Changes in meteorological variables that can trigger natural hazards in Norway

Abstract

Using a daily interpolated dataset, we studied several climate variables known to be potential triggers of natural hazards in Norway. A trend analysis for different time periods was performed to assess temporal changes in the climate variables, and trends were evaluated for field significance and average changes on a regional level. The study shows that the frequency of moderate to strong precipitation events has increased in most parts of the country since 1957, particularly in wet regions. Regional averages were mainly in the range of 10 to 30%, and positive trends were field-significant in most regions. The intensity of strong precipitation events also showed a general increase, except in parts of central and northern Norway. The average increase in some regions was as high as 90%; however, the changes might in part be a result of inconsistencies in the station network, which can affect the precipitation grid. Snow amounts have increased in colder areas, while in warmer areas, field-significant negative trends were found, with reductions of almost 50% in some regions. Analyzing large snowfalls and the number of snow days revealed similar patterns, but trends were weaker. The number of near-zero events, defined as days with mean temperature between -1.5 and 1.0°C, has mainly increased, except in coastal southern Norway. The detected trends may have led to an increased number of snow avalanches at higher elevations, and an increase in floods and some types of landslides. The climate dataset was shown to be a valuable supplement to the analysis of past climate on a regional scale. © Inter-Research 2012.