Surface and near surface trajectories - soliciting input

[john.j.franks]

Hello. I am looking to solicit some knowledgeable input to the question of chemical releases at the surface. If a chemical is released (generic, no specific chemical) and a hysplit run is requested, does anyone have a good idea as to what levels may be best accurate for an initial best first guess? I am thinking that surface, 10m, and 30m would be most accurate. Other suggestions in the same train of thought just start with a surface run and then jump to 500m.

Does anyone have experience with actual releases or know histories that would support the lower end, or is 500m not a bad level to have as a point?

I appreciate the time and thought put towards any response to my question. Thanks.

[MarkCohen]

Hi John,

I'm not quite sure what you are asking about. Is it any of these:

• 1. In a forward "concentration" simulation, what vertical levels should be used for a concentration grid?
  
  2. In a forward "trajectory" simulation, what should the starting height be for a source?
  
  3. In a backward "trajectory" simulation from a sampler, what starting height should be used?

If it's the 1st, then let me know and I'll try to provide some advice.

If it's the 2nd, then you can start at the height of source, and you can add some height to account for plume rise if you want.

If it's the 3rd, then my advice would be to use a feature in HYSPLIT that allows the user to specify the starting height as a fraction of the planetary boundary layer (PBL). And if one is using just one height, then a height of 0.5 would be best (i.e., one-half of the height of the PBL). I've posted some explanatory notes about this at the following URL (pptx and pdf versions of the same content)

http://www.arl.noaa.gov/documents/repor ... er_01.pptx

http://www.arl.noaa.gov/documents/repor ... ver_01.pdf

Hope this helps,
Mark