Why Is The Desert Cold At Night?

Thirty years ago I took my fiancée canoeing down the Green River in Utah for a week in July. It was on that trip that I learned that after camping in sand for several days, certain activities are extremely problematic.

When we went to bed, it was too hot to sleep, and when we woke up it was too cold to sleep. Because of the lack of humidity, temperatures would plummet over night. This is due to :

  • lack of greenhouse gas H2O
  • lack of vegetation to release heat
  • lack of latent heat of condensation
  • cold air sinking to the river bottom

About stevengoddard

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49 Responses to Why Is The Desert Cold At Night?

  1. Sleeping, the inactive activity.

  2. nickreality65 says:

    Eh, yep! And the black body radiation into a clear black sky. Might be different with an overcast, cloudy sky.

  3. Barrowice says:

    Camping in sand with a “girlfriend” can cause allsorts of untold irritation!

  4. There Is No Substitute for Victory says:

    What I want to know is if it was at first too hot to sleep… how did you manage to wake up from your conscious non-sleep state?

  5. jae43 says:

    It’s due solely to altitude.

  6. jae43 says:

    Phoenix and Atlanta are at the same elevation and latitude, and yet it is always hotter in the summer (on average) in Phoenix–day and night, despite all the greenhouse gas (water vapor) and clouds in Atlanta. Most deserts are high in elevation, so it gets cold at night and hot in the day. Look at the weather in Alamosa, which is certainly not a desert!

  7. jae43 says:

    See new PNAS article: http://hockeyschtick.blogspot.com/2014/11/new-paper-changes-fundamental.html
    The idea that the “atmospheric greenhouse effect” is caused by radiation is laughable.

  8. Mike Haseler says:

    You’ve missed it altogether. The main reason it is colder is because of lack of cloud cover. To give an example in Scotland, with cloud cover the IR thermometer reads around 6C, without cloud, it reads about -40C.

    And from outside the planet, the effect of the cloud, is that “space” sees a layer of suspended water at a colder temperature than the land surface. Therefore less heat is radiated.

    • Streetcred says:

      I think it was a ‘multiple guess-choice rhetorical’ question: lack of greenhouse gas H2O (cloud / humidity / etc)

  9. Billy Liar says:

    ▪ Separate tents?

    • emsnews says:

      The main question is, did his female companion make up for the fall in temperatures? We need to know more details. 🙂

  10. mkelly says:

    Steve says: “Because of the lack of humidity, temperatures would plummet over night.”

    Humidity is very important up north in winter. The dry Canadian air is sucks moisture out of furniture, skin and anything else exposed to it. We always have humidifiers out in the winter to assist with feeling warm.

  11. mjc says:

    There is no ONE factor that explains it. In fact, all the ones listed and probably more than that contribute to why it is colder, to some degree.

  12. spangled drongo says:

    Yes, Steve, all of the above but possibly mostly because [2] sand releases heat more than soil because of that lack of carbon, it just sucks out your body heat.

    Always made a bed of spinifex under my swag if I had to sleep in the sand hills.

  13. Rosco says:

    Surely convection is more significant than radiation where air temperature is concerned – 99% of the atmosphere apparently does not absorb or emit significant infra-red. How does it heat up or cool down ?

    I cannot believe anyone can actually claim that when the air temperature is 30+ C it is all due to the infra-red absorbing gases yet this is what is claimed by using the “greenhouse gas” argument.

    99% of the atmosphere has little interaction with infra-red but O2 and N2 undergo temperature changes every day, everywhere including at desert locations.

    The rapid cooling is due to an almost transparent atmosphere allowing the hot surface radiation to escape unimpeded and the clear skies allow unrestricted convection. This confirms the insignificance of 0.04% of the atmosphere that is the well mixed greenhouse gas – CO2.

    Cloudy skies restrict convection. Further, clouds are composed of a mixture of water drops and vapour and as such are more dense than the surrounding air and require a warmer temperature – an uplifting air current – to remain aloft.

    If convection were not a significant component of any surface cooling the warmed O2 and N2 would simply hang around maintaining a warm surface air temperature – while the surface (ground)temperature decreases – as happens when there is an inversion layer present.

    If O2 and N2 do not radiate significantly the only mechanisms available to lower air temperature are random collisions of molecules with IR active molecules – < 2% chance on average – or convection of these warmed molecules to altitude where their temperature – read kinetic energy in physics speak – is reduced by conversion to gravitational potential energy.

    But if they do not radiates significantly once warmed the only mechanism for loss of the gained energy is radiation to space – conversion from kinetic to potential energy is not energy loss – at least that is what thermodynamics teaches.

    • usJim says:

      Surely convection is more significant than radiation where air temperature is concerned – 99% of the atmosphere apparently does not absorb or emit significant infra-red. How does it heat up or cool down

      Too damn elementary; it is in contact with the ground (which is radiatively cooled) in what is termed ‘the boundary layer’. Geniuses like yourself otherwise have to explain how the temperature in Dallas goes down in the overnight hours in summer … WHEN OUR WINDS ARE FROM THE SOUTH FROM THE GENERAL DIRECTION OF HOUSTON! (Which, BTW, generally runs hotter than Dallas.)

      (No wonder the blog’s host becomes exasperated with “you people’.)

      Some of you people apparently have spent ALL your time in Mom’s basement, never experiencing even the most basic and elementary of meteorological events!

  14. Cheshirered says:

    Much as your dedication to solving the riddle of ‘climate change’ are appreciated, Steve, it would appear you had other research in mind on this particular field trip.

  15. Cheshirered says:

    ‘Are, ‘is’, ah bugger. Hate typo’s!

  16. All that weed made you sleep for 3 months, and you woke up in winter!

  17. SteveO says:

    You weren’t being too subtle about the greenhouse effect or the personal thing: it’s about power and energy 🙂 The resistor example, the dam example, the snuggling. Look at instantaneous power, multiply by time. This fits all of those models.

  18. Baa Humbug says:

    I have a couple of observations.
    ‘Sandman’ Steve is again describing what happens AT NIGHT in desert climes vs tropical humid climes.
    Yet THE EXACT OPPOSITE hapens during daylight hours.
    To determine if the net effect is one of warming or cooling, one must determine which effect is larger.
    Until such time, name calling and denigrating those who will not accept claims without evidence is behaviour no different to that of CAGW activist alarmist rentseekers.

    • I’m not discussing the “net effect”
      That is a different discussion. Why are you conflating them?

      • Baa Humbug says:

        I am conflating them Tony because talking about the effects of ghgs at night is only half the story.
        If I was to use the differences between deserts and tropics during daylight hours to claim CO2 cools, I’d be rightly chastised.
        Tony, you’ve made a bold claim, fair enough. But you need to also provide bold evidence to back up your claim. This you’ve done by talking about deserts and tropics, but you refuse to acknowledge that your evidence can also be used to refute your claim, which I’ve done by pointing out what happens during daylight hours is the exact opposite of what happens during night hours.
        The reason why your claim is bold (IMHO) is because almost ALL of our life experiences tell us that the presence of H2O – the overwhelming greenhouse gas – means cooler temperatures. Coastal land is cooler than dry inland, around any major body of water is cooler, tiny oasis in the desert is cooler etc etc.
        I understand that the above fact doesn’t disprove your hypothesis, but nor have you proven anything after having made the bold statement (s).
        Calling people stupid, or claiming that this subject is simple does no service, especially since this site quotes Feynman so often.
        I believe you’ve done a power of legitimate work to expose the scam perpetuated by the activists, you are a leader in this field. That’s why it makes it so disappointing when I read some of your denigrating comments about those with a different view.
        P.s. The moment you present empirical evidence to back up your claim, I will change my view.

        • emsnews says:

          I am a child of the Desert.

          Humidity makes it warmer at night. Zero humidity makes it colder. The desert, when night falls, becomes VERY cold especially the driest deserts: the Sahara, central Australia and where I lived once up on a time, Death Valley!

          The sun is HOT, the moon at night is cold! The minute the sun sets, a wind arises and the temperature plunges so by dawn, it drives all the reptiles into their burrows and it is why owls and mice love things, being warm and covered by fur or feathers.

          Not to mention the nocturne coyotes.

        • I didn’t make a bold claim at all. All I said is that the greenhouse effect is real – basic physics. It always astonishes me when people start arguing with me over things I didn’t say.

        • Baa Humbug says:

          @ Tony
          Please don’t be indignant about simple descriptive words.
          Your claim may not be bold to you, but it is bold to me (and I did explain why I thought the claim was bold did I not?).
          Nevertheless, lets not get hung up about it, take out the word ‘bold’ from my comment and respond to the rest.

          p.s. Yes I realise you claim CO2 is saturated and further additions makes very little difference if at all, but what’s already there causes a greenhouse warming effect. You used the desert situation as evidence to back up your claim of that greenhouse warming effect, I believe I countered that. You need to come up with new evidence, hopefully without the use of ‘stupid’ ‘simple’ and ‘basic’.

  19. Pasinby says:

    Sounds to me , what you did make , was a very poorly planed camping trip Tony !

  20. slimething says:

    On the flip side, deserts are hotter during the day time than tropical regions at the same latitude. Water plays a role in cooling as well.

  21. gymnosperm says:

    Something like the greenhouse effect is real, but the everyman notions like your car getting hot in the parking lot and greenhouse gasses acting like a blankets are not good analogies. A greenhouse is not a good analogy.

    Gasses not resonating are generally transparent to radiation so dry desert nighttime air lets lots of radiation escape to space and it gets cold. Rocks are different. Exactly how it works is somewhere on the frontier of physics but they obviously figure out a way to warm in shorter wavelength sunlight and radiate in long wave which your body absorbs like the rocks along with the radiation from the sun. All of this makes you rather unpleasantly warm in July on the Green River until you jump in and have another beer.

    July is usually before the monsoon kicks in and atmospheric moisture and towering thunderclouds move in from the gulf. When this happens the clouds (and that smattering of CO2) absorb the incoming long wave, reflect a lot of visible back to space, and leave only the measly UV and the remains of visible along with their recycled LW to warm you and the rocks. You quit worrying about your beer supply. At night the water in the air flings LW photons back at you instead of letting them off to space. Towards dawn these photons are actually warming the rocks.

    The earth would be more like a desert with less water in the air. Duh. That is the “greenhouse” effect.

    Congratulations on your float down the flat water section of the Green.

  22. 9NEWS meteorologist Kathy Sabine in her forecast tonight for the Denver metro area:

    … as the snow ends and the skies clear temperature’s going to drop like a rock without that blanket of clouds …

  23. philjourdan says:

    Actually, that is when you change your schedule. You do not go to sleep at dark, but play as it is finally cool enough to be outside. Then around midnight or so, you can wind down and get some sleep and get some good sleep because the temperature is good sleeping weather. Just do not get up with the sun (wait a couple of hours).

    I only “live” in the desert 2 weeks of the year. And it can be interesting when you are wearing shorts, the sun goes down and you get goosebumps on your legs. But then who wants it hot at night?

  24. MarcT77 says:

    Don’t forget the visibility, it often goes down with humidity. Also, humidity might be a greenhouse gas, but most of its effect on weather is unrelated to this fact. Saying that all weather is caused by greenhouse gases is like saying that all weather is caused by electrons. Electrons are present in all weather events.

    If we look at the greenhouse effect objectively, it is like putting a fishnet a few meters off the ground. If the threads are 1/8 in. wide, they have to be separated by about 6 to 12 in. in both directions. This is not going to have a huge impact on the diurnal temperature range.

    People like to use the blanket or coat analogies. But those are put on when the temperature gets colder. If some people put them on when the temperature got warmer, they would seem to increase the difference of temperature.

    In winter, if you put your coat on for a full hour before you go out, you feel very warm inside the house and pretty cold when you go outside. The reason you feel the variation is simple. Inside the house, your coat was in thermal equilibrium with the room temperature. So it was emitting as much as your body would have without the coat. So you lose the same amount of heat in both cases. But the coat might slow down the feeling of cooling if it has a large thermal capacity. In this case, the coat would take most of the hit.

    So the diurnal temperature range can change in two ways. The daily variation in heat content changes. Or the region of the atmosphere that experiences the variation in heat content changes.

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