Mar 27, 2021 09:00:00

Why are desert nights so cold?

The image of a desert is that it is dry and hot, but in reality the temperature difference between daytime and nighttime is very severe, and even if the average temperature during the daytime exceeds 30 degrees Celsius, it can cool down to below freezing at nighttime. There is. Live Science, a scientific media outlet, summarizes why desert nights are so cold and how desert creatures adapt to severe temperature differences.

Why do deserts get so cold at night? | Live Science

https://www.livescience.com/why-do-deserts-get-cold-at-night.html

Live Science explains that the extreme temperature difference in the desert is due to the combination of two factors, 'sand' and 'dryness.' When the heat of the sun hits the sand that covers the desert, the top layer of sand absorbs and releases the heat, raising the temperature of the surrounding air. However, sand cannot store heat because it releases heat immediately, and when the sun hides at night, it gets cold at once.

If the night temperature drops only because of sand, it is presumed that the temperature will drop sharply on sandy beaches in summer as well. However, while the sandy beaches are cool at night, they don't get cold enough to have to put on a coat at night. Live Science, on the other hand, cites 'dryness' as another factor in the rapid temperature drop in the desert.

The desert air is very dry, and the humidity in the air can be near zero , especially in low-precipitation deserts such as the Sahara and Atacama deserts. Zero humidity means that there is almost no water vapor contained in the air, and unlike sand, the lack of water that has the ability to store heat has a great effect on temperature. Water vapor in the air traps heat near the ground, which prevents extreme temperatures from dropping even at night without the sun, but in dry deserts water vapor does not store heat. Therefore, when the heat of the sun does not reach at night, it seems to cool down at once.

Despite the rapid temperature changes during the day and at night, there are many different creatures in the desert. 'Desert temperature changes tend to be relatively small problems for living things, and the bigger problem is finding enough food and water to survive,' said

Dale DeNardo, a professor of desert animals at Arizona State University. That's it. '

Reptile, which is a kind of animal that most live in the desert, body temperature varies depending on the surrounding environment temperature heterothermic is, you do not need to and also chilly trying to maintain their own body temperature. Poikilotherms use valuable energy for hunting instead of using energy to maintain a constant body temperature.

On the other hand, mammals such as camels are homeothermic animals and need to maintain a constant body temperature in order to maintain their body function. Therefore, the desert environment, which is exposed to the heat of the sun during the day and cools to below freezing at night, is harsh for mammals, but camels succeeded in maintaining a constant body temperature by acting as a heat insulating material with fat and thick fur. That's what Professor De Nardo says.

In addition, birds living in the desert cool their bodies using

heat of vaporization (heat of vaporization), which takes heat when the liquid changes to gas, like humans who sweat and dogs that stick out their tongues. .. Birds can fly to distant waters quickly, and some vultures may urinate to cool their feet.

Although animals can tolerate changes in temperature in a variety of ways, plants are more vulnerable to temperature changes, and Professor De Nardo commented, 'Plants face bigger problems than animals because they can't move.' Cacti that grow in the desert protect themselves with thorns and poisons so that precious water is not taken away by animals, but if the temperature at night drops too low, the water in the tissue freezes and swells, and the wounds that do not heal It seems that you may bear the burden. Therefore, desert plants are said to grow only in places where the nighttime temperature does not drop below 0 degrees Celsius for more than 2 hours, and this standard is called the 'freeze line'.

Global warming has been regarded as a problem in recent years, but it is uncertain how its effects will appear on the flora and fauna of dry deserts. But Professor De Nardo commented, 'There will definitely be changes. Most deserts are expected to have an average temperature rise of 1.7-2.2 degrees Celsius.' The biggest problem is that the annual rainfall in the desert, which is already low, may be further reduced, and the flora and fauna that depend on the slight rainy season may be seriously damaged.