Ground-based Ku-band microwave observations of ozone in the polar middle atmosphere.

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]