Unit 2: Temperature, Heat, and Radiation

Vocabulary practice flashcards covering temperature definitions, heat transfer mechanisms, electromagnetic radiation laws, energy balances, and meteorological measurement techniques.

Temperature

The measure of a substance's average kinetic energy, where warmer temperatures reflect faster molecular movement and colder temperatures reflect slower movement.

Kinetic Energy

The form of energy associated with the movement of particles or objects.

Heat

Energy in the process of being transferred from one object to another because of the temperature difference between them.

Latent Heat

The energy released or absorbed by a substance during a change of state.

Latent Heat Phase Changes

Thermodynamic state changes where heat energy is either taken from the environment (melting, evaporation, sublimation) or released into the environment (freezing, condensation, deposition).

Sensible Heat

Heat exchanged between systems that results in a measurable change of temperature.

Conduction

The direct transfer of heat moving from a warmer location to a colder location through molecular collisions.

Convection

The vertical transfer of heat resulting from warm fluids (liquids or gases) rising and creating circulation currents.

Radiation

The transmission of energy through space or matter in the form of electromagnetic waves.

Electromagnetic Radiation (EMR)

The movement of energy through space or a medium, composed of electric and magnetic waves oscillating perpendicular to each other in the direction of travel at the speed of light ($c = 3 \times 10^8\,\text{m/s}$).

Photon Energy Equation

The physical relationship stating photon energy is inversely proportional to wavelength: $E = \frac{h \times c}{\lambda}$, where $h = 6.626 \times 10^{-34}\,\text{J}\cdot\text{sec}$ (Planck's Constant) and $c = 3 \times 10^8\,\text{m/sec}$ (speed of light).

Wien's Law

The inverse relationship between temperature and wavelength of maximum radiant exitance ($\lambda_m$), represented by $\lambda_m = \frac{A}{T}$, where $A = 2898\,\mu\text{m}\cdot\text{K}$ and $T$ is temperature in Kelvin.

Radiative Equilibrium Temperature

The theoretical equilibrium temperature of Earth without an atmosphere ($255\,\text{K}$ or $-18\,^\circ\text{C}$), as compared to its actual average surface temperature of $288\,\text{K}$ ($15\,^\circ\text{C}$) produced by atmospheric greenhouse absorption.

Atmospheric Window

Wavelength bands in the electromagnetic spectrum (notably between $8\,\mu\text{m}$ and $11\,\mu\text{m}$) where atmospheric gases absorb very little radiation, allowing terrestrial infrared energy to escape directly to space.

Scattering

The dispersal and redirection of electromagnetic waves as light enters a medium that causes different wavelengths to slow down and alter direction.

Albedo

The proportional reflectance of a surface, expressing the fraction of incident electromagnetic radiation reflected back into space.

First Law of Thermodynamics (Radiation Budget)

The principle of energy conservation applied to solar input, stating that incident energy ($E$) must equal reflected ($R$), absorbed ($A$), and transmitted ($T$) energy: $E = R + A + T$.

Temperature Inversion

An atmospheric condition in the lower troposphere where air temperature increases with altitude, typically occurring on clear, calm nights when the ground cools more rapidly via radiation than the overlying air.

Thermal Belt

A zone of warmer air (above freezing) situated on hillside slopes at night between freezing air pooling at the valley floor and sub-freezing air higher up the slopes.

Thermal Expansion

The physical process in which a liquid expands and becomes less dense when heated, serving as the mechanical basis for liquid-in-glass thermometers.

Electrical Thermometer

A highly accurate automated sensor that determines temperature by measuring changes in electrical resistance across a conducting metal element.

Radiometer

A remote sensor (frequently mounted on satellites) that measures outgoing infrared energy escaping to space to determine surface and atmospheric temperatures.

Urban Heat Island (UHI)

An urban microclimate phenomenon characterized by elevated surface and atmospheric temperatures relative to surrounding rural areas, driven by artificial surface cover and thermal properties.

Heating Degree Day (HDD)

A metric used by utility companies to estimate residential heating fuel requirements, calculated when the daily mean temperature falls below $65\,^\circ\text{F}$.

Cooling Degree Day (CDD)

A metric used by utility companies to estimate residential air conditioning requirements, calculated when the daily mean temperature rises above $65\,^\circ\text{F}$.

Growing Degree Day (GDD)

An agricultural thermal index used to approximate crop development and harvest timing, determined relative to a crop's minimum threshold temperature (such as $50\,^\circ\text{F}$ for corn or $40\,^\circ\text{F}$ for peas).

Sensible Temperature

The human physiological sensation of environmental temperature, which varies throughout the year based on atmospheric conditions such as humidity and wind speed.

Wind Chill

The perceived drop in temperature experienced by exposed human skin on windy days caused by accelerated convective heat loss.