A study published in Nature Geosciences on Monday presents new support for the idea that when the sun’s intensity weakens, it favors weather patterns conducive to cold (and snow) over large parts of the U.S. and northern Europe.
The study “Solar forcing of winter climate variability in the Northern Hemisphere”, led by a team of scientists in the United Kingdom, examined how weather patterns changed when the amount of solar radiation reaching the Earth rises and falls. Using a model of the atmosphere and ocean, the authors reached this key conclusion: ...low solar activity, as observed during recent years, drives cold winters in northern Europe and the United States, and mild winters over southern Europe and Canada.
Of particular interest for the U.S., the study found temperature and pressure patterns associated with low solar activity resemble the negative phase of the North Atlantic Oscillation (NAO). A negative NAO is correlated with cold, snowy weather over the mid-Atlantic and Northeast U.S., including Washington, D.C.
During a negative NAO, pressures are above normal at high latitudes and lower to the south. This configuration, sometimes referred to as a blocking pattern, results in a northerly wind flow from the Arctic latitudes towards the mid-latitudes which results in cold air outbreaks. The inbound cold air often collides with warm air at lower latitudes, triggering storms.
This link between low solar activity and the negative NAO has also been identified in some older studies. A 2001 NASA study found that during the 17th century “Maunder Minimum” or “little ice age”, when sunspot activity was quite low, the negative NAO pattern dominated. Similarly, a 2009 study, identified links between solar minima and enhanced north to south (or “meriodonal”) flow (characteristic of a negative NAO).
The UK Met Office, in a blog about new study posits lower than normal activity in the last few years may have played in role in the winters’ weather:
The Sun has recently been in a quiet phase of its regular 11-year cycle, which coincided with three years in which the UK, along with other places in northern Europe and parts of the US, experienced cold conditions unusual in the recent record. But unusually warm weather was felt both further south, around the Mediterranean Sea, and further north in Canada and Greenland.
Understanding the links between the solar cycle and weather patterns may help improve seasonal forecasting.
“We hope this will open the door to improving ultralong-range predictions,” study co-author Adam Scaife told ScienceNews.
So where do we stand in the current solar cycle? Does this information offer insight into the upcoming winter and should the eastern U.S. expect another cold one?
Capital Weather Gang long-range forecasting specialist Matt Rogers says solar intensity is on the upswing, but that does not necesssarily mean it will be a warm winter.
“It may argue for less blocking [i.e. north to south flow and cold air outbreaks], but this solar maximum is forecast to be the weakest in about 100 years, so it remains to be seen about how much less we see,” he said.