Why does it get cold?

The reason why the weather will get cold is:

The cold air activity on the earth is the direct cause of the cold weather.

At the same time, because the earth revolves around the sun, when the direct point of the sun in the northern hemisphere moves south, these places in the northern hemisphere will get cold. Similarly, in the southern hemisphere of the earth, when the direct point of the sun moves northward, these places in the southern hemisphere will get cold.

It is not the reason why the earth revolves to perihelion and aphelion.

Extended data:

The earth's orbit around the sun is an ellipse that is very close to a perfect circle, with an average angular velocity of 360 degrees per year and an average linear velocity of 940,000,000 kilometers per year.

Most of the cold air masses in the northern hemisphere are formed in the polar regions and Siberia, with a range of thousands of kilometers and a thickness of several kilometers to dozens of kilometers. Cold air crossing the border will bring rain and snow. , will make the temperature plummet. The intensity of each cold air intrusion is different, strong or weak, and the cooling rate is also more or less. Cold air, such as tidal surge, affects a wide range, reaching more than 2000 kilometers. Because the moving path is different, the influence area is also different. The time and scope will also be different.

According to the intensity, cold air in China is divided into five grades: weak cold air, moderate cold air, strong cold air, strong cold air and cold wave.

The distant Arctic Ocean and cold Siberia are the cradles of cold air. The cold air originally came from the Arctic Ocean, and later strengthened through Siberia.

These areas have high latitude, long winter nights, short days and few sunshine hours. In the polar regions, there will even be extreme nights, and the sun never shows its face. Therefore, the earth's heat from the sun is very weak; However, at night, the ground radiates a lot of heat into space. With the continuous cooling of the ground, the temperature of the atmosphere near the ground is getting lower and lower, and the accumulation of cold air will increase.

Guided by the northwest airflow, this cold air mass with extremely low temperature in the northern hemisphere will push from north to south, affecting Mongolia, North China, East China or most parts of China.

The main influence of cold air intrusion is to bring cooling and strong winds, and sometimes there will be a wide range of rain and snow weather, which is the result of the intersection of cold and warm air. When the warm and humid air conditions are not good and the circulation conditions are unfavorable, the invasion of cold air does not necessarily bring precipitation weather. Therefore, it is not that the stronger the cold air, the stronger the rain and snow weather.

Baidu encyclopedia-cold air