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

Abstract

Ground-based observations of 11.072gGHz atmospheric ozone (O3) emission have been made using the Ny-Ålesund Ozone in the Mesosphere Instrument (NAOMI) at the UK Arctic Research Station (latitude 78g 55′0′′gN, longitude 11g 55′59′′gE), 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 62-98gkm. 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 version 2.0 data are binned according to the SABER instrument 60gd yaw cycles into nominal 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 9.6gμm O3 data. The winter night-time (solar zenith angle, SZAg≥g110g ) and twilight (75g g≤gSZAg≤g110g ) NAOMI and SABER 9.6gμm O3 volume mixing ratio (VMR) profiles agree to within the measurement uncertainties. However, for autumn twilight conditions the SABER 9.6gμm O3 secondary maximum VMR values are higher than NAOMI over altitudes 88-97gkm by 47g% and 59g%, respectively in 2017 and 2018. Comparing the two SABER channels which measure O3 at different wavelengths and use different processing schemes, the 9.6gμm O3 autumn twilight VMR data for the three years 2017-2019 are higher than the corresponding 1.27gμm measurements with the largest difference (58g%) in the 65-95gkm altitude range similar to the NAOMI observation. The SABER 9.6gμm O3 summer daytime (SZAg