Where is the file of PM10/PM2.5 fraction of Aitken, accumaltion and coarse mode?

How do define the PM10/PM2.5 fraction of Aitken, accumaltion and coarse mode in the combine Program?

There are multiple chemical mechanisms available with the CMAQ system. Each chemical mechanism has a corresponding “Species Definition” file that prescribes how model output variables should be combined to predict different gas, particle and deposition species. When you download the CMAQ code for version 5.2 or later, these definition files are automatically included under the subdirectory “CCTM/src/MECHS”. Within each of the listed mechanism folders, you will find files “SpecDef_MECH_NAME.txt” and “SpecDef_dep_MECH_NAME.txt” that contain a long list of species definitions and corresponding documentation. For example, to find out how to calculate PM2.5 using the CB05e51_ae6 mechanism, open the file “SpecDef_cb05e51_ae6_aq.txt” and read the documentation on PM2.5 calculations. The species definition file will indicate which species should be included in PM2.5 (for example: sulfate, ammonium, and organic carbon) as well as factors to obtain the fraction of each CMAQ size distribution mode that corresponds to 2.5 micron (diameter) and smaller particles. Similar information is available for calculating PM10 and PM1. These species definition files are designed to be used with the combine utility to extract model variables that can be matched to observed quantities from specific monitoring networks. Within the combine run script you will need to set the environment variable SPECIES_DEF to the path of the appropriate species definition file, e.g.,
setenv SPECIES_DEF ${CMAQ_HOME}/CCTM/src/MECHS/cb6r3_ae6_aq/SpecDef_cb6r3_ae6_aq.txt

Thank you for your reply! I also know these file to define PM. But I don’t search the value about PM10/PM2.5 fraction of Aitken, accumaltion and coarse mode. In addition, the program (combine) only the first Layer results can be output.

I want the fraction and use python program to calculate each layer PM2.5 or PM10 concentrations,eventually plot vertical profile.

All of these utilities are flexible. COMBINE can write multiple layers if you give it input files with multi-layer data. To save space, our standard run scripts have the ACONC files write to layer 1 only, but you can modify the run script to write all layers if you choose.

As for the question of the fraction of each mode that is PM25, that is what is PM25AT, PM25AC, and PM25CO are in the PMDIAG and APMDIAG files.


To add to Chris’ response, if you have input files with multiple layers, you can control whether COMBINE writes output for all of these layers or just the first layer (or any other specific individual layer) with the “#layer 1” entry on the third line of the SPECIES_DEF file. By default, this line is uncommented, so COMBINE only writes out species for the first layer. To write output for all layers, add a “!” before “#” or remove this line from the SPECIES_DEF file.

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Thank you! I learn it!:smile:


How can I download COMBINE? Could you send me the link, please?
Thank you

Dear @esm,

You don’t need to download COMBINE separately, it’s in POST file included in CMAQ. You just have to build it, that’s all.



Hi Catalyst 2682

Thank you.