Environmental Science and Engineering Seminar

Wednesday November 18, 2015 4:00 PM

Giant planet polar cyclones: lessons from terrestrial hurricanes

Speaker: Morgan O'Neill, Department of Earth and Planetary Sciences, Weizmann Institute of Science
Location: South Mudd 365

The poles of Saturn, Uranus and Neptune each have a 'hot spot' that is observable from Earth. Saturn, which has been observed in great detail by the orbiting Cassini mission, additionally exhibits Earth-sized hurricane-like cyclones on each pole. These massive cyclones have been present since they were first observed in 2004 and may be permanent. We propose a mechanism for their creation, informed by the study of hurricanes on Earth. A controversial theory for the intensification of terrestrial hurricanes maintains that small, energetic moist convective towers - thunderstorms - play a constructive role in hurricane strength. Intense thunderstorms also appear ubiquitous on Jupiter and Saturn. We hypothesize that a similar mechanism can occur in the polar environments of gas giants over long periods of time. We test this with a 2.5 layer shallow water model on a polar beta plane. Hundreds of simulations suggest that these very small, short-lived storms can build and maintain a deep, rapid, large polar cyclone like we see on Saturn. Furthermore, an exploration of cyclone sensitivity to the deformation radius and total energy density suggests that Uranus and Neptune have transient polar cyclones, and Jupiter will not exhibit them. This last prediction will be tested next year, when the NASA Juno mission reaches Jupiter and finally observes the Jovian poles.

Series Environmental Science and Engineering Seminar

Contact: Kathy Young at 626-395-8732 katyoung@gps.caltech.edu