Layers of Earth's Atmosphere - Windows to the Universe
Layers of Earth's Atmosphere
The Earth's Atmosphere
The atmosphere surrounds Earth and protects us by blocking out dangerous rays     from the sun. The atmosphere is a mixture of gases that becomes thinner until     it gradually reaches space. It is composed of Nitrogen (78%), Oxygen (21%),     and other gases (1%).
Oxygen is essential to life because it allows us to breathe. Some of the oxygen   has changed over time to ozone. The the ozone layer filters out the sun's harmful   rays. Recently, there have been many studies on how humans have caused a hole   in the ozone layer.
Humans are also affecting Earth's atmosphere through the greenhouse effect.   Due to increases in gases, like carbon dioxide, that trap heat being radiated   from the Earth, scientists believe that the atmosphere is having trouble staying   in balance creating the greenhouse effect .
The atmosphere is divided into five layers depending on how temperature changes with height. Most of the weather occurs in the first layer.
Layers of the Earth's Atmosphere
The atmosphere is divided into five layers. It is thickest near the surface     and thins out with height until it eventually merges with space.
The troposphere is the first layer above the surface and contains half     of the Earth's atmosphere. Weather occurs in this layer.
Many jet aircrafts       fly in the stratosphere because it is very stable. Also, the ozone layer       absorbs harmful rays from the Sun.
Meteors or rock fragments burn up in       the mesosphere.
The thermosphere is a layer with auroras. It is also where     the space shuttle orbits.
The atmosphere merges into space in the extremely       thin exosphere. This is the upper limit of our atmosphere.
The Average Temperature Profile of Earth's Atmosphere
The Troposphere
The troposphere is the lowest layer of the Earth's atmosphere. The air is very well mixed and the temperature decreases with altitude.
Air in the troposphere     is heated from the ground up. The surface of the Earth absorbs energy and   heats up faster than the air does. The heat is spread through   the troposphere because the air is slightly unstable.
Weather occurs in the Earth's troposphere.
The Stratosphere
In the Earth's stratosphere, the temperature increases with     altitude. On Earth, ozone causes the increasing temperature in the stratosphere.     Ozone is concentrated     around an altitude of 25 kilometers. The ozone molecules absorb dangerous   kinds of sunlight, which heats the air around them.
The stratosphere is located     above the top of the the troposphere.
Ozone - An Overview
The Ozone Hole. Pollution. Skin Cancer. Why does the topic of ozone make the   news so much? How important is the ozone in our atmosphere? Why are scientists   so concerned about its increase near the surface of the Earth and its disappearance higher up in the atmosphere?
First things first - what is ozone? Ozone is made   of three oxygen atoms (O3). The oxygen in our atmosphere that we breathe is   made up of two oxygen atoms   (O2). When enough ozone molecules are present, it forms a pale blue gas. Ozone   has the same chemical structure whether it is found in the stratosphere or   the troposphere. Where we find ozone in the atmosphere determines whether we consider it to be "good" or "bad"!
In the troposphere, the ground-level or "bad" ozone is an air pollutant   that damages human health, vegetation, and many common materials. It is a key   ingredient of urban smog. In the stratosphere, we find the "good" ozone   that protects life on Earth from the harmful effects of the Sun's ultraviolet   rays. We have good reason to be concerned about the thinning of the ozone layer   in the stratosphere. We also have good reason to be concerned about the buildup   of ozone in the troposphere. Although simplistic, the saying "Good up high and bad near by," sums up ozone in the atmosphere.
Ozone in the Stratosphere
About 90% of the ozone in the Earth's atmosphere is found in the region called   the stratosphere. This is the atmospheric layer between 16 and 48 kilometers   (10 and 30 miles) above the Earth's surface. Ozone forms a kind of layer in the stratosphere, where it is more concentrated than anywhere else.
Ozone and     oxygen molecules in the stratosphere absorb ultraviolet light from the Sun,     providing a shield that prevents this radiation from passing to the     Earth's surface. While both oxygen and ozone together absorb 95 to 99.9%   of the Sun's ultraviolet radiation, only ozone effectively absorbs the most   energetic     ultraviolet light, known as UV-C and UV-B. This ultraviolet light can cause     biological damage like skin cancer, tissue damage to eyes and plant tissue     damage. The protective role of the ozone layer in the upper atmosphere is   so vital that scientists believe life on land probably would not have evolved   - and could not exist today - without it.
The ozone layer would be quite good at its job of protecting Earth from too   much ultraviolet radiation - that is, it would if humans did not contribute   to the process. It's now known that ozone is destroyed in the stratosphere   and that some human-released chemicals such as CFCï¿½s are speeding up   the breakdown of ozone, so that there are "holes" now in our protective   shield.
While the stratospheric ozone issue is a serious one, in many ways it can   be thought of as an environmental success story. Scientists detected the developing   problem, and collected the evidence that convinced governments around the world   to take action. Although the elimination of ozone-depleting chemicals from   the atmosphere will take decades yet, we have made a strong and positive beginning.   For the first time in our species' history, we have tackled a global environmental issue on a global scale.
The Mesosphere
In the Earth's mesosphere, the air is relatively mixed together   and the temperature decreases with altitude. The atmosphere reaches its coldest   temperature of   around -90ï¿½C in the mesosphere. This is also the layer in which a lot of   meteors burn up while entering the Earth's atmosphere.
The mesosphere is on     top of the stratosphere The upper parts of the atmosphere, such as the mesosphere,   can sometimes be seen by looking at the very edge of a planet.
The Thermosphere
The thermosphere is the fourth layer of the Earth's atmosphere   and is located above the mesosphere. The air is really thin in the thermosphere.   A small change   in energy can cause a large change in temperature. That's why the temperature   is very sensitive to solar activity. When the sun is active, the thermosphere can heat up to 1,500ï¿½ C or higher!
The Earth's thermosphere also includes the region of the atmosphere called   the ionosphere. The ionosphere is a region of the atmosphere that is filled   with charged particles. The high temperatures in the thermosphere can cause molecules to ionize. This is why an ionosphere and thermosphere can overlap.
The Ionosphere
Scientists call the ionosphere an extension of the thermosphere.     So technically, the ionosphere is not another atmospheric layer. The ionosphere     represents       less than 0.1% of the total mass of the Earth's atmosphere. Even though   it is such a small part, it is extremely important!
The upper atmosphere is     ionized by solar radiation. That means the Sun's energy is so strong at this     level, that it breaks apart molecules. So there         ends up       being electrons floating around and molecules which have lost or gained   electrons. When the Sun is active, more and more ionization happens!
Different regions of the ionosphere make long distance radio communication   possible by reflecting the radio waves back to Earth. It is also home to auroras.
Temperatures in the ionosphere just keep getting hotter as you go up!
Regions of the Ionosphere
The ionosphere is broken down into the D, E and F regions. The breakdown is   based on what wavelength of solar radiation is absorbed in that region most frequently.
The D region is the lowest in altitude, though it absorbs the most     energetic radiation, hard x-rays. The D region doesn't have a definite starting     and stopping   point, but includes the ionization that occurs below about 90km.
The E region peaks at about 105km. It absorbs soft x-rays.
The F region starts around 105km and has a maximum around 600km. It is the   highest of all of the regions. Extreme ultra-violet radiation (EUV) is absorbed   there.
On a more practical note, the D and E regions reflect AM radio waves back   to Earth. Radio waves with shorter lengths are reflected by the F region. Visible   light, television and FM wavelengths are all too short to be reflected by the ionosphere. So your t.v. stations are made possible by satellite transmissions.
This image shows how the ionosphere is divided even further into layers:           D, E, and F layers.
The Sun's Effect on the Ionosphere
Invisible layers of ions and electrons are found in the Earth's atmosphere.   We call this region of atmosphere the ionosphere.
The main source of these layers is the Sun's ultraviolet light which ionizes   atoms and molecules in the Earth's upper atmosphere. During this process, electrons are knocked free from molecules or particles in the atmosphere.
Flares and other big events on the Sun produce increased ultraviolet, x-ray   and gamma-ray photons that arrive at the Earth just 8 minutes later (other   particles from the Sun may arrive days later) and dramatically increase the   ionization that happens in the atmosphere. So, the more active the Sun, the thicker the ionosphere!
This         image shows how different types of solar radiation (x-rays to infrared         radiation) penetrate into the Earth's atmosphere. It is this solar radiation         that ionizes the upper atmosphere, creating the ionosphere.
The Exosphere
Very high up, the Earth's atmosphere becomes very thin. The     region where atoms and molecules escape into space is referred to as the   exosphere. The exosphere   is on top of the thermosphere.
Last modified September 1, 2010 by Randy Russell .
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