Hello, I am using the offline CMAQ model (Version 5.4) and have a few questions:
First, I set 23 layers for my AELMO file, but only the first layer of AOD_550 shows valid values, while the other layers all display -9e+36. Does the AOD_550 in the first layer represent the AOD (Aerosol Optical Depth) across the entire vertical direction?
Second, does the first-layer result of PM2.5 and PM10 represent the total concentration throughout the entire vertical direction or just the concentration at the ground level?
Third, if I want to obtain accurate AOD results, should I use AOD_550 from AELMO or AOD_W550_ANGST from PHOTDIAG1? Additionally, does AOD_W550_ANGST only have 1 layer? Is it possible for me to get the AOD for each individual layer?
Yes, this value represents column-integrated AOD at 550nm, calculated from AOD at neighboring wavelengths using the Angstrom coefficient.
The layer 1 PM2.5 and PM10 concentrations in the AELMO file represent concentrations in the first model layer.
The AOD_550 values being written to the AELMO files are based on the same internal data arrays being written to the PHOTDIAG1 files as AOD_W550_ANGST.
You can obtain layer-specific aerosol extinction values from variable EXT_AERO_W550 from file PHOTDIAG3 (to obtain 3D output for PHOTDIAG2 and PHOTDIAG3, make sure to either comment out setenv NLAYS_PHOTDIAG “1” or set it to the total number of layers used in your model configuration)
Thank you for your patient response. I still have two questions I would like to confirm:
First, I set setenv NLAYS_PHOTDIAG "23". Does this mean that it will output 23 layers of EXT_AERO_550 for each layer in the PHOTDIAG file?
Second, I combined EXT_AERO_550 with the height layers and performed a cumulative operation, comparing it with AOD_550 in AELMO. I found that the cumulative result of EXT_AERO_550 is significantly greater than AOD_550 in AELMO. Is this reasonable?
Yes, that would be the expected behavior. Is that not what you saw in the PHOTDIAG3 file when you used that setting?
Could you please share the details on how you performed this calculation and by how much the values resulting from your calculation differed from the values obtained from AELMO? The total column AOD post-processed from the layer-specific extinction values in PHOTDIAG3 and the layer heights should be quite close to the column AOD calculated within the model and stored in PHOTDIAG1 and AELMO.
Thank you for your patient response. I carefully reviewed the code and identified an error. After the correction, the integral values of AOD_550 from AELMO and EXT_AERO_550 from PHOTDIAG3 are now more consistent.