Sunday, November 25, 2012

A new paper is under discussion under ACPD by Brugnara et al.,

Influence of the sunspot cycle on the Northern Hemisphere wintertime circulation from long upper-air data sets

Y. Brugnara1,2, S. Brönnimann1,2, J. Luterbacher3, and E. Rozanov4,5
1Institute of Geography, University of Bern, Bern, Switzerland
2Oeschger Centre for Climate Change Research, Bern, Switzerland
3Department of Geography, Climatology, Climate Dynamics and Climate Change, Justus-Liebig University of Giessen, Giessen, Germany
4Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, \newline Davos, Switzerland
5Institute for Atmospheric and Climate Science ETH, Zurich, Switzerland

 Abstract. Here we present a study of the 11-yr sunspot cycle's imprint in the Northern Hemisphere atmospheric circulation, using three recently developed gridded upper-air data sets which extend back to the early twentieth century. We find a robust response of the tropospheric late-wintertime circulation to the sunspot cycle, independent from the data set. This response is particularly significant over Europe, but results show that it is not directly related to a North Atlantic Oscillation modulation; instead, it reveals a significant connection to the more meridional Eurasian pattern. The magnitude of mean seasonal temperature changes over the European land areas locally exceeds 1 K in 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 on the existence of an influence of the 11-yr cycle on the European climate, although the signal is much weaker in the first half of the period compared to the second half. The last solar minimum (2005 to 2010), which was not included in our analysis, shows anomalies that are consistent with our statistical results for earlier solar minima.