Changes in storminess on the western coast of Estonia in relation to large-scale atmospheric circulation

Intensification of coastal erosion caused by windstorms is an important problem in the coastal regions of Estonia. The objective of this study was to analyse relationships between storms observed at Vilsandi, the westernmost station in Estonia, and large-scale atmospheric circulation. Statistical analyses reveal close correlation between parameters of atmospheric circulation and the number of storms. Windstorms are related to intense zonal circulation, i.e. westerlies, while reduced storminess is associated with meridional circulation. The Arctic Oscillation (AO) index has the highest correlation (0.68) with the frequency of storms during the winter season (December to February). Even the correlation coefficients for the local zonal circulation index for Estonia do not exceed this value. These results show that large-scale circulation patterns determine circulation on the local scale. Results of the conditional Mann-Kendall test confirm that the increasing trend in winter storminess is induced by a positive trend in the intensity of westerlies, as seen in time series of the AO index and in the frequency of the circulation form W of Vangengeirn. and Girs. These changes were most substantial in February.