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We validate a new high-resolution (3 km) numerical mesoscale weather simulation for offshore wind power purposes for the time period 2004-2016 for the North Sea and the Norwegian Sea. The 3 km Norwegian reanalysis (NORA3) is a dynamically downscaled data set, forced with state-of-the-art atmospheric reanalysis as boundary conditions. We conduct an in-depth validation of the simulated wind climatology towards the observed wind climatology to determine whether NORA3 can serve as a wind resource data set in the planning phase of future offshore wind power installations. We place special emphasis on evaluating offshore wind-power-related metrics and the impact of simulated wind speed deviations on the estimated wind power and the related variability. We conclude that the NORA3 data are well suited for wind power estimates but give slightly conservative estimates of the offshore wind metrics. In other words, wind speeds in NORA3 are typically 5% (0.5ms-1) lower than observed wind speeds, giving an underestimation of offshore wind power of 10 %-20% (equivalent to an underestimation of 3 percentage points in the capacity factor) for a selected turbine type and hub height. The model is biased towards lower wind power estimates due to overestimation of the wind speed events below typical wind speed limits of rated wind power (u < 11-13ms-1) and underestimation of high-wind-speed events (u > 11-13ms-1). The hourly wind speed and wind power variability are slightly underestimated in NORA3. However, the number of hours with zero power production caused by the wind conditions (around 12% of the time) is well captured, while the duration of each of these events is slightly overestimated, leading to 25-year return values for zero-power duration being too high for the majority of the sites. The model performs well in capturing spatial co-variability in hourly wind power production, with only small deviations in the spatial correlation coefficients among the sites. We estimate the observation-based decorrelation length to be 425.3 km, whereas the model-based length is 19% longer. [ABSTRACT FROM AUTHOR]

This paper presents selected results of the interdisciplinary research project Impacts of extreme weather events on infrastructure in Norway (InfraRisk) carried out between 2010 to 2013, as part of the program NORKLIMA (2004 2013) of the Research Council of Norway (RCN). The project has systematized large amounts of existing data and generated new results that are important for our handling of risks associated with future extreme weather and natural hazards threatening the transport infrastructure in Norway. The results of the InfaRisk project range widely, from the establishment of trends in key weather elements to studies of human response to threats from extreme weather. The analyses of weather elements have provided a clearer understanding of the trends in the development of extreme weather. The studies are based on both historical data and available future scenarios (projections) from climate models. Compared to previous studies, we calculated changes in climate variables that are particularly important in relation to nature hazards. Overall, the analyses document an increase in frequency as well as intensity of both precipitation and wind. Results of projections show that the observed changes will continue throughout this century. We could also identify large regional differences, with some areas experiencing, e.g., a reduction in the intensity of heavy rainfall events. However, most of the country will experience the opposite, i.e., both increased intensity and increased frequency of heavy precipitation. Our analyses show that at least 27 per cent of Norwegian roads and 31 per cent of railroads are exposed to rock fall and snow avalanches hazards. The project has also assessed relationships between different parameters that can affect the likelihood of debris flows. Variables such as terrain slope and size of watercourses are important, while local climate, which varies widely in Norway, determines threshold values for rainfall that can trigger debris flows. [ABSTRACT FROM AUTHOR]