The authors have presented a manuscript that identifies the health effect of heatwaves and ozone in Beijing, China. The authors identified this effect separately and combined. Furthermore, the authors proposed the identification of the effect for urbanization and synoptic systems, with the aid of composites. In general, the article is interesting but needs improvements. 

Major issues:

The methodology to identify episodes of interest is clear but the explanation about the exposure functions is weak. The authors just cite Liu et al (2021)  and Ying et al (2017) for the temperature and ozone parameters. Also, I do not understand why the authors use RR for Liu et al and ER for Ying (lines 120-125). Specifically, the authors state: "every 1°C increase in the daily Tmax above 31.5°C, the largest RR of mortality caused by high temperature in northern China was 1.002". Then, we see Table 3, the Tmax for Urban HW, the value is 36.1, then how the authors obtained 4.76(4,76,4.77)? I thought that It might be (36.1-31.5)*1.002 = 4.6092, but not. Please, clarify and include a similar explanation for ozone.

In Figure 5, the authors show the diurnal cycle for some variables claiming that there are significant differences. Do the authors mean statistical significant in the difference, perhaps after applying a test Mann-Withney? Was this test applied to the point values shown in Figure 5? Finally, neglecting the contribution of O3 precursors to explain the difference in O3 during HW events (line 160), I think it is wrong. Even the authors state in the manuscript that during HW events there are more biogenic VOC emissions. Also, the wind speed is higher during HW, which favours the transport of pollution, from rural to urban areas for instance. Actually, a recent paper published in ACP shows the contribution of local and regional emissions to air quality (https://acp.copernicus.org/articles/21/18195/2021/). 

Minor issues: 

Line 77-80, one paragraph of just one sentence. Each paragraph should have at least three sentences, intro, body and conclusion.

Line 115, then again, which beta did you use?

Line 123-124, why do the authors use RR for temperature and then ER for ozone?

Figure 2 is not good. Provide a better figure.

Line 151, which test do the authors use?

Lines 165-174: I understand that we might expect lower risk in traffic and urban station for ozone, but you mentioned in line 166 that ozone caused a reduction of  2.44% which means risk lower than 1. More explanation is needed.

Line 177, Please, do not overuse abbreviations, WPSH is not needed.

Line 196, UHI is not defined.

While the health influences of deteriorated air quality and extreme weather have been assessed extensively, this work took a step forward to assess the lumped effects under the joint occurrence of both contributors and distill the relative significance of synoptic weather and urbanization in these key patterns that we concern. The results provide new information that fills gaps in the understanding of integrated impacts of ozone and heatwave on public health in Beijing. However, several important issues need to be clarified and addressed before its publication.

Major comments

1. This work would need a professional edit before the final publication. The content is basically understandable but with a significant number of grammatical errors. Some terminology seems to be inappropriate such as “public mortality risk”, “compound risk”, “urban hyperthermia”, “ozone aggravated” etc. All these make it tough to read through in particular the introduction and discussion.

2. Some previous works are not properly referred at the introduction. For example, some cited literature in lines 39, 43, and 46 is not supportive of the corresponding statements.

3. Scientific theories and existing evidence should be referred to and expressed more precisely. For example, in line 59, “39.6% increase in premature mortality” is in against to the annual mortality in Beijing or other value? More statements can be refined for lines 37-38, line 39, and lines 166-167.

4. The introduction is not very organized and the overall logic flow is not fluent. The authors should further polish this section.

5. Although involved in the previous work, the weather type classification method should be at least briefly described to improve the integrity of the paper.

6. The first paragraph in section 3.1 (line 142-160) took efforts to presents the relationship of ozone concentration with different meteorological indicators, which however have been systematically studied already. I recommend simplifying this part.

Other comments:

1. Line 116, β is the coefficients of the exposure-response function rather than the exposure-response function itself,
2. In Table 3 and Tale 4, what does the red color represents?