Aircraft and Satellite Observations of Vortex Evolution and Surface Wind Asymmetry of Concentric Eyewalls in Hurricane Irma

Round 1

Reviewer 1 Report

Figure 1. The figure is difficult to read. It is not clear what is shown there. It is necessary to rethink it, and redo it from scratch.
Figure 3. The X's overly cover the trajectories

Author Response

Reviewer#1：

Figure 1. The figure is difficult to read. It is not clear what is shown there. It is necessary to rethink it, and redo it from scratch.

Reply:

We have distinguished the original Figure.1a into two parts as to separately show the geolocations of SAR images and aircraft radial legs more clearly.

Figure 3. The X's overly cover the trajectories.

Reply:

We have revised the Figure.3.

Reviewer 2 Report

Summary: The authors use SAR data to investigate the eyewall replacement cycle. A great deal of observations are processed to characterize the eyewall replacement cycle. Some physical insight is also provided.  I applaud the authors for the improvements that they have made in this paper! This version of the paper is highly engaging and fun to read.

Major comments:

1) Results, first paragraph: The physics for a tilted eyewall have been well explained by Andy Hazelton (Hazelton and Hart 2013), which would be a good citation to add in this paragraph. Note that the logic presented by Hazelton differs from that presented in this document.

2) Section 4.3: There are two modeling studies by Ahern et al. that examining (in a model rather than with observations) roles of asymmetry in hurricane intensity changes. It would be interesting to link the results presented here to the findings from those modeling studies. Linking the observations to these modeling studies might be insightful in this paper or suggested as future work. There is an additional paper in this series in press, but that will likely not be publicly available before revisions are due.

Minor comments:

3) Define CEM before it is used on line 60.

4) Line 121: the use of ‘we collected’ implies that the authors were involved in data collection. Please use different wording.

5) Line 223: Please be clear that these observations are for Hurricane Irma.

6) Line 285: duration is the wrong word.

7) Line 446: compensates seems like the wrong word.

Hazelton, A.T. and Hart, R.E., 2013. Hurricane eyewall slope as determined from airborne radar reflectivity data: Composites and case studies. Weather and forecasting, 28(2), pp.368-386.

Black, M., J. Gamache, F. Marks, C. Samsury, and H.Willoughby, 2002: Eastern Pacific Hurricanes Jimena of 1991 and Olivia of 1994: The effect of vertical shear on structure and intensity. Mon. Wea. Rev., 130 (9), 2291–2312.

Ahern, K., Bourassa, M.A., Hart, R.E., Zhang, J.A. and Rogers, R.F., 2019. Observed kinematic and thermodynamic structure in the hurricane boundary layer during intensity change. Monthly Weather Review, 147(8), pp.2765-2785.

Corbosiero, K. L., and J. Molinari, 2002: The effects of vertical wind shear on the distribution of convection in tropical cyclones. Mon. Wea. Rev., 130 (8), 2110–2123.

Reasor, P. D., R. Rogers, and S. Lorsolo, 2013: Environmental flow impacts on tropical cyclone structure diagnosed from airborne Doppler radar composites. Mon. Wea. Rev., 141 (9), 2949– 2969.

DeHart, J. C., R. A. J. Houze, and R. F. Rogers, 2014: Quadrant distribution of tropical cyclone inner-core kinematics in relation to environmental shear. J. Atmos. Sci., 71 (7), 2713–2732.

Gu, J.-F., Z.-M. Tan, and X. Qiu, 2016: Quadrant-dependent evolution of low-level tangential wind of a tropical cyclone in the shear flow. J. Atmos. Sci., 73 (3), 1159–1177.

Hazelton, A. T., R. F. Rogers, and R. E. Hart, 2017: Analyzing simulated convective bursts in two Atlantic hurricanes. Part I: Burst formation and development. Mon. Wea. Rev., 145 (8), 3073–3094.

Ahern, K., Hart, R.E. and Bourassa, M.A., 2021. Asymmetric Hurricane Boundary Layer Structure during Storm Decay. Part I: Formation of Descending Inflow. Monthly Weather Review, 149(11), pp.3851-3874.

Nguyen, L. T., R. F. Rogers, and P. D. Reasor, 2017: Thermodynamic and kinematic influences on precipitation symmetry in sheared tropical cyclones: Bertha and Cristobal (2014). Mon. Wea. Rev., 145 (11), 4423–4446.

Rios-Berrios, R., C. A. Davis, and R. D. Torn, 2018: A hypothesis for the intensification of tropical cyclones under moderate vertical wind shear. J. Atmos. Sci., 75 (12), 4149–4173.

Ryglicki, D. R., J. D. Doyle, D. Hodyss, J. H. Cossuth, Y. Jin, K. C. Viner, and J. M. Schmidt, 2019: The unexpected rapid intensification of tropical cyclones in moderate vertical wind shear. Part III: Outflow–environment interaction. Mon. Wea. Rev., 147 (8), 2919–2940.

Chen, X., Y. Wang, J. Fang, and M. Xue, 2018a: A numerical study on rapid intensification of Typhoon Vicente (2012) in the South China Sea. Part II: Roles of inner-core processes. J. Atmos. Sci., 75 (1), 235–255. 809

Chen, X., M. Xue, and J. Fang, 2018b: Rapid intensification of Typhoon Mujigae (2015) under different sea surface temperatures: Structural changes leading to rapid intensification. J. Atmos. Sci., 75 (12), 4313–4335. 

Author Response

Reviewer#2：

Summary: The authors use SAR data to investigate the eyewall replacement cycle. A great deal of observations is processed to characterize the eyewall replacement cycle. Some physical insight is also provided. I applaud the authors for the improvements that they have made in this paper! This version of the paper is highly engaging and fun to read.

Reply:

We appreciate your positive evaluation and give a point-by-point reply.

Major comments:

1) Results, first paragraph: The physics for a tilted eyewall have been well explained by Andy Hazelton (Hazelton and Hart 2013), which would be a good citation to add in this paragraph. Note that the logic presented by Hazelton differs from that presented in this document.

Reply:

We have cited the reference to explain the tilted vertical-structure in concentric eyewalls.

“This shows that CEs have a narrow appearance at the sea-surface level and tilt outward with height in the cross-section due to the vertical wind shear or the ocean heat content [33].”

[33] Hazelton, A.T.; Hart, R.E. Hurricane Eyewall Slope as Determined from Airborne Radar Reflectivity Data: Composites and Case Studies. Weather and Forecasting 2013, 28, 368–386.

2) Section 4.3: There are two modeling studies by Ahern et al. that examining (in a model rather than with observations) roles of asymmetry in hurricane intensity changes. It would be interesting to link the results presented here to the findings from those modeling studies. Linking the observations to these modeling studies might be insightful in this paper or suggested as future work. There is an additional paper in this series in press, but that will likely not be publicly available before revisions are due.

Reply:

Thank you for your evaluation and suggestion. This idea is interesting and worthy of further discussion. We have linked the observations to the relative mechanism form the model results and references as followed:

“On the other hand, model results have shown that TC asymmetric structure and intensity of boundary layer is linked to the vertical wind shear and storm motion [37-38]. Full-physics simulation of Hurricane Irma [38] pointed out that the descending inflow with amplified shear is identified as the conduit through which low-entropy air enters the inner-core TC boundary layer, resulting in storm decay.”

[37] Ahern, K.; Bourassa, M.A.; Hart, R.E.; Zhang, J.A.; Rogers, R.F. Observed Kinematic and Thermodynamic Structure in the Hurricane Boundary Layer during Intensity Change. Monthly Weather Review 2019, 147, 2765–2785.

[38] Ahern, K.; Hart, R.E.; Bourassa, M.A. Asymmetric Hurricane Boundary Layer Structure during Storm Decay. Part I: Formation of Descending Inflow. Monthly Weather Review 2021, 149, 3851–3874.

Minor comments:

3) Define CEM before it is used on line 60.

Reply:

We have added the full explanation of CEM as “concentric eyewalls maintained”.

4) Line 121: the use of ‘we collected’ implies that the authors were involved in data collection. Please use different wording.

Reply:

We have replaced the words “we collected” with “we extracted”.

5) Line 223: Please be clear that these observations are for Hurricane Irma.

Reply:

We have revised the sentence in Line 223 for “Fig. 5 shows the evolution of wind profile parameters at both the free-atmosphere and the sea-surface levels in Hurricane Irma (2017).”.

6) Line 285: duration is the wrong word.

Reply:

We have revised the sentence in Line 285 for “Compared with ERC01, Hurricane Irma’s intensity was much stronger in ERC02 than before because the outer eyewall formed closer to the inner eyewall at the same time.”.

7) Line 446: compensates seems like the wrong word.

Reply:

The word “compensates” only appeared in Line 467 once. We have replaced the word with “explains”.

Reviewer 3 Report

Thank you very much for the incorporated changes. I have no additional concerns.

Author Response

Thank you very much, and we appreciate for your work on review.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This work compare the vortex evolutions of eyewall replacement cycles (ERCs) between sea-surface and free-atmosphere levels and investigate the asymmetric structure of concentric eyewalls 15 (CEs) using data from aircraft and surface wind C- band SAR during Hurricane Irma (2017 ). The work is well structured and interesting even if it has some critical points. Mainly the bibliography is very poor. Secondly, the figures need to be made clearer, more representative and more legible. Furthermore, I suggest to the authors to investigate more the physical part of the phenomenon linking it to possible future perspectives and future applications, to be added in the conclusions.

• Bibliography is very poor. There are many interesting works studying this field, both with Airborne and with SAR. In order to better frame the problem, and the state of the art of the use of Airbrne-SAR technologies, in this sector, I suggest adding in “conclusion” section these additional quotes:

Hui et al 2016

Hui Shen, William Perrie & Yijun He (2016) Evaluation of hurricane wind speed retrieval from cross-dual-pol SAR, International Journal of Remote Sensing, 37:3, 599-614, DOI: 10.1080/01431161.2015.1134845

Gao et al 2021
Gao,Y.;Sun,J.;Zhang,J.; Guan, C. Extreme Wind Speeds Retrieval Using Sentinel-1 IW Mode SAR Data. Remote Sens. 2021, 13, 1867. https://doi.org/10.3390/rs13101867

Benassai et al 2012
Benassai, G., Migliaccio, M., Montuori, A., and A. Ricchi. "Wave Simulations Through Sar Cosmo-Skymed Wind Retrieval And Verification With Buoy Data." Paper presented at the The Twenty-second International Offshore and Polar Engineering Conference, Rhodes, Greece, June 2012.

Zhang et al 2017

Zhang B., Perrie W. (2017) High Wind Speed Retrieval from Multi-polarization SAR. In: Li X. (eds) Hurricane Monitoring With Spaceborne Synthetic Aperture Radar. Springer Natural Hazards. Springer, Singapore. https://doi.org/10.1007/978-981-10-2893-9_5

Gao et al 2018

Gao, Y., Guan, C., Sun, J., & Xie, L. (2018). A New Hurricane Wind Direction Retrieval Method for SAR Images without Hurricane Eye, Journal of Atmospheric and Oceanic Technology, 35(11), 2229-2239. Retrieved Mar 7, 2022, from https://journals.ametsoc.org/view/journals/atot/35/11/jtech-d-18-0053.1.xml

…etc

• Figure 1. The figure is very small, the geographical area is not well clear, the very important details for this representation of the cyclone are not highlighted. Masking the gap, coloring the coast internally, enlarging the figure within the page, increasing the font size.
• Figure 4. The crosses (X) on the image are really unclear, it is not clear what they represent and overlap, covering the trajectory. I suggest using another symbol, which allows you to glimpse what is in the background, for example an empty circle (o).
• Figure 10. Increase the font size.
• Figure 14, enlarge it on the page (follow the indications in figure 1)

Reviewer 2 Report

The topic is scientifically and societally interesting and seems well suited for Remote Sensing.

There is need for minor improvements in English. However, the organization of the paper is terrible! The results at the end are fascinating, suggesting that an improved paper would be quite interesting. The minor comments focus only on the first few pages because it became apparent that much larger problems needed to be addressed.  I look forward to seeing an improved version of this manuscript.

Major Comments

1) The paper is unreadable because of the poor organization and writing style The reason for presenting material is not provided before the material is discussed. The authors are presumably always talking about maximum winds, but that is never discussed. The quantity being validated is not well explained.

2) Presumably the Rankin vortex model is used to obtain maximum winds, but how is this done. How does this impact the analyses in section 4 (it does not appear to be relevant)?

3) How much averaging goes into determining the wind speeds in each quadrant of the storm? How does this impact interpretation?

4) The time between observations needs to be much more clearly addressed in the analyses.

5) What is the source of the SAR data? Please mention this earlier than section 2.2. Shortly before this section I was getting the impression that the SAR might have been airborne as mentioned in the title, but that doesn’t seem to be the case.

6) The Rankine vortex model is described before the need for it is given. If you are measuring winds why is this needed?

7) Figure 2 talks about the fit to wind speed, but does not say which wind speed. Clearly it is not all the wind speeds being observed.

8) What is being validated in Figure 5?

Minor comments

9) Lines 36-37: The dramatic changes are in the maximum winds and the central pressure, rather than the winds and pressure throughout the TC.

10) Line 84: what is meant by two continuous SAR images. How could that be achieved? What better wording be ‘two consecutive SAR images?

11) Line 113: The SFMR accuracies may have been quoted as stated, but the calibration for hurricane force winds is a little more uncertain than the average accuracy. Please make a more realistic statement of SFMR accuracy.

12) Line 118: Be aware that the adjustment factors for altitude are fine as a mean, but are very noisy.

Reviewer 3 Report

Thank you for the great work. Paper is very nicely written and I have enjoyed reading it. I really like your approach to data visualization and how you generated your figures for relatively complex data.

I have found several typos or possible copy/paste issues:

1. Page 1, Line 34: breaking of the word “cy-clones”.
2. Pages 3-4, Lines 122-127: Would it be possible to reposition Figure 1 in such a way so that the figure caption text does not break over two pages?
3. Page 4, Line 142: word “Modified” should start with capital “M”.
4. Pages 8-9, Lines 246-249: it seems that Figure 7 and Figure 8 are identical. Possible copy/paste issue? Judging by the time entries in Table 2, Figure 7 matches Table 2 times, so probably Figure 7 is right, in which case new Figure 8 is needed.
5. Page 9, Lines 253-254: Time entries in row 3 of the Table 2 (ERC03) show Starting Time later than Ending Time. Possibly Date change in End Time needed?