Wind comparisons between meteor radar and Doppler shifts in airglow emissions using field widened Michelson interferometers

Winds from two co-located two wind measuring instruments, a meteor radar and field widened Michelson interferometer at the Polar Environment Atmospheric Research Laboratory in Eureka, Nu, Canada (80 • N, 86 • W) are compared.The two instruments have very different temporal and spatial observational footprints.ERWIN provides airglow weighted winds from three nightglow emissions (O( 1 S) (oxygen green line, 557.7 nm), an O 2 line (866 nm), and an OH line (843 nm)) on a ∼5 minute cadence for measurements at all three heights.As with Fabry-Perot airglow wind observations, these winds are airglow 5 weighted winds from volumes of ∼8 km in height by ∼5 km radius.ERWIN's higher accuracy (1-2 m/s for the O( 1 S) and OH emissions and ∼4 m/s for the O 2 emissions) and higher cadence allows more detailed wind comparisons of airglow and radar winds than previously possible.The best correlation is achieved using Gaussian weighting of meteor radar winds with peak height and vertical width being optimally determined.Peak heights agree well with co-located SABER airglow observations.Offsets between the two instruments are ∼ 1 -2 m/s for the O 2 and O( 1 S) emissions and less than 0.3/s for the OH emission. 10Wind direction are highly correlated with a ∼ 1:1 correspondence.On average meteor radar wind magnitudes are ∼ 40% larger than those from ERWIN.Gravity wave airglow brightness weighting of observations is discussed.Non-quadrature phase offsets between the airglow weighting and gravity wave associated wind and temperature perturbations will result in enhanced or reduced layer weighted wind amplitudes.Copyright statement.TEXT confidence intervals for various derived quantities associated with height uncertainties.Recent papers have compared variations in Doppler airglow winds with meteor radar winds, and estimated heights of the layer [Yu et al. (2017) and Lee et al. (2021)].In this paper, we continue to investigate the character of these correlations, 60 albeit with a field-widened Michelson interferometer, the E-Region Wind Interferometer II (ERWIN) and a co-located meteor radar (SKiYMET) [Hocking et al. (2001)].The ERWIN and MWR winds used in this study are from the December 2017, and January 2018 period.The basic measurement process for the field-widened Michelson is the same as for the Fabry-Perot (both use Doppler shifts 65 from isolated spectral lines in airglow [Burrage et al. (1996); Fisher et al. (2000)]).However, ERWIN has a significantly faster temporal cadence and wind accuracy than the Fabry-Perot [Kristoffersen et al. (2013)]).These enhanced observation capabilities allow the relationship between wind measurements with the two techniques to be explored in more detail than previous analyses.Establishing the complementary relationship between these two techniques provides a foundation for future enhancements in ground based observations of wind and constituent transport.70This paper is organized as follows.Following this introduction, the instrument capabilities, the observation site and the instrument filter associated with each instrument are described.The character of the wind observations from the two instruments and the analysis of various correlation strategies comprise the content of the next section.The interpretation and implications of these results are then discussed.The final section summarizes the main results of the paper and future research directions. 2 InstrumentsThe instruments used in this study, the E-Region Wind Interferometer II (ERWIN ) [Kristoffersen et al. (2013)] and an All-Sky Interferometric Meteor Radar (SKiYMET) [Hocking et al. (2001)], are co-located at the Polar Environment Atmospheric Research Laboratory (PEARL; Eureka, Nu, Canada: 80 • N, 86 • W).These are two of a suite of instruments at PEARL mea-80 suring constituents, aerosols, temperature and wind from the ground to the thermosphere [Drummond and Team (2017)].They implement very different methods of wind measurement.ERWIN uses Doppler shifts in airglow emissions and the SKiYMET radar reflects radio waves off meteor trails.Wind measurements with ERWIN are through optical interferometric means.They consist of airglow radiance weighted 85 integrated line-of-sight winds with a small spatial cross section.Airglow consists of naturally occurring molecular and atomic emissions, which, in the MLT region at night, is associated with three body reactions involving atomic oxygen [Slanger and Copeland (2003)].Because of the height dependence of three-body reactions and the increase in quenching rates at lower altitudes, the height profile of airglow emissions is quasi-Gaussian shaped with half-widths of ∼8 km.In contrast, the meteor

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