When is the lowest temperature in a day?

In a day, the lowest temperature appears around sunrise.

The earth's orbit around the sun is an ellipse close to a perfect circle, and the sun is located at a focus of the elliptical orbit, so that the distance between the sun and the earth is constantly changing in a year or even a day.

At the beginning of June 5438+ 10 every year, the earth is at the perihelion of its orbit around the sun, and the distance between the sun and the earth reaches the minimum, which is about 1.4438+0 billion kilometers.

At the beginning of July every year, the earth is at the perihelion of its orbit around the sun, and the distance between the sun and the earth reaches the maximum, about 1.55438+0 billion kilometers.

Compared with the average distance between the sun and the earth (6.5438+49.6 million kilometers), the change difference of the distance between the sun and the earth within one year (05 million kilometers) is almost negligible. Then in one day, the change of the distance between the sun and the earth is even more insignificant.

The temperature change of the earth in a day or a year has nothing to do with the distance between the sun and the earth, but with the angle between the sunlight and the ground level.

At noon 12, the solar altitude angle is the largest, and the equivalent solar radiation passes through the shortest atmosphere, is weakened by the atmosphere at least, and reaches the ground at most. At the same time, the solar radiation is strongest at 12, because the solar altitude angle is the largest, the area affected by the same amount of solar radiation is the smallest, and the solar radiation per unit area is the most on the ground.

However, after noon, although solar radiation began to weaken, the heat gained on the ground was still more than the heat lost by ground radiation. The ground temperature continues to rise, the ground radiation continues to increase, and the temperature will continue to rise.

With the continuous weakening of solar radiation, at a certain moment, when the heat gained by the ground is less than the heat lost by the ground radiation, that is, when the heat on the ground changes from surplus to loss, the ground temperature will reach the maximum value within one day. It's about 13 in the afternoon.

Next, the ground will transfer heat to the atmosphere through radiation, convection, turbulence, etc., which still needs a process, so the temperature will not reach the highest until about 14 in the afternoon.