{"id":1365,"date":"2022-02-17T15:56:10","date_gmt":"2022-02-17T07:56:10","guid":{"rendered":"http:\/\/localhost\/wordpress\/?page_id=1365"},"modified":"2026-04-23T10:55:40","modified_gmt":"2026-04-23T02:55:40","slug":"%e6%b3%a2%e6%b5%aa","status":"publish","type":"page","link":"https:\/\/www.comc.ncku.edu.tw\/en\/%e6%9c%80%e6%96%b0%e6%b6%88%e6%81%af\/%e7%9f%a5%e8%ad%98%e6%8e%a8%e5%bb%a3\/%e6%b3%a2%e6%b5%aa\/","title":{"rendered":"Wave"},"content":{"rendered":"\t\t
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\n\t\t\t\t\t\u570b\u7acb\u6210\u529f\u5927\u5b78 \u8fd1\u6d77\u6c34\u6587\u4e2d\u5fc3<\/span>
\nCoastal Ocean Monitoring Center, National Cheng Kung University (COMC, NCKU)<\/b><\/span><\/span>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Wave<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Ocean waves are generally classified into two main types: wind waves and swell. The saying \u201cno wind, no waves\u201d reflects the fact that most ocean waves are generated by wind forcing. Waves formed by local winds are referred to as wind waves. In contrast, the phrase \u201cthree-foot waves even without wind\u201d describes swell, which originates from distant storm systems or remains after local winds have weakened or changed direction. Beyond their different origins, wind waves and swell also differ in their physical characteristics. Wind waves typically have a steep and irregular appearance, with relatively short wavelengths and periods. Swell, on the other hand, undergoes energy dissipation during propagation due to air resistance and internal water friction. This results in a reduction in wave height and an increase in wave period and wavelength. Consequently, swell appears smoother and more regular, with longer periods and wavelengths that can reach several hundred meters. Moreover, swell propagates much faster than the movement of weather systems. Swell generated by typhoons or southwest monsoon often serves as a precursor signal of approaching weather systems.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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\n\t\t\t\t\t\t\t\t\tSwell generally carries substantial energy. As it propagates into shallow coastal waters, interactions with seabed topography induce wave transformation processes. The lower part of the wave is slowed by seabed friction, while the wave crest continues to move forward at its original speed. This leads to a shortening of wavelength and an increase in wave height, eventually causing wave curling and breaking. Therefore, even under calm weather conditions with relatively tranquil sea surfaces, swell can still pose significant hazards to people near the shore or engaging in nearshore activities. For instance, before a typhoon reaches Taiwan, coastal winds and waves may still appear moderate; however, incoming swell can already impact nearshore areas, posing considerable risk to coastal users.\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Schematic Diagram of Wave Generation Factors<\/h6>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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In addition, Francis Beaufort, an admiral of the British Navy, established the first wind force classification system in 1805 based on extensive maritime observations. The relationship between wind speed and wave height defined on this scale can be used to estimate sea conditions in open-ocean environments. The Beaufort wind force scale and corresponding sea state scale are presented in the table below.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Beaufort scale<\/strong><\/th>Sea State<\/strong><\/th>Wind Speed<\/strong><\/th>Wave Height<\/strong><\/th><\/tr>
knots<\/td>m\/s<\/td>typical<\/td>max<\/td><\/tr>
0<\/td>–<\/td><1<\/td>0-0.2<\/td>m<\/td>m<\/td><\/tr>
1<\/td>light ripples<\/td>1-3<\/td>0.3-1.5<\/td>0.1<\/td>0.1<\/td><\/tr>
2<\/td>light ripples<\/td>4-6<\/td>1.6-3.3<\/td>0.2<\/td>0.3<\/td><\/tr>
3<\/td>small waves<\/td>7-10<\/td>3.4-5.4<\/td>0.6<\/td>1.0<\/td><\/tr>
4<\/td>small waves<\/td>11-16<\/td>5.5-7.9<\/td>1.0<\/td>1.5<\/td><\/tr>
5<\/td>moderate<\/td>17-21<\/td>8.0-10.7<\/td>2.0<\/td>2.5<\/td><\/tr>
6<\/td>strong<\/td>22-27<\/td>10.8-13.8<\/td>3.0<\/td>4.0<\/td><\/tr>
7<\/td>strong<\/td>28-33<\/td>13.9-17.1<\/td>4.0<\/td>5.5<\/td><\/tr>
8<\/td>very high waves<\/td>34-40<\/td>17.2-20.7<\/td>6.0<\/td>7.5<\/td><\/tr>
9<\/td>heavy<\/td>41-47<\/td>20.8-24.4<\/td>7.0<\/td>10.0<\/td><\/tr>
10<\/td>heavy<\/td>48-55<\/td>24.5-28.4<\/td>9.0<\/td>12.5<\/td><\/tr>
11<\/td>violent storm<\/td>56-63<\/td>28.5-32.6<\/td>11.5<\/td>16.0<\/td><\/tr>
12<\/td>violent storm<\/td>64-71<\/td>32.7-36.9<\/td>\u2265 14<\/td>\u2265 16<\/td><\/tr><\/tbody><\/table><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"

\u570b\u7acb\u6210\u529f\u5927\u5b78 \u8fd1\u6d77\u6c34\u6587\u4e2d\u5fc3 Coastal Ocean Monitoring Center, National …<\/p>\n

Wave<\/span> \u95b1\u8b80\u5168\u6587 »<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1360,"menu_order":1,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","site-sidebar-layout":"no-sidebar","site-content-layout":"page-builder","ast-global-header-display":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"disabled","ast-breadcrumbs-content":"","ast-featured-img":"disabled","footer-sml-layout":"","theme-transparent-header-meta":"enabled","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","footnotes":""},"class_list":["post-1365","page","type-page","status-publish","hentry"],"uagb_featured_image_src":{"full":false,"thumbnail":false,"medium":false,"medium_large":false,"large":false,"1536x1536":false,"2048x2048":false},"uagb_author_info":{"display_name":"PCLIN","author_link":"https:\/\/www.comc.ncku.edu.tw\/en\/author\/pclin\/"},"uagb_comment_info":0,"uagb_excerpt":"\u570b\u7acb\u6210\u529f\u5927\u5b78 \u8fd1\u6d77\u6c34\u6587\u4e2d\u5fc3 Coastal Ocean Monitoring Center, National...","_links":{"self":[{"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/pages\/1365","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/comments?post=1365"}],"version-history":[{"count":59,"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/pages\/1365\/revisions"}],"predecessor-version":[{"id":8769,"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/pages\/1365\/revisions\/8769"}],"up":[{"embeddable":true,"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/pages\/1360"}],"wp:attachment":[{"href":"https:\/\/www.comc.ncku.edu.tw\/en\/wp-json\/wp\/v2\/media?parent=1365"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}