Vertical shears in Saturnʹs eastward jets at cloud level

We have measured the vertical shear of the zonal winds in the cloud-haze upper layer of Saturn using Cassini ISS images obtained in the filters MT2 (753 nm methane absorption band, sensitive to the upper haze) and CB2 (adjacent continuum, sensitive to the lower cloud). Our radiative transfer models indicate that at the eastward jet peaks these filters are sensing clouds at the respective ∼100 mbar and ∼350 mbar levels. We have found a systematic velocity difference between those filters of 15 to 20 m s−1 only in the eastward jets peaks (27° S, 42° S, 55° S and 70° S) which implies a vertical shear of ∼10–20 m s−1 H−1. Our overall results agree with those derived from the thermal-wind relationship using CIRS thermal data [Fletcher, L.N., and 13 colleagues, 2008. Science 319, 79–81] and with previous equatorial measurements [Sánchez-Lavega, A., Hueso, R., Pérez-Hoyos, S., 2007. Icarus 187, 510–519].