This work reported simultaneous measurements of new particle formation events during an intensive campaign at an urban and a mountain station in China. It is a complex and extended study that fits well with to the scope of ACP and it is of interest for the international research community. However, there are some issues to be improved or corrected before it is published in ACP.
Major comments
1. The authors include a long paragraph in the introduction to summarize some results on the regional extension of NPF. This manuscript deals with the extension of NPF events but also with two different altitude sites (one mountain site). In my opinion, it is necessary to include a paragraph about the state-of-the-art of NPF events at mountain sites and the vertical distribution of NPF. Sellegri et al (2019) reviewed NPF events at mountain sites and it is not cited along the manuscript. This same manuscript also discusses the topography or preferred altitude of NPF events. In addition, there is some studies that attempt to look on the vertical distribution of NPF (e.g., Komppula et al., 2003; Boulon et al., 2011). Finally, there is also a recent and similar study that looks on the differences of NPF at two sites, also urban and mountain sites, (Casquero-Vera et al., 2020) and the differences or similarities of the results should be discussed with this similar study where the GR, J or CS are also discussed at two different altitude sites.
2. In P19 the authors stated that urban emissions affect the formation rates, but the NPF are of regional extension? Could local events happen without that regional phenomena? Could the emisisons of that huge city be the unique responsible of the regional NPF? In this same section, the authors suggest that “precursors needed for particle formation were much more abundant in the polluted urban environment (Wang et al., 2013), while those needed for growth are rather comparable”. The analysis of J is for 7nm size, that means these particles are not newly formed, these particles come from growth or could be emitted directly by i.e. traffic? At MT, 7 nm particles means that these particles could not be formed there or the vicinity? Please clarify these ideas.
3. Case studies are “special cases” but, in my opinion, they are not analyzed in depth. For example, shrinkage cases are of interest since there is not clear the origin of this phenomenon (e.g., Salma et al., 2016; Alonso-Blanco et al., 2017). In this sense, Section 3.6.3 makes an attempt to discuss the case of stagnant and shrinkage but unfortunately, there is not a real study or discussion of this special case. Please go further on this or remove these sections.
4. Please review the whole text, there is long sentences without any comma and not well connected along the manuscript.
Minor comments
L26 – Change “few” to “low”
L41 – “at urban site” is repeated
L128 – And the altitude of the urban site?
L138 – Cite format
L148-149 – Why do you mention Fig 2 here? Strictly, both instruments cannot correlate if they don’t measure at same time.
L160 – It “is” reasonable
L164 – What calibrations were done?
L181 – Space after dot
L221 – must have been?
L278 – Is it correct that the “dk” is included and the “du” is not? “[dk, du)”
L288 – NPF event “frequencies” is not an adequate title for this section. Maybe something on the “occurrence” but not the frequency. I suggest “Origin of NPF events at both sites”?
L291-293 – Rephrase
L300-303 – Rephrase, use comma.
L304 – “Common” is referred to “coincident” events? If it is, change the terminology.
L615 – Mechanisms are not really investigated
References
Alonso-Blanco, E., Gómez-Moreno, F. J., Núñez, L., Pujadas, M., Cusack, M., and Artíñano, B.: Aerosol particle shrinkage event phenomenology in a South European suburban area during 2009–2015, Atmos. Environ., 160, 154–164, https://doi.org/10.1016/j.atmosenv.2017.04.013, 2017.
Boulon, J., Sellegri, K., Hervo, M., Picard, D., Pichon, J.-M., Fréville, P., and Laj, P.: Investigation of nucleation events vertical extent: a long term study at two different altitude sites, Atmos. Chem. Phys., 11, 5625–5639, https://doi.org/10.5194/acp-11-5625-2011, 2011.
Casquero-Vera, J. A., Lyamani, H., Dada, L., Hakala, S., Paasonen, P., Román, R., Fraile, R., Petäjä, T., Olmo-Reyes, F. J., and Alados-Arboledas, L.: New particle formation at urban and high-altitude remote sites in the south-eastern Iberian Peninsula, Atmos. Chem. Phys., 20, 14253–14271, https://doi.org/10.5194/acp-20-14253-2020, 2020.
Komppula, M., Lihavainen, H., Hatakka, J., Paatero, J., Aalto, P., Kulmala, M., and Viisanen, Y.: Observations of new particle formation and size distributions at two different heights and surroundings in subarctic area in northern Finland, J. Geophys. Res.-Atmos., 108, 4295, https://doi.org/10.1029/2002jd002939, 2003.
Salma, I., Németh, Z., Weidinger, T., Kovács, B., and Kristóf, G.: Measurement, growth types and shrinkage of newly formed aerosol particles at an urban research platform, Atmos. Chem. Phys., 16, 7837–7851, https://doi.org/10.5194/acp-16-7837-2016, 2016.
Sellegri, K., Rose, C., Marinoni, A., Lupi, A., Wiedensohler, A., Andrade, M., Bonasoni, P., and Laj, P.: New particle formation: A review of ground-based observations at mountain research stations, Atmosphere, 10, 493, https://doi.org/10.3390/atmos10090493, 2019. |