pm2.5 values from wrfchem

[Abdoulaye Sarr]

Well, I am computing pm2.5 from a simulation outputting dust_1 to Dust_5 using below formula , pm25 = (d1 + d2 + 0.25 * d3) * rho,  the event simulation is spatially reasonable but the values look extremely high.

Any hint or formula suggestion more reasonable?

[Mary Barth]

Hi there,

There is a "tuning parameter" in the dust scheme that you can adjust to change the magnitude of the emissions. The paper by Kumar et al. 2014 ACP as one example of adjusting the tuning parameter. I am sure there are many more papers that explain this as well, so there may be information in the literature that can give you more guidance.

Mary

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Mary Barth 

Senior Scientist, NSF National Center for Atmospheric Research   

phone: 303-497-8186    email: bar...@ucar.edu

Staff web page  SIMA Web Site  MUSICA Web Site

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[Alice Burton]

Dear Abdoulaye,

I see that you are using the following formulation:

PM2.5 = (dust_1 + dust_2 + 0.25 × dust_3) × rho

I had a few questions regarding this approach. Could you please clarify why this specific equation was used? I would be interested to know the source or reference for this formulation, and in particular the reasoning behind applying the 0.25 factor to dust_3. Is this based on an assumed size distribution within that bin, or a standard approximation from the literature?

Also, I noticed that the model itself provides PM2.5 as a direct output variable. May I ask why that output was not used in this case? Is there a specific reason for deriving PM2.5 from the dust bins instead?

Finally, is there a known difference between the PM2.5 calculated using this equation and the PM2.5 variable directly provided by the model? For example, do they represent different assumptions, components, or processing methods?

I would appreciate any clarification you can provide, as it would help ensure we are interpreting the results correctly.

Best regards,

On Mon, Apr 27, 2026 at 3:36 PM Abdoulaye Sarr <abdoul...@gmail.com> wrote:

Well, I am computing pm2.5 from a simulation outputting dust_1 to Dust_5 using below formula , pm25 = (d1 + d2 + 0.25 * d3) * rho,  the event simulation is spatially reasonable but the values look extremely high.

Any hint or formula suggestion more reasonable?

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[Alexander Ukhov]

hello
you will find answer on your questions in this paper
https://gmd.copernicus.org/articles/14/473/2021/