Atmospheric Composition and Chemistry Practice Flashcards

A set of practice vocabulary flashcards based on lecture notes covering atmospheric composition, structure, radiative forcing, and chemical cycles.

Milankovitch cycles

Changes in the Earth's orbit and axis of rotation that led to historical changes in the amount of solar radiation received and partly caused past glacial cycles.

Mixing ratios

The ratio of the number of molecules (or volumes) of gaseous species to the total number of molecules (or volumes) of dry air.

Parts per million by volume (ppmv)

A mixing ratio unit representing parts in $10^6$.

Parts per billion by volume (ppbv)

A mixing ratio unit representing parts in $10^9$.

Parts per trillion by volume (pptv)

A mixing ratio unit representing parts in $10^{12}$.

Troposphere

The lowest layer of the atmosphere, containing $80\%$ of its mass, characterized by strong vertical mixing and a decrease in temperature with height.

Stratosphere

The atmospheric layer where temperature increases with altitude at a rate of approximately $2\,K\,km^{-1}$ due to the absorption of solar radiation by ozone ($O_3$).

Albedo ($A$)

The overall reflectivity of a planet, which determines the fraction of solar radiation reflected back to space.

Radiative Forcing

The change in net irradiance (solar plus long-wave) at the tropopause, typically calculated as the change since the industrial revolution ($1750$).

Radiative efficiency

The radiative forcing induced per unit mass, expressed in units such as $W\,m^{-2}\,kg^{-1}$ or $W\,m^{-2}\,ppm^{-1}$.

Global Warming Potential (GWP)

The potential of $1\,kg$ of a compound to contribute to radiative forcing relative to that of $1\,kg$ of a reference compound, usually $CO_2$.

Rayleigh Scattering

Elastic scattering that dominates when electromagnetic radiation interacts with particles smaller than the wavelength of light, proportional to $\lambda^{-4}$.

Mie Scattering

Scattering that occurs when the wavelength of radiation is similar in size to particles in the atmosphere, such as water vapor or dust.

Non-selective scattering

Scattering produced by large particles (e.g., water droplets in clouds) several times the diameter of the radiation, affecting all wavelengths of light equally.

Air mass ($m$)

The path length traversed by solar radiation to reach the earth's surface relative to the length of a vertical path through the atmosphere.

Photolysis rate constant ($j_A$)

A first-order rate constant for the photodissociation of a molecule upon light absorption, dependent on quantum yield, photon flux, and absorption cross section.

Hydroxyl radical (OH)

Known as the 'self-cleansing' agent of the atmosphere, this radical is primarily formed from the photolysis of $O_3$ followed by a reaction with water vapor.

Primary pollutants

Pollutants emitted directly into the air from sources, such as hydrocarbons, $SO_2$, $NO$, and combustion-generated particulate matter.

Secondary pollutants

Pollutants that result from chemical transformations of primary pollutants, including $O_3$, $NO_2$, and secondary organic aerosol.

$$NO_x$$

The sum of nitrogen oxide ($NO$) and nitrogen dioxide ($NO_2$), often produced during high-temperature combustion processes.

Volatile Organic Compounds (VOC)

Gaseous organic compounds whose atmospheric emissions are globaly dominated by biogenic sources.

Cloud Condensation Nuclei (CCN)

Small particles on which water vapor condenses to form cloud droplets when air is supersaturated.

Hygroscopic nuclei

Water-seeking particles, such as salt or sulfuric acid, that facilitate the condensation of water at or near $100\%$ relative humidity.

Kelvin effect

The phenomenon where smaller droplets have a higher vapor pressure than larger droplets due to increased curvature and surface tension effects.

Indirect effect

The cooling influence of aerosols on climate caused by the formation of a large number of small droplets, making clouds denser and more reflective.

Wet deposition

The physical removal of soluble gases or particulate matter from the atmosphere by transfer into rain droplets.

Scavenging coefficient ($S_i$)

A coefficient used to approximate the rate of transfer of species $i$ from the gas or particulate phase into rain during precipitation.

Dry deposition

The removal of gases and particles by direct contact with the surface, involving mechanisms like stomatal uptake by vegetation.

Atmospheric lifetime (\tau)

The e-fold decay time of a perturbation to a particular gas, representing the time taken to reach $1/e$ of its initial concentration.

Steady state analysis

An approximation assuming that the rate of production of a species is equal to its rate of destruction ($d[C]/dt = 0$).