Let’s take the Sahara for example, it’s a lot closer to the equator, yet at night temperatures fall to -4c (25f). Yet in the uk which is a lot further away from the equator, the night temperatures are around 15c (60f) during the summer. Why is this?
In: 97
There are few clouds to trap heat, and no bodies of water that will absorb and retain the heat for longer.
Large bodies of water act as a temperature shock absorber. Water is relatively difficult to heat or cool. That means large bodies of water tend to stay about the same temperature despite the ambient air temperature. When the air cools at night, the warmer water heats the air. The opposite happens during day when the warm air is chilled by the cooler water (which is still the same temperature as it was 12 hours prior). In the desert, there is no water to do this resulting in larger temperature swings between night and day.
In a word, water.
– Little to no water in the air at ground level (humidity)
– Little to no water in the air up high (cloud cover)
– No water on the ground (lakes or seas)
Because water absorbs and retains heat, each of those things will limit how much temperatures can swing on a 24 hour basis.
Radiative cooling, but more specifically [nocturnal surface cooling](https://en.wikipedia.org/wiki/Radiative_cooling#Nocturnal_surface_cooling).
On cloudless nights (where clouds absorb and in turn re-emit IR back to the surface) the surface can cool very quickly with very large deltaT (change in temperatures)
This happens elsewhere, not just in deserts. But deserts tend to be cloudless due to lack of regional water.
It all has to do with the lack of humidity in the air. When it’s humid, we don’t sweat as quickly and the air doesn’t hold heat very well. Think of how air conditioners work, that water you see draining off the AC unit was in the air in the room it is cooling. In the desert, the air has less water in it, hence the sky looks bluer to us and feels colder when the sun is gone.
The sky is extremely cold. At night, clouds act as a blanket, keeping heat in. When there are no clouds, the temperature falls quickly.
I have something interesting for you. Not sure where you live. But if it is cold in the winter, bring in your (assumed natural) Christmas tree from outside and lay a thermometer below it when you cut the netting or string off the tree.
Clouds act like a blanket for the earth, keeping it warm at night. Clouds are made out of water droplets. Since there is no water in the desert, it has no blanket at night and so it gets really cold.
Water as other commenters have said, is very important to even out temperatures to an extent. The other thing with deserts is the lack of moisture in the air or anything except for ground. There is nothing to absorb the warmth during the day and radiate it at night. You have the hot ground but after the sun goes, it gets no more heat and a breeze can take whatever remaining heat away. If you are in a forest or somewhere with cliffs, rocky outcrops, etc, they will retain the warmth and release it within a kind of localized blanket. If there is none of that and no water, there is nothing to retain the heat, so it gets cold. Stupidly cold.
Please correct me if I am wrong. All of the provided answers so far have dealt with water/humidity as the causing factors. But could it also be said that densely populated areas (while obviously still having a different temp than the desert due to weather effects), also have higher temps due to lighting, electricity, and other factors caused by the urbanization of an area?
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