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Title: Planetary wave activity in the stratosphere
Author: Li, Dingmin
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1991
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This thesis presents a diagnostic study into some aspects of stratospheric dynamics, from seeking a better approximation of winds using satellite derived data to the dynamics of wave activity and wave-mean flow interaction with the aid of newly developed theory. An approximation scheme named 'quasi-geostrophic wind', is tested and its merits discussed by comparison and contrast with some currently common used methods, vis. geostrophic, linear balance, nonlinear balance winds. The dynamical behaviour of the stratosphere is diagnosed, using LIMS data, in the form of definition of wave activity density given by Andrews (1987) and in terms of the generalized Eliassen- Palm flux theorem. As the theory is strictly applicable only to small amplitude waves, the study is mainly concentrated on a period of low wave activity in late Autumn. There is good agreement in the changes of terms of the generalized Eliassen-Palm flux theorem. Time-latitude plots of Eliassen-Palm flux divergence, wave activity density and its rate of change, together with wave dissipation show a day to day coherence. A good qualitative agreement is also found between the change of zonal mean wind and wave activity in accordance with the theorem. The balance among the terms in the theorem is only approximate, an indication of importance of nonlinear effects neglected in the linear premise. The balance is improved when the non conservative term is included. An analogous expression to the generalized Eliassen-Palm flux theorem but for chemical tracers is derived theoretically and a corresponding wave activity defined in terms of chemical tracers such as ozone is presented. This analogous expression shows the relation between the tracer transport and the wave transience; after some simplifications this gives a novel method of estimating the transport coefficients. In the middle atmosphere good agreement is found between wave activity defined in terms of ozone mixing ratio with that defined in terms of potential vorticity. Results of an attempt to estimate transport coefficients by tracer wave transiences and the corresponding parameterized flux are also presented and the contribution due to dispersion is discussed. The estimation by this method is found capable of reflecting the large effects of wave dispersion in late winter. The transport coefficients from dispersion of fluid parcels alone are not fully satisfactory due to appearance of a large area of negative coefficients in the monthly mean plots which may be caused by the limit of linear theory, the effects of chemical eddies (sources and sinks) or by the errors in the data that may hinder our estimation of wave transience.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available