Nonlinear equilibration of baroclinic eddies : the role of boundary layer processes and seasonal forcing

In this thesis, the influence of boundary layer processes and seasonal forcing on baroclinic eddy equilibration is studied to understand how the baroclinic adjustment is modified when taking into account these two factors. A modified [beta] plane multilevel quasi-geostrophic (QG) model with an interactive stratification and a simplified parameterization of atmospheric boundary layer physics is used as the atmospheric model in this study. Comparisons between experiments with the modified QG model and the traditional QG model with fixed stratification show that it is necessary to include the interaction between vertical eddy heat flux and stratification to obtain a realistic equilibrated state, i.e. robust isentropic slope. A slab surface model is also coupled with the atmospheric model to provide an interactive surface temperature distribution in some experiments in this study. The effect of boundary layer processes is first studied under the situation with fixed underlying surface temperature. The boundary layer vertical thermal diffusion, along with the surface heat exchange, is found primarily responsible for the limitation of the PV homogenization in the boundary layer. The boundary layer processes can influence the eddy activity in at least two competing ways. First, in the eddy energy budget, all the boundary layer processes act to damp the eddy energy directly. On the other hand, the boundary layer processes also influence the mean flow, which can further influence the eddy behavior. For the boundary layer thermal damping, the indirect effect on the eddy activity becomes dominant.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Zhang, Yang

Advisor dc:contributor.advisor

• Peter H. Stone.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/54843

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/54843