backscatter

Process by which up to 25% of radiant energy from the sun is reflected or scattered away from the surface by clouds.

band

In radio, a continuous sequence of broadcasting frequencies within given limits.

In radiometry, a relatively narrow region of the electromagnetic spectrum to which a remote sensor responds; a multispectral sensor makes measurements in a number of spectral bands.

In spectroscopy, spectral regions where atmospheric gases absorb (and emit) radiation, e.g., the 15 µm carbon dioxide absorption band, the 6.3 µm water vapor absorption band, and the 9.6 µm ozone absorption band.

bandwidth

The total range of frequency required to pass a specific modulated signal without distortion or loss of data. The ideal bandwidth allows the signal to pass under conditions of maximum AM or FM adjustment. (Too narrow a bandwidth will result in loss of data during modulation peaks. Too wide a bandwidth will pass excessive noise along with the signal.) In FM, radio frequency signal bandwidth is determined by the frequency deviation of the signal.

barometer

An instrument used to measure atmospheric pressure. A standard mercury barometer has a glass column about 30 inches long, closed at one end, with a mercury-filled reservoir. Mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the reservoir. High atmospheric pressure forces the mercury higher in the column. Low pressure allows the mercury to drop to a lower level in the column. An aneroid barometer uses a small, flexible metal box called an aneroid cell. The box is tightly sealed after some of the air is removed, so that small changes in external air pressure cause the cell to expand or contract.

base

A substance that forms a salt when it reacts with acid. A base is a substance that removes hydrogen ions (protons) from an acid and combines with them in a chemical reaction.

beamwidth

The measure of the 'width' of an antenna pattern, measured in degrees of arc. Generally an antenna with low gain has a wide pattern, receiving signals well from a number of different directions.

bearing

The combination of antenna azimuth and elevation required to point (aim) an antenna at a spacecraft. The bearing for geostationary (i.e., GOES) satellites is constant. The bearing for polar-orbiting satellites varies continuously.

berm

A platform of wave-deposited sediment that is flat or slopes slightly landward.

bioassay

A measurement of the effects of a substance on living organisms.

biodegradation

Decomposition of material by microorganisms.

biodiversity

The totality of genes, species, and ecosystems in a region or the world.

biogenic

Produced by natural processes. Usually used in the context of emissions that are produced by plants and animals.

biogeochemical cycles

Movements through the Earth system of key chemical constituents essential to life, such as carbon, nitrogen, oxygen, and phosphorus.

biomass

Organic nonfossil material of biological origin. For example, trees and plants are biomass.

biome

Well-defined terrestrial environment (e.g., desert, tundra, or tropical forest). The complex of living organisms found in an ecological region.

biosphere

Part of the Earth system in which life can exist, between the outer portion of the geosphere and the inner portion of the atmosphere.

biota

The plant and animal life of a region or area.

blackbody

An ideal emitter which radiates energy at the maximum possible rate per unit area at each wavelength for any given temperature. A blackbody also absorbs all the radiant energy incident on it; i.e., no energy is reflected or transmitted.

blizzard

A severe weather condition characterized by low temperatures and strong winds (greater than 35 mph) bearing a great amount of snow, either falling or blowing. When these conditions persist after snow has stopped falling, it is called a ground blizzard.

boreal

Northern; from the Greek name for the Goddess of the North Wind. A boreal forest is the set of forest ecosystems than can survive in the north.

Boreal Ecosystem-Atmosphere Study (BOREAS)

A global change project to study and understand the interaction between the boreal forest biome and the atmosphere.

See also:
Introduction to BOREAS
BOREAS Web Site

brightness temperature

A measure of the intensity of radiation thermally emitted by an object, given in units of temperature because there is a proportional correlation between the intensity of the radiation emitted and physical temperature of the radiating body.

broadleaf

The leaves of trees associated with deciduous forests.

bus

The basic frame of a satellite system that includes the propulsion and stabilization systems but not the instruments or data systems.

calibration

Act of comparing an instrument's measuring accuracy to a known standard.

calorie

The amount of heat needed to raise the temperature of one gram of water at 15 degrees centigrade one degree centigrade. Compare with British Thermal Unit.

canopy

The layer formed naturally by the leaves and branches of trees and plants.

carbohydrate

an organic compound present in the cells of all living organisms and a major organic nutrient for human beings; consists of carbon, hydrogen, and oxygen, and makes up sugar, starch, and cellulose.

carbon cycle

All parts (reservoirs) and fluxes of carbon. The cycle is usually thought of as four main reservoirs of carbon interconnected by pathways of exchange. The reservoirs are the atmosphere, terrestrial biosphere (usually includes freshwater systems), oceans, and sediments (includes fossil fuels). The annual movements of carbon, the carbon exchanges between reservoirs, occur because of various chemical, physical, geological, and biological processes. The ocean contains the largest pool of carbon near the surface of the Earth, but most of that pool is not involved with rapid exchange with the atmosphere.

carbon dioxide

A minor but very important component of the atmosphere, carbon dioxide traps infrared radiation. Atmospheric CO2 has increased about 25 percent since the early 1800s, with an estimated increase of 10 percent since 1958 (burning fossil fuels is the leading cause of increased CO2, deforestation the second major cause). The increased amounts of CO2 in the atmosphere enhance the greenhouse effect, blocking heat from escaping into space and contributing to the warming of Earth's lower atmosphere.

carbon sequestration

The uptake and storage of carbon. Trees and plants, for example, absorb carbon dioxide, release the oxygen and store the carbon. Fossil fuels were at one time biomass and continue to store the carbon until burned.

carbonates

chemical compounds derived from carbonic acid or carbon dioxide

carrying capacity

The steady-state density of a given species that a particular habitat can support.

cartography

The science of mapmaking.

celsius

Temperature scale proposed by Swedish astronomer Anders Celsius in 1742. A mixture of ice and water is zero on the scale; boiling water is designated as 100 degrees. A degree is defined as one hundredth of the difference between the two reference points, resulting in the original term, "centigrade" (100th part). To convert celsius to Fahrenheit: multiply the celsius temperature by 1.8 and add 32 degrees. F = 9/5 C + 32 To convert Fahrenheit to celsius: subtract 32 degrees from the Fahrenheit temperature and divide the quantity by 1.8. C = (F -32) / 1.8.

chlorofluorocarbon (CFC)

A family of compounds of chlorine, fluorine, and carbon, entirely of industrial origin. CFCs include refrigerants, propellants for spray cans (this usage is banned in the U.S., although some other countries permit it) and for blowing plastic-foam insulation, styrofoam packaging, and solvents for cleaning electronic circuit boards. The compounds' lifetimes vary over a wide range, exceeding 100 years in some cases.

CFCs' ability to destroy stratospheric ozone through catalytic cycles is contributing to the depletion of ozone worldwide. Because CFCs are such stable molecules, they do not react easily with other chemicals in the lower atmosphere. One of the few forces that can break up CFC molecules is ultraviolet radiation, however the ozone layer protects the CFCs from ultraviolet radiation in the lower atmosphere. CFC molecules are then able to migrate intact into the stratosphere, where the molecules are bombarded by ultraviolet rays, causing the CFCs to break up and release their chlorine atoms. The released chlorine atoms participate in ozone destruction, with a single atom of chlorine able to destroy ozone molecules over and over again.

International attention to CFCs resulted in a meeting of diplomats from around the world in Montreal in 1987. They forged a treaty that called for drastic reductions in the production of CFCs. In 1990, diplomats met in London and voted to significantly strengthen the Montreal Protocol by calling for a complete elimination of CFCs by the year 2000.

chlorophyll

Chlorophyll is a green compound found in leaves and green stems of plants. The intense green color of chlorophyll is due to its strong absorbencies in the red and blue regions of the spectrum, and because of these absorbencies the light it reflects and transmits appears green. It is capable of channeling the energy of sunlight into chemical energy through the process of photosynthesis. In this process the energy absorbed by chlorophyll transforms carbon dioxide and water into carbohydrates and oxygen.

cirrus

A type of cloud composed of ice crystals and shaped in the form of hairlike filaments. It is formed at an altitude of approximately 29,000 feet.

Clarke Belt

A belt 22,245 miles (35,800 kilometers) directly above the equator where a satellite orbits the Earth at the same speed the Earth is rotating. Science fiction writer and scientist Arthur C. Clarke wrote about this belt in 1945, hence the name.

climate change

The term 'climate change' is sometimes used to refer to all forms of climatic inconsistency, but because the Earth's climate is never static, the term is more properly used to imply a significant change from one climatic condition to another. In some cases, 'climate change' has been used synonymously with the term, 'global warming'; scientists however, tend to use the term in the wider sense to also include natural changes in climate.

climate model

A quantitative way of representing the interactions of the atmosphere, oceans, land surface, and ice. Models can range from relatively simple to quite comprehensive. Also see General Circulation Model.

climate system

The five physical components (atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere) that are responsible for the climate and its variations.

climatology

Science dealing with climate and climate phenomena.

cloud albedo

Reflectivity that varies from less than 10% to more than 90% of the insolation and depends on drop sizes, liquid water content, water vapor content, thickness of the cloud, and the sun's zenith angle. The smaller the drops and the greater the liquid water content, the greater the cloud albedo, if all other factors are the same.

cloud feedback

The coupling between cloudiness and surface air temperature in which a change in surface temperature could lead to a change in clouds, which could then amplify or diminish the initial temperature perturbation. For example, an increase in surface air temperature could increase the evaporation; this in turn might increase the extent of cloud cover. Increased cloud cover would reduce the solar radiation reaching the Earth's surface, thereby lowering the surface temperature. This is an example of negative feedback and does not include the effects of longwave radiation or the advection in the oceans and the atmosphere, which must also be considered in the overall relationship of the climate system.

cloud forcing

The difference between the radiation budget components for average cloud conditions and cloud-free conditions. Roughly speaking, clouds increase the albedo from 15 to 30%, which results in a reduction of absorbed solar radiation of about 50 W/m^2. This cooling is offset somewhat by the greenhouse effect of clouds which reduces the OLR by about 30 W/m^2, so the net cloud forcing of the radiation budget is a loss of about 20 W/m^2. Were the clouds to be removed with all else remaining the same, the Earth would gain this last amount in net radiation and begin to warm up.

clouds

A visible mass of liquid water droplets suspended in the atmosphere above Earth's surface. Clouds form in areas where air rises and cools. The condensing water vapor forms small droplets of water (0.012 mm) that, when combined with billions of other droplets, form clouds. Clouds can form along warm and cold fronts, where air flows up the side of the mountain and cools as it rises higher into the atmosphere, and when warm air blows over a colder surface, such as a cool body of water.

Clouds fall into two general categories: sheet-like or layer-looking stratus clouds (stratus means layer) and cumulus clouds (cumulus means piled up). These two cloud types are divided into four more groups that describe the cloud's altitude.

High clouds form above 20,000 feet in the cold region of the troposphere, and are denoted by the prefix CIRRO or CIRRUS. At this altitude water almost always freezes so clouds are composed of ice crystals. The clouds tend to be wispy, are often transparent, and include cirrus, cirrocumulus, and cirrostratus.

Middle clouds form between 6,500 and 20,000 feet and are denoted by the prefix ALTO. They are made of water droplets and include altostratus and altocumulus.

Low clouds are found up to 6,500 feet and include the stratocumulus and nimbostratus clouds. When stratus clouds contact the ground they are called fog.

Vertical clouds, such as cumulus, rise far above their bases and can form at many heights. Cumulonimbus clouds, or thunderheads, can start near the ground and soar up to 75,000 feet.

Clouds and the Earth's Radiant Energy System (CERES)

CERES measures both solar-reflected and Earth-emitted radiation from the top of the atmosphere to the surface. It also determines cloud properties including the amount, height, thickness, particle size, and phase of clouds using simultaneous measurements by other instruments. These measurements are critical for understanding cloud-radiation climate change and improving the prediction of global warming using climate models. CERES is flying, or will fly, on the Tropical Rainfall Monitoring Mission (TRMM), Terra, and EOS-PM. See CERES Web Site.

Coastal Zone Color Scanner (CZCS)

The first spacecraft instrument devoted to measurement of ocean color. Although instruments on other satellites have sensed ocean color, their spectral bands, spatial resolution, and dynamic range were optimized for geographical or meteorological use. In the CZCS, every parameter is optimized for use over water to the exclusion of any other type of sensing. The CZCS flew on the Nimbus-7 spacecraft.

coccolithophore

A single-celled marine plant that lives in large numbers throughout the upper layers of the ocean. See Coccolithophore fact sheet.

condensation

Change of a substance to a denser form, such as gas to a liquid. The opposite of evaporation.

conduction

The transfer of heat from one substance to another by direct contact. Denser substances are better conductors; the transfer is always from warmer to colder substances.

conifer

An evergreen, cone-bearing tree, as a fir or pine.

contrails

Condensation trails. Artificial clouds made by the exhaust of jet aircraft.

convection

The rising of warm air and the sinking of cool air. Heat mixes and moves air. When a layer of air receives enough heat from the Earth's surface, it expands and moves upward. Colder, heavier air flows under it which is then warmed, expands, and rises. The warm rising air cools as it reaches higher, cooler regions of the atmosphere and begins to sink. Convection causes local breezes, winds, and thunderstorms.

coriolis force

The apparent tendency of a freely moving particle to swing to one side when its motion is referred to a set of axes that is itself rotating in space, such as Earth. The acceleration is perpendicular to the direction of the speed of the article relative to the Earth's surface and is directed to the right in the northern hemisphere. Winds are affected by rotation of the Earth so that instead of a wind blowing in the direction it starts, it turns to the right of that direction in the northern hemisphere; left in the southern hemisphere.

coupled system

Two or more processes that affect one another.

cryosphere

One of the interrelated components of the Earth's system, the cryosphere is frozen water in the form of snow, permanently frozen ground (permafrost), floating ice, and glaciers. Fluctuations in the volume of the cryosphere cause changes in ocean sea-level, which directly impact the atmosphere and biosphere.

culmination

The point at which a satellite reaches its highest position or elevation in the sky, relative to an observer (aka the closest point of approach).

cumulonimbus

A cloud type that is dense and vertically developed and is associated with rain (particularly of a convective nature). It is heavy and dense with a flat base and a high, fluffy outline, and can be tall enough to occupy middle as well as low latitudes. This type of cloud is formed from about 10,000 to 12,000 feet of altitude.

cumulus

Clouds forming in the troposphere which are vertically formed with flat bases and fluffy, rounded tops. They have often been described as cauliflower-like in structure. They occur at heights of 500-6000 meters in elevation from the earth and most often occur scattered or in dense heaped packs. They are formed due to buoyant upward convection during warm, anti-cyclonic summer weather.

cyclone

An area of low pressure where winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. See anticyclone, wind.