# Validating CYGNSS Wind Speeds with Surface-Based Observations and Triple Collocation Analysis
## 5 Conclusions  
CYGNSS mean wind speed retrieval continues to improve, and this paper explores alternative validation techniques of the latest products using surface-based analysis for FDS v 3.2 and NOAA v1.2, and TCA for NOAA v1.2 and Merged v3.2. FDS was found to have good performance with RMSD values below 2 m/s and higher correlations in Australian high wind-speed events than NOAA. Coastal effects are the likely reason that the results in this paper were lower than in other studies using buoys. The similar results, despite using uncorrected anemometer values, allows for the use of coastal anemometer data as part of validating GNSS-R ocean wind products. Instead of relying upon a single reference dataset, TCA was able to provide error estimates at global coverage. TCA provided a novel comparison between NOAA and Merged, which revealed Merged to have lower errors and significantly underestimate values above 17 m/s with an average bias of \(-\)4.5 m/s. The latency of both Merged and NOAA products make neither suitable for TC monitoring, and future work will be performed to improve the ability to detect rapid intensification events using CYGNSS.  
Conceptualization, A.W., Y.K., S.C. and L.H.; methodology, A.W.; software, A.W.; formal analysis, A.W.; investigation, A.W.; data curation, A.W.; writing--original draft preparation, A.W.; writing--review and editing, Y.K., S.C. and L.H.; visualisation, A.W.; supervision, Y.K., S.C. and L.H.; project administration, S.C.; funding acquisition, Y.K. and S.C. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Data Availability Statement:** Pacific anemometer data [33] is publicly available at: http://www. bom.gov.au/oceanography/projects/spslcmp/data/index.shtml (accessed on 12 December 2024). Data from Australian weather stations provided courtesy of the Australian Bureau of Meteorology. All CYGNSS datasets are publicly available at: [[https://podaac.jpl.nasa.gov/cloud-datasets?](https://podaac.jpl.nasa.gov/cloud-datasets?)]([https://podaac.jpl.nasa.gov/cloud-datasets?](https://podaac.jpl.nasa.gov/cloud-datasets?)) values=CYGNSS&view=list&ids=Projects (accessed on 12 December 2024). JPL SMAP wind speed dataset [54] as part of sea surface salinity product, available at: [[https://podaac.jpl.nasa.gov/dataset/SMAP_JPL_L2B_SSS_CAP_V5](https://podaac.jpl.nasa.gov/dataset/SMAP_JPL_L2B_SSS_CAP_V5)]([https://podaac.jpl.nasa.gov/dataset/SMAP_JPL_L2B_SSS_CAP_V5](https://podaac.jpl.nasa.gov/dataset/SMAP_JPL_L2B_SSS_CAP_V5)). NOAA SAR (accessed on 12 December 2024) [35] was made available as a server download by contacting the authors, and is available as single downloads at: https://www.  
star.nesdis.noaa.gov/socd/mecb/sar/sarwinds_tropical.php (accessed on 12 December 2024). All scripts used for this article have been uploaded to a publicly accessible google drive folder, available at: [[https://drive.google.com/drive/folders/118](https://drive.google.com/drive/folders/118) jHMpkn1 nCeuav_Gyz2 NU8 gu7 lkc3l0?usp=sharing]([https://drive.google.com/drive/folders/118](https://drive.google.com/drive/folders/118) jHMpkn1 nCeuav_Gyz2 NU8 gu7 lkc3l0?usp=sharing) (accessed on 12 December 2024).  
We are grateful to colleagues from the Bureau of Meteorology and RMIT for their helpful advice and guidance.  
The authors declare no conflicts of interest.