The Earth's atmosphere consists of a layer of different gases held in place by gravity. The atmosphere protects Earth by absorbing solar radiation, retaining heat, and regulating temperature extremes. The atmosphere has five different levels: the exosphere, the thermosphere, the mesosphere, the stratosphere, and the troposphere. Since there are so many layers and we are limited in space, below are a few ideas to help get you started as well as an equation below to help you calculate for each layer's weight, which is actually called density.
The exosphere is the atmosphere's uppermost layer. The exosphere starts from the exobase, which is the top of the thermosphere, and extends until it merges with outer space. The exosphere starts at 700 km (440 mi) above sea level and extends to about 10,000 km (6,200 mi). The exosphere is also made up of the earth's lightest gases, which are mostly hydrogen, helium, carbon dioxide, and atomic oxygen.
The thermosphere is the second-highest level and extends from the mesosphere to what we call the thermopause, which is where the thermosphere ends. The altitude range of the thermosphere starts at about 80 km (50 mi) to 500-1,000 km (310-620 mi). The gases in the thermosphere, as well as in the troposphere, stratosphere, and mesosphere, consist of atomic oxygen, molecular oxygen, atomic nitrogen, molecular nitrogen, helium, and hydrogen.
If you are looking for the weight of each atmospheric level and the gases within each atmospheric level, you are actually looking for the density, specifically the air density or atmospheric density. One can simplify the equation for calculating atmospheric density by assuming the air is dry, giving only negligible errors in the results. The equation to calculate air density is
` ` `D=P/(R*T)`
` ` where: D = density, kg/m3
P = pressure, Pascals ( multiply mb by 100 to get Pascals)
R = specific gas constant , J/(kg*degK) = 287.05 for dry air
T = temperature, deg K = deg C + 273.15
So, if we know the temperature of each level and the air pressure within each level, we can calculate each level's density. We can also use for air pressure the International Standard Atmosphere (ISA) model, which is 101,325 Pascals. We can also use 287.05 as the specific gas constant for dry air. Using the exosphere as our example, the exosphere is understood to be extremely hot, at 2,500 degrees Celsius. So, plugging in our variables, we get
287.05 * 2,773.15
Therefore, the weight, or density of the exosphere is 0.1273 kg/m3 and calculations can be continued from there.
To calculate just the density of each layer of gas in each level of atmosphere, the equation is generally the same, density is the weight of the gas divided by the by the standard molar volume is 22.4 L/mol or
` `where FW represents the formula weight and is in g/mole. To find the formula weight, consult the periodic table of elements to find the grams per mole for the particular gas in question and then divide that by your standard volume.
The troposphere: About 7.5 miles from earth's surface. 99% of it is water vapor
The stratosphere: About 21 miles from the crust. This is where the Ozone layer is located
The Mesosphere: begins around 49.7 miles from the surface. A very thin blend of Nitrogen and Oxygen make up this layer
The Thermosphere: The very highest layer of our atmosphere. All the gases in this layer are very diluted because the temperature is so low that the molocules hardly collide with one another.
Earth's atmosphere consists of five different layers, the troposphere, stratosphere, mesophere, thermosphere, and exosphere.
Troposhere: Contains up to 75% of the Earth Mass. Primarily composed up of 78% nitrogen and 21% oxygen. The troposhere also contains 99% of the water vapor in the atmosphere. The troposhere is to 10 miles from the equator and 5-7 miles above the pole.
Stratosphere: About 6.2 miles above the ground at middle latitude. Contains little water vapor, so air is very dry. Has all the same gas as troposphere, but very little water vapor and there are small amount of ozone and monoatomic oxygen
Mesophere: 31-53 miles above Earth. Little is known about this atmosphere because scientists find it difficult to study this layer. This layer has a high concentration of iron and metal atoms
Thermosphere: 80% nitrogen and 20% oxygen. 56-321 miles above our planet.
Exosphere: Hydrogen, helium, carbon dioxide, and atomic oxygen.
There are five different layers of the atmosphere. The first, which is the closet to earth, is the troposphere. The troposphere consists of mostly water vapor and dust particles which is why most weather occurs in this layer. The air in this layer is the most dense. Air will get thinner as you go higher up.
The next layer is the stratosphere. This layer is around 31 miles and holds 19% of the atmosphere's gases. This layer is where the ozone is located which absorbs harmful sun rays.
Next is the mesosphere. Scientists don't know much about this layer because planes and jets cannot fly this high up. The mesosphere and the layers below it have a mixture of gases.
The thermosphere is what we would normally considered space because the air density is very low. In this layer the air is very thin and cold. Gases in this layer are very separated and collide infrequently. Air in lower layers contain mainly oxygen and nitrogen.
Lastly is the exosphere. This is the top layer of the atmosphere where atoms and molecules escape into space and the air is very very thin. The websites I have cited have a lot of information about the layers and their measurements/locations. Hope this helps :)
An Atmosphere is a thin layer wrapped around our planet. It is a mixture of gases that makes it easier for us to breathe and also protects us from dangerous rays of sun, retained by gravity.
Earth's atmosphere is about 300 miles (480 kilometers) thick, but most of it is within 10 miles (16 km) the surface. Air pressure decreases with altitude. At sea level, air pressure is about 14.7 pounds per square inch (1 kilogram per square centimeter). At 10,000 feet (3 km), the air pressure is 10 pounds per square inch (0.7 kg per square cm). There is also less oxygen to breathe.
The gases in Earth's atmosphere include:
- Nitrogen – 78 percent
- Oxygen – 21 percent
- Argon – 0.93 percent
- Carbon dioxide – 0.038 percent
Water vapor and other gases exist in small amounts as well.
Carbon dioxide and some other minor gases present in the atmosphere absorb some of the thermal radiation leaving the surface and emit radiation from much higher and colder levels out to space. These gases are referred to as greenhouse gases that act as a natural protective cover from the thermal radiation, known as greenhouse effect.
Purpose of Atmosphere
Our atmosphere filters the sunlight and keeps dangerous rays from reaching our planet. Without such a filter it would get too hot during the daytime. At night it prevents heat from escaping so it does not get too cold.
Can Life go on without Atmosphere?
Atmosphere is an essential part of universe. Without an atmosphere life on our planet would not be possible. It also makes our world a more pleasant place to live. Air carries sound waves, which let us hear voices or listen to music. The atmosphere creates rainbows, makes the sky turn blue on clear days and the sun red when it sets.
Weight and Pressure
We often think that the air is weightless but it isn’t. The whole weight of the earth’s atmosphere is about 5.5 quadrillion tons (55 followed by 14 zeros). Air is heaviest at sea level because the air molecules are pressed together. It also presses against our bodies but we have pressure inside , so we don’t feel it. When you move farther away from the earth’s surface the atmosphere gets lighter and lighter because there is more room between air molecules. The weight of the air decreases and so does air pressure.
At sea level, the air pressure is about 14.7 pounds per square inch. As your altitude increases (for example, if you climb a mountain), the air pressure decreases. At an altitude of 10,000 feet, the air pressure is 10 pound per square inch (and there is less oxygen to breathe).
Interactions - Atmosphere and Ocean
The oceans cover nearly three-quarters of the earth's surface and play an important role in exchanging and transporting heat and moisture in the atmosphere.
- Most of the water vapor in the atmosphere comes from the oceans.
- Most of the precipitation falling over land finds its way back to oceans.
- About two-thirds returns to the atmosphere via the water cycle.
The exchange of heat and moisture has profound effects on atmospheric processes near and over the oceans. Ocean currents play a significant role in transferring this heat poleward. Major currents, such as the northward flowing Gulf Stream, transport tremendous amounts of heat poleward and contribute to the development of many types of weather phenomena. They also warm the climate of nearby locations. Conversely, cold southward flowing currents, such as the California current, cool the climate of nearby locations.
Energy Heat Transfer
Practically all of the energy that reaches the earth comes from the sun. Intercepted first by the atmosphere, a small part is directly absorbed, particularly by certain gases such as ozone and water vapor. Some energy is also reflected back to space by clouds and the earth's surface.
Energy is transferred between the earth's surface and the atmosphere via conduction, convection, and radiation.
Meanwhile, the slow rotation of the earth toward the east causes the air to be deflected toward the right in the northern hemisphere and toward the left in the southern hemisphere. This deflection of the wind by the earth's rotation is known as the Coriolis effect.
Conduction is the process by which heat energy is transmitted through contact with neighboring molecules.
Convection transmits heat by transporting groups of molecules from place to place within a substance. Convection occurs in fluids such as water and air, which move freely.
Radiation is the transfer of heat energy without the involvement of a physical substance in the transmission. Radiation can transmit heat through a vacuum.
Energy travels from the sun to the earth by means of electromagnetic waves. The shorter the wavelength, the higher the energy associated with it. This is demonstrated in the animation below. As the drill's revolutions per minute (RPMs) increase, the number of waves generated on the string increases, as does the oscillation rate. The same principle applies to electromagnetic waves from the sun, where shorter wavelength radiation has higher energy than longer wavelength radiation.
Most of the sun's radiant energy is concentrated in the visible and near-visible portions of the spectrum. Shorter-than-visible wavelengths account for a small percentage of the total but are extremely important because they have much higher energy. These are known as ultraviolet wavelengths.
Layers of the Atmosphere
The Earth's atmosphere contains several different layers that can be defined according to air temperature.
- Troposphere (0 to 12 km)
- Stratosphere (12 to 50 km)
- Mesosphere (50 to 80 km)
- Thermosphere (80 to 700 km)
- Exosphere (>700 km)
Characteristics of Troposphere:
The word troposphere comes from tropein, meaning to turn or change. All of the earth's weather occurs in the troposphere.
The troposphere has the following characteristics:-
- It extends from the earth's surface to an average of 12 km (7 miles).
- The pressure ranges from 1000 to 200 millibars (29.92 in. to 5.92 in.).
- The temperature generally decreases with increasing height up to the tropopause (top of the troposphere); this is near 200 millibars or 36,000 ft.
- Winds increase with height up to the jet stream.
- The moisture concentration decreases with height up to the tropopause.
- The air is much drier above the tropopause, in the stratosphere.
- The sun's heat that warms the earth's surface is transported upwards largely by convection and is mixed by updrafts and downdrafts.
Characteristics of Stratosphere:
The stratosphere is the second layer.It starts above the troposphere and ends about 31 miles (50 km) above ground.
- This stratosphere contains about 19.9 % of the total mass found in the atmosphere.
- Very little weather occurs in the stratosphere.
- Occasionally, the top portions of thunderstorms breach this layer.
- The lower portion of the stratosphere is also influenced by the polar jet stream and subtropical jet stream.
- In the first 9 kilometers of the stratosphere, temperature remains constant with height.
- A zone with constant temperature in the atmosphere is called an isothermal layer.
- From an altitude of 20 to 50 kilometers, temperature increases with an increase in altitude.
- The higher temperatures found in this region of the stratosphere occurs because of a localized concentration of ozone gas molecules. These molecules absorb ultraviolet sunlight creating heat energy that warms the stratosphere.
- This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft).
- The atmospheric pressure at the top of the stratosphere is roughly 1/1000 the pressure at sea level.
- It contains the ozone layer, which is the part of Earth's atmosphere that contains relatively high concentrations of that gas.
- The stratosphere defines a layer in which temperatures rise with increasing altitude.
- Although the temperature may be −60 °C (−76 °F; 210 K) at the tropopause, the top of the stratosphere is much warmer, and may be near 0 °C.
- The stratospheric temperature profile creates very stable atmospheric conditions, so the stratosphere lacks the weather-producing air turbulence that is so prevalent in the troposphere.
The ozone layer is important to organisms at the Earth's surface as it protects them from the harmful effects of the sun's ultraviolet radiation. Without the ozone layer life could not exist on the Earth's surface.
Characteristics of Mesosphere:
The Mesosphere is characterized by temperature that quickly decreases as height increases.
- The mesosphere extends from the top of the stratosphere to about 80 km.
- The air becomes even thinner and the temperatures drop again.
- At the top of the mesosphere they may be lower than -75° C.
- Meteors or rock fragments burn up in mesosphere.
- The mesosphere starts at 31 miles (50 km) and extends to 53 miles (85 km) high.
- The top of the mesosphere, called the mesopause, is the coldest part of Earth's atmosphere with temperatures averaging about minus 130 degrees F (minus 90 C).
- Jets and balloons don't go high enough, and satellites and space shuttles orbit too high.
- The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere.
- Temperatures drop with increasing altitude to the mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85 °C (−120 °F; 190 K).
- The air is so cold that even the very scarce water vapor at this altitude can be sublimated into polar-mesospheric noctilucent clouds. These are highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or a similar length of time before sunrise.
- They are most readily visible when the Sun is around 4 to 16 degrees below the horizon.
Characteristics of Thermosphere:
The thermosphere ranges from 80 km to about 400 km above the earth. In this layer temperatures increase rapidly with altitude. At the bottom temperatures are below freezing, at the top they can reach over 1,000 °C. Satellites orbit the earth at this height. It includes the exosphere and part of the ionosphere.
- Temperatures in this layer can be as high as 1200°C.
- These high temperatures are generated from the absorption of intense solar radiation by oxygen molecules (O2).
- While these temperatures seem extreme, the amount of heat energy involved is very small. The amount of heat stored in a substance is controlled in part by its mass.
- The air in the thermosphere is extremely thin with individual gas molecules being separated from each other by large distances.
- The thermosphere is the second-highest layer of Earth's atmosphere.
- It extends from the mesopause (which separates it from the mesosphere) at an altitude of about 80 km (50 mi; 260,000 ft) up to the thermopause at an altitude range of 500–1000 km (310–620 mi; 1,600,000–3,300,000 ft).
- The height of the thermopause varies considerably due to changes in solar activity.
- Since the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase.
- The lower part of the thermosphere, from 80 to 550 kilometres (50 to 342 mi) above Earth's surface, contains the ionosphere.
- The temperature of this layer can rise as high as 1500 °C (2700 °F), though the gas molecules are so far apart that its temperature in the usual sense is not very meaningful.
- The air is so rarefied that an individual molecule (of oxygen, for example) travels an average of 1 kilometre (0.62 mi; 3300 ft) between collisions with other molecules.
- A person would not feel warm because of the thermosphere's extremely low pressure.
- This layer is completely cloudless and free of water vapor.
Characteristics of Exosphere:
In the outermost layer of the atmosphere temperatures are steady, averaging around 1200°C. Molecules in the exosphere are so far away from each other that they normally don’t collide. The layer extends into outer space and joins with the atmosphere of the sun and other planets. Atoms and particles escape the earth’s gravitation and float to outer space.
- The exosphere, the highest layer, is extremely thin and is where the atmosphere merges into outer space.
- It is composed of very widely dispersed particles of hydrogen and helium.
- It goes from 400 miles (640 km) high to about 800 miles (1280 km)
- The lower boundary of exosphere is called the critical level of escape, where atmospheric pressure is very low and the temperature is also low.
- This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase.
- The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another.
- Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind.
- The exosphere is located too far above Earth for any meteorological phenomena to be possible.
Within the five principal layers which are largely determined by temperature, several secondary layers may be distinguished by other properties:
- The ozone layer is contained within the stratosphere. In this layer ozone concentrations are about 2 to 8 parts per million, which is much higher than in the lower atmosphere but still very small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from about 15–35 km (9.3–21.7 mi; 49,000–115,000 ft), though the thickness varies seasonally and geographically. About 90% of the ozone in our atmosphere is contained in the stratosphere.
- The ionosphere is a region of the atmosphere that is ionized by solar radiation. It is responsible for auroras. During daytime hours, it stretches from 50 to 1,000 km (31 to 621 mi; 160,000 to 3,280,000 ft) and includes the mesosphere, thermosphere, and parts of the exosphere. However, ionization in the mesosphere largely ceases during the night, so auroras are normally seen only in the thermosphere and lower exosphere. The ionosphere forms the inner edge of the magnetosphere. It has practical importance because it influences, for example, radio propagation on Earth.
- The homosphere and heterosphere are defined by whether the atmospheric gases are well mixed. The surfaced-based homosphere includes the troposphere, stratosphere, mesosphere, and the lowest part of the thermosphere, where the chemical composition of the atmosphere does not depend on molecular weight because the gases are mixed by turbulence. This relatively homogeneous layer ends at the turbopause which is found at about 100 km (62 mi; 330,000 ft), which places it about 20 km (12 mi; 66,000 ft) above the mesopause.
- Above this altitude lies the heterosphere which includes the exosphere and most of the thermosphere. Here the chemical composition varies with altitude. This is because the distance that particles can move without colliding with one another is large compared with the size of motions that cause mixing. This allows the gases to stratify by molecular weight, with the heavier ones such as oxygen and nitrogen present only near the bottom of the heterosphere. The upper part of the heterosphere is composed almost completely of hydrogen, the lightest element.
- The planetary boundary layer is the part of the troposphere that is closest to Earth's surface and is directly affected by it, mainly through turbulent diffusion. During the day the planetary boundary layer usually is well-mixed, whereas at night it becomes stably stratified with weak or intermittent mixing. The depth of the planetary boundary layer ranges from as little as about 100 meters on clear, calm nights to 3000 m or more during the afternoon in dry regions.
The average temperature of the atmosphere at the surface of Earth is 14 °C (57 °F; 287 K)or 15 °C (59 °F; 288 K),
They are the troposphere, which is responsible for weather, stratosphere, which is our landscape, mesosphere, thermosphere, and exosphere.