The surface file contains observed and calculated surface variables, one record per hour. The adequacy of input data should be judged independently for each variable. The values for surface roughness, Bowen ratio, and albedo should reflect the surface characteristics in the vicinity of the meteorological tower, and should be adequately representative of the modeling domain. Finally, the primary atmospheric input variables including wind speed and direction, ambient temperature, cloud cover, and a morning upper air sounding should also be adequately representative of the source area. The vertical concentration distribution for convective conditions results from an assumed bi-Gaussian probability density function of the vertical velocity.
Chemical transformation is treated by simple exponential decay.
Actual separation between each source-receptor pair is used. Receptors may be located at user-specified heights above ground level. Plume concentration estimates are the weighted sum of these two limiting plume states. At a given height above ground, for a given hour, winds are assumed constant over the modeling domain. The effect of the vertical variation in horizontal wind speed on dispersion is accounted for through simple averaging over the plume depth.