This thesis describes the formulation and operation of a two-dimensional model of the atmosphere from 0 to about 100 km, using an isentropic vertical coordinate above the tropopause. The model is used in this thesis to study the dynamical effects of stratospheric planetary waves, arising from their transport of Ertel's potential vorticity (PV). The use of isentropic coordinates leads to conceptual simplifications, and to practical advantages in parameterising planetary-wave eddy fluxes in the stratosphere. The model has an interactive troposphere and reproduces the observed annual cycle of the equatorial tropopause temperature when an estimate of the planetary wave PV flux is included in the stratosphere. A feature of the radiation scheme used in this model, and apparently not shared by other 2D models, is the inclusion of the effect of the variation of daylight hours with height. This has a significant influence on the dynamical fields, especially during the equinoxes. The model simulates the observed stratosphere well during autumn and in the southern hemisphere (SH) winter. However, to simulate spring, summer and the NH winter, an accurate estimate of the real PV flux is needed. Since no such estimate was available, three methods were used in this thesis to derive values of the flux for the year from July 1980 to June 1981. One method calculated the flux directly from approximate winds, another estimated the flux due to thermal dissipation of zonal asymmetries in PV, and the third was a variation of an existing method, which finds the PV flux needed to produce the evolution of the observed zonal wind in conjunction with the diabatic circulation. Bearing in mind the significant uncertainties present in all three estimates, the following description of the actual PV flux was put forward. The flux, when large, takes the form of a single negative peak, moving from middle to high latitudes over its life-time.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:653448 |
| Date | January 1991 |
| Creators | Kinnersley, Jonathan Stewart |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15177 |
Page generated in 0.0021 seconds