The microphysics of clouds over the Antarctic Peninsula &ndash; Part 1: Observations

Lachlan-Cope, Tom; Listowski, Constantino; O'Shea, Sebastian

doi:https://doi.org/10.5194/acp-16-15605-2016

Articles | Volume 16, issue 24

https://doi.org/10.5194/acp-16-15605-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-16-15605-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 16, issue 24

Research article

|

19 Dec 2016

Research article |

| 19 Dec 2016

The microphysics of clouds over the Antarctic Peninsula – Part 1: Observations

Tom Lachlan-Cope, Constantino Listowski, and Sebastian O'Shea

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Final revised paper (published on 19 Dec 2016)
Preprint (discussion started on 27 May 2016)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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SC1: 'Comments on "The Microphysics of Clouds over the Antarctic Peninsula - Part 1: observations"', Amélie Kirchgaessner, 01 Jun 2016
- AC1: 'Reply to comment by Amélie Kirchgaessner', Tom Lachlan-Cope, 08 Sep 2016
RC1: 'Reviewer Comment on acp-2016-331', Anonymous Referee #1, 25 Jun 2016
RC2: 'Referree #2 comments', Anonymous Referee #2, 02 Jul 2016

Peer-review completion

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

AR by Tom Lachlan-Cope on behalf of the Authors (08 Sep 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (21 Sep 2016) by Martina Krämer

RR by Anonymous Referee #1 (21 Sep 2016)

RR by Anonymous Referee #2 (02 Oct 2016)

Suggestions for revision or reasons for rejection

Reviewer comments regarding previous major comments and authors' responses.

2) Regarding Averaging. I think the source of confusion is Page 4, lines 24-27 through Page 5 lines 1-2. This paragraph is confusing and does not cover all kinds of data shown here. It seems to me there are 5 ways the data are shown (1) All data for all flights, as in Fig. 14. (2) Averages over each flight in longitudinal bins, shown as points in Fig. 4. (3) Averages of the flight averages in the bins, shown as lines in Fig. 4. (4) Averages of (1) over the entire East and the entire West for each year and (5) averages of vertical profiles for all flights for each year and side of the Peninsula, as in Fig. 13. I think they are each handled better as they come up, so I recommend omitting this entire paragraph except the sentence about in-cloud periods. The last two sentences could be moved into the first paragraph of Section 3.1.

Also …

Page 5, lines 25 and 26, change “at each longitude” to “in each longitude bin.”

Page 5, line 27-28, change “bins on each side” to “bins, one on each side” and change “one from one from 67 to 74 ̊W and the other from…” to just “from 67 to 74 ̊W and from …”

Regarding the authors’ response: “Each flight did not go to every longitude bin and even when it a flight visited a longitude bin it did not necessarily enter a cloud. For example for the bin nearest Rothera the temperature and humidity show a large number of points as most flights will have data in this bin while for the cloud parameter graphs there are less points as it was normal to avoid clouds while taking off and landing and flying close to the mountains.”

Why not include this information in the paper?

Minor comments:

1) More detailed descriptions of the CIP and CAPs have been added, but the manuscript seems to go back and forth between them. I suggest reorganizing/rewriting the section on Page 3 Lines 11- 25 as follows. In addition, please rephrase, “although the hotwire sensor tends to under-read at high values of LWC” to indicate the implications. For example: “Part of this discrepancy is attributed to the hotwire sensor’s tendency to under-read at high values of LWC.”

The CAPS instrument contains three discrete instruments: The Cloud and Aerosol Spectrometer (CAS), the Cloud Imaging Probe (CIP), and the hotwire Liquid Water Content (LWC) sensor. Data from the hotwire LWC sensor was only used in this study to help validate the CAS data. The CAS and CIP are described in turn below.

The CAS measures the diameter of particles between 0.5 and 50 μm at a frequency of one Herz. While the CAS used in this campaign did not have a full anti-shatter inlet, modifications were made to reduce the effect of shattering on the inlet by removing the shroud that was originally fitted to the inlet. A previous study (Grosvenor et al., 2012), using a small subset of this data, reported errors with the data from the CAS instrument. In particular, it appeared to be over-counting when integrated water content from the CAS was compared with measurements from the hotwire LWC sensor. After investigation, this was found to be due to air accelerating in the tube of the CAS instrument. Studies in the Cambridge University Markham wind tunnel using a fine pitot tube to measure the speed within the tube showed an increase corresponding to an increase in the count of 1.47; this has been accounted for in this latest study. When this correction is applied the LWC calculated by integrating the CAS data for most flights agrees to within 15% with the hotwire sensor – although the hotwire sensor tends to under-read at high values of LWC.

The CIP images particles between a diameter of 25μm and 1.5mm, at a pixel resolution of 25 μm. While it had not at the time of this campaign been fitted with anti-shatter tips, a study of the particle inter-arrival times indicated very few shattered particles; these were removed by eliminating particles that arrived within 1 μs.

The CIP instrument produces shadow images …

2) There are still some small grammatical mistakes, but hopefully most can be fixed by the editors. A few suggestions for grammar/clarity are described here.

Page 2, line 29: Reads, “flights were made to study a variety of meteorological phenomena including boundary layer … and cloud studies.” Change “cloud studies” to “cloud microphysical properties”

Page 3 line 6: add an apostrophe in “Survey” to make it “Survey’s”

Page 3 lines 9-10. Remove the sentence, “The CAPS probe … to 1.5 mm.” since it is redundant with what follows.

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ED: Reconsider after minor revisions (Editor review) (11 Oct 2016) by Martina Krämer

AR by Tom Lachlan-Cope on behalf of the Authors (20 Oct 2016) Author's response

ED: Publish as is (25 Oct 2016) by Martina Krämer

Short summary

The paper presents observations of clouds over the Antarctic Peninsula (a 2500 m high barrier separating the Weddell and Bellingshausen seas) during summer 2010 and 2011. The observations of ice and liquid particles in the clouds reveal that more particles were seen during 2011 and that this is associated with an air mass that has spent longer close to the sea ice surface. This suggests that sea ice is a source of cloud nuclei.