What is the principle of the double illusion of Xi 'an Bell Tower caused by heavy rain?

I believe many people know a mirage, which is a very beautiful sight. Just this summer, the mirage of Xi 'an Bell Tower exploded the circle of friends.

I. Phantom of Xi 'an Bell Tower

This scene is a phantom of Xi 'an Bell Tower. In the video, you can see the sky above the bell tower. The outline of the bell tower is consistent from left to right, and the sky is colorful. This question surprised many netizens and was all forwarded. In fact, before this, some people doubted whether this mirage really existed, because it was looming in the sky and looked particularly beautiful.

Because Xi is an inland city, it is surprising that there will be a mirage. Experts have also said that the probability of a mirage is actually very low, because the conditions he needs are harsh, most of them will appear on the sea or in the desert, and most of them will not appear in places with too many buildings and no airflow. However, there are many buildings in Xi 'an, and there is air flow around them. In fact, a mirage is not only related to the region, but also to the weather. It just rained in the video, which usually happens, probably because of the weather.

2. What is the principle of mirage?

A mirage is a natural scene formed by refraction or total reflection of light, and a virtual scene formed by refraction of objects on the earth after reflected light passes through the atmosphere. In fact, the most essential thing is an optical phenomenon. The geographical location of mirage is closely related to the physical conditions of the earth and some specific climatic environments.

Mirage is closely related to geographical location, geophysical conditions and abnormal temperature. If in the desert in summer, when the sun is shining, the sand has been scorched by the sun. At this time, the specific heat of sand is small, and the temperature rises faster. This is near the sand, and the temperature of the lower air rises relatively high, while the temperature of the upper air is still relatively low. At this time, the temperature is abnormal, because the density of hot air in the lower layer of sand is relatively small and the density of air in the upper layer is relatively large, and the refractive index of air is low. The light reflected by tall objects in the distance will enter the air of books from dense air, and the refraction angle will gradually increase. When it reaches a critical point, total reflection will occur and people will see a mirage.

A mirage in the desert is a phenomenon that sunlight meets air with different densities. When exposed to the sun in the desert during the day, the surface temperature of the sand layer rises too fast, the air heat transfer performance is poor, and there will be obvious temperature difference when there is no wind. On the sea or river, there will also be such a mirage, which is an optical illusion and a virtual image formed by the reflected light of objects on the earth.