Simulating observed wet-snow icing in complex terrain in Iceland

Unique records of wet-snow icing events and systematic observations of ice loading in test spans in the complex orography of Iceland, as well as downscaled flow at high horizontal resolution are used to develop and improve methods to forecast wet snow accretion on structures. The simulated data is composed of 55 years of ECMWF-analysis downscaled to a horizontal resolution of 9 km and seventeen years downscaled to 3 km, using the WRF numerical system. Hundreds of observed wet snow icing events are logged in detail in an icing database, most of which include an estimate of the mean and maximum diameter of observed icing. Here, long time series of observed wet snow icing in South-Iceland are used to improve the existing methods for parameterizing atmospheric icing based on the downscaled atmospheric data. The improved methods are furthermore tested and validated for selected cases of observed widespread and intensive wet snow icing in South-Iceland. The results form a basis for mapping the climatology of wet snow icing in the complex terrain of Iceland as well as for preparing operational forecasts of wet snow icing and severe weather for overhead power transmission lines in complex terrain, based on simulated flow from state of the art atmospheric models. This work is done within the framework of the Nordic IceWind-project and the European COST-action WIRE (Weather Intelligence for Renewable Energies).