As part of the second SPARC (Stratosphere–troposphere Processes And their Role in Climate) water vapor assessment (WAVAS-II), we present measurements taken from or coincident with seven sites from which ground-based microwave instruments measure water vapor in the middle atmosphere. In the lower mesosphere, we quantify instrumental differences in the observed trends and annual variations at six sites. We then present a range of observed trends in water vapor over the past 20 years.

This study focuses on the analysis of astronomical medium-resolution spectra from the VLT in Chile to measure airglow pseudo-continuum emission of FeO in the optical regime. Compared to OH or Na emissions, this emission is difficult to measure. Using 3.5 years of spectroscopic data, we found annual and semi-annual variations of the FeO emission. Furthermore, we used WACCM to determine the quantum yield of the FeO-producing Fe + O₃ reaction in the atmosphere, which has not been done before.

Global concentration fields of Mg and Mg+ in the Earth's upper mesosphere and lower thermosphere (70-150km) are presented. These are retrieved from SCIAMACHY/Envisat satellite grating spectrometer measurements in limb viewing geometry between 2008 and 2012. These were compared with WACCM-Mg model results and a large fraction of the available measurement results for these species, and an interpretation of the results is done. The variation of these species during NLC presence is discussed.