Why does the east wind blow in spring? West wind blows in autumn?

The southeast wind comes from the ocean. Why did you do it again? We know that the decline of rain, on the one hand, of course, there must be a substance that condenses rain-water vapor; At the same time, it is necessary to have the conditions to turn these water vapor into clouds and rain. This situation, in the summer in the southeast plain, depends on the convection of heat or the front activity between two airflow from different directions.

Thermal convection occurs because the ground is extremely hot, and the air in the ground layer rises upward because of the principle of thermal expansion and contraction, bringing the water vapor from the ground to the upper air for cooling, resulting in clouds and rain. But if the wind is too strong and the air flow on the ground is too fast, it is impossible to concentrate on the ground and receive strong heat, and it is impossible to make the water vapor on the ground rise. Also, in the pure southeast wind, due to the high altitude sinking of its birthplace, there is often an inverse ratio between high altitude and low altitude warming; In this way, the air on the ground is difficult to rise. Therefore, although there is a lot of water vapor in the southeast wind, it is still impossible to cause rainfall. There is no sex and rain in summer, and the natural weather is very hot.

Secondly, speaking of positive activities. The front is the conflict area of two different airflow. One airflow is cold and heavy, and the other airflow is light and warm. When these two air streams meet, the light warm air stream only rises and does not fall. As a result, the water vapor on the ground was carried to high altitude, causing clouds and rain. At present, there is only southeast wind on the ground, which means that there is no other northerly airflow colliding with it to form a front, so the water vapor can't rise and clouds and rain appear.

* Northeast wind, too much rain. ("Tian Hang" winds up)

The northeast wind is an air flow that originates from the northern ocean surface, or from the northern ocean surface and passes through a long-distance ocean surface, and naturally contains less water vapor than the southeast wind; However, because it is a cold air flow, its lower part touches the relatively hot ocean surface or land surface in the south, making its upper part cold and its lower part warm, resulting in convection. As a result, the water vapor on the ground was brought to the sky and had sex.

In addition, the front of the cyclone must be where the northeast wind moves, so there is front precipitation.

According to the statistical results, in the case of pure northeast wind, the probability of rain is only 26% in winter and only 1 1% in summer, which means that the probability of no rain is 74% and 89%. If it is the northeast wind before the cyclone, that is, the northeast wind area with active front, the probability of rain will exceed that of sunny days. Therefore, the proverb'''''''' The northeast is too stormy''''''' is not necessarily completely reliable.

* The spring breeze blows the east wind, and the grandfathers get wet. (Changzhou, Jiangsu)

* The spring breeze is easterly, and the rain is murmuring. (Guangdong)

These two proverbs mean that the east wind blows in spring, which is a precursor to bad weather. This is because, on the one hand, the ground will get warmer in spring. On the other hand, the warm air is gradually active, the continental pressure is gradually decreasing, and the anticyclone moves eastward into the sea. An easterly wind will appear at the tail of the anticyclone. These easterly winds flow to warmer land, leading to the phenomenon that the upper part is warm and the lower part is cold. At this time, the air layer is unstable and prone to upward convection, so it is very likely to produce precipitation.

* East wind and rain for three days a day; On the third day, the east wind disappeared. (Guixian, Guangxi)

* East wind and rain for three days a day; Three days of east wind and nine days of eyes. (Wuchang, Hubei)

* East wind and rain for three days a day; Dongfeng has no rice for three days. (Guangxi)

Cooking without rice is the result of drought and no rain. The cyclone moved from west to east, with the east wind ahead, but it soon blew up, and turned to another wind direction because of the advance of the cyclone. So the east wind blows for only one day, or less than one day, and the wind direction changes, indicating that there is a cyclone coming, so it may rain for three days. If the east wind blows for three days without rest, it means that there is no cyclone approaching in the west, so there is no rain in this place.