Spatial distribution of Northern Hemisphere winter temperatures during different phases of the solar cycle

Abstract

Several recent studies have found variability in the Northern Hemisphere winter climate related to different parameters of solar activity. While these results consistently indicate some kind of solar modulation of tropospheric and stratospheric circulation and surface temperature, opinions on the exact mechanism and the solar driver differ. Proposed drivers include, e.g., total solar irradiance (TSI), solar UV radiation, galactic cosmic rays, and magnetospheric energetic particles. While some of these drivers are difficult to distinguish because of their closely similar variation over the solar cycle, other suggested drivers have clear differences in their solar cycle evolution. For example, geomagnetic activity and magnetospheric particle fluxes peak in the declining phase of the sunspot cycle, in difference to TSI and UV radiation which more closely follow sunspots. Using 13 solar cycles (1869-2009), we study winter surface temperatures and North Atlantic oscillation (NAO) during four different phases of the sunspot cycle: minimum, ascending, maximum, and declining phase. We find significant differences in the temperature patterns between the four cycle phases, which indicates a solar cycle modulation of winter surface temperatures. However, the clearest pattern of the temperature anomalies is not found during sunspot maximum or minimum, but during the declining phase, when the temperature pattern closely resembles the pattern found during positive NAO. Moreover, we find the same pattern during the low sunspot activity cycles of 100 years ago, suggesting that the pattern is largely independent of the overall level of solar activity.

Comparing Coronal and Heliospheric Magnetic Fields Over Several Solar Cycles

“…To assess this in a more quantitative way, Figure 4 shows the average polarity match percentage for each of the four phases of the solar cycle. We use the recently suggested solar cycle phase function (Maliniemi et al 2014), which divides the solar cycle into four phases according to the sunspot minimum and maximum times (ftp://ftp.ngdc. noaa.gov/STP/space-weather/solar-data/solar-indices/sunspotnumbers/cycle-data/table_cycle-dates_maximum-minimum.txt; maximum of cycle 24 is taken to be in 2014 April; extended here until 2015 December).…”

Solar forcing for CMIP6 (v3.2)

“…In particular, the production of odd nitrogen and odd hydrogen species causes changes in ozone abundances via catalytic cycles, potentially affecting temperature and winds (see, e.g., the review by Sinnhuber et al, 2012). Recent model studies and the analysis of meteorological data have provided evidence for a dynamical coupling of this signal to the lower atmosphere, leading to particleinduced surface climate variations on a regional scale (e.g., Seppälä et al, 2009;Baumgaertner et al, 2011;Rozanov et al, 2012;Maliniemi et al, 2014).…”

HEPPA-II model–measurement intercomparison project: EPP indirect effects during the dynamically perturbed NH winter 2008–2009

“…EPP-induced ozone changes are thought to modify the thermal structure and winds in the stratosphere which, in turn, modulate the strength of the Arctic polar vortex. The introduced signal could then propagate down to the surface, introducing significant variations of regional climate, particularly in the Northern Hemisphere (NH) (Seppälä et al, 2009;Baumgaertner et al, 2011;Rozanov et al, 2012;Seppälä and Clilverd, 2014;Maliniemi et al, 2014).…”