{"id":2080,"date":"2009-03-04T23:59:20","date_gmt":"2009-03-04T23:59:20","guid":{"rendered":"http:\/\/cimss.ssec.wisc.edu\/satellite-blog\/?p=2080"},"modified":"2009-03-06T15:14:05","modified_gmt":"2009-03-06T15:14:05","slug":"ship-tracks-over-the-gulf-of-alaska","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/archives\/2080","title":{"rendered":"Ship track plumes over the Gulf of Alaska"},"content":{"rendered":"
\"GOES-11<\/a>

GOES-11 visible images<\/p><\/div>\n

An impressive display of “ship track” plumes was seen on GOES-11 visible images (above; <\/strong>also available as a QuickTime animation<\/a>)<\/strong><\/em> over the Gulf of Alaska on 04 March 2009<\/strong><\/a>. Most of the ships in that region were traveling in a westward or a northwestward direction, but you can also see a handful of ships that were moving fairly quickly toward the northeast.<\/p>\n

The corresponding GOES-11 3.9 \u00c2\u00b5m shortwave IR images (below; <\/strong>also available as a QuickTime animation<\/a>)<\/strong><\/em> confirm that these features are indeed ship tracks — the solar reflection of the ship track plumes (which were composed of rather small water droplets)<\/em> caused an increasingly “warm signal” (darker gray enhancement)<\/em> to appear as long as the sun angle was high. Note how this “dark\/warm signal” was absent at the beginning and at the end of the animation, when the sun angle was low in the early morning and in the early evening hours.<\/p>\n

\"GOES-11<\/a>

GOES-11 3.9 \u00c2\u00b5m shortwave IR images<\/p><\/div>\n

A 1-km resolution NOAA-17 AVHRR visible image provides a closer view of the ship tracks (below)<\/strong><\/em>.<\/p>\n

\"NOAA-17<\/a>

NOAA-17 AVHRR visible image<\/p><\/div>\n

Using McIDAS to track the motion of the leading edges<\/strong> of 4 of\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 the northweastward-moving ship tracks yielded forward ship speeds of 15-25 knots (below, <\/strong>courtesy of Rick Kohrs, SSEC)<\/strong><\/em>.<\/p>\n

\"GOES-11<\/a>

GOES-11 3.9 \u00c2\u00b5m shortwave IR + ship track speed\/direction vectors<\/p><\/div>\n

\"GOES<\/a>

GOES visible images + GOES satellite-derived winds<\/p><\/div>\n

AWIPS images of the GOES visible channel with an overlay of GOES-derived satellite winds (above; <\/strong>also available as a<\/em> QuickTime animation<\/a>)<\/strong><\/em> displayed a number of wind vectors in the region of the ship track plumes, but all the winds in that particular area were assigned heights within the 775-600 hPa layer. The height assignments for these winds seem a bit too high though, given that studies such as\u00c2\u00a0 Durkee et al (2000)<\/a><\/strong> found that most ship tracks formed in marine boundary layers that were between 300 and 750 m deep. Nearly all of the satellite winds in the ship track region were derived using the GOES visible channel<\/strong><\/a>.<\/p>\n

An AWIPS image of the ASCAT scatterometer winds (below)<\/strong><\/em> confirmed that the surface winds were turning anticyclonically over the region where many of the ship tracks were exhibiting a strongly-curved appearance (before higher clouds moved overhead and obscured their view)<\/em>. The speeds of the ASCAT winds were similar to those of the GOES winds (generally 10-15 knots)<\/em>.<\/p>\n

\"GOES-11<\/a>

GOES-11 visible image + geostationary satellite and ASCAT winds<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

An impressive display of “ship track” plumes was seen on GOES-11 visible images (above; also available as a QuickTime animation) over the Gulf of Alaska on 04 March 2009. Most of the ships in that region were traveling in a westward or a northwestward direction, but you can also see a handful of ships that […]<\/p>\n","protected":false},"author":18,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[22,18,8,25],"tags":[],"class_list":["post-2080","post","type-post","status-publish","format-standard","hentry","category-avhrr","category-goes-11","category-marine-weather","category-satellite-winds"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/2080","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/users\/18"}],"replies":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/comments?post=2080"}],"version-history":[{"count":22,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/2080\/revisions"}],"predecessor-version":[{"id":2102,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/2080\/revisions\/2102"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media?parent=2080"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/categories?post=2080"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/tags?post=2080"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}