the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
High ice-nucleating particle concentrations associated with Arctic haze in springtime cold-air outbreaks
Abstract. The global variation of ice-nucleating particle (INP) concentrations is an important modulator of the cloud-phase feedback, where the albedo of mixed-phase clouds increases in a warming climate. Shallow clouds such as those observed in cold-air outbreaks (CAOs) are particularly important for cloud-phase feedbacks and highly sensitive to INPs. To investigate the sources and concentrations of INPs in CAOs, we made airborne measurements over the Norwegian and Barents seas as part of the March 2022 Arctic Cold-Air Outbreak (ACAO) field campaign. Aerosol samples were collected on filters at locations above, below and upwind of CAO cloud decks. Throughout the campaign, INP concentrations were comparable to the highest previously observed in the Arctic. Scanning electron microscopy analysis of samples taken upwind of cloud decks showed that super-micron aerosol was dominated by mineral dusts. Analysis of aerosol particle size measurements to obtain an INP active site density suggested sea spray was unlikely to be the dominant INP type. These site densities were also too great for mineral components alone to be the dominant INP type above -20 °C. Accordingly, it is likely that the dominant INP type was mineral dust mixed with other ice nucleating materials, possibly of biogenic origin. Back-trajectory analysis and meteorological conditions suggested a lack of local INP sources. We therefore hypothesise that the high INP concentration is most likely to be associated with aged aerosol in Arctic haze that has undergone long-range transport from lower latitude regions.
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Status: open (until 28 Jul 2024)
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RC1: 'Comment on egusphere-2024-1502', Armin Sorooshian, 07 Jun 2024
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Review of “High ice-nucleating particle concentrations associated with Arctic haze in springtime cold-air outbreaks” by Raif et al.
This study focuses on sources and concentrations of ice nucleating particles (INPs) in cold air outbreaks using airborne measurements during the March 2022 Arctic Cold-Air Outbreak (ACAO) field campaign over the Norwegian and Barents seas. Methods involved filter measurements upwind, below, and above cloud decks. This topic is critically important as shallow cumulus clouds are not well understood and understanding the nature and behavior of INPs is needed – there are scarce reports of these types of data the authors report. A key finding is that air upwind of the CAO cloud decks had supermicron particles comprised predominantly of mineral dust. In contrast, sea salt was not found to be as important. One key conclusion is that likely mineral dust was mixed with other ice nucleating materials that may have had biogenic sources. Sources of the INPs are thought to not be local but rather transported from lower latitude regions and associated with aged Arctic haze aerosol.
Major Comments:
A strength of this work is the dataset that adds to a growing archive of data needed to better understand INPs around the Arctic region. With so many campaigns being conducted around that vicinity, this work will get good attention in my view. The paper and methodology are generally well constructed. There are some typos/errors in the writing which I point to a few of below. I recommend publication and only have a few minor comments below for the authors to address.
Specific Comments:
Line 17: a bit weird that the “b” version of the Fletcher paper shows up first before the “a” version. This may just be a citation manager software type of detail and not a big deal but it caught my eye.
Line 58: “th” should be “the”
Line 61: the part starting with “understanding” should likely start as a new sentence.
Introduction: generally well written
Line 85: “subsequent” may work better than “later” here in the sentence. Not a big deal to change.
Line 92: would sound better to say “..each inlet so that different..”
Line 111: Can the aircraft really sample on a filter as low as 10 m? Seems highly unlikely for safety reasons so clarify better here what you mean about this lower bound of the altitude range.
Line 164: “Portions of filters…” might work better here
Line 196: “CDP data have”
Line 253: “plumes” spelled wrong
Line 277: “CDP data were…”
Line 283: “were approximately constant at..”
Line 297: “, .” needs to be fixed
Line 390: It’d be good to report which meteorological dataset was used in the HYSPLIT software to obtain trajectories and what the native spatial resolution is of that dataset. This can be helpful to others interested in doing similar analyses.
Line 489: “…measurements during specific meteorological..” may work better here
Line 503: “…campaign raise…”
Line 517: what are examples of these regions you are encouraging more work to be done for? Would be nice to share explicitly a few example.
Figure 1 = very nicely done!
Line 522: “Flight data from the …., are stored…”
Line 523: “…data….are stored…”
Table 2: I would suggest the authors define the four column headers on the far right of table in the caption.
Table A1: Suggest the authors define some of the column headers in the caption like a, b, vINP.
Throughout paper, it seems that the flight numbers are written in a different font which should be fixed.
Citation: https://doi.org/10.5194/egusphere-2024-1502-RC1
Data sets
ACAO INP Data and Metadata Erin Raif, Steven Abel, and Martin Daily https://doi.org/10.5281/zenodo.11221599
erin-raif/acao_inp_arctic_haze Erin Raif https://doi.org/10.5281/zenodo.11221399
ACAO Aircraft Data, flights c271-c279 Facility for Airborne and Atmospheric Measurements https://catalogue.ceda.ac.uk/uuid/01021a90c0c2481c909bdb145cb72398
ACAO Aircraft Data, flights c280-c282 Facility for Airborne and Atmospheric Measurements https://catalogue.ceda.ac.uk/uuid/6d7971a92d154bb29af3167dfb6f5a7e
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