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

Abstract

Abstract. The mesospheric OH Meinel emissions are subject of many theoretical and observational studies devoted to this part of the atmosphere. Depending on the initial vibrational level of excitation the altitude of the considered OH Meinel emission is systematically shifted, which has important implications for the intercomparison of different studies considering different transition bands. Previous model studies suggest that these vertical shifts are essentially caused by the process of collisional quenching with atomic oxygen. Following this hypothesis, a recent study found experimental evidence of a coherent seasonality at tropical latitudes between vertical shifts of different OH Meinel bands and changes in atomic oxygen concentrations. Despite the consistent finding of the above mentioned hypothesis, it cannot be excluded that the actual temporal variability of the vertical shifts between different OH Meinel bands may in addition be controlled or even dominated by other processes. It remains an open question whether the observed temporal evolution is indeed mainly controlled by the modulation of the collisional quenching process with atomic oxygen. By means of a sensitivity study which employs a quenching model to simulations made with the SD-WACCM4 chemistry climate model, we aim at assessing this question. From this study we find that the observed seasonality of vertical OH Meinel shifts is only partially controlled by temporal changes in atomic oxygen concentrations, while molecular oxygen has another noticeable impact on the vertical OH Meinel shifts. This in particular becomes evident for the diurnal variability of vertical OH Meinel shifts, which reveal only a poor correlation with the atomic oxygen species. Furthermore, changes in the H + O 3 source gases provide another mechanism that can potentially affect the diurnal variability in addition. By comparison with limb radiance observations from the SABER/TIMED satellite this provides an explanation for the less evident diurnal response between changes in O concentrations and vertical OH Meinel shifts. On the other hand, at seasonal timescales the coherency between both quantities is again evident in SABER/TIMED but less pronounced compared to our model simulations.

Nighttime Ozone Chemical Equilibrium in the Mesopause Region

“…Russell and Lowe (2003) used this assumption to infer the seasonal and global climatology of atomic oxygen by means of the Wind Imaging Interferometer on board the Upper Atmosphere Research Satellite. This assumption was used to investigate hydroxyl emission mechanisms, morphology, and variability in the upper mesosphere-lower thermosphere region (Kowalewski et al, 2014;Marsh et al, 2006;Xu et al, 2010Xu et al, , 2012. Kulikov et al (2006Kulikov et al ( , 2009 proposed algorithms for simultaneous retrieval of O, H, HO 2 , and H 2 O by joint OH and O 3 satellite measurements under the assumption of PEO.…”

Peak height of OH airglow derived from simultaneous observations a Fabry‐Perot interferometer and a meteor radar

“…In general, both the mean heights and standard deviations retrieved from ground-based measurements are slightly larger than those from SABER observations. It is well known that SABER is equipped with two channels sensitive to OH emissions: i.e., the 1.6 μm channel covers emissions from the OH(5,3)/OH(4,2) transitions and the 2.0 μm channel covers emissions from the OH(9,7)/OH(8,6) transitions [Russell et al, 1999;Kowalewski et al, 2014]. If we used the SABER OH 2.0 μm to retrieval airglow height, their yearly mean height is slightly higher than those from OH 1.6 μm, as well as larger in standard deviation.…”

Technical note: Evaluation of the simultaneous measurements of mesospheric OH, HO<sub>2</sub>, and O<sub>3</sub> under a photochemical equilibrium assumption – a statistical approach

“…Russell and Lowe (2003) applied PEO to infer the seasonal and global climatology of atomic oxygen using WINDII/UARS. PEO was deployed to investigate hydroxyl emission mechanisms, morphology, and variability in the MLT region (Marsh et al, 2006;Xu et al, 2010Xu et al, , 2012Kowalewski et al, 2014). Solomon (1991, 1993) and Mlynczak et al (2013b) used the equilibrium assumption to derive exothermic chemical heat.…”