How many degrees does it usually snow?
It usually snows around 0 degrees. The temperature of snow is not necessarily higher than 0 degrees (ground), depending on the humidity of air and the temperature of ice crystals at high altitude.
There are two conditions for the formation of snowfall:
One condition is that water vapor is saturated. Another condition is that there must be condensation nuclei in the air.
The size of snowflake crystals is closely related to the temperature at which water vapor condenses and crystallizes. The colder the weather, the lower the temperature and the smaller the snowflake crystal. When the weather is very cold, the diameter of snowflake crystals formed is often less than 0.05 mm. Meteorologists have observed that prismatic ice crystals will form when the temperature is between -8℃ and -5℃. When the temperature is -5℃ to -3℃, needle-like ice crystals are formed; When the temperature is -3℃ to 0℃, thin hexagonal plate-like ice crystals are formed. It can be seen that when the temperature is -3℃ to 0℃, the shape of snowflake is the largest and most complete. Snowflake crystals formed in very cold weather are so small that they are almost invisible to the naked eye. Only when they shine in the sun can people find them as fine powder. This kind of snow is called dry snow.
Why is it not cold when it snows?
Firstly, it is pointed out that the reasons are exothermic and endothermic. It is indeed exothermic and endothermic, but of course it does not mean that the snow is not cold. As far as temperature is concerned, the temperature of snow is definitely lower than that of snow. As for why people think it is hotter when it snows, it is because the sky is cloudy and the air is not clear when it snows. When it snows, the airflow is usually windy, so it will be cold.
Why doesn't the snow melt
According to experts from the Provincial Meteorological Observatory, it is a natural phenomenon that snowfall does not cool down. As the middle school physics teacher said: "When it snows, water vapor condenses into snowflakes, so we need to release some heat, which makes it not very cold before or when it snows;" But when it snows, water changes from solid to liquid, absorbs heat from the air and lowers the temperature. "That makes sense. But from the meteorological point of view, the formation of this natural phenomenon, on the other hand, is affected by the cold and warm air flow before and after snowfall.
According to reports, it is not cold when it snows, mainly because the warm and humid airflow is active before or when it snows in winter, accompanied by high-altitude southwest winds. The weather is getting warmer and warmer, and the cold and warm air meet. Warm air rises along the strong cold air, and water vapor condenses directly into small ice crystals of stars, flakes or columns. When the ice crystals grow up slowly and the air can't hold them, they will fall to the ground and form snow. The snow cleared up the day after tomorrow Generally speaking, cold air goes south and high altitude goes north. The ground is controlled by the quality of air conditioning, and the temperature will naturally drop.
Therefore, when the snow melts, the weather is colder than when it snows.
When is the coldest time of the year?
65438+1October 20th or 2 1 means "cold", which means the coldest time of the year. However, except in South China, the coldest period is in the middle of 1 month. The cold solar terms mainly appeared on April 9 and May 9, and the temperature began to rise slowly. However, cold and dry weather is a feature of severe cold.
The three solar terms "Winter Solstice", "Slight Cold" and "Great Cold" are called "Midwinter" by China people. In the dead of winter, there are about 5 days of cold air going south on average. Cold wave, frost and blizzard are the main disastrous weather in the middle of winter. In June 5438, the lowest temperature was below 0℃ for 20 days and it snowed for 3 days.
Historical stories about snow
1, Su Wu has tasted ice and snow.
Su Wu sent a mission to Xiongnu, so he detained Su Wu because his subordinates rebelled and angered Khan. Khan wants to accept Su Wu, but Su Wu is very loyal. Khan locks him in the cellar and won't let him eat or drink. So Sun Wu ate snow felt wool, and later Su Wu was banished to Beihai to graze. Su Wu was indomitable in Xiongnu 19 and became a well-known national hero.
2. Chengmen Sydney
In the Northern Song Dynasty, Shi Yang and his friends went to Cheng Yi to study. When he arrived, it happened that the meter was sleeping. When he saw the half-open door, Shi Yang didn't go in directly, but waited outside. It was snowing heavily, and it was always cold outside in Shi Yang. Finally, Cheng Yi was very moved. Teach him well. Shi Yang didn't live up to his high hopes, and the story has been widely circulated ever since. Tell us to respect the teacher and respect the road.
3. Sun Kang Xue Ying
It is said that a scholar named Sun Kang studied very hard. His family is poor, but he loves learning very much. But he didn't have the money to buy an oil lamp. He felt that he had wasted a lot of time. Later, he found that the snowy night was very bright, so he took a book and read by the night light reflected by the snow.
When it is cold, he goes running to keep warm. It is his efforts that make him an example of the world bachelor and tell us to study hard.