Description: Publication date: June 2018 Source: Icarus, Volume 307 Author(s): V. Hue, F. Hersant, T. Cavalié, M. Dobrijevic, J.A. Sinclair In this work, we aim at constraining the diffusive and advective transport processes in Jupiter’s stratosphere, using Cassini/CIRS observations published by Nixon et al. (2007,2010). The Cassini–Huygens flyby of Jupiter on December 2000 provided the highest spatially resolved IR observations of Jupiter so far, with the CIRS instrument. The IR spectrum contains the fingerprints of several atmospheric constituents and allows probing the tropospheric and stratospheric composition. In particular, the abundances of C 2 H 2 and C 2 H 6 , the main compounds produced by methane photochemistry, can be retrieved as a function of latitude in the pressure range at which CIRS is sensitive to. CIRS observations suggest a very different meridional distribution for these two species. This is difficult to reconcile with their photochemical histories, which are thought to be tightly coupled to the methane photolysis. While the overall abundance of C 2 H 2 decreases with latitude, C 2 H 6 becomes more abundant at high latitudes. In this work, a new 2D (latitude-altitude) seasonal photochemical model of Jupiter is developed. The model is used to investigate whether the addition of stratospheric transport processes, such as meridional diffusion and advection, are able to explain the latitudinal behavior of C 2 H 2 and C 2 H 6 . We find that the C 2 H 2 observations are fairly well reproduced without meridional diffusion. Adding meridional diffusion to the model provides an improved agreement with the C 2 H 6 observations by flattening its meridional distribution, at the cost of a degradation of the fit to the C 2 H 2 distribution. However, meridional diffusion alone cannot produce the observed increase with latitude of the C 2 H 6 abundance. When adding 2D advective transport between roughly 30 mbar and 0.01 mbar, with upwelling winds at the equator and downwelling winds at high latitudes, we can, for the first time, reproduce the C 2 H 6 abundance increase with latitude. In parallel, the fit to the C 2 H 2 distribution is degraded. The strength of the advective winds needed to reproduce the C 2 H 6 abundances is particularly sensitive to the value of the meridional eddy diffusion coefficient. The coupled fate of these methane photolysis by-products suggests that an additional process is missing in the model. Ion-neutral chemistry was not accounted for in this work and might be a good candidate to solve this issue.