Collection of Definitions ATM 005 001 FQ 2026

Precipitation

any liquid or frozen water that forms in the atmosphere and falls back to the Earth's

surface. This includes rain, snow, sleet, hail, graupel, and many more.

Climate

The pattern of variation in temperature, humidity, atmospheric pressure, wind, precipitation, atmospheric particle count and other meteorological variables in a given region over long periods.

Weather

the state of the atmosphere at a place and time with regards to meteorological variables such as dryness, sunshine, wind, rain, etc.

Latitude

measures the angular distance from the equator. It is given in degrees (from 0 to 90) either North or South of the equator

Longitude

measures the angular distance east or

west of the Prime Meridian. It is given in

degrees (from 0 to 180) either East or West.

The Tropic of Cancer

an imaginary line on the Earth found at approximately 23.5 degrees North latitude.

The Tropic of Capricorn

an imaginary line on the Earth found at approximately 23.5 degrees South latitude.

The Arctic Circle

an imaginary line on the Earth found at approximately 66.5 degrees North latitude.

The Antarctic Circle

an imaginary line on the Earth found at approximately 66.5 degrees South latitude.

Climate Zones

Climate zones are regions of similar or homogeneous climate.

Keeling curve

the CO2 monitoring program at Mauna Loa Observatory in 1958 and supervised it until his death in 2005. Carbon dioxide levels typically reach a maximum in the Northern Hemisphere Spring and minimum in the Northern Hemisphere Fall. As of 2020, CO2 has reached approximately 410ppm concentration. This is above pre-industrial levels of 280ppm and glacial periods when CO2 concentration was closer to 180ppm.

Thermosphere

(Edge of Space)

Temperature is very high and variable.

Short wavelength ultraviolet radiation

is absorbed here by oxygen.

Molecules are dissociated with high-

energy ultraviolet radiation from the

sun (λ < 0.1 μm). Temperatures can

get very high (up to 1000K), even

though air density is very low.

Mesosphere

Temperature increases towards the surface in this

layer, driven by increased ozone

concentration.

Stratosphere

Exhibits a temperature increase with altitude

due to the presence of the ozone

layer. The stratosphere is highly

stratified and poorly mixed (the

increase in temperature with

altitude makes the atmosphere

very stable).

Troposphere

Below the tropopause

(typically located between 8-16km

depending on latitude and season),

temperature increases strongly

towards the surface. It contains about

85% of the atmosphere’s mass and

essentially all the water vapor.

Tropopause

Anvil clouds like these form because rising (buoyant) tropospheric air cannot rise into the stable stratosphere.

Stratopause

Area below mesosphere and above the stratosphere

Mesopause

Area below thermosphere and above mesosphere

Weather Station

a collection of instruments and sensors used to measure atmospheric conditions in real time.

ASOS

the Automated Surface Observing System, a weather station that continuously monitors and reports real-time atmospheric conditions.

SNOTEL

SNOwpack TELemetry, an automated network of remote weather stations that measure snowpack and related climate data in the Western United States.

Weather Radar

an active remote sensing instrument that measures precipitation by transmitting electromagnetic pulses and listening for their reflections/echoes.

Temperature proxy

a measurement that can be used to calculate the value of temperature (for example when direct measurements are not available).

Dendroclimatology

Refers to studying the Earth’s climate through the study of tree rings.

δ18O

The difference in the [18O]/[16O] ratio between a sample and an associated standard, normalized by the ratio in the standard.

Milankovich Cycles

oscillations in the Earth’s orbital parameters that affects its climate over thousands of years.

Kinetic Energy

a measure of the energy of a substance due to motion. At a macroscopic scale

Temperature

temperature is a measure of the average kinetic energy of molecules in a particular substance (such as a parcel of air).

Conduction

Heat transfer due to contact. Molecules of a warm object bang against molecules of a cold object, causing “cold” molecules to move faster and “warm” molecules to move slower.

Convection

Heat transfer due to movement. A balloon full of warm air can move into a region of cold air and increase the average air temperature.

Radiation

Heat transfer due to photons (small bundles of electromagnetic energy). When these photons hit another molecule, kinetic energy is transferred.

Electromagnetic Spectrum

the range of all forms of electromagnetic radiation (light). Any photon of light (gamma rays, visible light, or radio waves) is completely characterized by its wavelength (a single number).

Energy Balance

If a system is in a state of energy balance then the total energy within the system must be unchanging, which implies:

Energy Emitted = Energy Recieved

Black Body

an idealized physical body that absorbs all incident electromagnetic radiation. A black body in thermal equilibrium (constant temperature) emits blackbody radiation in accordance with Planck’s law.

Solar Constant

the amount of solar energy received per unit area outside the Earth's atmosphere, measured on a surface perpendicular to the Sun's rays.

Insolation

a measure of the solar radiation energy received on a given surface area and recorded during a given time.