Atmospheric Layers and Circulation

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Atmosphere Noun

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[at-muh-sfeer]

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Atmosphere

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The mixture of gases held by gravity that surrounds a planet, protecting life and regulating the planet's temperature.

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Example: This diagram shows that the atmosphere is a blanket of gases around the Earth, organized into five main layers stacked on top of each other.

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Air Pressure Noun

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[air presh-er]

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Air Pressure

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The force exerted onto a surface by the weight of the atmosphere, which decreases as altitude increases.

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Example: This image uses a seesaw to show that air pressure is lower at high altitudes (less air above) and higher at low altitudes (more air above).

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Barometer Noun

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[buh-rom-i-ter]

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Barometer

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A scientific instrument specifically designed and used for measuring the pressure of the surrounding atmosphere.

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Example: This diagram shows how a barometer works: atmospheric pressure pushes down on the mercury in the dish, supporting a column of mercury inside the tube.

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Troposphere Noun

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[troh-puh-sfeer]

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Troposphere

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The lowest and densest layer of the atmosphere, containing most of its mass and where all weather occurs.

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Example: The troposphere is the lowest layer of Earth's atmosphere, located right above the ground, where all weather, like clouds and rain, happens.

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Stratosphere Noun

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[strat-uh-sfeer]

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Stratosphere

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The atmospheric layer above the troposphere where temperature increases with altitude due to the presence of the ozone layer.

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Example: This diagram shows the Stratosphere as the second layer of the atmosphere, located above the Troposphere and below the Mesosphere, where weather balloons fly.

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Ozone Noun

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[oh-zohn]

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Ozone

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A molecule of three oxygen atoms (O3) that absorbs most of the Sun's harmful ultraviolet (UV) radiation.

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Example: The ozone layer in the atmosphere acts like a shield, blocking most of the sun's harmful ultraviolet (UV) radiation from reaching Earth's surface.

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Chlorofluorocarbons (CFCs) Noun

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[klor-oh-floor-oh-kar-buhns]

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Chlorofluorocarbons (CFCs)

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A class of synthetic chemical compounds that are the primary cause of ozone layer depletion in the stratosphere.

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Example: This image identifies an aerosol can, a historical source of chlorofluorocarbons (CFCs), to introduce the term.

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Montreal Protocol Noun

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[mon-tree-awl proh-tuh-kol]

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Montreal Protocol

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An international treaty designed to protect the ozone layer by phasing out the production of ozone-depleting substances.

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Example: This image compares two scenarios: the Arctic ozone layer without the Montreal Protocol (left) and with it (right), showing how the international agreement prevented a large ozone hole from forming.

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Mesosphere Noun

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[mes-oh-sfeer]

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Mesosphere

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The middle and coldest layer of the atmosphere, which protects Earth by burning up most incoming meteoroids.

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Example: This diagram shows the Mesosphere as the atmospheric layer above the Stratosphere, located 50-80 km high, where meteors burn up upon entering.

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Thermosphere Noun

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[thur-moh-sfeer]

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Thermosphere

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The fourth atmospheric layer with very high temperatures due to solar radiation absorption, where the space station orbits.

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Example: The thermosphere is a layer of the atmosphere where the International Space Station orbits and where auroras occur, located above the mesosphere.