New paper finds amplification mechanism by which the Sun controls climate via pressure changes

Nov 12, 2013 Environmental Research Web

Sun’s magnetic field affects weather as far south as North Africa

The Sun’s fluctuating magnetic field has a greater influence on our weather system than at first thought, according to researchers from the British Antarctic Survey.

It has long been known that fluctuations in the solar wind result in meteorological effects on Earth, but Mai Mai Lam and her colleagues believe that these effects are presently poorly represented in weather and climate models.

"It has been assumed that the effect of the Sun’s magnetic field on our weather is strongest at the poles and negligible at low- and mid-latitudes," Lam told environmentalresearchweb. "While it is true that the effects are strongest at the poles, we have found effects as far down as North Africa and up to Uruguay."

Lam and colleagues discovered that changes in the surface pressure of the Earth’s atmosphere correlated with changes in the Sun’s magnetic field. While the changes at the poles were caused by a direct effect, an indirect effect was felt at lower latitudes: the change in surface pressure at the poles modulated weather patterns at mid-latitudes.

"The effects we saw were small, but not insignificant," said Lam. "If the Earth’s atmospheric pressure varies naturally +/− 30 hPa, we noticed an effect of around +/− 2 hPa, which is about the same size as the initial errors in ensemble weather forecasting. So while the effect is small, if it were incorporated into weather models, it could change forecasts."

According to Lam, previous proposals to link solar wind variations to significant weather or climate variability have been dismissed on the grounds that the magnitude of the energy change in the atmosphere associated with the solar wind variability is far too small to impact the Earth’s system. However, this argument neglects the importance of non-linear atmospheric dynamics. [i.e. solar amplification]

"We have shown that a relatively localized and small amplitude solar influence on the upper polar atmosphere could have an significant effect, via the nonlinear evolution of atmospheric dynamics, on critical processes such as European climate and the breakup of Arctic sea ice," said Lam. "We would ultimately like to see this effect incorporated into weather forecasting models, but first more research needs to be carried out to explore this effect and also to understand the mechanism behind it."

Related links

• The interplanetary magnetic field influences mid-latitude surface atmospheric pressure M M Lam, G Chisham and M P Freeman 2013 Environ. Res. Lett. 8 045001

This same paper was previously highlighted on The Hockey Schtick:

New paper finds multiple amplification mechanisms by which the Sun controls climate

A new paper published in Environmental Research Letters finds multiple solar amplification mechanisms by which small changes in the solar wind and interplanetary magnetic field [IMF] have significant global effects upon atmospheric pressures, the jet stream, weather & climate patterns such as the North Atlantic Oscillation [NAO], storm tracks, Eurasian winter temperatures, and the breakup of Arctic sea ice. 

According to the authors, "Previously, proposals to link solar wind variations to significant weather or climate variability have been dismissed on the grounds that the magnitude of the energy change in the atmosphere associated with the solar wind variability is far too small to impact the Earth’s system. However, this argument neglects the importance of nonlinear tmospheric dynamics"... "Consequently, we have shown that a relatively localized and small-amplitude solar influence on the upper polar atmosphere could have an important effect, via the nonlinear evolution of atmospheric dynamics on critical processes such as European climate and the breakup of Arctic sea ice." 
"In particular, [the solar interplanetary magnetic field changes] affects the structure of the Rossby wavefield, which is key in determining the trajectory of storm tracks [24]. The configuration of the North Atlantic jet stream is particularly susceptible to changes in forcing [25]. In turn, so are the location and the timing of blocking events in this region, in which vortices are shed from the jet stream leading to prolonged periods of low or of high pressure [26]. It has also been proposed that the low-frequency variability of the North Atlantic Oscillation (NAO) arises as a result of variations in the occurrence of upper-level Rossby wavebreaking events over the North Atlantic [27]. The NAO itself is key to climate variability over the Atlantic–European sector stretching from the east coast of the United States to Siberia, and the Arctic to the subtropical Atlantic [28, 25]."

"Our results may therefore provide part of the explanation for previously observed correlations between Eurasian winter temperatures and solar variability."