Gravity wave propagation directions inferred from satellite observations including smearing effects

We simulate space‐based, sublimb viewing observations of airglow brightness fluctuations caused by atmospheric gravity wave interactions with the O 2 atmospheric airglow, and we demonstrate that because of the geometry associated with such observations, the brightness fluctuations observed for the optically thick 0–0 band emission will always appear stronger for waves traveling toward the observer (the satellite). The effect should be most noticeable for waves having relatively small vertical wavelengths (∼10 km) and horizontal wavelengths of 50 km or greater. For waves of short (∼100 km) horizontal wavelength, the brightness fluctuation anisotropy with respect to viewing direction may also be evident in the optically thin 0–1 band emission. We demonstrate that the waves will be observable despite the fact that an instrument requires a certain finite integration time to achieve a desired signal‐to‐noise ratio. Therefore the 180° ambiguity in wave propagation direction associated with space‐based observations may be eliminated for waves of small vertical wavelength that are dissipating in the upper mesosphere and lower thermosphere. It is these same waves that may be expected to be important to the energy and momentum budgets of the mesosphere/lower thermosphere region.