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| Titel |
On the impact of short-term solar variability on the polar summer mesopause and noctilucent clouds |
| VerfasserIn |
C. von Savigny, C. Robert, N. Rahpoe, H. Winkler, E. Becker, H. Bovensmann, M. T. DeLand, J. P. Burrows |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068913
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| Zusammenfassung |
| The Earth’s middle atmosphere is affected by short-term solar variability in a variety of
ways. This contribution deals with two different short-term solar effects on the
polar summer mesopause region and on noctilucent clouds (NLCs) in particular.
First, the effect of solar proton events (SPEs) on the thermal conditions near the
polar summer mesopause and subsequently on NLCs is discussed. A proposed
physical mechanism to explain a dynamically induced warming at the polar summer
mesopause during and after SPEs is investigated using model simulations with the
Kühlungsborn Mechanistic General Circulation Model (KMCM). A second aspect related to
the effect of SPEs on NLCs is on the SPE-induced ion-chemical conversion of
H2O to HOx, leading to a possible sublimation of NLCs. However, detailed model
simulations of the ion chemistry and its effect on NLC particles demonstrate that this
effect is of minor importance compared to the dynamically induced temperature
effect.
Second, the recently discovered 27-day solar cycle signature in NLCs will be discussed,
which was identified in SCIAMACHY as well as SBUV satellite observations of NLCs using
cross-correlation analysis and the superposed epoch method. NLC occurrence rate and albedo
anomalies are anti-correlated with Lyman-α anomalies with a time-lag of 1 day at most. The
sensitivities of the NLC albedo anomalies to Lyman-α forcing in terms of the 27-day and the
11-year solar cycle were found to agree within their uncertainties. This finding suggests that
the same underlying physical mechanism drives the 27-day as well as the 11-year
solar cycle signature in NLCs. The exact mechanism is still unknown, however. |
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