Structure, Composition Of Atmosphere

Our planet, Earth, is truly one of a kind because it’s the only place in the vast universe where life exists. The air plays a crucial role in supporting life, and it’s not just a simple breeze – it’s a unique blend of different gases. Imagine a giant embrace from all directions – that’s the air surrounding Earth, creating a protective atmosphere. This special atmospheric blanket is essential for our existence, thanks to its strong connection with Earth through gravity. Think of the atmosphere as our planet’s bodyguard – it shields us from harmful ultraviolet rays and maintains the perfect temperature for life. Life as we know it wouldn’t be possible without the air; it’s like a safety net that makes our planet a cozy home. The atmosphere isn’t just a mix of gases; it also contains water vapor and tiny dust particles, adding to the complexity of this protective layer.

Structure of Atmosphere

Thermal Structure of the Atmosphere

Atmospheric layers are characterized by variations in temperature resulting primarily from the absorption of solar radiation; visible light at the surface, near ultraviolet radiation in the middle atmosphere, and far ultraviolet radiation in the upper atmosphere.

Troposphere:

The troposphere is like Earth’s cozy blanket, wrapping around the planet. It’s where about 80% of our atmosphere’s mass hangs out.
As you go up, things cool down. The higher you go in the troposphere, the colder it gets, and it’s the party place for weather events – rain, storms, and all that jazz.
Water vapor is the MVP here. It soaks up the sun’s love and Earth’s warmth, playing a big role in keeping our temperatures in check.
Water vapor likes to party more near the equator (up to 3%) and chills out a bit near the poles. It’s like the atmosphere’s mood varies with its location.
The troposphere’s top boundary, aka tropopause, is like its rooftop. It’s highest in summer and lowest in winter, giving it some seasonal flair.

Stratosphere:

Stratosphere is the cool cat layer right above the troposphere, reaching about 30 miles above Earth.
Up to 15 miles, it’s a chill zone with constant temperatures. Then, it starts warming up, thanks to the stratopause.
Ozone takes the lead here, absorbing sun’s rays and turning them into stratospheric warmth. It’s like sunscreen for the atmosphere.
The famous ozone layer sets up shop around 10-15 miles, making up 90% of the atmospheric ozone. It’s crucial for blocking harmful UV rays.

Mesosphere:

The mesosphere is like the freezer of the atmosphere, getting colder as you climb from 30 to 50 miles up.
The coldest vibe is at the top, especially during summer near the poles. Some folks jokingly call it the “ignorosphere” because it’s been less explored.

Thermosphere:

Above the mesosphere, we enter the thermosphere.
Air molecules are having a bit of a break here. They’re spread thin, and lighter gases like atomic oxygen take the spotlight.

Exosphere:

The exosphere is like the edge of Earth’s VIP section, starting around 150 miles up.
Up here, molecules can either escape to space or come back down, with low chances of bumping into each other.
The lower boundary, or thermopause, hangs out around 150-300 miles up, and the upper one plays around 120,000 miles, halfway to the Moon.
From space, you can see this exosphere party going on, stretching out to at least 60,000 miles.
It’s like the exosphere is the VIP lounge between our atmosphere and the cosmic space outside.

Magneto-Electronic Structure of the Atmosphere

The upper atmosphere is also divided into regions based on the behaviour and number of free electrons and other charged particles.

Ionosphere:

Think of the ionosphere as a layer in our atmosphere that affects how radio waves travel.
Above the peak electron concentration, we call it the Topside Ionosphere.

Plasmasphere:

The plasmasphere isn’t a perfect sphere; it’s more like a doughnut around Earth’s magnetic axis.
Made up of a special kind of matter called plasma, mainly hydrogen ions and electrons.
Picture a sharp boundary called the plasmapause.
It’s an extension of the ionosphere, and inside it, magnetic field lines rotate with the Earth.
The plasmasphere has a defined inner edge where protons take over from oxygen, usually at about 600 miles above Earth.

Magnetosphere:

Imagine a cavity around Earth where the magnetic field is influenced by the solar wind and interplanetary magnetic field.
It’s not a perfect sphere but more like a teardrop shape, with the narrow end pointing toward the Sun.
The outer boundary is called the magnetopause, located about 35,000 miles above the Earth on the day side.
The tail, or magnetotail, extends millions of miles into space on the night side.
Beyond the magnetopause, there are regions called the magnetosheath and bow shock, affected by the solar wind and Earth’s magnetic field.
The Moon is usually not within this magnetic field, except for a couple of days around the Full Moon.

Composition Of Atmosphere

Our atmosphere is a blend of various gases, including solid and liquid particles known as ‘aerosols.’
Some gases are constant components, maintaining a consistent proportion in the air volume. On the other hand, other elements fluctuate in quantity based on location and time.
If we exclude suspended particles, water vapor, and other variable gases, the atmosphere is remarkably stable as dry air, extending uniformly up to about 80 kilometers above Earth’s surface.
As we ascend to higher atmospheric layers, the gas composition undergoes changes. For instance, oxygen becomes almost negligible at an altitude of 120 kilometers, while carbon dioxide and water vapor are present only up to 90 kilometers.
Nitrogen and oxygen dominate, constituting nearly 99% of clean, dry air, with the remaining 1% comprised mainly of inert gases.
Beyond gases, significant amounts of water vapor and dust particles coexist in the atmosphere, playing a crucial role in shaping our climate.

Different constituents of the atmosphere, with their individual characteristics, are discussed below.

Gases of the Atmosphere

The atmosphere is the mixture of different types of gases, including water vapour and dust particles. Nitrogen and Oxygen are the two main gases of the atmosphere. 99 percent part of it is made up of these two gases. Other gases like organ, carbon dioxide, hydrogen, nion, helium etc. form the remaining part of atmosphere.

Nitrogen:

Nitrogen makes up a whopping 78% of the air we breathe. It’s kind of like the chill friend in our atmosphere because it doesn’t react much with other stuff.
One of its cool jobs is to keep things from getting too fiery. It hangs out with oxygen and dilutes it, making sure combustion doesn’t go out of control.

Oxygen:

Even though it only makes up about 21% of our air, oxygen is the VIP (Very Important Player). We, and all living things, need it to breathe.
Oxygen is also a social butterfly. It loves mingling with other elements to create important compounds, like oxides. And, let’s face it, no fire would exist without oxygen.

Carbon Dioxide:

Carbon dioxide is like the tiny but mighty member, making up only 0.03% of the air. It’s born from combustion, but it has a life mission.
Plants are its best friends. Through photosynthesis, they snatch carbon dioxide from the air and turn it into food. Also, it’s a bit of a climate hero, trapping heat and helping with the Earth’s temperature balance.
When we burn fossil fuels like coal and gas, we pump more carbon dioxide into the air, making it a bit too good at its heat-trapping job and messing with our climate.

Ozone:

Ozone is the rare gem, making up less than 0.00005% of our air. It’s like the superhero high up in the atmosphere.
Hanging out between 20 and 25 km above us, ozone shields us from the sun’s harmful UV rays. It’s like our atmospheric sunscreen, and we need to keep it in good shape.

Other Gases:

There’s a tiny, exclusive club of gases like neon, helium, and methane in our air, but they’re like the background characters – present but not stealing the spotlight.
They might be in negligible amounts, but they add a touch of variety to the atmospheric mix.

Water Vapour

Gaseous form of water persent in the atmosphere is called water vapour.
Water vapour present in the atmosphere has made life possible on the earth Water vapour is the source of all kinds of precipitation.
Its maximum amount in the atmosphere could be upto 4 percent.
Maximum amount of water vapour is found in hot-wet regions and its least amount is found in the dry regions.
Generally, the amount of water vapour goes on decreasing from low latitudes to high latitudes.
In the same way, its amount goes on decreasing with increasing altitude.
Water vapour reaches in the atmosphere through evaporation and transpiration.
Evaporation takes place in the oceans, seas, rivers, ponds and lakes while transpiration takes lace from the plants, trees and living beings.

Dust Particles

Dust particles are generally found in the lower layers of the atmosphere.
These particles are found in the form of sand, smoke and oceanic salt.
Sand particle have important place in the atmosphere.
These dust particles help in the condensation of water vapour.
During condensation water vapour gets condensed in the form of droplets around these dust particles.
Due to this process the clouds are formed and precipitation is made possible.

Read Also: Evolution of Atmosphere