the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Measurement report: High Arctic aerosol hygroscopicity at sub- and supersaturated conditions during spring and summer
- 1Department of Environmental Science, iClimate, Aarhus University, 4000 Roskilde, Denmark
- 2ROCKWOOL Group, 2640 Hedehusene, Denmark
- 3Extreme Environments Research Laboratory, École Polytechnique Fédérale de Lausanne, 1951 Sion, Switzerland
- 1Department of Environmental Science, iClimate, Aarhus University, 4000 Roskilde, Denmark
- 2ROCKWOOL Group, 2640 Hedehusene, Denmark
- 3Extreme Environments Research Laboratory, École Polytechnique Fédérale de Lausanne, 1951 Sion, Switzerland
Abstract. Aerosol hygroscopic growth and cloud droplet formation influence the radiation transfer budget of the atmosphere and thereby the climate. In the Arctic, these aerosol properties may have a more pronounced effect on the climate compared to the mid-latitudes. Hygroscopic growth and cloud condensation nuclei (CCN) concentrations of High Arctic aerosols were measured during two field studies in the spring and summer of 2016. The study site was the Villum Research Station (Villum) at Station Nord in the northeastern region of Greenland. Aerosol hygroscopic growth was measured with a hygroscopic tandem differential mobility analyzer (HTDMA) over a total of 23 days, and CCN concentrations were measured over a period of 95 days. Continuous particle number size distributions were recorded, facilitating calculations of aerosol CCN activation diameters and aerosol kappa (κ)-values. In spring, average CCN concentrations, at supersaturations (SS) of 0.1 to 0.3 %, ranged from 53.7 to 85.3 cm-3, with critical activation diameters ranging from 130.2 to 80.2 nm, and κCCN ranging from 0.28–0.35. In summer, average CCN concentrations were 20.8 to 47.6 cm-3, while critical activation diameters and κCCN were from 137.1 to 76.7 nm and 0.23–0.35, respectively. Mean particle hygroscopic growth factors ranged from 1.60 to 1.75 at 90 % relative humidity in spring, while values between 1.47 and 1.67 were observed in summer depending on initial dry size. Although the summer aerosol number size distributions were characterized by frequent new particle formation events, the CCN population at cloud-relevant supersaturations was determined by accumulation mode aerosols. This emphasizes the importance of accumulation mode aerosol sources to provide available CCN during summer. The influence of particle hygroscopic growth on the radiative transfer through aerosol-radiation interactions could be of major importance. The results of this study are directly applicable in the modeling of direct and indirect climate effects of Arctic aerosols. Targeted chemical and morphological analysis, based on filter samples or on-line techniques, could further clarify the role of primary organic marine influence on Arctic aerosol CCN concentrations and therewith climate effects.
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Andreas Massling et al.
Status: open (until 15 Aug 2022)
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RC1: 'Referee Comment on acp-2022-413', Anonymous Referee #1, 04 Aug 2022
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Results of aerosol hygroscopicity measurements from a CCNC and an HTDMA are presented for spring and summer periods in 2016 at the VIllum monitoring station in Greenland. These types of measurements are rare in the Arctic so the paper is a significant contribution to what is known about Arctic aerosol hygroscopicity. The research methods and analysis are thorough and the paper is well written. I only have the few comments listed below.
Figure 3. Were there no UVA measurements available between August 25 and September 29 or was there no measurable UVA?
Section 3.2 and Figure 4: The sampling periods are not the same in the text and the figure. For example, the text says 20 April – 10 May and the figure says 20 April – 8 May.
Line 441: Providing a theoretical value for ammonium bisulfate would be helpful.
Lines 552 – 566: This discussion is a little confusing. It is likely true that “the organic
mass fraction must be assumed to contribute significantly to the hygroscopicity of the observed aerosol at Villum”. However, the measurement techniques used focus on the particle size range where mass is negligible and number concentrations are highest. A more in-depth description of this discrepancy would be helpful along with more details on what is known about the size dependence of the organics in the Arctic. Nielsen et al. measured organics in PM1. Can more information be provided about how that organic mass is distributed across the PM1 size range? Perhaps from the Croft et al. results?
Line 589: “likely caused by the more numerous and diverse active aerosol sources during the summer measurement period”. Perhaps this should be local aerosol sources? Spring aerosol sources can be quite diverse given the long range transport that occurs during that time of year.
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RC2: 'Comment on acp-2022-413', Anonymous Referee #2, 12 Aug 2022
reply
Massling et al. present in their manuscript observational results of aerosol hygroscopicity and aerosol cloud activation from two field campaigns carried out in spring and summer 2016 at Villum Research Station in Northern Greenland. These are valuable observations from a part of the world where observations are generally scarce but are needed to better understand aerosol-cloud and aerosol-radiation effects on Arctic climate. As such, it is important that this data and findings will be published and be accessible to the scientific community.
The paper is well written, although sometimes very lengthy and the authors are encouraged to shorten and constrain their manuscript where possible. A few but important technical details are missing and need to be added to the revised version. In addition, further clarifications (described in detail below) should be made before the manuscript can be accepted for final publication.
Detailed comments (in chronological order):
- Abstract: The last three sentences are very general statements and partially more like an outlook. Suggest to delete them.
- Introduction (2nd paragraph): The authors might not be aware of it, but the effect of water-uptake on particle light scattering has been actually directly measured/studied in the Arctic by Zieger et al. (2010). The scattering enhancement is indeed significantly larger compared to other continental or maritime sites (see e.g. Burgos et al, 2019) due to the special interplay between size and hygroscopicity in the Arctic (Zieger et al., 2010).
- Introduction (3rd paragraph): The regional characteristics of the Arctic (and the corresponding aerosol properties) are actually quite diverse (see e.g. discussion in Schmale at e., 2021). Certain parts of the Arctic such as the Siberian Arctic are exposed to high levels of anthropogenic/industrial activities, while the high/central Arctic e.g. shows often different seasonality in aerosols properties than the lower Arctic. This is also important for the different drivers of new particle formation (which will be addressed later in the manuscript) as e.g. discussed in detail by Schmale and Baccarini (2021). I therefore recommend that the authors should more carefully define what they actually mean with “the Arctic” for their study and also mention the regional diversity.
- Introduction (4th paragraph): The work by Jung et al. (2018), which is cited later in the manuscript, should be mentioned here as well, since it represents a long-term study of CCNC measurements in the Arctic with the same instrumentation used here.
- One important missing part are the details on the particle sampling. Please add a of the actual set-up sketch to the revised version. Please also add information of the used tubing (type, inner diameter, length, etc.), the inlet type (with or w/o size cut? height above ground, manufacturer, etc.). Where were the meteorological parameters measured (e.g. is the temperature shown in Fig 2 and 3 measured directly at the inlet)?
- Concerning the SMPS: Was a pre-impactor used? Was the SMPS data corrected for losses? If yes, how and which assumption about the particle density was used? Were the size distributions validated to a total CPC?
- Concerning the HTDMA: It is important to also state information of the RH of the dry DMA / selected diameter (please also add this data column to the data).
- Line 208: As already mentioned above: Have you compared or used the total CPC to better judge which instrument was mal-functioning?
- Line 232: Is the RH accuracy given in absolute or relative terms?
- Section 3.2: For a better interpretation of the size distribution data, the authors could consider to present the particle size distributions as a contour plot (e.g. hourly and normalized; it could maybe be integrated within Figure 5 and 6). This would be more consistent with the other time series and could maybe help to facilitate the interpretation of the individual features seen in Fig. 5 and 6.
- I am still surprised about the extremely low uncertainties that were retrieved for the CCN concentrations in Table 1 and 2 from the curve fitting. Are they really meaningful?
- Trajectory analysis: The authors mention that they have performed a trajectory analysis (e.g. pager 15, 3rd paragraph and in Sect. 4), but the results are not shown. It would indeed strengthen some on the statements and claims made later on, if this analysis would be added to the revised manuscript. Even simply calculating the time over ice, ocean and land would maybe give some more insights to the respective aerosol sources.
- What is the reasoning of the HTDMA to measure the growth factors at two RH close-by at 85% and 90%? Would it maybe be easier for the interpretation of the results to convert (with kappa-Köhler) all GF-values to 90%? It is not 100% clear to me on what is gained by showing both timeseries of GF at 85% and 90% in Figures 7 and 8.
- Lines 506-509: There are some recent findings that Aitken-mode particles could also be of primary origin (e.g. Xu et al., 2022 or Lawler et al., 2021), it might not be only secondary particle formation.
- Page 23, 3rd paragraph: The authors could also reference and mention the work by Mauritsen et al. (2011) about the tenuous cloud regime in the Arctic and the susceptibility of Arctic clouds to changes in CCN concentration.
- Conclusions: As mentioned above, the results of the trajectory analysis are not really shown. Suggest to remove this part or add the results to the revised manuscript or SI.
- Figure 5 and 6: Are the total particle concentrations measured by a CPC or derived from integrating the SMPS size distributions?
- Data availability: It is great that the authors have already provided their data. I would recommend to also include the RH-data for the HTDMA (e.g. for the dry diameter, ambient, and measured at the inlet). It would also be good to clarify in the read-me if any of the data was corrected to STP (or not).
- SI (page 1): Add “the” before the “CCN counter”. Is the shown calibration a composite of all the four performed CCNC calibrations?
Minor comments:
- Line 23: Add “the” before “initial”
- Line 565: take -> taking; remove one of the “only”s
- Line 605: Add “%” behind 0.63
- Line 397: Suggest to remove the “substantial” or clarify what you mean with this.
References:
Burgos, M., Andrews, E., Titos, G., Alados-Arboledas, L., Baltensperger, U., Day, D., Jefferson, A., Kalivitis, N., Mihalopoulos, N., Sherman, J., Sun, J., Weingartner, E., and Zieger, P.: A global view on the effect of water uptake on aerosol particle light scattering, Scientific Data, 6, 157, https://doi.org/10.1038/s41597-019-0158-7, 2019.
Jung, C. H., Yoon, Y. J., Kang, H. J., Gim, Y., Lee, B. Y., Ström, J., Krejci, R., Tunved, P.: The seasonal characteristics of cloud condensation nuclei (CCN) in the arctic lower troposphere, Tellus B: Chemical and Physical Meteorology,70, 1-13, https://doi.org/10.1080/16000889.2018.1513291, 2018.
Lawler, M. J., Saltzman, E. S., Karlsson, L., Zieger, P., Salter, M., Baccarini, A., et al. (2021). New insights into the composition and origins of ultrafine aerosol in the summertime high Arctic. Geophysical Research Letters, 48(21), 1–11. https://doi.org/10.1029/2021GL094395
Mauritsen, T., Sedlar, J., Tjernström, M., Leck, C., Martin, M., Shupe, M., et al. (2011). An Arctic CCN-limited cloud-aerosol regime. Atmos-pheric Chemistry and Physics, 11(1), 165–173. https://doi.org/10.5194/acp-11-165-2011
Schmale, J., Zieger, P., & Ekman, A. M. L. (2021). Aerosols in current and future Arctic climate. Nature Climate Change, 11(2), 95–105. https://doi.org/10.1038/s41558-020-00969-5
Schmale, J., & Baccarini, A. (2021). Progress in unraveling atmospheric new particle formation and growth across the Arctic. Geophysical Research Letters, 48, e2021GL094198. https://doi.org/10.1029/2021GL094198
Xu, W., Ovadnevaite, J., Fossum, K.N. et al. Sea spray as an obscured source for marine cloud nuclei. Nat. Geosci. 15, 282–286 (2022). https://doi.org/10.1038/s41561-022-00917-2
Zieger, P., Fierz-Schmidhauser, R., Gysel, M., Ström, J., Henne, S., Yttri, K. E., Baltensperger, U., and Weingartner, E.: Effects of relative humidity on aerosol light scattering in the Arctic, Atmos. Chem. Phys., 10, 3875–3890, https://doi.org/10.5194/acp-10-3875-2010, 2010.
Andreas Massling et al.
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Datasets for 'High Arctic aerosol hygroscopicity at sub- and supersaturated conditions during spring and summer' Pernov, Jakob; Lange, Robert; Massling, Andreas https://doi.org/10.5281/zenodo.6787654
Andreas Massling et al.
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