Structure and transport properties of jets in the atmosphere and oceans

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Over the last several years, the strongly inhomogeneous nature ofatmospheric and oceanic mixing in diverse situations has becomeincreasingly apparent, as high resolution numerical simulations andobservations begin to represent accurately the detailed spatialstructure of air and water masses and their constituents. Mixing isnow known to be confined to distinct latitudinal regions, oftenseparated by sharp gradients that indicate dynamical transportbarriers. Inhomogeneous mixing by waves and eddies in atmospheres andoceans is intrinsically linked to the presence of zonally alignedjets, which not only arise as a result of the eddy mixing, but alsoorganize the mixing in distinct latitudinal regions. The combinedeffect is a dynamical feedback that is now known to operate under verygeneral conditions. Inhomogeneous mixing is important for thetransport of constituents such as water vapour, carbon dioxide, ozone,heat, and salinity; their inhomogeneous re-distribution impacts bothglobal radiative balances and regional climate change.Despite recent advances, a complete understanding of the way zonaljets organize inhomogeneous mixing, in particular the verticalstructure of such mixing, remains elusive. Progress in understandingthe horizontal structure of jets and mixing has been made recently, inparticular by focusing on the potential vorticity, a key dynamicalquantity that contains information about both horizontal rotationalmotion and density stratification. The aim of this project is tobuild on that recent work to develop a complete theory for thevertical structure of jets and mixing. In doing so, it willcontribute to our understanding both of the structure of the dominantjet structures in the atmosphere and oceans, as well as providingpredictions of how they will reach dynamical equilibrium underdifferent forcing conditions, conditions that may change in a changingclimate. It is anticipated that the new theory will allow us toassess the robustness of predictions made by climate models, which arenow beginning to accurately represent the complexities inherent in jetstructures.As well as advancing our fundamental understanding of basic dynamicalprocesses, we will study four specific issues of current importance inclimate science: (i) systematic transport of trace chemicals withinthe stratosphere; (ii) the coupling of the stratospheric andtropospheric circulations; (iii) the consequences of a climatic shiftin the tropospheric jet stream; and (iv) inhomogeneous transport andmixing associated with jets in the Southern Ocean. The projecthighlights how advances in fundamental science can be effectivelycombined with directed goals driven by specific applications.