GEOG1112 - Earth's Atmosphere

Vocabulary flashcards covering key terms and concepts from the lecture notes on Earth's atmosphere, its layers, composition, and related processes.

Atmosphere

A thin envelope of gases bound to Earth by gravity.

Kármán line

Approximately 100 km above Earth's surface; marks the theoretical altitude where air becomes too thin for winged flight.

Functional atmosphere

The portion of the atmosphere up to about 500 km that supports flight and weather processes.

32,000 km altitude (H and He)

Hydrogen and Helium have been found as far as about 32,000 km above Earth.

Mass distribution with height (percentages)

About 90% of the atmosphere’s mass is below 20 km, 99.9% below 50 km, and 99.99997% below 100 km.

Troposphere

The lowest atmospheric layer; temperature generally decreases with height and mass is concentrated here.

Tropopause

The boundary between the troposphere and the stratosphere.

Stratosphere

Layer above the troposphere where temperature increases with height due to ozone absorption.

Stratopause

The upper boundary of the stratosphere, around ~50 km, where temperature levels off near 0°C.

Mesosphere

Layer where temperature decreases with height; includes the Mesopause near ~80 km, the coldest part of the atmosphere.

Mesopause

Boundary between the mesosphere and the thermosphere.

Thermosphere

Layer where temperature increases with altitude; reaches the Thermopause around ~480 km.

Exosphere

Outermost part of the atmosphere transitioning into space.

Ozonosphere (Ozone layer)

Region roughly 19–50 km where ozone (O3) absorbs UV radiation, heating the layer.

Ozone (O3)

A molecule that absorbs UV radiation; in the stratosphere it protects living organisms from UV damage.

Ionosphere

Zone starting around 50 km outward; absorbs high-energy radiation and enables auroras.

Heterosphere

Atmospheric layer where gases are sorted by gravity and not well mixed.

Homosphere

Layer where gases are well mixed and composition is relatively uniform.

Atmospheric Composition

Study of gases present in the atmosphere and how they are distributed.

Water vapor (H2O)

Greenhouse gas; exists in gas, liquid, and solid phases; essential for hydrologic cycle; concentrations vary with location.

Permanent gases

Gases present everywhere in the lower atmosphere with long residence times (e.g., N2, O2, Ar).

Nitrogen (N2) and Oxygen (O2)

Major permanent gases; N2 is most abundant; O2 is essential for life.

Argon (Ar)

A permanent gas with an extremely long residence time. Exists in trace amounts in the atmosphere.

Variable gases

Gases whose concentrations vary in space and time (e.g., H2O, CO2, CH4) and often have shorter residence times.

Water cycle (Hydrologic Cycle)

Movement of water among the atmosphere, oceans, and land through evaporation, condensation, precipitation, runoff, etc.

Carbon Dioxide (CO2)

Greenhouse gas involved in the carbon cycle; residence time ~150 years; added by respiration, combustion, etc.; removed by photosynthesis and ocean uptake.

Carbon cycle transfers and stores

Carbon stored in land, ocean, and atmosphere; roughly 9 Gt/year added from fossil fuels and land-use changes, with ~2 Gt to oceans, ~3 Gt to land, and ~4 Gt remaining in the atmosphere.

CO2 concentration today

Measured atmospheric CO2 around 425 ppm (as of December 2024); historically much lower (180–300 ppm in glacial cycles over the last 800,000 years).

CO2 and temperature feedback

Positive feedback: warming increases atmospheric CO2, and higher CO2 reinforces warming.

Methane (CH4)

Greenhouse gas with concentration ~1908 ppb and residence time ~10 years; produced by fossil fuels, livestock digestion, and agriculture.

Surface ozone vs. stratospheric ozone

Ground-level (tropospheric) ozone is a pollutant; stratospheric ozone protects by absorbing UV radiation.

Antarctic Ozone Hole

Severe depletion of stratospheric ozone caused by CFCs and UV radiation initiating chlorine-catalyzed ozone destruction.

Montreal Protocol (1987)

International agreement to phase out ozone-depleting substances such as CFCs; associated with shrinking ozone hole.

Noctilucent Clouds

Clouds in the upper mesosphere (~80 km) formed from ice crystals on meteoric dust.

Surface pressure (sea level)

Average sea-level atmospheric pressure about 1013 mb (millibars); ~14.5 psi.

1 hPa = 1 mb

Units for atmospheric pressure: hectopascals and millibars are equivalent.

Normal lapse rate

Vertical temperature change with height in the troposphere: about 6.5°C per 1000 m.

Thermopause

Upper boundary of the thermosphere, near ~480 km.

Ozonosphere vs Ozone layer

Ozonosphere refers to the region containing ozone; the ozone layer is the portion in the stratosphere that shields UV.

Hydrologic cycle phases

Evaporation, condensation, precipitation, and cycles among atmosphere, oceans, and land.