## 5 Conclusions  
The 100-year return period of SWHs was estimated by applying the PoT method as one of representative EVA methods. The PoT-derived SWHs were compared with the maximum SWHs within the upper 0.1% of satellite observations in the Northwest Pacific. Despite many shortcomings, including the limitations of the PoT method and the unevenness of observations in satellite altimeter data, the PoT method supported our hypothesis by presenting higher SWHs than the maximum values observed from 1992 to 2016. The comparisons of the data were performed by classifying the extreme SWHs into two different regions--a typhoon region and non-tyhoon region--by defining the thresholds of the frequency of the number of typhoons in each bin. As a result, the PoT-derived 100-year extreme SWHs revealed the characteristic variations affected by not only typhoons in the East China Sea during typhoon periods in summer and fall but also by winter-time high SWHs in the northeastern part of the study region in the Northwest Pacific. Overall differences of SWHs between PoT-derived extremes and the maximum values appeared at approximately 4 m, and the highest differences were approximately 8 m.  
The present PoT method represents the SWHs in extreme events well. However, there is a potential limitation in terms of bias due to the few sampling problems when an altimeter observes the SWH along the track in the nadir direction. Nonetheless, satellite altimeter data are very valuable for estimating the extreme value of SWHs as they cover the global ocean as well as regional seas. In addition, if sufficient data are accumulated, it is also expected that the IORS could be a good candidate for investigating oceanic responses to the typhoons that frequently pass over the station.  
Conceptualization, K.-A.P.; data curation, H.-J.W.; methodology, H.-J.W. and K.-A.P.; writing--original draft preparation, H.-J.W.; writing--review and editing; K.-A.P. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Research Foundation of Korea (NRF), grant funded by the Korean government (MSIT) (No. 2020R1A2C2009464) and partly by \"Deep Water Circulation and Material Cycling in the East Sea\" (1525010256) funded by the Ministry of Oceans and Fisheries, Korea.  
Figure 15: Spatial distribution of along-track SWHs around the tropical cyclone named Bolaven at **(a)** 00 UTC, **(b)** 06 UTC, **(c)** 12 UTC, and **(d)** 18 UTC on 26 August 2012 and **(e)** 00, **(f)** 06, **(g)** 12, and **(h)** 18 UTC on 27 August 2012, where the backgrounds are infrared images from the Communication, Ocean, and Meteorological Satellite/Meteorological Imager (COMS/MI) and the red dot denotes the location of the Ioodo Ocean Research Center. The SWH data were obtained from satellite altimeters of **(b)** Jason-1 (right) and Jason-2 (left), **(d)** Jason-1 (right) and Jason-2 (left), **(e)** Cryosat-2 (middle), Jason-1 (right) and Jason-2 (left) in the upper right corner, and **(h)** Jason-1 (right) and Jason-2 (left).  
Data Availability Statement: All data used in this study are available from IFREMER (satellite altimeter SWH data, [[ftp://ftp.ifremer.fr/ifremer/cersat/products/swath/altimeters/waves/](ftp://ftp.ifremer.fr/ifremer/cersat/products/swath/altimeters/waves/)]([ftp://ftp.ifremer.fr/ifremer/cersat/products/swath/altimeters/waves/](ftp://ftp.ifremer.fr/ifremer/cersat/products/swath/altimeters/waves/)) (accessed on 20 January 2021)), KMA (buoy and COMS data, [[https://nmsc.kma.gov.kr/](https://nmsc.kma.gov.kr/)]([https://nmsc.kma.gov.kr/](https://nmsc.kma.gov.kr/)) (accessed on 20 January 2021)), or KHOA (IORS data, [[http://www.khoa.go.kr/](http://www.khoa.go.kr/)]([http://www.khoa.go.kr/](http://www.khoa.go.kr/)) (accessed on 20 January 2021)).  
In situ data from the Ieodo Ocean Research Station (IORS) was provided by the IORS project of the Korean Hydrographic and Oceanographic Agency, Korea.  
The authors declare no conflict of interest.