1 Evidence of trends in near-surface wind speeds over the Baltic

• Main Authors: S. C. Pryor, R. J. Barthelmie, J. Schoof
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Near-surface flow; Baltic basin; Trend analysis; General Circulation Models; North Atlantic; North Atlantic oscillation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.490.866; http://www.risoe.dk/vea/projects/endow/papers/pryoretal_trends.pdf

Annual mean wind speeds over the Baltic significantly increased over the period 1953-1999 with the majority of the increase being associated with increases in the upper quartile of the wind speed distribution and the winter season. Trends in annual and seasonal mean wind speeds are greatest in relative and absolute sense in the south-west of the Baltic basin where they are in excess of 0.25 m s-1 per decade for the annual mean. The majority of the increase in winter wind speeds is attributable to an increase in the frequency of westerly anticyclonic, westerly cyclonic and north-westerly cyclonic circulation types (defined by the Grosswetterlagen catalogue) which are in turn related to the recent prevalence of positive phase North Atlantic Oscillation. To address whether these trends will be maintained in the future we provide a highly provisional first prognosis for wind speeds during 2000-2030 based on simulations from the HadCM3 GCM. The results indicate that the first decades of the twenty-first century will be very similar to the 1990s with respect to the flow regime but that 2010’s may be characterized by slightly lower wind speeds. These results are highly preliminary because, as demonstrated, this GCM appears to underestimate wind speeds in the west of the Baltic, and slightly overestimate wind speeds in the northeast of the domain. Further evaluation of GCM simulations and use of downscaling techniques are advocated to provide more robust wind speed prognoses.