Polar Stratospheric Cloud Observations at Concordia Station by Remotely Controlled Lidar Observatory

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper describes the aerosol lidar system at Concordia Station in Antarctica (75°S, 123°E) and its potential to observe Polar Stratospheric Clouds (PSCs). Despite the harsh Antarctic conditions, the lidar is operated on a regular basis, partly from remote locations. The paper furthermore gives some introduction into the physics and sounding of PCSs. The paper is generally well written and needs only minor/moderate revision. Detailed comments are given below.

 

l. 66: At the end of Section 1, an overview over the structure of the paper is missing.

l. 86: Please fill xxx and yyy with information.

l. 175: Unfortunately, I have not found any comparison with CALIOP in this paper. I recommend adding this comparison in order to enhance the scientific value of the value. If CALIOP data shall not be shown, all references to the data and methods should be removed.

l. 212: Please define a “profile”. Is this a 32 min sounding as described above? Are the lidar soundings limited to CALIOP overpasses?

Fig. 4: The color code for the lidar data is nowhere explained. Does the color indicate the observed kind of PSC? If not, how to differentiate between, e.g., NAT and ice. What does the circles in the lower right part of the figure show?

l. 256: Fig. 4 does not allow a comparison with previous year’s temperatures, as only 2021 is shown.

l. 257/258: I do not agree that temperatures are too high for ice until end of June. The red contours shows ice temperatures already in mid of June.

l. 267/268: Please state clearly whether the observations in September show true PSCs or whether these results are within the uncertainty of the data. The existence of PSC at such high temperatures would be a very important result.

References: Please check all links. Some contain a double “https://”, some contain signs like “{}” that are not used in a URL.

Author Response

We thank the referee for his useful comments and answer point-by-point to his comments and suggestions:

• An overview of the structure of the paper has been inserted at the end of the introduction.
• The information about the 6-inch telescope has been inserted.
• We procured the PSC special product data set from Michael Pitts, NASA and compared with the CALIOP data of 2021.
• A profile is the average of 16 recordings of 2 minutes for a total of 32 minutes. This has been inserted in the text.
• The colour code of the different PSC classes has been explained in the figure caption. The circles indicate that lidar recordings have been made, but without observing any clouds.
• Here we show the data recorded in 2021 as an example. No comparison with other years has been made.
• The referee is right, the temperatures in the second half of June are sufficiently low for ice formation. This has been changed in the manuscript.
• The observation of PSCs in September might be due to instrumental effects. Some measurements might suffer from a high background due to sunlight and since the STS detection and classification is based on very small values of the optical parameters (R and beta_perp) there might be some unreliable data in the figure. This has been mentioned now in the text.
• The double url’s in the references have been eliminated.

Reviewer 2 Report

Comments and Suggestions for Authors

In the manuscript entitled "Polar Stratospheric Clouds Observations at Concordia Station by the Remotely Controlled Lidar Observatory", authors tried to study the characteristics of Polar Stratospheric Clouds(PSC) using Lidar observations over Concordia Station during winter season. The operational difficulties and solutions to achieve quality data has been discussed. Though the study is important in understanding the characteristics of PSC and back ground dynamics, the current version of the manuscript lacks in presenting their study in a systematic manner. The abstract gives more general information, rather than the brief findings of the manuscript. In the abstract it was mentioned the lidar observations are available from 2014 onwards, however, the results shows only for the year 2021. Also the CALIPSO methodology is explained in Figure.3 however, the results from CALIPSO using this methodology is not present in the manuscript. The two figures 4 and 5 is not sufficient to draw any conclusion. Moreover, with a single line conclusion presented, I feel the manuscript is incomplete and ended up suddenly. I suggest the authors to check the journal guidelines while preparing the manuscript. In addition to the scientific points mentioned above, there plenty of typographical and grammatical errors in the manuscript that authors need to take care in the revised version. Some of the specific comments are given here.

 

Line 1: between 15 and 25km...amsl? or above surface level?

LIne 8: 'operation of the observatory,' insert comma 

Line 15: 'brilliant colors,' insert comma 

Line 16: 'Later on, it was' .. insert comma

Line 22: 'From the beginning,' .. insert comma

Line 23-24: First discuss Type I and then Type II. 

Line 24: 'also' spelt wrong. Correct it

Line 25: change to 'divided in to sub-classes'

Line 181: 'comparison, we had'

Line 184: 'CALIOP observations,'

Line 187: 'observations,'

Line199: 'NAT mixtures,'

Line 212: 'Only 2-4 profiles per day?'

Line 218: 'threshold temperature,'

Line 234: 'NAT particles,'

Line 239: "TNAT however. The possibility" should be "TNAT. However, the possibility of....

Line 240: 'iwas?' Correct it

Line 260: 'and August,'

Line 261: what is the spatial resolution of MLS? What is the spatial homogeneity of MLS H2O with respect to Lidar observation site?

Figure 4: change it to 'PSCs observed by LIDAR over Concordia in 2021' for clarity from MLS data.

Figure 4. Moreover, the figure is clumsy with too many contours and colorbar should be given to understand the PSC feature. 

Line 269: In conclusion,

 

 

 

 

Comments on the Quality of English Language

The English language used in this manuscript requires extensive editing with the help of professional English editing tools. There are plenty of grammatical and typographical errors in the manuscript that needs to be corrected. Punctuations are missing at many sentences. 

Author Response

We thank the referee for his comments and criticisms. Too many typographical errors have been made and some grammatical errors were present. We paid due attention to the punctuation.  Here we address the general comments of the referee.

 

The abstract has been changed to better describe the content of the paper.

Lidar observations are available from 2014. Some have been discussed in a previous paper, other will be included in a forthcoming paper (in preparation). Here we describe the lidar observatory, with an emphasis on the remote operation and the harsh environment. The data of one season, the 2021 winter have been used as an example of PSC occurrence and its temperature dependence, showing how the local temperature is important for the PSC formation processes.

The text has been modified to explain this in more detail.

For the CALIOP PSC data we depend on NASA. Although part of the CALIOP data is publicly available, the PSC special data are not and have to be requested from the PIs. We It took some time to get the reprocessed data of 2021. Now they are included in the manuscript.

Figure 4 has been substituted with figures 8, 9 and 11. Figure 8 and 9 show a comparison of the ground based observations with nearby overpasses of CALIOP. Figure 8 considers a smaller area around Concordia station, while figure 9 considers a larger area in the longitudinal direction. The agreement for what concerns detection of PSCs is very good, the classification shows a reasonable agreement, as has been stated in a previous paper (Snels 2021). The larger area comparison is meant to illustrate that Concordia Station is reasonably representative for the Antarctic plateau. Figure 11 is shown to demonstrate how strong the relation between temperature and PSC formation is. The 2021 vortex was rather strong, cold and extended (see figure 10). This explains the frequent observation of ice PSCs.

 

All further comments have been addressed point-by-point.

 

 

• All typographical errors and few grammatical errors have been corrected. Numerous punctuation marks have been inserted to satisfy the referee’s requests.
• Type I and type II PSCs have been mentioned in the text. We don’t see why type I should be mentioned first in the text. Both have been mentioned in the same sentence.
• We measure 2-4 profiles per day, each recording having a duration of 32 minute plus 15-20 minutes of warming up of the laser. This amounts to about 3 hours per day of laser activity. One year of laser operation, including tests and special campaigns amount to about 50 M shots. In practice, flashlamps are changed every two years, after about 100 M shots.

On-site maintenance is performed by qualified personnel during summer, extra-ordinary maintenance requires the laser to be send to the laser supplier. This occurs every 3-4 years and implies a turnover time of one year. To guarantee a continuous operation of the observatory we have one spare laser, which is used while the other is in maintenance by the laser supplier. Use the laser more frequently would put more stress on the system and increase the risk of having to interrupt or stop lidar operation during the year.

• The vertical resolution of MLS is 1 km, the footprint 5 x 200 km. This is now mentioned in the text.
• The figure caption of figure 4 has been changed as suggested by the referee.

 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I appreciate the authors for revising the manuscript based on suggestions and comments given by the reviewers. Though there are few typo errors in the manuscript, I feel that doesn't affect the reader's interest.  The manuscript is scientifically sound enough to be accepted for publication. 

Comments on the Quality of English Language

English language is improved in the revised manuscript.