Zonal Winds in Titan’s Middle Atmosphere from a Stellar Occultation Observed with Keck Adaptive Optics

Abstract We present spatially resolved Keck/NIRC2 images of a stellar occultation by Titan on 2022 September 5 and compare them to predictions from concurrent Atacama Large Millimeter/submillimeter Array (ALMA) observations and a suite of general circulation model (GCM) simulations. ALMA data and GCM simulations can predict middle atmospheric zonal wind distributions, which in turn produce diagnostic occultation image sequences. We construct an occultation forward model using the temperature profile measured by the Huygens Atmospheric Structure Instrument, which is then distorted using latitudinal zonal wind profiles from the ALMA data or GCM simulations. The occultation forward model yields simulated light distributions around Titan’s limb, which we compare directly to the light distributions observed during the occultation. The GCM zonal wind profile corresponding to slightly before the time of the stellar occultation provides the best overall match to the data. The ALMA wind profile provided the best match to the occultation data when only the ingress data were considered, but it did not perform as well when data from ingress and egress were combined. Our data support the presence of stronger winds in the southern hemisphere during late northern summer.