The Ph.D dissertation Assessment of air quality in Northern China by using the COSMO-ART model in conjunction with satellite and ground-based data which was written by Stefanie Schrader in KIT German.
This thesis did a great job on applying the COSMO-ART in China and quantify the influence of dust plume and anthropogenic aerosol in North China on air quality.
The third chapter told about the calibration and validation of the source inventory. I think this chapter is quite essential for further discussion. The conclusion would be useful only if the meteorology condition, source inventory and the primary pollution diffusion, etc could be well reproduced.
So, the author choose three different source emission setting for 3 independent run(run A, run B and run C).
Three runs were performed for NO, NO2 and ozone. By comparing with observation data, she present the average value and pearson correlation coefficient like the figure below.
The NO and Ozone simulation results are all in good agreement with observation in run B and run C. But the NO2 simulation shows negative correlation. In the thesis, the author said:
" It can also be seen that correlation coefficients for measured and modelled NO2 are overall very low (Table 6), which is mainly determined by a general problem of NO2 simulation due to its complex chemical nature"
In my opinion, NO2 is the essential precursor for ozone formation. Ozone is generated by the NOx-VOC-O3 cycle. But the result here may reveal that the temporal variation of ozone concentration could be represented decent even the NO2 variation can't be performed.
Here is an illustration shows the classical ozone and NOx temporal variation.
I present my doubt here and want to hear some knowledge related.
PS: Rewrite my text as a question.
The simulation results from this dissertation for NO, NO2 and O3 performed differently. NO and O3 has a good agreement with the observation data by correlation analysis. But the NO2 temporal variation could not be reproduced(negative r). The author explain this phenomena due to the complex chemical nature of NO2.
But in my opinion, the NO2 is essential for O3 formation. How can the O3 variation be reproduced decently even though the true NO2 variation couldn't be reappeared.