Atmosphere: Layers, Radiation, Pollutants, and Air Quality

Vocabulary flashcards covering atmospheric layers, radiation interactions, pollutants, and air quality concepts from the lecture notes.

Troposphere

The lowest atmospheric layer where weather occurs; contains ~90% of the atmosphere’s mass; from the surface to about 18 km (variation with latitude); bounded by the tropopause.

Tropopause

The boundary between the troposphere and the stratosphere; around 18 km near the equator, 12 km mid-latitudes, and 8 km at the poles, with a temperature near -57°C.

Lapse rate

The rate at which temperature decreases with altitude; normal lapse rate ~6.4°C per kilometer.

Environmental lapse rate

The actual local rate of temperature change with altitude, which can differ from the normal lapse rate.

Stratosphere

Layer above the troposphere where temperature rises with altitude due to ozone absorbing UV; contains the stratopause at ~50 km.

Stratopause

The boundary between the stratosphere and the mesosphere, located around 50 km altitude (temperature ~0°C/32°F).

Mesosphere

Layer from about 50 to 80 km; temperature decreases with altitude; ends at the mesopause near 80 km (around -90°C). Noctilucent clouds form here from cosmic dust.

Mesopause

The boundary between the mesosphere and the thermosphere, at roughly 80 km altitude.

Noctilucent clouds

High-altitude clouds formed from cosmic dust, visible at high latitudes at twilight.

Thermosphere

Outermost atmospheric layer extending to ~480 km; temperature increases with altitude due to direct solar radiation, reaching very high values but with extremely low air density.

Ionosphere

Part of the upper atmosphere starting around ~50 km outward; contains ions, interacts with satellite signals, and hosts auroras.

Ozonosphere (ozone layer)

Region roughly 19–50 km up within the stratosphere rich in ozone (O3) that absorbs UV radiation and warms the layer.

Ozone (O3)

A triatomic oxygen molecule that absorbs UV radiation, producing heat in the stratosphere.

Albedo

The ratio of reflected solar radiation to incident solar radiation; snow and ice have high albedo (70–95%).

Insolation

Incoming solar radiation that reaches Earth.

Scattering

The process by which light is redirected in different directions without a change in wavelength, producing diffuse radiation.

Reflection

Radiation that is redirected back into space; contributes to albedo.

Transmission

The passage of energy through the atmosphere or water without absorption.

Absorption

Process by which gases/particles absorb solar energy and convert it to heat (notably CO2 and H2O).

Greenhouse gases

Gases such as CO2, H2O, CH4, CFCs, and NOx that trap heat by absorbing infrared radiation, leading to the greenhouse effect.

Energy balance

The balance between incoming solar radiation and outgoing infrared radiation, influenced by gases, clouds, and aerosols.

Arctic sea ice

Sea ice in the Arctic; highly reflective and crucial for cooling the planet; substantial decline (more than half since the 1970s).

Chlorofluorocarbons (CFCs)

Human-made compounds that release chlorine radicals upon UV exposure, which deplete ozone.

Chlorine monoxide (ClO)

A chlorine-containing molecule formed during ozone-depleting reactions; part of the catalytic cycle destroying ozone.

Photochemical smog

Smog formed when NO2 reacts with VOCs in sunlight to create ozone (O3) and peroxyacyl nitrates (PANs); harmful to health.

Sulfur dioxide (SO2)

A pollutant produced by burning fossil fuels; reacts with water to form sulfuric acid (H2SO4) and contributes to acid rain.

Acid rain/acid deposition

Precipitation or dry deposition containing sulfuric or nitric acids, harming ecosystems, buildings, and health.

Nitrogen oxides (NOx)

Pollutants from combustion; contribute to smog formation and acid deposition.

Carbon monoxide (CO)

Colorless, odorless, toxic gas produced by incomplete combustion; a major urban pollutant.

Volatile organic compounds (VOCs)

Organic compounds that vaporize easily; react with NOx and sunlight to form ozone and other pollutants.

Particulate matter (PM)

Tiny airborne particles that affect health and visibility; included in air quality measurements.

Air Quality Index (AQI)

A measure of daily air quality and health risk based on pollutants such as CO, NO2, SO2, O3, and PM.

Inversion (temperature inversion)

A layer of warm air over cooler air that traps pollutants near the surface.

Anthropogenic

Human-made; sources of pollution include transportation and industry.

Natural pollutants

Pollutants arising from natural sources such as wildfires, dust storms, and volcanic activity.