Please see the attached review.

The paper developed a RACM2B-VCP mechanism based on the RACM2_Berkeley2.0 mechanism to better represent the chemistry of VOC. They evaluate the performance of RACM2B-VCP for ozone and PM_2.5 by comparing WRF-Chem simulations with AQS surface network data and the previous RACM-ESRL-VCP mechanism. The RACM2B-VCP’s accuracy in representing NOx, CO, VOCs, PAN, and aerosols was also investigated. The temperature dependence of ozone, the effects of VCP, biogenic and fossil fuel emissions on VOC reactivity and ozone were analyzed.  

The new chemical mechanism proposed in this manuscript is meaningful for improving the simulation ability of air quality models for VOCs. However, the evidence presented in the paper to prove the superiority of the RACM2B-VCP chemical mechanism is far from convincing. The explanation for the differences in simulation results is almost missing throughout the whole manuscript. The manuscript needs to be carefully revised before it may be considered for publication.

Line 212: Please explain how to add isoprene emission in the RACM-ESRL-VCP mechanism?

Line253: What time does "noontime" refer to?

Line270: What is the unit of NMB?

Figure 4: The MDA8 O3 concentrations in RACM2B-VCP on days with lower and median temperature are lower than those in RACM-ESRL-VCP, while on days with higher temperature, RACM2B-VCP simulated higher MDA8 O3 values. Please explain the reasons for this difference.

Line 325: The comparison of the model evaluations of NOx, CO, and VOCs by RACM-ESRL-VCP and RACM2B-VCP should be presented simultaneously.

Line346: The author said, “Overall, we show that the R² is generally higher between model simulation and airborne measurements”. However, the NMDB and R² values shown in Table 1 and Figure 5 didn’t suggest that the simulation with the RACM2B-VCP mechanism is ideal. Please supplement a comparison of model simulation evaluation results with previous studies.

In sections 5 to 7, the author only presented a comparison between observation and simulation results, without providing any explanation for the reasons for simulation bias, nor did they present any comparison with previous studies to show the superiority of the RACM2B-VCP mechanism in simulating VOC chemistry, ozone, and other species.

Table 1: The NMDB of acetaldehyde was different from other VOC species and significantly higher in RECAP atmosphere than that in SUNVEx mobile and SUNVEx ground. Why?

Figure S8: It seems that the nitrate concentration simulated by the model is particularly low. What is the reason for this poor performance?

Figure S9: Why do biogenic VOCs contribute so much to the concentration of NOx?

Please unify the font of the figures in the main manuscript.