Today, the teacher said that sunny weather in winter is prone to inversion. Why is winter inversion stronger than summer? It's sunny, and sunny at night is better than cloudy at night.

The heat in the troposphere mainly comes from the long-wave radiation on the ground. Generally speaking, the farther away from the ground, the lower the temperature, that is, the temperature decreases with the increase of height. However, under certain conditions, the temperature at a certain height in the troposphere sometimes rises, which is called inversion.

There are many reasons for the upside down phenomenon. Here are some examples:

1. Ground radiation cooling: On a clear night without wind or breeze, the ground is rapidly cooled by radiation, and the atmosphere near the ground is also cooled. Because the closer the air is to the ground, the greater the influence of the ground, so the closer it is to the ground, the greater the temperature drop; The farther away from the ground, the less the temperature drops, thus forming an inversion from the ground. With the intensification of ground radiation cooling, the inversion temperature gradually expands upward and reaches its strongest at dawn. Generally, after sunrise, the solar radiation gradually increases, the ground temperature rises rapidly, and the inversion gradually disappears from bottom to top. Summer night is short, inversion layer is thin and disappears quickly, winter night is long and inversion layer is thick and disappears slowly.

2. Air sinking: It mostly occurs in mountainous areas. The cold air on the hillside sinks to the bottom of the valley, and the warm air at the bottom of the valley is pushed up by the cold air, causing inversion. This inversion is mainly formed under certain terrain conditions, so it is also called terrain inversion. For example, Los Angeles in the United States is surrounded by mountains on three sides, and there are more than 200 days of inversion every year.