{"id":10658,"date":"2014-05-24T19:15:51","date_gmt":"2014-05-25T02:15:51","guid":{"rendered":"http:\/\/blog.kootenay-lake.ca\/?p=10658"},"modified":"2014-05-24T19:15:51","modified_gmt":"2014-05-25T02:15:51","slug":"advection-fog","status":"publish","type":"post","link":"https:\/\/blog.kootenay-lake.ca\/?p=10658","title":{"rendered":"Advection fog"},"content":{"rendered":"

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Advection fog is the name given to the fogs that form, usually in the summer, when warm moist air from the land flows offshore (is advected) over a much colder ocean. Simple books will claim that it is merely the cooling of the air that produces the fog. Curiously, this is not true. It is also not true that such fogs are confined to oceans. The one that formed\u00a0last night was on a lake.\u00a0<\/p>\n

Condensation can result from two distinctly different processes: either the cooling of\u00a0water vapour,\u00a0or the mixing of two parcels of vapour\u00a0with different temperatures and moisture content. The latter process does not involve a net cooling, because\u00a0at the end of the mixing, the average temperature remains\u00a0unchanged.\u00a0<\/p>\n

Familiar examples of condensation produced by vapour cooling are\u00a0found in cumulus clouds, wave clouds and dew. Familiar examples of condensation produced by mixing are seeing one’s breath on a cold day, and\u00a0the steam fog often seen in the fall when cold air (and so cold vapour) flows over a\u00a0still warm lake. The colder vapour mixes with that warmed by the lake and the fog appears in the form of tiny convective towers because it is warmed from below (e.g., steam fog<\/a>).\u00a0<\/p>\n

An advection fog forms in much the same way as steam fog, but upside down. Now the lake is cold and is overlain with warm vapour. Vapour mixing, not cooling produces the fog.\u00a0<\/p>\n

It is spring and the Lake is still cold from the winter. A few warm days were\u00a0followed by rain which moistened the air at the surface. The layer of fog seen at\u00a0the water surface is an advection fog caused when\u00a0the warmer vapour from above mixes with the colder vapour just above the water. It forms a stable layer because, unlike the (convective) steam fog, the\u00a0layer is cold below and warm above. However, on the side of the mountain, wisps of steam fog rise off\u00a0the warm, moist trees. Both fogs were formed by vapour mixing, but look different owing to one being convective and the other stable.\u00a0
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  Advection fog is the name given to the fogs that form, usually in the summer, when warm moist air from the land flows offshore (is advected) over a much colder ocean. Simple books will claim that it is merely … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[12],"tags":[],"class_list":["post-10658","post","type-post","status-publish","format-standard","hentry","category-weather"],"_links":{"self":[{"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=\/wp\/v2\/posts\/10658","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10658"}],"version-history":[{"count":3,"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=\/wp\/v2\/posts\/10658\/revisions"}],"predecessor-version":[{"id":10663,"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=\/wp\/v2\/posts\/10658\/revisions\/10663"}],"wp:attachment":[{"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10658"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10658"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.kootenay-lake.ca\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10658"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}