Why is the desert so hot during the day and so cold at night?

Every time we mention the desert, everyone has an inherent impression that the temperature difference between day and night is very large in desert areas except drought and little rain. During the day, it is still a hot desert. Once at night, the temperature will drop rapidly, and the large temperature difference between day and night in the desert has become a "roadblock" for many explorers to challenge the limit. So, what's the secret behind the phenomenon that the desert is hot during the day and cold at night?

First of all, the phenomenon that the desert is hot during the day and cold at night is inseparable from the sand in the desert. Because the specific heat of sand is less than that of air, when the earth's surface absorbs solar radiation heat during the day, the temperature of sand with the same mass near the ground is higher than that of air, and the heat is transferred from sand to air. At the same time, due to the small specific heat of sand, sand absorbs heat and heats up quickly, which makes the air near the ground heat up quickly; At night, the surface radiates heat to the air, air convection, sand and stone exchange heat with cold air near the ground, and sand and stone are transferred to the air to cool down. This phenomenon is obvious in some areas of Xinjiang, China. Because the local ground landscape is mainly a desert with small heat capacity, it absorbs heat quickly and heats up quickly during the day. At night, it releases heat rapidly and cools rapidly. This is why the proverb "wear cotton-padded jacket early, gauze at noon and eat watermelon around the stove" is popular in Xinjiang.

Due to meteorological factors, the desert is hot during the day and cold at night. Clouds are very common in our daily life. It is a visible polymer, floating in the air, composed of small water droplets or small ice crystals, and condensed by water vapor in the atmosphere in cold weather. In nature, clouds play an important role. For example, clouds can "block the sun" and "keep warm". In other words, clouds can reduce the radiation of sunlight to the ground through reflection, and can also transfer heat to the ground through reverse radiation, that is, keep the ground warm. But the desert area is very dry, and there is not much evaporated water vapor, so there are almost no clouds over the desert.

During the day, the sun can bake the desert without hindrance, resulting in a sharp rise in temperature, so the desert is very hot during the day. As night falls, the sun sets and the ground radiation dominates. The ground constantly releases heat into the air. But there are almost no clouds in the desert and there is almost no reverse radiation, so it can't keep warm. As a result, the temperature keeps falling and the desert gets cold at night.