the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Dec 2024
In-cloud characteristics observed in US Northeast and Midwest non-orographic winter storms with implications for ice particle mass growth and residence time
Abstract. The spatial distribution of surface snowfall accumulation is dependent on the 3D trajectories of ice particles and their residence times through regions of ice mass increases and decreases. We analyze 42 non-orographic, non-lake effect winter storms in the Northeast and Midwest United States from the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) and Profiling of Winter Storms (PLOWS) field campaigns. In situ aircraft measurements (1 Hz, ∼100 m horizontal distance) yield key data on vertical air motions, RHice, and number concentration. When suitable airborne radar data are available, we sort the in situ measurements by distance from cloud radar echo top.
90 % of updrafts (vertical air motion ≥ 0.5 m s−1) were ≤ 1.2 km across. Measurements obtained within 3 km of cloud echo top were twice as likely (14 % versus 7 %) to have vertical velocities capable of lofting precipitation-sized ice compared to points sampled at lower levels. Below the near cloud top generating cell layer, most of the storm volume has RHice ≤ 95 % consistent with sublimation.
Rather than precipitation-ice growth within broad areas of vertical air motions, observations indicate that ice growth in these storms primarily occurs episodically within layers of overturning cloud-top generating cells with scales ≤ a few km. Below the generating cell layer, conditions for ice growth are rarer, and the ice particles usually either persist or shrink during most of their descent. The observed distributions of ambient in-cloud conditions provide benchmarks for evaluations of winter storm model output.
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RC1: 'Comment on egusphere-2024-3808', Anonymous Referee #1, 23 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3808/egusphere-2024-3808-RC1-supplement.pdf
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RC2: 'Comment on egusphere-2024-3808', Anonymous Referee #2, 18 Jan 2025
Review of “In-cloud characteristics observed in US Northeast and Midwest non-orographic winter storms with implications for ice particle mass growth and residence time”, by Allen and coauthors, egusphere-2024-3808
The authors address an important issue of ice particle generation and growth in cloud top generating cells found in winter storms sampled using observations from the IMPACTS and PLOWS field campaigns. The authors show that narrow updrafts of >0.5 m s-1 associated with such generating cells are primarily responsible for ice particle generation, growth, and particle lofting within the cloud top layer while ice growth is likely constant or decreasing beneath in most cases. The authors also do a great job explaining their findings in the context of previous work on these winter storms and how previous understandings were either incorrect or limited. The overall manuscript is very well written with clear findings and well produced figures to support and detail the main findings which make a significant contribution to the scientific knowledge for ice particle formation and growth in such storms. I have only some minor comments for the authors to address:
Line 37: I would add that gravity waves can also yield vertical motions.
Lines 42 – 54: Maybe start with explaining residence time first in this paragraph (after the first sentence) then explain the changes or “microphysical pathway” the hydrometeor undergoes. I think you can fold the paragraph from lines 51-54 into the paragraph above. That way you can remove the “timescale of snow falling to the surface” and just use residence time. Just a suggestion not a must fix.
Line 173: Reword end of sentence. “within these types winter storms available” doesn’t make sense.
Line 174: Just say “warm and/or occluded fronts” and remove “air mass boundaries”.
Line 202: The reference to Fig. 5 makes it appear as if the figures are out of order. It would be good to add that this figure will be discussed later on in the text.
Lines 374 – 379 summarizes the section very well
The discussion section is very well done
Lines 450 – 456: Not a must fix but I’m not sure this information is really needed for this paper.
Lines 463 – 472: Good description of future work possibilities for the IMPACTS data.
Figure 11 caption: should be -22 C not 22
Citation: https://doi.org/10.5194/egusphere-2024-3808-RC2 -
RC3: 'Reply on RC2', Anonymous Referee #2, 18 Jan 2025
The author of this Referee comment would like to reword in the first paragraph of the comment: "while ice growth is likely constant or decreasing beneath in most cases" to "while ice particle size is likely constant or decreasing beneath in most cases".
Citation: https://doi.org/10.5194/egusphere-2024-3808-RC3
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RC3: 'Reply on RC2', Anonymous Referee #2, 18 Jan 2025
Data sets
Data for the figures in "In-cloud characteristics observed in US Northeast and Midwest non-orographic winter storms with implications for ice particle mass growth and residence time" Luke R. Allen, Sandra E. Yuter, Declan M. Crowe, Matthew A. Miller, and K. Lee Thornhill https://doi.org/10.5281/zenodo.14224688
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