Environmental Physics Glossary

A thermodynamic process in which no heat is exchanged with the surroundings. Rising air parcels cool adiabatically due to expansion.

The fraction of incident solar radiation reflected by a surface, expressed as a value between 0 and 1.

The lowest part of the troposphere (1–2 km) directly affected by the Earth's surface through turbulent heat, moisture, and momentum exchange.

A relation describing the exponential attenuation of radiation intensity as it passes through an absorbing medium.

The theoretical maximum fraction (≈59.3%) of kinetic energy that can be extracted from wind by a turbine.

An idealized object that absorbs all incident electromagnetic radiation and emits radiation solely based on its temperature.

The equilibrium global mean temperature change resulting from a doubling of atmospheric CO₂ concentration.

Heat transfer through a material by molecular collisions without bulk motion of the material. Described by Fourier's law.

Heat transfer by the bulk movement of fluid (gas or liquid), driven by buoyancy differences from temperature variations.

The apparent deflection of moving objects due to Earth's rotation, directing motion to the right in the Northern Hemisphere.

The net movement of particles from a region of higher concentration to one of lower concentration, driven by random molecular motion.

The full range of electromagnetic radiation frequencies, from radio waves to gamma rays, including visible light.

The ratio of radiation emitted by a surface to that emitted by a blackbody at the same temperature. Ranges from 0 to 1.

A mathematical model predicting pollutant concentration downwind of a point source, assuming Gaussian distribution in crosswind and vertical directions.

The warming of Earth's surface caused by atmospheric gases that absorb and re-emit outgoing infrared radiation.

The continuous movement of water through evaporation, condensation, precipitation, and runoff, driven by solar energy and gravity.

The power of electromagnetic radiation per unit area incident on a surface, measured in watts per square meter (W/m²).

The rate at which atmospheric temperature decreases with altitude. The environmental lapse rate averages about 6.5°C/km in the troposphere.

The energy absorbed or released during a phase change (e.g., evaporation, condensation) without a change in temperature.

A dimensionless measure of the transparency of a medium to radiation. Higher optical depth means more absorption and scattering.

The generation of electric current when a semiconductor material is exposed to photons with energy above its band gap.

The net change in energy flux at the tropopause caused by an external driver, measured in W/m².

Energy derived from naturally replenishing sources such as sunlight, wind, water, and geothermal heat.

The total power radiated per unit area of a blackbody is proportional to the fourth power of its absolute temperature: $P = \sigma T^4$.

The lowest layer of Earth's atmosphere, extending from the surface to about 12 km altitude, where most weather occurs.