reasonable. In the next two sections it will be shown that the Ames two-dimensional model obtains results that are consistent with those from scale analysis. In later sections, where latitude dependent photochemistry is treated, scale analysis cannot be used. For such situations, there is no choice but to rely on the numerical model. In the following subsections, the effects of meridional advection and meridional diffusion will be considered first. These predictions will then be compared with those of Ames Research Center's two-dimensional model, the effects of including chemical reactions will be considered, the relevant chemistry will be discussed, and the results for various chemical species will be presented. Finally, the effects of uncertainties in some of the parameters will be discussed. Meridional Advection For sufficiently large injection rates, the injected material will be swept out of the region so slowly that there will be a detectable increase in the species concentration relative to that of the surrounding regions. The fractional increase, 17, of the abundance of the injected material in the corridor region is simply the mass increase, m, divided by the total mass, M, of that species in the ambient atmosphere in the same region: The mass of the species in the ambient atmosphere, M, is the product of the species density, p (kg/m3) and the area, A, of the corridor: where R is the radius of Earth, 0 is the latitude of the corridor, and L is a north-south length that specifies the half-intensity width of the corridor. Here, m is the product of the injection rate and a characteristic time, T: where v is an appropriate mean meridional speed. Typical values of |r| shown by Louis (6) for altitudes near the top of his model (50 km) range from 0.2 to 0.4 m/s. Recent model caluclations by Shoeberl and Strobel (7) and by Holton and Wehrbein (8) produce meridional wind speeds between 1 and 2 m/s. To compare the scaling results derived here with those from the Ames two- dimensional numerical model — which uses meridional velocities derived from the
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