Observations and Models of Storms on Jupiter and Saturn

California Institute Of Technology, Pasadena CA

Investigators

Abstract

This project will study moist (water-based) convection and lightning in giant planets. Moist convection is a fundamental process on Earth and the giant planets that occurs when excess water vapor in a rising air parcel condenses to form a cloud. It may regulate the cooling of the giant planets, help sustain Jupiter's Giant Red Spot, and provide energy for smaller storms. Areas of lightning indicate where moist convection is occurring, so the researchers will begin by combining images of the lightning storms on Saturn and Jupiter, taken by a variety of Cassini spacecraft instruments at different wavelengths. They will also focus on giant lightning storms on Saturn that occurred during the years 2010-2011. They will also model the atmospheric dynamics in order to better understand the multi-decadal intervals between Saturn's storms, the role of convection in Jupiter's and Saturn's cooling, and the deep water abundance, and the mechanisms for producing zonal jets. The result will be a 3-D picture of the distribution, composition, and motion of the clouds and their relation to convection and lightning. They will incorporate their research into university courses, and train a graduate student, and will make publicly available the GiantPlanetWRF modeling tool for modeling the full time-dependent dynamics of the planetary interior. The project has two main components: (1) Characterize lightning by analyzing archival data on both Jupiter and Saturn from the Cassini imaging system. The horizontal width of the flashes, their optical energy, and their spectrum are clues to the depth of the lightning and the charging mechanism. (2) Simulate the dynamics of moist convection with a state-of-the-art model. The proposing team will modify the existing Weather Research and Forecasting (WRF) model to simulate the deep sub-cloud layer of giant planet atmospheres. By nesting a high resolution computational domain between eastward and westward jet streams, they will study small scale processes like convection, precipitation, and lightning as they interact with the large-scale flow.