Simulation study for ground-based Ku-band microwave observations of ozone and hydroxyl in the polar middle atmosphere

Newnham, D.A. and Clilverd, M.A. and Kosch, M. and Seppälä, A. and Verronen, P.T. (2019) Simulation study for ground-based Ku-band microwave observations of ozone and hydroxyl in the polar middle atmosphere. Atmospheric Measurement Techniques, 12 (2). pp. 1375-1392. ISSN 1867-1381

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The Ku-band microwave frequencies (10.70-14.25GHz) overlap emissions from ozone (O3) at 11.072GHz 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 substorms produces large changes in polar mesospheric O3 and OH. The EEP typically peaks at geomagnetic latitudes of ĝ°1/465ĝ° and evolves rapidly with time longitudinally and over the geomagnetic latitude range 60-80ĝ°. Previous atmospheric modelling studies have shown that during substorms 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 (ĝ°1/498-58km) with 10-17km height resolution and ĝ°1/41ppmv uncertainty. For the equivalent 13.441GHz measurements with vertical sensor polarisation, OH could be profiled over 3×10-3-0.29 hPa (ĝ°1/490-56km) with 10-17km height resolution and ĝ°1/43ppbv 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. © Author(s) 2019.

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Journal Article
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Atmospheric Measurement Techniques
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Export Date: 21 March 2019 Correspondence Address: Newnham, D.A.; British Antarctic Survey (BAS), High Cross, Madingley Road, United Kingdom; email: Funding details: Academy of Finland, 276926 Funding details: National Eye Research Centre, NE/P003478/1, STO3RM Funding details: Natural Environment Research Council Funding text 1: Acknowledgements. This work has been supported in part by the UK’s Natural Environment Research Council (NERC) Technologies Proof-of-Concept grant reference NE/P003478/1 “Satellite TV-based Ozone and OH Observations using Radiometric Measurements (STO3RM)” awarded to David A. Newnham. The work of Pekka T. Verronen was supported by the Academy of Finland (project 276926 – SECTIC: Sun-Earth Connection Through Ion Chemistry). The authors thank the ARTS and Qpack development teams and Peter Kirsch at BAS for assistance configuring and running the code, Monika E. Andersson (FMI) for providing WACCM-D datasets, and Alan E. E. Rogers at the Massachusetts Institute of Technology (MIT) Haystack Observatory for helpful discussions. Aaron Hendry is acknowledged for providing computer code (GEO2CGM) to facilitate the conversion from spherical geographic coordinates to spherical corrected geomagnetic coordinates.
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21 Mar 2019 12:00
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15 Sep 2023 00:52