In the present work, seven different extreme precipitation events, that affected Liguria region (Italy) in the past ten years, were analysed in depth by means of sub-km resolution numerical simulations with the state-of-the-art non-hydrostatic Weather Research and Forecasting (WRF) mesoscale model. The study aims at evaluating the impact on quantitative precipitation forecast of an explicit description of atmospheric boundary layer turbulence through a Large-Eddy Simulation (LES) approach versus the classical Reynolds-Averaged Navier–Stokes (RANS) modelling framework. To this purpose, three different sets of simulations were carried out. In the first set, reaching a resolution of 1.1 km through three nested domains, the best performing planetary boundary layer (PBL) parameterization scheme identified in a preliminary sensitivity analysis, was imposed on each domain. This modelling setup was chosen as the reference one. Then, a further nested domain was introduced with horizontal resolution of 367 m, on which both RANS and LES simulations were performed. Quantitative precipitation forecasts were compared with observed data coming from the regional rain gauge network, composed of about 200 professional stations. In four out of the seven considered events, results show an evident LES contribution to improve model performances, regarding both intensity and/or location of precipitation. This improvement is observed both in cases of underestimation and overestimation by the reference simulations and is mostly associated to a better description of low-level dynamics as well as convection triggering and intensity. In other cases, the effect of LES is not remarkable and simulations closely resemble the reference ones. Further investigation is necessary to strengthen these conclusions, but the results of this study can suggest the possibility to integrate LES in operational simulations.

在目前的工作中，通过近千米的数值模拟和最新的非静水天气，对过去十年中影响利古里亚地区（意大利）的七个不同的极端降水事件进行了深入分析。研究和预测（WRF）中尺度模型。该研究旨在通过大涡模拟（LES）方法与经典雷诺平均Navier–Stokes（RANS）建模框架来评估大气边界层湍流的显式描述对定量降水预报的影响。为此，进行了三组不同的仿真。在第一组中，通过三个嵌套域的分辨率达到1.1 km，初步敏感性分析中确定了性能最好的行星边界层（PBL）参数化方案，被强加到每个域上。选择此建模设置作为参考。然后，引入了另一个嵌套域，其水平分辨率为367 m，在其上进行了RANS和LES仿真。将定量降水预报与来自约200个专业站组成的区域雨量计网络的观测数据进行了比较。在七个被考虑事件中的四个中，结果表明，在降水强度和/或位置方面，LES对改善模型性能有明显贡献。通过参考模拟在低估和高估的情况下都可以观察到这种改善，并且主要与对低层动力学以及对流触发和强度的更好描述有关。在其他情况下，LES的影响并不明显，并且模拟与参考模拟非常相似。为了加强这些结论，有必要进行进一步的研究，但是这项研究的结果可以暗示将LES集成到运营模拟中的可能性。