Initial Atmospheric Waves Experiment (AWE) Imaging Analyses: Gravity Wave Sources, Temperatures, Pseudomomentum Fluxes, and Horizontal Wavenumber Spectra at the OH Layer

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Abstract
The NASA Atmospheric Waves Experiment (AWE) employs an OH imager that began measurements aboard the International Space Station (ISS) on 22 November 2023. The motivation for AWE was to quantify gravity wave (GW) responses to diverse sources and their influences extending into the mesosphere and higher altitudes. AWE measures temperatures at 2‐km cross‐track resolution in a 600‐km wide imaging swath at ∼87 km during nighttime. AWE swaths reveal a remarkable range of nighttime GW and instability responses from small to very large spatial scales over diverse terrain, deep convection, and oceans where no sources are apparent. Mountain wave responses over small islands and large‐scale orography exhibit horizontal wavelengths of λ h ∼ 10–300 km or longer. Convective GWs likewise reveal λ h ∼ 10–300 km or larger over land and ocean sources. AWE also provides clear evidence of secondary GWs having λ h ∼ 50–500 km in response to strong MW sources. Additionally, the ISS orbit enables repeat observations over all sites at an ∼4‐day cadence and 2–3 successive swaths at an ∼1.5 hr cadence over all sites near the ISS orbit inclination of 51.6°. AWE swaths enable assessments of along‐track, cross‐track, and 2‐dimensional wavenumber spectra of GW temperatures, T′ 2 , and velocity covariances, < u h ' w ′>, for u h ′ = ( u ′, v ′) spanning GW horizontal wavelengths, λ h ∼ 30–1,000 km or longer. These spectral evaluations reveal the major contributions to GW pseudomomentum fluxes, ρ < u h ' w ′>, to occur at GW λ h ∼ 30–300 km.

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