Seven cold knowledge about snow
1. Are snowflakes all hexagonal?
Snowflake is a beautiful crystal, also known as Weiyanghua and Liuchu. It is a snow crystal polymer formed by snow crystals touching, bonding and hooking together. At present, there are about 2, known snowflake shapes, which can be said to be various and colorful.
However, the original "embryo" of snowflakes-snow crystals are basically hexagonal in shape, such as hexagonal branches, hexagonal sheets, etc., and the snowflakes grown from them also show hexagonal characteristics. Therefore, the ancients had a saying that "there are five more flowers of plants and trees, and six snowflakes alone".
The basic shape of snowflake is hexagonal, but it can show various shapes in different environments. There are almost no two identical snowflakes in nature, just as there are no two identical people on earth.
This is mainly because the temperature and humidity in the snow cloud change rapidly during the growth of snowflakes. As long as there is a slight difference, the shape of snowflakes will be different.
2. Can it be snowing in the sun?
There is a lyric in Nan Shan Nan: "You are in the sunny south, and it is snowing heavily", which seems illogical at first glance. However, this phenomenon did happen, and more than once. This phenomenon is called "solar snow".
It snows when the sun is shining, which is called "solar snow". This phenomenon is relatively common in the north of China and rare in the south, but it is a normal weather phenomenon.
Usually, "solar snow" is a kind of short-term snowfall, which occurs around 9-1 am or around 15-16 pm. During these periods, when the clouds that produce snowfall are not thick and the coverage is not large, there may be sunlight obliquely coming out of the cracks in the clouds, so you will see the scene of sunshine and snow appearing at the same time on the ground.
The "solar snow" is somewhat similar to the "solar rain" in summer, except that the temperature of the clouds that produce the "solar snow" is low, and the precipitation falls in the form of snow.
3. "Snow particles" are not snow?
Maybe everyone has seen this phenomenon: sometimes white "little balls" fall from the sky and bounce on the ground. In many places, it is called "snow grain" or "rice snow". In meteorology, this kind of thing is called graupel, also known as snowball or soft hail. Its diameter is generally between .3 and 2.5 mm, and it is crisp and easy to crush.
But do you know that graupel and snow are both solid precipitation, but they do not belong to the category of snow? The graupel usually lands when the ground temperature is not too cold, and usually lands before it snows, which can be said to be a "prelude" to snow. It is produced in a cloud with strong disturbance, and it is formed by a large number of snow crystals (or snow masses) colliding with Leng Yun drops to freeze and merge, and it is often in array.
4. How heavy is the snow?
We often use "dancing lightly" and "goose feather" to describe snowflakes, which shows their lightness. Snowflakes can only be weighed on an extremely accurate analytical balance, and about 3~1 snowflakes add up to one gram. However, it can collapse houses and gas stations!
The main reason is that when they are together, they can gather sand to make a tower and win by quantity. According to statistics, the number of snowflakes in a cubic meter of new snow can reach 8 billion!
to make it easier to understand, let's estimate the weight of snow from the perspective of precipitation. Under normal circumstances, the thickness of 8~1 mm of snowfall in the northern area of 1 square meter melts into water, which is equivalent to 1 mm of precipitation; In the south, the thickness of 6~8 mm of snowfall on an area of 1 square meter melts into water, which is equivalent to 1 mm of precipitation.
according to the density of water, it is not difficult for us to draw the conclusion that in the north, 8 ~ 1mm of snow weighs about 1kg in an area of 1m2, so 8 ~ 1mm of snow weighs 1kg in an area of 1m2. In the south, 6~8 mm of snow on 1 square meters weighs 1 kilograms. It can be seen that the snow with the same thickness is heavier in the south than in the north.
To be more specific, a 1-square-meter flat roof will bear more than 3-5 tons of heavy load if the snow is knee deep, which is equivalent to standing on the roof with more than 2 fat people weighing about 2 kilograms, and its weight can be imagined!
5. Can snowflakes be as big as seats?
"Yanshan snowflakes are as big as seats, and pieces fall on Xuanyuan terrace." This is a poem by Li Bai, a great poet in the Tang Dynasty. Can snowflakes really be as big as seats? In fact, don't say that there is no record in the history of snowflake science, even "goose feather and heavy snow" is not easy to encounter.
according to official website, the Guinness World Records, the largest reported snowflake record was discovered by farmer Matt Coleman in Fort Keogh, Montana, USA on January 28th, 1887. He measured that the snowflake was 38cm wide and 4mm thick, which was "bigger than a milk pot".
The New York Times said that "there is no conclusive evidence to support this statement", and now this record can't be found in Guinness official website.
In fact, the diameter of a single snowflake we can see is generally between .5 and 3. mm, and the maximum diameter will not exceed 1 mm, at most it will be as big as our nails. Those seemingly large snowflakes, such as the so-called "goose feather snow", are actually not a snowflake, but are formed by many snowflakes sticking together.
when the air is humid, the merging ability of snowflakes is particularly great, and many snowflakes are merged into one piece. Therefore, strictly speaking, goose feather snow can't be called snowflake, it is just the aggregation of many snowflakes.
6. Snowflakes all have "cores"?
To form snowflakes, there are two conditions: one is that water vapor is saturated, and the other is that there must be condensation nuclei in the air. Some people have done experiments, if there is no condensation nucleus, the water vapor in the air will be supersaturated to the degree of relative humidity above 5%, and it will be condensed into water droplets.
but such a large supersaturation phenomenon will not exist in the natural atmosphere. So without condensation nuclei, it is difficult for us to see rain and snow on earth.
condensation core is a particle that plays the role of condensation core in the process of material changing from gas to liquid or solid, or from liquid to solid. In the process of forming precipitation, the ideal condensation nuclei are those particles that absorb the most water, such as sea salt, sulfuric acid, nitrogen and other chemicals.
So, all the snowflakes we see actually have "cores".
7. Who was the first person to take pictures of snowflakes?
Wilson Bentley is an ordinary man who was born on a farm in Vermont in 1865. He has been interested in observing nature since he was a child, especially fascinated by snowflakes. Before he was 19 years old, he began to record his deep love for snowflakes and became the first person in history to take pictures of snowflakes.
He also devoted his whole life to snowflakes with "the strong love of his lover and the incomparable patience of scientists". In his life, he photographed more than 5, snowflakes without any repetition in shape, so he can be said to be a well-deserved "Snowflake Man".
Bentley's micrographs of snowflakes were published in scientific magazines, and Nature alone published 6 of them. These photos have influenced many scientists, photographers and museums. The "Snowflake Man" also became a scientist and wrote the book Snow Crystals.