Low PM10 in CMAQv5.4


I am wondering whether there is a major change in calculating PM10 in CMAQV5.4 compared to CMAQV5.3.1. With exactly the same configurations and same emission DESID I get very low PM10 in CMAQV5.4 compared to CMAQv5.3. I found the fraction of PM10 in coarse mode is quite low. There are new options in cmaq run script:

setenv IC_AERO_M2USE T
setenv BC_AERO_M2USE T

These options were set to F inititallly, however when I set them as T ( the default value), it would give higher PM10 values but still lower than CMAQV5.3.1. I am wondering how this change would be explained.


There were substantial changes to the representation of aerosol dry deposition in CMAQv5.4 for both the M3Dry and STAGE dry deposition schemes. Generally, these changes caused increased aerosol dry deposition and therefore lower concentrations. In addition, the changes were generally more pronounced in M3Dry than STAGE, though the effects vary spatially, temporally, and with PM size range. Please see the following CMAQv5.4 release documentation for additional information:

CMAQ Release Notes: Dry Deposition Air Surface Exchange: M3DRY
CMAQ Release Notes: Dry Deposition Air Surface Exchange: Surface Tiled Aerosol and Gaseous Exchange (STAGE)
What differences should I expect in my model results with v5.4 compared to v5.3.3?