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Gary350
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Joined: Mon Mar 23, 2009 1:59 pm
Location: TN. 50 years of gardening experience.

How is it possible to have frost at 38 degrees F, water freeze at 32 ?

I asked this question on the Physics forum after they explained I under stand it. You need to change how you think to under stand this. You need a very short Physics class lesson.

1. There is no such thing and cold energy. Cold is the absence of energy.

2. Heat is a form of radiation. Objects that are warm or hot have more heat energy.

3. If earth had no sun earths temperature would be -285 degrees F below 0.

4. Every day earth is heated by the sun. Every night heat radiation is lost into outer space. Clouds block heat radiation loss.

5. Every thing has a heat transfer rate. Example, Aluminum cools faster than steel. Aluminum heats up faster than steel.

6. Water is the standard by which all heat transfer rates are compared. Water has heat transfer rate of 1.

7. After dark all things give off radiation into outer space very fast if clouds are not blocking heat loss into outer space.

8. After dark every thing on earth tries to cool down to -285 degrees F below zero. Clouds slow this down by blocking radiation loss into outer space.

9. Plant leaves have a very high heat transfer rate they loose heat radiation into outer space faster than air.

10. A laser pointer thermometer will show plant leaf temperature can be 31 degrees F covered with frost at 5 am while air temperature is 38 degrees on a clear night with no clouds in the sky.

11. Heat loss radiation is no different than light from a flash light it goes throw invisible air and is gone into outer space at the speed of light. That is why covered plants get no frost heat radiation can not leave easy into outer space.
Last edited by Gary350 on Thu May 21, 2020 10:31 am, edited 1 time in total.

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applestar
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Joined: Thu May 01, 2008 7:21 pm
Location: Zone 6, NJ (3/M)4/E ~ 10/M(11/B)

Wow thanks for sharing this nugget/gem. I love it! :-()

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TheWaterbug
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Joined: Mon May 02, 2011 5:15 pm
Location: Los Angeles

https://glossary.ametsoc.org/wiki/Evaporation_frost
Last edited by TheWaterbug on Thu May 21, 2020 4:40 pm, edited 3 times in total.

told2b
Senior Member
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Joined: Thu Nov 06, 2014 4:07 pm
Location: North Jersey, Zone 6

Firefox detected a potential security threat and did not continue to glossary.ametsoc.org. If you visit this site, attackers could try to steal information like your passwords, emails, or credit card details.

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TheWaterbug
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Posts: 1082
Joined: Mon May 02, 2011 5:15 pm
Location: Los Angeles

Bleah. The forum is automatically putting a "s" after the "http", but the site is not secure. There's not inherently wrong with a site that doesn't use https, especially if it's not collecting any data, but visiting any site with https when it doesn't have a secure connection will generate that warning.

Anyway, here's what that site says:
evaporation frost

Frost caused by evaporative cooling due to dry winds over a moist surface, where the wind temperature is above freezing, but cooling below freezing occurs due to latent heat loss.

Agricultural term, where evaporation freezes the crop.

Nyan
Senior Member
Posts: 103
Joined: Thu Mar 24, 2016 10:44 pm
Location: North Alabama Zone 7B

Kinda like the evaporative home cooler I had in AZ. Just a fan blowing air through a flowing water mat, but it could be 112 outside and 62 degrees inside the house due to the water evaporation cooling effect.

Wish we could use them in the humid southeast...



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