USGS landuse not supported?

MCIP
21

Hi @DLyder –

Which version of CMAQ are you using, and which dry deposition model are you using?

– Tanya

22

Hi Tanya,

Thanks for the follow up. I am using CMAQ 5.4 and the issue was with the M3DRY model not understanding the Landuse data we were using. When we switched to the STAGE deposition model CMAQ worked.

Cheers,

David

23

@DLyder –

I think “worked” is likely an overstatement of what happened. I think STAGE is not quite set up for USGS28, and it may have been more forgiving than it should have been. Please stay tuned for more information.

– Tanya

24

Hi Tanya,

Thanks for the heads up. If there is a way to check the reasonableness of what we have produced I would really appreciate knowing how to do this.

Cheers,

David

25

Hello David,

unless you edited the STAGE_CUSTOM section of the CMAQ_Control_STAGE.nml namelist file to properly map the USGS28 categories to the 11 land use categories used in the STAGE dry deposition calculations (as defined in the STAGE_LU_DATA section of that file), the dry deposition calculations would not have used the correct land use.

More specifically, if you used the unedited default version of CMAQ_Control_STAGE.nml, the mapping defined for the 21 category “MODIS 21 high resolution lakes” example would have been applied to map the first 21 of your 28 USGS28 categories to the 11 categories used in the dry deposition calculations. Not only would that have ignored USGS28 categories 22 - 28, but it would also have mis-mapped categories 1 - 21. Put differently, USGS28 land use categories 1 - 21 (referenced by “Met_Index” in the namelist file) from the LUFRAC_CRO file would have been interpreted to represent the 21 categories listed in the STAGE_CUSTOM section. For example, USGS28 category 1 (representing urban) would have been mapped to evergreen needleleaf forest, category 2 (representing dry croplands) would have been mapped to evergreen broadleaf forest, etc.

If you wanted to update CMAQ_Control_STAGE.nml to properly map USGS28 to the 11 categories used by the STAGE dry deposition calculations, you would start by copying the MET_TO_STAGE_LU structure from the USGS24 section of the namelist to the STAGE_CUSTOM section of the namelist and then add four lines to map met indexes 25 - 28 (USGS28 categories 25 - 28) to the appropriate STAGE categories.

M3Dry does not remap land use for its dry deposition calculations and therefore exits when an unsupported land use type is encountered. Supported land use types are USGS24, MODIS, NLCD40, and NLCD50.

We hope to implement full support of USGS28 throughout the CMAQ system (dry deposition, photolysis, windblown dust, for both CMAQ offline and WRF/CMAQ and MPAS/CMAQ coupled applications) in a future release.