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

<p>Upper-atmosphere winds from a meteor radar and a field-widened Michelson interferometer, co-located at the Polar Environment Atmospheric Research Laboratory in Eureka, Nunavut, Canada (80° N, 86° W) are compared. The two instruments implement different wind-measuring techniques at similar heights and have very different temporal and spatial observational footprints. The meteor radar provides winds averaged over a <span class="inline-formula">∼</span> 300 <span class="inline-formula">km</span> horizontal area in 3 <span class="inline-formula">km</span> vertical bins between 82 and 97 <span class="inline-formula">km</span> on a 1 <span class="inline-formula">h</span> cadence. The E-Region Wind Interferometer II (ERWIN) provides airglow-weighted winds (averaged over volumes of <span class="inline-formula">∼</span> 8 <span class="inline-formula">km</span> in height by <span class="inline-formula">∼</span> 5 <span class="inline-formula">km</span> radius) from three nightglow emissions (<span class="inline-formula">O(¹S)</span>, oxygen green line, 557.7 <span class="inline-formula">nm</span>, 97 <span class="inline-formula">km</span>; an <span class="inline-formula">O₂</span> line, 866 <span class="inline-formula">nm</span>, 94 <span class="inline-formula">km</span>; and an <span class="inline-formula">OH</span> line, 843 <span class="inline-formula">nm</span>, 87 <span class="inline-formula">km</span>) on a <span class="inline-formula">∼</span> 5 <span class="inline-formula">min</span> cadence. ERWIN's higher precision (1–2 <span class="inline-formula">m s⁻¹</span> for the <span class="inline-formula">O(¹S)</span> and <span class="inline-formula">OH</span> emissions and <span class="inline-formula">∼</span> 4 <span class="inline-formula">m s⁻¹</span> for the <span class="inline-formula">O₂</span> emissions) and higher cadence allows more substantive comparisons between winds measured by meteor radar and Doppler shifts in airglow emissions than previously possible for similar meteor radar/airglow Doppler shift comparisons using Fabry–Perot interferometers. 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 <span class="inline-formula">∼</span> 1–2 <span class="inline-formula">m s⁻¹</span> for the <span class="inline-formula">O₂</span> and <span class="inline-formula">O(¹S)</span> emissions and less than 0.3 <span class="inline-formula">m s⁻¹</span> for the <span class="inline-formula">OH</span> emission. Wind directions are highly correlated with a <span class="inline-formula">∼</span> <span class="inline-formula">1:1</span> correspondence. On average, meteor radar wind magnitudes are <span class="inline-formula">∼</span> 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.</p>