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| Titel |
Temporal response of the polar troposphere and stratosphere to changes in the global atmospheric electric circuit associated with solar wind variability |
| VerfasserIn |
Mai Mai Lam, Gareth Chisham, Mervyn P. Freeman |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090992
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| Publikation (Nr.) |
 EGU/EGU2014-5257.pdf |
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| Zusammenfassung |
| The surface meteorological response in the polar regions to fluctuations in the dawn-to-dusk
interplanetary magnetic field (IMF) component, By, indicates that a coupling between the
Sun and Earth’s weather occurs via the global atmospheric electric circuit (GEC). In
particular, the difference between the mean surface pressures during times of high positive
and high negative IMF By is 1 - 2 hPa in Antarctica and occurs on a relatively fast timescale
compared to other proposed Sun-weather connections. Specifically, the observed time lag
between the solar wind perturbation of the ionosphere-to-ground electric potential (and hence
the vertical fair-weather current) and the ground level response is up to about 1 day. Here we
extend this result and present further evidence that a solar wind–lower atmosphere coupling
occurs via the GEC throughout the troposphere which in turn affects the stratosphere. We do
this using NCEP/NCAR reanalysis data to determine the time lag of the peak correlation
between IMF By and geopotential height for different pressure levels in the troposphere and
stratosphere.
In Antarctica, there is a statistically-significant correlation between IMF By and
geopotential height within the troposphere, but not within the stratosphere. The peak in the
correlation is observed at higher time lags in the upper troposphere (2 - 4 days) than in the
lower troposphere (0 - 1 day). The amplitude of the correlation has a periodicity of about 27
days, associated with the effect of the rotation of the Sun on the periodicity of the solar wind
magnetic field at Earth. In the Arctic, the time lag between IMF By and the meteorological
response is significant and similar at different pressure levels in the troposphere and is
about 0 - 1 day. A significant response is seen in the stratosphere with a time lag of
about 10 days. We interpret the existence of a time lag of less than a few days in the
troposphere as evidence in support of a mechanism involving the action of the GEC on
cloud physics within a part of the troposphere. The increase in the time lag with
increasing altitude is suggestive of an upward propagation of the influence of the
solar-wind-induced variability in the lower troposphere, by conventional meteorological
processes. This is in contrast to the apparent downward propagation of meteorological
effects to the lower troposphere from the stratosphere due to other mechanisms
associated with solar variability, involving ultra-violet radiation or energetic particle
precipitation. |
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