Some results are available from a general circulation calculation coded for the LARC. The primitive equations are used to advance velocity components, temperature, and water vapor at each of five pressure levels. Energy sources include calculated latent heat release and solar radiation heating; terrestrial radiation cooling is prescribed. Surface friction and evaporation are included. At present the 5-deg spatial mesh extends from 0 to 60N latitude; the time step of 10 min takes 15 sec of calculation. The surface is ocean with temperatures fixed at average January values.
A calculation has been carried out for seven months without instability. It shows evidence of zonal index cycles with periods of 6 and 20 days. The general behavior of the model is displayed through time lapse motion pictures of maps of surface pressure, 500-mb geopotential, and 600-mb temperature fields.
Some notes:
The motion pictures were made in both black and white and color. The color version was made by taking three black and white films and using the company Pacific Title to generate the color version.
In Paul Edwards 1997 MMD interview with Leith: Pacific Title. It's just a sort of a piece of a small warehouse down there, if I remember correctly, when I went there years ago. Stacked up was reels of film all over the place that they had been working on. But they had the technology for doing this sort of merging of different images onto the same thing, essentially what was needed in this case. And so we would produce three white-on-black line diagrams evolving in time, motion pictures, and then they would project them through filters onto a single frame. So you'd get, well, you wouldn't be able to see this, but for example surface pressure field or 500 millibar height field and so on can be all superimposed on each other and you could watch over the Northern Hemisphere, you can watch these things emerging. And the one that I have is essentially a polar projection of the Northern Hemisphere, and you can see the patterns moving in mid-latitudes. And that was kind of interesting when I did that early on.
Chuck Leith was aided by George Michael at Livermore to produce the animated films.
An exchange from them in an interview on December 7, 1994:
GAM: Well, you did many, many first things on the LARC. Do you remember we had the electronic page recorders - EPRs? And using them, you made some very interesting movies.
CL: Ah, yes. Well, then, of course, you helped me on that, George.
GAM: Well, never mind that. You did a polar projection?
CL: It's true that on that it was possible effectively to do graphics to look at single images of isobars on the northern hemisphere polar projection, for example, of isopressure or cloud patterns-things of that sort. And by doing this sequentially, of course, one could generate motion pictures. This was, I think, one of the first of the evolving motion picture displays from a computer-generated atmospheric model.
GAM: We did that.
CL: The way it was done, if you'll remember, was to print three successive black and white frames of 35mm film, which later in the printing process were printed through filters and superimposed so that we got a three-color image for single printing for every three frames that we made originally. With this display the evolving features of the global atmosphere were readily identified, and it led to a lot more interest in the way these models worked.
GAM: Listen, Chuck, it was nothing short of sensational, okay? It was great!
Kevin Hamilton's Paper: At the dawn of global climate modeling: the strange case of the Leith atmosphere model gives some more information concerning Leith's computer-animated film.