A clear temperature at night

In fact, a cloudless night itself is sunny weather.

I guess you want to know something about inversion.

When the inversion occurs, the near-surface temperature is relatively low-every 100 meters, the temperature drops by less than 0.6 degrees, and even the temperature increases with height. Contrary to the law that the troposphere temperature drops by 0.6 degrees every 100 meter, it is called "inversion".

The formation conditions of inversion can be considered from the following four aspects:

1. From the seasonal point of view, it generally appears in the winter half year, because the geothermal expenditure is far greater than the income at this time, which is conducive to the formation of inversion.

2. From the perspective of day and night, it generally appears at night, because there is only heat expenditure at night, and there is no heat income.

Judging from the weather, it usually appears on sunny days, especially on sunny nights. At this time, the atmospheric inverse radiation is weak and the near-surface temperature is low.

4. Topographically, it usually appears in basins. If the cold air around the basin sinks to the bottom of the basin on a clear night, and the local temperature is lower, inversion will occur.

When inversion occurs, the near-surface temperature is relatively low, the vertical movement of air is stable, it is not easy to convection, it is not easy to form rainy weather, the weather is clear, and the water vapor content in the air is less.

Sometimes there is a lot of water vapor in the air before the inversion phenomenon appears, so after the inversion phenomenon appears, the water vapor can cool and condense near the ground without rising, often forming foggy weather. The Sichuan Basin in China is a typical example. The local inversion leads to heavy fog, so Chongqing is known as the foggy city.

But after sunrise, the heat income began to exceed the expenditure, the inversion phenomenon disappeared, and the sun still shone in front of us. Therefore, as the saying goes; Ten fogs and nine sunny days.

To sum up, sunny nights provide a prerequisite for the formation of inversion; After the inversion is formed, the air is not easy to convection and the weather remains sunny; Even if there is heavy fog, it will clear up soon after sunrise, and it will still be sunny.

Supplement: Because the weather was clear the night before, the atmospheric inverse radiation was weak, and the temperature near the ground was low, it was easy to have inverse temperature, and the atmosphere was stable and not easy to convection. In this way, until the next day, the conditions for rainfall caused by convection are generally not available, so the next day is still sunny.