November 28, 2021

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If sand is the reason why deserts are hot during the day, what is cold at night?  |  Science

If sand is the reason why deserts are hot during the day, what is cold at night? | Science

In the 1962 Hollywood film Lawrence of Arabia, the hero of the film, a British lieutenant, travels through vast deserts for a few days, but it is not clear whether he will reach his destination or get lost and die endlessly in the desert.

When the hero of the film rests at night under the starlight, you will notice that he covers himself well with a heavy blanket. “Why does he have a blanket? Don’t the deserts get too hot?” “

The deserts are very hot during the day, but many do not realize that they can suddenly become cold at night. It may remind us of Mercury, the closest planet to the Sun, where the temperature drops to -170 degrees Celsius at night, while during the day it reaches 450 degrees Celsius.

Temperatures in the desert drop to an average of 42 degrees Celsius at night (communication sites)

But why is this happening in the desert? With the difference, of course, why might the temperature in the desert drop to an average of 42 degrees Celsius overnight?

According to the company NASA After sunset, temperatures can drop from an average of 38 degrees Celsius during the day to an average of -4 degrees Celsius at night. According to the site “Direct science(Direct science) It is a combination of two main factors: sand and moisture.

The sand heats the air

Sand is an interesting material; It is dry, but slippery, and its particles are larger than other types of soil, and this is the main reason why it does not absorb water well, as well as heat, and then hit the sand desert during heat and sunlight, absorbing the sand grains in the top layer of the desert, and then re-heating. It is released into the air by radiation, and the desert sand here acts as a glass and heats the air above the ground.

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You will notice that other landscapes such as forests, beaches, plains and mountains are not as hot as deserts because those deserts certainly do not spread in the air above their surface.

But if sand is the main reason why deserts are so hot during the day, what is it like to be cold at night?

In some arid deserts, such as the Sahara Desert and the Atacama Desert, the humidity is almost zero degrees (Getty Images)

Desert air and humidity

The main reason for the sharp change in temperature at night in the desert is that the desert air is very dry, and in some arid deserts such as the Sahara and the Atacama Desert in Chile, the humidity is almost zero degrees.

Unlike sand, water has a tremendous ability to store heat, so the vapor in the air, like an invisible giant blanket, clogs the heat near the ground and prevents it from dissolving into the atmosphere.

In normal terrain, when the sun warms the earth, it absorbs more heat. At night, when the sun sets from the sky, the earth releases some of the heat stored during the day, and as the air is moist, that heat is captured by the water content or moisture in the air. Those places.

In the desert, when the sun goes down and the sand begins to lose its heat through radiation, the air above the ground cannot retain or stop this heat because this air is not moist; This is why this heat is lost so quickly, which leads to a significant drop in temperature at night.

Also, deserts do not have much cloud cover, which makes it very difficult to retain heat above the Earth’s surface, and then the Earth’s heat escapes, leaving an unforgivable cold.

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The cold of the deserts at night is associated with a lot of humidity, even clouds and wind, but contrary to popular belief, not all deserts have moisture. Places like Kuwait and the United Arab Emirates on the Arabian Peninsula have higher humidity than other deserts, so these deserts do not get colder at night because their humid air retains some of the heat emitted by the earth.

Antarctica is technically a desert (Ca ‘Foscari University)

How desert is Antarctica?

When you think of the word “desert”, the first thing that comes to mind is the endless landscape covered with sand, but did you know that the Arctic, completely covered by snow, is actually a desert?

Lack or other forms of rainfall such as snow and ice are characteristic of the desert; Most deserts receive less than 300 mm per year, compared to more than 2,000 mm of rainforest.

Thus, Antarctica, covered by ice with a minimum temperature of -75 degrees Celsius, is technically desert; There is very little snow and rain throughout the year, making it one of the largest and driest deserts on the planet.

Some deserts, such as the Atacama Desert in South America, have no rain (Getty Images)

Why does it not rain in some deserts?

Most deserts receive little rainfall each year, but some deserts, such as the Atacama Desert in South America, receive no rainfall. Why is this happening? What places and conditions can create a desert?

Deserts are found on almost all continents, covering about 35% of the Earth’s surface, and they mainly see latitudes of 30 to 50 degrees, called mid-latitudes, and these areas are located approximately halfway between the equator and the north and south poles. .

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One of the main factors affecting the location of deserts is the physical property of air, which retains more water when it is hot.

Warm, humid air always rises from the equator; As hot air continues to rise from the equator, it pushes cold air; The cold air moves north and south 30 to 50 degrees north and south of the equator before turning towards the earth.

As the cold air begins to recede 30 to 50 degrees north and south of the equator, the falling air dries up the dry air, turning the land below into a desert.

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