Characterizing variability in OH* emission altitudes and variations in satellite mesopause temperature observations during the last solar cycle

This project has two main goals. Firstly, the temporal and spatial variability of OH-Meinel emission rate profiles will be characterized and quantified at temporal scales ranging from days to a decade. Secondly, trends and solar cycle variations (both 11-year and 27-day) of mesopause temperature will be investigated and quantified based on the available satellite data records for this atmospheric region. In terms of the first goal, an accurate knowledge of the variability of OH emission altitudes is of great importance for a correct interpretation on ground-based measurements of OH rotational temperatures. Measurements of this kind are currently carried out at more than 50 stations worldwide, and some of the time series span multiple decades. Unfortunately, the simultaneous observation of OH emission rate profiles is not possible from the ground. Yet, these profiles are required for a correct interpretation of the temperature measurements.

The foreseen research activities are largely based on nighttime limb measurements with the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) instrument on the European environmental satellite Envisat. SCIAMACHY allows the retrieval of both OH emission rate profiles and OH(3-1) rotational temperature. The focus of the investigations will be on the quantification of OH emission height variations due to seasonal and QBO effects, on the impact of solar variability (including variations in electromagnetic forcing as well as solar proton events (SPE)), and potential effects associated with the lunar semi-diurnal tide. Moreover, an empirical model will be provided that allows estimating OH emission altitude from ground-based measurements of OH emission rates.

One focus of the analysis of mesopause temperature is on the 27-day solar cycle signature. The existence of a 27-day solar cycle signature in middle atmospheric temperature has already been demonstrated, but many aspects and the underlying physical and/or chemical processes are not well understood.

Project duration:  01.09.2014 - 31.08.2017

Prof. Dr. Christian von Savigny (Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald) & Dr. Holger Winkler (Institut für Umweltphysik, Universität Bremen)

Prof. Dr. Christian von Savigny, csavigny@physik.uni-greifswald.de
Dr. Holger Winkler, hwinkler@iup.physik.uni-bremen.de

Kowalewski, S., von Savigny, C., Palm, M., McDade, I. C., and Notholt, J.: On the impact of the temporal variability of the collisional quenching process on the mesospheric OH emission layer: a study based on SD-WACCM4 and SABER, Atmos. Chem. Phys., 14, 10193-10210, doi:10.5194/acp-14-10193-2014, 2014.

Robert, C. E., C. von Savigny, N. Rahpoe, H. Bovensmann, J. P. Burrows, M. T. DeLand, and M. J. Schwartz, First evidence of a 27 day solar signature in noctilucent cloud occurrence frequency, J. Geophys. Res., 115, D00I12, doi:10.1029/2009JD012359, 2010.

von Savigny, C., K.-U. Eichmann, C. E. Robert, J. P. Burrows, and M. Weber, Sensitivity of equatorial mesopause temperatures to the 27-day solar cycle, Geophys. Res. Lett., 39, L21804, doi:10.1029/2012GL053563, 2012.

von Savigny, C., McDade, I. C., Eichmann, K.-U., and Burrows, J. P.: On the dependence of the OH* Meinel emission altitude on vibrational level: SCIAMACHY observations and model simulations, Atmos. Chem. Phys., 12, 8813-8828, doi:10.5194/acp-12-8813-2012, 2012.

von Savigny, C., O. Lednyts'kyy, On the relationship between atomic oxygen and vertical shifts between OH Meinel bands originating from different vibrational levels, Geophys. Res. Lett., 40(21), 5821 - 5825, 2013.

von Savigny, C., Variability of OH(3-1) emission altitude from 2003 to 2011: Long-term stability and universality of the emission rate - altitude relationship, submitted to J. Atmos. Sol.-Terr. Physics, 2014.