Radiation cooling

Apropos of nothing,

Anyway, here’s a question about cold. Currently, it’s 36 F degrees in Valley Village, CA. Yet I expect there to be frost on the roof of my house at 7 AM, even though the temperature won’t quite reach the freezing point of 32 F. When I was a kid in the San Fernando Valley, it seemed to get down to 28 F pretty regularly, but lately freezing temperatures are rare. As far as I can tell, the last time it got as low as 31 degrees F was December 28, 2015.

And yet in both December 2015 and December 2016, my Brazilian Bougainvillea bush was blasted by frost (recovering nicely by spring, fortunately).

My impression is that locally extremely low temperatures roll down off the roof onto the bushes. But how does that work? How does it get colder in some spots in my yard than the overall temperature?

iSteve
Los Angelenos Don’t Have a Lot of Different Words for “Snow”

A physics professor once explained this to me as a consequence of different types of heat transfer. Your roof and yard are not only attempting to match temperatures with the ambient air, although that constitutes the majority of the heat transfers going on. If the night sky is cloudless, they are also radiating heat into deep space. If there’s cloud cover or a canopy over the terrestrial surface, then that covering will radiate some heat back as a black body and the transfers more or less cancel. However, there is no such parity with deep space–heat radiated into the void is gone for good with no recompense. This can make a couple of degrees’ difference.

Looks like some people in the thread noted this as well. They also pointed out the much more obvious fact that cold air will pool in the lowest spot.

About Aeoli Pera

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10 Responses to Radiation cooling

  1. SirHamster says:

    David the Good has written about this, about micro-climates and deliberately creating/exploiting them for gardening.

    A tree can trap warmer air underneath it, or shade an area from sun during the day. A south facing wall can absorb heat all day and release it all night, functioning as a thermal battery.

  2. everlastingphelps says:

    The bush likely frosted as a result of evaporative cooling. Cold dry air settles, the dry air evaporates water from the leaves and ground and cools the surface. That’s likely also why it recovered — the process sucked out the excess water that would have crystallized inside the cells.

  3. Heaviside says:

    We sometimes get frost on the grass here during the coldest winders. It’s caused by transpiration (what EP said).

  4. Obadiah says:

    >Apropos of nothing

    I like where your head’s at. Let’s talk about emo music, the devil, his fallen angels, and the mass dissemination of occult themes under the guise of pop culture. Specifically, let’s talk about this song and music video:

    This video begins by portraying what we can assume to be a melonhead* brooding in his palatial tower, and then receiving some sort of note from a mysterious and elusive woman by way of what we can assume to be some sort of psychic communication. As the song picks up, the elite hermeticist melonboon walks over to the balcony area where he then delivers a torrent of charged, fiery oratory to a legion of enthralled, fervid cro-magnons.

    I think the mysterious woman who delivers the note to the singer is a female Traveler, who herself is under orders from Satan to deliver instructions to the Dark Meldar in the tower, who then uses his charisma to deliver the message to the mass of brainwashed human slaves.

    So what is the message he’s delivering to the human masses? Let’s look at the lyrics of the song to find out:

    Verse 1:

    “With just a look, they shook
    And heavens bowed before him
    Simply a look can break your heart
    The stars that pierce the sky
    He left them all behind
    We’re left to wonder why
    He left us all behind”

    “Heavens bowed before him”
    ^ Lucifer in Heaven

    “We’re left to wonder why
    He left us all behind”

    ^Lucifer’s angels, some of whom we now know as the Travelers

    Verse 2:

    “Dreams of his crash won’t pass
    Oh, how they all adored him
    Beauty will last when spiraled down
    The stars that mystified
    He left them all behind
    And how his children cried
    He left us all behind”

    “Dreams of his crash won’t pass
    Oh how they all adored him”

    ^Once again ruminating on Lucifer’s fall from grace.

    Finally, verse 3:

    “What’s the hook, the twist, within this verbose mystery?
    I would gladly bet my life upon it
    That the ghost you love, your ray of light will fizzle out
    Without hope
    We’re the empty set, just flowing through, wrapped in skin
    Ever-searching for what we were promised
    Reaching for that golden ring we’d never let go
    But who would ever let us put our filthy hands upon it?”

    “What’s the hook, the twist, within this verbose mystery?
    I would gladly bet my life upon it
    That the ghost you love, your ray of light will fizzle out
    Without hope”

    ^This is clearly referring to the intent of the demonic entities to make humans lose faith in God and the Holy Spirit.

    (*As one youtube commenter notes, the band’s lead singer is “really shaping up to be a great Final Fantasy boss”, to which another commenter replies, “Sephiroth maybe?”

    Indeed, and this is what the plot of Final Fantasy 7 is about.)

  5. Obadiah says:

    More weird stuff pertaining to AFI and the Travelers:

    Starting with Koanic’s original post on them:

    https://web.archive.org/web/20150322181812/http://www.koanicsoul.com/blog/2012/11/24/500-ziggurat-dwelling-demon-vampire-travelers-molest-melonhead-children-rule-the-world/

    If we look at AFI’s logo, it matches now-deceased melonhead Bane’s description of the Travelers:

    Bane:
    “As dawn broke, I awoke, and saw two human figures, with bat wings, flying up and over the trees, on a path from my car, to the Spanish house I have previously described.

    That was the last time I saw or felt their presence. I think they knew they’d worn out their welcome. Plus, as they looked into me, I looked into them. Dark. Dark. Dark. Not soulless, per se, but nothing you’d recognize as human.”

    https://ibb.co/S6dPzTQ

    Also, a search for the word “nephilim” on Urban Dictionary yields the follow definition as the seventh result:

    “Nephilim:

    an artistic logo that represents the once hardcore band, AFI. the nephilim is a bat with distorted eyes and tail, no feet.”

    (^It’s not a bat, but a fallen angel. No, Tex, ‘nephilim’ does not mean ‘feller’. It means ‘fallen’.)

    Finally, the date that the album “Decemberunderground”, upon which “Miss Murder” appeared was released on June 6, 2006.

    Koanic:
    “In this light, such stories as this one about the Illuminati become harder to ignore. Perhaps our pyramids have not disappeared after all, but only been replaced by more efficient means of occult dissemination and social control.”

  6. Obadiah says:

    The video for “Miss Murder” was also shot at Los Angeles City Hall:

  7. Obadiah says:

    “Spiritual beings exercise surprisingly little power in the material world. Their most extreme exercises of power are restricted to influence of human action, via illusions, suggestions, and selectively revealing esoteric knowledge. Thus, Satan’s influence is propagated by what I call the “demonic whispernet”, a disciplined intelligence network of allied spirits. These spirits influence events primarily through human collaborators who are cultivated for the purpose- roughly equivalent to double agents or house negroes in the antebellum. These collaborators are given greater power, responsibilities, and privileges in exchange- typically via esoteric knowledge and inclusion in the fraternity of empowered collaborators.”

    The lead singer of AFI has the sociopath chin to show for it.

  8. Aeoli Pera says:

    >Los Angeles City Hall:

    Subtle.

  9. Obadiah says:

    >Subtle.

    They went on the hit MTV show “Luciferianize my Municipal Building,” hosted by Xzibit.

  10. Obadiah says:

    He heard they liked pyramids so he put a pyramid on top of their pyramid so they can disseminate occult programming while they disseminate occult programming.

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