Hi everyone,
I am trying to use monitoring concentrations (PM2.5, PM10, etc.) to correct the initial field in CCTM-CGRID * (the model I am using is CMAQv5.4). However, I encountered a problem during the testing process.
The calculation formula for PM10 concentration in the model is:
PM10 = ATOTI * FPM10AIT + ATOTJ * FPM10ACC + ATOTK * FPM10COR.
This indicates that the calculation of PM10 concentration is not only influenced by its species concentration, but also by the fraction of FPM10AIT, FPM10ACC, and FPM10COR. Although I used monitoring data to correct the concentration of the species, the unreasonable distribution of FPM10AIT, FPM10ACC, and FPM10COR (the species had higher concentrations, but the fraction were lower), resulting in the final concentration results not being consistent with reality. Therefore, I would like to ask how the fraction of FPM10AIT, FPM10ACC, and FPM10COR are calculated, and if I can make adjustments to these fractions.
Hello,
Thank you for your question. It would be useful to have a bit more information about the comparison you are trying to do.
The FPM fractions are calculated online in CMAQ and are based on the properties of the aerosol size distribution at a given location and time. This takes into account their median diameter, the standard deviation of the modal distribution, the particle number concentration, the bulk density, and the water content.
Are you after the fraction of particles that are smaller than 10 um? Or are you comparing to measurements with diameters between 2.5 um and 10 um?
-Ben Murphy