During the day, the sand of the dunes of the Sahara is hot. It would be best if you had sturdy shoes and covered yourself from head to foot to avoid burning in the sun. However, as night falls, the temperature drops due to the poor heat transfer properties of sand.
It quickly gives back the energy accumulated during the day towards the space. Here are some details on this amazing thermal amplitude.
The intertropical zone, where sunshine is at its peak, is primarily home to hot deserts. The Sahel, for example, receives more than 3,200 hours of sunlight per year, while Paris, for instance, receives barely half that. The sun in deserts is omnipresent, heating the ground and the surrounding air. This phenomenon leads to extremely high temperatures and increased evaporation. In summer, in the Sahara, the average temperature is 40°C, and it drops to 20°C in winter.
The thermal amplitude of the desert
If it's hot during the day, the desert cools down harshly at night, and it can even freeze in winter. The thermal amplitude day-night can easily be higher than 20 °C. Two main factors explain this drop in temperature at night: the heat capacity of the sand and the clouds.
The silicates that make up sand particularly poorly retain the heat that accumulates during the day. As soon as the sun disappears, each grain of sand isolates itself from the others, thus accelerating thermal dissipation. In other words, the sandier the desert, the faster it loses the energy accumulated during the day.
Moreover, the nights are clear, and the absence of water vapor in the air considerably inhibits the formation of clouds. Without this natural barrier, the ground sends its infrared radiation directly toward space. The only source of heating in a hot desert in the intertropical zone is solar radiation.