## 5 Conclusions and Perspectives  
Surface wind speed is an important factor in TCs. Wind distribution has some interesting characteristics, which are dependent upon TC intensity and motion speed. Based on high-resolution SAR data and the wind retrieval model, some relationships between wind distribution and TC parameters, such as intensity, size and storm motion speed, can be investigated through various statistical methods, contributing to the study of TC wind field.  
In this paper, 1 km wind retrievals of 41 TC cases were used to analyse decay, symmetry and the differences between three wind sections. The results mentioned above indicate that a strong TC generally has the following characteristics: (1) wind speed decreases fast from \(r_{\rm m}\) to 200 km radius; and (2) wind field is more symmetric. In addition, wind speed and radius are more linearly dependent, if the wind speed decreases fast from the inner core to the outer region. Among three wind sections, the right side of the TC moving direction is often the strongest section for maximum and averaged wind speed. The averaged wind difference between the left and right side is dependent on TC motion speed. These characteristics may be conducive to detect a TC's motion situation from limited SAR images.  
In the future, efforts will be made to investigate the wind distribution based on more cases observed by passive radiometers. Additionally, the SAR constellation's continued observations will be utilized for TC wind structure study in the temporal dimension.  
Initiation of the idea: [PERSON]; Data processing and model proposing: [PERSON]; Writing and editing: all authors contributed; Supervision: [PERSON]; Funding acquisition: [PERSON], [PERSON] and C.G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Science Foundation of China under grants 61931025, U20A2099, and 41976017, the Fundamental Research Funds for the Central Universities under grant 20 CX06109A, the Qingdao Postdoctoral Foundation Funded Project under grant qdyy20200098.  
Not applicable.  
The Sentinel-1 SAR data were obtained from the Copernicus Open Access Hub database of the European Space Agency ([[https://scilub.copernicus.eu/](https://scilub.copernicus.eu/)]([https://scilub.copernicus.eu/](https://scilub.copernicus.eu/)), accessed date: 21 April 2021). The hurricane best tracks were obtained from the National Hurricane Center ([[https://www.nhc.noaa.gov/data/tcr/](https://www.nhc.noaa.gov/data/tcr/)]([https://www.nhc.noaa.gov/data/tcr/](https://www.nhc.noaa.gov/data/tcr/)), accessed date: 24 April 2021). The hurricane best tracks were obtained from the Joint Typhoon Warning Center ([[http://www.metec.navy.mil/jtwc/](http://www.metec.navy.mil/jtwc/)]([http://www.metec.navy.mil/jtwc/](http://www.metec.navy.mil/jtwc/)), accessed date: 5 July 2021). All data used in this study are available on request from the author.  
We thank the European Space Agency for making the Sentinel-1 data publicly available. We thank the National Hurricane Center of the National Oceanic and Atmospheric Administration for hurricane best tracks, and the Joint Typhoon Warning Center for typhoon best tracks.  
The authors declare no conflict of interest.