Impact of Lock-In Time Constant on Remote Monitoring of Trace Gas in the Atmospheric Column Using Laser Heterodyne Radiometer (LHR)

Round 1

Reviewer 1 Report

Review of the paper "Impact of lock-in time constant on remote monitoring of trace gas in the atmospheric column using laser heterodyne radiometer (LHR)", by Fengjiao Shen et al.

This paper describes the problems that can be encoutered when using a lock-in amplifier with a wrongly setted integration time, with respect to scan time.

In my activity I saw some papers, whose results were affected by such a problem, and a clarification is surely welcome.

There are some minor issues to be solved. Once clarified these points, I recommend publication.

Let's examine the issues in detail.

Line 24: The piece of information "ΔTscan equal to or longer than 14 times of the LIA time" is unuseful, if the meaning of ΔTscan is not specified. The same occurs in lines 66 and 115. The explanation in lines 89 and 126 should be anticipated here. See note about line 126

Line 38: At least a citation about this development should be added

Line 53: the acronym LIA is already described in the first line of the abstract (ine 13)

Figure 2: the size of all the panels should be increased, for the sake of clarity

Line 126: it would be better to define ΔTscan much earlier, in the abstract and at line 115

Figure 4: Most likely LO stands for Local Oscillator, but this is not specified at any point, neither here, nor at line 172

Line 193: why not a sawtooth, instead of a sine wave? A comment should be added.

Figure 5: I understand that this would complicate the figure, but plotting the residuals of each measurement would help quite a lot to understand the deviation of the experimental profile from the theoretical function

 

Typos

Line 37: "development" instead of "developments"

Line 48: "includes" should be "include"

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 2 Report

 

REVIEW

General comments

Authors should add a brief description of principle of operation of LHR.

Much more experimental data and their analyses from the field campaign should be added and they should be given in detail.

The agreement of different instrument should be investigated according to standard validation procedures and the results should be presented.

 

Specific comments

l.32: The meaning of the abbreviation TCCON FT-IR is missing. Add it.

l.40-41: This statement is totally wrong. Actually, it is the other way around. In any introductory atmospheric physics book is mentioned something like “…the vertical component of the three-dimensional velocity vector is more than three orders of magnitude smaller than the horizontal component” Wallace & Hobbs 2006 “Atmospheric Science”, Elsevier. Authors must correct it and be more careful. In addition, the link they mention as reference is incorrect. The reference [1] must be erased.

l.42: “vertical concentration contribution”: What do authors try to say here? Do they mean concentration profile of a trace gas i.e gas concentration at different altitudes?

l.41-44: Relevant references justifying these claims should be added.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Round 2

Reviewer 2 Report

Authors responded adequately to all my comments so I suggest the publication of the manuscript.