the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Jan 2025
Multi-seasonal measurements of the ground-level atmospheric ice-nucleating particle abundance on the North Slope of Alaska
Abstract. Atmospheric ice-nucleating particles (INPs) are an important subset of aerosol particles that are responsible for the heterogeneous formation of ice crystals. INPs modulate arctic cloud phase (liquid vs. ice), resulting in implications for radiative feedbacks. The number of arctic INP studies investigating specific INP episodes or sources has recently increased. However, existing studies are based on short-duration field data and long-term datasets are lacking. Continuous, long-term measurements are key to determining the abundance and variability of ambient arctic INPs and for constraining aerosol-cloud interactions, for example, to verify and/or improve simulations of mixed-phase clouds. Here, we present the first long-duration INP dataset from the Arctic: two years of immersion mode INP concentrations (nINP) measured continuously at the National Oceanic and Atmospheric Administration's Barrow Atmospheric Baseline Observatory on the North Slope of Alaska. A portable ice nucleation experiment chamber (PINE-03), which simulates adiabatic expansion cooling, was used to directly measure the ground-level INP abundance with an approximately 12-minute time resolution from October 2021 to December 2023. We document PINE-03 nINP measurements over a wide range of heterogeneous freezing temperatures from −16 to −31 °C from which we introduce new season-specific parameterizations suitable for modeling mixed-phase clouds. Collocated aerosol and meteorological data were analyzed to assess the correlation between ambient nINP, air mass origin region, and meteorological variability. Our findings suggest (1) very high freezing efficiency of INPs across the measured temperatures (≈ 2 x 108 – 1010 m−2 for from −16 to −31 °C), which is a factor of 10 − 1000 times greater efficiency as compared to that found in the previous mid-latitude INP measurements in autumn using the same instrument; (2) surprisingly high nINP for the examined temperatures throughout the year that were not measured by PINE-03 at other sites; and (3) high nINP in spring, possibly related to arctic haze episodes.
- Preprint
(2819 KB) - Metadata XML
-
Supplement
(4583 KB) - BibTeX
- EndNote
Status: open (until 07 Mar 2025)
-
RC1: 'Comment on ar-2025-1', Anonymous Referee #1, 22 Feb 2025
reply
Overall Evaluation:
I have reviewed the manuscript "Multi-seasonal measurements of the ground-level atmospheric ice-nucleating particle abundance on the North Slope of Alaska". This manuscript presents a comprehensive analysis of atmospheric ice-nucleating particles (INPs) based on long-term ground-based measurements in the Alaskan Arctic. The study is significant as it provides one of the first multi-seasonal datasets of INP abundance in this region. The authors utilize a portable ice nucleation experiment chamber (PINE-03) to collect high-resolution data over a two-year period, and analyze aerosol and meteorological data to assess the correlation between ambient nINP, air mass origin region, and meteorological variability. The manuscript is well-written, with clear language and logical organization. The introduction effectively sets up the research question, and the conclusion summarizes key findings concisely. While the study is well-structured and the results are relevant to the field of aerosol-cloud interactions, several aspects require further clarification and improvement. I believe that the conclusions of the manuscript are likely valid, and the manuscript is publishable subject to minor revisions. I have some specific concerns, listed below.Specific comments:
- The manuscript presents substantial new data on Arctic INPs, which fills a critical gap in long-term observations, especially using high resolution instruments. However, while the manuscript provides a novel dataset, the interpretation of the sources of INPs could be strengthened. The manuscript concludes high INP concentration in spring possibly related to arctic haze. It could be improved by incorporating a arctic haze event with high resolution INP measurement and aerosol , meteorological data.
- Line 110-112. In the first paragraph, I recommend providing additional details about the INP dataset, particularly addressing the significant data gaps observed during certain months, as mentioned in lines 386–387. This would help clarify the dataset's continuity and any potential implications for the study's conclusions.
- Line 134. In addition to discussing the time resolution, it would be beneficial to include information about the size range of aerosols that PINE-03 measures. This would provide a more comprehensive understanding of the instrument’s capabilities and its relevance to INP measurements.
- Line 275-285. As described in the manuscript and shown in Figure 1, the winter temperature in the study region is consistently below -20°C, with a recorded minimum of -37.2°C. Additionally, the relative humidity ranges from 60% to 80%, indicating that the dew point temperature is even lower. Given these conditions, I have concerns regarding the measurement of INPs that are activated at relatively higher temperatures (-16°C to -31°C). Could the authors clarify how the PINE-03 system measures INP activation at these temperatures under such ambient conditions? Specifically, can PINE-03 create chamber conditions where the INP. activation temperature is higher than the ambient air temperature? Further explanation of this aspect would enhance the understanding of the instrument’s capabilities and potential limitations.
- Line 286. What is the significance of averaging visibility in this context? For example, the average of a 10 km visibility and a 100 m visibility would be around 5 km, but this may not accurately reflect the actual atmospheric conditions. For INP analysis, it may be more relevant to focus on the statistics of low-visibility events, as these could be associated with fog, blowing snow, or dust events. Could the authors provide further clarification on this aspect?
- Figure 1. In Figure 1, are the wind direction and wind speed also averaged over six hours? Since wind direction and wind speed are vector quantities, they may not be directly suitable for simple averaging. Could the authors clarify how these values were processed?
- The x-axis in Figure 4 is too dense; I suggest adjusting it for better readability. Additionally, I recommend removing the black error bars, as they affect the visual aesthetics of the figure without significantly enhancing the clarity of the authors' intended message.
- Line 475-484. I suggest moving the explanation of the instrument's resolution to Section 2B, which discusses INP measurement data. Additionally, all data presented in the figures should be carefully selected and evaluated to support the study’s conclusions.
- Line 487. Regarding the comparison of Ns with previous studies, could the observed differences be attributed to variations in the calculation methods used for Ns? Additionally, are the surface area results obtained using the method in this study consistent with those measured by aerosol spectrometers (APS and SMPS)? Could the authors provide further clarification on this matter?
Citation: https://doi.org/10.5194/ar-2025-1-RC1 -
RC2: 'Comment on ar-2025-1', Anonymous Referee #2, 28 Feb 2025
reply
This study presents a long-term dataset of ice-nucleating particle (INP) concentrations in the Arctic, addressing a gap in understanding INP variability and their role in mixed-phase cloud processes. The use of continuous, high time-resolution measurements over two years at the Barrow Atmospheric Baseline Observatory provides valuable insights into seasonal INP dynamics and their potential drivers, such as Arctic haze and air mass origins. The development of season-specific INP parameterizations is a significant contribution to improving cloud microphysics models. However, the study would benefit from a deeper mechanistic explanation for the observed INP enhancements and their broader climatic implications.
Major comments:
1. At the current form, this paper is more like a measurement report rather than a scientific paper. A deeper exploration of mechanistic explanations for the seasonal INP variations is needed. I suggest the author to incorporate aerosol chemical composition data (e.g., organic markers, dust tracers) to clarify source contributions.
2. The comparison to results from mid-latitude studies and previous studies in the Arctic should contextualize environmental differences (e.g., seasonal biomass burning, anthropogenic emissions) that may explain efficiency disparities and seasonal INP variations.
3. The association of springtime nINP peaks with Arctic haze is plausible but not conclusively demonstrated. Backward trajectory analysis and correlations with aerosol chemistry during spring haze episodes should be conducted to confirm links to anthropogenic or Eurasian aerosol sources, as seen in prior Arctic aerosol studies. Whether the haze-INP relationship aligns with known INP properties of pollution aerosols (e.g., soot) or if other factors (e.g., aging processes) enhance INP activity should be discussed.
4. The authors mentioned they introduced new season-specific parameterizations suitable for modeling mixed-phase clouds. But I only see one ns(T) parameterization as a function of freezing temperatures rather than season-specific parameterizations. In addition, the parameterization is recommended to be tested in a cloud-resolving model, to assess their impact on simulated cloud phase and radiative properties. Whether this parameterization can apply only to ground-level INPs or if vertical INP gradients (unmeasured here) might affect their utility in modeling cloud processes should be verified.
Specific comments:
1. Abstract, Line 20, “Here, we present the first long-duration INP dataset from the Arctic”. Line 99, “This study represents one of the first efforts to elucidate seasonality in the abundance of immersion mode active INPs”. Such a description of “the first” is meaningless. Previous studies also reported year-round INP dataset from the Arctic, although based on offline measurements. For instance,
Pereira Freitas, G., Adachi, K., Conen, F., Heslin-Rees, D., Krejci, R., Tobo, Y., Yttri, K. E., and Zieger, P.: Regionally sourced bioaerosols drive high-temperature ice nucleating particles in the Arctic, Nat. Commun., 14, 10.1038/s41467-023-41696-7, 2023.
Wex, H., Huang, L., Zhang, W., Hung, H., Traversi, R., Becagli, S., Sheesley, R. J., Moffett, C. E., Barrett, T. E., Bossi, R., Skov, H., Hünerbein, A., Lubitz, J., Löffler, M., Linke, O., Hartmann, M., Herenz, P., and Stratmann, F.: Annual variability of ice-nucleating particle concentrations at different Arctic locations, Atmos. Chem. Phys., 19, 5293–5311, https://doi.org/10.5194/acp-19-5293-2019, 2019.
Creamean, J. M., Barry, K., Hill, T. C. J., Hume, C., DeMott, P. J., Shupe, M. D., Dahlke, S., Willmes, S., Schmale, J., Beck, I., Hoppe, C. J. M., Fong, A., Chamberlain, E., Bowman, J., Scharien, R., and Persson, O.: Annual cycle observations of aerosols capable of ice formation in central Arctic clouds, Nat. Commun., 13, 3537, 10.1038/s41467-022-31182-x, 2022.
2. Abstract, Line 24, which modes of ice nucleation can the ice nucleation experiment chamber (PINE-03) measure?
3. Abstract, Line 29, “(≈ 2 x 108 – 1010 m−2 for from −16 to −31 °C)”, What parameters are this data? Active site density ns ? It seems inconsistent with the main text results. What are the possible reasons?
4. Abstract, Line 33, “surprisingly high nINP for the examined temperatures throughout the year that were not measured by PINE-03 at other sites”, What are the concentration ranges for Arctic and other sites, respectively?
5. Abstract, Line 29-34, what are the possible reasons or implications for the findings (1) and (2)? These are the description of data, but not suggestions or implications.
6. Line 104, what does “natural aerosols” here mean? Sea spray aerosols? Biogenic aerosols?
7. Line 124, “40 feet” is unnecessary here.
8. Line 141-150, these descriptions are unnecessary in this scientific paper. The contents should be shortened or deleted. The section of “INP CONCENTRATION MEASUREMENT” covers about two pages. The vey detailed information of the instrument can be shortened and referred to previous works.
9. Line 190-201, How far is it between the two sites? What are the size ranges (upper limits) of measured particles for the two CPCs? The authors described a lot about the comparison between the results from the two CPCs. However, in the end, you only used the one at the Barrow site. Such an observation design and the descriptions make the readers confusing.
10. Section 5. AEROSOL DATA FLAGGING, why did you conduct this flagging. What does “contaminated” mean? More polluted air?
11. Figures 1, 3, 4, and 5: the readability of the figures is not good. The panels are too narrow, the slash lines are unclear, and the datapoints and legends are so crowded. Especially for Figures 4 and 5, the panels should be rearranged. Readers are difficult to get the information you want to transfer through these figures.
12. Line 389, “clean nINP(T) data”, ambiguous phrase
13. Line 398, IAF, are the size ranges of nINP(T), near the same?
14. Line 554-566, the descriptions are confusing. A much clearer description or figure illustration is required.
15. Section 4 is missing. Section 5 Conclusions is too long. The conclusion section should be concise. The discussion should be a separate section or in the section of Results and discussion.
Citation: https://doi.org/10.5194/ar-2025-1-RC2
Supplement
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 112 | 25 | 5 | 142 | 17 | 5 | 6 |
- HTML: 112
- PDF: 25
- XML: 5
- Total: 142
- Supplement: 17
- BibTeX: 5
- EndNote: 6
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1