The study focuses on the contribution of the canyon urban heat island intensity in the daytime and nighttime by analysing different datasets. The analysis is comprehensive and the whole story is also very organised. However, I have one major comment which suggests the author address.

Until now, studies have focused a lot on the mechanism of the canyon UHI, especially the intensity. Many previous studies have also focused on the reason for UHI. The study has two main conclusions: 1) CUHI is larger during nighttime and under the high-pressure system; 2) synoptic weather patterns have a more pronounced influence on day CUHII, but human activities dominated night CUHII.  These two points are not new findings; they can be easily found and learnt from the previous literature and even textbooks. Thus, what is the significant contribution of the current work? Indeed, authors applied more advanced and updated analysis methods, yet what are the new findings, which are similar to the previous or different to the previous?

I would also suggest the authors reconstruct the abstract and introduction. The current version of the abstract cannot fully reflect significance. In the introduction, authors should highlight the combination of the synoptic and human activities! Similarly, more discussion and explanation should focus on section 3.3 in the results. The analysis and results in the previous sections are a bit lengthy, which makes the focus of the article not sharp enough.

Minor comments:

Line 154, reference format typo.

Please also indicate the data period and temporal resolution of the ERA5 dataset.

Section 2.3.1: More explanation of the calculation of CUHII. There are 43 USs and 27 RSs, for each US, which RS is selected to be linked with to get the CUHII?

This study presents a comprehensive and detailed analysis of the diurnal drivers of the Canopy Urban Heat Island Intensity (CUHII) in the Yangtze River Delta Urban Agglomeration. The manuscript utilizes multiple datasets and methods, making it a robust piece of research. However, the manuscript appears a bit lengthy and the novelty of the findings is not clearly articulated. I have the following comments and questions, and need specific revisions/answers:

In the methodology section, I suggest including a workflow that outlines the datasets and methods used in the study.

Figure 1b: It is unclear whether the reference station shown in Figure 1b is the same as the one mentioned in Section 2.3.1. Could you please clarify this in the manuscript?

Line 205: The statement, "After 18:00 BJ, as the solar altitude angle decreases, the effective radiation in suburban areas gradually increases, accelerating atmospheric heat loss," is confusing. Typically, as solar altitude decreases, radiation decreases, which should not lead to an increase in effective radiation in suburban areas. Could you please provide a more detailed explanation or consider revising this statement for accuracy?

Line 210: The manuscript states, "Before sunrise, between 0:00 and 7:00, the cooling rates of urban and suburban temperatures are similar, causing the CUHII to gradually increase to its daily maximum value of 0.65 °C." However, it is generally understood that urban areas, due to their heat storage in built materials and the canopy structure, would have a slower cooling rate compared to suburban areas. Please provide reasons that support this claim of similar cooling rates.

What factors contribute to the similarity in CUHII magnitude during the night and daytime in July?

Line 425: Are there any potential reasons or mechanisms that could explain the significant decrease in daytime WS during Heat Wave?

While the study provides valuable insights into the modulation of CUHII by SWPs and human activities in the YRDUA, it would be beneficial to discuss whether these findings can be extrapolated to other regions.

Minor Comment:

Line 71: Please provide the full name of the WPSH at its first mention.