Question on Base Elevation and Ground Elevation Settings in CALPUFF with WRF Data

[nininini]

Dear CALPUFF Users,

I have a question regarding the correct elevation values to use for sources and receptors when running CALPUFF with WRF meteorological inputs.

For the sources, should the base elevation be set to the actual ground elevation (from real topography) or to the elevation given by the WRF terrain data? I notice that WRF sometimes overestimates or underestimates terrain heights compared to reality, but since the computational grid is based on WRF, I am not sure which is more appropriate.

For the receptors, how should the ground elevation be defined? Should it be left blank, set to the WRF terrain elevation, or to the real topographic elevation? I understand that the height above ground is always relative to the local terrain elevation, but I am uncertain which elevation reference CALPUFF expects in this case.

Any clarification or best practices on this would be greatly appreciated.

Best regards

[Jana Krajcovicova]

Hi,

CALPUFF only knows the terrain you give to it as input. In your case it is WRF. I understand it so that all source and receptor elevations should be given in your input resolution (WRF terrain in your case), otherwise you could get wrong meteorology (e.g., if the WRF terrain underestimates elevation at certain point source, if you input real elevation of the source base, you can get much overestimated winds at the stack tip as they would be computed relative to CALMET (wrf) terrain.

However, if I am right, it is confusing that they ask user to input base elevations as the program can determine it itself. So maybe I am wrong.  :-).

Jana

--
You received this message because you are subscribed to the Google Groups "european-calpuff-user-discussion-group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to european-calpuff-user-dis...@googlegroups.com.
To view this discussion, visit https://groups.google.com/d/msgid/european-calpuff-user-discussion-group/e7dfa00a-4ddc-4e1d-9bac-dad88edd160cn%40googlegroups.com.

[nininini]

Hi Jana,

Thanks a lot for your explanation, that helps. My concern is that it may actually be redundant to provide explicit elevations, since CALPUFF already has the terrain field. It seems it might be enough to leave them as zero and let the model assign elevations internally.

As for the X and Y coordinates, as far as I understand, we just provide the real-world coordinates of sources and receptors, without trying to match them manually to the WRF grid points. The model then assigns them internally to the computational grid.

So in that sense, I am not sure if specifying elevations explicitly adds anything.

To view this discussion, visit https://groups.google.com/d/msgid/european-calpuff-user-discussion-group/CAOcjp_BmMp4K34Fsenk4P-cRdEBbVFmnRVauRdcSMTGcxSuB3A%40mail.gmail.com.

[Jana Krajcovicova]

 It seems it might be enough to leave them as zero and let the model assign elevations internally.

I don't know if that's a good idea. Better to test it but we assign the source elevations based on the geodat file data.  

As for the X and Y coordinates, as far as I understand, we just provide the real-world coordinates of sources and receptors, without trying to match them manually to the WRF grid points. The model then assigns them internally to the computational grid.

It doesn't work like that in CALPUFF. It computes puff contributions based on actual coordinates of sources and receptors. 

So in that sense, I am not sure if specifying elevations explicitly adds anything.

El mié, 3 sept 2025 a la(s) 3:57 a.m., Jana Krajcovicova (jkr...@gmail.com) escribió:

Hi,

CALPUFF only knows the terrain you give to it as input. In your case it is WRF. I understand it so that all source and receptor elevations should be given in your input resolution (WRF terrain in your case), otherwise you could get wrong meteorology (e.g., if the WRF terrain underestimates elevation at certain point source, if you input real elevation of the source base, you can get much overestimated winds at the stack tip as they would be computed relative to CALMET (wrf) terrain.

However, if I am right, it is confusing that they ask user to input base elevations as the program can determine it itself. So maybe I am wrong.  :-).

Jana

On Wed, 3 Sept 2025 at 02:56, nininini <ninini...@gmail.com> wrote:

Dear CALPUFF Users,

I have a question regarding the correct elevation values to use for sources and receptors when running CALPUFF with WRF meteorological inputs.

For the sources, should the base elevation be set to the actual ground elevation (from real topography) or to the elevation given by the WRF terrain data? I notice that WRF sometimes overestimates or underestimates terrain heights compared to reality, but since the computational grid is based on WRF, I am not sure which is more appropriate.

For the receptors, how should the ground elevation be defined? Should it be left blank, set to the WRF terrain elevation, or to the real topographic elevation? I understand that the height above ground is always relative to the local terrain elevation, but I am uncertain which elevation reference CALPUFF expects in this case.

Any clarification or best practices on this would be greatly appreciated.

Best regards

--
You received this message because you are subscribed to the Google Groups "european-calpuff-user-discussion-group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to european-calpuff-user-dis...@googlegroups.com.
To view this discussion, visit https://groups.google.com/d/msgid/european-calpuff-user-discussion-group/e7dfa00a-4ddc-4e1d-9bac-dad88edd160cn%40googlegroups.com.

--
You received this message because you are subscribed to the Google Groups "european-calpuff-user-discussion-group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to european-calpuff-user-dis...@googlegroups.com.
To view this discussion, visit https://groups.google.com/d/msgid/european-calpuff-user-discussion-group/CAOcjp_BmMp4K34Fsenk4P-cRdEBbVFmnRVauRdcSMTGcxSuB3A%40mail.gmail.com.

--
You received this message because you are subscribed to the Google Groups "european-calpuff-user-discussion-group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to european-calpuff-user-dis...@googlegroups.com.

To view this discussion, visit https://groups.google.com/d/msgid/european-calpuff-user-discussion-group/CAF_kTpTjCYJn3%3DsQKGvHQXHMnqU%2BGgimWG_a2Kz_iros2Ux6qQ%40mail.gmail.com.