Name
Christian von Savigny
University Greifswald, Germany

Title
Variability of mesopause temperature and OH*-Meinel emissions: solar effects from months to decades

Time and place
Tue 19 March 2013, 11.15
Room C609, Arrhenius Laboratory, 6th floor

(This event has taken place)

 

Abstract

The OH* Meinel emission bands are one of the most prominent airglow features in the terrestrial atmosphere and they are routinely used to remotely sense mesopause temperature from the ground. One of the main complications for the interpretation of these ground-based temperature measurements is the variability in OH emission altitude and emission profile shape, if simultaneous observations of the OH* emission rate profile are not available. In order to characterize the variability in the OH emission altitude we use nighttime limb emission observations with SCIAMACHY on Envisat. Surprisingly, the SCIAMACHY observations do not show a pronounced 11-year solar cycle or long-term variation in annually averaged OH emission altitudes from 2003 to 2011, in contrast to earlier studies. However, the measurements show clear evidence that Meinel emissions from higher vibrational levels occur at slightly higher altitudes. These observations are complemented by model simulations indicating that quenching by atomic oxygen is the main process causing the vertical shifts between Meinel bands originating from different vibrational levels.

In the second part of the talk recent results on a solar-driven 27-day cycle in OH(3-1) rotational temperature – also retrieved from SCIAMACHY/Envisat – will be presented. Interestingly, the sensitivity parameter quantifying the dependence of mesopause temperature on solar forcing has very similar values for both the solar 27-day and the 11-year cycle, suggesting that the same physical/chemical processes cause solar-driven temperature variability at both time scales. A similar effect was recently reported by our group for NLC albedo.