Category Astrophysics

WHY IS THE STRATOSPHERE VITAL?

The stratosphere has a layer of ozone gas, which acts like a thick umbrella covering the layers beneath. By absorbing most of the harmful UV radiation from the Sun, the ozone layer prevents it from reaching the surface of the Earth, thus enabling the survival of life on the planet.

Stratosphere could be aptly called the ‘protection blanket’ of Earth. It extends up to 600 kms from the surface of the earth and it is the second layer of the Earth’s atmosphere, right above troposphere.

Stratosphere houses in it the most important layer called Ozone (O3), which acts as an absorber of the harmful UV radiations of the Sun (of about 90%) and thereby protecting us from diseases like Cancer, skin burn etc.

Its non-turbulance and stable, non-convection character makes it possible for the jets to cruise easily, hence they are flown here.

When Volcanic eruptions occur, the ejected material reaches as high as Stratosphere and it stays there for long period, as it doesn’t allow the circulation, there by leading to stratifying the volcanic particles and cooling down of the Earth surface.

However, such an important layer is being perforated by us through the extensive use of the chloro-fluro-carbons which happen to destroy the ozone molecules.

There is also an idea which the scientists are considering that could result in the slowing down of the Earth’s heating, i.e., by adding the man-made materials to stratosphere. Though the feasibility of this idea is yet to be verified. Thus, is the importance of the Stratosphere layer.

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IS THE ATMOSPHERE BUILT UP IN LAYERS?

Yes, the atmosphere has five layers. The lowest layer, closest to the surface of the Earth, is the troposphere. This is where weather is made, and most of the atmosphere’s gases are concentrated in it. Above it is the Stratosphere. No winds blow in this layer, nor are there any clouds. Beyond it lies the cold mesosphere, with very few gases. It is followed by the thermosphere, the thickest and hottest layer of the atmosphere, and lastly, the exosphere, on the edge of outer space.

Earth’s atmosphere is all around us. Most people take it for granted. Among other things, it shields us from radiation and prevents our precious water from evaporating into space. It keeps the planet warm and provides us with oxygen to breathe. In fact, the atmosphere makes Earth the livable, lovable home sweet home that it is.

The atmosphere extends from Earth’s surface to more than 10,000 kilometers (6,200 miles) above the planet. Those 10,000 kilometers are divided into five distinct layers. From the bottom layer to the top, the air in each has the same composition. But the higher up you go, the further apart those air molecules are.

Troposphere: Earth’s surface to between 8 and 14 kilometers (5 and 9 miles)

This lowest layer of the atmosphere starts at the ground and extends 14 kilometers (9 miles) up at the equator. That’s where it’s thickest. It’s thinnest above the poles, just 8 kilometers (5 miles) or so. The troposphere holds nearly all of Earth’s water vapor. It’s where most clouds ride the winds and where weather occurs. Water vapor and air constantly circulate in turbulent convection currents. Not surprisingly, the troposphere also is by far the densest layer. It contains as much as 80 percent of the mass of the whole atmosphere. The further up you go in this layer, the colder it gets.

Stratosphere: 14 to 64 km (9 to about 31 miles)

Unlike the troposphere, temperatures in this layer increase with elevation. The stratosphere is very dry, so clouds rarely form here. It also contains most of the atmosphere’s ozone, triplet molecules made from three oxygen atoms. At this elevation, ozone protects life on Earth from the sun’s harmful ultraviolet radiation. It’s a very stable layer, with little circulation. For that reason, commercial airlines tend to fly in the lower stratosphere to keep flights smooth. This lack of vertical movement also explains why stuff that gets into in the stratosphere tends to stay there for a long time. That “stuff” might include aerosol particles shot skyward by volcanic eruptions, and even smoke from wildfires. This layer also has accumulated pollutants, such as chlorofluorocarbons. Better known as CFCs, these chemicals can destroy the protective ozone layer, thinning it greatly. By the top of the stratosphere, called the stratopause, air is only a thousandth as dense as at Earth’s surface.

Mesosphere: 64 to 85 km (31 to 53 miles)

Scientists don’t know quite as much about this layer. It’s just harder to study. Airplanes and research balloons don’t operate this high and satellites orbit higher up. We do know that the mesosphere is where most meteors harmlessly burn up as they hurtle towards Earth.

The mesopause is also known as the Karman line. It’s named for the Hungarian-born physicist Theodore von Kármán. He was looking to determine the lower edge of what might constitute outer space. He set it at about 80 kilometers (50 miles) up.

The ionosphere is a zone of charged particles that extends from the upper stratosphere or lower mesosphere all the way to the exosphere. The ionosphere is able to reflect radio waves; this allows radio communications.

Thermosphere: 85 to 600 km (53 to 372 miles)

The next layer up is the thermosphere. It soaks up x-rays and ultraviolet energy from the sun, protecting those of us on the ground from these harmful rays. The ups and downs of that solar energy also make the thermosphere vary wildly in temperature. It can go from really cold to as hot as about 1,980 ºC (3,600 ºF) near the top. The sun’s varying energy output also causes the thickness of this layer to expand as it heats and to contract as it cools. With all the charged particles, the thermosphere is also home to those beautiful celestial light shows known as auroras. This layer’s top boundary is called the thermopause.

Exosphere: 600 to 10,000 km (372 to 6,200 miles)

The uppermost layer of Earth’s atmosphere is called the exosphere. Its lower boundary is known as the exobase. The exosphere has no firmly defined top. Instead, it just fades further out into space. Air molecules in this part of our atmosphere are so far apart that they rarely even collide with each other. Earth’s gravity still has a little pull here, but just enough to keep most of the sparse air molecules from drifting away. Still, some of those air molecules — tiny bits of our atmosphere — do float away, lost to Earth forever.

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HOW COLD IS THE ATMOSPHERE?

The atmosphere, with all its layers, extends up to 10,000 km from Earth’s surface. Temperatures vary in the different layers: the mesosphere can go down to -90 °C, the exosphere much, much lower, whereas the thermosphere can be as hot as 2000 °C!

Temperature varies greatly at different heights relative to Earth’s surface and this variation in temperature characterizes the four layers that exist in the atmosphere. These layers include the troposphere, stratosphere, mesosphere, and thermosphere.

The troposphere is the lowest of the four layers, extending from the surface of the Earth to about 11 km (6.8 mi) into the atmosphere where the tropopause (the boundary between the troposphere stratosphere) is located. The width of the troposphere can vary depending on latitude, for example, the troposphere is thicker in the tropics (about 16 km (9.9 mi)) because the tropics are generally warmer, and thinner at the poles (about 8 km (5.0 mi)) because the poles are colder. Temperatures in the atmosphere decrease with height at an average rate of 6,5°C (11,7 °F) per kilometer. Because the troposphere experiences its warmest temperatures closer to Earth’s surface, there is great vertical movement of heat and water vapour, causing turbulence. This turbulence, in conjunction with the presence of water vapour, is the reason that weather occurs within the troposphere.

Following the tropopause is the stratosphere. This layer extends from the tropopause to the stratopause which is located at an altitude of about 50 km (31 mi). Temperatures remain constant with height from the tropopause to an altitude of 20 km (12 mi), after which they start to increase with height. This happening is referred to as an inversion and it is because of this inversion that the stratosphere is not characterized as turbulent. The stratosphere receives its warmth from the sun and the ozone layer which absorbs ultraviolet radiation.

The next layer is called the mesosphere which extends from the stratopause to the mesopause, located at an altitude of 85 km (53 mi). Temperatures in the mesospere decrease with altitude and are in fact the coldest in the Earth’s atmosphere.This decrease in temperature can be attributed to the diminishing radiation received from the Sun, after most of it has already been absorbed by the thermosphere.

The fourth layer of the atmosphere is known as the thermosphere which extends from the mesopause to the ‘top’ of the collisional atmosphere. Some of the warmest temperatures can be found in the thermosphere, due to its reception of strong ionizing radiation at the level of the Van Allen radiation belt.

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IN WHICH LAYER OF THE ATMOSPHERE DO SATELLITES ORBIT EARTH?

You can consider most satellites to be in space, but in terms of the Earth’s atmosphere, they occupy regions called the thermosphere and the exosphere. The layer through which a satellite orbits depends on the satellite’s function and the kind of orbit it has. Since the launch of Sputnik in the 1950s, spacefaring countries have put thousands of satellites into orbit around the Earth and even other planets. They serve many different purposes, from complex space stations like the International Space Station to the Global Positioning System that helps you find your way home.

Thermosphere: High Temperatures

The thermosphere is a region of very high temperature that extends from the top of the mesosphere at around 85 kilometers (53 miles) up to 640 kilometers (400 miles) above the Earth’s surface. It is called the thermosphere because temperatures can reach up to 1,500 degrees Celsius (2,732 degrees Fahrenheit). However, despite the high temperatures, the pressure is very low, so satellites don’t suffer heat damage.

Exosphere: Farthest Reaches

Above the thermosphere sits a final layer called the exosphere, which extends up to 10,000 kilometers (6,200 miles) above the Earth, depending on how it is defined. Some definitions of the exosphere include all space up until the point where atoms get knocked away by solar wind. No distinct upper boundary exists since the exosphere has no pressure and molecules float freely here. Eventually, the exosphere gives way to space outside of the Earth’s influence.

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