Temporal changes in wind conditions at Svalbard for the years 1986–2015

Abstract

ABSTRACTThis paper presents trends in wind speed and wind direction indices at selected stations in Svalbard (Bjørnøya, Hopen and Ny-Ålesund) and in the NCEP/NCAR and ERA-Interim reanalysis for the period 1986–2015. The analysed wind indices include the sum of days (annual or seasonal) with the daily range wind speed or wind direction. Using the Mann-Kendall trend test, we look for temporal trends in these indices, compare the results for the measured and gridded datasets, and then analyse the spatial variability in those trends. For the stations, statistically significant decreasing trends are detected for the frequency of days with very low wind speed (≤2 m s−1) and for days with strong wind (>10 m s−1). From the reanalysis data, indices with wind speed of up to 5 m s−1 were characterized by decreasing trends, while indices with wind speed above the mentioned threshold show increasing trends. Wind direction indices are characterized by different tendencies in the Ny-Ålesund station, where local elements modify the dominant directions of the air mass advection. The trends vary in space for the given region. Reanalysis data show the biggest positive trend for the occurrence of northerly winds over the Greenland Sea and Arctic Ocean, which cannot be confirmed by measurements (no stations available). The trends in wind speed and direction indices may partly be explained by changes in the frequency of circulation patterns.