The effect of meteorological conditions and atmospheric composition in the occurrence and development of new particle formation (NPF) events in Europe

Bousiotis, Dimitrios; Brean, James; Pope, Francis D.; Dall'Osto, Manuel; Querol, Xavier; Alastuey, Andrés; Perez, Noemi; Petäjä, Tuukka; Massling, Andreas; Nøjgaard, Jacob Klenø; Nordstrøm, Claus; Kouvarakis, Giorgos; Vratolis, Stergios; Eleftheriadis, Konstantinos; Niemi, Jarkko V.; Portin, Harri; Wiedensohler, Alfred; Weinhold, Kay; Merkel, Maik; Tuch, Thomas; Harrison, Roy M.

doi:https://doi.org/10.5194/acp-21-3345-2021

Articles | Volume 21, issue 5

https://doi.org/10.5194/acp-21-3345-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-21-3345-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 5

Research article

|

04 Mar 2021

Research article |

| 04 Mar 2021

The effect of meteorological conditions and atmospheric composition in the occurrence and development of new particle formation (NPF) events in Europe

Dimitrios Bousiotis, James Brean, Francis D. Pope, Manuel Dall'Osto, Xavier Querol, Andrés Alastuey, Noemi Perez, Tuukka Petäjä, Andreas Massling, Jacob Klenø Nøjgaard, Claus Nordstrøm, Giorgos Kouvarakis, Stergios Vratolis, Konstantinos Eleftheriadis, Jarkko V. Niemi, Harri Portin, Alfred Wiedensohler, Kay Weinhold, Maik Merkel, Thomas Tuch, and Roy M. Harrison

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Final revised paper (published on 04 Mar 2021)
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Preprint (discussion started on 05 Aug 2020)
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AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review on the "The Effect of Meteorological Conditions and Atmospheric Composition in the Occurrence and Development of New Particle Formation (NPF) Events in Europe"', Anonymous Referee #1, 31 Aug 2020
RC2: 'Referee comment on acp-2020-555', Anonymous Referee #2, 26 Sep 2020
AC1: 'Author Comments (AC)', Roy M. Harrison, 15 Oct 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Roy M. Harrison on behalf of the Authors (15 Oct 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Nov 2020) by Gordon McFiggans

RR by Anonymous Referee #1 (04 Dec 2020)

Suggestions for revision or reasons for rejection

This work compiles already published results from 16 sites located in six European cities. Within this huge task, the effort is to identify relationships between meteo variables, gas phase composition and aerosol organic content with key NPF variables such as NPF frequency (the authors name it NPF probability), growth rate and formation rate. Several findings within this work justify publication; two most striking is the nonlinear relation of temperature with NPF probability and the fact that increased solar irradiance reduces the probability for NPF.

Some issues require attention though.

Starting from most important to least severe

The authors have chosen to use only Ia events and as a result the probability shown in Table 2 is several factors smaller than those reported in literature for the same sites. However, from a brief search, the difference can be up to a factor of six. It is well understood why the authors made such a choice as formation and growth rates can be calculated reliably from these type of events only. How does this choice reflect to the results shown? I strongly support that for one site (e.g. Hyytiälä) an intercomparison is carried out to indicate to the reader the tentative differences. My recommendation is to do so only for NPF probability. This is critical as most studies in the end classify NPF as events, undefined and non-events lumping Ia, Ib and II classes into one. The authors should add to the caption of Table 1 the fact that only Ia events are considered.

How coarse is the time resolution of OC and sulfate measurements examined in this study? The first impression for the former is that they are derived from the thermal optical method. For the latter AMS is mentioned. However, AMS is typically used for short-term campaigns and this is a multi-year study. Do the authors mean ACSM? If the resolution of these measurements is coarser than 1 h, are they reliable to be used in NPF studies? The authors should clarify the time resolution of these measurements, both OC and SO4, in the manuscript and discuss any complications. If the authors indeed use AMS measurements what fraction of the time period discussed do they cover? Also, it would be worthwhile to mention the publications that refer to these measurements.

In each pair of variables (e.g. NPF probability and RH; growth rate and temperature) presented in this work, there seems to be a norm and one (or more) site that is an exception. Since the authors cannot fully explain why (and this is perfectly understood), it is worthwhile to mention that in the abstract or the conclusions or in both.

There is little relationship between RH and CS at most sites. Is this because CS was based on dried measurements and was not corrected for hygroscopic growth? This would be understood since chemical composition was lacking on most sites. Please discuss if CS was corrected for hygroscopic growth and how that affects the results presented.

ANOVA is only valid for normally distributed populations. Have the authors tested for normality? The F-test is typically used. How did the authors treat skewed distributions? Please discuss.

In the supplement, several relationships are clearly non-linear, such as the temperature-NPF probability for a few sites, but the authors insist to use a linear fit (probably for consistency). May I ask the authors to note on the supplemental graphs in which cases linearity is not followed. The authors are better aware of the statistical significance of the related graphs than the reader is. In the case of Denmark Rural (S2b), it is not evident whether the deviation from linearity is statistically significant or not.
Please define in the methods section what is weak, strong and very strong correlation in this work. It will assist the reader further.

The effect of SO2 on NPF that the authors are discussing in Section 3.2.1 has been presented before. Please check the references below. These works relate particle acidity to NPF. Experimentally it has also been verified at the site named GRERU in this work.

Line 247. “The remaining data” is better use of English than the “data left”

If the authors prefer the term NPF probability it is fine. But please use it throughout the manuscript. The caption in Table 2 is a bit confusing.

References
Jung, J., P. J. Adams, and S. N. Pandis (2006), Simulating the size distribution and chemical composition of ultrafine particles during nucleation events, Atmos. Environ., 40, 2248–2259, doi:10.1016/j.atmosenv.2005. 09.082.

Jung, J. G., S. N. Pandis, and P. J. Adams (2008), Evaluation of nucleation theories in a sulfur-rich environment, Aerosol Sci. Technol., 42, 495–504, doi:10.1080/02786820802187085.

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RR by Anonymous Referee #2 (10 Dec 2020)

Suggestions for revision or reasons for rejection

General comments
The current version of the manuscript has improved. Readability is better. The authors followed most of the suggestions. However, there are still few minor aspects I encourage to improve.

The readability of the abstract and introduction could still be polished.

I am not convinced by the use of term “NPF probability”. You are probably aware that some readers might only (or first) check the abstract and conclusion. Using “NPF probability” term may be confusing. If you still think this is something you would like to keep, I suggest be more specific what it actually represents when discussing it in conclusion.

Please specify how the NPF frequency was calculated, and check values presented in Table 2. Which data is considered for this calculation? I think the answer was given in author’s response (AR) file but I missed mentioning of that in the main manuscript. Further, some comments are addressed in AR but these clarifications do not always appear in text. Please double check.

How sure are you that NPF occurred at UK sites if you only have SMPS data available >16 nm for these locations? Please comment in the manuscript. It is also one of the limitations of the study that you could mention. What was your approach for analysis of these sites?

I have noticed that frequently two other papers published/submitted by Bousiotis et al (2019, 2020) are mentioned in AR. It would be good if the authors make sure that these are also mentioned in relevant places throughout the manuscript (mentioning the issue raised by reviewers e.g.: “xx was explored in Bousiotis et al. xxxx and is not the focus in this paper” or “”xx can be found in…”).
Also make sure that crucial information on the study is provided in the current manuscript without the need to often look into two other papers to get a complete picture.

Table 3: please indicate in the caption what values “in bold” indicate
Figure 7a, 7b: make one caption for figure 7(a and b) and only indicate on corresponding plots “a” and “b”.

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ED: Publish subject to minor revisions (review by editor) (10 Jan 2021) by Gordon McFiggans

AR by Roy M. Harrison on behalf of the Authors (20 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (21 Jan 2021) by Gordon McFiggans

AR by Roy M. Harrison on behalf of the Authors (25 Jan 2021) Author's response Manuscript

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Short summary

New particle formation events from 16 sites over Europe have been studied, and the influence of meteorological and atmospheric composition variables has been investigated. Some variables, like solar radiation intensity and temperature, have a positive effect on the occurrence of these events, while others have a negative effect, affecting different aspects such as the rate at which particles are formed or grow. This effect varies depending on the site type and magnitude of these variables.