-11-01
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