In Situ Measurements of Cirrus Clouds on a Global Scale

Round 1

Reviewer 1 Report

review:  In-Situ Measurements of Cirrus Clouds on a Global Scale by Lloyd et al.

 

This paper presents an analysis of 7 years of IAGOS data on cirrus clouds.  It shows that the IAGOS data is consistent with what is known about seasonal cycles in high altitude cloudiness.  There is nothing fundamentally wrong with the paper, but it also doesn't present any new findings.  If it is accepted, the authors should revise based on the comments given below.

line 35:  IAGOS hasn't been around for 25 years...you can instead say:  "Routine measurements from commercial aircraft over the past 25 years have...."

line 36:  change "into a multitude" to "on a multitude"

line 41/42:  rewrite as  "This paper describes long term in situ observations of cirrus cloud macro-physical properties, location and frequency for the time period 2011-2018.

line 43:  change to "Cirrus is a broad term to describe high altitude ice clouds..."

Line 87:  change " We present 79 months of in-situ cloud measurements from the IAGOS fleet of commercial Airbus aircraft on a global scale before focusing on identifiable seasonal trends in different regions." to "We present a global analysis of 79 months of in-situ cloud measurements from the IAGOS fleet of commercial Airbus aircraft and then focus on identifiable seasonal trends in different regions."

Line 96/97 says " A fleet of 10 aircraft and 6 international airlines (Air France, Cathay Pacific, China Airlines, Hawaiian Airlines, Iberia and Lufthansa) made more than 8 years of flights."  Is the program ongoing, or did it end after 8 years?

line 109-111:  remove the "possibly" before generated...you've already deal with the uncertainty regarding the process by saying "possible artefacts".

line 115, "opearational" is spelled incorrectly.

line 137:  change to "by the BCP"  to "sampled by the BCP"

Line 140:  add a comma after "In contrast"

Line 145:  I don't understand how the sampling error folds into the low concentration threshold.

Line 149;  this first sentence is redundant (basically said in line 137.)  It could be deleted.  You could then change the second sentence in the paragraph to " Based on information about seasonality in different areas of the globe we selected the 6 regions identified in the map shows in Figure 4 for further analysis.

general comment:  I would change the term "seasonal trends" to "seasonal variations" or "seasonal cycle". Trends more implies changes over a long period of time.

line 180, The should not be capitalized.  Also, what do you mean by "strong signal".  I think you should just say "maximum" or "largest occurrence".

line 211:  instead of saying "increasing cloud fractions"  I think you should say "maximum cloud fraction" because none of the plots in the NH show an increase between SON and DJF

line 214:  the paper states " The driving force for these changes is the strengthening of the polar vortex during the Northern Hemisphere winter and the storm tracks that this produces across the North Atlantic."  Nowhere in the paper does it describe this process.  If it were true, wouldn't the maximum cloud fraction occur when the polar vortex has maximum strength?  Perhaps instead you should consider that the cloud fraction is directly related to proximity of the jet stream, rather than strength.

line 217:  this say there is a " there was also a trend to increasing cloud fractions during the summer period."  This isn't a trend, you just have max cloud fraction in summer in places where you have thunderstorms.

line 250:  it should be "drivers of cloudiness are"

 

Author Response

We thank the referee for their comments. Please find out responses attached.

Author Response File: Author Response.docx

Reviewer 2 Report

Please see attached file.

Comments for author File: Comments.pdf

Author Response

We thank the referee for their comments. Please find our responses attached.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I appreciate that the authors have made efforts to put their results in contrast with previous studies of clouds using IAGOS data, and that they propose explanations of why their numbers differ a lot from such studies.

However, I think that to be accepted for publication, the paper should do one of two things:

1. apply the same method as the previous articles using IAGOS data (Petzold et al. 2017) on the data presented here, so the numbers in the present paper can be compared with previous results and their quality validated, or

2. explicitly mention in the abstract and the conclusion that additional work is required to reconcile the numbers that are presented in the present paper with previous literature 

Author Response

Thank you for reviewing the updated manuscript with suggestions of how to proceed. At this time we have chosen to make it clear in both the abstract and conclusions that further work is needed to compare our results with previous studies.