Temporal Variation of Atomic Oxygen in the Upper Mesosphere from SOFIE

Atomic oxygen is an important species in the chemistry of the Earth’s upper mesosphere that extends from ~80 – 100 km. It impacts the photochemistry and the energy budget of this region, and thus, its seasonal and latitudinal variations are important to the chemistry of this region. Atomic oxygen is difficult to measure through in situ and remote sensing techniques in the upper mesosphere due to the absence of vibration and rotation spectra. The Solar Occultation for Ice Experiment (SOFIE) onboard the Aeronomy of Ice in the Mesosphere (AIM) spacecraft typically measures at high latitudes (between 65o-85o) in both hemispheres with a field of view of ~ 1.6 km. In this study, Level 2, Version 1.3 SOFIE ozone retrievals at 0.291 μm are used to derive daytime atomic oxygen assuming photochemical equilibrium and the Chapman equations for ozone production and destruction. The derived atomic oxygen from SOFIE is compared to coincident measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite and to NRLMSIS 2.0 (US Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar) model from 2008 to 2014. SABER and NRLMSIS 2.0 show qualitative agreement with SOFIE and exhibit differences owed to systematic and random differences in coincident retrieved profiles and sampling. Further, SOFIE measurements are used to investigate the latitudinal and seasonal variability of atomic oxygen in both hemispheres. This research establishes the robustness of SOFIE’s derived atomic oxygen measurements for scientific use.