HYSPLIT Forum: hysplitbbs.arl.noaa.gov

Hi all,

I was wondering if anyone could point me in the direction of some documentation about how the values of release height, release area, and heat release are incorporated into the model. I have a few technical documents regarding how HYSPLIT performs various calculations and processes meteorological data but I'm not sure where these specific values are used after they are included in the EMITIMES file. I know that the Briggs equation is used but when/where are the results used in the HYSPLIT model?

Thanks!

The model internally uses the values of heat that you provide in the EMITIMES file to estimate the release height from the Briggs equation.
Here is how the model calculates the plume rise:
The HYSPLIT modeling system includes a very simplified plume rise algorithm based on the method of Briggs (1969) with updates from Arya (1999). Plume rise is computed assuming an air parcel's rise is based only on the buoyancy terms using the heat release (H), the wind velocity (U), and the friction velocity (U*). For unstable conditions the following expression is applied to calculate vertical displacement (z) from the source:
z = 1.3 FB / (U U*2)
where FB is the buoyancy flux calculated from the heat release (H),
FB= 7.6 x 10-7 H
On the other hand, for stable conditions and U > 0.5 ms-1,
z = 2.6 FB/(U SSP)1/3
where SSP is the static stability parameter. And for calm conditions (U < 0.5 ms-1),
z = 5.3 FB0.25/(SSP)3/8


Briggs, G.A., 1969. Plume rise. USAEC Critical Review Series, TID-25075, National Technical Information Service, Springfield, VA, 81 pp.
Arya, S.P.,1999. Air Pollution Meteorology and Dispersion. Oxford University Press, New York, 310 p.

Great! Thanks! Can you also describe where/how the emission area (m^2) is incorporated?

The area is only incorporated if you are using a puff (top hat or gaussian). So, when the puff is emitted it get initialized with the area prescribed in the EMITIMES file.

Hello Ariel. I was going through the formula for the plume rise... I don't understand why you had a 2 behind the frictional velocity when computing under unstable conditions. Is it a power of 2?

Hello! With respect to my last question, I understand it better now. It was a matter of the writing style. Thank you.