{"id":1127,"date":"2022-12-17T23:35:23","date_gmt":"2022-12-17T23:35:23","guid":{"rendered":"https:\/\/tomeri.org\/journal\/?p=1127"},"modified":"2024-08-10T21:42:44","modified_gmt":"2024-08-10T21:42:44","slug":"snow-crenellations","status":"publish","type":"post","link":"https:\/\/tomeri.org\/journal\/2022\/12\/17\/snow-crenellations\/","title":{"rendered":"Snow Crenellations"},"content":{"rendered":"\n

Saturday, 17 December 2022<\/em><\/p>\n\n\n\n

I observed a curious phenomenon on my run today. I have been unable to find an authoritative account or name for it, so I will call them snow crenellations. <\/p>\n\n\n\n

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I noticed them on a long underpass with a wooden rail that passes beneath Lyndale Ave along Minihaha creek. At first glance it looks as though a very methodical child brought a stick down upon the snow every foot or so — but gently so that a depression was created that did not go all the way to the rail. At second glance one becomes impressed with the energy of the child, because the underpass is perhaps a quarter of a mile long. At third glance, one notices that the (increasingly hypothetical) child only acted on the rail on the south side, and entirely skipped a segment of the rail that veered off at an angle as the underpass approached its end. I think nature is the more likely culprit.<\/p>\n\n\n\n

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Close up of crenellations<\/figcaption><\/figure>\n\n\n\n
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Looking one way<\/figcaption><\/figure>\n\n\n\n
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Looking the other way<\/figcaption><\/figure>\n<\/figure>\n\n\n\n

<\/p>\n\n\n\n

About a quarter of a mile west on the path, I noticed another section of fence (albeit with a different top) that showed similar crenellation, although it was not so clean or distinct. On returning home I took a short walk and saw other instances of crenelation, though sometimes it devolved into humps or subtle ripple-patterns.<\/p>\n\n\n\n

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Crenellations on alley fence <\/figcaption><\/figure>\n\n\n\n
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Regular troughs…<\/figcaption><\/figure>\n\n\n\n
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Subtle waves: north-facing side<\/figcaption><\/figure>\n<\/figure>\n\n\n\n

<\/p>\n\n\n\n

For now I assume that this is due to snow ablation due to melting or sublimation that that creates a surface texture that leads to a positive feedback loop, similar to what one sees with suncups<\/a> or penitente<\/a>.
<\/p>\n\n\n\n

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Ablation hollows can be formed either by turbulent heat transfer or by radiative heating. With dirty snow, formation by turbulent transfer is favoured. Under a heat budget dominated by sensible heating, accumulations of detritus and their concentration by the normal-trajectory path can result in the initiation of a positive feed-back mechanism for the formation of ablation hollows; this occurrence is dependent on the thickness of the detritus, its albedo, and its heat conductivity.<\/p>\n\u2014 https:\/\/www.cambridge.org\/core\/journals\/journal-of-glaciology\/article\/mode-of-formation-of-ablation-hollows-controlled-by-dirt-content-of-snow\/F12E89574ABAD5FC84600BDE7C6133C3<\/cite><\/blockquote>\n

Views: 10<\/p>","protected":false},"excerpt":{"rendered":"

Saturday, 17 December 2022 I observed a curious phenomenon on my run today. I have been unable to find an authoritative account or name for it, so I will call them snow crenellations. Views: 10<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":4,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"federate","footnotes":""},"categories":[1,34,72,68],"tags":[],"class_list":["post-1127","post","type-post","status-publish","format-standard","hentry","category-daily_entry","category-has-pictures","category-ice-crystals-etc","category-nature"],"_links":{"self":[{"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/posts\/1127","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/comments?post=1127"}],"version-history":[{"count":9,"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/posts\/1127\/revisions"}],"predecessor-version":[{"id":1170,"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/posts\/1127\/revisions\/1170"}],"wp:attachment":[{"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/media?parent=1127"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/categories?post=1127"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tomeri.org\/journal\/wp-json\/wp\/v2\/tags?post=1127"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}