Impact Assessments and Projections in Microclimates: Working with End-Users

Local impacts of meteorological events are often shaped by the microclimates in which they occur and only by including understanding of these microclimates can robust assessments and projections of such events be made. However, co-production of knowledge with end users is also required in order to make the assessments useful for decision makers and for society as a whole. This work presents two studies working with end users around the European city of Bergen, Norway. The first study is on extreme winds assessment for larger-scale construction. While such an assessment is usually based on historical observations when the climate was more stationary, under a changing climate, infrastructure built to last for the next fifty years or more may experience events not seen in the observational period. The case study is presented for the newly completed Hardanger Bridge in Norway and demonstrates a novel method for incorporating estimates of future changes in extreme winds into the design process (figure 1). Given the close collaboration with the engineers involved in the bridge's construction, the method was tailored to fit with existing practices and standards. The second study focuses on air pollution events within the city that are favoured by persistent wintertime temperature inversions in the narrow Bergen valley. Using a temperature profile radiometer, these temperature inversions have been characterized and related to the local circulation in- and above the valley. There has been the assumption that the many large ships in Bergen harbour had a major contribution to high pollution events within the city. Results from this study however indicate that temperature inversions are mostly connected to down-valley winds. These should remove the ship-emissions from the city, giving the ships a much smaller impact on high air pollution events than previously assumed, something that is under further evaluation and of high interest for the local harbour authority. Figure 1. Extreme wind speed distributions at the Utsira meteorological station from observations (black), with future estimates based on multiple regional climate models (red and blue). Vertical lines indicate the 50-year return event.