Emission (mass/area/time) is a flux, and not related to concentration (volume). So they are 2 different quantities, and cannot be directly converted to each other.

Dear Setareh,

I agree with Amir, I don't think one can jump from a surface flux to a concentration without the use of a transport model to account for all physical phenomena in the atmosphere, and produce concentrations values that make sense.

Best,

Jerome

Dear Amir Hossein Nikfal & Jérôme Lasne

So many thanks for your advice. In some research papers that used RegCM model, I noticed that dust had a unit of ug/m3 (or ppm)! So I wonder how it could be possible. Because the in RegCM model there are two variables regarding dust amount:

1.emflx, that is: Surface emission flux [unit: mg m-2 day-1]

2.burden, that is: Tracer total burden [unit: mg m-2]

none of these variable are related to concentration. So how is this unit conversion done?

any idea please?

Best wishes,

Dear Setareh,

Indeed sources and sinks may be surface emission fluxes, based on which models produce concentrations values, which are useful to compare with observations and field measurements.

Nonetheless, I think that no trivial "conversion" between the two units can be made. You definitely need a model to simulate atmospheric processes in between emission and atmospheric concentrations.

As I have no expertise on the RegCM model, I suggest you have a look at this paper:

https://gmd.copernicus.org/articles/14/7705/2021/gmd-14-7705-2021-discussion.html

To "convert" your surface emission fluxes into concentrations for specific locations/atmospheric conditions, I suggest you contact a team with experience in modelling and see if they can make the simulations for you.

All the best,

Jerome