Influence of the sunspot cycle on the Northern Hemisphere wintertime circulation from long upper-air data sets
Here we present a study of the 11 yr sunspot cy- cle’s imprint on the Northern Hemisphere atmospheric circu- lation, using three recently developed gridded upper-air data sets that extend back to the early twentieth century. We find a robust response of the tropospheric late-wintertime circula- tion to the sunspot cycle, independent from the data set. This response is particularly significant over Europe, although re- sults show that it is not directly related to a North Atlantic Oscillation (NAO) modulation; instead, it reveals a signif- icant connection to the more meridional Eurasian pattern (EU). The magnitude of mean seasonal temperature changes over the European land areas locally exceeds 1Kin the lower troposphere over a sunspot cycle. We also analyse surface data to address the question whether the solar signal over Europe is temporally stable for a longer 250 yr period. The results increase our confidence in the existence of an influence of the 11 yr cycle on the Euro- pean climate, but the signal is much weaker in the first half of the period compared to the second half. The last solar min- imum (2005 to 2010), which was not included in our anal- ysis, shows anomalies that are consistent with our statistical results for earlier solar minima.