Hi there. I simulated the change of PM2.5 concentration over time in a pollution period, and set the output of PM_EXT_550 in CMAQ_Control_Misc.nml file according to CMAQ_UG_appendixF_elmo_output in Users_Guide. During the simulation, the operation is normal and no error is reported. After extraction, I found that only the sunrise time during the day (08:00-17:00) had value, while the night time was 0, which was the same as the rule of AOD_550. But I found that the extinction factor of lidar is constant throughout the day. Is my mode setting causing PM_EXT_550 to have no value at night?
Since the aerosol extinction (and its integrated value over the column, i.e., the aerosol optical depth) represent the scattering and absorbing effects of the atmospheric aerosol burden on solar radiation, it follows that these values will be zero when there is no sunlight. There is no setting as such that would provide non-zero values of these variables at night. I assume the lidar observations you are examining have non zero values since that represents the aerosol extinction of the lidar beam, though I am not certain why the extinction from the lidar is “constant throughout the day”. One could conceivably estimate aerosol backscatter and light extinction to the lidar beam using the model estimated 3-D aerosol composition and size distribution and a radiative transfer model, but that would need to be done off-line to the CMAQ model, with perhaps some more knowledge of the lidar retrieval algorithm.
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Thank you for your reply. Maybe my expression was wrong at first, which caused you difficulty in understanding. I mean, the extinction factor of liDAR is all day long. Then I knew I needed to do it offline. Thanks again.
Best
pbwang