I want to estimate the marginal damage associated with emissions from several power plants by matching the concentrations with GIS populations grids. However, HYSPLIT gives a suspiciously wide range of results. Is there anyway to change the simulation specification so that the concentration measurements are standardized across both

(1) one location at different points in time and,
(2) different locations at the same point in time

so that I have standard levels of concentration being measured for different plants at various points in time?

The primary factors controlling pollutant dispersion within a pollutant plume are wind speed, horizontal and vertical mixing, and the change of wind speed and direction with height. These factors vary with the passage of different weather systems and seasonally. In addition the specific concentration at a point in space depends upon the alignment between the pollutant source to the location and wind direction; another highly variable factor. The only suggestion I have is that you run many cases to develop a climatology. Then you can sort the results to determine the probability of exceeding different concentration levels. The probabilities should be more robust.

Roland Draxler