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."

Excerpts:

Introduction:

Meteorological effects resulting from fluctuations in the solar wind are presently poorly represented in weather and climate models. Indeed, the role of the Sun is one of the largest unknowns in the climate system [1]. The existence of a meteorological response in the polar regions to fluctuations in the dawn–dusk component of the interplanetary magnetic field (IMF), By, is well established [2–5] and is known as the ‘Mansurov effect’. More controversially, there is evidence to suggest that this Sun–weather coupling occurs via the global atmospheric electric circuit [4, 5]. Consequently it has been assumed [6] that the effect maximizes at high latitudes and is negligible at low and mid-latitudes because the perturbation by the IMF is concentrated in the polar regions [7, 8]. However, the spatial variation of the IMF[interplanetary magnetic field]-weather coupling has not been investigated over the whole globe.

In the most detailed study to date [5], variations in IMF By of 8 nT were associated with changes in high-latitude station surface pressure of 1–2 hPa. These correlations were statistically significant for Antarctica between 1995 and 2005, and in the Arctic between 1999 and 2002. The time lag between changes in IMF By and changes in the surface pressure was estimated to be approximately 0 -2 days. Here we extend the analysis, for zero time lag, using 12 UT NCEP/NCAR reanalysis surface pressure [9] data on a global grid ( ; ) where is latitude and is longitude (section 2). A similar spatial analysis of the ionospheric potential for different states of IMF By (section 3) is used to investigate the theory that the response of surface pressure to fluctuations in IMF By occurs via the global atmospheric electric circuit. Our results indicate that a mechanism that is known to produce atmospheric responses to the IMF in the polar regions is also able to modulate weather patterns at mid-latitudes.

Discussion:
...

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 atmospheric dynamics [20]. The amplitudes of the IMF-related changes in atmospheric pressure gradient are comparable with the initial uncertainties in the corresponding zonal wind used in ensemble numerical weather prediction (NWP) [21] of 1 m s􀀀1. Such uncertainties are known to be important to subsequent atmospheric evolution and forecasting [22]. 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 [23]. 

In particular, it 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 [29, 30], and for the ‘Wilcox effect’ where reductions in the areas of high vorticity in winter storms are seen at times of solar wind heliospheric current sheet crossings [31] (which are characterized by sharp changes between steady, opposite IMF By states).

Full article available here

Environmental Research Letters Volume 8 Number 4

M M Lam et al 2013 Environ. Res. Lett. 8 045001 doi:10.1088/1748-9326/8/4/045001

The interplanetary magnetic field influences mid-latitude surface atmospheric pressure

OPEN ACCESS FOCUS ON HIGH ENERGY PARTICLES AND ATMOSPHERIC PROCESSES

M M Lam, G Chisham and M P Freeman

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The existence of a meteorological response in the polar regions to fluctuations in the interplanetary magnetic field (IMF) component By is well established. More controversially, there is evidence to suggest that this Sun–weather coupling occurs via the global atmospheric electric circuit. Consequently, it has been assumed that the effect is maximized at high latitudes and is negligible at low and mid-latitudes, because the perturbation by the IMF is concentrated in the polar regions. We demonstrate a previously unrecognized influence of the IMF By on mid-latitude surface pressure. The difference between the mean surface pressures during times of high positive and high negative IMF By possesses a statistically significant mid-latitude wave structure similar to atmospheric Rossby waves. Our results show that a mechanism that is known to produce atmospheric responses to the IMF [interplanetary magnetic field] in the polar regions is also able to modulate pre-existing weather patterns at mid-latitudes. We suggest the mechanism for this from conventional meteorology. The amplitude of the effect is comparable to typical initial analysis uncertainties in ensemble numerical weather prediction. Thus, a relatively localized small-amplitude solar influence on the upper atmosphere could have an important effect, via the nonlinear evolution of atmospheric dynamics, on critical atmospheric processes.