Article reprinted from "Gezhi Discourse Forum"
The wind speed in the stratosphere is very large,
How big is it?
Wind speeds are greater than all typhoons and hurricanes on Earth.
Wei Ke · Associate Professor, Institute of Atmospheric Physics, Chinese Academy of Sciences
Gezhi Dao No. 44 | September 9, 2019 Beijing
Where is the stratosphere? Everyone looks up, over the ceiling and up, about 10 kilometers to 50 kilometers in the range is called stratosphere.
The stratosphere is generally above all the clouds we can see, the blue place. Because there is not much upward and sinking air flow here, the air is mainly horizontal flow, which is very suitable for aircraft flight, so we call it the stratosphere.
▲ The location of the stratosphere
The stratosphere's atmosphere doesn't have much upward and downward motion, so there aren't too many weather phenomena here either. Some friends may say, there is not much phenomenon, what is the use of studying it?
In fact, the stratosphere is closely related to our lives, especially the ozone layer, which is located between 20 and 30 kilometers. There are some beauty lovers who love and hate ozone and ozone-related ultraviolet rays.
The state of motion in the stratosphere has some very strange characteristics. For example, it has about half a year of east wind circulation, and the other half year is probably a west wind circulation. So, if you look over the North Pole in the summer, you'll see a clockwise circulation; in the winter, you'll see a counterclockwise circulation.
The wind speed in the stratosphere is very large, to what extent? Wind speeds are greater than all typhoons and hurricanes on Earth. So in the winter, the stratosphere has very strong westerly winds that imprison the world's coldest air in the Arctic.
Let's look at the two pictures on the left below, the shape of the stratosphere vortex in winter is not the same as in summer, summer is very regular, winter is not regular, and some distortion and deformation will occur at every turn.
▲ Engines with extremely cold air
When it is twisted and deformed, it means that there is cold air activity in the lower layer. So, I liken the stratosphere to an "engine of extreme cold air."
The winter of 2016 was very cold and was known as the "Overlord Cold Wave". If you look at the stratosphere a week or two before the "Overlord Cold Wave", you will see a third picture like this: the entire polar vortex is distorted and deformed, and cold air is constantly gushing out.
January 2019 was super cold in North America, and it felt like it had suddenly entered an ice age. This is because in January, the center of the Polar Vortex of the Arctic was split and deviated all the way over North America, which caused the weather in North America to be unusually cold. So, I liken the stratosphere to "global cold air, especially engines of extreme cold air."
▲ It is an engine with extreme cold air,
It is a ubiquitous umbrella, an amplifier of climate change
In addition, the stratosphere has also given us a large umbrella that is everywhere and everywhere. The stratosphere can also amplify climate changes.
The most cosmic radiation that Earth can receive is sunlight. Everyone thinks that the sunlight is warm, pure, and bright, in fact, the sunlight contains a lot of light that is invisible to the human eye, such as ultraviolet rays.
▲ The dispersion of sunlight
According to the wavelength from long to short, ultraviolet rays can be divided into UVA, UVB and UVC, of which UVC is the most dangerous ultraviolet rays. Under the long-term exposure of UVC, no life can survive. We often hear ultraviolet disinfection lamps, black lights, in fact, the light emitted by this lamp is invisible to the naked eye UVC, it can be used to disinfect, sterilization.
What are the effects of UVB? Under the long-term exposure of UVB, people are prone to skin cancer and cataracts, and every year there are many people who die of skin cancer and go blind due to cataracts in the world.
As for UVA, many beauty lovers hate it very much, because under the irradiation of UVA, the skin is easy to become old, black, and wrinkled, and aging begins with the skin first.
Fortunately, human beings are very lucky, because the stratosphere above our heads is like a large umbrella, which protects us everywhere and all the time.
▲ Stratosphere isolates UVC, UVB, and UVA
The ozone layer located at 20 km to 30 km can isolate 100% of the most dangerous UVC, 90% of UVB, and 50% of UVA. So, the ultraviolet rays that can reach the Earth's surface are only a small fraction of the ultraviolet rays.
Of course, there is still a part of ultraviolet light that reaches the earth's surface, how can we resist them? We have a lot of sunscreen products, take skin care products as an example, if the bottle is marked with "PA+++" or "PA++++", this means that the product contains anti-UVA ingredients; if the bottle is marked with "SPF30" or "SPF50+" and other words, it means that it can resist the damage of UVB.
Therefore, all beauty lovers should completely block UVA and UVB. When buying a related product, be sure to see if it has dual protection from PA and SPF.
Environmental crisis caused by the destruction of the ozone layer
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Do you think the ozone layer above your head is always there? In fact, if you look at the history of the earth, you will find that the formation time of the ozone layer is not particularly long, about 600 million years.
600 million years ago, an ozone layer with a concentration of only about 1/10 of the current concentration formed above the earth, and with this ozone layer, the earth's surface became safe.
Some people may say that there was life on Earth about 4 billion years ago, and since the surface of the Earth is so dangerous, where is that life? For a long 4 billion years, all life has crawled in the deep sea because the ocean surface and the Earth's surface are too dangerous.
So if you can cross, accidentally travel to 800 million years ago, the surface of the earth you see must be bare, there are no birds and flowers, no birds and animals, and ultraviolet rays shine on the surface of the earth without any hindrance.
It wasn't until the ozone layer formed about 600 million years ago that the Earth's surface began to become safer. A magnificent thing happened on the earth during this period - the Cambrian explosion.
About 540 million years ago, a variety of creatures suddenly appeared on the earth. Creatures that originally lived in the deep sea, because of the limited space of activity, the energy they could obtain was also very limited. Now, the surface of the ocean and the land are safe, which opens up the field of life evolution.
All life goes from the deep sea to the shallow sea, and then from the shallow sea to the land. That's why we say that life on land is only about 400 million years old. Compared to Earth's 4.6 billion years of history, humanity is really very fortunate that we haven't been lurking in the dark for a long time.
After entering the Cambrian explosion of life, the variety of life on Earth began to increase dramatically, and a variety of large animals appeared, such as dinosaurs. Dinosaurs dominated the earth for 160 million years, and it was only after the land became safe that it had room to survive.
▲ A clip of the Tyrannosaurus rex roaring in the film Jurassic Park 3
In the long history of the earth, human beings have only occupied a moment, but they are fortunate to be here today. And without the "protective umbrella" overhead, I think all life will be very simple, and it must continue to be hidden in the deep sea.
▲ Humans walked out of Africa 80,000 years ago
So, if we're looking for a habitable planet, we first have to think about whether it has water; second, whether it has a suitable atmosphere; and third, whether it has an ozone layer in its atmosphere.
Unfortunately, since the discovery of the stratosphere and the ozone layer, humans have often done some destructive things. Humans discovered the stratosphere in 1902, the ozone layer in 1913, and later began to invent various compounds, transport them into the stratosphere, and after the atmospheric circulation began to destroy the ozone layer. What are these compounds? Mainly Freon.
▲ Various compounds that destroy the ozone layer
For example, adding fluoride to the refrigerator, adding fluoride to the air conditioner; the kind of foam that sprays out of the old-fashioned fire extinguisher; and hairspray for hair styling, these substances are all substances that destroy the ozone layer.
In 1984, scientists discovered a huge ozone hole in antarctica, how big is this ozone hole? In 2000, its area was about 27 million square kilometers; in 2018, its area was about 23 million square kilometers. Of course, this ozone hole is not a real hole, but its ozone density value is much smaller than normal, like a hole.
▲ Changes in the Antarctic ozone hole
The normal ozone density should be 300 Dobson units, but in 1994, the minimum central value of the Antarctic ozone hole was only 92 Dobson units, and even in 2018, its value was only 112 Dobson units, which is equivalent to only 1/3 of the normal value. It is obviously unrealistic to have an umbrella that breaks 2/3 of the way, but we hope it will provide us with enough protection.
▲ The central value of the Antarctic ozone hole changes
In the 1980s, the discovery of the ozone hole caused serious panic around the world. Ozone, the basis for the survival of all living things in the world, is now being severely damaged.
▲ Crisis and response
So since the 1980s, all scientists and political scientists have been involved in discussions, all countries have begun to participate in action, and a number of conventions and protocols have been signed, including the 1985 Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol on the Control of Substances That Destroy the Ozone Layer (hereinafter referred to as the Protocol or the Montreal Protocol) signed in 1987 in montreal, an eastern Canadian city.
The Protocol decided to cease the production, sale and use of the five Freon substances and three halons, the most serious substances harmful to the ozone layer, with effect from 1 January 1989.
Now, the freons added to refrigerators and air conditioners, sprayed hairspray, foam materials in wall insulation, etc., have been completely replaced with new materials that do not destroy the ozone layer.
It's been exactly 30 years from 1989 to the present, and we've avoided a worst-case outcome. Without the joint efforts of the world in these 30 years, the ozone hole would have grown larger and larger; after 30 years of efforts, the ozone hole has been controlled to a degree that has not continued to deteriorate. It's basically getting back to what we call a bottoming out and is slowly recovering.
▲ Changes in the ozone layer from 1980 to 2025
Of course, illness comes like a mountain, and illness goes like a thread. The ozone hole will probably not return to the level of the 1980s until 2060, and it will not return to the level of the 1960s until 2100.
You can think about it, when the ozone hole is fully recovered, how old are you? So, all of you here are living in a story this life, and this story is called "restoration."
Of course, the response to the ozone hole crisis also shows that human beings can still unite to do something. We human beings are responsible and responsible. Former UN Secretary-General Kofi Annan said: "The Montreal Protocol we have signed is the most successful international agreement to date. ”
To what extent was it successful? The 196 Member States and territories of the United Nations (as of 2011, 193 States members of the United Nations, two observer States, together with the European Union) have all acceded to the Protocol and have scrupulously implemented its resolutions to cease the production, sale and use of all substances that destroy the ozone layer.
This is a very successful development. It also teaches us that in the face of future environmental crises, humanity can still make a difference.
The stratosphere is the amplifier of climate change
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The stratosphere is not only related to ozone changes, but also amplifies the effects of various natural processes. For example, we recently did some crazy experiments to simulate that in the process of ozone recovery (say, 2050 or 2100), there was a sudden supervolcano eruption that had never been seen in history.
▲ Effects of supervolcanoes (global average)
Simulation experiments tell us that if such a volcanic eruption does occur, the loss of ozone will still reach a very serious level. Therefore, we must now speed up the process of ozone recovery.
Will supervolcano eruptions affect climate change across the globe? In fact, such things have happened on Earth. Indonesia has a volcano called Toba, which is now a lake, but historically it was a crater, 100 kilometers long from north to south, 35 kilometers wide from east to west, a huge crater.
▲ Supervolcano: Super influence of the stratosphere
About 74,000 years ago, a very powerful eruption occurred at Toba, and ash was ejected into the stratosphere, because the atmosphere in the stratosphere was horizontal, so the ash spread throughout the stratosphere, blocking the radiation of the sun and causing a huge cooling of the Earth's surface.
▲ NASA Landsat satellite image（左）
Toba catastrophe theory（右）
Scientists have different views on the eruption, but everyone agrees that the eruption had a very bad impact on the development of species at the time. For example, it reduced the number of people to only 10,000 to 30,000, basically pushing humanity to the brink of extinction.
Now many scientists also use this disaster to explain why human genes are relatively single, including many animals and plants, because many animals and plants have become extinct in this disaster.
Of course, the frequency of supervolcano eruptions is very low, it may occur in tens of thousands or even hundreds of thousands of years, tens of millions of years, but the slightly less intense volcanic eruptions are also very destructive.
In 1815, there was an eruption of Mount Tambora in Indonesia, and the intensity of that eruption was seven. After the eruption, ash and various sulfates were ejected into the stratosphere, and with the horizontal winds of the stratosphere, these substances spread across the globe, blocking the sun's radiation. Because there are many small particles in the stratosphere, they scatter sunlight, so for a long time, the sky was red.
In everyone's common sense, after the wind and rain, the sky will turn blue; but during that time, even after the wind and rain, the sky is still red. The British landscape painter Turner painted two paintings, one before the eruption of the volcano and the other after the eruption.
▲ Before the eruption (left), after the eruption (right)
From this, we can clearly feel that the red sky after the volcanic eruption is so vicious. This eruption occurred in Indonesia, but the ash spread across the globe, affecting the global climate.
Another example is 1816, when many parts of the world were very cold. How cold is it? According to the news, it was still snowing in New York on June 6, and there were ice cubes in pennsylvania lakes in July.
Food production in Europe and the United States was reduced that year, and the European famine killed more than 200,000 people. If you are interested in Chinese history, you can check the relevant information, in 1816, many places in Anhui and Jiangsu have records of summer snow.
Therefore, stratospheric influences can amplify the entire climate process, turning the local process into a global climate process.
What else are the possible climate processes in the world? Nuclear winter.
▲ Nuclear winter
If there is a global nuclear war, it may lead to a nuclear winter. Nuclear winter means that nuclear weapons will cause the black smoke (black carbon) produced by the combustion of flammable materials to be sprayed into the stratosphere, and then spread to the whole world, blocking solar radiation, causing the ground to cool down, and making the surface appear as cold as winter.
Of course, after this theory was proposed in the 1980s, it had a very big impact on the world. At present, the power of peace is very strong, and it is no longer possible to have a very large nuclear war, but the risk of some small nuclear war still exists.
So the scientists did another crazy experiment: simulating a small nuclear war. For example, India and Pakistan launched a war for some reason, India dropped 50 nuclear warheads, Pakistan also dropped 50 nuclear warheads, 100 nuclear warheads caused 100 fires, and 100 cities were destroyed.
▲ A "small" war of 100 nuclear bombs
Of course, if the United States and the Soviet Union had waged a war, the scale of this simulated war would have been much smaller. The nuclear warheads in the simulation experiments were small, only 15,000 tons of TNT equivalent, equivalent to the equivalent of the atomic bomb "Little Boy" dropped by the United States on Hiroshima, Japan during World War II.
But even the simulated small-scale nuclear war in the experiment would inject about 5 million tons of black carbon into the world. After they enter the stratosphere, they quickly fill the entire stratosphere within half a year, from the South Pole to the North Pole, blocking solar radiation.
▲ Evolution of the mass mixing ratio of black carbon aerosols with time and height
Because the atmosphere in the stratosphere is mainly horizontal movement, the air is very stable, so even after 10 years, there will be about 1.1 million tons of black carbon in the atmosphere, which will cause global climate impacts, the most important embodiment of which is to affect agriculture.
The results of the scientists' simulations show that the agriculture of the United States and China, which did not participate in the war, will also be seriously affected: in the first five years of the war, China's winter wheat production may be reduced by 40%, spring wheat production will be reduced by about 35%, and the United States corn production will be reduced by about 20%.
▲ Comparison of changes in agricultural production between The Indo-Pakistani nuclear war around the past 10 years
In the second five years, the U.S. corn and soybean production fell by about 10 percent; China's grain production fell by about 15 to 25 percent.
Many people who study international politics should know that if crop production is reduced to this extent, it will inevitably bring about a global food crisis, and prices will soar, which will have the greatest impact on the poor.
What if the scale of the war was a little larger, turning into 1,000 nuclear warheads? There are now more than 10,000 nuclear warheads worldwide, and at its peak there are more than 70,000 nuclear warheads.
If 1,000 nuclear warheads exploded, about 50 million tons of black carbon would be sprayed into the stratosphere, and the global temperature would drop by about 3°C; if the number of nuclear warheads exploded increased to 3,000, the global temperature would drop by about 7°C.
▲ The impact of nuclear warhead explosions on global temperatures
Now the average global temperature is 15 °C, if it is reduced by 7 °C, it will go directly from the spring of 15 °C to about 8 °C of winter. A real nuclear winter will come. So, the stratosphere above our heads is very important to us, and it can amplify the climatic effects of various or man-made or natural processes.
To sum up, the stratosphere is the engine of extreme cold air around the world. At the same time, it provides us with a ubiquitous, ever-present umbrella that makes the planet more livable.
The implication is that in the future, if we are looking for a habitable planet, we must consider what the planet's atmosphere is like, whether it has a stratosphere, and whether there is an ozone layer in the stratosphere.
▲ Unsolved mysteries
The stratosphere has also prompted other disciplines to think that in the long history of the earth, the changes in various vicissitudes and mulberry fields, the changes in various paleoclimates, the birth and mass extinction of various organisms, and whether the stratosphere has played a very important amplification role.
After listening to my explanation, I hope that when you go out and look up at the sky, you will see the level above the clouds and have more thinking.
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