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Long-term changes in frequencies of wind directions on the western coast of Estonia Jaak Jaagus Institute of Geography, University of Tartu Second International ASTRA Conference Gdansk, 27 October 2006 Objective

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long term changes in frequencies of wind directions on the western coast of estonia

Long-term changes in frequencies of wind directions on the western coast of Estonia

Jaak Jaagus

Institute of Geography, University of Tartu

Second International ASTRA Conference

Gdansk, 27 October 2006

objective
Objective
  • Analyse long-term variability and trends in frequency of wind directions at Vilsandi meteorological station during different months and seasons
hypotheses
Hypotheses
  • Climate warming should be related to changes in frequencies of wind directions
  • Increasing trend in NAO index in winter should increase a percentage of westerly and southwesterly winds
  • Increase in frequency of wind directions bringing milder weather in winter (W, SW, NW), decrease in frequency of wind from the “cold” directions (N, NE, E, SE)
slide5
Data
  • Ordinary observations 8 times per day
  • Period 1966-2005
  • Monthly, seasonal and annual frequencies of N, NE, E, SE, S, SW, W and NW winds
  • Seasons: spring (MAM), summer (JJA), autumn (SON), winter (DJF)
  • Weathercock (1966-1976 Oct)
  • Anemorhumbometer (1976 Nov – 2003 Aug)
  • Automatic weather station (since September 2003)
method
Method
  • Linear regression analysis
  • Significance level P<0.05
changes in frequency of monthly wind direction
Changes in frequency of monthly wind direction
  • N winds: increase in March
  • NE winds: decrease in May and June
  • E winds: decrease in January
  • SE winds: decrease in January and February, increase in August
  • SW winds: increase in January and February
  • W winds: increase in January and May
  • NW winds: increase in January, decrease in September
conclusions
Conclusions
  • During 1966-2005, a significant increase in annual percentage of SW winds have occurred
  • Frequencies of NE, E and SE winds have slightly decreased
  • Changes in windrose in spring, summer and autumn are mostly insignificant, however a shift to W in spring, to S in summer and to SE in autumn is evident
  • Windroses in winter are changed dramatically, turning mostly from SE and E to SW and W