We often hear that there is a "mirage" somewhere along the eastern coast of China, such as Yantai and Penglai in Shandong, and the coastal areas of Jiangsu and Zhejiang. Mirages are not particularly rare. However, in fact, mirages often appear in the desert areas of northwest China. For example, on June 4, a mirage appeared in the Kumutage Desert in Shanshan County, Xinjiang, China.

recently, due to the continuous high temperature in northwest China, the temperature in many places in Xinjiang has exceeded 41. The Kumutage Desert in Shanshan County, Turpan is one of the hottest places in summer and daytime in China. On the 4th, a mirage appeared. It seems that a big lake suddenly appeared in the empty desert. From a distance, you can see the water waves rippling on the lake, the wind blowing the fine waves sparkling, and some oases looming.

It is said that from May to October every year, this kind of scene often occurs in some deserts in northwest China at certain times during the day, but sometimes it also occurs in winter.

For people who walk in the desert in summer, it is easy to feel hot and thirsty, and the big lake in the distance is undoubtedly very tempting, but if you really rush to this big lake, you will never find it, because when you go to the place where the original lake is, you will find that it is a sea of sand and there is no water at all, and the lake is still far away. And in the process of running to the lake, you will find that the distance from the lake is always so far, so it is very terrible for people living in desert oasis or near the desert to have a tempting "mirage" in the desert.

so why is there a mirage in the desert? In fact, the reason for the formation of this kind of thing is not complicated, it is the refraction of light in the atmosphere, and the reason for the refraction of light is the existence of light propagation media with different densities. For example, chopsticks are broken when inserted into water, which is why the light of chopsticks in water is refracted. The density of water and air is different, so chopsticks will refract, so mirage will only appear in air with different densities.

In fact, the common mirage in nature can be divided into two types. One is the "mirage" that often appears on the sea, which is mainly displayed in the air on the sea surface, with a relatively high position and an upright image; One is a "mirage" that often appears in the desert, which is mainly displayed on the desert ground in the distance, with a relatively low position and an inverted image.

However, the place where mirage appears is not only in the ocean and desert, but it can appear anywhere as long as conditions are met. It's just that it's easier to create forming conditions in the ocean and desert, so it appears more frequently.

Although both of them are produced by refraction of light, the formation mechanism of two kinds of mirage in the ocean and desert is different. The "mirage" on the sea surface appears in the air with high air density in the lower layer and low air density in the upper layer. At this time, the light reflected from the distant scenery will rise upward in angle, and the air will present a nihilistic scene. This is the reason for the mirage in the air, which usually appears when the ground temperature is cold and the air temperature is warm.

For example, on February 21th last year, an image of a moving high-speed train EMU appeared in the sky southwest of Huishan Avenue in Wuxi, which looked like a "train bound for heaven". The reason for this was that the air with different densities refracted the image of an EMU about 7 kilometers away.

The formation mechanism of a mirage in the desert is the opposite. When the air density on the ground is low and the air density at high altitude is high, the scenery light in the distant sky will be refracted downward to the ground. On June 4th, Xinjiang, a mirage appeared in the Kumutage Desert. The lake on the desert ground is actually the distant sky, and the light in the sky appears in the distant desert after refraction. Therefore, compared with the mirage on the sea, the formation mechanism of mirage in the desert is very special.

Due to transpiration on the desert surface, air currents with different densities will constantly shift the light, so the "lake in the desert" looks like water waves rippling and sparkling. As for the water plants and oasis trees in the lake, it is also formed by the light changes of objects in the sky or on the ground.

Reference:

Beijing Daily article "Mirage in Kumutage Desert, Shanshan County, Xinjiang" on June 4th.