Theories of Multiple Equilibria and Weather Regimes—A Critical Reexamination. Part II: Baroclinic Two-Layer Models

Priscilla Cehelsky Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139

Search for other papers by Priscilla Cehelsky in
Current site
Google Scholar
PubMed
Close
and
Ka Kit Tung Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139

Search for other papers by Ka Kit Tung in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Previous results based on low- and intermediate-order truncations of the two-layer model suggest the existence of multiple equilibria and/or multiple weather regimes for the extratropical large-scale flow. The importance of the transient waves in the synoptic scales in organizing the large-scale flow and in the maintenance of weather regimes was emphasized. Our result shows that multiple equilibria/weather regimes that are present in lower order models examined disappear when a sufficient number of modes are kept in the spectral expansion of the solution to the governing partial differential equations. Much of the chaotic behavior of the large-scale flow that is present in intermediate order models is now found to be spurious. Physical reasons for the drastic modification are offered.

We further note a peculiarity in the formulation of most existing two-layer models that also tends to exaggerate the importance of baroclinic processes and increase the degree of unpredictability of the large-scale flow.

Abstract

Previous results based on low- and intermediate-order truncations of the two-layer model suggest the existence of multiple equilibria and/or multiple weather regimes for the extratropical large-scale flow. The importance of the transient waves in the synoptic scales in organizing the large-scale flow and in the maintenance of weather regimes was emphasized. Our result shows that multiple equilibria/weather regimes that are present in lower order models examined disappear when a sufficient number of modes are kept in the spectral expansion of the solution to the governing partial differential equations. Much of the chaotic behavior of the large-scale flow that is present in intermediate order models is now found to be spurious. Physical reasons for the drastic modification are offered.

We further note a peculiarity in the formulation of most existing two-layer models that also tends to exaggerate the importance of baroclinic processes and increase the degree of unpredictability of the large-scale flow.

Save