1. 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

2. Objective Analyse long-term variability and trends in frequency of wind directions at Vilsandi meteorological station during different months and seasons

3. 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)

4. Vilsandi 58°23’N, 21°49’E

5. 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)

6. Method Linear regression analysis Significance level P<0.05

7. Annual windrose over Vilsandi

8. Seasonal windroses

9. Changes in annual windrose

11. Changes in spring windrose

12. Changes in summer windrose

13. Changes in autumn windrose

14. Changes in winter windrose

15. Percentage of SE and SW winds in winter

16. 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

17. 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