Review summary for Guo et al.

This study presents a comprehensive investigation into the formation of limonene-derived organonitrates (ON) under competing oxidation pathways (O₃, OH, NO₃) using both a chemical box model and a global model. The work addresses a critical gap in understanding how multiple oxidation pathways influence ON formation and their spatiotemporal variability, offering valuable insights into secondary organic aerosol (SOA) dynamics. The integration of explicit chemical mechanisms into global models is a significant advancement, enhancing predictive capabilities for atmospheric chemistry. The findings are novel and relevant to air quality and climate change, which would be interesting to the readers of ACP and the community. However, several aspects require clarification or improvement to strengthen the scientific rigor and clarity of the manuscript.

Major comments:

1. The branching ratios and rate constants for NO₃ addition (e.g., 0.63:0.34:0.03) and autoxidation pathways are critical to model outcomes. However, the justification for these values (e.g., experimental validation vs. analogy with similar compounds) is insufficiently detailed.  

2. While the comparison with observations is mentioned (Sect. S3), the manuscript lacks quantitative validation metrics (e.g., correlation coefficients, normalized mean bias) for limonene-derived ON in the global model.  

3. The statement that “enhancing OH-initiated pathways increases ON burden by 44.7%” (Sect. 3.3) contrasts sharply with box model results showing lower OH-initiated yields. The explanation for this discrepancy (e.g., regional precursor availability, diurnal variations) is underdeveloped.  

4. The exclusion of heterogeneous reactions or aerosol-phase processes (e.g., hydrolysis of ON) may underestimate ON loss pathways. You should show this uncertainty. 

5. The EVAPORATION and SIMPOL methods are mentioned, but their differences (and potential biases) are not discussed.

6. Central Africa shows the highest ON burden despite not having the highest limonene emissions (Amazon does). The explanation (oxidant competition with isoprene) is buried in the text.

Minor comments:

1. "Limonene has unique structure..." → "Limonene has a unique structure..."  

2. "The chemical mechanism of ON formation could have an influence..." → "The chemical mechanism of ON formation may influence..."  

3. "This difference contributes to the disparity between the global model results and the idealized experimental results from the box model..." → Revise for conciseness: "This discrepancy highlights differences between global-scale dynamics and idealized box model conditions."