Clouds 101: Pyrocumulus/ Pyrocumulonimbus Clouds

4/18/2013


Weather can be sneaky many times. It can play around with certain elements and conditions to create disasters and at the same time it can be kind enough to pour down exactly what makes a heaven-sent delight. Today I'm referring to a potent and magnificent mixture of forest-fires, droughts, cumulus clouds, strong winds, humidity, volcanoes, eruptions, columns of fiery rage and ease that extinguishes all flames. Let's start with forest-fires which as we know can be a natural ocurrence or man-made. Sometimes those same fires can actually create their own weather. Envision a ghastly, mad and angry fiery monster that feeds on and spits out flames, thunder and lightning. Forest fires can sometimes become unmanageable and inpredictible and strong enough to create their own weather systems of thunderstorms and rain. Forest fires are a powerful heat source on the ground and the rising hot air from the fire can create a local kind of cumulus cloud called a Pyrocumulus cloud. The prefix "pyro" comes from the Greek word for fire obviously indicating that pyrocumulus clouds are most likely to be found above a large fire. The heat source may be natural such as a volcanic eruption or forest fire or man-made.

Vrijeme ponekada umije da bude bas podlo i da se poigra sa odredjenim elementima i uvjetima kako bi kreiralo katastrofe. Istovremeno moze i da bude blago i milosrdno da izlije dugo ocekivano olaksanje. Danas govorim o mocnoj mjesavini sumskih pozara, susa, kumulusnih oblaka, jakih vjetrova, vlaznosti, vulkanima, erupcijama, stubovima vatrene stihije te olaksanja koje gasi sve plamene jezike. Pocnimo od sumskih pozara za koje svi znamo da mogu biti prirodna pojava ili da ih prouzrokuje covjek. Ponekada ti isti pozari mogu i sami kreirati vlastite vremenske uslove. Zamislite grozomorno, bijesno i pomahnitalo cudoviste koje guta i bljuje vatru, munje i grmljavinu. Sumski pozari se nekada mogu oteti kontroli i biti potpuno nepredvidivi te dovoljno snazni da stvore vlastite vremenske sisteme oluja i kise. Sumski pozari su mocan izvor topline na povrsini tla i taj vruci zrak koji se iz pozara izdize moze proizvesti vrstu kumulusnog oblaka pod nazivom Pirokumulus (pyrocumulus). Prefiks "pyro" potice od grcke rijeci za vatru sto direktno upuje na cinjenicu da se ovi oblaci najcesce formiraju iznad velike vatre. Izvor topline moze biti prirodan u vidu vulkanske erupcije ili spomenutog sumskog pozara i da ga je covjek izazvao.



The mechanism behind the creation of this amazing and fierce cloud is relatively simple and is pretty much identical with the formation of a regular cumulus cloud, just a tad hotter. Warm air from the fire is lighter than cool air and it rises up into the atmosphere but when it rises up to certain levels in the atmosphere, it inevitably gets in contact with colder air which cools it down. When this air cools, the moisture it carries condenses into water droplets, much the same way that water droplets condense on the outside of a glass of ice water. Where does the moisture come from? The hot air that is created from all the trees and plants burning also contains the moisture that was in plants burned by the fire, plus water from streams and ponds. That moisture along with ash and debris is pulled upward by moving air currents and that's the reason why pyrocumulus clouds are likely to be brownish or grayish unlike the pretty, crisp white regular cumulus clouds. You know, the ones kids usually draw and remind me of popcorn and cotton candy. The cute ones. Pyrocumulus clouds can be considered to be their nasty counterparts. So the fires create smoke columns which can get very large, the top of the column can be 20, 30 even 50,000 feet. It is difficult to locate the bottom of a pyrocumulus cloud as it is often obscure by the ash generated by the fire or the volcanic eruption. Pyrocumulus clouds are basically a cumulous cloud that is fed by the fire. If lots of water vapor is available, the pyrocumulus can develop into a cumulonimbus which is called a Pyrocumulonimbus (PyroCb) or evolve into the thunderstorm phase. When it does reach that phase it gets affected by high winds exactly like regular thunderstorms and that's how you get lightning and rain. Lightning from pyrocumulus clouds can actually start other fires. At the same time, rain from pyrocumulus clouds can sometimes put fires out. The biggest concern for firefighters when these conditions develop is the wind. Downdrafts created by the thunderstorm conditions can cause fires to suddenly switch directions, and can even causes powerful tornados of fire. A similar cloud can form above an erupting volcano because lava which is brought to the surface from deep underground contains moisture, which is added to any moisture from plants consumed by lava flows. Pyrocumulus clouds have also been seen above the biggest fires in cities or at large industrial sites like refineries.

Mehanizam koji stoji iza formiranja ovog nevjerovatnog i divljeg oblaka je relativno jednostavan te je skoro identican formaciji obicnih kumulusnih oblaka, samo sto je malcice topliji. Vruc zrak koji dopire od pozara je laksi od hladnog zraka i podize se u atmosferu ali kada dosegne odredjene nivoe atmosfere dolazi u kontakt sa hladnim zrakom koji ga ohladi. Kada se ohladi ovaj prethodno vruc zrak, sva vlaga koju je donio kondenzira se u kapljice vode na vrlo slican nacin na koji se vodene kapljice kondenziraju na vanjskoj strani case u kojoj se nalazi hladna voda. Odakle ta vlaga? Vruci zrak koji nastaje sagorijevanjem drveca i biljaka naravno da sadrzi i vlagu iz tih biljaka i drveca plus tu imamo i vodu iz okolnih potoka i jezera. Oslobodjena sagorijevanjem, zajedno sa pepelom i ostalim nusproduktima sagorijevanja, biva podignuta u visinu snaznim strujanjem vjetra i to je razlog zbog kojeg su pirokumulusi smedjkaste ili sivkaste boje za razliku od lijepih, cisto bijelih obicnih kumulusa. Znate na koje mislim oblacice? Njih djecica crtaju po svom djecijem nebu a mene podsjecaju na kokice i secernu vunu. To su najsladji pufnasti oblacici. Pirokumulusni oblaci bi mogli biti njihove zloceste polovine. I tako pozari stvaraju stubove dima koji mogu biti uistinu ogromni. Do te mjere da im vrh doseze 20, 30 pa nekada i 50,000 stopa. Tesko je odrediti bazu pirokumulusa zato sto je mutna i sakrivena pepelom pozara ili vulkanske erupcije. Pirokumulusi su u sustini kumulusi koji se hrane vatrom. Ako je u igri ogromna kolicina vodene pare ovi pirokumulusi se mogu razviti u kumulonimbus (olujni oblak) kioji se onda zove Pirokumulonimbus (Pyrocumulonimbus/PyroCb) koji ce da se razvije do faze potpuno formirane oluje. Kada dodje u tu kompletnu olujnu fazu podleci ce utjecajem visinskih vjetrova bas kao i obicni olujni oblaci i tako dobijemo grmljavinu, munje i kisu. Munje iz pirokumulusa mogu da izazovu nove pozare. U isto vrijeme, kisa koja pada iz pirokumulusa moze nekada i da ugasi pozar. Ono cega se vatrogasci najvise pribojavaju su uslovi koji se mogu razviti zbog vjetra. Struje vjetra koje pusu ka tlu iz pirokumulusa mogu promijeniti smjer pozara te nekada i prouzrokovati strasni tornado od vatre. Slican oblak se moze proizvesti iznad vulkana koji eruptira zbog lave koja putuje iz velikih dubina do povrsine i sa sobom nosi vlagu. Ta vlaga se onda pomijesa i sa kolicniom vlage iz biljaka koje je lava progutala. Pirokumulusni oblaci su vidjeni i iznad najvecih pozara u gradovima ili velikih industrijskih mjesta i rafinerija.


Image Source
Pyrocumulonimbus clouds caused by volcanic eruption
Pirokumulonimbusni oblaci izazvani vulkanskom erupcijom
Man-made Pyrocumulus 
Pirokumulusi izazvani covjekovim djelovanjem

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22 comments

  1. Hello from Spain: A very informative post about the weather. Some very interesting photos. Keep in touch

    ReplyDelete
    Replies
    1. Hello Baribie lover! <3 I remember you well, thank you for reading this post. I am thrilled when people are interested in clouds as much as I am :)

      Delete
  2. JAko volim tvoje postove o oblacima. :) Bas sam ga sad sa uzivanjem procitala.

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    Replies
    1. Ozbiljno? Nece biti sretnije osobe od mene ako neko stvarno voli citati ono sto pisem o oblacima i vremenu! Meni je srce kao kucerina koliko si me usrecila! <3 <3 <3

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  3. Obožavam promatrati oblake, priroda je potpuno nevjerojatna :)

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    Replies
    1. Jao i ja, jos otkako sam bila malecka djevojcica :))
      Priroda je skroz super i drago mi je sto je otvoreno volis. Jos ima nade za nas ljude :))

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  4. Replies
    1. Hvala ti puno, ako nista, barem su fotkice interesantne :)

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  5. sve sam ti slikice maznula!!!!

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    Replies
    1. Neka si! :)) Sto god te zanima ili ti se dopada, sve mi uzmi! (..evo me kao neki refren turbo folk pjesme hahaha :)))

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  6. U 1. razredu gimnazije učila sam nazive oblaka, sad sam se malo podsjetila, haha :D Priroda je uistinu fascinantna i drago mi je da si podijelila s nama ove slike :)

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    1. Haha znaci sjecas se da su nam ih onako ovlas spominjali :)) Bas mi je drago iz nekog razloga i da, prirodu strasno volim a moje je ogromno zadovoljstvo podijeliti sa vama ove krasote :)) Jos je vece zadovoljstvo znati da ih neko gleda i da cita ono sto napisem <3

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  7. Stunning!

    www.shareasecret.wordpress.com

    xoxo

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  8. really interesting post! great :)

    ReplyDelete
  9. hello new follower here
    Following you in bloglovin and GFC :)
    Hope you can follow me back
    Wish you could join my celebration :)

    1st Blog Anniversary giveaway (international) !!

    ReplyDelete
    Replies
    1. Hello Prerana, thanks for liking and following my blog :)
      I will surely follow back and join your wonderful giveaway! <3

      Delete
  10. Nice blog you have...wanna follow each other?
    please follow with GFC, just leave me a comment and I'll follow u back!
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    Replies
    1. Hello Elisa, I will visit you blog as soon as I can <3

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  11. Wow amazing pictures, nice post to see with time! Great.

    Big kiss from Barcelona!

    Check my new illustration on the blog for my new project. Hope you like!

    Álvaro - LESEASONNIER.COM

    ReplyDelete
    Replies
    1. Hello hun, thanks for stopping by and for not forgetting about me and my blog :))
      I will visit straight away! <3

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