Hong Kong Airport Wind Shear Now-Casting System Development and Evaluation
, Kate Johnson 1, Rose Jackson 1, Stephen Smith 1, Daniel Connolly 1, David Carruthers 1 and Pak-Wai Chan 2Round 1
Reviewer 1 Report
This paper presents an interesting test of the FLOWSTAR model for now-casting wind shear events at Hong Kong International Airport. The manuscript documents both successes and challenges in doing so, which highlight areas for further model refinement.
Major comments
1. The manuscript needs a discussion section that discusses the results rather than summarizing them (which is what the current Discussion section does). The current Conclusions section includes text that I (for one) would typically expect to appear in a Discussion.
2. The Conclusions section should be revised to highlight the main conclusions from the study, areas for future work, and the potential broader applicability of FLOWSTAR or similar models (if there are any!).
3. Section 2: I realize that the bulk of the model description is given in previously published papers, but I found it difficult to visualize the model grid configuration and how the 'vertical slices' are chosen and used. Consider adding a figure to show the model grid and its alignment with the runway, and which 'vertical slice' you select for figures 4, 6, and 7.
Minor comments
4. Lines 92 (and elsewhere in the manuscript): A radiometer is an instrument that measures radiation; please clarify what data from the radiometer you use as input to FLOWSTAR (is this a microwave radiometer from which you calculate air temperature based on radiation measurements? or do you mean the radiosonde at Kings Park, as noted in Table 1?); update all uses of the term "radiometer" if needed.
5. Figure 1: Please add the location of the (microwave?) radiometer.
6. Line 202: these are counts, not frequencies
7. Lines 272-273: how much of the time does the wind advect directly from Cheung Chau to HKIA? 50%? 20%? 70%?
8. Lines 288-289: how often does "reverse flow" occur?
9. Table 2: it will be helpful to define the notation in the table heading, so that readers don't need to search for it in the text
10. Line 508: is a negative headwind equal to a tailwind?
11. Lines 518-519 (and figures 6 and 7): suggest including the synoptic map for these two cases
12. Lines 521-522: the figures don't describe how these values are calculated, they show the calculated values
13. Lines 537-538: What does this tell you about the utility of the other metrics (if anything)? This is an example of something you can talk about in the Discussion section.
14. Lines 538-539: How do you conclude this based on figures 8a and b, which are labeled as horizontal accelerations?
15. Lines 588-590: The horizontal and vertical parameters look about the same in fig 11c, so what's the basis for stating that vertical parameters are slightly better?
16. Lines 610-613: Is this equally true for the other runway corridors? *Are* the differences statistically significant?
17. Lines 613-614: explain why half a runway is better than (or about as good as) a full runway?
18. Lines 628-629: explain a little more how you draw this conclusion?
19. Line 664: what is the basis for the claim that this one 4-month period represents "a full range of meteorological conditions"?
20. Line 739: spell out APC
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
General comments:
This paper is an interesting study of wind shear now-casting system. The analysis and results in this study would be valuable for wind shear alerting. This paper has a well-organized structure and gives six wind shear metrics and quantification of now-cast skill. Before the manuscript can be recommended for acceptance for publication, I have several suggestions and comments here that need to be addressed.
Specific comments:
1. Line 29: The reference cited in the manuscript should use numerical notation in brackets for bibliographic citations. The numerical notations in the manuscript are confusing.
2. Line 16: It would be better to give the full name of “ROC”, when it first appears, although it is in the abstract.
3. Line 149: The radial speed obtained by the lidar system is the component of the wind vector along the laser beam, thus, the magnitude of the velocity obtained by the lidar are depended on the intersect angle between the laser beam pointing direction and the extended center line of the runway. The reference mentioned here is the report of the first lidar system configured at HKIA in 2002. Limited by the size and the weight of the LiDAR system, the LiDAR were configured on the roof of the buildings inside the airport. The intersect angle between the laser beam pointing direction and the centerline of the runway is larger than 30 degrees. With the development of the laser technique, the smart pulsed coherent Doppler lidar system have been widely utilized in the identification of the low-level wind shear events. The smart PCDL systems in ZLLL and ZBAA have been configured close to the centerline of the runway to reduce the influence induced by the large intersect angles. It is suggested to explain the shortcomings of LIDAR more objectively in this place, such as insufficient observation of cross wind, easy to be affected by small-scale turbulence, and easy to be affected by rainfall or fog.
4. Line 191: It should be “right (R)” instead of “right I”.
5. Line 192: The “A” is abbreviation of the “Approach” or the “Arrivals”? I have checked the “Manual on Low-level Wind Shear” published by the ICAO, the “Approach” and “Departure” are the common expressions.
6. Line 202-203: How do you obtain the headwind changes here? It would be better to provide more information.
7. Line 337: The Figure 4 illustrated in the manuscript has poor clarity. It is recommended to be replaced with a good quality. The label “Distance” of the X-axis in the figure is the distance from the runway. Since the runway has a certain width and length, the distance from the runway should be indicated. If possible, it can be marked in the topographic map in Figure 1.
8. Line 343-344: What are the “positive wind shear” and “negative wind shear”? Please explain better.
9. Line 478 (Figure 6): It would be better to keep the same ticks of the x-axis (Distance from runway) in Fig. 6a, 6b and 6c.
10. Line 521-522: It is not very clear how to calculate the horizontal and vertical acceleration parameters. Please explain better.
11. Now-casting system is defined as the prediction of the present or the very near future. How does the wind shear now-casting system described in this paper give the prediction of the near-future wind shear? How long in advance could it predict the wind shear?
12. The time window of 20 minutes and up to 80 minutes have been illustrated in the manuscript. Please analysis the factors that influence the scale of the time window.
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I appreciate the authors' work to respond to my initial comments.
Author Response
Thank you for reviewer 1's comment.
