An important unsolved problem in atmospheric dynamics is how the jets in the atmosphere emerge spontaneously from turbulence. In this project, Farrell and his group will develop, and explore the implications of, a new theory of jets, using an analytical theory, that builds on their previous work in stochastic dynamics (the dynamics of randomly forced systems, like turbulent fluid flows). In this theory, the turbulent eddies, which are the familiar highs and lows of weather maps, are treated as randomly forced perturbations to the zonally averaged flow. With the assumption that these eddies are small perturbations, such that their equations are linear, a closed self-consistent theory for the emergence of jets can be developed.
Preliminary results from the theory show that it predicts the scales and structures of jets in good agreement with those observed in Earth's atmosphere. In the present project, this work will be extended by:
. Exploring how the jets and their stability depend upon the parameters of the problem: the strength of the stochastic forcing and the values of dissipation parameters. . Generalizing the problem to include meridional dependence, so as to treat the problem of an eddy-driven polar jet coexisting with the subtropical jet. . Generalizing the problem to non-zonally symmetric jets, so as to treat the problem of the zonally isolated jets and storm tracks of the Northern Hemisphere.
The broader impacts of this project are in obtaining a deeper and more general understanding of the climate system. For example, abrupt changes in climate may be associated with abrupt changes in jet regimes that are described by this theory. A graduate student will be supported.
