Evidence for Gravity Waves in the Thermosphere of Saturn and Implications for Global Circulation
Description
Gravity wave data corresponding to the article, "Evidence for Gravity Waves in the Thermosphere of Saturn and Implications for Global Circulation," Brown et al. (2022). Temperature profiles were derived from Cassini Grand Finale stellar occultation measurements originally reported in "A Pole-to-Pole Pressure-Temperature Map of Saturn's Thermosphere from Cassini Grand Finale Data" from Brown et al. (2020). Because gravity waves are disturbances superimposed on the mean flow/state, the vertical temperature profiles T(z) have been separated into the mean temperature and wave-induced perturbations, T′=T−<T>, where <T> denotes averaging over temporal and spatial scales much larger than wave phases. The difference between the local and mean temperature (T') gives wave amplitudes, from which energy, momentum fluxes and forcing imposed on the mean flow can be derived. See Brown et al. (2022) for details, including observation latitudes (Supporting Information Table S1).
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Steps to reproduce
Temperature retrievals from stellar occultation data are described in Brown et al. (2020). Average temperatures profiles (<T>(z)) were derived by applying the sliding-window least square polynomial fitting method of Whiteway and Carswell (1995) modified as described in the paper of Starichenko et al. (2021). The profiles were obtained by fitting cubic polynomials within sliding 600-km windows with observational errors used for assigning a significance to the measurements at each point. The width of the interval was selected in order to resolve relatively small vertical-scale gravity wave harmonics (shorter than a few density scale heights, H), where H varied with altitude from ∼50 to 150 km. The 600-km sliding intervals were shifted up from bottom to top by 110 km, and then the procedure was repeated from the top to bottom. The overlapping values of the polynomials were then averaged, and the resulting profiles smoothed by applying a moving average.