The unit of ext_coefficient in Photdiag3 is m-1 in CMAQ5.3 . However the results of EXT are consistent with the order of magnitude of km-1 in the PMVIS in CMAQ5.2.
Thanks for finding and mentioning the error. The extinction coefficients have the wrong units and should be km-1. Version 5.3.2 and lower use Mm-1 so in self-defense, the incorrect units seem a typo-graphic error.