Testing theories of baroclinic adjustment in the laboratory and in simple atmospheric models

Wright, S

Thesis

Testing theories of baroclinic adjustment in the laboratory and in simple atmospheric models

Abstract:: The mean state of the Earth’s climate is the result of a balance between the destabilising effect of radiative forcing and the dynamics which transport heat through the atmosphere. The contribution of baroclinic instability to maintaining this balance is not quantitatively well understood. Two prominent groups of existing ideas which attempt to explain the effect of baroclinic eddies on the mean state are baroclinic adjustment and geostrophic turbulence theories. The former suggests that the efficiency of eddy transport increases rapidly with imposed forcing such that the system adjusts to some preferred neutral state and only small departures from this state are allowed. The latter implies that the efficiency of eddy transport is set locally by an eddy diffusivity which varies smoothly with the forcing.

This thesis describes the use of a new approach, centred on a novel configuration of a lab experiment, to provide insights useful for understanding the impacts of various instabilities on the dynamical equilibration of the thermal structure of the atmosphere. The lab experiment is a new rotating annulus configuration particularly suited to studying meridional heat transfer as its thermal structure is representative of that observed in Earth’s atmosphere. Within this thesis we describe the development of a three dimensional simulation of this experiment using the dynamical core of the Met Office Unified Model. The main advantages of using this model are that the numerics can be tested against the experimental data and the same model can be used to simulate Earth-like atmospheres.

Our findings suggest that the theories of baroclinic adjustment and geostrophic turbulence may apply in different regimes which are described by the size of the baroclinic deformation radius relative to the domain size. We found this behaviour to be consistent between simulations of the annulus experiments and simulations of idealised planetary atmospheres.

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APA Style

Wright, S. (2019). Testing theories of baroclinic adjustment in the laboratory and in simple atmospheric models [PhD thesis]. University of Oxford.

MLA Style

Wright, S. Testing Theories of Baroclinic Adjustment in the Laboratory and in Simple Atmospheric Models. University of Oxford, 2019.

Chicago Style

Wright, S. 2019. “Testing Theories of Baroclinic Adjustment in the Laboratory and in Simple Atmospheric Models.” PhD thesis, University of Oxford.
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