Convenor: Colin Hines
Monday, June 14 1:00-3:05 PM
The point of departure for this workshop is the panel discussion that followed Charles McLandress's tutorial presentation at the 1997 CEDAR meeting, and, more specifically, Dave Fritts's segment of the discussion. That segment will be rerun via video (13 min), to set the stage, at the start of the workshop.
There will follow a tutorial by Colin Hines designed to identify and elucidate the roles of various types of nonlinearity because, contrary to common perception, they are not all of a kind. Instead, different approaches can lead to some degree of understanding of various nonlinearities separately. Most particularly, the Eulerian advective nonlinearity is peculiar to Eulerian coordinates alone: it can be avoided totally by use of Lagrangian coordinates.
There is a corresponding Lagrangian nonlinearity that can be avoided totally by use of Eulerian coordinates. No one in their right mind would advocate the use of Lagrangian coordinates when the latter nonlinearity is relevant by itself, and symmetry suggests that no one in their right mind should advocate the use of Eulerian coordinates to deal with the exclusively Eulerian nonlinearity, at least for mathematical developments. On the other hand, aeronomic observers deal almost exclusively with Eulerian coordinates, so they would want results of the mathematical developments transcribed to those coordinates. As will be discussed, the consequence of doing so is the production of a small-wavelength (large-wavenumber) "Eulerian tail" to any and every broad spectrum. If this tail is observed but not correctly identified as such -- as "wavulence" -- serious errors of interpretation can arise.
The tutorial will be designed to elucidate the physical origins of the tail as well as its mathematical origins, in the hope of bringing understanding to an otherwise obscure area in the interpretation of middle-atmosphere wave spectra. It should then serve as a basis for a more informed discussion of both linear and nonlinear theories of observed spectra, to which the workshop will next turn. It is hoped that this discussion will help to make up for the fact that the 1997 discussion had to be terminated, because of time constraints, just as it was heating up. With the extra time now available, some fireworks may result.
At the moment, an open-forum form of discussion is anticipated. However, if there are other new developments of concept that lend themselves to the style of a short tutorial that will clarify physical assumptions and consequences of former theories, or that will open up new theories, they will be considered for possible formal inclusion upon application to the workshop convenor, Colin Hines, at 15 Henry Street, Toronto M5T 1W9, Canada; phone 416-977-8355; fax 416-591-7118; email hines@windic.yorku.ca