The unit of EXT may be wrong in PHOTDIAG3

CMAQ
1

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.

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.

3

The units seem wrong in CMAQ5.3.1 (they all are indicated to be in Mm-1 in the model output). I see the values for EXT_W607 are much higher (few thousands Mm-1) while those for EXT_AERO_W607 are about 3 orders of magnitude smaller, again in Mm-1. Why are these so different? These two should be very close, as GAS_EXT_W607… values are ~0.006 Mm-1. Could you please provide some clarification here regarding these units, for CMAQ5.3.1.

Also, is there any recommendation on how to compute total extinction at 550 nm? Probably a simple interpolation won’t work?

Thank you.