This study is well done and the paper clear and concise. However, the focus is rather local.

One recommendation is to put the findings of the paper into better context. For instance, the NO titration effect is well documented in the literature over the last 30+ years in the US and Europe and more recently in China. So, is it a surprise that you see this effect in Shanghai and other large Chinese cities? Not really as you indicate. Other large world cities have struggled with the issue of decreasing emissions enough to begin seeing reductions in ozone. It would be worth discussing the literature on this topic.

It would also be helpful to discuss better (a few paragraphs) on how HCHO/NO2 and ozone trends have evolved over the satellite record. You only looked at TROPOMI, but the OMI data record is much longer (2005-present). How has the HCHO/NO2 evolved over time in Shanghai and other Chinese cities? This analysis would help to put the magnitude of the 2022 LCD into historical context and help policy-makers to know what VOC and NOx emissions reductions will be required to see ozone decrease. There are studies in the literature that have looked at the historical HCHO/NO2 in China, so you may not need to do your own analysis.

These two recommendations will help you to more broadly discuss the implications of your work for other Chinese cities and to better put the importance of your work (e.g., Summary and Implications) into context. I'm recommending this since your local focus on Shanghai may not fit the aims of ACP: "The journal scope is focused on studies with important implications for our understanding of the state and behaviour of the atmosphere. Articles with a local focus must clearly explain how the results extend and compare with current knowledge."

Line 222: "wug" is not a word. "with"?

This study describes a study in 2022 Shanghai lockdown by investigating the spatiotemporal variations in surface MDA8 O₃ and NO₂ concentrations, TROPOMI-based HCHO and NO₂ concentrations, and the cause of high O₃ concentrations during the 2022 LCD from two aspects: meteorological conditions and O₃ formation regimes. It have great insight on O₃ concentration increased in 2022 LCD, having greatly detailed data and substantial content. I am glad that the author can report the recent ozone pollution situation to us in a short time and make an in-depth analysis. But there are some problems, which must be solved before it is considered for publication. Below I have reported the lines in the text that require further investigation and clarification.

1. L25: the abbreviations of nitrogen should be NO_xrather than NOx. Elsewhere the abbreviation is correct
2. 2.1 section: There is a lack of description of contaminant monitoring instruments and their detection limits.
3. L63: 3.3.1 title “Effects of meteorological conditions on O₃ concentrations in Shanghai”, I suggest changing the “O₃ concentrations” to “O₃ pollution”.
4. L164: “A large body of literature has indicated that meteorological conditions can significantly affect O₃ concentrations …”. there are only two references in the back, which seems a little weak. Suggest adding more references.
5. Fig.2: the inset figures show the monthly average concentrations, but the y-axis is missing units.
6. L126: based on the coverage in Shanghai that 2020 LCD date from 23 Jan to 23 Mar, but in this paper is 23 Jan to 12 Feb. Hope you can reconfirm it.
7. L209 (Fig.9): in this picture, your x-axis is HCHO/NO₂ ratio, and y-axis is MDA8 O₃ (ug/m³), but OMI HCHO/NO₂ and high-O₃ Probability (%) in your reference paper, respectively (Wang et al., 2021). Can you explain this difference? Weather the change of axis will affect O₃ formation regimes?