Interdecadal variations of surface wind direction in Lund, southern Sweden, 1741–1990

By uni‐ and bimodal mean vector analysis it is concluded that the decadal pattern of surface‐wind‐direction frequencies in Lund, southern Sweden, has changed substantially between 1741 and 1990. Trend analysis shows that statistically significant decreasing trends for north and north‐east winds are present during all seasons, whereas a decline in easterly wind is most prominent in July‐September. These trends are paralleled by increases of south‐east (January‐May and August‐November) and south‐west winds (April‐September and November‐January). These trends promote milder autumns, winters, and springs and a somewhat cooler summer. The investigation period is divided into three phases on the basis of similar flow patterns, which in general terms agree with Scandinavian temperature records: (i) 1741–1840‐a continental low‐zonality period featuring extreme bimodal flow of wind with relatively high frequencies of east winds, which indicate a continental climate. Warm summers and cold winters are produced by this flow pattern. The severity of winters was enhanced by a high frequency of north and north‐east winds. (ii) 1841–1910‐a transition period with decreased continentality and low yearly temperatures. This circulation type caused a temperature drop except during winter. (iii) 1911–1990‐a maritime high‐zonality period featuring further strengthening of the westerly flow. A warm maritime phase with least expressed warming in summer. Severe winters are further counteracted by low frequencies of north and north‐east winds.