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Title: Towards a 3D interactive chemical-dynamical representation of the atmosphere
Author: West, Vicky
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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Studies of atmospheric change, including the climatic effects of ozone depletion require the coupling of chemistry and general circulation models (GCMs). Such work requires that both the chemical and dynamical processes be accurately represented. We begin by showing the information that can be gained from the 2D THIN-AIR coupled model of the atmosphere, and highlight its limitations. As part of the UGAMP modelling effort we are currently involved in implementing coupled chemical-dynamical modelling in the 3D Unified Model (UM). As a first step in this process, the ability of the GCM to reproduce known transport mechanisms in the stratosphere and upper troposphere is assessed with different configurations of the model. The UM is run in troposphere-stratosphere mode and includes simulation of passive and simple-source tracers. We find that the results are very sensitive to the advection scheme implemented, with the age of stratospheric air varying from 3 years with the Roe scheme to 5.5 years with the Heun scheme. Simulations of the stratospheric tape recorder signal reveal a signal which ascends at a good speed with the Heun scheme, but does not decay with height as expected due to amplification of the signal by spurious oscillations. We find barriers to tropical - extratropical exchange which have similar properties both above and below the tropopause, and these are consistent with recent work, suggesting that the tropopause should be conceived as a ‘layer’ of several kilometres, whose properties change from being wholly tropospheric at the lower boundary, to stratospheric at its upper limits. Work presented here provides a useful framework for understanding more recent studies, which have incorporated chemical routines into the UM.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available