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Title: The impact of changes in stratospheric water vapour on climate
Author: Maycock , Amanda Claire
ISNI:       0000 0004 2726 6108
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2011
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. There is now overwhelming evidence that the stratosphere and troposphere behave as a two-way dy- namically coupled system, such that changes in temperature and wind in the stratosphere can influence the tropospheric circulation and vice versa. This has motivated interest in the role of the stratosphere in determining the climate response to forcing. Observations show that stratospheric water vapour (SWV) increased by ",30% between 1980 and 2000. Despite this, few studies have assessed the tropospheric dynamical response to SWV trends; this is the main aim of this thesis. The first part of the thesis focuses on modelling the radiative response to changes in SWV. It is shown that there are differences of up to ",70% in the magnitude of the temperature response to a given SWV perturbation between two different broad-band radiation codes. The physical basis for the structure of the purely radiative temperature response to an increase in SWV is then considered. The largest cooling occurs in the lower stratosphere and is enhanced in the extratropics compared to the tropics. The typically low concentration of SWV (a few ppmv) and the horizontal gradient in tropopause height are shown to be the dominant drivers of this structure. The second part of the thesis considers the response to SWV perturbations in global climate models (GCMs). An advanced GCM (H~dGAM I) is used to test the response to changes in SWV in the absence of changes in sea surface temperatures (SSTs). A uniform doubling in SWV results in a poleward shift in the rnidlatitude jets, a more positive annular mode index and an increase in the strength of the Brewer- Dobson circulation. In the more simplified Reading IGCM, the inclusion of the changes in SSTs causes a negative feedback, which reduces the amplitude of the tropospheric circulation response to a uniform SWV perturbation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available