Nighttime atomic oxygen in the mesopause region retrieved from SCIAMACHY O(1S) green line measurements and its response to solar cycle variation

Abstract

AbstractThis paper presents new data sets relating to the abundance of atomic oxygen in the upper mesosphere and lower thermosphere, which were derived from the nighttime green line emission measurements of the SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY) instrument on the European Environmental Satellite (Envisat). These are compared to recently published data sets from the same SCIAMACHY green line measurements through the application of a different photochemical model and to data collected by the Sounding of the Atmosphere using Broadband Emission Radiometry instrument. We find that the retrieved atomic oxygen concentration depends on the choice of the underlying photochemical model. These dependencies explain a large proportion of the differences between recently published data sets. The impact of the 11 year solar cycle on volume emission rates and atomic oxygen abundances was analyzed for various data sets, with the finding that the solar cycle effect varies with the atomic oxygen data set used. The solar cycle impact on the SCIAMACHY data increases with altitude. Above 96 km, it is significantly larger than predicted by Hamburg Model of the Neutral and Ionized Atmosphere. Investigations indicate that these variations are primarily driven by total density compression/expansion variations during the solar cycle, rather than different photolysis rates.