{"id":994,"date":"2008-02-23T09:30:54","date_gmt":"2008-02-23T01:30:54","guid":{"rendered":"http:\/\/www.intmath.com\/blog\/?p=994"},"modified":"2015-04-21T08:17:21","modified_gmt":"2015-04-21T00:17:21","slug":"sine-wave-in-the-sky-over-singapore","status":"publish","type":"post","link":"https:\/\/www.intmath.com\/blog\/mathematics\/sine-wave-in-the-sky-over-singapore-994","title":{"rendered":"Sine wave in the sky over Singapore"},"content":{"rendered":"<p>I had a friend who was heavily into gliding. He would become very excited when he observed \"wave\" in the sky.<\/p>\n<p>Gliders (aka sailplanes) don't have engines, of course, so you spend all your time looking for lift. <\/p>\n<p><img src='\/blog\/wp-content\/images\/2008\/02\/glider.jpg' alt='glider' \/><br \/>\n<span style=\"font-size:8pt;\">[Image source: Boeing]<\/span><\/p>\n<p>The lift comes from thermals (rising hot air, usually over dark-colored ground) or waves that are the result of wind blowing over mountains. When airflow is lifted by a mountain range, it is called 'orographic uplift'.<\/p>\n<p><img src='\/blog\/wp-content\/images\/2008\/02\/orographic.gif' alt='Orographic uplift wave' \/><br \/>\n<span style=\"font-size:8pt;\">[Image <a href=\"http:\/\/publishing.cdlib.org\/ucpressebooks\/view?docId=ft3t1nb2pn&chunk.id=0&doc.view=print\">source<\/a>, from <i>Natural History of the White-Inyo Range, Eastern California.<\/i>]<\/span><\/p>\n<p>So in gliding, \"wave\" is a standing <a href=\"https:\/\/www.intmath.com\/trigonometric-graphs\/1-graphs-sine-cosine-amplitude.php\">sine curve<\/a> on the leeward side of a mountain.<\/p>\n<p>I saw the following wave pattern over Singapore recently. The clouds are much higher than where gliders can reach, but there is evidence of alternating rise and fall of the moist airmass. In this case, the wave could be the result of air passing over mountains in Indonesia (there are no mountains in Singapore).<\/p>\n<p><img src='\/blog\/wp-content\/images\/2008\/02\/sky-sine-wave-450.jpg' alt='sine wave in the sky' \/><br \/>\n<span style=\"font-size:8pt;\">[Photo: LimPH].<\/span><\/p>\n<p class=\"alt\">See the <a href=\"https:\/\/www.intmath.com\/blog\/mathematics\/sine-wave-in-the-sky-over-singapore-994#comments\" id=\"comms\">4 Comments<\/a> below.<\/p>\n","protected":false},"excerpt":{"rendered":"<p><a href=\"https:\/\/www.intmath.com\/blog\/mathematics\/sine-wave-in-the-sky-over-singapore-994\"><img src='\/blog\/wp-content\/images\/2008\/02\/sky-sine-wave-450.thumbnail.jpg' alt='sine wave in sky' class='imgRt' \/><\/a> This is evidence of wind passing over a mountain range and creating a standing sine wave on the leeward side.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mo_disable_npp":""},"categories":[4],"tags":[134],"_links":{"self":[{"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/posts\/994"}],"collection":[{"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/comments?post=994"}],"version-history":[{"count":0,"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/posts\/994\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/media?parent=994"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/categories?post=994"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.intmath.com\/blog\/wp-json\/wp\/v2\/tags?post=994"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}