Monday 30 Nov 2015: Jupiter's unearthly jet streams: a new turbulent model exhibiting statistical steadiness without large-scale dissipation (GAFD seminar)
Dr Stephen Thomson - University of Exeter
A longstanding mystery about Jupiter is the straightness and steadiness of its weather-layer jet streams, quite unlike the Earth’s strong jet streams with their characteristic unsteadiness and long-wavelength meandering. Also mysterious is Jupiter's distribution of moist convection, which is only observed within regions of cyclonic shear.
Models of Jupiter’s atmosphere have often struggled to reproduce these three observed properties. Results from our new idealised model will be presented, which addresses this problem in two steps. The first is to take seriously the classic Dowling-Ingersoll (DI) 1-1/2-layer scenario and its supporting observational evidence, pointing toward deep, massive, zonally-symmetric zonal jets in the underlying dry-convective layer. The second is to improve the realism of the model stochastic forcing used to represent the effects of Jupiter's moist convection as far as possible within the 1-1/2-layer dynamics.
The resulting model is successful in producing straight and steady jets with moist-convection confined to regions of cyclonic shear, and does so without the use of large-scale dissipation. The relevance of our idealised model to the real Jupiter will be discussed.
This work was conducted with my PhD supervisor Michael McIntyre, and is summarised in a paper currently in press with JAS -- http://dx.doi.org/10.1175/JAS-D-14-0370.1 (Also on Arxiv http://arxiv.org/abs/1412.4684).