The 1962 Hollywood film Lawrence of Arabia was inspired by the life of a British lieutenant, and you may remember the long, arduous journeys he takes through the desert. He has no idea if he will reach his target or if he would become hopelessly lost in the desert and eventually die.
The huge stretches of desert he crosses at night provide him with the perfect opportunity to sleep outside under the stars. After seeing that part of the film, I couldn’t help but wonder.
Although deserts are well-known for their unbearable daily temperatures, few are aware that they may really be rather chilly at night.
Sand Heats the Air Above it
Sand is a fascinating material. It’s dry but slick, and it doesn’t absorb water well since its particles are larger than those in other soil types.
Deserts are so hot because sand is poor at insulating against the sun’s rays.
In deserts, the sand doesn’t retain the sun’s warmth when it’s heated by the sun. Instead, it reflects the sun’s rays and warms the air above the ground.
Forests, beaches, plains, and mountains don’t radiate as much heat to the air above their surfaces as deserts do, thus they don’t get as hot.
Why Are Deserts So Hot During the Day and Cold at Night?
The dramatic shift in temperature that occurs between the day and night in a desert is one of nature’s most striking extremes.
Human occupants might be subjected to agonising pain at scorching temperatures. After dark, though, the situation flips, and a warm coat could be handy.
The Sahara Desert in Africa experiences extreme diurnal temperature swings, with daytime highs of 100 °F and nighttime lows of 25 °F on average. Why does this happen?
Blame the Sand
Sand is a good heat sink, allowing the sun’s rays to be reflected back into the atmosphere. However, it is poor at keeping heat inside. When the sun goes down, the sand quickly gives up its stored heat.
Humidity is the one thing that could keep warm air in the desert overnight, but there isn’t much of it. Heat is retained by the air due to the presence of water vapour.
It’s similar to a blanket in that it traps air inside, making it difficult for temperature to change. The vapour will keep the heat for a long time after the heat source is turned off. The desert will rapidly cool without the sun or humidity to trap the day’s heat.
Deserts, despite having the same average temperature as other regions, may feel much warmer due to the higher humidity levels.
Compared to a dry climate, which makes direct use of the sun’s heat, water vapour requires a great deal of energy to heat up.
Extreme heat is generated during the day because the sand absorbs and radiates the sun’s rays, causing the air around it to become extremely hot.
However, when the sun goes down, the temperature drops dramatically and the sand’s heat quickly radiates into the air.
According to an article published in Science Times, extreme temperature swings in deserts can be attributed to the lack of moisture in the air.
The Science Times explains that deserts like the Atacama and Sahara have almost no humidity because water vapour has a greater capacity to trap heat than sand.