Information about snow? Urgently beg

Water is the foundation of all kinds of life on the earth, and its changes and movements have created our world today. On the earth, water is constantly circulating. The water in the ocean and on the ground is heated and evaporated into the sky. The water vapor moves to other places with the wind. When they encounter cold air, they form precipitation and return to the earth's surface. There are two kinds of precipitation: one is liquid precipitation, which is rain; The other is solid precipitation, which is snow or hail.

The precipitation that falls on the earth's surface in the form of solid in the atmosphere is called atmospheric solid precipitation. Snow is one of the most extensive, universal and main forms of atmospheric solid precipitation. There are many kinds of atmospheric solid precipitation, including beautiful snowflakes, hail that can cause great harm, and snow graupel and ice particles that we don't often see.

Due to the difference of meteorological conditions and growth environment in the sky, all kinds of atmospheric solid precipitation are caused. The names of these atmospheric solid precipitation vary from place to place, from person to person, varied and extremely inconsistent. For convenience, the International Ice and Snow Committee under the International Hydrological Association held a special international conference in 1949 on the basis of consulting experts from various countries, at which the proposal of "Concise Classification of Atmospheric Solid Precipitation" was adopted. This concise classification divides atmospheric solid precipitation into ten types: snowflake, star snowflake, columnar snowflake, needle snowflake, multi-branch snowflake, axial snowflake, irregular snowflake, graupel, ice particle and hail. The first seven kinds are collectively called snow. Why can't the last three be called snow? It turns out that there are two processes for gaseous water vapor to become solid water. One is that water vapor first becomes water, and then water condenses into ice crystals. Another is that water vapor directly becomes ice crystals without water. This process is called condensation of water. Therefore, snow is solid precipitation formed by condensation of water vapor in the sky. (The diagram on the right shows ten kinds of atmospheric solid precipitation, from top to bottom: snow flakes, star-shaped snow flakes, columnar snow crystals, needle-shaped snow crystals, multi-branched snow crystals, axial snow crystals, irregular snow crystals, graupel, ice particles and hail).

Si Nuo's close relatives.

In summer, in mountainous areas, there are often many supercooled water droplets frozen around the crystal nucleus in the sky, forming a white and dim round particle. Meteorology calls this kind of thing graupel, and in many places it's called Michelle or snow graupel. Generally, the diameter of graupel is between 0.3 and 2.5 mm, which is brittle and easy to break. Polonium does not belong to the category of snow, but it is also a kind of atmospheric solid precipitation.

Ice particles and hail

In summer, in the northern plain, two other kinds of atmospheric solid precipitation are often encountered, namely ice particles and hail. Ice particles and hail are relatively large translucent ice beads formed by flowing water droplets freezing around condensation nuclei layer by layer. Meteorology, the particle size less than 5 mm is called ice particles, and the particle size greater than 5 mm is called hail. Hail brings great harm to agricultural production. According to records, the largest hail in the world is bigger than a fist, with a diameter of over 1 0cm and a weight of over1kg.

Frost and rime In addition to atmospheric solid precipitation, another kind of "ground growth type" solid precipitation often appears on the ground, which is frost, rime and rime.

Although these solid precipitation are not atmospheric solid precipitation, they are only formed by condensation, crystallization and freezing of surface water vapor. But these solid precipitation also have a great impact on human production activities. Everyone is familiar with frost, which often reduces agricultural production. In order to avoid freezing injury, people have worked hard. Rime and rime are not very friendly to human beings, and generally appear in high mountains. In supercooled weather, when tiny raindrops or fog drops hit the surface of a severely cooled object, rime and rime will be formed on it.

The intensity and scale of this solid precipitation are sometimes amazing. Often in a day or two, an ice shell more than one meter thick can gather on the windward side of the object, and the scenery is very magical, just like the artistic conception in fairy tales.

Formation of snowflakes

How does the water vapor in the air movement form snowfall in the sky? Is the temperature below zero enough? No, if water vapor wants to crystallize, two conditions must be met to form snowfall:

One condition is that water vapor is saturated. The maximum amount of water vapor that air can hold at a certain temperature is called saturated water vapor. The temperature at which air reaches saturation is called dew point. When saturated air is cooled to a temperature below the dew point, the excess water vapor in the air becomes water droplets or ice crystals. Because the saturated water vapor content of ice surface is lower than that of water surface, the water vapor saturation required for the growth of ice crystals is lower than that of water droplets. That is to say, water droplets can grow only when the relative humidity (relative humidity refers to the ratio of the actual vapor pressure in air to the saturated vapor pressure of air at the same temperature) is not less than 100%; As for ice crystals, they tend to grow when the relative humidity is less than 100%. For example, when the temperature is -20℃ and the relative humidity is only 80%, ice crystals can grow. The lower the temperature, the less humidity is needed for the growth of ice crystals. Therefore, in the high-altitude and low-temperature environment, ice crystals are more likely to be produced than water droplets.

Another condition 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 only condense into water droplets if it is supersaturated to a relative humidity of more than 500%. 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 the earth. Condensation nuclei are tiny solid particles suspended in the air. The ideal condensation nuclei are those particles that absorb the most water. Such as sea salt, sulfuric acid, nitrogen and other chemicals. So we sometimes see clouds in the sky, but there is no snow. In this case, people often use artificial snowfall.

Non-condensing snowflakes in the sky

Snow falls from the sky. How can there be non-condensing snowflakes in the sky?

1in the winter of 773, a newspaper in Petersburg, Russia reported a very interesting news. According to news reports, at a dance, due to the large number of people and the burning of hundreds of candles, the ballroom was hot and stuffy, and the ladies and gentlemen in poor health almost fainted in front of the God of Joy. At this time, a young man jumped on the windowsill and smashed the glass with one punch. As a result, an unexpected miracle appeared in the ballroom. Beautiful snowflakes danced in the hall with the cold airflow outside the window and fell on the hair and hands of people who were dizzy with heat. Someone rushed out of the ballroom curiously to see if it was snowing outside. Surprisingly, the sky is dotted with stars and the crescent moon is as silver as water.

So, where did the snowflakes in the hall come from? This is really a puzzling question. Is anyone playing any magic tricks? But no matter how clever a magician is, he can't play with snowflakes in the hall.

Later, scientists solved the mystery. It turns out that the breath of many people in the ballroom is full of water vapor, and the burning of candles has scattered many condensation nuclei. When the cold air outside the window breaks through the window, it forces the saturated water vapor in the hall to condense and crystallize immediately and turn into snowflakes. So as long as it snows, it will snow in the house.

The basic shape of snowflakes

The scenery is beautiful when it snows, but scientists and artists appreciate the exquisite snowflake patterns. Glaciologists began to describe the shape of snowflakes in detail more than a hundred years ago.

Ding Duoer, the originator of western glaciology, described the snowflakes he saw on Luoza Peak in his classic glaciology works: "These snowflakes ... are all composed of small ice flowers, each of which has six petals, some of which release beautiful little lateral tongues like Su Hua, some are round, some are arrow-shaped, or zigzag, some are complete, and some are lattice-shaped, but they are not beyond.

In China, as early as 100 BC in the era of Emperor Wendi of the Western Han Dynasty, there was a poet named Han Ying who wrote a biography of Han Poetry, which clearly pointed out that "there are six snowflakes everywhere."

The basic shape of snowflakes is hexagonal, but there are almost no two identical snowflakes in nature, just as there are no two identical people on earth. Many scholars have observed thousands of snowflakes with microscopes. These studies finally show that it is impossible to form snowflakes with the same shape and size and partial symmetry in nature.

Among these observed snowflakes, even the regularly symmetrical snowflakes are deformed. Why do snowflakes deform? Because the water vapor content in the atmosphere around snowflakes can't be the same in all directions, as long as there is a slight difference, the side with more water vapor content always grows fast.

There are many collectors of snowflake patterns in the world. They collect all kinds of snowflake photos like stamp collectors. An American named Bentley took nearly 6,000 photos in his life. Soviet photographer Siger Mountain is also a photographer of snowflake photos. His charming works are often used as models of structural patterns by artists. Japanese Nakatani Yoshijiro and his colleagues worked hard for 20 years, shooting and studying thousands of snowflakes in the cold room of the laboratory of Hokkaido University in Japan and in the tent on the snowfield in northern Japan.

However, although snowflakes have various shapes, they remain unchanged, so scientists may classify them into the above seven shapes. Among these seven shapes, hexagonal snowflake and hexagonal prism snowflake are the most basic forms of snowflake, and the other five are only the development, transformation or combination of these two basic forms.

Effects of Snow on Human Health

In winter, it snows endlessly. People often ignore the role of snow when watching Yushu Qionghua. Snow has many benefits to human health. Compendium of Materia Medica has long recorded that snow water can detoxify and cure the plague. There is a folk prescription for treating fire burns and frostbite with snow water.

Taking a bath with snow water often can not only enhance the resistance between skin and body, reduce diseases, but also promote blood circulation and enhance physical fitness. Drinking clean snow water for a long time can prolong life. This is one of the "secrets" of those who have lived in the deep mountains and forests for a long time.

Why does snow have such strange functions? Because snow water contains less heavy water than ordinary water 1/4. Heavy water will seriously inhibit the life process of living things. After testing, fish will die quickly in water containing 30-50% heavy water. The most basic condition for the formation of rain and snow is the existence of "condensation nuclei" in the atmosphere, and solid impurities such as dust, coal particles and minerals in the atmosphere are the most ideal condensation nuclei. If meteorological factors such as water vapor and temperature in the air reach certain conditions, water vapor will condense into snowflakes around these condensation nuclei. Therefore, snowflakes can clean a lot of pollutants in the air. So every time after the heavy snow, the air is particularly fresh.

According to the measurement, the density of new snow is generally 0.05-0. 10g per cubic centimeter. Therefore, the reflectivity of ground snow to sound waves is extremely low, which can absorb a lot of sound waves and help reduce noise.

Thermal insulation function of snow

Snow is like a wonderful carpet, covering the earth, so that the temperature of the ground will not drop too low because of the cold in winter. This heat preservation effect of snow is inseparable from its own characteristics.

As we all know, it is warm to wear a cotton-padded jacket in winter. Why is it warm to wear a cotton-padded jacket? This is because the porosity of cotton is very high, and the pores of cotton are filled with a lot of air, which has poor thermal conductivity. This layer of air prevents the heat of human body from spreading outward. The snow covering the breast of the earth is very similar to cotton, and the porosity between snowflakes is very high. It is this layer of air that drills into the pores of the snow to protect the ground temperature from falling very low. Of course, the thermal insulation function of snow changes with the density at any time. It's like wearing a new cotton-padded jacket, which is especially warm, and the old cotton-padded jacket is not very warm. The density of fresh snow is low, and there is a lot of air stored in it, so the heat preservation effect is particularly strong. Chen Xue is like an old cotton-padded jacket, with high density and weak heat preservation effect, because there is less air stored in it.

Why does the more air an object stores, the stronger the heat preservation effect?

This is because air is a bad conductor. As we know, any object itself can transfer heat, and this property of transferring heat is called the thermal conductivity of the object. Among several common substances in nature, air has the worst thermal conductivity. Therefore, the more air an object contains, the worse its thermal conductivity. Because the amount of air contained in snow changes greatly, the thermal conductivity of snow also changes greatly. Generally, the newly fallen snow has large pores and the best heat preservation effect. In the late stage of snow melting in spring, snow is soaked by water, and its thermal conductivity is closer to that of water, so the thermal insulation effect of snow tends to disappear.

nivation

Erosion caused by frequent melting and frost heaving of snowfields in periglacial climate. Snow erosion occurs in polar and sub-polar regions without ice sheets, as well as in alpine regions below the snow line and above the tree line. The annual average temperature there is about 0℃, which belongs to permafrost region. On the one hand, the alternate freezing and thawing of the edge of the snowfield destroys the surface material through ice cracking; On the one hand, snow melting will take away the crushed fine substances, so snow erosion includes two functions: denudation and transportation. With the deepening of the bottom of the snowfield and the expansion of its periphery, a wide and shallow basin-shaped concave land with small peripheral slope is gradually formed on the hillside, that is, the snow melting concave land. Its shape, origin and spatial distribution are different from those of ice buckets, but they are related. When the climate becomes cold and the snow line drops, the snow-eroded depression can develop into an ice bucket; On the contrary, when the climate warms and glaciers recede, ice buckets can degenerate into snow-melting depressions. Under different natural and geographical conditions, the way and speed of snow erosion are different. Where the latitude is low, the precipitation is high and the freezing and thawing days are many, the snow erosion rate is faster, and the snow erosion is deep and large. For example, snow erosion is very common in Xiaoxing 'anling area of Northeast China. On the contrary, snow erosion is weak in places with high latitude, little precipitation and low temperature in summer. The influence of ground slope is: the slope is steep > 40, and the snow field is not easy to exist; Snow erosion on the flat land is slow; Snow erosion is most active on the slope of about 30.

The flood season when snow melts into water in warm spring is called spring flood.

Many people feel that the snow melting day is colder than the snowy day, mainly because the melting of snow requires a lot of heat. The latent heat of melting of snow is relatively large, and it takes 79.67 kcal for 1 g of zero-degree snow to melt into zero-degree water. In other words, this heat can heat the same weight of zero-degree water to 79.67℃. Because snow melting needs to consume a certain amount of heat, in the spring flood season, the temperature on the earth can't rise yet, and there will be a period of spring cold.

Every summer, the Yangtze River, the Yellow River and other major rivers in China have to fight floods, because this is the flood season of these rivers, and the rivers have the largest amount of water. However, some rivers in the world, such as the Irtysh River, ob river River, Yenisei River and Lena River in the Soviet Union, have their main flood season not in summer but in spring, and the spring flood season is the largest in the whole year, far exceeding the scale of summer flood season.

It turns out that the plains where these rivers flow have thick snow, and there are often warm air masses in these areas in spring. When the warm air mass passes through the border, the water vapor will cool and condense when it meets the snow surface. 1 g The latent heat released when water vapor condenses is 597 calories, which can melt 7.5 g of snow. Therefore, despite the deep snow, some places in the plain area can be completely melted by the warm air mass within a few days, and the melted snow water flows into a large number of rivers, which is the main reason for the flood in spring.

In some inland rivers in western China, the spring flood is also the biggest flood season there, and it is particularly fierce, sometimes causing floods. However, in summer in these places, the river water volume decreases rapidly and enters the dry season. For example, Emin River, which originated in the mountainous area on the border of Junggar, is particularly rich in water in spring and very little in summer. It is crystal clear and will not be cut off because of a small amount of groundwater infiltration.

These rivers mainly originate in mountainous areas, and the snow will not melt in winter. In spring, the snow will be melted by solar radiation, forming a rare flood season for inland rivers. In some alpine areas, the top of the mountain is covered with snow all year round, but the snow above a certain height will not melt all year round. This is called the snow line, and only the snow below the snow line will melt in spring. Most inland rivers in China flow through arid areas with little water. However, in the spring flood season, the river is particularly concentrated and needs flood control, so it is not impossible for floods to occur in desert areas.

In most parts of northern China, spring flood is the most precious water source for irrigated farmland. The amount of snowfall in winter, the size and morning and evening of spring flood after snow melting are closely related to the agricultural and animal husbandry production in northern China. Generally speaking, there is less seasonal snow in China, which is a dry country with little snow. Therefore, many places are not worried about too much spring flood, but suffer from insufficient spring flood and spring drought. Spring drought often occurs in parts of North China and Northwest China. In contrast, spring drought rarely occurs in the northeast plain, because there is a lot of snowfall in winter, and the spring flood season is not fierce but lasts for a long time.

The flood season when snow melts into water in warm spring is called spring flood.

Many people feel that the snow melting day is colder than the snowy day, mainly because the melting of snow requires a lot of heat. The latent heat of melting of snow is relatively large, and it takes 79.67 kcal for 1 g of zero-degree snow to melt into zero-degree water. In other words, this heat can heat the same weight of zero-degree water to 79.67℃. Because snow melting needs to consume a certain amount of heat, in the spring flood season, the temperature on the earth can't rise yet, and there will be a period of spring cold.

Every summer, the Yangtze River, the Yellow River and other major rivers in China have to fight floods, because this is the flood season of these rivers, and the rivers have the largest amount of water. However, some rivers in the world, such as the Irtysh River, ob river River, Yenisei River and Lena River in the Soviet Union, have their main flood season not in summer but in spring, and the spring flood season is the largest in the whole year, far exceeding the scale of summer flood season.

It turns out that the plains where these rivers flow have thick snow, and there are often warm air masses in these areas in spring. When the warm air mass passes through the border, the water vapor will cool and condense when it meets the snow surface. 1 g The latent heat released when water vapor condenses is 597 calories, which can melt 7.5 g of snow. Therefore, despite the deep snow, some places in the plain area can be completely melted by the warm air mass within a few days, and the melted snow water flows into a large number of rivers, which is the main reason for the flood in spring.

In some inland rivers in western China, the spring flood is also the biggest flood season there, and it is particularly fierce, sometimes causing floods. However, in summer in these places, the river water volume decreases rapidly and enters the dry season. For example, Emin River, which originated in the boundary mountain of Junggar, is particularly rich in water in spring and crystal clear in summer, and will not be cut off only by a small amount of groundwater infiltration.

These rivers mainly originate in mountainous areas, and the snow will not melt in winter. In spring, the snow will be melted by solar radiation, forming a rare flood season for inland rivers. In some alpine areas, the top of the mountain is covered with snow all year round, but the snow above a certain height will not melt all year round. This is called the snow line, and only the snow below the snow line will melt in spring. Most inland rivers in China flow through arid areas with little water. However, in the spring flood season, the river is particularly concentrated and needs flood control, so it is not impossible for floods to occur in desert areas.

In most parts of northern China, spring flood is the most precious water source for irrigated farmland. The amount of snowfall in winter, the size and morning and evening of spring flood after snow melting are closely related to the agricultural and animal husbandry production in northern China. Generally speaking, there is less seasonal snow in China, which is a dry country with little snow. Therefore, many places are not worried about too much spring flood, but suffer from insufficient spring flood and spring drought. Spring drought often occurs in parts of North China and Northwest China. In contrast, spring drought rarely occurs in the northeast plain, because there is a lot of snowfall in winter, and the spring flood season is not too fierce but lasts for a long time.

Snow is like a wonderful carpet, covering the earth, so that the temperature of the ground will not drop too low because of the cold in winter. This heat preservation effect of snow is inseparable from its own characteristics.

As we all know, it is warm to wear a cotton-padded jacket in winter. Why is it warm to wear a cotton-padded jacket? This is because the porosity of cotton is very high, and the pores of cotton are filled with a lot of air, which has poor thermal conductivity. This layer of air prevents the heat of human body from spreading outward. The snow covering the breast of the earth is very similar to cotton, and the porosity between snowflakes is very high. It is this layer of air that drills into the pores of the snow to protect the ground temperature from falling very low. Of course, the thermal insulation function of snow changes with the density at any time. It's like wearing a new cotton-padded jacket, which is especially warm, and the old cotton-padded jacket is not very warm. The density of fresh snow is low, and there is a lot of air stored in it, so the heat preservation effect is particularly strong. Chen Xue is like an old cotton-padded jacket, with high density and weak heat preservation effect, because there is less air stored in it.

Why does the more air an object stores, the stronger the heat preservation effect?

This is because air is a bad conductor. As we know, any object itself can transfer heat, and this property of transferring heat is called the thermal conductivity of the object. Among several common substances in nature, air has the worst thermal conductivity. Therefore, the more air an object contains, the worse its thermal conductivity. Because the amount of air contained in snow changes greatly, the thermal conductivity of snow also changes greatly. Generally, the newly fallen snow has large pores and the best heat preservation effect. In the late stage of snow melting in spring, snow is soaked by water, and its thermal conductivity is closer to that of water, so the thermal insulation effect of snow tends to disappear.

World champion of human sprint, but running 1 1 meter per second; Cheetah, the champion of sprint in the animal kingdom, is as fast as lightning when chasing prey, but it runs 30.5 meters per second; 12 strong typhoon, but it runs 32.5 meters per second. But avalanches can reach an astonishing degree of 97 meters per second. For example, the avalanche in Peru 1970 flew 14.5 km in less than three minutes. In other words, the average speed per second is nearly 90 meters.

The destructive power of avalanche is very strong, which is mainly related to its speed. A high-speed moving object will produce a strong impact. A bullet, when you hold it in your hand and touch the human body, you can't see any danger at all. But when it flies out of the barrel at high speed, it can kill people. Planes are most afraid of hitting birds in the air, because high-speed planes are often hit by birds and break the front cabin glass.

The impact of the avalanche is amazing. The avalanche with high speed can bear 40 ~ 50 tons of force per square meter on the surface of the hit object. Nothing in the world can withstand such a huge impact. Even a lush forest will be swept away like a barber clipper when it encounters a high-speed avalanche.

Another cause of avalanche disaster is air billow caused by avalanche. In the process of high-speed movement, the avalanche body can cause violent oscillation of the air and generate powerful air churning in front of the avalanche faucet. This kind of air churning is somewhat similar to the shock wave when the atomic bomb exploded, and it is very powerful. The tumbling in the air caused by the Peru 1970 avalanche raised rock fragments on the ground and caused a strange "stone rain" nearby.

Avalanches may be stopped where steep rocks or valleys turn sharply. However, the avalanche air billow is hard to stop, and it will continue to climb mountains and mountains along the direction of avalanche movement. Therefore, the range of action of avalanche air billow is much larger than that of avalanche body. Avalanches in air billow can also destroy forests, houses and other engineering facilities. When it crosses the traffic line, it can even overturn the vehicle. People encounter it, even if they can't scrape it off, they will be suffocated by it.

Avalanches, like wars, bring endless disasters to people, and there seems to be an indissoluble bond between them. There are many wars related to avalanches in history.

In ancient North Africa, there was once a very famous military power called the Carthaginian Empire. Later, due to conflicts of interest, this empire fought many wars with the Roman Empire on the northern shore of the Mediterranean. In 2 18 BC, Hannibal the famous Carthaginian was ordered to make an expedition to the Roman Empire. He commanded 38,000 infantry, 8,000 cavalry and 37 elephants, bypassed Spain and France, and crossed the snowy Alps at the end of 10. Because Hannibal's horses lacked the basic knowledge of snow and avalanches, his troops were confused by avalanches in the Alps and suffered heavy losses. Eighteen thousand soldiers and two thousand war horses died, and several African elephants were buried in Xue Hai.

In modern times, the French emperor Napoleon prepared to invade Italy separated by the snow-capped Alps. Napoleon was much cleverer than Hannibal. He first sent spies to the mountains for reconnaissance. The spy came back trembling and said, "Maybe it will pass, but …". Napoleon immediately stopped the spy from going on: "The longer the better, there will be no buts. Go to Italy immediately! " "1796, Napoleon personally led 40,000 troops, arranged in a 30-kilometer long snake formation, and crossed the snowy Alps from northwest to southeast. Although Napoleon made full preparations in advance, the avalanche in the Alps buried nearly a thousand of his soldiers.

During the First World War, Italy and Austria fought in the Troll region of the Alps, and the number of people killed by avalanches on both sides was no less than 40,000. Both sides often deliberately bombard the snowy hillside with artillery, creating artificial avalanches to kill the enemy. Later, an Austrian officer lamented in his memoirs that "the Alps in winter are more dangerous enemies than the Italian army."