HAPpy Hour Seminar : Modelling Atmospheric Icing in the Norwegian Arctic: Impact of Resolution, Elevation, and Microphysics

Abstract: Atmospheric icing is a global term that describes all types of ice growth due to frozen water substances and poses significant challenges for infrastructure in cold, mountainous regions. 

In this study, we investigated in-cloud icing at a complex terrain site in the Norwegian Arctic during the period August 2022–July 2023 using the Weather Research and Forecasting (WRF) model, supported by observational data. Our findings highlight that horizontal resolution has a substantial impact on the model’s ability to accurately capture icing events. We observed that icing intensity increases with elevation up to 200 meters above ground level. 

Additionally, terrain height accuracy proved critical: at one site, using the correct geographic location but with terrain roughly 200 meters too low in WRF led to a threefold underestimation of icing. In contrast, selecting a nearby point with a more accurate elevation significantly improved the results. A case study of the 22 – 25 February 2023 icing event showed that reducing the cloud droplet number concentration enhanced model performance. From an application standpoint, we assessed icing intensity and estimated production loss at a new wind farm site for the year 2017 using WRF. Results indicate that turbines at higher elevations experience more severe icing, with annual meteorological icing exceeding 20% at the most affected site. This work underscores the importance of accurate terrain representation, microphysical tuning, and high-resolution modeling for reliable icing assessments in complex terrain.