Abstract Terrain challenges the prediction of near-surface atmospheric conditions, even in kilometre-scale numerical weather prediction (NWP) models. In this study, the ALADIN-HIRLAM NWP system with 0.5 km horizontal grid spacing and an increased number of vertical levels is compared to the 2.5-km model system similar to the currently operational NWP system at the Norwegian Meteorological Institute. The impact of the increased resolution on the forecasts’ ability to represent boundary-layer processes is investigated for the period from 12 to 16 February 2018 in an Arctic fjord-valley system in the Svalbard archipelago. Model simulations are compared to a wide range of observations conducted during a field campaign. The model configuration with sub-kilometre grid spacing improves both the spatial structure and overall verification scores for the near-surface temperature and wind forecasts compared to the 2.5-km experiment. The sub-kilometre experiment successfully captures the wind channelling through the valley and the temperature field associated with it. In a situation of a cold-air pool development, the sub-kilometre experiment has a particularly high near-surface temperature bias at low elevations. The use of measurement campaign data, however, reveals some encouraging results, e.g. the sub-kilometre system has a more realistic vertical profile of temperature and wind speed, and the surface temperature sensitivity to the net surface energy is closer to the observations. This work demonstrates the potential of sub-kilometre NWP systems for forecasting weather in complex Arctic terrain, and also suggests that the increase in resolution needs to be accompanied with further development of other parts of the model system.

中文翻译：

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冬季北极峡湾系统中亚公里 NWP 系统的评估

摘要 地形对近地表大气条件的预测提出了挑战，即使在公里尺度数值天气预报 (NWP) 模型中也是如此。在这项研究中，将水平网格间距为 0.5 公里且垂直层数增加的 ALADIN-HIRLAM NWP 系统与类似于挪威气象研究所当前运行的 NWP 系统的 2.5 公里模型系统进行了比较。研究了 2018 年 2 月 12 日至 16 日期间在斯瓦尔巴群岛北极峡湾系统中分辨率提高对预报代表边界层过程能力的影响。模型模拟与实地活动期间进行的广泛观察进行了比较。与 2.5 公里的实验相比，具有亚公里网格间距的模型配置提高了近地表温度和风预测的空间结构和整体验证分数。亚公里实验成功地捕捉到了穿过山谷的风和与之相关的温度场。在冷空气池发展的情况下，亚公里实验在低海拔处具有特别高的近地表温度偏差。然而，测量活动数据的使用揭示了一些令人鼓舞的结果，例如，亚公里系统具有更真实的温度和风速垂直剖面，并且表面温度对净表面能的敏感性更接近于观测值。