HYSPLIT Forum: hysplitbbs.arl.noaa.gov

Hello I am running into a problem with the Dust Storm function, and I think I may be misunderstanding something. I am a relatively new HYSPLIT user and I was using the Dust Storms: Simplified Algorithm tutorial. I retrieved the Control File, and changed the advanced settings to match the tutorial and ran the dust storm special run. Based on the contol file and the starting locations included I expected a grid of emission sources spaced at .25 degrees with the lower left corner being 38 -115, and the upper right being 41, -110. However upon when displaying, it seems like this grid is cut off, not allowing any points to be created below 40 degrees, and between -114 and -113 degrees. I saw the same thing on the image given by the tutorial, only the difference was that they had four additional points around 39, -113. Is there some sort of method that I am misunderstanding that explains why only certain emission points are generated out of what I thought would be a larger grid?

Images are from the tutorial

For the simple algorithm the locations which are allowed to emit dust are determined from the landuse file.
Only locations coded as desert locations are allowed to emit.