How is snow formed?

Snow is formed by direct condensation of water vapor in the atmosphere. The low temperature in the cloud makes water vapor form ice crystals. When the temperature is low enough, when ice crystals fall to the ground or snow falls, it is snowing. Snow absorbs heat when it melts, so the ground temperature will be lower when it melts than when it snows.

The conditions for the formation of snow are that the atmosphere needs to contain cold ice crystal nuclei and sufficient water vapor, and the temperature is below 0℃ (freezing point).

biographical notes

Snow is a form of precipitation, which is crystalline solid ice falling from the clouds, usually in the form of snowflakes. Snow is composed of small ice particles, which is a granular substance. Its structure is open, so it looks soft. Snowflakes have different shapes and sizes due to different temperatures and humidity. If the snow melts during the landing and then freezes again, it will form spherical snowfall, such as graupel, graupel and hail.

Extended data:

1, snowfall

The process of snowfall is called snow or snowfall. Many water droplets in the cloud with a temperature below 0℃ collide and condense on ice crystals to form snow beads, which are composed of many tiny white ice particles. When the cold air moves forward gradually, the updraft weakens, and the water vapor in the cloud condenses directly on the ice crystals into a larger form, which is the snowflake we see.

If the temperature is close to freezing point, wet snow will fall and form bigger snowflakes, especially when there is no wind. Large star-shaped snowflakes can reach 5 to 7 cm in diameter. Most snowflakes melt into rain when they fall to the ground. Only when the air near the ground is cold enough can snowflakes fall to the ground and become snow.

2. Where can it snow

Snowfall is generally formed in the area where the air around the temperate cyclone moves upward. With the warm front weather system, snow may fall in the polar direction. Lightning and snowfall may occur in the comma head of cyclone and the precipitation area of Great Lakes effect. In mountainous areas, the uphill airflow reaches a critical point on the windward side of the hillside during the rising process. If the air is cold enough at this time, there may be snowfall.

There will be opportunities for snowfall where the climate zone belongs to the middle latitude to the high latitude (that is, the area south of the Tropic of Cancer/north of the Tropic of Cancer), and there will be the same opportunities if there are some mountains or plateaus with terrain above 2000 meters above sea level in the low latitude area.

Ocean airflow will also indirectly affect the probability of snow in this area. If there are more warm currents in high latitudes, it will reduce the chance of snow in this area (such as Honshu to Kyushu, Japan).

3. Great Lakes Effect

In places with relatively warm water bodies (such as lakes), the Great Lakes effect snowfall is very important. Snowfall caused by the Great Lakes effect generally occurs in the downwind of warm lakes and in the cold air cyclone after temperate cyclones, which can cause a lot of snowfall in some areas.