This paper investigates the quasi-weekly oscillation of PM_2.5 transport over China. The period analysed extended during the winters of 2015-2019 and PM_2.5 concentrations included data from 1079 stations. The statistical procedure considered the extended empirical orthogonal function. Two transport flux patterns were identified and 8 phases of the regional PM_2.5 transport over central and eastern China were isolated. Moreover, the synoptic pattern influence on the quasi-weekly oscillation of the regional PM_2.5 transport was analysed. Since this is a complex study, the paper may be accepted for publication in Atmospheric Chemistry and Physics after the inclusion of the following minor changes.

The authors have identified this quasi-weekly oscillation with a complex statistical procedure. Potential readers could ask if this oscillation could be observed with simpler procedures. If this oscillation responds to an atmospheric pattern, perhaps it could be perceived by direct measurements.

If this oscillation responds to an atmospheric pattern, the authors should highlight the main advantages of the employed procedure (extended empirical orthogonal function), which is not easy, against other procedures. Moreover, the authors should indicate if alternative and simple procedures exist to get similar results.

The authors should inform about processes similar to that described in this paper around the world.

The number of references for discussion should be increased. They should be used to compare results of this study with those from previous analyses.

Strengths and weaknesses of the current study should be included.

Minor remarks.

L. 279. “H. Huang” should be “Huang”.

The regional transport of air pollutants driven by atmospheric circulation is one of the important causes for air pollution in atmospheric environment change. However, the driving mechanisms of atmospheric circulation have been poorly understood in the variations of regional Pair pollutant transport. Therefore, it is interesting in this study on the quasi-weekly oscillation (QWO) of regional PM_2.5 transport over China regulated with the influence of synoptic-scale disturbance of the monsoon circulation. The paper is well organized and fit the scope of the ACP journal. There are some minor issues need to be improved before publication.

1. The quasi-weekly oscillation (QWO) of the monsoon circulation is a driver for the regional transport of air pollutants. Please include a discussion regarding the quasi-weekly oscillation of the East Asian winter monsoon circulation system.
2. It would strengthen the manuscript to include a quantitative comparison of the changes in PM2.5, specifying the extent of any reductions or increases. A clear data comparison can make the manuscript more rigorous.
3. The manuscript provides a detailed analysis of regional PM2.5 transport from the North China Plain to the Twain-Hu Basin; however, there is insufficient discussion regarding the impact of this transport on PM2.5 over the Twain-Hu Basin. Please include a paragraph in the Discussion that addresses potential impacts and offers a comparison with existing literature on this topic.

Minor comments:

1. Line 45: The citation "X. Huang et al., 2020" appears to be formatted incorrectly. A similar issue is observed in lines 88-91 with "Y. Yang et al., 2021" and "W. Yang et al., 2021." Please correct these references and conduct a thorough check of the entire manuscript to ensure the accuracy of the citation format.
2. Line 93: The authors should provide a more detailed explanation of the term "susceptibility zone" to enhance comprehension of this concept.
3. Lines 289-290: The sentence "The source-receptor relationship between NCP and THB during the regional PM2.5 transport over CEC is discussed in detail in the next section" does not significantly contribute to the manuscript. As it serves primarily as a transition to the next section, it could be removed for clarity.
4. Please improve English writing include grammar and expression in the manuscript.

Comments on “Quasi-weekly oscillation of regional PM2.5 transport over…”

This study investigates how the synoptic-scale circulations influence the transport of air pollutants from North China Plain to central and eastern China. They found the quasi-weekly oscillation of the air pollutants in North and East China is mainly attributed to both East Asia winter monsoon disturbance and the periodic activities of Siberian High. I enjoyed reading this manuscript and found its topic is very interesting. The authors gave a clear description of their methods and results. I have only minor comments, as shown below:

• Butterworth filter: I do not understand this technique. I suggest the authors could add more explanation of this method.
• In equation (6): Is the distance d in the unit of meter/kilometer or degree in longitude and latitude cause the authors mentioned 0.25 by 0.25 grid spacing in Line 159.
• Line 204: Delete “found”
• Line 69: It should be “have not yet”
• Line 71: Change it to “one of the most active”
• Lines 77–78: It is not clear. Do you mean the pollutants can be removed by circulations at the regional scale?
• Line 101: Delete “be beneficial to”.
• Line 121–122: What observations 4 times a day are used? ERA5-land is not observational dataset.
• Line 132: The units for PM2.5 mass concentration TF is not right. Units in the current form is for mass TF.
• Line 179: should be observations
• Line 201–204: It needs to be revised.
• Figure 1: What do grid cells of white color mean in panel (b)?
• Line 245: Do you mean “temporal structure”?
• For figures showing shadings: please add units for all color bars in the figure.