Deposition

Topics about the HYSPLIT dispersion model.
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MichaelK
Posts: 3
Joined: December 17th, 2021, 12:37 pm
Registered HYSPLIT User: No

Deposition

Post by MichaelK »

Dear all,

I would like to simulate dispersion of pm2.5 emissions of wildfires during 5-7 days. The simulation should include dry and wet deposition. I checked the user guide and had a look at similar questions in the forum. Unfortunately that did not answer my questions.
The way I understand is that I set the following options in the CONTROL file:
  • (26) 1 (Number of pollutants: I have one pollutant, pm2.5)
  • (27) 0.8. 2, 1 (Diameter, density and shape: I used Rolph et al. 2009 as reference.)
  • (28)? (Deposition velocity)
  • (29) 0.0 8.0E-05 8.0E-05 (Wet removal)
My questions are the following:
  • Is this approach correct in general?
  • (27): I used the values provided in Rolph et al. (2009) for diameter and density. I did not find any information about the shape parameter. Is it correct to use 1.0 in order to tell HYSPLIT that is a particle, or do I have to use another value?
  • (28): I don`t know what value I have to use. Is there any information for pm2.5?
  • (29): Same problem as in (28): Is it ok to use the recommended values?
Thank you in advance for your help!

Best,
Michael
Tianfeng.Chai
Posts: 24
Joined: September 18th, 2017, 2:20 pm
Registered HYSPLIT User: No

Re: Deposition

Post by Tianfeng.Chai »

Yes, your approach is correct in general.

(26) 1 (Number of pollutants: I have one pollutant, pm2.5)
(27) 0.8. 2, 1 (Diameter, density and shape: I used Rolph et al. 2009 as reference.)

They are fine.

28(2)- Deposition velocity (m/s), Pollutant molecular weight
(Gram/Mole), Surface Reactivity Ratio, Diffusivity Ratio,
Effective Henry's Constant
Default: 0.0 0.0 0.0 0.0 0.0

Without knowing about the dry deposition, it is ok to use the default setting "0.0 0.0 0.0 0.0 0.0".
It is probably better to set molecular weight to a positive number to turn on the resistance method to calculate dry depostion velocity. Note that for particles the molecular weight itself is not used, a positive value is used as a flag to turn on the resistance method for dry depostion velocity calculation.

(29) 0.0 8.0E-05 8.0E-05 (Wet removal)
It is OK to use those values when no better parameters are available.
However, it should be noted that those values are not obtained for smoke particles.
So there are large uncertainties for the wet removal.
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