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Ground-based observations of 11.072 GHz atmospheric ozone (O3) emission have been made using the Ny-Ã…lesund 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 &#956m 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 &#956m 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 &#956m 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. [ABSTRACT FROM AUTHOR]

The Ku-band microwave frequencies (10.70–14.25GHz) overlap emissions from ozone (O3) at 11.072 GHz and hydroxyl radical (OH) at 13.441GHz. These important chemical species in the polar middle atmosphere respond strongly to high latitude geomagnetic activity associated with space weather. Atmospheric model calculations predict that energetic electron precipitation (EEP) driven by magnetospheric sub storms produces large changes in polar mesospheric O3 and OH. The EEP typically peaks at geomagnetic latitudes ~65° and evolves rapidly with time longitudinally and over the geomagnetic latitude range 60°–80°. Previous atmospheric modelling studies have shown that during sub storms OH abundance can increase by more than an order of magnitude at 64–84km and mesospheric O3 losses can exceed 50%. In this work, an atmospheric simulation and retrieval study has been performed to determine the requirements for passive microwave radiometers capable of measuring diurnal variations in O3 and OH profiles from high latitude northern hemisphere and Antarctic locations to verify model predictions. We show that, for a 11.072GHz radiometer making 6h spectral measurements with 10kHz frequency resolution and root mean square baseline noise of 1mK, O3 could be profiled over 8×10−4–0.22hPa (~98–58km) with 10–17km height resolution and ~1ppmv uncertainty. For the equivalent 13.441GHz measurements with vertical sensor polarisation, OH could be profiled over 3×10−3–0.29hPa (~90–56km) with 10–17km height resolution and ~3ppbv uncertainty. The proposed observations would be highly applicable to studies of EEP, atmospheric dynamics, planetary scale circulation, chemical transport, and the representation of these processes in polar and global climate models. Such observations would provide a relatively low cost alternative to increasingly sparse satellite measurements of the polar middle atmosphere, extending long-term data records and also providing ground truth calibration data. [ABSTRACT FROM AUTHOR]