Solar activity affects the occurrence of synoptic types over Europe

The solar effects on tropospheric circulation over Europe are investigated by counting the occurrence of Hess-Brezowsky synoptic types under various levels of solar activity. Solar minima are accompanied by a lower incidence of westerly types and a higher incidence of easterly and northerly types. The types with a northeast and northwest flow are most frequent under a moderate solar activity. There is a weak tendency towards the anticyclonic (cyclonic) types to be less (more) frequent under moderate solar activity. Our results are in accord with previous studies, indicating a strengthened zonal flow in solar maxima and changes in the modes of low-frequency circulation variability. The results point to the fact that the effects of solar activity are not linear.