1. MS 169-237,
2. MS 183-601, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA
3. School of Geosciences, University of Edinburgh, Crew Building, The King's Buildings, West Mains Road, Edinburgh EH9 3JN, UK
4. Department of Physics and Astronomy, University of Maine, 5709 Bennett Hall, Orono, Maine 04469, USA
5. Astronomy Department, 601 Campbell Hall, University of California, Berkeley, California 94720-3411, USA
6. Code 667, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
7. Department of Astronomy, University of Florida, 211 Bryant Space Science Center, PO Box 112055, Gainesville, Florida 32611-2055, USA
8. Institute for Astronomy, University of Hawaii, 2880 Woodlawn Drive, Honolulu, Hawaii 96822, USA
9. Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada
10. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA
11. MS 79-5, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA
12. Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, Hawaii 96720, USA
13. Department of Computer Science, 4732 Boelter Hall, University of California, Los Angeles, California 90095, USA
14. Langley Research Center, Hampton, Virginia 23681-2199, USA
15. Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford, Oxfordshire OX1 3PU, UK
16. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA
17. Ball Aerospace & Technologies Corp., Civil Space Systems, PO Box 1062, Boulder, Colorado 80306, USA
18. MS 183-501, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA
19. Department of Radiophysics & Space Research, 206 Space Sciences Building, Ithaca, New York 14583, USA
20. W. M. Keck Observatory, 62-1120 Mamalahoa Highway, Kamuela, Hawaii 96743, USA
21. NASA Infrared Telescope Facility, Institute for Astronomy, 640 North A'ohoku Place, Hilo, Hawaii 96822, USA
22. Deceased.

Correspondence to: Glenn S. Orton¹ Correspondence and requests for materials should be addressed to G.S.O. (Email: glenn.orton@jpl.nasa.gov).

Observations of oscillations of temperature and wind in planetary atmospheres provide a means of generalizing models for atmospheric dynamics in a diverse set of planets in the Solar System and elsewhere. An equatorial oscillation similar to one in the Earth's atmosphere^{1, 2} has been discovered in Jupiter^{3, 4, 5, 6}. Here we report the existence of similar oscillations in Saturn's atmosphere, from an analysis of over two decades of spatially resolved observations of its 7.8-m methane and 12.2-m ethane stratospheric emissions, where we compare zonal-mean stratospheric brightness temperatures at planetographic latitudes of 3.6° and 15.5° in both the northern and the southern hemispheres. These results support the interpretation of vertical and meridional variability of temperatures in Saturn's stratosphere⁷ as a manifestation of a wave phenomenon similar to that on the Earth and in Jupiter. The period of this oscillation is 14.8  1.2 terrestrial years, roughly half of Saturn's year, suggesting the influence of seasonal forcing, as is the case with the Earth's semi-annual oscillation¹.