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Troposphere

Troposphere is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Troposphere rather than just read about it. In short: The troposphere is the lowest layer of the atmosphere of Earth. Pronounced , the name comes from Ancient Greek τρόπος (trópos) 'turning, change' and -sphere.

Troposphere — main illustration
Troposphere — illustration

Key takeaways

  • Troposphere belongs to earth science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Troposphere to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Troposphere from memory before moving on to harder problems.

Reference excerpt

The troposphere is the lowest layer of the atmosphere of Earth. Pronounced , the name comes from Ancient Greek τρόπος (trópos) 'turning, change' and -sphere. It contains 80% of the total mass of the planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the planetary surface of the Earth, the average height of the troposphere is 18 km (11 mi; 59,000 ft) in the tropics; 11 km (6.8 mi; 36,000 ft) in the middle latitudes; and 6 km (3.7 mi; 20,000 ft) in the high latitudes of the polar regions in winter; thus the average height of the troposphere is 13 km (8.1 mi; 43,000 ft). The term troposphere derives from the Greek words tropos (rotating) and sphaira (sphere) indicating that rotational turbulence mixes the layers of air and so determines the structure and the phenomena of the troposphere. The rotational friction of the troposphere against the planetary surface affects the flow of the air, and so forms the planetary boundary layer (PBL) that varies in height from hundreds of meters up to 2 km (1.2 mi; 6,600 ft). The measures of the PBL vary according to the latitude, the landform, and the time of day when the meteorological measurement is realized. Atop the troposphere is the tropopause, which is the functional atmospheric border that demarcates the troposphere from the stratosphere. As such, because the tropopause is an inversion layer in which air-temperature increases with altitude, the temperature of the tropopause remains constant. The layer has the largest concentration of nitrogen.

Structure

Composition The Earth's troposphere is composed of a mixture of gases, which when dry is by mole fraction 78.08% nitrogen as N2, 20.95% oxygen as O2, 0.93% argon, 0.04% carbon dioxide as CO2, and other trace gases. Additionally, the troposphere contains the vast majority of water vapor in the atmosphere. The flux of water vapor in the troposphere can slightly change these numbers, but even at the most humid, water vapor constitutes less than 5% of the local tropospheric composition. Local phenomena like combustion, volcanic eruptions, and industrial air pollution can also affect the local tropospheric composition.

Pressure The maximum air pressure (weight of the atmosphere) is at sea level and decreases at high altitude because the atmosphere is in hydrostatic equilibrium, wherein the air pressure is equal to the weight of the air above a given point on the planetary surface. The relation between decreased air pressure and high altitude can be equated to the density of a fluid, by way of the following hydrostatic equation:

d P d z = − ρ g n = − m P g n R T {\displaystyle {\frac {dP}{dz}}=-\rho g_{n}=-{\frac {mPg_{n}}{RT}}}

where:

gn is the standard gravity ρ is the density z is the altitude P is the pressure R is the gas constant T is the thermodynamic (absolute) temperature m is the molar mass

Temperature The planetary surface of the Earth heats the troposphere by means of latent heat, thermal radiation, and sensible heat. The gas layers of the troposphere are less dense at the geographic poles and denser at the equator, where the average height of the tropical troposphere is 13 km, approximately 7.0 km greater than the 6.0 km average height of the polar troposphere at the geographic poles; therefore, surplus heating and vertical expansion of the troposphere occur in the tropical latitudes. At the middle latitudes, tropospheric temperatures decrease from an average temperature of 15 °C (59 °F) at sea level to approximately −55 °C (−67 °F) at the tropopause. At the equator, the tropospheric temperatures decrease from an average temperature of 20 °C (68 °F) at sea level to approximately −70 to −75 °C (−94 to −103 °F) at the tropopause. At the geographical poles, the Arctic and the Antarctic regions, the tropospheric temperature decreases from an average temperature of 0 °C (32 °F) at sea level to approximately −45 °C (−49 °F) at the tropopause.

Altitude

The temperature of the troposphere decreases with increased altitude, and the rate of decrease in air temperature is measured with the environmental lapse rate ( − d T / d z {\displaystyle -dT/dz} ), which is the numeric difference between the temperature of the planetary surface and the temperature of the tropopause divided by the altitude. Functionally, the ELR equation presumes that the planetary atmosphere is static and that there is no mixing of the layers of air by either vertical atmospheric convection or winds that could create turbulence. The difference in temperature derives from the planetary surface absorbing most of the energy from the sun, which then radiates outwards and heats the troposphere (the first layer of the atmosphere of Earth) while the radiation of surface heat to the upper atmosphere results in the cooling of that layer of the atmosphere. The ELR equation also assumes that the atmosphere is static, but heated air becomes buoyant, expands, and rises. The dry adiabatic lapse rate (DALR) accounts for the effect of the expansion of dry air as it rises in the atmosphere, and the wet adiabatic lapse rate (WALR) includes the effect of the condensation-rate of water vapor upon the environmental lapse rate.

… excerpt ends here. Continue reading the full article.

Illustrations

Troposphere: A picture of Earth's troposphere with its different cloud types of low to high altitudes casting shadows. Sunlight is reflected off the ocean, after it was filtered into a reddish light by passing through much of the troposphere at sunset. The above lying stratosphere can be seen at the horizon as a band of its characteristic glow of blue scattered sunlight.
A picture of Earth's troposphere with its different cloud types of low to high altitudes casting shadows. Sunlight is reflected off the ocean, after it was filtered into a reddish light by passing through much of the troposphere at sunset. The above lying stratosphere can be seen at the horizon as a band of its characteristic glow of blue scattered sunlight.
Troposphere: Atmospheric circulation: the three-cell model of the circulation of the planetary atmosphere of the Earth, of which the troposphere is the lowest layer.
Atmospheric circulation: the three-cell model of the circulation of the planetary atmosphere of the Earth, of which the troposphere is the lowest layer.
Troposphere: The atmosphere of the Earth is in five layers: (i) the exosphere at 600+ km; (ii) the thermosphere at 600 km; (iii) the mesosphere at 95–120 km; (iv) the stratosphere at 50–60 km; and (v) the troposphere at 8–15 km. The distance from the planetary surface to the edge of the stratosphere is ±50 km, less than 1.0% of the radius of the Earth.
The atmosphere of the Earth is in five layers: (i) the exosphere at 600+ km; (ii) the thermosphere at 600 km; (iii) the mesosphere at 95–120 km; (iv) the stratosphere at 50–60 km; and (v) the troposphere at 8–15 km. The distance from the planetary surface to the edge of the stratosphere is ±50 km, less than 1.0% of the radius of the Earth.
Troposphere: A picture of Earth's atmosphere as viewed from an airplane, traveling over the Arctic.
A picture of Earth's atmosphere as viewed from an airplane, traveling over the Arctic.
Troposphere: Zonal Flow: a zonal flow regime indicates the dominant west-to-east flow of the atmosphere in the 500 hPa height pattern.
Zonal Flow: a zonal flow regime indicates the dominant west-to-east flow of the atmosphere in the 500 hPa height pattern.

Worked examples

Example 1 — a first encounter with Troposphere

Start with the simplest possible case. Write down what Troposphere claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Troposphere before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Troposphere ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Troposphere

In research
Troposphere appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Troposphere in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Troposphere is common in secondary-school and first-year university syllabi. It links to neighbouring topics Atmosphere, Atmosphere of Earth, Atmospheric thermodynamics, so understanding it makes those chapters shorter.
In everyday life
Look for Troposphere outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Troposphere in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Troposphere means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Troposphere out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Troposphere in simple terms?

The troposphere is the lowest layer of the atmosphere of Earth. Pronounced , the name comes from Ancient Greek τρόπος (trópos) 'turning, change' and -sphere.

Why does Troposphere matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Troposphere?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Troposphere.

Tags

  • Atmosphere
  • Atmosphere of Earth
  • Atmospheric thermodynamics

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