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Title: Observations of barriers to mixing in the stratosphere
Author: Morrey, Martin William
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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Interhemispheric differences in the zonal mean of water vapour mixing ratios are studied on equivalent latitude. Results indicate that the southern vortex of late-winter 1992 was fairly well contained at 530K, and not acting like a "flowing processor". The northern vortex of late-winter 1993 also appears to have been well contained, but a significant amount of air appears to have been mixing across the edge of the northern vortex of late-winter 1992. The southern vortex of late-winter 1992 is shown to contain significant internal structure in the lower and middle stratosphere, unlike the northern vortices which appear well mixed. The evolution of the southern vortex is studied over the 35 days of observations available during southern late-winter. The structure inside the southern vortex in the lower and middle stratosphere degrades almost completely over this period. There is a significant change in the difference between the average mixing ratios in mid-latitudes and those of the vortex mixing in the middle-upper stratosphere. This is interpreted as being due to mixing of mid-latitude air into the vortex, on a timescale with an upper bound of ˜50-70 days. The variation of the meridional gradient in PV at the equator is studied, and compared with the variation of zonal wind and water vapour mixing ratio. The strength of meridional gradients in PV at the equator is shown to be directly related to the meridional shear in zonal wind, as modulated by the QBO. In the upper stratosphere, meridional PV gradients at the equator are related to SAO winds. Significant cross-equatorial differences in the signal of the "tropical tape-recorder" are revealed in water vapour mixing ratios. These cross-equatorial differences indicate there may be significant inhibition of mixing across the equator, but they are not obviously dependent on the strength of the meridional PV gradient.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available