Barotropic Model Simulations of Low-Frequency Variability

Unforced, subcritical nonlinear simulations fail to produce meaningful variability, indicating that forcing is necessary in maintaining the low-frequency variability in the barotropic system under subcritical condition. Stochastically forced experiments are conducted using spatially homogeneous forcing. In the weakly subcritical cases, the model produces spatially and temporally coherent variability, with the first two EOFs of the perturbation field resembling the phase quadrature of the leading normal mode. In this case, the normal mode and retrograde wave structures emerge without normal mode instability. In the strongly subcritical cases, the stochastically forced solutions generally exhibit poor coherence. A stochastically-driven scenario works only in the weakly subcritical regime. The characteristics of the optimal perturbations in the barotropic system are examined. A more general type of spectrally-constrained optimal perturbation is discussed.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Atmospheric Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Huang, Huei-Ping

Contributors dc:contributor

• Robinson, Walter A.

• Physics, Atmospheric Science

Language dc:language

eng

Identifier

(MiAaPQ)AAI9737135

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/85980