Extremely low NO2 concentration

[yan2024]

Hi teachers,

I used the 2020 baseline scenario of the DPEC emission inventory (which follows the same format as the MEIC inventory for future scenarios), ERA5 meteorological data, WRF version 3.8.1, and CMAQ version 5.4 to simulate ozone (O₃) and nitrogen dioxide (NO₂) concentrations over the Yangtze River Delta region for January 2020.

However, the simulation results are quite unsatisfactory, especially for NO₂, which appears to be nearly zero across most of the domain. I have attached the run scripts and log files for your reference. For now, I have only included anthropogenic emissions, and all other sources (e.g., biogenic, light) have been turned off.

I suspect that the problem may be related to the emission files. For example, HONO—which is assigned a large portion of the NOₓ emissions—shows extremely low values, and in most time steps and regions, the values are zero.

Could this be the reason for the unrealistically low NO₂ concentrations?

run_cctm_Bench_2016_12SE1.csh (38.1 KB)
CTM_LOG_174.v54_intel_case1_20200102.txt (4.2 MB)
PA_REPORT.20200102.txt (115.2 KB)
PA_REPORT.20200103.txt (115.2 KB)
（This log file was artificially interrupted when CMAQ was just run）

emission file (max and min for NO NO2 HONO):

extreme low NO2 result (unit is ppb):

Comparison between obs and simu of O3 :

[cgnolte]

The upper range of the emissions shown in your ncview plots seems reasonable, but why are the cells all blue? Do you have cells with emissions toward the upper end of the range? Toggle the “linear” button to “low” – does the spatial distribution of NO, NO2, and HONO emissions look right?

[yan2024]

The overall distribution appears to cover the target region, but as shown in the figure, there are very few grid cells with values close to the maximum. Most of the grid cells have very small emission values. Could you please confirm if this is expected?

[yan2024]

Hi cgnolte,

I fixed the problem of emissions and I run CMAQ again. But I found that accumulation of NO2 seems to fail again. I selected several steps of CCTM_ACONC of one day here. It seems that pollutants are cleared whihin a day and that is why it always maintain in a low level of NO2 I guess.

step1:

step2:

step3:

step4:

step5:

step6:

run_cctm.csh is attached for your reference:
run_cctm_Bench_2016_12SE1.csh (38.2 KB)