Annular mode-like responses to external forcings in a simple atmospheric general circulation model

In this thesis, I investigate the response of a simple atmospheric general circulation model to applied forcings to learn whether the annular mode patterns are a preferred model response to the forcings. The thesis is inspired by the appearance of annular mode patterns in Earth's atmosphere in response to a number of forcings. Climatologies of the model under the influence of applied torques or perturbations to the reference temperature profile are compiled and compared to a control run with neither type of forcing. In most cases the differences in climatologies are annular mode-like, suggesting the patterns are the preferred response of the model to the forcings. The strength of the response typically increases for either an increase in the strength of the forcing, or an increase in the strength of the projection of the forcing on the model's annular mode patterns. Trials with a response which was not annular mode-like usually featured a poor projection of the forcing on the annular modes, or substantial interference with tropical dynamics. A zonally symmetric version of the model is also used to test the direct response of the model to the forcing versus the response caused by changes in eddy feedback processes. The direct forcing alone is found to be insufficient to produce either the correct strength or shape of the annular mode patterns. Instead the changes in eddy fluxes must be included to produce the correct shape and amplitude of the anomalies.

Department dc:contributor.department

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

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Ring, Michael J., 1979-

Advisor dc:contributor.advisor

• R. Alan Plumb.

• 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/1721.1/43152

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/43152