Sometimes the weather is very cold, why not snow?

Sometimes the weather is very cold, why not snow?

Very cold weather is not necessary for snow. Snow needs several necessary conditions: temperature, water vapor, condensation nuclei, etc. If there is not enough water vapor or condensation nuclei, it will not snow even if it is very cold.

On the one hand, the earth's heat and cold have a certain relationship with solar activity. Every 10 years or so, there will be a low tide of solar activity, and the earth will be particularly cold.

On the other hand, as far as the specific situation is concerned, it is getting colder and colder in winter because of the greenhouse effect caused by environmental problems. In addition, some places are sometimes hot, but some places are sometimes cold. The greenhouse effect does not mean that the temperature has been rising. In Europe, global warming will be manifested as getting hotter in summer and colder in winter.

snow

In winter, the temperature is quite low, and the ground temperature is below zero, so the temperature of high-altitude clouds is even lower. Water vapor in the cloud can be directly condensed into small ice crystals and small snowflakes. When these snowflakes increase to a certain extent, the airflow will not hold, and it will fall from the clouds to the ground. This is snow.

snow

Because there is a strong updraft, the air temperature is very high, and snowflakes grow in the clouds for a long time, so the falling snowflakes are very large. At the same time, because of the large area and great resistance, snowflakes fly in the air and will not fall to the ground soon. Therefore, they collide with other snowflakes in the air and stick together, getting bigger and bigger, and when they are close to the ground, it is the time when heavy snow is raging.

snow

Snow is a form of precipitation, which is called solid precipitation in meteorology. In a cloud with both ice crystals and supercooled water droplets, this cloud is called ice-water mixed cloud. In this cloud, supercooled water droplets are constantly evaporated into water vapor, and the water vapor is constantly rushing to the surface of ice crystals, where it condenses and settles, so that ice crystals gradually increase and form flowers. After the flower is formed, it falls. In the process of falling, when you meet other flowers, they tend to stick together and grow up slowly. When encountering the updraft, the small flowers rise faster than the big flowers, and the small flowers catch up with the big flowers and stick together. After repeated many times, it gradually became a ball like cotton and goose feathers, with a diameter of several centimeters.

snow

When the updraft in the air can no longer hold these flowers, they will fall from the clouds. If the temperature of the lower air is below 0℃, flowers will fall to the ground, that is, people will see snow.