Abstract
Ground based observations of 11.072 GHz atmospheric ozone (O3) emission have been made using the Ny Ålesund Ozone in the Mesosphere Instrument (NAOMI) at the UK Arctic Research Station (latitude 78°55’0” N, longitude 11°55’59” E), Spitsbergen. Seasonally averaged O3 vertical profiles in the Arctic polar mesosphere lower thermosphere region for night-time and twilight conditions in the period 15 August 2017 to 15 March 2020 have been retrieved over the altitude range 62–98 km. NAOMI measurements are compared with corresponding, overlapping observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. The NAOMI and SABER data are binned according to the SABER instrument 60 day yaw cycles into 3 month ‘winter’ (15 December–15 March), ‘autumn’ (15 August–15 November), and ‘summer’ (15 April–15 July) periods. The NAOMI observations show the same year-to-year and seasonal variabilities as the SABER 9.6 μm O3 data. The winter night-time (solar zenith angle, SZA ≥ 110°) and twilight (75° ≤ SZA ≤ 110°) NAOMI and SABER 9.6 μm O3 volume mixing ratio (VMR) profiles agree to within the measurement uncertainties. However, for autumn twilight conditions the SABER 9.6 μm O3 secondary maximum VMR values are higher than NAOMI over altitudes 88–97 km by 47 % and 59 % respectively in 2017 and 2018. Comparing the two SABER channels which measure O3 at different wavelengths and use different processing schemes, the 9.6 μm O3 autumn twilight VMR data for the three years 2017–19 are higher than the corresponding 1.27 μm measurements with the largest difference (58 %) in the 65–95 km altitude range similar to the NAOMI observation. The SABER 9.6 μm O3 summer daytime (SZA < 75°) mesospheric O3 VMR is also consistently higher than the 1.27 μm measurement, confirming previously reported differences between the SABER 9.6 μm channel and measurements of mesospheric O3 by other satellite instruments.
Highlights
1.1 Background informationOzone (O3) is an important trace species in the mesosphere and lower thermosphere, affecting atmospheric heating rates and the chemical and radiative budgets of the middle atmosphere (Brasseur & Solomon, 2005; Sinnhuber et al, 2012; Palmroth et al, 2021)
3.1 Ozone retrieval 185 Ozone retrievals were performed for the winter and autumn night-time, and autumn twilight, periods where mesospheric O3 abundances were higher than during sunlit conditions
The SABER secondary maximum volume mixing ratio (VMR) values are higher by 47% and 59% respectively compared to NAOMI for the two years, 2017 and 2018, where autumn twilight measurements were made
Summary
1.1 Background informationOzone (O3) is an important trace species in the mesosphere and lower thermosphere, affecting atmospheric heating rates and the chemical and radiative budgets of the middle atmosphere (Brasseur & Solomon, 2005; Sinnhuber et al, 2012; Palmroth et al, 2021). The abundance of odd hydrogen (HOx) from FUV photo-dissociation of water vapour leads to a deep minimum in O3 abundance. 40 The tertiary O3 peak in the middle mesosphere is observed from early autumn until late spring between 30° latitude and the equatorward edge of the polar-night terminator (Hartogh et al, 2004). The spatial and temporal structure of the tertiary O3 layer in the polar winter mesosphere, and its night-time variability, has been reported (Smith et al, 2015, 2018; Sofieva et al, 2009). D-region ionisation due to EPP increases mesospheric HOx and odd nitrogen 45 (NOx) which impact on O3 abundances (e.g., Daae et al, 2012; Andersson et al, 2014; Verronen & Lehmann, 2015; Zawedde et al, 2018). Atmospheric dynamical processes including meridional circulation, vertical diffusion, planetary and gravity wave activity, atmospheric tides, polar mesospheric cloud occurrences, and sudden stratospheric warming events modify O3 distributions in the middle atmosphere (e.g., Pancheva et al, 2014; Limpasuvan et al, 2016; Siskind et al, 2018; Smith-Johnsen et al, 2018)
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